Flexible sensor is an important component of flexible wearable electronic devices, which have attracted great attention due to their wide applications in many emerging areas including health-monitoring, human-machine interaction and smart robots. Conventional single-axis pressure sensors are not sufficient for the demands of complex and advanced intelligent systems, while flexible three-dimensional force sensors with unique multi-axis and all-around mechanical detection capabilities have become a popular topic. To achieve the goal of developing the flexible three-dimensional force sensors with high performance, it is necessary to consider multiple factors such as sensing mechanism, structural design, material, and decoupling method. In recent years, many researchers have dedicated to the design and fabrication of high performance flexible three-dimensional force sensors, including innovations in structure design and novel materials, improvement of data processing and machine learning algorithms. These multiple innovations are driving further development in these areas. This article aims to outline the research progress of flexible three-dimensional force sensors. Firstly, various sensing mechanisms of flexible three-dimensional force sensors have been introduced and their characteristics have been analyzed and compared. Additionally, progress in structural design, material, decoupling method, and their interrelationship as well as the applications in the related fields, containing intelligent robot arms, motion detection, human-machine interaction, and wireless health monitoring are summarized. Finally, the current challenges of flexible three-dimensional force sensor are analyzed, and its future development is prospected.

Magnesium alloy corrosion resistance is poor, in engineering applications often due to corrosion and failure, through surface engineering technology to magnesium alloy surface modification or protection, is an important means used in engineering applications. In this work, the supersonic plasma spray (SPS) process was used to prepare Al-Al₂O₃ composite coating on the surface of AZ61 magnesium alloy, in which the mass fractions of Al₂O₃ were 30%, 50% and 70% (hereinafter referred to as AA30, AA50 and AA70), and the effects of Al₂O₃ content on the microstructure, porosity, electrochemical properties and corrosion resistance of Al-Al₂O₃ composite coatings were studied. The results show that the surface of the coating presents a wave-like morphology formed by the spread and stacking of molten droplets, the powder is fully melted, and the internal bonding of the coating is tight. And the coating was composed of Al, α-Al₂O₃ and γ-Al₂O₃ phases. The porosity of AA70 coating was significantly higher than that of AA30 and AA50, reaching 6.71%. In the electrochemical polarization test, each coating showed higher electrode potential and lower self-corrosion current density than that of AZ61 magnesium alloy. The test revealed that AZ61 self-corrosion current density was 5.144 mA·cm^-2, while AA30, AA50 and AA70 self-corrosion current densities were 2.950 mA·cm^-2, 3.084 mA·cm^-2 and 2.496 mA·cm^-2, respectively. The coatings of AA30, AA50 and AA70 showed a lower corrosion rate than that of the base metal AZ61. The electrochemical impe-dance test results showed that the R_ct of the three coatings reached about twice that of the AZ61 magnesium alloy matrix, showing lower anodic solubilization activity. In the salt spray test, a large number of corrosion products and cracks are produced on the surface of AZ61 magnesium alloy. Coatings AA30 and AA50 have a large number of cracks in the coating due to the accumulation of corrosion products, and galvanic corrosion occurs at the interface between the coating and the substrate. Eventually, as the surface of the substrate corrodes, the coating peels off. The coating AA70 has minimal corrosion rate and provides optimum corrosion resistance for long-term protection of the substrate.

Lithium-ion batteries have the advantages of high energy density, good rate performance, long cycle life and low self-discharge rate, and are currently the most important type of mobile energy storage. The anode of commercial batteries is mainly made of graphite, and its theoretical capacity is low, which is the main bottleneck limiting the capacity of lithium-ion batteries. Silicon, on the other hand, is characterized by high theoretical capacity, suitable operating voltage, high natural abundance, etc. Therefore, it is a typical electrode material for the new generation of lit-hium-ion batteries. However, due to the large volume changes of silicon anodes during charging and discharging, low initial Coulombic efficiency, relatively poor electrical conductivity, and unstable solid electrolyte interface, silicon-based anodes have significant stability problems that hinder practical applications. To solve these problems, modifying silicon anodes with carbon is a more commercial approach. In this paper, the silicon/carbon anode materials in recent years are divided into 0D-nanoparticles, 1D-nanowires and nanotubes, 2D-nanosheets and 3D-micron spheres according to the structure and size of silicon materials, and the structures and electrochemical properties of carbon-based silicon/carbon compo-sites are discussed. In addition, the progress and limitations of the existing silicon/carbon composite anodes are summarized and the prospects for industrialization in this field are highlighted.

The scientific issue was investigated for the spherical mechanisms of α phase in near α titanium alloy with erbium, aimed to preparate the α phase with random crystal orientation. A novel high temperature titanium alloy with erbium was studied to clarify the micro-structural evolution on the thermal mechanical conditions. Meanwhile, the micro-structure model was established to clarify the dynamic and static spherical mechanisms of α phase. During the thermal-mechanical deformation, the spherical mechanism of lamellar α colony was the continuous dynamic recrystallization, controlled by the mechanical rotation of the sub-grain followed by dislocation climbing and annihilation by diffusion. During the thermal process, the static spheroidization was developed on basics of the β inserted model. During the thermal-mechanical deformation, the sub-structure was induced by the interaction between the slipping dislocation with b of 1/3[2112]. And then, the mis-orientation was increased to develop to the dynamic recrystallization. During the thermal process, the static spherical process, the equiaxial α_p grains and retained β transformed microstructures were prepared. Furthermore, retained β transformed microstructures consisted of β phase and secondary α_s lamellar with the thickness of 30 nm.

