
Masao KimuraHigh Energy Accelerator Research Organization | KEK · Institute of Materials Structure Science
Masao Kimura
Doctor of Engineering
About
167
Publications
21,641
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1,761
Citations
Introduction
Techniques: Microscopic spectroscopy, Imaging, In situ observation, Synchrotron radiation
Materials: Metal, Carbon fiber reinforced plastic (CFRP), Battery, Catalyst
Skills and Expertise
Additional affiliations
October 2012 - September 2013
October 1995 - September 2012
Nippon Steel Co.
Position
- Senior Researcher
April 1987 - August 1992
Nippon Steel Co.
Position
- Senior Researcher
Publications
Publications (167)
The reducibility and mechanical properties of iron ore sinter in blast furnace is critical to effective plant operation. The reduction reaction of sinters progresses heterogeneously owing to microstructures with various mineral phases and pore networks. The reduction process was investigated by semi-microbeam synchrotron X-ray multimodal analysis....
X-ray spectromicroscopy is extensively utilized for nondestructive mapping of chemical states in materials. However, understanding and analyzing the geometric and topological aspects of such data pose challenges due to their representation in 4D space, encompassing (x, y, z) coordinates along with the energy (E) axis and often extending to 5D space...
Iron can exist in serpentinite in various oxidation states. Changes in the oxidation state of Fe play a crucial role in geological processes, including supporting diverse biological systems on the ocean floor and the redox states of aqueous fluids released in subduction zones. Synchrotron X-ray absorption near-edge structure (XANES) spectroscopy ha...
We applied pump-flow-probe X-ray absorption fine structure (PFP-XAFS) spectroscopy to photoexcited electron transfer from semiconductor to cocatalyst in a single atom(SA)-Pt/CoOOH photocatalyst to trace the process with microsecond (μs) time-resolution. Upon photoirradiation, photoexcited electrons in the CoOOH semiconductor are found to transfer i...
Fluid inclusions in high- and ultrahigh-pressure metamorphic rocks provide direct information on the composition of the fluids that evolved during metamorphism and fluid-rock interactions in deep subduction zones. We investigate the fluid inclusions in the Khungui eclogite of the Zavkhan Terrane, Central Asian Orogenic Belt. Fluid inclusions are ob...
The reducibility and mechanical properties of iron ore sinter in blast furnace is critical to effective plant operation. The reduction reaction of sinters progresses heterogeneously owing to microstructures with various mineral phases and pore networks. The reduction process was investigated by semi-microbeam synchrotron X-ray multimodal analysis....
EXAFS is powerful to obtain the structure information around the X-ray absorbing atom at the atomic size level. EXAFS is usually analyzed by the curve fitting method, one of the least square methods to optimize structure parameters. However, the curve fitting method demands the experience of scientists when they analyze the EXAFS of materials with...
In this study, we performed scanning transmission X-ray microscopy with a spatial resolution of approximately 50 nm to investigate the two-dimensional mapping of the chemical states of carbon in Fe–C alloy. The lamellar texture (pearlite) consisting of ferrite (α-Fe) and θ-Fe3C with an interval of approximately 100 nm was identified by absorption f...
Nanometer-sized crystals (nanolites) play an important role in controlling eruptions by affecting the viscosity of magmas and inducing bubble nucleation. We present detailed microscopic and nanoscopic petrographic analyses of nanolite-bearing and nanolite-free pumice from the 2021 eruption of Fukutoku-Oka-no-Ba, Japan. The nanolite mineral assembla...
Pore fluid pressure on subduction zone megathrusts is lowered by fluid drainage into the overlying plate, affecting subduction zone seismicity. However, the spatial and temporal scales of fluid flow through suprasubduction zones are poorly understood. We constrain the duration and velocity of fluid flow through a shallow mantle wedge based on the a...
With the aim of introducing data-driven science and establishing an infrastructure for making X-ray absorption fine structure (XAFS) spectra findable and reusable, we have integrated XAFS databases in Japan. This integrated database (MDR XAFS DB) enables cross searching of spectra from more than 2000 samples and more than 700 unique materials with...
This paper proposes a data analysis method using persistent homology and nonnegative matrix factorization. A concatenated persistence image technique is used to extract coexisting structures from the persistence diagrams of different dimensions hidden behind the data. To demonstrate the potential of our method, we apply the method to 3D voxel data...
