MECHANISM OF PARTICLE FORMATION BY HOMOGENEOUS AND HETEROGENEOUS NUCLEATIONS IN GAS-PHASE, LIQUID-PHASE AND SOLID-PHASE

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Control of particle size plays a critical role because the final material properties usually depend on the size of the primary particles. Homogeneous nucleation has been extensively studied in the past. However, the complexity of the available theory prevents its practical use in applied fields such as materials manufacturing. Thus apart from the classical thermodynamical theories on nucleation, the model which enables accurate estimation of the number concentration and average size of the nucleated particles as a function of the operating conditions and materiel properties has been proposed. Liquid-phase nucleation experiments in which silver particles were generated by a chemical reduction method have successfully confirmed the predictions of the model. The objective of this research is to check the validity of the previous model, using various method of particle formation. The results obtained can be summarized below. At the first year, the effect of monomer diffusion coefficient on … More particle generation, which is one of the factors included in the previous model, was studied for systems where silver particles were generated by a reduction method in liquid phase. The monomer diffusion coefficient was controlled by changing viscosity of the solution by addition of a thickener, and it was found experimentally that the number concentration of particles generated was inversely proportional to monomer diffusion coefficient resulting in particle size reduction, which quantitatively supported the model. At the second year, the mechanism of aerosol particle formation from a condensing vapor is examined using a simple but practical homogeneous nucleation model. The model, which is an extension to the kinetic regime of a model previously developed and successfully tested for liquid-phase homogeneous nucleation, allows reliable estimation of the average size and number concentration of the generated particles as a function of material properties and operating conditions. The model predictions taken into accout for diffusion losses and wall condensation are in excellent agreement with the experimental results. Less