Answers are grounded in this paper and cite their sources.
Infrared (IR) spectroscopy, in combination with magnetic methods, was used to study the thermally induced transformation of synthetic lepidocrocite (γ-FeOOH) to maghemite (γ-Fe 2 O 3 ). Magnetic analyses showed that the thermal conversion began at about 175°C with the formation of superparamagnetic maghemite clusters. The overall structural transformation to ferrimagnetic γ-Fe 2 O 3 occurred at 200°C and was complete around 300°C. At higher temperatures, the maghemite converted into hematite (α-Fe 2 O 3 ). Observation of the transformation from γ-FeOOH to γ-Fe 2 O 3 using variable-temperature IR spectroscopy indicated that dehydroxilation on a molecular level was initiated between 145°C and 155°C. The lag time between the onset of the breaking of OH bonds and the release of H 2 O from lepidocrocite around 175°C can be explained by diffusive processes. Overall dehydroxilation and the subsequent breakdown of the lepidocrocite structure was complete below 219°C. The comparison of the magnetic and IR data provides evidence that the dehydroxilation may precede the structural conversion to maghemite.
No takes yet. Share an insight, caveat, or question.
Gehring et al. (1994) studied this question.
Synapse has enriched 10 related papers. Consider them for comparative context: