新型超高硬度纳米聚晶金刚石的合成研究

Polycrystalline diamond with grain size of several micrometers, hundreds nanometers, dozens nanometers, and less than 20 nanometers will be synthesized by the direct conversion method and powder sintering method in the project. The polycrystalline diamond has a homogeneous fine structure that consists of fine-grained diamond particles which are randomly oriented, and has a Knoop hardness no less than 100 or 001 plane of single-crystal diamond. Both the influence of pressure, temperature and duration on the growth of diamond grains, and the relationship of grain size and mechanical properties of polycrystalline diamond (such as hardness) will be researched. The effects of grain size, morphology and distribution, the interfacial microstructure and grain binding manner also weill be investigated. High-performance polycrystalline diamond is not only considered as the next generation of super-hard materials, on behalf of the new direction of development of superhard materials and tools, but also further increase the pressure range of static high pressure science.

本项目将采用直接转化和粉末烧结的方法合成晶粒尺寸为几至十几纳米、几十纳米、几百纳米和数微米的聚晶金刚石块体。该聚晶金刚石块体的努普硬度不低于单晶金刚石的100或001面，具有微观组织结构单一、晶粒均匀的特点。本项目将获知压力、温度条件以及温/压度持续时间对金刚石晶粒生长影响的规律；晶粒尺寸与纳米聚晶金刚石块体力学性能（如硬度）之间的规律；并探索晶粒尺寸、界面形貌及分布、界面微观结构及晶粒间结合方式对多晶物质硬度的影响。高性能聚晶金刚石块体不仅被认为是下一代超硬材料，代表超硬材料工具新的发展方向，而且还能进一步提高静高压科学研究的压力极限。

使用自主设计的二级6-8型大腔体静高压装置的组装和加热结构，以玻璃碳为原料通过直接转化法成功制备纳米聚晶金刚石块体，初步得出当压力温度高于石墨向金刚石直接转化的温压条件时，温压作用时间对金刚石晶粒生长有较大的影响；此外还研究了硒体积占比、压力、温度、烧结时间对硒-多晶金刚石烧结体力学性能的影响，获得维氏硬度约为70 GPa的硒-多晶金刚石烧结体，同时发现硒与金刚石的反应条件至少约12.5 GPa、1850 ℃，高于硒与石墨的反应条件9.6 GPa、1850 ℃。这一发现将加深对金刚石触媒的认识，为工业生金刚石提供指导。