Slip Casting of Alumina Suspensions in a Strong Magnetic Field

Textured alpha-alumina ceramics were processed by slip-casting suspensions with different mean-sized particles in a strong magnetic field of 9.4 T, followed by pressureless sintering at 1650 degrees C for 2 h in air. The dispersed crystalline particles in the colloidal suspensions could be oriented in a strong magnet when the energy of the crystal anisotropy overcomes the thermal motion energy. According to the theoretical model, the energy of the crystal anisotropy increases with an increasing particle size, which was confirmed by the experimental results revealing that the orientation in the green deposit increased with the increasing starting powder size. After sintering, however, anisotropic grain growth accompanied with excellent texture formation was observed for the ceramic fabricated from the finest starting powder grade, whereas the modest orientation factor of the largest starting powder-based ceramic hardly changed after sintering.