The gradual development of new energy power lithium batteries towards high energy density has driven the trends development of high performance, such as ultra-thin, low profile and high mechanical properties of anode copper foil collectors. As one of the key auxiliary materials for lithium batteries, the quality and properties of electrolytic copper foil for lithium batteries play a key role in battery performance. Therefore, the precise regulation of performance and directional modification of structure of the copper foil are of great significance to improving the performance of lithium batteries. This paper introduces the principle and process of copper electrodeposition and the current copper foil market from the perspective of lithium battery copper foil electrodeposition technology, summaries the mechanism of the influence of physical, chemical and surface properties of lithium copper foil on the electrochemical performance of lithium batteries, and provides a reference for the subsequent precise regulation of copper foil performance. It also further illustrates two comprehensive methods to improve the performance of lithium copper foil and lithium battery performance, namely raw foil process parameter optimization and modification treatment, and analyses the current status and development of copper foil structural modification. Finally, this paper illustrates the problems of electrolytic copper foil as lithium battery anode collectors, and looks forward to its future development trends, which guides the development and application of high-performance copper foil for lithium batteries.

Honeycomb sandwich structure is a laminated composite material with excellent mechanical properties, which has been widely used in aerospace, construction and automobile industries. Due to the complexity of its structure and service conditions, honeycomb sandwich structures are prone to various defects such as skin-core interface debonding, skin delamination, inclusions, core lattice deformation, collapse, nodefracture, water accumulation, etc., during the manufacturing and service stages. Therefore, it is of great significance to carry out research on nondestructive testing (NDT) methods for honeycomb sandwich structures. In this paper, the NDT methods for honeycomb sandwich structures reported in domestic and international literature are reviewed, and the principles, application advantages and limitations of these methods are analyzed. Afterwards, the hybrid testing methods that combine multiple single methods for detecting all defects in the honeycomb sandwich structures are briefly outlined, and it is pointed out that the application of intelligent algorithms enables the quantification and classification of potential defects in honeycomb sandwich structures. Finally, a brief conclusion regarding the research status and application trend of the NDT methods for honeycomb sandwich structures is given.

Conducting polymer hydrogels (CPH) here refer to hydrogels contain polyaniline, polypyrrole or polythiophene as conducting components in their matrix. The water rich environment of hydrogels is beneficial for maintaining the protonic acid doped state of conducting polymers, whereas the conducting polymers with organic backbone are more appropriate to be incorporated into hydrogel matrix in compassion with other conducting fillers. Conducting polymer hydrogels thus exhibit highly tunable properties especially interesting strain sensing behaviour, and become a highly concerned material for flexible electronics at present. This review focused on the construction strategies to CPH and summarized the methods to combine the hydrophilic polymer networks with rigid conducting polymers. The key issues to improve the mechanical, conducting, and anti-freezing properties of CPH were analyzed, and the strain sensing behavior of recently reported CPH were also evaluated.

Perovskite quantum dots (PQDs) have emerged as one of the promising candidates for its adjustable bandgap, stable performance, and low-cost solution synthetic process in photovoltaic cells. In this review, we focus on the multifunctional applications of PQDs in the solar cells, including absorption materials, passivation materials, and interface buffer materials. The latest development and the current bottlenecks such as stability, lead toxicity, and film-forming process of PQDs have been discussed. In addition, various optimization methods are also presented about the performance improvement of PQDs. In the end, a summary and perspectives are presented to promote the future commercialization application of PQDs with higher performance and stability.

Due to their simple manufacturing processes, low-temperature film-forming technology, negligible hysteresis, and suitability for preparation of multi-stack devices with conventional solar cells, inverted perovskite solar cells (PSCs) have been extensively researched. In the past se-veral years, the power conversion efficiency of inverted PSCs has increased from 3.9% to 25.37%. As a major component of PSCs, the electron transport layer (ETL) plays a critical role in extracting and transporting carriers, blocking holes, modifying energy levels, and preventing charge recombination. Because of their ease of synthesis and purification, high electron mobility, good solubility, and excellent chemical/thermal stability, organic materials such as fullerene and its derivatives, perylene diimide, and naphthalimide have been most commonly used in the ETLs of inverted PSCs. This review mainly introduces the research status of organic ETLs, modification methods for improving device performance by ETL doping, and interface modification in inverted PSCs, thus providing basic theoretical guidelines for developing new organic ETLs.

