Composites for Electrical Contact Applications

Abstract

Two general groups of physical composite properties can be distinguished. The first group comprises the "combination properties", which can in turn be subdevided into "sum properties" and "product properties". The first are due to an addition of the properties, and the latter to the interaction of the components involved. The second group comprises the "structural properties", i.e. properties which are determined by the geometry and the size of rhe phases.Since many years metallic compositcs like laminated composites, particle composites, infiltrated composites and fibre composites have been used for electrical contact applications. Fibre composite contact materials like silver-nickel, copper-nickel and copper-palladium can be fabricated in a simple and thus inexpensive way by bundling sheated wires and subjecting this bundle to severe cold forming with subsequent heat treatments.Silver-nickel fibre composites with up to 7 0 w.-% nickel are used as electrical contacts for igniters in gas discharge lamps. Moreovcr composites with very thin nickel fibres show excellent magnetic properties. Electrical contacts made of copperpalladium fibre composites show extremely low material transfer when switching direct currents. Like contact materials, materials for spark plug electrodes have to exhibit a low are erosion, a high thermal conductivity and a good corrosion resistance. Good results have been obtained with copper nickel fibre composites.