As the cornerstone of the digital economy, chips are advancing toward integration, low power consumption, intelligence, and functionality. Chemical-mechanical polishing (CMP) has become a critical technology for achieving ultrasmooth and defect-free global and local planarization in chip manufacturing. The abrasives in polishing slurry act as a “bridge” to facilitate the synergistic mechanical and chemical processes that are essential for high-precision material removal. Moreover, abrasives play crucial roles in achieving efficient, atomic-level, and smooth manufacturing of various materials, and they have become focal points of CMP research. Over the past few years, extensive efforts have been devoted to developing high-performance abrasives for chip manufacturing. In addition to being integral to the mechanical aspects of CMP, where they perform the physical removal of materials, abrasives also contribute chemically by interacting with the materials being polished. Hence, CMP performance is significantly influenced by the properties of the abrasives, including their dispersion stability, mechanical properties, morphology, particle size, and chemical reactivity. Maintaining the dispersion stability of abrasives is vital for prolonging the shelf lives of polishing slurries and minimizing defects, such as scratches. Furthermore, precise control over the morphology and size distribution of the abrasives can significantly reduce scratches on polished surfaces. Chemically reactive abrasives enable efficient material removal, which improves the overall polishing rate and surface quality. The research progress on typical abrasives used in CMP for semiconductor manufacturing is reviewed, with a focus on materials such as SiO₂, Al₂O₃, CeO₂, and diamond. SiO₂ abrasives are especially renowned for their abilities to satisfy the ultra-high-precision surface quality requirements of advanced semiconductor devices as well as their versatility across a wide range of materials and processing conditions. SiO₂ abrasives are essential for the manufacturing of modern electronics, particularly for applications that require exceptionally smooth and defect-free surfaces. Al₂O₃ abrasives are widely used in the CMP of substrates such as SiC, GaN, and sapphire, and they contribute to a favorable balance between performance and cost. CeO₂ abrasives are highly effective for achieving efficient material removal and fine surface finishes owing to their unique combination of mechanical hardness and chemical reactivity, which makes them ideal for specialized CMP applications. Diamond abrasives are essential for planarizing ultra-hard materials, including diamonds and other hard substrates, for which conventional abrasives are ineffective. In addition to these conventional abrasives, there is growing interest in novel abrasives and the integration of energy-field-assisted polishing techniques. These techniques utilize external energy fields (such as electric, magnetic, or optical fields) to enhance the physical and chemical interactions between abrasives and substrates, thus helping overcome the limitations of conventional abrasives when working with hard or chemically inert materials by providing an additional energy input. Moreover, there is ongoing research on the behavior of abrasives at the nanoscale, as semiconductor manufacturing is advancing toward smaller and more complex devices. Advanced characterization techniques and computational simulations were also used to gain a deeper understanding of the CMP process at the nanoscale, with the aim of understanding the atomic-level interactions between abrasives and substrates. Improving the precision and efficiency of the CMP processes is crucial, particularly for the production of next-generation semiconductor devices. Additionally, a forward-looking outlook on the application of abrasives in chip CMP is provided, and the needs for continued process optimization and the development of novel abrasives are emphasized. Furthermore, the theoretical mechanisms that govern CMP behavior must continue to be explored, as this will provide a strong foundation for future innovation in the field. This study aims to provide valuable insights and theoretical support to guide future research and development in CMP for the purpose of ultimately driving advancements in semiconductor manufacturing technology.

Novel intelligent lubricating materials and surfaces exhibit on-demand responsiveness and adaptability. The biomimetic self-regulating mechanism empowers in-service tribo-pairs with the autonomy to sense external environmental stimuli and adaptively modulate interfacial lubrication states. Such capabilities provide a groundbreaking solution for the “online sensing-decision-execution” intelligent transformation of advanced equipment in aerospace and defense sectors. Concurrently, the AI-driven intelligent inverse design of lubricating materials has revolutionized the traditional trial-and-error paradigm, enabling highly efficient and demand-responsive customization of lubrication for mechanical interfaces. This innovation provides a novel pathway for establishing a scientific framework for high-performance and high-reliability lubrication materials and surface systems capable of addressing diverse complex operational conditions. The intelligent evolution of lubricating materials and surfaces is progressively redefining the research paradigms in mechanical interface science, potentially unlocking breakthrough opportunities to advance frontier tribological theories and technologies. This paper discusses current research on self-lubricating, self-repairing, and self-diagnosing intelligent lubricating materials and surfaces, the frontier progress of AI-accelerated inverse design, and their future development trends, taking intelligent lubricating materials and surfaces and their AI paradigms as the pointcut. Currently, self-lubricating tribo-pairs that are environmentally robust and operationally adaptable use solid lubricating materials as the matrix, with liquid or solid-liquid-coupled lubricants as the dispersed phase. Effectively enhancing the interfacial lubrication performance can be achieved by releasing trace liquid lubricants to form fluid or boundary films. Two primary approaches are used for incorporating liquid lubricants into a tribo-pair matrix: porous-based self-storing and lubricating strategies and capsule-based self-storing and lubricating strategies. The development of capsule-based self-storage and lubrication techniques makes it a novel solid superlubrication method after carbon-based superlubrication and two-dimensional material superlubrication. This method enables macroscopic superlubrication at temperatures between 0 and 250 ℃. Although intelligent capsule-based self-storing and lubricating technologies can significantly reduce friction and wear on tribo-pair surfaces, material degradation and surface damage are inevitable during prolonged service. It is important to promptly repair wear and damage to improve the wear resistance and service life of tribo-pair materials. Intelligent surface healing technologies for tribo-pairs can be broadly categorized into extrinsic and intrinsic types. Extrinsic repair typically employs stimulus-responsive materials (for example, microcapsules or microvascular networks) to encapsulate active repair agents that are autonomously released upon external stimulus-induced damage, thereby facilitating physicochemical reactions for localized repair. Intrinsic repair leverages the reversible reorganization of dynamic covalent bonds (for example, Diels-Alder (DA) bonds, acylhydrazone bonds, and disulfide bonds) or non-covalent interactions (for example, hydrogen bonds, metal-ligand coordination, and host-guest interactions) to enable autonomous damage repair. Moreover, excessive wear on tribo-pair surfaces generates clearance, and its enlargement exacerbates vibration during equipment operation and reduces service life. Thus, it is imperative to endow tribo-pairs with self-diagnostic capabilities for real-time monitoring of wear locations and damage severity, enabling intelligent lifecycle management and predictive maintenance of equipment. Three approaches are the primary focus of the current intelligent self-diagnostic technologies: dye-based chromatic detection, electrical signal diagnostics, and optical signal diagnostics. The latest paradigm in the research and development of lubricating materials and surfaces, driven by AI, is the fourth paradigm after empirical, theoretical, and computational science paradigms. The primary technical approach involves employing machine-learning models to establish potential mapping relationships between the properties (such as composition and structure) of lubricant materials and surfaces and their lubrication performance. This enables prediction of the lubrication performance of new materials and surfaces. Furthermore, by integrating optimization algorithms or deep-reinforcement-learning techniques, global optimization within the high-dimensional nonlinear design space of lubricant materials and surfaces can be achieved rapidly, thereby facilitating the efficient inverse design of materials and surfaces with target attributes. This transformative research paradigm is expected to decipher the lubrication and friction reduction mechanisms at mechanical interfaces, overcome the efficiency limitations of traditional trial-and-error iterative methods, and ultimately realize demand-driven customization of lubricant materials and surface designs.

Thermal barrier coatings (TBCs) technology has been widely employed in the thermal protection of aero-engine blades. The blade surfaces are coated with ceramic materials that exhibit excellent thermophysical properties, high-temperature stability, mechanical strength, and resistance to high-temperature corrosion, thereby ensuring the longevity of aero-engines. However, the traditional 6wt.%-8wt.% Y₂O₃-stabilized ZrO₂ (YSZ), commonly used to prepare TBCs, undergoes a phase transition with severe volume expansion, rapid sintering and severe high-temperature melt corrosion above 1 200 ℃, leading to premature coating failure. To address the increasing service temperature of high-performance aero-engine, developing the novel TBCs material is urgently required. Recent advancements in research of ‘high-entropy' alloys have inspired the application of the composition design of novel ceramic materials. The synthesis and performance evaluation of high-entropy ceramic materials have thus provided new avenues for the development of novel TBC materials. The outstanding performance of the high-entropy ceramic materials is primarily attributed to four inherent effects: ① thermodynamically high-entropy effect; ② dynamically sluggish diffusion effect; ③ severe lattice distortion; ④ cocktail effect. Relevant studies have demonstrated that these four distinctive effects associated with high-entropy materials provide a degree of flexibility in composition design and property regulation, which is not present in traditional TBCs or single-component TBCs materials. Furthermore, the comprehensive performance of high-entropy TBCs ceramics is comparatively better, as evidenced reduced thermal conductivity, a coefficient of thermal expansion (CTE) that is well-matched with the alloy substrate, and the exceptional high-temperature stability. This paper presents a summary of the current research status of high-entropy thermal barrier ceramics offering an analysis of component design and performance optimization based on the characteristics and the nature of bonding in the crystal structure. The analysis covers five key aspects: thermal conductivity, thermal expansion performance, high-temperature resistance to sintering and phase stability, mechanical properties and resistance to high-temperature CaO-MgO-Al₂O₃-SiO₂ CMAS corrosion. Elements with large mass disorder and ionic radius disorder are used for the synthesis of high-entropy TBCs materials to form a larger degree of lattice distortion, which can expand the phonon collision chances, decreasing the phonon mean free path and reducing the thermal conductivity. Anions and cations with minor differences in electronegativity can form ionic bonds with weak bonding strengths to obtain materials with higher CTE. Similarly, the formation of ionic bonds with strong bonding strength is beneficial for improving the mechanical properties, such as hardness and fracture toughness. The ions with the large radius difference compete for the same lattice site together, forming a more severe lattice distortion, which hinders matter diffusion. It leads to the sluggish diffusion phenomenon that contributes to high temperature stability. The concept of high entropy, based on the nature of multi-component single-phase solid solutions, offers a novel approach to the composition design and property regulation of novel TBCs materials, which has attracted considerable research interest. By summarizing and analyzing the radius disorder, mass order, and bond strength, the high-entropy thermal barrier ceramics with optimized composition based on the nature of ion can exhibit enhanced thermal physical properties, CTE, mechanical properties, high-temperature resistance to sintering and phase stability, and resistance to CMAS corrosion, exhibiting the potential for further development. However, the preparation and performance of high-entropy thermal barrier ceramic materials is the research mainstream, which is not entirely applicable. Moreover, several problems need further research and to provide solutions during manufacturing, thereby promoting its development and maturity, such as element segregation and phase transition. In this study, the theoretical guidance on the composition, design, performance optimization, and regulation of high-entropy TBCs materials and an outlook on the prospective applications is offered.

Single-crystal diamond (SCD), owing to its exceptional physical properties—including an ultrawide bandgap of 5.5 eV, an extremely high breakdown electric field of 9.9 MV / cm, and an outstanding thermal conductivity of 22 W / (cm·K)—is widely recognized as a revolutionary material capable of overcoming the performance limitations of silicon-based integrated circuits (ICs). However, the extraordinary hardness (Mohs hardness of 10) and extreme chemical inertness of diamonds present significant challenges for achieving atomic-level surface polishing, which is crucial for their application in high-end chip manufacturing. This study focuses on the development of atomic-level polishing techniques for SCD, systematically reviews the evolution of polishing technologies from micro / nanoscale to atomic precision, and identifies key breakthroughs to overcome existing machining limitations. Additionally, this study examines the characteristics and applicability of various polishing methods, thus providing valuable insights for practical implementation. First a mechanical polishing techniques, including conventional and ultrasonic-assisted methods, are investigated comprehensively. Whereas these approaches offer straightforward processes, the inherent “hard-on-hard” friction inevitably introduces surface defects, thus rendering it difficult to achieve subnanometer surface smoothness. Subsequently, high-energy beam polishing technologies, such as lasers, ion beams, and plasma polishing, are examined. Although these methods replace abrasive particles with high-energy particles, issues such as inferior selectivity, deep thermally affected zones, and particle implantation limit their ability to achieve low subsurface damage and subnanometer planarization. The third category, i.e., multifield coupled polishing, which includes chemical-mechanical polishing and plasma-assisted polishing, leverages synergistic effects for surface planarization. However, these methods are characterized by complex processes and low polishing rates. Based on a detailed comparative analysis, this study highlights the significant challenges in satisfying the stringent requirements of IC manufacturing: subnanometer precision, minimal damage, and high processing rates. The findings suggest that, although existing polishing techniques are adopted in specific applications, they remain inadequate for completely satisfying the abovementioned demanding criteria. Achieving atomic-level surface polishing requires not only gradual process improvements but also systematic innovations in theoretical understanding and process development. This study emphasizes the necessity of cross-scale control from macroscopic process parameters to microscopic atomic behavior to precisely regulate material removal mechanisms, including the synergy between mechanical shear and chemical etching, as well as the energy threshold for atomic bond breaking. At the fundamental research level, the development of atomic-resolution in-situ characterization techniques and first-principles computational models is crucial for establishing quantitative relationships between process parameters and atomic surface configurations. The results indicate that atomic-scale manufacturing must rely on multifield synergistic regulation combined with in-situ atomic-level monitoring and intelligent control to achieve precise process optimization and further advance ultraprecision manufacturing. Despite significant progress, several technical bottlenecks remain in achieving atomic-level polishing for SCD. First, multifield coupling mechanisms are yet to be fully understood, thus resulting in trade-offs between the material-removal rate and surface quality in mechanical polishing, as well as issues such as high equipment costs and instability in energy-beam polishing. Additionally, multifield coupling techniques present challenges such as dynamic parameter mismatches (e.g., pH fluctuations and uneven light distributions), thus hindering stable and efficient processing. Second, intelligent control systems for polishing processes remain underdeveloped, with limited real-time optimization capabilities and insufficient integration of smart algorithms with in-situ characterization techniques. This results in a trial-and-error approach for process optimization. Third, the industrialization of green and efficient processes is hampered by key obstacles such as high energy consumption, environmental risks, and low process repeatability, which pose significant constraints for large-scale applications. Hence, future research should focus on three key directions: (1) deepening the understanding of multifield coupling mechanisms, including the interactions between mechanical forces, chemical etching, and energy fields (e.g., light, sound, and plasma), and establishing quantitative models of parameter synergy; (2) advancing intelligent control technologies, such as machine learning-based algorithms for real-time process optimization, and developing high-precision multifield coupling equipment to enhance process stability and consistency; and (3) promoting green and efficient processes, including the development of environmentally friendly chemical systems and energy-saving machining methods, as well as establishing standardized protocols for industrial implementation. The key innovation of this study is its systematic evaluation of polishing technologies and the identification of critical research directions to overcome diamond-machining challenges. By comprehensively assessing the strengths and limitations of existing methods, this study provides a solid foundation for the development of next-generation diamond-based ICs as well as offers valuable insights for academic researchers and industry professionals in advanced semiconductor manufacturing.

Chemical mechanical polishing (CMP) is a pivotal process in advanced semiconductor manufacturing that enables wafer surface planarization. CMP endpoint detection (EPD) technology achieves precise control over the wafer surface topography and material removal rates by dynamically adjusting the polishing pressure in different zones through real-time measurements of the thin film thickness. However, current EPD techniques face challenges in accurately capturing material removal rate variations in localized regions of wafers with complex patterns and nonuniform density distributions, leading to discrepancies between the detection signals and actual polishing states. Moreover, polishing processes involving multi-material systems suffer from limited signal resolution and selectivity, making it difficult to precisely detect interface changes. Thus, the investigation and optimization of CMP EPD technologies are crucial for addressing the challenges posed by multi-material and novel structures and improving the precision and stability of the process. This paper systematically reviews the current research on CMP EPD technologies, focusing on the principles, characteristics, and advancements in offline (e.g., the time method) and online (e.g., friction-based, optical, and eddy-current techniques) detection methods. In the early or stable stages of the CMP processes, endpoint control relies predominantly on experience and time-based polishing and lacks precise online detection. With technological advancements, four-probe offline detection instruments have been employed for post-polishing evaluations. However, these methods require extensive data accumulation and an understanding of the process parameters to determine the optimal polishing time for each material and process. Advanced CMP processes involve diverse materials, such as shallow trench isolation, interlayer dielectrics (SiO₂), metal interconnects (Cu), and barrier layers (Ti / TiN), each with distinct polishing rates and removal mechanisms. Offline detection methods struggle to adapt to these variations in real-time. In addition, time-based offline detection fails to account for wafer-to-wafer differences, rendering it insufficient to meet the demands of advanced CMP processes for real-time monitoring and rapid response. Consequently, online detection methods are often required to ensure process stability and product quality. Online EPD technologies enable real-time monitoring and analysis of polishing conditions during the CMP process, ensuring the achievement of the desired endpoints. These technologies are pivotal for automating the polishing process and enhancing the integrated circuit yield. Friction-based online EPD techniques offer strong real-time performance and ease of integration, making them particularly suitable for capturing dynamic mechanical interactions during polishing. However, these methods are significantly influenced by process conditions, such as pad wear and slurry flow, with signal noise and external disturbances undermining the detection accuracy and reliability. Future advancements in friction-based EPD should include the introduction of adaptive calibration mechanisms to mitigate external disturbances and the development of high-sensitivity friction sensors to explore the nanoscale film removal characteristics and meet the requirements of advanced process nodes. Optical EPD techniques typically achieve sub-nanometer resolutions for film thickness measurements. However, optical methods are highly sensitive to environmental conditions, with polishing slurry, debris, and surface contamination potentially interfering with signals and reducing detection precision. Future improvements in optical EPD systems should focus on enhancing the optical system design to resist interference from slurry, contaminants, and environmental fluctuations. Eddy-current EPD provides nanometer-level thickness measurements at a relatively low cost and can be easily integrated with CMP equipment. However, its insensitivity to insulating materials, such as dielectric layers, limits its ability to independently detect dielectric and nonmetallic films. Furthermore, the development of eddy-current sensors capable of achieving high-precision (nano- / sub-nanometer scale) measurements under large lift-off variations remains critical for future research. In the future, multi-physics field fusion methods will play a pivotal role in enhancing the detection performance to address the challenges posed by multilayer film stacks and heterogeneous material systems in 3D devices for advanced process nodes. By integrating optical, eddy-current, and friction-based techniques with multi-sensor collaborative acquisition and data fusion algorithms, the selectivity and accuracy of EPD can be significantly improved. Furthermore, AI-driven intelligent signal processing equipped with robust feature learning, pattern recognition, and intelligent decision-making capabilities enables the analysis and prediction of complex three-dimensional structural signals while adaptively adjusting the parameters, thereby enhancing the adaptability of EPD technologies. Additionally, flexible and customizable sensor designs combined with micro-area detection techniques contribute to increased spatiotemporal resolution, facilitating the precise monitoring and dynamic regulation of localized polishing conditions.

