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The Investigation on Hydroxyapatite Coating on Magnesium Alloy and Its Properties

Mazaheri Kalahrood, Amir | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42802 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Afshar, Abdollah
  7. Abstract:
  8. Magnesium and its alloys are biodegradable materials with mechanical properties similar to the bone tissue, therefore these materials are suitable for producing orthopedic implants. Unfortunately Magnesium and its alloys are corroded too fast in physiological environment which is the main obstacle for usage of these materials as orthopedic implants. Producing Hydroxyapatite(HA) coatings on surface of Magnesium and its alloys is one of the popular and useful methods for reducing the corrosion rate in physiological environment. HA is a biocompatible and bioactive coating with the ability to bond chemically with the bone tissue and therefore it is largely used as a bioactive coating on the surface of orthopedic implants. In this project the possibility of production of HA on surface of Magnesium alloy AZ31 in an one-step process with the pulse electrode position method, is investigated. The as-deposited coating is characterized by XRD and SEM/EDS analysis and the corrosion behavior is examined by polarization test in SBF solution at 370C. The result of XRD analysis showed that the HA coating can be obtained directly on the surface of Magnesium alloy by pulse electrode position method. This coating has preferred orientation along (002) planes and has a high degree of crystallinity. Also the result of EDS analysis showed that the HA coating is Calcium-deficient and the Ca/P ratio of the coating is about 1.40-1.43 which is dependent on the pH of coating bath. SEM observations showed that the coating either has needle-like morphology or platelet-like morphology which is dependent on the pH of coating bath. The shear strength of the coating which is obtained in optimized pulse electrode position is about 38.76Mpa. The polarization test is proved that the HA coating is an effective method for reducing the corrosion rate of AZ31 alloy and reduce the corrosion rate around 1000 times comparing to the bare alloy
  9. Keywords:
  10. Magnesium Alloy ; Electrochemical Deposition ; Pulse Current ; Hydroxyapatite ; Physiologic Environment

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