Manufacture of wire from platinum/metal oxide composites

Abstract

In order to enhance high-temperature mechanical properties of platinum a dispersed particle hardening was developed by W. C. Heraeus, Hanau. A suitable compound impeding grain growth and migration of dislocations is zirconia. There are indications that significantly increased amounts of oxides might also stabilise erosion resistance of spark plug electrodes while reducing the percentage of cost-intensive precious metal. Two different process technologies of manufacturing platinum/metal oxide composites are presented and compared: 1) melting and subsequent oxidation and 2) mixing of metal and oxide powders followed by extrusion. In both cases wires with typical diameters of 0.8 to 0.6 mm are fabricated. Samples with approx. 6 vol.-% of zirconia dispersed in a platinum matrix were successfully tested under real life conditions in a combustion engine.Keywords: Spark plugs, particle hardening, wire fabrication, internal oxidation, extrusion