铁基触媒中金刚石单晶的生长对初生渗碳体的消耗

利用扫描电子显微镜观察了不同合成时间的金刚石合成效果以及相应触媒的组织结构,结果表明:随着压力、温度的升高,铁基触媒全部熔化为液态后约20秒内,熔体对碳的溶解度可达到极大的过饱和程度,生成数量极大的初生渗碳体,同时,金刚石单晶在这种环境中生成。随着时间的延长,金刚石单晶长大、数量增多,熔体对碳的过饱和程度逐渐降低。触媒组织中的初生渗碳体量逐渐减少。分析表明:石墨碳与触媒首先发生冶金反应生成初生渗碳体,在高温高压作用下,初生渗碳体分解,碳原子脱溶,然后堆积到金刚石上。金刚石的生长通过对初生渗碳体的消耗得以进行。

Single Crystal Diamond Growth Depending on Consumption of Original Cementite in Iron-based Catalyst

SEM was used to investigate the structures of catalyst and corresponding synthetic effect of diamonds grown in different times.The results showed that with the increase of temperature and pressure,a considerable amount of original cementite formed within 20 seconds after the iron-based catalyst melted completely,and the carbon solubility reached a maximum saturation.At the same time single crystals diamond were produced in that condition.The prolonging time would cause the single crystals diamond to grow up,quantity increase,carbon supersaturation of solution reduce and original cementite decrease in the structure of catalyst.Analyses demonstrated that the graphite carbon reacted with the metal catalyst and produced an original cementite.Carbon atoms decomposed from the original cementite and accumulated on the diamond surface under the high-pressure and high-temperature.So the diamond growth up depends on the consumption of original cementite.