Qn distribution in stoichiometric silicate glasses: thermodynamic calculations and 29Si high resolution NMR measurements

Schneider, José Fabián; Mastelaro, Valmor Roberto; Zanotto, Edgar Dutra; Shakhmatkin, B. A.; Vedishcheva, Natalia M.; Wright, Adrian C.; Panepucci, Horácio Carlos

doi:10.1016/s0022-3093(03)00332-6

Cited by 99 publications

(92 citation statements)

References 14 publications

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“…Similar conclusion was also drawn from NMR investigations (Maekawa et al, 1991;Maekawa and Yokokawa, 1997;Zhang et al, 1997;Schneider et al, 2003;Xue and Kanzaki, 2004;Malfait et al, 2007a;Davis et al, 2011;Morizet et al, 2014b) for various types of compositions from simple binary M n O-SiO 2 systems but also for more complex Al-bearing systems. This reaction implies that for a given chemical composition three Q-species are in equilibrium in glasses.…”

Section: Introductionsupporting

confidence: 80%

A NMR and molecular dynamics study of CO2-bearing basaltic melts and glasses

2015

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International audienceThe presence of volatile, especially carbon dioxide (CO2), in silicate liquids is considered as a key parameter to magmatic degassing and eruptive processes. Unfortunately, due to experimental difficulties, our current knowledge on the CO2 effect on silicate melt structure is weak and relies on the observation of ex-situ recovered CO2-bearing glasses.In the present work, we confront the results obtained from NMR spectroscopic observations of glass synthesised at pressure between 0.5 and 3.0 GPa and theoretical investigations from first-principles molecular dynamics (FPMD) simulations conducted at 5.0 and 8.0 GPa on high temperature melt for a simplified basaltic composition.The results obtained on the aluminosilicate framework (molar fraction of silicon species and Al average coordination number) suggest that both ex-situ and in-situ results compare adequately. The results are in agreement with our current knowledge on the change in aluminosilicate melt/glass structure with changing intensive conditions. Increasing pressure from 0.5 to 8.0 GPa induces 1) an increase in the average Al coordination number from 4.1 to almost 5.0 and 2) an increase in the degree of polymerisation with NBO/Si changing from 1.30 to 0.80.The presence of CO2 does not seem to induce a dramatic change on both the average Al coordination number and the NBO/Si. FPMD simulations performed with 0 and 20 wt.% CO2 at 8.0 GPa result in a change from 4.84 to 4.96 for the average Al coordination number and in a change from 0.87 to 0.80 for the NBO/Si value, respectively.On the contrary, there is a lack of consistency in between the CO2 speciation obtained from NMR spectroscopy and from FPMD simulations. Whereas the analysis of glasses does not reveal the presence of CO2mol species, the FPMD simulation results suggests the existence of a small proportion of CO2mol. Further work with in-situ experimental approach is therefore required to explain the observed lack of consistency between the CO2 speciation in glass and in high temperature melt with basaltic composition

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Section: Introductionsupporting

confidence: 80%

A NMR and molecular dynamics study of CO2-bearing basaltic melts and glasses

2015

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“…11 However, Ca tends to cause a shift of δ Si to a more negative chemical shift. 22 The effect of Ca concentration variation from one gel to another may counterbalance any variations in polymerization. We then cannot rule out the hypothesis that some gels are more polymerized than others.…”

Section: Gel Compositionmentioning

confidence: 99%

Impact of alkali on the passivation of silicate glass

et al. 2018

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Amorphous silica-rich surface layers, also called gels, can passivate silicate glass and minerals depending on environmental conditions. However, several uncertainties remain on the mechanisms controlling the formation of these layers. In this paper, the influence of exogenous ions supplied by solutions is studied, both on the formation and on the properties of the gel formed on international simple glass (ISG). ISG was altered at 90°C, pH 90°C 7, in silica-saturated solutions containing various alkaline cations separately (Li + , Na + , K + , and Cs + ). The alteration kinetics observed with Li and Na in the solution is similar to that observed with no ions, while K and Cs in the solution tend to decrease glass alteration. Furthermore, for K or Cs ions, the kinetics decreases as the ionic strength of the solution increases. The passivation layer formed in these solutions shows a selectivity toward cations following the series K > Cs > Na >> Li. These alkalis replace Ca from pristine glass in the altered structures, leading to differences in [AlO 4 ] − units charge compensation. Importantly, exchange between Ca and alkali also affects the total quantity of water inside each gel and this effect is well correlated with the observed drop in glass alteration.

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“…Taking this into consideration, one can notice that N-ZK7 has more BO 4 (1B, 3Si) while N-BK7 and S-BSL7 have a predominance of BO 4 (0B, 4Si). The 29 Si signal for Borofloat and N-ZK7 corresponds to mostly Q4 contributions while for the two other materials the band which is centered around -100ppm is certainly generated by a mix of Q3 and Q4 units [18] [19] [20].…”

Section: Pristine Glassesmentioning

confidence: 99%

High thermal neutron flux effects on structural and macroscopic properties of alkali-borosilicate glasses used as neutron guide substrate

Boffy

Peuget

Schweins

et al. 2016

Nuclear Instruments and Methods in Physics Research Section B:

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The behaviour of four alkali-borosilicate glasses under homogeneous thermal neutron irradiation has been studied. These materials are used for the manufacturing of neutron guides which are installed in most facilities as devices to transport neutrons from intense sources such as nuclear reactors or spallation sources up to scientific instruments. Several experimental techniques such as Raman, NMR, SANS and STEM have been employed in order to understand the rather different macroscopic behaviour under irradiation of materials that belong to a same glass family. The results have shown that the remarkable glass shrinking observed for neutron doses below 0.5 · 10 18 n/cm 2 critically depends upon the presence of domains where silicate and borate network do not mix.

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Qn distribution in stoichiometric silicate glasses: thermodynamic calculations and 29Si high resolution NMR measurements

Cited by 99 publications

References 14 publications

A NMR and molecular dynamics study of CO2-bearing basaltic melts and glasses

A NMR and molecular dynamics study of CO2-bearing basaltic melts and glasses

Impact of alkali on the passivation of silicate glass

High thermal neutron flux effects on structural and macroscopic properties of alkali-borosilicate glasses used as neutron guide substrate

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