Fabrication of multi-anionic high-entropy carbonitride ultra-high-temperature ceramics by a green and low-cost process with excellent mechanical properties

As a new category of ultra-high-temperature ceramics(UHTCs),multi-anionic high-entropy(HE)carbonitride UHTCs are expected to have better comprehensive performance 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_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C,N_(1-x) powders is achieved by sol-gel combined with the carbothermal reduction/nitridation method for the first time.The as-synthesized(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C_(x)N_(1-x) powders possess high compositional uniformity and controllable particle size.In addition,the obtained bulk ceramics prepared at 1800℃exhibit superior fracture toughness(Kic)of 5.39±0.16 MPa·m^(1/2) and high nanohardnesof 35.75±1.23 GPa,lastic modulus(E)of 566.70±8.68 GPa,and flexural strength of 487±41 MPa.This study provides a feasible strategy for preparing the high-performance HE carbonitride ceramics in a more environmentally friendly and economical manner.