Effect of particle size on rate of coalescence of silica nanoparticles

In high temperature processes, at high concentrations, aerosol particles grow by collisions and coalescence. The rate of coalescence is an important parameter for predicting the final primary particle size. For some materials, particularly silica, predictions of final primary particle size using coalescence rates based upon bulk material properties are not in agreement with experimental results, One explanation may be that the high internal pressure in very small particles (less than 10 nm in diameter) affects the mobility of material within the particles and hence the coalescence rate. In this Note, a new approach for estimating rates of coalescence of particles in the initial stages of growth is presented. Coalescence of liquid particles is assumed to be rate-limited by atomic mobility, and the effect of internal pressure on diffusivity is considered. (C) 1999 Academic Press.