Diamond-like carbon (DLC) films are renowned for their exceptional wear resistance, low friction factor, and high hardness, which have led to their widespread application in the automotive, aerospace, and mechanical manufacturing industries. Various advanced techniques have been developed to control the properties of DLC films and prolong the service lives of mechanical components under wear and corrosion conditions, thereby enhancing their performance. The body of research in this field is continuously being enriched and refined. However, there is a scarcity of comprehensive review papers, which are crucial for guiding the development of the entire industry and academic domain. In response to this need, this study systematically summarizes the existing research on the wear-resistant properties of DLC films from both domestic and international perspectives, focusing on aspects such as preparation technology, process parameter optimization, modification through element doping, gradient construction, and surface texturing. A comprehensive aggregation of the research results strongly suggests that the meticulous adjustment of the process parameters is indispensable for marked enhancements in the hardness and wear resistance of DLC coatings. Element doping can improve the structure and properties of DLC films to achieve high elastic recovery as well as low friction and wear; gradient construction can strengthen the adhesion, hardness, and wear resistance of DLC films; and surface texturing can enhance the tribological performance of DLC films. Therefore, by finely controlling the process parameters, types and contents of doping elements, and design of surface structures, the microstructures of DLC films can be effectively altered to achieve an increase in the wear resistance, a reduction in the friction coefficient and wear rate, and enhanced adhesion, hardness, and wear resistance. These improvements are beneficial for extending the service lives of mechanical components under severe operating conditions. By comprehensively adjusting the manufacturing processes and other strategies for DLC films, this study achieves an overall upgrade in wear-resistant performance, thus filling the void in the industry for a systematic review on the optimization of DLC film properties. The research summarized in this study covers a range of deposition techniques, including physical vapor deposition (PVD), chemical vapor deposition (CVD), and plasma-enhanced chemical vapor deposition (PECVD), which are vital for achieving the desired film properties. The optimization of process parameters, such as the substrate temperature, deposition pressure, ion energy, and gas flow rates, is discussed, as all these parameters are critical for controlling the structure and performance of the film. The role of element doping in modifying the properties of films is investigated, with a focus on the use of transition metals, rare earth elements, and other alloying agents to enhance certain characteristics of DLC films. Furthermore, the study explores the concept of gradient construction, where the compositions and structures of films are varied throughout their thicknesses to create a gradient that can improve adhesion to the substrate and enhance mechanical properties. The study also addresses surface texturing, which involves the creation of micropatterns on the surface of a film to reduce friction and wear, which is a feature of particular importance for applications in which tribological performance is critical. In conclusion, this study provides a thorough overview of the research and development in DLC film technology by highlighting the key areas that are essential for the advancement of the field. This study underscores the importance of a holistic approach to the design and fabrication of DLC films and emphasizes the interplay among preparation techniques, process optimization, material modification, and surface engineering to achieve superior wear-resistant performance. This comprehensive review is significant in guiding future research and fostering innovation in the application of DLC films across various industries, and it serves as an essential reference for the further development of related technical fields.

Nickel-based single-crystal superalloys are widely used in aviation and industrial gas turbine blades owing to their excellent mechanical properties at high temperatures. However, under extreme service conditions, these superalloys are susceptible to fatigue, wear, corrosion, and oxidation damage, which pose significant risks to engine safety. Laser shock peening (LSP) is an advanced surface-strengthening technology that utilizes laser shock waves to induce severe plastic deformation at the surface, alter the microstructure, and introduce compressive residual stress (CRS), thereby enhancing the fatigue resistance and other properties of the alloy. Some studies have investigated the laser shock strengthening of nickel-based single-crystal superalloys for turbine blades. However, there is a notable lack of a systematic summary on this topic. This study begins by examining the technical characteristics of various LSP technologies, including traditional high-energy laser shock, low-energy laser shock without an absorption layer, warm LSP (WLSP), and femtosecond LSP (Fs-LSP). The effects of these technologies on the microstructures and properties of nickel-based single-crystal superalloys are compared, highlighting their respective advantages and disadvantages. This summary revealed that the strengthening effects of various LSP technologies on single-crystal superalloys differ. Ns-LSP and WLSP can achieve millimeter-level strengthening layer depths; LSPwC reaches several hundred micrometers; and Fs-LSP results in depths of tens of micrometers. The strengthening mechanisms of the four LSP processes for nickel-based single-crystal superalloys are distinct. Ns-LSP primarily strengthens by introducing high-density crystal defects and CRS during the shock process. WLSP improves the density, uniformity, and stability of crystal defects. LSPwC not only introduces crystal defects and CRS but also generates in-situ nano-oxide particles that further impede the dislocation motion, enhancing the strengthening effect. Fs-LSP introduces both crystal defects and CRS, and simultaneously builds surface periodic micro-nanostructures, achieving a synergistic optimization of strengthening effect and functional structure. Each of these processes has unique features and provides diverse technical paths for the performance enhancement of single-crystal alloys. Despite the different depths of strengthening layers, the core mechanism of these techniques lies in the large number of crystal defects and CRS introduced by LSP. The large plastic deformation induced by Ns-LSP and WLSP may lead to recrystallization of the single-crystal superalloy during the strengthening/service process, thereby damaging its high-temperature creep performance. Therefore, further research is needed to explore how LSP technology can achieve efficient and high-quality strengthening of single-crystal superalloys, and obtain ideal single-crystal structures. When LSPwC is used to strengthen single-crystal superalloys, the laser directly acts on the alloy surface, leading to surface remelting and oxidation, which in turn reduces the surface quality. Therefore, further research is required to improve the surface quality of the LSPwC-treated single-crystal superalloys and enhance their strengthening effect. The paper also discusses the challenges and difficulties faced in the LSP of nickel-based single-crystal superalloys and offers insights into future development trends. LSP technology has already been commercially applied in other alloy fields, and research has shown that it can improve issues such as fatigue, wear, oxidation, and corrosion in nickel-based single-crystal superalloys. To further advance this technology and expand its market penetration, it should be developed in several directions: composite strengthening process innovation, upgrading of residual stress detection equipment, innovations in equipment manufacturing technology, and the establishment of intelligent processing systems.

Accelerator-based boron neutron capture therapy (AB-BNCT) has attracted significant attention as an emerging cancer-treatment technology. The establishment of a stable neutron production target system is crucial, and the design and fabrication of a reliable anti-hydrogen embrittlement layer is crucial in ensuring long-term stability. This study investigates the effects of substrate pretreatment on the structure and performance of an anti-hydrogen embrittlement layer for accelerator-based neutron production. The substrates were treated using glass beads of varying mesh sizes, followed by the deposition of tantalum (Ta) coatings of different thicknesses via magnetron sputtering. This approach facilitated the analysis of the growth mechanism of the Ta coatings on pretreated substrates. Laser scanning confocal microscopy (LSCM) and scanning electron microscopy (SEM) were used to examine the substrate microstructure before and after sandblasting. The surface roughness was evaluated using LSCM before and after film deposition. The results revealed that as the glass bead mesh size increased from 36 to 360, the surface roughness of the substrate decreased from 5.76 nm to 1.53 nm, representing a reduction of 4.23 nm. A moderate increase in the roughness of the surface enhanced the adhesion of the anti-hydrogen embrittlement layer to the substrate, thereby improving its protective performance. SEM and LSCM observations indicated that the deposited coating inherited the initial morphology of the substrate, forming a continuous layer at a thickness of 5 μm. The crystal structure of the anti-hydrogen embrittlement layer was analyzed by X-ray diffraction (XRD), and the chemical properties of the films were further investigated by X-ray photoelectron spectroscopy (XPS). Finally, stress measurements were conducted to evaluate the overall quality of the films. However, at a thickness of 20 μm, samples with higher surface roughness exhibited growth-induced voids. X-ray diffraction (XRD) analysis revealed that, as the coating thickness increased, the crystallographic structure of the Ta coating evolved on the copper (Cu) substrate. During the nucleation stage (1 μm), α-Ta was preferentially formed, whereas during the growth stage, α-Ta gradually transformed into β-Ta. When the coating thickness reached 20 μm, samples with lower roughness were predominantly composed of the β phase. Increased roughness contributed to grain refinement; however, for coatings beyond a certain thickness, finer grains were observed in samples S4 (5 μm) and S5 (20 μm). No cracks or delamination were observed in the 20 μm-thick Ta coatings deposited on all pre-treated substrates. Film quality was further assessed through stress measurements, revealing an inverse relationship between coating thickness and internal stress. Measurements demonstrated a significant stress reduction with increasing film thickness. This reduction was attributed to the stronger influence of the substrate on 1 μm-thick coatings. Notably, after sandblasting the substrate with 360-mesh glass beads, the stress of the 20 μm-thick Ta coating was reduced to only 0.35 GPa. Additionally, the pits generated by sandblasting induced compressive stress during the intermediate growth stage, promoting adhesion between the Ta antihydrogen embrittlement layer and substrate. Comparative analysis of different samples demonstrated that, under identical magnetron sputtering parameters, substrates treated with 220-mesh glass beads exhibited a smooth and dense surface morphology, with the corresponding 20 μm-thick Ta coating exhibiting a stress level of only 0.35 GPa. The fabrication of an anti-hydrogen embrittlement layer was successfully achieved by sandblasting pre-treatment combined with magnetron sputtering. An optimal sandblasting mesh size was selected to ensure reliable adhesion of the subsequent lithium reaction layer. This study provides valuable insights into the development of stable and efficient accelerator-based neutron production targets for AB-BNCT while addressing critical engineering challenges when implementing anti-hydrogen embrittlement layers in accelerator-driven neutron production targets.

Cold-sprayed Zn coatings have attracted considerable attention as a topic of active research in materials science and surface engineering owing to their superior resistance to corrosion. Thus, techniques based on cold-sprayed Zn coatings have been developed rapidly over the past few decades, with a focus on enhancing their performance and broadening potential areas of application. In this study, we provide an in-depth review of recent works on cold-sprayed Zn coatings to offer a comprehensive summary of advancements in pure Zn, Zn-alloy, and Zn-based composite coatings. First, we examine the microstructure and properties of cold-sprayed pure Zn coatings. Studies have shown that the deposition process results in a unique microstructure characterized by fine grains and high density, which confers excellent initial resistance to corrosion. However, it still needs some improvement in terms of the mechanical properties of the coatings such as their hardness and tensile strength. Research efforts have concentrated on optimizing spraying parameters such as gas pressure and temperature to enhance the density and uniformity of the coatings to improve their overall performance. Secondly, we systematically review the relevant literatures on cold-sprayed Zn coating, Zn-alloy coating, and Zn-ceramic composite coating. The adding elements such as Al, Mg, or Ni can significantly alter the microstructure and properties of Zn coatings. For example, studies have shown that the formation of intermetallic compounds in Zn-Al alloy coating plays a crucial role in enhancing corrosion resistance and mechanical strength. These compounds act as barriers against corrosion and strengthen the coating. In Zn-ceramic composite coating, the incorporation of ceramic particles such as alumina (Al₂O₃) or titanium dioxide (TiO₂) can improve coating’s hardness and wear resistance. A study on Zn-Al₂O₃ coating found that the wear rate of the coating was significantly reduced under specific tribological test conditions with the addition of a certain proportion of Al₂O₃ particles. The key findings of these studies provide valuable insights to guide future research and development. Additionally, we also review the common additive phases in cold-sprayed Zn coatings and their impacts on mechanical and tribological properties and corrosion resistance. Adding materials such as graphene, carbon nanotubes, and various nanoparticles have been introduced to achieve synergistic effects. For example, graphene forms a barrier layer within Zn coating that remarkably enhances its resistance to corrosion. Research indicates that when an appropriate amount of graphene is added to Zn coating, the corrosion current density is greatly reduced compared with Zn coating, which indicates a significant improvement in corrosion resistance. These additions can also improve tribological properties and reduce friction and wear. Furthermore, we also summarized post-treatment technologies such as heat treatment and shot peening. The influence of these post-treatment methods on cold-sprayed Zn-based coatings are evaluated based on experimental results and theoretical analysis. In general, heat treatment can relieve internal stress, improve crystallinity, and enhance the bonding strength between the Zn-based coating and the substrate. In an experiment with heat treatment, the adhesive strength was increased significantly when the samples were heated to an appropriate temperature and maintained for a certain period. Similarly, shot peening can refine surface grains, increase the surface hardness, and enhance fatigue resistance. Finally, we also outline prospects for future developments in cold-sprayed Zn-based coatings. It is expected that more advanced spraying techniques and new adding materials will emerge to further optimize the performance of cold-sprayed Zn-based coatings.

As the dimensional scaling and functional integration of high-end semiconductor devices accelerate, ultra-precision finishing of substrates such as monocrystalline Si, SiC, AlN, Ga₂O₃, and GaN is now constrained by atomic-level accuracy targets; while this context motivates the field, the present review concentrates on what enables—and limits—atomic-level grinding (ALG) as a deterministic route for planarization and thinning of semiconductor wafers, synthesizing mechanism-level knowledge with process engineering practice to clarify how ALG governs surface integrity, subsurface damage (SSD), total thickness variation (TTV), and mid-spatial-frequency (MSF) errors that ultimately control device yield and performance. We first dissect material-removal mechanisms from the atomic to the mesoscale and explain how ductile-regime grinding can be stabilized by connecting lattice bonding, elastic-plastic anisotropy, fracture resistance, and tribochemistry with the thermomechanical fields at the tool-work interface: for Si, pressure-induced phase transformation and subsequent tribo-oxidation support ultra-smooth shearing of a metastable / altered layer; for SiC, amorphization under high contact stress combined with oxidation-assisted weakening suppresses brittle fracture and enables Å-level topographies; for III-N and ultra-wide-bandgap oxides (GaN, AlN, Ga₂O₃), defect-mediated shear coupled with chemistry- or field-assisted bond weakening—via alkaline or oxidative chemistries and hydration reactions—reduces the effective activation energy for interfacial slip. Across materials, we highlight controlling nondimensional groups, particularly the ratio of undeformed chip thickness to the critical depth for ductile removal, that demarcate transitions among brittle chipping, quasi-ductile ploughing, and true ductile cutting, yielding mechanism maps that relate abrasive size and morphology, contact pressure, temperature, and chemistry to SSD depth, residual stress, and roughness. Building on these mechanisms, we catalog processing strategies and system-integration choices that operationalize ALG at wafer scale: fixed-abrasive ultra-fine diamond grinding with electrolytic inprocess dressing (ELID), ultrasonic-vibration-assisted modes that lower effective cutting forces, and laser / thermal assistance that locally softens the surface to tip the balance toward plasticity; chemo-mechanical synergy using oxidants, complexants, and pH / redox control to form and continuously renew a weak interfacial layer that can be sheared at nanometric depths of cut; and co-design of tooling and kinematics—resin / metal / ceramic bonds, abrasive size distributions, wheel-topography conditioning, and path planning (spiral / raster with dwell control)—to suppress TTV and MSF on 200-300 mm wafers. We summarize robust process windows from successful reports—high wheel speed, low feed and depth to keep the undeformed chip thickness sub-critical, ultra-stiff low-runout spindles, temperature-stabilized machine / wafer stacks, and low-noise workholding to prevent chatter—while analyzing fluid chemistry as a lever that intersects with frictional heating and contact time to regulate altered-layer thickness and face-dependent removal selectivity. Metrology and control are treated as first-class topics: in-situ force / acoustic- emission / temperature sensing for contact-state identification; optical interferometry for shape and MSF; and XPS / TEM / Raman for altered-layer chemistry and SSD, all feeding model-based and data-driven control frameworks that span multiscale simulation (DFT / MD to continuum) for predicting critical depths and stress fields, physics-informed machine learning for tuning parameters to minimize SSD at target MRR, and digital twins that couple thermal-structural drift, wheel-wear evolution, and wafer geometry for adaptive compensation of TTV and edge roll-off. From this synthesis, we make explicit the principal challenges: robust suppression of brittle events on hard, chemically inert wafers without sacrificing throughput; quantitative control of SSD at tens of nanometers or less with verifiable, crystallographic-face-dependent selectivity; wafer-scale flatness and TTV control during thinning, including edge roll-off mitigation; MSF management induced by periodic wheel topography or path artifacts; tool wear, self-sharpening, and wheel-state observability; thermal and dynamic stability of large, low-stiffness wafer stacks; seamless integration with downstream CMP without re-introducing defects; and greener chemistries that maintain mechanochemical efficacy. Finally, we identify emerging directions likely to be most impactful: hybrid energy fields (ultrasonic / laser / plasma-assisted ALG) to expand the ductile window; closed-loop, sensor-rich control with real-time detection of critical-depth excursions; physics-guided AI for multi-objective optimization of roughness / SSD / MRR subject to throughput and sustainability constraints; micro- / nano-textured abrasive tools that engineer contact states and chip evacuation; and standardized protocols plus open datasets for cross-material benchmarking. Collectively, the review delivers mechanism maps, process-integration guidelines, and a research agenda aimed at deterministic attainment of sub-nanometer roughness and minimal SSD in semiconductor substrate grinding, offering theoretical insights and technical references to guide future advancements in atomic-level grinding for semiconductor manufacturing.

