Macroscopic solid superlubricity (with a friction factor on the order of 0.001) in diamond-like carbon (DLC) films has attracted widespread attention in the academic community in recent years due to its significant potential in the domain of solid lubrication under extreme working conditions, such as vacuum, high contact pressures, and wide temperature ranges. However, the deposition methods and bonding structures of DLC films are diverse, and specific intrinsic compositions and structures, as well as external working conditions, are required to achieve macroscopic superlubricity in DLC films. Thus, this review discusses current research progress on the structural regulation of DLC films, diverse superlubricity behaviors in DLC films, key influencing factors, and their corresponding mechanisms. First, the current structural classification, deposition methods, and recent research on the bonding structure regulation principles of DLC films for solid superlubricity were summarized. An effective strategy for synthesizing DLC films with superior solid superlubricity is to adjust the composition and energy of deposition ions to balance the surface chemisorption and subsurface implantation growth modes, leading to an optimized combination of mechanical stiffness and hydrogen content of DLC films. Subsequently, the research trajectory on superlubricity in DLC films was reviewed, and the latest developments categorized by mechanisms were introduced. The combinations of DLC and environmental media available for superlubricity are diverse, and include hydrogenated amorphous carbon (a-C:H) in dry inert atmospheres, doped a-C:H in humid air or water-based liquids, hydrogen-free DLC in oil-based liquids, and DLC films in nanomaterial-containing environments. Furthermore, the influencing mechanisms of the internal elemental composition and bonding structure of DLC films, as well as external working conditions such as the environment, contact pressure, and temperature on the superlubricity behavior of DLC are discussed in detail. Sufficient hydrogen content is necessary for DLC films to achieve superlubricity in dry inert atmospheres, such as N₂, Ar, and vacuum. The self-lubrication properties of DLC films can be significantly affected by O₂ and H₂O molecules in humid air, due to intensified interfacial chemical bonding, disordered water adsorption layers, enhanced hydrogen bonding forces, and van der Waals forces caused by tribo-chemically generated highly polar groups. Elemental doping with Si, S, and Ti can effectively suppress the moisture sensitivity of DLC films via their participation in the structural evolution of sliding interfaces. Sufficiently high contact pressure is also necessary for solid superlubricity in DLC films, which is mainly due to the self-lubrication effect of contact-pressure-triggered locally short-range-ordered layered-like sp² nanoclustering structures. Overly high contact pressure deteriorates the superlubricity state of DLC films through hydrogen detachment and microstructural destruction of the counterpart surfaces. Ultralow temperature (<-100 ℃) can increase the friction factor of DLC films due to the suppression of thermal activation and structural evolution of sliding interfaces. On the contrary, high temperature (>300 ℃) facilitates the failure of a-C:H films due to excessively promoted hydrogen detachment, graphitization, and oxidation in air. Additionally, the mechanism behind the solid superlubricity of DLC is discussed from the perspective of interfacial bonding structural evolution. The tribo-generated transfer films on smooth-stiff surfaces, hydrogen passivation of surface dangling bonds, and generation of short-range ordered graphite-like nanostructures are key factors for the establishment of superlubricity in DLC films, which simultaneously suppress the three main contributors of macroscopic friction force: interfacial abrasion, shearing, and adhesion effect. Finally, the unresolved issues and related research trends in the underlying science and engineering applications of DLC are summarized. The connection of deposition parameters with growth theories, the nanostructure of superlubricious sliding surfaces and their evolutionary pathway, the environment and working condition sensitivity, and the influencing mechanisms of multi-element, multilayer, micro-nano textured, and media-synergistic lubrication strategies require further research. These findings can provide technical support for the design and application of superlubricious DLC films for dry-sliding friction pairs under extreme engineering conditions.

In the current era of industrial manufacturing and materials science, continuously enhancing material properties to meet the growing application challenges is an ongoing task. Metal materials play a key role in many industries because of their excellent mechanical properties and wide range of applications. Nevertheless, these metals are often subjected to wear, corrosion, and fatigue damage during practical use, which severely reduces their service life and reliability. Therefore, studying effective surface modification technologies that can improve the surface integrity and properties of metals has become a core issue in materials science research. Ultrasonic surface rolling processing (USRP) is an advanced material surface modification technology that combines ultrasonic energy and high-frequency mechanical vibrations to nano-strengthen the metal surface. This technology can cause plastic deformation on the surface of the material and significantly improve its surface integrity and mechanical properties. USRP can generate residual compressive stress on the surface of a material, effectively preventing the formation and expansion of cracks and reducing the permeability of the corrosive medium. In addition, this technology can form a nanostructured layer with a gradient grain size and orientation, thereby significantly enhancing the surface hardness and wear resistance of the material. This review summarizes the research progress in USRP in the fields of steel, aluminum alloy, titanium alloy, magnesium alloy, nickel alloy, and high-entropy alloy. It is demonstrated that these materials have achieved remarkable results in surface nano-strengthening and microstructural and performance improvement following USRP treatment. USRP technology can not only refine the grain size, reduce the surface roughness, and improve the surface hardness, but also convert the residual tensile stress into residual compressive stress to obtain a deeper nano-gradient hardened layer and residual compressive stress-affected area. This compensates for the low production efficiency of traditional mechanical processing methods as well as the mismatch between the working environment and performance requirements of high-performance materials. Finally, future application prospects and development directions of USRP are discussed. It is expected that focus will be placed on the refinement of theoretical models and the diversification of working methods. This research will further explore the theory of contact mechanics and surface integrity to develop a prediction model that can optimize the process parameters. In addition, USRP technology will be adapted to deal with complex parts and improve the efficiency and performance through multi-field coupling and process integration. The expansion of the application range will include composite materials and high-tech fields, including deep-sea exploration and aerospace satellites.

The NiCrAlY＋(ZrO₂＋Y₂O₃) thermal barrier coating was prepared on the surface of refractory steel (1Cr18Ni9Ti) by plasma spraying technique. SEM observation showed that the bonding between thermal barrier coating and substrate was good. The surface hardness of 1Cr18Ni9Ti was improved, the microhardness of coating surface was about 673HV after the thermal barrier test at 850℃. The test results showed that the thermal barrier properties were improved remarkably. The phases and microstructure of the thermal barrier coating were determined by SEM.

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.

The advancement of technology in today’s society has led to higher performance demands for machining tools, and tool coatings have become a primary method for enhancing tool performance. To fully exploit the inherent properties of coated tools, post-treatment is essential. This paper aims to summarize the commonly used post-treatment methods for coated tools, which include sandblasting, polishing, heat treatment, energy field / beam treatments, and others. Sandblasting is the most widely used post-treatment method for coatings. The effectiveness of the post-blasting treatment is determined by three key parameters: grit, pressure, and time. Careful analysis of these variables shows that sandblasting can efficiently remove larger particles from the coated surface while enhancing its overall quality, provided that appropriate conditions are met. Another traditional surface-polishing technique is mechanical polishing, which uses flexible polishing tools, abrasive particles, and other media to modify the workpiece surface. This process effectively removes burrs and larger particles, resulting in a significant reduction in surface roughness. Both sandblasting and mechanical polishing contribute to achieving finer surface finishes on coated materials. Heat treatment is another widely adopted method for both tool treatment and post-treatment of coated tools. During the deposition of tool coatings, the substrate temperature remains low, causing rapid cooling of the coating material. Due to differences in the thermal expansion coefficients between the grains within the coating, thermal stress arises, which can accelerate tool failure. Heat treatment plays a crucial role in relieving some of the strain energy within the coating, adjusting the state of the coating-substrate interface, enhancing microstructural properties, and ultimately improving the performance of coated tools. A recent advancement in post-treatment methods for coatings is the use of energy fields or beam treatments. Energy field treatments include various techniques such as magnetic fields, electron beams, ion beams, lasers, and other similar methods. Compared to mechanical and heat treatments, energy field treatments offer greater controllability and a broader range of action. Research indicates that applying different energy field parameters during post-treatment can enhance not only the surface integrity of the coating but also the bonding strength between the coating and the underlying substrate. This technique involves localized heating of specific areas on the coating using high-density energy, leading to surface remelting and changes in roughness. Additionally, rapid heating and the ensuing energy waves generate thermal stress, which strengthens the coating, substrate, and bonding interfaces. As a result, this process significantly enhances the bonding strength between the coating and the substrate, thereby improving the overall performance of the coating.Although progress has been made in the post-treatment of coated tools, these methods are not yet widely applied in practice, with the exception of polishing. By analyzing the advantages and disadvantages of each post-treatment method, this study clarifies their respective scopes of application, addresses the fragmentation of research in this field, improves understanding of post-treatment methods for tool coatings, and provides a useful reference for the future development of post-treatment technology for coated tools.

The precise modulation of adhesion properties on superhydrophobic surfaces is recognized as a critical pathway for advancing functional surface engineering, with extensive applications in mechanical, aerospace, and biomedical engineering. In this context, the adhesion behavior of water droplets interacting with engineered surfaces is systematically summarized, with particular emphasis on the influence of surface microstructures, chemical compositions, and external stimulation on the adhesion of superhydrophobic surfaces. By drawing inspiration from natural superhydrophobic biological systems, such as lotus leaves, rose petals, and butterfly wings, which exhibit tailored adhesion properties, the fundamental mechanisms underlying solid-liquid adhesion behavior are elucidated, and advanced strategies for its modulation are developed. Currently, advanced characterization techniques have been standardized to quantify adhesion forces and validate modulatory mechanisms between solid and liquid. Contact angle (CA) measuring instrument systems are utilized to measure the minimum angle at which a water droplet begins to slide on an inclined surface, with a high-speed camera capturing dynamic water droplet behaviors during sliding. Adhesion measuring instruments coupled with a high-speed camera enable the nanoscale mapping of adhesion forces under controlled water droplet volume and speed of motion of the carrier table conditions. In addition, computational fluid dynamics (CFD) simulations are employed to model the solid-liquid interactions, providing insights into the mechanisms affecting adhesion on the superhydrophobic surfaces. The adhesion behavior between solid and liquid is primarily governed by the surface microstructures and chemical composition. The surface microstructures with different shapes are fabricated through laser irradiation, template replication, or lithography technologies. For instance, microstructures with various geometries are fabricated through precise adjustments of laser processing parameters, such as energy density, scanning pitch, and scanning speed, to enhance air entrapment and minimize solid-liquid contact areas. Concurrently, densely arranged micropillar arrays or porous networks are designed to change the solid-liquid contact state, enabling controlled water droplet pinning or directional transport. In addition, the transformation between low-adhesion superhydrophobic surfaces and high-adhesion superhydrophobic surfaces is further modulated by changing the chemical composition of the surface. Self-assembled monolayers (SAMs) terminated with fluorinated groups or silane derivatives are uniformly applied to reduce the surface energy, integrating stimuli-responsive polymers, such as pH-sensitive polyelectrolytes or thermoresponsive poly(N-isopropylacrylamide) (PNIPAM), to enable dynamic adhesion transitions. A synergistic combination of structural patterning and chemical modification is demonstrated to generate adhesion patterns for programmable water droplet manipulation, as exemplified by spatially selective plasma etching followed by region-specific silanization. Furthermore, external stimulation, including light irradiation, magnetic fields, and temperature variations, is employed to achieve reversible and real-time modulation of adhesion on the superhydrophobic surfaces. Photoresponsive surfaces embedded with azobenzene derivatives or titanium dioxide (TiO₂) nanoparticles are engineered to undergo light-triggered adhesion transforms. Under ultraviolet (UV) illumination, azobenzene-modified surfaces exhibit cis-trans isomerization, which alters the adhesion properties, whereas TiO₂-coated surfaces leverage photocatalytic decomposition to remove hydrophobic layers, enabling dynamic switching between low and high adhesion states. Similarly, thermoresponsive coatings are designed to undergo hydrophilic and hydrophobic transitions above specific critical temperatures, thereby facilitating temperature-dependent adhesion control. Magnetic field-responsive superhydrophobic surfaces are constructed by embedding ferrofluids or paramagnetic particles into superhydrophobic matrices, which allows noncontact water droplet manipulation through external magnetic gradients. The method of modulating surface adhesion through electric fields has been developed to modulate the solid-liquid contact state via applied voltages, achieving precise solid-liquid adhesion transformation. Practical implementation of tunable adhesion superhydrophobic surfaces is demonstrated across diverse domains. In microfluidic systems, programmable adhesion gradients have been engineered to guide water droplet routing for high-throughput bioassays, whereas ice-phobic superhydrophobic surfaces with tunable adhesion have been developed to mitigate ice accretion on aerospace components. Self-cleaning technologies exploit low-adhesion superhydrophobic surfaces to achieve contaminant removal by sliding water droplets, whereas high-adhesion superhydrophobic surfaces are tailored for targeted drug delivery, thereby enabling the non-destructive release of site-specific therapeutic agents. This review emphasizes the importance of research on the mechanisms and methodologies of adhesion modulation on superhydrophobic surfaces. By addressing the existing challenges and integrating emerging technologies, the development of tunable adhesion superhydrophobic surfaces exhibits excellent prospects for advancing developments across various scientific and engineering disciplines.

