Language：Japanese   Publisher：Japan Foundry Engoneering Society  

DOI： 10.11279/jfeskouen.184_91

CiNii Research

Language：Japanese   Publisher：Japan Foundry Engoneering Society  

DOI： 10.11279/jfeskouen.184_90

CiNii Research

Language：Japanese   Publisher：Japan Foundry Engoneering Society  

DOI： 10.11279/jfeskouen.184_92

CiNii Research

Language：Japanese   Publisher：Japan Foundry Engoneering Society  

DOI： 10.11279/jfeskouen.184_14

CiNii Research

Publisher：Proceedings of SPIE - The International Society for Optical Engineering  

GEO-X (GEOspace X-ray imager) is a small satellite mission to visualize the Earth's magnetosphere through Solar Wind Charge eXchange (SWCX). SWCX is known as soft X-ray emissions generated by the charge exchange between highly charged-state heavy ions and neutral atoms in the Earth's exosphere. The GEO-X satellite is aimed to be launched during the upcoming solar maximum around 2025-2027 and is planned to be injected to a low-latitude orbit which allows visualization of the magnetosphere from outside the magnetosphere. The satellite will carry a light-weight X-ray imaging spectrometer, dramatically improving the size and weight of those onboard past X-ray astronomy satellites.

DOI： 10.1117/12.3018746

Web of Science

Scopus

Publisher：Proceedings of SPIE - The International Society for Optical Engineering  

We have been developing ultra-lightweight Wolter type-I X-ray telescopes fabricated with MEMS technologies for GEO-X (GEOspace X-ray imager) which is a small satellite mission to perform soft X-ray imaging spectroscopy of the entire Earth's magnetosphere. The telescope is our original type of micropore optics and possesses lightness (∼5 g), a short focal length (∼250 mm), and a wide field of view (∼5◦ × ∼5◦). The MEMS X-ray telescope is made of 4-inch Si (111) wafers. The Si wafer is first processed by deep reactive ion etching, which has numerous curvilinear micropores (a 20-µm width) whose sidewalls are utilized as X-ray reflective mirrors. High-temperature hydrogen annealing and chemical mechanical polishing processes are applied to make those sidewalls smooth and flat enough to reflect X-rays. After that, the wafer is plastic-deformed into a spherical shape and Pt-coated by a plasma atomic layer deposition process to focus X-rays with high reflectivity. Finally, we assemble two optics bent with different curvatures (1000- and 333-mm radii) and complete the Wolter type-I telescope. We optimized each process and conducted an X-ray irradiation test to assemble the full-processed optics into an EM telescope for the GEO-X mission, which enabled to complete the telescope to achieve an angular resolution of ∼4.8 arcmin in FWHM in the assembled telescope. We report on our latest development status and the X-ray imaging performance of the GEO-X EM telescope.

DOI： 10.1117/12.3020669

Web of Science

Scopus

Language：English   Publisher：The Japan Institute of Metals and Materials  

<p>A technique, which can explain the behavior of fires by using microstructural and oxide examinations of melted marks on copper wire, has been required for fire investigators. However, a study on the microstructural and oxide evolution after a fire is insufficient due to various and complicated fire conditions. In this research, changes in surface morphology, oxide layer thickness, oxidation kinetics, and microstructure were investigated at various annealing temperatures and times on the melted mark on the copper wire. The results show that the copper dendrites surrounded by (Cu+Cu₂O) eutectic structure under Cu₂O and CuO surface is the fingerprint of melted mark on copper wire annealed between 220°C and 600°C. At an annealing temperature of 800°C to 1000°C, the characteristic microstructure of the melted mark is Cu₂O precipitates without dendrites in grains under a single layer of Cu₂O. Moreover, the diffusion processes contributed to Cu₂O growth could be as follows: lattice diffusion at 220°C to 400°C and grain boundary diffusion at 400°C to 1000°C.</p>

DOI： 10.2320/matertrans.f-m2023807

Web of Science

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

<p>A primary melted mark (PMM) on copper wire has been expected to identify the fire origin. However, the solidification microstructure under various cooling conditions has not been extensively studied. In this research, the effects of cooling conditions on PMM microstructure before and after heat treatment were investigated. The results represent dendrite growth direction to the surface of the melted mark with copper dendrites surrounded by (Cu+Cu₂O) eutectic structure for air and water-cooling specimens. Moreover, the melted mark cooled in the air has more than twice of secondary dendrite arm spacing (SDAS) than the water-cooling sample in the case of pre-heat treatment. After heat treatment and cooled down in the furnace, air, and water: the dendritic structure disappears and Cu₂O precipitates on the copper matrix. The smaller crystallite size and oxide layer cracking could be found in a higher cooling rate case. Therefore, by connecting thermal history with solidification structure and surface oxidation morphology, the change in microstructures and physical parameters of PMM could be expected to be helpful for fire investigation.</p>

DOI： 10.2320/matertrans.F-M2023806

Web of Science

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Journal of Astronomical Telescopes, Instruments, and Systems  

GEOspace X-ray imager (GEO-X) is a small satellite mission aiming at visualization of the Earth's magnetosphere by X-rays and revealing dynamic couplings between solar wind and the magnetosphere. In-situ spacecraft have revealed various phenomena in the magnetosphere. X-ray astronomy satellite observations recently discovered soft X-ray emissions originating from the magnetosphere. We are developing GEO-X by integrating innovative technologies of a wide field of view (FOV) X-ray instrument and a small satellite for deep space exploration. The satellite combines a Cubesat and a hybrid kick motor, which can produce a large delta v to increase the altitude of the orbit to about 30 to 60 RE from a relatively low-altitude (e.g., geo transfer orbit) piggyback launch. GEO-X carries a wide FOV (5 × 5 deg) and a good spatial resolution (10 arcmin) X-ray (0.3 to 2 keV) imaging spectrometer using a micro-machined X-ray telescope and a CMOS detector system combined with an optical blocking filter. We aim to launch the satellite around the solar maximum of solar cycle 25.

DOI： 10.1117/1.JATIS.9.3.034006

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Iron and Steel Institute of Japan  

<p>In the industrial steel manufacturing process, such as continuous casting and ingot casting, macrosegregation occurs due to the effect of bridging and contraction flow during the middle and end periods of solidification. Since the macrosegregation results in a nonuniform structure and eventually cracks, there has been a demand for technological development that does not cause macrosegregation in the casting process. In this study, model experiments using the medium-carbon steel cast with a laboratory-scale local-chilled mold at different superheating have been carried out to investigate the relationship between solidified structure and macrosegregation occurred by local bridging during casting. The morphology of shrinkage porosities and dendrite structures was observed. The concentrations of the alloying elements were analyzed for macrosegregation by an electron probe micro-analyzer. Chill plates successfully formed the columnar dendrite bridging area and the columnar dendrite shell in the sample with high superheating. During solidification, the negative pressure of the region below the bridging increased, and the concentrated contraction flow flowed into the bottom of the large shrinkage porosity. Finally, V segregation was formed in the bridging area, large shrinkage porosities remained below the bridging area, and point-like or band-like positive macrosegregation occurred in the interdendritic region between columnar dendrites and equiaxed dendrites below the bridging. In comparison, a lower casting temperature increased the grain density and formed shrinkage porosities that were smaller in size but larger in number and more dispersed.</p>

DOI： 10.2355/isijinternational.ISIJINT-2022-541

Web of Science

Scopus

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Iron and Steel Institute of Japan  

<p>Currently, steel products are manufactured by continuous casting or large-sized ingot casting, and macrosegregation that occurs during the manufacturing process significantly impacts product quality in terms of cracks and deterioration of mechanical properties. To clarify the principle of casting defects, such as shrinkage porosity and macrosegregation due to the formation of bridging of the columnar dendrite of the medium-carbon steel, in this experiment, a laboratory-scale local-chilled mold in which the middle part was forcedly cooled was designed to cause bridging, shrinkage porosities, and macrosegregation. Enough risers were also designed to simulate realistic gravity casting as much as possible. The solidification structure morphology was observed, concentration analysis of alloying elements was performed, and the effect of bridging on macrosegregation was investigated. Solidification proceeded preferentially from the chill plate, and the bridging was formed successfully at a high casting temperature. The high casting temperature condition could cause bridging, but large shrinkage porosities would be formed as well. On the contrary, the lower casting temperature condition could increase the grain density and form shrinkage porosities that are smaller in size but larger in number and more dispersed, compared with the case cast with no chill plate mold. Due to the formation of bridging, macrosegregation was formed, and the difference between positive and negative segregation was increased from the longitudinal center of the sample.</p>

DOI： 10.2355/isijinternational.ISIJINT-2023-038

Web of Science

Scopus

CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2355/tetsutohagane.TETSU-2022-068

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2355/tetsutohagane.TETSU-2022-068

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3390/forensicsci3010002

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.3390/forensicsci3010002

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Materials Transactions  

A primary melted mark (PMM) on copper wire has been expected to identify the fire origin. However, the solidification microstructure under various cooling conditions has not been extensively studied. In this research, the effects of cooling conditions on PMM microstructure before and after heat treatment were investigated. The results represent dendrite growth direction to the surface of the melted mark with copper dendrites surrounded by (Cu+Cu2O) eutectic structure for air and water-cooling specimens. Moreover, the melted mark cooled in the air has more than twice of secondary dendrite arm spacing (SDAS) than the water-cooling sample in the case of pre-heat treatment. After heat treatment and cooled down in the furnace, air, and water: the dendritic structure disappears and Cu2O precipitates on the copper matrix. The smaller crystallite size and oxide layer cracking could be found in a higher cooling rate case. Therefore, by connecting thermal history with solidification structure and surface oxidation morphology, the change in microstructures and physical parameters of PMM could be expected to be helpful for fire investigation. [doi:10.2320/matertrans.F-M2023806].

