Fabrication of multi-anionic high-entropy carbonitride ultra-high-temperature ceramics by a green and low-cost process with excellent mechanical properties
Liansen Xia, Shun Dong, Jianqiang Xin, Kaixuan Gui, Peitao Hu, Yongshuai Xie, Dongdong Yang, Xinghong Zhang, Yanchun Zhou
Abstract
As a new category of ultra-high temperature ceramics (UHTCs), multi-anionic high-entropy (HE) carbonitride UHTCs are expected to have better comprehensive performances than conventional UHTCs. However, how to realize the green and low-cost synthesis of high-quality multi-anionic HE carbonitride UHTC powders and prepare bulk ceramics with excellent mechanical properties still faces great challenges. In this work, a green, low-cost and controllable preparation process of (Ti<sub>0.2</sub>Zr<sub>0.2</sub>Hf<sub>0.2</sub>Nb<sub>0.2</sub>Ta<sub>0.2</sub>)C<em><sub>x</sub></em>N<sub>1-<em>x</em></sub> powders is achieved by a sol-gel combined with carbothermal reduction/nitridation method for the first time. The as-synthesized (Ti<sub>0.2</sub>Zr<sub>0.2</sub>Hf<sub>0.2</sub>Nb<sub>0.2</sub>Ta<sub>0.2</sub>)C<em><sub>x</sub></em>N<sub>1-<em>x</em></sub> powders possess high compositional uniformity and controllable particle size. In addition, the obtained bulk ceramics prepared at 1800 ℃ exhibit a superior fracture toughness of 5.39±0.16 MPa·m<sup>1/2</sup>, high nanohardness of 35.75±1.23 GPa, elastic modulus of 566.70±8.68 GPa and flexural strength of 487±41 MPa. This study provides a feasible strategy for preparing high-performance HE carbonitride ceramics in a more environmentally friendly and economical manner.