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An Investigation on Production a Biomedical Mg Alloy-carbon Nanotube Composite Using Mechanical Alloying, Sintering & Hot Equal Channel Angular Pressing Process

Hosseini, Mohammadreza | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51713 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Karimi Taheri, Ali
  7. Abstract:
  8. Nowadays, the research of biodegradable alloys with high corrosion and strength properties, along with a modulus of elasticity close to that of bone tissue, especially the magnesium alloys, which has a good biocompatibility and can be used as a biomedical material, has been considered by the medical industry. On the other hand, carbon nanotubes have been used as an reinforcing phase in composites due to their high mechanical properties. The aim of this project is to produce a biocompatible composite with magnesium alloy and carbon nanotube by powder metallurgy. In order to achieve this, first the raw powder of the alloying elements in the matrix without reinforcement and then with weight percentages of 1 and 1.3 of carbon nanotube were ball milled for 8 hours in a grinding mill to produce the composite powder. The ground powder was then cold pressed in a cylindrical die by pressure of 500 MPa. After this operation, the pressed powder was sintered at a temperature range of 250-450 ° C for 2 to 4 hours in an electric furnace. Subsequently, the sintered part was again hot pressed in an ECAP die, at various temperatures and times, to improve its microstructure. Metalography examination by optical and electron microscope (FESEM), X-ray diffraction, and shear punch test were used to assess the optimum conditions for the production of this nanocomposite. The results indicated that the optimum strength and ductility is achieved in the composite containing 1%wt. carbon nanotube and sintered for 4 hours at 400 ° C without any pressing operation by ECAP. The shear strength of this composite was increased by 22% and 67% compared with those of the Mg alloy. Moreover, it was found that the ECAP operation, improves the yield and ultimate shear stress by 22% and 60%. The results of the corrosion polarization experiment showed that by increasing the percentage of carbon nanotube to 1%wt. the corrosion resistance is improved and the improvement is maintained up to 1.3%wt. of CNT
  9. Keywords:
  10. Biodegradable Composite ; Biodegradable Magnesium Alloys ; Carbon Nanotubes ; Magnesium-Carbon Nanotube Alloy Composite ; Equal Channel Angular Pressing (ECAP) ; Shear Punch Test ; Mechanical Alloying

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