Mechanical properties at high temperature of high purity mullite ceramics

The mechanical properties at hgh temperature, which were the flexural strength and creep resistance of high-purity mullite ceramics were investigated. The Al2O3/SiO2 ratio of mullite samples were 72wt% Al2O3/28wt% SiO2 and 75wt% Al2O3/25wt% SiO2. Some samples contained a little ZrO2 due to prepared using ZrO2 media All samples were fabricated using the Sol-C;el method and sintered near theoretically. The strength at R. T. depended not on the Al2O3/SiO2 ration and rat increased as the grain size decreased On the other hand, the ratio of the strength at high temperature for at R T. was influenced not only. on the Al2O3/SiO2 ratio, but also on the grain size. And also the degradation ratio decreased with increasing the amount of alkalis and ZrO2. The strain-late of the composition with Al2O3-rich, little alkalis and ZrO2 and larger grain size was smaller. The fracture surface of the composition with lower strain-rate indicated the small slow crack growth region The Al2O3/SiO2 ratio, the amount of alkalis and ZrO2 and the grain size dependence of the stain-late showed similar tendency to those of the ratio of strength at high temperature for at R. T..