Fe-C-H_2O体系中金刚石成核特性

NUCLEATION CHARACTERISTIC OF DIAMOND IN Fe-C-H_2O SYSTEM

用国产SPD6×1200型六面顶压机,在Fe粉末触媒和石墨(Fe-C)体系中添加不同比例的H2O,高温高压条件下合成出了金刚石单晶。通过扫描电子显微镜和Mossbauer谱研究了合成样品中金刚石的成核状态和Fe-C-H2O体系中H2O对金刚石成核的影响。结果表明:在5.7GPa,1600℃条件下,当H2O的质量含量少于5%时,Fe-C-H2O体系可合成出金刚石;随着Fe-C-H2O体系中H2O含量的增加,样品中金刚石成核量逐渐减少;当H2O含量达到5%时,金刚石将不能成核生长。在合成过程中,Fe-C-H2O体系中的Fe与H2O首先发生氧化还原反应,生成FeO和FeHx。与Fe-C体系相比,H2O对金刚石成核具有明显的抑制作用,而且随着H2O含量的增加,抑制作用越明显。讨论了H2O对金刚石成核和生长抑制的机理。

Diamond single crystals were synthesized from an Fe powder-carbon powder（Fe-C） system added with different amounts of H2O,by a cubic press under high pressure and high temperature.The nucleation characteristics of diamond crystals and the effect of H2O content in the Fe-C-H2O system on the nucleation and growth of diamond were investigated by scanning electron microscopy and Mossbauer spectroscopy.The results show that when the content of H2O is less than 5% in mass in the Fe-C-H2O system,the diamond can be synthesized under a pressure of 5.7 GPa at 1 600 ℃,and the nucleation numbers of diamond decrease gradually with the increase of content of H2O.The diamond can be not nucleated when the content of H2O reached 5%.The result of oxidation-reduction reactions between Fe and H2O first forms FeO and FeHx in the Fe-C-H2O system,and then diamond nucleation occurs.Compared to the Fe-C system,the nucleation of the diamond can be restrained with the addition of H2O,and this effect becomes serious with the increase of the content of H2O.The mechanism of the restraint of nucleation and growth of diamond by H2O in Fe-C-H2O systems is discussed.