A new apparatus for study of heterogeneous nucleation on single micron-sized insoluble particles.

摘要

The purpose of this research was to develop and test an apparatus for the experimental study of heterogeneous nucleation on single insoluble micron-sized particles. A numerical model to describe the vertical motion of an insoluble particle in the chamber was developed. Combination of thermal diffusion and electric levitation proved to be an effective method of suspension of the insoluble micron-sized particles.;The present study examined soda-lime glass, mixed glass and nickel particles. Oscillatory motion of the glass particles was observed when a fixed electric field was applied in excess of that required to levitate the insoluble particles. The numerical model was used to calculate the critical saturation ratio, the radius and the electric charge of the glass particles based on the experimentally measured period and amplitude of oscillations. As predicted by the numerical model, the amplitude of oscillation of the glass particles is much more sensitive to a change of the electric field strength than is the period. Values determined for the radius are consistent with the information provided by the manufacturer. The critical saturation ratio for the observed glass particles is in good agreement with previous studies on glass surfaces.;Variations of the critical saturation ratio for individual glass particles over several oscillations were studied. No general trends were found. Cycle to cycle variations in the critical saturation ratio are smaller than variations from particle to particle. Therefore it is likely that nucleating abilities of the particles are predominantly affected by variations in their surface properties, rather than by the stochastic nature of the heterogeneous nucleation process. The results of the present study suggest that the surface charge density of the particles largely accounts for the particle-to-particle variability in the critical saturation ratio for soda-lime glass particles.