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(Referência obtida automaticamente do Web of Science, por meio da informação sobre o financiamento pela FAPESP e o número do processo correspondente, incluída na publicação pelos autores.)

Applications of DQ-DRENAR for the structural analysis of phosphate glasses

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Ren, Jinjun [1, 2] ; Eckert, Hellmut [1, 3]
Número total de Autores: 2
Afiliação do(s) autor(es):
[1] Univ Munster, Inst Phys Chem, D-48149 Munster - Germany
[2] Chinese Acad Sci, Shanghai Inst Opt & Fine Mech, Key Lab Mat High Power Laser, Shanghai 201800 - Peoples R China
[3] Univ Sao Paulo, Inst Fis Sao Carlos, BR-13566590 Sao Carlos, SP - Brazil
Número total de Afiliações: 3
Tipo de documento: Artigo Científico
Citações Web of Science: 5

A new solid state NMR technique entitled DQ-DRENAR (Double-Quantum based Dipolar Recoupling Effects Nuclear Alignment Reduction) has been recently described for measuring homonuclear dipole-dipole interactions in multi-spin-1/2 systems under magic-angle spinning conditions. As in rotational echo double resonance (REDOR), the homonuclear dipole-dipole coupling constant can be extracted from a plot of a normalized difference signal (S-0-S')/S-0 versus dipolar mixing time, where S is the signal amplitude with the DQ-Hamiltonian present, and So is the signal amplitude in the absence of the DQ-Hamiltonian, which is used for normalization. Within the range of (S-0-S)/S-0 <= 0.3-0.5 such ``homo-nuclear REDOR curves{''} can be approximated by simple parabolae, yielding effective squared dipole-dipole coupling constants Sigma b(jk)(2) summed over all the pairwise interactions present. The effect of glassy disorder has been studied by simulations, replacing singular-valued internuclear distances by Gaussian distance distributions with the same central value. This situation results in a systematic over-estimation effect, which tends to compensate the implicit under-estimation effect caused by the parabolic fitting approach. The present contribution describes applications to a number of phosphate-based glasses and glass ceramics. The method turns out to be well suited for the differentiation of the various Q((n)) phosphate species, for characterizing the spatial distribution of isolated orthophosphate ions and for the detection of incipient nano-segregation and/or phase separation effects in glass ceramics. (C) 2015 Published by Elsevier Inc. (AU)

Processo FAPESP: 13/07793-6 - CEPIV - Centro de Ensino, Pesquisa e Inovação em Vidros
Beneficiário:Edgar Dutra Zanotto
Linha de fomento: Auxílio à Pesquisa - Centros de Pesquisa, Inovação e Difusão - CEPIDs