Deposition of Carbon on Diamond Seed Crystals

摘要

The reaction rates of hydrogen with pyrolytically deposited graphite and with natural diamond powder were investigated in order to determine the optimal conditions for removing graphite from diamond. The work covered the temperature range from 1000C to 1100K and the pressure range from 52 to 69 atmospheres of hydrogen. At 52 atm. and 1271K the reaction rate of diamond is three orders of magnitude less than that of graphite, indicating that graphite can be selectively removed with little loss of diamond. The experimentally determined rate equations were used to compute plots of percent diamond reacted versus temperature with pressure, reaction time, and percent graphite removal as parameters. By using these figures, one can determine the optimal conditions for removing the graphite from the diamond subject to various constraints placed on the system. More depositions of carbon on diamond seed crystals were performed and net weight increases of the seed crystals observed. The deposited structure has a reaction rate with hydrogen similar to that of diamond. Preliminary X-ray diffraction studies show only the presence of sharp diamond lines. (Author)