Experimental Evidence for Nucleation and Growth Mechanism of Diamond by Seed-Assisted Method at High Pressure and High Temperature

• Published in: Crystal growth & design 2010-07, Vol.10 (7), p.2895-2900
• Main Authors: Liu, Xiaobing, Jia, Xiaopeng, Guo, Xinkai, Zhang, Zhuangfei, Ma, Hong-an
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Fullerenes and related materials; diamonds, graphite; General studies of phase transitions; Materials science; Methods of crystal growth; physics of crystal growth; Nucleation; Physics; Solid-solid transitions; Specific materials; Specific phase transitions; Theory and models of crystal growth; physics of crystal growth, crystal morphology and orientation
• ISSN: 1528-7483; 1528-7505
• DOI: 10.1021/cg901168s

In this paper, the diamond growth mechanism at high-pressure and high-temperature (HPHT) conditions from solvent-graphite system was investigated by growing diamond on different seeds and tracking the particular shapes of the seeds before and after treated under HPHT conditions. According to the results, we established a direct correlation between the morphology of the diamond and the original shape of the seeds. The crystallization of carbon phases (diamond-graphite) in the Fe−Ni−C system is depicted in detail in the P−T diagram. Experimental results show the synthetic pressure obviously decreases when diamond seed crystals are added into the original synthetic system, which confirms that the energy barrier of the diamond nucleation is higher than that of growth. In addition, we detected in our experiments that the diamond growth at HPHT conditions belongs to two-dimensional growth. Furthermore, we also found crystal direction and original shape of seed play important roles in the formation of diamond morphology in the early growth stage and the synthetic temperature will further affect the crystal shape in the following growth process.