Diamond micropowder synthesis via graphite etching in a microwave hydrogen plasma

Diamond micro powders have been synthesized by chemical vapor deposition via etching a graphite substrate in hydrogen microwave plasma, without a hydrocarbon (methane) gas addition. The graphite temperature, varying from 700 to 1000 degrees C, was found to significantly affect the diamond nucleation and growth, the growth rate of the diamond particles increasing from 2.4 to approximate to 4 mu m/h with the temperature. The diamond powders had a better crystalline quality at the substrate temperature of 900 degrees C. Because of low adhesion of the deposited grit to the substrate the particles can be collected easily and mechanically disaggregated. The average size of 12 pm of the dispersed particles grown for 5 h, was determined with a laser particle size analyzer, while the maximum grain size estimated with electron microscopy, varied between 12 and approximate to 20 mu m. The particle's surface exhibited many micro-pyramids with sharp tips, that could be beneficial for abrasive applications. X-ray diffraction and Raman spectroscopy revealed high purity and quality of the diamond powders. (C) 2017 Elsevier B.V. All rights reserved.