Bipolar membrane is important for application in the fields of carbon capture, energy conservation, comprehensive utilization of resources, etc, due to its unique water dissociation properties and easy integration with other technologies. However, the existing bipolar membranes suffer from low water dissociation efficiency, poor selective permeability and stability, which severely limit the wide application. Therefore, a lot of research works have been carried out in recent years on the improvement of water dissociation performance. In this paper, the performances improvement and optimization strategies of bipolar membranes, have been reviewed from both domestic and international aspects including optimization of bipolar membrane ion exchange layers and interface layer catalyst and geometry control of bipolar membrane. The research progress of water dissociation catalysts, laws governing membrane structure were emphasized, providing outlook on the major challenges and future development directions in this field. The aim is to provide a reference for the development of bipolar membranes with high water dissociation performance, so as to promote their application in energy conversion and resource reuse.

Due to its excellent performance, epoxy resin (EP) is widely used in coatings, adhesives, and composite materials. However, its high crosslinking density and poor ability to resist crack initiation and propagation have made EP toughening modification a hotspot for the global research community. Core-shell particles (CSP) added as a second phase to EP can achieve significant toughening effects without significantly compromising the thermodynamic properties. Compared with traditional toughening agents, CSP has a promising development prospect. Based on an explanation of the different toughening mechanisms of EP, this article introduces the toughening mechanism, main types, and preparation methods of CSP toughening agents. The research results on the effects of CSP material, particle size, and core-shell ratio on the mechanical properties of EP are evaluated, and the impact of using CSP toughening methods on the rheological behavior and curing kinetics of EP as a composite material matrix is analyzed.

The carbonyl iron powder (CIP) and acetylene black (CB) were introduced into the medium temperature curing prepreg resin system as absorbent agents. The influence of the addition of absorbent agents on the properties of prepreg resin was determined by testing the rheological properties, gel time, curing characteristic temperature, and thermogravimetric properties of the prepreg resin. The results showed thatthe addition of CIP and CB absorbent particles had little effect on the gel time and curing characteristic temperature of prepreg resin, but great effect on the rheological properties of prepreg resin. In order to meet the requirements of process performance, the mass ratio of CIP and CB absorbent particles to resin should be controlled from 0 to 2.5, and the mass ratio of CB to resin should be controlled from 0 to 0.03. Compared with the single-layer structure absorbing composite material, the two-layer structure absorbing composite material had better absorbing performance. Considering its forming process performance and absorbing performance comprehensively, the material combination of C3C as the wave penetrating layer and Fe250C as the loss layer had the best comprehensive performance. And its maximum effective absorbing bandwidth is 3.85 GHz, the corresponding thickness of the wave penetrating layer and the loss layer are 0.9 mm and 1.5 mm. The minimum RL value is -35.46 dB, the corresponding thickness of the wave penetra-ting layer and the loss layer are 0.5 mm and 1.4 mm, respectively.

Silicon anode material has become an ideal material to replace graphite anode due to its high theoretical capacity (4 200 mAh/g), low opera-ting voltage (0.2—0.3 V vs Li/Li⁺) and abundant raw materials on the earth for energy storage. However, the volume expansion of silicon anode materials would lead to electrode degradation during the cycle. Therefore, in this paper, chitosan/graphite@silicon (C/G@Si) composite was prepared by using chitosan and graphite to achieve carbon coating and compositing on nano silicon through physical methods. For C/G@Si, the structure, morphology and electrochemical properties of the composites were studied. The results showed that with the increase of graphite addition, the reversible specific capacity decreased slightly, while the cycle performance and conductivity improved significantly. When 50wt% graphite was added, the specific capacity of the first discharge was 1 136.1 mAh/g under the current density of 100 mA/g, and the residual capacity remained at 658.5 mAh/g after 100 cycles of charging/discharging, which exhibits excellent electrochemical performance and has certain reference value for further promotion of silicon-carbon anode materials.

As a mature surface treatment technology, plasma spraying for substrate play an increasingly important role in surface-enhanced process due to its wide application range, high production efficiency and good quality. Meanwhile, more and more results demonstrated that ceramic coatings play a critical role in overall performance improvement and service lifetime extension of materials. This paper reviews the development of ceramic coatings prepared by conventional plasma spraying technique, including atmospheric plasma spraying, supersonic atmospheric plasma spraying, suspension plasma spraying, vacuum plasma spraying and low pressure plasma spraying. Then, the advantages and shortcomings of each preparation method have also been summarized. Finally, based on above contents, the future development of plasma sprayed ceramic coatings are prospected.

The hard carbon anode has significant research value and promising application prospects due to its excellent specific capacity, high-rate fast charging capability, absence of lithium branches crystal, and lack of volume expansion behavior. It plays a crucial role in the electrochemical performance of lithium-ion batteries (LIBs). In recent years, numerous scholars have conducted extensive research on hard carbon anodes, particularly focusing on the lithium storage mechanism and the optimizing strategies of lithium storage performance. This article provides an overview of the formation process and lithium storage mechanism of hard carbon. It offers a theoretical foundation and scientific basis for designing high-performance hard carbon anodes. This paper subsequently summarizes the latest advancements in preparation techniques, structural regulation, morphology design, and heteroatom doping for modifying hard carbon anodes. These advancements are based on two categories of precursors:biomass and polymers. Furthermore, conjugated microporous polymers hard carbon is proposed as a future direction for optimizing lithium storage performance. Finally, the challenges and future research directions for hard carbon as anodes are discussed.

