Toward Inexpensive Superhard Materials: Tungsten Tetraboride-Based Solid Solutions
Toward Inexpensive Superhard Materials: Tungsten Tetraboride-Based Solid Solutions
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DOI：
10.1021/ja308219r
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发表时间：
2012-12-26
影响因子：
15
通讯作者：
Kaner, Richard B.
中科院分区：
文献类型：
--
作者：
Mohammadi, Reza;Xie, Miao;Kaner, Richard B.
为了提高四硼化钨（WB 4）的硬度，四硼化钨是后过渡金属硼化物中成本较低的成员，我们已经合成并表征了这种材料与钽（Ta）、锰（Mn）和铬（Cr）的固溶体。这些过渡金属元素的各种浓度，范围从0.0至50.0原子。%，以金属为基础。采用电弧熔炼法从纯元素中合成了这些难熔化合物。利用X射线能谱仪（EDS）和X射线衍射仪（XRD）分析了样品的元素纯度和相纯度，并利用显微硬度计测量了在0.49-4.9 N载荷下的维氏硬度。XRD结果表明，其溶解度极限低于10 at. %的Cr和低于20 at. %，而Ta可溶于高于20 at. %.当与2.0、4.0和10.0 at.相似时，在0.49 N的施加载荷下，实现了52.8 +/- 2.2、53.7 +/- 1.8和53.5 +/- 1.9 GPa的优化维氏硬度值。%的Ta、Mn和Cr分别添加到WB 4中。受这些结果的启发，产生WB 4的三元固溶体，保持WB 4中Ta的浓度固定在2.0 at. %和改变Mn或Cr的浓度。这导致组合W0.94Ta0.02Mn0.04B4和W0.93Ta0.02Cr0.05B4的硬度值分别为55.8 +/- 2.3和57.3 +/-1.9GPa（在0.49N的载荷下）。原位高压XRD测量收集到高达65 GPa产生的体积模量为335 +/- 3 GPa的最硬的WB 4固溶体，W0.93Ta0.02Cr0.05B4，并显示抑制压力诱导的相变先前观察到的纯WB 4。
To enhance the hardness of tungsten tetraboride (WB4), a notable lower cost member of the late transition-metal borides, we have synthesized and characterized solid solutions of this material with tantalum (Ta), manganese (Mn), and chromium (Cr). Various concentrations of these transition-metal elements, ranging from 0.0 to 50.0 at. %, on a metals basis, were made. Arc melting was used to synthesize these refractory compounds from the pure elements. Elemental and phase purity of the samples were examined using energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD), and microindentation was utilized to measure the Vickers hardness under applied loads of 0.49-4.9 N. XRD results indicate that the solubility limit is below 10 at. % for Cr and below 20 at. % for Mn, while Ta is soluble in WB4 above 20 at. %. Optimized Vickers hardness values of 52.8 +/- 2.2, 53.7 +/- 1.8, and 53.5 +/- 1.9 GPa were achieved, under an applied load of 0.49 N, when similar to 2.0, 4.0, and 10.0 at. % Ta, Mn, and Cr were added to WB4 on a metals basis, respectively. Motivated by these results, ternary solid solutions of WB4 were produced, keeping the concentration of Ta in WB4 fixed at 2.0 at. % and varying the concentration of Mn or Cr. This led to hardness values of 55.8 +/- 2.3 and 57.3 +/- 1.9 GPa (under a load of 0.49 N) for the combinations W0.94Ta0.02Mn0.04B4 and W0.93Ta0.02Cr0.05B4, respectively. In situ high-pressure XRD measurements collected up to 65 GPa generated a bulk modulus of 335 +/- 3 GPa for the hardest WB4 solid solution, W0.93Ta0.02Cr0.05B4, and showed suppression of a pressure-induced phase transition previously observed in pure WB4.