扩散处理对Ag-Cu复合电触头界面区域组织、成分及导电性的影响

通过等离子喷涂工艺制备Ag-Cu复合电触头试样,研究扩散退火对触头界面区域微观组织、成分分布以及导电性的影响.结果表明:400℃扩散处理使Ag-Cu复合电触头涂层在高温下产生烧结现象,涂层裂纹、孔隙减少,导电率上升;600℃扩散处理在界面区域有Cu的第二相析出,使电子散射几率下降,导电率显著上升,但随着退火时间延长,涂层内部因体积收缩,涂层裂纹、空隙增加,导电率呈现下降趋势.

Electrical characteristics and detailed interfacial structures of Ag/Ni metallization on polycrystalline thermoelectric SnSe

SnSe is a promising thermoelectric material with a high figure of merit in single crystal form, which has stimulated continuous research on polycrystalline SnSe. In this study, we investigated a metallization techniques for polycrystalline SnSe to achieve highly efficient and practical SnSe thermoelectric modules. The Ag/Ni metallization layers were formed on pristine polycrystalline SnSe using various deposition technique: sputter coating Ni, powder Niand foil Ni by spark plasma sintering. Structural analysis demonstrated that the microstructure and con tact resistance could be different according to the metallization process, despite using the same metals. The Ag/Ni metallization layer using foil Ni acted as an effective diffusion barrier and minimized electrical contact resistance (2.3×10^-4Ωcm^2). A power loss in the thermoelectric module of only 5% was demonstrated using finite element simulation.

Interface structure of Ag(111)/SnO_(2)(200)composite material studied by density functional theory

Electric contact material of Ag/SnO2 was successfully synthesized by in situ process method.The in-terface structure was characterized by high-resolution transmission electron microscopy(HTEM) and simulated at atomic scale on computer.The mean-square displacements of atoms near the interface were calculated,and the results showed that near the interface both Ag side and SnO2 were mis-matched and this effect decays rapidly far from the interface.By inspecting the calculated density of states(DOS),we found that the electric-conductivity of this composite material was decreased because of the localized 4d and 2p electrons of Ag and O near the Fermi surface,respectively.Electron density changed acutely across the interface,so that there was no extra compound precipitated.A mi-cro-electric field also formed in the whole material due to the interface structure,and this may affect the electron conduction and the related electric-conductivity of the composite.It is found that the interface cohesive energy of Ag(111)/SnO2(200) was-3.50 J/m2,which is higher than the experimental results.

Interface Structure of Ag/SnO_2 Nanocomposite Fabricated by Reactive Synthesis

The electric contact material of Ag/SnO2 composite was achieved by reactive synthesis method. The compositions and microstructure of Ag/SnO2 composite were analyzed and characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and high-resolution electron microscopy （HRTEM）. The struc- tural feature was typical of the particle reinforced composites. The HRTEM images revealed that the observed Ag/SnO2 interface was absence of the precipitated phase and the lattice contrast across the interface was clear and sharp. The average particle size of SnO2 in composite was near 50 nm and it was well dispersed in spherical shape. The thermodynamic mechanism of reactive synthesis method was also discussed. The electronic density distribution analysis of the interface showed the charges of Ag atoms transmitted to 0 atoms and the conductivity of the material was also affected. No extra compounds expected such as AgxOy formed at interface. The distribution of electrons was of inequality near the interface which explained why the mechanical property of the metal/ceramic materials was improved but the machining property declined.

(CuO,Fe2O3)掺杂Ag/SnO2电接触材料的物理性能

以CuO、Fe2O3为掺杂剂,采用机械合金化方法结合冷压-烧结-热压工艺制备(CuO,Fe2O3)掺杂Ag/SnO2电接触材料。利用X射线衍射(XRD)仪、扫描电镜(SEM)、透射电镜(TEM)、金属电阻率仪、热导率仪和霍尔效应测量仪等分析了不同掺杂比例Ag/SnO2电接触材料的微观结构和物理性能。结果表明:热压可显著改善电接触材料中SnO2颗粒与Ag基体的界面结合;CuO和Fe2O3单一掺杂可分别提高Ag/SnO2电接触材料的导电性能和导热性能,而复合掺杂的Ag-11.5SnO2-0.3CuO-0.2Fe2O3电接触材料的导电导热性能最佳,其电阻率为2.25μΩ·cm,硬度(HV0.5)为748MPa,在室温下的热扩散系数和热导率分别为111.4 mm2/s和338.6 W/(m·K)。复合掺杂的SnO2增强相对Ag基体的平均润湿角为62.7°,界面润湿效果好;SnO2与Ag晶粒之间界面结合良好,SnO2(200)晶面与Ag(111)晶面的界面晶格错配度为14.25%。

Y_2O_3/Ag复合材料界面微观结构与性能研究

采用透射电子显微镜对粉末冶金法制备的Y_2O_3/Ag复合材料的界面微观结构进行了深入研究。结果表明:复合材料界面结合紧密且无任何反应物。Ag基体的(111)面与Y_2O_3颗粒的(440)晶面保持半共格关系:Y_2O_3(222)//Ag(111),Y_2O_3(440)//Ag(111),界面处基体中可以看到由于晶格错配而产生的刃位错,说明基体与增强颗粒晶面间距接近时,基体可以依靠增强颗粒表面结晶并长大,即增强颗粒作为基体异质形核的质点,并从晶体学角度对界面的形成原因进行了解释。由力学和电学性能测试得到复合材料的强度和电阻率随Y_2O_3含量的增加而升高。