The research progress and application of high speed steel are introduced, and the research characteristics of high speed steel are summarized systematically, including brief history, alloy composition, preparation process, heat treatment process, mechanical properties, computational science, practical application and prospect. A high speed steel material with excellent properties must be combined with its composition, microstructure, process and properties, which will directly determine the service life of the material. This will provide substantial value for the research of high speed steel. In addition, the application scope of computer science is expanding, which is an indispensable research mean, facilitating the research of metal wear resistant materials tending to be diversified. Finally, five directions of future research are put forward, which are mainly based on the problems and challenges of the research technology in the high speed steel materials, strengthening the development of high speed steel industry technology innovation as a result.

Mycotoxins are secondary metabolites produced by fungi. The three largest groups are aflatoxins, fumonisins, and ochratoxins. Food pro-ducts are susceptible to mycotoxin contamination during storage, processing, and transportation. In most cases, multiple mycotoxins occur simultaneously and create a superimposed effect that can be highly toxic, causing food safety problems and posing a serious health risk to humans. Simultaneous detection of multiple mycotoxins in food would be extremely helpful. This paper reviews the progress of research into the development of fluorescent biosensors for the detection of mycotoxins both domestically and abroad, with particular focus on multiplexed and simultaneous detection of mycotoxins, especially the types and composition of fluorescent biosensors. It also addresses detection methods and strategies involving aptamer and immunoassay techniques. The limitations and challenges of existing mycotoxin detection are discussed, and directions for future research are outlined with a view to providing theoretical support for mycotoxin detection research.

Recycled fine powders area kind of particles with particle size less than 75 μm produced in the process of preparing recycled aggregate from construction waste with concrete, brick and tile as the main components. Their main chemical composition is similar to that of fly ash and has certain potential activity. The use of recycled fine powders as admixture can reduce the demand for raw materials, reduce the pollution to the environment, and realize the recycling of resources.
Recycled fine powders have the characteristics of complex composition, large water demand and low activity index, which are not conducive to the performance of mortar or concrete when used directly as admixture. However, the content of SiO₂, CaO and Al₂O₃ in recycled fine powders are high, which have a good activity potential. After appropriate technical treatment, it can effectively stimulate their activities and improve the utilization efficiency. The main activation modes of recycled fine powders currently include physical, chemical, and thermal activation. Thermal activation can burn up the organic impurities in the recycled fine powders, and change the composition of some substances, so as to stimulate their activity. Physical activation increases the specific surface area of recycled fine powders by mechanical force, thereby improving the activity of the recycled fine powders. Chemical activation mainly provides an alkaline environment or ions that can participate in the reaction by adding alkaline activators, thus promoting the hydration degree to improve the activity of recycled fine powders. Relevant scholars have conducted in-depth research on the active excitation method of recycled fine powders and its application in mortar and concrete, which has played a positive role in the application of recycled fine powders.
Based on the existing literature, this paper comprehensively reviews the physical properties, chemical composition, activation mode, activation mechanism and application status of recycled fine powders, analyses the problems in the current research of recycled fine powders and looks forward to their application prospect, in order to provide a research basis for the high-quality utilization of recycled fine powders.

Microcellular foam molding devices are crucial for fundamental research and preparation of microcellular foam materials. The design and innovation of these devices are directly related to fundamental research on microcellular foaming, as well as improved foam product quality and enhanced production efficiency. There are four main types of molding devices for microcellular foam materials based on the molding methods:batch foam molding, continuous extrusion foam molding, injection foam molding and compression foam molding devices. In this review, we explain the design principles and structural characteristics, present the advantages and disadvantages of different foam molding devices, and summarize the designs of various visualization devices. Free-foaming visualization devices have a simpler structure, lower cost, and are easier to operate compared to visualization devices based on extrusion and injection foam molding methods. Thus, they are currently the most studied and applied devices. However, there is a significant difference between the foaming environment and the conditions during actual production, making it challenging for practical applications. Finally, this paper reviews the current issues to be addressed in designing microcellular foaming material molding devices and proposes design ideas and research prospects of the microcellular foaming material molding devices.

Different from the design concept of traditional alloys, high-entropy alloys are composed of at least five elements at equal atomic ratios or nearly equal atomic ratios, and exhibit many properties that traditional alloys do not have. Among them, CoCrFeMnNi high-entropy alloy, as the first developed high-entropy alloy, has attracted wide attention from researchers. The development of preparation technology plays an important role in developing high-entropy alloys with excellent properties and promoting their practical applications. In this paper, the working principle and characteristics of the main preparation techniques of high entropy alloys are introduced, including mechanical alloying, powder atomization, mel-ting and casting, powder metallurgy, additive manufacturing, magnetron sputtering and laser cladding. The microstructure and properties of CoCrFeMnNi alloys prepared by different methods are compared and analyzed. Finally, on this basis, the future development of high-entropy alloy preparation technology is prospected.

