Doctoral Dissertations

Date of Award

12-1993

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Metallurgical Engineering

Major Professor

Thomas T. Meek

Committee Members

R. A. Buchanan, R. S. Benson, B Wunderlich

Abstract

Microwave technology is a rapidly expending field in the processing of ceramics sind glass materials. Many researchers proposed a number of different theories for loss mechanisms of glass materials at microwave frequencies, but there was no comprehensive analysis available which would describe how glass materials interact with microwave radiation. If the explanation of the basic nature of the microwave interactions with glass materials is available, it will be of a great use. Therefore, the structural analysis of a microwave melted vitreous silica can be a very useful tool for characterizing the microwave heating process and understanding glass-microwave interaction. In this investigation, the structural difference of the microwave melted vitreous silica and the conventionally melted vitreous silica was examined using the X-ray diffraction method. To get accurate intensity data, CuKα radiation was applied at lower k values, smd MoKα radiation with Zr-Y balanced filter was applied at higher k values. The different X-ray patterns between the microwave sample and the conventional sample were analyzed in terms of pair function distribution and distance distribution function. These analyses provided the structural differences between the microwave sample and the conventional sample. Data on bond distance distributions and bond angle distributions yielded information on the structural units which made up the random network model. The microwave treated vitreous silica experienced an increase in non-bridging oxygens, resulting in a change in the random network, which, in tern, resulted in a shift of Si-O-Si bond angle distributions and in a broader distance distributions of Si-O, O-O, and Si-Si pairs. The coupling of the microwave radiation to vitreous silica is enhanced due to the increase in concentration of broken Si-O bonds.

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