Evolution of Local Structural Ordering and Chemical Distribution upon Delithiation of a Rock Salt–Structured Li1.3Ta0.3Mn0.4O2 Cathode

Lithium‐rich disordered rock‐salt oxides have attracted great interest owing to their promising performance as Li‐ion battery cathodes. While experimental and theoretical efforts are critical in advancing this class of materials, a fundamental understanding of key property changes upon Li extraction is largely missing. In the present study, single‐crystal synthesis of a new disordered rock‐salt cathode material, Li_1.3Ta_0.3Mn_0.4O₂ (LTMO), and its use as a model compound to investigate Li concentration–driven evolution of local cationic ordering, charge compensation, and chemical distribution are reported. Through the combined use of 2D and 3D X‐ray nanotomography, it is shown that Li removal accompanied by oxygen oxidation is correlated with the development of morphological defects such as particle cracking. Chemical heterogeneity, quantified by subparticle level distribution of Mn valence state, is minimal during Mn redox, which drastically increases upon the formation of cracks during oxygen redox. Density functional theory and bond valence sum mismatch calculations reveal the presence of local short‐range ordering in the pristine oxide, which gradually disappears along with the extraction of Li. The study suggests that with cycling the transformation into true cation–disordered state can be expected, which likely impacts the voltage profile and obtainable energy density of the oxide cathodes.     

Combining molybdenum carbide with ceria overlayers to boost Mo/CeO2 catalyzed ammonia synthesis

The design of an efficient non-noble metal catalyst is of burgeoning interest for ammonia synthesis. Herein, we report a Mo₂C/CeO₂ catalyst that is superior in ammonia synthesis activity. In this catalyst, molybdenum carbide coexisted with the ceria overlayers which is from the ceria support as the strong metal–support interaction. There is a high proportion of low-valent Mo species, as well as high concentration of Ce³⁺ and surface oxygen species. The presence of Mo₂C and CeO₂ overlayers not only leads to enhancement of hydrogen and nitrogen adsorption, but also facilitates the desorption and exchange of adsorbed species with the gaseous reagents. Compared with the Mo/CeO₂ catalyst prepared without carbonization, the Mo₂C/CeO₂ catalyst is more than sevenfold higher in ammonia synthesis rate. This work not only presents an explicit example of designing Mo-based catalyst that is highly efficient for ammonia synthesis by tuning the adsorption and desorption properties of the reactant gases, but opens a perspective for other elements in ammonia synthesis.     

Oxide-Scale Evolution on a New Ni–Fe-Based Superalloy at High Temperature

Oxidation of Metals - The isothermal oxidation behavior and oxide-scale evolution on a newly developed Ni–Fe-based superalloy were investigated. Three oxidation stages were generally...     

Study on Wettability and Corrosion Behavior of Al2O3 Doped Polyurea Coatings

Protection of Metals and Physical Chemistry of Surfaces - The Al2O3 powder was added as a filler to polyurea and the effect of doping amount on Shore hardness and wetting property were...     

Fabrication of dense nano-laminated tungsten carbide materials doped with Cr3C2/VC through two-step sintering

This work investigates the critical roles of two-step sintering (TSS) and laminated structure on the sintering behavior and mechanical properties of functionally graded WC-TiC-Al₂O₃ nanostructured composite materials doped with Cr₃C₂/VC. Results show that excellent mechanical properties are achieved for tailored TSS conditions with a hardness of 27.91?±?2.3?GPa and a flexural strength of 1423.3?±?23.5?MPa. The desirable mechanical properties are attributed to the suppressed grain growth without densification deterioration. TSS is more effective in facilitating the favorable dispersion of secondary phase toughening nano-particulates in a WC matrix than conventional sintering (CS). Cr₃C₂/VC dopant plays an important role in maximizing and shifting the temperature range of the kinetic window for WC-Al₂O₃ composites. Al₂O₃ crack deflection, transgranular Al₂O₃, microcracking, WC crack bridging and plate-like WC crack deflection are the major toughening mechanisms. Residual surface compressive stress induced by the graded structure is also an appreciated contribution to the improvement of mechanical properties.     

畜禽骨蛋白质材料化利用的研究现状与发展趋势分析

作为畜禽屠宰的副产物,动物骨因其丰富的蛋白质和广阔的深加工利用的发展前景而成为当今环境、农业和能源等领域的研究热点.受自身骨骼结构和综合利用技术的制约,骨骼的深加工利用率不足2％,造成了严重的资源浪费与环境污染.蛋白水解作为蛋白质资源深加工领域最有效的技术手段,可实现大宗蛋白质资源的高效回收利用;而蛋白水解物优异的溶解性、可降解性、生物相容性和独特的生物功能活性使其具有开发高值材料的潜力.随着石化资源的短缺和人们健康环保意识的增强,人们对环保型可再生型新材料的需求逐渐迫切,而畜禽骨蛋白质材料的开发利用紧密结合国家新型战略产业——生物制造业,将促进农副产品加工业的持续健康发展.针对畜禽骨蛋白质材料化开发利用的发展历程及当前的研究热点,本文阐述了絮凝剂、粘结剂、可降解塑料、表面活性剂、医用材料等近年来研究较广的畜禽骨蛋白质材料化利用途径,并总结了各种利用途径的应用效果和局限性;同时,总结分析了现今利用蛋白水解物开发新型材料的相关理论及研究成果,为开发畜禽骨蛋白质材料提供了理论支持;最后,基于目前生物基材料的发展趋势及畜禽骨深加工技术的难点问题,客观展望了畜禽骨蛋白质材料的制备及应用发展方向.     

Transparent niobate glass-ceramics for optical limiting

The construction of nonlinear optical materials featuring asymmetric transmission of light is of great technological importance for various applications, including optical switching and optical power limiting. A significant challenge is the scalable fabrication of material candidates with good photochemical stability, high optical transmittance, and excellent optical limiting performance. Here, we present a nanocrystallization avenue for constructing hybrid optical limiting materials that exhibit ultrafast and robust optical limiting performance. The experimental results show that the controllable relaxation of a niobate glass may lead to the clustering of Nb-O units and contracting of the bandgap. It results in the notable improvement in nonlinear optical properties, including the enhanced saturation irradiance (380 GW/cm²), doubly increased nonlinear coefficient, and decreased limiting threshold (200 GW/cm²). Our results suggest a promising material that exhibits promising applications for protecting eyes and sensitive components from laser-induced damage.     

Effect of an abrupt change in pulling rate on microstructures of directionally solidified Al2O3-Er3Al5O12 eutectic and off-eutectic composite ceramics

Directionally solidified microstructures of Al₂O₃-Er₃Al₅O₁₂ eutectic and off-eutectic in situ composite ceramics were explored under abrupt-change pulling rate conditions. Corresponding temperature distributions and interface locations were studied. In eutectic composition, fluctuation of eutectic spacing occurred when the pulling rate increased abruptly. A gradually increase or abrupt increase in eutectic spacing was observed when the pulling rate decreased abruptly. In hypoeutectic and hypereutectic compositions, formation of the primary phases were suppressed when the pulling rate increased abruptly from 10?µm/s to 100?µm/s, while primary phases precipitated when the pulling rate decreased abruptly from 100?µm/s to 10?µm/s. The interface altitude decreased after the pulling rate increased abruptly, but increased after the pulling rate decreased abruptly. The liquid composition restriction (around the eutectic composition) at the eutectic interface plays an important role in the suppression of the primary dendrite and coupled eutectic oxides can be obtained in off-eutectic compositions even under higher solidification rate conditions.