Preparation And Applications Of Superhydrophobic Materials

With the development of economy, accidents of oil and organic solvent leakage have occurred more and more frequently. During severe accidents of oil leakage, traditional methods can not remove the oil completely. There is always a small amount of oil floating on the water, forming an oil film to block the gas exchange between water and atmosphere. Besides, trace oil pollution are often met in daily life, such as oil film on the water in the aquarium and the oil on the chopsticks and the tables in the kitchen, etc. The trace oil pollution impacts the environment and the daily life, but it is troublesome to wipe it off completely with an effective strategy.In this thesis, superhydrophobic materials are used to clean the trace oil pollution in the water. Superhydrophobicity is determined by the wettability of the solid surfaces, and wettability is determined by the chemical component, geometrical formation and the property of the liquid. In surface chemistry, superhydrophobic surface is defined as the surface that has a water contact angle larger than 150° and a water sliding angle smaller than 10°, on which water can not spread but form drops that are easy to slide off. There are two main ways to prepare superhydrophobic surface. The one is to make rough structures on surfaces which have low surface energy; the other is to modify rough surfaces with some substances with low surface energy, such as fluoric and silicious-containing chemicals. Researchers have studied the superhydrophobic phenomena, and have synthesized various superhydrophobic materials. However, these synthesis strategies suffer from complicated processes and high-tech facilities, which hinder them from being industrialized. Thus, exploration of a facile, low-cost method to generate superhydrophobicity has its significance. In this thesis, two methods are employed to prepare superhydrophobic materials successfully. The prepared superhydrophobic materials are superhydrophobic paper and superhydrophobic graphene membrane. Both of them have shown outstanding adsorptive properties with oils and organic solvents from water. Besides, the specified materials are soft and can be used in different environment.The creativity and conclusions of the thesis are listed as:1. Superhydrophobic phenomenon in nature is introduced, besides with a summary of the theoretical basis and models. The research progress and potential application fields of the superhydrophobic materials is discussed in this thesis.2. Novel superhydrophobic functional papers (SFP) with both superhydrophobicity and superoleophilicity was prepared through a facile process. Firstly, immerse a tissue into solution which contains silica nanoparticles and polydimethylsiloxane (PDMS). The silica nanoparticles aggregate on the tissue to increase the surface roughness of the paper. Secondly, cure the PDMS to lower the surface energy of the tissue, and SFP is prepared. SFP is soft and has strong capillary force, and its size and shape can be adjusted easily by the original tissue. SFP can adsorb several kinds of oils and organic solvents, and separate oil from water-oil mixtures with high efficiency. Because of significant capillary force. SFP can adsorb trace oil on and under water, which is very difficult for conventional adsorbents. Besides, SFP’s mechanical properties were improved compared with the original tissue. Even after being soaked in dodecane for two weeks, SFP still maintained good mechanical properties. These characteristics and low cost contribute to the advantages in mass production and applications in practice.3. Superhydrophobic membranes based on graphene materials have been prepared. The basic method is to treat hydrophobic graphene membrane with flame soot to increase its roughness. The specific processes are:First, spray the graphene oxide (GO)/ethanol solute with a sprayer on a hot substrate. Second, chemically reduce the GO membrane with hydrazine steam to get graphene membrane. Third, modify the surface of graphene membrane with flame soot treatment. Superhydrophobic graphene membrane was then prepared. Characterizations include Raman spectrometry, FT-IR(Fourier Translation Infrared Spectrum)and XRD(X-ray Diffraction), giving the information of elimination of oxygen-containing groups. Before modification, the graphene membrane is strongly water-adhesive, and its wettability depends on the substrate temperature. When higher temperature, the water contact angle(WCA) of modified graphene membrane was larger. The modified graphene membrane was superhydrophobic when the temperature of the substrate was above 50℃. Superhydrophobic graphene membrane showed flexibility and adsorbing properties. It can adsorb organics both on and under water. We believe the superhydrophobic graphene membrane has broad potentials in the future.