INFLUENCE OF THE PREFERRED ORIENTATION OF BOEHMITE CRYSTALLITES ON ALPHA-Al2O3 CRYSTALLISATION

Monolithic boehmite gels were prepared from commercial peptisable Condea product. The gels were modified by nanoparticle SiO2 addition. Preferred orientation of boehmite crystallites in the gels and phase composition of sintered samples was observed by XRD analysis. To determine the effect of gel st...

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Bibliographic Details
Published in:Ceramics (Praha) 2005-01, Vol.49 (1), p.34-39
Main Authors: Bodisova, K, Pach, L, Kovar, V
Format: Article
Language:English
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Summary:Monolithic boehmite gels were prepared from commercial peptisable Condea product. The gels were modified by nanoparticle SiO2 addition. Preferred orientation of boehmite crystallites in the gels and phase composition of sintered samples was observed by XRD analysis. To determine the effect of gel structure and eventually of SiO2 addition on sintering and crystallisation, DTA, SEM and bulk density measurement were used. Boehmite crystallites align themselves spontaneously during gelation into preferred orientation states that can be avoided by ultrasonication or by the nanoparticle SiO2 addition. The ordered or disordered gel microstructure has only marginal influence on high-temperature processes (crystallisation, sintering). These processes are significantly influenced by addition of foreign SiO2 nanoparticles, which decrease coordination of boehmite particles suppressing thus alpha-Al2O3 nucleation. Spread of SiO2 on the surface of Al2O3 particles inhibits alpha-Al2O3 crystallisation up to 1350 C. 14 refs.
ISSN:0862-5468