No abstract

In the present research we employed the newly developed cryosol technique for the preparation of nanocrystalline Al(OH) 3 . The technique yields sols of aluminum hydroxide stable under a wide range of pH values and concentrations. Freeze-drying of the sols results in the formation of aluminum hydroxide powders with extremely low density and small particle size. Thermal behavior and phase evolution of the cryosol-derived aluminum hydroxide has been studied. According to X-ray diffraction data, annealing of cryosol-derived aluminum hydroxide results in amorphous alumina stable up to 800°C. However DTA, electron diffraction, and 27 Al NMR studies indicate that the samples amorphous to X-ray diffraction are composed of crystalline nanoparticles. The thermal stability of nanocrystals is supposed to be due to the high uniformity of the particles size distribution, the latter resulting from the synthetic method employed.