纳米结构TaC高温高压烧结体硬度的研究

Study of the Hardness of Nanostructured HTHP TaC Sinter

采用国产DS6×800T铰链式六面顶压机技术,对纳米结构碳化钽(TaC)粉末样品进行了高温高压烧结,并进行了物理表征。在加载负荷为29.4N时,烧结压力为3GPa,烧结温度分别为1100℃和1300℃时,测试得到纳米结构TaC烧结体的硬度分别为16.5±0.5和17.2±0.4GPa。当我们把烧结压力升高到4GPa,烧结温度仍分别为1100℃和1300℃时,测试得到烧结体的硬度分别为17.0±0.3和19.2±0.6GPa。说明超高压力更有利于使样品致密化,并同时可以降低烧结温度。为了比较,我们将添加了体积比为5%钴(Co)粘结剂的纳米结构TaC粉末烧结体进行了烧结和硬度测试,发现其在烧结压力为3GPa、烧结温度为1100℃时的硬度下降为11.3±0.8GPa。根据断裂韧度与硬度和杨氏模量之间的关系,进一步得到了纳米结构TaC的平均断裂韧度为5.0±0.2 MPa m^(1/2)。通过基于密度泛函理论的第一性原理,模拟计算得到TaC的硬度为20GPa,并与实验值进行了比较。

Nano-structured tantalum carbide（TaC）powder sample has been sintered under high temperature and high pressure（HTHP）conditions through domestic DS6×800T hinge type cubic press technology by Qinghai University and the physical characterization of it has been recorded.The hardness of nano-structured TaC sinter are 16.5±0.5and17.2±0.4GPa respectively at temperature of 1100 ℃ and 1300 ℃ under load of 29.4N and sintering pressure of 3 GPa.When the sintering pressure increases to 4 GPa,the hardness of the sinter are 17.0±0.3and 19.2±0.6GPa respectively under the same temperature of 1100℃and 1300℃.The result indicates that the ultrahigh pressure will help to densify the samples and reduce the sintering temperature.For the sake of comparison,we have conducted a sintering and hardness test for nano-structured TaC powder sinter with 5% volume ratio of Co binder.Result shows that when the sintering pressure is at 3GPa and the temperature is at 1100 ℃,the hardness of it drops to 11.3±0.8GPa.According to the relationship between fracture toughness and Young modulus,the average fracture toughness of nano-structured TaC has been calculated as 5.0±0.2 MPa m1/2.The hardness of TaC has been calculated as 20 GPa through analog computation according to the first principle calculation based on density function theory.The figure has been compared with the experiment value.