Effect of Technological Parameters on Synthesis ofⅡa Type Synthetic Diamonds by HPHT
In response to the issues of low nucleation crystal sead,a small proportion of high-quality crystals,and numerous growth defects in the synthesis of type II a diamonds formed by a cubic press at high temperature and high pressure in China,this paper optimized the process parameter curves before and after the crystal synthesis.The results show that the optimal process plan is as follows.In the first 20 h of the growth stage,the diamond is slowly heated under low temperature and high pressure environment and taken insulation measures for a period of time.Then the constant power is heated to the set temperature,where the diamond grows for 3 days under high temperature and pressure.Within 2 h after the synthesis,the low-speed pressure relief with heating power in phases is adopted,which effectively controls the defects such as cracks and metal inclusions and improves the quality of synthetic crystals.The final number of seed nucleation is 25,and the proportion of excellent crystals is 92%.
high temperature and high pressuretype Ⅱa synthetic diamondsynthesis stagenumber of nucleated granulesoptimal crystal ratecrackmetal inclusion
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