Center for High Pressure Science (CHiPS), State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao, China.
Key Laboratory for Microstructural Material Physics of Hebei Province, School of Science, Yanshan University, Qinhuangdao, China.
Nature. 2022 Jul;607(7919):486-491. doi: 10.1038/s41586-022-04863-2. Epub 2022 Jul 6.
Understanding the direct transformation from graphite to diamond has been a long-standing challenge with great scientific and practical importance. Previously proposed transformation mechanisms, based on traditional experimental observations that lacked atomistic resolution, cannot account for the complex nanostructures occurring at graphite-diamond interfaces during the transformation. Here we report the identification of coherent graphite-diamond interfaces, which consist of four basic structural motifs, in partially transformed graphite samples recovered from static compression, using high-angle annular dark-field scanning transmission electron microscopy. These observations provide insight into possible pathways of the transformation. Theoretical calculations confirm that transformation through these coherent interfaces is energetically favoured compared with those through other paths previously proposed. The graphite-to-diamond transformation is governed by the formation of nanoscale coherent interfaces (diamond nucleation), which, under static compression, advance to consume the remaining graphite (diamond growth). These results may also shed light on transformation mechanisms of other carbon materials and boron nitride under different synthetic conditions.
理解从石墨到金刚石的直接转变一直是一个具有重大科学和实际意义的长期挑战。以前提出的转变机制基于缺乏原子分辨率的传统实验观察，无法解释在转变过程中石墨-金刚石界面上出现的复杂纳米结构。在这里，我们通过高角度环形暗场扫描透射电子显微镜，在从静态压缩中回收的部分转变的石墨样品中，识别出由四个基本结构基序组成的相干石墨-金刚石界面。这些观察结果为转变的可能途径提供了深入了解。理论计算证实，与以前提出的其他途径相比，通过这些相干界面的转变在能量上是有利的。石墨到金刚石的转变是由纳米级相干界面（金刚石成核）的形成控制的，在静态压缩下，这些界面会向前推进，消耗剩余的石墨（金刚石生长）。这些结果也可能为在不同合成条件下其他碳材料和氮化硼的转变机制提供启示。
