Environmentally Protective Coatings for Ceramic Matrix Composites

In order to make ceramic matrix composites (CMCs) into a useful class of materials for fabricating aerospace structures, there are several key issues that need to be resolved. One of these issues concerns the performance of CMC at intermediate-high temperatures. Oxidation of the interface coating used to control the crack deflection properties and other serious issues related to the ingress of moisture can significantly impact the long-term reliability of CMCs. The goal of this program is to develop and confirm the effectiveness of a low cost, easily applied coating system to both reduce the open porosity and provide an effective oxidation barrier. A simple external sealant is unlikely to provide the long-term protection required for CMCs in operational use. There are a number of issues to be overcome in order for any coating system to be effective. This proposal identifies many of those issues and details an approach for overcoming them