Microstructure, ablation behavior and thermal retardant ability of C/C-HfB2 composites prepared by precursor infiltration pyrolysis combined with chemical vapor infiltration

C/C-HfB2 composites were fabricated by precursor infiltration pyrolysis combined with chemical vapor infiltration. Ablation behavior, oxidation performance and thermal retardant ability of the prepared composites were investigated. The results showed that the oxidation products of HfB2 could enhance the oxidation performance and ablation property of C/C-HfB2 composites. During ablation in the heat flux of 2.38 MW/m2 under oxyacetylene torch, a protective HfO2 layer was covered on ablated surface, acting as an efficient barrier to heat transfer and denudation of the oxyacetylene torch. As the heat flux increased to 4.18 MW/m2, thermal energy concentration and denudation enhancement of the oxyacetylene torch resulted in the spalling of the HfO2 layer. Based on microstructure evolution, thermal retardant ability test, thermogravimetric analysis and measurement of residual flexural strength, oxidation as well as ablation mechanism of the C/C-HfB2 composites was discussed.