High-temperature thermodynamic properties of the thorium-oxygen system. [2400 to 2655/sup 0/K]

Conference · Mon Jan 01 00:00:00 EST 1979

OSTI ID:5920546

Ackermann, R. J.; Tetenbaum, M.

Thermodynamic properties of the Th-O system at high temperatures were investigated by means of mass effusion, mass spectrometric, and transpiration techniques over compositions ranging from the congruently vaporizing composition to the lower phase boundary composition. A very sharp decrease in O potential occurs when stoichiometric thoria is reduced but slightly from the stoichiometric composition. The small extent of reduction over a wide range of O potentials measured in the temperature range 2400 to 2655/sup 0/K is a clear illustration of the higher stability of the ThO/sub 2-x/ phase compared with actinide oxides such as UO/sub 2-x/, PuO/sub 2-x/, as well as other metal oxide systems. Estimates of ..delta..H-bar/sub O/sub 2//, ..delta..S-bar/sub O/sub 2//, and the standard free energy of formation of bivariant ThO/sub 2-x/ compositions were made. A substantial increase in the total pressure of Th-bearing species occurs when stoichiometric thoria is reduced toward the lower phase boundary. The increase in pressure can be attributed primarily to the increasing contribution of the ThO gaseous species. Total pressures of Th-bearing species above ThO/sub 2-x/ compositions calculated by means of experimental O potentials and the known or estimated free energy of formation values of the gaseous species and condensed phase are in reasonable agreement with experimental values.

• Research Organization: Argonne National Lab., IL (USA)
• Sponsoring Organization: USDOE
• DOE Contract Number: W-31-109-ENG-38
• OSTI ID: 5920546
• Report Number(s): CONF-790761-1; TRN: 79-020851
• Resource Relation: Conference: International colloquium on materials for high-temperature energy, Toronto, Canada, 16 Jul 1979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
THORIUM OXIDES
THERMODYNAMIC PROPERTIES
EVAPORATION
FORMATION FREE ENERGY
PHASE DIAGRAMS
PHASE STUDIES
REDUCTION
VERY HIGH TEMPERATURE
ACTINIDE COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTIONS
DIAGRAMS
ENERGY
FREE ENERGY
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
THORIUM COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties
360202 - Ceramics
Cermets
& Refractories- Structure & Phase Studies