CVD Coating of Ceramic Monofilaments

In many composite systems it has become apparent that coatings on the reinforcements are necessary to achieve high toughness materials. In order to examine materials which may be used as coatings on ceramic monofilaments and remain stable in high temperature, oxidizing environments, the deposition of a number of refractory metals has been attempted. The results of coating experiments using silicon carbide fibers as substrates as well as general observations concerning the prospects of continuously coating long lengths of fibers will be discussed. The materials studied include carbon, cobalt, zirconium, molybdenum, tantalum, tungsten, and iridium. Carbon has been deposited from methane and propylene onto both SiC and sapphire fibers. Deposition of the metals has been achieved by direct chlorination of the metals followed by hydrogen reduction at the fiber. Iridium(III)2,4-pentanedionate has been used to deposit iridium metal. All metals were deposited at low pressure in a hot wall reactor with fibers continuously spooled through the reactor.