硫醇改性超疏水铜表面的耐候性及失效机理

Weather Resistance and Failure Mechanism of Superhydrophobic Copper Surface Modified by Mercaptans

目的探究户外环境中导致硫醇改性超疏水铜表面失效的因素及其超疏水性失效的机制。方法通过化学刻蚀法在铜表面构筑纳米结构,利用正十二硫醇进行表面改性,得到具有超疏水性的铜表面。将该表面置于户外进行耐候性研究,并通过4种模拟户外环境实验探究超疏水性失效的原因,包括组合循环实验(循环条件含紫外辐射、淋雨和凝露)、紫外辐射实验、水环境实验和温度实验。结果超疏水铜表面经过10 d的户外实验后,其接触角由初始状态的158.5°降至131.1°,表明该表面的超疏水性能已失效。经过2次组合循环实验(每次循环的时间为12 h)、20 d紫外辐射实验及30 d水环境实验后,该表面的接触角分别降至130.3°、124.5°、131.7°,表明该表面均已失去超疏水性;经过40 d高温实验后,表面的超疏水性开始失效。XPS谱图表明,在超疏水性失效后该表面不存在硫元素,即正十二硫醇已经脱离表面。结论超疏水铜表面的硫醇分子脱落是超疏水性失效的根本原因。紫外辐射、水和高温是导致超疏水铜表面超疏水性失效的主要因素。其中,紫外辐射或水对超疏水性的破坏速度比高温快。相较于单一因素(紫外辐射、水或高温),三者的协同作用更加速了硫醇分子从表面的脱落,导致超疏水性失效的速度更快。

The superhydrophobic copper surface has a very broad application prospect in the fields of self-cleaning,anti-frost,anti-corrosion,reduction of resistance and residue of fluid in copper pipes,etc.However,the weather resistance of the superhydrophobic copper surface in the real application environment is not clear,and there is still short of systematic research.Therefore,the work aims to explore the failure factors of mercaptan modified superhydrophobic copper surface in outdoor environment and the mechanism of superhydrophobic failure.The nanostructure was constructed on the copper surface by chemical etching,and then the surface was modified with 1-dodecanethiol to obtain a superhydrophobic copper surface(SCS).The SCS was placed outdoors to study its weather resistance.The mechanism of failure was explored by four kinds of experiments simulating outdoor conditions.Simulation experiments included combinatorial cycle experiment(cyclic conditions including UV radiation,rain and condensation),UV radiation experiment,water environment experiment and temperature experiment("high temperature"in this work referred to the high temperature in the outdoor environment).The mechanism of superhydrophobicity failure of SCS was verified by the environmental weather resistance of hydrophobic copper surface(HCS)without rough microstructure.Scanning electron microscope(SEM),contact angle measurement and X-ray photoelectron spectrometer(XPS)were used to characterize the morphology,wettability and chemical composition of SCS,respectively.After 10 days of outdoor experiments,the water contact angle of SCS was reduced from the initial 158.5°to 131.1°.According to the SEM diagram and Energy Dispersive Spectrometer(EDS)analysis,impurities containing metal/non-metal inorganic substances and organic matter were absorbed on the surface.The experimental results showed that the superhydrophobic performance of SCS failed and the self-cleaning performance was also lost.The water contact angle of SCS decreased to 130.3°,124.5°and 131.7°after 2 combinatorial cycle experiments(12 hours of each cycle),20 days of UV radiation experiment,and 30 days of water environment experiment respectively,indicating that SCS lost its superhydrophobic property.After 20 days of high temperature experiment,SCS still maintained superhydrophobic property,but the superhydrophobic property began to fail after 40 days of high temperature experiment.XPS spectrum indicated that sulfur element was no longer present on SCS after the failure of superhydrophobic properties,i.e.1-dodecanethiol was removed from SCS.The shedding of mercaptan molecules on the SCS was the root cause of superhydrophobic failure.UV radiation,water and high temperature were the main factors leading to the failure of superhydrophobicity of SCS.The superhydrophobic property of SCS was destroyed faster by UV radiation or water than by high temperature.Compared with the effect of a single factor(UV radiation,water or high temperature),the synergistic effect of the three accelerated the shedding of mercaptan molecules from SCS,thereby accelerating the rate of superhydrophobic failure.By studying the weather resistance and failure mechanism of HCS,it is found that the wettability change trend of HCS is consistent with that of SCS,and the hydrophobicity failure of HCS without rough microstructure is also caused by the shedding of mercaptan molecules on the surface.The results verify that the mercaptan molecule detachment from the surface results in the superhydrophobic failure of SCS.