In response to the evolving landscape of high-speed aircraft, characterized by an expansive airspace, prolonged flight durations, and increased velocities, the thermal protection requirements for key structures such as the nose cone, leading edge, and engine combustion chamber have become more exacting. This necessitates a concerted focus on the development of high-performance thermal protection materials capable of withstanding extreme conditions. Ultra-high temperature ceramic composites have emerged as noteworthy candidates, showcasing exceptional oxidation and ablation resistance. Despite their commendable properties, the inherent brittleness of these composites poses a significant obstacle to widespread engineering applications. To address this limitation, there is a growing emphasis on toughening through structural modulation. Simultaneously, the imperative to enhance aircraft payload capacity underscores the demand for lightweight ultra-high temperature ceramic composites. This paper provides a systematic overview of the major research advances made in recent years on ultra-high temperature ceramic composites, including preparation methods such as pressure sintering, slurry infiltration, precursor impregnation and pyrolysis, reactive melt infiltration, chemical vapor infiltration/deposition, and “solid-liquid” combination process, toughening methods such as particles, whiskers, soft-phase materials, short-cut fibers, and continuous fibers, as well as oxidation ablation resistant properities and mechanisms, and lightweighting design. The relationship between the components, microstructures and properties of ultra-high temperature ceramic composites is discussed in depth, and the current challenges as well as the future development trends of ultra-high temperature ceramic composites are presented.

The development of high-speed flight technology has put forward an urgent demand for high- performance thermal structure materials. High-entropy carbides (HECs) ceramics are a fast-emerging family of materials that combine the excellent properties of high-entropy ceramics and ultra-high temperature ceramics. HECs have a broad application prospect in extreme service environments, which has received extensive attention from scholars in recent years. Compared with traditional ultra-high temperature carbides containing only one or two transition metal elements, HECs have a greater potential for development because of their improved comprehensive performance and greater designability of composition and properties. After successive exploration of HECs in recent years, researchers have obtained many interesting results, developed a variety of preparation methods, and gained comprehensive understanding of microstructure and properties. The basic theories and the laws on HECs obtained from experimental process are reviewed in this paper. Preparation methods of HECs including powders, blocks, coatings and films, as well as fiber-reinforced HECs-based composites are summarized. Research progress on the properties of HECs, such as the mechanical properties, thermal properties, and especially the oxidation and ablation resistance related to high-temperature applications, is reviewed and discussed. Finally, the scientific issues that need to be further explored in this area are emphasized, and the prospects are proposed.

As a kind of important functional material, flexible piezoelectric materials can realize the effective conversion between mechanical energy and electrical energy, with the advantages of good toughness, high plasticity and light weight. Therefore, they can be attached to the human body to obtain human or environment information in real time, which is widely used in the fields of motion detection, health monitoring, and human-computer interaction. Due to high requirements of various three-dimensional (3D) structures of the flexible piezoelectric materials, additive manufacturing has been extensively utilized to fabricate different kinds of piezoelectric materials. This technology is expected to break the bottleneck of traditional processing of piezoelectric material by improving the structural design freedom and the performance of flexible piezoelectric materials, and provides enormous potential and opportunities for the application of flexible piezoelectric materials. Based on the introduction of the classification and features of flexible piezoelectric materials, this paper explained the main additive manufacturing technologies, including fused deposition modeling, direct ink writing, selective laser sintering, electric-assisted direct writing, stereolithography, and inkjet printing that commonly used in processing these materials. Then, various structural designs, such as multi-layer structure, porous structure, and interdigital structure for the flexible piezoelectric materials produced by different additive manufacturing approaches were reviewed. Moreover, the applications of additive manufactured flexible piezoelectric materials in energy harvesting, piezoelectric sensing, human-computer interaction, and bioengineering were introduced. Finally, the challenges faced by additive manufacturing on processing flexible piezoelectric materials and the development trends in the future were summarized and prospected.

Ammonia serves not only as a primary raw material in synthetic fertilizers, but also as a novel high-energy- density fuel. In recent years, electrocatalytic nitrate reduction for ammonia synthesis has gained extensive attention as a green and sustainable approach due to its potential as an eco-friendly and sustainable way that could replace the energy-intensive and high-carbon-emission Haber-Bosch process. Nevertheless, the efficient electrocatalytic ammonia synthesis is still hampered by low reaction efficiency and product selectivity as well as catalyst stability. Hence, there is a pressing need to develop efficient catalysts to advance electrocatalytic nitrate reduction for ammonia synthesis. Recently, metal oxide catalysts have been at the center of attention for their superior performance in electrocatalytic nitrate reduction for ammonia synthesis. This review consolidates the developments of metal oxide electrocatalysts converting nitrate to ammonia, focusing on elucidating the reaction mechanism and introducing typical metal-based (Cu, Fe, Ti, etc.) catalysts. Additionally, it discusses the latest research progress in enhancing catalytic reaction efficiency, product selectivity, and material stability through strategies like morphology control, surface reconstruction, oxygen vacancy engineering, element doping, metal-assisted catalyst loading, etc. Finally, the paper outlines the challenges and future research directions in the realm of electrocatalytic nitrate reduction for ammonia synthesis.

Bentonite is an abundant, cheap and readily available natural clay mineral, with montmorillonite (MMT) as its main mineral composition. MMT possesses excellent ion exchange, adsorption and ion transport properties due to its unique two-dimensional layered nanostructure, abundant pore structure, and high specific surface area. Moreover, it also possesses excellent thermal, chemical and mechanical stabilities. In recent years, MMT has attracted extensive attention in the field of electrochemical energy storage owing to the above excellent characteristics, especially the inherent fast ion (Li⁺, Na⁺, Zn²⁺, etc.) transport properties. Thus, the bentonite-based functional materials have been widely applied to the key components (i.e., electrodes, polymer electrolytes, and separators) of electrochemical energy storage devices and show good application prospects. In this review, the structure and physicochemical properties of bentonite are firstly introduced, and then the research progress of bentonite-based functional materials in the field of electrochemical energy storage, mainly including metal anodes, lithium-sulfur battery cathodes, solid/gel polymer electrolytes, and polymer separators, is comprehensively summarized. On the basis of these facts, the ion transport promotion mechanism of bentonite-based functional materials during the process of electrochemical energy storage is elaborated. Finally, the current problems and challenges faced by application of bentonite-based materials in electrochemical energy storage devices are pondered, and the possible future research directions are prospected. This review provides useful guidance for the design and development of bentonite-based electrochemical energy storage functional materials.

Oxide ceramics, known for their outstanding strength and excellent oxidation and corrosion resistance, are prime candidates for high-temperature structural materials of aero-engines. These materials hold vast potential for application in high-end equipment fields of the aerospace industry. Compared with traditional ceramic preparation methods, laser additive manufacturing (LAM) can directly realize the integrated forming from raw powders to high-performance components in one step. LAM stands out for its high forming efficiency and good flexibility, enabling rapid production of large complex structural components with high performance and high precision. Recently, research on LAM for melt-grown oxide ceramics, which involves liquid-solid phase transition, has surged as a hot topic. This paper begins by outlining the basic principles of LAM technology, with an emphasis on the process characteristics of two typical LAM technologies: selective laser melting and laser directed energy deposition. On this basis, the paper summarizes the microstructure characteristics of several different oxide ceramics prepared by LAM and examines how process parameters influence these microstructures. The differences in mechanical properties of laser additive manufactured oxide ceramics with different systems are also summarized. Finally, the existing problems in this field are sorted out and analyzed, and the future development trend is prospected.

