Magnesium analogues of aluminosilicate inorganic polymers (geopolymers) from magnesium minerals

Mackenzie, Kenneth J. D. and Bradley, Siobhan and Hanna, John V. and Smith, Mark E. (2013) Magnesium analogues of aluminosilicate inorganic polymers (geopolymers) from magnesium minerals. Journal of Materials Science, 48 (4). pp. 1787-1793. ISSN 0022-2461

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Attempts to synthesise magnesium-containing analogues of aluminosilicate geopolymers from the 1:1 and 2:1 layer magnesiosilicate minerals chrysotile and talc, as well as the magnesium mineral sepiolite are reported. The effect of pre-treating these starting minerals by grinding and/or dehydroxylation was also investigated by XRD, 29Si and natural-abundance 25Mg solid-state magic angle spinning (MAS) NMR spectroscopy. The products from sepiolite most closely resembled an aluminosilicate geopolymer, setting at 40 °C to an X-ray amorphous product containing a broad characteristic 29Si MAS NMR resonance at −90 ppm. The 25Mg MAS NMR spectrum of this product also showed evidence that some of the Mg was located in tetrahedral sites, as expected for a conventional geopolymer. A similar 25Mg MAS NMR result was obtained for chrysotile, but talc proved to be extremely resistant to geopolymer synthesis, requiring treatment at 120 °C for 3 days to set to a friable material retaining the XRD and NMR characteristics of the original talc or its crystalline dehydroxylation products. This lack of reactivity may be related to the 2:1 layer-lattice talc structure, or to the fact that a suitably reactive amorphous product is not formed upon dehydroxylation.

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Journal Article
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Journal of Materials Science
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Date of Acceptance: 05/10/2012
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14 Apr 2015 13:34
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20 Sep 2023 00:42