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.

The perovskite-type oxynitride with AB(O,N)3 formula is a new type of functional ceramic materials, which have unique dielectric/magnetic/photocatalytic properties and prospective applications in the field of energy storage and conversion. However, the traditional preparation process takes a long time and the product purity is low. In this study, SrTa(O,N)3 ceramic powder was synthesized and densified by a pressureless spark plasma sintering equipment with urea as nitrogen source and metal oxides as precursors. Effects of heating rate and synthesis temperature on the composition and microstructure of the powder were deeply investigated, and the dielectric properties of the optimized ceramic bulks were characterized. The results show that higher heating rate and moderate synthesis temperature are beneficial to sufficient nitridation, while the SrTa(O,N)3 powder prepared at 100 ℃/min and 1000 ℃ possesses the highest purity (~97% oxynitride phase content) with a particle size distribution of 100-300 nm. Elements of Sr, Ta, O and N are evenly distributed. The optimized densification process is firstly sintering at 1300 ℃, with heating rate of 300 ℃/min, and dwelled for 1 min. After sintering, the density of SrTa(O,N)3 ceramic pellet can reach >94% with a high purity. Dielectric constant and loss tangent of the material are 8349 and 10-4 level at 300 Hz, respectively, which are superior to that reported in the literature. The high dielectric constant prepared in this study is closely related to standard density and purity, because the existence of pores and impurities can reduce the dielectric constant of materials. Therefore, high density and purity are the key factors to obtain excellent dielectric properties of SrTa(O,N)3 oxynitride ceramics.

In recent years, all-inorganic cesium-lead halogenated perovskite CsPbX3 (X=Cl, Br, I) nanocrystalline (NCs) materials have become the focus of scientific research due to their unique properties such as long carrier life, strong light absorption, low-cost manufacturing, and band gap adjustability. However, the transient photoconductivity of CsPbBr3 nanocrystals have been hardly researched. In this work, CsPbBr3 nanocrystals were prepared by ligand-assisted re-precipitation method. Then their photoconductive sample preparation and test device of vacuum transient photoconductivity were improved. Effects of different temperatures and different excitation powers on transient photoconductivity of CsPbBr3 nanocrystals were studied. Experiment results show that the photo-generated current decay rate is gradually reduced within the temperature range from 133 K to 273 K, and increases gradually within the temperature range from 273 K to 373 K with temperature increasing. Results of excitation power-dependent show that the photo-generated current decay rate increases when the excitation power increases from 200 to 1000 mW. The research method of this study provides a new idea for studying the dynamics related behavior of photoexcited photo-generated carriers.

Long afterglow materials have wide application in the fields of safety indication, anti-counterfeiting and biological imaging, whereas their defect regulation and afterglow mechanism remain unclear. Self-activated long afterglow materials attracted attention due to their simple composition and structure, which is convenient for revealing the mechanism of long afterglow. A series of calcium doped self-activated zinc germanate long afterglow materials Zn2-xCaxGeO4 (x=0, 0.1, 0.2, 0.3, 0.4, 0.5) were synthesized by high temperature solid reaction. The results showed that yellow luminescence peak of calcium doped zinc germanate sample was observed when excited by 376 nm UV light. Upon 267 nm excitation, the fluorescence intensity of Zn1.5Ca0.5GeO4 increased by 6.2 times. According to the afterglow spectra and their decay curves, the initial afterglow intensity is enhanced by 25.1 times. In addition, Zn1.5Ca0.5GeO4 maintains an afterglow intensity nearly 5 times that of zinc germanate during the first 300 s afterglow duration. Further characterization of TL curves show that the depth of the main trap is about 0.7 eV. After adding proper concentration of Ca2+, the TL peaks become significantly stronger, indicating that the trap density increases significantly after calcium doping. Finally, taking advantage of the difference of the afterglow decay rate of different emission wavelengths, the dynamic change of the "flower" color is realized, which indicates that the obtained materials have the potential application in the field of dynamic anti-counterfeiting.

