Abstract
Evaporation behavior of ZnCl2 melts and ZnCl2–ZnO mixtures in Ar–O2–H2O atmosphere was observed at 873 K by measuring change of weight and chemical composition. When water vapor or oxygen was added, weight loss of ZnCl2 decreased, and the effect of water vapor on repression of weight loss was much stronger than that of oxygen. Especially, weight loss stagnated after 20 min at 40% of weight loss in Ar–5%H2O atmosphere. It is considered that the reaction product between zinc chloride and water vapor covered the surface of melt.
In the case of ZnCl2–ZnO melt, weight loss reached and stagnated at about 60% of initial weight in Ar and Ar–O2 atmospheres. This value is close to initial ZnCl2 content. However, weight loss reached and stagnated at about 50% of initial weight in Ar–H2O atmosphere, and the residue was converted to zinc oxide after 60 min experiments. From these results, formation of zinc oxide by the reaction between zinc chloride and water vapor in Ar–H2O atmosphere was confirmed. It is concluded that zinc oxide formed by the reaction on surface of melt prevented the contact between zinc chloride and gas phase, and the evaporation of zinc chloride. This phenomenon caused the stagnation of weight loss with atmosphere containing water vapor.
