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September 22, 2009

Interfaces between alumina and refractory glasses for high temperature applications

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Joining of alumina ceramics with glasses for high temperature applications was investigated. A range of glass formulations encompassing ternary (Al//2O//3-CaO-SiO//2, Al//2O//3-SiO//2-MgO), and quaternary (Al//2O//3-CaO-SiO//2- ZrO//2) glasses was selected. The glasses were selected so that they would reach chemical equilibrium with the alumina component during sealing at temperature above 1500 degree C. The results of wetting and joining experiments using five refractory glasses, and microstructural and microchemical analyses of the interfacial regions is presented. Wetting experiments suggest that four of the five glasses produced crack- free joint regions. A higher sealing temperature might have prevented cracking for the other glass. Interfacial microstructures were analyzed using optical and scanning electron microscopy. EDS and microprobe results were used to identify the phases that developed during sealing at 1600 degree C, and during cooling to room temperature. In all cases, there was a residual glass at the interface. In most cases, the crystalline phases are consistent with the equilibrium phase diagram, indicating that these diagrams provide a useful tool for selecting and modifying the compositions of glasses for joining applications. In conclusion, at least a subset of these glasses appear to be suitable for joining alumina assemblies intended for high temperature applications. (Author abstract) 8 Refs.

Tomsia, A.P. Glaeser, A.M. Moya, J.S.

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