Investigation of Nanoparticle Formation Using a Plasma Expansion Process

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It is proposed an experimental and theoretical study of nanoparticle synthesis using a plasma process. Silicon carbide particle synthesis will be studied as a model of systems which involve chemical nucleation of microcrystals. The experimental apparatus will consist of a thermal plasma reactor into which reactants are injected and then expanded through a converging nozzle. Particles will nucleate in the nozzle, and then will exit to a free expansion so that coagulation is suppressed. The advantages of this approach are that (1) the process is capable of generating nanosize particles with narrow size distributions; (2) the nozzle flow environment can be well-characterized; (3) key process variables such as cooling rates can be controlled; and (4) the processcan be scaled for high-rate industrial production. A hypersonicimpactor located immediately downstream of the nozzle will be used to collect particles as small as 5 nm. Particles will be characterized by techniques such as scanning tunneling microscopy and high resolution transmission electron microscopy. A theoretical model will be developed which corresponds to the experimental conditions, and which combines first-principles molecular dynamics calculations of cluster properties with a dynamic model for particle nucleation and growth. The knowledge and technology base will be develop for nanoparticle synthesis in a plasma reaction, with a broad range of applications for advanced materials.