Combined effects of neutron irradiation and hydrogen absorption on mechanical properties of pure iron

To obtain a fundamental knowledge of the combined effect of neutron-irradiation and hydrogen, mechanical properties and the fracture mode were studied for pure neutron irradiated iron, followed by hydrogen charging. The effect of interaction between neutron irradiation and hydrogen absorption for a pure iron could be clarified. Under the hydrogen charged condition, the ductility is higher in the neutron irradiated specimen than in the unirradiated. The cause could be sought in hydrogen trap sites of the iron and the fracture mode. As a result of interaction between many irradiation defects and hydrogen atoms, the fracture mode of a hydrogen charged specimen after irradiation, is a mixed mode of quasi-cleavage crack and dimple pattern. That of a hydrogen charged unirradiated specimen is predominantly intergranular cracking.     

High-temperature strengths of aluminium composite reinforced with continuous SiC fibre

Aluminium alloys were reinforced unidirectionally with 30, 35, 40 and 50 vol %SiC fibres by a liquid-pressing method. The SiC fibres for reinforcement were produced from a polycarbosilane and were yarns consisting of 500 continuous filaments of length 300 m and diameter 13m, having a tensile strength of 2000 MPa. High-temperature tensile and bending strengths of the composites were examined in air in the temperature range from room temperature to 500° C. The strengths were not influenced by temperature up to 400° C, but were decreased at 500° C. The decrease is considered to be caused by the reduction in transfer efficiency of the stress accompanying the decrease in adhesion between fibres and matrix.     

Effect of Ageing of Pipe and Lining Materials on Elemental Composition of Suspended Particles in a Water Distribution System

Water samples collected from a drinking water supply system were assessed for elemental composition (Al, Si, Ca, Mn, Fe and Zn) of suspended particles. Particulate Fe, Mn and Al concentrations were significantly correlated even though their origins are considered to be different. The results of Principal Component Analysis (PCA) and cluster analysis revealed that elemental compositions can vary according to pipe and lining materials and service ages. Differences in concentrations of the particulate elements were calculated between upstream and downstream sites and then subjected to further PCA. In PC1, Fe, Mn and Al exhibited high factor loadings, whereas only Ca was a high contributor for PC2. This implies that ageing-related corrosion and degradation of mortar lining can affect the elemental composition of suspended particles in water distribution systems. We concluded that the elemental composition of suspended particulates can be used to detect ageing pipes in water distribution systems.     

InSb-added TiO2 nanocomposite films by RF sputtering

This study investigates the preparation of InSb-added TiO₂ nanocomposite films by RF sputtering. The optical absorption spectra are obviously shifted to visible and near-infrared regions. High-resolution transmission electron microscopy indicates that sphere-shaped InSb nanocrystals with a size of about 15 nm are dispersed in a matrix. The X-ray diffraction result reveals that the matrix forms a phase mixture of TiO₂ and In₂O₃, which is also produced by decomposing the InSb during postannealing at 723 K. Therefore, the absorption shift is clearly due to quantum size effects of the InSb nanocrystals embedded in the wide-gap oxides TiO₂ and In₂O₃.     

The fracture toughness measured on sensitized 304 stainless steel in simulated reactor water

The environmental conditions chemically equivalent to BWR primary water, e.g. 288°C, 0.2 ppm O₂ and/or 98°C, air-saturated, were found to influence considerably the in-water fracture toughness values of furnace-sensitized Type 304 stainless steel.Notched compact tension and three point bend specimens sampled from two heats of standard materials (0.06% C) showed significant reduction in dJ/da values reflecting consistently the effects of loading rate, temperature, dissolved oxygen concentration and degree of sensitization. In particular the crack enhancement with lowering the loading rate was significant. The effect became apparent with dJ dt at and below 1× 10−1 kg·mm/mm²/min (1.6 × 10 J/m²/s) in the typical BWR environment.Based on the results, it is suggested that a critical consideration is needed on the significance of such an environmental effect in the LWR structural safety evaluation, in particular that the probability of instable fracture at the “rings” of sensitized material near welded joints is subject to reviewing.     