Nanometer-sized crystals (nanolites) play an important role in controlling eruptions by affecting the viscosity of magmas and inducing bubble nucleation. We present detailed microscopic and nanoscopic petrographic analyses of nanolite-bearing and nanolite-free pumice from the 2021 eruption of Fukutoku-Oka-no-Ba, Japan. The nanolite mineral assembla...
This paper proposes a data analysis method using persistent homology and nonnegative matrix factorization. A concatenated persistence image technique is used to extract coexisting structures from the persistence diagrams of different dimensions hidden behind the data. To demonstrate the potential of our method, we apply the method to 3D voxel data...
Reduction behavior of various multi-component calcium ferrites at 900°C were investigated by using in situ X-ray diffraction (XRD) and X-ray absorption spectroscopy. Reaction products (intermediate components) were determined by XRD and change in X-ray absorption spectra of Fe and Ca K-edges were analyzed to determine reaction rate constants. SFCA-...
The damping of metal contact surfaces considerably influences the dynamic characteristics of machines. However, the contact damping mechanism has not yet been sufficiently clarified because it is difficult to directly observe metal–metal contact surfaces. In this study, the deformation of the metal surface asperity caused by a tangential load was a...
In this study, we performed scanning transmission X-ray microscopy with a spatial resolution of approximately 50 nm to investigate the two-dimensional mapping of the chemical states of carbon in Fe–C alloy. The lamellar texture (pearlite) consisting of ferrite (α-Fe) and θ-Fe3C with an interval of approximately 100 nm was identified by absorption f...
Nanoscale fracture mechanism in CFRPs is still debated owing to the considerable difficulty in determining the three-dimensional mechanism of fracture using conventional techniques such as optical and/or electron microscopy relying on side-surface- and fracture-surface-based observation. In this study, microscopic damages such as fiber/matrix debon...
Chemical-state imaging of materials using X-ray microscopes has been developed and applied to various materials such as composites, batteries, ceramics and so on. In this article, after features of X-ray microscopy are discussed, analytical approaches for chemical-state imaging are reviewed by showing typical application to materials : scanning tra...
To effectively control the mechanical properties of structural materials and design their safety margins, understanding the properties of metal fracture is essential. However, it is difficult to experimentally investigate the atomic structures at the moment of fracture; therefore, the detailed fracture mechanism remains an active area of research....
Solid lubricants are used to lubricate the mechanical equipment of various spacecraft and launch vehicles. Tungsten disulfide (WS2) is one of the solid lubricants that can be used in a variety of applications at elevated temperatures in outer space. In this study, WS2 coatings on a metal disc were applied via the shot peening method using WS2 powde...
Reduction behavior of various multi-component calcium ferrites at 900°C were investigated by using in situ X-ray diffraction (XRD) and X-ray absorption spectroscopy. Intermediate components were determined by XRD, and change in X-ray absorption spectra of Fe and Ca K-edges were analyzed to determine reaction rate constants. SFCA-I (Ca3(Ca,Fe)(Fe,Al...
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 usi...
The mass fraction of each crystalline phase in inorganic materials can be investigated using the Rietveld refinement of the X-ray diffraction (XRD) patterns. For quantitative analysis, differences in the values of the linear absorption coefficient, μ, among the crystalline phases must be considered when certain X-ray sources are used, because such...
To investigate the performance of the size measurement by asymmetric flow field-flow fractionation (AF4), the measurement results of gold nanoparticles were compared among AF4, transmission electron microscopy (TEM), and small-angle X-ray scattering (SAXS) in terms of the average size and full width at half maximum (FWHM) of the size distribution....
The kinetics of phase transformation in the Fe–C system during cooling are of great importance for controlling its microstructure and mechanical properties. However, real-time observation of the phase transformation has been a challenging task because of experimental difficulties. Here, we developed an analytical technique for time-resolved observa...
A simple and easy surface sensitive spectroscopic method using hard X-rays has been developed and applied to observe the surface oxide reduction reaction. The method named TREXS, Total REflection X-ray Spectroscopy, records the total reflection of incident X-rays at sample surfaces. The surface reduction reaction of Co oxide (Co3O4) to Co metal was...
