Fractal Geometry Approach to Describe Mesostructured Boehmite and Gamma-Alumina Nanorods

Mesoporous boehmite and gamma-alumina with nanorod-like morphology, exhibiting a high surface area and large pore volume, have been prepared by a nonsurfactant-templating sol-gel technique with a simple precursor system, aluminum isopropoxide, ethanol, 2-propanol, or 2-butanol as solvents, and sulfuric or hydrochloric acid as peptizing agents. The effect of the solvent-type and the peptizing agent were studied, and optimum conditions were determined. A fractal geometry approach was adopted to describe the subtle alterations in the smoothness of the surface as a function of the synthesis conditions. Boehmite and gamma-alumina nanorods were characterized by nitrogen physisorption, wide- and small-angle XRD, SAXS, Al-27 MAS NMR spectroscopy, TEM, and TGA-DTA. Both boehmite and gamma-alumina nanorods have a large surface area, pore volume, and pore size.