基底形貌及润湿性对表面异质形核的影响

Effects of Surface Topography and Wettability on Surface Heterogeneous Nucleation

采用化学刻蚀及氟硅烷修饰的方法,制备了具有不同粗糙程度及润湿特性的纯铝基底,将基底置于NH4Cl-70%H2O溶液中,以激冷的方式触发NH4Cl晶粒形核,并考察了基底形貌及润湿性对表面异质形核的影响规律和机制。结果表明,未修饰的粗糙纯铝基底表面与氯化铵晶胚之间的反应性润湿特性,使异质形核较易发生,随着粗糙度因子的增大,形核点增加;修饰后的粗糙基底表面覆有的氟硅烷抑制了反应性润湿特性,使异质形核不易发生,且随着粗糙度因子的增大,形核点减少。所观察到的实验现象与基于Wenzel模型的粗糙基底异质形核分析结论有较好的吻合。

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 NH4CI-70wt% H20 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 NI-LC1 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 Wenzcl model.