High temperature performance of mullite whisker-reinforced ZTA

Abstract

In this work, an oxide-based ceramic matrix composite (CMC) consisting of a zirconia toughened alumina (ZTA) matrix and reinforced with mullite whiskers is produced with the purpose of providing more oxidation resistance and cost-effective alternative to covalent discontinuously reinforced ceramics. ZTA has enhanced toughness, strength and creep resistance over single-phase alumina or zirconia. ZTA can further be strengthened by the inclusion of SiC whiskers; however, these whiskers are prone to oxidation at temperatures above 1000℃ leading to loss of properties. In this work, mullite whiskers are used as the reinforcement due to its stability in oxidizing atmospheres are high temperatures. Mullite whiskers are grown through the molten salt method and incorporated into the ZTA matrix using a colloidal processing route. The microstructure and room temperature properties have been reported in an earlier paper. Whisker additions have been shown to improve the flexural strength of ZTA at 1200℃ by 59.31%. There is some concern over the stability of large diameter whiskers at high temperatures, especially in environments with excessive moisture content or residual alkali contamination. Further work will be carried out to address these concerns as well as to develop a statistical analysis of the results presented.