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.

Densification of ceramic materials by conventional sintering process usually requires a high temperature over 1000 ℃, which not only consumes a lot of energy, but also forces some ceramic materials to face challenges in phase stability, grain boundary control, and co-firing with metal electrodes. In recent years, an extremely low temperature sintering technique named cold sintering process (CSP) was proposed, which can reduce the sintering temperature to below 400 ℃, and realize the rapid densification of ceramic materials through the dissolution- precipitation process of ceramic particles by using the transient solvent in liquid phase and uniaxial pressure. The advantages of CSP, including low sintering temperature and short sintering time, have attracted extensive attention from researchers, since it was firstly reported in 2016. At present, CSP has been applied to the sintering of nearly 100 kinds of ceramics and ceramic-matrix composites, involving dielectric materials, semiconductor materials, pressure-sensitive materials, and solid-state electrolyte materials. This paper firstly introduces the low-temperature sintering techniques’ development history, process and densification mechanism. Then, application of CSP in the field of ceramic materials and ceramic-polymer composites is summarized. Based on differences of solubility, application of CSP mainly on Li₂MoO₄ ceramics, ZnO ceramics, BaTiO₃ ceramics, and their composites preparations are introduced. Auxiliary effect of the transient solvent on cold sintering process is emphatically analyzed. Moreover, the high pressure issue in the cold sintering process and the possible solutions are discussed. At last, future development trend of cold sintering process is prospected.

The outbreak of corona virus disease 2019 (COVID-19) has aroused great attention around the world. SARS-CoV-2 possesses characteristics of faster transmission, immune escape, and occult transmission by many mutation, which caused still grim situation of prevention and control. Early detection and isolation of patients are still the most effective measures at present. So, there is an urgent need for new rapid and highly sensitive testing tools to quickly identify infected patients as soon as possible. This review briefly introduces general characteristics of SARS-CoV-2, and provides recentl overview and analysis based on different detection methods for nucleic acids, antibodies, antigens as detection target. Novel nano-biosensors for SARS-CoV-2 detection are analyzed based on optics, electricity, magnetism, and visualization. In view of the advantages of nanotechnology in improving detection sensitivity, specificity and accuracy, the research progress of new nano-biosensors is introduced in detail, including SERS-based biosensors, electrochemical biosensors, magnetic nano-biosensors and colorimetric biosensors. Functions and challenges of nano-materials in construction of new nano-biosensors are discussed, which provides ideas for the development of various coronavirus biosensing technologies for nanomaterial researchers.

Continuous silicon carbide fiber reinforced silicon carbide composite (SiC_f/SiC) is a key material for the advanced aero-engines. It is required to possess excellent high-temperature creep resistance for SiC_f/SiC to meet the long-term service lifetime of the aero-engines. Here, tensile creep behaviors of a plain woven Cansas-II SiC_f/SiC (2D-SiC_f/SiC) were investiged in the temperature of 1200-1400 ℃ with the stress levels of 80 to 140 MPa. Its microstructure and fracture morphology were observed, and composition was analyzed. Results show that creep-rupture time of 2D-SiC_f/SiC is more than 500 h and steady-state creep rate is 1×10^-10-5×10^-10 /s at stresses lower than the proportional limit stress (σ_PLS). The creep behaviors are controlled by matrix and fibers. The creep-rupture time is significantly reduced, and the steady-state creep rate is increased by an order of magnitude when the stress is higher than the σ_PLS. The matrix, fibers and interfaces of the composite are greatly oxidized, and the creep behaviors are mainly controlled by the fibers.

Since the beginning of the 21st century, the third generation wide band gap (E_g>2.3 eV) semiconductor materials represented by gallium nitride (GaN) and zinc oxide (ZnO) are becoming the core supporting materials for development of semiconductor industry. Due to difficult growth and high cost of GaN and ZnO single crystal, epitaxial technology is always used as the substrate materials to grow GaN and ZnO films. Therefore, it is crucial to find an ideal substrate material for the development of third generation semiconductor. Compared with traditional substrate materials, such as sapphire, 6H-SiC and GaAs, scandium magnesium aluminate (ScAlMgO₄) crystal, as a new self-peeling substrate material, has attracted much attention because of its small lattice mismatch rate (~1.4% and ~0.09%, respectively) and suitable thermal expansion coefficient with GaN and ZnO. In this paper, based on structure of ScAlMgO₄ crystal, the unique trigonal bipyramid coordination and natural superlattice structure, the basis for its thermal and electrical properties, are introduced in detail. In addition, the layered structure of ScAlMgO₄ crystal along the c-axis makes it self-peeling, which greatly reduces its preparation cost and has a good application prospect in the preparation of self-supported GaN films. However, the raw material of ScAlMgO₄ is difficult to synthesize, and the crystal growth method is single, mainly through the Czochralski method (Cz), and growing techniques now in China lag far behind that in Japan. Therefore, it is urgent to develop a new growth method of growing high quality and large size ScAlMgO₄ crystals to break the technical barriers.

