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ZnO Coating, Containing SiO2 Nano Particles, Prepared by Sol-gel Process and Investigation of Surface Properties

Rostami, Rahman | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 44118 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Ghorbani, Mohammad; Askari, Masoud
  7. Abstract:
  8. Zinc oxide thin films due to special specification and properties have variable application in different industries. Recently because of wide application of zinc oxide doped SiO2 in optoelectronics and sensors, lots of investigation have been focus on it. Meanwhile due to the SiO2 hydrophilic properties, doping of ZnO with SiO2 can improve self-cleaning properties zinc oxide membrane.It this project zinc oxide and ZnO doped SiO2 thin films with different composition were made by sol-gel and dip-coating process used for coating of mentioned sol over the quartz surface(15*25 mm). At first point different sol with different components was mixed with each other to make composite films but due to fast sedimentation and high particle size distribution of mixed sol, this way was not workable that’s way using the other way of sol preparation selected to make the stable sol.In this case new way of preparation was used .SiO2 precursor was added to zinc oxide sol to make clear and stable sol with different molecular percent of silica in zinc oxide solution (0,10,20,30,40%).after sol preparation ,the sol’s powders was drying at 150C for 48 hours in oven and then was annealed at 500C for one hour. FTIR characterization presented the existence of zinc oxide and silica particles obtained particle size of the zinc oxide powders was 23,25,28,30,34 nm. Optical, surface properties and wettability of the annealed membrane at 500C was evaluated too .estimated crystallite size of the ZnO, ZnO-10%wt SiO2 and ZnO-20%wt SiO2 were 17, 21, 24 nm respectively. For the other two layers because of lack of any peck, estimation of the crystallite size was impossible.According to AFM characterization, the surface roughness was decreased with addition of more silica and homogeneity of the surface was increased too which it was obtained by FESEM. Visible light adsorption and band gap energy was increase from 3.27 eV to 3.4 eV base on addition of more silica content.
    self-cleaning properties of the surface was evaluated under effect of UV light, by addition of 20% of silica to zinc oxide, hydrophilic properties of the surface was enhanced .The obtained contact angle was 15.5 that it proves hydrophilic properties of surface
  9. Keywords:
  10. Zinc Oxide ; Silica ; Nano Layers ; Sol-Gel Method ; Hydrofilicity ; Self-Cleaning

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