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

被引:16
作者
Jayaraman, V [1 ]
Periaswami, G
Kutty, TRN
机构
[1] Indira Gandhi Ctr Atom Res, Mat Chem Div, Kalpakkam 603102, Tamil Nadu, India
[2] Indian Inst Sci, Ctr Mat Res, Bangalore 560012, Karnataka, India
关键词
beta-alumina; ionic conductivity; wet chemical synthesis; gel to crystallite conversion;
D O I
10.1016/S0254-0584(98)80005-9
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
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. (C) 1998 Elsevier Science S.A.
引用
收藏
页码:46 / 53
页数:8
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