Tough and strong bioinspired high-entropy all-ceramics with a contiguous network structure

Abstract

Developing bioinspired all-ceramics with plastic phases is considered one of the most effective ways to simultaneously achieve enhanced strength and toughness in ceramic materials for high-temperature applications. Here we explore tough and strong bioinspired high-entropy all-ceramics with a contiguous network structure that are able to serve up to 1300 °C. Specifically, we develop the high-entropy all-ceramics, featuring a unique contiguous network distribution of the Cr₇C₃ plastic phase within the predominant high-entropy carbide (HEC) hard phase, through a high-entropy composition-engineering strategy. The resulting materials exhibit impressive fracture initiation toughness of 12.5 ± 1.5 MPa·m^1/2 and flexural strength of 613 ± 52 MPa at room temperature, as well as ~97% strength retention up to 1300 °C due to their good high-temperature stability, surpassing the performance of most other reported bioinspired ceramics. Further experimental and theoretical investigations demonstrate that the Cr₇C₃ phase can undergo plastic deformation by forming nanoscale shear bands with significant crystal defects, resulting in multiple toughening mechanisms involving crack-bridging of unfractured Cr₇C₃ ligaments and crack deflection in the HEC/Cr₇C₃ all-ceramics. This work successfully develops tough and strong bioinspired high-entropy all-ceramics capable of serving up to 1300 °C, offering an innovative strategy that facilitates further design of bioinspired ceramics applicable at higher temperatures.