NI-CATALYZED CARBON INFILTRATION OF CARBON-FIBER SUBSTRATES

Experimental studies were conducted to assess catalytic chemical vapor infiltration (CVI) of carbon-carbon composites as a potential improvement to conventional CVI processing. Carbon fiber felts and composite substrates were impregnated with Ni by the incipient wetness technique, and in thermogravimetric experiments Ni was found to be a highly active carbon deposition catalyst with deposits forming at temperatures as low as 375-degrees-C and at very high rates, representing substantial improvements over noncatalytic processes. However, the effects of catalytic carbon on material properties were not tested. The catalytic carbon was deposited as fine filaments at low Ni loadings, and as densely packed filaments at high loadings. It was found that the amount of catalytic carbon formed could be controlled by manipulation of operating conditions, primarily the Ni loading and the gas phase concentration of H-2.