Abstrakt
Bentonite/iron oxide system is prepared by isothermal calcination of powder composed of bentonite clay and precursor containing ferric acetate. This preparation technique enables one to get the composite material directly, that is, iron oxide particles embedded in a bentonite matrix.
Calcination temperature T-calc is varied from 320 degrees C to 700 degrees C. The resulting series of samples is characterized by local methods based on hyperfine interactions: Fe-57 nuclear magnetic resonance (NMR) and the Mossbauer spectroscopy.
The results show that the phase composition changes significantly in dependence on calcination temperature. The amount of maghemite phase rapidly increases up to T-calc = 420 degrees C and decreases abruptly for T-calc higher than 460 degrees C.