High pressure synthesis of new super hard materials in the boron suboxide system and their functional evaluation

在二十面体硼团簇的菱面体晶胞空腔内含有氧原子或轻金属的亚氧化硼系统中的新型超硬材料，在高压下与其他超硬材料复合烧结。研究了复合材料的力学性能、化学性能和电学性能。项目期间取得的主要成果和结论总结如下。亚氧化硼(B_6O)及其与金刚石的复合材料高压烧结是一种化学稳定性高的超硬材料，也是近年来热电转换的靶材。然而，这种材料非常脆，很难烧结，因此它作为工业材料的实际应用被推迟了。本研究以B_2O_3和无定形硼为原料，采用高压烧结法制备了B_6O单相烧结体，并对其力学性能和热性能进行了研究。为了在不降低硬度的前提下提高压坯的断裂韧性，研究了B6O与金刚石的二元复合体系。在使用细晶金刚石粉的情况下，制备了具有较高断裂韧性的超硬复合材料，其室温电导率高达10^&lt；-3；S/cm。高压烧结及其与其他超硬材料的复合材料也是一种超硬材料，具有类似于B_6O的晶体结构，并有望表现出更高的机械强度。以本实验室合成的粉末为原料，首次在高压下制备了AlMgB_(14)&gt；的单相烧结体。这种压坯的硬度高达B_6O，但断裂韧性也很低。用B_6O或TiB_2组成的AlMgB_(14)&Gt；复合体系具有较高的硬度，但断裂韧性较低。

New super-hard materials in the boron suboxide system, which contains oxygen atom or light mmetals in the cavity of the rhombohedral unit cell of icosahedral boron clusters, were sintered in composite with other super-hard material under high pressure. The mechanical properties of these composites were investigated along with their chemical and electrical properties. The main results and conclusions in the project term were summarized as follows.1. High pressure sintering of boron suboxide (B_6O) and its composite with diamondB_6O is known as a super-hard material with high chemical stability and also a target material for thermoelectric conversion recently. However, this material is so brittle and difficult to sinter that its actual application as an industrial material is delayed. In the present study, we prepared the sintered compact of B_6O by high pressure sintering of B_6O powder synthesized from B_2O_3 and amorphous boron, and elucidated the mechanical and thermal properties of B_6O single phase sintered compact. In order to enhance the fracture toughness of the compact without decreasing its hardness, the binary composite system of B_6O and diamond was investigated. In case of using fine-grained diamond powder, a superl-hard composite with an increased fracture toughness was prepared and its electrical conductivity at room temperature was as high as the magnitude of 10^<-3> S/cm.2. High pressure sintering of AlMgB_<14> and its composite with other super-hard materialAlMgB_<14> is also a super-hard material with analogous crystal structure to B_6O and expected to exhibit higher mechanical strength. Single phase sintered compact of AlMgB_<14> was prepared originally under high pressure using the powder synthesized in our laboratory. This compact showed the hardness as high as B_6O, though the fracture toughness was similarly low. Presentation of the composite systems of AlMgB_<14> with B_6O or TiB_2 resulted in higher hardness, hut lower fracture toughness.