Preparation of Mullite Nanocomposites Powders from Coal Fly Ash via Hydrothermal Crystallization
Mullite nanocomposites powders have been successfully synthesized from high-aluminium coal fly ash via hydrothermal crystallization process. The mullite nanocomposites powders are investigated and charactered by laser particle size analysis, BET surface area analysis, X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) analysis, selected area electron diffraction (SAED) analysis and energy-dispersive X-ray (EDX) analysis. Moreover, the reaction mechanism is speculated according to MAS-NMR results. The experimental results show that mullite nanocomposites powders can be prepared at 80-90 °C for 3 h with NaOH concentration of 2-4 mol/L and L/S ratio (liquid/solid ratio in mass) of 10 mL/g. The powder size of D50 is about 1.88-3.27 mm. Mullite nanocomposites are mainly rod-like, acicular and fibroid in shape with an range of 30-80 nm in length and an range of 4.5-30 nm in diameter. MAS-NMR analysis indicates that the nano-size mullite grow around the central atom-Al, Si of [AlSi]O4 tetrahedral and the growth unit Al[OH]4- is existed in this process definitely.
Guangfan Li, Yong Huang and Chaohe Chen
L. X. Tong et al., "Preparation of Mullite Nanocomposites Powders from Coal Fly Ash via Hydrothermal Crystallization", Advanced Materials Research, Vols. 250-253, pp. 3313-3319, 2011