Film capacitors are the core electronic components of modern power devices and electronic equipment. However, due to the low dielectric constant, it is difficult to obtain high energy storage density (effective energy storage density or discharged energy density) for present film capacitors, leading to a large device size and high application cost. To improve the energy storage density of film capacitors, a nanocomposite approach is an effective strategy via combining high dielectric constant of the ceramic nanoparticles with high breakdown strength of the polymer matrix. Nevertheless, for single-layer structure of 0-3 polymer/ceramic composites, the dielectric constant and breakdown strength are difficult to be effectively enhanced at the same time, which limits the further improvement of energy storage density. To solve this contradiction, researchers have combined the composite film with high dielectric constant and high breakdown strength in a superposition to prepare 2-2 type multilayer composite dielectrics, which can achieve synergistic regulation of polarization strength and breakdown strength to obtain high energy storage density. The optimization of electric field distribution and the synergistic regulation of dielectric constant and breakdown strength can be achieved through mesoscopic and microstructural modulation of multilayer composite dielectrics. In this paper, the research progress of multilayer polymer-based composite dielectrics including ceramic/polymer multilayer structure and all-organic polymer multilayer structure in recent years is reviewed. Effect of multi-layer structure control strategy on the improvement of energy storage performance is emphasized. Moreover, enhancement mechanism of energy storage performance of polymer-based multilayer structure composite dielectric is summarized. Finally, challenges and development directions of multilayer composite dielectrics are discussed.

Compared with the first and second generation semiconductor materials, the third generation semiconductor materials exhibit higher breakdown field strength, higher saturated electron drift velocity, outstanding thermal conductivity, and wider band gap, suitable for manufacturing of electronic devices with high frequency, high power, radiation resistance, corrosion resistant properties, optoelectronic devices and light emitting devices. As one of the representatives of the third generation of semiconductor materials, gallium nitride (GaN) is an ideal substrate material for preparing blue-green laser, radio frequency (RF) microwave and power electronic devices. It has broad application prospects in laser display, 5G communication, phased array radar, aerospace, etc. Hydride vapor phase epitaxy (HVPE) method is the most promising method for growth of GaN crystals due to its simple growth equipment, mild growth conditions and fast growth rate. Due to the widely used quartz reactors, unintentionally doped GaN obtained by HVPE method inevitably has donor impurities (Si and O). Therefore, the grown GaN shows n-type electrical properties, high carrier concentration and low conductivity, which limits its application in high-frequency and high-power devices. Currently, doping is the most common method to improve the electrical performance of semiconductor materials, through which different types of GaN single crystal substrates can be obtained with different dopants to improve their electrochemical characteristics and meet the different needs of market applications. In this article, the basic structure and properties of GaN semiconductor crystal material are introduced, and the recent progress of the high quality GaN crystals grown by HVPE method is reviewed; and the doping characteristics, dopant types, growth process and the influence of doped atoms on the electrical properties of GaN are introduced. Finally, the challenges and opportunities faced by the HVPE method to grow doped GaN crystals are briefly described, and the future developments in several directions are prospected.

Ceramic materials are widely used in aerospace, medicine and energy transportation concerned for their excellent over-all mechanical and chemical properties, such as corrosion resistance, high temperature resistance and oxidation resistance. Especially, joining ceramic materials themselves and connecting them with metals are of great significance for the practical engineering applications. Compared with traditional joining technology, electric-assisted joining technology possesses a variety of advantages, such as low temperature and short time, owing to the special influence of the electric field on some ceramic materials. This paper focuses on the development of the electric-field assisted joining technologies of ceramics and ceramic matrix composites, and summarizes their research status in recent years. From the views of joining mechanism, typical interface microstructure and joint strength and influencing factors, the electric-field assisted diffusion bonding (FDB), spark plasma sintering (SPS) joining, and the new low-temperature rapid flash joining (FJ) are reviewed. Moreover, the applicable scope and limitations of different electric-field assisted joining technologies are expounded. In addition, the development trend of the electric-field assisted joining technology of ceramic materials is prospected.

In recent years, inspired by the unique operation mode of the human brain, emulation of the perception and computing functions of synapses and neurons by artificial neuromorphic devices has attracted more and more attention. So far, many researches have been reported about neuromorphic transistors (NMT), but most devices are fabricated on rigid substrates. The flexible neuromorphic transistors can not only realize signal transmission and training learning at the same time, but also carry out nonlinear spatio-temporal integration and cooperative regulation of multiple signals. It can also closely fit the soft human skin and withstand the high physiological strain of organs and tissues. More importantly, flexible neuromorphic transistors have unique advantages and application potential in detecting low amplitude signals at physiologically relevant time scales in biological environments due to their designable flexibility and excellent biocompatibility. Flexible neuromorphic transistors have been widely used in electronic skin, artificial vision system, intelligent wearable system, and other fields. At present, it is one of the most important tasks to develop low-power consumption, high-density integrated flexible neuromorphic transistors. In this paper, the research progress of NMT based on different flexible substrates is reviewed. In addition, the bright application prospect of flexible neuromorphic transistors is prospected. This review provides a reference for the development and application of flexible neuromorphic transistors in the future.

For the conventional von Neumann based vision systems, the sensing, memory, and processing units are separated. Shuttling of redundant data between separated image sensing, memory, and processing units causes a high latency and energy consumption. To break these limitations, the next-generation neuromorphic visual systems, which integrate light information sensing, memory, and processing, can reduce the data transfer, thus improving their time and energy efficiencies. As the basis of the hardware-implementing of neuromorphic visual systems, optoelectronic artificial synapse devices have been extensively investigated in recent years. By integrating the functions of synaptic devices and light-sensing elements, the optoelectronic artificial synapse devices pave the way for constructing new neuromorphic vision systems with low latency, high energy efficiency and good reliability. Many materials are widely utilized for optoelectronic artificial synapse devices, and operation mechanisms of the present optoelectronic artificial synapse devices mainly include the ionization and dissociation of oxygen vacancy, the trapping/detrapping of photogenerated carriers, the light-induced phase change, and the interaction between light and ferroelectric materials. In this short review, the recent progresses in optoelectronic artificial synapse devices are introduced from the perspectives of their operation mechanisms. Besides, advantages and challenges of the devices are analyzed from the view of operation mechanisms. Finally, the advanced prospect and research aspect of optoelectronic artificial synapse devices are outlined for the application.

