MAX/MAB phases are a series of non-van der Waals ternary layered ceramic materials with a hexagonal structure, rich in elemental composition and crystal structure, and embody physical properties of both ceramics and metals. They exhibit great potential for applications in extreme environments such as high temperature, strong corrosion, and irradiation. In recent years, two-dimensional (2D) materials derived from the MAX/MAB phase (MXene and MBene) have attracted enormous interest in the fields of materials physics and materials chemistry and become a new 2D van der Waals material after graphene and transition metal dichalcogenides. Therefore, structural modulation of MAX/MAB phase materials is essential for understanding the intrinsic properties of this broad class of layered ceramics and for investigating the functional properties of their derived structures. In this paper, we summarize new developments in MAX/MAB phases in recent years in terms of structural modulation, theoretical calculation, and fundamental application research and provide an outlook on the key challenges and prospects for the future development of these layered materials.
Methane is the second greenhouse gas contributing greatly to global warming, about 80 times of CO2. Considering background of global warming and atmospheric methane growth, to catalyze total oxidation of atmospheric methane is of great importance to mitigate greenhouse effects and slow this global warming. However, catalytic oxidation of methane has always been a big challenge due to its high structural stability. In this article, research progress in total oxidation of methane under thermal-, photo- and photothermal-catalysis was reviewed. High temperature in thermal catalysis increases the energy loss and accelerates the deactivation of catalysts speedingly. Therefore, development of catalysts that oxidize methane under moderate temperatures is the main research interests. Photocatalysis provides a way to eliminate methane at ambient conditions with the assistance of solar energy, but the reaction rates are lower than that in thermal catalysis. It is worth mentioning that photothermal catalysis, developed in recent years, can achieve efficiently catalytic total oxidation of methane under mild conditions, showing a high potential application prospect. This article reviews development of three modes of catalysis, analyzes their different reaction mechanisms, advantages and disadvantages under different reaction conditions. Finally, prospects and challenges of this catalytic total oxidation are pointed out, which is expected to provide references for future research on this field.
X-ray detection has been widely used in medical imaging, security inspection, and industrial non-destructive tests. Halide perovskite X-ray detectors have attracted increasing attention due to their high sensitivity and low detection limit, but the notorious ion migration leads to poor operational stability. It is reported that the low dimensional structure can effectively suppress the ion migration of perovskites, thus greatly improving the stability of the detectors. This review introduces the working mechanism, key performance parameters of perovskite X-ray detectors, and summarizes the recent progress of low-dimensional perovskite materials and their application in direct X-ray detectors. The relationship between the structural characteristics of low-dimensional perovskite materials and their X-ray detection performance was systematically analyzed. Low-dimensional perovskite is a promising candidate for the preparation of X-ray detectors with both high sensitivity and stability. Further optimization of detection material and device structure, preparation of large-area pixelated imaging devices, and study of working mechanism in-depth of the detector are expected to promote the practical application of perovskite X-ray detectors.
Organic-inorganic hybrid perovskite solar cells (PSCs) have attracted widespread attention due to their high power conversion efficiency (PCE) and low manufacturing cost. Although the certified PCE has reached 25.8%, the stability of PSCs under high temperature, high humidity, and continuous light exposure is still significantly inferior to that of traditional cells, which hinders their commercialization. Developing and applying highly stable inorganic hole transport materials (HTMs) is currently one of the effective methods to solve the photo-thermal stability of devices, which can effectively shield water and oxygen from corroding the perovskite absorption layer, thereby avoiding the formation of ion migration channels. This paper outlines the approximate classification and photoelectric properties of inorganic HTMs, introduces relevant research progress, summarizes performance optimization strategies for inorganic HTMs devices, including element doping, additive engineering, and interface engineering, and finally prospects the future development directions. It is necessary to further study the microstructure of inorganic HTMs and their relationship with the performance of PSCs to achieve more efficient and stable PSCs.
Semiconductor materials are the core of modern technology development and industrial innovation, with high frequency, high pressure, high temperature, high power, and other high properties under severe conditions or super properties needed by the “double carbon” goal, the new silicon carbide (SiC) and gallium nitride (GaN) as representative of the third generation of semiconductor materials gradually into industrial applications. For the third-generation semiconductor, there are several development directions in its packaging interconnection materials, including high-temperature solder, transient liquid phase bonding materials, conductive adhesives, and low-temperature sintered nano-Ag/Cu, of which nano-Cu, due to its excellent thermal conductivity, low-temperature sintering characteristics, and good processability, has become a new scheme for packaging interconnection, with low cost, high reliability, and scalability. Recently, the trend from material research to industrial chain end-use is pronounced. This review firstly introduces the development overview of semiconductor materials and summarizes the categories of third-generation semiconductor packaging interconnect materials. Then, combined with recent research results, it further focuses on the application of nano-Cu low-temperature sintering in electronic fields such as packaging and interconnection, mainly including the impact of particle size and morphology, surface treatment, and sintering process on the impact of nano-Cu sintered body conductivity and shear properties. Finally, it summarizes the current dilemmas and the difficulties, looking forward to the future development. This review provides a reference for the research on low-temperature sintered copper nanoparticles in the field of interconnect materials for the third-generation semiconductor.
