Continuous SiC fibers reinforced SiC ceramic matrix composites have wide applications in the aerospace and nuclear fields owing to their excellent high-temperature resistance, good oxidation resistance and mechanical properties. The precursor-derived method has been the most important method for preparing continuous SiC fibers. The introduction of specific hetero elements could effectively improve properties of SiC fibers. Based on the research work on precursor-derived SiC fibers of high performance carried out by our group in the past forty years, this review firstly summarizes the addition methods of hetero elements, mainly including physical blending or chemical modification methods; The role and mechanism of hetero elements have been elucidated from several aspects: increasing the ceramic yield of the precursor, facilitating densification during sintering of the precursor-derived SiC fibers, improving high-temperature resistance of the final SiC fibers, and generating functions of SiC fibers; The composition, microstructure, properties, and developmental status of SiC fibers containing hetero elements, such as Ti, Al, Zr, Fe, B, as well as refractory metals (Hf, Ta, Nb), have been introduced. Furthermore, future research in the development of precursor systems, quantitative study of the relationship between the types and contents of hetero elements and properties of derived fibers, as well as engineering applications of the precursor-derived SiC fibers, has been prospected.

TCGH(TC4+GH4169)composite material was prepared by selective laser melting(SLM). The optimum forming process parameters of TCGH composite material were investigated, and the microstructure and mechanical properties of as-deposited samples and heat-treated samples were studied. The results show that the optimum process parameters for fabrication of TCGH composite material are scanning speed of 900 mm/s with laser power of 150 W, and density higher than 99.5%. The addition of GH4169 powder changes the solid phase transformation behavior of TC4 titanium alloy material, and the as-deposited structure shows obvious high temperature solidification characteristics, which makes the forming characteristics of progressive scanning overlap and layer-by-layer scanning accumulation obvious. The original coarse columnar β grain size along the printing direction is significantly reduced, and the tensile strength of the composite is improved. Compared with the as-deposited sample, the microstructure of the heat-treated sample is transformed into a near-equiaxed structure. At the same time, with the increase of heat treatment temperature, the dissolution of the second phase leads to the dominant solid solution strengthening effect of the composite material, which improves the tensile strength and plasticity of the composite material.

Nickel-based superalloys have attracted significant attention due to their outstanding high-temperature strength, corrosion resistance, and oxidation resistance, and are widely used in aerospace and other fields. This article provides a comprehensive review of the preparation methods, common grades, and microstructure and properties of additive manufactured nickel-based superalloys, summarizes the current issues, and proposes future areas for exploration. Nickel-based superalloys prepared by metal additive manufacturing technology have excellent performance, can achieve precise forming of complex components, and have minimal material waste during the manufacturing process. They are expected to become an important production process for nickel-based superalloys components in fields such as aerospace. Common methods for additive manufacturing of nickel-based superalloys include laser powder bed melting, directed energy deposition, and arc additive manufacturing. Powder bed melting is widely used for manufacturing high-precision and complex parts, but it has a relatively slow manufacturing speed and higher equipment and material costs. Directed energy deposition has higher degrees of freedom and flexibility and can be used to prepare functional gradient materials, but it has lower accuracy. Arc additive manufacturing has lower equipment and material costs and is suitable for rapid manufacturing of large parts, but the surface roughness of the alloy produced by this method is poor and requires additional processing or post-treatment. Nickel-based superalloys widely studied in the additive manufacturing process include IN625, Hastelloy X, and other solid solution strengthened alloys, as well as IN718, CM247LC, IN738LC, and other precipitation strengthened superalloys. Compared with traditional casting and forging methods, the unique layer-by-layer forming and rapid cooling and heating process of additive manufacturing result in a coarse columnar grain structure and a unique microstructure with a large number of fine grains. It also forms unique melt pool structures and dislocation cell structures. However, the alloys obtained by additive manufacturing generally require heat treatment to control grain structure and precipitated phases, which affects the mechanical properties of the alloy. In addition, the mechanical properties of additive manufactured nickel-based superalloys are also related to specific preparation methods and alloy types. Although additive manufacturing has been widely used in the preparation of nickel-based superalloys, there are still issues such as anisotropy in microstructure and properties, high sensitivity to alloy cracking, and a lack of corresponding specifications and standards. In the future, further exploration is needed in areas such as heat treatment, customization and development of specialized alloys, investigation of the process-structure-function relationship, and computational modeling.

TiB was planted into the matrix titanium alloy through the rapid solidification process, and the new ultrafine network reinforced titanium matrix composites (TMCs) powder was formed. Based on the laser additive manufacturing technology, a new titanium matrix composite with alternate distribution of equiaxed network and columnar network structure were creatively fabricated, the formation mechanism of the network structure was systematically discussed, and the mechanical properties of the super-solidified TMCs by additive manufacturing were tested. The results indicate that the network structure (about 9 μm) of the additively manufactured TiB/Ti composites is mainly composed of in-situ nano-TiB whiskers, presenting two crystal structures of B₂₇ and B_f. The direct introduction of B element is easy to form constitutional supercooling at the solidification interface. The equiaxed α phases are obtained by promoting the alternating formation of equiaxed/columnar network structure and refining the grain size. In addition, the formed nano-TiB network structure, not only inhibits the crack deflection and passivate cracks, but also confines the large number of slip lines inside the TiB network structure via in-situ observation, inducing high-density dislocations at the grain boundaries, which limites its plastic deformation, and greatly improves the strength of the composites. The additively manufactured TiB/Ti composites increases the tensile strength by 42%, and maintains the elongation of about 10%.