DOI： 10.2320/matertrans.MT-M2023066

Scopus

Publisher：Materials Transactions  

A technique, which can explain the behavior of fires by using microstructural and oxide examinations of melted marks on copper wire, has been required for fire investigators. However, a study on the microstructural and oxide evolution after a fire is insufficient due to various and complicated fire conditions. In this research, changes in surface morphology, oxide layer thickness, oxidation kinetics, and microstructure were investigated at various annealing temperatures and times on the melted mark on the copper wire. The results show that the copper dendrites surrounded by (Cu+Cu2O) eutectic structure under Cu2O and CuO surface is the fingerprint of melted mark on copper wire annealed between 220°C and 600°C. At an annealing temperature of 800°C to 1000°C, the characteristic microstructure of the melted mark is Cu2O precipitates without dendrites in grains under a single layer of Cu2O. Moreover, the diffusion processes contributed to Cu2O growth could be as follows: lattice diffusion at 220°C to 400°C and grain boundary diffusion at 400°C to 1000°C.

DOI： 10.2320/matertrans.MT-M2023047

Scopus

Language：Japanese   Publisher：Japan Foundry Engoneering Society  

DOI： 10.11279/jfeskouen.181_51

CiNii Research

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Proceedings of SPIE - The International Society for Optical Engineering  

We are developing a novel Bragg reflection X-ray polarimeter using hot plastic deformation of silicon wafers. A Bragg reflection polarimeter has the advantage of simple principle and large modulation factor but suffers from the disadvantage of a narrow detectable energy band and difficulty to focus an incident beam. We overcome these disadvantages by bending a silicon wafer at high temperature. The bent Bragg reflection polarimeter have a wide energy band using different angles on the wafer and enable focusing. We have succeeded in measuring X-ray polarization with this method for the first time using a sample optic made from a 4-inch silicon (100) wafer.

DOI： 10.1117/12.2629635

Web of Science

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Proceedings of SPIE - The International Society for Optical Engineering  

We have been developing an ultra-lightweight Wolter type-I X-ray telescope fabricated with MEMS technologies for GEO-X (GEOspace X-ray imager) which is an 18U CubeSat (similar to 20 kg) to perform soft X-ray imaging spectroscopy of the entire Earth's magnetosphere from Earth orbit near the Moon. The telescope is our original micropore optics which possesses lightness (similar to 15 g), a short focal length (similar to 250 mm), and a wide field of view (similar to 5 degrees x similar to 5 degrees). The MEMS X-ray telescope is made of 4-inch Si (111) wafers. The Si wafer is firstly processed by deep reactive ion etching such that they have numerous curvilinear micropores (20-mu m width) whose sidewalls are utilized as X-ray reflective mirrors. High-temperature hydrogen annealing and chemical mechanical polishing processes are then applied to make those sidewalls smooth and flat enough to reflect X-rays. After that, the wafer is plastic-deformed into a spherical shape and Pt-coated by plasma atomic layer deposition (ALD) process to focus X-rays with high reflectivity. Finally, we assemble two optics bent with different curvatures (1000- and 333-mm radius) into the Wolter type-I telescope. Optimizing the annealing and polishing processes, we found that the optic achieves an angular resolution of similar to 5.4 arcmins in HPW. This is comparable with the requirement for GEO-X (similar to 5 arcmins in HPD at single reflection). Our optic was also successfully Pt-coated by a plasmaenhanced ALD process to enhance X-ray reflectivity. Moreover, we fabricated an STM telescope and confirmed its environmental tolerances by conducting an acoustic test with the H-IIA rocket qualification test level and a radiation tolerance test with a 100 MeV proton beam for 30 krad equivalent to a 3-year duration in the GEO-X orbit.

DOI： 10.1117/12.2630501

Web of Science

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Proceedings of SPIE - The International Society for Optical Engineering  

GEO-X (GEOspace X-ray imager) is a small satellite mission aiming at visualization of the Earth's magnetosphere by X-rays and revealing dynamical couplings between solar wind and magnetosphere. In-situ spacecraft have revealed various phenomena in the magnetosphere. In recent years, X-ray astronomy satellite observations discovered soft X-ray emission originated from the magnetosphere. We therefore develop GEO-X by integrating innovative technologies of the wide FOV X-ray instrument and the microsatellite technology for deep space exploration. GEO-X is a 50 kg class microsatellite carrying a novel compact X-ray imaging spectrometer payload. The microsatellite having a large delta v (>700 m/s) to increase an altitude at 40-60 R-E from relatively low-altitude (e.g., Geo Transfer Orbit) piggyback launch is necessary. We thus combine a 18U Cubesat with the hybrid kick motor composed of liquid N2O and polyethylene. We also develop a wide FOV (5x5 deg) and a good spatial resolution (10 arcmin) X-ray (0.3-2 keV) imager. We utilize a micromachined X-ray telescope, and a CMOS detector system with an optical blocking filter. We aim to launch the satellite around the 25th solar maximum.

DOI： 10.1117/12.2629107

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Theoretical and Applied Fracture Mechanics  

This study systematically investigates the effects of annealing heat treatment on the microstructure, plastic strain manifestation, and the consequent fracture process in products fabricated via selective laser melting (SLM). Several Mg-9%Al-2%Ca alloy round bars and cubic specimens were fabricated and heat-treated subsequently. The round bar specimens were subjected to tensile testing and subsequent fracture surface and electron backscatter diffraction analyses for the observation of plastic strain. The microstructural and microhardness analyses of the cut cubic specimens showed that the coarse microstructure at the melt pool borders dissipated owing to the annealing effect, and the overall hardness of the material was significantly reduced. Consequently, when tensile stresses were applied, stable crack propagation was enabled by microstructure homogenization instead of the sudden interruption of propagation, a phenomenon exclusively responsible for fracture under as-built conditions. Accordingly, the annealed specimens showed an increase in ductility but a reduction in the ultimate tensile strength. Furthermore, the fracture toughness value, which is a critical parameter used to predict unstable fractures under as-built conditions, can no longer be considered for the annealed specimens due to the elimination of the crack propagation interruption. Therefore, this study discusses the validity of applying an R-curve. Accordingly, a concrete analysis of the fracture process in annealed specimens can provide valuable insights for determining the conditions under which annealing would be an optimal process for the end product.

DOI： 10.1016/j.tafmec.2022.103411

Web of Science

Scopus

Language：Japanese   Publisher：Japan Foundry Engoneering Society  

DOI： 10.11279/jfeskouen.180_12

CiNii Research

Language：Japanese   Publisher：Japan Foundry Engoneering Society  

DOI： 10.11279/jfeskouen.180_33

CiNii Research

Language：Japanese   Publisher：Japan Foundry Engoneering Society  

DOI： 10.11279/jfeskouen.179_20

CiNii Research

Language：Japanese   Publisher：Japan Foundry Engoneering Society  

DOI： 10.11279/jfeskouen.180_8

CiNii Research

Language：Japanese   Publisher：Japan Foundry Engoneering Society  

DOI： 10.11279/jfeskouen.180_34

CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2355/tetsutohagane.TETSU-2021-020

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1364/AO.401644

Language：English   Publishing type：Research paper (scientific journal)  

The microstructure evolution in ductile cast iron with magnesium addition was observed in situ by using X-ray radiography (two-dimensional observation) and time-resolved tomography (three-dimensional observation) in the BL20XU of a synchrotron radiation facility, SPring-8 (Hyogo, Japan). In the two-dimensional observation, graphite nodules nucleated in the melt and floated up immediately after nucleation. The floating was terminated by engulfment of graphite nodules into austenite dendrites. The radiography indicated that the average floating distance was shorter than the dendrite arm spacings in the 100-μm-thick specimen. Because the short distance could be influenced by the sample confinement, time-resolved tomography was performed by using a pink X-ray beam in the BL28B2 of SPring-8. Graphite nodules that nucleated in the melt (probably on magnesium–oxygen–sulfur inclusions in the melt) floated and were engulfed by austenite dendrites within several seconds, even in the bulk specimen. Although the average distance in the bulk specimen was approximately twice as large as that in the 100-μm-thick specimen, floating after nucleation and engulfment into austenite dendrites within a short duration were observed commonly from both techniques. The sequence of nucleation and engulfment had a critical effect on the number and size of the graphite nodules.