Two-dimensional (2D) perovskite displays great potential in optoelectronic applications due to its inherent quantum well structure, large exciton binding energy and good stability. However, facile preparation of high-quality 2D perovskite films with low cost remains a huge challenge. In this work, high-quality two-dimensional perovskite (PEA)2PbI4 films were prepared by solution method at low annealing temperature(80 ℃) without other special treatments, and further applied in the field of photodetectors. The results show that this photodetector possessed a low dark current (10-11 A), good responsiveness illuminated at a wavelength of 450 nm (107 mA·W-1), high detection rate (2.05×1012 Jones) and fast response time (250 μs/330 μs). After 1200 s continuous illumination, the device maintains 95% initial photocurrent. In addition, the photocurrent remains almost unchanged after storage for 30 d. This work provides promising strategy to develop stable and high-performance optoelectronic devices.
With rapid development of lithium ion batteries (LIB) and sodium ion batteries (SIB), hard carbon (HC) as new anode material has earned much attention. Besides its rich precursor sources and low cost, HC has higher Li+ storage capacity and better rate performance than graphite for LIB. Furthermore, it is also recognized as the most commercially potential anode material for SIB. However, low initial Coulombic efficiency is a common issue for HC. In addition, it is believed that the specific capacity can be further improved with the clarification of the Li/Na ion storage mechanism. In recent years, many researches on electrochemical mechanism have been conducted with some model assumptions proposed for better understanding the mechanism. This review introduced the structures and preparation approaches of HC as well as its application in LIB and SIB. The advantages, especially in fast charging, coating and other subdivision were discussed, and the different modification strategies such as pore structure design, doping, optimizing interface between electrode and electrolyte were summarized, aiming at the increase of capacity and the improvement of Coulombic efficiency of batteries.
Two-dimensional transition metal carbon/nitride MXenes show promising applications in various fields due to their remarkable electrical and mechanical properties. Recently, the research of high performance MXenes nanocomposites (including one-dimensional fibers, two-dimensional films and three-dimensional blocks) has made remarkable progress. However, the mechanical properties are still far lower than the intrinsic mechanical properties of MXenes nanosheets, mainly due to the key scientific problems of voids, misalignment of MXenes nanosheets and weak interfaces. In order to solve the above problems, the intrinsic mechanical properties of MXenes nanosheets are firstly discussed in this work, then the development of high performance MXenes nanocomposites are summarized, and the latest research progress of high performance MXenes nanocomposites is discussed in detail, including how to eliminate void, improve the orientation of MXene nanosheets and enhance the interface interaction. Meanwhile, the applications of high performance MXenes nanocomposites in the fields of electric heating, thermal camouflage, electromagnetic shielding, sensing and energy storage are introduced. Finally, the challenges and future development directions of high performance MXenes nanocomposites are proposed.
MXene is a large family of two-dimensional transition metal carbides, nitrides or carbonitrides. Its characteristics (various compositions, two-dimensional atomic layer structures, metallic electrical conduction, active surfaces, etc.) render MXene unique interactions with electromagnetic waves at different frequencies (visible light, infrared, terahertz, microwave, etc.), deriving a variety of electromagnetic functional applications. In the infrared range, MXene has a wide range of infrared radiation properties, and its active surface endows tunable infrared absorption. These features have attracted researchers’ interest in exploring infrared properties of MXene and the corresponding applications in recent years. In this perspective, the intrinsic infrared characteristics and manipulation strategies of different MXenes are systematically summarized, and the research progress of representative infrared applications are briefly introduced, including infrared identification/camouflage, surface plasmon, photothermal conversion, and infrared photodetection. Particularly, the contribution and mechanism of MXene in these applications are discussed. Finally, the outlook for infrared functional applications with MXenes is proposed.
With the rise of the third-generation wide-bandgap semiconductors represented by SiC and GaN, power electronic devices are developing rapidly towards high output power and high power density, putting forward higher performance requirements on ceramic substrate materials used for power module packaging. The conventional Al2O3 and AlN ceramics are inadequate for the new generation of power module packaging applications due to low thermal conductivity or poor mechanical properties. In comparison, the newly developed Si3N4 ceramics have become the most potential insulating heat dissipation substrate materials due to its excellent mechanical properties and high thermal conductivity. In recent years, researchers have made a series of breakthroughs in the preparation of high strength and high thermal conductivity Si3N4 ceramics by screening effective sintering additive systems and optimizing the sintering processes. Meanwhile, as the advancement of the engineering application of coppered Si3N4 ceramic substrate, the evaluation of its mechanical, thermal, and electrical properties has become a research hotspot. Starting from the factors affecting thermal conductivity of Si3N4 ceramics, this article reviews the domestic and international research work focused on sintering aids selection and sintering processes improvement to enhance the thermal conductivity of Si3N4 ceramics. In addition, the latest progress in the dielectric breakdown strength of Si3N4 ceramic substrates and the evaluation of properties after being coppered are also systematically summarized and introduced. Based on above progresses and faced challengies, the future development direction of high strength and high thermal conductivity Si3N4 ceramic substrates is prospected.
Inspired by gene scissor concept in biological genetic engineering, chemical scissors, as important research tools, play an important role in the study of structure editing and application of materials. We aim to review the research progress of chemical scissors in structural editing and applications of materials. First of all, we introduce the basic concept and mechanism. Chemical scissors strategy refers to a methodology for material editing through which the main crystal structure is preserved but targeted atoms or structural units are knocked out, replaced, repaired or reconstructed in order to realize special functionality. Subsequently, the specific applications of chemical scissors in materials structure editing are discussed in depth, including the methods and functional designs for precise structure modulation of materials by chemical shearing, modification, synthesis, as well as etching and intercalation. Finally, the future research direction of chemical scissors in the field of material structure editing is envisioned, including developing new chemical scissors that are more intelligent and efficient, exploring more innovative strategies for material structure editing, understanding the underlying chemical mechanism, and further expanding the applicability of chemical scissors. Overall, we summarize the research progress and potential of material structural editing, which provides important theoretical and experimental support for further exploring and developing the application of chemical scissors in the field of materials.
