Effects of Y2O3 on Crack Healing Ability and High Temperature Strength of Structural Mullite
Kotoji ANDO, Kiichi TSUJI, Masahiko NAKSTANI, Min-Cheol CHU, Shigemi SATO and Yasuyoshi KOBAYASHI
Abstract:Crack healing behavior and high temperature strength of Mullite/SiC composite ceramics have been investigated systematically, as a function of Y2O3 added(0`2.5wt“). The specimen was sintered by hot-pressing at 1650Ž. Semi-elliptical surface crack of 100ƒÊ‚ in diameter was made on the specimen. Cracked specimen was heat-treated at 1100Ž for 3hours, or at 1300Ž for 1hour in an air. Bending strength was measured by a 3-point bending test system. The bending strengths of smooth specimens were reduced to 40%-25% by the above cracking. For the case of mullite/SiC/Y2O3, the bending strength of heat-treated specimens with crack recovered completely up to that of smooth specimens. On the contrary, for the case of mullite/Y2O3(Y2O3=0`2.5wt“), the bending strength was recovered incompletely. This strength recovery of both materials was caused by crack-healing. This crack-healing ability was increased considerably by adding SiC particle to mullite. By adding 0.5`2.0wt“ Y2O3 to mullite/SiC composite ceramics, heat-resisting limit temperature of crack-healed sample was increased from about 1100Ž to 1200Ž. Key Words:Mullite,Crack healing ability, Crack-healed zone, Strength recovery, High temperature strength, Effect of Y2O3, Effect of SiC