Effect of Synthesis Conditions on the Structure and Properties of Ultradispersed Aluminium Oxyhydroxides

Properties of aluminium oxyhydroxides (AOH) that were obtained through oxidation of electroexplosive ultradispersed (nano-) powder of aluminium by water (55 o C) and subsequent calcination of the initial sample in a temperature range 100–1150 o C have been investigated. These materials were taken up as highly effective adsorbents for special complex water treatment. With the use of X-ray diffraction, thermal analysis, and porosimetry methods, the basic structural characteristics of samples have been determined. It was found that initial AOH contains two modifications: pseudo-boehmite and bayerite. Depending on conditions of heat treatment, the following phase transitions are observed: bayerite → η-Al2O3 → θ-Al2O3 → α-Al2O3 and pseudo-boehmite → γ-Al2O3 → δ-Al2O3 → θ-Al2O3 → α-Al2O3. The oxyhydroxides that were obtained at relatively low calcination temperatures are characterized by high specific surface and by existence of a microporous structure. A decrease in the calcination temperature leads to disappearance of micropores and to an increase in the volume and size of mesopores.