As one of the most popular advanced functional ceramics, silicon carbide (SiC) has many excellent characteristics, such as low coefficient of expansion, high thermal conductivity, and radiation resistance. In recent years, brake materials prepared using SiC have been widely used in braking systems such as cars and aircraft. However, owing to its high hardness, SiC is difficult to process using conventional methods. At the same time, the intrinsic hydrophilic characteristics of SiC make its surface prone to fouling and icing. This not only shortens the service life of the material and reduces its utilization efficiency and braking performance but also poses potential safety hazards. These issues limit the broader application of SiC in various fields. Therefore, improving the surface properties of SiC materials through composite processing has become the key to broadening their applications. In this study, a laser-chemical composite processing method was developed to fabricate superhydrophobic SiC surface. First, regular hexagonal and smooth quadrilateral periodic micro-nanostructures were constructed on the surface of SiC materials by nanosecond laser ablation. Subsequently, superhydrophobic surfaces were successfully prepared by further silane-ethanol mixed solution modification and heat treatment. The surface morphology of superhydrophobic SiC materials was characterized by laser confocal microscopy and scanning electron microscopy, and the surface chemical composition was analyzed using energy-dispersive spectrometry and X-ray photoelectron spectroscopy. Furthermore, the influence of the surface structure and surface chemistry on wettability was clarified. Experimental results demonstrated that the surface roughness of the SiC material treated by the composite process increased significantly, forming a regular groove structure. As the laser scanning rate decreased, the depth of the surface grooves gradually increased. This reduction in air retention led to a decrease in the contact area between the water droplets and material surface, thereby affecting the surface wettability. Within a certain range, with the decreases in the laser scanning rate and scanning pitch, the surface wettability was improved, resulting in a composite Wenzel-Cassie state. The maximum contact angle of the material surface was 156.4°, and the minimum rolling angle was 1.3°. The O content on the surface of the untreated SiC material was 2.75%, and the functional groups of C-C and C-Si were the main components. After laser processing, the O content rapidly increased to 28.83%, resulting in a large number of C=O and Si-O-Si functional groups. After laser-chemical composite processing treatment, O accounted for 17.04% of the chemical components on the surface. Simultaneously, a large number of hydrophilic groups, such as C=O and C-O, were decomposed and broken. In addition, the distribution density of Si was notably different. Hydrophilic groups, such as C=O and C-O, were decomposed and fractured, resulting in the formation of a large number of hydrophobic functional groups, such as Si-O-Si. The surface of the superhydrophobic SiC material exhibited several enhanced functional properties. First, its surface could delay icing for over 250 s. Second, its corrosion resistance was significantly improved. Finally, it exhibited excellent self-cleaning performance. Moreover, compared with the smooth quadrilateral structure, the surface roughness of the regular hexagonal micro-nano structure was increased by more than 3 μm. The surface had a more obvious fence structure, and the ability of the grinding wheel to resist cyclic friction was increased by four times. The icing time was delayed by an additional 40 s, and it was completely frozen into ice droplets at 280 s. Therefore, the application requirements of the brake disc were satisfied. As demonstrated by the performance characterization experiments, the surface of the superhydrophobic SiC material exhibited excellent self-cleaning capability, corrosion resistance, icing resistance, and wear resistance. These properties indicate that the laser-chemical composite processing method can be used to prepare superhydrophobic SiC surfaces with stable performance. Ultimately, this process provides a theoretical and practical approach for the preparation of SiC material surfaces with desirable properties, thereby satisfying the application requirements of SiC brake pads. This study utilized fluorine-free chemical reagents, which are known for their low environmental impact and reduced costs. This approach is expected to further establish a foundation for the laser functionalization of SiC materials. It also has the potential to expand the scientific research and engineering applications of SiC materials in various fields.

Recent developments over these years on the surface treatment for aluminum and its alloys by micro-arc oxidation (MAO) were reviewed. The effects of the substrates and the electric parameters such as current density, voltage and frequency on the growth, composition, structure and properties of the MAO coatings on aluminum alloys were emphasized. The common electrolyte systems used in the MAO treatment for aluminum alloys were analyzed. The characteristics of kinetics and the growth mechanism of the MAO coatings on aluminum alloys were described. It was pointed out that the control of electric parameters and adjustment of composition and concentration of electrolyte would be the study emphases of MAO technique for aluminum alloys in the future.

Based on the background of the anticipated Industry 4.0 era, the promotion of “Made in China 2025” and the strategy of maritime power, traditional marine anti-fouling coating materials have gradually withdrawn from the historical stage and been replaced by new biomimetic and intelligent marine anti-fouling coating materials. However, a comprehensive and systematic review of new biomimetic and intelligent marine anti-fouling coating materials is still lacking. Therefore, this study reviews the research progress of biomimetic anti-fouling coating materials constructed by biomimetic anti-fouling strategies, such as micro-nanostructure surface, release of green anti-fouling agent, super-slippery surface, dynamic surface, and self-healing. Meanwhile, the research progress of intelligent anti-fouling coating materials formed by intelligent anti-fouling strategies, such as pH, temperature, and light response control, is reviewed. The research progress of synergistic anti-fouling coating materials constructed by the synergistic anti-fouling strategies, namely the combination of biomimetic and intelligent anti-fouling strategies, is also reviewed. Finally, the preparation methods, anti-fouling mechanisms, effects, advantages and disadvantages, and the development trends of the above coating materials are summarized. The emerging biomimetic and intelligent marine anti-fouling coating technology are currently recognized in marine anti-fouling, and has achieved good research results; however, some problems are yet to be resolved. For example, the toxic components of current coating materials have uncertainties and potential risks to the growth and reproduction of marine organisms and marine ecosystems; the surface structure of biomimetic anti-fouling coating is complex; weak anti-fouling durability, stability, and high cost. The response of intelligent anti-fouling coating to external conditions is singular; the anti-fouling stability is not high, and the intelligent anti-fouling evaluation system and mechanism are unclear. Other issues include multi-strategy combined anti-fouling coatings and limited research on the synergistic anti-fouling mechanism between various strategies. Furthermore, the future development direction of anti-fouling coating materials constructed by biomimetic and intelligent multi-antifouling strategies is suggested. In selecting coating materials, the marine environment affinity components are used to replace the toxic components to reduce the risk of toxic substance release into the marine environment; adhering to the principle of "from the ocean, to the ocean" vigorously tap the marine biological resources, extract or synthesize new and efficient bio-antifouling agents to block the related signals and metabolic pathways of fouling organisms to inhibit the deposition and attachment of fouling organisms, rather than direct poisoning, thereby reducing the genetic risk to marine organisms; strengthening the basic research of bionics and biomimetic technology, and studying the microstructure surface, metabolism, and release law and stress behavior of anti-fouling attached organisms to quickly improve the overall design level of biomimetic anti-fouling coating; an intelligent “on-off” anti-fouling system with multiple conditional response was designed, which meets the requirements of convenient and accessible practical application environment and can quickly start and stop according to the specific environment, promoting the broad application of biomimetic and intelligent marine anti-fouling coating materials; increasing the research of multi-strategy combined anti-fouling method systems, such as expanding various anti-fouling strategies and an in-depth study of the synergistic anti-fouling mechanism between various strategies to solve the problem of a single anti-fouling strategy failing to meet the requirements of long-term, stable anti-fouling in the actual complex marine environment, thus ensuring long-term stable and efficient anti-fouling of coating materials. The multi-strategy combined anti-fouling method system will become an important development trend in marine anti-fouling in the future. This study mainly proposes the guiding viewpoint of the method system of the synergistic effect of biomimetic and intelligent multi-antifouling strategies, addressing the issue of limited review articles in the industry. Given the continuous progress of science and technology, the multi-strategy joint anti-fouling method system is expected to promote new breakthroughs in the marine anti-fouling industry in China. Biomimetic and intelligent marine anti-fouling coating materials will become a major development direction of marine anti-fouling in the future. In addition, they have important reference value for the development of national defense and military, marine engineering, maritime transportation, marine fishery, and other fields.

Laser cladding technology is widely used in the field of surface protection and remanufacturing because of its advantages, such as metallurgical bonding between the cladding layer and substrate, high processing efficiency, low dilution rate, and high energy input. It improves the wear resistance and corrosion resistance of the substrate, as well as the life of the cladding layer of the parts. However, instantaneous melting and rapid solidification of the melt pool during the laser cladding process lead to uneven stress within the cladding layer. It has been shown that even if the basic parameters are the same, the scanning paths and scanning time intervals of different lasers significantly influence the temperature distribution, and an uneven temperature distribution further leads to an uneven distribution of thermal stresses, which can cause coating quality issues. To analyze the effect of the scanning paths on the residual stress and tribological properties of the multi-pass laser cladding layer, a multi-pass laser cladding layer of Inconel 718 was prepared on 316L stainless steel using different scanning paths, and the distribution of residual stress in the cladding layer was investigated based on the thermoelastic-plastic model and the residual stress analyzer. The microstructure and hardness distribution of the cladding layer were studied using an X-ray diffractometer, a metallurgical microscope, and a hardness testing system. The tribological properties of the cladding were evaluated using a comprehensive material surface property tester and a laser confocal microscope. The results show that, owing to the difference in temperature cycling during the cladding process, the reciprocating scanning path has the shortest interval between each cladding pass and the lowest surface residual stress. The isotropic and dispersive scanning paths exhibit intermediate surface residual stress levels, while the shrinkage scanning path, which has the largest accumulation of heat in the central region of the cladding layer, exhibits the highest surface residual stress. The isotropic scanning path results in the most homogeneous microstructure due to the differences in temperature cycling during the process. In terms of microstructure, the isotropic scanning path exhibits the most uniform microstructure. Due to the consistent time intervals between each fusion cladding pass, the cooling process remains stable, resulting in minimal changes in crystal size from the cladding layer to the fusion zone. The shrinkage path has the largest accumulation of heat in the fusion cladding layer, and the low cooling rate allowed the crystals more time to grow, which resulted in significant changes in the size of the crystals at the bottom. Owing to the differences between the primary arm spacing and the volume fraction of the Laves phase in the fused cladding, the isotropic scanning path has a uniform distribution with a low content of the Laves phase and the lowest abrasion rate of the fused cladding layer. The reciprocating and dispersive scanning paths have intermediate abrasion rates, while the shrinkage-type scanning path has the highest abrasion rate due to its larger number of Laves phases. Therefore, a reciprocating scanning path should be selected for multi-pass cladding to reduce residual stresses in the cladding layer, and an isotropic scanning path should be selected to reduce the wear rate of the cladding layer. The results of the different scanning paths are expected to provide a theoretical basis for the selection of process parameters in the fields of surface protection and remanufacturing.