DOI： 10.1007/s40962-020-00424-3

Language：English   Publishing type：Research paper (scientific journal)  

The in-situ measurements of the solute partition coefficients, k, between the solid and liquid phases in Fe–Cr–Ni–Mo–Cu alloys were conducted using X-ray transmission imaging and X-ray fluorescence spectroscopy (EDS) in a synchrotron radiation facility, SPring-8. A nearly planar solid/liquid interface was achieved in a furnace with a temperature gradient (5–10 K/mm) using X-ray transmission imaging. The measurement points in the solid and liquid phases and close to the solid/liquid interface were determined by X-ray imaging. The compositions of the solid and liquid phases were measured by EDS. The solute partition coefficients along the solidification path in the Fe - 19.89–25.82mass% Cr - 24.73–34.81mass% Ni - 4.46–10.28mass% Mo - 1.47–5.79mass% Cu alloy were determined at 56 different liquid compositions. At the beginning of solidification, the partition coefficients of Cr, Ni, Mo and Cu were 0.96, 0.97, 0.70 and 0.86, respectively. The partition coefficients of Cr and Ni were almost constant during the unidirectional solidification. The partition coefficient of Mo gradually changed from 0.7 to 0.6, leading to a severe microsegregation at the end of solidification. In contrast, the partition coefficient of Cu was dispersed in the range from 0.8 to 0.9. This study demonstrated that the in-situ measurement was effective for systematic measurement.

DOI： 10.2355/isijinternational.ISIJINT-2019-444

Language：English   Publishing type：Research paper (scientific journal)  

Time-resolved tomography (4D-CT) and X-ray diffraction (XRD) were combined to observe growing dendrites and to measure their crystallographic orientation in a CrMnFeCoNi high-entropy alloy with an FCC structure. The evolution of the dendritic grains cooling at 0.083 K/s was reconstructed using 200 projections over a 180° rotation every 4 s from 4D-CT and a phase field filter. The voxel size was a 6.5-µm cube. Simultaneously, the crystallographic orientations of the dendritic grains were measured by XRD. The dendrite arms grew preferentially along the

DOI： 10.2320/matertrans.MT-MK2019006

Language：English   Publishing type：Research paper (scientific journal)  

Dendrite arm fragmentation is considered in solidification structure tailoring. Time-resolved and in situ imaging using synchrotron radiation X-rays allows the observation of dendrite arm fragmentation in Fe–C alloys. Here we report a dendrite arm fragmentation mechanism. A massive-like transformation from ferrite to austenite rather than the peritectic reaction occurs during or after ferrite solidification. The transformation produces refined austenite grains and ferrite–austenite boundaries in dendrite arms. The austenite grains are fragmented by the liquid phase that is produced at the grain boundary. In unidirectional solidification, a slight increase in temperature moves the ferrite–austenite interface backwards and promotes detachment of the primary and secondary arms at the δ–γ interface via a reverse peritectic reaction. The results show a massive-like transformation inducing the dendrite arm fragmentation has a role in formation of the solidification structure and the austenite grain structures in the Fe–C alloys.

DOI： 10.1038/s41467-019-11079-y

Language：English   Publishing type：Research paper (scientific journal)  

Time-resolved in situ tomography of dendritic growth in Fe-0.45 mass% C carbon steel was performed using synchrotron radiation X-rays at SPring-8 synchrotron radiation facility (Japan) with improvement of the image quality using a physics-based filter. The voxel size of the reconstructed image was approximately 6.5 μm × 6.5 μm × 6.5 μm, and the time resolution (duration of 360° rotation) was 4 s (0.25 rps). Three-dimensional images of the dendrites were reconstructed even without image processing; however, the low contrast resolution in Fe-C alloys led to poor image quality. Consequently, it was impossible to precisely track the solid/liquid interface or evaluate the average curvature. To improve the image quality, a physics-based filter (a PF filter) was developed using a phase-field model. In the PF filter, images were retrieved in terms of interface curvature. The PF filter significantly improved the computed tomography image quality. As a result, dendritic growth was clearly observed even in Fe-C alloys. Moreover, the average curvature of the solid/liquid interface was evaluated as a function of solidification time (solid fraction). The ability to systematically characterize growing dendrites will be beneficial for modeling and simulation of solidification phenomena.

DOI： 10.1088/1757-899X/529/1/012023

Language：English   Publishing type：Research paper (scientific journal)  

For a long time, the γ phase in metallic alloys has seemed to be produced through a peritectic reaction between the δ and liquid phases. However, direct observations have shown that a massive-like transformation, in which the δ phase transforms into the γ phase in the solid state, is dominant during or after solidification of the δ phase in carbon steels. To characterize such massive-like transformation, we use time-resolved tomography (4D-CT) to demonstrate the volume change during cooling from the melt and the crystallographic orientation relationship between the δ and γ phases. The volume changes from solidification and from the massive-like transformation from the δ to the γ phase were -3% and -0.5%, respectively. The transformation from the δ to the γ phase finished quickly, as demonstrated by the volume change. Fine γ grains were produced even in a single δ grain through the massive-like transformation. Also, the refined γ grains showed a wide crystallographic distribution.

DOI： 10.1088/1757-899X/529/1/012013

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1088/1757-899X/424/1/012074

Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/PVSC.2017.8366265

Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.4028/www.scientific.net/MSF.925.104

Language：English   Publishing type：Research paper (other academic)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2355/tetsutohagane.TETSU-2017-077

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1109/PVSC.2016.7749826

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.egypro.2016.07.068

Language：English   Publishing type：Research paper (other academic)  

Radiography was performed to examine solidification and melting behaviors in hypereutectic cast iron specimens with / without Mg addition. The specimens without Mg addition showed that graphite particles exhibited spherical shape at the beginning and then transformed to the flake-like shape. Growth of γ-Fe dendrites was followed by nucleation of graphite particles ahead of the eutectic front. In contrast, growth of graphite particles and γ-Fe dendrites occurred nearly at the same time in the specimens with Mg addition and the spherical graphite particles were engulfed by γ-Fe or eutectic. The addition of 0.05mass%Mg significantly reduced the temperature range in which the graphite particles grew as the primary phase. Image-based analysis of melting behavior clearly proved that even 0.05mass% addition modified the phase equilibrium of the liquid, γ-Fe and graphite phases.

Language：English   Publishing type：Research paper (other academic)  

DOI： 10.1109/PVSC.2014.6925560

Language：English   Publishing type：Research paper (scientific journal)  

A noncontact crucible method was used to investigate the process by which a Si₃N₄ coating material forms Si₃N₄ particles or precipitates on the surface of Si melts and ingots. Si ingots were grown using crucibles with and without a mixture of α- and β-Si ₃N₄ particles. The oxygen and nitrogen concentrations in the ingots were measured by Fourier transform infrared spectrometry analysis. The nitrogen concentration in the ingots grown using crucibles with a Si ₃N₄ coating was significantly higher than that in ingots grown using crucibles without a Si₃N₄ coating because the nitrogen from the Si₃N₄ coating material dissolved into the Si melt. From orientation image maps analyzed using electron backscattering diffraction patterns of Si_xN_y particles on the surface of the ingots, it was clarified that most of the Si_xN_y particles were β-Si₃N₄. This was also confirmed by X-ray diffraction measurements. The Si₃N₄ particles on the surface of the ingots had several morphologies such as needle-like, columnar, leaf-like, and hexagonal structures. There were two cases in which floating Si₃N₄ particles were formed on the surface of the Si melts, i.e., the removal and dissolution of the Si₃N₄ coating material. The removed or dissolved Si₃N₄ coating materials, which consisted of a mixture of α- and β-Si ₃N₄ particles, are considered to have finally changed into β-Si₃N₄ in the form of transformers or precipitates on the surface of the Si melt, and these β-Si₃N₄ particles became attached to the surface of the ingots.

DOI： 10.1016/j.jcrysgro.2013.12.006

Language：English   Publishing type：Research paper (scientific journal)  

The noncontact crucible method was used to prepare square Si single bulk crystals. The size of the square part of the ingots was determined by the side-face width of the four-cornered pattern that appeared on the top surface. We obtained square Si single crystals with sizes of 9.4 ' 9.7 and 10.9 ' 11.0cm2 that had no fan-shaped {110} faces and had diagonal lengths of up to 91% of the crucible diameter. To obtain large square Si single bulk crystals with a large side-face width using the present method, the importance of establishing a larger low-temperature region in the Si melt while maintaining a smaller initial temperature reduction was considered.

