摘要
The exceptional characteristics of mullite render it a significant candidate for application across several domains. However, finding ways to lower the synthesis temperature of mullite without compromising its purity has been an acknowledged challenge. In this work, we synthesized colloidal mullite precursors featuring a composite structure via ion exchange method and hydrolytic precipitation reaction of hydroxyl-aluminum chloride and effectively prepared high-content mullite materials at low temperatures. The crystalline phase transformations of the composite precursors with varying abundances of aluminum and silicon atoms during the calcination process were examined using X-ray diffraction and thermal analyzer techniques. The silicon-rich precursor was observed to form the mullite phase at 550 °C, with a mullitization rate of approximately 20.08 wt%. In addition, the molecular characterization of the calcined samples, utilizing nuclear magnetic resonance to analyze the near-neighborhood environment and X-ray photoelectron spectroscopy to elucidate surface structure, revealed that no substantial structural rearrangement occurs in the Si-rich samples as the calcination temperature increases. More aluminum and silicon atoms form a homogeneous structure and contribute to the mullite crystallization process. Based on the provided characterization analyses, it is plausible to deduce that the low-temperature crystallization of mullite is associated with the significant mixing of Al and Si species in the precursor at the atomic level. More specifically, the abundance of amorphous silica particles in the Si-rich samples facilitates the formation of massive mullite-like Si-O-Al bonds with aluminum, owing to its migratory and viscous deformation characteristics. Therefore, during the calcination process, the grains begin to grow exponentially through the grain boundary migration mechanism once the crystallization of the mullite phase is complete.
危险品化学品经营许可证（带存储）