Continuous SiC fiber-reinforced SiC (SiC_f/SiC) composites possess high specific strength, high specific modulus, high-temperature resistance, and radiation resistance, making them suitable for applications in hot-end parts of advanced aero-engines and claddings of nuclear reactors. SiC_f/SiC composites are composed of fibers, interfaces and matrix, endowing them with complex multi-scale structural characteristics. These composites are designed to serve in harsh environment, and their damage and failure process are complex. A profound understanding and accurate analysis of damage and failure mechanisms of SiC_f/SiC composites under service environments are of great significance for the optimized design of materials and the reliable service of components. Traditional “post-mortem analysis” methods are incapable of acquiring data during the damage and failure process of materials under complex service environments. Therefore, there is an urgent need to develop in-situ characterization techniques for composites under high-temperature service environments. This paper reviewed the principles, advantages, and limitations of in-situ monitoring methods based on scanning electron microscopy, digital image correlation, micro computational tomography, acoustic emission, and electrical resistance. It focused on the latest research progress in the high-temperature mechanical characterization of SiC_f/SiC composites using various in-situ monitoring methods and combinations thereof. It summarized the challenges in the in-situ monitoring technologies of SiC_f/SiC composites under high-temperature environments and provided a preliminary outlook on the future development directions, such as the combined use of multiple in-situ monitoring techniques, new detection technologies like terahertz radiation, and in-situ damage monitoring methods for complex components.

In comparison to Li-ion batteries, Na-ion batteries offer the benefits of low cost, good low-temperature performance, and safety, attracting great attention in the cost- and reliability-sensitive applications. With high capacity and low cost, Prussian blue-like materials (PBAs) stand as promising cathode materials for Na-ion batteries. However, the presence of crystalline water within their structure induces fast performance decay of the battery, serving as a critical bottleneck limiting their application. This work reports a facile thermal treatment strategy to effectively remove crystalline water from PBAs cathode materials, improving capacity retention from 73% to 88% after 340 cycles. The in-situ analysis uncovers that the initial loss of Coulombic efficiency of PBAs cathode is a result of its irreversible transformation from a trigonal form to cubic phase during the charging and discharging process. This issue can be addressed by introducing of Na₂C₂O₄ to compensate the irreversible Na loss in the cathode. On this basis, a high-performance quasi-solid-state Na-ion battery is built by pairing a low-water-content PBAs cathode with Na₂C₂O₄ additive and a hard carbon (HC) anode within a poly(ethylene glycol) diacrylate (PEGDA)-based quasi-solid-state electrolyte with high ionic conductivity and electrochemical stability. This battery exhibits the specific capacities ranging from 58 to 105 mAh·g^-1 at current densities from 20 to 500 mA·g^-1, capable of sustaining stable cycling for over 200 cycles. This study underscores the significant improvement in stability and capacity of PBAs cathode materials by the efficient removal of crystalline water in them.

Absorptive materials, by absorbing electromagnetic wave energy, effectively mitigate electromagnetic interference through reduction or elimination of wave reflection. The electromagnetic parameters of materials determine their electromagnetic wave absorption performance. Traditional control strategies, such as adjusting filler ratio, changing macroscopic morphology, and regulating composite methods, have certain limitations to control their structure and cannot fundamentally alter their electromagnetic parameters, which severely hinders their further development. Now, micro-nanostructure design strategies can basically change electromagnetic parameters of the materials by altering their electrical conductivity, charge density and magnetic properties, showing significant advantages in controlling electromagnetic wave absorption capacity. However, the precise micro-nanostructure design and the mass production still face challenges to be overcome. Additionally, structure-property relationship between micro-nanostructures and electromagnetic wave response, and its underline mechanisms are still not fully understood. Herein, a comprehensive review on these relationships was introduced to elucidate the advantages of micro-nanostructure design strategies for regulating electromagnetic wave absorption capacity. Moreover, by introducing these strategies, such as element doping, surface effect modulation and nucleation-controlled growth, this review provides researchers with deep insights and theoretical guidance for modulating electromagnetic properties through micro-nanostructure design. Finally, the research progresses on electromagnetic performance modulation through micro-nanostructure design based on the case of quantum dots, nanocrystals and nanowires, as well as the current research status and prospects in the field of electromagnetic absorption were summarized, providing a theoretical foundation and strategic support for the development of micro-nanoparticles.

Recently, organic-inorganic hybrid perovskite solar cells have demonstrated a broad commercial prospect due to their high photoelectric conversion efficiency (PCE) and low fabricating costs. During the past decades, the highest reported PCE of small-area (<1 cm²) perovskite solar cells (PSCs) rose to 26.10%, and those of large-area (1-10 cm²), mini-module level (10-800 cm²) and module level (>800 cm²) PSCs increased to 24.35%, 22.40% and 18.60%, respectively. The performance of PSCs decreases dramatically with the area increasing due to limitation of the deposition method and the poor quality of large-area perovskite films. Spin-coating method is not suitable for actual industrial production, while the scalable deposition methods including blade-coating and slot-die coating still face the difficulty of precisely controlling nucleation and crystallization of the perovskite films with large area. This review summarized preparation methods of large-area perovskite films, and discussed the film-forming mechanism and strategies for high-quality perovskite films. Finally, relevant outlooks on technologies and applications for large-area PSCs with high performances and stabilities were analyzed. This review is expected to provide insights on the research of large-area PSCs with high performance.

Nowadays, we are facing increasingly serious energy and environmental problems, which urgently need more efficient chemical industry technologies to meet the requirements of low cost, high yield and sustainability. Developing efficient catalysts is of great significance for improving production efficiency, expanding economic benefits, optimizing energy structure, and ameliorating industrial structure. Single-atom catalysts (SACs), featuring unique properties arising from their single-atom dispersion on support surface, have demonstrated exceptional activity, selectivity and stability in energy catalysis, environmental catalysis and organic catalysis. Therefore, preparation methods and catalytic mechanisms of SACs have become a hot research topic on the international catalytic community. This review describes three strategies for preparing SACs: bottom-up synthesis, top-down synthesis and quantum dots cross-linking/self-assembly. Specifically, methods such as co-precipitation, immersion, atomic layer deposition, high-temperature atom thermal transfer, and high-temperature pyrolysis are presented in detail. These approaches precisely control the location and distribution of metal atoms, maximizing their utilization and catalytic efficiency. In addition, the challenges and development prospects faced by SACs related to stability, integrated control and industrial scalability are also summarized.

Compared to Li-ion batteries, Na-ion batteries hold significant advantages and market value for achieving low-cost and large-scale energy storage, thanks to the utilization of cheap and abundant Na resources. However, the use of highly flammable liquid electrolytes with leaky risk raises safety concerns for conventional Na-ion batteries under abuse conditions such as mechanical damage, short-circuiting, and thermal runaway. Limited electrochemical stability of liquid electrolytes also hinders further enhancement of the performance of Na-ion batteries for practical use. This study reports a facile way for the preparation of high-performance gel polymer electrolyte (GPE) by thermal-driven radical in-situ polymerization of dipentaerythritol penta-/hexa-acrylat (DPEPA). This GPE exhibits an ionic conductivity of 1.97 mS·cm^-1, a Na⁺ transference number of 0.66, and a broad electrochemical stability window. The DPEPA displays a lower lowest unoccupied molecular orbit (LUMO) energy level than that of ethylene carbonate (EC) and diethyl carbonate (DEC) solvents, allowing for its preferential decomposition alongside NaPF₆ on the anode surface. This leads to a stable organic-inorganic composite film of solid-state electrolyte interphase, inhibiting the decomposition of electrolyte solvents on the anode surface. The quasi-solid-state Na-ion battery employing Na(Ni _1/3Fe_1/3Mn _1/3)O₂ (NFM) cathode and hard carbon (HC) anode in this GPE exhibits a high capacity retention rate of 92% after 300 stable cycles at a current density of 120 mA·g^-1, while achieving the specific capacities of 99-120 mAh·g^-1 within a wide temperature range of 20-80 ℃. In-situ X-ray diffractometer analysis reveals the highly reversible structural evolution of the NFM cathode during Na storage and the “adsorption-pore-filling” mechanism of Na⁺ storage in the HC anode. All data in this research demonstrates that introducing polymers with low LUMO energy levels proves an effective approach to enhance the electrochemical stability of solid-state Na-ion batteries while improving cell safety.

