High porosity and low thermal conductivity high entropy (Zr0.2Hf0.2Ti0.2Nb0.2Ta0.2)C

Porous ultra-high temperature ceramics (UHTCs) are promising for ultrahigh-temperature thermal insulation applications. However, the main limitations for their applications are the high thermal conductivity and densification of porous structure at high temperatures. In order to overcome these obstacles, herein, porous high entropy (Zr0.2Hf0.2Ti0.2Nb0.2 Ta-0.2)C was prepared by a simple method combing in-situ reaction and partial sintering. Porous high entropy (Zr0.2Hf0.2Ti0.2Nb0.2Ta0.2)C possesses homogeneous microstructure with grain size in the range of 100-500 nm and pore size in the range of 0.2-1 mu m, which exhibits high porosity of 80.99%, high compressive strength of 3.45 MPa, low room temperature thermal conductivity of 0.39 W.m(-1) K-1, low thermal diffusivity of 0.74 mm(2).s(-1) and good high temperature stability. The combination of these properties renders porous high entropy (Zr0.2Hf0.2Ti0.2Nb0.2Ta0.2)C promising as light-weight ultrahigh temperature thermal insulation materials. (C) 2019 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.