In the production process of a hundred-meter-long high-speed railway track, the rolling mill serves as a key component, bearing the effects of alternating high-temperature rolling parts and cooling water. It also faces significant extrusion, shear, and thermal stresses on the surface, resulting in problems such as short service life and severe roller surface wear due to failure. As a primary consumable component in the production processes of many industries, the scrapping a large number of rolls results in considerable waste of energy and resources in China. To repair the surface of scrapped rolls and improve their thermal fatigue performance, we developed the powder composition of iron-based powder, leveraging the good compatibility between the iron-based powder and the matrix material and the reduced cracking during the melting process. Considering the actual production conditions of the rolling mill, selecting an appropriate strengthening element is necessary to improve the performance of the repaired surface. Mo exhibits a good solid-solution strengthening effect and forms carbides, thereby enhancing the strength and wear resistance of the substrate. To further improve the wear resistance of the cladding layer while ensuring good thermal fatigue performance, elemental V was added to improve high-temperature stability, allowing the cladding layer material to maintain good performance at elevated temperatures. A laser cladding technique was used to prepare an iron-based coating using T504 as the base powder, with Mo and V added to the surface of a fatigue- failed 160CrNiMo roller material. The crack propagation rate and mechanism in the base material and cladding layer during thermal fatigue were analyzed using optical microscopy, scanning electron microscopy, and thermal fatigue testing machines. The results show that the average hardness of the cladding layer with Mo and V ratios of 1:0.5, 1:1, and 1:1.5 is 59.2 HRC, 59.9 HRC, and 59.1 HRC, respectively, representing an average increase of 33.4% compared to the substrate; The driving force for crack propagation during thermal fatigue tests primarily arises from the thermal stress generated by cold and hot cycles. After 2000 thermal fatigue testing cycles, the crack length in the matrix material sample measured 11.289 mm. Due to its high carbon equivalent, the brittle phase of eutectic M₇C₃, which contains a higher Cr content than the surrounding material, exhibited a different coefficient of thermal expansion. This mismatch became the main channel for crack propagation during the thermal fatigue testing process, where cracks primarily propagated in a transgranular form. The crack lengths of the samples with added Mo and V mass ratios of 1:0.5, 1:1, and 1:1.5 in the cladding layer were 3.185 mm, 16.596 mm, and 8.401 mm, respectively. The high hardness of the cladding layer, resulting from the addition of Mo and V, increased its brittleness. As the V content increased, the eutectic structure of the cladding layer gradually appeared to break down; the initial boundary became clear and blurred, compromising the integrity of the structure and leading to an increase in the number and length of microcracks. During thermal fatigue testing, the propagation of fatigue cracks was predominantly brittle and transgranular, exhibiting a rapid propagation rate. The sample completed the rapid crack propagation stage after 50-100 cycles. However, appropriate addition of V can improve high-temperature stability and result in shorter cracks. When the mass ratio of Mo to V was 1:0.5, the thermal fatigue performance of the roller material before repair improved by 71.7%. A comparison of the thermal fatigue characteristics of the iron-based coatings with different Mo and V mass ratios provides an experimental basis for selecting iron-based coating systems for roller repair.

Within the orbital altitude range of 180 km to 650 km, oxygen molecules in the atmosphere tend to decompose into atomic oxygen when exposed to ultraviolet light. Due to its strong oxidizability, atomic oxygen, is capable of causing erosion effects on the surface materials of spacecraft. Complex structural evolutions, such as mass loss, thickness reduction, and changes in surface morphology are involved in this process. So that performance degradation inevitably occurs, highlighting the importance of protecting the surface materials of low-orbit spacecrafts. The adoption of protective coatings is an effective way to improve the atomic oxygen protection performance of materials and ensure the long lifespan and high reliability of low-orbit spacecraft. The research progress of atomic oxygen protective coatings is briefly reviewed, and the factors affecting the performance of atomic oxygen protective coatings are studied. The results show that surface roughness, defects composition and structure of the coating have significant influences on its atomic oxygen protection effect. A rough surface of the coating has advantage in increasing the probability of collisions between atomic oxygen and surface materials, while defects in the coating provide more channels for atomic oxygen and enhance the erosion effects, and the composition and structure of the coating will affect the probability of atomic oxygen reactions. The types of space atomic oxygen protective coatings are investigated, and the characteristics of different types of coatings are analyzed. Atomic oxygen protective coatings can be divided into inorganic coatings, organosilicon coatings, and composite structure coatings. Among them, inorganic coatings are generally solid oxides with a dense structure, and this type of coatings has excellent protective performance but poor flexibility. Organosilicon coatings are mainly composed of elements such as Si, H, C, and O. Good flexibility is achieved through the formation of a polymer-like network structure in organosilicon coatings. When eroded by atomic oxygen, a dense silicon oxide layer appears during the reaction between atomic oxygen and Si atoms located at the surface of coatings, which prevents further erosion. However, under the action of high flux atomic oxygen, the coating surface is prone to shrinkage, resulting in a “tiled” surface and coating cracking. The composite structure atomic oxygen protective coatings can make up for the shortcomings of single-structure coatings and adapt to the needs of different application conditions, however, the performance of this type of coatings is highly correlated with their structure and requires. The coating preparation methods are sorted and summarized, while the advantages / disadvantages and application objects of different preparation techniques are analyzed based on a comprehensive comparison: inorganic coatings with dense morphology can be obtained through magnetron sputtering process, which is mainly suitable for preparing coatings / films on rigid or semi-rigid substrates. Plasma-enhanced chemical vapor deposition in coating preparation corresponds to lower deposition temperature, less thermal damage to substrates. And a wider application range because both inorganic coatings and organic coatings can be achieved in this way. However, due to process limitations, this technology can only be applied to planar substrates and cannot be applied to three-dimensional complex structural parts; ion beam co-deposition can conveniently prepare multi-component composite structure coatings, so it is the main preparation technology for composite atomic oxygen protective coatings; atomic layer deposition has precise coating thickness control, a dense coating structure, no pinholes and other defects, and can form a uniform film on the substrate surface with complex configurations such as steps and grooves. Moreover, it can repair the defects on the substrate surface, therefore having obvious advantages in atomic oxygen protection and achieving good atomic oxygen protection performance at a relatively thin thickness. However, the disadvantage is the low deposition rate, low efficiency, and high stress when preparing thick coatings. Cracks are prone to occur when applied on flexible substrate surfaces. The sol-gel method for preparing coating materials has a low temperature during the process, uniform coating structure, easy control of the reaction process, and low cost. However, in general, the coating thickness is relatively high, requiring tens of microns or more and high quality, which is not conducive to the light weighting of spacecraft. Therefore, it is mainly applied to small structural parts. The precursor photolysis / hydrothermal curing method requires post-treatment such as irradiation and heating when preparing coatings, and the uniformity control is more difficult when implemented on a large area. Therefore, it is suitable for local coating and repair of easily damaged areas on the surface of structural parts. The further development trend of atomic oxygen protective coatings is analyzed and introduced. The research provides the necessary research basis and reference for the atomic oxygen protection of materials for low-orbit spacecraft in China and provides research ideas for the further development of atomic oxygen protective coating technology.

The structure of BCN amorphous nano-films were studied by XPS. The characteristic peak of three elements of Ar, contamination carbon and deposited monolayer Au were considered as reference peak to correct the shift of the XPS spectra caused by charging effect during the XPS analysis process, and the results of XPS and FTIR analyses were compared to estimate the correctness of this method. The investigation results indicated that the calculated binding energy of BCN film depends on reference peak selection, and the correct structures can be obtained when the bonding energy was adjusted by selecting appropriate characteristic peak. The bonding structures of films corrected by Ar are quite similar with the results of FTIR analysis. This method is suitable for analyzing BCN films prepared in Ar-contained sputtering atmosphere, and is also suitable for analyzing the inner structure of films. There is an obvious deviation in bonding energies between the true value and adjusted by contamination carbon or by deposited monolayer Au.

采用低压等离子喷涂技术在镍基单晶高温合金上制备了NiCoCrAlYTa涂层,研究了不同功率参数制备的涂层在900℃175 h氧化后的特性,探讨了该涂层的氧化和退化机理.结果表明,3种功率制备的涂层都达到完全抗氧化级水平,其平均氧化速率分别为0.01 g/m2·h、0.01g/m2·h和0.0026g/m2·h,但不同涂层的氧化行为有所不同.3种试样氧化后表面形成了大量的β-Al2O3,并在涂层表面发生选择性氧化.X衍射分析表明,涂层发生了退化.

Additive manufacturing technology can realize the integral molding of complex components of ceramic materials, but defects exist, including the “step effect” multiphase distribution, and porosity on the surface of the components. Moreover, subsequent precision machining struggles to meet the urgent demand for high-performance silicon-carbide ceramic components for space optical detectors and semiconductor manufacturing equipment. Therefore, this study proposes a novel approach by which to repair surface defects in ceramic additive manufacturing using the chemical vapor deposition (CVD) of high-purity, high-density silicon carbide coatings. However, the proposed method still faces problems of interfacial bonding with the additive ceramic substrate and the growth pattern of the coating. Hence, the effects of the deposition temperature on the interfacial bonding, micromorphology, surface hardness, and machinability of chemical vapor-deposited silicon carbide on additive manufacturing ceramic surfaces were systematically investigated. This study used rapid laser prototyping and the silicone infiltration composite method to manufacture silicon carbide ceramic substrates and prepare silicon carbide coatings via chemical vapor deposition. The silicon carbide coatings were deposited at different temperatures of 1 200, 1 300, 1 400, and 1 500 ℃. The coatings were then deposited on the surfaces of ceramic substrates at the same temperature. The effects of the deposition temperature on the hardness, deposition efficiency, interfacial bonding, microstructure, and processability of the SiC surface coatings were systematically investigated using various techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), surface roughness measurements, micro-computed tomography (micro-CT), and scratch tests. The results showed that the hardness of the additively fabricated SiC ceramic was only 1 226 HV_0.5 before any coating was deposited, and the roughness after polishing was 1 980 nm. Because of the presence of multiple phases, the roughness was too high to achieve a mirror effect. At a deposition temperature of 1 200 ℃, a peak of free silicon (Si) appeared in the coating owing to the high precursor gas concentration. However, the temperature was insufficient to promote uniform surface deposition, which resulted in an apparently homogeneous deposition in which free Si atoms in the gas phase were deposited directly onto the substrate. As the deposition temperature increases, the deposition rate accelerates, and the critical nucleation radius of the new phase gradually increases. The critical nucleation free energy also increases, resulting in the formation of larger SiC grains. The Si-C bonds within these grains remained intact, contributing to the overall hardness. However, at an excessively high deposition temperature, pores begin to form between the grains, resulting in low density and high porosity of the substrate and coating. Despite these problems, the silicon carbide coatings deposited at all temperatures formed good bonds with additively fabricated ceramic substrates. Notably, as the deposition temperature reaches 1 400 ℃, the silicon in the substrate begins to evaporate, and defects and porosity appear on the substrate surface. These defects provide additional nucleation points for the coating, and the morphology of the coating at the interface becomes columnar. As the coating grows to a certain thickness, it transforms into a dense structure. The columnar crystals significantly enhance the bond strength of the coating and improve its surface workability, which reduces its roughness to 9.08 nm. After polishing, the coating exhibited a mirror-like finish at all deposition temperatures. Thus, this study demonstrates that the application of CVD SiC coatings can significantly improve the surface quality of additively manufactured ceramics. This approach provides a theoretical basis for engineering applications of high-performance ceramic components in advanced devices.

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.

