ABSTRACT
The local Zr and Fe arrangements in the nanocomposite system Fe(x)/ZrO2 (x=0-0.2) obtained by sol-gel method were studied by EXAFS. The phase composition was found to vary significantly on iron loading. For the samples calcined at 500 or 600 degrees C, at x< or =0.01, the formed ZrO2 is a mixture of monoclinic and tetragonal structures. Only tetragonal structure is revealed at x > or = 0.05 with the exception of Fe0.2/ZrO2, calcined at 500 degrees C, where new non-typically short Zr-Zr distances (3.29, 3.43A) were observed. At low iron loading (less than one monolayer) Fe3+ ions were found to localize within the pre-surface layers of ZrO2 nanoparticles showing property of isolated ions. For greater Fe loading, iron exhibits either two-dimensional layer structure or two-phase system.
ABSTRACT
The solvent system of alcohol-acid-water gradually forms an equilibrated amount of ester which facilitates the separation of di- and tri-carboxylic acids on paper chromatograms. Using the system of n-butanol-formic acid-water (3:1:1) as an illustration, two methods of accelerating the system ageing are demonstrated: 1) butanol-acid mixture at a required ratio is kept for several hours before water is added and 2) butanol-acid mixture is passed through the KU-2 layer in the H-form. The effect identical to that achieved as a result of 5-day storage of the solvent system under usual conditions can be reached with the first scheme during 6 hours and with the second scheme during 20-30 min.
