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Hydroxyapaptite Coating on Zirconia Toughened Alumina Nanocomposite by Biomimetic Method

Esfahani, Hamid | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40062 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Nemati, Ali; Salahi, Esmaeil
  7. Abstract:
  8. Zirconia toughened alumina (ZTA) Nanocomposites were prepared using nano sized Zirconia (ZrO2) powders doped with 3% mol of yttria (Y2O3) nanopowders and the sintering behavior at different temperature (1450 °C, 1550 °C and 1650 °C) were studied. The ZTA composite with different amount of partially stabilized Zirconia (PSZ)(5, 10, 15 and 20% mol) were prepared via axial pressing and then sintered to achieve maximum densification. After that phase changes of the samples were monitored. SEM was used for microstructural study and hardness and fracture toughness were determined by means of Vickers indentation. X-ray diffraction pattern showed that at constant composition, tetragonal zirconia was increased with temperature increasing due to the intensification of diffuse coefficient of alumina as well as yttria into the Zirconia lattice network in the system which drive monoclinic – tetragonal martensitic transformation. At constant temperature, remained monoclinic Zirconia was increased with Zirconia content increasing. The hardness and Elastic modulus were decreased with increasing ZrO2 content. Identification of cracks propagated around the indent illustrated that fracture toughness was decreased by increasing of zirconia up to 10 mol% and this value rose for additions over 10 mol% . Apatite Layer was coated by biomimetic method. Super saturation solutions with 1.5 and 2 multiply concentration of simulated body fluid (SBF) were prepared and the effect of immersion time on the morphology of the precipitate was monitored with electron microscopy. X Ray Diffraction (XRD) method and FTIR spectroscopy were used to identify phases. XRD Patterns and FTIR spectroscopy showed that Hydroxyapatite phase has been changed to β-tri calcium phosphate (β-TCP) after 0.5 hr heat treatment at 700°C.

  9. Keywords:
  10. Alumina ; Nanocomposite ; Zirconia ; Fracture Toughness ; Hydroxyapatite ; Biocompatibility ; Apatite Coating ; Calcium Phosphate

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