Simple model of particle formation by homogeneous and heterogeneous nucleation

Particle formation processes by homogeneous and heterogeneous nucleation ar e becoming increasingly important for the preparation of functional materia ls. However, the complexity of the presently available nucleation theory, w hich considers the classical thermodynamics of the process, prevents its pr actical use. To overcome this, a simple and practical engineering model of particle formation by homogeneous and heterogeneous nucleation in the liqui d phase has been proposed, which can predict the number concentration of nu cleated particles as a function of the operating conditions. If the number concentration of nucleated particles can be predicted, their mean diameter can be determined from a mass balance. Experiments in which the precursor m onomers were generated by several methods have successfully confirmed the p redictions of the model. Furthermore, the original model developed for liqu id-phase nucleation is extended to the case in which the precursor monomers are generated in a gas-phase system. A relationship between number concent ration and mean volume diameter of nucleated aerosol particles and operatin g conditions is obtained considering the free molecular regime vapor conden sation onto the critical nuclei, which is the main difference with the liqu id-phase model, The predictions are in excellent agreement with the results obtained in gas-phase nucleation experiments. In the present paper, the si mple model and the comparison of experimental results with the theoretical predictions are summarized.