Microhardness of Pyrolytic Graphite and Siliconated Pyrolytic Graphite

Abstract

The micro Vickers hardness of pyrolytic graphite (PG) and siliconated pyrolytic graphite [PG (Si)] prepared by pyrolysis of a mixture of commercial propane gas and silicon tetrachloride vapor under various conditions has been measured. The hardness is almost independent of the angle from the deposition plane and increases with decreasing deposition temperature. PG is harder than PG (Si) prepared at the same deposition temperature. This difference results from the difference in their structural features (density, interlayer spacing, crystallite size and preferred orientation factor). Relations between the hardness and the structural features show different behaviors above and below the temperature at which a minimum density is obtained. From the experimental results, it is considered that the hardness of PG is affected by cross-links among crystallites, while the hardness of PG (Si) is related to the presence of SiC in PG matrix.