2013, №1

сс. 57-68

Effects of clustering of VO2+ ions in the sub- and supercritical water. An in situ EPR study

2013, №1

сс. 57-68

Цитировать

S.N. Trukhan, V.F. Yudanov, O.N. Martyanov

Key words: ESR, supercritical water, in situ spectroscopy, VO2+, VOSO4, clustering, heterogeneous catalyst, temperature gradient

Temperature variations of the EPR spectra of VO2+ ions in sub- and supercritical water, under isothermal and temperature gradient conditions are investigated using an in situ EPR. A broadening of the hyperfine structure at increasing temperature and appearance of an unresolved broad low intensity line (ΔHpp ≈ 300 Oe) in the supercritical state are observed in the absence of temperature gradients, indicating the increase of exchange interaction between VO2+ ions in supercritical water. Exchange-narrowed anisotropic absorption line is observed under the temperature gradient conditions in the subcritical water near the transition to supercritical state. The shape of this line is close to that observed in the solid salt VOSO4·3H2O. It is shown that in situ EPR allows us to investigate the effects of changing the local environment of paramagnetic ions, which is preceding a well-known process of clustering and formation of amorphous oxide particles in sub- and supercritical conditions.

doi:10.1134/S1990793113080113