Events Calendar

AME - Department Seminar

Speaker: Hai Wang , Professor Department of Aerospace & Mechanical Engineering University of Southern California

Talk Title: Nanoparticles - Transport Theory, Flame Synthesis and Selected Applications

Abstract: Synthesis of metal oxide nanoparticles in premixed stagnation flames offers significant advantages over other flame methods. Particles produced usually have good crystallinity, high phase purity, and narrow and controllable size distributions. Past studies have shown that when the stagnation surface is translated relative to the flame sheet, particle synthesis and film deposition can be achieved in a single step. The technique enables high-throughput film deposition and is scalable with respect to the deposition area. The first part of this talk will be on the stagnation flame technique for preparation of phase-pure titania nanoparticle films for applications in dye sensitized solar cells and for conductometric CO sensing.

It was recognized that a fine control of the particle property requires a rather precise knowledge about the time-temperature history of the particles behind the flame. Determined by the drag and thermophoretic forces acting on the growing cluster and nanoparticles, this history dictates the particle nucleation and size growth environment and time. This motivated us to re-examine the transport theories of nanoparticles in dilute gases. Through a gas-kinetic theory analysis, we obtained mathematical formulations for these forces in two limiting models of gas-particle interactions: specular and diffuse scattering. It has been shown that our expressions are more fundamental than the earlier Epstein expressions, and they offer the possibility of a unified description of particle transport, from molecules to cluster and nanoparticles. The origin of diffuse scattering has been explained by molecular dynamics. The remaining problem lies in a missing first-principle based description for the transition from elastic specular scattering to inelastic diffuse scattering at several nanometers of particle size, as will be discussed in detail.

More Info: http://ae-www.usc.edu/seminars/2-6-13-wang.shtml

Location: Seaver Science Library (SSL) - Room 150

Audiences: Everyone Is Invited

Contact: April Mundy

Event Link: http://ae-www.usc.edu/seminars/2-6-13-wang.shtml