To further expand the application of advanced ceramic materials in helicopters, this paper reviews their application in helicopter structures both domestically and internationally. It emphasizes the technical maturity and development trends of various ceramic materials in helicopter specific structural applications, such as energy impact protection parts, energy conversion components, and corrosion protection areas. By comparing the gaps between domestic and international use of advanced ceramic materials in helicopter specific structures, the paper provides suggestions for the future development. Recommendations include the use of reaction-sintered contoured integrated opaque armor ceramics and polycrystalline transparent armor ceramics for the high-speed dynamic impact energy protection parts, cermet composite coatings compatible with epoxy resin composite substrates for the low-energy impact protection parts, and hybrid ceramic matrix composite/polymer matrix composite (HCMC-PMC) materials for the thermal shock protection parts. Additionally, multifunctional composite materials, such as high-performance miniature piezoelectric ceramic thin film functional devices and flexible hybrid electronic structures based on micro-piezoelectric ceramic materials, should be developed for the mechanical and electrical energy conversion components. Microwave-absorbing ceramic composites derived from polymer-derived ceramics that are compatible with epoxy resin composite substrates are recommended for the electromagnetic and thermal energy conversion components. Furthermore, high-performance abrasion-resistant and corrosion-resistant Sol-Gel coatings are suggested for the corrosion protection areas. It is also essential to establish a high-speed dynamic energy impact protection mechanism for helicopters, optimize the ballistic performance of protective materials, and develop advanced ceramic materials digital testing and verification technologies, represented by multi-functional composite materials for helicopter specific structures. These efforts will greatly shorten the application cycle of advanced ceramic materials and reduce the verification cost.

Owing to the high strength/toughness and excellent anti-oxidation ability, continuous fiber reinforced ceramic matrix composites have become the preferred candidates for high temperature structural materials in aerospace field. Reactive melt infiltration can achieve the large-scale, short-cycle and low-cost production of ceramic matrix composites, which has been widely considered to be one of the most promising technologies from a commercial perspective. However, the mechanical and anti-oxidation/ablation properties of obtained composites prepared by conventional reactive melt infiltration are not satisfactory due to the existence of residual carbon and corroded fibers. In order to address the problems, relevant researchers constructed porous carbon matrix to replace conventional densified structure to promote its ceramic transformation and the consumption of reactive melt, thus achieving the improved performance of ceramic matrix composites. This paper reviewed the research progress about the preparation of SiC ceramics, SiC/SiC composites, C/SiC composites, and ultra-high temperature ceramic matrix composites by porous carbon ceramization strategy. Besides, the superiority of the method was verified compared to conventional reactive melt infiltration. The development of preparation methods for porous carbon matrix was also summarized. Finally, in term of the requirements of basic theory and technology for advanced ceramic matrix composites, the prospect for the future development of improved reactive melt infiltration to prepared ceramic matrix composites was discussed.

The development trend of high voltage, high current and high-power density of power semiconductor devices has raised the requirement for the heat dissipation capability and reliability of ceramic substrates in devices. Silicon nitride (Si₃N₄) ceramics, known for their high thermal conductivity and excellent mechanical properties, have emerged as a preferred thermal dissipation substrate material for high-power electronic devices. However, there is a significant gap between experimental and theoretical values of thermal conductivity in Si₃N₄ ceramics. The long period of heat preservation during preparation leads to excessive grain growth, compromising mechanical properties and increasing costs, which hinders large-scale application. Lattice oxygen defects act as main factor limiting thermal conductivity of Si₃N₄ ceramics. Now, researchers are exploring ways to promote removal of lattice oxygen and full development of bimodal morphology formation of Si₃N₄, by selecting non-oxide sintering additives to reduce the oxygen content in the system, adjusting the composition and properties of the liquid phase, constructing a “nitrogen-rich-oxygen-deficient” liquid phase, and regulating the dissolution and precipitation process in the liquid phase. These efforts aim to the synergistic optimization of thermal conductivity-mechanical properties of Si₃N₄ ceramics. Based on the elemental classification, we review the non-oxide sintering additives developed at domestic and abroad, explain how they improve the thermal conductivity of Si₃N₄ ceramics from liquid-phase modulation and microscopic morphology control, analyze the grain development and morphology evolution laws, and discusse the mechanism of lattice oxygen removal. The out look on future development of high thermal conductivity Si₃N₄ ceramics is also prospected.

Carbide ultra-high temperature ceramics (UHTCs) have emerged as ideal coating materials for the thermal protection systems of hypersonic vehicles due to their high melting point (>3000 ℃), high hardness, low thermal conductivity, excellent heat resistance, and good chemical stability. This review provides a comprehensive overview of structure and properties of carbide UHTCs, namely TiC, ZrC, HfC, NbC, and TaC. Furthermore, it summarizes recent developments in preparation of carbide UHTC coatings using various methods, including chemical vapor deposition, plasma spraying, and solid-phase reaction. Effects of coating microstructure, composition, structural design, and heat flux on the ablation behavior are analyzed. Data from recent literature corroborate that the added second phase can facilitate formation of complex oxides, generate an oxidation layer during ablation to undergo moderate sintering, protect structural integrity, and enhance oxygen barrier properties. Multi-layer structural designs utilize gradient layering and multi-functional structures, which effectively alleviate thermal stress within the coating, suppress crack propagation, and facilitate synergistic enhancing effects among different layers. Finally, the challenges and opportunities in development of carbide UHTC anti-ablation coatings are prospected.

High-entropy transition metal nitrides (HENs) are renowned for their thermal stability, corrosion and oxidation resistance, and exceptional mechanical properties, endowing them suitable for use as surface protection films for structural and moving components. However, mapping relationship between broadly adjustable metal components and mechanical properties of HENs is quite complex due to their diversity of HENs components. Taking (NbMoTaW)N_x thin film as the research object, this study prepared (NbMoTaW)N_x (x = 0, 0.59, 0.80, 0.95) thin films with different nitrogen contents by regulating nitrogen flow velocity during the film growth process based on the magnetron sputtering technique. Following analysis of (NbMoTaW)N_x thin films' composition, structure, morphology, and performance, the primary influence mechanism that govern their mechanical properties were explored. The findings revealed that by manipulating nitrogen vacancy, coordinated regulation over the lattice distortions of the nitrogen and metal sublattices was achieved. Due to high degree of the nitrogen and metal sublattice distortions, the (NbMoTaW)N_0.80 sample demonstrated the highest hardness and best wear resistance performance. After excluding factors such as electronic structure, residual stress, and grain size that affect mechanical properties, a direct relationship between lattice distortions and mechanical properties of HENs films was confirmed. In summary, this research has unearthed a straightforward strategy for controlling the lattice distortions, offering a novel approach to adjust and optimize the performance of nitride films, and ultimately providing a more effective solution to address the mechanical damage issues that arise in the context of complex service environments.

