关键词： Silicon-carbon composites   Yolk-shell structure   Soft carbon   Microstructure design   Lithium-ion battery  

摘要： Silicon-carbon composites have proved to be effective in addressing the issues of silicon anodes, however, few works focus on understanding the effect of the microstructure of the carbon component on their electrochemical performance. Herein, we prepare a series of yolk-shell structured silicon-carbon nanocomposites with adequate voids through a facile and scalable process. By deliberately selecting the pitch species and delicately adjusting the heat treatment temperature, the microcrystal texture and pore structure of the soft carbon can be easily tuned. Finally, a well matching of the crystalline and pore structure ensure the rapid charge transport and the good structural robustness, further endowing the optimal lithium storage, cycle performance and rate capability of the electrodes. The Si/C composite with an optimized carbon shell delivers a reliable cycle stability with a capacity retention ratio of 55% after 300 cycles at 0.2 A g(-1) and a remained capacity of 743 mAh g(-1) at a high current density of 2.0 A g(-1). Importantly, the correlation between the lithium storage of the Si/C composites and the microstructure features (crystallinity and pores) of the carbon shell has been established, which may provide an effective guidance for optimizing the microstructure design of the promising Si/C anode materials. (C) 2021 Elsevier Ltd. All rights reserved.

关键词： 薄膜   铁酸铋   离子掺杂   微结构   铁电性  

摘要： 采用化学溶液法结合层层旋涂退火工艺,在掺氟氧化锡导电玻璃基片上制备了BiFe_(0.9)5Mn_(0.05)O_(3)和Bi_(0.9)Nd_(0.1)FeO_(3)纳米晶铁电薄膜,并分析比较了其微结构和铁电性能。结果表明:2组分样品均为单相多晶钙钛矿结构,晶粒细小均匀,表面平整,结构致密。两薄膜均获得了饱和电滞回线,且BiFe_(0.9)5Mn_(0.05)O_(3)薄膜具有向上的择优取向极化和更优异的铁电性能,其剩余极化强度(Pr)达60mC·cm^(–2),在1~50 k Hz频率范围与25~200℃温度区间内铁电极化响应稳定,保持时间长达1′10^(3) s工作与反复极化翻转高达1′10^(9)次表现出优异的电荷保持力和抗疲劳稳定性。

关键词： 六铝酸钙   多孔材料   氧化铝源   物相组成   固相反应  

摘要： 用Al(OH)3、Al_(2)O_(3)微粉(uf-Al_(2)O_(3))、工业Al_(2)O_(3)粉作为氧化铝源,CaCO_(3)为钙源,通过高温固相反应合成了六铝酸钙(CA_(6))材料,研究了氧化铝原料对材料物相组成、显微结构和性能的影响。结果表明,以Al(OH)3、Al_(2)O_(3)微粉、工业Al_(2)O_(3)为氧化铝源的试样在1300℃时开始有CA_(6)相生成,各试样固相反应结束温度为1500℃,继续提高烧成温度对物相组成没有影响。反应生成的CA_(6)显微形貌因氧化铝原料不同而不同,以Al(OH)3为氧化铝源时,CA_(6)的显微形貌多为片状结构;以工业Al_(2)O_(3)为原料时,CA_(6)的显微形貌多为板片状和颗粒状;但以uf-Al_(2)O_(3)为氧化铝源时,CA_(6)的显微形貌则多为等轴状晶粒。以uf-Al_(2)O_(3)为氧化铝源时,制备的材料耐压强度和体积密度最高,气孔率最低;以Al(OH)3为氧化铝源时,制备的材料耐压强度和体积密度最低,气孔率最高。

关键词： Misch-metal   Microstructural design   Sintered magnet   Rare earths  

摘要： LaCe-based sintered magnets with different microstructural features and distinct rare earth elemental distribution were designed by dual-alloy *** sample prepared by fine LaCe-containing powder and coarse LaCe-free powder possesses higher remanence(~13.41 kGs),whereas another sample prepared by fine LaCe-free powder and coarse LaCe-containing powder possesses higher coercivity(~5.67 kOe).Additionally,these samples are with the same nominal compositions and their elemental distribution features are obviously different in matrix grains *** remanence difference is mainly affected by the saturation magnetization difference caused by the distribution variation of the rare earth elements at the matrix *** coercivity difference is affected by the component of the grain boundary phase between the adjacent grains and the distribution variation of the rare earth elements at the matrix *** findings may provide a new prospect for the utilization of LaCe mischmetal in 2:14:1-type permanent magnets.

