DIFFUSION AND ELECTROTRANSPORT OF IRON, COBALT AND NICKEL IN THORIUM METAL

The diffusion and electrotransport parameters for iron, cobalt and nickel were measured in α (f.c.c.) and β (b.c.c.) thorium over the temperature range 965 - 1625 °C. All three solutes have negative Z* values corresponding to migration toward the anode and a marked temperature dependence of Z* in both phases. From a least-squares treatment of the diffusivity data, values of D0 and Q in the equation D = D0 exp(- Q R) were obtained for each solute as follows: iron, D0 = 5 × 10-3 cm2s-1 and Q = 19.3 kcal mol-1 in α-thorium and d0 = 4 × 10-3 and Q = 17.1 in β-thorium; cobalt, D0 = 5 × 10-4 cm2 s-1 and Q = 13.2 kcal mol-1 in α-thorium and D0 = 4 × 10-3 and Q = 15.6 in α-thorium; nickel, D0 = 4 × 10-3 cm2 s-1 and Q = 18.6 kcal mol-1 in α-thorium and D0 = 4 × 10-4 and Q = 9.1 in (β-thorium. The D0 and Q values are more characteristic of interstitial solute behavior than of substitutional solutes, as are the electromigration velocities for the temperature range investigated. These results indicate that iron, cobalt and nickel are fast diffusing solutes in thorium metal. © 1979.