As thenovel transparent conductive films, silver nanowires film has the advantages of good conductivity, good flexibility, low cost and high light transmittance. In this paper, the principles, tools and research status of various techniques applied in the simulation of silver nanowires thin films were introduced in terms of electrical properties, mechanical properties and optical properties. The simulation research on the electrical properties of silver nanowires thin films has been improved, and it is able to establish a more accurate simulation model from micro to macro. The commonly used models include the junction-dominated assumption (JDA) model, multi-nodal representation (MNR) model, which can simulate and predict the resistance of silver nanowire thin films clearly. The mechanical simulation of silver nanowires thin films failed to establish a macro-level model, and the mechanical properties of single silver nanowires or multiple silver nanowires could only be simulated by molecular dynamics method. FDTD methods have been used to simulate the optical properties of a small number of silver nanowires, and attempts have been made to establish optical models of large and complex silver nanowire thin films. However, a multi-physical field coupled simulation model that can reflect the comprehensive optical, electrical, thermal, and mechanical properties of the silver nanowire film has not yet been established, and future researchers need to continue to work on it.

All-inorganic cesium lead halide perovskite nanocrystals CsPbX₃ (X=Cl,Br,I) exhibit excellent photoelectric properties, such as high photoluminescence quantum yield, long carrier lifetime, narrow emission line width, and adjustable band gap. They show great application prospects in the fields of light-emitting diodes (LED), solar cells, photoelectric detection, etc. However, perovskite nanocrystals present poor stability under the conditions of water, light and temperature due to the inherent ionic features, which seriously hinders the application of nanocrystals in the field of optoelectronics. In recent years, researchers have reported various methods to improve the stability of perovskite nanocrystals, including ion doping, surface passivation and surface coating. Compared with ion doping and surface passivation, the surface coating strategy not only isolates the CsPbX₃ nanocrystals from the environment, but also avoids their anion exchange from different anionic components of perovskite nanocrystals, and thus significantly improves the stability of nanocrystals. Therefore, we introduce the coating mechanism of all inorganic cesium lead halide perovskite nanocrystals in detail, and focus on the advantages of this strategy from the aspects of polymer films, oxides, metal orga-nic frameworks, zeolite and other coating materials. Finally, the applications of coating materials in lighting and display are summarized.

Transition metal/nitrogen/carbon (M/N/C) catalysts are the most promising candidates to replace platinum-based catalysts for oxygen reduction reaction (ORR). Zeolitic imidazolate frameworks (ZIFs) are ideal precursors for the preparation of M/N/C catalysts since they combine the high stability of inorganic zeolites and the high specific surface area, high porosity, and tunable pore structure of MOFs materials. In this work, FeN/C-Z_x catalysts were synthesized using FeSO₄·7H₂O, 1, 10-phenanthroline, and ZIFs as iron, nitrogen, and carbon precursors, respectively. The effect of using different ZIFs as carbon precursors on the ORR activity of FeN/C-Z_x catalysts were investigated. The structure of the catalyst was characterized by X-ray diffraction, specific surface area and pore size distribution test, and transmission electron microscope. The catalytic activity of the catalyst for ORR was tested by linear scanning voltammetry. The results show that the FeN/C-Z₈ catalyst exhibits the best ORR activity, a small Tafel slope (64.98 mV/dec) with a nearly four-electron reaction process, and a good stability with only 20 mV negative shift in half-wave potential after 25 000 cycles of accelerated degradation tests. The Fe₃C compound, which can effectively improve the catalytic activity, present in the FeN/C-Z₈ catalyst;the high specific surface area (550.09 m²/g) and pore volume (1.36 cm³/g), the abundant micropore and mesoporous structure, as well as the uniform distribution of transition metals on the ZIFs materials and the small catalyst particles size due to the volatilization of Zn²⁺ during the carbonization process, are the possible reasons to increase the ORR catalytic performance of FeN/C-Z₈ catalyst.

Electrochemical nitrate reduction to ammonia (NRA) could realize the green synthesis of ammonia and remove nitrate pollutant through electrochemical pathways by using nitrate and water as sources of nitrogen and hydrogen, respectively, which is of significance for alleviating energy crisis and environmental problems. However, nitrate to ammonia is a complex eight-electron transfer process accompanied by intense hydrogen evolution side reactions, which seriously limits the selectivity and Faraday efficiency of ammonia synthesis. Therefore, nickel foam-supported copper oxide nanoflower catalyst was prepared by hydrothermal synthesis and subsequent heat treatment process, and its electrocatalytic performance for nitrate reduction to ammonia was explored. By adjusting the synthesis conditions such as the ratio of copper nitrate to urea and pyrolysis temperatures, the uniform CuO nanoflowers loaded on nickel foam (NF) was achieved. The results show that when n(Cu(NO₃)₂)∶n(CO(NH₂)₂) is 1∶6, the obtained target catalyst (CuO-6@NF) shows the best performance in terms of Faraday efficiency, NH₃ yield, selectivity and nitrate conversion. At -0.23 V vs. RHE, the yield of CuO-6@NF ammonia reached 1.15 mmol·h^-1·cm^-2, the selectivity was 89.36%, and the removal rate of total nitrogen was as high as 96.71%. In addition, the catalyst exhibits good reproducibility, high stability, and applicability over a wide range of concentrations.

