Synthesis of Submicron Diamond Powders by CO₂-Laser Pyrolysis of C₂H₄

Abstract

Diamond powders with grain diameters up to 0.3 μm were obtained by CO₂-laser induced decomposition of C₂H₄ and mixtures of C₂H₄/H₂/SiH₄ at low pressures and temperatures in a gas-flow reactor. Solid products were produced in a yellow-to-orange coloured flame (500–550°) and collected in filters. The product contained polyaromatic species, high molecular polymers, graphite, amorphous carbon, and spherical diamond particles. Several diamond particle populations, with mean diameters of 6.2–122 nm, were observed by transmission electron microscopy. Both diamond modifications, cubic and hexagonal, were identified by electron diffraction.