ISSN:
1573-4846
Keywords:
mullite
;
mullite-alumina
;
composites
;
gels
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract Ceramic composite gels in the mullite-alumina system (with mullite phase contents ranging from 20 to 100 wt%) were prepared by sol-gel in acid media and using a water/alkoxide molar ratio of 4. Powders were uniaxially pressed to obtain discs. The effect of heat treatment on the materials was followed by thermal analysis and X-ray diffraction (XRD). The crystalline phases formed from the gels were dependent upon the sample composition and the heat treatment temperature. For samples with composition close to the stoichiometric mullite composition the crystallization of mullite was observed after heat treatment at temperatures ≥900°C, and corundum appeared at higher temperatures. For samples with higher alumina contents mullite formation together with the spinel phase was observed at the lower heat treatment temperatures, while mullite, silimanite, corundum, and other transient phases of alumina were also detected at higher temperatures. The densities and microstructures of materials sintered at 1400°C were studied. Densification of the samples was low due to the agglomeration of the powders, as confirmed by scanning electron microscopy.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1008656817575
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