The development of nuclear reactor structural materials with excellent comprehensive performance is the basis of nuclear energy development, and it is one of the difficulties that have long restricted the promotion of nuclear energy. Multiprincipal element alloys(MEAs) have been recognized as candidate materials for advanced reactor structural materials due to their good irradiation resistance and mechanical properties, which has expanded a broad space for the design of new radiation-resistant materials. In recent years, the research on the irradiation damage of multiprincipal element alloys has tried to reveal the influence of some factors and characteristics of multiprincipal element alloys on the formation and evolution of defects in the irradiation process. For example, the type, number and concentration of alloying elements, lattice distortion, chemical short range order, etc. Although some existing research results show that the above factors can improve the resistance of multiprincipal element alloys to irradiation damage, under different irradiation conditions, the influence mechanism of the above factors on the formation and evolution of defects in multiprincipal element alloys is quite different, and it is difficult to draw generalization conclusions. Focusing on the four aspects of irradiation swelling, helium bubble formation, irradiation-induced element segregation and phase transition, irradiation hardening of FCC and BCC systems.The research progress of multiprincipal element alloys in irradiation damage in recent years was reviewed, the mechanism of action of multiprincipal element alloys to improve radiation resistance was summarized.And based on this, the future research directions for multiprincipal element alloys used in nuclear power structures were prospected, including tuning short-range order, high-entropy ceramics, additive manufacturing technology, accelerating development of new materials by integrating high-throughput computing with machine learning, etc. Finally, it is pointed out that new radiation-resistance MEAs must be designed based on the actual environment of material service from the perspective of composition design.

The pollution of heavy metal ions in wastewater has caused serious harm to human health, and the adsorption method has attracted much attention because of its high efficiency, economy, simplicity, and good selectivity. SiO₂ aerogel is a potential adsorbent for removal of heavy metal ions in wastewater due to its high specific surface area (>500 m²/g), high porosity (>80%), controllable surface group and good physical/chemical stability. Herein, the preparation methods of SiO₂ aerogel and its effect on microstructure were briefly introduced, focusing on the functionalization methods of SiO₂ aerogel and the adsorption performance and factors of functionalized SiO₂ aerogel for the adsorption of heavy metal ions in wastewater, and the adsorption mechanism and adsorption kinetics process of functionalized SiO₂ aerogel as heavy metal ions adsorbent were analyzed. It was pointed out that the controllable preparation with low cost and short process, effective functionalization and efficient adsorption of various heavy metal ions are the future development directions of SiO₂ aerogels as absorbent.

Continuous fiber reinforced and toughened ceramic matrix composites (CMCs) are key thermal structural materials in aerospace and other fields. Mechanical connectivity, as one of the most reliable connectivity methods, is an essential method to achieve connectivity of large and complex CMCs components. At present, research on CMCs joints is rapidly developing, but there is few comprehensive review literature on CMCs joints. Based on the research work in the field of CMCs joints in recent years, the preparation and mechanical property characterization methods of CMCs fasteners were summarized in this paper, the damage and failure mechanism of CMCs fasteners were systematically stored and discussed, and focusing on the influencing factors and laws of mechanical properties of CMCs fasteners from the perspective of material properties and external environment. The research work on CMCs mechanical joints was presented, and the damage law, failure mechanism, finite element simulation and reliability of CMCs connectors were prospected.

Advanced polymeric composites (APC) are important structural materials for realizing the lightweight of aerospace vehicles. However, unfavorable factors such as low manufacturing efficiency, high cost, and serious energy consumption hinder the further expansion of APC applications. Resistance implant welding (RIW) technology has the advantages of simple equipment, high welding efficiency, energy saving and environmental protection, and is suitable for the connection of large structural parts with curved surface. It can replace the traditional bonding process and promote APC structural parts to realize green manufacturing, re-manufacturing and recycling. The research progress of APC resistance implant welding process and its application technology were presented in this paper. The challenges faced by APC resistance implant welding technology were introduced. The research status of thermoplastic composite RIW, process parameter optimization for welding pressure and welding time, implant types, thermosetting composite RIW and the application technology of RIW in the manufacturing of large APC structural parts were summarized systematically. The existing problems of APC resistance implant welding were pointed out, which relate to material design, process optimization and fixture manufacturing. In the future, the research on RIW technology of TPC structure is expected to focus on the development of higher strength welding binder, the design of HE with new structure and the improvement of interface bonding strength between binder and HE to improve the bearing capacity of joints. The research on mechanical constitutive model, fatigue strength and service life of RIW joints will be strengthened; the research on welding equipment and fixtures for specific APC components will be carried out to promote RIW engineering to fill the gaps in this area in China.

MXenes are a new type of two-dimensional layered transition metal carbides and nitrides prepared by selective etching of MAX phase materials. Due to their excellent physical, electronic and chemical properties, MXenes have been widely used in electromagnetic shielding, biomedicine, energy storage, sensors, water purification and other fields. At the same time, MXenes and their composites can effectively improve the catalytic efficiency of noble metal catalysts or directly serve as a class of non-precious metal catalysts due to their large specific surface area, excellent electrical conductivity and stability, and are regarded as a promising class of fuel cells electrocatalysts or supports. The structure, properties and preparation methods of MXenes were introduced in this paper, and the latest application research results of MXenes and their composites in the fields of oxygen reduction, formic acid oxidation, methanol oxidation and ethanol oxidation reactions were overviewed, and the main problems existing in MXenes materials were pointed out (for example, it is difficult to preparing uniformly dispersed multi-layer MXenes flakes or few or even single-layer MXenes flakes, which are easy to re-stack due to higher surface energy, etc.), preparing more new MXenes and composite them with various materials were put forward, in order to promote the application of MXenes and their composites in the field of fuel cells.

