29Si MASNMR investigations of the thermochemistry of laponite and hectorite

Mandair, Arvind; Michael, Paul J.; McWhinnie, William R.

doi:10.1016/s0277-5387(00)86228-2

Cited by 35 publications

(21 citation statements)

References 13 publications

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“…This was explained as the first sign of structural destabilization. The occurrence of thermally generated radicals in the present hectorite agrees well with the findings of Mandair et al (1990). In their study on synthetic hectorite, they observed a change in the 29 Si NMR signal at~400ºC and explained it by an increase in oxygen anions which are not bridging SiO 4 tetrahedra.…”

Section: Spectroscopic Evidence For the Conversion Of Hectoritesupporting

confidence: 91%

“…The fact that Cu(II) triggers the formation of Mg-F richterite at a small fluoride content supports this assumption. However, this cannot be verified unambiguously by the EPR data, since enstatite also contains distorted octahedral sites which generate Cu(II) spectra (Mandair et al, 1990) similar to those found for the present samples. The stability of the Cu(II) signal at 1000ºC, where no richterite was found by XRD, proves Cu(II) in enstatite.…”

Section: Spectroscopic Evidence For the Conversion Of Hectoritecontrasting

confidence: 62%

“…On the other hand, Mosser et al (1997) postulated, based on electron paramagnetic resonance (EPR) spectra, that heating of Cu(II)-exchanged hectorite to~200À300ºC led to migration of Cu(II) into the structure, and offered the Hofmann-Klemen effect to explain this behavior. Mandair et al (1990) reported that Cu(II)-exchanged hectorite converts thermally to enstatite and an amorphous Si phase. The newly formed enstatite contained Cu(II) in its structure.…”

Section: Introductionmentioning

confidence: 99%

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The transformation of synthetic hectorite in the presence of Cu(II)

Fischer

Weidler

Grobéty

et al. 2009

Clays and clay miner.

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Abstract-The influence of Cu(II) on the hydrothermal and thermal transformations of a synthetic hectorite was investigated by a combined approach using mainly X-ray diffraction, thermal analyses, and electron paramagnetic resonance spectroscopy. The presence of Cu(II) during hydrothermal treatment increased the crystallite size. Copper (II) was both structure-bound and associated with the inner surfaces of the particles. Upon heating, structural destabilization of the hectorite began at~400ºC as indicated by the formation of free radicals. Between 600 and 700ºC, the hectorite converted to enstatite, and in the presence of Cu(II), to enstatite and richterite. The formation of richterite as an additional conversion product is explained by the creation of structural weakness due to structure-bound Cu(II) in F-containing hectorite. Our results suggest that traces of Cu(II), typical of natural environments, may influence the conversion products in high-temperature geochemical systems.

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Section: Spectroscopic Evidence For the Conversion Of Hectoritesupporting

confidence: 91%

Section: Spectroscopic Evidence For the Conversion Of Hectoritecontrasting

confidence: 62%

Section: Introductionmentioning

confidence: 99%

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The transformation of synthetic hectorite in the presence of Cu(II)

Fischer

Weidler

Grobéty

et al. 2009

Clays and clay miner.

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“…8,9,21 The silicon and magnesium atoms are connected to a total of twenty oxygen atoms and four hydroxyl groups. There also exists silanol groups (mostly located at the edges) [8][9][10]28 that, combined with the interlayer exchangeable sodium ions of pristine laponite, allows two kinds of modifications.…”

Section: Synthesis Of Dual-functionalized Laponitesmentioning

confidence: 99%

Synthesis and characterization of dual‐functionalized laponite clay for acrylic nanocomposites

Wang

Wheeler

Jarrett

et al. 2007

J of Applied Polymer Sci

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Dual-functional laponites were synthesized by a condensation reaction with silane coupling agents followed by cation exchange reaction with quaternary ammonium salts. Si DP/MAS NMR spectra indicated that clay silanol groups reacted with silane coupling agents by a decrease in the silanol peak and appearance of a new SiÀ ÀOÀ ÀSi peak. Dual-functionalized laponites showed improved dispersion in organic solvents and vinyl monomers. One dual-functional laponite modified with both photosensitizer and coinitiator photo-initiated polymerization of an acrylate (2-phenoxyethyl acrylate, PEA) and a methacrylate (MHMA, methyl a-hydroxymethylacrylate). TEM showed laponite clay sheets were exfoliated in poly(PEA); while a combination of exfoliated, intercalated and tactoid morphologies was found in poly(methyl a-hydroxymethylacrylate). The other dual-functionalized laponite clay with edge-bound methacrylate units copolymerized with methyl methacrylate and led to a high grafting amount and graft efficiency. PMMA nanocomposites showed higher storage modulus both below and above the glass transition temperature compared to the PMMA control.

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“…Differential thermal analysis data for hectorite and montmorillonite were measured with a Stanton Redcroft DTA 673-4 instrument, utilizing a heating rate of 20~ Mandair et al (1990) analyzed the sample of hectorite by XRD and DTA; an X-ray fluorescence analysis (XRF) was also performed. XRD data gave d(001) = 12.83/~ and also revealed a calcite impurity, which was removed mechanically prior to exchange to the sodium form; the ion-exchange capacity was determined to be 58 meq/100 g (Davison, 1987) DTA traces were typical of those previously reported for hectorite (Davison, 1987;Mackenzie, 1957).…”

Section: Other Techniquesmentioning

confidence: 99%

X-Ray Photoelectron Spectroscopic Study of Cobalt(II) and Nickel(II) Sorbed on Hectorite and Montmorillonite

Davison

McWhinnie

Hooper

1991

Clays and clay miner.

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Abstract--The safe disposal of 6~ 63Ni, and 59Ni has required considerable information on the interactions of Co 2+ and Ni 2+ with clay minerals in the geosphere. X-ray photoelectron spectroscopy (XPS) has been used to probe the sorption sites for Co 2+ and Ni 2+ on hectorite and montmorillonite. The spectra were measured for Co-hectorite, Ni-hectorite, and Ni-montmorillonite immediately following ion exchange and after washing the clay two and five times with distilled water. The spectra, recorded following etching of the surface with an argon ion beam, differentiate two sorption sites; a labile (to washing) fraction sorbed as ion pairs, and a non-labile fraction sorbed by ion exchange at broken bond and interlamellar sites. The data were consistent with the sorption of metal ions (Co 2 § NP +) in a c o m m o n "MO6" ligand environment.C& § had a greater affinity for exchange on hectorite than did NiZ+; but NP + had a greater affinity for the surface of montmorillonite than for hectorite. The argon ion etching of Ni-montmorillonite gave rise to a new photopeak of 853 eV, which was probably due to elemental Ni formed consequent to the chemical violation of the surface by ion etching.

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29Si MASNMR investigations of the thermochemistry of laponite and hectorite

Cited by 35 publications

References 13 publications

The transformation of synthetic hectorite in the presence of Cu(II)

The transformation of synthetic hectorite in the presence of Cu(II)

Synthesis and characterization of dual‐functionalized laponite clay for acrylic nanocomposites

X-Ray Photoelectron Spectroscopic Study of Cobalt(II) and Nickel(II) Sorbed on Hectorite and Montmorillonite

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