Anti-oxidation and ablation properties of carbon/carbon composites infiltrated by hafnium boride

To improve the anti-oxidation and ablation properties of carbon/carbon (C/C) composites, they are modified by hafnium boride (HfB₂) using a two-step process of in situ reaction and thermal gradient chemical vapor infiltration. X-ray diffraction is used to monitor the composition of the samples. Scanning electron microscope images show that the carbon fibers are uniformly coated by HfB₂ particles. The oxidation onset temperature of carbon fibers is greatly increased from 300 to 700 °C after HfB₂ coating. After modification with HfB₂, the linear and mass ablation rates of the C/C composites are decreased by 51.80% and 24.32%. During oxidation and ablation, the interface between carbon matrix and fiber is effectively protected by HfB₂ due to the reaction of HfB₂ with the oxygen, and the resultant hafnium oxide may form the liquid film to resist the oxygen at high temperature.