SiC ceramics exhibit high strength and thermal stability, rendering them highly suitable for applications in space and thermal components. However, the growing demand for large-sized and complex-shaped SiC ceramics necessitates advanced manufacturing techniques. In comparison to traditional reduction and equal material manufacturing methods, 3D printing technology offers significant advantages in various aspects, such as manufacturing cycle, effective cost, and reliability. There are many 3D printing methods, each with distinct characteristics. Stereolithography (SLA) is capable of achieving high precision and superior surface quality. However, its practical applications often necessitate special design of support structures. Additionally, issues such as residual stress and low solid content significantly hinder its further development. Selective laser sintering (SLS) exhibits strong material compatibility, which is suitable for a wide range of materials, including polymers, metals and ceramics. This technology enables large-scale rapid prototyping at low manufacturing costs. But its surface quality of the formed billet is typically insufficient, which needs additional post-processing. Fused deposition modeling (FDM) though facilitates the preparation of SiC ceramics via reaction sintering, proves unsuitable for constructing large components which restricts its applicability in actual production contexts, due to its inadequate interlayer bonding strength coupled with pronounced surface striations and slower forming speeds. This paper reviews the latest research progresses of 3D-printed SiC ceramics and analyzes the subsequent high-temperature densification treatments of green bodies, along with their fundamental physical properties. Finally, it proposes some prospects of 3D printing of SiC ceramic materials, and strengthens integration of new 3D printing technologies and various printing methods for fine regulation of ceramics’ macro- and micro-structures.

With the rising of the gas inlet temperature in front of the turbine of aero-engine, ceramic matrix composites (CMCs) have emerged as the preferred matrix material for the new generation of high-temperature components in aero-engine due to their light weight, high strength, oxidation resistance, insensitivity to crack, and excellent temperature durability. However, because of their limited resistance to high temperature water vapor and oxygen erosion, development of thermal spray coating technology for hot-end components of CMCs engines has become an urgent challenge to be overcome. In this paper, based upon changes of material selection strategies and application examples of foreign aero-engines, technical limitations of the employed superalloys + film cooling + thermal barrier coatings (TBCs) for hot-end components of aero-engines were analyzed, and technical advantages of the utilized CMCs + appropriate film cooling + environmental barrier coatings (EBCs) were consolidated. Thermal and environmental barrier coatings (TEBCs) and environmental barrier coatings-abradable sealing coatings (EBCs-ASCs) for CMCs were reviewed on the basis of recent research findings from domestic and oversea scholars. Finally, opportunities and challenges associated with thermal spraying EBCs for higher temperature gas flow were analyzed, and the direction of design and preparation on a certain composition and structure for TEBCs was clarified, among which the focal points of future research endeavors were prospected.

In response to the urgent demand for ultra-high temperature ceramic matrix composites with integrated thermal protection and load-bearing capabilities for high-speed aircrafts, this study prepared stable ceramic slurry from submicron HfC ceramic powder, and utilized the slurry pressure impregnation-assisted precursor infiltration pyrolysis (PIP) process to fabricate C/HfC-SiC composites with uniformly distributed HfC matrix to overcome the shortcomings of the existing reaction-derived HfC precursor, such as high cost, low efficiency, and poor densification effect. The influence of HfC content on the microstructure, mechanical properties, and ablation resistance of composites was investigated. Results showed that the composites had density of 2.20-2.58 g·cm^-3 and open porosity of approximately 5% when the actual volume fraction of HfC was in range of 13.1%-20.3%. Utilizing a single layer of carbon cloth to impregnate the ceramic slurry with pressure, HfC particles were able to disperse into the interior of the fiber bundle and distributed relatively evenly in the composites. Increasing the HfC content resulted in reducted fiber content, and decreased mechanical properties of composites. Specifically, when HfC volume fraction was 20.3%, the composites exhibited density, tensile strength and fracture toughness of 2.58 g·cm^-3, 147 MPa and 9.3 MPa·m^1/2, respectively. Following 60 s of ablation under an oxygen acetylene flame, the composites demonstrated linear ablation rate of 0.0062 mm/s and mass ablation rate of 0.005 g/s. The molten phase Hf_xSi_yO_z formed during the ablation process could effectively cover the composites surface and provide protection.

Hydrogen generation from electrolyzed water has received extensive attention in the scientific community due to its green and environmentally friendly properties, as well as the high purity of hydrogen produced. However, the slow oxygen evolution reaction (OER) during electrocatalytic water splitting has significantly hampered the development of hydrogen production, posing numerous challenges in its practical application. In this study, a novel three-dimensional (3D) core-shell heterostructure catalyst with crystalline NiMoO₄ nanorods as “core” and amorphous CoFe-LDH nanosheets as “shell” was successfully fabricated on a conductive nickel foam (NF) substrate by using a combination of hydrothermal and electrodeposition strategy. This special 3D core-shell structure fully stimulates the electrocatalytic potential of NiMoO₄ and CoFe-LDH, which greatly enhances the efficiency of the overall water-splitting. Through the synergistic interaction of NiMoO₄ and amorphous CoFe-LDH, the NiMoO₄@CoFe-LDH/NF nanocatalysts generates more active sites and exhibits highly efficient electron transfer ability and excellent OER electrocatalytic activity. Electrochemical tests show that NiMoO₄@CoFe-LDH/NF exhibits the most excellent electrochemical performance when the electrodeposition time is 60 s. The overpotentials η₁₀ and η₁₀₀ at 10 and 100 mA·cm⁻² are only 168 and 216 mV, respectively, which shows a very small Tafel slope and excellent long-term stability. Meanwhile, the overall water-splitting system of NiMoO₄@CoFe-LDH||NiMoO₄ exhibits a low driving voltage, which can produce a current density of 10 mA·cm⁻² at 1.57 V. In conclusion, this work provides new ideas for design and development of efficient catalytic materials for electrolyzed water.

Silicon sludge, the photovoltaic cutting silicon waste, has become one of the expected raw materials for the key silicon carbon anode materials used in high energy density batteries above 300 Wh·kg^-1 due to its low cost, two-dimensional lamellar structure and ultrahigh specific capacity (4200 mAh·g^-1). However, silicon sludge requires systematic modification because of its challenges such as complex composition, large particle size, poor electrical conductivity, low stability and poor electrochemical performance. This paper systematically reviews the application status and research progress of silicon sludge in lithium-ion batteries. Firstly, the important effects of metal and non-metal impurities on battery performance are summarized, in which metal impurities are normally removed by magnetic separation and acid pickling, and non-metallic impurities are removed by liquid-liquid extraction and heat treatment. Secondly, detailed elucidation about the initial performance and modification methods of the silicon sludge is provided. Concretely, silicon sludge can be nano-sized to reduce expansion by grinding, etching, electrothermal shock, and alloy dealloying, enhance electrical conductivity through doping the intrinsic silicon and doping the carbon layer on the silicon surface, improve stability through the construction of inert layer, conductive layer and functional group, and obtain mechanical support and protection through silicon-carbon composite. Finally, the challenges, development directions and future prospects of silicon-based anode based on silicon sludge are put forward, aiming to provide a reference for converting silicon sludge into treasure and promote the rapid development of high energy density lithium-ion batteries.