Bacteria and viruses always posed a threat to human health. Most impressively, SARS-CoV-2 has raged around the world for almost three years, causing huge loss to human health. Facing increasing challenges of drug-resistance and poor treatment efficacy, new solutions are urgently needed to combat pathogenic microorganisms. Recently, nanozymes with intrinsic enzyme-like activities emerged as a promising new type of “antibiotics”. Nanozymes exhibit superior antibacterial and antiviral activities under physiological conditions by efficiently catalyzing generation of a large number of reactive oxygen species. Moreover, enhanced therapeutic effects are achieved in nanozyme-based therapy aided by the unique physicochemical properties of nanomaterials such as photothermal and photodynamic effects. This paper reviews the latest research progress in the field of anti-microbial nanozymes, systematically summarizes and analyzes the principles of nanozymes in the treatment of bacteria and viruses from a mechanistic point of view. An outlook on the future direction and the challenges of new anti-microbial infection nanomaterials are proposed to provide inspiration for developing next generation anti-microbial nanozymes.

Perovskite solar cells (PSCs) with structure of TiO₂/ZrO₂/carbon triple-layer are attractive recently because of their inexpensive raw materials, scalable fabrication process, and outstanding stability. But little progress has been made in the low temperature fabrication of TiO₂/ZrO₂/carbon triple-layer structured PSCs. A major reason is that it is rather difficult to construct the ZrO₂ spacer layer at low temperature. Herein, we report a facile low-temperature spray-coating method to prepare effective ZrO₂ spacer layer in TiO₂/ZrO₂/carbon triple-layer PSCs using urea to tune the porosity. After optimizing the amount of urea and the thickness of zirconia to 1100 nm, power conversion efficiencies (PCE) of 14.7% for a single cell and 10.8% for a module with 5 cells connected in series (5×0.9 cm× 2.5 cm) were achieved. Furthermore, the PSCs could be stable for 200 d at constant temperature (25 ℃) and humidity (40%). With this spray coating method, the zirconia layer on flexible substrate can endure 50 times of bending without any cracking. Compared to the conventional screen-printing method of ZrO₂ spacer layer, the spray-coating alternative developed in this work shows advantages of more convenient to process, preparation under lower temperature, and compatibility to flexible substrate.

The analog channel conductance modulation of electrolyte-gated transistors (EGTs) is a desirable property for the emulation of synaptic weight modulation and thus gives them great potential in neuromorphic computing systems. In this work, an all-solid-state electrochemical EGT was introduced with a low channel conductance (~120 nS) using amorphous Nb₂O₅ and Li-doped SiO₂ (Li_xSiO₂) as the channel and gate electrolyte materials, respectively. By adjusting the applied gate voltage pulse parameters, the reversable and nonvolatile modulation of channel conductance were achieved, which was ascribed to reversible intercalation/deintercalation of Li⁺ ions into/from the Nb₂O₅ lattice. Essential functionalities of synapses, such as the short-term plasticity (STP), long-term plasticity (LTP), and transformation from STP to LTP, were simulated successfully by conductive channel modulation of the EGTs. Based on these characteristics, a simple associative learning circuit was designed by parallel a resistor between the gate and the source terminals. The Pavlovian dog classical conditioning behavior was simulated based on associative learning circuit, where the resistor represented the unconditioned synapse and shared the gate voltage with EGT according to the proportion of its resistance, and the resistance between gate and source for negative feedback regulation of synaptic weights. These results demonstrate the potential of EGT for artificial synaptic devices and provide an insight into hardware implementation of neuromorphic computing systems.

Photocatalysis is widely used for the removal of refractory organic pollutants in water, but the catalytic activity of semiconductor photocatalysts is significantly inhibited due to the high recombination rate of photogenerated electrons and holes. In this study, an S-scheme BiOBr/ZnMoO₄ composite was successfully prepared by a facile solvothermal method. The structure analysis, in-situ XPS, work function test, free radical capture and ESR experiment confirmed that the BiOBr/ZnMoO₄ composite formed an S-scheme heterojunction. The experimental results show that BiOBr/ZnMoO₄ heterojunction with appropriate ZnMoO₄ content can significantly improve the photocatalytic performance of BiOBr. Compared with pure BiOBr and ZnMoO₄, 15% BiOBr/ZnMoO₄ exhibits the best photocatalytic activity under visible light irradiation, and the photocatalytic degradation rate of bisphenol A reaches 85.3% (90 min). The rate constants of photodegradation of ciprofloxacin are 2.6 times that of BiOBr and 484 times that of ZnMoO₄, respectively. This can be attributed to the tight interfacial bonding between BiOBr and ZnMoO₄ and the formation of S-scheme heterojunction, which enables the efficient spatial separation and transfer of photogenerated carriers. This work provides a simple and efficient method for the directional synthesis of Bi-based S-scheme heterojunction photocatalytic materials, and provides a new theory and experimental basis for further understanding of the structure-activity relationship of Bi-based multi-heterojunction photocatalytic materials.