Stress corrosion cracking (SCC), as an important research direction in the interdisciplinary of material mechanics and corrosion electrochemistry, is one of the main failure modes of stainless steel components. Compared with traditional wrought technology, additive manufacturing (AM) 316L stainless steel has complicated microstructure and inherent defects including pores and lack of fusion places (LOF) caused by additive manufacturing process, resulting in more complex SCC behavior. Herein, the basic SCC behavior of 316L stainless steel was discussed in detail on the basis of the researches of AM316L stainless steel at home and abroad. The main contents include two stress corrosion mechanisms of hydrogen induced cracking and anodic dissolution. Two behavior of transgranular cracking and intergranular cracking were described. The effects of microstructure on SCC behavior of AM316L, including twins, different crystal interface, pores, LOF, and element segregation were summarized. The current situation and advantages of three in-situ characterization methods, including electrochemical noise, high-resolution neutron diffraction and three-dimensional morphology characterization were introduced, which are of great significance to explore the SCC behavior of AM316L. Finally, the prospective future of the research directions of SCC behavior of additive manufacturing stainless steel were proposed, including the research of SCC characteristics under high temperature irradiation environment and the principle of stress distribution and restructuration at crack tips.

In recent years, the global environmental problems caused by excessive emissions of carbon dioxide(CO₂) have become severe gradually, which attract widespread concern all over the world. The electrochemical reduction of CO₂ to clean energy and high-value chemicals not only can effectively alleviate greenhouse effect, but also provide an alternative to solve the energy crisis. The reaction principle of electrochemical reduction of CO₂ was briefly described in this review, and some binary metal catalysts with high product selectivity reported in recent years were classified and summarized. The influences of the bimetallic materials physico-chemical properties, including element and composite, atomic ratio, microscopic morphology, particle size, etc. on CO₂ reduction performance were reviewed, and the explanation of high selectivity for partial typical catalysts derived from DFT calculation was presented. Finally, the main problems and future research challenges for the selective conversion of CO₂ on bimetallic catalysts with high efficiency were also discussed.

High-entropy alloys have attracted great attention in various fields due to their high-entropy effect, severe lattice distortion, slow diffusion and special and excellent material performance due to the combination of various alloying elements in equal or near-equal molar proportions. Its high strength and hardness, fatigue resistance, excellent corrosion resistance, radiation resistance, near-zero thermal expansion coefficient, catalytic response, thermoelectric response and photoelectric conversion make high-entropy alloys have potential applications in many aspects. High-throughput computation and machine learning technology have rapidly become powerful tools to explore the huge composition space of high-entropy alloys and comprehensively predict material properties. The basic concepts of high-throughput computing and machine learning were introduced in this paper as well as the advantages of first-principles calculation, thermodynamic/kinetic calculation and machine learning in the research of high-entropy alloys. The application research status of high-entropy alloy composition screening, phase and microstructure calculations and performance prediction were summarized. In the final part, the existing problems, and the solutions and future prospects of this field were summarized, including developing tools for first-principles calculations and machine learning of high-entropy alloys, building high-quality databases for high-entropy alloys and integrating high-throughput computing with machine learning to globally optimize the mechanical property and service performance of high-entropy alloys.

MXene has a wide application prospect in energy storage, electromagnetic interference shielding, catalysis, medicine and other fields due to its unique layered structure, high electronic conductivity and rich surface chemical properties.Ti₃C₂T_x, as the earliest discovered MXene material, has the possibility to achieve both high energy density and power density in the field of sodium ion batteries because of its inherent metal conductive characteristics, wide layer spacing and abundant surface functional groups, which is attracted by many researchers. Based on this, the research progress of Ti₃C₂T_x based materials in sodium ion batteries in recent years was reviewed in this paper. Firstly, the structure and electrochemical properties of Ti₃C₂T_x materials with multi-layer and few-layer were summarized by introducing the preparation of Ti₃C₂T_x. Then, combined with the application trend of the study, the influences of layer spacing modification, doping modification and morphology regulation on the sodium storage behavior of the two kinds of Ti₃C₂T_x materials were summarized. The structural design ideas of the two kinds of Ti₃C₂T_x based composites applied to the anode of the sodium ion battery were also analyzed. It was pointed out that the reasonable structural design is vital to the battery performance. Finally, some suggestions for the problems and challenges faced by Ti₃C₂T_x based composites in the field of sodium ion batteries were given.

Interface is a key factor affecting the comprehensive performance of magnesium matrix composites, and how to carry out interfacial modulation has been a hot research topic in magnesium matrix composites. Focusing on three types of interface structures of magnesium matrix composites (coherent, semi-coherent and incoherent) and two key issues (interfacial wettability and interfacial reaction) affecting the interface properties, the research progress of interface optimization schemes was reviewed in this paper and the guidelines for the design and regulation of interfacial structures to achieve good interfacial bonding were proposed: good wettability and slight interfacial reaction. In view of the improvement of interface properties of magnesium matrix composites, the addition of rare earth elements can be considered in the future to purify the interface and improve wettability. The matrix and reinforcement are selected according to engineering needs to obtain composite materials with excellent performance in certain aspects. New reinforcement surface coatings will be developed to fully enhance the capabilities of interfacial bonding. First-principles and other computational simulation methods will be used to deeply explore the relationship between interface structure and interface performance.

