Phase and microstructural evolution in the ceramization of alumina- silica single-phase and multi-phase gels verified by molecular dynamics: Unraveling the mechanisms of gel ceramization

ZY Sun and HJ Lin and XY Cai and L Zhang and T Feng and SS Jiang and N Meng and ZX Wen, MATERIALS CHARACTERIZATION, 230, 115665 (2025).

DOI: 10.1016/j.matchar.2025.115665

This study investigated the phase and microstructural evolution of Al2O3-SiO2 single-phase and multi-phase gels during ceramic formation under heat treatment from 900 degrees C to 1400 degrees C. By integrating experimental characterization with molecular dynamics simulations, based on atomic-scale binding energy theory, the fundamental reasons for the observed discrepancies in experimental results were revealed. At 900 degrees C, crystallization of the ceramic matrix initiated, forming pores and depressions. Amorphous SiO2 acted as a flexible interfacial barrier, reducing defect formation. Densification began by 1100 degrees C, followed by alpha-Al2O3 recrystallization and mullite formation at 1200 degrees C, accompanied by pore-grain structures. Further heating to 1300 degrees C and 1400 degrees C induced secondary recrystallization. Molecular dynamics results showed that adding amorphous SiO2 enhanced the system's average binding energy and thermal stability. This provided atomic-level support for the experimentally observed differences in phase transformation and microstructure.

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