Thermal conductivity and hardness of three single-phase high-entropy metal diborides fabricated by borocarbothermal reduction and spark plasma sintering
Thermal conductivity and hardness of three single-phase high-entropy metal diborides fabricated by borocarbothermal reduction and spark plasma sintering
复制标题
DOI：
10.1016/j.ceramint.2019.11.186
复制
发表时间：
2020-04-01
影响因子：
5.2
通讯作者：
Luo, Jian
中科院分区：
文献类型：
--
作者：
Gild, Joshua;Wright, Andrew;Luo, Jian
用碳化硼和石墨对金属氧化物进行硼碳热还原，再进行放电等离子烧结，合成了四种高熵金属二硼化物并进行了致密化。其中（Hf0.2Zr0.2Ti0.2Ta0.2Nb0.2）B-2、（Hf0.2Zr0.2Ti0.2Ta0.2Mo0.2）B-2和（Hf0.2Zr0.2Ti0.2Ta0.2Cr0.2）B-2具有单一的高熵相，烧结密度达到理论密度的99%。第四个（Hf0.2Zr0.2Ti0.2Mo0.2W0.2）B-2试样除含有原生金属二硼化物相外，还含有富含Ti-Mo-W的二次相。硼碳热还原法制备的样品硬度比高能球磨和火花等离子烧结法制备的样品有明显提高。有趣的是，单相（Hf0.2Zr0.2Ti0.2Ta0.2Mo0.2）B-2和（Hf0.2Zr0.2Ti0.2Ta0.2Cr0.2）B-2（两者的维氏硬度值均为-25 GPa）比（Hf0.2Zr0.2Ti0.2Ta0.2Nb0.2）B-2 （20.5 GPa）硬得多，尽管MoB2和CrB2通常被认为是较软的成分。这些单相高熵金属二硼化物的热导率较低，为12 ~ 25 W/mK，约为HfB2和ZrB2的1/10 ~ 1/5。
Four high-entropy metal diborides have been synthesized and densifled by borocarbothermal reduction of metal oxides with boron carbide and graphite and subsequent spark plasma sintering. Three of them, (Hf0.2Zr0.2Ti0.2Ta0.2Nb0.2)B-2, (Hf0.2Zr0.2Ti0.2Ta0.2Mo0.2)B-2, and (Hf0.2Zr0.2Ti0.2Ta0.2Cr0.2)B-2, possess single high-entropy phases and have been sintered to > 99% of the theoretical densities. The fourth (Hf0.2Zr0.2Ti0.2Mo0.2W0.2)B-2 specimen contained a Ti-Mo-W rich secondary phase in addition to the primary metal diboride phase. The specimens made by borocarbothermal reduction exhibit improved hardnesses in comparison with those samples previously fabricated via high energy ball milling and spark plasma sintering. Interestingly, the single-phase (Hf0.2Zr0.2Ti0.2Ta0.2Mo0.2)B-2 and (Hf0.2Zr0.2Ti0.2Ta0.2Cr0.2)B-2 (both of which have Vickers hardness values of -25 GPa) are substantially harder than (Hf0.2Zr0.2Ti0.2Ta0.2Nb0.2)B-2 (20.5 GPa), despite MoB2 and CrB2 being typically considered as softer components. These single-phase high-entropy metal diborides were found to have low thermal conductivities of 12-25 W/mK, which are similar to 1/10 to similar to 1/5 of the reported values of HfB2 and ZrB2.