Preparation of Γ-alumina from Aluminum Aminoalkoxides

The synthesis of materials with tailored properties is one of the most active areas of material science [1, 2]. Among so many materials, γ-alumina due to the significant application in catalysis, electronic and ceramic industry has been studied extensively [3]. Various processes have been employed for the preparation of high quality alumina, including sol-gel processing from aluminum alkoxides. The advantage of sol-gel route for the synthesis of alumina, such as high surface area, purity, narrow size and pore distribution, with respect to conventional routes is well established [4, 5]. The commercially available aluminum alkoxides are very sensitive to moisture and in order to be used as a precursor for preparation of alumina, a chelating agent for control of hydrolysis-condensation and improving quality of alumina is require [6,7]. It is well known that the coordination number of aluminum atom in aluminum alkoxides increases by introducing chelating agent and consequently rate of hydrolysis-condensation decreases and that reflect on the properties of final materials. However, large amount of carbon in the precursor gels, as shown by thermal analysis [8], will prevent from complete crystallization of alumina at lower temperature; and calcination at higher temperature will led to aggregation or phase transformation. Furthermore, trace amount of carbon residue in the final product can have negative impact on quality of powder, which will be an obstacle for the preparation of high quality materials for advanced technology. In similar context, modification of aluminum alkoxides with externally chelating agents for stabilization of sol and fabrication of alumina thin films is not suitable. The aim of this work is to use internally coordinated aluminum aminoalkoxides instate of commercially available aluminum alkoxides, in order to reduce the rate of hydrolysis, and explore possibility for the preparation of transparent gel and fabrication of monolithic part by conventional hydrolysis or preparation of high quality alumina by hydrothermal route, which is not accessible from commercial precursors.