谢卫东
,
党春梅
,
李兆楠
,
彭晓东
,
汪浩
稀有金属
doi:10.3969/j.issn.0258-7076.2012.02.008
结合Si-Fe相图,分析了硅铁热还原制镁(皮江法)反应过程中Si-Fe中形态,结果显示:初始含Si量75％的Si-Fe在1200℃基本处于固态,硅铁热还原制镁还原反应主要为固-固反应,反应过程中,物料间的热量及质量传输较困难,反应难于快速、彻底进行.介绍了采用Si-Cu合金还原剂实现固-液还原的Si-Cu热还原制镁新思路、新方法,结合Si-Cu相图,分析了Si-Cu热还原制镁中Si-Cu的形态,结果显示:Si-Cu热还原制镁时,初始含Si量低于35％的Si-Cu在1200℃几乎全过程保持液态,还原反应基本为固-液反应,反应较易快速、彻底进行.采用热力学分析方法,推演出了Si-Cu热还原制镁的主要反应式、吉布斯自由能估算式,临界反应温度估算式,分析了影响吉布斯自由能、临界反应温度及还原反应热力学可行性的因素,结果显示:Si-Cu热还原制镁反应的热力学临界温度随系统气压降低及Si-Cu中Si含量增加而减小；对应于常规真空硅热还原制镁(皮江法)温度( 1473 K)和系统气压(13.3 Pa),Si-Cu合金中的Si含量只需高于0.034％,Si-Cu热还原制镁即具备热力学可行性.
关键词:
镁冶炼
,
热力学
,
热还原
,
真空
,
Si-Cu合金
王璞
,
努丽燕娜
,
杨军
稀有金属
doi:10.3969/j.issn.0258-7076.2007.01.014
采用高能球磨方法制备了用作锂离子电池负极材料的Si-Cu/C复合材料.X射线衍射和扫描电子显微镜结果表明,复合材料中Si和Cu5Si是共存的,活性硅颗粒均匀地分散在石墨和惰性的铜硅合金基体中.电化学测试在电流密度0.2mA·cm-2,电压范围0～1.4 V条件下进行,其结果表明高分散Si-Cu/C复合材料首次可逆容量为524 mAh·g-1,远高于目前普遍使用的中间相碳微球;循环寿命也远优于同粒度的硅单体,经过30次循环后容量仍保持531 mAh·g-1.其高比容量和良好的循环性能表明:高分散Si-Cu/C复合材料有望替代碳成为锂离子电池负极材料.
关键词:
锂离子电池
,
负极
,
球磨
,
硅-铜/碳复合材料
Journal of Materials Research
A Pd-Si-Cu bulk nanocrystalline material was prepared by quenching the melted Pd78Si16Cu6 alloy at a cooling rate of 200 K/s under 2-6 GPa. It was found that the nanocrystalline material. consists of Pd(Cu) disordered solid solution and a metastable phase-II, Pd4Si. The grain size was found to decrease with increasing pressure. The influence of high pressure on the grain size of bull; nanocrystalline material is discussed, and a possible formation mechanism is proposed.
关键词:
Journal of Applied Physics
Structural characteristics of Fe73.5Cu1Nb3Si13.5B9 soft magnetic alloys that were rapidly solidified and then annealed at various temperatures between 400 and 600-degrees-C have been studied. Variations of the Si content in the nanocrystalline alpha-Fe(Si) phase for the alloys with the annealing temperatures are determined. A maximum volume fraction, less than 70%, of the alpha-Fe(Si) phase is given by the Si-content results. The relationship between the structural characteristics and the magnetic properties for the alloys is discussed.
关键词:
ultrafine grain-structure
Journal of Physical Chemistry C
The low-temperature hydrothermal synthesis method has been drawing ever-growing attention due to the fact that it has many advantages over conventional methods for preparing promising cathode material LiFePO(4). However; the mechanism for hydrothermal synthesis of LiFePO(4) remains unclear. Here, the hydrothermal reaction mechanism of LiFePO(4) is systematically studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), trail mission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and specific surface analysis. As evidenced by apparent precursor dissolution, fast hydrothermal formation, and significant decrease in particle size with adding alcohols and/or carbon black in the reaction system, a dissolution-precipitation mechanism accounts for the hydrothermal synthesis of LiFePO(4). Moreover, we identified tetraphosphate in the LiFePO(4) precursor. This compound undergoes hydrolysis upon heating during the hydrothermal process, resulting in a remarkable decline of pH value.
