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Accueil du site > LPCNO > Séminaires > 2013 > Topologic, Geometric, and Chemical Order in Materials : Insights from Solid-State NMR

Topologic, Geometric, and Chemical Order in Materials : Insights from Solid-State NMR

Date : 19/03/2013 à 10:00

Titre : Topologic, Geometric, and Chemical Order in Materials : Insights from Solid-State NMR

Intervenant : Dominique Massiot

Provenance : CEMHTI - Conditions Extrêmes et Matériaux : Haute Température et Irradiation UPR3079 CNRS - Orléans, FRANCE

Salle : Salle des thèses

Résumé : Local order, as opposed to the long-range order of the ideal crystalline structures, can be considered as an intrinsic characteristic of real materials, being often the clue to the tuning of their properties and their final applications. While ordering can be easily assessed in two-dimensional imaging techniques with resolution approaching the atomic level, the diagnostic, description, and qualification of local order in three dimensional systems is much more challenging.
Solid-state nuclear magnetic resonance [NMR] and its panel of constantly developed new instruments and methods enable local, atom selective characterization of structures and assemblies ranging from atomic to nanometer length scales. This opens unique opportunities for characterizing a variety of materials, ranging from crystalline compounds to amorphous or glassy materials, for which we show that it becomes possible to separate topologic, geometric and chemical contributions to the order or disorder, in cooperation with other experimental techniques and in-silico approaches.
As identified by solid state NMR, the local structure of amorphous materials or glasses consists of well-identified structural entities up to at least the nanometer scale. Instead of speaking of disorder, we propose a new paradigm to describe their structures in terms of a continuous assembly of locally defined structures, reminiscent of locally favored structures (LFS). This draws a comprehensive picture of amorphous structures based on fluctuations of chemical composition and structure over different length scales. We hope that these new local or molecular insights could open new possibilities for considering key questions related to nucleation and crystallization, as well as chemically (spinodal decomposition) or density driven (polyamorphism) phase separation, which could enable future applications.

1. D.Massiot, S.Cadars, M.Deschamps, V.Montouillout, N.Pellerin, E.Véron, R.J.Messinger, M.Allix, P.Florian, F.Fayon, Topologic, Geometric, and Chemical order in Materials : Insights from Solid-State NMR, Accounts Chem. Res. (submitted)
2. E.Véron, M.N.Garaga, D.Pelloquin, S.Cadars, M.Suchomel, E.Suard, D.Massiot, V.Montouillout, G.Matzen, M.Allix, Synthesis and structure determination of CaSi1/3B2/3O8/3, a new calcium borosilicate, Inorg. Chem. ASAP (2013)
3. F.Fayon, C.Duée, T.Poumeyrol, M.Allix, D.Massiot, Evidence of Nanometric-Sized Phosphate Clusters in Bioactive Glasses as Revealed by Solid-State 31P NMR, J. Phys. Chem. ASAP (2013)
4. P.Florian, E.Véron, T.Green, J.R.Yates, D.Massiot, Elucidation of the Al/Si ordering in Gehlenite Ca2Al2SiO7 by combined 29Si and 27Al NMR spectroscopy / quantum chemical calculations, Chem. Mater. 24 4068–4079 (2012)
5. R.N.Kerber, A.Kermagoret, E.Callens, P.Florian, D.Massiot, A.Lesage, C.Copéret, F.Delbecq, X Rozanska, P.Sautet, Nature and structure of aluminum surface sites grafted on silica from a combination of high field aluminum-27 solidstate NMR spectroscopy and first principle calculations, J. Am. Chem. Soc. 134 6767–6775 (2012)