High spatial resolution thermal conductivity mapping of SiC/SiC composites

[摘要] Silicon carbide (SiC) ceramic matrix composites are being investigated as a new generation of fuel cladding materials due to its higher accident tolerance compared to Zircaloy. Characterization of the thermal conductivity of SiC constituents and their interfaces and interphases in SiC/SiC composites is needed as inputs to models of cladding performance. We used time-domain thermoreflectance (TDTR) to map the thermal conductivity with a spatial resolution of 2 mu m. The SiC/SiC composite is comprised of Hi-Nicalon Type S fibers in a matrix made by chemical vapor infiltration (CVI matrix). The interphase material is a pyrolytic carbon/SiC multilayer. We report thermal conductivity maps of the SiC fiber and SiC matrix at temperatures of 25 degrees C, 90 degrees C, 164 degrees C, and 250 degrees C. The fiber has a uniform and isotropic thermal conductivity of 22 W m(-1) K-1 at 25 degrees C; the thermal conductivity of fiber is approximately independent of temperature. The matrix thermal conductivity is not uniform and varies from 50 to 120 W m(-1) K-1 at 25 degrees C; the thermal conductivity of the matrix scales approximately with the inverse of the square root of temperature, i.e., proportional to 1/T-1/2. The thermal conductivity of the interphase at room temperature is 6 W m(-1) K-1. The calculated spatially averaged thermal conductivity of this SiC/SiC composite at 1000 degrees C is 29 W m(-1) K-1. (C) 2020 Elsevier B.V. All rights reserved.

[发布日期] 2020-12-15

[关键词] SiC/SiC composites;Thermal conductivity mapping;Ceramic matrix composites;Alternative fuel cladding