β-FeSi₂, an environmentally friendly and high temperature oxidation-resistant thermoelectric material, has potential applications in the field of industrial waste heat recovery. Previous studies have shown that phosphorus (P), an ideal n-type dopant in the silicon (Si) site of β-FeSi₂, can easily lead to the formation of a secondary phase, thereby limiting the enhancement of thermoelectric performance. In this study, a series of FeSi_2-xP_x (x=0, 0.02, 0.04, 0.06) samples were synthesized using an induction melting method, which greatly inhibited the formation of the secondary phase. Then, the influence of P doping on the electrical and thermal transport properties of β-FeSi₂ was studied. The results indicate that the solubility limit of P in β-FeSi₂ is about 0.04, consistent with earlier theoretical predictions based on the defect formation energy. It is also discovered that P doping enhanced the thermoelectric performance of β-FeSi₂, culminating in an optimal figure of merit (ZT) of FeSi_1.96P_0.04 approximately 0.12 at 850 K, which is much higher than the previous results (ZT about 0.03 at 673 K). However, compared to β-FeSi₂ doped with other n-type elements like cobalt (Co) and iridium (Ir), which can achieve carrier concentrations up to 10²² cm^-3, P-doped β-FeSi₂ exhibits lower carrier concentrations, with the highest of only 10²⁰ cm^-3. This results in a weaker electron-phonon scattering effect, which in turn constrains the overall enhancement of the thermoelectric performance. If the carrier concentration could be further increased, the thermoelectric performance of the material is expected to evolve significantly.

Calcium bismuth niobate (CaBi₂Nb₂O₉) is a typical bismuth layered structure piezoelectric material with high Curie temperature (about 943 ℃) and high stability, which is an important candidate functional element for high temperature vibration sensors above 600 ℃. However, its low piezoelectric coefficient and high temperature resistivity seriously limit the signal acquisition of high-temperature piezoelectric vibration sensor. To improve the comprehensive performance, in this work, W/Cr co-doped CaBi₂Nb_1.975W_0.025O₉-x%Cr₂O₃ (CBNW-xCr, 0<x≤0.2) Aurivillius phase ceramics were prepared via conventional solid-state sintering route. The effects of W/Cr co-doping on the crystal structure and electrical properties of CBN piezoelectric ceramics were investigated. The results show that co-doping of W/Cr elements transforms crystal structure of the ceramics from orthorhombic to tetragonal crystal system, enhances distortion of the crystal structure, and significantly improves piezoelectric and insulating properties of the piezoelectric ceramics. When x=0.1, the Curie temperature is 931 ℃, the piezoelectric coefficient is 15.6 pC/N, the resistivity reaches the order of 10⁶ Ω∙cm at 600 ℃, and the dielectric loss is only 0.029, which endows the system an important potential application in the field of high-temperature piezoelectricity.

The investigation of novel materials exhibiting exceptional resistance to calcium-magnesium-aluminum- silicate (CMAS) corrosion at temperatures of 1300 ℃ and above has emerged as a pivotal objective in the advancement of environmental barrier coatings for aircraft engines in recent years. In this study, atmospheric plasma spraying (APS) technology was employed to fabricate YAG(Y₃Al₅O₁₂)/Al₂O₃ coatings with eutectic composition, which was acknowledged as a promising material possessing outstanding CMAS corrosion resistance, thereby rendering it suitable for application in environmental barrier coatings. The as-deposited coatings were annealed at 1100, 1300, and 1500 ℃ to obtain different microstructures, and the corrosion resistance as well as mechanism of YAG/Al₂O₃ coatings against CMAS were investigated by comparing the corrosion results after exposure to CMAS at 1300 ℃. The reaction products between YAG/Al₂O₃ coatings and CMAS were found to be garnet-structure solid solution, CaAl₂Si₂O₈, and Ca₂MgSi₂O₇. The nearly continuous distribution of the garnet-structure solid solution layer at the reaction interface between YAG/Al₂O₃ coating annealed at 1100 ℃ and CMAS effectively impedes the diffusion of CMAS corrosion elements. For YAG/Al₂O₃ coating annealed at 1500 ℃, the increase in grain size and decrease in grain boundaries reduce the dissolution rate of the coating. Both of the above can affect the competitive precipitation of various products by influencing the ion transport rate in the corrosion process, and then improve the CMAS corrosion resistance of the coating. Moreover, heat-treatment temperature can tailor grain size, which influences both dissolution-precipitation rate and competitive precipitation of reaction products during CMAS corrosion. These findings provide guidance for selecting appropriate heat-treatment temperature and offer a novel approach to optimize CMAS corrosion resistance of YAG/Al₂O₃ coatings through microstructure optimization.

High-entropy boride ceramics (HEBs) consisting of four or more principle metallic elements rapidly develop in recent years due to their outstanding unique physical properties and excellent elevated temperature properties, showing extraordinary promise as potential thermal protection materials applied in extreme environments. However, on the basis of unclear role of each element on their oxidation reaction, HEBs are generally difficult to densify because of their low self-diffusion coefficients and possible sluggish diffusion effect, resulting in limited mechanical properties and low oxidation resistance. In this work, a novel type of HEBs, (Ti_0.25Zr_0.25Hf_0.25Ta_0.25)B₂-B₄C composites, were prepared by boro/carbothermal reduction method combined with hot-pressing sintering at 1900 ℃. The effect of B₄C at the volume fractions ranging from 10% to 30% on the mechanical properties and oxidation resistance of the composites was systematically investigated. Microstructure analyses indicate that homogenously distributed B₄C can suppress grain growth of the HEBs matrix and promote toughening mechanisms such as crack deflection and crack branching, consequently resulting in strengthening and toughening composites. When the volume fraction of B₄C is 20%, the as-prepared composite shows a high relative density (96.1%) and good mechanical properties with Vickers hardness of (24.6±1.1) GPa, flexural strength of (570.0±27.6) MPa and fracture toughness of (5.58±0.36) MPa·m^1/2. In addition, exploration on the oxidation resistance of (Ti_0.25Zr_0.25Hf_0.25Ta_0.25)B₂-B₄C composites at temperatures ranging from 800 ℃ to 1400 ℃ shows that excellent oxidation resistance occurs at the chosen temperatures due to the formation of a dense and continuous oxidation scale, which acts as a barrier layer preventing oxygen inward diffusion. The main compositions of the oxide scale are TiO_x, (Zr, Hf)O₂ oxides and B₂O₃ at 800 ℃, while multicomponent oxidation products of (Zr, Hf, Ta)O_x, (Zr, Hf)O₂ and TiTaO₄ are formed in the oxide scale at 1100 ℃. As the temperature increased to 1400 ℃, thickness of the oxide layer significantly increases due to their volatilization of B₂O₃, while continuous B₂O₃ glassy phase plays a crucial role in the oxidation process of HEBs. When the B₄C volume fraction not less than 20%, TiTa₂O₇ and TiO₂ which were embedded in B₂O₃ glass, could effectively insulate inward oxygen and interfacial oxide thickness and enhance oxidation resistance of the composites. In summary, the primary work can be used as a reference to the researches relating to optimizing mechanical properties and oxidation resistance for HEBs.

