【摘要】 高熵陶瓷是陶瓷领域近几年的研究热点，过渡金属硼化物中熵、高熵陶瓷以其优异的性能、化学反应惰性和极高的熔点，成为耐极端环境的重要候选材料。本工作首次研究了B₄C过量含量对中熵硼化物粉体合成、陶瓷致密化、微结构演变和高温弯曲强度的影响，确定了低氧含量、高烧结活性（Ti,Zr,Hf）B₂粉体的制备工艺。采用热压烧结工艺在1800℃制备的（Ti,Zr,Hf）B₂中熵陶瓷致密度高达99%以上。B₄C过量15wt%的（Ti,Zr,Hf）B₂陶瓷晶粒尺寸为5.0±2.1μm，随着B₄C过量含量增加到25wt%，晶粒尺寸明显细化至2.4±0.7μm。过量的B₄C一部分与球磨引入的Si₃N₄原位反应生成BN相，另一部分B₄C以第二相形式存在，BN和B₄C相的引入可以有效抑制中熵陶瓷烧结过程中的晶粒生长，同时也提升了材料的高温弯曲强度。B₄C过量25 wt%时，（Ti,Zr,Hf）B₂中熵陶瓷在1600℃具有优异高温弯曲强度，为631±62 MPa。更多还原

【Abstract】 High entropy ceramics are the research hotspot in recent years. Transition metal boride medium entropy and high entropy ceramics have become important candidate materials for extreme environment resistance, due to their excellent mechanical properties, chemical reaction inertia and high melting point. In this work, the effects of B₄C excess content on the densification,microstructure and high temperature flexural strength of medium entropy boride ceramics were studied for the first time, and the preparation process of（Ti,Zr,Hf）B₂ powder with low oxygen content and high sintering activity was synthesized. The entropy ceramic density of（Ti,Zr,Hf）B₂prepared by hot pressed sintering method at 1800℃ is over 99%, and the grain size of（Ti,Zr,Hf）B₂ceramics with excess content of 15 wt% B₄C is 5.0±2.1μm. As the excess content of B₄C increases to25 wt%, the grain size is significantly refined to 2.4±0.7μm. The part of excess B₄C reacts with Si₃N₄ introduced by ball milling, to produce BN phase by in situ reaction, while the other part of B₄C exists in the matrix as a second phase. The introduction of BN and B₄C phases can effectively suppress grain growth during the sintering process of medium entropy ceramics, while also improving the high-temperature flexural strength of the ceramics. When B₄C exceeds 25 wt%, the（Ti,Zr,Hf）B₂ medium entropy ceramics have the highest high-temperature flexural strength at 1600℃of 631±62MPa.更多还原