Aluminum-based intermetallic compounds are recognized for their excellent high-temperature mechanical properties, high resistance to oxidation and corrosion at elevated temperatures, and low density. These characteristics make them suitable for a broad range of applications, including protective coatings and structural components in aerospace and other industries. High-energy-beam additive manufacturing technologies, such as laser and electron beam melting processes, are effective for the rapid fabrication of complex metal structures. However, depositing aluminum-based intermetallic compounds remains challenging due to their complex phase structures and inherent brittleness, which often lead to flaws and defects, particularly cracks. Cold spraying, a process characterized by low processing temperatures and high deposition rates, shows significant potential for the low-heat-input fabrication of aluminum-based intermetallic compounds. This paper summarizes and analyzes recent advancements in the preparation of aluminum-based intermetallic compounds using cold spraying. Effects of powder design and fabrication routes on deposition behavior and deposit properties are discussed. These routes include intermetallic compound powder deposition, mixed elemental metal powder cold spraying followed by heat treatment, and cold spraying of mechanically ball-milled pseudo-alloy powders with subsequent heat treatment. First, the deposition behavior of intermetallic compound powders is reviewed and discussed. In the cold spraying process, successful deposition and bonding of spraying particles rely on plastic deformation induced by particle impact. However, due to the intrinsic brittleness of intermetallic compounds at room temperature, it is difficult to deposit particles directly using intermetallic compound powders as feedstock. In practice, when relatively soft materials are used, only a single layer of intermetallic particles can be mechanically embedded into the substrate layer. Subsequent spraying does not contribute to building up of the deposit because achieving successful bonding between intermetallic particles is highly challenging. Although high gas temperatures, even up to 1 000 ℃, are used to soften intermetallic particles, depositing a thick, high-quality deposit remains elusive. Thus, preparing intermetallic deposits using intermetallic feedstock powders continues to be a challenge. To address this issue, an alternative strategy involving the formation of intermetallic compounds during or after deposition has been extensively investigated. Following this strategy, mechanically mixed powders containing aluminum (Al) and other elemental powders, such as iron (Fe), nickel (Ni), or titanium (Ti), are used as feedstock materials. Due to the excellent plastic deformability of elemental metal powders, deposits containing mixed elemental metal particles can be easily deposited by cold spraying at relatively low gas temperatures and pressures. Post-spray heat treatment or annealing is then performed to activate interdiffusion between the Al and Fe / Ni / Ti phases, facilitating the formation of intermetallic compounds. However, the higher deposition efficiency of Al powder compared to Fe / Ni / Ti powders often results in cold-sprayed composite deposits with a higher Al content than the feedstock powder, complicating precise control of the chemical composition. This challenge is particularly pronounced when the feedstock powder contains more than three elemental metal powders. Additionally, during heat treatment, the long diffusion paths required for intermetallic compound formation frequently lead to the creation of numerous Kirkendall pores, and achieving a single intermetallic phase proves difficult. To overcome these challenges, a method involving the cold spraying of mechanically milled pseudo-alloy powders, followed by heat treatment, is proposed. By controlling the intensity and duration of high-energy ball milling, pseudo-alloy powders with alternating submicron lamellae of various metals can be prepared from mechanically mixed metal powders. The composition of the pseudo-alloy powder can be precisely controlled by adjusting the proportions of the raw materials. Moreover, the pseudo-alloy powder retains the plastic deformation capability of the original elemental metals, ensuring efficient deposition during cold spraying. The fine microstructure of the alternating submicron metal lamellae significantly shortens diffusion paths during heat treatment, effectively mitigating the formation of Kirkendall pores in the deposit. Finally, the effects of post-treatments such as friction stir processing (FSP) and hot isostatic pressing (HIP) on the microstructure and properties of the deposit are summarized. FSP treatment greatly refines the microstructure of deposits sprayed with mechanically mixed elemental metal powders, resulting in structures featuring alternating submicron metal lamellae and partially formed intermetallic compounds. This refinement significantly shortens diffusion paths between phases and prevents the formation of Kirkendall pores. However, it is challenging to process parts with complex shapes using this method. In contrast, HIP applies isostatic pressure during treatment, closing Kirkendall pores and making it suitable for parts with complex geometries. Overall, cold spraying of mechanically mixed elemental metal powders followed by HIP treatment, as well as cold spraying of mechanically milled powders combined with subsequent heat treatment, have been shown to produce aluminum-based intermetallic compounds with low porosity and high hardness. By comparing and analyzing the advantages and limitations of different technological routes, this study aims to provide guidance for the cold-spraying additive manufacturing of aluminum-based intermetallic compounds.

With the continuous advancement of technology, the requirements for the processing accuracy of optical components in fields such as advanced optics and integrated circuits have gradually increased. From the initial nanometer-level precision to the current pursuit of sub-nanometer-level precision, this transition represents not only an extreme challenge to technology but also necessary support for the future development of science and technology. However, faced with such stringent requirements, current mainstream traditional processing technologies, such as chemical mechanical polishing (CMP), fluid jet polishing (FJP), magnetorheological finishing (MRF), and ion beam polishing (IBP), despite their significant application effects in their respective fields, all have insurmountable limitations. These traditional technologies often struggle to achieve the goal of manufacturing atomically smooth surfaces while ensuring high efficiency. Therefore, manufacturing optical components with sub-nanometer roughness and low subsurface damage while ensuring processing efficiency has become a critical technical challenge in the field of ultraprecision manufacturing that must be urgently addressed. In this context, gas cluster ion beam (GCIB) technology, as an innovation and upgrade to traditional ion beam technology, is gradually emerging in the field of ultraprecision processing owing to its unique processing mechanism and excellent performance, demonstrating significant application potential. Therefore, it is necessary to discuss the principles, irradiation characteristics, and potential applications of GCIB technology. Herein, first, the principles of GCIB technology are explained, and the unique irradiation characteristics of GCIB technology are elaborated. GCIB is an ion beam processing technology based on gas clusters, which are tiny clusters composed of tens to thousands of atoms or molecules. This technology first condenses gas molecules into microclusters through supersonic expansion and then forms an uncharged GCIB through ionization, acceleration, focusing, and neutralization. During processing, these ions strike the workpiece surface at a certain speed and remove the material through physical sputtering to achieve polishing, etching, and other purposes. Compared with traditional ion beam technology, GCIB technology has a series of unique irradiation characteristics that endow it with significant advantages in the field of ultraprecision processing, such as low energy per atom, high sputtering yield, lateral sputtering effect, and dense energy deposition. Based on these characteristics, GCIB technology has broad application prospects in fields such as polishing, etching, thin-film deposition, and secondary ion mass spectrometry (SIMS). To systematically study GCIB technology, this research summarizes its application status in different fields. In the field of polishing, utilizing the low-energy and high sputtering yield characteristics of GCIB enables high-precision surface polishing. In the field of etching, GCIB technology exhibits excellent etching accuracy and controllability, enabling precise etching at the micrometer or even nanometer scale. In the field of thin-film deposition, precise deposition of various types of thin films can be achieved by adjusting parameters such as the composition and energy of GCIB. This deposition method not only has high deposition rates and uniformity but also enables precise control and modification of the films. In the field of SIMS, GCIB technology can also be used as an excitation source to analyze the elemental composition and distribution of materials. Finally, this research discusses the shortcomings and future development directions of GCIB technology. As an emerging technology, existing research has only validated the effectiveness of GCIB technology in laboratory environments and has not proven the feasibility of GCIB processes in actual manufacturing. Additionally, the production cost of GCIB equipment is relatively high, and while its processing efficiency is better than that of IBP, it is still lower than those of CMP and MRF. Therefore, future efforts are still needed to optimize equipment, reduce costs, and improve processing efficiency.

Titanium dioxide nanotubes (Titanium dioxide nanotubes, TiO₂ NTs) have garnered significant attention in recent years owing to their unique nanostructures, high specific surface areas, and exceptional antibacterial and drug-release capabilities. As innovative surface-modification materials, TiO₂ NTs show great promise for use in biomedical applications, particularly in infection control and drug delivery. The remarkable properties of TiO₂ NTs, including their abilities to interact with biological systems, have made them a focal point of research for the development of new therapeutic strategies, particularly for combating bacterial infections. This review systematically examines the fabrication methods of TiO₂ NTs and their applications in the antibacterial field, focusing on their roles in controlling bacterial infections and regulating drug release mechanisms. The methods used to fabricate TiO₂ NTs, such as anodization, sol-gel processes, and hydrothermal synthesis, are critical for controlling their size, morphology, and surface properties, all of which directly influence their performance in various biomedical applications. These fabrication techniques allow for precise control over nanotube structures, which optimizes their drug-loading capacity and ensures their effectiveness in both infection prevention and controlled drug release. Moreover, TiO₂ NTs are highly effective at preventing bacterial adhesion and biofilm formation, which are key challenges in medical treatments. Further, TiO₂ NTs can be functionalized by loading various antibacterial agents, such as antibiotics, silver nanoparticles, and other bioactive compounds, to enhance their therapeutic effects. This review discusses various loading techniques, including physical adsorption, layer-by-layer self-assembly, and solution impregnation, for improving the efficiency of drug delivery. Physical adsorption is a simple and widely used technique for loading antibacterial agents, where the agents are adsorbed onto the surfaces of nanotubes. In contrast, layer-by-layer self-assembly creates a more complex structure with multiple layers, thus allowing for a more controlled and sustained release of drugs. Solution impregnation, which is another important technique, facilitates the incorporation of therapeutic agents into nanotubes and ensures that the drugs are released gradually, thus enhancing their antibacterial effects over an extended period. Additionally, sealing technologies are crucial for enhancing the drug release efficiency. Sealing methods typically involve the use of polymers or composite materials that encapsulate drugs, which prevents their premature release and ensures a more controlled and sustained-release profile. These sealing technologies improve the stability and performance of TiO₂ NTs in biological environments and thereby optimize their therapeutic benefits. Despite the promising antibacterial properties and biocompatibility of TiO₂ NTs, their practical applications face several challenges. Issues such as the structural stability of TiO₂ NTs in biological environments, precision of drug release, and long-term safety must be addressed. The degradation and morphological changes in TiO₂ NTs in biological fluids can compromise their functionality and biocompatibility. Moreover, ensuring precise drug release is challenging because the careful design of the nanotube structure and loading methods are required. Long-term safety, particularly the potential toxicity of TiO₂ NTs and their degradation products, must be further evaluated to ensure their safe use in medical applications. Future research should focus on optimizing the design of TiO₂ NTs by exploring new fabrication techniques and developing multifunctional composite materials that combine TiO₂ NTs with other materials, such as polymers, natural biomolecules, or nanoparticles. These composite materials can enhance the stability and drug loading as well as control the release of TiO₂ NTs, which thereby expands their applications in a variety of therapeutic contexts. Furthermore, clinical trials are required to validate the long-term safety and efficacy of TiO₂ NTs in real-world medical applications. By addressing these challenges and advancing the development of TiO₂ NTs, their potential for widespread use in the medical field can be realized to thereby provide innovative solutions for infection prevention, controlled drug delivery, and other biomedical treatments.

It is often the case that extreme conditions are frequently encountered in high-tech equipment, where conventional materials often prove inadequate inmeeting the requirements of intended application. It is therefore imperative that ultra-high-performance materials and technologies be developed to tackle these challenges. In view of the demand for lubricating and wear-resistant surface technology in the development of national frontier equipment under harsh conditions, this study presents a review of recent advancements in this special materials field, with particular focus on the aerospace and nuclear energy sectors. It takes the adhesive solid lubricant coatings developed by our team as object, emphasizing key common technical challenges and addressing practical engineering issues. Including key technologies such as the modification of tough and strong integrated basic resins, the improvement of atomic oxygen resistance by POSS modified resins, the design and adaptive control of lubrication components over a wide temperature range, the design of surface and interface of coatings resistant to special media, and the control of system compatibility. Additionally, a compilation of representative products developed based on this basis is listed, together with an illustration of their exemplary applications in addressing friction-related challenges under extreme conditions within high-tech equipment domains. The application in key components of aircraft and aviation engines, in key components of rockets and satellites, especially in the docking mechanism of space stations, has solved the lubrication and wear problems of components under many extreme conditions in aerospace. This underscores the indispensable and crucial role played by advanced lubrication and wear-resistant surface engineering technologies in driving forward national advancements in high-tech equipment. Finally, considering future developmental requirements for cutting-edge manufacturing at a national level, potential directions for further advancing extreme condition lubrication and wear-resistant surface engineering technologies are explored. This article provides a comprehensive understanding of the demand for extreme condition lubrication and wear-resistant surface engineering technology in the national high-tech field, promotes the high-tech application of related technologies and products, and develops higher limit performance lubrication and wear-resistant surface engineering technology for future high-tech equipment needs. It offers a valuable reference point and provides guidance significance on these matters.