Nanoprecision surface manufacturing technology has important applications in many high-tech fields, such as semiconductor photovoltaic and integrated circuit manufacturing. Chemical mechanical polishing (CMP), the most critical technology in ultraprecision surface manufacturing, guarantees and promotes the application and development of high-end technologies. Gallium arsenide (GaAs) is the most important second-generation semiconductor substrate, and it is widely used in microelectronics and optoelectronics. High-quality GaAs substrates require the absence of surface / subsurface damage, preservation of lattice integrity, and sub-nanometer level surface roughness. CMP is currently the most effective technology to achieve these requirements. As material removal in CMP is predominantly governed by tribochemical reactions, understanding these mechanisms is essential for enhancing the surface quality. In this study, the tribochemical removal mechanisms during CMP of GaAs were investigated by conducting nano-wear experiments using an atomic force microscope (AFM) equipped with a silicon dioxide (SiO₂) microsphere tip under acidic (pH ≈ 4), neutral (pH ≈ 7), and alkaline (pH ≈ 10) conditions. Material-removal regions were characterized using high-resolution transmission electron microscopy (TEM). Density functional theory (DFT) calculations were employed to elucidate the atomic removal mechanisms. The results indicate that material removal on the GaAs surface is the most severe in alkaline conditions, with removal depths and volumes being significantly higher compared with those in neutral and acidic conditions. Specifically, the material removal depths in the acidic, neutral, and alkaline conditions were approximately 9.4, 19.2, and 24.2 nm, respectively. Similarly, the material removal volume increased from 4.99×10⁶ nm³ in acidic conditions to 8.84×10⁶ nm³ in alkaline conditions. A TEM analysis revealed that the lattice structure in the material-removal regions remained intact, suggesting that tribochemical reactions dominated the removal process without causing significant damage to the underlying atomic structure. The significant change in the charge density at the GaAs / SiO₂ interface, as calculated by DFT, suggests the formation of Si-O-Ga bonds. Furthermore, interfacial charge transfer was the most pronounced in alkaline conditions, where OH^- ions promoted the formation of Si-O-Ga bond bridges and weakened Ga-As bonds, facilitating material removal. The calculations showed that the charge transfers in the subsurface region of GaAs were 0.032, 0.039, and 0.042 e / ų under acidic, neutral, and alkaline conditions, respectively. This increased charge transfer in alkaline conditions leads to a more significant weakening of the Ga-As bonds, making the material more susceptible to removal. Additionally, CMP experiments conducted under the same pH conditions confirmed that the surface roughness and material removal rate (MRR) were optimal in alkaline conditions. The surface roughness (Sa) values were approximately 3.61, 1.87, and 0.81 nm for acidic, neutral, and alkaline conditions, respectively. The MRR values followed a similar trend, with the highest rate observed in alkaline solutions (22.6 nm / min), compared with those in neutral (19.4 nm / min) and acidic (13.2 nm / min) conditions. This consistency between the nanowear experiments and CMP results underscores the importance of pH in controlling the tribochemical removal process. These findings suggest that the presence of OH^- ions in alkaline conditions enhances the formation of Si-O-Ga bonds and increases charge transfer at the GaAs / SiO₂ interface, leading to more efficient material removal. This study provides valuable insights into the pH-dependent tribochemical removal mechanisms during the CMP of GaAs, providing a foundation for optimizing CMP processes for other binary materials. The integration of single-abrasive material removal experiments based on AFM, TEM, and DFT calculations presents a comprehensive approach for understanding and improving CMP techniques for semiconductor materials. By elucidating the role of pH in the tribochemical removal process, this study contributes to the development of more efficient and precise CMP methods that ultimately enhance the performance of semiconductor devices.

Ultraprecision surface grinding and polishing are crucial for manufacturing high-end aluminum nitride (AlN)-based wide-bandgap semiconductor chips and devices. When traditional ultra-precision surface processing methods such as nanogrinding are used to process AlN, the material removal rate is low, and processing-induced damage is difficult to control owing to the hard-brittle properties of AlN. It has been proven that inducing ultrasonic vibrations can increase the material removal rate and reduce subsurface damage during grinding. However, the material-removal mechanisms of ultrasonic vibration-assisted nanogrinding of AlN are not completely understood, and the influencing law and microscopic mechanisms of amplitude and frequency remain unclear. To this end, molecular dynamics simulations of ultrasonic vibration-assisted nanogrinding of AlN surfaces with single diamond abrasives under different conditions were performed to investigate the influence of amplitude and frequency on the removal of nanoscale / sub-nanoscale materials and subsurface lattice damage at the atomic level. The Vashishta potential function was used to describe the interatomic interactions within the AlN workpiece, and the Lennard-Jones potential function was used to describe the C-Al and C-N interactions between the diamond abrasives and the AlN workpiece. The microstructure of the AlN workpiece during nanogrinding was characterized by the dislocation extraction algorithm (DXA) and identify diamond structure (IDS) to discuss the effects of amplitude and frequency on subsurface lattice damage such as dislocations, stacking faults, and amorphization. Based on a comprehensive analysis of the data of the grinding force, grinding morphology, removal volume, subsurface microstructures, temperature distribution, and von Mises stress distribution, the mechanism of ultrasonic vibration-assisted nanogrinding under different amplitude and frequency conditions on the nanoscale / sub-nanoscale material removal and subsurface lattice damage at the atomic level was explored. The simulation results demonstrate that both amplitude and frequency significantly affect the grinding force, and the instantaneous tangential and normal contact areas between the diamond abrasives and AlN workpieces during nano-grinding are reduced with increasing amplitude or frequency, leading to a decrease in tangential and normal forces. Increasing the amplitude or frequency can significantly increase the material-removal volume, reduce the roughness of the grinding surface, and reduce the lattice damage in the subsurface. As the amplitude increases, the grinding force decreases linearly, the removal volume increases linearly, the dislocation distribution range decreases, and the material-removal behavior gradually changes from plastic-dominated to composite removal. When the vibration frequency reaches 1 GHz, the ultra-high-frequency vibration enhances the impact effect of the diamond abrasive on the AlN workpieces and causes the atoms to acquire high instantaneous energy, thus generating high-temperature zones at the abrasive-workpiece contact area. Owing to the more intense thermal activity of the atoms, the Al and N atoms linked via covalent bonds in these high-temperature zones can be broken more easily. Hence, material removal is facilitated, the grinding force decreases, and the removal volume increases sharply. The surface of the groove is smooth, almost reaching the atomic level of flatness, and the two sides of the groove show obvious atomic-laminar removal features. At this point, the subsurface obtains a state of almost no damage; that is, no dislocations or amorphous structures are formed except for slight stacking faults in the subsurface. In contrast, when the vibration frequencies are 10 and 100 MHz, the surface roughness is high, and many dislocations and stacking layers appear in the AlN workpiece. The analysis results suggest that ultrahigh-frequency vibration induces a localized temperature increase in the abrasive-workpiece contact area and enhances the impact of the abrasive. The research results can provide a theoretical reference for optimizing the process conditions for high-efficiency and low-damage ultraprecision grinding of hard-brittle semiconductor materials.

Marine biofouling poses a persistent challenge for submerged mechanical equipment, leading to accelerated corrosion, operational inefficiencies, and significant economic losses. The accumulation of microbial communities on marine surfaces not only damages equipment but also substantially increases maintenance costs, creating a critical bottleneck for sustainable marine resource development. Addressing this issue through effective antifouling solutions has become a global research priority in marine engineering. Current antifouling technologies primarily encompass mechanical removal, ultrasonic cleaning, and protective coatings, with antifouling coatings emerging as the most widely adopted solution due to their cost-effectiveness, ease of application, and superior performance. There is a wide variety of antifouling coatings, each with distinct antifouling mechanisms. However, comprehensive reviews on the antifouling performance, advantages, and disadvantages of both traditional and novel antifouling coatings remain scarce. Thus, a comprehensive review is conducted on the research advancements of both traditional and novel antifouling coatings, such as natural antifoulant coatings, biomimetic coatings, self-healing coatings, etc. Their research status, antifouling mechanisms, and remaining challenges are discussed. Traditional antifouling coatings can be categorized into matrix-insoluble and matrix-soluble types. The former operate through the gradual release of embedded biocidal compounds that deter or eliminate fouling organisms. However, these coatings exhibit significant limitations, including short service lifetimes and complex application requirements, which restrict their widespread adoption in marine applications. Self-polishing antifouling coatings (SPCs), the most currently commercially successful matrix-soluble system, dominating 90% of the global market, utilize hydrolyzable polymer side chains to enable controlled antifoulant release. However, their uneven release kinetics (initial excess followed by insufficiency) compromises long-term performance, and their dependence on toxic biocides raises environmental concerns. In contrast to these traditional coatings that rely on biocidal agents, fouling-release coatings achieve antifouling effects solely through their low surface energy, preventing fouling organisms from firmly adhering. Under water flow, fouling organisms detach easily, providing excellent antifouling performance without harming the marine environment. However, these coatings perform poorly under static conditions, and their adhesion to substrate needs improvement. Natural antifoulant coatings derive their active substances from antifouling compounds secreted by plants and animals or their synthetic analogs. They reduce marine biofouling by inhibiting adhesion processes and interfering with microbial signaling systems. Compared to traditional antifoulants, natural antifoulants are less toxic and significantly reduce environmental impact. However, challenges such as broad-spectrum efficacy and long-term durability remain unresolved. Biomimetic coatings utilize micro- and nanostructures from self-cleaning natural surfaces (via 3D printing, laser etching, or transfer techniques) to achieve efficient and eco-friendly antifouling effects, showing high application potential. However, these coatings often suffer from low mechanical strength, poor adaptability, and high production costs. Self-healing marine coatings integrate specialized repair agents that autonomously mend surface damage, overcoming key limitations of conventional systems by extending service life and maintaining antifouling efficacy. Despite their potential for significant economic and performance benefits, commercialization challenges persist, including complex fabrication, high costs, and difficulties in scaling beyond laboratory prototypes. Photocatalytic coatings rely on photocatalysts to undergo redox reactions under specific light wavelengths, decomposing seawater and dissolved oxygen to generate reactive oxygen species (ROS). These ROS penetrate cell membranes, damage microbial DNA, and cause cell rupture, achieving antifouling through microbial inactivation. These coatings are safe, efficient, non-toxic, and pollution-free. However, their performance is highly dependent on UV intensity and light energy utilization, requiring further improvements in stability. Hydrogel coatings contain high water content (typically >70%, even >90%), forming a dense and dynamic hydration layer through hydrogen bonding between polymer chains and water molecules. This layer effectively blocks fouling organism attachment. However, their poor mechanical properties and weak adhesion limit broader applications. Despite the variety of marine antifouling coatings available, single mechanism approaches generally fail to meet the complex demands of marine environments, particularly regarding long-term efficacy, broad-spectrum performance, and environmental safety. To overcome these limitations, we propose the strategic integration of multiple antifouling mechanisms within hybrid coating systems. This synergistic approach aims to combine the advantages of different technologies while mitigating their individual weaknesses, paving the way for next-generation antifouling solutions that balance performance, durability, and ecological sustainability. The findings provide valuable insights for developing advanced marine coatings.

Single-crystal silicon carbide (SiC), as a wide-bandgap semiconductor material with excellent properties, is widely used in high-power electronic devices and optoelectronic fields. However, its high brittleness, extreme hardness, and strong chemical inertness pose significant challenges for achieving efficient and low-damage polishing. Chemical mechanical polishing (CMP) cannot meet industrial efficiency requirements owing to its slow reaction kinetics. Therefore, this study introduces ultrasonic vibration into the photocatalytic chemical mechanical polishing (PCMP) method to investigate the synergistic enhancement mechanism of ultrasonic-assisted photocatalysis and the material removal mechanism under multi-energy field interactions, with the aim of advancing the development of multi-energy field collaborative polishing technology. Three different experiments were designed to evaluate the effects of ultrasonic frequencies (0, 22, 25, 28, and 40 kHz) on the chemical and mechanical performance. This study combined photocatalytic oxidation with ultrasonic vibration, using nano-TiO₂ as a catalyst under UV irradiation to induce cavitation effects. The Oxidation performance characterization tests utilized a methyl orange solution as an indicator, with the decolorization time of the polishing solution under ultrasonic-assisted photocatalytic conditions used to assess oxidative strength being shorter, indicating a stronger oxidation capability. The static corrosion tests involved immersing the SiC samples in the polishing solution for 2 h under ultrasonic-assisted photocatalytic conditions. The resulting oxide layers were quantified using scanning electron microscopy and X-ray photoelectron spectroscopy. Ultrasonic-assisted PCMP experiments were conducted using SiO₂ abrasive slurry for 2 h, with the material removal rates and surface roughness measured to evaluate polishing performance. At 22 kHz ultrasonic vibration, the methyl orange decolorization time was 229 s, the oxygen content on the corroded surface reached 2.94at.%, the material removal rate was 503.47 nm / h, and the surface roughness was 48.28 nm. Compared with photocatalytic oxidation alone, ultrasonic assistance reduced the decolorization time by 117.90%, increased the oxygen content by 215.96%, improved the material removal rate by 52.63%, and reduced the surface roughness by 91.30%. The electron-hole pairs generated by the photocatalyst under illumination effectively promoted the formation of highly oxidative radicals (e.g.,·OH) in the reaction environment, accelerating the formation of oxide layers. The·OH in the polishing solution oxidized the surface, forming oxide layers primarily composed of Si and C oxides, which exhibited significantly lower hardness, strength, and bonding strength compared with the original SiC surface, thereby allowing easy removal using diamond or silica abrasives. Ultrasonic vibration enhanced both the chemical oxidation and mechanical removal stages of the polishing process. During ultrasonic propagation in liquids, cavitation bubbles formed and collapsed rapidly upon reaching a critical size during the compression cycles, generating localized high-energy microenvironments with temperatures exceeding 5 000 K and pressures up to 1 000 atm. Ultrasonic effects accelerated the mass transfer among the reactants, catalysts, and radicals, reduced the diffusion resistance, rapidly removed intermediate products generated during photocatalytic reactions, prevented reaction blockage, promoted electron-hole pair separation, reduced recombination rates, increased·OH concentration, and significantly improved the photocatalytic oxidation efficiency. The collapse of the cavitation bubbles enhanced the kinetic energy of the catalysts and abrasives, increasing the contact frequency and efficiency between the workpiece, catalysts, and abrasives, thereby improving the oxidation rate and mechanical removal efficiency of SiC. Ultrasonic vibrations also promoted the uniform distribution of photocatalysts and abrasives, eliminated catalyst agglomeration, increased the reactive surface area, enhanced the photocatalytic efficiency, and improved the surface uniformity and consistency. In addition, the localized high-temperature environments generated by cavitation bubbles further enhanced the chemical reactions. Notably, lower ultrasonic frequencies exhibited stronger cavitation effects, significantly improving the efficiency of ultrasonic-assisted PCMP. Owing to the synergistic effects of ultrasonic vibration, photocatalysis, and mechanical forces, the wear characteristics of the surface were significantly different from those after traditional grinding and polishing. Ultrasonic action improves the fracture toughness, facilitates plastic removal, and reduces subsurface damage. Therefore, integrating ultrasonic vibration into PCMP enhances the photocatalytic activity and abrasive kinetic energy, increases the oxidation rates and removal efficiency, and enables more efficient polishing of single-crystal SiC.

