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Preparation of Hydroxyapatite-Graphene Nano Composite Coating on Ti-6Al-4V Alloy Using Plasma Electrolyte Oxidation

Mohammadipour, Erfan | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54777 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Ghorbani, Mohammad
  7. Abstract:
  8. Hydroxyapatite-Graphene Nanocomposite coatings were formed on Ti-6Al-4V alloy by Plasma electrolytic oxidation. PEO electrolyte contains calcium acetate and calcium glycerophosphate. The effect of adding graphene to PEO electrolyte on the corrosion, mechanical, and biocompatibility properties of the coating investigated. Before adding graphene to the electrolyte, working parameters such as voltage, current density, process time were optimized using scanning electron microscopy (SEM), potentiodynamic polarization test, and thickness measurement. Examination of the coating morphology showed that due to thermal stresses, surface cracks formed at Voltages above 350 V. The results of the potentiodynamic polarization test showed that the corrosion rate increases with increasing current density. The phase structures, surface morphologies, functional groups of molecules, chemical compositions of the surface in the coating were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), respectively. Raman spectroscopy was used to confirm the presence of graphene particles in the hydroxyapatite-graphene Nanocomposite coating. The corrosion properties of the samples were evaluated using a potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS). By adding 0.2 gr/lit graphene to the coating electrolyte, the corrosion current density decreased from 0.4 to 0.14 μA/cm2. Cytotoxicity (MTT) assay results showed that nanocomposite coatings have more cell viability than hydroxyapatite coatings. Also, mechanical properties showed that the nanocomposite coatings have higher hardness and lower porosity, surface roughness, coefficient of friction, and wear rate than the coatings without graphene. The results showed that by increasing graphene concentration, mechanical, corrosion, and biocompatibility properties improved.
    Keywords: (PEO)
  9. Keywords:
  10. Graphene ; Hydroxyapatite ; Corrosion ; Nanocomposite ; Titanium Alloy 6AL-4V ; Plasma Electrolytic Oxidation

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