Recently, with the development of research techniques, researchers have discovered numerous new phenomena in nanowires with potential applications. Clearly depicting the structure-activity relationship between nanowire structure and mechanical properties has important guiding significance for the design, service and performance optimization of nanodevices. Firstly, several typical in-situ testing methods of mechanical properties of nanowires were summarized. Secondly, the mechanical properties such as elasticity and strength of various nanowires in tensile tests were introduced. The size-dependent plastic deformation of nanowires was described. In addition, the unique mechanical behavior of nanomaterials in the in-situ tests was discussed. In the future, it is necessary to systematically study the effect of electron beam irradiation on the deformation behavior of nanowires during in situ electron microscopy characterization and to investigate the mechanical properties exhibited by nanowires under complex external field environments. Thus, a complete set of theoretical guidance systems can be established, which is an important development direction in the field of in situ characterization of nanomaterial properties.

Porous tantalum metal has good biocompatibility and osteoconductivity, with a lower modulus of elasticity and a higher coefficient of friction to avoid stress-shielding compared with traditional implant metal materials. In addition, its porous structure, similar to that of human cancellous bone. Porous tantalum has received increasing attention in recent years due to its advantages in mechanical properties and excellent biological properties, and has been developed and applied in the treatment of various bone defects. With the progress of the preparation methods of porous tantalum materials and the proposal of various modification methods, the prosperity of porous tantalum in clinical applications has been further demonstrated. In this paper, the application of porous tantalum implant in bone defects treatment was reviewed, considering its preparation technology, cytotoxicity, osseointegration properties, and current clinical applications. Furthermore, the developments of porous tantalum including surface modification for establishing composite systems, optimization of preparation processes and personalized preparation techniques are expected to facilitate the clinical application of porous tantalum implants in the treatment of bone defects.

In recent years, carbon-ceramic matrix composite materials have become a hot topic due to their high temperature resistance, low density, good corrosion resistance, low thermal expansion coefficient, and strong performance design. Biomorphic carbon-ceramic composites have been prepared by introducing the wood-derived pore structure into ceramic matrix.The pore structure, preparation process, properties and application prospects of biomorphic carbon-ceramic matrix composites were reviewed. The importance of designing the microstructure of materials was emphasized, and the key technology in the preparation process of carbon-ceramic matrix composites-infiltration technology were specified, including: chemical vapor infiltration, melt infiltration, sol-gel infiltration, slurry infiltration, polymer precursor infiltration, and molten salt infiltration. The solutions to the existing problems of each technology were proposed. Composite strength and fracture strength of biomass carbon-ceramic matrix composites were reviewed. Suggestions for future research directions on the performance were put forward. It was pointed out that the mechanical properties of materials should be tested under high temperature, strong acid and strong alkali, and alternating cold and heat environments. The potential applications of biomorphic carbon-ceramic matrix composites were discussed in three aspects, including aero-engine blades, automobile exhaust gas purifiers, and catalyst carriers. Existing challenges and practical limitations such as complex molding, strong mechanical properties and thermal stability were outlined. Finally, the improvement of the preparation process and the study of mechanical properties of biomorphic carbon-ceramic matrix composites were prospected, which provides theoretical basis and guidance for the development and application of biomorphic carbon-ceramic matrix composites.

With the rapid development of the new energy automotive industry, consumers' requirements for the range of electric vehicles have been increasing. The Ni-rich ternary lithium-ion battery has become the most promising power battery in electric vehicles due to its high specific energy, but the battery system still faces the problem of poor performance at low temperature.The research progress on low temperature performance of Ni-rich ternary power battery in recent years was summarized in this review. The influence factors on the low temperature performance of Ni-rich ternary power battery were summarized emphatically. On the one hand, the effects of low temperature performance from thermodynamics were analyzed, including the structural change of the Ni-rich ternary cathode materials and graphite anode materials, electrolytic phase transformation and solvation structure changes, and glass transition of binder. On the other hand, rate controlling step in the low temperature discharge process in the Ni-rich ternary lithium-ion battery was summed up. According to this, main modification measures of low-temperature performance in Ni-rich ternary power battery were summarized. Low temperature electrolyte was designed by optimizing solvents, improving lithium salts and applying new additives. In order to improve the low temperature performance of electrode materials, three methods were mainly employed: substitution, surface modification and smaller material particle size. The remaining shortcomings of the research on low-temperature performance of the battery were summarized, and the research on the low temperature thermodynamic characteristics of batteries is not clear enough. In addition, the research methods for the low temperature kinetic process of batteries are single, and the influence of the reaction sequence in batteries is insufficiently understood.

