13 October 1994 Preparation and characterization of xerogels obtained from aluminum isopropoxide
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Abstract
The sol-gel process allows the production of alumina with high purity and homogeneity, controlled nanostructure and in several shapes. These aspects are important to provide some characteristics to alumina that enable the application of this material in advanced devices, such as in opto-electronic devices. In this work, aluminum isopropoxide was synthesized and used in the preparation of alumina-gels. The effect of some of the variables of the mixture step such as hydrolysis temperature, pH and water/alkoxide ratio, in peptization and gelation, were evaluated. The obtained gels were dried at 105 degree(s)C and analyzed by x-rays diffraction, infrared spectroscopy, nitrogen adsorption and thermogravimetric analysis. It was noted the influence of temperature of alkoxide hydrolysis in the behavior of hydrolyzed mixture. So, acid addition enhances the gelation time of mixtures hydrolyzed at 30 degree(s)C and reduces the gelation time of mixtures hydrolyzed at 90 degree(s)C. The structural analysis showed the presence of an amorphous phase in xerogels derived from mixtures hydrolyzed at 30 degree(s)C and the presence of pseudoboehmite in xerogels derived from mixtures hydrolyzed at 90 degree(s)C. The different behavior of mixtures hydrolyzed at low and high temperatures was suggested to be caused by different mechanisms of surface charge formation in the structurally different hydroxides. It also could be noted that pseudoboehmite gels have less structural water and volatiles than amorphous gels. Pseudoboehmite gels produced in low pHs should be formed by a randomly and less compact arrangement of particles with plate shape.
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Rodrigo Lambert Orefice, Wander Luiz Vasconcelos, "Preparation and characterization of xerogels obtained from aluminum isopropoxide", Proc. SPIE 2288, Sol-Gel Optics III, (13 October 1994); doi: 10.1117/12.189011; https://doi.org/10.1117/12.189011
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