Solid-state high-resolution 29Si NMR in zunyite

Grimmer, A.‐R.; Lampe, F. von; Tarmak, M.; Lippmaa, É.

doi:10.1016/0009-2614(83)85013-1

Cited by 34 publications

(8 citation statements)

References 9 publications

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“…The chemical shifts of crystals were studied first for different Q n units . Later, more silicate melts associated with Q n species are reported. , Usually, the chemical shift of quartz, which is composed of Q 4 , is about −107.3 ppm; the chemical shifts of anorthite which is composed of Q 2 and Q 3 are about −83 and −89 ppm; the chemical shift of diopside which is composed of Q 3 is about −85 ppm; the chemical shifts of mullite which is composed of Q 3 and Q 4 are about −87, −90, and −94 ppm; and the chemical shift of rankinite which is composed of Q 1 is about −73 ppm. ,,, However, for coal ash melts, the signal peaks of different Q n overlap each other, which make it difficult to distinguish different Q n units.…”

Section: Resultsmentioning

confidence: 99%

“…This article investigates the Q n units in three coal slags and seven synthetic slags using the experimental method: 29 Si magic-angle spinning (MAS) NMR, an advanced spectroscopic method which has been already used in silicon melts, − and the simulation method: MD applied to study the structural details regarding the chemical bond and bond energy. ,, These two methods are effective to characterize the structure, and a combination of these two can increase the reliability of the quantitative structural results. Because Si is the most important contributor for polymerization and the quantitative determination of different Q n units is only available for 29 Si spectra, the Q n units in which Si acts as the centered atom are concerned in this article.…”

Section: Introductionmentioning

confidence: 99%

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Quantitative Study of Si Structural Units in Coal Slags and Their Influence on Viscosity

Wang

Zhang

2019

Energy Fuels

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The properties of coal slags in slagging gasifiers such as viscosity are intrinsically determined by the structure. In this article, the structure of 10 coal slags is investigated by a combination of the nuclear magnetic resonance (NMR) experiment and molecular dynamics (MD) simulation quantitatively. The proportions of different structural units Q n with Si as the centered atom are determined, and the results from the NMR experiment and MD simulation agree well. As the basicity increases, the proportion of the Q4 unit decreases, while those of Q3, Q2, and Q1 increase, which indicate that the polymerization degree decreases with an increase of basicity. A structural parameter, QSi, is proposed to characterize the polymerization degree, and the relationship between QSi and basicity can be described by a linear equation. Also, an exponential function between the viscosity and the proposed polymerization parameter QSi is discovered. Viscosity experiments are performed to verify the predictions, and the result shows a good consistency between experiments and predictions above the temperature of critical viscosity (T cv).

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Quantitative Study of Si Structural Units in Coal Slags and Their Influence on Viscosity

Wang

Zhang

2019

Energy Fuels

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“…The 27 Al and 29 Si MAS NMR spectra have been previously obtained (Grimmer et al 1983, Sherriff et al 1991, Dirken et al 1995. Although assignments of the major peaks at -97 and -128 ppm for 29 Si, and 72 and 10 ppm for 27 Al, in the MAS NMR spectra of zunyite have been determined, there is still controversy over a minor 29 Si peak at -91 ppm and the 27 Al peaks at about 46 ppm and -3 ppm.…”

Section: Background Informationmentioning

confidence: 99%

“…The 29 Si peak at -96 ppm is assigned to Si(1)P in the outer tetrahedra of the pentamer group with Q 1 (1Si) configuration (Grimmer et al 1983, Sherriff et al 1991, Dirken et al 1995. The peak at -128 ppm is assigned to the Si(2) at the inner tetrahedron with Q 4 (4Si) configuration, which is at a very low frequency owing to four almost straight <Si-O-Si> angles (Grimmer et al 1983, Sherriff et al 1991. Grimmer et al (1983) assumed that the 29 Si peak at -91 ppm is caused by an impurity of nacrite in their sample of zuynite.…”

Section: Tetrahedral Sitesmentioning

confidence: 99%

“…The peak at -128 ppm is assigned to the Si(2) at the inner tetrahedron with Q 4 (4Si) configuration, which is at a very low frequency owing to four almost straight <Si-O-Si> angles (Grimmer et al 1983, Sherriff et al 1991. Grimmer et al (1983) assumed that the 29 Si peak at -91 ppm is caused by an impurity of nacrite in their sample of zuynite. From the bond distances in the pentamer, Baur & Ohta (1982) showed that excess Al replaces some Si atoms at the inner tetrahedron of the pentamer unit.…”