High-strength aluminum alloys (2××× and 7×××, etc.) are widely used in aerospace, automobile and other fields because of their high specific strength and good machinability. With the development of high thrust-weight ratio engine and automobile lightweight technology, the demand for lightweight structural materials is increasing. Meanwhile, parts also present the "thin-walled, hollow and composite" tendency gradually, and the traditional processing methods of high-strength aluminum alloy are increasingly difficult to meet the requirements. As a common metal additive manufacturing (AM) technology, selective laser melting (SLM) is a great potential manufacturing technology for complex parts. SLM is expected to become an emerging technology to expand the application of high-strength aluminum alloys. However, due to their poor casting and welding properties, high-strength aluminum alloys easily produce the periodic hot cracks and coarse columnar grains during SLM, leading to unsatisfactory mechanical properties. Grain refinement is the key to overcome the inherent hot-tearing crack of SLMed high-strength aluminum alloys. The research progress in microstructure and mechanical property control of SLMed high-strength aluminum alloys in recent years was reviewed. The mechanical properties of alloys with different compositions were summarized. Importantly, the main strategies to suppress hot-crack formation in SLMed high-strength aluminum alloys were highlighted, including optimization of SLM process parameters and grain refinement by microalloying or addition of nanoparticles. It was pointed out that the main issue of SLMed high-strength aluminum alloys was the change of alloy composition on the comprehensive properties and heat treatment process was still unclear. The development trends were forecasted, such as designing new high-strength aluminum alloys and evaluating their comprehensive performances, using post-treatment process and other means to further improve the comprehensive performances of the alloys, and designing special grain refiners for SLM and investigating refinement mechanism.

Melt growth ceramics (MGC) is a new type of ceramic material with microstructure obtained by melting and solidification of raw materials. The clean and high-strength bonding interface shared by atoms makes it have excellent high-temperature mechanical properties and microstructure stability close to the melting point. It shows great application potential in the field of high thrust weight ratio aero-engine and heavy gas turbine hot end components in the future. Laser directed energy deposition (LDED) technology can effectively overcome the limitations of traditional preparation methods of MGC in terms of cycle, energy consumption and structural complexity. It provides a new solution for direct additive manufacturing of MGC components, and has become a research hotspot at home and abroad. Based on the introduction of the process principle of LDED technology, the microstructure characteristics and properties of different MGCs prepared by this technology at home and abroad were summarized in this paper, and the main research on the control of microstructure and cracking behaviour was comprehensively discussed. Based on the existing research progress, the development trend and key scientific problems to be further solved in this field were discussed. It was pointed out that inhibiting cracking and improving microstructure and properties are the primary problems faced at present. The development of materials and new processes is the key to breaking through the existing bottleneck and promote the development and application of MGC-LDED.

Pure copper/copper alloy has excellent thermal and electrical conductivity, which is an important industrial material. Laser powder bed fusion, which represents the laser additive manufacturing technology, has excellent design freedom and forming accuracy, and is the mainstream development direction of additive manufacturing. Compared with traditional processing and manufacturing technology, the laser powder bed fusion of pure copper/copper alloy can give better play to the excellent performance of copper, and has broad application prospects in the fields of high thermal conductivity/electrical conductivity such as electrical and electronic, automotive, aerospace and other fields. The current research status of laser powder bed fusion of laser high-reflective materials represented by pure copper/copper alloys, the important problems they face, and the analysis of corresponding solutions were reviewed in this paper. On this basis, combined with the team's experience in the laser powder bed fusion process of pure copper/copper alloy, it was pointed out that the use of blue, green and other short-wavelength lasers for the powder bed laser fusion of pure copper/copper alloy and other highly reflective materials is a future study hot spots and development directions.

The formation mechanisms of the precursor film (PF) at high temperature were reviewed, i.e., surface diffusion mechanism, evaporation-condensation mechanism, subcutaneous infiltration mechanism, and rapid absorption then film overflow mechanism. In the experimental metallic systems, the most possible mechanism is the subcutaneous infiltration mechanism, which is related to the apparent contact angle, contact radius, height of gap between the substrate metal and oxide film. In the metal/ceramic system, the formation of precursor film is usually rapid absorption then film overflow mechanism. The appearance of PF for adsorption mechanism needs to meet the contradiction of relative inertia and high affinity at the liquid/solid interface. Meanwhile, another possible mechanism of precursor film in high temperature reactive wetting system, namely film transport mechanism, is introduced. It was pointed out that the difficulty of studying precursor film lies in the unpredictability and instability of precursor film, and its development direction should be systematic, and the corresponding theoretical model should be established.

With the rapid development of portable and wearable electronic devices, research on flexible energy storage devices has gradually shifted to the directions of miniaturization, softness and intelligence. At the same time, people have higher requirements for the energy density, power density and mechanical properties of the device. As the core part of flexible energy storage devices, electrode material is the key to determining device performance. With the development of flexible energy storage electronic devices, there is an urgent need for new battery technology and fast, low cost and precise control of their microstructure preparation methods. Therefore, the research and development of new energy storage devices such as flexible lithium/sodium-ion batteries, flexible lithium-sulfur batteries, and flexible zinc-air batteries have become the current research hotspots in academia. The current research status of flexible energy storage battery electrodes in recent years was discussed in this paper, the design of flexible electrode materials (independent flexible electrodes and flexible substrate electrodes), and the preparation process of flexible electrode materials of different dimensions (one-dimensional materials, two-dimensional materials and three-dimensional materials) and applications of flexible energy storage electrodes (flexible lithium/sodium ion batteries, flexible lithium-sulfur batteries, flexible zinc-air batteries) were compared and analyzed, and the structural characteristics and electrochemical properties of electrode materials were discussed. Finally, the current problems faced by flexible energy storage devices were pointed out, and the future focus of flexible energy storage devices was the research and development of new solid electrolytes, the rational design of device structures and the continuous optimization of packaging technology.