Plasma Immersion Ion Implantation and Deposition technology (PIIID) can obtain a uniform and perpendicular ion implantation on the components with sophisticated shape. It has shown great potential in surface modification for industrial components. After its invention, PIIID has developed rapidly in recent years. However, in order to get wide commercial applications, the methods for high efficiency ion implantation, inner surface ion implantation and large area ion implantation should be proposed.

The rapid development of flexible electronics, microelectromechanical systems (MEMS), and integrated circuits has led to a pressing demand for surface microfabrication of materials. Existing chemical wet processes or low-pressure plasma processing technologies have been widely used for surface microfabrication; however, these microfabrication technologies have certain shortcomings, such as complex processes, high processing costs, low energy efficiency, and environmental unfriendliness. To achieve patterned surface microfabrication, traditional microfabrication methods require the use of masks or photolithography processes which limit the efficiency and application scope of the microfabrication method. Therefore, there is an urgent need to explore new surface microfabrication methods that are low-cost, green, maskless, versatile, and noncontact. An atmospheric-pressure cold plasma jet is a plasma plume formed using the action of airflow and an electric field to produce plasma in the discharge region and eject it from an orifice at a low gas temperature. Atmospheric-pressure cold plasma jet microfabrication technology is found to be advantageous because it is environment-friendly, low-cost, low-temperature, strongly reactive and pure dry method having no mechanical contacts. Atmospheric-pressure cold plasma jets have been widely used in localized surface modification, maskless surface etching, and direct deposition of functional thin films. However, microfabrication still faces challenges in terms of plasma jet stability, processing accuracy, and collaborative processing. Therefore, it is extremely essential to explore the research progress, existing problems, and future development trends in the generation mode, surface microfabrication methods, and processes related to atmospheric-pressure cold plasma jets. Firstly, the generation modes and commonly used electrode structures of atmospheric-pressure cold plasma jets were summarized and analyzed. By comparing the characteristics of four common discharge modes, namely, corona discharge, dielectric barrier discharge, arc discharge, and spark discharge, the commonly used discharge mode that generates an atmospheric-pressure plasma jet was demonstrated. Furthermore, the characteristics and applicable scenarios of single-needle, ring, needle-ring, and plate-plate type electrode structures were analyzed. Then, the research scenario of surface microfabrication technology of atmospheric-pressure cold plasma jets on surface modification, material etching, and film deposition was elaborated. Plasma jet surface modification is a general “equal material processing” method. According to the different modified surfaces, the application of plasma jets in material modification research can be roughly divided into three aspects: modifying the substrate to meet specific requirements, modifying the functional layers of devices to achieve specific functional requirements, and as an auxiliary processing method, providing assistance for other surface microfabrication methods. Herein, a systematic summary and analysis of the three surface modifications are presented. Atmospheric-pressure cold plasma jet etching, as a “subtractive processing” method, can etch substrates and also selectively etch some functional layer materials. In addition, the etching mechanism of an atmospheric-pressure cold plasma jet is summarized and discussed. As an “additive processing” method, a comprehensive review of atmospheric-pressure cold plasma jet surface deposition is also presented. This method can deposit various types of thin films or coatings with different properties, such as organic polymer, inorganic and conductive metal thin films. Finally, the main challenges that exist in plasma jet surface microfabrication technology are discussed, and its future development direction is highlighted. This review can be used as a basis for more in-depth research on methods and technologies for the surface microfabrication of atmospheric-pressure cold plasma jets and to improve the application level of atmospheric-pressure cold plasma jets in advanced manufacturing fields such as flexible electronics, MEMS, and integrated circuits.

In this work, the main content for service life of military aircraft was introduced briefly, the typical corrosion cases were illustrated, and the harm of environmental corrosion to aircraft was described. It is significant and urgent to research the anti–corrosion technique and calendar life of aircraft. The service environment, application feature and corrosion status of active military aircrafts were discussed. The main existing problems for corrosion and calendar life of active aircrafts were analyzed and the key techniques that should be studied mainly now were advanced.

3D-printed silicon carbide (SiC) ceramics have excellent qualities such as high strength and temperature resistance and they permit flexible molding of complex shapes, leading to their wide use in energy processing and advanced aerospace applications in recent years. However, they have poor surface abrasion resistance. Using atmospheric plasma spraying (APS) is an economically feasible method for applying high-temperature abrasion-resistant coating on the surface of parts. Among the common self-lubricating wear-resistant coatings, YSZ coating, with its excellent high-temperature stability and oxidation resistance, is generally used in high-temperature environments. However, to improve the performance of the spraying process and reduce friction, a second phase is often added. This paper proposes (1) doping the coating with both low- and high-temperature lubricants to enable wide-temperature lubrication, (2) adding alumina to reduce the melting point of the powder and improve the coating densification, and (3) using a sol-gel-coated powder to improve the bonding between the base and second phases of the coating. In this study, three composite powders with different compositions of YSZ-Al₂O₃-CaF₂-C were prepared using the sol-gel method and centrifugal atomization drying. The corresponding composite coatings (Ca0C0, Ca5C10, and Ca10C5) were deposited on the surface of 3D-printed SiC ceramics using the APS technique. The microstructures, friction properties, and wear mechanisms of the composite coatings were studied at room temperature and 600 ℃. The results show that the coatings have a typical laminated structure. Both the coatings and abrasion marks were primarily composed of YSZ, Al₂O₃, and m-ZrO₂ phases, with CaF₂ and C phases in Ca10C5 and Ca5C10 coatings. No other chemical reactions occurred during the coating application or owing to friction. The Ca0C0 coatings without CaF₂ and C lubrication phases had the highest hardness, lowest wear rates, and largest friction factor at room temperature and 600 ℃. The strong bonding of the coating to the friction partner at 600 ℃ led to a friction coefficient of more than 1. The stabilized friction factor of Ca10C5 and Ca5C10 coatings were, respectively, 0.239 and 0.130 at room temperature and 0.175 and 0.288 at 600 ℃. The friction factor of Ca5C10 and Ca10C5 coatings considerably reduced upon the addition of CaF₂ and C lubrication phases at both room temperature and 600 ℃, reflecting improved self-lubricating properties. However, the addition of the lubrication phases led to a decrease in the hardness of the coatings and an increase in the porosity defects inside the coatings, accompanied by an increase in wear rate. The Ca5C10 coatings with higher C additions were more prone to abrasive debris generation because of the higher volume fraction of C and lower hardness, resulting in higher wear rates. Based on the abrasion mark morphology, the wear mechanism of the coating was concluded to be primarily adhesive and abrasive. The YSZ-10Al₂O₃-10CaF₂-5C coating had a lower friction factor and wear rate (1.02×10^-5 mm³ / (N·m) at room temperature and 0.84×10^-5 mm³ / (N·m) at 600 ℃) compared with YSZ-10Al₂O₃-0CaF₂-0C and YSZ-10Al₂O₃-5CaF₂-10C coatings in this study. This implies that YSZ-10Al₂O₃-10CaF₂-5C coating has good self-lubricating and wear-resistant properties and can well improve the surface properties of 3D-printed SiC.

Gas nitriding-quenching (N+Q) compound treatments on GCr15 steel were carried out and compared with single processing of gas nitriding and quenching. The phases, microstructures, and the dry sliding friction properties of samples were studied. By single gas nitriding at 530℃ for 9 h, the compound layer was composed of ε phase with a thickness of about 40 μm. However, the nitride of ε phase in the compound layer were completely decomposed in N+Q compound treatment, which promoted N element to diffuse into the matrix, and the thickness of the diffusion region was about 900 μm. Compared with the single quenching hardness of GCr15 steel, the hardness of diffusion region was improved about 200 HV_0.1, because of soluble N element. However, the surface hardness dropped down, due to the porosity resulting from the decomposition of nitrides. Furthermore, under the loads of 20 N and 100 N, the dry reciprocating sliding frictions were carried out respectively. The results show that the friction co-efficients (COF) of both single gas nitriding and N+Q compound processing are lower than that of single quenching treatment. The wear resistances of N+Q compound treatment samples are improved, compared with nitriding and quenching samples at a load of 20 N, and decreases at a load of 100 N due to the surface porosity during initial steps. However, after the initial steps, the anti-wear ability of N+Q compound treatment samples increases again.

Micro-arc oxidation (MAO) is a surface treatment method widely used for fabricating ceramic coatings on light metal substrates. MAO significantly enhances the properties of these metals, including their corrosion resistance, wear resistance, and thermal control capabilities. This paper provides a comprehensive review of recent developments in MAO technology, focusing on the design and application of functional ceramic coatings.
The growth mechanism of MAO coatings involves several key stages: linear voltage increase, local discharge, voltage stabilization, and coating stabilization. In these stages, a ceramic coating with numerous micropores and microcracks is formed, which significantly impact the properties of the coating. By modifying the electrolyte composition, the morphology and properties of the resulting coating can be optimized to satisfy specific requirements.
One of the primary applications of MAO coatings is corrosion protection. The corrosion resistance of MAO coatings can be enhanced by adjusting the electrolyte composition to improve the density and reduce the porosity of the coating. The incorporation of micro-nanoparticles into the electrolyte can further enhance the corrosion resistance of the coating. The addition of certain compounds to the electrolyte during the MAO process can increase the density and thickness of the coating, thereby reducing its porosity and improving its protective properties. Another effective method for improving corrosion resistance is the creation of composite coatings, in which post-treatment techniques are used to seal the pores, thereby enhancing the long-term stability of the coating.
In addition to corrosion protection, MAO coatings provide improved wear resistance and lubrication. The in situ formation of the coating was achieved by adding micro- and nanoparticles to the electrolyte during the MAO process. These particles influence the formation of the coating and contribute to its self-lubricating, high-density, and hard surface properties. Furthermore, post-treatment methods, such as filling the coating pores with lubricating agents or combining the coating with polymer composites, can enhance the wear resistance and lubricating properties of the coating. These post-treatment techniques exploit the porous structure of MAO coatings to improve the adhesion and bonding strength of the lubricants or polymers used.
The thermal protection properties of MAO coatings can be tailored by adjusting electrolyte additives and electrical parameters. By incorporating specific soluble or insoluble additives, it is possible to regulate the optical properties of the coating, such as its solar absorptivity and infrared emissivity. This makes MAO coatings suitable for application in aerospace engineering where heat control is critical. The addition of materials such as metal oxides, which are generated during the MAO process, can further optimize the thermal performance of the coating.
For electrical insulation, high-density MAO coatings with reduced porosity provide excellent dielectric properties. By adjusting the electrical parameters and optimizing the electrolyte composition, it is possible to fabricate coatings with high electrical insulation performance. The porosity, thickness, and density of MAO coatings can be precisely controlled to meet specific requirements for insulation.
Despite these advancements in MAO technology, there are still challenges to overcome. The long-term stability of functional coatings remains a concern because the complex formation process can lead to coating surface porosity and nonuniformity, which may affect the coating performance under extreme conditions. In addition, precise controlling of microstructure and performance of MAO coating—such as porosity, thickness, and density—remains a challenge. Ensuring the comprehensive performance of composite coatings, especially those produced through MAO plus post-treatment processes, presents challenges in different environmental conditions.
In summary, this paper systematically reviews the progress in MAO technology, emphasizing various strategies for optimizing MAO coatings for different applications. The research presented here provides valuable insights into the potential of MAO coatings in a wide range of functional fields. This paper also discusses future directions for improving the performance and expanding the applications of MAO technology, providing a theoretical foundation for further research and practical applications.

