Green Synthesis of Highly Pure Nano-Silver Sols—Electrolysis

以两高纯银片作电极,以去离子水为电解液,PVP作为辅助电解质和稳定剂,通过电解法制备了高纯纳米银溶胶.探讨了PVP含量、电解时间、电流密度对形成的纳米银溶胶的影响.结果表明:当PVP质量分数为5％、电解150 min、电流密度为1～2 mA/cm2时,所得球形银粒子的粒径1～3 nm、单分散,浓度达130 μg/g,而且有极好的存放稳定性,室温避光存放6个月无任何可见的变化.

Formation Process of Joints Brazing with Amorphous Filler Metal

The formation, wetting and spreading process of the liquid amorphous filler metal were investigated. The results indicate that the eutectic phase of the amorphous filler metal is damaged and plenty of high melting-point copper solid solution and copper-nickel compound are generated due to the full solid-phase diffusion before melting. Therefore, relatively less liquid phase is produced by amorphous filler metal than crystalline filler metal and the liquid phase spreading and flow is weak. However, the crystalline filler metal generates a large amount of liquid phase. Spreading and flowing of the liquid phase is the main process of crystalline filler metal brazing. As the amorphous filler metal is very thin, the atomic diffusion distance is very short in the filler metal, which is quite favorable for the rapid dissolution into the base metals. The ordinary filler metal is relatively thick, and it tends to take longer time to dissolve than the amorphous filler metal. The thickness of the residual filler metal decreases with the increase of brazing temperature and dwell time. The thickness of the residual layer of amorphous filler metal is smaller than that of the crystalline filler metal under the same brazing temperature and dwell time.