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以Si和Al2O3为原料,采用原位生成法在带有SiC内涂层的炭/炭(C/C)复合材料表面制备出Si-Al2O3-mullite(莫来石)抗氧化涂层。采用X射线衍射、扫描电镜和氧化实验研究了Al2O3含量等工艺因素对Si-Al2O3-mullite涂层的物相组成、结构形貌、抗氧化性能影响。结果表明:Al2O3质量含量为30%~40%时,涂层主要由Si,mullite和Al2O3三相组成,涂层致密无裂纹,抗氧化性能最佳。在1 500℃等温氧化测试显示,SiC/Si-Al2O3-mullite复合涂层比单一的SiC涂层抗氧化性能有明显提高,1 500℃等温氧化75 h试样失重为4.6%。涂层试样失重的主要原因是涂层中产生了不可愈合的孔隙缺陷。
Si-Al2O3-mullite anti-oxidation coating was prepared on the surface of carbon / carbon (C / C) composites with SiC inner coating by in-situ forming method using Si and Al2O3 as raw materials. X-ray diffraction, scanning electron microscopy and oxidation experiments were carried out to study the effect of Al2O3 content and other factors on the phase composition, morphology and oxidation resistance of Si-Al2O3-mullite coating. The results show that when the mass fraction of Al2O3 is 30% ~ 40%, the coatings consist of three phases of Si, mullite and Al2O3. The coatings are dense and crack-free and their oxidation resistance is the best. The isothermal oxidation test at 1 500 ℃ showed that the oxidation resistance of the SiC / Si-Al2O3-mullite composite coating was significantly higher than that of the single SiC coating, and the weight loss was 4.6% after the isothermal oxidation at 115 ℃ for 75 h. The main reason for the weight loss of the coated samples is the presence of non-healing porosity defects in the coating.