Validation of Unipolar Diffusion Charging Models for Spherical and Agglomerated Nanoparticles

An ion-jet diffusion charger was used in this study to investigate the diffusion charging of spherical and agglomerated nanoparticles, and validate corresponding theoretical models. Results show that the limiting-sphere model and White's theory could preferably predict the diffusion charging of spherical particles, compared with other models. As to agglomerated particles, it is affected by primary particle size and sintered morphology to some extent. Especially for loose agglomerate which is point-to-point contact, obviously more charges could be acquired at same mobility diameter in unipolar diffusion charger. In addition, it was validated that all of Chang's theory, normalized capacitance model and collision kernel model are in good agreement with experiments results. Chang' theory and normalized capacitance model, however, are more concise and could be used to evaluate diffusion charging of non-spherical particles in real occasions.