Al-1wt%Mg合金表面層における水素同位体の挙動

概要

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Aluminum alloys are of great interest in their application for D-T burning fusion experimental devices because of their low induced activity and low-out-gassing nature. From the viewpoint of tritium inventory for this application, we studied the capturing and motion hydrogen isotopes by/in an Al-1wt%Mg alloy by means of X-ray photoelectron spectroscopy and secondary ion mass spectrometry. Deuterium was implanted into the alloy samples with ion bombardment (5 keV) or electrochemical charge. It was observed that the sample surfaces were covered with aluminum oxides of 6-8x10-5 cm thickness and deuterium implanted was captured in two different states in the subsurface region of the samples: one is the deuterium trapped by metals (Al and Mg) and the other by oxygen. Their mobility differed from each other in the order of Al-H>Mg-H>O-H. This is considered to be due to the difference in stability of those bonds. In the case of the electrochemical charge, the penetration depth of deuterium (1.4x10-4 cm) was about one order of magnitude greater than that for ion implantations (6x10-6cm). This indicates that deuterium is in the ionic state in the surface oxide layer and enhanced diffusion takes place with the presence of electric field gradient. The present results suggest that tritium inventory in aluminum alloys will be greatly influenced as a result of the presence of an oxide layer as well as the alloy composition.
富山大学の論文