Abstract
The gold surface was contaminated with a small amount of salt particles and its effect on water adsorption was measured by means of quartz crystal microbalance. The salts employed were NaCl, MgCl2⋅6H2O and (NH4)2SO4 and the amounts of contamination were ranged from 0.01 to 1.0μg/cm2. The critical relative humidity where the water adsorption sharply increases, depends on the amount of contamination as well as the kinds of salts. The water adsorption was analyzed by Frenkel-Halsey-Hill (FHH) model and was classified into three stages according to the interaction parameter r in the FHH isotherm equation. The three stages can be attributed to the existence of different stages of absorbed water molecules.
Stage I (r<0.8): Adsorbed water molecules exist as clusters and water molecules adsorbs on the clusters as relative humidity rises.
Stage II (0.8<r): The transition stage between the stage I and II. The adsorbed water molecules coalesce and form an island.
Stage III (2.0<r): The adsorbed water molecules grow from cluster into a form of island and begin to exhibit the liquid water characteristics. Gradually this leads to the formation of continuous water film on the surface as the amount of water adsorption increases.
