Ablation resistance and thermal conductivity of carbon/carbon composites containing hafnium carbide

Ablation properties and thermal conductivity of carbon/carbon (C/C) composites containing hafnium carbide (HfC) were investigated. The C/C composites containing 6.5wt.% HfC exhibit the best thermal conductivity and ablation resistance. The improvement of the thermal conductivity is attributed to the increased phonon-defect interaction produced by the thermal motion of CO released from the reaction of carbon and ZrO₂. High thermal conductivity of the composites can slow down the ablation of carbon. When the HfC mass fraction is greater than 6.5wt.%, cracks generated act as diffusion channels for an oxidizing atmosphere and thus accelerate the ablation of the composites.