preparation of pure cordierite through heat treatment of combustion synthesized magnesium aluminate spinel and silica nanoparticles

In the present work, cordierite single-phase powders with high purity were synthesized during a two-step process. first, magnesium aluminate spinel powders were prepared via the kcl-assisted solution combustion route. then, synthesized spinel particles and nanosilica were planetary milled for 24 h, followed by post-heating at different temperatures for 3 h. results showed that post-heating at 700 and 900 °c did not change the sample phases. however, a magnesium aluminate spinel phase appeared for particles post-heated at 1100 °c. further heating up to 1200 °c led to the phase transformation of amorphous silica to cristobalite, which reacted with magnesium aluminate spinel to form a cordierite phase. finally, at 1300 °c, the remaining spinel and cristobalite reaction was completed, and single-phase cordierite powders without additional phases were obtained. moreover, there was considerable radial shrinkage, and scanning electron microscope micrographs showed the liquid phase sintering of cordierite occurred.