FRACTAL PROPERTIES OF A PARTIALLY CRYSTALLINE ZIRCONIUM-OXIDE AEROGEL

A zirconium oxide aerogel with a 70% by weight degree of crystallinity was prepared from zirconium n-propoxide with an excess of water being used in the hydrolysis process. The small-angle X-ray scattering (SAXS) technique revealed that this system had a mass-fractal character. The elementary building blocks had a size of about 50 angstrom and displayed a nonfractal (smooth) boundary surface. The mass-fractal dimension, D(m), was found by SAXS to be equal to 1.95 (5). The novelty of this fractal system lies in the fact that the elementary blocks are made up of zirconium oxide particles with a high degree of crystallinity (preponderantly tetragonal in form). The crystalline nature of this system has allowed an interesting comparison to be made between the particle size determined by the crossover in the log I(h) versus log h SAXS plot and the crystallite size determined by the line-broadening X-ray diffraction analysis.