Borosilicate wetting on ceramic matrix composites and Si-based substrates
November 5-9, 2017
The oxidation of Ceramic Matrix Composites (CMCs) is a complex process due to the combined oxidation of ceramic fibers, matrix, and an interphase. In previous work, the oxidation of CVD SiC coated SiC/BN/SiC CMCs with a single uncoated face exposing the fibers, matrix, and interphase was studied at temperatures of 800, 1200, and 1300°C. The thermal oxidation of the exposed face was characterized to understand crack-sealing in CMCs during use. During thermal oxidation, the exposed face of the CMC was sealed by borosilicate glass formation. Oxide droplets were observed to form at BN/SiC interfaces. In this work, stand-alone borosilicate glass cylinders situated on SiC, Si, or SiO2 substrates were heated in air and visualized in situ using a heating microscope. Changes in oxide morphology, volatility, and wetting were characterized as a function of borosilicate and substrate composition. Results from stand-alone glasses were compared with the observations from exposed CMC faces to elucidate mechanisms of composite sealing during thermal oxidation.
Megan Wilson, Elizabeth Opila, and Tim Keenan, "Borosilicate wetting on ceramic matrix composites and Si-based substrates" in "Advanced Ceramic Matrix Composites: Science and Technology of Materials, Design, Applications, Performance and Integration", Yutaka Kagawa, Tokyo University of Technology, Japan Dongming Zhu, NASA Glenn Research Center, USA Ram Darolia, GE Aviation (retired), USA Rishi Raj, University of Colorado, Boulder, USA Eds, ECI Symposium Series, (2017). http://dc.engconfintl.org/acmc/28