Regularities in Chemical Vapour Infiltration of Carbon and in Properties of Resulting Carbon/Carbon Composites

Abstract

Kinetics of chemical vapour infiltration of porous carbon bodies are governed by processes in the gas phase, depending on the open porosity, but also on infiltration conditions and geometrical factors. They do not depend on the substrate nature, except for the short initial period θ during which the substrate is being coated by pyrocarbon and stationary infiltration conditions established. The distinction between the processes of pore filling and pore closing as well as determination of θ have been done. Relationships describing dependence of open porosity on infiltration time, apparent density on open porosity and properties of the composites (flexural strength and modulus, hardness and electrical resistivity) on their apparent density have been determined. A number of conclusions relative to effects of various factors on kinetics of infiltration, formation of pyrocarbon and properties of the resulting composites have been derived. Results relative to infiltration of some systems other than carbon/carbon indicate that the regularities found have a general significance.