Thin coating on ultrafine aerosol particles

This article presents the results of an experimental investigation on gas-phase coating of nanometer-sized NaCl aerosol particles with a condensing vapor of ZnCl2. The coating process has been carried out in a commercially available Venturi aspirator, where the NaCl at ambient temperature is mixed with the supersaturated ZnCl2 vapor. The operating conditions (ZnC12 vapor temperature, and ZnCl2/NaCl flow rate ratio) at which the ZnCl2 vapor preferentially nucleates onto the surface of the seed NaCl particles forming a coating layer on them, have been determined. Particle size growth as a function of the original seed diameter has also been determined. Smaller particles undergo a larger relative size growth ratio. It has also been shown that the presence of a coating layer does not affect the charge distribution of the original seed particles.