The Surface Graphitization of Diamond Grains in the Process of Sintering Polycrystalline Diamond

The surface graphitization of diamond grains, which is induced in the process sintering polycrystalline diamond under high pressure, is studied. The results of analysis by micro-area X-ray diffraction, XPS and laser Raman spectrum etc. show that no graphitization is detected in the area where the doped agents have not been liquefied or permeated although the sintering process was undergone. The most active period of the surface graphitization is at the moment when he doped agents are just liquefied and permeated into the spaces among diamond grains. The surface graphite of diamond grains will be eliminated and the sintering of polycrystalline diamond will be completed with the spaces being filled fully and the doped agents reacting with the diamond grains.