聚合物浸渍裂解法制备C/C-ZrC-SiC复合材料的氧化行为及抗烧蚀性能研究

Oxidation Behavior and Ablation Resistance of C/C-ZrC-SiC Composites Prepared by Polymer Infiltration and Pyrolysis

采用热梯度化学气相渗透和聚合物浸渍裂解法制备了ZrC-SiC改性C/C复合材料（C/C-ZrC-SiC），借助SEM、XRD等手段研究了该复合材料的微观形貌与相组成，并对其在1 500 ℃恒温静态空气环境、室温至1 400 ℃变温过程的氧化行为以及氧乙炔抗烧蚀性能进行了研究。结果表明：室温~1 400 ℃动态氧化时C/C-ZrC-SiC复合材料出现增重→缓慢失重→剧烈失重→稳定4个过程；在1 500℃ 静态氧化时，C/C-ZrC-SiC出现增重→缓慢失重→动态稳定→剧烈失重→稳定5个过程。ZrC和SiC优先氧化分别生成ZrO2骨架和SiO2玻璃层包裹基体和碳纤维，一定程度上减缓了基体和碳纤维的氧化。经过1 200 s氧乙炔烧蚀，材料线烧蚀率和质量烧蚀率分别为9.27×10^-4 mm·s^-1和6.67×10^-4 g·s^-1。在烧蚀过程中，试样表面能形成一个ZrO2外层/SiO2内层的双层结构保护膜。ZrO2骨架层能减缓烧蚀火焰对材料内部的热力学和热化学烧蚀，而致密的SiO2层能够弥合材料的裂纹、孔洞等缺陷，阻挡有氧气氛进一步进入材料内部，使材料表现出优异的抗烧蚀性能。

C/C-ZrC-SiC composites were prepared by thermal gradient chemical vapor infiltration （TCVI） and precursor infiltration and pyrolysis （PIP） process. The microstructures and phase compositions of C/C-ZrC-SiC composites after oxidation were analyzed by scanning electron microscopy and X-ray diffraction, respectively. Isothermal oxidation behavior at 1 500 ℃, dynamic oxidation behavior from room temperature to 1 400 ℃ and long-term ablation resistance of the composites were investigated. The results show that dynamic oxidation behavior from room temperature to 1 400 ℃ can be divided into four stages ： mass gain, slow mass loss, severe mass loss and constant. While the isothermal oxidation behavior of C/C-ZrC- SiC at 1 500 ℃ can be divided into five stages： mass gain, slow mass loss, constant, severe mass loss and constant. ZrC and SiC trend to be oxidized preferentially and generate ZrO2 and SiO2, which wrap and protect C/C matrix and fibers partly. After ablated for 1 200 s by oxyacetylene flame, the linear and mass ablation rates of composites are 9. 27 ×10^-4 mm·s^-1 and 6. 67 ×10^-4 g ·s^-1, respectively. ZrO2 and SiO2 are formed by the oxidation of ZrC and SiC , respectively. ZrO2 can alleviate the thermal-physical and thermal-chemical erosion caused by the oxyacetylene torch, and dense SiO2 glassy film can seal the defects such as cracks and holes, leading to a good ablation resistance of C/C-ZrC-SiC composites.