Reply to the comment by Malfait on “Spectroscopic studies of oxygen speciation in potassium silicate glasses and melts”

2015 ◽  
Vol 93 (5) ◽  
pp. 581-587 ◽  
Author(s):  
H.W. Nesbitt ◽  
G.M. Bancroft ◽  
Y. Thibault ◽  
R. Sawyer ◽  
R.A. Secco
Keyword(s):  
Nmr Spectra ◽  
Spectroscopic Studies ◽  
Spectroscopic Technique ◽  
Mas Nmr ◽  
Potassium Silicate ◽  
Silicate Glasses ◽  
Major Difficulty ◽  
Low Resolution ◽  
Nmr Spectrum

Malfait challenges our XPS results by arguing that the XPS spectroscopic technique cannot be used to determine small amounts of O2– in potassium silicate glasses. Instead, he claims that there is no free oxide (O2–) in potassium silicate glasses based primarily on his 29Si MAS NMR spectroscopic results. In this rebuttal, we demonstrate that O1s XPS and well-resolved 2D 29Si MAF NMR spectral results of potassium disilicate (K2Si2O5) glass are consistent with each other and that both techniques indicate the presence of a few mol% of O2– in the glass. Neither of these techniques, however, supports the interpretation of the 29Si MAS NMR results presented in the comments of Malfait. The major difficulty relates to the low resolution of the 29Si MAS NMR spectra, which does not reveal the Q4 signal beneath a strong Q3 peak in these spectra. The proof is provided by the 2D 29Si MAF NMR spectrum of potassium disilicate glass in which both Q3 and Q4 peaks are revealed; the 2D 29Si MAF NMR results for potassium disilicate glass are far more informative than 29Si MAS NMR spectra. It demonstrates that the potassium disilicate glass (K2Si2O5) contains greater Q4 intensity, is more polymerized than previously considered, and that O2– is present at ∼2 (±1) mol% in the potassic glass. This O2– value confirms our O1s XPS results. Specific points raised by Malfait are rebutted in Appendix A .

Comment on “Spectroscopic studies of oxygen speciation in potassium silicate glasses and melts”

2015 ◽  
Vol 93 (5) ◽  
pp. 578-580 ◽  
Author(s):  
Wim J. Malfait
Keyword(s):  
Oxygen Content ◽  
Nmr Spectra ◽  
Equilibrium Constants ◽  
Compositional Analysis ◽  
Spectroscopic Studies ◽  
Peak Position ◽  
Potassium Silicate ◽  
Silicate Glasses ◽  
Nmr Data ◽  
Peak Assignment

Recent O1s XPS studies suggest that significant free oxide (O2– or K–O–K) is present in potassium silicate glasses, in contrast with what was concluded from 29Si and 17O solid-state NMR data. An alternative peak assignment of the Qn peaks in the 29Si NMR spectra was proposed to bring the 29Si NMR data in line with the O1s data, but this reassignment (i) is not supported by any evidence other than the resulting agreement between the NMR and XPS data, (ii) is at odds with the spectral properties of the bands (peak position and width), (iii) ignores the strong evidence for the original peak assignment, and (iv) results in highly implausible equilibrium constants for the Qn speciation reactions. More likely causes for the apparent discrepancy between the XPS and NMR data are the incorrect estimation of the precision of the bridging oxygen content from the O1s XPS data, the systematic overestimation of the bridging oxygen content from the O1s XPS data, and (or) the incorrect estimation of the accuracy of the compositional analysis, which was based on the precision rather than the accuracy of the electron microprobe analysis. Thus, the available evidence strongly suggests that the original assignment of the 29Si NMR spectra is correct. Neither the 29Si NMR nor the O1s XPS data support the presence of significant amounts of free oxide in potassium silicate glasses with K2O/SiO2 ≪ 2.

Spectroscopic studies of oxygen speciation in potassium silicate glasses and melts

2015 ◽  
Vol 93 (1) ◽  
pp. 60-73 ◽  
Author(s):  
Ryan Sawyer ◽  
H. Wayne Nesbitt ◽  
G. Michael Bancroft ◽  
Yves Thibault ◽  
Richard A. Secco
Keyword(s):  
Chemical Shift ◽  
Nmr Spectra ◽  
Spectroscopic Studies ◽  
Potassium Silicate ◽  
Silicate Glasses ◽  
Xps Spectra ◽  
Nmr Study ◽  
Peak Areas ◽  
Nmr Techniques ◽  
Good Agreement