DOI： 10.7567/JJAP.53.025501

Language：English   Publishing type：Research paper (other academic)  

A noncontact crucible method was proposed to obtain a crystal-diameter as large as a crucible-diameter. In this method, a Si melt used has a large low-temperature region in its central upper part to ensure Si crystal growth inside it. Therefore, the present method has several merits such as the convex shape of the growing interface in the growth direction, the possibility of growing large ingots even using a small crucible, and the growth of square-like single bulk crystals. In these ingots, dislocations in the ingot moved to the periphery of the ingot from its center during crystal growth, and the dislocation density was on the order of 10²-10³/cm². The effective minority carrier lifetime was measured to be as high as 750 μs by the Quasi-Steady-State Photoconductance (QSSPC) method after phosphorus diffusion gettering and Al₂O₃ thin-film passivation. Especially, this method has a possibility to attain a high growth rate using a high cooling rate because the growth rate was determined by the expansion rate of the low-temperature region in Si melts. The growth rate increases as the cooling rate increases. At the cooling rate of 0.4 K/min, the horizontal growth rate became higher to 1.5 mm/min in the <110> direction. The vertical growth rate was determined as 0.3-0.6 mm/min, and it had a tendency to increase as the depth of Si melts increased. The diameter of ingots can be kept constant during crystal growth using a high cooling rate because the horizontal growth rate increases as the cooling rate increases. An ingot with a diagonal length of 24.5 cm was obtained using the high cooling rate of 0.4 K/min. The diagonal length was as large as 82% of the crucible diameter.

DOI： 10.1109/PVSC.2014.6924870

Language：English   Publishing type：Research paper (other academic)  

MEMS technolgies can provide future space missions with ultra light-wight and high resolution optics. We conducted an X-ray irradiation test of our first MEMS-based Wolter type-I optic. However, a focus was weak and wide spread. Hence, we improved fabrication processes and an alignment system. In this paper, we report on results of the latest X-ray irradiation test of our new Wolter type-I optic. The angular resolution and effective area were 4.1 arcmin and 32 mm² both of which are 3 and 40 times better than those in the first test.

DOI： 10.1109/OMN.2014.6924555

Language：English   Publishing type：Research paper (other academic)  

Silicon is brittle and easily cracks even under a small load. The difficulty in shaping silicon has prevented breakthroughs in the mass production of silicon lenses for terahertz and infrared technology. We developed a novel method of deforming bulk single-crystal silicon into the required shape by one-shot pressing at a temperature just below the melting point of silicon, despite its brittleness and covalent nature, and realized the near-net shaping of the material into the plano-convex shape with the curvature radius R=7.5 mm for a infrared transmission lens. The crystallographic quality of the obtained lens could be improved by primary recrystallization. The simple method of 'pressing' will enable the mass production of not only silicon lenses but also lenses with a complex shape, such as aspherical lenses, and lens arrays by using dies with desired shape.

Language：English   Publishing type：Research paper (other academic)  

We have been developing novel ultra lightweight X-ray optics based on MEMS technologies, aiming at future space missions whose objectives include X-ray astronomy, planetary exploration, and Earth observation. Sidewalls of DRIE- micro pores through thin silicon wafers are used for X-ray mirrors. Recently, we built a prototype of a 4-inch Wolter type-I optic and fabricated a 12-inch single-stage op-tic. In this paper, we review our development and future space applications.

DOI： 10.1109/OMN.2014.6924553

Language：English   Publishing type：Research paper (other academic)  

We have been developing original MEMS-based X-ray optics toward future astronomical missions such as a planetary exploration mission. In this paper, we report results on the first X-ray irradiation test for a 2-stage MEMS-based optic. The obtained FWHM of the focusing image is 13±2 arcmin. However, an occultation effect and a deformation accuracy possibly affect a reduction of effective area.

DOI： 10.1109/OMN.2013.6659086

Language：English   Publishing type：Research paper (other academic)  

A noncontact crucible method for reducing stress in Si bulk crystals was proposed. In this method, the Si melt used has a large low-temperature region to ensure natural Si crystal growth inside it. Compared with the conventional growth methods, the present method has several merits such as the convex shape of the growing interface in the growth direction, the possibility of growing large ingots even with the use of a small crucible, and the low O concentration in the ingots because of the small convection in the Si melt due to existence of the large low-temperature region. We have confirmed that by using crucibles without coating Si₃N₄ particles, p-type Si single bulk crystals can be grown inside a Si melt without contacting with the crucible wall. The single bulk crystals grown had low dislocation densities (on the order of 10³/cm²). The diameter of the ingot obtained using a crucible with a 30 cm diameter was 22cm. The O concentration in the present ingots was relatively lower than that in ingots grown by the CZ method. An n-type ingot was grown using a crucible without Si₃N₄ coating. Several Σ3 twin grain boundaries were observed in the cross section of the ingot. The average minority carrier lifetime of an n-type wafer was higher than that for p-type wafers.

DOI： 10.1109/PVSC.2013.6744123

Language：English   Publishing type：Research paper (other academic)  

Our development of ultra light-weight X-ray micro pore optics based on MEMS (Micro Electro Mechanical System) technologies is described. Using dry etching or X-ray lithography and electroplating, curvilinear sidewalls through a flat wafer are fabricated. Sidewalls vertical to the wafer surface are smoothed by use of high temperature annealing and/or magnetic field assisted finishing to work as X-ray mirrors. The wafer is then deformed to a spherical shape. When two spherical wafers with different radii of curvature are stacked, the combined system will be an approximated Wolter type-I telescope. This method in principle allows high angular resolution and ultra light-weight X-ray micro pore optics. In this paper, performance of a single-stage optic, coating of a heavy metal on sidewalls with atomic layer deposition, and assembly of a Wolter type-I telescope are reported.

DOI： 10.1117/12.925811

Language：English   Publishing type：Research paper (other academic)  

We have been developing our original MEMS-based X-ray optics for future astronomical missions. To date, we verified the focusing of optical light and X-ray for the first time. The concept and recent advances are reviewed.

DOI： 10.1109/OMEMS.2012.6318815

Language：English   Publishing type：Research paper (other academic)  

Conventional crystal growth methods using crucibles cannot control the stress caused by expansion due to the solidification of the Si melt. We proposed a noncontact crucible method using a conventional crucible that reduces the stress in Si multicrystalline ingots. In this method, nucleation occurs on the surface of a Si melt using seed crystals, and crystals grow inside the Si melt without touching the crucible walls. Then, the ingots continue to grow while being slowly pulled upward to ensure that the crystal growth remains in the Si melt. A Si ingot with a diameter of 23 cm was obtained in a crucible with a diameter of 30 cm. The maximum solidification ratio in the growth was more than 80%. We have confirmed that such noncontact crucible growth was possible using a conventional crucible.

DOI： 10.1109/PVSC.2012.6317949

Language：English   Publishing type：Research paper (other academic)  

Implementation of a MEMS-based Wolter type-I optic that is suitable for future planetary exploration missions is described. A devised alignment system permits independent adjustment of position and angular settings of x-ray mirrors.

DOI： 10.1109/OMEMS.2012.6318814

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1364/OL.37.000779

Language：English   Publishing type：Research paper (other academic)  

We report a novel micromachined X-ray optics using DRIE formed micro mirrors for future space astronomical missions. We have fabricated a test optics and measured its imaging quality using X-rays. We have successfully verified the X-ray focusing using this type of optics for the first time in the world. The obtained angular resolution was about 20 arcmin and 3.1 mm. This result was consistent with the expected angular resolution based on the surface roughness of the DRIE formed side walls. To achieve a better angular resolution, we will condition annealing and magnetic field assisted finishing processes.

DOI： 10.1109/TRANSDUCERS.2011.5969715

Language：English  

The effect of microstructure on the residual stresses in directionally solidified eutectic (DSE) Al2O3/Y3Al5O12 (YAG) ceramic composite were investigated by X-ray diffraction technique and finite element method (FEM). In the X-ray stress measurement, the YAG skeleton derived from the Al₂O₃/YAG composite by dioxidation of the Al₂O₃ phase was used as a reference specimen without thermally-induced stress, and the X-ray stress measurements with CuKα1 irradiation were performed on the two faces of a cubic specimen, namely, the faces parallel and perpendicular to the solidification direction, respectively. On the other hand, a numerical analysis using finite element method (FEM) which represents the actual microstructure features of the experimental specimen was carried out in different local regions with different morphologies to reveal the effect of microstructure on the distribution of residual stress in the composite. The distributions of residual stresses in both constituting phases were mapped by FEM calculation. Meanwhile, the mapping of residual stress indicated that the distribution of residual stress in the interior of each phase was not homogeneous being dependent on the solidification direction and local morphologies of constituting phases such as curvature of interfaces, array and volume fraction. The experimentally measured residual stresses were accounted for by the FEM analysis.

Language：English   Publishing type：Research paper (international conference proceedings)  

An X-ray imaging test for an X-ray optical system based on MEMS technologies was conducted at the ISAS 30 m beamline. An X-ray reflection and focusing were successfully verified at Al K_α 1.49 keV for the first time. The image quality estimated as a half power diameter was ∼20 arcmin. This was consistent with the angular resolution estimated from the surface roughness of 200 nm rms at 100 ìm scale. In this paper, the experimental setup and the result of X-ray imaging analysis are reported.

