通过向垂直放有铜片的烧杯中滴加 AgNO 3溶液,在铜片上制备出水接触角从平整铜表面的90．8°升至151．4°的梯度润湿表面；结合前期以碱辅助氧化法制备亲水区间的梯度润湿表面,实现了在无低表面能物质修饰时,构建从超疏水(151．6°)至超亲水(3．7°)的高梯度润湿铜表面.制得的润湿性梯度在近100℃的水浴中浸泡10 h,各点的接触角变化最大不超过10°.采用扫描电镜(SEM)和 X 射线衍射(XRD)等对样品表面形貌演变和结构进行分析,表明在铜表面分别沉积具有相对疏水的银粒子和亲水特性的氢氧化铜粒子,并形成合理的粗糙结构,可使铜片分别达到超疏水和超亲水状态,从而形成高梯度润湿铜表面.由于平整的银表面和氢氧化铜表面的水接触角分别为72．8和62°,这也从另一侧面说明亲水与疏水的界限在65°可能更加合理.%Gradient wettability surface changing from the original contact angle of copper (90.8°)to surperhy-drophobic (15 1.4°)was prepared on copper substrate via a facile chemical displacement technique,by adding dropwise AgNO 3 solution into a beaker with copper foil vertically placed inside.By combining with the previous-ly reported alkali-assistant-oxidation technique for creating hydrophilic wettability gradient,the high wettability gradient surface from 15 1.6 to 3.7°was further fabricated on the copper substrate.The copper foil may keep its gradient wettability property after immersed in water bath around 100 ℃ for 10 h,with a maximum change of contact angle less than 10°.The scanning electron microscopy (SEM),X-ray diffraction (XRD)and surface to-pography instrument (3D)were employed to analyze the morphologies evolution and crystal structures of the silver nanoparticles on copper substrate.The results show that the high gradient wettability surface from super-hydrophilic to superhydrophobic may be constructed by depositing the hydrophilic copper hydroxide particles and relatively hydrophobic silver particles,respectively,in both end parts of the copper foil and in turn forming gradient roughness structures.As the water contact angle of flat silver surface and smooth surface of copper hy-droxide are 72.8 and 62°respectively,the results found in this paper may suggest another example for defining hydrophobicity and hydrophilicity by a critical contact angle of 65°.
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