In recent years, the sudden rise of high entropy alloys (HEAs) has become a hot research topic in the field of metal materials. The high entropy alloy is located in the central region of phase diagram, which has broad alloy composition space and possible formation of microstructure. The synergistic regulation of composition and preparation process can obtain richer structure. Unconventional chemical structure is expected to break through the performance limit of traditional anti-wear and lubricating alloys. In this work, the classification of wear-resistant HEAs was discussed. The effects of the addition of chemically active metals, soft metals and refractory metals on the wear resistance and lubrication properties of HEAs were analyzed. The effects of non-metallic elements and ceramic phases on the tribological properties of HEAs matrix composites were summarized. The effects of heat treatment and surface engineering technology on the surface microstructure and tribological behavior of HEAs were reviewed. The design method of HEAs with anti-wear lubrication under severe working conditions was discussed. The future research and application of HEAs in the field of friction and wear were prospected. High entropy alloys have great potential to solve the bottleneck problems of traditional alloys, such as to realize stable lubrication and anti-wear under extreme working conditions and to ensure anti-wear under specific functions.

Ceramics are widely used as dental restorative materials because of their superior wear resistance, chemical stability, biocompatibility, and aesthetic features. In this paper, the chemical compositions, microstructures and mechanical properties of dental ceramics were introduced, based on the wear mechanisms of typical dental ceramics and their abrasiveness with opposing human teeth, the main progress concerning the tribological performance optimization of dental ceramics were summarized, and it was pointed out that the mismatch of tribological properties between ceramics and human teeth seriously restricts the clinical application of dental ceramics. Then the in vitro test methods of tribological properties of dental ceramic materials are analyzed and summarized from the aspects of laboratory test medium, friction pair, load, displacement and cycle times. Finally, the future development trends of dental ceramics were discussed from the perspective of bionic tribology. It was pointed out that bionic design of ceramic matrix composites is a promising strategy for overcoming the mismatch of tribological property between dental ceramic restorations and human teeth.

Solid phase additive manufacturing based on friction stir is a new technology for manufacturing of large lightweight alloy components, which has become one of the hot research topics in advanced manufacturing field at home and abroad.The research status of metal solid phase additive manufacturing technology based on friction stir and related process mechanism were analyzed and summarized. The solid phase additive manufacturing technology based on friction stir can be divided into three categories.One is friction stir additive manufacturing(FSAM), which is based on the principle of friction stir lap welding, the plates are stacked layer by layer. Another is additive friction stir deposition(AFSD) technology, which usually uses a hollow tool to conduct AFSD by additive powder or wire through the hollow.The third one is friction surfacing deposition additive manufacturing (FSD-AM) technology, which is based on the principle of friction surfacing by using a rotating consumable bar to deposit materials to form the designed components. The research and application status of solid phase additive manufacturing technology of metal materials based on friction stir were analyzed, and the characteristics, advantages and disadvantages of three kinds of solid phase additive manufacturing technology based on friction stir were compared.Finally, the future research direction of solid phase additive manufacturing technology based on friction stir was proposed, including revealing their process mechanism, integrated controlling of the formation and property of the AM components, modifying the process assisted with second energy, application of new materials and optimization with artificial intelligence, etc.

Magnesium alloy has the advantages of low density, good damping and noise reduction and good electrical conductivity. It is the lightest metal structural material in applications. However, they are easily corroded due to the low potential of magnesium alloy electrodes, which limits their wide application in industry. At present, surface coating protection technology is one of the most effective methods to improve the corrosion resistance of magnesium alloys. Graphene oxide (GO) has excellent thermal, mechanical and barrier properties, and has broad application prospects in metal protection. GO-based composite coatings can provide a good physical barrier to corrosive media and have become one of the candidate materials for anti-corrosion coatings. In this article, the solutions were proposed for the limitations of single-component GO nanosheets, such as agglomeration and poor compatibility. The preparation methods, types and corrosion protection research progress of GO composite coatings were mainly summarized and its protection mechanism was analyzed in depth. Finally, the future development trend of GO application of magnesium alloy surface corrosion protection coating were prospected. The preparation methods and types of GO composite coatings on magnesium alloys were mainly described. The research progress and corrosion protection mechanism of GO coating on magnesium alloy were summarized.

Based on different high-entropy alloys (HEAs) systems, the latest research progress in additive manufactured high-entropy alloys was reviewed. The rapid solidification microstructure, segregation and precipitation behaviors of high-entropy alloys fabricated by additive manufacturing with different compositions were described. Especially, the analysis was focused on the mechanical properties, deformation and strengthening mechanisms. It was pointed out that the appropriate additive manufacturing process should be selected for different high-entropy alloy systems, and the influencing factors of forming quality need to be further studied. Finally, it was proposed that high-entropy alloys with both excellent strength and high plasticity can be developed and prepared by additive manufacturing technology.

Solid oxide fuel cell (SOFC) is a clean and efficient energy conversion device that can directly convert chemical energy to electricity.The state-of-the-art cermet anodes face various issues such as carbon deposition, sulfur poisoning and poor redox stabilities, which limit the application of SOFC. In order to avoid the problems of the cermet anodes, the perovskite anode materials with mixed electronic-ionic conductivities have drawn considerable attention in recent years.Among them, Sr₂Fe_1.5Mo_0.5O_6-δ perovskite has good stability, high conductivity, suitable thermal expansion coefficient and excellent electrochemical performance, and thus has been widely studied, especially element doping.The element doping was discussed at A-site, B-site and O-site of Sr₂Fe_1.5Mo_0.5O_6-δ perovskite, and the effects of doping elements and doping content on crystal structure, stability, electronic conductivity, thermal expansion and electrochemical performance were summarized.These doping strategies provide some novel ideas for modifying Sr₂Fe_1.5Mo_0.5O_6-δ perovskite anode, which can also be used to modify other similar perovskite anode materials.Finally, the development direction of Sr₂Fe_1.5Mo_0.5O_6-δ and typical ceramic anode materials was prospected. On one hand, the strategies of anion doping and co-doping could be adopted to improve the performance of ceramic anode materials. On the other hand, the mechanism of element doping will be further clarified through the combination of doping strategy and theoretical calculation.

