Natural Graphite-CVD Carbon Composites

Abstract

Graphite-carbon composites have been fabricated using a natural graphite powder which was molded at low pressures and room temperature and infiltrated by a CVD technique at 700°C using propylene as a source of carbon. The rate of removal of open porosity by carbon infiltration is proportional to open porosity up to an infiltration time of at least 24 hr. Flexural strength, Young's modulus and electrical conductivity of the composites progressively increase with increasing apparent density (d), being approximated by expressions of the type Y=ad^b over most of the infiltration range. Knoop hardness is increased by infiltration but remains much less than that found for cellulose carbon-CVD composites of comparable infiltration. Infiltration has interesting effects on CTE parallel and perpendicular to the original molding direction and CTE ratios. Heat treatment of infiltrated composites up to 2400°C results in density decreases and some degradation in mechanical properties.