Effects of solid solution on the high-low inversion of cristobalite and the stabilization of high cristobalite

The inversion temperature of cristobalite was investigated by incorporating TiO₂, AlPO₄, and BPO₄ into the cristobalite phase using solid state reactions. The combination of TiO₂ and AlPO₄ proved to be most effective in lowering the inversion temperature of cristobalite. Phase diagrams at the high silica corner were constructed for the respective systems. High cristobalite was stabilized for compositions prepared from the CaO-Al2₂O₃-SiO₂ and CuO-Al₂O₃-SiO₂ system using sol-gel processing. The stabilization mechanism is attributed to the surface energy effect resulting from the formation of fine crystals. The structural evolution from the x-ray amorphous gel to high cristobalite was examined by FTIR and Raman spectroscopy. The thermal expansion of the stabilized high cristobalite was characterized by high temperature x-ray. Changes in bond angle continue to dominate the thermal expansion of high cristobalite.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Materials Engineering Science

Department dc:contributor.department

Materials Engineering Science

Grantor dc:publisher

Virginia Polytechnic Institute and State University

Year dc:date.issued

1989

Author dc:creator

• Sun, Tawei

Chair dc:contributor.committeechair

• Brown, Jesse J., Jr.

Committee members dc:contributor.committeemember

• Gibbs, Gerald
• Swanson, Robert E.
• Lytton, Jack L.
• Bloss, F. Donald

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/10919/54793

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/54793