23Na NMR chemical shifts and local Na coordination environments in silicate crystals, melts and glasses

Xue, Xianyu; Stebbins, Jonathan F.

doi:10.1007/bf00215100

Cited by 223 publications

(315 citation statements)

References 30 publications

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“…8) Na MAS-NMR for pure Jd has been reported previously at 11 ppm [44][45][46][47] , which when corrected for field effects (14.1T) the peak comes at 0 ppm. This is clearly seen, at 0 ppm, the site for DJ1.…”

Section: Ht Glassesmentioning

confidence: 59%

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MAS-NMR studies of glasses and glass-ceramics based on a clinopyroxene–fluorapatite system

et al. 2010

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Glasses and glass-ceramics based on the ternary system CaMgSi 2 O 6 -NaAlSi 2 O 6 -Ca 5 (PO 4 ) 3 F (diopside(Di)-jadeite(Jd)-fluorapatite(FAp)) have been studied with magic angle spinning (MAS) NMR, powder x-ray diffraction (XRD) and thermal calorimetry. In this silicate system Na 2 O and Al 2 O 3 has been progressively substituted for CaO and MgO: (CaMgSi 2 O 6 ) 1-x -(NaAlSi 2 O 6 ) x -(Ca 5 (PO 4 ) 3 F) y where 0 ≤ x ≤ 30mol% and y = 7 mol%. 29Si MAS-NMR of the glasses showed a peak corresponding to a mixed Q

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Section: Ht Glassesmentioning

confidence: 59%

“…Sodium occupies the M2 cation site in these coupled substituted solid solutions 5,44 . In contrast to the M1 site occupied by Al and Mg, the M2 site can be distorted and therefore the NMR shift changes with the amount of Na that is substituted into the solid solution (going from DJ1-DJ5).…”

Section: Ht Glassesmentioning

confidence: 97%

MAS-NMR studies of glasses and glass-ceramics based on a clinopyroxene–fluorapatite system

et al. 2010

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“…Thus, a variety of structural parameters such as coordination number, bond length and modifier ion nature should be involved. For example, 23 Na NMR investigations of silicate and alumina-silicate crystals and melts have shown that a decrease in the degree of network polymerization within the structure produces an increase in the 23 Na chemical shift [16]. The phosphate glasses show a different trend, where the variation in C Q is not significant, suggesting that the chemical environment around the sodium cations is constant.…”

Section: Single Fibre Tensile Test (Sftt)mentioning

confidence: 99%

Structure–properties relationships in fibre drawing of bioactive phosphate glasses

et al. 2017

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New bioactive phosphate glasses suitable for continuous fibre production are investigated in this work. The structure of both bulk and fibres from Na 2 O-CaO-MgO-P 2 O 5 glasses has been studied by means of Raman and 31 P and 23 Na Nuclear Magnetic Resonance spectroscopies, and the structural results have been correlated with the mechanical properties of the fibres and the dissolution rate of the bulk glasses. It has been observed that the mechanical properties of the phosphate glass fibres are influenced by the glass network connectivity, whilst the dissolution rates are governed by the Q i speciation of the PO 4 units. As seen in previous studies, molar volume seems to play an important role in the fragility behaviour of phosphate glasses. Here, a lower molar volume resulting from the increase in the oxygen packing density, hinders the cooperative flow of the PO 4 units throughout the glass network and, therefore, causes a reduction in the kinetic fragility.

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“…27 Al and 23 Na MAS and multiple quantum MAS (MQMAS) NMR experiments were conducted on samples compressed at 1 GPa or annealed at 0.92Tg for 168 h and subsequently ion exchanged in molten KNO3 at 410°C for 10 h. A 16.4-T magnetic field was used in conjunction with a commercial spectrometer (Agilent) and 1.6 mm MAS NMR probe. The resonance frequencies at this external magnetic field were 182.34 and 185.12 MHz for 27 Al and 23 Na, respectively. Samples were crushed and loaded into 1.6 mm zirconia rotors, which gave a small 27 Al background signal that was identified by running duplicate MAS NMR experiments on the empty rotors.…”

Section: Methodsmentioning

confidence: 99%

“…However, compression at temperatures at or below 450°C prevented the subsequent ion exchange from effectively increasing the hardness of the glass. Based on 23 Na magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy measurements, the latter finding was attributed to a structural modification of the sodium environment during compression, which in turn led to a modification of the structural setting of the potassium ions incorporated during subsequent ion exchange. By increasing the compression temperature to 600°C (Tg = 652°C), this structural modification was reversed, and a significant increase in hardness was observed (Svenson et al, 2014a).…”

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confidence: 99%

Effects of Thermal and Pressure Histories on the Chemical Strengthening of Sodium Aluminosilicate Glass

et al. 2016

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Glasses can be chemically strengthened through the ion exchange process, wherein smaller ions in the glass (e.g., Na + ) are replaced by larger ions from a salt bath (e.g., K +). This develops a compressive stress (CS) on the glass surface, which, in turn, improves the damage resistance of the glass. The magnitude and depth of the generated CS depend on the thermal and pressure histories of the glass prior to ion exchange. In this study, we investigate the ion exchange-related properties (mutual diffusivity, CS, and hardness) of a sodium aluminosilicate glass, which has been densified through annealing below the initial fictive temperature of the glass or through pressure quenching from the glass transition temperature at 1 GPa prior to ion exchange. We show that the rate of alkali interdiffusivity depends only on the density of the glass, rather than on the applied densification method. However, we also demonstrate that for a given density, the increase in CS and increase in hardness induced by ion exchange strongly depend on the densification method. Specifically, at constant density, the CS and hardness values achieved through thermal annealing are larger than those achieved through pressure quenching. These results are discussed in relation to the structural changes in the environment of the network modifiers and the overall network densification.

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23Na NMR chemical shifts and local Na coordination environments in silicate crystals, melts and glasses

Cited by 223 publications

References 30 publications

MAS-NMR studies of glasses and glass-ceramics based on a clinopyroxene–fluorapatite system

MAS-NMR studies of glasses and glass-ceramics based on a clinopyroxene–fluorapatite system

Structure–properties relationships in fibre drawing of bioactive phosphate glasses

Effects of Thermal and Pressure Histories on the Chemical Strengthening of Sodium Aluminosilicate Glass

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