Piezoelectric multilayer actuators feature large displacement generation at a relatively low driving voltage and are widely used in various fields. As the most commonly used material in multilayer actuators, soft lead zirconate titanate (PZT) ceramics have higher dielectric constant and loss, which often lead to higher power consumption and heat generation that in turn affect fatigue characteristics and stability of piezoelectric multilayer actuators. In this work, Mn-doped (in mole fraction) Pb(Sb_1/2Nb_1/2)_0.02Zr_0.51Ti_0.47O₃-0.6%MnCO₃ (PSN-PZT) hard ceramic was selected as base material in order to prepare piezoelectric ceramics that have low heat generation and are suitable for the application of piezoelectric multilayer actuator. Certain amount of Li₂CO₃ was doped as sintering aid for lowering sintering temperature of ceramics, and above-Curie-temperature polarization was utilized to enhance electric properties of ceramics. Eventually, multilayer actuator composed of this material was fabricated via tape-casting process and compared with Pb(Mg_1/3Nb_2/3)_0.25(Ti_0.48Zr_0.52)_0.75O₃ (PMN-PZT) actuator prepared with the same parameters. The results indicated that the sintering temperature of PSN-PZT ceramic was decreased to 1050 ℃ due to Li₂CO₃ sintering aid, which introduced liquid sintering during the sintering process. PSN-PZT ceramics poled above the Curie temperature obtained optimal electric performance with 0.1% (in mass) Li₂CO₃ doping, and the piezoelectric coefficient (d₃₃) and unipolar strain at 2 kV/mm reached 388 pC/N and 0.13%, respectively. The results of temperature rise and strain degradation of both multilayer actuators indicated that the temperature rise of hard PSN-PZT actuator was about 20 ℃ lower than that of PMN-PZT actuator under 200 Hz and the strain decreased by 6% after 5×10⁶ cycles. It indicates that PSN-PZT ceramics with Li₂CO₃ doping for lowering sintering temperature have some advantages in heat generation and fatigue characteristic while having descent piezoelectric properties, which endows it an important potential application in high-power, high-frequency and other demanding working conditions.

Among all options of carbon neutrality, conversion of CO₂ into valuable chemicals by electrocatalytic reduction exhibit outstanding performance. However, due to the numerous products and complex pathways of CO₂ electrocatalytic reduction, the exact factors affecting the activity of CO₂ electrocatalytic reduction have not yet been identified. In addition, the CO₂ electrocatalytic reduction process is often accompanied by hydrogen evolution reaction (HER). Therefore, it is still challenging to design a catalyst with high selectivity and high activity for specific product. Herein, this study systematically investigated the potential of 3d transition metal-based single-atom catalysts (SACs) positioned at graphene single vacancies (TM@C_SV), as well as double vacancies (TM@C_DV), for the CO₂ reduction reaction (CO₂RR) using first-principles. The exploration encompassed substrate stability, CO₂ adsorption, and the HER as the main competing reaction. Through the careful screening of 20 catalysts formed by Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn doped graphene defects, several promising catalysts were identified: Sc@C_SV situated on graphene single vacancies, Sc@C_DV and Ti@C_DV situated on graphene double vacancies. They could not only effectively adsorb CO₂ molecules, but also inhibit HER, the main competing reaction. In assessing their performance in CO₂RR, all exhibited selectivity toward HCOOH. Notably, Sc@C_DV demonstrated the best selectivity, requiring the lowest ΔG (0.96 eV) for efficient CO₂ conversion to HCOOH. Electronic structure analysis revealed that Sc@C_DV outperforms due to its optimal balance between ΔG of hydrogenation and the product desorption achieved through a moderate number of active electrons.

In the process of electrolyzing water to produce hydrogen, the sluggish electrocatalytic kinetics of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) limit the energy conversion efficiency. High-entropy materials have been considered as potential catalysts due to their unique structural features and excellent performance, which could potentially replace traditional metal oxides and precious metals for energy conversion and water electrolysis. Due to the incompatibility between different metals and non-metals, there have been few reports on the synthesis of high-entropy compounds, especially high-entropy metal phosphides. In this study, a series of carbon-based high-entropy alloy phosphide nanoparticles were synthesized using citric acid as complexing agent and ammonium dihydrogen phosphate as phosphorus source via a low-temperature Sol-Gel method with different elemental metals. In 1 mol·L^-1 KOH solution, FeCoNiMoCeP/C exhibited good water electrolysis performance at a current density of 10 mA·cm^-2, with overpotentials of 119 and 240 mV for the HER and OER, respectively. Similarly, in overall water splitting studies, FeCoNiMoCeP/C also showed excellent catalytic activity. When operating at a current density of 10 mA·cm^-2, FeCoNiMoCeP/C required only 1.53 V as the combined anode and cathode voltage for electrolyzing water. This is due to the synergistic effects among the atoms of high-entropy phosphide catalysts which provide more reaction sites to increase reaction activity and selectivity. This study is expected to expand the potential applications of high-entropy alloys in the field of electrocatalysis.

Recently, perovskite solar cells have developed marvelously of which power conversion efficiency (PCE) achieved 26.1%, but the mechanical bending and environmental stability of flexible perovskite solar cells (F-PSCs) have remained major obstacles to their commercialization. In this study, the quality and crystallization of perovskite thin films were enhanced by adding agarose (AG). The interaction mechanism, PCE, mechanical bending and environmental stability of the assembled F-PSCs were investigated. It was found that the perovskite films modified by the optimal concentration of AG (3 mmol/L) exhibited denser and smoother morphology, higher crystallinity and absorbance, the lowest defect state density, and lower charge transfer resistance of 2191 Ω. Based on the optimal photoelectric properties, PCE increased from 15.17% to 17.30%. TiO₂ nanoparticles (0.75 mmol/L) were further introduced to form a synergistic interaction with AG (3 mmol/L), which provided a rigid backbone structure, and thus enhanced the mechanical and environmental stability of perovskite layers. After 1500 cycles of bending (3 mm in radius), the AG/TiO₂ co-modified F-PSCs maintained 84.73% of initial PCE, much higher than the blank device (9.32%). After 49 d in the air, the optimal F-PSCs still maintained 83.27% of initial PCE, superior than the blank device (62.21%). This work provides possibility for preparing highly efficient and stable F-PSCs.

Ferroferric oxide (Fe₃O₄) magnetic nanoparticles are widely used as passive targeting carriers in gene therapy, due to their simple preparation, targeting under external magnetic field and easy surface grafting. This study synthesized oil phase Fe₃O₄ nanoparticles with controllable particle sizes in the range from 4 to 9 nm by regulating the accumulation growth time in the solvothermal method. Then, meso-2, 3-dimercaptosuccinic (DMSA) was employed to double exchange oleic acid molecules on its surface to provide good water dispersibility. Finally, Fe₃O₄-DMSA-PEI magnetic nanoparticles were obtained by grafting branched polyethylenimine (PEI) onto Fe₃O₄-DMSA surface through amidization reaction. The results demonstrate that the Fe₃O₄-DMSA-PEI magnetic nanoparticles have a surface Zeta potential of (52.50 ± 1.94) mV, remaining a certain degree of superparamagnetism (14.48 emu/g, 1 emu/g=1 A∙m²/kg). When the mass ratio of Fe₃O₄-DMSA-PEI magnetic nanoparticles to plasmid DNA is 15 : 1, it can completely block DNA and its loading capacity is as high as 6.67%. The Fe₃O₄-DMSA-PEI magnetic nanoparticles prepared in this study have a certain gene delivery ability and are expected to be used as gene carriers in the field of gene transfection.

