The real origin of lognormal size distributions of nanoparticles in vapor growth processes

In modern nanoparticle production methods, such as inert-gas evaporation, a strong effort is made to avoid coagulation of particles. Therefore, the classical coagulation models are not suitable for predicting the particle size distribution. This paper presents a new model that explains lognormal particle size distributions from first principles in a physically realistic way, without coagulation. The model is completely different from the previously applied growth models; it is based on a random residence time approach, where the time available for the particles to grow is random and determines the size distribution. The model is generally relevant in fields such as nanoparticle physics, aerosol science, environmental science and fractal growth, whenever particle growth occurs during transport through a growth zone due to diffusion and drift. Predictions made from the model agree with published experimental data obtained with the inert-gas evaporation technique. (C) 1999 Acta Metallurgica Inc.