Fabrication and Property of Textured Nanocomposites of Alumina/Mullite/Silicon Carbite by Partial Oxidation and Reaction Sintering

Abstract

Nanocomposites with nanoparticles dispersed as the second phase have been reported to have improved mechanical properties. In spite of this potential processing methods to produce these nanocomposites are not well established. In this study, Al₂O₃/mullite/SiC nanocomposites were prepared by the reaction sintering of green compacts prepared by slip casting of a mixture of SiC and Al₂O₃ powders. Here, the surface of the SiC particles was first oxidized to produce SiO₂ and to reduce the core of the SiC particles, and then the surface SiO₂ was reacted with Al₂O₃ to produce mullite. By applying a strong magnetic field during slip casting, the Al₂O₃/mullite/SiC nanocomposites were fabricated with Al₂O₃ oriented, but not with mullite, Al₂O₃ was oriented so that the c-axis of the crystal was parallel to the direction of the strong magnetic field. The density was low due to the agglomeration of SiC raw powder. The bead mill using fine zirconia beads of 50 μm was effective to disperse the agglomerated particles and succeeded in obtaining high-density Al₂O₃/mullite/SiC with no agglomeration of SiC nanoparticles. The bending strength was greatly improved by dispersing the particles, but such improvement was not observed by texturing.