U Diffusion in IV-B Elements in their HCP Phase

摘要

A comparative diffusion study of U in Ti and Zr in their hep phase was performed by means of α-spectrometry in an extended temperature range, below half the melting point, which are the temperatures of technological interest (between 500 and 850 °C). The present diffusion coefficient (D) values for α-Ti differs from previous work in the literature, measured in samples with higher amount of impurities and less accurate techniques, in more than two orders of magnitude, whereas the present diffusion parameters Q = 297 kJ mol~(-1) and D0 = 5x10~(-3) m~2 s~(-1), are close to the self-diffusion ones, which is compatible with a mechanism of diffusion assisted by vacancies. Diffusion data for U in α-Zr shows a curvature in the Arrhenius plot similar to the observed for a-Zr self-diffusion, with D values very close to the self-diffusion ones, which also indicates an assisted by vacancies diffusion mechanism, as expected.