铁基金属包膜内Fe_3C的行为与高温高压金刚石单晶生长

BEHAVIOR OF Fe_3C IN THE Fe-BASED METAL COVERING FILM AND DIAMOND SINGLE CRYSTAL GROWTH AT HTHP

利用电子探针、X射线衍射和扫描电镜等手段,表征了包围着高温高压金刚石单晶的铁基合金触媒和铁基金属包膜的组织结构.结果表明:随合成时间增加,金属包膜内呈现出越来越少的条状Fe_3C组织;金刚石生长较好时,包膜内则未发现条状Fe_3C.利用余氏理论分析了Fe_3C晶格内C—C键组成晶面和与之对应的金刚石晶面的共价电子密度,发现它们在一级近似下存在连续性,满足程氏理论提出的原子界面边界条件.据此分析认为,高温高压金刚石单晶的生长与铁基金属包膜内的Fe_3C分解有关.

Electron probe microanalysis （EPMA）, X-ray diffraction （XRD） and scanning electron microscope （SEM） were employed to investigate the metal thin film and solvent metal covering on diamond single crystal synthesised by Fe-based alloy catalyst and graphite plate at high temperature and high pressure （HTHP）. The results show that there existed less and less stripe Fe3C in the metal film as prolonged the synthesis time, and no stripe Fe3C was found in the metal film covering on super quality diamond. The covalent electron densities （obtained by empirical electron theory of solid and molecule, EET） of the crystal faces from C-C bonds in Fe3C are very close to those corresponding to the crystal faces in diamond, which accords with the boundary condition from the improved Thomas-Fermi-Dirac theory by Cheng （TFDC）. Hereby, diamond growth should be closely related to decomposition of Fe3C in the metal film.