Fast transport cobalt in thorium
Three investigations associated with the fast transport behavior of cobalt in thorium were conducted. These include (1) a study of a metastable ThCo{sub x} phase and the solid solubility of cobalt in thorium in dilute thorium-cobalt alloys, (2) a study of the mechanism of fast diffusion of cobalt in thorium using diffusion and internal friction experiments and (3) a study of the thermotransport behavior of cobalt in thorium. A metastable plate phase, having a stoichiometry of about ThCo{sub 0.08}, forms in alloys containing greater than 0.004 at.% Co that are quenched from the single-phase field. Upon aging between 773 and 1073 K the plate phase transforms to rod-like precipitates of the equilibrium Th{sub 7} Co{sub 3} phase. The solid solubility of cobalt in thorium increases from 0.05 at.% at 1120 K to 0.4 at.% at 1350 K. The terminal solid solubility at the eutectic temperature of 1373 K is 0.45 at .%. The activation energy for diffusion of cobalt in {alpha} thorium is 83.7 kJ/mol whereas that associated with the anelastic relaxation process for cobalt in thorium is 78.0 kJ/mol. The diffusion and internal friction results can be interpreted as supporting either the host-solute diplon mechanism or the interstitial mechanism of fast diffusion. The observed cobalt internal friction peak may be due to a host-solute diplon or a substitutional-interstitial pair.
- Research Organization:
- Iowa State Univ. of Science and Technology, Ames, IA (USA)
- OSTI ID:
- 5249771
- Country of Publication:
- United States
- Language:
- English
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