Ceramic-based porous structures not only inherit the excellent properties of dense ceramic materials such as high-temperature resistance, electrical insulation, and chemical stability, but also have unique advantages similar to porous structures, including low density, high specific surface area, and low thermal conductivity. They show great potential in various applications, such as thermal insulation, bone tissue engineering, filtration and pollutants removal, and electronic components. However, there still exist some challenges for shaping complex geometries on the macro- scale and adjusting pore morphologies on the micro- and nano-scale through the conventional preparation strategy of ceramic-based porous structures. In recent decades, researchers have been devoting themselves to developing novel manufacturing techniques for ceramic-based porous structures. The direct-ink-writing 3D printing, as one of the representative additive manufacturing technologies, has become a current research hotspot, rapidly developing a series of mature theories and innovative methodologies for fabricating porous structures. In this work, the conventional strategies and additive manufacturing strategies for obtaining porous structures were firstly summarized. The direct-write assembly processes of pore structures were further introduced in detail, mainly including pseudoplastic ink formulation, solidification strategy, drying, and post-treatment. Meanwhile, the feasibility of direct-ink-writing 3D printing technologies combined with conventional manufacturing strategies in constructing ceramic-based hierarchical pore structures was analyzed emphatically. The new perspectives, developments, and discoveries of direct-ink-writing 3D printing technologies were further summarized in the field of manufacturing complex ceramic-based porous structures. In addition, the developments and challenges in the future were prospected according to the actual application status.
Silicon carbide (SiC) has wide application in electric vehicles, rail transit, high voltage power transmission and transformation, photovoltaic, and 5G communication owing to its excellent physical and chemical properties. 8-inch SiC substrate has great potential in reducing unit cost of devices and increasing capacity supply, and has become an important technology development direction of the industry. Recently, Shandong University and Guangzhou Summit Crystal Semiconductor Co., Ltd. have made a major breakthrough in the control of dislocation defects in 8-inch SiC substrates. The 8-inch n-type 4H-SiC single crystal substrate with low dislocation density has been fabricated by physical vapor transport (PVT) method, of which the threading screw dislocation (TSD) density is 0.55 cm-2, and the basal plane dislocation (BPD) density is 202 cm-2.
In recent years, organic-inorganic hybrid perovskite solar cells have received a lot of attention for their excellent performance and low manufacturing cost. However, the toxicity of lead in organic-inorganic hybrid perovskite solar cells and instability inhibits its further commercialization. Double perovskite Cs2AgBiBr6 possess excellent stability, low toxicity, long carrier lifetime, and small effective carrier mass, and is considered as a promising photovoltaic material. It has been applied in solar cells and displayed superior performance. However, the power conversion efficiency of Cs2AgBiBr6 perovskite solar cell still lags behind organic-inorganic hybrid perovskite solar cells, and its development faces various challenges. This review firstly introduces the crystal structure and the structural parameters such as tolerance factor of Cs2AgBiBr6. And then, the progress of thin film preparation technologies such as solution processing method, anti-solvent assisted film forming method, vapor deposition processing method, vacuum-assisted film forming method, spray-coating method are summarized, and the advantages and disadvantages of various preparation technologies are discussed. The performance optimization strategies of Cs2AgBiBr6 perovskite solar cells are analyzed from three aspects: element doping, additive engineering, and interface engineering (interface energy level matching and interface defect passivation), and the research progress in recent years is reviewed. Finally, the challenges faced by Cs2AgBiBr6 perovskite solar cells are pointed out, and future research directions are prospected from three aspects: precursor solvent engineering, bandgap engineering, and device degradation mechanism.
Developing novel low-dimensional materials for terahertz electromagnetic shielding and absorbing applications represents a critical research frontier. Their unique electrical, mechanical, and electromagnetic responses hold great potential in enabling more efficient solutions for electromagnetic shielding and absorbing. Two-dimensional transition metal carbides, nitrides, and carbonitride MXenes have already demonstrated excellent electromagnetic shielding and absorbing performance in the low-frequency spectrum. MXenes possess high conductivity, low density, and high flexibility, which are advantageous for future portability and integration of terahertz devices and systems. However, practical implementation of MXene-based terahertz electromagnetic shielding and absorption materials faces challenges in adhesion stability, environmental resilience, and high-temperature tolerance, hindering their suitability for aerospace and future next generation communication applications. Moreover, in terahertz frequency band, lacking more comprehensive and reliable electromagnetic scattering and absorbing measurement methods limits the development of THz shielding and absorbing materials. Extensive research efforts have targeted on these limitations, exploring fundamental architectural and theoretical aspects of prevalent electromagnetic materials. This review specifically highlights the terahertz electromagnetic shielding and absorption characteristics inherent in various MXenes and their compositions, such as Ti3C2Tx, Mo2Ti2C3Tx, Mo2TiC2Tx, Nb4C3Tx, and Nb2CTx. Additionally, this review envisages the forthcoming challenges and prospects of MXenes as a pivotal electromagnetic shielding and absorbing material within the terahertz frequency band.
