Surface durability of powder-forged roller treated by shot peening

To investigate the influence of shot peening on the surface durability of powder-forged rollers, the case-hardened powder-forged rollers with a forging density of 7.5 g/cm³ treated by the single shot peening and the double shot peening were fatigue-tested under a sliding-rolling contact condition. The surface roughness, the surface hardness and the surface compressive residual stress of the rollers were increased by the shot peening. In addition, the pores near the roller surface were deformed by the shot peening. The failure mode of all the test rollers was spalling due to subsurface cracking. The fatigue lives of all the test rollers were improved by the shot peening, and that of the test roller S08, which was shot-peened with the hardest steel shots in this experimental range, was especially improved. The surface durability of the test roller S08 was also most improved by the shot peening. Cracks became difficult to occur and propagate under the roller surface since the pores near the roller surface were deformed by the stronger shot peening. In this study, double shot peening, which generally restrains the increase in surface roughness, was not particularly effective for the improvement in the surface durability of the powder-forged rollers, because the influence of tangential force on fatigue was not always great in a case of subsurface cracking.     

Pt-promoted α-Al2O3-supported Ni catalysts: Effect of preparation conditions on oxi-reduction and catalytic properties for hydrogen production by steam reforming of methane

The effect of Pt addition on the oxi-reduction properties of α-Al₂O₃-supported Ni catalysts, with different degrees of interaction between NiO and the α-Al₂O₃ support, was studied using atmospheres of H₂, H₂/H₂O, and CH₄/H₂O. The effect of Pt promotion on the reduction of NiO with H₂ was significant for NiO species that interacted more strongly with the alumina surface, but was much lower when a NiAl₂O₄-like bulk phase was formed. For samples activated with H₂, although metal dispersion decreased with increasing Pt content, the activity was maintained constant by the presence of Pt sites. For samples activated with a CH₄/H₂O mixture, the activity increased with increasing Pt content, due to the higher reducibility of Ni in the Pt-promoted catalysts. The Pt promotion effect was stable; there was no important decrease in the influence of Pt on NiO reduction, even after high temperature re-oxidation of the catalysts.     

Room temperature aging behavior of Ti-Nb-Mo-based superelastic alloys

The effect of room temperature (RT) aging on the superelasticity of Ti-Nb-Mo-based superelastic alloys is investigated. The results show that annealing at relatively low temperatures such as 973 K after severe cold rolling results in poor resistance to the effect of RT aging. The transformation stress increases considerably due to the formation of an isothermal ω phase at RT. Addition of Sn is partially effective in suppressing the RT aging effect in the specimens annealed at 973 K. The RT aging effect is suppressed by increasing the annealing temperature, due to the annihilation of lattice defects or non-equilibrium vacancies introduced during cold rolling, which are responsible for accelerating the diffusion process, however, superelasticity is reduced by annealing at higher temperatures, due to a decrease in the critical stress for slip deformation (σ_CSS). The specimen annealed at 1173 K followed by aging at 773 K exhibits stable superelasticity with a high resistance to the effect of RT aging. Annealing at 1173 K causes the annihilation of lattice defects or non-equilibrium vacancies, while aging at 773 K induces precipitation of the α phase, which in turn causes an increase in σ_CSS, and further enhances the resistance to the RT aging effect by enriching the matrix with β-stabilizing elements.     

Variations in signal intensity with periodical temperature changes in vivo in rat brain: analysis using wide-field optical coherence tomography

In a previous study, we reported measurements of three-dimensional (3D) optical coherence tomography (OCT) images through a thinned skull by reducing temperatures from 28 °C to 18 °C in vivo in the rat brain to show negative correlation coefficients (CCs) between ratios of signal intensity (RSI) and temperature for applications to monitoring brain viability. In this study, using the same OCT system, we measured 3D OCT images of the rat brain by periodically changing tissue temperatures from 20 °C to 32 °C in vivo. In the evaluation of CCs among RSI, temperature, and heart rate, the largest number of periods was four, and the longest measurement time was 570 min. Averaged CCs between RSI and temperature, and between RSI and heart rate, were -0.42 to -0.50 and -0.48 to -0.64, respectively. RSI reversibly changed subsequent variations of temperatures and finally increased rapidly just before cardiac arrest. These results indicate that RSI could correspond to decreases in viability because of local ischemia and recovery.     

Lifetime test and heritage on orbit of coolers for space use

This report describes the results and operating status of ground lifetime testing and achievements on orbit of coolers for space use. Ground lifetime tests of coolers of three types were conducted to demonstrate their long life and reliability. Three single-stage Stirling coolers were tested for 89,016, 71,871 and 68,273 h from 1998, a two-stage Stirling cooler was tested for 72,906 h, and a 4-K class cooler with a two-stage Stirling cooler and a Joule–Thomson cooler was tested for over 2.5 years. After lifetime tests were completed, a few coolers were investigated to determine the cause of the cooling performance degradation. Additionally, the filled gas of the coolers was analyzed. These coolers have shown good results on orbit. Three single-stage Stirling coolers were carried on the X-ray astronomical satellite “SUZAKU” (launched in July 2005), Japanese lunar polar orbiter “KAGUYA” (launched in September 2007), and the Japanese Venus Climate Orbiter “AKATSUKI” (launched in June 2010). Two units of a two-stage Stirling cooler were carried on the infrared astronomical satellite “AKARI” launched in February 2006. A 4-K class cooler was carried on the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) aboard the Japanese Experiment Module (JEM) of the International Space Station (ISS). SMILES was launched in September 2009.     

