Selected properties of AG-based composite contacts reinforced with TiB2, SiC, and WO2
Agata Ciuman-Krzemień, Lidia Burzyńska, Marek Galanty Akademia Górniczo-Hutnicza, Wydział Metali Nieżelaznych, al. Mickiewicza 30, 30-059 Kraków, Poland
Quarterly No. 2, 2008 pages 152-157
DOI:
keywords: cathodic reduction of solid compounds, silver powder, powder metallurgy, silver-ceramics composites, titanium boride, silicon carbides, tungsten dioxide, electrical contacts
abstract The simple method for producing silver-ceramics composite contacts was presented. The composite matrix comprises powdered silver that has unique properties, which is obtained in a cathodic reduction of Ag+-ions with AgCl in the Zn|0.5MH2SO4,AgCl|Ag cell. This method enables the recycling of secondary or waste raw materials that contain silver. It is also allowed to use zinc, steel, or aluminum scrap as the anode. The reinforcing phase consists of ceramic powder materials - titanium boride, silicon carbide, or tungsten dioxide. Silver was combined with ceramic materials using powder metallurgy technologies (mixing-pressing-sintering). The composites were pressed under 500 MPa of pressure and subsequently sintered at 850C for 45 minutes in an argon atmosphere. The effect of the chemical composition of the obtained composites on the mechanical and electrical properties was examined. The increase of the content of the ceramic additives in the silver composites is accompanied with the deterioration of the compressibility of pressed samples. The addition of ceramics in powdered silver prevents compact growth during the sintering process, as compared to a silver compact. There exists a correlation between the relative density of silver-ceramics sinters and their hardness and electrical conductivity. The obtained silver-ceramics composite contacts have a high electrical conductivity (even above 40 MS/m) and low contact resistance (decreasing with growing contact force and independent of the applied current). The open porosity of the obtained materials is low.