Two-Mode Behavior in Complex Perovskite Materials

Infrared reflection and Raman spectra have been measured for two complex perovskite ceramic materials, Ba(Mn_1/3Ta_2/3)O₃ and Ba(Ni_1/3Ta_2/3)O₃. Two-mode behavior was observed for both of the compounds in the inner vibrations of the BO₆-type octahedrons, where B indicates Mn, Ta, and Ni ions. This behavior indicates that the local symmetry about Mn, Ni, and Ta ions is octahedral (O_h), although the superlattice structure of the compounds (D_3d) is observed by XRD analysis.     

Quantitative analysis of {332}〈113〉 twinning in a Ti-15Mo alloy by in situ scanning electron microscopy

We have performed quantitative analysis of {332}〈113〉 twinning in a β-Ti-15Mo (wt.%) alloy by in situ scanning electron microscopy and electron backscattering diffraction (EBSD). Microstructure-twinning relations were evaluated by statistical analysis of the evolving twin structure upon deformation at room temperature. Our analysis reveals that at the early stages of deformation (ε < 1.5 to 2.0%), primary twinning is mainly determined by the applied macroscopic stress resolved on the twin system. Most of the primary twins (~70–80% of the analyzed twins) follow Schmid’s law with respect to the macroscopic stress, and most of the growth twins (~ 85% of the analyzed twins) correspond to the higher stressed variant. In the grain size range studied here (40–120 μm), we find that several twin parameters such as number of twins per grain and number of twins per grain boundary area exhibit grain size dependence. We ascribe these effects to the grain size dependence of twin nucleation stress and apparent critical resolved shear stress for twinning, respectively.     

PAH Metabolism in Cultured Mammalian Lung Epithelial Cells

In vitro cultures of mammalian cells have an advantage over animal experiments in that human cells can be directly compared with various other mammalian cells. In this study we compared the metabolism of several polycyclic aromatic hydrocarbons (PAH) (benzo[a]pyrene, chrysene, pyrene, phenanthrene, benz[a]anthracene) in epithelial cells from hamster, rat and human lung.

The cells investigated in our system yielded more or less qualitatively similar metabolic profiles for all PAH mentioned above except benz[a]anthracene in the three species. Additionally, species-specific differences were prominent between human and rodent cells with regard to the ratio of phase I and phase II metabolites.

Indications have been obtained that monooxygenase induction is required in fetal cells prior to metabolic conversion of those PAH which lack an inductive potential for CYP450.     

A high-precision positioning servo controller based on phase/frequency detecting technique of two-phase-type PLL

This paper presents a new method proposed for high-precision positioning servomechanisms. The servo controller uses a two-phase-type phase-locked loop (PLL) to detect position tracking error and speed fluctuation with high resolution. Because the two-phase-type PLL has a wide frequency range and high noise suppression performance, we applied the new controller to high-power and high-velocity servo-spindles and achieved high control performance. The developed servo-spindles were used by a high-productivity numerically controlled gear grinding machine. Experiments of gear grinding were carried out, and the results confirmed the performance of the developed controller.     

Investigation of inorganic compounds on the surface of cathode materials using Li and O K-edge XANES

Inorganic compounds on the surfaces of the cathode materials LiNi_0.80Co_0.15Al_0.05O₂ and LiCoO₂ were studied using Li and O K-edge X-ray absorption near edge structure (XANES) measurements. Rietveld analysis revealed that the LiNi_0.80Co_0.15Al_0.05O₂ sample contained 2% Li₂CO₃, while the LiCoO₂ sample was single-phase. The Li and O K-edge XANES spectra indicated that the surface of LiCoO₂ was almost free of residual Li₂CO₃. In contrast, the presence of both residual Li₂CO₃ and an additional cubic phase were observed, respectively, on and near the surface of LiNi_0.80Co_0.15Al_0.05O₂. These results demonstrate that the XANES technique, using a combination of the total electron yield and fluorescence methods, is an effective tool for probing the surfaces of cathode materials.     

Room-temperature tensile and high-cycle-fatigue strength of fine TiB particulate-reinforced Ti-22Al-27Nb composites

To further improve the mechanical properties of a Ti-22Al-27Nb (mol pct) alloy, based on the ordered orthorhombic Ti₂AlNb (O phase), a TiB particulate-reinforced Ti-22Al-27Nb matrix composite was prepared using the gas-atomized powder metallurgy method. Because of the rapid solidification during the gas atomization process, the TiB particulates dispersed in the composite were extremely fine, with an average diameter of less than 1 μm and lengths ranging up to 5 μm. This composite (PM composite) showed higher tensile and high-cycle-fatigue properties at room temperature than both an unreinforced Ti-22Al-27Nb matrix alloy and a Ti-22Al-27Nb/TiB composite produced using a conventional ingot metallurgy method (IM composite) with relatively coarse (average diameter 5 μm and average length 40 μm) TiB particulates. These coarse TiB particulates in the IM composite were thought to provide only classical composite strengthening effects. On the other hand, the fine TiB particulates in the PM composite showed additional effects, such as blocking the movement of dislocations.     

Superconducting compact synchrotron light source

A superconducting compact synchrotron light source, the NIJI-III, has been completed. The development of the NIJI-III was assigned to Sumitomo Electric Industries Ltd. by the Research Development Corporation of Japan and was deemed successful in October 1991 with the attainment of the design goal of the stored beam current of 200 mA at the final beam energy of 600 MeV. The lattice has a four-sector configuration: four superconducting bending magnets and eight quadrupole magnets, achieving the optimum beam characteristics for lithography. The world's first superconducting bending magnet was developed and adapted, and was characterized by a cosθ type without an iron, a large bore of 200 mm, and a strong curvature of 0.5 m. Furthermore, a newly developed vacuum system and an rf system were installed. The high-speed electron-beam wobbling method was investigated at a 20-Hz triangular wave for the exposure of the vertical field of synchrotron light. It was demonstrated that the expansion of the vertical exposure area agreed with the theoretical calculation, and that there was no effect on the beam lifetime. The achievement of the NIJI-III can be expected to contribute much to the development of various research applications of synchrotron light.     

Improvement in the durability of carbon black-supported Pt cathode catalysts by silica-coating for use in PEFCs

Commercially available Pt metal catalysts supported on carbon black (Pt/CB) for polymer electrolyte fuel cell (PEFC) cathodes were covered with silica layers to improve their durability under the severe cathode operating conditions. The Pt metal particles in the Pt/CB catalyst grew in size during the accelerated durability tests (potential cycling between 0.6 and 1.0 V vs. RHE in an aqueous HClO₄ electrolyte). Thus, the Pt/CB catalyst was seriously deactivated for the oxygen reduction reaction over the course of the durability tests. In contrast, the silica layers, which wrapped around the Pt metal particles in the silica-coated Pt/CB catalyst, prevented the migration of the Pt metal particles on the carbon supports and the diffusion of Pt cations out of the silica layers. Thus, the silica-coated Pt/CB catalysts maintained a high activity for the oxygen reduction reaction over the course of the durability tests. In addition, the silica-coated Pt/CB prepared from methyltriethoxysilane showed a higher activity than that prepared from tetraethoxysilane. The porous structures and hydrophobicity of silica prepared from methyltriethoxysilane promoted the diffusion of oxygen and water molecules in the silica layers of the silica-coated Pt catalysts.