The mass fraction of each crystalline phase in inorganic materials can be investigated using the Rietveld refinement of the X-ray diffraction (XRD) patterns. For quantitative analysis, differences in the values of the linear absorption coefficient, µ, among the crystalline phases must be considered when certain X-ray sources are used, because such...
In this study, an azimuthal-rotation sample holder compatible with scanning transmission X-ray microscopy was developed. This holder exhibits improvement in the accuracy of rotation angles and reduces the displacement of the rotation axes during azimuthal rotation by using a crossed roller bearing. To evaluate the performance of the holder, the aut...
The mechanical properties of carbon fibers (CFs) can be controlled by their internal structures such as the distribution of π-orbital-oriented domains, as well as the diameter and cross-sectional shape of the fiber. In this study, we investigated the carbon chemical structure maps of commercial polyacrylonitrile (PAN)- and pitch-based CFs using sca...
The crack initiation and propagation under the application of opening load were analyzed in situ using nondestructive synchrotron radiation X-ray computed tomography (nanoscopic SR X-CT) with a spatial resolution of ∼50 nm. The results show that the voids and cracks initiation are not only the result of local stresses but also are due to two compet...
Crack initiation and propagation in carbon fiber-reinforced plastic (CFRP) was observed in situ under the application of an opening load using nondestructive synchrotron radiation X-ray computed tomography (nanoscopic SR X-CT) at a high spatial resolution of ∼50 nm. Two datasets of reconstructed and segmented images were produced in typical regions...
A pulse stretcher providing a 5.2 keV quasi-continuous beam has been developed for use with a pulsed slow-positron beam generated by an electron linear accelerator operated with a repetition frequency of 50 Hz. Pulses of positrons, of width 1.2 µs, were trapped in a Penning-Malmberg trap and then gradually released downstream, stretching the pulse...
To investigate the performance of the size measurement by asymmetric flow field-flow fractionation (AF4), the measurement results of gold nanoparticles were compared among AF4, transmission electron microscopy (TEM), and small-angle X-ray scattering (SAXS) in terms of the average size and full width at half maximum (FWHM) of the size distribution....
Voids and cracks can fatally degrade structural materials such as metals and ceramics but are tolerated in carbon fibre-reinforced plastic (CFRP) composites if monitored to prevent their growth to a critical size. Thus, the use of CFRPs as aeronautical structural materials requires an understanding of microscopic crack formation. However, this crac...
The mechanism of recrystallization texture development of cold-rolled metal and steel largely depends on the material chemical composition, cold-rolling reduction, and annealing treatment conditions. To clarify the mechanism, it is important to identify the locations where recrystallization starts and progresses within cold-rolled materials.
Using...
Plastic deformation of polycrystalline materials under shock wave loading is a critical characteristic in material science and engineering. However, owing to the nanosecond time scale of the shock-induced deformation process, we currently have a poor mechanistic understanding of the structural changes from atomic scale to mesoscale. Here, we observ...
A void formation at nanoscale and a crack initiation at micrometer scale in CFRP during a tensile test were investigated by means of positron annihilation and X-ray computed tomography (X-CT). Free volumes in bisphenol-A epoxy resin in CFRP were probed, and a mean diameter of free volumes at room temperature was determined to be 0.49 nm. The crack...
X‐ray absorption fine structure (XAFS) spectroscopy is one of the most widely used methods at synchrotron radiation facilities. XAFS gives us information on chemical states and local structures. Fundamentally, XAFS is bulk sensitive, not surface sensitive. If a surface sensitive XAFS method was available, surface chemical reactions can be observed...
Macroscopic properties of carbon fiber‐reinforced plastic (CFRP) and environmental barrier coating (EBC), widely used for airplanes, can be deteriorated by local cracks or degradation (“trigger sites”). We have tried to find these trigger sites using x‐ray microscopy (XM), which can provide the 2D or 3D images of the chemical states and microstruct...
A novel in situ cell was developed for simultaneous X-ray absorption fine structure and X-ray diffraction (XAFS/XRD) measurements at high temperatures up to 1773 K in a gas atmosphere such as air containing reactive oxygen, in which typical heat-resistant or environmental-barrier materials are used. This new cell can provide multimodal information...
The thermodynamic model of a silico-ferrites of calcium and aluminum solution, SFCA phase (Ca2(Fe, Ca)6Oct(Fe, Al, Si)6TetO20) was newly developed in the framework of the Compound Energy Formalism (CEF). Preferred substitution of Al atoms to tetrahedral sites in the SFCA solution was verified by X-ray absorption near edge structure (XANES) analysis...
