烧结助剂对高气孔率SiC陶瓷结构和性能的影响

摘要

由叔丁醇、丙烯酰胺和SiC粉及烧结助剂组成固相含量为10%(体积分数)的陶瓷浆料,采用凝胶注模成型和无压烧结工艺制备多孔SiC陶瓷,研究Al2O3和Al2O3+SiO2这两种烧结助剂体系对多孔SiC陶瓷的气孔率、显微结构和力学性能的影响.结果表明:Al2O3+SiO2复合烧结助剂明显改善SiC陶瓷的烧结性能,与采用单一的Al2O3烧结助剂相比,SiC样品的烧结温度和莫来石的生成温度均降低50℃左右;两种不同的烧结助剂制成的试样中的气孔均呈很窄的单峰分布,中位孔径为2 μm左右;随烧结温度的升高压缩强度增大,而气孔率变化不大;以Al2O3+SiO2为烧结助剂、在1 400℃烧结的试样的气孔率和强度分别达到70.57%和17.74 MPa.%The porous SiC ceramics were fabricated by gel-casting and pressureless sintering process in air atmosphere with a solid loading of 10％ slurry constituting of tert-butyl alcohol, acrylamide, SiC powder and sintering additives. The effects of two kinds of sintering additives, Al2O3 and Al2O3+SiO2, on the porosity, microstructure and mechanical properties of the porous SiC ceramics were studied. The results show that the sintering additive of Al2O3+SiO2 obviously improves the sinterability of SiC ceramics, and compared with that only using Al2O3 as sintering additive, both sintering temperature of SiC specimen and formation temperature of mullite phase are decreased by about 50 ℃. The median pore diameter of the porous SiC ceramics is about 2 μm and presents single peak distribution. The compressive strength of the porous SiC ceramics increases with increasing the sintering temperature, whereas the porosity has little change. Using Al2O3+SiO2 as sintering additive, the porosity and compressive strength of SiC porous ceramics sintered at 1 400 ℃ reach 70.57％ and 17.74 MPa, respectively.