In contrast to conventional solid-phase sintering, molten salt method can provide a fast mass transfer and nucleation process at lower temperatures which has potential to synthesize the ceramic solid solution for immobilization of high-level nuclear waste (HLW). In this work, Nd-doped zircon (ZrSiO4) ceramics (Zr1-xNdxSiO4-x/2 (0≤x≤0.1)) were prepared by the molten salt synthesis(MSS) at different sintering temperatures (1100, 1200, 1300, 1400, 1500 ℃) for different sintering time (3, 6, 9, 12, and 15 h). Chemical stability of Nd-doped zircon ceramics in simulated geological disposal environment was studied by static leaching test (PCT). Zr1-xNdxSiO4-x/2 was synthesized by the molten salt method under the optimum molar ratio of molten salt to oxide at 10:1, sintering temperature at 1200 ℃ and sintering time of 6 h with the solid solution of Nd in ZrSiO4 being increased to 8% (in mol). The MSS can reduce the synthetic temperature, shorten the sintering time and save the solid solution. The immobilizing mechanism of ZrSiO4 ceramics for trivalent actinide nuclides is lattice immobilizing. Experimental results show that the normalized leaching rate (LRNd) of Nd is as low as ~10-5 g·m-2·d-1. ZrSiO4 ceramics have no phase evolution before and after leaching, suggesting good structural stability. TLeaching model consolidates that Nd leaching is due to dissolution of the ceramic surface layer. Data from this study show that MSS is a promising method to synthesize ceramics solid solution.

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.

To enhance the surface morphology and surface energy of silicon carbide to improve its surface wetting properties, picosecond pulsed laser surface treatment and chemical modification techniques were used, respectively. Additionally, a confocal laser microscope was used to analyze the microfabrication microstructure and the relationship between ablation pattern, laser properties, and processing parameters. Results demonstrated that ablation and remelting were the dominant factors influencing the laser processing effect. An inverted triangle-shaped ablation groove was observed due to ablation threshold of silicon carbide and Gaussian distribution of laser energy in the spot. Fluoroalkyl silane modifier used in the experiments could transform the silicon carbide surface from hydrophilic to hydrophobic. By varying processing parameters of pulsed laser treatment, contact angle of the modified silicon carbide surface increased to a maximum of 157°. To better understand the effect of micro-textures on hydrophobicity, we developed a solid-liquid contact angle model based on the actual morphological parameters which elucidated the mechanism of contact angle variation with characteristic parameters of micro-textures, providing theoretical guidance for finding micro-textures with optimal hydrophobic performance.

Zintl-phase Mg3(Sb,Bi)2-based thermoelectric (TE) compounds have attracted extensive attention due to their excellent TE performance in the medium and low temperature region (27-500 ℃). However, the reactive nature of Mg and Sb elements leads to violent interfacial diffusion reactions with electrodes during long-term high-temperature service, degrading TE performance and shortening lifespan of TE devices. Consequently, it is crucial to select diffusion barrier layer (DBL) with low interfacial contact resistivity to block violent interdiffusion of components. In this work, the n-type Mg3SbBi (Mg3.2SbBi0.996Se0.004) sample, with ZT~1.4@300 ℃, and the “sandwich” structure of Mg3SbBi/Nb/ Mg3SbBi was prepared by hot pressing sintering process. Composition and microstructure of the interfacial layer and evolution of resistance with aging time were investigated systematically. Accelerated aging results (525 ℃/70 h, 525 ℃/170 h, 525 ℃/360 h) indicated that Mg-Sb/Bi components segregation occurred in the Mg3SbBi-Nb DBL junctions, and cracks formed on the surface. However, the interfaces were well conjunctive after polishing the pellets. And the thickness of diffusion layer slowly increased to 1.6 μm after aging. Besides, resistivity of the Nb/Mg3SbBi interface slightly increased from initial 12.9 μΩ·cm2 to 19.8, 27.4 and 31.8 μΩ·cm2, respectively, indicating the Nb DBL still displaying excellent barrier properties except for the faint diffusion during aging. Based on these data, Nb is a better choice to effectively suppress the diffusion of Mg and Sb elements achieving reliable connection, to be the DBL material in the Mg3(Sb,Bi)2-based TE families. In conclusion, Nb can effectively improve the Mg3(Sb,Bi)2-based devices' thermal stability and promote the application over the medium temperature power generation.

Lithium-sulfur batteries (LSBs) have attracted wide attention due to their high energy density, abundant raw material reserves and environmental friendliness. However, the shuttle effect of polysulfides, the large volume expansion during the reaction, and the poor electron conductivity of sulfur greatly limit their practical development. In this work, a ZIF-8 derived flower-like two-dimensional (2D) porous carbon nanosheet/sulfur composite (ZCN-SnS2-S) combined with SnS2 nanoparticles is designed as the cathode for LSBs. The unique 2D flower-shaped porous structure not only effectively alleviates the volume expansion during the reaction process, but also provides a fast channel for Li+ and electron transport. The presence of heteroatom N further promotes the adsorption of polysulfide. In particular, the polar SnS2 enhances the chemical adsorption on polysulfides, resulting in excellent electrochemical performance. The ZCN-SnS2-S electrode exhibits high reversible specific capacity of 948 mAh·g-1 after 100 cycles at 0.2C (1C=1675 mA·g-1), demonstrating the capacity retention rate of 83.7%. Even at a high current density of 2C for 300 cycles, it still has a reversible specific capacity of 546 mAh·g-1.

