Abstract
In this project, magnesia-alumina composite granules were prepared using spray drying method. Next, the synthesized powder was sintered at 1400°C for 15 min under 100 MPa pressure through spark plasma sintering without using any sintering aid. The effect of two sintering temperatures of 1400 °C and 1500 °C was explored on the phase formation, density, fracture toughness, and optical transmission within visible and IR ranges. SEM results indicated that the magnesia-alumina composite granules had spherical morphology with the mean particle size of 21 micrometers. The XRD pattern showed that after the spark plasma sintering stage at 1400 °C and 1500 °C, the spinel phase of magnesium aluminate was obtained as in situ. The disc sintered at 1400 °C had greater maximum transmission compared to the samples sintered at 1500 °C (47% vs. ~70%) within the middle IR region because of lower porosity of the sample. The magnesium aluminate spinel sintered at 1400 °C had a density 99.98% of the theoretical density, hardness 18 GPa, and fracture toughness 1.6 MPam1/2.
Fabrication and evaluation of sol-gel derived magnesium aluminate spinel-clad sapphire fiber
