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.     

Analytical Investigation of Prior Austenite Grain Size Dependence of Low Temperature Toughness in Steel Weld Metal

Prior austenite grain size dependence of the low temperature impact toughness has been addressed in the bainitic weld metals by in situ observations.Usually,decreasing the grain size is the only approach by which both the strength and the toughness of a steel are increased.However,low carbon bainitic steel with small grain size shows a weakening of the low temperature impact toughness in this study.By direct tracking of the morphological evolution during phase transformation,it is found that large austenite grain size dominates the nucleation of intragranular acicular ferrite,whereas small austenite grain size leads to grain boundary nucleation of bainite.This kinetics information will contribute to meet the increasing low temperature toughness requirement of weld metals for the storage tanks and offshore structures.     

Impurity Effects on Energy Gap in Bi<Subscript>2</Subscript>Sr<Subscript>2</Subscript>CaCu<Subscript>2</Subscript>O<Subscript>8+<Emphasis Type="Italic">y</Emphasis></Subscript> Investigated by Electronic Raman Scattering

The Raman scattering experiments were carried out in Zn-doped and Zn-free Bi₂Sr₂CaCu₂O_8+y with optimal hole concentration below and above T _c . The energy of pair-breaking peak in the B _1g Raman spectrum, corresponding to the magnitude of superconducting gap 2Δ ₀, is suppressed by 1% Zn-doping. In the normal state, the B _1g Raman spectrum for Zn-doped sample shows no pseudogap behaviour, suggesting that the pseudogap is strongly smeared by Zn-doping.     

Atom probe tomography of nanoscale microstructures within precipitate free zones in Al–Zn–Mg(–Ag) alloys

Solute distributions in the vicinity of grain boundaries in Al–Zn–Mg(–Ag) alloys were studied using a three-dimensional atom probe, in order to elucidate the mechanism of formation of precipitate free zones (PFZs) and the fundamental role of Ag in controlling PFZ width. It is shown that nanoscale clusters are formed within the PFZ in Al–Zn–Mg, despite the solute concentration remaining at the levels in the as-quenched state. Such observations have not previously been possible, and show unambiguously that vacancy depletion is the dominant mechanism of formation of PFZs in this alloy. In the Ag-containing alloy, a narrower PFZ is observed, with a reduced solute level, showing that here the dominant mechanism of PFZ formation is solute depletion. The role of Ag in this change of mechanism appears to be due to its favorable interactions not only with Mg and Zn atoms but also with vacancies.     

Size-controlled recrystallization of fullerene by gas–antisolvent process

Gas–antisolvent (GAS) process using CO₂ successfully prepared crystals of fullerene (C₆₀) from a toluene solution through a precipitation. Particle sizes of precipitated C₆₀ could be easily controlled by changing the initial pressurization rate of CO₂, the temperature at the initial pressurization, and the quantity of C₆₀. Fullerene particles obtained by GAS method had regular octahedral shapes, whereas the particles obtained by adding liquid ethanol as an antisolvent to C₆₀ solution did not have such shape. Particle sizes could be changed in a range of 1.0–8.5 μm by GAS method; they were wider than the range of particles obtained by ethanol addition (0.7–1.8 μm).     

High-cycle fatigue characteristics of quasi-isotropic CFRP laminates over 10 cycles (Initiation and propagation of delamination considering interaction with transverse cracks)

High-cycle fatigue features of over 10⁸ cycles, particularly the initiation and propagation of edge delamination considering the effects of transverse cracks, were investigated using quasi-isotropic carbon-fiber-reinforced plastic (CFRP) laminates with a stacking sequence of [45/0/−45/90]_s in this study. In the relationship between a transverse crack density and initiation and growth of edge delamination, it was found that fatigue damage growth behavior varied depending on applied stress. It was observed that edge delamination initiated and grew at parts where transverse cracks were dense at ordinary applied stress, whereas it was observed that edge delamination grew before or simultaneously with transverse crack propagation at a low applied stress and high-cycle loading. In addition, the critical transverse crack density where delamination begins growing was calculated to evaluate the interaction between transverse crack and edge delamination growth.