关键词:
dissolution-precipitation mechanism;barium-titanate powders;electrochemical properties;phase-transition;reduction method;olivine;lifepo4;iron phosphate;route;fepo4;morphologies
Applied Surface Science
Cu film and Ti/Cu film on polyimide substrate were prepared by ion implantation and ion beam assisted deposition (IBAD) techniques. Three-dimension white-light interfering profilometer was used to measure thickness of each film. The thickness of the Cu film and Ti/Cu film ranged between 490 nm and 640 nm. The depth profile, surface morphology, roughness, adhesion, nanohardness, and modulus of the Cu and Ti/Cu films were measured by scanning Auger nanoprobe (SAN), atomic force microscopy (AFM), and nanoindenter, respectively. The polyimide substrates irradiated with argon ions were analyzed by scanning electron microscopy (SEM) and AFM. The results suggested that both the Cu film and Ti/Cu film were of good adhesion with polyimide substrate, and ion beam techniques were suitable to prepare thin metal film on polyimide. (C) 2010 Elsevier B.V. All rights reserved.
关键词:
Metal film;Polyimide;Ion implantation;Ion beam assisted deposition;Adhesion;assisted deposition;adhesion properties;copper-films;thin-film;implantation;limitations;substrate;polymers
Journal of Power Sources
Screen-printing technology was developed to fabricate Ce0.8Sm0.2O1.9 (SDC) electrolyte films onto porous NiO-SDC green anode substrates. After sintering at 1400 degrees C for 4 h, a gas-tight SDC film with a thickness of 12 mu m was obtained. A novel cathode material of Ba0.5Sr0.5Co0.8Fe0.2O3-delta Was subsequently applied onto the sintered SDC electrolyte film also by screen-printing and sintered at 970 degrees C for 3 h to get a single cell. A fuel cell of Ni-SDC/SDC (12 mu m)/Ba0.5Sr0.5Co0.8Fe0.2O3-delta provides the maximum power densities of 1280, 1080, 670, 370, 180 and 73 mW cm(-2) at 650, 600, 555, 505, 455 and 405 degrees C, respectively, using hydrogen as fuel and stationary air as oxidant. When dry methane was used as fuel, the maximum power densities are 876, 568, 346 and 114 mW cm(-2) at 650, 600, 555 and 505 degrees C, respectively. ne present fuel cell shows excellent performance at lowered temperatures. (c) 2006 Elsevier B.V. All rights reserved.
关键词:
solid oxide fuel cells;screen-printing;electrolyte films;Ce0.8Sm0.2O1.9;Ba0.5Sr0.5Co0.8Fe0.2O3-delta;thin-film;temperature sofcs;electrolyte;performance
Applied Physics Letters
We use only nitrogen as the reaction gas to deposit on the cleaned Si wafer an extra-thin Si nitride film (similar to 40 Angstrom) by electron cyclotron resonance method. Electroluminescence (EL) with its peak wavelength at about 7000 Angstrom from the semitransparent Au/extra-thin Si nitride film/p-Si structure has been detected. The effects of forward bias and annealing on the EL have been studied. (C) 1996 American Institute of Physics.
关键词:
Applied Physics Letters
In this letter, film growth for amorphous Nb/Si multilayers has been studied by using x-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM). Results from XRD and XTEM show that the structures of amorphous Nb/Si multilayers deposited at room temperature and 550 degrees C are quite different. The influences of surface mobility of adstoms and interfacial reaction on interfacial roughness are discussed. (C) 1996 American Institute of Physics.
关键词:
x-ray-diffraction;interfacial roughness;superlattices;deposition;diffusion
Electrochimica Acta
A carbon coated Li3V2(PO4)(3) cathode material for lithium ion batteries was synthesized by a sol-gel method using V2O5, H2O2, NH4H2PO4, LiOH and citric acid as starting materials, and its physicochemical properties were investigated using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) spectroscopy, scanning electron microscopy (SEM), energy dispersive analysis of X-ray (EDAX), transmission electron microscope (TEM), and electrochemical methods. The sample prepared displays a monoclinic structure with a space group of P2(1)/n, and its surface is covered with a rough and porous carbon layer. In the voltage range of 3.0-4.3 V, the Li3V2(PO4)(3) electrode displays a large reversible capacity, good rate capability and excellent cyclic stability at both 25 and 55 degrees C. The largest reversible capacity of 130 mAh g(-1) was obtained at 0.1C and 55 degrees C, nearly equivalent to the reversible cycling of two lithium ions per Li3V2(PO4)(3) formula unit (133 mAh g(-1)). It was found that the increase in total carbon content can improve the discharge performance of the Li3V2-(PO4)(3) electrode. In the voltage range of 3.0-4.8 V, the extraction and reinsertion of the third lithium ion in the carbon coated Li3V2(PO4)(3) host are almost reversible, exhibiting a reversible capacity of 177 mAh g(-1) and good cyclic performance. The reasons for the excellent electrochemical performance of the carbon coated Li3V2(PO4)(3) cathode material were also discussed. (c) 2007 Elsevier Ltd. All rights reserved.
关键词:
Li3V2(PO4)(3);sol-gel method;carbon surface layer;electrochemical;performance;lithium-ion batteries;carbothermal reduction method;state synthesis;routine;vanadium fluorophosphate;electrode materials;phosphates;lifepo4;li3fe2(po4)(3);composites;insertion
