Preparation And Characterization Of Composite Super-Hydrophobic Film On Copper Surface

In recent years, super-hydrophobic surface has been concerned as its self-cleaning, water repellency property and special frictionalbehaviour. As important industrial raw material, copper is applied in the fields of wires, microelectrode and micro-electronics.But like other metals, copper surface can be easily polluted and corroded. Assembling super-hydrophobic films not only can enhance self-cleaning and corrosion abilities, but also can keep the metal luster of copper substrates.The purpose of this study is to find an inexpensive and simple way to prepare super-hydrophobic surface on copper substrates.Firstly, we selected suitable substrates and self-assembly precursors. Copper foils with roughness of 5.5μm-7.5μm had been used as substrates,which could remove the procedure of sand-papering. We chose (3-mercaptopropyl) trimethoxysilane (MPTS) which has two kinds of active groups (-SH, -OH) after hydrolysis and octyltriethoxysilane(OS) which has only one kind of active group (-OH) as self-assembly precursors. MPTS is toxicity with foul smell, but it contains–SH which can bond with Au, Ag and Cu steadily.OS can not bond with Cu by self-assembling, but it has long carbon chain and an advantage of easy availability. Thus MPTS/OS composite super-hydrophobic films were prepared on copper substrates by layer-by-layer self-assembly technology.Compared with routine methods which use fluorinated organic compounds as precursors, this method has the advantage of low cost.Next, the parameter for the preparation of film was optimized, and the method of super-hydrophobic surface on copper was obtained. MPTS water/alcohol solution was prepared and hydrolyzed for 24h. The ratio of MPTS/DI water/ethanol was 1/5/94(v/v/v). OS solution was prepared and hydrolyzed for 76h, the ratio of OS/DI water/ethanol was 5/20/75(v/v/v). The OS solution pH was adjusted from its natural pH of 6.0 to 4.0 by adding acetic acid. Copper substrates were degreased by ultrasonic cleaning for 15min with acetone, etched with HNO₃(6.5 wt.%)for 60s, then washed by tap water and ultrasonic cleaned for 5min with DI water. The substrates were immersed in MPTS solution for 24h, washed with ethanol, and then dried with air. The substrates were then immersed in OS solution for 20min, washed with ethanol and cured in oven for 10min at 120℃.The process of OS self-assembling was repeated for 3 times. All of these experiments were conducted in 35℃water-bath. In the end, the property of the super-hydrophobic surface was detected by using contact angle meter, electronic scanner microscope (SEM), infrared spectrometer and seawater experiment. The results showed that the water contact angle of copper surface coated with MPTS/OS films was 158.6°and sliding angle was 3°. A lot of etching pits were found on the substrates surface which had been etched with HNO₃. As the pretreated copper was coated with silane films by using layer-by-layer self-assembly method, the white translucent membrane was obtained on the surface of etched substrates. The results of FI-IR indicated that there were a lot of associating hydroxyl and methylene in the film, and Si-O-Si bond also existed in silane films. Seawater experiment showed that only the treatment with MPTS or OS separately could not promote the anticorrosion ability of the substrates, but the substrates assembled with MPTS and OS had excellent anticorrosion ability.The innovative points of this experiment are as follow: (1) We chose the copper foils with some special surface roughness (5.5μm-7.5μm) as substrates, which could remove part of the surface-roughing process. (2) MPTS which has two kinds of active groups was chosen as solder. In this way, the MPTS/OS composite super-hydrophobic films were prepared on copper surface.