Extreme Ultra-Violet (EUV) lithography utilizes Laser Produced Plasma (LPP) technology to generate EUV light with a 13.5 nm wavelength by bombarding tin liquid droplets with high-power lasers. Piezoelectric high-temperature nozzle based on inverse-piezoelectric effect is the key component for obtaining high-frequency tin droplet targets. Here, breakthroughs have been made in the composition design, fine preparation of high-temperature micro piezoelectric ceramic tubes that can withstand temperatures up to 250 ℃, and structure design, fabrication and precise driving control of the piezoelectric high-temperature nozzle. Based on a self-constructed high-temperature tin droplets generation platform, a stable output of high-temperature tin droplet targets with repetition frequency of 20 kHz and diameter of 100 μm is successfully achieved.
SiCf/SiC ceramic matrix composites have excellent prospects in aeroengine applications. Importantly, the interface design becomes a research focus. Multilayered interfaces can effectively improve the oxidation resistance of ceramic matrix composites, while their effect on the mechanical properties and damage mechanism are still unclear. Here, SiCf/SiC minicomposites with BN and (BN/SiC)3 interfaces were fabricated via the chemical vapor infiltration (CVI) method. Then, effect of multilayered interfaces on the failure mechanism of SiCf/SiC composites was evaluated. According to the two kinds of mechanical experiments and acoustic emission (AE) detection, the damage mechanism of minicomposites was analyzed. Results indicate that the minicomposites prepared by CVI have an obvious interface structure and a dense matrix. The maximum load of BN and (BN/SiC)3 minicomposites was 139 and 160 N, respectively. Besides, the two types of minicomposites possess typical load-displacement curves, and the damage processes of composites with different interfacial coatings exhibit various load-acoustic characteristics correspondingly. The AE characteristics of two mechanical loading tests can effectively assess the damage evolution of the minicomposites at each stage. In conclusion, multilayered interfaces can deflect cracks better, delay cracks extending to fibers, and thus improving mechanical properties of SiCf/SiC composites.
Smart windows have gained tremendous attention because of their ability to dynamically modulate the solar radiation to minimize energy consumption and improve indoor living comfort. Vanadium dioxide (VO2) is one of the most attractive thermochromic materials for energy-saving smart windows due to its reversible metal-to-insulator transition at a critical temperature of ~68 ℃ and accompanying great change of its optical transmittance. However, VO2 itself has a couple of significant limitations as a smart window material: high phase transition temperature (τc), low luminous transmittance (Tlum) and insufficient solar energy modulation ability (ΔTsol). Several methods have been used to grow VO2 thin films with improved properties to meet the specific requirements for smart windows applications. The phase transition temperature (τc) should be reduced to near room temperature, in the meantime luminous transmittance (Tlum) and solar energy modulation ability (ΔTsol) should be high enough for the modulation of indoor temperature self-adapted to seasons and climate. The most common way to reduce τc is by doping. To enhance Tlum and ΔTsol, multilayer structures and/or nanocomposite film have been widely adopted. Chemical vapor deposition (CVD) is a promising technique to produce high quality and highly uniform VO2 thin film with different morphologies in large scale and at low costs. In this paper, various CVD techniques, such as atmospheric pressure chemical vapor deposition (APCVD), aerosol-assisted chemical vapor deposition (AACVD), low-pressure chemical vapor deposition (LPCVD), metal-organic chemical vapor deposition (MOCVD), atomic layer deposition (ALD) and plasma-enhanced chemical vapor deposition (PECVD), are examined with respect to their advantages for VO2 deposition, film quality and the strategies for film quality improvement. Finally, challenges and opportunities for further research and development of VO2 thermochromic films using PECVD technique are emphasized.
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.
MAX phase ceramics, with their mixed covalent-metallic-ionic atomic bonds, can uniquely combine the advantages of both metals and ceramics, offering a series of distinctive characteristics. The particular layered atomic structure further endows them with decent fracture toughness, good damping capacity, and self-lubricating property. As such, MAX phase ceramics are more appealing to serve as reinforcements for metal matrix composites (MMCs) than conventional ceramic materials. Here, we foused on the development. To date, fabrication of MMCs reinforced by MAX phase ceramics still involves the use of stir casting, powder metallurgy, and melt infiltration techniques. The obtained composites made by different methods may display distinct differences in their structural characteristics, show notable enhancement in strength, hardness, and stiffness as compared to their metal matrices, and exhibit good wear resistance, high electrical conductivity and remarkable arc erosion resistance. Moreover, ultrafine MAX phase platelets can be preferentially oriented and aligned, e.g., by using vacuum filtration or ice templating techniques. By infiltrating metal melt into partially sintered porous ceramic scaffolds, bioinspired composites with nacre-like architectures can be obtained, thereby affording further improvement in strength and fracture toughness. Sufficient combinations of mechanical and functional properties enable the MMCs reinforced by MAX phase ceramics promising for a variety of applications, such as load-bearing structures, electrical contact materials. These composites can offer enhanced strength, stiffness, and wear resistance, making them ideal candidates for these applications.
