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Effect of Heating on Microcrystalline Synthetic Goethite

Published online by Cambridge University Press:  02 April 2024

Christian J. W. Koch ,
Morten Bo Madsen ,
Steen Mørup ,
Gunnar Christiansen ,
Leif Gerward  and
Jørgen Villadsen
Christian J. W. Koch
Affiliation:
Chemistry Department, Royal Veterinary and Agricultural University, DK-1871 Copenhagen V, Denmark
Morten Bo Madsen
Affiliation:
Laboratory of Applied Physics II, Technical University of Denmark, DK-2800 Lyngby, Denmark
Steen Mørup
Affiliation:
Laboratory of Applied Physics II, Technical University of Denmark, DK-2800 Lyngby, Denmark
Gunnar Christiansen
Affiliation:
Laboratory of Applied Physics III, Technical University of Denmark, DK-2800 Lyngby, Denmark
Leif Gerward
Affiliation:
Laboratory of Applied Physics III, Technical University of Denmark, DK-2800 Lyngby, Denmark
Jørgen Villadsen
Affiliation:
Haldor Topsøe Research Laboratories, DK-2800 Lyngby, Denmark
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Abstract

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The effect of heating synthetic microcrystalline goethite at 60°, 80°, and 105°C was studied by X-ray powder diffraction, electron microscopy, weight-loss measurements, and Mössbauer spectroscopy. Heating led to no detectable changes in the unit-cell parameters or crystallite size (210, 150, and 170 Å in the [020], [110], and [120] directions, respectively), however, some of the X-ray diffraction lines were broadened due to an increase in microstrain in these crystallographic directions. The superferromagnetic transition temperature increased from 43° to 46°, 53°, and 54°C after heating to 60°, 80°, and 105°C, respectively, showing that the desorption of water from the surfaces led to an enhanced magnetic coupling among the crystallites.

Keywords

Crystallite sizeGoethiteMicrostrainMössbauer spectroscopyThermal treatmentX-ray powder diffraction
Type
Research Article
Information
Clays and Clay Minerals , Volume 34 , Issue 1 , February 1986 , pp. 17 - 24
Copyright
Copyright © 1986, The Clay Minerals Society

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