2022 marks the 110th anniversary of X-ray diffraction (XRD), which is a powerful technique used to find out the nature of materials. Rietveld refinement method, as an important means of extracting material structure information, plays a significant role in establishing the relationship between structure and performance of materials. Cathode materials are a vital part of lithium-ion batteries (LIBs). In-depth understanding of their crystal structure and atomic distribution is extremely helpful to promote the development of cathode materials for LIBs. Cathode materials for LIBs are generally the hosts of lithium. Studies on lithium occupation and transfer are inseparable from a deep understanding of its structural characteristics. This review summarizes XRD Rietveld structure refinement and its application in cathode materials for LIBs. XRD Rietveld structure refinement in synthesis, degradation, and structural modification of cathode materials are analyzed by using several types of typical cathode materials as examples. XRD Rietveld method could provide useful structural information of the cathode materials, including phase ratio in composite and crystallographic parameters (e.g., cell parameters, key atomic occupation, and atomic coordinates). Therefore, exploring structure of cathode materials assisted with XRD Rietveld refinement method is of great significance for the development of high-performance cathode materials for LIBs. Finally, the opportunities and challenges in the field of X-ray diffraction technology in detecting structure of cathode materials for LIBs are prospected.

With the progress of nuclear radiation technology in China, radiation detection has been developed rapidly in recent years for the wide usage in radiation safety monitoring, radioactive medicine diagnosis/treatment, X-ray security inspection, industrial non-destructive detection, microscopic particle track detection, and many other fields. Radio-photoluminescence (RPL), as a new radiation detection method, is a phenomenon in which a new luminescence center is generated inside a material under a ionizing radiation which can be excited by ultraviolet light to emit a special light. RPL materials usually have characteristics of storing radiation information, almost no attenuation of information, good linear dose response, high radiation sensitivity, low energy dependence, and repeatable reading, which can overcome the shortcomings in stability and reusability of optically stimulated luminescence (OSL) materials and thermally stimulated luminescence (TSL) materials. Since the RPL phenomenon was reported, RPL materials have emerged constantly, from the traditional materials as Ag-doped phosphate glass, Al₂O₃:C, Mg and LiF, to the novel materials such as Cu-doped RPL system, Sm-doped RPL system and undoped RPL system materials. Meanwhile, applications of RPL materials have also been explored, enabling them to become one of the indispensable materials in the field of radiation detection. Based on above aspects, this paper summarizes the latest development of RPL materials, focuses on the luminescence principle, performance characteristics and applications of traditional and novel RPL materials, and especially compares the performance of different RPL materials in radiation detection. Finally, advantages and disadvantages, accompanied by prospected development trend of RPL materials are summarized and analyzed

Large-sized crystalline materials are the basic raw materials in semiconductors, lasers, and communications. Preparation of large-scale, high-quality crystalline materials has become a bottleneck restricting the development of related industries. Breaking through the preparation theory and technology of large-sized crystal materials is the key to obtaining high-quality large-sized crystals. Preparation process of crystal materials often undergoes nucleation and growth stages, including multiple processes at spatiotemporal scale: from atom/molecules, through clusters and nuclei, to bulk crystals. To further explore and accurately understand the crystal growth mechanism, we need intensively study the multiscale process,multi-scale in situ characterization techniques, and computational simulation methods. Among them, the latest in situ characterization methods for crystal growth includes optical microscopy, electron microscopy, vibration spectra, synchrotron radiation, neutron technology, and especially, machine learning method. Thus, the multi-scale computational simulation techniques for crystallization is introduced, for example, first principles calculation at atom/molecular scale, molecular dynamics simulation, Monte Carlo simulation, phase field simulation at mesoscopic scale, and finite element simulation at macroscopic scale. A single in situ characterization or simulation technique can only explore crystallization information over a specific time and space scale. To accurately and fully reflect the crystallization process, a combination of multi-scale methods is introduced. It can be speculated that the establishment of in situ characterization technology and computational simulation methods for the actual large-sized crystal growth environment will be the future development trend, which provides an important experimental and theoretical basis for developing crystallization theory and controlling crystal quality. Furthermore, it can be deduced that the combination of in situ characterization technology with machine learning and big data technology will be the trend for large-sized crystal growth.

Wearable instruments are functional devices that can be worn on human body, sensing, transmitting and processing body or environmental information in real time, and show broad application prospects in medical health, especially artificial intelligence, sports and entertainment. With the development of wearable instruments, various flexible sensors have emerged. Flexible mechanical sensors based on piezoelectric effect have attracted much attention because of their advantages of wide sensing frequency, fast response, good linearity, and self-power supply. However, traditional piezoelectric materials are mostly brittle ceramics and crystalline materials, which limit their application in flexible devices. With the deepening of research, more and more flexible piezoelectric materials and piezoelectric composites continue to emerge, injecting new development vitality into flexible wearable mechanical devices. This article mainly summarizes the cutting-edge progress of flexible wearable piezoelectric devices, including piezoelectric principle, preparation and performance improvement methods of flexible piezoelectric materials. In addition, the main application directions of flexible wearable piezoelectric devices, including medical health and human-computer interaction, as well as the challenges and opportunities encountered, are summarized.

