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Towards a Clearer Picture of Complex Borosilicates NMR of Borate Model Glasses

Towards a Clearer Picture of Complex Borosilicates NMR of Borate Model Glasses. Scott Kroeker Department of Chemistry, University of Manitoba. Solid-State NMR of Nuclear-Related Materials Cambridge, September 23, 2005. Medium-Range Order Cesium Borate Glasses. 11 B MAS NMR 11.7 T

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Towards a Clearer Picture of Complex Borosilicates NMR of Borate Model Glasses

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  1. Towards a Clearer Picture of Complex BorosilicatesNMR of Borate Model Glasses • Scott Kroeker • Department of Chemistry, University of Manitoba • Solid-State NMR of Nuclear-Related Materials • Cambridge, September 23, 2005

  2. Medium-Range OrderCesium Borate Glasses • 11B MAS NMR • 11.7 T • R = Cs/B = 0.2 22 18 14 10 6 2 -2 -6 ppm

  3. Tetrahedral Boron FractionCesium Borate Glasses • Quantify contributions to N4 • Smooth variation with R

  4. Tetrahedral BoronAlkali Borate Glasses • 11B MAS NMR • 14.1 T • R = 0.1

  5. Tetrahedral Boron FractionAlkali Borate Glasses • Dispersion in N4 trends at higher alkali • Heavier vs. lighter alkali • Light alkalis stabilize tetrahedral boron?

  6. Li Na K Rb Cs Shear ModulusAlkali Borate Glasses • Steady increase (Li,Na) • Complex behaviour (K,Rb,Cs) • Discontinuities related to spectroscopic data Feller et al. Phys. Chem. Glasses  (2003), 44,  117-120.

  7. Theoretical CalculationsChemical Shifts Pentaborate (LiB8O18H8) Di-triborate (Li2B8O18H10) Non-ring [4]B (LiB5O12H8) Diborate (Li2B8O17H8) Triborate (LiB7O15H10) B3LYP/cc-pVTZ//HF/6-31G*

  8. Borosilicate GlassesCs2O-2B2O3-4SiO2 R = 0.5, K = 2 R = Cs/B K = Si/B

  9. Phase HeterogeneityCsB-60

  10. REDORCrystalline Cesium Triborate • Test experiment and simulations • Dipolar field of 120 Hz (3.49 Å ) • Actual distances: 3.53 - 3.63 Å

  11. REDORCesium Borate Glasses

  12. 11B MQMASCsB-54

  13. 17O MAS NMRCsB-54 (enriched) • 5% NBO • Chemical shift

  14. 11B{1H} CPMAS 29Si{1H} CPMAS REDOR of BorosilicatesDatolite • CaBSiO4(OH) • [4]B surrounded by [4]Si trigonally

  15. Conducting PolymersPoly(anilineboronic acid)

  16. Paramagnetic MaterialsSilver Cyanide Compound • 15N MAS • Orientational CN disorder

  17. Paramagnetic MaterialsNickel Cyanide Compound 13C MAS Structure: Draper N., Batchelor R.J., Sih B.C., Ye Z-G., Leznoff D.B., Chem. Mater, 15, 2003, 1612-1616

  18. Paramagnetic MaterialsTourmalines < 1% Fe/Mn

  19. 210 mg 22.5 hrs S/N = 40 B2O3 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.

  20. Summary and Conclusions • Simple MAS • Alkalis behave differently • Phase heterogeneity • Calculations effective for clusters • Double-resonance methods • Conducting samples • Paramagnetic samples • Sensitivity enhancement

  21. Acknowledgements

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