SiC陶瓷表面高温耐碱腐蚀Ca_(0.6)Mg_(0.4)Zr_4(PO_4)_6涂层的制备

采用浆料浸渍涂覆法在SiC陶瓷表面制备Ca_0.6Mg_0.4Zr_4(PO_4)_6(C_0.6M_0.4ZP)涂层,以改善其高温耐碱腐蚀性能.通过在C0.6M0.4ZP溶胶中加入平均粒径为40 nm的C_0.6M_0.4ZP粉体和聚乙烯醇(PVA),制备高固含量的稳定胶态悬浮浆料,并在SiC陶瓷上制备C_0.6M_0.4ZP涂层.浆料固含量为40% (质量分数, 下同)、pH=6、PVA加入量为6%时,在1400 ℃保温3 h烧成后可获得致密的C_0.6M_0.4ZP涂层,一次涂覆涂层厚度可达200 μm,且涂层与SiC陶瓷基体结合良好.经1000 ℃,96 h碱腐蚀后,涂层试样没有明显的质量损失,而未涂覆试样质量损失达到20.1%;涂层试样的强度衰减5.7%,远低于未涂覆试样的40.5%.

Improvement of Alkali Corrosion Resistance of SiC Ceramics by Depositing Ca_(0.6)Mg_(0.4)Zr_4(PO_4)_6 Coating

Ca_0.6Mg_0.4Zr_4(PO_4)_6 (C_0.6M_0.4ZP) coating was deposited on SiC ceramic by slip dip-coating technique to improve its alkali corrosion resistance at high temperature. The thick C_0.6M_0.4ZP coating on SiC ceramic was obtained by dispersing the nanocrystalline C_0.6M_0.4ZP powder and PVA into stable C_0.6M_0.4ZP sol to form a colloidal suspension with high solid content. The prepared C_0.6M_0.4ZP coating on SiC ceramic is homogeneous and dense, and has a thickness of about 200 ìm for only once coating, with solid loading of 40wt%～45wt%, pH=6, 6wt% PVA and sintered at 1400 ℃ for 3 h. SEM microstructural examination revealed good bonding between the C_0.6M_0.4ZP coating and SiC ceramic. The C_0.6M_0.4ZP coated SiC ceramic shows no obvious mass change after exposure to alkali vapor in air and at 1000 ℃ for 96 h, but the mass loss of uncoated sample reaches 20.1%, and the strength degradation for coated and uncoated are 5.7% and 40.5%, respectively.