Gas-Solid Reactions in Thermal Plasma Environments: Synthesis of Non-Oxide Ceramic Powders

摘要

General reactor design considerations andinterpretations for the formation mechanism of severalnon-oxide ceramic powders are presented, as well as thepossible chemical reactions involved in the processesunder the high temperatures generated in a thermalplasma. Silicon carbide, titanium carbide, titaniumdiboride, zirconium carbide, titanium carbide-iron andboron nitride powders have been synthesized using oxidesas precursors. For each ceramic system the precursorsare vaporized completely in the hot zone of the reactorwhere the plasma source is located; the vapors thentravel down the temperature gradient to meet conditionswhere specific chemical reactions may occur (withsubsequent nucleation and/or growth); this is followedby rapid quenching to minimize back reactions oradditional growth, thus enhancing the formation ofmetastable compounds that are consequently stabilizedat room temperature. A description of the reactor systemis presented along with theoretical and experimentalresults and conclusions from experiments.