Fabrication of Transparent MgAl2O4 Spinel by Using Alumina-Magnesia Nanopowders through Slip Casting and Spark Plasma Sintering (SPS)

In this study, transparent magnesium aluminate (MgAl2O4) spinel was fabricated from commercial MgO and Al2O3 nanopowders under controlled conditions using slip casting and spark plasma sintering (SPS). The slip casting parameters, including the pH of the alumina/magnesia slurry and the concentration of the dispersant (Dolapix CE64), were optimized to 12 and 1 wt.%, respectively. Dolapix CE64 was selected for its effectiveness in reducing slurry viscosity at low concentrations while minimizing impurities. The casting was performed with a solid loading of 75 wt.%, and the SPS process was conducted at 1450 degrees C under a pressure of 70 MPa for 15 min. The morpho-structural and optical properties of the fabricated spinel were analyzed using several techniques, including field emission scanning electron microscopy (FESEM), x-ray diffraction (XRD), energy dispersive x-ray spectroscopy, Fourier transform infrared spectroscopy, and UV-visible spectroscopy. XRD patterns confirmed the formation of a single-phase, high-purity MgAl2O4. FESEM images estimated the grain size of the slip-casted and calcined sample at 800 degrees C to be approximately 200 nm with a non-spherical morphology. The minimum porosity in the as-cast alumina-magnesia nanocomposite was achieved through a stable slurry with a high solid loading and 1 wt.% Dolapix CE64, resulting in a transmission of 71% in the infrared region and 40-48% in the visible region after the SPS process.