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.

The microreactor was constructed by using the block copolymer (P123)/sodium dodecyl sulfate (SDS) hybrid emulsion. Horseshoe-shaped hollow porous carbon was prepared by hydrothermal carbonization of xylose. The results showed that hydrothermal reaction of xylose occurred at interface between microreactor and solution. Hydrophilicity of PEO (hydrophilic block in P123) decreased at hydrothermal temperature of 160 ℃. Hybrid emulsion was swelled and destroyed gradually because PEO ran into the interior of emulsion. Furthermore, the morphology of microreactor could be regulated by the mass ratio of P123/SDS and the opening angle, and cavity diameter could be controlled by the hydrothermal time. Owing to the open cavity, the capacity of charges and ions was magnified and transport distance was reduced. In addition, specific capacitance and energy density of porous carbons were improved and showed positive correlation with cavity diameter. The horseshoe-shaped hollow porous carbon with largest opening angle (63°), cavity diameter (80 nm) and optimal supercapacitor performance was obtained at a P123/SDS mass ratio of 1.25 : 1 by hydrothermal method for 12 h. In a three-electrode system, the product showed a high specific capacitance of 292 F·g-1 at a current density of 1 A·g-1. In a two-electrode system, the product showed an excellent energy density (6.44 Wh·kg-1), specific capacitance of 185 F·g-1 at a current density of 0.2 A·g-1 and outstanding cycling stability (94.83%) after 5000 cycles at a current density of 5 A·g-1.

One of the basic challenges of CO2 photoreduction is to develop efficient photocatalysts. As an effective strategy, constructing heterostructure photocatalysts with intimate interfaces can enhance interfacial charge transfer for realizing high photocatalytic activity. Herein, a novel photocatalytic material, Bi4O5Br2/CeO2 composite fiber (B@C-x, x refers to the amount of reactant), was constructed by embeding CeO2 nanofibers on Bi4O5Br2 nanosheets via an electrospinning combined with hydrothermal method. Its composition, morphology and photoelectric properties were characterized. The results show that Bi4O5Br2/CeO2 heterojunction with appropriate Bi4O5Br2 content can significantly improve the photocatalytic performance of CeO2 nanofibers. Compared with pure Bi4O5Br2 and CeO2, B@C-2 exhibited the best photocatalytic activity under simulated sunlight. The Bi4O5Br2/CeO2 exhibited improved photocatalytic CO2 reduction performance with a CO generation rate of 8.26 μmol·h-1·g-1 without using any sacrificial agents or noble co-catalysts. This can be attributed to the tight interfacial bonding between Bi4O5Br2 and CeO2 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 directional synthesis of Bi-based photocatalytic composites with S-scheme heterojunction and illustrates an applicable tactic to develop potent photocatalysts for clean energy conversion.

Poly(methyl methacrylate) (PMMA) bone cement is widely used in orthopaedic surgery as an injectable artificial bone repair material due to its advantages such as desirable mechanical properties, suitable curing time and low toxicity. However, its bioinert polymer may lead to aseptic loosening of the prostheses after long-term implantation. Here, silanized mesoporous borosilicate bioglass microspheres (MBGSSI) composite with PMMA bone cement was prepared to obtain ideal bone repair material with desirable bioactivity and mechanical properties. Mesoporous borosilicate bioglass microspheres (MBGS) were prepared by template method and modified by silane coupling agent γ-methylacryloxy propyl trimethoxysilane (γ-MPS) to obtain MBGSSI. The results indicated that MBGSSI possessed increased specific surface area and decreased total pore volume than MBGS did by the binding between γ-MPS and MBGS occurred on the near surface of mesoporous microspheres. Compared with MBGS/PMMA, MBGSSI/PMMA composite bone cements demonstrated improved mechanical properties, which met the mechanical properties requirements of ISO 5833:2002 because γ-MPS improved the combination between inorganic and organic phases of composite. In addition, the hydroxyapatite (HA) could widely form on the surface of both MBGS/PMMA and MBGSSI/PMMA composite bone cements after immersing in SBF for 42 d, demonstrating the excellent bioactivity. Hence, it is suggested that MBGSSI/PMMA can be a potential bone repair material.

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.

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.