Direct observation of X-ray induced atomic motion using scanning tunneling microscope combined with synchrotron radiation

X-ray induced atomic motion on a Ge(111)-c(2 x 8) clean surface at room temperature was directly observed with atomic resolution using a synchrotron radiation (SR)-based scanning tunneling microscope (STM) system under ultra high vacuum condition. The atomic motion was visualized as a tracking image by developing a method to merge the STM images before and after X-ray irradiation. Using the tracking image, the atomic mobility was found to be strongly affected by defects on the surface, but was not dependent on the incident X-ray energy, although it was clearly dependent on the photon density. The atomic motion can be attributed to surface diffusion, which might not be due to core-excitation accompanied with electronic transition, but a thermal effect by X-ray irradiation. The crystal surface structure was possible to break even at a lower photon density than the conventionally known barrier. These results can alert X-ray studies in the near future about sample damage during measurements, while suggesting the possibility of new applications. Also the obtained results show a new availability of the in-situ SR-STM system.     

Compositional optimization of magnetite thin films prepared by rf sputtering from a composite target of wüstite and Ge

This study investigated the compositional optimization of magnetite (Fe₃O₄) thin films containing a small amount of Ge to enhance magnetization. No substrate bias was applied during deposition. In a pure Ar atmosphere, the film structure changed from the phase mixture of magnetite and wüstite (Fe_1 − xO) to the weak appearance of wüstite with increasing Ge content. The antiferromagnetic wüstite thus obtained was employed as a starting material to prepare single-phase magnetite, and a gas mixture of Ar and O₂ was then applied. Single-phase magnetite thin films exhibit ferrimagnetic behavior with maximum magnetization of 0.42 T at 1196 kA m⁻¹(15 kOe), which exceeds that of a composite target of ceramic magnetite with Ge chips. Simultaneously adding Ge to the iron-excess wüstite target therefore effectively enhanced magnetization.     

Relationship between sensitivity and waveguide position on the diaphragm in integrated optic pressure sensors based on the elasto-optic effect

The sensitivities of integrated optic pressure sensors with diaphragms theoretically are known to be strongly dependent on the position of the sensing waveguide on the diaphragm. According to the theoretical results, the diaphragm edge is the best position for the waveguide of a sensor based on the elasto-optic effect. The relationship between sensitivity and the waveguide position, however, has not been investigated experimentally, although it is important in the designing of such a sensor and in determining the misalignment tolerance of the sensing waveguide. In this study, this relationship in a glass-based integrated optic sensor by use of an intermodal interference was examined experimentally.     

Femtosecond-Picosecond Laser Photolysis Studies on Proton Transfer Process of Excited 1-Pyrenol-Triethylamine Hydrogen Bonding Complex in Solutions

The proton transfer (PT) process in the excited hydrogen bonding (HB) complex of 1-pyrenol and triethylamine, leading to the formation of a hydrogen-bonded ion pair (HBIP*) of excited pyrenolate anion and triethylammonium cation, PyO^−* ··· H-N⁺(C₂H₅)₃, and subsequent reaction processes of HBIP* in various solvents were investigated by picosecond and femtosecond laser photolysis, as well as by steady-state absorption and fluorescence measurements. Time constants for the PT process taking place in the time region of a few picoseconds were almost independent of the polarity of the solvent and it was suggested that the intermolecular slow motion in the HB complex, such as the intermolecular vibration and/or the torsional motion of the two moieties, might regulate the PT process. Moreover, the ionic dissociation process following the photoinduced PT process in polar solvent was directly measured. The dynamic behaviors of the excited intermolecular HB complex and underlying mechanisms are discussed by comparing these results with those on the intramolecular photoinduced PT process and with results of investigations of electron transfer systems.     

Observation and quantitative analysis of rat bone marrow stromal cells cultured in vitro on newly formed transparent β-tricalcium phosphate

To observe living cell morphology on ceramics by light microscopy, we fabricated a new material—transparent β - tricalcium phosphate (t-β TCP) ceramic—for the purpose of serving as a tissue culture substrate. Bone marrow stromal cells (BMSCs) were obtained from rat femora and cultured on both t-β TCP ceramic disks and culture grade polystyrene (PS) dishes in an osteogenic medium. After 1 day of culture, cell attachment and spreading on both the t-β TCP and PS substrata were equally and clearly detected by ordinary light microscopy. After 14 days of culture, extensive cell growth, alkaline phosphatase (ALP) staining, and bone mineral deposition could be detected on both substrata. In addition, quantitative biochemical analyses revealed high DNA content, ALP activity, and osteocalcin content of these cultures. This experiment is significant in that all of the results were similarly observed on both the t-β TCP and PS substrata, indicating the excellent properties of β TCP ceramics for BMSCs culture towards osteogenic differentiation.