Evaluation of Fine Particle Formation by CVD in Laminar-Flow Aerosol Reactor

The nucleation and growth of aerosol particles by gas-phase chemical reaction in a laminar -flow aerosol reactor (LFAR) has been studied experimentally and theoretically. Titanium tetraisopropoxide (TTIP) vapor and gas mixture was introduced into a heated pipe in a laminar flow, and the particle number and size distribution of TiO2aerosol produced by homogeneous nucleation were measured under various conditions. The effects of initial concentration of TTIP vapor, temperature profiles of the reactor, and carrier gas on the properties of homogeneously nucleated aerosols were clarified experimentally. In the theoretical analysis, the simplified reaction and coagulation model was used to evaluate the particle formation by gas -phase chemical reaction, and the aerosol general dynamic equation expressing the simultaneous phenomena of generation of TiO2 monomer by thermal decomposition of TTIP vapor, Brownian coagulation and Brownian diffusion of TiO2 monomer, cluster and particle in the LFAR was solved. The observed experimental results were explained well by the theoretical analysis, and it was found that the deposition of TTIP vapor, monomer, cluster and particles produced onto the reactor wall is enhanced by low temperature, low concentration of feed TTIP vapor and carrier gas with large mean free path.