Electrochromic materials with dynamic color change and optical modulation have potential applications in the fields of automotive anti-glare mirror, smart window, low-power display, and electronic paper, attracting worldwide attention. NiO and MnO₂ are typical anodic coloration materials with a comfortable neutral tone. However, the low transmittance of single NiO or MnO₂ films in bleaching states leads to small optical modulation. Herein, a porous nickel-manganese layered double hydroxide (NiMn-LDH) film with neutral color for visible electrochromic application was prepared. The NiMn-LDH films were grown directly on fluorine-doped tin oxide (FTO) conductive glass substrates by a one-step solvothermal method using NiCl₂·6H₂O and MnSO₄·H₂O as the raw materials. The crystalline phase and micromorphology of the as-grown NiMn-LDH films were characterized and the electrochromic and electrochemical performances were also investigated. The results indicate that the film grown by solvothermal method is composed of NiMn-LDH nanosheets with porous surface morphology, leading to a large optical modulation of 61.9% at 550 nm. The coloration and bleaching time are calculated to be 15.8 and 13.2 s, respectively. A high coloration efficiency of 63.1 cm²·C^-1 is also achieved for the as-grown NiMn-LDH nanosheet film. Meanwhile, the NiMn-LDH film electrode demonstrates good cycle stability, retaining 87.0% of its maximum optical modulation after 160 cycles. Furthermore, the NiMn-LDH film electrode delivers an area capacitance of 10.0 mF·cm^-2 at a current density of 0.1 mA·cm^-2. These results consolidate that the as-prepared NiMn-LDH film electrode is a promising candidate for both electrochromic and energy-storage applications.

Mechanoluminescent (ML) materials, due to their unique mechanical-to-optical energy conversion, hold significant promise in stress sensing and are poised to become the next generation of visual strain-sensing materials. Currently, expanding ML material systems and enhancing their performance remain focal points of research. In this study, a series of Tb³⁺-doped green ML phosphors was synthesized using BaSrGa₄O₈ matrix (hexagonal crystal system, space group P6₃, with a non-centrosymmetric structure) via high-temperature solid-state synthesis. These materials emitted bright green light under various mechanical excitations (tension, compression, and torsion). Clear note mappings were observed by writing B, S, G, O, T, and b on the prepared ML elastomer with a glass rod. By analyzing the colormap, the stress conditions during the writing process could be traced. This is the first observation of ML phenomenon in the above-mentioned matrix doping system. Under 254 nm ultraviolet (UV) excitation, BaSr_1-xGa₄O₈: xTb³⁺ phosphors exhibited bright green emission at 543 nm, which was attributed to ⁵D₄-⁷F₅ transition of Tb³⁺, and shared the same luminescent center as ML. The samples continued to display strong long persistent luminescence after UV irradiation was removed. By combining ML, photoluminescence (PL), and long persistent luminescence (LPL) with thermoluminescence (TL) analysis, further insights into their intrinsic connections were elucidated. In conclusion, this study broadens the range of high-performance ML material systems, showcasing potential applications in visual strain sensing, information security, and anti-counterfeiting.

Electrochemical reduction of CO₂ to high value-added hydrocarbon fuels and chemicals has emerged as an effective strategy to achieve carbon neutrality. In conventional electrocatalytic powder-coated electrodes fabricated by spraying method, poor contact between electrocatalyst and substrate can severely impact the electrocatalytic activity and stability. Herein, a self-supporting nanotree electrode (Bi@Cu NTs) for efficient electroreduction from CO₂ to formate was structured by combing facile electrodeposition method and galvanic replacement reaction. The advantages of self-supporting nanotree structure including: 1) minimization of the interfacial resistance and improvement of the spatial structure stability; 2) rich active sites and plentiful pore structures. The charge transfer resistant could be effectively reduced while ensuring the stability of the electrode operation. Results demonstrated that the prepared Bi@Cu NTs electrode exhibited outstanding performance for CO₂ conversion in both electrochemical activity and long-term operation stability. In a wide operating potential window from -1.4 to -0.8 V (vs. RHE), the proposed Bi@Cu NTs electrode presented excellent formate selectivity, where the Faradaic efficiency of CO₂-to-formate (FE_Formate) at each operating potential was above 90%. Typically, at -1.2 V, the proposed electrode achieved a high FE_Formate of 97.9% and a current density of 170.6 mA·cm^-2, simultaneously. Meanwhile, the self-supporting Bi@Cu NTs electrode also revealed excellent stability in a long-term operation, as evidenced by maintaining an average FE_Formate of more than 90% and an average current density higher than 110 mA·cm^-2 over 50 h of continuous electrolysis at a controlled potential of -1.0 V without any degradation in performance.

Ceramics are one of the earliest synthetic materials in human civilization, which is originated in China. They represent not only the nation's glory but also the testament to the wisdom and innovation of her people. After millennia, ceramics have evolved into a vital material system encompassing both traditional and advanced varieties, with structural ceramics holding a key position. Their high-temperature resistance, corrosion resistance, and superior mechanical properties endow them indispensable in harsh environments where metals and polymers are still in struggle, underscoring their role as a cornerstone of modern technological progress. Ceramic matrix composites have mitigated the brittleness of structural ceramics, garnering global attention for their irreplaceable advantages, particularly in extreme conditions like ultra-high temperatures, intense radiation, and severe corrosion, across sectors such as aerospace, transportation, and advanced nuclear energy.
Despite peaking in the 1980s with innovations like ceramic engines and high-performance cutting tools, the development of structural ceramics encountered a slump due to limitations in fabrication techniques and reduced industrial demand. Nevertheless, persistent research efforts have led to significant advancements, broadening application scope of these materials.
Invited by Journal of Inorganic Materials, we have curated the special issue of “Frontiers of Structural Ceramics” featuring contributions from eminent domestic research groups, including Northwestern Polytechnical University, Wuhan University of Technology, Harbin Institute of Technology, Nanjing University of Aeronautics and Astronautics, Beihang University, National University of Defense Technology, Jilin University, Northeastern University, Zhengzhou University, Chang’an University, Institute of Metal Research, Chinese Academy of Sciences, and Shanghai Institute of Ceramics, Chinese Academy of Sciences, etc. The special issue is delving into the design, preparation, simulation, performance evaluation, and exploration for damage mechanisms of new structural ceramics.
We aim for this publication to deepen researchers’ insights into structural ceramics, provide a platform for exploring recent advancements, and foster the progression of the field. We extend our heartfelt gratitude to the experts who contributed despite their busy schedules, acknowledging their dedication and support that made this publication possible.

The integration of ceramic matrix composites with environmental barrier coatings (CMC-EBC) represents the most promising thermal structural material system in the aerospace field. This paper provides an overview of the advancements in research on the failure mechanisms and numerical models of CMC-EBC. It commences with a concise review of the evolution and primary fabrication techniques of CMC-EBC material system. Subsequently, it summarizes the typical damage modes and failure mechanisms of CMC-EBC under operational conditions, identifying that the interplay between the CMC preform structure, porosity defects, and EBC inner cracks is a critical determinant of the material’s lifespan. However, current mechanistic studies are chiefly focused on the performance evaluation of the coating itself and its susceptibility to environmental factors, disregarding the synergistic effects of the coating and composite architecture during damage progression. This review proceeds with an examination of the history and current status of research on failure simulation and prediction models for CMC-EBC, highlighting issues related to modeling environmental factors and simulating coupled damage evolution. Though much effort has directly developed separate failure models for CMC and EBC, predicting the failure of CMC-EBC components should account for the coupling effects between damage evolution and microstructure. In conclusion, this review offers a perspective on development and service performance prediction methods for CMC-EBC system, which points out that considering the interdependent failure modes of the CMC substrate and EBC is pivotal. Integrated design and analysis of structural and functional aspects are emerging trends in CMC-EBC component research.

