X-ray microscopy and time-resolved observation using synchrotron radiation are reviewed based on recent reports on in situ observation of cracking and degradation of structural materials. X-ray microscopy can provide three-dimensional images of microstructures and chemical states with a high spatial resolution down to 50 nm. In situ observation using X-ray microscopy successfully revealed crack initiation and propagation in carbon fiber reinforced plastic (CFRP) while a stress was applied to the specimen. X-ray microscopy was applied to ceramic coating or CFRP to perform chemical-state mapping, which is essential for understanding the trigger sites of degradation. In situ observation of time-resolved X-ray diffraction and/or X-ray absorption spectroscopy was carried out with a time resolution down to a few nanosecond by synchronizing an X-ray pulse with a laser pulse. This technique was applied to investigate the mechanism of deformation and fracture or structural phase transitions of metal and alloys after the laser shock.

Soft-x-ray absorption spectroscopy is a suitable approach to conduct in situ observation of molecular processes at surfaces and interfaces. The following three different approaches using soft-x-ray absorption spectroscopy and their application studies on molecular processes at catalytic surfaces and interfaces are introduced : (1) Wavelength-dispersed Auger-electron-yield soft-x-ray absorption for ammonia formation on Rh(111), (2) In situ fluorescence-yield soft-x-ray absorption for humidity dependent chemical changes of polymer electrolyte in a fuel cell and (3) Near-ambient-pressure Auger-electron-yield soft-x-ray absorption for ethylene epoxidation on Ag(111). Recent and future developments of in situ observation using soft-x-ray absorption spectroscopy are described as a powerful tool to unveil molecular processes.

The oxidation reaction kinetics on Ti(0001) and Ni(111) surfaces were observed by real-time photoelectron spectroscopy using synchrotron radiation to investigate the oxidation state and oxide thickness. After the Ti(0001) surface was wholly covered by TiO with a thickness of 1.2 nm, the rapid growth of n-type TiO₂ proceeded through the diffusion of Ti^4＋ ions to the TiO₂ surface at 400℃. A saturation of oxygen uptake on the TiO surface indicates that the O₂ sticking coefficient on the TiO surface is negligibly small and the segregation of Ti to the TiO surface is a trigger to initiate the TiO₂ growth. On the Ni(111) surface at 350℃, a thermally stable NiO_x layer was formed preferentially and then the growth of p-type NiO was initiated. The time evolution of NiO thickness was represented by a logarithmic growth model, where the NiO growth is governed by the electron tunneling to the NiO surface.

Li-ion batteries are preferred energy storage technology for portable electronics, electric and hybrid vehicles. For the large-scale commercialization of electric vehicles and the utilization of renewable energy, the energy storage capacity, cycle life, rate capacity and safety of most commercial batteries still need to be improved. To further improve battery performance it is essential to analyze the reaction mechanism under practical operation for future Li-ion batteries. In this work, the crystal structure of cathode and anode materials in non-equilibrium states during the charge and discharge processes was investigated by laboratory operando X-ray Diffraction (XRD). It was found that the charge and discharge processes differ markedly between the high rate and the low rate. Furthermore, the relationship between the graphite anodes of the different particle sizes and the changes in the crystal structures during charge and discharge process is discussed.

Controlling magnetic anisotropy by orbital magnetic moments related to interfacial strains has considerable potential for the development of future devices using spins and orbitals. In this study, we developed an electric-field (E)-induced X-ray magnetic circular dichroism (XMCD) technique to apply E to a ferroelectric BaTiO₃ substrate. We reversibly tuned the interfacial lattice constants of Ni/Cu multilayers on BaTiO₃ using this technique. The strained Ni layer that induces the perpendicular magnetic anisotropy without E is released at E＝8 kV/cm, and in-plane magnetization also occurs. We observed that electric-field-induced XMCD measurements clarified the origin of the reversible changes in perpendicular magnetic anisotropy and established the relationship between macroscopic inverse magneto-striction effects and microscopic orbital magnetic moment anisotropy.

X-ray topography is a unique technique to visualize crystal defects, e.g., dislocations and stacking faults, for the whole wafer. It has more than 60 years history and still used for investigating quality of the crystals. For example, dislocation free Si single crystal wafer can be easily accessed at the present time. However, it could be often damaged and made defects at the device manufacturing process. Other newly developed single crystal materials, such as SiC and GaN are still having a lot of dislocations. The principle and instruments of the X-ray topography is briefly reviewed and presented how the dislocations are visible. Advanced three-dimensional topography and examples of in-situ topography observations are also introduced.