To resolve discrepant results between O1s XPS and 29Si and 17O NMR techniques, O1s XPS spectra were collected and fitted for 15 potassium silicate glasses containing 10−37 mol% K2O. The effects of melting on the compositions of the glasses are documented and quantified, as are uncertainties associated with fitting the O1s spectra. These spectra are well resolved into two symmetric peaks: a narrow peak due to NBO (Si−O−K) plus “free oxide” (O2– or K−O−K) and a broader peak due to BO (Si−O−Si). Values of mol% BO (uncertainties of ±1%) are obtained from the computed peak areas and indicate 2.2 (±0.8) mol% O2– for glasses containing 32 (±1) mol% K2O. Reassignment of Q species for previously published 29Si NMR spectra leads to BO and O2– values in good agreement with these O1s XPS spectra. A recent 17O NMR study on potassium silicate glasses concluded that there is <1 mol% O2– in these glasses based mainly on the assumption that the 17O chemical shift for O2– should be similar in the glasses and the oxide in crystalline K2O. This assumption is questionable. Free oxide in these glasses should be highly reactive toward gases such as CO2 (via CO2 + O2– → CO32–) and it seems likely that the reactive species in silicate glasses is O2– rather than NBO as often assumed. The small amounts of CO2 found in reacted glasses are qualitatively consistent with the abundance of O2– obtained from these O1s XPS spectra of silicate glass.

A multinuclear MAS NMR study of the short-range structure of fluorophosphate glass

1992 ◽  
Vol 7 (7) ◽  
pp. 1892-1899 ◽  
Author(s):  
R.K. Brow ◽  
Z.A. Osborne ◽  
R.J. Kirkpatrick
Keyword(s):  
Nmr Spectra ◽  
Chemical Shifts ◽  
Spectroscopic Studies ◽  
Magic Angle Spinning ◽  
Mas Nmr ◽  
Magic Angle ◽  
Nmr Studies ◽  
Nmr Study ◽  
Fluorophosphate Glass ◽  
Angle Spinning

We have examined the bonding arrangements in Na–P–O–F and Na–Al–P–O–F glasses using 19F, 27Al, and 31P solid-state magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. For the Al-free series of glasses, the 19F NMR spectra are dominated by peaks near +90 ppm, representative of F terminating P-chains. The formation of these bonds has little effect on the 31P chemical shifts, indicating that F preferentially replaces bridging oxygen on the phosphate tetrahedra, consistent with previous NMR studies of crystalline fluorophosphates and other spectroscopic studies of fluorophosphate glass. For the Na–Al–P–O–F glasses, 27Al NMR detects only octahedral Al-sites, the 19F NMR spectra include a second peak near −12 ppm due to F bonded to Al, and the 31P NMR spectra contain signals due to Q1-sites with one or more Al next-nearest neighbors. The relative intensity of the two 19F peaks correlates well with previous spectroscopic studies and shows that a greater fraction of F–P bonds forms when the base glass is remelted in NH4HF2.

NMR studies of 1-phenylazo-3-substituted-2-naphthols in solution and in the solid state

1990 ◽  
Vol 55 (1) ◽  
pp. 193-201 ◽  
Author(s):  
Antonín Lyčka ◽  
Miroslav Nečas ◽  
Josef Jirman ◽  
Jaroslav Straka ◽  
Bohdan Schneider
Keyword(s):  
Hydrogen Bond ◽  
Solid State ◽  
Nmr Spectra ◽  
Equilibrium Mixture ◽  
Mas Nmr ◽  
Nmr Studies ◽  
Nmr Spectrum ◽  
Cp Mas Nmr ◽  
Hydrazone Form

The 1H and 15Nα-enriched 1-phenylazo-3-X-2-naphthols, where X = COOH (I), X = COOCH3 (II), and X = CONHC6H5 (III), have been measured in various solvents. The values of 1J(15Nα, H) and σ(15N) indicate that in CDCl3, C6D6, CCl4, and CD3NO2 solutions the compounds I and III exist practically completely in their hydrazone forms. The hydrazone form is stabilized by the hydrogen bond of COOH or CONH protons to the C(2)=O group. The compound II represents an equilibrium mixture of azo and hydrazone forms, since it cannot form a similar hydrogen bond. Moreover, the 15N NMR spectra of compounds I-III have been measured in solid state by the CP/MAS technique. The results indicate the existence of two conformers differing by the conformation of COOCH3 group in compound II, which is supported by the 13C CP/MAS NMR spectrum of compound II.