The accelerated development of modern industry and information technology has resulted in a notable surge in demand for high-performance materials capable of functioning in extreme environments, particularly in the domains of friction and electromagnetic wave absorption. MXene-based materials have attracted considerable interest owing to their exceptional properties, including high electrical conductivity, a unique layered structure, outstanding mechanical properties, chemical stability, and abundant surface functional groups. However, a comprehensive and systematic review of recent progress in the application of MXene-based materials in tribology and electromagnetic wave absorption remains unavailable. To address this gap, an in-depth and systematic review of the structural properties, preparation methods, and performance mechanisms of MXene-based materials in these applications is presented. The fundamental structural characteristics of MXene are examined, including its two-dimensional configuration, chemical composition, and surface modifications. These attributes are considered to be critical in understanding the multifunctional performance of MXene. Furthermore, the intrinsic properties of MXene, including its exceptional electrical conductivity and mechanical flexibility, are analyzed in detail. The preparation and processing techniques of MXene and its derivatives are also explored, with a focus on the ways in which various processes, ranging from conventional wet chemical etching to advanced composite fabrication methods, are employed to tailor MXene materials for specific performance requirements. In the field of tribology, MXene-based materials have the potential to significantly reduce friction and enhance wear resistance. The preparation and processing of MXene has been the subject of considerable study, and the results have highlighted notable advantages over traditional two-dimensional materials, such as graphene and molybdenum disulfide. In particular, the achievement of lower coefficients of friction and wear rates has been demonstrated. These superior tribological properties are primarily attributed to the unique two-dimensional structure and surface chemistry of MXene. The integration of MXene into lubricants or composites has been demonstrated to enhance friction reduction and anti-wear performance, yielding coefficients of friction and wear rates that exceed those of conventional materials. Furthermore, MXene functions effectively as a cross-linking agent in polymer systems, significantly improving their tribological characteristics by reinforcing their mechanical integrity and enhancing surface interactions. In the field of electromagnetic wave absorption, MXene-based materials demonstrate exceptional wave energy attenuation capabilities, attributable to their high electrical conductivity, superior dielectric loss, and tunable surface chemistry. These properties facilitate the efficient conversion of electromagnetic energy into other forms of energy, enabling optimal absorption performance across a wide frequency range. The surface functionalization and formation of composites with materials such as polymers, magnetic nanoparticles, or carbon-based structures have further enhanced the efficiency and bandwidth of the absorption process. Furthermore, the layered structure of MXene facilitates multiple internal reflections of electromagnetic waves, thereby significantly enhancing its absorption capabilities. A comparative analysis of various composite designs and processing techniques demonstrates that MXene-based materials outperform traditional wave-absorbing materials, such as ferrite and carbonyl iron powders, particularly in lightweight and flexible applications. These advantages position MXene-based materials as a highly promising solution for modern electronic devices, stealth technology, and electromagnetic interference shielding, addressing critical demands in these advanced technological fields. Despite the remarkable properties and potential of MXene-based materials across a range of applications, a number of challenges remain. These include stability issues under extreme conditions, such as limited resistance to oxidation and thermal degradation, as well as the complexity involved in designing multifunctional composites and the high costs associated with large-scale production. To overcome these obstacles, several improvement strategies are proposed. These include surface functionalization to enhance environmental stability, the integration of MXene with other nanomaterials to augment multifunctionality, and the optimization of preparation processes to reduce production costs. The implementation of these strategies is expected to significantly broaden the practical applications of MXene-based materials, thereby rendering them more feasible for industrial and technological use. In conclusion, the present study offers a systematic review of the research progress on MXene-based materials in the fields of tribology and electromagnetic wave absorption. This includes a detailed analysis of their unique properties, underlying mechanisms, and preparation methods. The findings provide a comprehensive understanding of the current advancements while identifying critical challenges and future research directions. Given their exceptional performance characteristics and versatile potential, MXene-based materials are anticipated to play a pivotal role in addressing the demands of modern industry and advanced technologies. It is likely that their continued development will yield innovative solutions for applications in high-performance friction materials, electromagnetic interference shielding, and beyond, underscoring their importance as a transformative material platform.

K9 glass is widely used in aerospace, military, and optoelectronic applications owing to its high mechanical strength, exceptional wear resistance, superior optical transparency, and excellent thermal stability. However, as a typical hard-brittle material characterized by low fracture toughness, K9 glass is more prone to subsurface damage and crack formation during machining processes. Chemical mechanical polishing (CMP), which is recognized for its high processing efficiency, simplified equipment configuration, and cost-effectiveness, has been extensively adopted for the surface finishing of optical glasses and other hard-brittle materials. Cerium oxide (CeO₂) abrasives are widely used in the surface planarization of optical glasses owing to their unique chemical reactivity with silica. Moreover, their particle size distributions play critical roles in determining both the material removal rate and surface quality. To meet the stringent requirements for a high material removal rate and superior surface quality in K9 glass polishing, this study systematically investigated the effects of five distinct particle sizes of CeO₂ abrasives on the CMP performance of K9 glass, both individually and in hybrid configurations. To isolate and quantify the contributions of the chemical and mechanical actions of the abrasives, the chemical effects of the CeO₂ abrasives were suppressed via the hydrogen peroxide (H₂O₂) treatment of the polishing slurry. This approach enables the decomposition of the total removed material into three fundamental components: mechanical action, chemical action, and synergistic interactions. In conjunction with an surface analysis using X-ray photoelectron spectroscopy (XPS), the surface chemical properties of CeO₂ abrasives with varying particle sizes were systematically characterized to elucidate the material removal mechanisms of different CeO₂ abrasives during a polishing process. The results showed that the material removal rate of K9 glass initially increased and then decreased as the particle size of the single CeO₂ abrasive increased. In contrast, the surface roughness exhibited the opposite trend. A high material removal rate (99.53 nm / min) and low surface roughness (1.27 nm) were achieved at particle sizes of 50 and 300 nm, respectively. Moreover, the combination of CeO₂ abrasives with particle sizes of 50 and 300 nm significantly improved the removal rate of K9 glass. When the mass ratio of the combination was 1∶2, the K9 glass exhibited an excellent removal rate (121.72 nm / min) and surface roughness (1.24 nm). When H₂O₂-treated CeO₂ slurries were employed to suppress chemical interactions, neither mechanical abrasion from the polishing pad nor pure chemical action by abrasives contributes measurably to material removal. The pure mechanical action of abrasives achieved a relatively low material removal rate. Moreover, the ratio (K) of the pure mechanical removal rate to the total removal rate exhibited an increasing trend with an increase in abrasive particle size. Specifically, the values of the parameter K for abrasives with particle sizes of 20 nm and 1 μm were 3.32% and 18.9%, respectively. The results of a surface analysis via XPS revealed that the surface Ce³⁺ concentration decreased as the particle size of the CeO₂ abrasives increased. Specifically, the Ce³⁺ concentrations for abrasives with particle sizes of 20 nm and 1 μm were measured at 29.5% and 25.33%, respectively. In the chemical-mechanical polishing of K9 glass, the synergistic interaction between the chemical and mechanical actions of the CeO₂ abrasives served as the dominant material removal mechanism. Smaller CeO₂ abrasive particles exhibited stronger chemical activity, and the surface Ce³⁺ concentration significantly influenced the material removal rate. Mechanical action was an indispensable component of this process. In contrast, larger abrasive particles demonstrated weaker chemical effects but exhibited enhanced mechanical grinding capabilities. The hybrid abrasive system, which effectively combined the enhanced chemical reactivity of small particles with the superior mechanical grinding capability of large particles, significantly improved the polishing performance of K9 glass. These results provide valuable theoretical and practical insights for the development of advanced polishing slurries for the precision machining of K9 glass and other optical materials.

C_f / SiC composites are characterized by high hardness, high brittleness, anisotropy, and heterogeneity, which induce machining defects such as matrix cracking and fiber pull-out during conventional mechanical processing, severely undermining the service performance and lifespan of components. To address this challenge, a novel single-excitation longitudinal-torsional ultrasonic elliptical vibration turning (LTUVT) device was designed and developed in this study. The primary objective was to achieve stable elliptical tool-tip motion through a simplified vibration system, thereby improving the machinability of the C_f / SiC composites. This study was conducted systematically, encompassing structural design, theoretical analysis, simulation verification, performance testing, and machining experiments. First, based on the principle of longitudinal-torsional vibration coupling, the core components of the device—the transducer and the horn—were structurally designed. Spiral grooves with the defined parameters were machined onto the horn surface. This design decomposes the longitudinal vibration generated by a single piezoelectric ceramic excitation into longitudinal and torsional vibration components with a specific phase difference. The three-dimensional elliptical trajectory of the tool tip, superimposed with the workpiece rotation, tool feed, and ultrasonic vibration, was analyzed through kinematic modeling. Motion equations were derived to elucidate the conditions for intermittent cutting and the friction reduction mechanism. Second, the dynamic characteristics of the designed transducer were investigated via finite element analysis using the COMSOL software. Modal analysis identifies an ideal longitudinal-torsional coupled vibration mode near 21 830 Hz, with the maximum amplitude concentrated at the output end and nearly zero amplitude at the flange, validating the structural rationality. Harmonic response analysis further shows that the longitudinal and torsional amplitudes at the output end at the target frequency are approximately 15 and 10.5 μm, respectively, with a ratio of about 0.7, falling within the preset range of 2-15 μm. Subsequently, the vibrational performance of the fabricated turning device was experimentally tested. The impedance analysis shows that the actual resonant frequency is 21 061 Hz, with a deviation of 5.3% from the preset frequency of 20 000 Hz. The admittance circle is well-formed, indicating good resonant characteristics. Amplitude testing using a laser Doppler vibrometer demonstrates that both longitudinal and torsional amplitudes increase synchronously with the ultrasonic power supply’s output power, reaching maximum values of 12.84 and 11.2 μm, respectively, with an average ratio of about 0.9. These results are consistent with the simulation and design expectations, confirming the capability of the device to deliver stable and controllable elliptical vibrations. Finally, systematic comparative turning experiments were performed on the prepared C_f / SiC composite workpieces using polycrystalline diamond (PCD) tools. The influence of ultrasonic amplitude on the cutting forces, workpiece surface morphology, and tool wear was comprehensively investigated. The results indicate that the LTUVT significantly reduces the cutting forces. Compared with the CT, under the optimal parameters, the radial force, main cutting force, and feed force are reduced by an average of 25.8%, 23.9%, and 26.4%, respectively. Cutting forces decrease continuously with increasing ultrasonic amplitude, reaching minimum values (F_x=3.3 N, F_y=8.8 N, F_z=4.9 N) at a longitudinal amplitude of 9 μm. The LTUVT effectively suppresses the machining damage. Compared to the significant fiber pull-out, matrix cracking, and chip adhesion observed in CT, LTUVT promotes material removal modes dominated by fiber shear and brittle fractures. The fewest defects, such as fiber pull-out and pits, and maximum surface integrity are achieved at a longitudinal amplitude of 6 μm. LTUVT substantially mitigates tool wear. In contrast to the deep and continuous wear-land formed on the tool flank face in CT, LTUVT results in shallower wear grooves and a smaller wear-land area. The tool flank wear area first decreases and then increases with increasing amplitude, reaching a minimum average value of 50 150 μm² at a longitudinal amplitude of 6 μm, representing a reduction of approximately 79.95% compared to CT. However, excessive amplitude (9 μm) leads to aggravated micro-chipping of the cutting edge. The optimal process parameter identified is a longitudinal amplitude of 6 μm (corresponding to a torsional amplitude of approximately 5.4 μm), which balances superior surface quality with minimal tool wear. This study provides an effective ultrasonic vibration-assisted machining solution for the precise and efficient processing of difficult-to-machine composites, such as C_f / SiC, with significant theoretical and practical engineering value.

Mobile additive repair and remanufacturing in complex on-site environments face three overarching challenges: the multi-constrained nature of operational conditions and repair targets, discrete and highly variable quality domains of service-degraded materials, and demand for precise control and reliable assessment of repair quality in dynamically changing field scenarios. To address these challenges, this review examines the connotations, technical characteristics, and intrinsic difficulties associated with mobile additive repair and remanufacturing, with particular emphasis on the unique requirements of on-site operations. Drawing on recent developments and practical application cases, this article outlines the system composition, core modules, and functional architecture of mobile additive repair systems, including mobile deployment platforms, digital modeling and reconstruction tools, adaptive material-process subsystems, and multidimensional sensing and evaluation frameworks. By analyzing advances in design, materials, processes, and equipment, this review highlights the emergence of integrated mobile systems capable of operating in constrained spaces, interacting with heterogeneous surface states, and maintaining deposition stability under fluctuating environmental conditions. This study further analyses the main research directions and representative technical routes that shape the development of mobile additive repair technologies. These include environment-aware process planning strategies that consider geometric limitations, thermal boundary shifts, and accessibility constraints; material adaptation methodologies designed to accommodate substrate degradation, oxidation, or microstructural heterogeneity; and intelligent thermal and shielding control approaches that stabilize melt-pool behavior and improve layer quality in open or partially confined environments. Substantial progress has also been made in real-time monitoring and multiscale quality evaluation, where optical, infrared, acoustic, and laser-based sensing are increasingly combined to track dilution, defect initiation, interfacial bonding, and microstructure evolution during deposition. Based on these developments, this review identifies several key enabling technologies that enable reliable onsite additive repair of components located in special environments or within large-scale equipment that cannot be disassembled. Representative advances include portable and modular mobile repair platforms with enhanced environmental adaptability, digital twin-assisted repair workflow designs that link defect characterization with predictive simulation, and adaptive process control frameworks responsive to real-time disturbances. These innovations collectively form a new technical system that unifies design methodologies, material strategies, process optimization, equipment engineering, and closed-loop quality assurance. Across multiple industrial case studies, such integrated technical systems have demonstrated strong potential for delivering high-quality and efficient on-site repair of damaged components, ranging from turbine casings and reactor vessels to heavy machinery parts and aerospace structures. Commonly reported improvements include enhanced deposition uniformity in restricted or variable environments, stronger metallurgical bonding to service-degraded substrates, reduced incidence of common defects such as porosity or microcracks, and more predictable dimensional restoration with lower post-processing requirements. By consolidating these advances and mapping their interconnections, this review provides a coherent perspective on the evolution of mobile additive repair and remanufacturing technologies. Simultaneously, it identifies persistent scientific and engineering challenges—such as robust material-process matching for severely degraded substrates, more reliable prediction of repaired-component lifecycle performance, and further miniaturization and intelligent control of mobile platforms—that are likely to drive future research. Overall, this review summarizes the progress in establishing a new generation of mobile additive repair systems capable of providing high-quality, efficient, and reliable on-site restoration of critical components for the energy and chemical industries, heavy-duty equipment, and aerospace applications, and outlines the technological foundations required for continued advancement in this rapidly developing field.

Owing to their remarkable combination of high strength and superior corrosion resistance, titanium alloys have found extensive applications across a diverse range of industries, including aerospace and biomedicine. However, the difficult-to-machine nature of titanium alloys leads to poor surface quality and low material removal rates during conventional grinding. To overcome the limitations of conventional titanium alloy grinding processes, energy field-assisted machining has become a research hotspot. Ultrasonic-assisted grinding (UAG) couples high-frequency, low-amplitude vibrations with conventional grinding motions to create a periodic “contact-separation-contact” machining pattern between the workpiece and tool. This alters the material removal mechanism, significantly reduces grinding forces and temperatures, and improves the surface integrity of the workpiece. This paper first analyzes the coupled motion characteristics of ultrasonic vibrations, covering one-dimensional vibration modes such as axial, radial, and tangential modes, as well as two-dimensional and three-dimensional composite vibrations. These vibration modes can alter the trajectory of abrasive grains, shorten the effective contact arc, enhance chip removal, and promote material removal dominated by intermittent shearing. This paper summarizes numerical simulation and analytical modeling methods to explain the evolution of undeformed chip thickness, local plastic deformation, and thermo-mechanical interactions under ultrasonic assistance. Furthermore, it reviews various grinding force models developed for different vibration modes to elucidate how ultrasonic vibration affects deformation forces, plowing resistance, and frictional behavior. Experimental observations consistently demonstrate that ultrasonic-assisted grinding improves surface integrity and reduces tool wear. Previous research has shown that ultrasonic-assisted grinding can improve surface quality by 30%-50% and reduce tool wear by up to 40%. In addition, this paper discusses tool wear mechanisms such as abrasive microcracks, bond degradation, and adhesive wear, focusing on the role of ultrasonic vibration in maintaining cutting edge sharpness and enhancing self-sharpening. Surface morphology prediction and subsurface damage modeling further demonstrate that ultrasonic vibration can improve surface finish, suppress surface defects, and contribute to a more favorable residual stress state in titanium alloy parts. Besides single-field ultrasonic grinding, this paper also explores the rapid development of multi-energy-field ultrasonic grinding technology. Representative methods include ultrasonic-plasma oxidation, ultrasonic-electrochemical grinding, ultrasonic-micro-lubrication, ultrasonic-jet-assisted grinding, and ultrasonic-mechanical-chemical coupling. These hybrid methods utilize the synergistic effect of ultrasonic vibration and additional physical or chemical energy fields to enhance lubrication, reduce friction, promote material removal, and stabilize temperature rise during grinding. This hybrid approach also helps improve surface integrity and more effectively control the grinding interface. Combining multiple energy fields with ultrasonic vibration opens up new possibilities for further improving machining performance, especially for difficult-to-machine materials such as titanium alloys. This paper reviews the current research progress, theoretical framework, and mechanistic insights into ultrasonic-assisted grinding and multi-energy field grinding of titanium alloys. The research results provide valuable guidance for advancing efficient, high-precision, and low-damage grinding technologies.