DOI： 10.1109/OMEMS.2010.5672138

Language：English   Publishing type：Research paper (international conference proceedings)  

X-ray optics based on MEMS technologies can provide future astronomical missions with ultra light-weight and high-performance optical systems. Curvilinear micropores vertical to a thin wafer are made by using DRIE (Deep Reactive Ion Etching) or X-ray LIGA. The side walls are smoothed by using magnetic field assisted finishing and annealing technologies in order that the walls can reflect X-rays. Two or four such wafers are bent to spherical shapes with different curvature of radii and stacked, to focus parallel X-rays from astronomical objects by multiple reflections. In this paper, the concept and recent advances of the MEMS X-ray optics are reviewed.

DOI： 10.1109/OMEMS.2010.5672121

Language：English   Publishing type：Research paper (international conference proceedings)  

Formation mechanism of twin boundaries in silicon multicrystals during crystal growth was investigated by using in-situ observation of the growth interface and following characterization of microstructures of the grown crystal. The crystal growth experiments were performed under two different conditions, which are constant cooling rate and intentionally changed crystal growth rate. Under both the conditions, twin boundaries were more frequently formed when the growth rate drastically increased than when the growth rate was constant in high value. Based on these new findings, formation mechanism of twin boundaries are discussed in terms of formation energy.

DOI： 10.1109/PVSC.2010.5617200

Language：English   Publishing type：Research paper (international conference proceedings)  

In estimation of fracture toughness of small diameter (5∼15 um) fibers, the difficulty arises from the small physical dimensions, due to which proper method to introduce small notches is limited. Also, the diameter is usually different among the fiber test specimens. Accordingly, a proper method to introduce an artificial notch in the specimens is required, and the fracture toughness value shall be estimated for each fiber test specimen. In the present work, as the method to introduce artificial notch, focused-ion (Ga ⁺)-beam was used, with which a mode I type straight-fronted edge notch was introduced in the fiber specimens. The notch-tip radius was around 25 nm. The fracture strength (a_f), notch depth (a) and fiber diameter (D) were measured for each fiber test specimen. The correction factor Y for the present straight-fronted edge notch, which is a function of a relative notch depth a/D was calculated by the finite element method. The fracture toughness KI_c was estimated for each fiber specimen by substituting the measured values of a, D and σ_f and calculated value of Y into KI_c=Yσ_f (πa)^1/2. Such an approach was applied to the polycrystalline SiC fiber (Tyranno-SA® with diameter 5∼11μm) and amorphous SiC fiber (Tyranno-ZMI® with diameter 9∼14 um). The fracture toughness values of the polycrystalline and amorphous SiC fibers were estimated to be 2.7±0.4 and 1.8±0.3 Mpa ^*m^1/2, respectively. The fracture toughness value was almost independent of the fiber diameter and notch depth in both fibers.

Language：English   Publishing type：Research paper (international conference proceedings)  

We invented novel ultra-lightweight and high-resolution MEMS (Micro Electro Mechanical Systems) X-ray optics for space X-ray telescopes. As a first step of R&D, we conducted optical image analysis of a spherically-shaped test optic with a radius of curvature of 1000 mm. Focusing of the parallel light was verified with our optic for the first time.

DOI： 10.1109/OMEMS.2009.5338574

Language：English   Publishing type：Research paper (scientific journal)  

Si and Ge hemispherical concave wafers can be prepared by plastic deformation using Si and Ge single- and polycrystal wafers. Deformation regions in which such Si and Ge hemispherical wafers can be obtained by high-temperature plastic deformation were systematically studied. The deformation regions in which well-shaped Si concave wafers can be obtained were studied for (1 0 0), (1 1 1), and polycrystal Si. It was found that Si (1 1 1) crystal wafers can be more easily deformed to a perfect hemispherical shape than (1 0 0) wafers because of the crystallographic symmetry. Si hemispherical wafers with a small radius of 25 mm can be perfectly deformed when 0.5-mm-thick Si (1 1 1) crystal wafers are used. Ge hemispherical wafers with a radius of 100 mm can be perfectly deformed when 0.5-mm-thick Ge crystal wafers are used. Ge hemispherical concave wafers with a perfect shape can be more easily obtained using Ge (1 1 1) wafers than (1 0 0) wafers. According to these results, the deformation behavior of Ge wafers is very similar to that of Si wafers at a normalized pressing temperature. As both the radius and the load on Si and Ge hemispherical wafers increase, thicker Si and Ge wafers can be used to obtain hemispherical wafers with a perfect shape. The dislocation density in the shaped wafers markedly decreases as the pressing temperature and hemisphere radius increase. Thus, it is suggested that Si and Ge shaped wafers are of sufficient quality and have the high potential for use as several types of lens such as those in Si and Ge X-ray monochromators.

DOI： 10.1016/j.jcrysgro.2009.08.021

Language：English   Publishing type：Research paper (international conference proceedings)  

We report on our development of hot plastic deformation of silicon wafer for high-resolution and light-weight X-ray optics. The highly polished silicon wafer with an excellent flat surface is a promising candidate for the next generation space X-ray telescopes. Deformation accuracy and stability, especially if elastic deformation is used, are issues. The hot plastic deformation of the silicon wafer allows us 3-dimensional shaping without spring back after the deformation. As a first step of R & D, we conducted the hot plastic deformation of 4-inch silicon (111) wafers with a thickness of 300 μm by using hemispherical dies with a curvature radius of 1000 mm. The deformed wafer kept good surface quality but showed a slightly large curvature of 1030 mm. We measured the X-ray reflectivity of the deformed wafer at Al K _α 1.49 keV. For the first time, we detected the total X-ray reflection on the deformed wafer. Estimated rms surface roughness was 0-1 nm and no significant degradation from the bare silicon wafers was seen.

DOI： 10.1117/12.823932

Language：English   Publishing type：Research paper (international conference proceedings)  

We have been developing ultra light-weight X-ray optics using MEMS (Micro Electro Mechanical Systems) technologies.We utilized crystal planes after anisotropic wet etching of silicon (110) wafers as X-ray mirrors and succeeded in X-ray reflection and imaging. Since we can etch tiny pores in thin wafers, this type of optics can be the lightest X-ray telescope. However, because the crystal planes are alinged in certain directions, we must approximate ideal optical surfaces with flat planes, which limits angular resolution of the optics on the order of arcmin. In order to overcome this issue, we propose novel X-ray optics based on a combination of five recently developed MEMS technologies, namely silicon dry etching, X-ray LIGA, silicon hydrogen anneal, magnetic fluid assisted polishing and hot plastic deformation of silicon. In this paper, we describe this new method and report on our development of X-ray mirrors fabricated by these technologies and X-ray reflection experiments of two types of MEMS X-ray mirrors made of silicon and nickel. For the first time, X-ray reflections on these mirrors were detected in the angular response measurements. Compared to model calculations, surface roughness of the silicon and nickel mirrors were estimated to be 5 nm and 3 nm, respectively.

DOI： 10.1117/12.823933

Language：English   Publishing type：Research paper (scientific journal)  

In order to develop lightweight and high angular resolution x-ray mirrors, we have investigated hot plastic deformation of 4 in. silicon (111) wafers. A sample wafer was deformed using hemispherical dies with a curvature radius of 1000mm. The measured radius of the deformed wafer was 1030mm, suggesting that further conditioning is indispensable for better shaping. For the first time to our knowledge, x-ray reflection on a deformed wafer was detected at Al K _α 1:49keV. An estimated surface roughness of <1nm from the x-ray reflection profile was comparable to that of a bare silicon wafer without deformation. Hence, no significant degradation of the microroughness was seen.

DOI： 10.1364/AO.48.003830

Language：English   Publishing type：Research paper (international conference proceedings)  

A series of tensile tests was performed on powder metallurgical processed open cell stainless steel foams with different densities and average pore sizes of 150, 300 and 600 μm, respectively to examine the effect of porosity as well as the cell wall thickness on the foams tensile mechanical properties. Moreover, a state of the art strain measuring device, which is not in touch with the sample's surface, was used to determine the strain and the other tensile properties accurately. The function of this device is based on the usage of a laser (CCD) camera. The laser (CCD) camera monitors the dimensional changes during loading by detecting the positional changes of special markers clipped on the sample's surface representing the gauge length. Thus we can avoid the constraint effects caused by using the conventional extensometers of contact type. By using the Weibull distribution function, the average fracture stress of the individual foam cells was statistically measured. The results showed a strong dependence of foams' mechanical properties on their porosity and thickness of their cell walls. Foams with small pores displayed higher mechanical properties than foams with larger ones. Foams with thick cell walls failed at larger stresses than foams having thin cell walls or struts.

Language：English   Publishing type：Research paper (scientific journal)  

Pre-polished Ge(111) single-crystal wafers were deformed just below the melting temperature to prepare point-focusing Johansson monochromator crystals. The (111) lattice plane had curvature 2R in the focusing plane and R perpendicular to it, with a hemispherical inner surface with a radius of R = 600 mm. By using Cu Kα radiation, the diverging X-ray beam was focused onto a small spot.

DOI： 10.1107/S0021889808016282

Language：English   Publishing type：Research paper (scientific journal)  

The bending strains of Bi2223 filaments in Ag-sheathed superconducting composite tapes at the Bi2223/Ag sheath boundary have been evaluated by X-ray diffraction utilizing synchrotron radiation at room temperature. The strain in the Bi2223 filaments was found to be asymmetric between the sides under tension and compression, suggesting that the fracture strain is also asymmetric between tension and compression. The outermost part of the Bi2223 filaments is at the multiple fracture stage in the tension side.

