towards a clearer picture of complex borosilicates nmr of borate model glasses scott kroeker...
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Towards a Clearer Picture of Complex Borosilicates
NMR of Borate Model Glasses
Scott KroekerDepartment of Chemistry, University of Manitoba
Solid-State NMR of Nuclear-Related Materials
Cambridge, September 23, 2005
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Medium-Range OrderCesium Borate Glasses
ppm
-6-22610141822
11B MAS NMR
11.7 T
R = Cs/B = 0.2
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Quantify contributions to N4
Smooth variation with R
Tetrahedral Boron FractionCesium Borate Glasses
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11B MAS NMR
14.1 T
R = 0.1
Tetrahedral BoronAlkali Borate Glasses
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Dispersion in N4 trends at higher alkali
Heavier vs. lighter alkali
Light alkalis stabilize tetrahedral boron? 0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80
R (alkali/boron)
N4
Li
Na
K
Rb
Cs
Tetrahedral Boron FractionAlkali Borate Glasses
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Li
Na
K
Rb
Cs
Steady increase (Li,Na)
Complex behaviour (K,Rb,Cs)
Discontinuities related to spectroscopic data
Feller et al. Phys. Chem. Glasses (2003), 44, 117-120.
Shear ModulusAlkali Borate Glasses
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Pentaborate(LiB8O18H8)
Diborate(Li2B8O17H8)
Di-triborate(Li2B8O18H10)
Triborate(LiB7O15H10)
Non-ring [4]B(LiB5O12H8)
B3LYP/cc-pVTZ//HF/6-31G*
Theoretical CalculationsChemical Shifts
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R = 0.5, K = 2R = Cs/BK = Si/B
Borosilicate GlassesCs2O-2B2O3-4SiO2
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Phase HeterogeneityCsB-60
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Test experiment and simulations
Dipolar field of 120 Hz (3.49 Å )
Actual distances: 3.53 - 3.63 Å
REDORCrystalline Cesium Triborate
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REDORCesium Borate Glasses
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11B MQMASCsB-54
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5% NBO
Chemical shift
17O MAS NMRCsB-54 (enriched)
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REDOR of BorosilicatesDatolite
CaBSiO4(OH)
[4]B surrounded by [4]Si trigonally
11B{1H} CPMAS
29Si{1H} CPMAS
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Conducting PolymersPoly(anilineboronic acid)
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Paramagnetic MaterialsSilver Cyanide Compound
15N MAS
Orientational CN disorder
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Paramagnetic MaterialsNickel Cyanide Compound
Structure: Draper N., Batchelor R.J., Sih B.C., Ye Z-G., Leznoff D.B.,Chem. Mater, 15, 2003, 1612-1616
13C MAS
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Paramagnetic MaterialsTourmalines
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< 1% Fe/Mn
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Sensitivity Enhancement17O NMR of B2O3
MultiRAPT pulse sequence (Grandinetti)
Signal enhancement Decrease
experiment time 16-fold
17O in under 24 hrs
Kwak et al. Solid State NMR (2003), 24, 71-77.
B2O3 210 mg
22.5 hrs
S/N = 40
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Summary and Conclusions
Simple MAS Alkalis behave differently Phase heterogeneity
Calculations effective for clusters Double-resonance methods Conducting samples Paramagnetic samples Sensitivity enhancement
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Acknowledgements
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