Polyimide resins have so many excellent properties such as high mechanical strength, high flame resistance, high thermal stability and low dielectric constants. They are widely used in the fields of aerospace, microelectronics. Polyimide aerogels have excellent thermal insulation along with mechanical properties due to their abundant 3D nanoporous network structure combine with the properties of polyimide. However, due to the presence of abundant nanoporous network structure, the high temperature resistance of polyimide aerogels is significantly lower than that of polyimide resins, which greatly limits the application of polyimide aerogels in the field of thermal protection in aerospace high temperature environment. Based on the research status, this paper aimes at the problem of insufficient high temperature resistance of polyimide aerogels, linear and cross-linked polyimide aerogels and their main preparation methods are introduced, and systematic reviews the main strategies of domestic and foreign scholars to improve the high temperature resistance of polyimide aerogels. The applications in aerospace, pressure sensing, environmental remediation and thermal insulation of polyimide aerogels are also mentioned in the paper. Furthermore, considering the main challenges currently faced by polyimide aerogels, its future research trends have prospected.

Aerogel composites are one of the most prominent new thermal insulation materials due to their structural functional properties such as low density, large specific surface area, high porosity and low thermal conductivity. This paper briefly describes the development history of aerogel composites, new methods for the preparation process of aerogel composites, analyzes the thermal insulation performance and mechanism of aerogel composites in terms of their microscopic morphological structure, heat transfer composition, thermal insulation and heat transfer characterization, and highlights the new progress made in recent years in the application of the thermal insulation performance of aerogel composites in many fields such as military aerospace, building energy conservation and environmental protection, energy storage and transformation, extreme environmental materials, electric vehicle batteries, refrigerated or frozen transportation and heating boiler pipelines. At the same time, the problems encountered in their application in various fields are discussed in detail and suggestions are given. In addition, the paper ends with an outlook on future research directions in the development, production and application of aerogel composites.

As an important member of coal-based solid waste, the appropriate utilization of coal gangue has always been a hotspot issue. During the past decades, the utilization efficiency of coal gangue in China has been greatly improved as the relevant theory and technology developed rapidly, which leads to a successful transformation of coal gangue from so-called ‘waste to treasure’ in many fields, such as energy, chemical, and civil engineering. In particular, civil engineering has become a vital way that can not be ignored for the tremendous consumption of coal gangue, because of its large demand for raw materials and the advanced ‘co-disposal of multiple solid wastes’ technology. This paper reviews the latest research progress of coal gangue as cementitious material/SCM/aggregate in cement, mortar, concrete, geopolymer, road enginee-ring, underground engineering, etc. The technical points, barriers, quality-control measurements, and modification methods are summarized and compared when coal gangue is used in different roles in construction materials. However, some valuable resources in coal gangue are usually ignored when the coal gangue is applied as building materials. Besides, the long-term durability of gangue structures and monitoring of potential environmental risks also need to be carried out. In conclusion, considering the physical and chemical properties of coal gangue, utilization technology level, experience, policy support, and other regionalized factors, raw coal gangue used for preparing various types of building materials still lack a clear and standardized classification management and graded disposal method that is tailored to local conditions in their production. The development, improvement, and organic combination of ‘multi-field technology-standards-policies’ is the key to the establishment of an efficient and orderly gangue building materials market and industry chain in the future.

Chemical oxidation-reduction is a relatively mature method for preparing reduced graphene oxide (RGO) in industry. In this study, graphite was first oxidized using the modified Hummers method, and then the graphene oxide (GO) with lamellar structure could be obtained by spray drying. After that, four types of RGO samples were prepared, respectively, by using vitamin C (VC) chemical reduction, rapid-heating reduction, slow-heating reduction, and combined VC reduction with rapid-heating reduction methods, and the comprehensive physicochemical cha-racterization was carried out. The results show that the reduction method has a significant effect on the morphology, structure, and conductivity of the obtained RGO. By using VC chemical reduction, spherical RGO with large specific surface area and micro-meso hierarchical pore structure could be produced, and it exhibits low reduction degree and conductivity. The layered RGO samples with high reduction degree and good conductivity can be fabricated by thermal reduction, especially the rapid heating would be conducive to the expansion and peeling of RGO and thus effectively improve its specific surface area. When VC reduction and rapid-heating reduction are used in combination, the generated porous spherical RGO possesses high specific surface area and reduction degree, nevertheless, duing to the large contact resistance between RGO particles, its conductivity is inferior to corresponding RGO sheets produced by thermal reduction.