DOI： 10.1016/j.scriptamat.2007.12.003

Language：English   Publishing type：Research paper (international conference proceedings)  

Because of the attractiveness in superior oxidation resistance, high stability of the microstructure and excellent high temperature mechanical properties in oxidative environment, directionally solidified eutectic (DSE) oxide/oxide ceramic composite have been considered as one of the most potential structural materials for advanced energy generation systems and space propulsion systems. However, due to the mismatch in coefficient of thermal expansion (CTE), the residual strains are always generated from the fabrication process and thermal cycling in use, which would have an influence on properties of DSE ceramic composites. Therefore, the investigation of magnitude, state and distribution of residual strains in oxide ceramic composites is a crucial work. In this study, the residual strains of YAG phase in directionally solidified eutectic Al₂O₃/Y₃Al₅O₁₂ (YAG) ceramic composite were estimated by X-ray diffraction technique and finite element method (FEM). In the X-ray strain measurement, the YAG skeleton specimen derived from the composite by removing the Al₂O₃ phase was used as un-strained reference specimen. The X-ray strain measurements with CuKα irradiation were performed on the two faces: parallel and perpendicular to the solidification direction. The principal residual strains measured from the family of 888 diffraction in YAG phase indicated that YAG phase in composite is in compression. The measured residual strains are varied from -2.19±0.32 (×10^-4) to -4.22±0.08 (×10^-4) on faces parallel and perpendicular to the solidification direction respectively. The experimental results were accounted for by the FEM simulation.

Language：English   Publishing type：Research paper (scientific journal)  

A method to estimate the thermally induced residual strain accumulation under varying temperature in a Bi2223/Ag/Ag alloy composite superconductor was presented, in which the mechanical property values measured from the stress-strain curves of the samples with different residual strain states, the residual strain value of Bi2223 filaments in the composite tape at room temperature measured by x-ray diffraction and the reported coefficients of thermal expansion of the constituents (Bi2223, Ag and Ag alloy) in the relevant temperature range were incorporated. This method was applied to estimate the change of the residual strain of all constituents of the high critical current type composite tape fabricated by American Superconductor Corporation as a function of temperature. The residual strain value at 77K estimated by this method and the reported fracture strain of Bi2223 filaments accounted well for the measured strain tolerance of the critical current at 77K.

DOI： 10.1088/0953-2048/20/3/015

Language：English   Publishing type：Research paper (scientific journal)  

The degradation mechanism of the amorphous silicon carbide fiber, Tyranno-ZMI®, exposed in air at 1173-1873 K for 20ks were studied. The average strength of the bare fiber, which was prepared by etching away the oxidation layer on the fiber surface, decreased with increasing exposure temperature, especially when exposed at the temperature higher than 1673 K. The measurement of the crystallite size of β-SiC in the fiber with Sherrer method revealed that coarsening of the crystalline occurred in the fiber exposed at the temperatures higher than 1773K. The scanning electron microscope observation of the fiber surface showed that the many defects formed on the fiber surface. By introducing an artificial notch directly into the fiber specimens using a focused-ion(Ga+)-beam, the fracture toughness values of the as-supplied fiber and of the fiber exposed at 1673 and 1773 K were determined to be 1.8 ± 0.3, 1.9 ± 0.4 and 1.3 ± 0.4 MPa√m, respectively. Based on these results, the reason for the degradation of the fiber was attributed to the extension of the surface defect which was enhanced by the reduction in fracture toughness due to coarsening or the β-SiC crystalline.

DOI： 10.2320/matertrans.48.111

Language：English   Publishing type：Research paper (international conference proceedings)  

SiC fiber reinforced SiC matrix (SiC/SiC) composites are one of the most promising materials for high temperature structural applications such as power generation and propulsion systems. SiC/SiC composites are, however, susceptible to accelerated attacks in water vapor environments through oxidation and volatilization reaction, so Environmental Barrier Coatings (EBCs) are indispensable. We have investigated some oxides and rare-earth silicates as topcoat candidates for EBCs. Topcoat materials must be stable in the high-water-vapor pressurized environments at high temperatures. Also, it is important that the thermal expansion coefficient of topcoat materials is similar to that of SiC/SiC composites. In this study, rare-earth silicates such as lutetium silicates, 8YSZ and ZrO₂-SiO₂ were selected as topcoat candidates. They were exposed in the water containing atmosphere at a temperature 1673K for 100 hr under a total pressure 0.96 MPa and under an atmospheric pressure. Mass changes, structure of crystals and microstructures were investigated after the exposure experiments in order to evaluate the thermal stability of those materials. After this evaluation, lutetium silicates were considered to be promising for topcoat materials. Lutetium silicates were coated on SiC/SiC composites, and their fracture toughness and microstructures were investigated and reported in this paper.

Language：English   Publishing type：Research paper (scientific journal)  

The present work attempted to describe the tensile stress-strain behavior of the Bi2223 filaments in the composite tape and its influence on critical current by means of a Monte Carlo-shear lag simulation method, in which the distribution of strength within the filament was given by a Monte Carlo method and the stress distribution in the filament was calculated with a shear-lag analysis. With this approach, (a) the stress-strain curve of the Bi2223 filament in the composite tape measured by X-ray method, (b) the observed fracture morphology of the filament in which transverse (perpendicular to tensile axis) and longitudinal (parallel to tensile axis) fractures take place consecutively, and (c) the measured change of critical current with increasing applied tensile strain, could be described fairly well.

DOI： 10.1016/j.physc.2006.05.018

Language：English   Publishing type：Research paper (scientific journal)  

The fracture toughness of a crystalline silicon carbide fiber, Tyranno-SA®, was determined by introducing an artificial notch directly into the fiber test specimens using a focused-ion (Ga ⁺) beam. The relation between fracture strength and notch size was determined experimentally, while the relation among the notch size, fiber diameter, applied stress at infinity, and stress intensity factor was analyzed by the finite element method. By applying the analyzed result to the experimental results, the fracture toughness of the fiber was determined to be 2.7 ±0.4 MPa√m.

DOI： 10.1111/j.1551-2916.2006.01116.x

Language：English   Publishing type：Research paper (scientific journal)  

SiC fiber reinforced SiC matrix (SiC/SiC) composites are one of the most promising materials for high temperature structural applications such as power generation and propulsion systems. SiC/SiC composites are, however, susceptible to accelerated attacks in water vapor environments through oxidation and volatilization reaction. For protection from such attacks, Environmental Barrier Coatings (EBCs) are indispensable. We have investigated some oxides and rare-earth silicates as topcoat candidate materials for EBCs. Topcoat materials must be stable in the high-water-vapor pressurized environments at high temperatures. Also, it is important that the thermal expansion coefficient of topcoat materials is similar to that of the SiC/SiC composites. In this study, first, zirconium oxides, lutetium silicates and yttrium silicates were selected as topcoat candidate materials. They were exposed in a water-containing atmosphere at a temperature of 1673 K for 100 h under a total pressure 0.96 MPa. Mass changes, structure of crystals and microstructures were investigated after the exposure experiments in order to evaluate the thermal stability of these materials. After their estimation, lutetium silicates were considered to be promising for topcoat materials. Then, lutetium silicates were coated as the topcoat of an EBC system on SiC/SiC composites, and their fracture toughness and microstructures were investigated after exposure to an oxidizing atmosphere. The evaluation results of the topcoat materials are reported in this paper.

Language：English   Publishing type：Research paper (scientific journal)  

Axial strain of Bi2223 superconducting filaments in Ag-sheathed superconducting composites reinforced by stainless steel lamination has been evaluated by in situ synchrotron-radiation diffraction. The Bi2223 filaments in the laminated composites were under 0.11% of compressive residual strain, whereas the residual strain of filaments in the composite after removing stainless steel layers was only 0.02% in compression. Under large tensile load, the composite showed a clear multiple fracture with an almost constant filament strain of about 0.11% in tension.

DOI： 10.1016/j.scriptamat.2006.06.027

Language：English   Publishing type：Research paper (scientific journal)  

The damage evolution in Bi2223 filaments and its influence on critical current was described by a Monte Carlo-shear lag simulation method. The experimentally observed zigzag crack propagation across aligned Bi2223 grains under tensile strain was effectively modelled by including transverse and longitudinal failure modes for individual grains. From the simulated stress-strain curve, the survival parameter (slope of the stress-strain curve normalized with respect to the original Young's modulus) was estimated with increasing applied strain. With this parameter combined with the strain sensitivity of the critical current, the measured change of critical current of the composite tape with applied strain could be described well.