Eutrophication caused by nitrogen, phosphorus and organic pollutants is a common problem which has attracted much attention in China. Ammonia nitrogen, as a main pollutant, should be removed efficiently to avoid the extension of eutrophication. In this research, Prussian Blue (PB), which can not only capture ammonia nitrogen by vacancy in crystal cell but also degrade organic pollutants by Fenton oxidation, was combined with modified biochar to increase efficiency of ammonia nitrogen removal. Several characterization methods were used to investigate the structure and morphologies of the biochar composite. Adsorption capacity of biochar composite material (BC700-PB) was tested by NH₄Cl solution. The results show that the maximum adsorption capacity to ammonia nitrogen is 24.4 mg/g and the removal efficiency is over 95% within 60 min under the condition of pH 8, which is 101.3% higher than that of the unmodified biochar. The adsorption mechanism of BC700-PB was investigated with Langmuir model and pseudo-second-order kinetic equation which reveal that the adsorption including physical adsorption by biochar and coordination adsorption by PB. Meanwhile, Fenton oxidation process is conducted by PB nanoparticles in the biochar composite material with existence of H₂O₂. The biochar composite material could catalyze H₂O₂ to generate •OH, and achieve degradation of organic pollutants and adsorption of ammonia nitrogen. The PB/biochar composite material can be recycled easily by NaCl solution for several times. In conclusion, the PB/biochar composite is a promising material for eliminating multi-component eutrophication wastewater.

Memristor, fusing the functions of storage and computing within a single device, is one of the core electronic components to solve the bottleneck of von Neumann architecture. With the unique volatile/non-volatile resistive switching characteristic, memristor can simulate the function of synapses/neurons in brain well. In addition, due to the compatibility with traditional complementary metal-oxide-semiconductor (CMOS) processes, metal-oxide-based memristors have received a lot of attention. In recent years, many kinds of metal-oxide memristors based on single dielectric layer have been proposed. However, there are still some problems such as the instability of switching voltage, fluctuation of high/low resistance state and poor endurance of memristive device. Thus, the researchers have successfully optimized the device performance by introducing the double dielectric layer into the metal-oxide memristors. In this article, we introduce the advantages of double dielectric layers-based metal-oxide memristors, and discuss their mechanism and design of double dielectric layers-based metal-oxide memristors. Eventually, we introduce their potential applications in neuromorphic computing. This review provides some enlightenment on how to design high-performance metal-oxide memristor based on double dielectric layers.

Single crystal diamond is a kind of crystal material with excellent performance, which has important application value in advanced scientific field. In the field of single crystal diamond growth by microwave plasma chemical vapor deposition (MPCVD), improvement of crystal growth rate is still a key challenge, although corrent high energy density plasma has been a ralatively effective method. In this work, a special plasma focusing structure was designed through magnetohydrodynamic (MHD) model simulation which then was used in the growth experiment based on the simulation. The plasma properties were studied by means of spectral analysis and plasma imaging, and late on single crystal diamond samples were synthesized. The simulation results show that the core electric field and electron density under focusing conditions were 2 times higher than those under normal conditions. The growth experiment results show that plasma with high energy density (793.7 W/cm³) is obtained under conventional microwave power (3500 W) and growth pressure (18 kPa), which is consistent with the model calculation results. We find that a certain amount of nitrogen instead of high energy density growth conditions can significantly change the growth morphology and affect the quality of the crystal. With those findings, we realize the growth rate of single crystal diamond up to 97.5 μm/h. Different from the way to obtain high energy density by increasing the growth pressure, single crystal diamond can be synthesized with high energy density under normal growth pressure and microwave power.

Silicon carbide ceramic matrix composites have been widely used in aerospace, friction brake, fusion fields and so on, and become advanced high-temperature structural and functional composites, due to their high specific strength and specific modulus, excellent ablation and oxidation resistance, and high conductivity and good thermal shock resistance. This paper reviews the latest research progress in preparation and property of silicon carbide ceramics matrix composites (CMCs) with high thermal conductivity. Researchers have improved the thermal conductivity of silicon carbide CMCs, including by introducing highly thermal conductive phases for reinforcing heat transport, such as diamond powders, and mesophase pitch-based carbon fibers (MPCF), by optimizing the interface between pyrolytic carbon (PyC) and silicon carbide matrix for reducing interfacial thermal resistance, by heat-treating for obtaining silicon carbide matrix with higher crystallinity and better thermal conductivity, and by designing preform structure for establishing continuous thermal conduction path. Meanwhile, research interests on silicon carbide CMCs are to explore new preparation with high efficiency and low cost through optimising their influencing factors, and to obtain isotropic highly thermal conductivity with dimensional stability and physical properties through deep understanding their thermal conductive mechanism, and flexible method based on the structure-activity relationship.

As a colossal magnetoresistance material, the perovskite manganese oxide La_1–xSr_xMnO₃ (LSMO) has broad application prospects in magnetic sensors and other fields. However, it is difficult to obtain a significant colossal magnetoresistance effect at a low magnetic field at room temperature. To improve its magnetoresistance effect and transition temperature, La_0.8Sr_0.2Mn_1–xAl_xO₃ (0≤x≤0.25) (LSMAO) polycrystalline samples were prepared by traditional solid-state reaction method in present work. Effects of Al³⁺ doping on the electrical transport property and magnetoresistance of LSMO were systematically analyzed. The X-ray diffraction (XRD) results indicate that all samples crystallize in a single rhombohedral structure with the space group of $\text{R}\bar{3}\text{C}$. Result of electrical transport property shows that resistivity of the samples increases exponentially with the increment of Al³⁺ doping amount, and the metal-insulator transition temperature is increased by an external magnetic field. This phenomenon may be attributed to dilution of the Mn³⁺/Mn⁴⁺ ions network by Al³⁺, which increases the magnetic disorder but reduces the number of carriers. In addition, the conduction mechanism of LSMAO ceramics change from the small polaron hopping model (SPH) to the variable range hopping model (VRH) after doping of Al³⁺, reflecting that the non-magnetic Al³⁺ weakens the carrier exchange between the ferromagnetic clusters. As a result, the thermally activated neighbor transition of small polarons is suppressed. Magnetoresistance effect of LSMAO is enhanced from 21.03% to 59.71% with x increasing from 0 to 0.25, which proves that the doping of Al³⁺can effectively enhance the magnetoresistance effect of LSMAO.

