Facile synthesis of aluminum hydroxides nanorods and formation of urchin shaped hollow particles

초록

The metal oxide nano materials have been intensively studied because they not only exhibit various interesting properties but also can be widely used in industrial applications. The property and application of metal oxides are largely depended on size, morphology, and internal structure. Aluminum hydroxides have been used extensively as catalysts, catalyst support, and adsorbents. In order to prepare aluminum hydroxide nanoparticles with controlled structures, several methods, such as template based synthesis, hydrothermal reaction, and emulsion process, have been developed. However, these methods either involved multi-step synthesis/harsh reaction condition or produced the product with heterogeneous impurities which limit their industrial application. In this study, the facile synthetic route for crystalline aluminum hydroxide nanorods and urchin shaped hollow particles was described. By controlling reaction conditions, aluminum hydroxide nanomaterials with different morphologies and porosities could be obtained from an aqueous sodium aluminate (NaAlO2) solution. Non-crystalline spherical particles were prepared at low temperature of 15 degrees, while crystalline urchin shaped hollow particles of aluminum oxide hydroxide (AlOOH) were obtained at 60 degrees. With the increase of sodium aluminate concentration in aqueous solution, the crystal structure of product changed from aluminum oxide hydroxide (AlOOH) to beyerite aluminum hydroxide (β-Al(OH)3). CP-MAS 27Al NMR spectrum of AlOOH and β-Al(OH)3 powders exhibited the single resonance from octahedral structure at 10 ppm, while that of sodium aluminate (NaAlO2) powders showed two peaks at 79 and 10 ppm, respectively. Urchin shape hollow particles with AlOOH structure were completely converted to γ-Al2O3 structure without changing an external morphology by the heat treatment at 700 degrees for 30 min.