Mitsugu Nagano1, Yasunori Hayashi2, Namio Ohtani2, Minoru Isshiki3 and Kenzo Igaki3
1Graduate School, Kyushu University, Fukuoka. Present address: Graduate School, Tohoku University, Sendai
In order to study the isotope effect and the trapping effect, the diffusion coefficients of hydrogen and deuterium in high purity iron were measurred by the electrochemical alternating current method at temperatures between 222 and 322 K. This method enables us to separate the surface effect from the permeation process, and gives an accurate diffusion coefficient. The diffusion coefficient of hydrogen obtained above 290 K is proposed to be DH (m2/s)=4.90×10-8 \exp (-4200 (J/mol)/RT), though it was not expressed by a single Arrhenius equation over the whole temperature range studied because of the trapping effect by structural defects and impurity atoms. The activation energies of diffusion for the two isotopes were equal at 4200 J/mol, and the ratio of D0H to D0D was determined to be 1.24, which was slightly smaller than the classical ratio 1.41. At low temperatures, the trapping effect for deuterium was more remarkable than that for hydrogen.
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