Studies of flow and particle transport in hypersonic plasma particle deposition and aerodynamic focusing

Nanostrucutured materials are often found to have properties superior to those of conventional bulk materials. A thermal plasma expansion process was used to nucleate nanoparticles, which were subsequently deposited by hypersonic impaction to form nanostructured films and micropatterns. The hypersonic plasma particle deposition process was extended to synthesize nanocomposite thin films to explore superhardness of such nanocomposite films for potential applications in friction- and wear-resistant coatings.; Flow and particle transport models were developed to understand the impaction of nucleated nanoparticles. The model predicted that the bulk of the nanoparticles, in the range 1–100 nm, impact the substrate with very high velocities (>1 km/s) and that particles as small as 5 nm could be successfully deposited using a supersonic expansion of a particle-laden plasma jet.; Using a numerical design-of-experiments study, a particle nucleation nozzle was designed to mitigate the generation of macroparticles, which adversely affect the properties and nanostructure of the film. Experimental observations have shown that the new nozzle design reduces the generation of macroparticles and increases the rate of growth of the deposited film.; Beams of nanoparticles have found widespread applications in aerosol measurements and analysis. In this study, such beams are studied numerically as well as experimentally for potential applications in coating or fabrication of superior microelectromechanical system (MEMS) components. To this end, a numerical model was developed enhancing the understanding of the flow and particle transport through an aerodynamic lens assembly in the compressible flow regime. The model led to a redesign of the aerodynamic lens assembly to generate collimated beams of nanoparticles in the size range of a few tens of nanometers. The defocusing of collimated nanoparticle beams due to the effect of Brownian motion was addressed using a phenomenological model and a stochastic model. The predictions from the model reveal the limit to which the nanoparticles can be focused and help in understanding the limitations of the aerodynamic focusing phenomenon for very small particles.