ISSN:
1573-4803
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract Powder of mullite composition (3Al2O3·2SiO2) has been made by a coprecipitation method. The evolution of mullite in this precursor powder during heat treatment has been studied using differential thermal analysis, electron microscopy and X-ray diffraction techniques. It is shown that during calcination below 1100°C the coprecipitate develops γ-Al2O3 and perhaps cristobalite crystallites within the basic grains, whose morphology is otherwise invariant with temperature. Mullite forms above 1100°C by reaction of these γ-Al2O3 and SiO2 crystallites, and the grain morphology changes markedly. Small exothermic events occur at 1000 and 1250 °C. The former is associated with the decomposition of a small content of aluminosilicate or perhaps with the conversion of γ- to θ-Al2O3, and the latter with mullite formation. For comparison, the behaviour of a polymeric mullite precursor during calcination is also examined. This material showed a large exothermic event at 1000°C which could be associated with the decomposition of the (amorphous) aluminosilicate to crystalline γ-Al2O3 and SiO2, and a small exothermic event at 1250° C due to mullite formation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00581109
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