The development of precision medicine requires efficient, stable, and multifunctional biomechanical interfaces. The abundant micro / nanostructures and functional mechanisms found in nature provide important inspiration for interface design; however, research on biomimetic bio-machine interfaces for precision medicine still lacks in-depth and systematic reviews. This paper systematically summarizes representative biomimetic strategies in interface design, with a particular focus on the principles and applications of antifouling, adhesion enhancement, directional liquid transport, and microneedle penetration structures in interface construction. It further discusses the advantages and limitations of advanced manufacturing technologies, such as laser processing and 3D printing, for the fabrication of multiscale biomimetic structures. Typical applications in precision medicine, including antifouling electrosurgical scalpels, adhesive patches, wearable microfluidic diagnostic sensors, and drug delivery systems, have demonstrated the remarkable benefits of biomimetic structures for improving interfacial adaptability, functional integration, and clinical applicability. Finally, this study explores the crucial role of emerging technologies, such as artificial intelligence, stimuli-responsive materials, and multi-material 3D printing, in driving the advancement of biomimetic bio-machine interfaces. Despite notable progress in biomimetic design and manufacturing, this field remains in its early stages and faces multiple challenges. For instance, natural multifunctional interfaces often exhibit highly complex material compositions and hierarchical multiscale features, making high-precision and consistent biomimetic reconstruction across the macro- and microscales highly dependent on breakthroughs in advanced manufacturing. Current biomimetic approaches are largely confined to isolated structural or material mimicry, with limited progress in the integrated codesign of structures, materials, and functions. Moreover, the intelligent responsiveness and multifunctional integration of interface systems remain underdeveloped, and achieving external-field-driven control (e.g., mechanical, thermal, acoustic, optical, electrical, and chemical) of interface properties is key to advancing system intelligence. Currently, most biomimetic functional interfaces remain in the proof-of-concept stage, and their long-term durability, biocompatibility, and safety require further validation for clinical and real-world applications. Biomechanical interfaces are expected to evolve beyond static designs to dynamic and adaptive systems. By integrating stimuli-responsive materials with flexible sensing networks, such interfaces can achieve real-time environmental perception and feedback regulation, enabling closed-loop intelligent medical devices, such as adaptive neural interfaces and dynamic drug-delivery microneedle arrays. Multiscale simulations (e.g., molecular dynamics and finite element analysis) can accurately predict the mechanical, electrical, and biological behaviors at the interface. Furthermore, coupling biomimetic design with artificial intelligence, particularly machine and deep learning, promises to establish data-driven platforms for interface design, enabling an integrated workflow from natural structure extraction and material selection to manufacturing pathway planning and performance prediction, thus advancing the paradigm from experience-driven to data-driven biomimetic design. Breakthroughs in key technologies such as multimaterial cooperative printing and scalable micro / nanoscale manufacturing are critical for establishing standardized and modular fabrication systems with improved reproducibility and consistency. Simultaneously, systematic frameworks for long-term biocompatibility assessment must be developed to ensure clinical safety and stability. In summary, this study proposes two guiding strategies—dynamic biomimetic design enabled by smart materials and intelligent interface design enabled by artificial intelligence—to fill a critical gap in the literature. These perspectives provide valuable insights for the future development of biomimetic interface design and manufacturing for precision medicine.

Copper-based powder metallurgy materials have emerged as attractive candidates for the brakes and clutches of high-speed trains, wind power yaw systems, mining trucks, and automobiles, owing to their good thermal conductivity, excellent wear resistance, and stable friction coefficient. However, the reliability and safety of equipment services have been drastically reduced by the increasingly harsh working environment, which is heavily influenced by the wear of copper-based powder metallurgy materials, functional degradation of parts, potential internal fatigue, and other problems caused by friction and vibration. Finally, friction-induced vibration and noise (FIVN) is triggered, a phenomenon that has puzzled researchers for several years. After years of sedimentation, although extensive research methods and theories related to FIVN have been developed, relevant research still needs to be pursued due to the arcane mechanism of its generation and the limited effectiveness of suppression methods. To address the severe challenges caused by friction and wear, innovations in surface texture technology, which play an increasingly important role in antifriction and antiwear applications, should be urgently developed to ensure the safe and reliable service of components. Considering that interface wear and debris rheology are the main culprits of the FIVN, a previous study found that a surface filled with gray iron HT300 could reduce interface wear, maintain the steady-state of the friction syetem, and effectively inhibit the generation of the FIVN. Therefore, to further explore the application scope of the surface filled with gray iron HT300 to reduce FIVN and fully reveal the mechanism of its interface tribological behavior is critical. In this study, the tribological performance of copper-based powder metallurgy materials is improved, and the design method for a surface filled with gray iron HT300 is further extended to a flat-to-flat contact configuration. First, grooves are machined on the surfaces of friction blocks made from copper-based powder metallurgy, and the grooved blocks are then filled with gray cast iron (HT300) to obtain three types of samples with different surface characteristics: original friction blocks, grooved friction blocks, and friction blocks filled with gray cast iron. Tribological tests are then performed on friction block samples with different surface characteristics and friction disc samples in a flat-to-flat contact configuration. By combining finite element simulations and numerical analyses, the synergistic effects of surface grooves and gray cast iron on the frictional behavior of copper-based powder metallurgy materials are thoroughly explored. Based on signal processing, micromorphology analysis, and theoretical analysis, the results show that copper-based powder metallurgy friction blocks with different surface characteristics exhibit varying wear properties and interface contact states, ultimately leading to different system responses. Compared with the original and grooved friction blocks, the friction blocks filled with gray cast iron significantly increased the contact area at the disc-block interface. They expanded the contact area, thereby alleviating stress concentration and effectively improving interface wear. Compared with the original and grooved friction blocks, the friction blocks filled with gray cast iron significantly enhance the disc-block interface contact degree and expand the contact area, thereby alleviating stress concentration and effectively improving the wear state at the interface. Additionally, the friction blocks filled with gray cast iron reduced the contact inclination angle at the disc-block interface, thus enhancing the system stability and effectively attenuating FIVN intensity. Therefore, an innovative surface design combining surface grooves with gray cast iron fillers meets the requirements for improving the tribological performance of copper-based powder metallurgy materials.

Thermal barrier coatings (TBCs) are a core technology for protecting hot-end components in the aerospace, aviation, and energy sectors and play a critical role in ensuring the safe and stable operation of these high-temperature systems. Since the concept of TBCs was proposed by NASA in the 1950s, this vital technology has gone through nearly 80 years of continuous development and evolution. During this period, several researchers worldwide devoted tremendous time, energy, and expertise to advancing its material systems, preparation processes, and overall performance, laying a solid foundation for its widespread application in key industries. With the rapid development of high-entropy alloys (HEAs) and high-entropy ceramics (HECs) in recent years, high-entropy materials engineering has emerged as a crucial and promising development direction for TBC material systems. This shift toward high entropy has created new avenues for overcoming the performance limitations of traditional TBC materials. However, systematic reviews that comprehensively discuss the structural evolution of coatings, their damage mechanisms, and innovation directions in the context of high-entropy engineering remain relatively scarce. This limitation makes providing effective theoretical and technical support for collaboration between research and practical applications in the TBC field difficult, hindering the translation of lab-based achievements into industrial practice. To address this gap, this paper systematically sorts out the changes in TBC demand driven by the continuous advancements in industrial production (such as energy equipment upgrades) and aerospace transportation (including aircraft and spacecraft development) from the perspective of the need for heat management and control. It shows that the operating conditions of hot-end components (such as gas turbine blades and aero-engine parts) are gradually breaking through the 1200 ℃ temperature resistance limit of traditional TBCs, making it urgent to research and develop new types of ultra-high-temperature TBCs that can withstand more extreme thermal environments. Subsequently, this paper explains the core service mechanism of these advanced TBCs, which achieve synergy through two key approaches: reducing the thermal conductivity through phonon scattering and improving the thermal emissivity. It also analyzes the key damage mechanisms that threaten TBC longevity, including the growth of thermally grown oxide (TGO) at the coating interface, coupled corrosion caused by multiple factors, erosion-induced spallation, and sintering densification. This elaborates the innovation directions of high-entropy TBCs: the focus is moving toward multi-layered, gradient, and complex designs of the coating surface; the bond coat alloy is becoming more diversified and highly entropic through doping and dissolving refractory elements (such as W, Mo, and Ta) into its structure (to enhance high-temperature stability); and the top ceramic layer is undergoing structural diversification and high-entropy engineering based on classic structures such as fluorite, pyrochlore, and perovskite (to balance thermal insulation and corrosion resistance). Additionally, this review examines the application prospects of multi-principal component coating design driven by computational materials science, represented by machine learning, first-principles calculations, and phase diagram calculations, as well as the use of refractory high-entropy coatings under extreme operating conditions (such as hypersonic flight and nuclear energy systems). Finally, this paper proposes that developing new coating preparation technologies and combining them with existing mature ones while focusing on the efficient and low-cost preparation of high-entropy TBCs is the key path to the wide application of high-entropy coatings in hot-end component protection. This paper is expected to provide clear guidance for the development of high-performance coatings and contribute to the collaborative advancement of coating research and applications under harsh working conditions.

With the progress of science and technology and improvements in living standards, the demand for electronic equipment has gradually changed from rigid and bulky to flexible and lightweight. Consequently, flexible electronic devices have become increasingly popular. Flexible wearable electronic devices are the development and innovation of flexible devices and have gained wide attention in the fields of healthcare, motion tracking, and environmental monitoring owing to their advantages such as light weight, portability, high integration, and good shape preservation. However, the long-term stability of wearable devices is challenged by their complex working environments, both from the external environment and secretions of human skin (rain, sweat, food residue, etc.). Inspired by the special biological surfaces in nature, the realization of special functions of materials or devices by regulating surface wettability has become a research hotspot. Surface wettability regulation has significant advantages for optimizing the design of solid-liquid interface interactions. Because liquid droplets can form spheres and quickly roll off, superhydrophobic surfaces have versatile functionalities such as waterproofing, self-cleaning, anti-corrosion, and antibacterial properties. This provides new opportunities to improve the performance and prolong the life of wearable electronic devices. For example, its excellent waterproof function can prevent external moisture intrusion, reduce the risk of short circuit and corrosion, and extend the service life, thus ensuring the stable operation of the device in wet environments. Self-cleaning and anti-contamination properties can keep the device clean, ensure accurate signal transmission and stable performance, eliminate the hassle of frequent cleaning, and improve the user experience. In addition, the superhydrophobic surface can reduce liquid accumulation, maintain device cleanliness, and improve comfort levels, laying the foundation for the wide application of superhydrophobic surfaces in flexible wearable electronics. This study focuses on the application of superhydrophobic surfaces in flexible wearable devices. First, the working principle of a superhydrophobic surface is introduced. The key to obtaining a superhydrophobic surface is to reduce the surface energy and increase the surface roughness. The preparation methods for superhydrophobic surfaces, including electrochemical deposition, electrospinning, chemical vapor deposition, and etching, are briefly described. This is followed by the application of superhydrophobic surfaces in flexible electronic devices. First, the application of superhydrophobic coatings in sensors is introduced. When a superhydrophobic coating is applied in the microchannel modification of a sweat sensor, the sweat transfer rate is significantly increased; thus, the sensing performance is improved. Superhydrophobic surfaces can provide sensors with moisture resistance, liquid resistance, self-cleaning, and weather resistance properties, significantly improving their service life. Second, the applications of superhydrophobic coatings in energy-conversion devices (such as nanogenerators) are described. Because the working principle of friction nanogenerators is to collect the electrostatic energy generated by contact charging, the waterproofing performance of the superhydrophobic coating helps friction nanogenerators collect more energy from the flowing water. Subsequently, the application of superhydrophobic coatings to energy-storage devices that provide energy support for flexible wearable electronic devices is introduced. Superhydrophobic coatings can significantly improve the safety and stability of energy storage devices. Although superhydrophobic coatings have certain applications, their service stability still faces challenges. Finally, it is pointed out that high mechanical stability, good environmental durability, and high light transmittance are challenges for the future development of superhydrophobic surfaces for wearable devices.

The accumulation of surface ice poses significant safety risks for operating engineering machinery, which can potentially lead to severe security incidents and economic losses. Presently, the pursuit of stable and effective anti-icing techniques for engineering applications is a significant scientific problem. Conventional anti-icing strategies, such as the utilization of chemical anti-icing agents, thermal anti-icing, and mechanical anti-icing, are characterized by low efficiency, high costs, and environmental unfriendliness. In response to these issues, researchers actively explored biological organisms with anti-icing properties in nature and proposed multiple strategies based on the principles of bionics, such as bio-inspired superhydrophobic anti-icing coatings, bio-inspired super-slippery anti-icing coatings, and bio-inspired antifreeze protein anti-icing coatings. Bio-inspired anti-icing coatings showed excellent anti-icing performance with low costs and low energy consumption, providing a foundation for the large-scale engineering application of anti-icing coatings. This review summarizes the latest research progress of bio-inspired anti-icing coatings for engineering applications, describing the anti-icing mechanisms and the preparation processes of anti-icing coatings, respectively. The three primary types of examined bionic coatings are superhydrophobic surfaces (SHS), slippery liquid-infused porous surfaces (SLIPS), and antifreeze protein (AFP) coatings. Superhydrophobic anti-icing coatings are inspired by the self-cleaning properties of the lotus leaf, which exhibits remarkable water-repellence because of its micro- and nanostructured surface. Superhydrophobic coatings effectively deter ice nucleation by minimizing water contact and reducing surface energy. However, it remains the challenges of improving their durability and resistance to environmental, particularly in industrial settings. Super-slippery anti-icing coatings modeled after the slippery surfaces of pitcher plants use a liquid lubricant trapped within a porous structure to create a non-stick surface. This design prevents ice from adhering to the coated surface, even under dynamic and fluctuating conditions. Super-slippery coatings demonstrate exceptional anti-icing performance; however, their dependence on specific lubricants raises concerns related to environmental compatibility and long-term maintenance. The antifreeze protein anti-icing coatings mimic the antifreeze proteins found in Antarctic fish, which inhibit ice crystal growth at the molecular level. Although antifreeze protein anti-icing coatings are promising in laboratory settings, their scalability and cost-efficiency for industrial applications remain areas requiring further exploration. This review encapsulates a variety of methodologies employed for evaluating the anti-icing efficacy of coatings, which are designed to replicate the stringent environmental conditions encountered in practical scenarios and for quantifying the resistance to ice formation and adhesion. Laboratory-based assessments, which include freeze-thaw cycle experiments, measurements of ice adhesion strength, and ice accretion delay tests, are delineated, thereby providing a comprehensive overview. Complementary to these, outdoor environmental experiments are discussed for contributing to validating the performance of the coatings under real-world circumstances. Further, this review addresses deficiencies inherent in the current assessment protocols and advocates for standardizing evaluation methods to guarantee the precise and consistent measurement of coating performance. This review provides an in-depth examination of the construction technology research pertaining to biomimetic anti-icing coatings and delineates the intricate process of preparing these coatings, encompassing the selection of raw materials, optimization of ingredient ratios, and coating methodologies. Further, this review presents a series of application tests that demonstrate the effectiveness of bionic anti-icing coatings in multiple sectors, such as aviation, construction, and transportation infrastructure. These tests affirm the high efficiency and reliability of the coatings in inhibiting ice formation, validating their utility in preventing hazards associated with icing in these critical domains. These studies advanced the process of bio-inspired anti-icing coating engineering applications and improved efficiency and stability in practice. Finally, based on the current research status, this review summarized the challenges and limitations of bio-inspired anti-icing coatings in the process of engineering applications, aiming to provide valuable references and insights for promoting the engineering applications of anti-icing coating.