DOI： 10.1088/0953-2048/18/12/004

Language：English   Publishing type：Research paper (international conference proceedings)  

The temperature- and displacement speed-dependence of unnotched and notched strengths at 1873-2023 K of directionally solidified eutectic Al ₂O₃/YAG (Yttrium-Aluminum Garnet with the composition of Y₃Al₅O₁₂) composite was investigated experimentally by tensile test and analytically by the finite element method. The notched specimens fractured in a brittle manner at low temperatures and at high displacement speeds, but in a ductile manner at high temperatures and at low displacement speeds. The notched strength increased, reaching maximum, and decreased with increasing temperature under a given displacement speed and with decreasing displacement speed under a given temperature. For the finite element analysis, the temperature dependence of the Young's modulus was measured to be 345-0.0361T (T: temperature, K) GPa and the temperature- and strain rate-dependence of the flows stress in the plastic deformation stage of unnotched specimens was estimated as {(strain rate)/(1.23×10 ⁵)}^1/5 exp{1.81×10⁴/T} from the reported data. From the comparison of the experimental- with analytical results, the increase in the notched strength with increasing temperature and decreasing displacement speed up to the maximum notched-strength value was accounted for by the increase in plastic zone size ahead of the notch. Also the decrease in notched strength with further increasing temperature and decreasing displacement speed was accounted for by the loss of the stress carrying capacity of the yielded ligament due to the softening.

Language：English   Publishing type：Research paper (international conference proceedings)  

The fracture behavior of the Tyranno-ZMI fiber exposed in air at 1173 ∼ 1673K for 2×10⁴s was studied. The average strength of the fiber with SiO₂ layer on its surface decreased and the scatter of strength increased with increasing exposure temperature. The fracture of the fiber was controlled by the propagation of the crack made by the premature fracture of the SiO₂ layer into fiber. The average strength of the fiber without SiO₂ layer prepared by etching away the SiO₂ layer from the fiber exposed in air, decreased also with increasing exposure temperature, whereas it was far higher than that of the fiber with SiO ₂ layer. The fracture toughness of the fiber, which was originally amorphous decreased with increasing exposure temperature due to the crystallization. In this way, the high temperature-exposure in air caused degradation of the fiber itself and the SiO₂ layer-originated crack propagation.

Language：English   Publishing type：Research paper (scientific journal)  

It has been reported that SiC/SiC composite has high strength and toughness, but is degraded when exposed in air at high temperatures due to the propagation of the crack made by the premature fracture of the SiO₂ layer. The present work aimed to describe such a behavior with a computer simulation. For this aim, the shear lag - Monte Carlo simulation method was applied. The variation of strength of the composite as a function of thickness of the SiO₂ layer and change of fracture morphology with progressing oxidation could be reproduced satisfactorily by this method.

Language：English   Publishing type：Research paper (scientific journal)  

The deformation and fracture behavior at 1773-2023K of the unidirectionally solidified eutectic Al₂O₃/YAG (Yttrium-Aluminum Garnet with the composition of Y₃A₁₅O₁₃) ceramic composite was investigated. The stress-stain curve and strength of unnotched and notched specimens, measured by bending and tensile tests, showed that (a) both unnotched and notched specimens fractured in a brittle manner at low temperatures and at high displacement speeds, but in a ductile manner at high temperatures and at low displacement speeds, and (b) the notched strength increased, reaching maximum, and decreased with increasing temperature and decreasing displacement speed. The increase in the notched strength with increasing temperature and decreasing displacement speed up to the maximum value was accounted for by the increase in plastic zone size ahead of the notch, and the decrease with further increasing temperature and decreasing displacement speed by the loss of the stress carrying capacity of the yielded ligament, based on the finite element analysis.

Language：English   Publishing type：Research paper (scientific journal)  

An attempt was made to recover the strength of a PIP-processed SiC/SiC composite exposed in air at high temperatures by means of the deoxidization treatment with CO gas. By deoxidation treatment at 1723 and 1823 K for the composite specimen oxidized at 1573 K, the strength of deoxidized specimens became higher by around 4 and 1.5 times than that of oxidized one, respectively.

DOI： 10.1163/156855405774984057

Language：English   Publishing type：Research paper (scientific journal)  

It is known that SiC/SiC composite has high strength and toughness, but is degraded when exposed in air at high temperatures due to the propagation of the crack made by the premature fracture of the SiO₂ layer. It is also known that the fracture morphology of this composite varies from fiber pull-out type to non pull-out type with progressing oxidation. The present work aimed to describe such a behavior with a computer-aided Monte Carlo shear lag simulation method. The experimentally measured variation of strength of the unidirectional composite as a function of thickness of the SiO₂ layer and also as a function of exposure time and temperature, and the experimentally observed variation of fracture morphology with progressing oxidation, could be reproduced satisfactorily by this method.

DOI： 10.1163/156855405774984048

Language：English   Publishing type：Research paper (scientific journal)  

In situ strain measurement was made for Bi2223 superconducting filaments in Ag-sheathed Bi2223 composite tapes utilizing synchrotron radiation. The residual strain was 0.05 ± 0.01% in compression. A small deviation from linear relationship between strain of the Bi2223 filaments and the average strain of the sample was found, meaning a decrease in elastic modulus of the filament even below the irreversible strain.

DOI： 10.1016/j.physc.2004.05.019

Language：English   Publishing type：Research paper (scientific journal)  

Influences of the continuity of the matrix on Young's modulus and tensile strength of unidirectional SiC/SiC mini-composite prepared by the polymer impregnation and pyrolysis method were studied experimentally by observation of appearance of matrix and tensile test and analytically by a shear lag-Monte Carlo simulation. The continuity of the matrix was improved by the addition of particles such as ZrSiO₄, barium magnesium aluminosilicate, and Pyrex (borosilicate glass) into the matrix. The improved continuity of the matrix led to the increase in stress carrying capacity of the matrix and therefore to the increase in Young's modulus and tensile strength of the composite. Such a correlation between the continuity of the matrix and the property of the composite was verified numerically by the shear lag-Monte Carlo simulation.

DOI： 10.1557/JMR.2004.0290

Language：English   Publishing type：Research paper (scientific journal)  

Influences of the continuity of the matrix on Young's modulus and tensile strength of unidirectional SiC/SiC mini-composite prepared by the polymer impregnation and pyrolysis method were studied experimentally by observation of appearance of matrix and tensile test and analytically by a shear lag-Monte Carlo simulation. The continuity of the matrix was improved by the addition of particles such as ZrSiO₄, barium magnesium aluminosilicate, and Pyrex (borosilicate glass) into the matrix. The improved continuity of the matrix led to the increase in stress carrying capacity of the matrix and therefore to the increase in Young's modulus and tensile strength of the composite. Such a correlation between the continuity of the matrix and the property of the composite was verified numerically by the shear lag-Monte Carlo simulation.

DOI： 10.1557/JMR.2004.0290

Language：English   Publishing type：Research paper (scientific journal)  

Room temperature residual strength of the SiC/SiC composite exposed in vacuum at high temperatures (823-1673 K) was studied and compared with that exposed in air. The vacuum-exposed composite showed only the fiber-pullout type fracture, and the pullout length increased with increasing exposure temperature and time, while the fractured mode of the air-exposed one changed with progressing oxidation; from the fiber-pullout type to the nonfiber-pullout one characterized by the overall fracture perpendicular to the tensile axis without fiber-pullout. The reduction in residual strength in the case of vacuum exposure was attributed mainly to the extension of the decomposition-induced defects on the fiber surface into fiber, while that in the case of air exposure mainly to the extension of the crack made by premature fracture of the SiO ₂ layer into the fiber. A simple model based on the kinetics of the growth of the defects and fracture mechanics was presented to describe the variation of composite strength as a function of exposure temperature and time for the vacuum exposure, which could describe the experimental results.

DOI： 10.1016/j.compositesa.2003.09.006

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.compositesa.2003.09.005

Event date： 2023.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Life Science Center, Senri-Chuo, Osaka, Japan   Country：Japan  

Event date： 2023.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Life Science Center, Senri-Chuo, Osaka, Japan   Country：Japan  

Event date： 2023.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Life Science Center, Senri-Chuo, Osaka, Japan   Country：Japan  

Event date： 2023.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Life Science Center, Senri-Chuo, Osaka, Japan   Country：Japan  

Event date： 2023.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Life Science Center, Senri-Chuo, Osaka, Japan   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ホテルサンルートソプラ神戸   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：とやま自遊館, 富山   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：富山大学五福キャンパス   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：富山大学五福キャンパス   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：富山大学五福キャンパス   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：富山大学五福キャンパス   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：富山大学五福キャンパス   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：富山大学五福キャンパス   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：富山大学五福キャンパス   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：富山大学五福キャンパス   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ホテルサンルートソプラ神戸   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ホテルサンルートソプラ神戸   Country：Japan  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ホテルサンルートソプラ神戸   Country：Japan  

Event date： 2023.7

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：之出水道水道機器株式会社 佐賀工場   Country：Japan  

Event date： 2023.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Banff, Alberta   Country：Canada  

Event date： 2023.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：近畿大学 東大阪キャンパス   Country：Japan  

Event date： 2023.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：近畿大学 東大阪キャンパス   Country：Japan  

Event date： 2023.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：近畿大学 東大阪キャンパス   Country：Japan  