关键词： 搅拌摩擦加工   电子背散射衍射(EBSD)   微结构   织构  

摘要： 采用搅拌摩擦加工(FSP)方法制备Al-Pb表面复合材料,以提高其减摩抗磨性能,使用SEM、EBSD、纳米压痕仪和显微硬度计等分析其微观组织、织构和硬度分布。结果表明:使用FSP方法制备Al-Pb表面复合材料,Pb颗粒受到重力和搅拌作用,主要分布于盆状搅拌加工区的底部。塑性金属对流形成的洋葱环结构中,存在富Pb片层和形变铝基体片层。富Pb片层内的Pb颗粒,起到了良好的细化晶粒作用。形变铝基体片层分布有少量直径约100 nm的新生Pb粒。受到细晶强化作用影响,富Pb颗粒区的硬度显著高于形变铝基体。加工区底部的SZ-AS区形成强Cube再结晶织构;SZ-RS区形成Cube织构和少量Brass织构;CSZ区的Cube织构较少,{111}织构增强;上部的AS区形成强Goss织构,RS区织构相对随机。

关键词： Severe plastic deformation   Vortex extrusion   Streamline approach   Microstructure   Mechanical properties  

摘要： Vortex extrusion (VE), as a severe plastic deformation technique, uses a novel designed stationary die that imposes intense strain to the processed material. Materials in the VE process experience torsional deformation and simultaneous reduction in area. The amount and intensity of this additional deformation vary according to the radius moving from the center to the surface of the VE die due to variations in the path of the material through a radius proposed by the Beziers' formulation. In the present study, the VE die is designed through a streamline approach based on a cubic Beziers' formulation that was employed to investigate the microstructural and mechanical properties of the processed samples and to link the results to those obtained through a finite element analysis of this technique. The results of the microstructural characterization exhibit a higher fraction of high-angle grain boundaries of the VE processed samples compared to what can be achieved by conventional extrusion-processed. Consequently, a significant improvement was observed in tensile properties of the samples after SPD processing using the proposed streamlined VE die.

关键词： Absorbable metals   Zinc   Mechanical properties   Degradation behaviour   Cytotoxicity   Antibacterial property  

摘要： Zinc (Zn) alloys seem to be promising candidates for application in orthopaedic or cardiovascular medical implants. In this area, high standards are required regarding the biocompatibility as well as excellent mechanical and tailored degradation properties. In the presented study, a novel Zn-0.8Mg-0.2Sr (wt%) alloy has been fabricated by the combination of casting, homogenization annealing and extrusion at 200 degrees C. As a consequence of its fine-grained homogenous microstructure, the prepared material is characterized by an excellent combination of tensile yield strength, ultimate tensile strength and elongation corresponding to 244 MPa, 324 MPa and 20% respectively. The in vitro corrosion rates of the Zn-0.8Mg-0.2Sr alloy in the physiological solution and the simulated body fluid were 244 mu m/a and 69.8 mu m/a, respectively. Furthermore, an extract test revealed that Zn0.8Mg-0.2Sr extracts diluted to 25% had no adverse effects towards L929 fibroblasts, TAg periosteal cells and Saos-2 osteoblasts. Moreover, the Zn-0.8Mg-0.2Sr surface showed effective inhibition of initial Streptococcus gordonii adhesion and biofilm formation. These results indicated the Zn-0.8Mg-0.2Sr alloy, which has superior mechanical properties, might be a promising candidate for materials used for load-bearing applications.

关键词： Solid wastes management   Underground filling engineering   Abandoned salt caverns   Mechanical properties   Microstructure  

摘要： Alkali solid waste from soda industries has previously been stacked on surface and contaminated soil and groundwater. In China, an engineering method of filling alkali wastes into abandoned salt caverns is adopted. This method can solve the problem of waste disposal and the potential geological disasters associated with salt caverns. In such filling projects, the engineering properties of alkali wastes are important for the safety and stability of salt caverns. In this study, the microstructural and mechanical properties of alkali wastes were investigated. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to analyze the microstructure and mineralogy of such wastes. Direct shear tests were conducted to evaluate the mechanical performance and to obtain the strength parameters of alkali wastes. The basic physical characteristics, microstructure, mineral compositions, and mechanical properties of alkali wastes vary significantly at different burial depths. Moreover, the strength properties of alkali wastes are close to those of the two other common filling materials, sandstone-mudstone mixtures and tailings. The research results can be used as a reference for similar filling projects and can also be beneficial for the cyclic utilization of alkali wastes.

关键词： 汽车  

ISBN: (纸本)9787111672319

摘要： 本书着重介绍微结构材料在结构设计及轻量化应用方面的关键技术。全书共十一章，包括：天然微结构材料——动物启发、天然微结构材料——植物启发、微结构材料特性、人工微结构材料、微结构材料制备方法等。

关键词： 4D printing   Laminates   Polymers   Microstructure   Shape memory property  

摘要： Four-dimensional (4D) printed laminated structures, created by combining three-dimensional (3D) printing technology with shape memory polymer, have tremendous potential for applying in functional devices and sequentially controlled actuators. This work is aimed to study the tunable shape recovery behavior and recovery force of 4D printed laminated strips based on the microstructural design of raster angle and infill percentage. The effects of raster angle and infill percentage on the shape recovery properties of the printed specimens were investigated. The recovery force of the printed specimens was measured using dynamic mechanical analysis (DMA). The microstructural parameters had a significant influence on the shape recovery behavior and recovery force. Finally, the sequential shape-morphing behavior of 4D printed laminated strips using a single material was demonstrated. (c) 2020 Elsevier B.V. All rights reserved.