Transformations of Gibbsite under Microwave Irradiation
In this paper, we report the observation of unusual bulk amorphization that occurs within the initial gibbsite microcrystals. A specific feature of amorphization is the formation of small atomic size aluminium-oxygen complexes in tetrahedral coordination [AlO4]. By analogy with the method of rapid heating («flash»-processes) this method for enhancing the reactivity of solid reagents was named “microwave activation” (MA). The chemical formula for the amorphous component can be represented in the general form as Al2O3∙xH2O (0,5<x<3,0). The possible transition of the amorphous component in boehmite with a high yield was established under certain conditions MA of gibbsite (GB). Based on this effect, we suggest a new approach to synthesis of well crystallized boehmite from products of microwave activation of GB. Moreover an unusual property of the obtained amorphous product is the ability to crystallize upon contact with water under mild temperature conditions to form new compounds.