Brain-inspired neuromorphic computing refers to simulation of the structure and functionality of the human brain via the integration of electronic or photonic devices. Artificial synapses are the most abundant computation element in the brain-inspired system. Memristors are considered to be ideal devices for artificial synapse applications because of their high scalability and low power consumption. Based on Ohm’s law and Kirchhoff’s law, memristor crossbar arrays can perform parallel multiply-accumulate operations in situ, leading to analogue computing with greatly improved speed and energy efficiency. Oxides are most widely used in memristors due to the ease of fabrication and high compatibility with CMOS processes. This work reviews the research progress of oxide memristors for brain-inspired computing, mainly focusing on their resistance switching mechanisms, device structures and performances. These devices fall into three categories: electrical memristors, memristors controlled via both electrical and optical stimuli, and all-optically controlled memristors. The working mechanisms of electrical memristors are commonly related to microstructure change and Joule heat that are detrimental to device stability. The device performance can be improved by optimizing device structure and material composition. Tuning the device conductance with optical signals can avoid microstructure change and Joule heat as well as reducing energy consumption, thus making it possible to address the stability problem. In addition, optically controlled memristors can directly response to external light stimulus enabling integrated sensing-computing-memoring within single devices, which are expected to be used for developing next-generation vision sensors. Hence, the realization of all-optically controlled memristors opens a new window for research and applications of memristors.
With improvement in service temperature of thermal structural components for the new generation hypersonic aircraft, higher requirements are put forward for the phase stability and ablation resistance of the thermal protection coatings (TPCs). Carrying out high-entropy design for traditional transition metal oxide ZrO2 and HfO2 coatings, solid-phase reaction and supersonic atmosphere plasma spraying (SAPS) were applied to prepare (Hf0.125Zr0.125Sm0.25Er0.25Y0.25)O2-δ (M1R3O), (Hf0.2Zr0.2Sm0.2Er0.2Y0.2)O2-δ (M2R3O), (Hf0.25Zr0.25Sm0.167Er0.167Y0.167)O2-δ (M3R3O) high-entropy oxide (HEO) coatings. The effects of rare earth content on phase structure evolution, phase stability and ablative resistance of HEO coatings were investigated. M2R3O coating and M3R3O coating possessed excellent phase stability and ablation resistance, which maintained stable phase structure after ablation by oxygen-acetylene flame with heat flux density of 2.38-2.40 MW/m2, without decomposition of solid solution and precipitation of rare earth components. Mass ablation rate and linear ablation rate of M2R3O coating after cyclic ablation for 180 s are 0.01 mg/s and -1.16 μm/s, respectively. Compared with M1R3O coating (0.09 mg/s, -1.34 μm/s) and M3R3O coating (0.02 mg/s, -4.51 μm/s), the reductions of ablation rate are 88.9%, 13.4%, respectively, and 50.0%, 74.3% for M2R3O coatings, respectively, presenting the best ablation resistance. M2R3O coating exhibits excellent ablation resistance due to its high melting point (>2200 ℃) and low thermal conductivity ((1.07±0.09) W/(m·K)), which effectively protects the internal SiC transition layer and C/C composites from oxidation damage, avoiding interface cracking caused by the formation of SiO2 phase.
Continuous silicon carbide fiber reinforced silicon carbide composite (SiCf/SiC) is a critical structural material for the development of next-generation aircraft engines. The interfacial property is one of the important factors determining the material mechanical properties. Therefore, this study characterized the interfacial mechanical properties of domestic third-generation 2.5D SiCf/SiC and investigated its relationship with tensile properties. The residual stress of the 2.5D SiCf/SiC constituents and interfacial sliding stress (IFSS) were quantitatively analyzed by hysteresis characteristics during the cyclic tension loading/unloading test. Statistical distributions of the in-situ fiber strength $({{\sigma }_{\text{fu}}})$ were obtained based on the fracture mirror radius of pull-out fibers. Interfacial shear strength (ISS) and interfacial debonding energy (Gi) were obtained through the push-in method. Results show that combination of macroscopic and microscopic methods can comprehensively describe the interfacial mechanical performance of 2.5D SiCf/SiC from crack initiation to final debonding. The IFSS, ISS, and Gi of 2.5D SiCf/SiC are 56 MPa, (28 ± 5) MPa, and (2.7 ± 0.6) J/m², respectively. Values of ISS and Gi indicate weak interface bonding, causing it susceptible to cracking under shear stress, while the large IFSS suggests that relative fiber sliding is inhibited after interface debonding, hindering fiber pull-out. The obtained interfacial properties can predict the proportional limit stress (${{\sigma }_{\text{PLS}}}$) accurately according to the ACK model. Based on the interfacial properties and the in-situ fiber strength (${{\sigma }_{\text{fu}}}$), the tensile strength of 2.5D SiCf/SiC is predicted to be higher than the experimental value, which is related to the interfacial radial compressive residual stress and residual tensile stress endured by the fiber.
As a reversible, non-volatile, and resistive state mutation information storage and processing device, the resistive switching (RS) memory is expected to solve the inherent physical limitations of the traditional memory and von Neumann bottleneck, and has received widespread attention. Taking advantage of rapid carrier migration characteristics and excellent photoelectric conversion performance, halide perovskite optoelectronic RS memory devices present excellent resistive switching performance. In recent years, researches on storage and computing applications of the halide perovskite RS memory developed unprecedentedly; whereas, the working mechanisms of halide perovskite RS memory still remain unclear. This review analyzes the working mechanism of halide perovskite RS memory, compares the regulation characteristics of conduction filaments (CFs) and energy level matching (ELM), summarizes the constraints of various mechanisms, reveals the repeated formation and dissolution of CFs under light illumination and electric field, as well as Schottky barrier between the perovskite transfer layer and other layer, dominates the On/Off ratio, threshold (Set/Reset) voltage and performance stability of halide perovskite optoelectronic RS memory, and prospects the applications of halide perovskite RS memory in artificial intelligence bionic synapses, in-memory computing, and machine vision.
