Gas Evaporation of Zinc under Low Gravity with a Drop Capsule.

Fine zinc particles were produced in an argon gas atmosphere and in a helium gas atmosphere of 1.33 ×104 Pa without thermal convection. To investigate the initial process of crystal growth, particles deposited at various places and at different moments during evaporation were collected. The shape and size of the particles were observed using a scanning electron microscope. When the evaporation time increased, the mean size of the deposited particles decreased in the argon gas atmosphere, while it increased in the helium gas atmosphere. These experimental results can be interpreted in terms of the assumption that nucleation and crystal growth are dominated only by the diffusion of vapor from the evaporation source.