We have developed hard X-ray spectromicroscopes at various scales using synchrotron radiation to elucidate the origin of the function of materials at Photon Factory (PF), Institute of Materials Structure Science (IMSS), High Energy Accelerator Research Organization (KEK) in Japan. One is a 2D scanning X-ray microscope with ∼20-µm spatial resolution...
The Materials Chemistry Group of the Institute of Materials Structure Science, KEK, aims to clarify irreversible reaction processes such as structural changes of materials induced by laser shock or temperature. We have developed an experimental system using dispersive X-ray absorption fine structure (DXAFS) spectroscopy and a laser to observe these...
We have developed a type of surface sensitive x-ray spectroscopy, which is called total reflection x-ray spectroscopy (TREXS). As x-ray absorption fine structure (XAFS) spectroscopy is used to study many materials, TREXS provides structural and electronic information with the surface sensitivity of ~2–3 nm, and will be a powerful method to study su...
Materials Chemistry Group of Institute of Materials Structure Science, KEK, researches to clarify irreversible reaction processes such as structural change of materials induced by laser shock and temperature. To observe these processes in real time, we have developed an experimental system using DXAFS and a laser. We have used a simple sample excha...
3D Spectromicroscopic Observation of Yb-Silicate Ceramics Using XAFS-CT - Volume 24 Supplement - Yasuo Takeichi, Toshiki Watanabe, Yasuhiro Niwa, Satoshi Kitaoka, Masao Kimura
In situ XRM Observation of Cracking in CFRP during Nanomechanical Testing - Volume 24 Supplement - Toshiki Watanabe, Yasuo Takeichi, Yasuhiro Niwa, Masao Kimura
Non-Empirical Identification of Trigger Sites in Image Data using Persistent Homology: Crack Formation during Heterogeneous Reduction of Iron-Ore Sinters - Volume 24 Supplement - M. Kimura, I. Obayashi, Y. Takeichi, R. Murao, Y. Hiraoka
The initial stage of degradation process of yttria partially stabilized zirconia thermal barrier coatings during heating at 1000–1450 K were observed in situ by transmission electron microscopy. The observation directly demonstrated that the formation of several kinds of oxides and resulting void growth started above 1000 K in the bond-coat layer n...
Persistence diagrams have been widely recognized as a compact descriptor for characterizing multiscale topological features in data. When many datasets are available, statistical features embedded in those persistence diagrams can be extracted by applying machine learnings. In particular, the ability for explicitly analyzing the inverse in the orig...
The present state of XAFS databases, particularly in Japan, and proposals for future directions are presented. International collaboration is important for enlarging the database for further development of XAFS spectroscopy.
Round robin studies have been used across fields of science for quality control testing and to investigate laboratory dependencies and cross-platform inconsistencies as well as to drive forward the improvement of understanding of experimental systems, systematic effects and theoretical limitations. Here, following the Q2XAFS Workshop and Satellite...
Analysis techniques for quantifying crystal structures of mineral phases and their fractions in iron ore sinters have been developed using the Rietveld analysis of X-ray diffraction patterns and applied to iron ore sinters of different mechanical strength, which were prepared by laboratory-scale sinter pot testing. The Rietveld analysis successfull...
Macroscopic phenomena, such as fracture, corrosion, and degradation of materials, are associated with various reactions which progress heterogeneously. Thus, material properties are generally determined not by their averaged characteristics but by specific features in heterogeneity (or 'trigger sites') of phases, chemical states, etc., where the ke...
The thermodynamic model of a silico-ferrites of calcium and aluminum solution, SFCA phase (Ca2 (Fe,Ca)6Oct (Fe,Al,Si)T6etO20 ) was newly developed in the framework of the Compound Energy Formalism (CEF). Preferred substitution of Al atoms to tetrahedral sites in the SFCA solution was verified by X-ray absorption near edge structure (XANES) analysis...
A low-energy positron diffraction (LEPD) experiment station was developed at the Slow Positron Facility, High Energy Accelerator Research Organization (KEK). An electron-accelerator-based slow-positron beam with an energy of 5 keV was magnetically transported and focused on a transmission-type Ni remoderator to achieve a 50 eV–500 eV brightness-enh...