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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.)

Monitoring crystallization in lithium silicate glass-ceramics using Li-7 -> Si-29 cross-polarization NMR

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Autor(es):
Schroeder, Cornelia [1] ; Carlos Villas-Boas, Mariana de Oliveira [2] ; Serbena, Francisco C. [3] ; Zanotto, Edgar D. [2] ; Eckert, Hellmut [4, 1]
Número total de Autores: 5
Afiliação do(s) autor(es):
[1] WWU Munster, Inst Phys Chem, D-48149 Munster - Germany
[2] Univ Fed Sao Carlos, Lab Mat Vitreous LaMaV, BR-13565905 Sao Carlos, SP - Brazil
[3] Univ Estadual Ponta Grossa, Dept Fis & Astron, BR-84030900 Ponta Grossa, PR - Brazil
[4] Univ Sao Paulo, Inst Fis Sao Carlos, BR-13566590 Sao Carlos, SP - Brazil
Número total de Afiliações: 4
Tipo de documento: Artigo Científico
Fonte: Journal of Non-Crystalline Solids; v. 405, p. 163-169, DEC 1 2014.
Citações Web of Science: 2
Resumo

Quantification of the crystalline versus amorphous fraction is an important objective for the structural characterization of glass-ceramics. Owing to its well-documented ability of differentiating between crystalline and amorphous materials and its inherently quantitative character, magic-angle-spinning solid state nuclear magnetic resonance (MAS-NMR) spectroscopy is an excellent method for this objective. For the technologically important lithium disilicate glass-ceramics, the applicability of Si-29 MAS-NMR is, however, seriously impeded by poor signal to noise ratios and extremely long spin-lattice relaxation times (on the order of magnitude of hours). The detection sensitivity problem can be overcome by magnetization transfer from Li-7 nuclei to the Si-29 spins (Li-7 -> Si-29 cross-polarization). While this method is inherently non-quantitative owing to the influence of various relaxation processes involved, we show that it can be successfully calibrated to yield quantitatively reliable crystalline fractions that are similar to those determined by alternative methods (optical microscopy and X-ray powder diffraction). In addition, this method can be used to detect very low (similar to 1%) crystallized volume fractions. (C) 2014 Elsevier B.V. All rights reserved. (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