As integrated circuit (IC) manufacturing technologies advance and feature sizes reduce to the nanoscale, the chemical mechanical polishing (CMP) process is imposed by increasingly stringent precision requirements. This is because slight variations in material removal can cause device failure. In particular, for metal CMP processes, achieving accurate real-time endpoint detection is essential for ensuring controllable material removal and maintaining high-quality process outcomes. Compared with other conventional endpoint detection methods based on frictional or optical principles, the eddy-current method has emerged as an optimal solution for detecting the copper film thickness variation during copper CMP process. As a non-destructive testing technique characterized by high sensitivity, rapid response, and high resistance to environmental interference, the eddy-current method provides a reliable approach for in-situ thickness measurements under complex polishing conditions. Focusing on the challenges in detecting nanoscale metal film thicknesses, a simulation model of the eddy-current sensor is established in this study by coupling an electromagnetic field and an electrical circuit. Based on the numerical simulations, the effects of fundamental parameters, including coil parameters (e.g., excitation frequency, wire diameter, inner radius, turns, and diameter-height ratio), and signal-conversion module parameters of the detection-circuit (e.g., parallel capacitance, voltage division resistance, and bridge arm resistance) on sensor performance are systematically revealed. Then the coil parameters are further optimized. And the optimal parameter values are determined specifically for CMP applications under a lift-off distance of 2 mm (corresponding to the typical thickness of a polishing pad). Subsequently, the detection circuit is optimized with emphasis on the signal-conversion module, including two fundamental circuit topologies, i.e., an LC resonant circuit and an AC bridge circuit, by determining their respective optimal values of key electrical parameters, meanwhile, the other modules, such as the signal-generation module and peak-detection module are well accomplished for a good measurement performance. Furthermore, the influences of environmental parameters, particularly lift-off distance and temperature, on the output characteristics of the detection coil is revealed. To quantify the influence of lift-off distance variations, a quantitative thickness-error assessment model is developed that correlates the film thickness, measurement error, and lift-off distance. Additionally, a decoupling calculation method is proposed by establishing a mathematical relationship correlating the output voltage, film thickness, and temperature, thereby diminishing the influence of temperature variations on the thickness measurement. Finally, a nanoscale metal film thickness eddy-current detection system is developed. The system comprises an eddy-current sensor, precision displacement modules, and a vacuum-based wafer-holding module featuring a microporous ceramic vacuum chuck. The probe is mounted on a non-metallic cantilever beam fixed to the linear-displacement module to minimize lift-off distance variations, whereas the vacuum chuck ensures stable wafer holding on the rotary-displacement module. The coordinated motion of the linear- and rotary-displacement modules enables precise thickness measurements at multiple locations on the wafer surface. According to the experimental testing at a lift-off distance of 2 mm, the self-developed detection system demonstrates a sensitivity of 1.38 mV/nm and a linearity coefficient of 0.986 9 within a measurement range of approximately 1.5 μm. And a comprehensive evaluation of the measurement performance, based on the output-voltage fluctuation and sensitivity, shows that the detection system can achieve a nanoscale precision measurement of copper film thickness over a wide range. This study facilitates advancements in high-precision in-situ detection technology for high-quality polishing processes.

Overlaying and thermal spraying, core technologies in modern material surface engineering, have been indispensable in industrial manufacturing and equipment restoration since the 20th century. However, accelerated industrialization has imposed increasingly stringent demands on material surface properties—such as wear resistance, corrosion resistance, and high-temperature resistance—in sectors including machinery, energy infrastructure, and aerospace, exposing the limitations of conventional overlaying and thermal spraying techniques in addressing material protection and functional enhancement under complex operational conditions. By reviewing the integration and evolution of overlaying technology within surface engineering, this article highlights key advancements and applications in both fields over the past decade while outlining their developmental trajectories. Technological advancements in materials, processes, and equipment in the field of overlaying technology have been systematically summarized using various methods. These include arc surfacing techniques, such as shielded metal arc surfacing, submerged arc surfacing, gas metal arc surfacing, self-shielded arc surfacing, tungsten inert gas surfacing, and cold metal transfer surfacing; high-energy beam surfacing approaches like plasma arc surfacing and laser cladding; and specialized surfacing technologies such as oxy-acetylene surfacing. Although traditional high-chromium iron-based wear-resistant flux-cored wires remain mature for engineering applications, recent efforts have prioritized cost-effective high-boron iron-based alternatives. Nickel-based, cobalt-based, and metal-ceramic composites continue to dominate material research, with high-entropy alloys (HEAs) emerging as focal points in laser cladding. Process studies emphasize the optimization of parameters such as current, speed, and powder / wire feeding rates, along with auxiliary techniques such as ultrasound, magnetic fields, and heat treatment, to enhance the layer microstructure and performance. Advancements in overlaying equipment have primarily focused on enhancing the efficiency, quality, and precision of the surfacing processes. Additionally, the article provides a detailed overview of the practical implementation of surfacing technology across industries such as petrochemicals, cement and mining, metallurgical and power generation, agricultural and forestry machinery, aerospace, medical devices, and nuclear energy. Current research in the field of thermal spraying focuses on technologies such as cold spraying, plasma spray-physical vapor deposition, suspension plasma spraying, and detonation spraying, each with distinct priorities. Cold spraying focuses on theoretical research, development of high-performance equipment, standardization of raw materials, and optimization of coating performance. Plasma spray physical vapor deposition concentrates on optimizing process parameters, such as powder feeding rate, plasma gas composition, and spraying distance, to regulate coating growth patterns and microstructures with the aim of achieving high-performance coatings. Suspension plasma spraying explores the fabrication of high-performance thermal barrier oxide ceramic coatings. The development of high-frequency focused-energy detonation spraying technology has resulted in an order-of-magnitude improvement in efficiency and significantly enhanced coating quality. Additionally, the applications of thermal spray coatings, including wear resistance, thermal barriers, corrosion resistance, and functional coatings, are summarized. Regarding the future development trends of overlaying and thermal spraying technologies, it points out that high-end equipment overlaying materials, composite overlaying technology, as well as the automation, intelligence, and flexibility of overlaying processes will be the future development directions for overlaying technology. For thermal spraying technology, the development of new materials, novel processes, and improvements in the coating density remain key advancement priorities. These findings provide theoretical support and directional guidance for the technological evolution and industrial applications of overlaying and thermal spraying technologies.

Diamond-like carbon films that exhibit exceptional properties including high hardness, low friction factor, wear resistance, corrosion resistance, and good biocompatibility, making them a valuable tool for coating tools, automotive parts, biomedicine, and other fields. Physical vapor deposition (PVD) is one of the most common techniques used to deposit diamond-like carbon films. However, the characteristics of carbon films produced by different PVD techniques exhibit notable disparities that constrain their applicability in industrial contexts. To address this issues, this study summarizes the research progress in the preparation of diamond-like carbon films using PVD technologies and the current improved technologies that have been developed in response to the poor comprehensive mechanical properties of carbon films caused by large droplets during the deposition of DLC films using CAE technology. These include imposed pulse cathode arc evaporation, filtered cathodic vacuum arc, pulsed laser-induced cathodic vacuum arc, and thermoionic vacuum arc technologies. To address the challenges posed by HiPIMS technology in an Ar atmosphere, such as the inability to effectively ionize the graphite target and the resulting low hardness and density, novel technologies have been developed to enhance the performance of carbon films by modulating the sputtering gas and optimization of the discharge process of the power supply. These techniques include short-pulse HiPIMS, deep oscillation magnetron sputtering, mixed-mode HiPIMS, and bipolar HiPIMS. Using short-pulse HiPIMS, deep oscillation magnetron sputtering, and mixed-mode HiPIMS technologies has been demonstrated to enhance the ionization rate of graphite targets. Furthermore, bipolar HiPIMS improves the efficiency of carbon ion transport. A comparative analysis of the properties, advantages, and disadvantages of DLC films deposited using these techniques was conducted to evaluate their application potential. In addition, research progress on the adhesion, tribological, and multi-factor coupling properties of diamond-like carbon films is summarized. In the following discussion, the efficacy of elemental doping and multilayer composite structures for enhancing the performance of DLC films in diverse service environments is examined. Patterning DLC films with different segmented structures is a novel technique for enhancing the tribological properties of carbon films. The current state of DLC films in engineering applications is introduced, and the structural and performance requirements of DLC films in different application scenarios are summarized. Finally, the new PVD technologies are compared for the above application scenarios. Tool coating represents a prevalent application domain for DLC films. However, the wear of carbon films at elevated temperatures and low bond strength represent pressing challenges to be addressed in the large-scale production and application of DLC tool coatings. In contrast to conventional nitride and carbide ceramic films, DLC films enhance the corrosion resistance and conductivity of metal bipolar plates in fuel cells, indicating their promising application in fuel cell bipolar plate coatings. The preparation of diamond-like carbon films using PVD technology is a promising future path, and the emerging HiPIMS and its improved technology can provide a cost-effective coating solution that is well suited for industrial applications. Nevertheless, there remains a significant disparity between our high-performance DLC film deposition technology and equipment, and advanced international standards. In addition, exploring coupled damage and detection methods in various complex environments is a promising avenue for future research. This study presents a comprehensive review of the development status and trends in diamond-like carbon films prepared using PVD technology aiming to establish a foundation for developing cost-effective, high-performance DLC technologies better suited for industrial applications.

45CrNiMoVA high-strength steel is widely used in manufacturing the torsion shafts of armored vehicles owing to its high strength, high toughness, high plasticity, and excellent fatigue resistance. However, it was suffered from stress corrosion cracking in corrosive environments; to address this issue, protective coatings are typically applied to the substrate surface to extend the service life of the components. In this study, an iron-based coating was prepared on the surface of 45CrNiMoVA high-strength steel using (by) laser cladding technology, and the coating surface was strengthened using ultrasonic impact treatment (UIT). Currently, research on the changes in microstructure and mechanical properties of high-hardness coatings after ultrasonic impact is limited, with most studies focusing on coatings with hardness below 600 HV_0.1. The objective of this study was to investigate the strengthening effect of UIT on high-hardness coatings and explore the combined effect of laser cladding and UIT on the strengthening of high-strength steel components. A laser confocal microscope was used to determine the surface roughness values of the coatings before and after UIT. The phase compositions and cross-sectional microstructures of the coatings before and after UIT were observed by X-ray diffraction analysis and optical microscopy. The residual stress values of the coating before and after UIT were measured using an X-ray stress analyzer. The microhardness of both types of coatings was tested using a Vickers microhardness tester. Electrochemical corrosion tests were conducted on the substrate and the coating (both before and after UIT) in 3.5wt.% NaCl solution using a three-electrode system electrochemical workstation. The results is showed that the surface roughness of the iron-based coating reached 12.76 μm. After UIT, the peak-shifting and valley-filling effects induced by surface plastic flow made the surface smoother and reduced the surface roughness to 2.05 μm (83.93% reduction). The iron-based coating primarily consisted of equiaxed grains, dendrites, and columnar grains. After UIT, an impact layer of thickness ~15 μm was formed on the surface, with grain fragmentation, compression, and elongation observed in the surface layer, along with plastic flow along the processing direction. The grain density increased; however, no significant grain changes were observed in the subsurface or interior of the coating. After UIT, the coating surface transformed from the Fe-Cr phase to a mixture of Fe-Cr and Cr0.19Fe0.7Ni0.11 phases. The (110) diffraction peak shifted to the right and its width increased, indicating grain refinement and the presence of residual compressive stress. The stress state of the coating after UIT changed from residual tensile stress (97 MPa) to residual compressive stress (-200 MPa). The maximum residual compressive stress was observed at the surface, and the residual compressive stress gradually decreased along the depth of the coating. Hardness testing was revealed that the maximum hardness at the top increased from 772 HV_0.1 to 889 HV_0.1. Because of the greater hardness of the coating, its resistance to plastic deformation was strong. After UIT, the coating hardness significantly increased within a 100-μm distance from the surface, with the improvement effect gradually weakening along the depth. The substrate exhibited poor corrosion resistance, the coating potential shifted positively by 130 mV after UIT, and the self-corrosion current density decreased by 56.48%. The reduced surface roughness, grain refinement, work hardening, and the presence of residual compressive stress on the UIT-treated coating hindered the infiltration of corrosive ions, making the coating more resistant to corrosion in the 3.5wt.% NaCl solution. Therefore, the process adopted in this study helped overcome the difficulties associated with surface strengthening of traditional hard coatings and provided a reference for future research and application of laser cladding and UIT for high-hardness coatings.

Additive remanufacturing technology can be applied to directly form titanium alloy components. However, the mechanical properties of the as - deposited remanufactured components are either inferior to or only comparable to those of cast parts. This technology struggles to meet the emergency demand for direct deposition and immediate use in additive remanufacturing. A method of using pulsed plasma arc additive remanufacturing is studied to repair the surface of titanium alloys. To investigate the influence of different pulse frequencies on the microstructure and properties of deposited layers with different thicknesses, deposition experiments were conducted using pulse frequencies ranging from 1 to 100 Hz at intervals of 10 Hz. Single - pass single - layer and single - pass multi - layer specimens were deposited, and their microstructures and mechanical properties were analyzed. The influence of different thicknesses of pulsed plasma arc surface deposits on the microstructure and mechanical properties of remanufactured titanium alloy components was studied. The research results indicate that the surface roughness and hardness of the titanium alloy deposited by pulsed plasma arc are related to the cooling rate during deposition. A higher microhardness corresponds to a greater cooling rate, and the change rule of larger surface roughness is consistent with a higher cooling rate during deposition and solidification. Additionally, the distribution of hardness values at the bottom and top in the deposition direction is that the microhardness of the martensite structure > the grain boundary > the Widmanstätten structure with basket - weave characteristics. It can be inferred that the disturbing effect of the arc and droplet transfer enhances the cooling gradient during the solidification process, thereby affecting the surface roughness and microhardness. The microstructure of titanium alloy parts fabricated through pulsed plasma arc deposition is characterized by a composite structure composed of acicular martensite and Widmanstätten structure. During the deposition process, the perturbation effect of pulse frequency on droplet transfer plays a crucial role in promoting grain refinement. This is clearly demonstrated by the equiaxed grain structure observed in the first deposited layer. Pulsed plasma arc deposition was employed to fabricate multi - layer components. Subsequently, electron backscatter diffraction (EBSD) was utilized for phase analysis. The research results show that in the multi-deposited layer structure, the proportion of the α phase is 99.9%, and the proportion of grain size ≤ 15 μm reaches 86%. It can be seen that under the multi - layer thermal cycle, the decomposition of the metastable martensite structure in the deposition layer promotes the precipitation of secondary nano - α phase, further improving the interface strength of the mechanical properties of the titanium alloy repaired by plasma arc additive remanufacturing. Comparing the specimens with the substrate interface and the deposited layers, the former has higher tensile properties than the latter, and the mechanical properties under the 70Hz process reach the forging level, which is the best. Moreover, when comparing titanium alloy parts deposited at different pulse frequencies, the tensile strength of the as - deposited parts from high to low is 70 Hz > 50 Hz > 90 Hz. The reason is that the thermal cycle input of the 70Hz pulsed plasma is most conducive to maximizing the disturbing effect on the droplet transfer, resulting in the largest cooling gradient in the deposition layer of the pulsed plasma arc - deposited titanium alloy. Furthermore, due to the promotion of secondary nano-α phase precipitation by multiple thermal cycles, the mechanical properties of the components processed under this regime have been further enhanced. The research on the pulse plasma arc additive remanufacturing method for titanium alloys can effectively improve the mechanical properties of the as-deposited state of components during online repair. This provides a theoretical and technical foundation for the repair of advanced equipment.

High-end equipment, such as aero-engines, gas turbines, and advanced CNC machine tools, plays a critical role in national defense and industrial sectors. These systems are characterized by their high technological complexity, long development cycles, diverse structural and functional requirements, and stringent service conditions. The development and iterative upgrading of such equipment are crucial for maintaining national strategic capabilities and require extensive interdisciplinary, inter-industry, and inter-regional collaboration. As a core aspect of full life-cycle management, remanufacturing high-end equipment offers significant economic and strategic benefits. It effectively reduces costs, extends service life, and facilitates generational equipment upgrades, capabilities essential for keeping pace with technological advancements and maintaining competitive advantage across industries. In this study, aero-engines are used as a representative case to analyze the value chain activities involved in high-end equipment remanufacturing. The research identifies several key challenges, including complex coupling between design and manufacturing interfaces, insufficient information sharing, and a disconnect between knowledge accumulated during remanufacturing and its integration into the development of new models. These issues hinder the effective functioning of the remanufacturing value chain and limit its potential in terms of cost reduction, technological advancement, and sustainability. To address these challenges, this study proposes a comprehensive value-chain framework for high-end equipment remanufacturing, organized across four dimensions: “value chain entities, value activities, full life cycle of development, key technology support”. This framework offers a systematic approach to organizing and optimizing collaboration among stakeholders, including design institutes, manufacturers, suppliers, users, research institutions, and remanufacturing enterprises, across different stages of the equipment life cycle, spanning from design and manufacturing to maintenance and remanufacturing. The framework is supported by four key technology pillars: data intelligence, process intelligence, platform intelligence, and agile intelligent systems engineering. Data intelligence ensures continuous data flow and accurate feedback throughout the equipment life cycle. Constructing a multimodal closed-loop data system enables the creation of a high-fidelity digital twin, thereby facilitating real-time decision-making and information sharing. Process intelligence enhances this process by enabling the reconstruction and dynamic optimization of business processes through cross-stage modeling and self-learning algorithms. This allows for the continuous improvement of processes throughout the life cycle of the equipment, moving beyond simple repair and towards a more comprehensive system optimization. Platform intelligence, supported by the Industrial Internet, optimizes multi-stakeholder collaboration by enabling role allocation, dynamic incentives, and seamless resource and data sharing. It provides a common platform for all participants to interact and share resources and data, ensuring efficient coordination and collaboration among manufacturers, suppliers, users, and research institutions. Agile intelligent systems engineering ensures that the system can dynamically adapt to evolving conditions through interdisciplinary simulation and iterative optimization, enabling rapid responses to unforeseen challenges and technological demands. Implementing this remanufacturing value chain framework reduces total life-cycle costs, extends equipment service life, and enables the restoration of equipment to better than new condition. It also facilitates generational upgrades of high-end equipment, thereby enhancing resilience and self-controllability across the industrial chain. The integration of artificial intelligence with high-end equipment remanufacturing is expected to drive the development of advanced, adaptive, and sustainable manufacturing systems. Despite these benefits, several challenges remain, including limitations in organizational incentive mechanisms, barriers to data interconnection and sharing, and insufficient model interoperability across different stages and sectors. Future research should focus on developing demonstrative cross-domain collaboration models, standardizing data-sharing protocols, and improving organizational structures to promote high-quality development in the high-end equipment remanufacturing industry. Addressing these challenges will help fully realize the potential of the proposed value chain framework and advance global manufacturing technology.