Polymer-derived SiCN ceramics benefiting from advantages of light mass and low coefficient of thermal expansion, have received wide attention in electromagnetic wave absorption field. However, the wave absorptive performance of SiCN ceramics needs to be further improved due to its monomer loss mechanism and insufficient temperature resistance. Enhancing their wave absorptive performance with the aid of multicomponent synergy is a feasible way, but still facing some challenges in preparation and wave absorption. In this work, four types of nanoceramics, SiHfCN, SiHfCN-C, SiHfCN-B, and SiHfCN-N were obtained by single-source modification of polysilazane combining different compounds. The results showed that SiHfCN generated HfO₂ and SiO₂ for up to 13.5% (in mass) oxygen content in the Hf source, resulting in the minimum reflection loss (RL_min) of only -13.8 dB and the effective absorption bandwidth (EAB) of only 0.42 GHz. Compared to SiHfCN, the co-modification of the Hf-containing polymer with C, B and N sources increased the interface and conductive phases of polymer-derived ceramics, real and imaginary parts of SiHfCN-C, SiHfCN-B, and SiHfCN-N gave rise to 1.4-1.8 and 2.7-3.9 times higher, respectively, with RL_min of -50.6, -57.3 and -63.5 dB, and EAB of 3.53, 3.99 and 4.01 GHz, showing a significant improvement in their wave absorptive properties. The SiHfCN-C inhibited the generation of HfO₂ for massive free carbon, which could enhance the conductivity loss. The SiHfCN-B generated B-N and B-C bonds, and precipitated nanorods of HfSiO₄ to provide more heterogeneous interfaces, increasing the polarization loss. The SiHfCN-N increased the content of N-C bond due to the introduction of abundant N, enhancing the dipole polarization loss, while the generated carbon nanosheets not only enhanced the conductivity loss but also provided rich interfaces, which improved the impedance matching and amplified the polarization loss, thus exhibiting excellent wave absorptive performance.

Hf_xTa_1-xC is a very promising candidate for thermal protection materials above 2000 ℃ due to its excellent properties such as high melting point, high hardness, high strength, high electrical conductivity, and high thermal conductivity. However, the rules of its mechanical properties and melting temperature varying with the composition remain elusive. Firstly, the mechanism of the variation of mechanical properties of Hf_xTa_1-xC system solid solutions with its components was systematically investigated from the microscopic point of view of covalent bond strength and valence electron concentration (VEC) based on the special quasirandom structures (SQS) method and first-principles calculations. It revealed that among the five components of solid solutions (i.e., HfC, Hf_0.75Ta_0.25C, Hf_0.5Ta_0.5C, Hf_0.25Ta_0.75C and TaC), the Hf_0.25Ta_0.75C solid solution possessed the largest elastic modulus and shear modulus. It was mainly attributed to two reasons: (1) the component possessing the strongest covalent bonding strength among the above ternary compounds; (2) the special bonding states between the p-orbital from C and the d-orbital from Hf or Ta strongly resisting the deformation and being completely filled near VEC=8.75 (for Hf_0.25Ta_0.75C). Secondly, the melting curves of the Hf_xTa_1-xC system solid solutions were calculated using the ab initio molecular dynamics (AIMD)-based molecular dynamics Z method. It showed that there existed indeed the phenomenon for anomalous increase in the melting temprature of Hf_xTa_1-xC system solid solutions, and the highest melting temperature of 4270 K was predicted on Hf_0.5Ta_0.5C, which was mainly attributed to the synergistic effect of the conformational entropy and the strength of the covalent bond. The results provide a theoretical guidance for the experimental selection of the optimal components of high melting temprature and high mechanical properties for Hf_xTa_1-xC system solid solutions in the thermal barrier coating applications, as well as a reference for the study of other transition metal carbides.

Compared with antibiotics and other drugs with poor functionalities and risk to induce bacterial resistance, inorganic functional nanomaterials with catalytic activity occupy an increasingly important position in the treatment of pathogenic infections by advantages of high response to the infected microenvironment (e.g. weak acid, high H₂O₂ concentration) or external physical stimuli (e.g. laser, ultrasound) and broad-spectrum sterilization. However, the acidic infection microenvironment is weak and unstable, and light or sound signals with high power density will cause damage to human cells. In addition, antimicrobial applications of alternative magnetic field (AMF), a non-invasive signal type with high tissue penetration, convenience to be remotely controlled, and effective magnetoelectric catalysis based on AMF have not been reported. In this study, an AMF-responsive nanocatalytic strategy based on the magnetostrictive-piezoelectric catalytic effect was applied to antibacterial research, and the surface of CoFe₂O₄-BiFeO₃ magnetoelectric nanoparticles (BCFO) was modified with the nitrogen-containing group L-arginine (LA) to achieve a magneto-electric responsive controlled release of powerful bactericide reactive nitrogen species (RNS). In AMF, BCFO simultaneously generates reactive oxygen species (ROS) hydroxyl radical (·OH) and superoxide anion (·O₂^-). The former reacts with LA to release nitric oxide (NO), and the latter combines with NO to produce peroxynitrite (ONOO^-), a typical RNS. As a highly active nitrification and oxidation agent, ONOO^- could exhibit stronger antibacterial activity than ROS under biofriendly AMF. Successful production of ONOO^- and achievement of stronger bactericidal efficiency were validated in this study. This work not only applies magnetoelectric nanocatalysis for antibacterial purposes, but also significantly improves the antibacterial ability through the conversion of ROS to RNS.

High-entropy carbide (HEC) ceramics are distinguished by their high hardness, oxidation resistance, corrosion resistance, wear resistance, and high thermal conductivity, positioning them as promising candidates for application in extreme environments. However, inherent brittleness of these high-entropy ceramics limits their further application. In order to enhance the toughness of HEC ceramics, polycarbosilane (PCS), a precursor of silicon carbide (SiC), was added into the precursor of (Zr, Hf, Nb, Ta, W)C high-entropy ceramic. The in-situ formed SiC (SiC_i) by pyrolysis of PCS can serve as reinforcement for HEC ceramics. The results demonstrate that the volume fraction of SiC in the ceramics obtained from the pyrolysis of PCS is 23.38%. The SiC phases, with an average grain size of 1.19 μm, are evenly distributed in the high-entropy ceramic matrix. The pyrolysis process of ceramic precursors was investigated, revealing that the pyrolysis products of PCS exit as amorphous O_x-Si-C_y at low pyrolysis temperature, while a crystalline SiC phase emerges when the pyrolysis temperature exceeds 1500 ℃. Bulk (Zr, Hf, Nb, Ta, W)C-SiC_i ceramic was prepared by hot-pressing of precursor-derived ceramic powders obtained through pyrolysis at 1600 ℃. Mechanical properties of (Zr, Hf, Nb, Ta, W)C-SiC_i ceramic bulk were investigated, and composite ceramic bulks toughened by commercial silicon carbide nanopowders or silicon carbide whiskers were also prepared for comparison. Compared with (Zr, Hf, Nb, Ta, W)C ceramic, all composite ceramic bulks exhibit enhanced flexural strength and toughness. Notably, the in-situ generated SiC_i via precursor-derived method shows the most significant toughening effect. Flexural strength and fracture toughness of (Zr, Hf, Nb, Ta, W)C-SiC_i ceramic are (698±9) MPa and (7.9±0.6) MPa·m^1/2, respectively, representing improvements of 17.71% and 41.07% compared to that of (Zr, Hf, Nb, Ta, W)C ceramic bulk. Taking all above data into comprehensive account, the improvement is mainly due to the small grain size and uniform distribution of SiC in the composite ceramics prepared via precursor-derived method, which enhance energy consumption and hinder crack propagation under external stress.