Plasma spraying low thermal expansion alumino-silicate glasses

<p>"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.</p><p>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.</p><p>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.</p>

Name thesis:degree_name

Ph. D. in Metallurgical Engineering

Grantor

University of Missouri--Rolla

Year dc:date.available

2016

Author dc:creator

• Weaver, Douglas T.

• Metallurgy

Repository record dc:identifier

https://scholarsmine.mst.edu/doctoral_dissertations/1392

OAI identifier oai:identifier

oai:scholarsmine.mst.edu:doctoral_dissertations-2394