Thermal expansion of chemically modified mullite

Solid-state reaction and sol-gel, processing techniques were used extensively to form chemically-modified mullite solid solutions in an effort to lower their thermal expansion coefficients. TiO₂, B₂O₃, CrPO₄, P2O₅, Ga₂O₃, Cr2O₃, and WO₃ and the half-breed SiO₂ compounds AlPas, BPO₄, GaPO₄, BAsO₄, AIAsO₄, GaAsO₄, and GeO₂ were chosen as the modifiers. The results indicate that, apart from TiO₂, none of the substitutions made in mullite significantly change the thermal expansion properties. The solubility of 3 wt% TiO₂ in mullite reduces the coefficient of thermal expansion by about 10%; That corresponds to a reduction in AAl₂O₃/SiO₂ molar ratio ( < 1.5) compared to stoichiometric mullite (3Al₂O₃·2SiO₂). The formation of TiO₂-modified mullite depends on processing condition and heat treatment. The possible mechanism of lowering the CTE of mullite by the addition of TiO₂ is discussed in terms of the bond strength. The axial expansion of a Ga2O₃-modified mullite was measured' up to 1200°C to show that the expansion is increased along the c-axis compared with that of the stoichiometric mullite.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Materials Engineering

Department dc:contributor.department

Materials Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

1988

Author dc:creator

• Tu, Jie

Chair dc:contributor.committeechair

• Brown, Jesse J. Jr.

Committee members dc:contributor.committeemember

• Swanson, Robert E.
• Ribbe, Paul H.

Statement dc:rights

• In Copyright

Licence dc:rights.uri

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

Language dc:language.iso

en

Dc Identifier Other

etd-06102012-040330

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/43063