Development of innovative means to clarify the mechanisms of anomalous behaviors in the surface "nano" region of fusion reactor materials

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The present study aims to clarify "in-situ" the mechanisms of anomalous behaviors in the surface "nano" region of fusion reactor materials through innovative techniques, in which atmosphere-controllable high temperature mass spectrometry is accompanied with high temperature Kelvin probe. The Knudsen cell was joined with capillary tube to allow the introduction of DィイD22ィエD2 as well as DィイD22ィエD2O to study the vaporization behavior of Li-containing ceramics under exposure to these gases at temperatures close to 2000 K. On the other hand, further improvement of the high temperature Kelvin probe was accomplished, which enabled the measurement of "contact potential difference" (CPD), between the specimen (Li-containing ceramics) and reference electrode of Pt, as small as 【approximately equal】0.1 mV.According to the results of vapor pressure measurements on various Li-bearing ceramics, the vaporization behavior was observed to be dependent on the oxygen potential in the cases of LiィイD24ィエD2 … More SiOィイD24ィエD2 and LiィイD22ィエD2ZrOィイD23ィエD2. This observation led the authors to assume an existence of oxygen-deficient surface layer in these ceramics. In order to further investingate the thermochemical behavior of Li-bearing ceramics, a high temperature Kelvin probe was employed. The work function changes of LiィイD24ィエD2SiOィイD24ィエD2 (973 K) and LiィイD22ィエD2ZrOィイD23ィエD2 (943 K) were measured. The work function change due to oxygen vacancies formation/annihilation was observed, followed by the change due to adsorption/desorption. In the cases of LiィイD22ィエD2TiOィイD23ィエD2 (933 K) and LiィイD22ィエD2O (823 K), where a single step of the work function change, due to adsorption/desorption was observed. These results supported the authors' interpretation of the results of the high temperature mass spectrometry described above, indicating possible relevance between macroscopic and microscopic behaviors of hydrogen at the surface of ceramic breeders.Further innovation is being carried out to allow "in-situ" measurement of electric conductivity through Seebeck probe. Less