Microwave plasma processing of unique ceramic particulate materials

A novel technology for generating specifically particulate materials was developed. We have shown that the microwave generated atmospheric pressure plasma can be employed to create novel particulate materials. Yet, in our initial work we were only able to make simple correlation between operating parameters and material characteristics. Direct correlation between material modification and measured plasma characterization would enable the process to be scaled. In brief, the three stages of this thesis were: Understanding novel particulate generation technology, thorough characterization of the afterglow region of the plasma, and finally developing a model of the coupler region of a low pressure plasma.; The material processing focused on developing a new technique for generating spherical alumina particles of controlled size. This development led to a patent. In brief, we showed that passing an aerosol containing irregularly shaped precursor particles, could be controlled to generate spherical ceramic particles of selected size. A mechanistic model of growth successfully explained observations. First, particles melt in the plasma hot zone, next they collide with others to form larger agglomerates and finally they are quenched to form the solid spherical particles in the afterglow region.; A thorough and systematic investigation of the afterglow region of an atmospheric pressure argon plasma under various operating conditions was performed. It was shown that the plasma is not in an equilibrium state. That is, the gas, electron and excitation temperatures of the plasma are greatly different. This points out that a multi-temperature model is more appropriate than the one-temperature model. This experimental data is valuable for future modeling work, as well as possible processing optimization strategies.; Finally, a novel multi-temperature model of a low-pressure microwave plasma was developed. We successfully solved the Boltzmann equation for a low pressure microwave generated hydrogen plasma. Taken together with an appropriate set of reactions and iteration procedure this has enabled us to determine the electron energy distribution function as well as the density and temperature of all the other species present. The model developed was not for the plasma employed in material modification. It is a simpler system, and hence represents a step along the path toward modeling a high pressure, multi-temperature microwave generated plasma.