三元过渡金属硼化物Os1-xRuxB2的制备及其结构和性能研究

以高纯锇(Os)、钌(Ru)、硼(B)粉为原料, 在常温常压下采用机械化学法制备了三元过渡金属硼化物Os_1-xRu_xB₂粉末, 并对合成的粉末进行无压烧结使其致密化。研究了机械化学法合成Os_1-xRu_xB₂的反应过程、Ru含量对OsB₂相结构的影响、合成粉末的热稳定性及烧结后块体材料的力学性能。采用X射线衍射(XRD)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)对Os_1-xRu_xB₂粉末及块体的相成分、表面形貌和微观结构进行表征, 并通过维氏硬度计测得其烧结后块体材料的显微硬度。实验结果表明: 合成过程中生成了中间产物Os_1-xRu_xB_1.1, 随着球磨时间的延长有少量Os_1-xRu_xB₂生成, 球磨24 h后合成粉末的主相为Os_1-xRu_xB₂, 继续球磨到40 h, 粉末中相成分不再发生变化。当x≤0.1时, 合成粉末的主相为六方结构Os_1-xRu_xB₂; 而当x≥0.15时,合成粉末的主相为正交结构的Os_1-xRu_xB₂。经1450℃(保温1 h)热处理后的粉末中有部分六方结构的Os_1-xRu_xB₂向正交结构发生相变, 并生成了低硼化物 (Os_1-xRu_x)₂B₃。合成的OsB₂和Os_0.85Ru_0.15B₂粉末经1700℃无压烧结后颗粒呈板条状, 其致密度均为85%左右, 在0.49 N载荷下测得其硬度分别(27±2) GPa和(21±1) GPa。

Preparation,Microstructure and Property of Ternary Transition Metal Boride Os1-xRuxB2

Ternary Os_1-xRu_xB₂ powders were synthesized by using mechanical alloying (MA) technique with Os (Osmium), Ru (Ruthenium) and B (Boron) powders as raw materials. The synthesis process and effect of Ru content on phase composition, and thermal stability of the as-milled powders, and mechanical properties of the samples were studied. X-Ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to study chemical composition and microstructure of the as-synthesized powders and the as-sintered bulk samples. Result showed that Os_1-xRu_xB_1.1 was formed as an intermediate product during the formation process of solid-state reaction of Os_1-xRu_xB₂ from Os, Ru and B powders. After milled for 24 h, the main phase mixture powders were Os_1-xRu_xB₂ which kept unchanged till milled for 40 h. When x≤0.1, the main phase of the mixture powders was ReB₂-type Os_1-xRu_xB₂ with hexagonal structure; when x≥0.15, the main phase of the as-milled powders was RuB₂-type Os_1-xRu_xB₂ with orthogonal structure. After heat treatment at 1450℃ for 1 h, the ReB₂-type Os_1-xRu_xB₂ partially converted to the orthorhombic phase, while the structure of RuB₂-type Os_1-xRu_xB₂ kept unchanged. The as-sintered OsB₂ and Os_0.85Ru_0.15B₂ samples by pressure-less sintering at 1700℃ showed rod-like particles with small pores, the density of the two samples was about 85%, and the micro hardness under a load of 0.49 N was (27±2) GPa and (21±1) GPa, respectively.