Surface vibrational modes of silanol groups on silica

Morrow, B. A.; McFarlan, Andrew

doi:10.1021/j100182a068

Cited by 298 publications

(227 citation statements)

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“…This band is assigned to the isolated surface silanols of the amorphous silica expelled from halloysite (Morrow and McFarlan, 1992). For Hal-700, the 3745 cm À1 band was more intense (Figure 4e), indicating the continued formation of amorphous silica.…”

Section: Resultsmentioning

confidence: 96%

Changes in Structure, Morphology, Porosity, and Surface Activity of Mesoporous Halloysite Nanotubes Under Heating

Yuan

Tan

Annabi-Bergaya

et al. 2012

Clays and clay miner.

187

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Abstract-The objective of the present study was to investigate changes in the structural, textural, and surface properties of tubular halloysite under heating, which are significant in the applications of halloysite as functional materials but have received scant attention in comparison with kaolinite. Samples of a purified halloysite were heated at various temperatures up to 1400ºC, and then characterized by X-ray diffraction, electron microscopy, Fourier-transform infrared spectroscopy, thermal analysis, and nitrogen adsorption. The thermal decomposition of halloysite involved three major steps. During dehydroxylation at 500À900ºC, the silica and alumina originally in the tetrahedral and octahedral sheets, respectively, were increasingly separated, resulting in a loss of long-range order. Nanosized (5À40 nm) g-Al 2 O 3 was formed in the second step at 1000À1100ºC. The third step was the formation of a mullite-like phase from 1200 to 1400ºC and cristobalite at 1400ºC. The rough tubular morphology and the mesoporosity of halloysite remained largely intact as long as the heating temperature was <900ºC. Calcination at 1000ºC led to distortion of the tubular nanoparticles. Calcination at higher temperatures caused further distortion and then destruction of the tubular structure. The formation of hydroxyl groups on the outer surfaces of the tubes during the disconnection and disordering of the original tetrahedral and octahedral sheets was revealed for the first time. These hydroxyl groups were active for grafting modification by an organosilane (g-aminopropyltriethoxysilane), pointing to some very promising potential uses of halloysite for ceramic materials or as fillers for novel clay-polymer nanocomposites.

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Section: Resultsmentioning

confidence: 96%

Changes in Structure, Morphology, Porosity, and Surface Activity of Mesoporous Halloysite Nanotubes Under Heating

Yuan

Tan

Annabi-Bergaya

et al. 2012

Clays and clay miner.

187

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“…7a). The peak near 780 cm À1 in turn becomes now apparent, and it can readily be assigned to silanol bending modes (Morrow & McFarlan, 1992;Davis & Tomozawa, 1996). Room-temperature INS spectra of Opal C1 and Opal A3 (Fig.…”

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confidence: 94%

Ordering of water in opals with different microstructures

Eckert¹,

Gourdon²,

Jacob³

et al. 2015

ejm

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Opal has long fascinated scientists. It is one of the few minerals with an amorphous structure, and yet, compared to silica glass, it is highly organized on the mesoscale. By means of inelastic neutron scattering (INS), we could document that in four samples of opal at low temperature an ice-like structure of water is present, with details depending on microstructural characteristics. While FTIR spectra for all samples are nearly identical and thus not very informative, INS shows clear differences, highlighting the significance of microstructures. Neutron diffraction at 100 K on one of the opal samples provides evidence for crystalline cubic ice.

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“…With respect to the high hydrogen selectivity of the IINS method it can be argued that the band at about 130 cm −1 can be due to a low frequency torsional movement of silanol groups. According to conclusions of Morrow and McFarlan a torsional mode of Si-OH can be expected at this energy [10]. Neutron scattering on vitreous silica led to the conclusion that bands at about 800 -1200 cm −1 are due to Si-O stretching modes and those at 300 -400 cm −1 to Si-O bending modes [11].…”

Section: Resultsmentioning

confidence: 99%

Low-frequency Vibrational Dynamics of Amorphous and Crystalline Silica

Albers¹,

Michael

Rotgerink

et al. 2012

Zeitschrift Für Naturforschung B

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RCrystalline silica shows strong, sharp signals at about 77 and 130 cm −1 in the inelastic neutron scattering spectrum that are missing or strongly different, broadened and shifted to lower frequency for the case of precipitated and fumed silica. The presence or absence of these signals is a sensitive signature of crystallinity or amorphicity in silica. The low-frequency phonon density of states of precipitated and fumed silica is typical for completely amorphous materials. This observation is in perfect agreement with data from X-ray diffraction and high-resolution transmission electron microscopy. The amorphicity is retained during granulation post-treatments.

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Surface vibrational modes of silanol groups on silica

Cited by 298 publications

References 0 publications

Changes in Structure, Morphology, Porosity, and Surface Activity of Mesoporous Halloysite Nanotubes Under Heating

Changes in Structure, Morphology, Porosity, and Surface Activity of Mesoporous Halloysite Nanotubes Under Heating

Ordering of water in opals with different microstructures

Low-frequency Vibrational Dynamics of Amorphous and Crystalline Silica

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