(2004-01-06) (Data obrony: 2007) Ciuman-Krzemień, Agata Wydział Metali Nieżelaznych
Simply method of processing a secondary raw material containing silver into final product like silver-ceramics composite electrical contacts was elaborated. The recycling of silver from difficultly soluble AgCl by its direct reduction was investigated in the cell $Zn|H_{2}SO_{4},AgCl|Ag$. Silver chloride did not directly contact with the reducing metal. It was found that the reduction of Ag+ ions process probably runs under activation control. The silver powder obtained by this method shows high purity and fine grain with average chord about 1 [µm] and perfectly fulfills as the matrix of composite. The silver was strengthened by obtaining material containing 2–40 wt% of ceramics like $TiB_2$, $SiC$ or $WO_2$. Composite contact materials were obtained by powder metallurgy method (pressing-sintering). Samples were pressed (p = 100 – 700 [MPa]) and then sintered at temperature 850ºC for 45 minutes in an argon atmosphere. It was found that the increase of the compacting pressure causes the increase of density of compacts. The compressibility of the pressed samples deteriorates with the increase of content of ceramic additions. It was also found that the ceramic addition in the silver powder prevents from the growth of compacts during sintering process. It was found that there is a correlation between the relative density of sintered silverceramics composite and their hardness and also their electrical conductivity. Studied composites are characterized by high conductivity and low contact resistance. Uniform distribution of ceramic particles in the metallic matrix is obtained.
