过剩压法合成金刚石的表面特征与体缺陷的形成原因分析

利用不同的高温高压条件在石墨-Ni70Mn25Co5体系中合成出金刚石晶体.借助于多功能光学显微镜的明场和暗场观察,分析了金刚石几种常见晶面的表面特征和内部缺陷.实验观察到一些有规律性的生长现象:当过剩压力太大时,较低的合成温度容易形成骸晶;当过剩压力适度时,较低的合成温度会使金刚石产生大量的包裹体并形成枝蔓状的粗糙表面,而较高的合成温度导致金刚石形成生长台阶;当压力有明显的波动时,金刚石晶体出现层状结构甚至间断生长.在此基础上,提出了合成优质金刚石的必要条件.

Analysis of Surface Features and Body Defects in Diamond Synthesis Based on Excess-pressure Method

Diamond crystals were synthesized from graphite-Ni70Mn25Co5 system under high pressure and high temperature. With the help of bright or dark field of a multi-function optical microscope, the features on some common surfaces and the interior defects of diamonds were investigated. Some regular phenomena of diamond growth were observed. Diamond crystals with frame growth are synthesized at high excess-pressure. Diamonds with inclusions in the interior and dendritic patterns on the surfaces are made at a moderate pressure but relatively low temperature. Octahedral diamonds with growth steps are produced at a moderate pressure but relatively high temperature. Diamonds with laminated and even discontinuous growth are manufactured at strikingly fluctuating pressures. On the basis of the analysis, some necessary synthetic conditions were suggested for quality-diamond.