EFFECTS OF GRAVITY AND TEMPERATURE-GRADIENT ON THE DIAMOND FORMATION DURING SYNTHESIS AT 4.4-GPA AND 1300-DEGREES-C

Abstract

In diamond synthesis, it is observed that the number of diamond particles on each solvent surface are determined by the coupled effects of gravity and temperature gradient in the specimens. At the beginning of the diamond synthesis, the effect of temperature gradient is relatively stronger than that of gravity, which makes more diamond particles form on the bottom surface of the lowest solvent layer in the bottom cool end. As the synthesis proceeds, the diamond particles grow and float up through the liquid solvent from the bottom surface to the top surface. Buoyancy due to the difference in the specific gravities of diamond and liquid solvent causes a difference in the number of the diamond particles formed on the top and bottom surfaces of each solvent layer. More diamond particles are always observed on the top surfaces of the solvent layers than on the bottom surfaces in the respective solvent layers, except for the lowest solvent layer at the beginning of the synthesis.