Thermodynamic properties of mullite

Journal Article · Thu Oct 05 04:00:00 EDT 1978 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100509a010· OSTI ID:6578140

Howald, R A; Eliezer, I

Mullite can be considered as a solution of cristobalite in corundum, and with these reference states the activities of SiO/sub 2/ and AlO/sub 1/./sub 5/ can be expressed as functions of temperature and mole fraction using equations of the Redlich--Kister form. The Redlich--Kister coefficients are evaluated from experimental data on sillimanite and mullite. They can be used to calculate the mole fractions and SiO/sub 2/ activities for mullite saturated with corundum (X/sub 1/ = 0.7702, a/sub 1/ = 1.000, and a/sub 2/ = 0.4221 at 2123/sup 0/K). These calculations suggest that mullite is not saturated with corundum at its incongruent melting point, X/sub 1/ = 0.7508, 2123/sup 0/K. It is proposed that mullite melts incongruently to liquid and a high-temperature form of alumina in which SiO/sub 2/ is appreciably soluble. This suggestion is shown to reconcile apparently contradictory data on the AlO/sub 1/./sub 5/--SiO/sub 2/ system, and a new phase diagram is calculated using Redlich--Kister coefficients for mullite, and liquid and ..gamma..-alumina phases.

• Research Organization: Montana State Univ., Bozeman
• OSTI ID: 6578140
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 82:20; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CHALCOGENIDES
CHEMICAL ACTIVATION
COMPARATIVE EVALUATIONS
CORUNDUM
DIAGRAMS
DISPERSIONS
ENTHALPY
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MINERALS
MIXTURES
MULLITE
OXIDES
OXYGEN COMPOUNDS
PHASE DIAGRAMS
PHYSICAL PROPERTIES
QUANTITY RATIO
SATURATION
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SOLID SOLUTIONS
SOLUTIONS
TEMPERATURE DEPENDENCE
THERMODYNAMIC PROPERTIES
VERY HIGH TEMPERATURE