Microstructural Characteristics Controlling Thermophysical Properties of High Density Pitch Based Carbon/Carbon Composites

摘要

Carbon/carbon composites are unique class of materials having attracted attention as candidate material for thermal management systems including heat sinks, substrates for electronic elements and plasma facing components of fusion devices. These strategic applications need materials to have high thermal conductivity, low coefficient of thermal expansion and good mechanical strength. A great deal of work has been done to investigate the effect of structure of fiber and matrix, void and fiber/matrix interface on the mechanical properties of carbon/ carbon composites. Thermophysical properties are comparatively very structure sensitive and the heat transfer mechanism is governed by atomic level structure in the composites. The effective heat transfer mechanism requires highly oriented graphitic phases within the fiber and matrix. The transmission of thermal energy is hindered by phonon interactions such as phonon-phonon interaction, phonon-defect interaction and phonon-crystal boundary interaction. In the present studies Carbon/carbon composites have been developed with different fiber/matrix combinations and heat treated to different temperatures under pressure. Microstructure of these composites has been evaluated using SEM and polarized optical microscopy. Thermophysical properties i.e. thermal conductivity, coefficient of thermal expansion and specific heat has also been evaluated. It has been found that transmission of thermal energy is influenced by amount of heat absorbed i.e. specific heat by the composites at that particular temperature. It reduces magnitude of thermal diffusion in the composites. The temperature dependence of thermal diffusion, specific heat, thermal conductivity and coefficient of thermal expansion has been studied and correlated with microstructure of carbon/carbon composites.