Si anodes hold immense potential in developing high-energy Li-ion batteries. But fast failure due to huge volume change upon Li uptake impedes their application. This work reports a facile yet low-toxic gas fluorination way for yielding F-doped carbon-coated nano-Si anode materials. Coating of nano-Si with F-doped carbon containing high defects can effectively protect Si from huge volume change upon Li storage while facilitating Li+ transport and formation of stable LiF-rich solid electrolyte interphase (SEI). This anode exhibits high capacities of 1540-580 mAh·g-1 at various current rates of 0.2-5.0 A·g-1, while retaining >75% capacity after 200 cycles. This method also addresses the issues of high cost and toxicity of traditional fluorination techniques that use fluorine sources such as XeF2 and F2.
Power conversion efficiency of single-junction solar cells is fundamentally limited by the Shockley- Queisser (S-Q) limit. The most promising practical technology to break through the S-Q limit is to use two-terminal tandem structure which can simultaneously solve the problems, spectral mismatch and thermal relaxation energy loss, in single-junction devices. As one of the important components of the interconnecting layer, the recombination layer in the two-terminal tandem solar cells can provide recombination sites for electrons and holes extracted from the electron transporting layer and the hole transporting layer, avoiding the open-circuit voltage loss caused by charge accumulation and promoting the current flow of tandem solar cells. The recombination layer is considered as one of the key factors of achieving high-performance tandem devices. The ideal recombination layer should possess high conductivity to improve the charge recombination rate, high optical transmittance to ensure effective light absorption of the rear subcells, good chemical stability to reduce the damage caused by the solvent, and low preparation cost to promote the commercial production process. At present, a variety of materials have been used in two-terminal tandem solar cells, such as thin metals, transparent conductive oxides, conductive polymers, graphene oxide, etc., which play an important role in perovskite-perovskite, perovskite-organic, and perovskite-silicon two terminal tandem devices. In this review, the research progress of recombination layers in different types of tandem solar cells is summarized, together with types, design principles, preparation processes, and their advantages and disadvantages. Meanwhile, problems and challenges of the current recombination layers are proposed, which provides a useful reference for the design of high-performance tandem cells.
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.
Atomic-thin transition metal carbonitrides (MXenes), as an emerging class of two-dimensional (2D) materials, become a highly active research topic. Since the discovery of graphene nearly 20 years ago, many 2D materials (graphene, transition metal dichalcogenides, and black phosphorus) have been extensively studied in the field of micro-nano electronics. However, research on MXenes-based micro-nano electronics has just begun. MXenes exhibit rich elemental compositions and unique physicochemical properties, such as hydrophilicity, tunable work function, adjustable functional groups, fast ion and electron transport, superconductivity, surface plasmons, photo- thermo-electricity, and electromagnetic absorption, and some MXenes even possess high conductivity. These characteristics make MXenes hold great potential for device applications at the microscale or even nanoscale. In recent years, the Alshareef research group has been dedicated to bringing MXenes into the field of micro-nano electronics and has defined the emerging academic field of MXene electronics, known as MXetronics, in 2019. This perspective briefly summarizes and evaluates representative research progress in this field, including the challenges in synthesis, processing, property investigation, and device applications at the microelectronic level. Furthermore, we will propose several key research directions and unexplored subfields in this area.
Transparent ceramic materials have excellent strength, hardness and optical properties, which have important application prospect in light-weight transparent protective armor. However, the preparation of transparent ceramic components with large protection area and high transmittance properties is the main challenge to achieve application. In this work, large-size yttrium aluminum garnet (Y3Al5O12, abbreviated as YAG) transparent ceramics with low deformation and excellent optical quality were fabricated by reactive sintering in vacuum using domestic high-purity Al2O3 and Y2O3 powders as starting materials, and the key technologies including dry pressing, calcining, high-temperature vacuum sintering and optical performance were broken through. In addition, as the upgrading of molding and sintering equipment, the dimension of YAG transparent ceramic was enlarged to 1040 mm×810 mm×15 mm, laying a substantial foundation for future applications.
Nickel molybdate (NiMoO4) is a material with excellent performance in the field of energy storage and catalysis, but lacking of further explorations in the field of electrochromism. In this work, porous NiMoO4 films were grown on transparent conductive glasses by hydrothermal method without using seed layer. Crystalline phase and micromorphology of NiMoO4 nanosheet films were characterized by grazing incidence X-ray diffractometer (GIXRD) and field-emission scanning electron microscope (FESEM), and the electrochromic and electrochemical properties were also investigated by using a UV-Vis-NIR spectrophotometer and an electrochemical workstation. The results show that the NiMoO4 electrochromic films have a porous structure, which can provide sufficient channels for ion migration and reactive sites for the dynamic process of ion intercalation/deintercalation into NiMoO4 film. Therefore, the NiMoO4 films exhibit excellent electrochromic performance, including large optical modulation of 79.6% at 480 nm and high coloring efficiency of 86.2 cm2·C-1. Meanwhile, the coloration and bleaching response time of the NiMoO4 films are 9.5 and 12.7 s, respectively. Interestingly, there is a two-step process in the bleached process of NiMoO4 electrochromic films, including a fast process and a slow process. And the optical modulation can still be maintained at 99.7% of the maximum optical modulation after 100 cycles. In addition, the NiMoO4 films exhibit a large area specific capacitance of 49.59 mF·cm-2 at 0.3 mA·cm-2. These excellent properties support NiMoO4 nanosheet films with promising application in high-performance electrochromic devices. And the next step is to focus on finding the suitable electrolyte and matched counter electrodes in the device assembly.
