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X-ray powder diffraction study of chromium-vanadium oxide compounds prepared by “soft chemistry” methods

100%

Pozdnyakova O. , Megyeri J. , Kuzmann E. , Szirtes L.

tom 4

nr 4

760-772

A novel aqueous method was used to synthesise mixed chromium-vanadium oxide hydrates with various chromium content, via the reaction of peroxo-polyacids of chromium and vanadium. The resulting materials are gelatinous. The dehydration of the gels result in a brown coloured amorphous powder. Depending on the chromium content, the compounds have a different characteristic crystallisation temperature upon the further heating. The crystalline compounds, except for the low chromium ones, go on a phase transition and decompose with increasing temperature. By refining the XRPD measurement data of the compounds, the type and parameters of the unit cells were determined. The experimental data were in concordance with the calculated values, using the PWC code. The lattice parameters and the crystalline structure were changed with the variation of chromium content.

The radioactivity and the chemical nature of additives as factors determining the photocatalytic activity of TiO2

88%

Milanova M. , Kovacheva P. , Kralchevska R. , Kolev J. , Zaharieva J. , Todorovsky D.

nr 6

1850-1858

Microcomposites consisting of TiO2 and ThF4 or UO3 (0.5–2% of the TiO2 mass) are produced by sol-gel synthesis of TiO2 in presence of the respective additives. X-ray diffraction study reveals small effect of the latter on TiO2 phase composition and cell parameters and significant influence on the crystallite size and UV/Vis reflectance spectra. The photocatalytic tests in presence of TiO2-ThF4 microcomposites under UV and solar irradiation show a non-monotonic increase of the Malachite Green degradation rate constant with the increase of ThF4-content. No changes in the photocatalytic activity are observed in the presence of UO3 but the latter composites exhibit activity in darkness. The results are compared with previously reported data on the performance of TiO2-ThO2 photocatalyst with the same radioactivity and suggest that both radioactivity and the chemical nature of the dopants are responsible for the photocatalytic performance of TiO2-based composites containing radioactive substances. [...]