| abstract |
An alumina comprising composition protective overlayer ( 20 ) for protecting a ceramic matrix composite material ( 12 ) from a high temperature, moisture-containing environment. Alumina may be used as a protective overlayer to protect an underlying mullite layer to temperatures in excess of 1,500° C. The coating may have porosity of greater than 15% for improved thermal shock protection. To prevent the ingress of oxygen to an underlying ceramic material, an oxide barrier layer may be optionally disposed between the alumina coating and the ceramic material. Such a protective overlayer may be used for an article having a ceramic oxide or non-oxide substrate. |