As a multifunctional opto-electro material, Bi₁₂GeO₂₀ crystal shows high-speed photorefractive response in visible range, excellent piezoelectric, acousto-optic, magneto-optic, optical rotation, and electro-optic properties, etc. Presently, Czochralski (Cz) method, which is commonly used to grow Bi₁₂GeO₂₀ crystals, has several bottle-necks, such as high growth cost, irregular crystal boule shapes, low growth yield, poor optical quality in large crystals, and small effective crystal cross-sectional area. In this study, large Bi₁₂GeO₂₀ crystals were firstly grown by using modified vertical Bridgman method in platinum crucibles and air atmosphere. Morphology, distribution, and constitutes of main macroscopic defects in as-grown Bi₁₂GeO₂₀ crystals were investigated, and the formation process and causes of the main macroscopic defects during the crystal growth were studied. Dendrite and tubular inclusions are two types of main macroscopic defects existed in as-grown Bi₁₂GeO₂₀ crystals. The formation of dendrite inclusions is closely related to the platinum corrosion, while the formation of tubular inclusions is associated with precipitation of platinum, a mismatch in the stacking of growth units due to instability of the seeding interface, and instability temperature field. Technical approaches to eliminate or reduce these two types of macroscopic defects during the growth using vertical Bridgman method were proposed. High optical quality, large Bi₁₂GeO₂₀ crystals with sizes up to 55 mm×55 mm×80 mm and significantly improved optical transmittance were grown reproducibly by reducing control temperature, decreasing period of melt preserved at high temperature, and selecting seed crystals with better quality.

Ferroelectric superlattices are artificial film materials with layered periodic structure formed by an alternate growth of two or more ferroelectric materials or non-ferroelectric materials at unit cell scale. Ferroelectric superlattices can exhibit excellent ferroelectric, piezoelectric, dielectric, and pyroelectric properties due to the existence of a large number of heterogeneous interfaces and the remarkable interface effect, and even show new functional properties that are not available in their constituent materials. Therefore, ferroelectric superlattices not only provide an ideal platform for studying interactions between charges and lattices at the interface of complex oxide materials, but also play an indispensable role in the next generation of integrated ferroelectric devices. With the development of preparation and characterization methods, researchers can design and control the microstructure and chemical composition at atomic scale to improve the functional properties of ferroelectric superlattice thin films. Ferroelectric polarization is the most basic property of ferroelectric film materials. In addition to being used for information storage devices, ferroelectric polarization also plays an important role in regulating the energy conversion performance of integrated ferroelectric devices such as piezoelectric devices, photovoltaic devices and electrocaloric devices. Therefore, the ferroelectric polarization intensity of ferroelectric superlattices directly determines their functional characteristics and practical application value of integrated ferroelectric devices composed of them. In this short review paper, we firstly introduced the structural characteristics, classification and several typical functional characteristics of ferroelectric superlattices, and then focused on several factors affecting the polarization performance of ferroelectric superlattices based on recent research results, including strain effect, electrostatic coupling effect, defect effect, and period thickness. Finally, we looked forward to the future research directions in ferroelectric superlattices to provide reference for the research in this field.

Indium-gallium-zinc-oxide (IGZO)-based electric-double-layer (EDL) transistors have great applications for neuromorphic perception and computing systems because of their low processing temperature, high homogeneity, and plentiful ionic dynamics. However, IGZO-based EDL transistors have problems of high leakage current (>10 nA), high energy consumption and abnormal current spikes, which are the main obstacles to the development of neuromorphic computing systems based on such devices. In this work, a novel IGZO neuromorphic transistor with Al₂O₃/chitosan stacked gate dielectric was proposed. Compared with the monolayer chitosan gate dielectric transistor, the device with Al₂O₃/chitosan layer showed low subthreshold swing of 78.3 mV/decade, a low gate leakage current of 1.3 nA (reduced by about 98%), a large hysteresis window of 3.73 V (increased by about 3.4 times), a low excitable postsynaptic current of 0.86 nA (decreased by about 97%) and an energy consumption of 1.7 pJ for a spike event (0.5 V, 20 ms). Additionally, the emulation of spiking synaptic function and the synergistically modulation of the channel current were also realized, and the abnormal current spike caused by high leakage in synaptic plasticity simulation was also effectively avoided. The results suggest that the inserting of high-k dielectric layer can effectively improve the leakage current, energy consumption and performance of neuromorphic devices, which has substantial value for future ultra-low energy consumption neuromorphic perception and computing systems.

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.

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.

