Due to the relatively small mass of solid particles present in many aerosol systems, the particles exhibit phenomena that are not observed in systems composed of more massive particles. One such phenomenon of interest is thermophoretic deposition, which refers to the tendency of light particles that are suspended in a warm fluid to deposit on relatively cool surfaces. The phenomenon of thermophoresis occurs when a particle is suspended in a gas of nonuniform temperature; because the particle is bombarded by molecular collisions with greater force on the "hot side" (due to the higher velocity of "hot" molecules), the particle acquires a velocity in the direction of decreasing temperature gradient. The resulting deposition on cool surfaces plays an important role in a wide variety of applications; efforts here are focused on deposition that occurs in aerosol flow reactors.

Research Areas of Interest

Effect of Buoyancy on Thermophoretic Deposition. Although aerosol flow reactors can be used to synthesize a wide variety of advanced materials, thermophoretic deposition in these systems can lead not only to product loss, but also to reactor blockage. In this project, the production of aluminum nitride in a vertical reactor is being considered. Because this reaction is exothermic, product particles have a tendency to deposit on the relatively cool reactor walls. A mathematical model that accounts for both the gas phase and the solid phase is currently being used to ascertain the effects of buoyancy on thermophoretic deposition. This work is being done in collaboration with Prof. Alan Weimer of the Department of Chemical Engineering, University of Colorado and Prof. Sotiris Pratsinis, ETH, Zurich.