Study On Fabrication And Properties Of Superhydrophobic Copper Materials With Long-term Durability

Copper is widely applied in our daily life and industry production due to its excellent properties such as high conductivity, high thermal conductivity, suitable strength, machinability, etc. Copper powder is mainly used to manufacture the friction materials, diamond products, electrical contact materials, and so on. However, copper can be corroded inevitably in the process of use. The superhydrophobic technology is an effective method of improving the materials corrosion resistant property. Moreover, which can bring the copper with the self-cleaning capability, and so on.In this dissertation, two methods are developed to modify the copper powder, and the superhydrophobic copper blocks are obtained after optimizing the preparation process paramerters. Then the phase structure, chemical structure, and surface morphology of the as-prepared superhydrophobic samples are studied. Additionally, the long-term stability of the superhydrophobic samples, and the self-cleaning capacity and renewable capacity of the superhydrophobic copper materials are investigated while the mechanism of superhydrophobicity is discussed. The main contents and results are described as follows:(1) The copper-based superhydrophobic blocks are constructed as follows: the copper powder is washed firstly and then oxidized by Na OH-(NH4)2S2O8 and Ag NO3. Finally, the sample is modified with lauryl mercaptan(DM) and then mould-compressed into a block sample(namely, Scheme I). The optimal process parameters are determinced after various experimentals by a single-factor method. The superhydrophobic copper-based materias with a contact angle of 153.2° and a rolling angle of 7° are obtained when concentrations of Na OH/(NH4)2S2O8, Ag NO3, and DM are 0.6 mol/L/0.26 mol/L, 0.03 mol/L, and 0.15 mol/L while DM immersion time is 24 h and pressure is 150 MPa. The phase structure surface morphology, and chemical composion of samples after each steps are investigated by techniques as XRD, EDS, SEM, and FT-IR, and results show that long chains of DM are assembled onto the surface of copper-based materials successfully and the superhydrophobic copper-based material surfaces take on finger-like micro-nano two-scale roughness. In addition, the length of a single finger-like structure is 1-3 ?m while the width of a single finger is about 60 nm. This microstructure together with the assembled long hydrophobic alkyl-chains is the significant reason for copper-based material with superhydrophobic propertyproperty.(2) The preparation procedure in Scheme 1 is simplified, and the copper-based superhydrophobic blocks are prepared by Ag NO3(without Na OH/(NH4)2S2O8) oxidization, DM surface modification, and then compression(i.e., Scheme II). A superhydrophobic copper block with contact angle and rolling angle of 155.2° and 5° can be resulted after the selected optimal experimental conditions as follows: Ag NO3 concentration of 0.03 mol/L, DM concentration of 0.15 mol/L for 16 h, and pressure of 80 MPa. The phase and chemical structure after each steps are investigated by techniques as XRD, FT-IR, and EDS, while the morphology of the superhydrophobic copper is observed with SEM. Results show that large number of accumulation/kames present at the block surfaces which are composed of many cauliflower-like micro- and nano-meter structure, while the long chains of DM are assembled onto the surface of copper-based materials successfully. As a result, the copper-based materials win the superhydrophobic property.(3) Long-term durability and stabilty of the superhydrophobicity of the prepared superhydrophobic copper-based materials are investigated, and results show that the as-prepared superhydrophobic copper-based materials still keep their good superhydrophobic property when the samples are placed for 10 months and above, indicating that the sample prepared by two schemes have long-term durability and stability. Additionally, the water contact angle can remain 150° and above after samples prepared by Scheme I are soaked in the distilled water for 20 days or by Scheme II for 15 days. This result shows that the as-prepared copper-based superhydrophobic blocks have very good stability in water as well. Furthermore, when the water droplets with different p H are dripped on the superhydrophobic samples prepared by two schemes, it can be found that the copper-based materials can still keep excellent water-repellent property in a wide p H as 3-14.(4) Self-cleaning and regenerability properties of the as-prepared copper-based superhydrophobic blocks are examined. When the surfaces of the samples are spreaded with cigarette ash and chalk powder and then are tilted for ca. 5°, and next the water droplets are applied at the surfaces. Surprisedly, it can be found that the water droplet quickly roll and take the cigarette ash and chalk powder away, demonstrating that the copper-based superhydrophobic materials take on self-cleaning effect. On the other hand, once the superhydrophobic surfaces are pressed by a finger and polluted by oil droplets, it can be observed that to the samples achieve the superhydrophobicity again after grinding. This indicates that the superhydrophobicity can be regenerated, and which is due to the as-prepared superhydrophobic materials have the similar structure and composition in both the interior and at the exteriot.