The Role of Si-H Functionality in Oxycarbide Glass Synthesis

1992 ◽  
Vol 271 ◽  
Author(s):  
Anant K. Singh ◽  
Carlo G. Pantano
Keyword(s):  
Nmr Spectroscopy ◽  
Chemical Analysis ◽  
Carbon Concentration ◽  
Mas Nmr ◽  
Silicon Oxycarbide ◽  
Total Carbon ◽  
Primary Interest ◽  
Hydrolysis And Condensation ◽  
Oxycarbide Glass

ABSTRACTSilicon oxycarbide gels and glasses were synthesized using various ratios of methyldimethoxysilane and TEOS. These gels and glasses were compared with those made from methyltrimethoxysilane and TEOS. The effect of the Si-H functionality in the methyldimethoxysilane was of primary interest. Hydrolysis and condensation processes were monitored using 1H and 29Si-NMR spectroscopy. The structures and the oxycarbide fractions of the glasses, obtained after heating the gels to 900°C in flowing argon, were investigated with 29si-MAS NMR. The total carbon and silicon contents of the glasses were determined using chemical analysis. The glasses covered the range of carbon concentration from ∼1 to 15%, while the silicon concentrations were constant at about 40%. The concentration of the oxycarbide species was enhanced in the glasses synthesized with the Si-H functionality in the precursor.

Crystallinity and structuring role of water in native and recrystallized starches by 13C CP-MAS NMR spectroscopy

1999 ◽  
Vol 39 (4) ◽  
pp. 327-339 ◽  
Author(s):  
M Paris ◽  
H Bizot ◽  
J Emery ◽  
J.Y Buzaré ◽  
A Buléon
Keyword(s):  
Nmr Spectroscopy ◽  
Mas Nmr ◽  
Cp Mas Nmr ◽  
13C Cp Mas Nmr

Progress in Structural Elucidation of Glasses by and 1B Satellite Transition NMR Spectroscopy

1995 ◽  
Vol 50 (4-5) ◽  
pp. 413-422 ◽  
Author(s):  
G. Kunath-Fandrei ◽  
D. Ehrt ◽  
C. Jäger
Keyword(s):  
Nmr Spectroscopy ◽  
Quadrupole Interaction ◽  
Chemical Shifts ◽  
Glass Structure ◽  
Structural Elucidation ◽  
Mas Nmr ◽  
Interaction Parameters ◽  
31P Mas Nmr ◽  
Satellite Transition

The structure of Na2O-Al2O3-B2O3 and Na2O-Al2O3-P2O5 glasses with 70 mole% B2O3 or P2O5 and varied Na/Al ratio is investigated using standard 31P MAS NMR and 27Al and UB Satellite Transition NMR spectroscopy. The role of the two network formers on the glass structure is discussed. For the AlOx units and BO3 and BO4 groups both chemical shifts and quadrupole interaction parameters including their distribution widths are reported. Besides this, the advantages of Satellite Transition spectroscopy are demonstrated both for 27A1 and 11B NMR

A kinetic study of the phase transformations in Al2O3 and Na2O · 6Al2O3 by a combined use of 27Al MAS NMR spectroscopy and x-ray diffraction: Importance of nucleation

1991 ◽  
Vol 6 (12) ◽  
pp. 2701-2705 ◽  
Author(s):  
S. Prabakar ◽  
K.J. Rao ◽  
C.N.R. Rao
Keyword(s):  
Nmr Spectroscopy ◽  
Phase Transformations ◽  
Mas Nmr ◽  
X Ray Diffraction ◽  
X Ray ◽  
Combined Use ◽  
27Al Mas Nmr ◽  
First Time ◽  
Kinetics Of

Phase transformations of Al2O3 and Na2O · 6Al2O3 prepared by the gel route have been investigated for the first time by 27Al MAS NMR spectroscopy in combination with x-ray diffraction. Of particular interest in the study is the kinetics of the γ → α and γ → β transformations, respectively, in these two systems. Analysis of the kinetic data shows the important role of nucleation in both these transformations.

The role of water in the degradation process of paper using 1H HR-MAS NMR spectroscopy

2016 ◽  
Vol 18 (48) ◽  
pp. 33335-33343 ◽  
Author(s):  
Carmelo Corsaro ◽  
Domenico Mallamace ◽  
Sebastiano Vasi ◽  
Luciano Pietronero ◽  
Francesco Mallamace ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Nmr Spectroscopy ◽  
Dynamic Properties ◽  
Degradation Process ◽  
Mas Nmr ◽  
Cellulose Paper

We combine 1H HR MAS NMR and multi-component relaxation time to study the dynamic properties of the different components of cellulose–paper and water separately.

scholarly journals Sampling Method Affects HR-MAS NMR Spectra of Healthy Caprine Brain Biopsies

Metabolites ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 38
Author(s):  
Annakatrin Häni ◽  
Gaëlle Diserens ◽  
Anna Oevermann ◽  
Peter Vermathen ◽  
Christina Precht
Keyword(s):  
Nmr Spectroscopy ◽  
Sampling Method ◽  
Magic Angle Spinning ◽  
Mas Nmr ◽  
Magic Angle ◽  
1H Nuclear Magnetic Resonance ◽  
Rapid Changes ◽  
Tissue Degradation ◽  
Angle Spinning

The metabolic profiling of tissue biopsies using high-resolution–magic angle spinning (HR-MAS) 1H nuclear magnetic resonance (NMR) spectroscopy may be influenced by experimental factors such as the sampling method. Therefore, we compared the effects of two different sampling methods on the metabolome of brain tissue obtained from the brainstem and thalamus of healthy goats by 1H HR-MAS NMR spectroscopy—in vivo-harvested biopsy by a minimally invasive stereotactic approach compared with postmortem-harvested sample by dissection with a scalpel. Lactate and creatine were elevated, and choline-containing compounds were altered in the postmortem compared to the in vivo-harvested samples, demonstrating rapid changes most likely due to sample ischemia. In addition, in the brainstem samples acetate and inositols, and in the thalamus samples ƴ-aminobutyric acid, were relatively increased postmortem, demonstrating regional differences in tissue degradation. In conclusion, in vivo-harvested brain biopsies show different metabolic alterations compared to postmortem-harvested samples, reflecting less tissue degradation. Sampling method and brain region should be taken into account in the analysis of metabolic profiles. To be as close as possible to the actual situation in the living individual, it is desirable to use brain samples obtained by stereotactic biopsy whenever possible.

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