Abstract
The diamond-to-graphite transformation at diamond-stable conditions is studied by temperature gradient method (TGM) under high pressure and high temperature (HPHT), although it is unreasonable from the view of thermodynamic considerations. It is found that, at diamond-stable conditions, for example, at 5.5 GPa and 1550 K, with fine diamond grits as carbon source and NiMnCo alloy as metal solvent assisted, not only large diamond crystals, but metastable regrown graphite crystals would be grown by layer growth mechanism, and the abundance of carbon source in the higher temperature region is indispensable for the presence of metastable regrown graphite crystals. From this transformation, it is concluded that, with metal solvent assisted, although the mechanism of crystal growth could be understood by the macro-mechanism of solubility difference between diamond and graphite in metal solvents, from the point of micro-mechanism, the minimum growth units for diamond or graphite crystals should be at atomic level and unrelated to the kinds of carbon source (diamond or graphite), which could be accumulated free-selectively on the graphite with sp2п or diamond crystals with sp3 bond structure.
References
Bundy F P, Hall H T, Strong H M, et al. Man-made diamonds. Nature, 1955, 176: 51–55
Wentorf Jr R H. Some studies of diamond growth rates. J Phys Chem, 1971, 75: 1833–1837
Strong H M, Chrenko R M. Further studies on diamond growth rates and physical properties of laboratory-made diamond. J Phys Chem, 1971, 75: 1838–1843
Lerner E J. Industrial diamonds gather strength. The Industrial Physicist, 2002, August/September: 8–11
Shigley J E, McClure S F, Breeding C M, et al. Lab-grown colored diamonds from Chatham created gems. Gems Gemology, 2004, 40: 128–145
Xu B, Li M S, Yin L W, et al. Microstructure of metallic film and diamond growth from Fe-Ni-C system. Chinese Sci Bull, 2002, 47: 1258–1262
Li L, Xu B, Li M S. Analysis of the carbon source for diamond crystal growth. Chinese Sci Bull, 2008, 53: 937–942
Yang Z J, Li H Z, Peng M S, et al. Study on the HPHT synthetic diamond crystal from Fe-C(H) system and its significance. Chinese Sci Bull, 2008, 53: 137–144
Pavel E. Combinative mechanism of HP-HT catalytic synthesis of diamond. Physica B, 1998, 245: 288–292
Zang C Y, Jia X P, Ma H A, et al. Effect of regrown graphite on the growth of large gem diamonds by temperature gradient method. Chinese Phys Lett, 2005, 22: 2415–2417
Strong H M, Hanneman R E. Crystallization of diamond and graphite. J Chem Phys, 1967, 46: 3668–3676
Kanda H. Effect of solvent metals upon the morphology of synthetic diamonds. J Cryst Growth, 1989, 94: 115–124
Zang C Y, Huang G P, Ma H A, et al. Surface structure of large synthetic diamonds by high temperature and high pressure. Chinese Phys Lett, 2007, 24: 2991–2993
Cardew P T, Davey R J. The kinetics of solvent-mediated phase transformation. Proc R Soc Lond A, 1998, 398: 415–428
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Supported by the National Natural Science Foundation of China (Grant No. 50572-032), Foundation of He’nan Educational Committee (Grant No. 2009A430014), and Open Research Fund Program of State Key Laboratory of Superhard Materials of Jilin University (Grant No. 200801)
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Zang, C., Chen, X., Hu, Q. et al. Mechanism of diamond-to-graphite transformation at diamond-stable conditions. Chin. Sci. Bull. 54, 2535–2538 (2009). https://doi.org/10.1007/s11434-009-0401-2
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DOI: https://doi.org/10.1007/s11434-009-0401-2