Impact of concentration and Si doping on the properties and phase transformation behavior of nanocrystalline alumina prepared via solvothermal synthesis

摘要

Solvothermal reaction of 20 g aluminum isopropoxide (AIP) in mineral oil at 300 degrees C for 2 h gave chi-alumina showing high thermal stability while the reaction with higher amounts of starting AIP (30 and 40 g) contributed contamination of pseudoboehmite. The chi-alumina thus obtained directly transformed into alpha-alumma completely at approximately 1400 degrees C bypassing the other transition alumina phases whereas some part of the contaminated product transformed to gamma-alumina through theta-alumina and finally alpha-alumina. When silicon was doped in the alumina matrix (5, 10, 20 and 50 at.) using tetraethylorthosilicate as the silicon (Si) precursor, chi-alumina was still observed without any contaminations at low concentration doping (5-20 at.). Amorphous structure was obtained by doping 50 at. Si. The phase transformation temperature was shifted to the high temperature after loading the Si. The a-phase transformation did not go to completion even after calcinations at 1500 degrees C. This could be due to the incorporation of Si atom in alumina lattice forming SiO2-Al2O3 solid solution. (C) 2007 Elsevier B.V. All rights reserved.