| 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 53826 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Ghorbani, Mohammad
  7. Abstract:
  8. In the preceding years, hydroxyapatite (HA)-based coatings and scaffolds have been known as the best biomaterials for dental and orthopedics applications. Biocompatible and bioactive hydroxyapatite-based Coatings on metallic implants is one of the best methods for reaching both suitable mechanical properties and appropriate bioactivity, leading to better osseointegration and osteoblast proliferation. The ultimate goal of this project is characterization as well as mechanical and electrochemical behavior investigation of Hydroxyapatite- Chitosan nanocomposite coating by electrophoretic deposition (EPD) method on Plasma Electrolyte Oxidation (PEO) treated titanium substrates and Magnesium (Mg) effects. HA needle-shaped nanoparticles were synthesized by Sol-Gel method with 230-250 nm length and 30-40 nm diameter without any post-heat treatment with 82% crystallinity, and their average crystalline size is 143 nm. HA needle-shaped nanoparticles were characterized by XRD, FE-SEM, and EDX. HA-1% Chitosan nanocomposite, which contain different concentrations of Mg, were coated onto PEO treated titanium substrate for 5 min in a suspension including 17% ethanol, distilled water, HA nanoparticles, chitosan, and 0, 1, 3, 5% Mg(OH)2 for 5 min under 20-30 V/cm by DC power. PEO surface treatment was also done in the silicate-phosphate-based electrolyte under 150, 250, 350, 450 A/cm2 DC-Pulse current density, which the best porosity/ roughness ratio formed in 250 A/cm2 according to FE-SEM images. Final coated specimens’ electrochemical behavior was investigated by linear polarization and electrochemical impedance spectroscopy, which revealed that corrosion resistance increases by adding Mg concentration to 3% then decreases. Also, Nanoindentation and Nanoscratch tests showed that hardness increases by Mg concertation from 0.18 GPa for 0% Mg to 0.25 GPa for 3% Mg then decreases. Moreover, surface roughness is increased from Rq= 67.4 nm and RA= 51.1 nm for 0% Mg to Rq= 80.9 and RA= 64.6 for 3% Mg. These properties make this implant promising for bone implant applications to improve osseointegration and osteoblast proliferation
  9. Keywords:
  10. Implant Surface Treatment ; Hydroxyapatite-Chitosan Nanocomposite ; Hydroxyapatite Synthesis ; Electrophoretic Co-Deposition ; Plasma Electrolytic Oxidation ; Bone Scaffold

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