|
Yu. D. Ivakin, M. N. Danchevskaya, G. P. Muravieva
State of manganese
ions in structure of corundum synthesized in supercritical water fluid
Abstract
Kinetics and mechanism of doped corundum
formation in supercritical water fluid (SCW) from hydrargillite in the presence
of manganese ions are investigated. It was established that due to the
reversible dehydroxylation in a water medium happens the solid-phase
transformations of hydrargillite into boehmite and then corundum with the
formation of well-faceted corundum microcrystals uniformly doped with
manganese. It was found that when the Mn2+ ions or
MnO4– anions added to the reaction medium, in synthesized
corundum the ions Mn5+, Mn4+, Mn3+ and Mn2+ are
observed. In this case in the corundum structure is formed a complex defect,
including the manganese ions, oxygen vacancies and hydroxyl groups. Defects in
corundum, doped with manganese in SCW, differ from defects in corundum doped
with high-temperature synthesis.
Copyright (C) Chemistry Dept., Moscow State University, 2002
|
|