With the rapid development of high power laser and optical communication technology, how to eliminate the reflected noise generated inside the optical system is a crucial challenge. The magneto-optical isolators are magnetically active devices designed according to the Faraday effect, which can effectively isolate most of the reflected light to ensure the stable operation of the optical system. As the core component of the magneto-optical isolator, research and application of Faraday magneto-optical materials are promoting the update and development of the magneto-optical isolators. CeF₃ crystals have the advantages of high transmittance, wide transmission range and high Verdet constant, and have received widespread attention in recent years for the excellent magneto-optical property. But its traditional growth methods have some disadvantages such as high cost and long cycle. In this study, multiple CeF₃ crystals were successfully obtained by the porous crucible technology through optimizing the temperature field structure and process of Bridgman growth technology. Compared with commercial TGG(Tb₃Ga₅O₁₂) crystals, CeF₃ crystals have a significantly high transmittance up to 92%, and a comparable Verdet constant in the near-infrared wavelength, and the thermal performance test results show that CeF₃ crystals have high specific heat, indicating a strong thermal shock resistance and a high laser damage resistance. Therefore, the porous crucible technology is a large-scale and low-cost production method, which can be used to grow CeF₃ crystals achieving with excellent physical properties, exhibits great potential to develop magneto-optical isolators in the near-infrared band.

Compared with other electric energy storage devices, dielectric capacitors made of dielectric composites have great advantages in fast charging and discharging capacity with high power density. A dilemma of improving the energy density of dielectric composites and synchronous optimizing their breakdown performance is becoming an intriguing research direction. To further adjust the contradiction between dielectric constant and dielectric breakdown performance, here a finite element numerical simulation based on dielectric breakdown model (DBM) was proposed to study the effect of the distribution of inorganic fillers on the electric field and breakdown damage morphology in flexible polydimethylsiloxane(PDMS) based dielectric composite system. The results show that a large dielectric difference is observed between filler and matrix, which indicates that polymer matrix with a large dielectric constant or inorganic filler with a small dielectric constant can realize reducing the size of the high electric field area at the interface and improving the breakdown resistance of the material. This study further reveals that the more dispersed structure of inorganic fillers, the more likely its dendritic damage channels tend to branch, indicating that this situation is conducive to the increase of damage sites of dielectric breakdown dendritic damage channels, the decrease of damage rate, and the improvement of breakdown resistance of materials. All above data demonstrate that this study provides certain guidance for the development of organic-inorganic dielectric composites with both high energy storage and excellent breakdown performance.

Currently, although Er³⁺ and Yb³⁺ co-doped YAG crystals are widely used in high power solid state lasers, there are still many challenges in growing large size, low defect doped YAG crystals using the Czochralski (Cz) method. In this paper, large-sized Er³⁺ and Yb³⁺ co-doped YAG bulk crystal with a diameter of 80 mm and a length of 230 mm was obtained by the fast Cz growth method. Their structure, doping concentration, optical absorption, luminescence performances, and etching defects were evaluated.According to the Raman detecting results, there is no significant variation in the peak positions and full width at half maxima (FWHM) of the Raman peaks at different locations on the wafer, indicating that the crystal structure and strain at central and edge section of thel wafer are uniformity. The etching results show that the corrosion pits are evenly distributed over the entire corrosion surfacewithout dislocation corrosion pit, which means that the crystals are highly near perfect. Strong luminescence peaks of Yb³⁺ and Er³⁺ at different wavelengths and glow discharge mass spectrometry results demonstrate the successful doping of rare earth ions in Er,Yb:YAG single crystals. This work successfully used the Cz method to grow large-sized, low-defect Er,Yb:YAG single crystals, confirming that the fast growth method is effective for doping double rare-earth ions in YAG crystals.

Indium phosphide (InP) is a kind of important compound semiconductor material, now increasingly used in high frequency electronic devices and infrared optoelectronic devices. Currently, the price of InP devices is much higher than that of GaAs devices, mainly because of its low yield of single crystals and increase of epitaxy, and device process cost due to smaller wafer diameter. Increasing the diameter of InP single crystals is critical to reducing wafer and semiconductor process costs. The main difficulties in preparing large diameter InP single crystals are increasing crystal yield and reducing stress in the crystal. The vertical gradient freeze (VGF) and the liquid encapsulated Czochralski (LEC) methods are commonly used in the industry to prepare InP, while the VGF method has little success in preparing 6-inch InP crystals, and the crystals prepared by the LEC method tend to have higher stress and dislocation density. Here we reported a semi-sealed Czochralski (SSC) method to grow large diameter InP crystals. Numerical simulations were used to analyze the temperature distribution in melt, crystal, boron oxide, and atmosphere in LEC and SSC method, with emphasis on temperature field of the SSC method. As a simulation result, the temperature gradient in the crystal of SSC method is 17.4 K/cm, significantly lower thanthat of 28.7 K/cm in the LEC method. And temperature of atmosphere near the crystal shoulder in the diameter control stage of the SSC method is 504 K higher than that of the LEC method. Then the used thermal field of SSC method was optimized according to the simulation results, and 6-inch (1 inch=2.54 cm) S doped InP single crystals with low defect density and no cracks were prepared by this optimized method, which confirmed that the optimized SSC method is promising for growing large-size InP single crystals.

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.

SiC_f/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, SiC_f/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 SiC_f/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 SiC_f/SiC composites.

