Fabrication of diamond nanopowder using microwave plasma torch technique

This article presents a manufacturing process for diamond nanopowder by using a microwave plasma torch technique in a laboratory at near atmospheric pressure. The unique technique utilized in the arrangement is the hybrid plasma torch which was patented in 1997 by Dr. Cheng-Ming Wu in Taiwan. It has the advantage of working at near atmospheric pressure and does not require an extreme vacuum system, which is a necessary condition for fabrication of a large amount of nanoparticles. The applied constituents of gas mixtures for synthesizing diamond nanopowder in the process are CH4 with AR and CH4 with N-2, where AR and N-2 serve as catalysts. In processing the reaction chamber, it is first pumped to varied pressures from 40-300 Torr to induce plasma; then, the input reactive gas CH4 is fixed at a constant flow rate of 0.6 l/min and mixed up with varied input flow rate of the catalysts Ar and N-2 from 0.6-1.2 l/min. The particle size of synthesized diamond nanopowder is within about 25--50 nm diameter, which mainly depends on flow rate of CH4:AR and CH4:N-2.