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Electron Beam Induced Phase Transformations from Metakaolinite to Mullite

Published online by Cambridge University Press:  02 July 2020

Y. J. Kim  and
S. Lee
Y. J. Kim
Affiliation:
Division of Analysis & Measurement, Korea Basic Science Institute, Taejon, 305-333, Korea
S. Lee
Affiliation:
Department of Earth System Sciences, Yonsei University, Seoul120-749, Korea
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Extract

The kaolinite-mullite reaction series by heating has been controversial since the proposal of a new transformation mechanism. Recently energy-filtered electron diffraction data obtained from the specimen furnace-heated at 920 °C indicated that the spinel-type phase coexisted topotactically with metakaolinite. On the other hand, mullite first appeared from the specimen furnace-heated at 940 °C without showing any crystallographic relationship to the parent metakaolinite.

Direct beam heating experiments of the 920 °C-heated specimens using an energy-filtering TEM supported the previous results and ideas. Fig. 1 displays topotactic coexistence of metakaolinite and the spinel-type phase (spots in hexagonal arrangement) before beam heating. Electron beam heating gave rise to a noticeable change in the diffraction pattern, that is, the formation of mullite rings and enhancement of the diffuse intensity around the direct beam shown in Fig. 2. Comparison of EDS data for the specimen before beam heating and after beam heating (Fig. 3) indicates considerable increase of Si and O peaks by beam heating.

Type
Geology/Mineralogy
Information
Microscopy and Microanalysis , Volume 5 , Issue S2: Proceedings: Microscopy & Microanalysis '99, Microscopy Society of America 57th Annual Meeting, Microbeam Analysis Society 33rd Annual Meeting, Portland, Oregon August 1-5, 1999 , August 1999 , pp. 530 - 531
Copyright
Copyright © Microscopy Society of America

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References

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