As the basic and essential unit of neuromorphic computing system, artificial synaptic devices exhibit great potential in accelerating the high-performance parallel computation, artificial intelligence, and adaptive learning. Among them, electrolyte-gated synaptic transistors (EGSTs) have received increasing attention as the next generation neuromorphic devices owing to its controllable channel conductance. The devices exhibit the abilities of simulating the short-term plasticity (STP) and long-term plasticity (LTP) of the neural synapses. However, most of EGSTs exhibit short persistence for LTP and their channel conductance is difficult to be adjusted due to the rapid self-discharge of the electric double layer. In this work, the EGSTs based on water-induced In₂O₃ as the channel and chitosan as gate electrolyte were constructed and the O₂ plasma treatments were performed. The formation of traps on the channel surface is caused by the O₂ plasma treatments, which leads to capturing hydrogen ions at interface of the electrolyte/channel layer, and the device performance exhibits an enlarged hysteresis window, so as to regulate LTP of EGSTs. Biological synaptic functions, including excitatory postsynaptic current (EPSC), paired-pulse facilitation (PPF), STP, and LTP, were mimicked by electrochemical doping and electrostatic coupling effects. Meanwhile, based on the experimentally verified potentiation/depression characteristics of the EGSTs, a three-layer artificial neural network is applied for handwritten digit recognition, and simulation tests can obtain high recognition accuracy of 94.7%. These results reveal that surface plasma treatment is one of the key technologies to affect the device performance, which has great potential in regulating synaptic function of EGSTs.

Suffering from strong electrostatic interactions between divalent Zn²⁺ and host framework, molybdenum disulfide exhibits slow reaction kinetics as cathode for aqueous zinc-ion batteries. The narrow layer spacing of MoS₂ is difficulty in accommodating large size insertion of hydrated Zn²⁺, resulting in a lower discharge specific capacity. Here, NH₄⁺ expanded MoS₂-N was prepared by a simple ammonia-assisted hydrothermal. The result showed that the ammonia promoted hydrolysis of thioacetamide to provide reduced S^2- and generated a large amount of NH₄⁺ as intercalating particles. These particles expanded the layer spacing of pristine MoS₂ from 0.62 nm to 0.92 nm, greatly reducing the Zn²⁺ inserting energy barrier (with its charge transfer resistance of MoS₂-N only 35 Ω), and increased the discharge specific capacity to 149.9 mAh·g⁻¹ at the current density of 0.1 A·g^-1, 2 times that of MoS₂ electrode without NH₄⁺ expansion. Consequently, it exhibited a stable discharge capacity of about 110 mAh·g^-1 at the current density of 1.0 A·g^-1 with nearly 100% Coulombic efficiency after 200 cycles. The approach of ammonia-assisted layer expansion proposed in this study enriches the modification strategy to enhance the electrochemical performance of MoS₂ and provides a new idea for subsequent cathode development.

The exploration of flexible electronic devices with information processing functions of biological neurons is of great significance for the development of intelligent wearable technologies. Due to lack of inherent mechanical flexibility, conventional threshold-switching memristor based on rigid materials that can implement the computing functions of biological neurons is difficult to fulfill the requirements for potential applications in the future. In this work, an intrinsically stretchable threshold-switching memristor was prepared by using silver nanowire-polyurethane composite as the dielectric layer and liquid metal as the electrodes, respectively. Under application of a sweeping voltage, the device exhibited reliable threshold switching characteristics, which was switched from the high resistance state (HRS) to the low resistance state (LRS) during device programming and spontaneously relaxed to the HRS upon voltage application. Further analysis shows that the underlying mechanism can be attributed to the dynamic formation and rupture of discontinuous silver conductive filaments formed between silver nanowires. In the pulse programming mode, memristor device is able to emulate the integration and firing characteristics of biological neurons, suggesting its great potential as an artificial neuron. Moreover, the pulse amplitude and pulse interval modulated neuronal spiking behaviors are successfully replicated using such devices. Under 20% tensile strain, the threshold-switching memristor shows negligible changes in the operating parameters during device switching and neuronal function implementations, suggesting its excellent mechanical flexibility and stability. This work provides important guidelines for the development of high-performance stretchable artificial neuronal devices and next-generation intelligent wearable systems.

SiAlON-based phosphor has become a research hotspot due to its excellent chemical and physical stability. Especially in the LEDs field, it has received extensive attention in recent years. Rare earth doped SiAlON phosphor is expected to become a new generation of lighting source. However, due to the lack of cyan light emission, the color rendering performance of white-LED (wLED) is often insufficient. In this research, β-Si₅AlON₇:Eu phosphors were synthesized by the traditional high-temperature solid-state route. The structure, morphology, elements and valence states were examined. The wavelength range of excitation spectrum and emission spectrum of Si₅AlON₇:Eu, as well as the thermal quenching performance were studied. It is found that the excitation wavelength range covered the ultraviolet to blue region, and the emission spectrum is a typical broad feature of Eu²⁺ transition. At 300 ℃, the emitted light intensity of the sample can still reach about 40% that of the room temperature, while the thermal activation energy (E_a) reaches 3.7 eV. Compared with the commercial YAG:Ce³⁺ (YAG) phosphor, the thermal stability of Si₅AlON₇:Eu is improved. The wLED with high color rendering of R_a=87 is realized after compounding with the blue chip, and the corresponding color temperature reaches the warm white light range (CCT=4501 K). In this study, SiAlON-based cyan emission is realized, and the phosphor with excellent thermal stability is obtained. Compared with commercial YAG, it also has obvious advantages in the sustainability of luminescence.