Pangilinan Lisa E, Turner Christopher L, Akopov Georgiy, Anderson Mackenzie, Mohammadi Reza, Kaner Richard B
Department of Chemistry , Iowa State University , Ames , Iowa 50011 , United States.
Ames Laboratory , U.S. Department of Energy , Ames , Iowa 50011 , United States.
Inorg Chem. 2018 Dec 17;57(24):15305-15313. doi: 10.1021/acs.inorgchem.8b02620. Epub 2018 Dec 5.
Solid solutions of tungsten diboride (WB) with increasing substitution of tungsten (W) by tantalum (Ta) and niobium (Nb)-ranging from 0 to 50 at. % on a metals basis-were synthesized through resistive arc melting. Samples were characterized using a combination of powder X-ray diffraction (PXRD) for phase identification, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy for elemental composition, Vickers microindentation for hardness measurements, and thermogravimetric analysis for thermal stability. The solubility limit was found to be less than 8 at. % for Nb and less than 10 at. % for Ta, as determined by PXRD. Vickers hardness ( H) values were measured to be 40.3 ± 1.6 and 41.0 ± 1.2 GPa at 0.49 N for 6 at. % Nb and for 8 at. % Ta substitution, respectively. In addition, the hardest solid solution (WTaB) showed oxidation resistance up to ∼570 °C, approximately 70 °C higher than that of tungsten carbide (WC). Although pure WB is known not to be superhard, these results demonstrate the formation of superhard solid solutions through the substitution of tungsten by small amounts of transition metals. This increase in hardness can be attributed to solid solution hardening.
通过电阻电弧熔炼合成了二硼化钨（WB）的固溶体，其中钨（W）被钽（Ta）和铌（Nb）取代的比例不断增加——基于金属计算，范围为0至50原子百分比。使用粉末X射线衍射（PXRD）进行相鉴定、能量色散X射线光谱和X射线光电子能谱进行元素组成分析、维氏显微硬度测试进行硬度测量以及热重分析进行热稳定性分析，对样品进行了表征。通过PXRD确定，Nb的溶解度极限小于8原子百分比，Ta的溶解度极限小于10原子百分比。在0.49 N的载荷下，对于6原子百分比的Nb取代和8原子百分比的Ta取代，维氏硬度（H）值分别测量为40.3±1.6 GPa和41.0±1.2 GPa。此外，最硬的固溶体（WTaB）在高达约570°C的温度下表现出抗氧化性，比碳化钨（WC）的抗氧化温度高约70°C。尽管已知纯WB不是超硬的，但这些结果表明通过用少量过渡金属取代钨形成了超硬固溶体。硬度的增加可归因于固溶强化。
