An atmospheric microwave plasma jet for ceramic material processing

Ceramic fibres are used in fibre reinforced polymer composites and cermets to improve their mechanical, thermal and chemical properties. This paper describes a microwave plasma system that is being developed to produce these fibres from a spinning ceramic rod. The system operates at 2.45 GHz and uses a waveguide-based applicator to generate a microwave plasma jet (MPJ) at atmospheric pressure. The plasma is formed outside the cavity due to the strong electric field, generated by the microwave power, which occurs between the gas nozzle and an aperture in the applicator. The MPJ system has produced plasmas using a variety of gases and gas mixtures, including argon, helium, oxygen and nitrogen. This paper describes how the properties of the plasma jet can be tailored to suit different tasks, by adjusting the various parameters such as the type of the gas, the power, the nozzle aperture size and the flow rate, and how the speed of the spinning ceramic rod can be controlled to vary the size of the particles produced. Results obtained using quartz glass and alumina are reported.