Nanosecond laser direct writing (NDLW) is an advanced surface processing technique that utilizes high-energy nanosecond pulsed lasers to induce localized modifications on metallic materials. Due to its ability to precisely control surface morphology through mechanisms such as laser ablation, photothermal, and photochemical reactions, NDLW has been widely adopted in the fabrication of microscale surface structures. When applied to polished metal substrates, NDLW typically results in a highly (super)hydrophilic surface due to the formation of oxides and increased surface roughness. However, these laser-induced surfaces can undergo further wettability transformation toward (super)hydrophobicity through post-treatment strategies that are environmentally friendly and free of chemical modifiers. In recent years, there has been growing interest in developing green, sustainable methods to regulate surface wettability, especially for applications in aerospace, biomedical engineering, and energy systems. These applications demand robust, durable, and multifunctional surface properties, including anti-icing, self-cleaning, antibacterial, and drag-reduction functionalities. Unlike traditional chemical modification methods that involve hazardous fluorinated compounds or silanes, emerging approaches focus on physically driven processes such as air exposure, thermal annealing, and secondary laser treatments to modify surface chemistry and energy without introducing environmental burdens. This paper provides a comprehensive overview of the theoretical basis of wettability, including classical models such as the Young, Wenzel, and Cassie-Baxter models, and elaborates on the role of surface roughness and surface energy in determining hydrophobic or hydrophilic behavior. Special attention is given to the mechanisms by which nanosecond laser processing induces micro / nano-hierarchical structures and alters surface states on metals such as titanium, aluminum, stainless steel, and copper. Subsequent to NDLW, environmental exposure often results in gradual absorption of low-surface-energy organic compounds from ambient air. This spontaneous aging process, albeit slow (often taking weeks), transforms laser-textured metal surfaces into superhydrophobic states, as confirmed by contact angle measurements and surface chemical analyses using XPS. To accelerate this transition, low-temperature annealing has been widely studied. Heating laser-treated samples in air at moderate temperatures (100-200  ℃) significantly shortens the hydrophilic-to-hydrophobic transition period by facilitating the decomposition and adsorption of airborne hydrocarbons and by reducing the concentration of polar hydroxyl groups on the surface. Another effective and scalable method involves secondary laser treatment. This technique enhances the complexity and dual-scale nature of the surface textures, leading to a more stable Cassie-Baxter state. Furthermore, advanced laser interference strategies, such as direct laser interference patterning (DLIP), can precisely fabricate periodic structures, improving water repellency and surface durability. Hybrid techniques like combining NDLW with ion implantation have demonstrated superior performance. For instance, post-laser carbon ion implantation not only modifies surface energy but also improves mechanical robustness and corrosion resistance, enabling the formation of long-lasting superhydrophobic surfaces suitable for harsh environments. The findings reviewed in this study demonstrate that nanosecond laser-based surface texturing, followed by eco-friendly post-treatments, offers a versatile and sustainable route to engineer functional metallic surfaces without relying on hazardous chemicals. The resulting superhydrophobic surfaces exhibit excellent durability, tunable wettability, and enhanced environmental compatibility. In conclusion, this work outlines the fundamental mechanisms, recent advancements, and technological trends in the field of laser-induced wettability engineering on metallic substrates. It highlights the synergy between laser-generated microstructures and environmentally benign surface modifications, providing a valuable reference for future research and industrial applications aimed at achieving high-performance and sustainable surface functionalities.

Thermal barrier coatings serve as a prevalent advanced heat protection method in aviation engines. The working environment for the coatings becomes increasingly challenging with a rise in engine operating temperatures. Investigating the failure modes of the coatings under high-temperature and high-temperature gradient conditions is essential to improve the operational lifespan of the coatings. A ceramic coating with a thickness of 0.12 mm, comprised of Gd₂O₃-Yb₂O₃-Y₂O₃ co-doped ZrO₂, was produced on the GH3536 substrate using the atmospheric plasma spraying technique. A burner rig test device has been designed to simulate the service environment of coatings. This generates a super high-temperature flame by burning a mixture of aviation kerosene and oxygen, ensuring high temperatures on the sample surface. The sample is of a hollow structure with high-pressure cooling water flowing inside, which ensures low temperatures on the back of the sample, thus generating a severe temperature gradient. The use of various characterization methods allowed for an analysis of the microstructural changes in the coating, leading to a discussion of the failure mechanisms of the coating under high temperature and high temperature gradient conditions. The results show that after burner rig test with surface temperature of about 2350 ℃, the coating life of single long-time test is greater than 1200 s, and the coating life of multiple short-time test is 3 times. The coating showed obvious gradient sintering along the thickness direction. The top area of the coating is heavily sintered, which is called the sintered zone, and the porosity and grain size are distributed in gradient along the thickness direction. After multiple 25 s tests, there was an observed increase in the depth of the sintered zone, a higher quantity of vertical cracks, and an expansion in both the width and length of transverse cracks as the number of tests increased. Furthermore, the thermal growth oxide (TGO) transitioned gradually from alumina to spinel, and there was an expansion of the micro-transverse cracks formed by TGO. After the 1200 s test, the coating maintained a singular cubic phase and demonstrated excellent stability at high temperatures. In contrast to the single 25 s test, the sintering depth increased, leading to a higher number of vertical cracks. However, the quantity of transverse cracks remained consistent, confirming that transverse cracks arise from thermal-mismatch stress during repetitive thermal shock processes. In summary, the failure of the coating under high temperature and high temperature gradient conditions can be attributed to a combination of high-temperature sintering, thermal-mismatch stress, and TGO. The failure process can be summarized as the rapid propagation of early-stage vertical cracks caused by high-temperature sintering, the generation of intermittent transverse cracks at the interface due to thermal mismatch stress. The micro-transverse cracks produced by the thermal growth oxide connect the intermittent transverse cracks at the interface, and the connection through the vertical cracks and the continuous transverse cracks causes the coating to finally fall off. Failures occur earlier and the failure mechanism is more complex under high temperature and high-temperature gradient conditions compared to that in conventional thermal shock tests. The research results provide some support for the development of new thermal barrier coatings. The premature failure of coatings can be alleviated by improving the sintering resistance of coatings, increasing the thickness of coatings appropriately and designing multilayer structures.

In recent years, laser cladding for the preparation of high-entropy alloys (HEAs) has attracted widespread attention in aerospace, transportation, and marine applications. FeCoCrNi-series high-entropy alloys are among the most widely studied transition-metal HEAs. Due to their unique properties (i.e., high-entropy effect, lattice distortion effect, slow diffusion effect, and cocktail effect), FeCoCrNi-series entropy alloys can achieve synergistic improvement in strength and toughness. Many studies have confirmed that laser-cladding FeCoCrNiAlTi HEA coatings offer excellent mechanical properties, including high strength, toughness, corrosion resistance, and oxidation resistance at high-temperatures. However, there are currently few studies on the friction and wear mechanism of FeCoCrNiAlTi HEA coatings under corrosion-friction coupling, and the interaction between alloy elements, microstructure, wear, and corrosion resistance remains unclear. In this study, a FeCoCrNiAl_0.5Ti_0.5 HEA coating was prepared on an AISI 1045 steel substrate using laser-cladding technology. Dry and wet friction tests were performed on the coating and substrate immersed in the solution for different durations. The dry and wet friction was tested using a ball-on-disc wear test. After grinding and polishing, the microstructure of the sample surface was characterized, followed by corrosion in an aqua regia solution (75 mL HCl and 25 mL HNO₃ per 100 mL solution) for 30 s. The hardness pits of the sample and the transition from the coating to the substrate were observed via optical microscopy (OM). After the wear test, the depths and widths of the wear scars were measured using a three-dimensional profilometer. The microstructures and wear scar characteristics of the samples were characterized using a scanning electron microscope (SEM) equipped with an energy-dispersive X-ray spectroscope (EDS) and an electron backscatter diffraction (EBSD) detector. The phase compositions of the powder and sample were characterized using X-ray diffraction (XRD). The dry and wet friction behaviors of the coating related to atmospheric and corrosive environments were investigated in combination with the friction and wear test results. The results indicated that the microstructure of the laser-cladded FeCoNiCrAl_0.5Ti_0.5 HEA coating mainly consisted of a dendrite region (DR) with a body-centered cubic (BCC) phase and an interdendritic region (IR) with a face-centered cubic (FCC) phase. In addition, under spinodal decomposition, a portion of the BCC phase in the lamellar eutectic structure of the coating transformed into the L2₁ phase. The laser-clad FeCoNiCrAl_0.5Ti_0.5 HEA coating demonstrated excellent wear resistance. The friction factor of HEA coating and the dry friction factor of AISI steel substrate were 0.69 and 0.75, respectively, with wear rates of 5.04×10^-5 mm³ / (N·m) and 1.41×10^-4 mm³ / (N·m), respectively. The immersion time in a 3.5wt.% NaCl solution significantly influenced the wet friction and wear properties of the laser-cladded FeCoNiCrAl_0.5Ti_0.5 HEA coating. The wet friction wear rate of the coating increased with the immersion time. The wet friction wear rate of the unimmersed coating was 1.11×10^-5 mm³ / (N·m), while that of the coating immersed for 15 days increased by 1.77 times, reaching 3.08×10^-5 mm³ / (N·m). The main forms of dry friction and wear of the laser-clad FeCoNiCrAl_0.5Ti_0.5 HEA coating were three-body wear and abrasive wear, whereas the wet friction wear process was affected by corrosion, oxidation wear, and three-body wear. The wet friction wear process is lubricated by water and oxide films between the friction pairs; therefore, the wear rate is significantly lower than that in dry friction. However, under wet friction conditions, the oxide film was easily corroded, leading to the formation of microcracks and film delamination, ultimately resulting in three-body wear.

Inspired by Nepenthes pitcher plants, slippery liquid-infused porous surfaces (SLIPS) were first created in 2011 to offer a novel approach to surface engineering. Unlike conventional superhydrophobic surfaces (SHS), which rely on air lubrication, SLIPS utilize liquid lubrication with superior durability and pressure stability. With such advances, SLIPS possess outstanding liquid and ice repellency, self-healing, and enhanced optical transparency, which can be implemented in a wide range of energy applications, such as industrial anti-icing, anti-fouling, anti-frosting, and droplet-based power generation. Because most industrial application scenarios for SLIPS frequently encounter impacts of droplets, a mechanistic understanding of the dynamic interactions between SLIPS and impacting droplets is essential for the effective use of SLIPS under specific application conditions. This review systematically examines droplet impacting dynamics on SLIPS. In section 1, we introduce the thermodynamic conditions required to form effective SLIPS and their fabrication methods. There are two major criteria to achieve stable SLIPS: 1. lubricant spreading on the substrate, characterized by the spreading parameter (S) and 2. stabilization by van der Waals forces, characterized by the disjoining pressure or corresponding Hamaker constant (A). The fabrication of SLIPS involves structural treatments on substrates that are followed by chemical functionalization and the final lubrication selection. Based on the substrate structure, SLIPS can be categorized into 1D-SLIPS, 2D-SLIPS, and 3D-SLIPS based on the structural hierarchies varying from one-dimensional mono-molecule layers to two-dimensional micro- / nano-surface structures to three-dimensional crosslinked polymer matrices, respectively. In section 2, we summarize the dynamic behaviors of droplet impacts on SLIPS, including deposition, complete rebound, partial rebound, jet, and splash behaviors under conditions with different Weber numbers or other related dimensionless numbers. As the Weber number increases, the dynamic behaviors of droplets impacting SLIPS transitions from deposition to rebound and eventually to splash. The higher Weber number of a droplet indicates higher inertia before impacting the surface, which introduces stronger inertial forces to overcome the capillarity of the droplet. Eventually, these properties force the droplet to splash into smaller drops. Compared with many solid surfaces, SLIPS demonstrate a higher probability of droplet rebound, resulting in their advantages in the applications of anti-icing and anti-frosting. In section 3, we analyze the spreading dynamics, retraction dynamics, and contact time of SLIPS. In general, the droplet impacting on SLIPS experiences spreading and retraction processes. During the spreading process, the diameter of the droplet in contact with the surface gradually increases until the droplet spreading diameter reaches its maximum, driven by inertial forces. Subsequently, the droplet enters the retraction process under capillary and viscous resistant forces. The maximum spreading diameter can be scaled as β_max ~ We^1/4 in most conditions. Moreover, the retraction dynamics dominated by viscous forces are affected significantly by the lubricant viscosity. With the increase of the contact angle and the decrease of the lubricant viscosity, the retraction velocity tends to be higher. Further, the contact time is mainly affected by the diameter of the droplet and the lubricant viscosity but is independent of the droplet impact velocity. Compared with superhydrophobic surfaces, the contact time on SLIPS is generally longer owing to viscous retention. In section 4, the different application potentials of SLIPS are systematically summarized. The stability and self-healing of SLIPS are advantageous for the applications, including anti-icing, anti-fouling, fog harvesting, and electricity generators. These applications with SLIPS may revolutionize the modern biomedical devices, solar panels, wind turbines, and small-scale energy generators. Finally, the dynamic characteristics of droplets impacting the SLIPS and the research direction are summarized and prospected. This review provides a comprehensive understanding of the key physical principles underlying the phenomena of droplet impacts on SLIPS as well as further application conditions of SLIPS in energy industries, including industrial anti-icing, defrosting, surface-enhanced heat transfer, and electricity generation from droplets.

