Investigation of the evaporation thermodynamics and stationary states (so-called ''congruent states'') in the study of oxides and their mixtures by the effusion method--application to Al/sub 2/O/sub 3/, CaO, and the mixtures Al/sub 2/O/sub 3/-CaO and Ti/sub 2/O/sub 3/-TiO/sub 2/

Journal Article · Fri Jan 01 00:00:00 EST 1982 · High Temp. Sci.; (United States)

OSTI ID:5487614

Banon, S; Chatillon, C; Allibert, M

The congruent vaporization of oxides and oxide mixtures during Knudsen effusion has been studied, taking into account the nature of the equilibrium reactions between samples and crucible materials, the complexity of the resulting gaseous phases, and the possibility of an oxygen leak by diffusion through the crucible walls. The influence of the crucible reaction and of oxygen diffusion is estimated for pure CaO and Al/sub 2/O/sub 3/ and for the mixtures CaO + Al/sub 2/O/sub 3/ and Ti/sub 2/O/sub 3/ + TiO/sub 2/, in molybdenum cells. The results show a systematic shift of the effusion flow composition toward a reducing composition--either by crucible reaction or by establishment of a diffusion process. In the case of the Ti/sub 2/O/sub 3/-TiO/sub 2/ system, calculations of the expected congruent evaporation from JANAF standard pressures and our activity measurements indicate that the standard pressure of TiO/sub 2/ gas over solid TiO/sub 2/ must be increased by a factor of 4 to 14 to agree with the results from our studies of the congruent vaporization of solid Ti/sub 3/O/sub 5/. The congruent vaporization of liquid Ti/sub 2/O/sub 3/-TiO/sub 2/ mixtures occurs in the composition range Ti/sub 2/O/sub 3/-Ti/sub 3/O/sub 5/, an with inert crucible, a molybdenum crucible, or diffusion through the walls.

• Research Organization: Laboratoire de Thermodynamique et Physico-Chimie Metallurgiques, Saint Martin d'Heres, France
• OSTI ID: 5487614
• Journal Information: High Temp. Sci.; (United States), Vol. 15:2/3
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM OXIDES
EVAPORATION
CALCIUM OXIDES
TITANIUM OXIDES
CRUCIBLES
KNUDSEN FLOW
MIXTURES
THERMODYNAMICS
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
CALCIUM COMPOUNDS
CHALCOGENIDES
DISPERSIONS
FLUID FLOW
GAS FLOW
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties