Efficient fabrication of light C <sub>f</sub>/SiHfBOC composites with excellent thermal shock resistance and ultra-high-temperature ablation up to 1800 °C
Yang Lyu, Zhihong Han, Guangdong Zhao, Yuan Cheng, Shanbao Zhou, Xinghong Zhang, Guiqing Chen, Wenbo Han
Abstract
In this paper, a high-yield Hf-modified SiHfBOC ceramic precursor was developed, and a high-pressure assisted impregnation pyrolysis method was proposed to achieve the preparation of 3D PyC-C<sub>f</sub>/SiHfBOC composites. This high-pressure assisted impregnation method significantly improves the impregnation filling effect of the precursor in and between fiber bundles compared to dozens of traditional impregnation cycles. After undergoing just 9 PIP cycles, the composites achieved a relative density of approximately 90% and a density of 1.64 g/cm<sup>3</sup>. The critical temperature difference of 3D PyC-C<sub>f</sub>/SiHfBOC composites after the shock of RT-1000 °C is as high as 650 °C, which is twice that of the traditional ceramic material, showing good thermal shock resistance. Under the effect of Hf modification, a dense HfO<sub>2</sub>-SiO<sub>2</sub> oxide layer (thickness 93μm) was formed in situ on the surface of the 3D PyC-C<sub>f</sub>/SiHfBOC composites, effectively preventing further erosion of the composite matrix by high-temperature oxidation gas. Even in the ultra-high temperature oxygen-containing environment at 1800 °C, it still exhibits an excellent non-ablative result (with a linear ablation rate of 0.83×10<sup>-4</sup> mm·s<sup>-1</sup>). This work not only enriches the basic research on lightweight ultra-high temperature ceramic composites converted from Hf ceramic precursors but also provides strong technical support for their application in ultra-high temperature non-ablative thermal protection materials for high-speed aircraft.