Continuous-fiber-reinforced resin-based composite materials represent a novel class of high-performance composites that have gained traction in recent years. The use of additive manufacturing technology for fabricating these composite materials offers significant advantages, including enhanced manufacturing flexibility and high forming efficiency, thereby making it a key research focus. Herein, the characteristics of both resin matrix and fiber materials are summarized, followed by an examination of the extrusion and impregnation processes involved in the additive manufacturing of continuous fiber-reinforced resin-based composites. Furthermore, the impact of process parameters such as temperature, printing speed, and printing spacing on the material are discussed. Additionally, the microstructure at the fiber-matrix interface and between layers are discussed, in addition to the mechanical properties of the material, including tensile and bending strengths. Finally, the challenges associated with increasing demand and performance limitations in the additive manufacturing of these composites are highlighted, proposing recommendations for their development, such as enhancing material recyclability and optimizing the additive manufacturing process. Both thermoplastic and thermosetting resins typically serve as matrix materials. Thermoplastic materials, exhibiting relatively low melting temperatures, facilitate processing in additive manufacturing. However, the high viscosity of these materials contributes to the low impregnation between fibers and resin, resulting in relatively lower mechanical properties than those of continuous fiber-reinforced composite materials produced via conventional methods. Conversely, thermosetting materials exhibit low viscosity, thereby enhancing fiber impregnation. However, they present challenges in the formation of composite materials, thereby increasing production costs. Additionally, additive manufacturing of thermosetting composite materials generates waste, contributing to material loss. Therefore, investigating the recyclability of these materials remains a crucial area for future research. The additive manufacturing process for continuous fiber-reinforced composite materials is influenced by factors such as fiber impregnation, material extrusion, fiber volume fraction, fiber orientation, and processing temperature, all of which influence material formation. However, significant challenges persist in additive manufacturing, and further improvements in the manufacturing process are essential. Research indicates that compared with composite materials produced via conventional processes, those fabricated via additive manufacturing exhibit lower mechanical properties. The primary factors influencing the mechanical properties of the final material include the bonding between the fiber-matrix interfaces as well as between layers. Inadequate bonding between the materials results in pore formation, causing stress concentration within the material and reducing its mechanical properties, thereby accelerating material failure. To further enhance the performance of fiber-reinforced composite materials and address existing limitations, future research must prioritize the following aspects. First, different matrix materials exhibit distinct effects on the performance of composite materials. Selecting an appropriate matrix material is crucial, necessitating further research into novel resin matrix materials. Additionally, as the use of composite materials increases, their recyclability has become as a critical constraint for industrial applications. Therefore, future research on material recyclability must be prioritized. Second, in the context of additive manufacturing of composite materials, in addition to the inherent properties of the materials, multiple avenues for process improvement exist. The impregnation process can be optimized via auxiliary techniques, such as plasma and oxidation treatments. Furthermore, controlling process parameters such as printing speed, temperature, and environmental conditions is essential for ensuring consistent material properties. Further investigation into the influence of these parameters on the material properties is necessary. Third, defects such as low interface performance and porosity in composite materials are typically attributed to insufficient compaction during the manufacturing process. Improving the compaction process or performing post-processing on the material can significantly enhance the performance of additive manufacturing.

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.

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 automotive part, mold, machine tool, medical equipment, and aerospace industries are involved in the cutting of difficult-to-machine materials. The cutting process is subjected to a strong coupling of force and heat, and a hard coating on the surface of the cutting tool can reduce the cutting force and heat generated during the cutting process. With the continuous development of the high-end manufacturing industry in China, cutting tools will be affected by the lack of toughness of the hard coatings, which could lead to premature damage and even catastrophic fractures in the machining processes of critical components. In recent years, inspired by biomaterials, researchers have devoted themselves to overcome the limitations of mechanical properties, such as the hardness and toughness of conventional materials, and endowing them with special functions through the design of gradient structures. Therefore, this paper summarizes several typical gradient hard tool coatings. The current research status and prospects of gradient hard tool coatings are systematically outlined to provide a reference for the development of high-performance tool coatings. First, the properties of hard coatings and their preparation techniques are introduced. Hard coating materials, such as transition metal nitride coatings, are widely used in machining and forming tool industries owing to their excellent properties, including their outstanding hardness, wear resistance, thermal stability, and corrosion resistance. To meet the growing industrial demands, hard coating preparation technologies have evolved from single and conventional coating preparation technologies to diverse composite technologies. Next, the advantages of the gradient hard coatings are analyzed in terms of the gradient design of the elemental composition, deposition parameters, and gradient design of multilayer structures. Gradient structure design can enable the coating to exhibit one or more unique properties and thereby improve the working efficiency and service life of the coated parts. In terms of composition design and structure optimization, the elemental composition gradient structure can effectively solve the problem of sudden changes in the internal properties of the coating and enhance the matching between the coating and the substrate as well as that between the coatings to thereby reduce the internal stress of the coating and inhibit the generation and expansion of cracks. Compared with the elemental composition gradient coating, the multilayer gradient structure can combine the advantages of the multilayer and gradient structures to improve the comprehensive performance of the coating. Moreover, the multilayer gradient structure is easier to realize. Subsequently, the comprehensive performance of the gradient hard coatings was evaluated in terms of microstructure, static performance, and in-service performance. Owing to the wide variety of materials, structures, preparation processes, and technologies used for gradient hard coatings, analyses of the microstructures and properties of gradient coatings can help select appropriate coatings and preparation processes according to specific application scenarios. The static properties mainly include the hardness, bond strength, and thermal stability of the coating, whereas the service properties focus on the wear resistance of the coating, that is, the machining wear of the coating during the actual cutting process. In terms of the performance evaluation of gradient hard tool coatings, the mechanical properties of the coatings are currently primarily analyzed via experimental intuition. Fast and efficient performance evaluations of coatings via experiments combined with simulation calculations or machine learning methods remains a challenge. Finally, the current state of research and future directions for gradient hard coatings are summarized. Computational simulations and data-driven approaches accelerate and simplify material design and discovery processes. Because both material composition and structure affect their properties, in many cases, the structure and composition of gradient coatings and their properties are complex nonlinear relationships that are difficult to represent via experimental experience or theoretical models. In contrast, machine learning can be used to predict the coating properties as well as the design and optimization of gradient structures by constructing models for the interconnections between the composition and structure to inform the design and optimization of gradient structures. This study focuses on the gradient design of hard tool coatings and their performance evaluation to provide a theoretical understanding of the gradient design and performance evaluation of hard tool coatings.

Amorphous carbon film, which mainly comprises a network of sp³ and sp² carbon atoms, has been widely used in many fields because of its excellent mechanical and tribological properties, corrosion resistance, chemical inertness, and superb biocompatibility. Amorphous carbon nitride (CN_x) coating has been demonstrated to be a promising lubricating material because of its excellent tribological performance, such as low friction and high wear resistance, during sliding in inert gas environments. However, the deeper mechanism of superlubricity under inert environments remains unclear, which severely limits its industrial application. Previous studies mainly focused on the formation of the sp²-rich carbon tribo-layer on the mating surface and ignored the physical and chemical changes during the sliding process. The high power pulse magnetron sputtering (HiPIMS) technology developed in recent years can effectively improve the ionization rate of the plasma and produce high density, uniform thickness, smooth-surface, and high-adhesion films. Thus, in this study, HiPIMS was used to deposit four kinds of CN_x films. The nitrogen gas flow rates were controlled to deposit different amounts of nitrogen content on the films to obtain CN_x-0, CN_x-50, CN_x-80, CN_x-160, respectively, which allowed exploration of the effect of nitrogen content on the microstructure, mechanical structure and tribological properties of CN_x films. The morphology of the films showed small roughness (Ra ~4.80 nm, CN_x-50, for example) in scanning electron microscopy (SEM) and atomic force microscopy (AFM). In Raman shifts, the sp²-C concentration of CN_x films increased from CN_x-0 to CN_x-80, then suddenly decreased, at a nitrogen gas flow rate of 0.16 L / min. The X-ray photoelectron spectroscopy (XPS) measurements confirmed that the nitrogen concentration gradually increased from 8.99% to 12.37% with the raising of the nitrogen flow rate from 0.05 to 0.16 L / min. In addition to component analysis, the fitted XPS spectra exhibited bond evolution according to different binding energies. The proportion of sp²-C component in the CN_x films increased from 45.99% at 0 L / min to 58.28% at 0.08 L / min and then suddenly decreased to 48.62% at 0.16 L / min, which is consistent with the results of Raman shifts and confirmed by the N1s spectra. In terms of mechanical properties, the nanoindentation test generated a series of complex results. The introduction of nitrogen increased film hardness, and the elastic module first increased from 0 L / min to 0.08 L / min, and then decreased at 0.16 L / min. However, the adhesion of CN_x films decreased at 0.05 L / min and then increased from 0.08 to 0.16 L / min. All the deposited CN_x films had a high degree of graphitization, and they all performed well in the nitrogen gas environment after pre-sliding. Although the effect of the running-in process on friction behavior has not been investigated so far, its effect on reducing wear rates and friction coefficients was verified by our experiments. By introducing 1100 cycles of pre-sliding in relative ambient humidity (RH ~50%), a minimum wear rate (0.60×10^-7 mm³·N^-1·m^-1) was obtained for the CN_x-80 film, and superlubricity (coefficient of friction (COF) < 0.01) was observed for CN_x-50 film for about 40 mins. Optical microscope, focused ion beam high-resolution transmission electron microscopy (FIB-HRTEM), and three-dimensional time-of-flight secondary ion mass spectrometry (3D TOF-SIMS) were used to provide reliable, visual, and direct contact area images of the sliding interface for the analysis of tribological chemistry during the friction test, which showed that the origin of low frictional performance in a nitrogen gas environment is mainly attributed to the termination of the interface by hydrophilic groups such as -OH, -COOH, and -H and the formation of an sp²-rich carbon nitride network tribo-layer on both the mating and top surfaces of the CN_x film. The reconstructed film surface after sliding and the synergy of tribochemical reactions promoted superlubricity. This approach offers a new method for reducing COF and wear of amorphous carbon films and provides a reference for the tribological behavior of carbon nitride films with different nitrogen content.

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.

