Amirhossein Nassajpour
THESIS (MSc, 2016-2018): Spark Plasma Sintering of MgAl2O4 /Si3N4 transparent nanocomposite
This research aimed at optimizing the slip casting process as a pre-processing step for the preparation of spark plasma sintered MgAl2O4-xSi3N4(0 < x < 5 wt%) transparent nanocomposites. In this research, different amounts of Si3N4 nanoparticles (1,3, and 5 wt%) were added to the slurries of spinel to prepare transparent MgAl2O4-xSi3N4 (0 < x < 5 wt%) nanocomposites. The green bodies were prepared from slurries with 60 wt% solid loading and 1 wt% Dolapix CE64 as a dispersant. Slurries were jar milled before slip casting to make sure that powders were homogeneously mixed. Slurries were then cast in a mold, made of alumina. Rheological characteristics of slurries, containing Si3N4 nanoparticles, were thoroughly investigated. The results of viscometry showed that any increase in the Si3N4 content of the slurry is associated with an increase in the viscosity. Bulk spinel-3wt% Si3N4 nanocomposite was prepared by spark plasma sintering (SPS) at 1550 °C under pressure of 85 MPa for 20 min. Field emission scanning electron microscope (FESEM), X-Ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and UV–Visible spectrometer were used to study the structure and optical properties of prepared composites. XRD patterns of sintered spinel-based nanocomposite showed great stability of spinel phase during sintering. Results also showed that the consolidated sample shows a maximum transmission of 70% and 60% in the wavelength of near-IR and mid-IR, respectively.
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