Morphological and structural evolution of mesoporous calcium aluminate nanocomposites by microwave-assisted synthesis

• Calcium aluminate nanocomposites were firstly prepared by microwave-assisted route.
• Ca12Al14O33 has a special dual-structure of polycrystalline nanorods and mesopores.
• A formation mechanism of Ca12Al14O33 crystal growth is also proposed.

Novel special dual-structure calcium aluminate nanocomposites consisting of mesoporous Ca-containing Al2O3 nanonetworks with Ca12Al14O33 polycrystalline nanorods have been successfully synthesized using the microwave-hydrothermal (M-H) process in an alcohol solution consisting of calcium nitrate and mesoporous alumina, followed by calcination at a lower temperature (e.g., less than 600 °C). The mesoporous Ca-containing aluminate nanocomposites possessed a specific surface area of 51 m2 g−1 and a broad pore size distribution of 4–12 nm in diameter, as observed from N2 adsorption/desorption measurements. The results showed that highly dispersed Ca12Al14O33 nanorods grown on the mesoporous nanostructure were obtained by varying the molar ratio of Ca/Al or by controlling microwave heating time, as characterized by scanning electron microscopy (SEM), transmission electron microscopy/electronic energy loss spectroscopy (TEM/EELS) and powder X-ray diffraction (PXRD). The Ca12Al14O33 nanorods with diameters of 50–100 nm and lengths of 200–400 nm were grown in and on the one-dimensional mesochannels. A formation mechanism of the mesoporous Ca-containing aluminate nanocomposites involving amorphous mesoporous hydrated-Al2O3 was also proposed.

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