Ultrastrong and High Thermal Insulating Porous High-Entropy Ceramics up to 2000 °C

摘要

High mechanical load-carrying capability and thermal insulating performance are crucial to thermal-insulation materials under extreme conditions. However, these features are often difficult to achieve simultaneously in conventional porous ceramics. Here, for the first time, it is reported a multiscale structure design and fast fabrication of 9-cation porous high-entropy diboride ceramics via an ultrafast high-temperature synthesis technique that can lead to exceptional mechanical load-bearing capability and high thermal insulation performance. With the construction of multiscale structures involving ultrafine pores at the microscale, high-quality interfaces between building blocks at the nanoscale, and severe lattice distortion at the atomic scale, the materials with an approximate to 50% porosity exhibit an ultrahigh compressive strength of up to approximate to 337 MPa at room temperature and a thermal conductivity as low as approximate to 0.76 W m-1 K-1. More importantly, they demonstrate exceptional thermal stability, with merely approximate to 2.4% volume shrinkage after 2000 degrees C annealing. They also show an ultrahigh compressive strength of approximate to 690 MPa up to 2000 degrees C, displaying a ductile compressive behavior. The excellent mechanical and thermal insulating properties offer an attractive material for reliable thermal insulation under extreme conditions. @@@ A multiscale design strategy is proposed to fabricate 9-cation porous high-entropy diborides (9PHEBs) with exceptional mechanical load-bearing capability and high thermal insulating performance via an ultrafast high-temperature synthesis technique. The as-fabricated 9PHEBs possess ultrahigh compressive strength (approximate to 337 MPa) and low thermal conductivity (approximate to 0.76 W m-1 K-1). More importantly, they show superior thermal stability and strength retention up to 2000 degrees C.image

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