复合电镀制备透射电镜试样

Preparing Thin Foil for TEM by Composite Electroplating

用透射电镜 (TEM)观察粉末产品 ,当粉末样品颗粒直径 (即厚度 )大于 0 .5 μm时 ,由于电子束不能穿透 ,是不能进行电子显微结构分析的 ,把复合电镀技术引入到粉末颗粒电镜试样制备的方法中 ,在减薄镀层的同时实现了粉末颗粒的减薄。以平均粒径 8μm的氧化钴锂LiCoO2 (二次锂离子电池正极材料 )为例 ,将其散布到CuSO4电镀液中进行复合电镀。将悬浮在电镀液中的颗粒连同镀金层金属离子共同沉积在电极上 ,通过选择合理的电镀工艺参数 ,形成厚度适宜、颗粒分布密度高、包埋紧实且易于剥离的复合镀层 ,然后将其电解双喷和离子减薄形成颗粒薄区 ,使电子束可以穿透。对用此方法制备的试样所做的透射电镜电子像和电子衍射谱分析表明 ,通过复合电镀包埋颗粒再减薄颗粒的方法对于电镜粉末大颗粒样品制备有实用价值。还探讨了复合电沉积时粉末颗粒的运动特点。

Microstructure analysis using TEM will not be carried out while the diameter or thickness of powder sample is larger than 0.5 μm for electron beam can not penetrate through. Introducing of composite electroplating into sample making of inorganic nonmetal particle for TEM observe, it can reduce the powder particle while made the plating thin. For example, composite electroplating of LiCoO_2 (cathodic material of rechargeable lithium battery) with diameter 8 μm was processed in CuSO_4 bath. The particles suspended in electrolyte were deposited on cathode together with Cu^(2+) ion, forming composite coating with moderate thickness. The particles buried in Cu coating had enough distributing density, and the composite coating was easily peeled off from the cathode. Then the coating was twinjet electrolysis polished and ion thinned to form thin particle, which could be penetrated by electron beam. TEM and SAED analysis of LiCoO_2 show that the method has practical value for TEM sample preparing of large powder particle. Kinetics processing of composite electrodeposition is also presented.