Molecular Structure of Tri(2-thienyl)borane

1996 ◽  
Vol 51 (12) ◽  
pp. 1811-1814 ◽  
Author(s):  
Bernd Wrackmeyer ◽  
Wolfgang Milius ◽  
Elias Molla
Keyword(s):  
Molecular Structure ◽  
Solid State ◽  
Nmr Spectra ◽  
Structural Parameters ◽  
Mas Nmr ◽  
Monoclinic Space Group ◽  
Nmr Spectrum ◽  
Π Interactions ◽  
Cp Mas Nmr ◽  
C Nmr

The molecular structure of tri(2-thienyl)borane (1) was determined [monoclinic, space group P21/ c; a = 12.216(2), b = 7.765(2), c = 12.605(2) Å, β = 93.13(2)°]; two of the three thienyl groups are disordered, as is also indicated by the solid-state 13C CP/MAS NMR spectrum of 1. The 13C NMR spectra of 1 were measured at variable tem perature in solution and the barrier to rotation about the B-C bonds was found to be <35 kJ/mol. Thus, CB(pp)π interactions must be regarded as rather weak, in spite of suggestive δ11 B. δ13C data and structural parameters.

Textural and spectroscopic studies on hydrothermal dumortierite from an Al-rich clay deposit, southeastern Korea

2003 ◽  
Vol 67 (4) ◽  
pp. 799-806
Author(s):  
C. O. Choo ◽  
Y. Kim
Keyword(s):  
Chemical Shifts ◽  
Volcanic Rocks ◽  
Structural Formula ◽  
Spectroscopic Studies ◽  
Mas Nmr ◽  
Thin Layers ◽  
Axially Symmetric ◽  
Nmr Spectrum ◽  
Clay Deposit ◽  
Two Peaks

AbstractDumortierite occurs as small nodules or thin layers along horizontal fractures in the altered volcanic rocks of the Milyang clay deposit, southeastern Korea. Textural evidence shows that dumortierite is associated with pyrophyllite, suggesting that the silica activity increased with decreasing B and Al activities during the hydrothermal alteration. Dumortierite chemistry shows a slight excess of Al, possibly due to common occurrence of Al-rich minerals in the clay deposit. The structural formula of dumortierite is recalculated as Al6.93(Fe0.03Mg0.07)B(Si2.99Al0.01)O18. An absorption peak at 1387 cm–1 in the IR spectrum indicates that B is present in three-fold coordinated sites. The 29Si MAS NMR spectrum has two peaks at –90.9 and –95.5 ppm, showing that Si in dumortierite is located in two different crystallographic sites and is linked to four octahedral Al atoms. The 27Al MAS NMR spectrum shows only one asymmetrical peak near 0 ppm, suggesting that there is no substitution of Al for Si. The 11B MAS NMR spectrum at 17.5 ppm shows a typical second order quadrupole pattern represented by the three-fold coordinated B. The 11B chemical shifts indicate that all of the B occupies such sites, indicating that the B sites are axially symmetric or nearly so in a very well defined site.

Solid State MAS-NMR and FTIR Study of Barium Containing Alumino-Silicate Glasses

2007 ◽  
Vol 361-363 ◽  
pp. 825-828 ◽  
Author(s):  
Fei Wang ◽  
Artemis Stamboulis ◽  
D. Holland ◽  
Shigeki Matsuya ◽  
Akari Takeuchi
Keyword(s):  
Nmr Spectra ◽  
Magic Angle Spinning ◽  
Mas Nmr ◽  
Silicate Glasses ◽  
Magic Angle ◽  
Ftir Study ◽  
Alumino Silicate ◽  
31P Mas Nmr ◽  
Angle Spinning ◽  
Second Peak

The glass based on a 1.5SiO2-Al2O3-0.5P2O5-CaO-0.67CaF2 composition was produced and substituted gradually by barium. The structure of the glasses was studied by multinuclear Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR) and Fourier Transform Infrared Spectroscopy (FTIR). It was indicated by 29Si and 31P MAS-NMR spectra that silicon was present as Q4 (4Al) and Q3 (3Al) species and phosphorus was in a Q1 pyrophosphate environment. 29Al MAS-NMR spectra showed that four fold coordinated aluminum Al (IV) was the dominant species with a second peak assigned to octahedral aluminum Al (VI). The 19F spectra suggested that the barium addition caused the formation of Al-F-Ba(n) and F-Ba(n) species. Furthermore, a distribution of silicate network including Si-O-Si stretching (Q4 and Q3) and Si-O-[NBO] (Q3) per SiO4 was reflected by the FTIR study.

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