Section: Tetrahedral Sitesmentioning

confidence: 99%

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NUCLEAR MAGNETIC RESONANCE STUDY OF Al:Si AND F:OH ORDER IN ZUNYITE

Zhou¹,

Sherriff²,

Taulèlle³

et al. 2003

The Canadian Mineralogist

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Zunyite [Al 13 Si 5 O 20 (OH,F) 18 Cl] possesses an unusual combination of an Al 13 O 16 (OH) 24 Keggin structure and a Si 5 O 16 pentamer unit. We used 19 F, 27 Al, 29 Si MAS and 27 Al MQMAS NMR spectroscopy of a series of samples with varying Al:Si and F:OH ratios to investigate the degree of atomic order in zunyite. The quadrupole coupling constant (C Q) and asymmetry parameter () obtained from simulations of 27 Al MAS and MQMAS spectra were compared with those derived from the electric field gradients (EFG), which were calculated from an ab initio cluster quantum model using the program Gaussian 98W. This comparison led to unequivocal assignments for 29 Si, 27 Al and 19 F MAS NMR peaks and showed that the number of Al substituting for Si(1) in the pentamer increases with Al content. The number of Al octahedra with one F atom increases with F content, whereas the number with two F atoms remains negligible, indicating that F preferentially occupies AlO 4 OHF octahedra.

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Hochauflösende Festkörper‐NMR‐Untersuchungen an Kieselsäuren. I. Hochauflösende ²⁹Si‐Festkörper‐NMR‐Untersuchungen an polykristallinen Phyllokieselsäuren (H₂Si₂O₅)_x bei tiefem und hohem Magnetfeld

Heidemann

Grimmer

Hubert

et al. 1985

Zeitschrift anorg allge chemie

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29Si‐NMR‐Untersuchungen an zwei verschiedenen Formen von Phyllokieselsäure (H2Si2O5)x zeigen, daß sich die isotropen Werte der chemischen Verschiebung unterscheiden, während Betrag und Vorzeichen der Anisotropie des Abschirmtensors übereinstimmen. Die isotropen Werte der chemischen Verschiebung können daher zur Charakterisierung der beiden Proben herangezogen werden. Die untersuchte Probe A (α‐Form) ist eine reine Phyllokieselsäure mit Schichtstruktur, während die untersuchte Probe B (δ‐Form) eine Phyllokieselsäure mit partiell höherkondensierten Bereichen darstellt. Aus den NMR‐Daten wird ein Modell zur Beschreibung dieser Struktur abgeleitet. Die Feldabhängigkeit der Linienbreiten der NMR‐Signale beider Formen weist auf eine Verteilung von Strukturparametern der SiO4‐Tetraeder in den Phyllokieselsäuren hin. Die Diskussion der Anisotropie des Abschirmtensors führt für beide (H2Si2O5)x‐Formen zur Strukturaussagen, die im Widerspruch zur bekannten Struktur von (H2Si2O5)x‐I stehen.

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Solid-state high-resolution 29Si NMR in zunyite

Cited by 34 publications

References 9 publications

Quantitative Study of Si Structural Units in Coal Slags and Their Influence on Viscosity

Quantitative Study of Si Structural Units in Coal Slags and Their Influence on Viscosity

NUCLEAR MAGNETIC RESONANCE STUDY OF Al:Si AND F:OH ORDER IN ZUNYITE

Hochauflösende Festkörper‐NMR‐Untersuchungen an Kieselsäuren. I. Hochauflösende ²⁹Si‐Festkörper‐NMR‐Untersuchungen an polykristallinen Phyllokieselsäuren (H₂Si₂O₅)_x bei tiefem und hohem Magnetfeld

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Solid-state high-resolution 29Si NMR in zunyite

Cited by 34 publications

References 9 publications

Quantitative Study of Si Structural Units in Coal Slags and Their Influence on Viscosity

Quantitative Study of Si Structural Units in Coal Slags and Their Influence on Viscosity

NUCLEAR MAGNETIC RESONANCE STUDY OF Al:Si AND F:OH ORDER IN ZUNYITE

Hochauflösende Festkörper‐NMR‐Untersuchungen an Kieselsäuren. I. Hochauflösende 29Si‐Festkörper‐NMR‐Untersuchungen an polykristallinen Phyllokieselsäuren (H2Si2O5)x bei tiefem und hohem Magnetfeld

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Hochauflösende Festkörper‐NMR‐Untersuchungen an Kieselsäuren. I. Hochauflösende ²⁹Si‐Festkörper‐NMR‐Untersuchungen an polykristallinen Phyllokieselsäuren (H₂Si₂O₅)_x bei tiefem und hohem Magnetfeld