期刊
SCRIPTA MATERIALIA
卷 191, 期 -, 页码 40-45出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.scriptamat.2020.09.008
关键词
High-entropy ceramics; Rare-earth pyrosilicates; Environmental barrier coatings; Thermal conductivity
类别
资金
- Office of Naval Research [N00014-18-1-2647]
- Department of Education [P200A150037]
This study demonstrates that using high-entropy ceramics as thermal environmental barrier coatings can effectively reduce thermal conductivity, thus protecting and insulating SiC-based ceramic matrix composites. By incorporating additional rare earth cations, thermal conductivity can be further reduced, making them strong candidates for future TEBCs.
Dense thermal environmental barrier coatings (TEBCs) with low thermal conductivities are needed for the protection and insulation of SiC-based ceramic matrix composites (CMCs) in future gas-turbine engines. Here we demonstrate experimentally that the high-temperature thermal conductivity of dense beta-Yb2Si2O7 pyrosilicate ceramic can be reduced progressively in beta-(Y0.1Yb0.9)(2)Si2O7 and beta-(Y0.5Yb0.5)(2)Si2O7 solid-solutions for TEBC application. We also demonstrate that by going to a dense five-component equi-atomic single-phase beta-(Y0.2Yb0.2Sc0.2Gd0.2Lu0.2)(2)Si2O7 pyrosilicate high-entropy ceramic (HEC), the thermal conductivity can be reduced further to 1.52 W.m.K-1 (at 10 00 degrees C). This is attributed to enhanced phonon scattering due to the increased mass-disorder with the incorporation of the additional RE3+ cations in the HEC. Although the high-entropy aspect and bonding-disorder do not appear to contribute significantly to the phase stability or the low thermal conductivity in such HECs, they are strong candidates for future TEBCs for CMCs. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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