Membrane distillation technology has attracted much attention because of its advantages such as low operating pressure, small temperature difference, pure distillation liquid, highsalt rejection rate and direct separation of crystal products. However, the lack of distillation membranes with excellent hydrophobic properties is an important factor limiting its application. So far, researchers have carried out a lot of work in the hydrophobic theory research of membrane materials and functional modification of superhydrophobic distillation membranes, and made great progress in developing new modification methods and finding new modification additives. Based on the contact angle model, the researchers improved the surface roughness by introducing nanoparticles containing silicon or carbon into the membrane surface, selected modified additives containing fluorine groups to reduce the surface energy, dispersed raw materials with different solvents and selected different film-forming met-hods, which greatly improved the hydrophobic performance of the prepared distillation membrane.
In this paper, the research progress of functional modification of superhydrophobic distillation membranes in recent years is reviewed, and the modification effect is compared and discussed. The results of classification research show that the surface coating method is suitable for different types of base membranes, which can realize the simultaneous modification of membrane skeleton and its surface, not only increase the membrane flux but also improve the antifouling property. The operation is simple and can be applied to large-scale production. Compared with the coating method, the membrane modified by the electrostatic spinning doping method can maintain the stability to the maximum extent, improve the water permeability and reduce the influence of the modified substances on the flux, but the application range is limited by the base membranes. The chemical deposition method can obtain gradient deposits or mixed coatings. Compared with the coating method, it is easier to control the composition and thickness of the coating, and can carry out a more accurate film surface modification process. Unconventional methods such as plasma are mostly the combination of several methods, which has opened up a new direction for the modification of distillation membranes from the aspects of modifier materials, operating process, operating conditions, etc. The hydrophobic additives, dispersants, operating methods and conditions used in different modification processes are classified and analyzed, and the membrane flux, porosity, salt rejection rate, filtration pe-riod and other indicators after modification by different methods are compared. The advantages and disadvantages of different modification met-hods are evaluated in combination with the filtration methods, and the problems and development prospects of commercial application of superhydrophobic modified distillation membranes are prospected, aiming to provide beneficial help for the development of superhydrophobic distillation membranes with low cost, simple operation, high membrane flux and strong anti-pollution ability.

The electrochemical production of hydrogen peroxide via the two-electron oxygen reduction reaction (ORR) is a green, mild, and on-demand strategy. The key to this process is highly active, selective, and stable electrocatalysts. Noble metal catalysts are the most effective catalysts for the electrochemical production of hydrogen peroxide due to their unique physical and chemical properties. However, low-cost catalysts are essential for achieving the large-scale production of hydrogen peroxide. Therefore, reducing the dosage of precious metals or finding affor-dable and readily available alternatives has been a topic of considerable research interest in recent years. Numerous non-precious metals or non-metallic materials have been used in oxygen reduction electrocatalysts, some of which have comparable or even superior electrochemical perfor-mances compared to noble metal catalysts. Furthermore, the band structures and surface structures of two-dimensional materials are easier to adjust than those of bulk materials. Two-dimensional materials exhibit faster electron transportation, achieve higher atomic utilization, and possess more exposed active sites. This review discusses the reaction mechanisms of the two-electron ORR for hydrogen peroxide production based on reported experimental results and theoretical calculations, and collates recent reports on the use of graphene, two-dimensional transition metal chalcogenide compounds, two-dimensional MOFs/COFs, g-C₃N₄, and MXenes as electrocatalysts for the ORR. Finally, the remaining challenges of the application of two-dimensional materials as oxygen reduction electrocatalysts are briefly summarized.

Electronic nose (E-nose) technology has been widely used as an effective method of olfactory simulation and odor recognition. The E-nose system is composed of an array of gas sensors that utilize their cross-reactivity for qualitative and quantitative gas analysis. Machine learning algorithms are commonly used in the E-nose system, with artificial neural networks being particularly prevalent. In addition to traditional machine learning algorithms, deep learning algorithms are also gradually being applied in E-nose systems. The E-nose system features high selectivity, precision, rapid response, stability, and scalability, and has been applied in various fields, such as toxic gas detection, air quality management, and food freshness and quality prediction. This paper reviews the latest research progress in the gas identification of E-nose systems, including the composition of gas sensor arrays based on MEMS technology, signal acquisition and processing units, and the classification of pattern recognition algorithms. Finally, the current problems and development prospects of E-nose system gas identification are summarized and discussed.

Because of their superior high-temperature properties, superalloys are widely utilized in aerospace engines and industrial combustion turbines, and ceramic shells are required for the production of superalloy castings.This paper reviews the evolution of ceramic shell preparation technology over the past few years.It discusses the current state of research on the selection of ceramic shell matrix material, the influence of binder, the modification of fiber material, the preparation process, etc.Moreover, it analyzes and discusses the interfacial reaction between ceramic shells and superalloys, summarizes the mechanism of interfacial chemical reaction and wettability, and summarizes the influence of ceramic material/alloy component elements on the interfacial reaction as well as the limitations of existing studies.This paper concludes by identifying the most important directions for future research based on ceramic shell preparation technology for precision casting of superalloy.

Polymer composite microspheres have important applications in the fields of medicine, sensing, optics and display, especially in clinical diagnosis, pathological imaging and drug delivery in the field of medicine. However, due to the complex synthesis route and low processing efficiency, conventional technologies are often difficult to take into account the good particle size dispersion, low production cost and high yield of microspheres. In recent years, based on Plateau-Rayleigh fluid interface instability (PRI) in fibers, laminar hydrodynamic methods can prepare highly monodisperse polymer microspheres at micro or nano scale with controllable cost and considerable yield. In this paper, the principle of fluid interface instability, the preparation process of fiber core layer PRI method, the preparation of functional microspheres and structural microspheres of fiber core layer PRI method and the improvement of fiber core layer PRI method are reviewed.

