Title page for ETD etd-06102012-040330


Type of Document Master's Thesis
Author Tu, Jie
URN etd-06102012-040330
Title Thermal expansion of chemically modified mullite
Degree Master of Science
Department Materials Engineering
Advisory Committee
Advisor Name Title
Brown, Jesse J. Jr. Committee Chair
Ribbe, Paul H. Committee Member
Swanson, Robert E. Committee Member
Keywords
  • Mullite
Date of Defense 1988-05-05
Availability restricted
Abstract
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, B203, CrPO4, P205, Ga203, Cr203, and WO3 and the half-breed

Si02 compounds AlPas, BPO4, GaPO4, BAsO4, AIAsO4, GaAsO4, and Ge02 were chosen as the modifiers.

The results indicate that, apart from Ti02, 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 A1203/Si02 molar ratio ( < 1.5) compared to stoichiometric mullite

(3A1203•2Si02). The formation of Ti02-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 Ga203-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.

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