Synthesis, Characterization and Hydrophobicity of Teflon Coated Tungsten Nanostructure Thin Films

Bayat, Amir | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43765 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Moshfegh, Ali Reza; Azimirad, Rouhollah
  7. Abstract:
  8. Hydrophobic and superhydrophobic surfaces find many applications in different fields of science. The aerospace industry is one such field that can take the advantage of superhydrophobicity for anti-icing coatings. In order to make hydrophobic and superhydrophobic surfaces on hydrophilic materials, two-step process is usually need, at first, making a rough surface and then modifying it with hydrophobic coatings with low surface free energy. In this research, we have used glancing angle deposition (GLAD) RF sputtering technique to fabricate Teflon coated tungsten on glass substrate for obtaining hydrophobic surface. GLAD approach is a method to grow structures such as nanorods and zigzag columns. GLAD is a physical vapor deposition (PVD) technique, in which a high melting point material (such as W) flux is incident onto the substrate from a glancing deposition angle, α, to enhance atomic shadowing effects. In our experiments, The tungsten layer was formed in one step by using GLAD technique and by varying angular speeds from 5 to 30 RPM. After deposition of W thin film nanostructure, Teflon was coated on top of W layer by utilizing RF sputter deposition in different growth times (2, 15, 30, and 60 min). During Teflon deposition experiments, the discharge power was fixed at 80 W with an Ar working gas pressure of 10×〖10〗^(-3) Torr. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed to determine surface morphology of the deposited composite (PTFE /W/glass) nanostructures. According to our AFM images, we have calculated the roughness factor (r) for all these samples and hydrophobic properties of PTFE /W/glass layer was studied by water contact angle measurements. A water droplet of 2 μL was dispensed on the surface of the samples using a syringe. The picture of water droplet appears on monitor screen. After an additional coating with a thin layer of Teflon, the tungsten nanostructures have shown an improve water repellency property. Based on our data analysis, the contact angle varied with angular speed and deposition time. Finally, it was found the PTFE/W/Glass hydrophobic system obeys Cassie-Baxter model
  9. Keywords:
  10. Hydrophobicity ; Contact Angle ; Surface Tension ; Polytetrafluoroethylene(PTFE) ; Cassie-Baxter Model

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