High porosity and low thermal conductivity high entropy(Zr_0.2Hf_0.2Ti_{0.2Nb0.2Ta0.2}C

Heng Chen^1,2，Huimin Xiang¹，Fu-Zhi Dai¹，Jiachen Liu²，Yiming Lei³，Jie Zhang³，Yanchun Zhou^1,2

1. Science and Technology on Advanced Functional Composite Laboratory,Aerospace Research Institute of Materials & Processing Technology2. Key Laboratory of Advanced Ceramics and Machining Technology of Ministry of Education,School of Materials Science and Engineering,Tianjin University3. Shenyang National Laboratory for Materials Science,Institute of Metal Research,Chinese Academy of Sciences

摘 要：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(Zr_0.2Hf_0.2Ti_0.2Nb_0.2Ta_0.2)C was prepared by a simple method combing in-situ reaction and partial sintering.Porous high entropy(Zr_0.2Hf_0.2Ti_0.2Nb_0.2Ta_0.2)C possesses homogeneous microstructure with grain size in the range of 100–500 nm and pore size in the range of 0.2–1μm,which exhibits high porosity of 80.99%,high compressive strength of 3.45 MPa,low room temperature thermal conductivity of 0.39 W·m^-1K^-1,low thermal diffusivity of 0.74 mm²·s^-1and good high temperature stability.The combination of these properties renders porous high entropy(Zr_0.2Hf_0.2Ti_0.2Nb_0.2Ta_0.2)Cpromising as light-weight ultrahigh temperature thermal insulation materials.

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