高性能金刚石纳米粉体的高压制备及性能调控

In this project, diamond nanopowders will be synthesized from onion carbon nanopowder precursors distinguished by particle size. We plan to investigate the structure evolution of onion carbon nanopowders before and after the phase transition under high pressure high temperature, and clarify the mechanism of phase transition. Also, we will characterize the microstructural features (e.g., particle size, average thickness of nanotwins within the particle, etc.), mechanical properties, and thermal stability of diamond nanopowders, and elucidate the relation between structures and properties. Through the implementation of this project, we expect to regulate the particle size, microstructure, and properties of diamond nanopowders with high pressure, and develop an effective method to prepare diamond nanopowders with good crystallinity, excellent mechanical properties, high thermal stability, and controllable particle size.

本项目拟采用不同粒径范围的洋葱碳纳米粉前驱体制备金刚石纳米粉体。我们将研究高温高压条件下洋葱碳纳米粉前驱体相变前后的结构演化规律，阐明相变机制；表征金刚石纳米粉体的显微组织结构特征（颗粒大小、颗粒内孪晶的平均厚度等）、力学性能及热稳定性，阐明结构与性能的内在联系；实现孪晶结构的金刚石纳米粉体粒径、组织结构和性能的高压调控，发展出结晶性好、力学性能优异、热稳定性高、粒径可控的金刚石纳米粉体的高效制备技术。

本项目围绕高性能金刚石纳米粉体的高压制备、性能调控以及金刚石材料显微结构调控开展研究，成功制备了平均粒径低于100nm的孪晶结构金刚石和cBN纳米粉体，并对其结构进行了细致的表征；实现金刚石块材相关力学性能的进一步优化及调控。合成了纳米孪晶金刚石超硬复合材料，该材料在继承了纳米孪晶金刚石块材极高硬度的同时，由于孪晶增韧、层压复合增韧、相变增韧效应的协同作用，其断裂韧性高达26.6MPa·m^1/2，是人工合成金刚石断裂韧性的5倍，已高于镁合金且与铝合金相当；合成出具有择优取向的纳米孪晶金刚石块材，该块材中长度2-10μm、宽度200nm的纳米孪晶束择优取向，平均孪晶厚度低至2.9nm。这种独特的显微结构赋予金刚石块材力学性能极大的各向异性，在平行孪晶取向和垂直孪晶取向的方向上，块材的努氏硬度分别为129±9GPa和233±8GPa。相关研究加深了人们对共价材料体系增硬增韧机制的理解，为进一步设计合成高力学性能共价材料提供了重要指导。