Salt effects on dynamic bubble nucleation on hydrophobic surfaces in air super‐saturated water

Abstract

AbstractEffect of salts (NaCl and CaCl2) on dynamic bubble nucleation on hydrophobic bitumen and silanated glass in air‐supersaturated water was examined using an autoclave at air saturation pressure of 700 kPa and temperature of 80°C. The results showed that at a low salt concentration, there was virtually no difference in the sizes of bubbles nucleated on the surface (0.06‐0.2 cm in diameter), as compared to the cases without salt addition. At a higher salt concentration (0.2 M CaCl2, or 0.3 M NaCl), the size of bubbles nucleated on the surfaces reduced drastically (more than 10‐fold smaller), with the surface being entirely frosted with small bubbles lined up neatly. The observed sizes of surface bubbles were up to more than 3600 times larger for the cases without salts, and 600 times larger at the high salt concentrations, than the critical equilibrium bubble diameter under given test conditions (~328 nm). Possible reasons for the observed phenomena were briefly discussed.