Local thermal conductivity measurements to determine the fraction of α-cristobalite in thermally grown oxides for aerospace applications

Devitrification of the thermally grown oxide that forms in aerospace coatings used to protect ceramic matrix composites is a contributor to the mechanical failure of these coatings at high operating temperatures. Current methods used to identify the formation of a-cristobalite are time consuming and difficult, due to the limited differences in properties as well as the size scale over which these phase contrasts occur. This study employs time-domain thermoreflectance to spatially profile the thermal conductivity of thermally aged samples, providing a practical method to understand the spatial distribution of alpha-cristobalite in partially- and fully-devitrified amorphous silica. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.