Synthesis of Magnesium Aluminate Spinel Nanoparticles Using Chemical Method and Investigation of the Effect of Zirconia on Spinel Composites Properties

Maddahi, Vahid | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42854 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Nemati, Ali
  7. Abstract:
  8. In this research, a powder containing magnesium-aluminate spinel particles is prepared based on co-precipitation method and 5% , 10%, 15% and 20% zirconia-contained composites are produced as second phase from the synthesized powder. The raw materials used in the synthesis comprise hexa-hydrated magnesium nitrate, nona-hydrated aluminum nitrate, ammonium bicarbonate, 28% ammonium solution and distilled water. The properties of the powder is then investigated using STA, XRD and SEM tests. Also, XRD and SEM analyses as well as triple point flexural strength and Vickers hardness tests are carried out in order to investigate the effect of adding zirconia to the powders. The variations of the fracture toughness of composites are finally analyzed using the data obtained from mechanical properties experiments. The XRD patterns of the powder shows the acceptable synthesis process of magnesium-aluminate spinel particles. Moreover, SEM images show the size of the particles is in nanometer and the non-existence of zirconia and spinel intermediate phases in sintering temperature is proved based on XRD patterns. The investigation of the mechanical properties of composites demonstrates that flexural strength of the specimens is firstly reduced up to 5% volume fraction of zirconia and is then increased after that this fraction passes from 10%. Furthermore, the rate of the Vickers hardness of the specimens is increased by adding the more zirconia due to the sliding reduction of the spinel matrix in the existence of the zirconia. As one of the other results, it is noted that the fracture toughness of the specimens is improved by increasing the volume fraction of zirconia which is for the sake of its fracture toughness mechanisms.
  9. Keywords:
  10. Spinel ; Nanoparticles ; Co-Precipitation ; Bending Strength ; Hardness ; Fracture Toughness

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