The surface treatment of titanium alloy fasteners is one of the main methods for preventing “sticking” and “biting” during assembly and disassembly. It is necessary to investigate the frictional and wear characteristics of titanium alloy samples after different surface treatments, reveal their wear mechanism, and improve the tribological properties of their surfaces. In addition, it is crucial to reduce the factor of friction, improve wear resistance, and design highly reliable titanium-alloy fasteners. In this study, a manual-spraying method was developed for applying aluminum and MoS₂ treatments to samples after pulse-anodizing treatment (PA) to leave the surface untreated. Four surface states of TC4 titanium alloy (no treatment [LT], pulsed-anodizing treatment, pulsed-anodizing and aluminum-coating composite treatment [PA-Al], and pulsed-anodizing and molybdenum disulfide composite treatment [PA-MoS₂]) were investigated, and a 10-mm-diameter TC4 titanium alloy ball was used as the grinding object. The frictional and wear characteristics of TC4 titanium alloys in different surface states were determined under 1 and 4 N loads using a UMT-3 friction- and wear-testing machine. The wear morphologies of the wear marks and wear spots on the surface of the ball were characterized using an ultradepth field microscope, a three-dimensional white-light interferometer, a focused-ion beam scanning electron microscope, and an accompanying energy dispersive spectrometer. The wear volume and wear rate were calculated to determine the differences in wear resistance, examine the wearing mechanism, and analyze the differences in wear resistance under different test loads. Under test loads of 1 and 4 N, the wear marks of the LT sample are the widest and deepest, the factor of friction fluctuates significantly with an average value of approximately 0.53, and the main element is Ti. In addition, Al, V, O, and C are observed, and the wear mechanisms are mainly plowing and adhesive wear. The wear morphology of the PA-Al sample shows discontinuous spalling, the factor of friction fluctuates slightly, and the stability value is approximately 0.58. More Al and O elements are observed on the surface of the sample, and alumina is formed on the surface, indicating high hardness and brittleness; thus, the sample is prone to brittleness. Spalling pits are formed on the surface, effective solid lubrication films rarely form on the surface of the sample, the run-together period is extended, and the coefficient of friction is high. The wear mechanisms of the PA-Al sample are spalling and abrasive wear. The wear marks on the PA-MoS₂ samples are shallow and continuous, the factor of friction fluctuates slightly, the stability value is approximately 0.25, and the main elements are S and Mo, with low amounts of C, O, and Si. Relatively dense TiO₂ coatings are generated on the surface of the PA sample, indicating high hardness, good antifriction, and high bonding strength with the substrate; therefore, the wear resistance of the material improves significantly. The wear mark of the PA sample is the narrowest, and the factor of friction is approximately 0.16. The wear rates under the low and high loads are 5.8×10^-4 and 5.7×10^-4 mm³ / (N·m), respectively, indicating that the sample exhibits the best wear resistance. Its main elements are Ti and O, with low amounts of Al, C, P, and Mo. The wear rates of the samples are ranked from high to low as follows: PA-Al>PA-MoS₂>LT>PA. This demonstrates that the pulse-anodized-treated TC4 titanium alloy exhibits the best antifriction wear resistance, and the interlayer shearing force of MoS₂ on the surface of the PA-MoS₂ sample is small. This improves the lubrication characteristics; however, because it has a rough surface microstructure, the frictional resistance is the second best, and the wear resistance further decreases under a load of 4 N. This proves the significant advantages of PA in improving the antifriction wear resistance of TC4 titanium alloys and provides a strong technical support and experimental basis for the surface treatment of titanium alloy fasteners.

Ultrahigh-temperature boride-silicon carbide-based ceramics are highly promising thermal-protection materials for the thermal components of high-speed aircraft owing to their high melting point, excellent thermal conductivity, and superior ablation resistance. This review systematically summarizes recent studies pertaining to the oxidation and ablation resistance of ultrahigh-temperature boride-silicon carbide coating materials. It focuses on the enhancement mechanisms achieved by incorporating various modification phases, including refractory metal silicides, rare-earth oxides, and other additives, such as borides, carbides, oxides, and metallic / non-metallic elements. The incorporation of SiC as a second phase significantly enhances the oxidation and ablation resistance of ZrB₂ and HfB₂ ceramics. The formation of a SiO₂-rich glassy phase effectively prevents oxygen diffusion. However, in high-temperature environments exceeding 1 800  ℃, SiC undergoes active oxidation. This results in the formation of a porous SiC depletion layer, which severely degrades the oxidation and ablation resistance of the ultrahigh-temperature boride-silicon carbide coating material. To suppress this phenomenon, researchers have introduced various modification phases to improve the oxidation and ablation resistance by regulating the structure of the oxide scale, increasing the viscosity of the glass phase, and inhibiting oxygen diffusion. Refractory metal silicides (e.g., MoSi₂, WSi₂, TaSi₂, ZrSi₂, and HfSi₂) enhance the oxidation and ablation resistance by providing an additional Si source, thereby resulting in complex glass phases and promoting densification. MoSi₂ and WSi₂ form volatile MoO₃ and WO₃ during oxidation, thus reducing the surface temperature; however, their excessive addition increases porosity. The modifying effect of TaSi₂ exhibits significant temperature dependence. At an intermediate temperature (approximately 1 600 ℃), TaSi₂ effectively inhibits the formation of a SiC depletion layer. The oxidation product Ta₂O₅ dissolves in the glass phase or reacts with ZrO₂ / HfO₂, thus resulting in a denser oxide scale. At ultrahigh temperatures (>1 900 ℃), Ta-containing oxidation products have relatively low melting points and tend to form low-melting eutectic phases, thus reducing the stability of the oxide scale. ZrSi₂ and HfSi₂ enhance the stability of the oxide scale by forming (Zr,Hf)O₂ solid solutions, which inhibit oxygen diffusion. Rare-earth compounds (e.g., La₂O₃, Y₂O₃, Sm₂O₃, and Yb₂O₃) improve the oxidation and ablation resistance of coatings by refining grains, stabilizing ZrO₂ / HfO₂ structures, increasing the viscosity of the glass phase, and enhancing material emissivity. Rare-earth cations dissolve in the ZrO₂ / HfO₂ lattice, thus suppressing volume changes during phase transition. Additionally, La₂O₃ and LaB₆ facilitate the formation of a stable La-Si-O glass layer. Y₂O₃ can react with SiO₂ to form silicate nanocrystals, such as Y₂Si₂O₇ or Y₂SiO₅, which disperse in the glass phase and increase the viscosity. Sm₂O₃ significantly enhances the emissivity of the coatings, strengthens thermal radiation, and reduces the surface temperature. Yb₂O₃ effectively increases the viscosity of the glass phase owing to its small ionic radius and high field strength. However, excessive addition of rare-earth elements may weaken the glass-phase structure and increase the oxygen-vacancy concentration, thus weakening the oxidation and ablation resistance of the coatings. Other modification phases, such as borides (TaB and WB), carbides (ZrC, WC, and TaC), oxides (MgO and Al₂O₃), and metallic / non-metallic elements (W, Si, and C), can enhance oxidation and ablation resistance through different mechanisms. ZrC can occupy the pores by forming ZrO₂, which inhibits the formation of the SiC depletion layer. The oxidation of WC forms WO₃, which promotes the liquid-phase sintering of ZrO₂. Graphene modification significantly improves the thermal conductivity and reduces the surface temperature of the coatings. The introduction of elemental Si directly increases the Si content and suppresses the active oxidation of SiC. Currently, the thermal-protection performance of ultrahigh-temperature boride-silicon carbide coating materials is limited to 2 300 ℃. Future studies should focus on the following aspects: first, the dynamic evolution mechanisms and quantitative evaluation methods for oxide scales should be investigated comprehensively. Second, data-driven approaches can be used to screen for modification phases and predict material performance. Finally, new active-passive synergistic thermal-protection mechanisms must be identified.

Remanufacturing has emerged as a critical strategy for resource recycling and promoting sustainable industrial production. In this context, microcrack detection in remanufactured blanks constitutes an essential aspect of quality control throughout the remanufacturing process, directly influencing the integrity, reliability, and service life of recycled components. This paper presents a systematic review of recent advances in active infrared thermography (IRT) as a nondestructive testing method for microcrack detection in remanufactured blanks. The fundamental principles of active IRT are introduced, emphasizing its capability for rapid, full-field, and noncontact inspection. The paper also provides a detailed analysis of the three predominant excitation mechanisms, namely eddy current, ultrasonic, and laser-based approaches, highlighting their respective physical principles, advantages, and limitations in the context of remanufacturing. Eddy current thermography is particularly effective for conductive materials, enabling high-speed scanning and surface crack detection; ultrasonic thermography excels in detecting subsurface defects through vibrothermal effects; and laser-based thermography offers superior resolution for precise characterization of fine surface cracks. In addition to excitation mechanisms, this review thoroughly examines advanced signal-processing techniques that are essential for enhancing defect visibility and interpretation. These include conventional image processing methods (e.g., Fourier transform and pulsed-phase thermography), data decomposition and dimensionality reduction approaches (such as principal component analysis and tensor decomposition), and emerging deep-learning-enabled intelligent recognition algorithms that improve automated flaw identification and classification. The performance of these techniques is discussed in terms of signal-to-noise ratio enhancement, defect contrast improvement, and computational efficiency. A comprehensive summary of applications and performance evaluations demonstrates the effectiveness of active IRT across various case studies involving remanufactured components. This paper further addresses persistent challenges that limit wider industrial adoption, including limited detection accuracy for microscale cracks, poor adaptability to complex and curved surfaces, susceptibility to environmental interference, and difficulties in achieving reliable quantitative characterization of crack dimensions and morphology. Several future research directions are proposed to address these challenges. Emphasis is placed on the development of intelligent signal processing frameworks that integrate real-time deep learning, multisensor data fusion, and adaptive noise suppression. The design of high-efficiency excitation sources aimed at improving the thermal contrast while reducing energy consumption is also discussed. Other promising research avenues include multiphysics coupling methodologies that combine thermal, ultrasonic, and electromagnetic stimulations for enhanced defect detectability, as well as digital-twin integration for virtual-physical system interoperability and predictive maintenance. Finally, the development of portable, cost-effective, and robust inspection systems tailored for in-situ remanufacturing environments is highlighted as a critical step toward field deployment. The results of this review demonstrate that active IRT offers considerable advantages and holds promise for accurate and efficient microcrack assessment in remanufactured components. With continued innovation and system integration, active infrared thermography is expected to provide robust technical support for quality enhancement and sustainable transformation in the remanufacturing industry.

Current-carrying friction pairs are critical components in high-end applications such as motors, rail transit, and aerospace systems. These components serve dual functions: transmitting electrical energy and sustaining mechanical friction. Consequently, their reliability is essential to overall system performance. One key factor affecting their performance is current polarity, which significantly affects overheating, arcing, and surface degradation. This study investigates the causes and consequences of polarity effects through field investigations of carbon brush-collector ring systems in hydroelectric generators, supported by failure case analyses and theoretical frameworks. It was found that current polarity primarily governs the oxidation and transfer of surface films at the contact interface of current-carrying friction pairs, thereby regulating the physical and chemical properties of these films. In particular, polarity influences the growth of oxide layers and electrochemical reactions within the water film at the interface—a phenomenon broadly classified as anodic oxidation (AO). Material transfer from the anodic to the cathodic friction pair is attributed not only to arc-induced material migration but also to anodic oxidation mechanisms. For instance, in the carbon brush-steel slip ring system, the negative slip ring (acting as the anode) displayed more intense surface oxidation, forming a film primarily composed of metal oxides. Conversely, the positive slip ring (acting as the cathode) exhibited suppressed oxidation, with a surface film dominated by carbon-transfer deposits. These findings clearly demonstrate the strong influence of current polarity on surface film formation. Further analysis revealed a significant asymmetry in contact resistance under different polarities. This variation is attributed to the distinct surface film compositions and their associated conduction mechanisms. Additionally, current polarity impacts contact temperature, which in turn affects the thermal stability of the friction pair. By integrating case studies, the research systematically examines the interrelationships among contact resistance, localized temperature rise, and arc generation—placing particular emphasis on the severe damage caused by surface arcing. The results indicate that arc erosion characteristics are closely tied to current polarity. Specifically, anodic current-carrying components are more susceptible to thermal erosion, including melting and evaporation—an effect collectively referred to as “anodic evaporation”. This study provides a comprehensive analysis of the fundamental mechanisms, contributing factors, and final manifestations of polarity effects. It explores how polarity governs surface film formation, how these films affect contact resistance and temperature, and how these factors collectively affect arc probability and surface degradation. The interplay among surface films, temperature rise, and arc formation is examined in detail. Focusing on the carbon brush-steel slip ring system, the study highlights differences in wear and surface damage under opposing polarities, explaining the severe erosion of negative slip rings and abnormal wear on negative carbon brushes. Based on these findings, a mitigation strategy is proposed: reducing temperature through optimized cooling structures to interrupt the positive feedback loop between heat buildup and arc formation. Finally, the study summarizes the intrinsic mechanisms underlying polarity effects in current-carrying friction pairs, using the carbon brush-steel slip ring system as a representative case. It introduces the principle of “anodic protection” to provide both theoretical support and practical guidance for the optimal design, long-term reliability, and maintenance of such systems. Ultimately, this study aims to deepen the understanding of polarity effects on surface film formation, interface degradation, and system performance, while offering new insights for future research in this field.

Titanium alloy blades and engine cases experience local temperature increases under extreme conditions, such as impact and friction, causing titanium alloy parts to catch fire. The NiCrFeAl / BN thermal insulation flame-retardant coating can effectively prevent the occurrence of titanium fires. Preparing thermal insulation and flame-retardant coatings on the surface of titanium alloys is crucial to prevent titanium fires. The thermal insulation effect and crack propagation of the NiCrFeAl / BN flame-retardant coating during thermal shock cycles have not been thoroughly studied. The temperature and stress distribution of the coating system with NiCrFeAl / BN as the thermal insulation layer, YSZ as the flame-retardant layer, and NiCoCrAlY as the bonding layer during the thermal shock cycles were simulated using the finite element method, and the development process of cracks during the thermal shock cycle was studied. A thermal-mechanical coupled two-dimensional finite element model of the coating system was established to study the temperature and stress changes of the coating and substrate during the thermal cycles. The crack initiation and propagation model was built by combining the extended finite element method (XFEM) and cohesive element. Using this combined model, the initiation and propagation behavior of the surface crack, internal crack, and interface crack in the coating system was simulated. The conventional finite element method must reconstruct the mesh when solving crack propagation problems, which limits its application. The XFEM uses extended shape functions to describe discontinuous displacement fields, which have significant advantages in simulating crack propagation without updating the mesh model. XFEM allows cracks to propagate freely under stress, rather than being forced to propagate along grid boundaries, and can penetrate the grid during propagation. Therefore, the Abaqus software XFEM was used to study the initiation and propagation of vertical cracks. The four materials of the substrate and coatings are divided into four cross-sectional zones. Each layer, from bottom to top, is as follows: a titanium alloy TC11 substrate with a thickness of 10 mm, a NiCoCrAlY metal bonding layer with a thickness of 0.15 mm, a YSZ ceramic thermal insulation layer with a thickness of 0.2 mm, and a NiCrFeAl / BN sealing surface layer with a thickness of 1.2 mm. In the alternating cold and hot environment, thermal stress is generated inside the coating. When the thermal stress accumulates to a certain degree, the coating may crack. Based on the actual thermal cycling experiment process of the coating sample, a transient analysis of the thermal coupling of the sample model is performed to simulate the cyclic process of the coating from heating to the insulation stage and then to water cooling. The temperature is raised from 20 ℃ to 750 ℃ within 15 s, maintained at 750 ℃ for 300 s, and finally cooled from 750 ℃ to 20 ℃ by water cooling within 30 s, which is considered as one cycle. A small crack is pre-set on the surface of the coating. During the first heating and insulation stage, the crack in the coating does not propagate. However, during the cooling stage, stress concentrates at the crack tip. When the stress reaches the failure criterion, the crack begins to increase along the direction of maximum stress. In the subsequent thermal cycle, the vertical crack continues to propagate, and if the coating is subjected to sufficient thermal stress, the vertical crack may penetrate the coating. With the increase in thermal shock cycles, the initial microcracks gradually spread to the interior of the coating and gradually approach a state of stability. When subjected to 400 cycles of water cooling and heating, no interface cracks appear between the coating and the substrate, and the maximum stress occurs at the interface between the coating and the substrate. After 543 thermal cycles, interface cracks are observed, starting from the vicinity of the NiCoCrAlY bonding layer and extending horizontally. At this point, stress is redistributed, and the cracked coating is nearly free from the influence of stress. The substrate is subjected to significant stress, and the evolution of interface cracks ultimately led to coating peeling and failure.

