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The Effect of Solvent Type on the Characteristic of TiO2 Nanometric Coatings Produced by Electrophoretic Method

Farrokhi Rad, Morteza | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40032 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Ghorbani, Mohammad
  7. Abstract:
  8. Titania is semiconductor material and have many applications including photocatalysis, photochromic, air and water purification, sensors, and solar cell. In electrophoretic deposition, charged particles dispersed in a stable suspension move towards an oppositely charged electrode, and form dense layer of deposit on it. In this investigation electrophoretic deposition of titania nano-particles in suspensions prepared by different solvents (methanol, ethanol and butanol) with and without dispersant (triethanolamine and polyethylenimine), was studied. Well stabilized suspensions, prepared for electrophoretic deposition. The effects of solvent type, additive concentration, mechanism of particles charging in suspensions with and without additive, adsorption of additive on the particles surface, zeta potential and size distribution of particles in suspension were investigated. It was found that triethanolamine is effective additive for dispersing titania nano-particles in ethanol and butanol, but in methanolic suspension addition of triethanolamine causes in quick sedimentation of particles. Unlike triethanolamine, polyethylenimine addition to methanolic suspension, results in increasing in suspension stability. Electrophoretic deposition in various voltages and times from suspensions with different solvents and concentration of additive was performed and the effects of various parameters on microstructures of coatings, packing density, variation of current density during EPD, mechanisms of deposit formation and deposit rate were investigated. It was observed that from ethanolic and butanolic suspension, only at higher voltages (above 100V) deposit formation is possible, but from methanolic suspension deposition at low voltages was possible. With addition of triethanolamine, deposit formation from ethanolic and butanolic suspension in low voltages becomes possible. Addition of triethanolamine to suspension at optimum concentration results in modified coatings microstructures. The obtained results showed that resistance of coatings deposited from methanolic suspension is higher than coatings deposited from ethanolic and butanolic suspensions. The packing density of coatings initially increases with deposition time and reaches to a maximum amount, and then decreases with duration time. The roughness of coatings increases with increasing deposition voltage. Sintering of coatings in high temperatures in order to eliminate pores and reaching to high strengths was performed and the effects of sintering temperature, duration and phase transformation were studied. And finally the photoelectrochemical behavior of coatings sintered at different temperatures was determined. It was found that with increasing sintering temperature the ultraviolet illumination current increases.

  9. Keywords:
  10. Triethanolamine ; Methanol ; Ethanol ; Nanoparticles ; Titania ; Electrophoretic Deposition ; Polyethylenimine ; Butanol

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