Numerical simulations are powerful tools for analyzing the rolling process of metal composite plates. However, the current numerical models for simulating the cold-rolling compounding of dissimilar metal-layered plates mostly adopt either interface binding or friction constraints. These approaches fail to accurately judge and simulate dynamic compounding at the interface, making it difficult to achieve precise predictions of the true stress-strain field, macroscopic warping, and thickness ratio of composite plates. Additionally, simulations involving high reduction rates in a single pass often suffer from severe mesh distortion and nonconvergence issues, hindering the integrated development of simulations in the field of rolling compounding. In this paper, we propose a novel numerical model to overcome these limitations. The finite element modeling of the Cu/Al plates in this model employs elongated meshes with an aspect ratio of at least 2. This improvement addresses the shortcomings of previous compounding criteria, which only considered normal forces, by incorporating tangential force constraints. This enhancement allows for a more accurate representation of the actual rolling compounding process, which involves the combined action of normal and tangential forces. The research objectives of this study are multifaceted. First, we aim to develop a robust numerical model that can accurately simulate the rolling compounding process of dissimilar metal-layered plates. Second, we seek to predict the quality of the composite metal plates in terms of their stress-strain field, warping degree, and post-rolling thickness ratio. The study's methodology involves several key steps. Initially, we developed a finite element model using elongated meshes with aspect ratios of at least 2. This choice of mesh design helps reduce mesh distortion and improves the convergence of the simulations. We then incorporated tangential force constraints into the model to address the limitations of previous models that only considered normal forces. This dual consideration of normal and tangential forces allows for a more realistic simulation of the rolling compounding process. The model's performance was evaluated through a series of simulations involving Cu/Al plates with various thickness ratios (2:4, 3:3, and 4:2) and reduction rates ranging from 40% to 60%. The simulation results were analyzed to assess the accuracy of the model in predicting the stress-strain field, degree of warping, and post-rolling thickness ratio of the composite plates. One of the key innovations of this model is its ability to mitigate severe mesh distortion and non-convergence issues that plague high-reduction-rate simulations. Using elongated meshes and incorporating tangential force constraints, the model provides a more realistic simulation of the rolling compounding process. This allows for more accurate predictions of the stress-strain field, warping degree, and post-rolling thickness ratio of the composite plate. The simulation results demonstrated that the proposed model can effectively simulate the rolling compounding process of Cu/Al plates with various thickness ratios and reduction rates. The predictions of the warping degree and post-rolling thickness ratio of the model were accurate, with errors within acceptable limits. Specifically, the error in predicting the degree of warping was less than 7.40%, and the error in predicting the post-rolling thickness ratio was generally less than 10%. This shows that the model can be used to predict the mass of the composite metal plates and has the potential to explore the internal mechanism of the rolling composite. In conclusion, the proposed numerical model addresses the limitations of existing models by incorporating elongated meshes and tangential force constraints. This allows for more accurate simulations of the rolling compounding process, leading to better predictions of the stress-strain field, warping degree, and post-rolling thickness ratio of the composite plate. The model initially solves serious mesh distortion and calculation non-convergence problems in high-pressure rate simulations and provides a reference for the process optimization of composite metal plates.

Rolling bearing surface failure is a key factor that restricts the development of mechanical devices and their service life when facing the harsh working conditions of high speed and heavy load coupled with multiple factors. In a physical vapor deposition (PVD) hard coating-steel substrate system, the mechanical properties of the coating and substrate steel have differences, leading to the insufficiency of the bond strength of coating and substrate, and then, in the high-speed and heavy-duty conditions are prone to cracking, peeling, and ultimately premature failure. PVD technology can protect rolling parts under the rolling contact and reduce surface friction and wear with its high controllability, low deposition temperature, wide range of plateable substrate materials, good mechanical properties, and excellent tribological properties. Further, rolling bearings with the PVD coating can show a longer service life and higher reliability under the same operating conditions; however, there is a lack of systematic introduction on the factors affecting the bond strength and tribological properties of PVD coatings. This paper reviews the latest research results of PVD coatings and discusses effective approaches to improve the bond strength of PVD coatings from multiple perspectives, including coating structure, process conditions, deposition substrate, post-treatment of coatings, and elemental doping: (1) selecting the reasonable coating structure according to different substrates and coating materials; (2) selecting appropriate process parameters such as current, bias voltage, and temperature, according to different coating systems; (3) selecting appropriate coating types according to the mechanical characteristics of the substrate materials; (4) adopting appropriate post-treatment methods; (5) appropriately enhancing the surface roughness of the substrate; and (6) selecting appropriate elements for doping. According to the material properties of different substrates and coatings, different treatment methods are adopted to maximize the coating bond strength and extend the service life of rolling bearings. In addition, this paper introduces the excellent performance of high entropy alloy coating, providing a new solution for the surface protection of rolling bearings under harsh working conditions and effectively improves the rolling bearing surface wear and coating spalling and other failure problems. Further, it has a very large potential application prospects for rolling bearings under harsh working conditions. In addition, this paper introduces the excellent performance of high entropy alloy coating, which provides a new solution for the surface protection of rolling bearings under harsh working conditions and can effectively improve the rolling bearing surface wear, coating spalling, and other failure problems. It also has a very large potential application prospect for rolling bearings under harsh working conditions. In addition, this paper promotes the application of PVD coating in rolling bearings by employing element doping to enhance the comprehensive performance of PVD coating, and suggests the combination of PVD and post-treatment, surface pretreatment, and other methods to form “PVD with pre-treatment,” “PVD with post-processing,” and other composite surface treatment technologies. Thus, the early failure of rolling bearing surface coating caused by an insufficient bond strength and tribological properties can be solved. However, the research on a variety of PVD composite treatment technology remains lacking, and the research on its mechanism and treatment process is insufficient. In the future, if a standardized treatment process is formed, the PVD composite surface treatment technology can solve the early failure phenomenon of rolling bearing surface coatings because of the insufficient bond strength and tribological properties and promote the wider application of physical vapor deposition coatings in the field of bearings.

Conventional nitride coatings cannot satisfy the growing demand for surface protection. In 2004, Ye Junwei broke away from the traditional alloy design concept and creatively proposed a new material design concept for multi-principal element high-entropy alloys. Over the past 20 years, the elements chosen for high-entropy coating research have mostly been transition metals, and it has been difficult to exceed 1 000 HV. Owing to their unique composition and microstructure, high-entropy alloy nitride coatings exhibit excellent mechanical, wear, and corrosion resistance properties, thus providing prospects for the surface protection of industrial components used in harsh environments. Nano-multilayer structures, as an effective means of tailoring the microstructure and properties of conventional hard wear-resistant coatings, have been applied to the design and preparation of these coatings. In this study, self-organized nano-multilayer multi-element AlCrNbSiTiN high-entropy nitride coatings were deposited via cathodic arc ion plating. A self-organized nano-multilayer structure was achieved by optimizing the process parameters to control the spatial distribution of the plasma components. Nano-multilayer AlCrNbSiTiN / CrN coatings and single-layer CrN coatings have also been synthesized via cathodic arc ion plating. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were employed to study the crystals and microstructures of the coatings. A nanoindentation, a friction and wear tester, and an electrochemical workstation were used to investigate the hardness, friction factor, and corrosion behavior of the coatings. Scanning electron microscopy and energy-dispersive X-ray spectroscopy (EDS) were used to observe the wear and corrosion morphologies as well as the compositions of the coatings. The results showed that the CrN, AlCrNbSiTiN, and AlCrNbSiTiN / CrN coatings had face-centered cubic structures. The AlCrNbSiTiN coatings had a self-organized multilayer nanostructure with a modulation period of 12 nm, and the AlCrNbSiTiN / CrN coatings had a multilayer nanostructure with a modulation period of 24 nm. The highest hardness of the AlCrNbSiTiN coatings is 34.5 GPa, with H / E and H³ / E² values of 0.076 and 0.166, respectively. The AlCrNbSiTiN / CrN coating had the lowest friction factor of 0.389, whereas those of the CrN and AlCrNbSiTiN coatings were 0.437 and 0.514, respectively. The AlCrNbSiTiN / CrN coatings show the highest corrosion potential of -47 mV, whereas the AlCrNbSiTiN coatings have the lowest corrosion potential of -157 mV. The AlCrNbSiTiN / CrN coatings had the highest critical pitting potential of 900 mV, which was higher than the 690 mV for the CrN coatings and slightly higher than the 883 mV for the AlCrNbSiTiN coatings. The passivation width of the AlCrNbSiTiN coatings was 943 mV, which was higher than the 66 mV of the CrN (645 mV) and AlCrNbSiTiN / CrN coatings. The corrosion current density of the AlCrNbSiTiN coatings was 2.49×10^-8 A / cm², and the passivation current density was 1.41×10^-6 A / cm², which were less than the corrosion current density of the CrN coatings of 3.04×10^-8 A / cm² and passivation current density of 1.32×10^-5 A / cm². This value was also less than the corrosion current density of the AlCrNbSiTiN / CrN coatings of 5.06×10^-8 A / cm² and the passivation current density of 6.67×10^-5 A / cm². The AlCrNbSiTiN coatings exhibited the smallest pitting holes on the surface. Compared with the CrN and AlCrNbSiTiN / CrN nano-multilayer coatings, the self-organized AlCrNbSiTiN nano-multilayer coatings showed the best comprehensive performance with a hardness of 34.5 GPa, friction factor of 0.514, critical pitting potential of 883 mV, passivation width of 943 mV, and corrosion current density of 2.49×10^-8 A / cm². Based on these results, self-organized nano-multilayer high-entropy nitride coatings can be prepared using arc ion plating technology by regulating the spatial distribution of plasma components. Self-organized nano-multilayer high-entropy nitride coatings exhibit superior mechanical, frictional, and corrosion resistance. This study provides a new approach for preparing nano-multilayer multi-element structured coatings.

Bearing current damage is a primary cause of electromechanical equipment failure. When such damage occurs, the release of discharge energy generates localized high temperatures and leads to the ablation of the metallic materials of the bearings and deterioration in the functionality of the lubricants, which significantly affects the service lives of the bearings. In-depth research on the electrical damage mechanisms of rolling bearings under current-carrying friction is currently lacking. In ball bearings, the simultaneous presence of friction and electric current on the same surface results in electrical damage, which is influenced by their combined effects. A coupling relationship exists between rolling friction damage and electrical erosion damage, thus indicating the necessity for a comprehensive study of electrical damage in bearings that integrate both operational conditions and electrical parameters during bearing operation. In this study, 6006ZZ ball bearings were used as test samples, and a current-carrying friction wear test rig was established to simulate various operating conditions of the rolling bearings. Experiments were designed based on parameters such as the electrical breakdown frequency, rotational speed, and lubrication media, focusing on the electrical breakdown characteristics and wear properties under current-carrying friction. This investigation aimed to explore the influence of operating parameters on the electrical insulation performance of rolling bearings. After the experiments, scanning electron microscopy (SEM) was employed to observe the micro-morphology of the bearing raceway surface. Additionally, energy dispersive spectroscopy (EDS) was used to analyze the elemental composition and distribution on the surface after testing, thus providing further insights into the characteristics and mechanisms of electrical damage associated with current-carrying friction. The results showed that the critical breakdown voltage of the ball bearings decreased with an increase in the number of breakdowns but increased with higher rotational speeds. Under the operating conditions of 400 r / min and ISO VG32 oil lubrication, the critical breakdown voltages in the three consecutive current breakdown tests were 1.066, 1.006, and 0.954 V, showing a decreasing trend. When the rotational speed increased from 200 to 800 r / min, the critical breakdown voltage of the bearing increased from 0.706 to 1.083 V, and the system resistance after breakdown increased from 0.44 to 0.51 Ω. The breakdown voltage was related to the viscosity of the lubricating medium. Under grease-lubricated conditions, the bearing was more likely to form a stable lubricating oil film at low speeds, which significantly increased the breakdown voltage at the same speed. Compared with lubricating oil, ball bearings lubricated with grease exhibited significant increases in critical breakdown voltages of 42.3%, 13.1%, and 12.8% at rotational speeds of 200, 400, and 800 r / min, respectively. Current breakdown is a necessary condition for the formation of electrical damage on the surface of bearing raceways. Without breakdown and under pure mechanical rolling friction, the surface damage of the bearing raceways was mainly characterized by scuff marks and abrasive wear. However, after the breakdown, dense, small-arc high-temperature ablation pits appeared on the surfaces of the bearing raceways, and the pit density increased with the applied voltage. Through experimental investigations, this study elucidated the influence of operating parameters on the electrical insulation performance of rolling bearings. Additionally, this study delves into the characteristics of the electrical damage induced by current-carrying friction and conducts a thorough analysis of the mechanisms underlying current-induced damage in bearings. The research findings provide valuable guidance for the safe operation of ball bearings under current-carrying conditions and for the further exploration of protective measures against electrical damage in bearings.