Event date： 2022.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：広島大学   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：広島大学   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：広島大学   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：広島大学   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：広島大学   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡工業大学   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡工業大学   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡工業大学   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡工業大学   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡工業大学   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：新潟大学 五十嵐キャンパス   Country：Japan  

Event date： 2022.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Palais de congres de Montreal, Quebec, Canada   Country：Canada  

Event date： 2022.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Palais de congres de Montreal, Quebec, Canada   Country：Canada  

Event date： 2022.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2022.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2022.6

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2022.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2022.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2022.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2022.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2022.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2022.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2022.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2022.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大同大学   Country：Japan  

Event date： 2022.4

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2022.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：青山学院大学 相模原キャンパス   Country：Japan  

Event date： 2022.3

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2022.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2022.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2022.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2022.1

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.11

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.6

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.6

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.4

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.4

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.3

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.3

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2021.3

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2020.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2020.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催   Country：Japan  

Event date： 2020.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京工業大学　大岡山キャンパス   Country：Japan  

Event date： 2020.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京工業大学　大岡山キャンパス   Country：Japan  

Event date： 2020.1

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：生産科学工学研究所   Country：Japan  

Event date： 2020.1

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：生産科学工学研究所   Country：Japan  

Event date： 2020.1

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：宇宙科学研究所 相模原キャンパス   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：岡山大学津島キャンパス   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：岡山大学津島キャンパス   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：岡山大学津島キャンパス   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：岡山大学津島キャンパス   Country：Japan  

Event date： 2019.9

Language：English   Presentation type：Oral presentation (general)  

Venue：岡山大学津島キャンパス   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡国際会議場   Country：Japan  

Event date： 2019.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：熊本県民交流館パレア   Country：Japan  

Event date： 2019.6

Language：English   Presentation type：Oral presentation (general)  

Venue：熊本県民交流館パレア   Country：Japan  

Event date： 2019.6

Language：Japanese  

Venue：熊本県民交流館パレア   Country：Japan  

Event date： 2019.6

Language：Japanese  

Venue：熊本県民交流館パレア   Country：Japan  

Event date： 2019.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：熊本県民交流館パレア   Country：Japan  

Event date： 2019.5

Language：English   Presentation type：Oral presentation (general)  

Venue：千葉工業大学　津田沼キャンパス   Country：Japan  

Event date： 2019.4

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：TKPガーデンシティ天神   Country：Japan  

Event date： 2019.4

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：TKPガーデンシティ天神   Country：Japan  

Event date： 2018.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Paris   Country：France  

Event date： 2018.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：葉工業大学 新習志野キャンパス   Country：Japan  

Event date： 2017.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学 札幌キャンパス   Country：Japan  

Event date： 2017.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：首都大学東京 南大沢キャンパス   Country：Japan  

Event date： 2016.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大阪大学　豊中キャンパス   Country：Japan  

Event date： 2016.8

Language：English  

Venue：Kyoto   Country：Japan  

Event date： 2016.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京理科大学　葛飾キャンパス   Country：Japan  

Event date： 2015.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京大学 駒場Iキャンパス   Country：Japan  

Event date： 2014.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大阪キャッスルホテル   Country：Japan  

Event date： 2014.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋大学   Country：Japan  

Event date： 2013.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Las Vegas  

Event date： 2013.8

Language：English   Presentation type：Oral presentation (general)  

Venue：Warsaw   Country：Poland  

Event date： 2012.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：京国際フォーラム   Country：Japan  

Event date： 2012.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：愛媛大学，松山大学   Country：Japan  

Event date： 2012.9

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：愛媛大学，松山大学   Country：Japan  

Event date： 2011.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：沖縄   Country：Japan  

Event date： 2011.8

Language：English   Presentation type：Oral presentation (general)  

Venue：Quebec   Country：Canada  

Event date： 2010.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：京都   Country：Japan  

Event date： 2010.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東海大学   Country：Japan  

Event date： 2010.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：筑波大学   Country：Japan  

Event date： 2006.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：京大会館   Country：Japan  

Event date： 2006.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：新潟大学   Country：Japan  

Event date： 2006.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Kawatabi   Country：Japan  

Event date： 2006.4

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ウェル戸畑   Country：Japan  

Event date： 2006.3

Language：Japanese  

Venue：早稲田大学   Country：Japan  

Event date： 2006.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：早稲田大学   Country：Japan  

Event date： 2005.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大阪府立大学   Country：Japan  

Event date： 2005.9

Language：Japanese  

Venue：広島大学   Country：Japan  

Event date： 2005.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：京大会館   Country：Japan  

Event date： 2005.8

Language：English   Presentation type：Oral presentation (general)  

Venue：Gwangju   Country：Korea, Republic of  

Event date： 2005.4

Language：Japanese  

Venue：東京理科大学   Country：Japan  

Event date： 2005.3

Language：English   Presentation type：Oral presentation (general)  

Venue：Turin   Country：Italy  

Event date： 2005.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：横浜国立大学   Country：Japan  

Event date： 2004.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Beijing   Country：China  

Event date： 2004.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：秋田大学   Country：Japan  

Event date： 2004.8

Language：English   Presentation type：Oral presentation (general)  

Venue：Kyoto   Country：Japan  

Event date： 2004.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京工業大学   Country：Japan  

Event date： 2003.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学   Country：Japan  

Event date： 2003.8

Language：English   Presentation type：Oral presentation (general)  

Venue：Daejeon   Country：Korea, Republic of  

Event date： 2003.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：千葉大学　西千葉キャンパス   Country：Japan  

Event date： 2003.1

Language：Japanese  

Venue：大阪科学技術センター   Country：Japan  

Language：Japanese   Presentation type：Symposium, workshop panel (public)  

Venue：オンライン開催   Country：Japan  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：JR博多シティ   Country：Japan  

Language：English   Presentation type：Oral presentation (general)  

Venue：JR博多シティ   Country：Japan  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：くまもと県民交流館パレア   Country：Japan  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：くまもと県民交流館パレア   Country：Japan  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：くまもと県民交流館パレア   Country：Japan  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：くまもと県民交流館パレア   Country：Japan  

Language：Japanese   Presentation type：Oral presentation (general)  

DOI： 10.11279/jfeskouen.183_79

CiNii Research

Language：Japanese   Presentation type：Oral presentation (general)  

DOI： 10.11279/jfeskouen.183_78

CiNii Research

Language：Japanese   Presentation type：Oral presentation (general)  

DOI： 10.11279/jfeskouen.183_77

CiNii Research

Language：Japanese   Presentation type：Oral presentation (general)  

DOI： 10.11279/jfeskouen.183_76

CiNii Research

Language：Japanese   Presentation type：Oral presentation (general)  

DOI： 10.11279/jfeskouen.183_19

CiNii Research

Language：Japanese   Presentation type：Oral presentation (general)  

DOI： 10.11279/jfeskouen.180_35

CiNii Research

Language：Japanese   Presentation type：Oral presentation (general)  

<p>The solidification microstructure of Ni-hard type cast iron was investigated to evaluate the influence of Mo and W additions on the formation of carbides and graphite. The specimen was prepared based on the composition of Fe-3.3%C-0.8%Si-0.8%Mn-4.4%Ni in mass%, and Mo or W was added to the reference specimen to a maximum of 6.7%Mo or 2.9%W, respectively. Each alloy was cast into a permanent mold for the microstructural analysis. The solidification process of each alloy was also investigated by thermal analysis and quenching experiments. According to EDS and XRD analyses, it is revealed that the solidification microstructure of standard Ni-hard type cast iron consists of primary γ, γ+M₃C eutectic structure and graphite, and the addition of Mo and W provides γ+M₂C eutectic structure. The further addition of Mo and W increases the amount of γ+M₂C eutectic structure and decreases the amount of γ+M₃C eutectic structure, whereas it has little effect on the amount of primary γ. The quenching experiment reveals the graphite formation as eutectic structure between the formations of γ+M₂C eutectic structure and γ+M₃C eutectic structures. The addition of Mo reduces the amount of graphite, while addiction of W increases the amount of graphite. The influence of each alloying element on graphite formation could be estimated by carbon solubility and the composition of the residual liquid.</p>

DOI： 10.2355/tetsutohagane.tetsu-2023-119

Scopus

CiNii Research

Language：Japanese   Presentation type：Oral presentation (general)  

DOI： 10.11279/jfeskouen.183_22

CiNii Research

Language：Japanese   Presentation type：Oral presentation (general)  

DOI： 10.11279/jfeskouen.181_52

CiNii Research

Language：Japanese   Presentation type：Oral presentation (general)  

DOI： 10.11279/jfeskouen.183_81

CiNii Research

Language：Japanese   Presentation type：Oral presentation (general)  

DOI： 10.11279/jfeskouen.181_65

CiNii Research

Type：Peer review 

Number of peer-reviewed articles in foreign language journals：3

Type：Competition, symposium, etc. 

Number of participants：100

Type：Competition, symposium, etc. 

Number of participants：100

Type：Competition, symposium, etc. 

Number of participants：600

Type：Competition, symposium, etc. 

Number of participants：135