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Chitosan–Bioactive Glass Composite Coating on Nd-Fe-B Magnetic Alloy Substrate by Electrophoretic Deposition

Mehdipour, Mehrad | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40977 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Afshar, Abdollah
  7. Abstract:
  8. This research work deals with application of poly-saccharide to improve coating process of bioactive ceramic composite on aNd-Fe-B magnetic alloy substrate. Bioactive glass particles were synthesized through a sol-gel process and coated in the form of composite with poly-saccharide onto a magnetic substrate by electrophoretic deposition technique. Stable suspensions of 0.5 gr/lit polysaccharide polymer-ceramic were prepared using bioactive glass particles (<1µm), acetic acid 1%. The influence of added water to ethanol, pH and tri-ethanol-amine (TEA) additive on suspension stability, deposition rate and coating’s structure was investigated. It was shown that by increasing the water to ethanol percentage, the suspension stability improves but deposition rate and homogeneity of the coating is reduced; also, increased acidity led to a reduction in deposition rate and homogeneity. Effective parameters of electrophoretic process were determined by studying the structure and thickness of the coating. A suspension of 30% water to alcohol content with desirable stability and high deposition rate wasprepared, and it was shown that by the addition of TEA to the suspension, its stability was slightly reduced, though the homogeneity of the coating was increased. In order to evaluate the coating, structure, electrochemical properties and its bonding to the substrate were studied. The results of these studies indicated that increasing the deposition time and voltage led to an increase in particle size, porosity and thickness, and also induced cracks in the coating. TEA addition to the suspension led to a decrease in zeta potential, indicating agglomeration of the particles which was then confirmed by structural studies by SEM. For increasing the coatings bonding to the substrate, it was sand-blasted and the bonding between polysaccharide-bioactive glass composite coating to the substrate was improved from 2 MPa to 5.5 MPa. In the presence of the polymer-ceramic coating, current density in saliva simulated fluid was decreased and corrosion potential shifted toward more noble values.

  9. Keywords:
  10. Ilmenite ; Magnetic Alloy ; Polysaccaride ; Sol-Gel Method ; Electrophoretic ; Bioactive Glass

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