In situ X-ray diffraction of surface oxide on type 430 stainless steel in breakaway condition using synchrotron radiation

Changes in the crystal structure of type 430 stainless steel and the oxides on its surface were studied in situ at 1373 K using a high-intensity synchrotron X-ray source provided by SPring-8 in Japan. The surface of the steel was initially covered with Cr₂O₃, which was then converted to FeCr₂O₄, and finally Fe₃O₄ and Fe₂O₃ formed on it. These results indicated that the reason for the breakaway oxidation in type 430 stainless steel is Cr depletion beneath Cr₂O₃ layer and the subsequent ionisation of Fe, not the simple mechanical failure of Cr₂O₃.     

Structure and compositional evolution in epitaxial Co/Pt core-shell nanoparticles on annealing

We report on the alloying of epitaxial Co/Pt core-shell nanoparticles using transmission electron microscopy (TEM) and electron diffraction. In as-deposited nanoparticles followed by in situ annealing at 823 K for 10.8 ks, high-angle annular dark-field (HAADF) imaging by scanning TEM (STEM) clearly revealed formation of Co-shell/Pt-core structures due to the large atomic number (Z) difference between Co (Z = 27) and Pt (Z = 78). We identified a formation of locally ordered areas of the L1₀ ordered phase at the core of the nanoparticles. After ex situ annealing at 873 K for 0.6 ks, some of the ordered areas showed complicated contrasts in the HAADF-STEM images. Based on image simulations, we found that these atypical contrasts arise from the stacking of two orthogonal variants of the L1₀ phase in the electron beam direction. Furthermore, the simulation showed that image contrast strongly reflects the structure of the variant located closer to the beam entrance rather than to the bottom side. Solid solution phase was formed by further annealing at 873 K for 3.6 ks, while high-density {111} stacking faults were observed inside the Co-Pt alloy nanoparticles. Magnetic coercivity remained at values as low as ~ 15.9 kA/m at 300 K, irrespective of the formation of local L1₀ ordered areas and/or a high-density stacking faults.     

The contemporary JAEA Japanese voxel phantoms

Average adult Japanese male (JM-103 phantom) and female (JF-103 phantom) voxel (volume pixel) phantoms were newly constructed by modifying the JM and JF phantoms previously developed at Japan Atomic Energy Agency. The JM-103 and JF-103 have average characteristics with respect to organ masses and body sizes. Their tissue segmentations were based on International Commission on Radiological Protection (ICRP) Publication 103. The anatomical and dosimetric characteristics of JM-103 and JF-103 were compared with those of ICRP adult reference male (AM phantom) and female (AF phantoms) phantoms. This study discusses their anatomical and dosimetric characteristics, and applications to the dose assessment of the atomic bomb survivors.     

Electronic structure of the buried interface between an organic semiconductor, N,N'-bis(3-methylphenyl)-N,N'-diphenylbenzidine (TPD), and metal surfaces

The electronic structures of buried interfaces between an organic semiconductor, N,N'-bis(3-methylphenyl)-N,N'-diphenylbenzidine (TPD) and metal surfaces of Au, Ag, Al and Ca were examined by the new experimental method that we have developed recently. In this method the energy levels at the organic/metal interface can be examined without changing the film thickness and related physical parameters e.g., the vacuum levels of the sample in contrast to the widely-used thickness-dependent photoemission experiments. The results were discussed in view of large interfacial dipole moment of the TPD and metal (Au and Ag) contacts.     

Photochemical production of hydrogen from water using microporous porphyrin coordination lattices

In this study, we investigated the photochemical production of hydrogen from water using bio-inspired heterogeneous microporous porphyrin coordination lattices (PCLs), [Ru2(MTCPP)BF4] (M = H2 (PCL-1), Zn (PCL-2); TCPP = Tetrakis(4-carboxyphenyl)porphyrin), under visible (380 nm <) and UV (320 nm <) light irradiations. In the presence of Na2EDTA (as a sacrificial donor) and MV2+ (methyl-vilologen; as a electron relay), PCLs exhibits photocatalytic activity for hydrogen evolution; the maximum amounts of turnover numbers (TONs) of PCL-1 and PCL-2 at 24 h irradiation were 20.8 and 29.9, respectively. In the catalytic reactions, the relation between PCLs and MV2+ was similar to the relation between a [cytochrome c3 hydrogenase] pair and lysine residues in enzymatic reactions. By using the hydrogen production rate and the MV+ (methyl-vilologen radical-cation) concentration, kinetic parameters such as affinities between MV+ and PCLs, maximum reaction rate, and total efficiency of the reaction are introduced using the Michaelis-Menten equation. These parameters indicated that PCLs are good artificial enzyme model catalysts. The stability of the PCLs after the catalytic reactions was confirmed by X-ray photoelectron spectroscopy and Fourier transform-infrared spectra. These results indicated that the frameworks of PCLs are stable for this catalytic reaction.