Abstract: To reduce the cost and improve the performance,ZrB₂ ceramics were prepared using ZrO₂,B₄C,and carbon black as the raw materials,with n(ZrO₂)∶n(B₄C)∶n(C) ratios of 2∶1∶3,2∶1.1∶3,2∶1.2∶3,2∶1.3∶3,by the boron/carbothermal reduction combined with hot pressing sintering.The probabilities and initial reaction temperatures of various reactions in the ZrO₂-B₄C-C system in different CO partial pressures (10⁵,10²,1,10^-2 Pa) were calculated using reaction thermodynamics.The effects of the n(ZrO₂)∶n(B₄C)∶n(C) ratios and the heat treatment temperatures (1 800,1 850,1 900,and 1 950 ℃) on the properties,phase composition,and microstructure of the specimens were investigated.The results indicate that:(1)low CO partial pressure significantly reduces the initial temperature of each reaction in the ZrO₂-B₄C-C system;(2)as the B₄C addition increases,the content of ZrB₂ increases;when n(ZrO₂)∶n(B₄C)∶n(C)=2∶1.2∶3,the oxygen content in the synthesized ZrB₂ powder (in the form of B₂O₃ and ZrO₂) is only 0.333 mass%;(3)with increasing heat treatment temperature,the specimen density and hardness gradually increase,while flexural strength and fracture toughness initially increase and then decrease;when the heat treatment temperature is 1 900 ℃,the specimen exhibits the best comprehensive performance,with the relative density,fracture toughness,flexural strength,and cold hardness of 91.75%,4.87 MPa·m^1/2,525 MPa,and 18.6 GPa,respectively

Key words: boro/carbothermal reduction, hot pressing sintering, ZrB₂, mechanical properties

摘要： 为降低制备成本,提高ZrB₂陶瓷的性能,以ZrO₂、B₄C、炭黑为原料,按n(ZrO₂)∶n(B₄C)∶n(C)分别为2∶1∶3、2∶1.1∶3、2∶1.2∶3、2∶1.3∶3配料,采用硼/碳热还原结合热压烧结法原位制备了ZrB₂陶瓷。利用反应热力学计算了不同CO分压(10⁵、10²、1和10^-2 Pa)下ZrO₂-B₄C-C体系中各反应发生的概率和起始反应温度。研究了原料配比和热处理温度(1 800、1 850、1 900和1 950 ℃)对ZrB₂陶瓷试样性能、物相组成和显微结构的影响。结果表明:1)低CO分压显著降低该体系中各反应的起始温度;2)随B₄C加入量的增加,ZrB₂相含量增多,当n(ZrO₂)∶n(B₄C)∶n(C)=2∶1.2∶3时,制备出氧含量仅为0.333%(w)的ZrB₂粉(以B₂O₃和ZrO₂的形式存在);3)随热处理温度的升高,试样的致密度和硬度逐渐增大,弯曲强度和断裂韧性呈先上升后下降的趋势。当热处理温度为1 900 ℃时,试样的综合性能最佳,其相对密度、断裂韧性、弯曲强度和硬度分别为91.75％、4.87 MPa·m^1/2、525 MPa、18.6 GPa。

关键词: 硼/碳热还原, 热压烧结, ZrB₂, 力学性能