Hisashi Tanigawa

XPS and UPS studies on electronic structure of Li2O

Abstract The adsorption behavior of H2O on Li2O was studied by X-ray photo electron spectroscopy (XPS) and ultraviolet photo electron spectroscopy (UPS). XPS and UPS spectra of Li2O single crystals which were exposed to different pressure of H2O vapor were observed. In O(1s) region, two peaks were observed and they were assigned to O(1s) in precipitated LiOH on the surface and O(1s) in Li2O. After H2O exposure, a peak broadening and an appearance of a new peak were observed at the higher binding energy region than O(1s) in Li2O. They were attributed to surface −OH and H2O molecule adsorbed on the surface. The adsorption behavior of H2O was discussed from the observation of electronic structure in Li2O surface.

H2O trapping on various materials studied by AFM and XPS

Abstract Adsorption and desorption of water on thin films of iron oxide formed on the iron surface were studied by AFM and X-ray photoemission spectroscopy (XPS). The morphological change of iron oxide or water droplets on the surface of iron oxide were observed by AFM. Electronic state of O 1s was observed by XPS after a sample was exposed to distilled water. Several peaks appeared and assignment to oxygen-containing surface species was discussed.

FT-IR study on interaction of hydrogen isotopes with defects in lithium oxide

The existing state of hydrogen isotopes in lithium oxide (Li2O) was studied using Fourier transform infrared absorption spectroscopy (FT-IR). Infrared spectra in Li2O single crystals which were treated by thermal absorption and consequent quenching were observed from room temperature to 773 K. Multiple peaks were observed in the O–D stretching vibration region and these peaks had different dependence on temperature. These peaks were attributed to the stretching vibrations of O–D presenting as LiOD or Li2O–D+ in bulk Li2O with or without defects. Above 623 K, most of the deuterium ions in Li2O exist as Li2O–D+ and the infrared absorption peak for them was observed around 2520 cm−1. The absorbance decrease of this peak during the isothermal annealing was well analysed by a diffusion model. Diffusion behaviour of hydrogen isotopes in Li2O was discussed from the in-situ observation of O–D.

Ab-initio study on interaction of hydrogen isotopes with charged defects in lithium oxide

Abstract The interaction of hydrogen isotopes with defects in Li 2 O was studied by ab-initio quantum chemical calculations. Three kinds of F-centers and the lithium vacancy were considered. The relaxation of ions around the vacancy and the stable position of a proton were calculated when the vacancy was produced in the Li 2 O crystal. From the obtained energies and the electronic charge density maps for each configuration, the effects of the vacancies on the proton were discussed.

The oxygen-related defect complexes in AlN under gamma irradiation and quantum chemistry calculation

Abstract Oxygen-related defect complexes are important intrinsic defects in AlN ceramics, and their dynamic behavior has a close relationship with physical properties at high temperature. Gamma-ray irradiation has a major effect on the electronic excitation of intrinsic defects. Hence, thermoluminescence measurements after irradiation by gamma-ray can show the dynamic behavior of intrinsic defects or oxygen-related defect complexes in AlN ceramics. By choosing different kinds of AlN ceramics, the basic types of oxygen-related defect complexes (VAl–ON–3N and VAl–2ON–2N) are reflected by studying the spectra of luminescence measurements in the present research. The results of a quantum chemistry simulation indicates that the stability of the VAl–2ON–2N defect system is higher than that of the VAl–ON–3N defect system, and the difference in total energy for two kinds of defects is 0.56 eV.

Quantum Chemical Calculation of O-H Vibration in LiOH Ab-initio Analysis of Hydrogen Isotopes in Ceramic Breeder Materials

The stretching vibrational frequency of O-H in LiOH crystal was calculated using CRYSTAL98 code. Hartree-Fock (HF) and hybrid (B3LYP) methods were used. By taking account of reduced mass, O-D or O-T frequencies could be also estimated. The obtained O-D frequencies were 2,994 cm-1 in HF level and 2,740 cm-1 in B3LYP. Agreement with experimental data, 2,713 cm-1 reported by Buchanan et al., was much better in B3LYP than in HF. The result of the present calculation supported the assignment in our previous FT-IR study, where O-D vibration in the Li2O single crystal that was treated by thermal absorption of D2 was observed. The peak observed at 2,715 cm-1 was attributed to O-D in LiOD phase. The present study showed that the quantum chemical analysis combined with the FT-IR was a powerful tool to study the behavior of hydrogen isotopes in the ceramic breeder materials.

Quantum chemical analysis of hydrogen isotopes in lithium oxide

Abstract In order to clarify the existing states and the diffusion process of hydrogen isotopes in Li2O, the quantum chemical analysis has been conducted especially emphasising interaction with charged defects such as F-centers. Using two calculation codes based on different theories, treatment of charged defects was discussed. From the comparison with FT-IR or diffusion model studies, the interaction of hydrogen isotopes with defects was explained taking electron transfer between them into consideration.

Progress of Design and R&D of Water Cooled Solid Breeder Test Blanket Module

Abstract Development of Water Cooled Solid Breeder (WCSB) TBM, the primary candidate of ITER Test Blanket Module (TBM), has been performed in Japan, according to the TBM milestones, which are necessary for acceptance of the TBM in ITER for testing from the first day of plasma operation. The TBM milestones consist of milestones on safety assessment, module qualification and design integration in ITER. For the safety milestones, essential source terms were evaluated, and failure modes and effect analysis (FMEA) was performed. Based on the results of FMEA, safety assessment was performed. For the milestones of the design integration, detailed structural design of the TBM and the interface structure with the ITER test port were performed. Based on the design, performance analysis such as thermo-mechanical analysis in over-pressurization was performed. For the milestones of the qualification of fabrication technology, essential fabrication technology was developed and near full size first wall of the TBM was successfully fabricated and demonstration of the integrity in heat flux equivalent to ITER. The development of the WCSB TBM is showing steady progress toward the installation in ITER.

UPS study on the interaction of hydrogen isotopes with L2O surface

Abstract The electronic states of Li2O were observed using ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS). By exposing to the different pressures of H2O vapor, the peak attributed to the surface hydroxyl groups was observed. After exposing to the enough pressure to compose LiOH, an obvious change has not been observed in UPS spectra by the precision of the present study although the change was observed in XPS. The density of states (DOS) of Li2O was calculated using CASTEP code, and the obtained spectra were discussed using the results of the calculation.