Shen Qianhong

A Novel Method for the Preparation of Ag/SnO2 Electrical Contact Materials

Abstract A novel method was presented to prepare Ag/SnO2 (12 wt% SnO2) electrical contact materials. First, Ag-SnO2 nano composite powder with 42 wt% SnO2 synthesized by a coprecipitation method was characterized. XRD results reveal that the synthesized composite powder is composed of cubic Ag and rutile type of SnO2. SEM and TEM images show that nano-Ag and nano-SnO2 particles are homogeneously dispersed in the composite powder. The preparation process of nano composite powder was analyzed with the help of the TG-DTA curves of the precipitation. Then, the obtained Ag-SnO2 nano composite powder was mixed with Ag powder to prepare Ag/SnO2 electrical contact materials (ECM) by powder metallurgy process and the prepared Ag/SnO2 electrical contact materials was characterized. The results demonstrate that owing to the higher dispersion of nano SnO2 particles in Ag matrix, the physical properties of ECM prepared by the new method, such as the density, hardness and conductivity are better than that by the traditional method.

Anti-Arc Erosion Properties of Ag-La2Sn2O7/SnO2 Contacts

Abstract La2Sn2O7/SnO2 composite powder was synthesized by chemical co-precipitation, and Ag-La2Sn2O7/SnO2 electrical contact material was prepared by a powder metallurgy method. Anti-arc erosion properties, mass loss and Vickers hardness of the Ag-La2Sn2O7/SnO2 composite were investigated, and its anti-arc erosion mechanism was discussed. Results show that the welding force of Ag-La2Sn2O7/SnO2 composite is much better than that of Ag-SnO2, because the new phase La2Sn2O7 can increase the viscosity of melt pool and improve wettability between silver and tin oxide to some extent. Meanwhile, Flatter arcing area and “beads-like” particles embedded scatteredly in the surface could decentralize arc energy via “pinning effect”, which decreases temperature rise and weakens the damage of surface structure, and better anti-welding property is obtained. Ag-La2Sn2O7/SnO2 composite could be a leading candidate material for electrical contacts in the future.