Inhibition of sintering by Si during the conversion of Si-rich ferrihydrite to hematite

Inhibition of sintering by Si during the conversion of Si-rich ferrihydrite to hematite

The distribution and chemical state of Si in a synthetic 2-line ferrihydrite with a Si/(Si+Fe) molar ratio of 0.11 was studied. Heat treatment under oxidizing conditions shows that Si-rich ferrihydrite is stable to 400°C. The transformation to hematite and the formation of a polymerized amorphous-si...

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Bibliographic Details
Published in:Clays and clay minerals Vol. 48; no. 1; pp. 51 - 56
Main Authors: Glasauer, Susan M, Hug, Paul, Weidler, Peter G, Gerhring, Andreas U
Format: Journal Article
Language:English
Published: Boulder, CO Clay Minerals Society 01-02-2000
Subjects:
chemical properties
chemical reactions
clay mineralogy
Earth sciences
Earth, ocean, space
Exact sciences and technology
experimental studies
ferrihydrite
geochemistry
hematite
Mineralogy
Non silicates
oxides
polyhedra
sed rocks, sediments
Sedimentary petrology
silicon
sintering
X-ray diffraction data
experimental studies
crystal chemistry
oxides
X-ray diffraction
hematite
X-ray spectroscopy
heat treatment
specific surface
hydroxides
silicon
ferrihydrite
oxidizing environment
transformations
temperature
reducing environment
infrared spectroscopy
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Summary:The distribution and chemical state of Si in a synthetic 2-line ferrihydrite with a Si/(Si+Fe) molar ratio of 0.11 was studied. Heat treatment under oxidizing conditions shows that Si-rich ferrihydrite is stable to 400°C. The transformation to hematite and the formation of a polymerized amorphous-silica phase occur at 850°C. At this temperature, the specific surface area decreases greatly and the average pore diameter increases, which is indicative of sintering. Heating under severe reducing conditions causes a segregation of Si from Fe and results in a mixture of elemental Fe and SiO2. Surface and structural data suggest that Si is located near the particle surface where it limits the rearrangement of Fe octahedra to form hematite.
ISSN:0009-8604
1552-8367
DOI:10.1346/ccmn.2000.0480106