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 cl assical coagulation models are not suitable for predicting the particle siz e distribution. This paper presents a new model that explains lognormal par ticle size distributions from first principles in a physically realistic wa y, without coagulation. The model is completely different from the previous ly 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 n anoparticle physics, aerosol science, environmental science and fractal gro wth, whenever particle growth occurs during transport through a growth zone due to diffusion and drift. Predictions made from the model agree with pub lished experimental data obtained with the inert-gas evaporation technique. (C) 1999 Acta Metallurgica Inc.