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.