As a rising two-dimensional conductive material, MXene has attracted researchers' interest in the design and application of electrodes and electrolytes of energy storage devices. In recent years, the performance of lithium sulfur batteries have significantly improved for the excellent conductivity of MXene material and its adsorption to polysulfides. The functionalized design of MXene can avoid the defects of self-stacking, regulate the adsorption strength of polysulfides, and catalyze the redox reaction of polysulfides. From the perspective of functionalized MXene, the main preparations and their influence on the surface functional group of MXene are reviewed. The adsorption to polysulfides and mechanism of shuttle effect inhibition, and the enhancement mechanism of redox kinetics of functionalized MXene are analyzed. The possible problems and modification prospects of MXene in the application of lithium sulfur batteries are discussed.

The improved catalytic activity of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) can significantly improve the performance of hybrid electrolyte lithium-air batteries. The two-dimensional material V₂C (MXenes) has attracted much attention due to its rich composition, high specific surface area, and strong stability. Based on the first principles approach of density functional theory (DFT), this work investigated the electronic properties of V₂C, the optimal adsorption sites of oxygen on the V₂C surface under alkaline conditions, and the redox process of oxygen on the V₂C surface, calculated the free energy and overpotential, and finally compared it with the MnO₂ catalyst commonly used in hybrid electrolyte lithium-air batteries. The results showed that V₂C has a lower overpotential than the commonly used MnO₂ catalyst when used as a catalyst for hybrid electrolyte Li-air batteries, indicated that the catalyst can improve the catalytic performance of the electrode and was a promising bifunctional catalyst for ORR and OER.

Hydrogen embrittlement is both a common phenomenon in high-strength steel (HSS) and an urgent problem that must be solved inthe deve-lopment of HSS. To deeply study the relationship between hydrogen embrittlement and defects of HSS, researchers have developed many macroscale experiments and evaluation methods, such as slow strain rate tensile, linear increase stress, constant load tensile, thermal desorption spectroscopy, and electrochemical hydrogen permeation. These methods are directly used to evaluate the hydrogen embrittlement susceptibility of HSS, which accords with HSS’s parameters like plastic loss, maximum fracture stress, fracture time, stress intensity factor, hydrogen capture energy, and diffusion rate. However, these macroscale experiments cannot accurately explain the causes of HSS’s hydrogen embrittlement in depth. Therefore, researchers have also developed some mesoscale and microscale experiments to locally test changes in HSS’s pro-perties and accurately detect the position where the hydrogen atom was captured. These mesoscale and microscale experiments and characte-rization means include the indentation method, nanoindentation method, micro cantilever bending experiment, atomic probe technology, hydrogen micro-printing technology, scanning Kelvin probe microscope, and so on, which provide a more accurate basis for explaining the mechanism of hydrogen embrittlement and understanding the interaction between hydrogen and HSS’s defects. In this paper, we introduce and compare the above experiments, investigate the research progress of multiscale test evaluation of HSS’s hydrogen embrittlement. Then, we summarize the current research status and mainstream test evaluation methods of HSS’s hydrogen embrittlement so that we provide some ideas on how to use these experiments to further explore HSS’s hydrogen embrittlement.

As a lightweight material with sufficient reserves, high specific strength and specific modulus, the application of magnesium is very promising. The poor corrosion resistance of magnesium seriously limits its application, and galvanic corrosion caused by larger precipitates is an important reason for the poor corrosion resistance of magnesium alloys. In this work, the as-cast Mg-5Zn-0.6Zr alloy was selected as the object of study, and this alloy was friction stir processed. The microstructure and electrochemical properties were examined and analyzed before and after friction stir processing (FSP). The results indicated that after processed by FSP, the Mg-5Zn-0.6Zr alloy exhibited a strong (0001) basal texture with low dislocation density in most regions. The grain size was refined from 66.4 μm to the order of 1.6 μm, and there was a certain level of fragmentation and dispersed distribution of the precipitates. In a 3.5%(% refers to the mass fraction, if not otherwise stated) NaCl aqueous solution, the corrosion current density decreased from 38.3 μA/cm² to 17.0 μA/cm² at open circuit potential. Moreover, the polarization resistance increased from 48.98 Ω·cm² to 197.02 Ω·cm².The study indicated that FSP could effectively improve the corrosion resistance of magnesium alloy.

Sodium-ion batteries with cost advantages are considered a useful complement to lithium-ion batteries and the development of low-cost, high-performance electrode materials is the key to the commercialization of sodium-ion batteries. As for anode materials, with the advantages of easy availability of carbon source, easy preparation, and high structural adjustability, hard carbon has great potential of being commercialized. Among the many precursors of hard carbon materials, biomass is favored due to its abundant source and low cost. However, the pore structure and surface characteristics of biomass based hard carbon anode materials have a significant impact on their sodium insertion and extraction performance. In this paper, we summarize the research progress in recent years from the performance influencing factors of biomass-based hard carbon anode, and further discuss the challenges in the commercialization process of biomass-based hard carbon anode for sodium-ion batteries and its future research directions, hoping to provide useful guidelines for future research and commercialization.