Enhanced electrochemical activity and long-term stability of Ni–YSZ anode derived from NiO–YSZ interdispersed composite particles

Nickel oxide–yttira stabilized zirconia (NiO–YSZ) interdispersed composite (IC) particles were prepared by a mechanochemical processing using NiO and YSZ nanoparticles. Transmission electron microscopy (TEM) revealed that primally particles of YSZ (75 nm) and NiO (160 nm) were presented alternatively in the composite particles. Specific surface area (SSA) decreased from 8.6 to 7.1 m²/g during the mechanochemical processing. The SSA reduction suggested that the chemically bound NiO/YSZ hetero-interfaces were formed during the processing. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) visualized that the anode made from the IC particles consisted of three-dimensional textured structure of fine Ni and YSZ networks (grain size of them was approximately 500 nm) with 34 vol% of porosity. The anode demonstrated not only low polarization of 152 mV at 1 A/cm² even under the operation at 700 °C but also long-term stability for 920 h.     

Inelastic stress-strain response for notched specimen of Cr-1Mo steel at 600°C

Following a series of cooperative studies A-I and A-II (phase III) concerning the inelastic behaviour of high temperature materials under uniform state of stress, finite element analyses were carried out on circumferential notched cylinders subjected to plasticity-creep interaction conditions. Using an electric capacitance type extensometer “Strain-Pecker”, which is capable of measuring a local strain response with a gauge length of 0.5 mm under high temperature conditions, stress-strain responses for both global and local regions near the notch root were evaluated. Ten kinds of inelastic constitutive model were introduced into a finite element code, and the responses for four kinds of loading pattern were examined for two types of notch shape.     

Surface melting technique of small diameter stainless steel pipe by means of yttrium aluminium garnet laser

A new method of surface melting by using a high power yttrium aluminium garnet laser was developed. This method is applicable to a long distance and narrow space, because of the good accessibility of the laser beam through optical fibre.A desensitization of sensitized type 304 stainless steel pipe was demonstrated by using this technique. A melted layer of thickness approximately 200 μm had a very finite solidification structure, which contained approximately 1.5% δ-ferrite. The average chemical composition of this layer was almost the same as that of type 304 stainless steel, and a band of 300 μm thickness under the melted layer underwent solution heat treatment (SHT).As a result of such surface melting, the melted layer exhibited superior resistance to intergranular stress corrosion cracking (IGSCC). Since the SHT layer is highly resistant to IGSCC generally, it may be possible to improve the IGSCC resistance of base metal to a comparatively deep extent (500 μm from the surface) by this technique.     

Construction Engineering Approach for Lunar Base Development

Studies on lunar base construction conducted by the writers' research group are summarized. A desirable lunar base design was first discussed by employing a systems engineering approach and by defining an evolutionary scenario, which emphasized resource utilization. Several lunar-base-related concepts were examined from the viewpoint of construction engineering including construction materials, structural design, and construction methods. The research also addressed resource utilization for the production of oxygen and construction materials. A commericial approach toward future lunar development is proposed.     

Piezoelectricity in the Field-Induced Ferroelectric Phase of Lead Zirconate-Based Antiferroelectrics

The piezoelectric characteristics were investigated in the field-induced ferroelectric phase of the antiferroelectric Pb_0.99 Nb_0.02[(Zr_0.6Sn_0.4) _{1 − y} Ti _y ]_0.98O₃ family. The electromechanical coupling factors k _p and k _t were measured, and the piezoelectric anisotropy was calculated. The piezoelectricity was controlled easily by the applied electric field pulse. The large piezoelectric anisotropy of these materials in comparison to that of conventional PZT piezoelectric materials makes them very applicable for ultrasonic probes and surface acoustic wave filters.     

Symbiosis system for transmutation on nitride fuel FBR and ADS

A conceptual scheme for mass flow of transmuting Plutonium (Pu), minor actinides (MA) and long-lived fission products (LLFP) is studied. In this feature, the existing light-water reactors (LWRs) cycle will be main stream for nuclear electric generation during a long-term period more than 50 years, and Pu will be utilized in mixed oxide fuel (MOX)-LWRs. In future, when Pu recycling system will be achived by introducing high-conversion LWRs (HCLWRs) and/or fast breeder reactors (FBRs), the accelerator driven transmutation system (ADS) transmutes Pu, MA and Iodine from Purex or Dry reprocessing. This is due to reduce burden for transmuting the excess or remained Pu, MA and LLFP by commercial reactor plants in Pu-recycling system. For this purpose, we introduce a concept of symbiosis system for transmutation based on nitride fuel FBR and ADS. The core design for lead-bismuth (Pb-Bi) cooled FBRs and ADS, Pb-Bi technologies, 15N enrichment and 14C toxicity are studied. And the mass flows for MA and Iodine are discussed based on an estimated scenario for nuclear electric plants introduction in future.     

Fuel-to-cladding gap evolution and its impact on thermal performance of high burnup fast reactor type uranium-plutonium oxide fuel pins

Drastic evolution of fuel-to-cladding gap is observed in high burnup JOYO Mk-II driver and MONJU type uranium-plutonium oxide fuel pins. The effect of the evolution is examined from viewpoints of fuel restructuring, gaseous FP release and retention and cesium migration behaviors. Its thermal impact on fuel pin performance is also studied by one-dimensional steady state thermal analysis. Threshold condition of the evolution depends on fuel pellet characteristics, burnup and probably temperature. The evolution directly relates to as-fabricated microstructures and to gaseous FP release and retention behavior. A comparison of fuel restructuring with predicted temperature profiles indicates that, even where large residual gaps are observed, non-gaseous filler always improves the heat transfer across the gaps.     

Electronic States of Natural and Metal-ion Doped DNA

Electronic states of pristine and metal ion doped salmon DNA’s are studied with EPR and SQUID. Intrinsically no EPR signal is observed in purified salmon DNA, consistent with a semiconducting nature of the pristine DNA, but inconsistent with a metal or a superconductor as reported previously. Although we obtained successfully the divalent metal ion-DNA complexes with one-dimensional array of ions located in between the bases of a base pair, substantial EPR signal except for the case of 3d transition metal ions is not observed. This leads to the conclusion that divalent metal ions counterbalances two phosphate anions instead of Na counter ions in B-DNA, which contradicts the metallic behavior reported previously (A. Rakitin, et al., PRL 86, 3670 (2001)). A comment will also be given on the recent report: “Intrinsic Low Temperature Paramagnetism in B-DNA” (S. Nakamae et al., PRL 94, 248102 (2005)).     

Weight change mechanism of randomly oriented GFRP panel immersed in hot water

This study deals with the weight changes of the fiber/matrix interface and the weight change mechanisms of the randomly oriented E-glass fiber continuous strand mat reinforced unsaturated polyester panels. The weight changes were evaluated by introducing the weight gain due to water absorption (M_g) and the weight loss due to matrix dissolution (M_l). The weight changes of the fiber/matrix interface (M_gI and M_lI) were obtained from the difference of M_g and M_l between GFRP and neat resin. Water absorption of the interface occurred after water absorption of matrix resin reached saturation. Weight loss due to dissolution of binder on glass-fiber mat and matrix from the interface occurred after water penetration into the interface. The debondings at the fiber/matrix interface occurred due to water penetration, and as a result, the binder and matrix dissolved easily in the water through the interface. The weight changes of the GFRP panel were classified into three phases. In phase I, only the resin matrix absorbed water. In phase II, the fiber/matrix interface absorbed water. After that phase, water absorption into the fiber/matrix interface and matrix dissolution from the interface occurred simultaneously.