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Influence of the preparative conditions on the precursor phases formed during the synthesis of beta-alumina by the wet chemical gel to crystallite conversions

Jayaraman, V and Periaswami, G and Kutty, TRN (1998) Influence of the preparative conditions on the precursor phases formed during the synthesis of beta-alumina by the wet chemical gel to crystallite conversions. In: Materials Chemistry and Physics, 52 (01). pp. 46-53.

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Abstract

Hydrated alumina gel, Al2O3 . yH(2)O (80<y<120) reacts with sodium hydroxide in water-miscible organic solvents yielding crystallites of either NaxAlOx(OH)(3-x) (0.17<x<0.23), having the gibbsite structure with inserted sodium ions, or NaxAlO1+x(OH)(1-x) (0.17<x<0.23) of boehmite structure. On calcination at elevated temperatures these precursors yield phase-pure beta "-(Na) alumina. A detailed investigation has been undertaken regarding the influence of preparative parameters on the precursor phases formed. It is observed that the non-aqueous solvents destabilise the gel irreversibly in the presence of alkali hydroxide by decreasing the effective ionic pressure within the gel cavities, and at the same time prevent the back diffusion of alkali ions inserted within the precursor lattice. In the presence of strongly desiccative (water attracting) solvents, dehydroxylation of (Na) gibbsite takes place under wet chemical conditions to yield pseudoboehmite. On calcination, both these phases give rise to intermediate alumina which, in turn, converts to beta "-alumina through a continuous solid state process

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Elsevier Science.
Keywords: beta-alumina;ionic conductivity;wet chemical synthesis;gel to crystallite conversion.
Department/Centre: Division of Chemical Sciences > Materials Research Centre
Date Deposited: 21 Aug 2009 11:46
Last Modified: 19 Sep 2010 05:25
URI: http://eprints.iisc.ernet.in/id/eprint/18743

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