BaO-Al2O3-SiO2环境隔离涂层的制备与耐腐蚀性能表征

FABRICATION OF BaO–Al_2O_3–SiO_2 ENVIRONMENTAL BARRIER COATINGS AND CHARACTERIZATION OF THEIR CORROSION RESISTANCE

应用柠檬酸溶胶–凝胶法制备BaO–Al2O3–SiO2(BAS)溶胶,将BAS溶胶直接刷涂在碳纤维(carbon fiber,Cf)/SiC–SiC基底上制备出BAS涂层,并在1250℃,50%(体积分数,下同)H2O–50%O2和0.1MPa压力下对涂覆和未涂覆BAS涂层的样品进行腐蚀试验。用红外光谱仪、热重–差示扫描量热分析仪、X射线衍射仪、扫描电镜表征了BAS溶胶–凝胶及涂层的性能;采用电子天平、电子万能试验机对涂覆和未涂覆BAS涂层的样品耐腐蚀性能进行表征。结果表明:将pH控制在4～5,柠檬酸与金属离子Ba2+和Al3+的摩尔比分别为2和3时,可成功合成均匀、透明、稳定的BAS溶胶。BAS溶胶1次刷涂烧结的涂层厚度约为10μm,4次可达50μm左右。在1250℃的水氧耦合条件下腐蚀200h后,与未涂覆BAS的Cf/SiC–SiC比较,涂覆BAS的Cf/SiC–SiC强度保持率达88%,并且质量无明显损失。

BaO-Al2O3-SiO2 （BAS） sol was prepared by the citric acid sol-gel method. The BAS sol was coated onto carbon fiber （Cf）/SiC-SiC substrate directly using a brush-coating process. The corrosion resistances of samples with and without BAS coating were determined under 1 250 ℃, 50% （in volume） H2O--50% O2 and an atmospheric pressure environment. The flexural strengths of samples before and after the corrosion were tested. The characteristics of BAS sol-gel as well as BAS coating were measured by Fourier transform infi＇ared spectroscopy, thermogravimetry-differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy. The results indicate that the BAS sol synthesized at a pH value range of 4-5 is uniform, transparent and stable with the mole ratios of citric acid to metal ion Ba^2＋ and Al^3＋ of 2 and 3, respectively. The thickness of BAS coating for one deposition is approximately 10 um. After the application of four layers of coating, the thickness of the BAS coating is about 50 um. The Cr/SiC-SiC composites with BAS coating can remain 88% of their original flexural strength even after 200 h corrosion. Compared with Cr/SiC-SiC composites without BAS coatings, those with BAS coatings do not have any obvious mass loss after corrosion.