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 6.5 wt.% 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 6.5 wt.%, cracks generated act as diffusion channels for an oxidizing atmosphere and thus accelerate the ablation of the composites.