Nowadays, artificial intelligence (AI) is playing an increasingly important role in human society. Running AI algorithms represented by deep learning places great demands on computational power of hardware. However, with Moore's Law approaching physical limitations, the traditional Von Neumann computing architecture cannot meet the urgent demand for promoting hardware computational power. The brain-inspired neuromorphic computing (NC) employing an integrated processing-memory architecture is expected to provide an important hardware basis for developing novel AI technologies with low energy consumption and high computational power. Under this conception, artificial neurons and synapses, as the core components of NC systems, have become a research hotspot. This paper aims to provide a comprehensive review on the development of oxide neuron devices. Firstly, several mathematical models of neurons are described. Then, recent progress of Hodgkin-Huxley neurons, leaky integrate-and-fire neurons and oscillatory neurons based on oxide electronic devices is introduced in detail. The effects of device structures and working mechanisms on neuronal performance are systematically analyzed. Next, the hardware implementation of spiking neural networks and oscillatory neural networks based on oxide artificial neurons is demonstrated. Finally, the challenges of oxide neuron devices, arrays and networks, as well as prospect for their applications are pointed out.
MXene material has gained popularity among scientists since its discovery in 2011. It has shown great potential in various fields such as energy storage, catalysis, environment, wave absorption, biotherapy, and high-performance composite materials. A series of special perspectives have been organized to provide an overview of the latest research progress and challenges in MXene material science. The invited experts have shared their research highlights and discussed existing problems and future directions.
Synthesis is the foundation of MXene research, with nearly all studies employing chemical methods that use fluoride etchants to transform MAX phases into MXenes. Strategies like Lewis acid molten salt etching and “chemical scissors” for structural editing offer new perspectives for customized synthesis. MXene possesses key physicochemical properties crucial for electronic applications, significantly impacting the study of electronic devices. MXene materials have broad application prospects in flexible photodetectors, solar cells, electronic devices, and energy applications. Moreover, MXene’s metallic conductivity and accordion-like structure make it useful for pressure sensors and electromagnetic shielding. MXene is also a hot topic in the field of energy storage, such as the latest developments in anodes, cathodes, and electrolytes/separators for zinc-ion batteries. Journal of Inorganic Materials expresses gratitude to the invited experts and reviewers for their contributions and looks forward to more updates on MXene research findings.
In summary, MXene materials have shown great potential due to their unique properties and have made significant breakthroughs in various fields. However, there are still many challenges to be addressed, such as the environmental stability and packaging technology of MXene materials. With continuous efforts from researchers, it is expected that more exciting findings and breakthroughs will be achieved in the future.
Bioceramic scaffolds with excellent osteogenesis ability and degradation rate exhibit great potential in bone tissue engineering. Akermanite (Ca2MgSi2O7) has attracted much attention due to its good mechanical property, biodegradability and enhanced bone repair ability. Here, akermanite (Ca2MgSi2O7) scaffolds were fabricated by an extrusion-type 3D printing at room temperature and sintering under an inert atmosphere using printing slurry composed of a silicon resin as polymer precursor, and CaCO3 and MgO as active fillers. Furthermore, the differences in structure, compressive strength, in vitro degradation, and biological properties among akermanite, larnite (Ca2SiO4) and forsterite (Mg2SiO4) scaffolds were investigated. The results showed that the akermanite scaffold is similar to those of larnite and forsterite in 3D porous structure, and its compressive strength and degradation rate were between those of the larnite and forsterite scaffolds, but it showed a greater ability to stimulate osteogenic gene expression of rabbit bone marrow mesenchymal stem cells (rBMSCs) than both larnite and forsterite scaffolds. Hence, such 3D printed akermanite scaffold possesses great potential for bone tissue engineering.
Advanced ink printing techniques, such as printing and coating, have overcome the limitations of traditional manufacturing methods, allowing for rapid prototyping of films and electronic devices with sophisticated structures and specific functions. These techniques hold enormous potential in wearable smart identification, energy storage, electromagnetic shielding and absorption, touch display, and so on. The key to printing advanced energy and electronic devices lies in the development of cutting-edge functional inks and their corresponding printing technologies. MXene, a family of two-dimensional compounds composed of transition metal carbides, nitrides, or carbonitrides, was discovered in 2011. MXene exhibits remarkable physical and chemical properties, including high conductivity, pronounced hydrophilicity, and diverse surface chemistry, which has garnered significant attention within the research community and made it particularly suitable as inks in printing applications. Conducting research on the printing behavior and mechanisms of MXene inks is crucial not only for achieving high-precision patterns but also for establishing a solid foundation for manufacturing techniques that can precisely create multiscale, multimaterial and multifunctional films, and electronic devices. This article begins with a brief discussion of MXene flakes’ synthesis and colloidal stability, followed by a detailed examination of its rheological characteristics, printable ink formulation, and printing methods. Additional, special attention is given to the latest advances of MXene ink in energy, health, and sensing applications. The perspective concludes with a summary of current research challenges and future directions in this area, offering new perspectives and insights for researchers.
