Synthesis of new materials through microwave discharge initiated by pulses of high power gyrotron in the mixtures of metal and dielectric powders

Abstract

Herein we describe a new plasma chemical method for synthesis of new materials. Plasma was generated as a result of microwave discharge initiated by pulses of high power gyrotron in the mixtures of metal and dielectric powders. The gyrotron operates at frequency of 75 GHz giving pulses with duration of 2-12 ms and power up to 550 kW. Mixtures of Al with Al2O3, AlN, melamine and NH4Cl were treated with the pulses in the specially constructed plasma chemical reactor, which allowed to collect products of the process and to carry out real time monitoring of the process with low- and high-speed cameras and spectrometers. We observed a complicate oscillating process, which led to formation of micro dispersed materials containing phases usually formed at high temperatures. It was shown that plasma temperature in all the experiments was at least 2500 K in all reaction areas and above 3500 K in main reaction zone. We also realized that addition of hydrogen-containing substances (e.g. C2B10H12) resulted in a noticeable intensification of the process - highly likely due to the change of reactions pathways through an involvement of hydrogen into the intermediate stages. Obtained data confirm that microwave discharge is a promising method for synthesis of new materials including fine structure materials, e.g. consisting of major phase micro particles covered with a thin layer of minor phase.