With the improvement of alloy manufacturing level and the complexity of performance requirements, high-entropy alloys (HEAs) have gradually attracted great attention.At present, the research in the field of material processing mainly focuses on brazing and surface engineering.In the field of brazing, HEAs can be used as filler material for brazing at high temperature and low temperature, the empirical parameters related to high entropy were summarized. The application of the simulation and calculation methods such as first-principle method and calculation of phase diagram were described in the field of HEAs design for filler metals development. The latest research progress of HEAs fillers for brazing of nickel-based superalloys and dissimilar ceramics-metals, as well as low temperature packaging was introduced. The influence of welding process parameters on microstructure and properties of HEAs brazing joints was also analysed.In the field of surface engineering, the application direction and preparation methods of HEAs in film/coating were discussed. The research progress in high-temperature protective coating, hard protective layer and other application directions was summarized. At the same time, the problems existing in the research and application of HEAs in the fields of brazing and surface engineering were summarized. The future trends were put forward in order to decrease the melting temperature of HEAs filler, improve high temperature mechanical properties of welds, and develop the eutectic HEAs filler/coating.

To meet the development needs of advanced aeroengines, the structure of aeroengine turbine blades is becoming increasingly complex, and the content of refractory elements is increasing in single crystal superalloys, which are the preferred materials for turbine blades. As a result, the tendency to form the grain defects increases during the preparation of single crystal turbine blades, which directly affects the quality of single crystal turbine blades. In this paper, a kind of grain defect that appears in the directional solidification process of single crystal superalloys—freckle was discussed. The research works on the formation mechanism, the criterion model and the control method of freckles formation during the directional solidification of single crystal superalloys in recent years was reviewed. The influence of the alloy composition, blade structure, directional solidification process and crystal orientation of single crystal castings on the formation of freckles was analyzed. Considering the influence of the alloying elements in different alloy systems and the parameters of the directional solidification process on the freckle formation, further studying the freckle formation mechanism of the single crystal turbine blade with complex structures, establishing an effective method for prediction and control of freckles are the future research directions.

Electromagnetic interference problems have become an increasing issue with the rapid development of wireless information technologies, which has attracted global attention. The key solution to this challenge is to develop materials that can absorb electromagnetic waves. The ideal absorbing material should be a structural material integrating load bearing, heat protection and strong absorption. The carbon-based, ceramic-based composites and their electromagnetic absorption properties in recent years were summarized in this review. The ultimate goal of these absorbers is to achieve broader effective absorption frequency bandwidth at a thin coating thickness. The synthesis methods, structures and electromagnetic wave loss mechanism of several typical and well-received composites were introduced. The superiorities, research status and main problems of absorbing materials were described. Based on these progresses, the potential development direction of absorbing materials in the future was predicted.

The MAX phase of the ternary layered compound and the recently attracted attention of the MAB phase have become the research hotspots in the field of structural ceramics for more than 20 years because of their common characteristics of ceramics and metals. The high damage tolerance and high fracture toughness are different from the essential characteristics of traditional ceramics. The overall development of MAX phase and the latest research progress of MAB phase were briefly reviewed in this article, focusing on the analysis of the effect of multi-scale layered structure on macro-mechanical behavior and its internal mechanism. Based on the results of first-principles calculations, the bond stiffness model was established and the quantitative characterization of chemical bond strength was realized, and more importantly, it was clarified that "sufficiently" weak interlayer bonding is the root cause for the extraordinary mechanical properties of ternary layered ceramics. The magnetocaloric effect (MCE) of Fe₂AlB₂ near room temperature shows the good application prospects of MAB phase compounds in the functional field. After more than 20 years of continuous research, the structure and performance of MAX-phase compounds have gradually become clear. At present, application research for specific scenarios is vigorously carried out all over the world. However, the current knowledge of MAB phase compounds is still very limited. Therefore, synthesizing and characterizing the structure, mechanical properties, physical properties, and service behaviour of existing MAB phase compounds are the important tasks at this stage. First-principles numerical simulation based on density functional theory (DFT) can play an important role, just as in understanding the extraordinary properties of MAX phase compounds and discovering new compounds.

Metamaterials have drawn extensive attention for their fine regulation of electromagnetic waves at subwavelength scales. They have abundant electromagnetic modes, and support highly confined and enhanced electromagnetic fields on the surface which are highly sensitive to the surrounding dielectric environment, so they can be used in label-free optical biosensing. Compared with traditional optical biosensors, metamaterial biosensors have many advantages, such as miniaturization, integration, high sensitivity and multi-function customization. The recent progress of metamaterial biosensors in visible light and near infrared, middle infrared, and terahertz spectrums was summarized in this paper, including refractive index biosensing, surface-enhanced Raman scattering, surface-enhanced infrared absorption, and terahertz biosensing.

