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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。
A pure aluminum substrate with different roughness and wetting properties was prepared by chemical etching and fluorosilane modification. The substrate was placed in NH4Cl-70% H2O solution to quench NH4Cl grain nucleation in chilling mode, The effects of substrate morphology and wettability on the surface heterogeneous nuclei were also investigated. The results show that the reactivity wettability between unmodified rough pure aluminum substrate and ammonium chloride embryos makes the heterogeneous nucleation easier to occur. The nucleation sites increase with the roughness factor increasing. Fluorosilane coated on the rough substrate surface inhibits the reactive wetting characteristics and makes the heterogeneous nucleation less likely to occur. With the increase of the roughness factor, the nucleation sites decrease. The experimental phenomena observed are in good agreement with the conclusions of the rough basal heterogeneous nuclear analysis based on the Wenzel model.