Carbon-based perovskite solar cells (C-PSCs) play an important role in industrialization research due to their stability and low cost. In this work, high-quality NiOx mesoporous layer was selected as a hole transport layer (HTL) based on MAPbI3 material to enhance the performance of C-PSCs. The effect of preparation methods of the NiOx mesoporous layer on the solar cell performance and the optimum thickness of the NiOx mesoporous layer were investigated. It was found that mesoporous layers prepared by screen-printing process with well-distributed pores facilitated the filling of perovskite (PVK) precursor solution in the underlayer mesoporous scaffold. Finally, an HTL-contained perovskite solar cell with high efficiency and almost negligible hysteresis was achieved, possessing an open-circuit voltage (VOC) of 910 mV, a power conversion efficiency (PCE) of 14.63%, and certified efficiency reached 14.88%. Moreover, PCE of the solar cell displayed outstanding stability after being stored in air for nearly 900 h.
Perovskite light-emitting diodes (PeLEDs), owing to their unique photoelectric performance, show promising prospects in display applications. Red, green, and blue monochromatic PeLEDs have achieved remarkable breakthroughs, but the study of red/green/blue perovskite co-electroluminescence is still delayed. This study proposed a strategy that an intermediate connection layer (ICL) with hole/electron generation and transport capability is introduced between perovskites. On the one hand, introduction of the ICL can inhibit ion exchange and energy transfer. On the other hand, ICL has a charge-generation function that ensures different perovskite centers capture enough carriers. Furthermore, the thickness of the hole transport layer (NPB) is optimized. Furthermore, the thickness of the hole transport layer (NPB) is regulated, the blue/green tandem PeLED achieved relatively balanced luminescence and exhibits the largest EQE of 0.33%. The developed red/green/blue tandem PeLED exhibits the highest EQE of 0.5%, which is the first report in the field of PeLEDs, and exhibits the largest External Quantum Efficiency(EQE) of 0.33%. The developed red/green/blue tandem PeLED exhibits the highest EQE of 0.5%. In conclusion, this work provides a reference strategy for the co-electroluminescence of multicolor perovskites, which is expected to promote the development of perovskite in display applications.
The shoulder of the crystals grown by the Czochralski method is generally inclined, leading to poor quality and difficult processing, which then result in low utilization rate of the grown crystal. Take congruent lithium niobate (CLN) crystal as an example, this study used numerical simulation and experimental method to investigate the thermal field and growth process of flat shoulder crystal growth by the Czochralski method which can well acceptedly overcome the above problems. The result shows that the shape of the solid-liquid interface should be convex toward melt at the stage of shouldering. Temperature gradient near solid-liquid interface can be reduced by lowering the after-heater position (10 mm) to avoid the formation of polycrystalline. Control of the shouldering speed is the main way while control heating power is the accurate way to ensure the trend of shouldering. Accelerating the speed at the initial stage of shouldering (ϕ≤30 mm) and slowdown the speed at the middle and later stage of shouldering (ϕ≥35 mm) can shorten the period of shouldering and avoid defect inclusion. The pulling rate (0-1.5 mm/h) can be changed rapidly (1.5-2 h) without affecting the trend and quality of shouldering by adjusting power with a small amplitude (Δt=10 min, ∆v= 0.2 mm/h). By using these adjusting ways to thermal field and growth process, a series of 3-inch (1 inch=25.4 mm) flat shoulder CLN crystals with good optical homogeneity have been successfully grown.
The question of what qualities excellent medical bioceramics must possess to ensure satisfactory prognosis for bone healing and reconstruction remains a topic of great interest in both clinical and biomaterial sciences. Our team has been dedicated to researching medical bioceramics since the 1990s, involving basic scientific research, applied translational research, and clinical trials. Consequently, we have amassed a wealth of research and implementation experience. In this article, we aim to explore the subject of “Functional Bioadaptability in Medical Bioceramics”, specifically focusing on calcium phosphate-based materials. We summarized how to effectively combine bioadaptability with design and manufacturing of medical bioceramics in the background of orthopedic clinical application, with the following aspects of structural adaptability, degradative adaptability, mechanical adaptability, and application adaptability. Hopefully, some suggestions put forward can ultimately provide valuable insights and recommendations for the design, production, supervision, and application of the upcoming medical bioceramics.
AgBi2I7 thin film is one of the important candidates for constructing heterojunction ultraviolet photodetectors, due to their great optoelectronic properties and environmental stability. In this study, AgBi2I7 thin films were prepared by solution method and their photodetecting properties were investigated. By optimizing technological parameters such as concentration of the precursor solution and type of solvent (n-butylamine and DMSO), their photodetecting performance were investigated. AgBi2I7 thin films were fabricated on wide-bandgap GaN by optimal scheme to construct an AgBi2I7/GaN heterojunction. The heterojunction has a great selective detection of UVA-ray of which full width at half maximum is about 30 nm. Under 3 V bias and 350 nm UV irradiation, the On/Off ratio of the device exceeds 5 orders of magnitude, achieving a high responsivity of 27.51 A/W and a high detection rate of 1.53×1014 Jones. Therefore, the present research indicates that AgBi2I7 thin films prepared by solution method are promising to be applied to construct high-performance heterojunction ultraviolet photodetectors.