DIAMOND FIBER MICROHEATERS

Free standing diamond fibres with 125 mu m diameter tungsten wire or c arburised steel cores coated by chemical vapour deposition with simila r to 35 mu m thick diamond were heated by passing an electric current through the cores. Tungsten wire cord fibres were heated to 1000 degre es C in a vacuum without any visible change in the fibres. In air the diamond oxidised above similar to 550 degrees C. The diamond fibres wi th the carburised steel core reached a maximum temperature of similar to 200 degrees C before melting at a local hot spot. This core was als o ferromagnetic and thus the fibre had a unique combination of propert ies. Oxidation produced a large increase in the diamond surface area a nd this effect might be used to enhance heat transfer in diamond fibre sensors and in diamond fibre-metal matrix composite thermal conductor s. (C) 1997 The Institute of Materials.