Nano minimal quantity lubrication (NMQL) has become a research hotspot in the field of green manufacturing, which significantly improves the cooling, lubrication, and friction reduction properties of bio-lubricants. However, the stability of nanofluids, multi-field coupling mechanism and industrial applicability are still the key challenges limiting its wide application. This paper systematically reviews the latest research progress in NMQL, focusing on the preparation methods, physicochemical properties, and tribological behavior of nanofluids, along with their performance enhancement mechanisms under the coupling of electric, cryogenic, and magnetic fields. It is demonstrated that nanoparticles (e.g., MoS₂, graphene, Al₂O₃) contribute to reduced grinding temperatures and improved workpiece surface quality owing to their high thermal conductivity, extreme pressure anti-wear properties. Hybrid nanofluids further optimize the load-bearing capacity and thermal conductivity of the lubricating film through synergistic mechanisms. In addition, the introduction of multi-physical fields, such as magnetic field induced directional alignment of nanoparticles and regulation of fluid viscosity, electric and ultrasonic fields for enhanced droplet wettability, and cryogenic fields for suppressing grinding thermal damage provides new pathways for the precise regulation of NMQL performance. This paper also discusses challenges related to the sustainability, cost-effectiveness, and scalable application of NMQL, and proposes future research directions, including optimizing the long-term stability of nanofluids, developing intelligent adaptive lubrication systems, and elucidating multi-field coupling mechanisms. This review aims to provide theoretical support and technical reference for the engineering application of NMQL in efficient and green machining. Currently, most reviews on NMQL focus primarily on the physicochemical properties and mechanisms of nanofluids. There remains a lack of systematic analysis of the coupling mechanisms involving different physicochemical properties such as viscosity, surface tension, nanoparticle size, and shape of various nanojets under multi-field conditions, which hinders further development and application of NMQL technology. Current research in nanofluid minimal quantity lubrication is evolved from single-particle systems toward hybrid formulations and multi-field regulation strategies. In terms of nanoparticle selection, materials such as molybdenum disulfide, graphene, and aluminum oxide are demonstrated to be effective in reducing grinding temperatures and improving workpiece surface quality due to their high thermal conductivity and extreme-pressure anti-wear properties. These nanoparticles are widely recognized for their ability to form protective tribofilms on friction surfaces, thereby enhancing lubrication efficiency and wear resistance. Hybrid nanofluids, through synergistic interactions between different particle types, are employed to further enhance the load-bearing capacity and thermal conductivity of the lubricating film. The combination of different nanoparticles is often designed to leverage their complementary physical and chemical characteristics for optimal performance. Regarding performance modulation, multi-field intervention is shown to offer distinct advantages: magnetic fields are utilized to enable directional alignment of nanoparticles and viscosity regulation, electric and ultrasonic fields are applied to improve droplet wettability, while cryogenic fields are used to help mitigate grinding thermal damage. These approaches are regarded as new strategies for precisely controlling nanofluid performance. Nevertheless, key challenges are still required to be addressed, including ensuring long-term nanofluid stability, developing intelligent adaptive lubrication systems, and clarifying multi-field coupling mechanisms. These aspects are discussed in this review to provide theoretical guidance and technical support for the engineering application of NMQL in efficient and sustainable machining processes.

Ceramic matrix composites, characterized by high hardness, high brittleness, and poor material consistency, are widely used in the manufacture of key components, such as radomes in the aerospace industry. During machining, material properties lead to high cutting temperatures and significant vibrations, which can easily cause tool wear and undermine the processing quality and production efficiency of the products. Current research has primarily focused on metal material processing, and there has been relatively little research on tool wear prediction in composite material processing, particularly in ceramic matrix composite material machining. This study focuses on special ceramic matrix composites, collecting and analyzing tool cutting vibration signals during machining, and establishing models to predict tool wear. First, a ceramic matrix composite cutting tool wear prediction framework based on the cutting vibration was designed. Under this framework, cutting vibration data processing and tool wear prediction are at the core and receive data from machine tools and smart tool holders. Time-frequency domain feature extraction, correlation analysis, and feature extraction processing of the cutting vibration data were performed. Furthermore, a gated recurrent neural network was used to train a tool wear prediction transfer function model, thereby achieving tool wear prediction and analysis. Based on the prediction and analysis results, control of the tool change and machine start-stop was implemented. Second, through Spearman’s correlation coefficient analysis of the time-frequency domain feature data, the time-domain average and minimum values showed no significant correlation with tool wear, whereas the center of gravity frequency showed a significant negative correlation with tool wear, indicating that as tool wear intensifies, the low-frequency vibration induced by spindle rotation becomes more severe, and the remaining data showed a significant correlation with tool wear, with significance levels above 99%. It can be concluded that there is a significant correlation between the cutting vibration and tool wear data. Utilizing the time-frequency domain characteristics of the cutting vibration data can effectively guide tool wear prediction and cutting parameter optimization. Ceramic matrix composite samples were then used as test objects for the research. Orthogonal experiments were conducted to elucidate the influence of various factors on the cutting force and vibration, determine the main influencing factors, and select the optimal parameter combination. Through orthogonal experiments and range analysis, the optimal parameter combination for balancing tool life and processing vibration was determined: cutting width of 1.0 mm, cutting depth of 1.0 mm, spindle speed of 1 600 r / min, and feed rate of 2 400 mm / min. Single-factor experiments were conducted with the optimal cutting parameter combination to provide data support for the subsequent tool wear prediction analysis. Subsequently, a prediction model for tool wear was established based on a gated recurrent unit network. The model was trained using cutting data, and a real-time prediction evaluation of tool wear was conducted based on the measured operating condition data and mean squared error (MSE). Finally, the optimal validation MSE of the model was 68.528 2, and the prediction error conformed to a normal distribution with a mean of 0. The regression value R approached 1, indicating the effectiveness of the prediction model. Another set of tools was used to conduct cutting experiments with the same process parameters, obtaining 83 sets of time-frequency domain feature data. These 83 datasets were used as validation data for input into the tool wear prediction model, outputting the predicted tool wear values. The curves of the predicted and actual values were plotted, and the predicted curve aligned well with the actual curve. The prediction error range was -39.652 4 to 66.974 6 μm, indicating the model’s effectiveness under real data. In summary, the proposed method provides a theoretical and technical foundation for improving the processing quality and reliability of ceramic matrix composite products.

Titanium alloys have excellent physical and mechanical properties and are widely used in many industries; however, their poor machinability not only reduces the machining efficiency but also the surface integrity, thus significantly decreasing the fatigue life. Based on the electroplastic effect and sliding electric-contact principles, electric pulse-assisted cutting can effectively reduce the workpiece strength and improve the tribological behavior between tool-chip / workpiece interfaces during cutting, thus significantly improving the machinability of metal materials to enhance the surface integrity of the workpiece. However, research on the fatigue performance of titanium alloys based on electric pulse-assisted cutting is insufficient. Considering the high-fatigue requirement of machined titanium-alloy components, this study performed electric pulse-assisted cutting on titanium alloys to investigate their surface integrity after they were subjected to electric pulse-assisted turning. A surface roughness tester, Vickers microhardness tester, scanning electron microscope, and electron backscattered diffraction system were used to characterize the workpiece surface roughness, surface morphology, surface work hardening, surface microstructure, and surface thickness of the plastic-deformation layer. Workpiece surface defects, including bonding, tearing, and tool marks, were significantly eliminated; the Vickers hardness reduced with increasing pulse-current parameters; and severe plastic deformation occurred on the workpiece surface along with significant grain refinement. Compared with the results of conventional dry turning, the surface roughness and work hardening of TC4 titanium alloy subjected to electric pulse-assisted turning decreased by 35.7% and 4.7%, respectively; the thickness of the strengthening layer increased by 2.14 times; and more α phases were changed to the β phase in the workpiece strengthening layer. The fatigue performance of the TC4 titanium alloy subjected to electric pulse-assisted turning was investigated using a fatigue-testing machine and scanning electron microscope. The fatigue life of the workpiece machined via electric pulse-assisted turning reached 528.18 × 10⁴ cycles, whereas that achieved via conventional turning was only 35.35 × 10⁴ cycles, thus signifying an improvement by 14.9 times. The fracture morphology of the fatigue specimen was observed using a scanning electron microscope. Fatigue cracks primarily originated from the machined workpiece surface owing to surface defects and stress concentration, whereas they were transferred from the surface to the subsurface in the machined workpiece, which resulted from the low surface roughness, smooth surface morphology, small surface work hardening, and large thickness of the plastic-deformation layer. In particular, the electroplastic effect accelerated dynamic recrystallization and reduced the dislocation density, thereby better coordinating the strain of the plastic-deformation layer on the machined-workpiece surface. Numerous fatigue striations were observed microscopically in the crack-propagation region. The fatigue striations were primarily formed by repeated sharpening and passivation of the crack tip under cyclic compressive and tensile stresses, and the direction of the fatigue striations was perpendicular to the crack-propagation direction. Each fatigue striation was equivalent to one cycle of load or strain, and the fatigue-striation width was closely related to factor such as the workpiece surface roughness, work-hardening rate, and microstructure. The fine grains, small dislocation density, and large plastic-deformation depth might have reduced the fatigue-striation width, thus hindering fatigue-crack propagation. The fatigue-striation width resulting from electric pulse-assisted turning was less than that yielded by the conventional turning. The fatigue-striation width at 50 ℃-0.4 A / mm²-500 Hz was 0.194 μm, which was 78.7% lower than that yielded by the conventional turning.

TC4 titanium alloys are extensively used in marine engineering owing to their exceptional strength, light weight, and excellent corrosion resistance. However, the high-salinity, high-humidity corrosion environment and long-term mechanical wear significantly accelerate the tribocorrosion of TC4. This process leads to the destruction and shortened lives of marine engineering components. Therefore, there is an urgent need to develop an effective technology to enhance the anti-corrosion and wear resistance of marine equipment in harsh marine environments. The aim of this study is to enhance the tribocorrosion properties of a TC4 titanium alloy by developing a thermal treatment-anodized composite carbon fiber coating (TAD-CF). This method combines anodization, spraying, and coating techniques to form a strong protective layer that effectively reduces wear and corrosion. Specifically, the TC4 titanium alloy was anodized in a glycol electrolyte at 60 V for 20 min to obtain a nanoparticle porous titanium dioxide (TiO₂) layer and then heat-treated for 3 h to improve its structural integrity and protective properties. Subsequently, the substrate surface was coated with a uniform ceramic adhesive layer and then with carbon fiber, which firmly adhered after curing. The integration of carbon fibers into the coating is expected to provide additional mechanical strength and improve the wear resistance of the coating. Furthermore, comprehensive analyses of the surface morphology and elemental distribution of TAD-CF were conducted using scanning electron microscopy (SEM) and confirmed the successful formation and uniform distribution of the coating. These results indicate the successful formation of the nanoporous TiO₂ coating under the specified anodic oxidation conditions. To evaluate the performance of the TAD-CF coating, a multifunctional fretting corrosion tester was employed to assess its corrosion resistance and tribological properties in air and simulated marine environments. Electrochemical corrosion tests demonstrated that the self-corrosion potential of TAD increased significantly and that the corrosion current density decreased significantly, with a measured value of 65.2 nA / cm². Concurrently, the polarization resistance increased to 0.743 GΩ, indicating that the corrosion resistance of TAD is greatly enhanced, compared with that of TC4. Under static corrosion conditions, the corrosion current density of the TAD-CF samples decreased to 8.57 nA / cm², whereas the polarization resistance increased to 9.08 GΩ, further confirming its excellent corrosion protection. Friction and wear tests revealed that the average coefficient factor for the TAD-CF samples was significantly lower than those of the untreated TC4 samples, which proves that the TAD-CF coating significantly improves the tribological properties of TC4 in a marine environment. In conclusion, TAD-CF exhibited remarkable corrosion and abrasion resistance, thereby indicating its broad application prospects in marine corrosion protection. Furthermore, this study not only demonstrates the potential of TAD-CF coatings to improve the durability of marine engineering components but also provides important insights into the development of advanced protective coatings that can address a variety of challenges. However, it must be recognized that sliding friction can cause damage to the coating structures of TAD and TAD-CF samples, which potentially weakens their long-term protective effect. Future research should focus on resolving the influence of sliding friction on the integrity of the coating to optimize its protective properties.

Ultra-low-pressure plasma spraying (ULPPS) is a critical enabling technology for developing advanced aero-engines that can achieve high-quality coating with customized design across scales and efficient non-line-of-sight deposition, and it is widely recognized as the ideal fabrication method for high-performance thermal barrier coatings (TBCs) in advanced aero-engines. The coatings produced exhibit high deposition efficiency, dense structure, controllable microstructure, high thermal strain tolerance, and strong adhesion to the substrate. China’s entry into the field of technologies such as PS-PVD has been relatively recent, with research focused on spraying processes, and equipment development heavily constrained by foreign technologies. A novel ULPPS system has been domestically developed, addressing the urgent need for import substitution in advanced thermal barrier coatings (TBCs) manufacturing. This innovation specifically targets the critical requirements of China’s aerospace sector for high-performance turbine blade protection with enhanced deposition efficiency. Research has been conducted to solve core technical issues of traditional and existing PS-PVD spraying power supplies, such as low effective output power, large output current ripple, and poor dynamic adaptability and stability of the arc. A two-stage structure of “rectification + chopping voltage reduction” has been adopted based on the high-frequency chopping main circuit topology scheme and multiphase interleaved parallel technology to achieve low ripple, high power, high stability, and high dynamic response characteristics of voltage and current output control. Based on the active modulation technology scheme of the power supply, a fully digital control strategy for high-frequency chopping power supply has been developed using methods such as high-frequency sampling digitization of input signals, control strategy discretization digitization, control output digitization, and communication digitization to enhance the response speed, dynamic applicability, and output stability of the power supply from the bottom-level control logic. A steady-state and dynamic mathematical model of the high-frequency chopping power supply has been established, and a low ripple intelligent control algorithm based on the single neural network has been developed for reducing the output current ripple and enhancing the stability of the plasma arc. The laws of arc changes throughout the spraying process and corresponding changes in equivalent load impedance have been analyzed. A mathematical model and mapping relationship of the spraying state and equivalent impedance change patterns have been established, thereby developing a dynamic adaptation strategy for the plasma arc that predicts the spraying state and equivalent impedance in real-time, which enhances the stability of the spraying process. The performance of the spraying power supply has been verified and optimized, and a related vacuum system and auxiliary systems have been developed for achieving PS-PVD functionality. A diversified intelligent collaboration and highly integrated automated monitoring and control system for the entire spraying process has been developed for addressing the complex control issues involving multiple variables, parameters, and systems in PS-PVD equipment and spraying processes. The online monitoring of the entire process of spraying processing quality is achieved by collecting, storing, and analyzing process parameters and working state information such as voltage, current, gas flow, and powder feeding speed during the spraying process, and data support is provided for the quality traceability of spraying product production. A graphical human machine interaction interface based on PC terminals was developed to improve the level of visualization and system integration, reducing operational complexity. Yttria-stabilized zirconia (YSZ) ceramic materials, which have been validated for the feasibility and applicability of spraying processes, have been used for sample spraying tests to process efficiency. The tests proved that the vacuum system can achieve closed-loop pressure control in a wide pressure range of 3-80 kPa and 50-1 000 Pa, with an ultimate vacuum degree less than 10 Pa. The power supply rated current can reach 3 000 A, with a spraying power exceeding 120 kW, which is adaptable to different working conditions of 100 V / 1 200 A and 250 V / 480 A. The system can perform low-pressure plasma spraying (3-80 kPa) and ULPPS (50-1 000 Pa) within a wide pressure range from 50 Pa to 80 kPa and achieve plasma physical vapor deposition functions. After the verification of the spraying process, tests of low-pressure spraying operation for 1 h and ULPPS operation for 2 h have been completed, proving that the equipment is safe, reliable, and stable, meeting user specifications, and put to use. The domestic equipment reached the technical indicators of new products from foreign monopolistic enterprises, solving the domestic substitution problem of PS-PVD equipment, ensuring the autonomy, controllability, and security of China’s related industry chains and supply chains. Thus, it is of great significance for China to establish a strategic backup of key national defense technologies.