Superfluous Carbon Source and Growth of Large Diamond Crystals

When growing large diamond crystals by temperature gradient method under high temperature and high pressure,if all the diffused carbon source from higher temperature region cannot be absorbed by the seed crystals,the different present forms of superfluous carbon source,regrown graphite or diamond nuclei,would have great effects on the growth process of large diamond crystals.Different from the diamond nuclei,when unabsorbed carbon source precipitates as the form of regrown graphite,the growth rate of large diamonds would be restrained greatly.For example,with NiMnCo alloy as the metal solvent,as the grown temperature increasing,when the diamond nucleus formed by superfluous carbon source is replaced by a large amount of flake regrown graphite,the growth rate decreases from 3.0mg/h at 1255℃ to 1.0mg/h at 1295℃.Also,with the pressure decreased from 5.5GPa to 5.2GPa,the growth rate also decreases from 3.0mg/h to 1.0mg/h,and the present form of unabsorbed carbon source changes from regrown graphite to diamond crystals.