NiTi-based shape memory alloys (SMAs) are one of the SMAs with most outstanding properties, and have been widely applied in aviation, space, electronics, construction, biomedicine and other fields. In recent years, the elastocaloric refrigeration based on elastocaloric effect (eCE) of NiTi alloys has attracted increasing attentions since their excellent mechanical properties, huge elastocaloric strength and good machinability. However, conventional binary NiTi alloys cannot meet the requirements of long-life service since their large superelastic stress hysteresis and poor cyclic stability of superelasticity and eCE. In this paper, the research progress of eCE for NiTi-based alloys was reviewed. The effect of doping alloying element, thermomechanical treatment and novel processing techniques on eCE of NiTi-based alloys were surnmarized. In addition, the developed elastocaloric devices or prototypes based on NiTi-based alloys were also briefly introduced. However, the current researches on NiTi-based elastocaloric materials and the development of prototypes are still in the experimental stage. To realize their commercial application requires further in-depth research and optimization. In the future, the research priorities for the former will concentrate on material miniaturization, alloying or applying special treatment as well as changing circulation methods and so on. On the other hand, the research priorities for the latter will focus on improving heat transfer efficiency, strengthening heat exchange, reducing friction and other losses, and improving mechanical loadings as well as circulation modes.

Introducing coherent precipitates is an important method to strengthen alloys. Recently, it is found that the introduction of coherent B2 phase in multi-principal element alloys with BCC structure can improve the mechanical properties significantly, developing a new class of important series alloys. The up-to-date knowledge of these alloys from the perspectives of composition, microstructure, phase stability, and mechanical properties was summarized. These alloys exhibit high yield strength over a wide temperature regime, but the ductility presents different characterization due to the compositional difference. At present, their engineering application is limited due to their weaker thermal stability at elevated temperature, especially above 500℃, and furthermore, the design of compositional content appears to be more easy method to resolve the problem. This paper aims at providing guidance to further design of multi-principal element alloys with coherent BCC/B2 dual-phases.

Self-healing polymer materials are able to self-repair damage and recover themselves after cracks generating to maintain their structural and functional integrity. According to whether additional repair agent is added, self-healing polymers are mainly divided into two categories, namely extrinsic- and intrinsic-based polymers.The key materials of electrochemical energy storage devices will experience irreversible mechanical damage in extreme condition applications, for example, the energy storage device more prone to physical damage inwearable devices during the multiple bending and deformation processes. These problems severely reduce the stability of energy storage and delivery, and shorten the life of the devices. Therefore, the application of self-healing polymers in electrochemical energy storage devices to improve the stability and life of devices has become one of the research hotspots in recent years. Herein, this article summarizes the repair mechanism of self-healing polymer materials (capsule-based, vascular-based, and intrinsic polymers), with main focus on intrinsic self-healing polymer and its research progress in the field of electrochemical energy storage, which based on molecular interactions to achieve multi-time reversible healing without any additional repair agent.The self-healing electrode and electrolyte system were reviewed respectively, and then the self-healing mechanism and its influence on the electrochemical performance of energy storage devices were described. The research progress of self-healing functional polymer as high specific energy electrode binder, interface modification layer and self-healing electrolyte were summarized in detail. Finally, the future perspectives regarding the future development of self-healing polymer materials were also discussed.

As one of the most promising nanofiller, carbon nanotube has attracted more and more attention due to its extraordinary stiffness and strength. While it is not feasible to obtain the effects of carbon nanotubes on the mechanical properties of composites by solely relying on experimental methods, cleaving and analysing the influence of various parameters of carbon nanotubes on the mechanical properties of composites through numerical simulation methods has become a tendency. Based on the morphology of carbon nanotubes, the nano-meso scale model was proposed. Then three numerical simulation methods were classified depending on the differences between the way of modelling and the objects of discussing. In the end, the influencing law of carbon nanotubes on the mechanical properties of composites was reviewed from two aspects(intrinsic properties of carbon nanotubes, content and distribution of carbon nanotubes), which is expected to provide support to the credibility of results from numerical simulation method. In addition, due to the variety of numerical simulation methods and the diversity of carbon nanotube variables, the numerical simulation research of carbon nanotubes reinforced FRP composites still has great potential.

With the increasing emission of volatile organic compounds (VOCs), the environmental problems become serious. The VOCs treatment technology is the research hot point of environmental protection. The research progress of decomposition, recycling and combination methods of VOCs treatment technology was reviewed. The traditional decomposition technology is the main method for the degradation of industrial VOCs due to its low cost, maturity, high yield, and efficiency. The emerging technology will be a research hotspot for its high purification efficiency and no secondary pollution and low powder, especially novel decomposition technology. Finally, the combined technology can break through the limitation of a single technology and purify the multi-component VOCs in the end-of-line by synergistic effect.

The refractory high-entropy alloys (RHEAs) usually form a multi-principal elements alloy with equal atomic ratio or near equal atomic ratio via adding a variety of high melting point elements, showing simple phase composition and excellent high temperature properties, and processing a broad application prospect in the field of superalloy. Based on the performance characteristics and preparation process of RHEAs, and from the perspective of the current situation and challenges in fabrication and forming, the property tuning methods and its research progress of RHEAs were summarized, as well as the achieved breakthrough and the facing dilemma of the additive manufactured RHEAs. A prospection on the composition design and optimization, material preparation and processing, and additive manufactured forming of RHEAs was also proposed.The following suggestions are put forward for the key research trend of RHEAs in the future: tuning phase composition and phases interface to overcome the strength-ductility trade-off of RHEAs, designing alloys by combining the mature traditional strengthening and toughening theory with the properties of RHEAs, modifying the formability and properties of RHEAs by drawing support from the processing characteristics of additive manufacturing technology, and investigating the servicing performance and failure mechanism in high temperature or multi-field coupling condition of RHEAs.