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 degrees 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. (C) 2012 Elsevier Ltd. All rights reserved.