Activation of Ultrafine particles by supersaturation in condensational process

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Abstract
The Activation of ultrafine particles as the condensation nuclei, or heterogeneous nucleation of ultrafine particles, has been observed in various supersaturated vapors. Monodisperse NaCl, ZnCl2, Ag and silicon oil particles, 5–15 mm in diameter, are used as the condensation nuclei and water, hexanol, dibutyl phthalate (DBP) and di‐2‐ethyl‐hexyl sebacate (DEHS) are used as teh vapors. The supersaturated atmosphere is formed in the mixing type condensation nucleus counter (CNC) where a room temperature aerosol is mixed with warm air saturated by each vapor and the supersaturation ratio is controlled by changing the temperature of the saturated air. The number ratios of activated particles to total particles are observed at various supersaturation ratios. It is found that the activation of particles depends in a complicated manner on the combination of the substances of particles with condensing vapors, that is, activation in some particle‐vapor systems is explained by the Kelvin effect but not in others.