A Prediction of Young\u27s Modulus for Tin Containing Phosphate Glasses using Quantitative Structural Information

A Rigid Unit Packing Fraction (RUPF) Model Was Used to Better Understand the Influence of Local Structural Units on the Young\u27s Elastic Modulus (E) of Binary and Ternary Tin Phosphate Glasses. Quantitative Analyses of the Units that Constitute the Glass Structure, Obtained from X-Ray/neutron Diffraction and 31P MAS-NMR Spectroscopy, Were Used to Calculate Polyhedral Packing Fractions that, with Tabulated Bond Dissociation Energies, Were Used to Predict E based on a Modification of the Makashima-Mackenzie Relationship, Which Uses Ion Sizes to Calculate Packing Fractions. Predictions based on the RUPF Model Are Better Than Those based on Ion Sizes, and Extending the RUPF Model to All Cation-Polyhedra Accounts for the Compositional Dependence of the Sn-Coordination Number

Solid State NMR: A Powerful Tool for the Characterization of Borophosphate Glasses

This review will show how solid state nuclear magnetic resonance (NMR) has contributed to a better understanding of the borophosphate glass structure. Over the last fifteen years, 1D and 2D magic angle spinning (MAS)-NMR has been used to produce key information about both local and medium range organization in this type of glass. After a brief presentation on borophosphate glasses, the paper will focus on the description of the local order of phosphate and borate species obtained by 1D P-31-and B-11-MAS-NMR experiments, with a special emphasis on the improvements obtained at high magnetic fields on the borate speciation description. The last part of this review will show how correlation NMR provided new insights into the intermediate length scale order. Special attention will be paid to the quantitative data retrieved from B-11/P-31 REDOR-based NMR sequences and to the qualitative connectivity schemes observed on the 2D B-11/P-31 maps edited with the heteronuclear multiple quantum coherence (HMQC) NMR techniques

Étude de l effet d Al2O3, B2O3 et SiO2 sur les verres de phosphate possédant une faible Tg (approche structurale par RMN 1D/2D)

Les verres de phosphates à faible Tg et forte stabilité thermique sont étudié dans le système (66-x)ZnO- xNa2O-33.4 P2O5. Les mesures DSC ont montré un écart Tx-Tg de 197 C et une Tg de 339 C pour x= 20. La RMN 31P 1D/2D révèle la diminution du désordre due à la substitution progressive de Zn par Na. Les formulations x=20 et x=33 ont été dopé par de l Al2O3, B2O3 et SiO2 (1-4 % mol.) et ses effets sur les propriétés physiques comme la température de transition vitreuse, la stabilité thermique et la durabilité chimique ont été investiguées. La DRX et la RMN 31P ont été réalisés pour suivre le processus de cristallisation en isotherme à 130C (au-delà de la Tg). La plus forte stabilité thermique a été identifiée pour les verres dopés au bore. Le Raman et la RMN 31P ont mis en évidence l existence de connections P-O-X (X=27Al ou 11B). La RMN a entre autre montré la coordinence majoritaire VI, IV et IV respectivement pour l aluminium, le bore et la silice. L utilisation de D-INEPT, REDOR et DQ-SQ permet d approfondir nos connaissances sur la structure particulièrement sur les connectivités P-O-X mais également la diversité des connections possibles.Pyrophosphate glass with low Tg and high stability is investigated within the (66-x) ZnO- xNa2O-33.4 P2O5 system. DSC measurement indicated Tx-Tg=197 C with Tg = 339 C at x= 20. 1D/2D 31P NMR revealed the decrease in extent of disorder with the progressive substitution of Zn by Na. The x=20 and x=33 formulations were doped with (1-4 mol.%) of Al2O3, B2O3 and SiO2 and its effect on the physical properties such as the glass transition temperature, thermal stability and chemical durability is investigated. XRD and 1D 31P solid state NMR were used to monitor the isothermal crystallization process occurring at 130 C above Tg and the highest thermal stability is presented by the B-doped glasses. Raman and 31P NMR suggested the existence of P-O-X (X=27Al or 11B) bonds. The MAS NMR distinguished the dominant coordination states of doping elements AlVI , BIV and SiIV respectively. The use of D-INEPT, REDOR and DQ-SQ helped in producing deeper insights onto the glass structure about the P-O-X connectivity, the wide range of phosphate speciation.LILLE1-Bib. Electronique (590099901) / SudocSudocFranceF

Measurement of through-space connectivities between spin-1/2 and quadrupolar nuclei in solid-state NMR: The TEDOR-MQMAS method

International audienceWe present the transferred echo double-resonance multiple-quantum MAS (TEDOR-MQMAS) method that allows to analyze under high resolution the through-bond connectivities between spin-1/2 and quadrupolar nuclei. This method avoids some of the limitations related to the spin-lock of half-integer quadrupolar nuclei under MAS. However, the losses observed during the TEDOR transfer are related to the T′2 constants, and they may thus be more important than those observed during the CP-MAS transfer, which are related to T1p > T′

Inhibition of the catalytic oxidation of carbon/carbon composite materials by an aluminophosphate coating

International audienc