Thermal expansion of pyrolytic carbon with various textures

Thermal expansion of differently‐textured pyrolytic carbon matrices (pyrocarbons) of carbon/carbon composites was studied with a high temperature X‐ray diffraction at temperatures ranging from 25°C to 1400°C. The composites were synthesized by chemical vapor infiltration of a carbon fiber felt, using methane as a carbon source. From the linear dependence of the lattice displacement on temperature, coefficients of thermal expansion (CTE) of the pyrocarbons were calculated. One‐dimensional thermal expansion along the (002)‐direction ( c ‐axis) of the pyrocarbons was found to be proportional to the composite synthesis temperature. A correlation between CTE and pyrocarbon texture was found: low‐textured pyrocarbon with an extinction angle ( Ae ) of 10° exhibits a smaller CTE of 2.02 × 10 ‐5 K ‐1 , whereas high‐textured pyrocarbon with an Ae of 22° exhibits a considerably higher CTE of 2.65 × 10 ‐5 K ‐1 . However, CTE of high‐textured pyrocarbon is still smaller than that of graphite, which is 2.9 ×10 ‐5 K ‐1 .