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Negahdari, Zahra ; Willert-Porada, Monika:
Comparison of Microwave and Conventional Sintering of LHA Ceramics and Functionally Graded Alumina-LHA Ceramics.
In: Advances in Science and Technology.
Bd. 63
(Oktober 2010)
.
- S. 332-339.
ISSN 1662-0356
DOI: https://doi.org/10.4028/www.scientific.net/AST.63.332
Abstract
The low thermal conductivity of Lanthanum hexaaluminate, abbreviated as LHA, combined with high structural reliability of alumina matrix ceramics attracted our attention to develop a new functionally graded layered LHA-Al2O3-composite, with a LHA and a porosity gradient along the thickness of a bulk oxide ceramic. LHA is formed by in--situ reaction during sintering of the alumina/LHA composite. The high sintering temperature required for completion of LHA formation in LHA-rich layers causes grain growth and a degradation of mechanical strength in alumina-rich layers. Therefore, microwave hybrid heating was investigated as a method to enhance the reaction rate without excessive grain growth. Comparison of conventionally and microwave assisted sintered homogenous composite ceramics with 20--80 volume percent LHA showed that utilization of microwave heating could enhance the solid--state reaction and densification in samples containing more than 20 volume percent LHA. Enhanced microwave absorption in LHA rich layers assisted the sintering of a functionally graded composite at lower temperatures, enabling LHA formation without any abnormal grain growth in alumina rich layers.