期刊
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
卷 396, 期 1-2, 页码 392-402出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.msea.2005.02.002
关键词
matakaolin; alkali; silicate anions; polymerisation process; NMR
A systematic study of Si-29 and Al-27 MAS-NMR has been carried out in an attempt to understand the reaction mechanism of the geopolymer formation at room temperature. For selected compositions, reactions were followed at selected times after the initial mixing of the reactants until the final products formed. The reactants were silicate anions, metakaolin and aqueous alkali. Silicate anions from various sources, such as sodium orthosilicate (Na4SiO4) and two types of sodium silicate solutions (2SiO(2)center dot Na2O and 4SiO(2)center dot Na2O) were investigated. Further, silicate anions formed from the reaction of colloidal silica and aqueous alkali-was also studied as a source for silicate anions. Interaction of silicate anions with Al sites of metakaolin soon after the mixing was obvious as, Si-29 MAS-NMR resonance lines of silicate anions were shifted to less shielded values. As the reaction progressed, the coordination of Al (IV, V, VI) in metakaolin changed almost completely to IV. It was indicated by NMR observation that polymeric silicate anions of high cross-linked densities were better than monomeric silicate anion in the geopolymerisation process. (c) 2005 Elsevier B.V. All rights reserved.
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