Fluidized bed chemical vapor deposition of pyrolytic carbon-III. Relationship between microstructure and mechanical properties

Pyrolytic carbon (PyC) coatings with different densities were produced by fluidized bed chemical vapor deposition under different deposition conditions. Their Young's modulus and hardness were measured by nano-indentation, whereas the deformation behavior was studied through analyzing the force-displacement curves of the indentations. The deformation mechanism of PyC under indentation is attributed to the slip of the graphene planes, and its reversibility is discussed in terms of the defects of the microstructure. We observed a linear relationship between the density of PyC's and their Young's modulus and hardness, for densities lower than 1.9 g/cm³. Above this value, the mechanical properties were controlled by the amount of interstitial defects. Samples were also heat treated at 1800°C and 2000°C, and their changes in microstructure, hardness and Young's modulus are discussed as a function of density.