"Near-stoichiometric cordierite (2MgO-2Al2O3-5SiO2) glasses doped with 6.3, 8.3 and 10.1 weight percent TiO2 were plasma sprayed onto SiO2-based refractory concrete substrates. Substrate temperatures were controlled such that the maximum surface temperature exceeded the crystallization temperature during plasma spraying. The surprising aspect of this study is that with increasing preheat temperature the structure of the plasma sprayed coating does not promote surface crystallization. This result seems to be related to the improved surface wetting that results from increased preheat temperature. Bulk nucleation occurred in compositions above 8wt.% TiO2 and the presence of Al2TiO2 was detected in these compositions.
Crystallization behavior and thermal expansion of near-stoichiometric cordierite glasses and glass-ceramics doped with TiO2 were investigated. The activation energy for growth of surface nucleated crystals was shown to be 433kJ/mol. and was related to titanium cation diffusion in cordierite glass. Coefficients of thermal expansion increased with increased TiO2 concentration. Analyses indicated that the solid solution limit of TiO2 in cordierite is less than 2.9wt.%. Volume nucleation was achieved by the addition of approximately 8wt.% TiO2, with Al2TiO5 acting as the volume nucleating phase.
La2O3-Al2O3-SiO2 glasses ranging in composition from 5.2La2O3-25.2Al2O3-69.6SiO2 to 15.4La2O3-29.7Al2O3-54.9SiO2 on a molar percentage basis were studied. Glasses containing approximately 15.5mole % La2O3 exhibited a large degree of phase separation that resulted in partial melting of specimens during crystallization. Coefficients of thermal expansion increased and glass transition temperatures decreased with increasing La2O3 content"--Abstract, page iv.
Van Aken, David C.
Smith, Jeffrey D.
Askeland, Donald R.
Brow, Richard K.
Peaslee, Kent D., 1956-2013
Materials Science and Engineering
Ph. D. in Metallurgical Engineering
University of Missouri--Rolla
Journal article titles appearing in thesis/dissertation
- The Role of Bulk Nucleation in the Formation of Crystalline Cordierite Coatings Produced by Air Plasma Spraying
- The Role of TiO2 in the Devitrification of Near-Stoichiometric Cordierite
- Effects of Lanthanum Content on Alumino-Silicate Glasses
xv, 96 pages
© 2001 Douglas Trent Weaver, All rights reserved.
Dissertation - Restricted Access
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Electronic access to the full-text of this document is restricted to Missouri S&T users. Otherwise, request this publication directly from Missouri S&T Library or contact your local library.http://merlin.lib.umsystem.edu/record=b4708086~S5
Weaver, Douglas T., "Plasma spraying low thermal expansion alumino-silicate glasses" (2001). Doctoral Dissertations. 1392.
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