Except hsiehs and ges reports mechanical properties

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Except Hsieh’s and Ge’s reports, mechanical properties of the existing coatings have rarely been reported. Some of the reports only choose one or two kind of polar liquids to test oleophobicity of coatings. Our group has been making effort towards mechanically durable coatings for self-cleaning and anti-icing applications [34-36]. In this study, a new method of combining both low and high surface energy SiO 2 nanoparticles will be employed to prepare superhydrophobic and superoleophobic coating. By tuning the molar ratio of low and high surface energy nanoparticles, surface roughness and surface energy of the coating surface can be adjusted, leading to different oleophobicity. The hydrophobicity and oleophobicity of the coatings was analyzed by both polar and non-polar liquid droplets with surface energy ranging from 72.4 to 29.5 mJ/m 2 . In addition, mechanical properties have been extensively explored, including pencil scratch, cross-cut tape adhesion, nano-indentation and
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ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT 4 pull-adhesion test. The proposed coating provides a novel and efficient way for developing of mechanically robust self-cleaning, anti-fouling, anti-corrosion and anti-icing surfaces. 2. Experiment Work 2.1 Materials Tetraethylorthosilicate (TEOS), SiO 2 nanoparticles with particle size around 10-20 nm, 3- Glycidoxypropyltrimethoxysilane (GLYMO), 1H,1H,2H,2H–Perfluorooctyltriethoxysilane (PFOTES) and itaconic acid catalyst were obtained from Sigma-Aldrich. Methanol (99%, obtained from Fisher Scientific) was used as solvent to prepare all solutions. The organic liquids used to test the contact angle of coatings, including glycerol, formamide, diiodomethane, diethanolamine, ethylene glycol, a- bromonaphthalene, castor oil, sunflower oil, hexadecane and dodecane, were all purchased from Sigma-Aldrich. 2.2 Preparation of low surface energy PFOTES-coated SiO 2 nanoparticles The hydrolysis of PFOTES solution was according to a previous report [19]. Hydrolyzed PFOTES solution (total polymer concentrations is 1 wt.%) was diluted in methanol with volume ratio of 1:2. Then a certain amount of SiO 2 nanoparticles were added to the diluted PFOTES solution at room temperature. The mixture was firstly placed in an ultrasonic bath for 30 min, and then magnetically stirred for 12 hr. After stirring, the mixture is centrifuged at 2000 rpm for 5 min then dried at 80 C for 0.5 hr. The obtained hydrophobic silica is subsequently denoted as PFOTES-SiO 2 . 2.3 Preparation of coatings with different molar ratio of PFOTES -SiO 2 to SiO 2 nanoparticles The above prepared PFOTES -SiO 2 nanoparticles were used as low surface energy fillers. The original SiO 2 nanoparticles obtained from Sigma-Aldrich were used as high surface energy fillers. The sols
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ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT 5 were prepared in three steps. Firstly, the hydrolysis of TEOS and GLYMO sol was prepared by magnetic stirring for 4 hr. The sol contains 100 ml methanol, 2 ml 1 wt. % PFOTES solution, 0.01 mol TEOS, 0.052 mol Glymo and 0.2 mol DI water. Itaconic acid was used to acidified the sol to pH 3~4.
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  • Fall '19
  • Surface tension, nU, Surface energy

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