Mössbauer Study of Transformations Induced in Clay by Firing

Simopoulos, A.

doi:10.1346/ccmn.1975.0230512

Cited by 34 publications

(5 citation statements)

References 9 publications

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“…Induced stresses and distortions leading to a highly disorganized calcined montmorillonite structure due to the oxidation of iron accompanied with increasing quadrupole splitting values was partly confirmed by (Miller et al, 1963;Simopoulos et al, 1975;Tichit et al, 1988). Figure 9a-b shows images of the raw Clay A.…”

Section: Mössbauer Spectroscopymentioning

confidence: 81%

Characterisation of calcined raw clays suitable as supplementary cementitious materials

Danner

Norden

Justnes

2018

Applied Clay Science

111

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The potential use of two raw clays (Clay A: kaolin; Clay B: calcareous montmorillonite) as supplementary cementitious material (SCM) in blended cements was investigated. Cement replacement in mortars by 20% calcined Clay A and Clay B resulted in a considerable 28 day compressive strength improvement. The pozzolanic reactivity of Clay A and B is explained by characterization of the structural changes upon calcination with XRD, ICP-MS, FT-IR, 27Al-NMR, Mössbauer spectroscopy and SEM. At the temperature giving highest pozzolanic reactivity, kaolinite and montmorillonite were completely dehydroxylated, while calcite from Clay B was not completely decomposed. FT-IR, 27Al-NMR and Mössbauer spectroscopy revealed considerable structural deformations of kaolinite in Clay A and montmorillonite in Clay B resulting in an amorphous, reactive state. Oxidation of iron in Clay B during calcination contributed to strong distortions of the octahedral sheet in the montmorillonite structure. Additionally, the formation of a glass phase due to reaction of coccoliths (CaCO3) and montmorillonite was observed.

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Section: Mössbauer Spectroscopymentioning

confidence: 81%

Characterisation of calcined raw clays suitable as supplementary cementitious materials

Danner

Norden

Justnes

2018

Applied Clay Science

111

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“…The fact that any following oxidizing step does not sinter these moieties to pillars with larger diameters is explained by our assumption that the Fe 3+ ions uptaken from the intercalant solution occupy the interlayer space. If the Fe oxides were coveting the outer surface of the clay platelets, their size would increase by sintering during firing in air (Simopoulos et al, 1975). The deduced decrease of the lateral size of these oxide particles is probably due to a reorganization of their crystallographic structure upon the reduction of Fe 3+ to Fe 2+.…”

Section: Discussionmentioning

confidence: 99%

Redox Treatment of an Fe/Al Pillared Montmorillonite. A Mössbauer Study

Bakas

Moukarika

Papaefthymiou

et al. 1994

Clays and clay miner.

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Abstract--Pillared structures with an interlayer opening of ~ 0.3 nm were obtained after successive heat treatments of the PILC precursor in reducing and oxidizing conditions. This precursor was prepared by reacting a Na+-montmorillonite with an intercalant containing A1 and Fe oxo-hydroxides (A1/Fe = 1). Powder X-ray diffraction, elemental analysis, 57Fe Mrssbauer spectroscopy, catalytic activity measurements and surface area data were used to characterize the samples. On the basis of M6ssbauer spectra taken at temperatures between 4.2 and 300 K, it is deduced that oxidizing steps produce A1 substituted maghemite which converts into A1 substituted magnetite upon reducing heat treatment. Firing the precursor in oxidizing atmosphere forms pillars of few nm in diameter. However, heating under reducing conditions yields pillars of smaller diameter. This later behaviour is maintained even after reheating the material in oxidizing atmosphere. From the temperature dependence of M6ssbauer spectra it is deduced that the diameter of the Fe oxide particles in the pillars is smaller than 10 nm.

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“…It has been found that under oxidizing conditions, all clays behave similarly (Aburto er (11. 1979;Bouchez et al 1974;Chevalier et al 1976;Kostikas et al 1976;Salazar et al 1983;Simopoulos et al 1975;Wagner ef al. 1986).…”

Section: Claysmentioning

confidence: 99%

Firing Analysis of South‐eastern Missouri Indian Pottery Using Iron Mössbauer Spectroscopy*

Berhane

May

1998

Archaeometry

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The Mossbauer spectra ofprehistoric pottery and clay from the Malden Plain of south-eastem Missouri, USA, were examined. The pottery dates from AD 500 to 1400. The earlier sherds were tempered with sand and the later ones with shell. The sherds and clay contain a mixture of illite. smectite, and kaolinite. Most samples of clay and sherds contained both ferric and ferrous species. The spectral parameters for the ferric species were AEp-0.7-1. 1 mmsC' and 6-0.0-0.3mms-' for the ferrous species, AEQ-2.1-2.7rnms-' and 6-0.7-1.0mms-'. The ferric to ferrous ratio is more accurately determined from the spectra than from consideration of the d o u r or the jiring core of the sherds, which are not always related to the iron species ratio. Dlferences among sherds in the ferrous AEQ can be related to original temperature of heating but with low precision.Large Large a Black core sizes, as percentage of sherd thickness: small ~5 0 % . medium 50-7070, large >70%.

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Mössbauer Study of Transformations Induced in Clay by Firing

Cited by 34 publications

References 9 publications

Characterisation of calcined raw clays suitable as supplementary cementitious materials

Characterisation of calcined raw clays suitable as supplementary cementitious materials

Redox Treatment of an Fe/Al Pillared Montmorillonite. A Mössbauer Study

Firing Analysis of South‐eastern Missouri Indian Pottery Using Iron Mössbauer Spectroscopy*

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