Effects of Surface Topography and Wettability on Surface Heterogeneous Nucleation

Aluminum substrate surfaces with different wettability and roughness were prepared by chemical etching and fluorination treatment,and the nucleation behaviors on chilled substrate surfaces in solution of NH4Cl-70wt%H2O were experimentally investigated to describe the effects of surface morphology and wettability on the heterogeneous nucleation process.The results indicate that the reactive wetting property between the as-etched surface and NH4Cl nuclei makes heterogeneous nucleation easier,and the number of nucleation sites increases with the increase of surface roughness.In comparison,the per-fluoroalkylsilane coating on the modified surface inhibits reactive wetting property and thus restricts heterogeneous nucleation,moreover,higher surface roughness leads to less number of nucleation sites.This phenomenon is in good accordance with the analysis result of heterogeneous nucleation on rough surfaces based on Wenzel model.