Structural characterization of mullites synthesized by thermal decomposition of topaz

The structure of mullite obtained by thermal decomposition of topaz at 1340 C and after additional thermal treatment at 1600 C was characterised by 29Si and 27Al MAS NMR spectroscopy and XRD. No amorphous phase was detected. The 29Si MAS NMR spectra of the mullite samples showed four resonance peaks...

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Published in:	Materials research (São Carlos, São Paulo, Brazil) Vol. 10; no. 1; pp. 75 - 78
Main Authors:	Soares, Robson de Miranda, Sabioni, Antônio Claret Soares, Resck, Inês Sabioni, Falcomer, Viviane Aparecida Silva, Dias, José Alves, Silva, Naira Machado da, Menezes, Sônia Maria Cabral de, Costa, Geraldo Magela da
Format:	Journal Article
Language:	English
Published:	ABM, ABC, ABPol 01-03-2007 Associação Brasileira de Metalurgia e Materiais (ABM); Associação Brasileira de Cerâmica (ABC); Associação Brasileira de Polímeros (ABPol)
Subjects:	27Al and 29Si MAS NMR, XRD characterization ENGINEERING, CHEMICAL MATERIALS SCIENCE, MULTIDISCIPLINARY METALLURGY & METALLURGICAL ENGINEERING mullite synthesis topaz topaz 27Al and 29Si MAS NMR, XRD characterization mullite synthesis
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Summary:	The structure of mullite obtained by thermal decomposition of topaz at 1340 C and after additional thermal treatment at 1600 C was characterised by 29Si and 27Al MAS NMR spectroscopy and XRD. No amorphous phase was detected. The 29Si MAS NMR spectra of the mullite samples showed four resonance peaks at -81, -86, -90 and -94 ppm. The peak at -81 ppm corresponded to silicon near oxygen vacancies in the mullite structure. The peak at -86 ppm was related to a sillimanite-type site and was the major contribution, ranging from 42 to 50%. The two other peaks, at -90 ppm and -94 ppm, were interpreted as resulting from rearrangements of the sillimanite-type site by the replacement of AlO4 by SiO4 tetrahedra. The 27Al MAS NMR data of the two samples exhibited three different peaks, two of which were attributed to tetrahedral sites at 40-45 and 63-67 ppm, while the third was assigned to an octahedral site at about -6 ppm. The ratio of tetrahedral to octahedral aluminium sites was found to depend on the temperature applied during the preparation of the mullite and was higher at 1600 C. 22 refs.
Bibliography:	ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23
ISSN:	1516-1439 1980-5373 1516-1439
DOI:	10.1590/S1516-14392007000100016