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941.
942.
Jinkai Wang Lei Zhu Fang Li Tianhao Yao Ting Liu Yonghong Cheng Zongyou Yin Hongkang Wang 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(33)
Sodium‐ion batteries (SIBs) have been recognized as the promising alternatives to lithium‐ion batteries for large‐scale applications owing to their abundant sodium resource. Currently, one significant challenge for SIBs is to explore feasible anodes with high specific capacity and reversible pulverization‐free Na+ insertion/extraction. Herein, a facile co‐engineering on polymorph phases and cavity structures is developed based on CoMo‐glycerate by scalable solvothermal sulfidation. The optimized strategy enables the construction of CoMoOxSy with synergized partially sulfidized amorphous phase and yolk–shell confined cavity. When developed as anodes for SIBs, such CoMoOxSy electrodes deliver a high reversible capacity of 479.4 mA h g?1 at 200 mA g?1 after 100 cycles and a high rate capacity of 435.2 mA h g?1 even at 2000 mA g?1, demonstrating superior capacity and rate capability. These are attributed to the unique dual merits of the anodes, that is, the elastic bountiful reaction pathways favored by the sulfidation‐induced amorphous phase and the sodiation/desodiation accommodatable space benefits from the yolk–shell cavity. Such yolk–shell nano‐battery materials are merited with co‐tunable phases and structures, facile scalable fabrication, and excellent capacity and rate capability in sodium storage. This provides an opportunity to develop advanced practical electrochemical sodium storage in the future. 相似文献
943.
Propulsive performance and vortex shedding of a foil in flapping flight 总被引:10,自引:0,他引:10
Summary. The propulsive performance and vortex shedding of an oscillating foil, which mimics biological locomotion, are investigated based on a computational fluid dynamics analysis. The objectives of this study are to investigate unsteady forces, in particular a thrust force, for the foil in pitching and plunging motion, and to deal with the relations of the propulsive performance with leading-edge vortex structure and vortex shedding in the near wake. The two-dimensional incompressible Navier–Stokes equations in the vorticity and stream-function formulation are solved by fourth-order essentially compact finite difference schemes for the space derivatives and a fourth-order Runge-Kutta scheme for the time advancement. To reveal the mechanism of the propulsive performance, the unsteady forces and the shedding of the leading- and trailing- edge vortices of the foil in the pitching and plunging motion are analyzed. Based on our calculated results, three types of the leading-edge vortex shedding, which have an effective influence on the vortex structures in the wake of the oscillating foil, are identified. The effects of some typical factors, such as the frequency and amplitude of the oscillation, the phase difference between the pitching and plunging motions, and the thickness ratio of the foil, on the vortex shedding and the unsteady forces are discussed. 相似文献
944.
Just-in-time (JIT) and reverse logistics are two important philosophies. Coincidentally, both are related to reducing the impact on the environment. However, they are sometimes in conflict with each other. The former focuses on moving the materials smoothly which require a stable demand and supply, but the latter is weak in terms of predicting how many returned products will be processed. Therefore, there is a need to investigate the impact of JIT to reverse logistics systems. After an extensive literature review based on a model developed for this purpose, different functions, namely reverse logistics structure, process model, product life cycle, information system model, and JIT performance, have been identified that have great impact on integrating JIT with reverse logistics. In short, a process model with JIT can have a better control on cost and efficiency of reverse logistics activities, and product life cycle management with JIT helps to design the product that consider the reverse activities in various process models. An information system can support both process model and product life cycle management for JIT reverse logistics. Details are presented in this paper. 相似文献
945.
Y. Xia P. Yang Y. Sun Y. Wu B. Mayers B. Gates Y. Yin F. Kim H. Yan 《Advanced materials (Deerfield Beach, Fla.)》2003,15(5):353-389
This article provides a comprehensive review of current research activities that concentrate on one‐dimensional (1D) nanostructures—wires, rods, belts, and tubes—whose lateral dimensions fall anywhere in the range of 1 to 100 nm. We devote the most attention to 1D nanostructures that have been synthesized in relatively copious quantities using chemical methods. We begin this article with an overview of synthetic strategies that have been exploited to achieve 1D growth. We then elaborate on these approaches in the following four sections: i) anisotropic growth dictated by the crystallographic structure of a solid material; ii) anisotropic growth confined and directed by various templates; iii) anisotropic growth kinetically controlled by supersaturation or through the use of an appropriate capping reagent; and iv) new concepts not yet fully demonstrated, but with long‐term potential in generating 1D nanostructures. Following is a discussion of techniques for generating various types of important heterostructured nanowires. By the end of this article, we highlight a range of unique properties (e.g., thermal, mechanical, electronic, optoelectronic, optical, nonlinear optical, and field emission) associated with different types of 1D nanostructures. We also briefly discuss a number of methods potentially useful for assembling 1D nanostructures into functional devices based on crossbar junctions, and complex architectures such as 2D and 3D periodic lattices. We conclude this review with personal perspectives on the directions towards which future research on this new class of nanostructured materials might be directed. 相似文献
946.
Jian-zhong Wang Xuan-hui Qu Hai-qing Yin Ming-jun Yi Xian-jie Yuan 《Frontiers of Materials Science in China》2008,2(4):392-396
Iron powders with two different particle size distributions were compacted by high velocity compaction. The influences of
particle size distribution and impact velocity on green properties, including green density, springback, tensile strength
and bending strength etc., were studied with scanning electron microscopy (SEM) and a computer controlled universal testing
machine. The results show that the particle size distribution and the impact velocity strongly affect its properties. Wider
size distribution results in green compact with higher density and better strength. Furthermore, springback of compacts is
lower produced by the powder with wider size distribution, especially for radial springback. As impact velocity increases,
its green density and green strength gradually increases, but the increasing rate of density decreases gradually. No special
relation is found between springback and impact velocity. In addition, the axial springback and the bending strength are higher
than the radial springback and the tensile strength, respectively. 相似文献
947.
利用机械合金化法制备了La2Mg17+200%(质量分数)Ni复合储氢合金,并对不同球磨时间时合金的微观结构和电化学性能进行研究。结果发现,在球磨过程中Ni粉诱导了La-Mg-Ni非晶/纳米晶结构的形成。XRD和HRTEM结果共同表征了球磨80h时,合金中有Ni金属的存在,且XRD衍射峰强度较低,宽化严重,SAD为宽化的多环,表明形成非晶结构。电化学及其反应动力学测试结果发现,不同球磨时间的电化学反应的动力学控制机理是不同的。球磨60和80h后合金中不仅存在La-Mg-Ni非晶相,同时也有催化剂金属Ni,使合金的表面电荷转移反应电阻较小,氢在合金体相内的扩散系数D和极限电流密度I L均最大,最终导致80h的放电容量为最大值948.3mAh/g。然而,当合金的球磨时间为100和120h时,合金粉化到纳米级,100h的电荷转移反应电阻R ct最大,合金表面电化学反应缓慢,且合金体相内的极限电流密度和氢扩散系数均最小,属于合金电解液表面间的电荷转移和氢向体相内扩散联合控制的过程,必然导致其放电比容量较小。 相似文献
948.
949.
Artificial Protection Film on Lithium Metal Anode toward Long‐Cycle‐Life Lithium‐Oxygen Batteries
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950.
Co3O4 Hexagonal Platelets with Controllable Facets Enabling Highly Efficient Visible‐Light Photocatalytic Reduction of CO2
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