Fabrication of large area diffraction grating using LIGA process

X-ray imaging is a very important technology in the fields of medical, biological, inspection, material science, etc. However, it is not enough to get the clear X-ray imaging with low absorbance. We have produced a diffraction gratings for obtaining high resolution X-ray phase imaging, such as X-ray Talbot interferometer. In this X-ray Talbot interferometer, diffraction gratings were required to have a fine, high accuracy, high aspect ratio structure. Then, we succeeded to fabricate a high aspect ratio diffraction grating with a pitch of 8 μm and small area using a deep X-ray lithography technique. We discuss that the diffraction gratings having a narrow pitch and an large effective area to obtain imaging size of practical use in medical application. If the pitch of diffraction gratings were narrow, it is expected high resolution imaging for X-ray Talbot interferometer. We succeeded and fabricated the diffraction grating with pitch of 5.3 μm, Au height of 28 μm and an effective area of 60 × 60 mm².     

Engineering Transition Metal Layers for Long Lasting Anionic Redox in Layered Sodium Manganese Oxide

Oxygen-redox-based-layered cathode materials are of great importance in realizing high-energy-density sodium-ion batteries (SIBs) that can satisfy the demands of next-generation energy storage technologies. However, Mn-based-layered materials (P2-type Na-poor Na_y[A_xMn_1−x]O₂, where A = alkali ions) still suffer from poor reversibility during oxygen-redox reactions and low conductivity. In this work, the dual Li and Co replacement is investigated in P2-type-layered Na_xMnO₂. Experimentally and theoretically, it is demonstrated that the efficacy of the dual Li and Co replacement in Na_0.6[Li_0.15Co_0.15Mn_0.7]O₂ is that it improves the structural and cycling stability despite the reversible Li migration from the transition metal layer during de-/sodiation. Operando X-ray diffraction and ex situ neutron diffraction analysis prove that the material maintains a P2-type structure during the entire range of Na⁺ extraction and insertion with a small volume change of ≈4.3%. In Na_0.6[Li_0.15Co_0.15Mn_0.7]O₂, the reversible electrochemical activity of Co³⁺/Co⁴⁺, Mn³⁺/Mn⁴⁺, and O^2-/(O₂)^n- redox is identified as a reliable mechanism for the remarkable stable electrochemical performance. From a broader perspective, this study highlights a possible design roadmap for developing cathode materials with optimized cationic and anionic activities and excellent structural stabilities for SIBs.     

CO2 reduction using hydrothermal method for the selective formation of organic compounds

The reduction of CO₂ under hydrothermal conditions has been investigated. In typical experiment, Fe-powder, Ni-powder, solvent, and CO₂ have been reacted in a batch-type micro autoclave under hydrothermal conditions for several hours. Methane, formic acid, and hydrogen were generated after treatment in water. With the rise of Ni amount, the methane yield increased while hydrogen and formic acid decreased. It is supposed that Ni has acted as a hydrogenation catalyst. In basic solution, CO₂ was converted to formic acid selectively at 300°C involved with trace of methane. Considering the reduction characteristics of formic acid, the reaction pathway has been discussed. In experiments with the mixture of Fe and Fe₃O₄, trace of methanol was detected at the experiments with less amount of metallic Fe. It is inferred that the control on the effect of reductant is indispensable for oxygenated organic compound formation. Experiment on the effect of water has been conducted using hydrogen. Ethane yield increased with the amount of water, while there was no drastic change in the yield of methane. From these results, it is supposed that the steam reforming reaction of methane was involved in the reduction of CO₂, and effected on the C–C bond formation.     

High Temperature Schottky Barrier on n-Type SrTiO3 and Its Sensitivity to Ambient Gases

Metal or oxide electrodes (Pt, Au, Ag, (La, Sr)CoO₃) were deposited on single crystals of 0.02 mol% Nb doped SrTiO₃ by pulsed laser deposition. Current-voltage and capacitance-voltage responses were measured using three-terminal electrode configuration. Under high oxygen partial pressures, clear rectification behaviors were observed. Diffusion model well explained the current vs. voltage relationship with ideality factors close to unity. The barrier height varied reversibly with oxygen partial pressure, and was almost independent of the electrode materials, which suggested that the Fermi level at the interface was pinned by the surface states. The origin of the surface states was discussed in terms of oxygen adsorption or oxidative formation of metal vacancies around the surface. Chemical interaction between the surface and oxygen and resulting cation rearrangement was concluded to play an important role from the long stabilization time on oxygen partial pressure change. The water vapor pressure dependence of the barrier height was also explained by competitive adsorption of oxygen and water.     

A new method for estimating initial rotor phase of self‐excited hybrid‐field synchronous motors

This paper proposes a new method for properly estimating the rotor initial phase (i.e., the position) of the newly emerging self‐excited hybrid‐field synchronous motors (SelE‐HFSMs), which have the rotor held by both a permanent magnet and a diode‐shorted held winding. The proposed method injects a spatially rotating high‐frequency voltage and detects the rotor phase directly by evaluating the norm of the associated current. The method is very simple, but has a high degree of usability. 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 173(3): 49–58, 2010; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.21027     

The effect of polar groups on the dielectric loss of polyethylene

The dielectric loss tangent for polyethylene with low dielectric loss was approximated by tan δ = C_f Σ(nμ²), where n and μ are the number and dipole moment of polar groups, respectively, and C_f is a parameter. The type and number of polar groups in the polyethylenes were mainly determined from infrared spectra obtained with a Fourier transform spectrometer. It was found that the contribution of hydroxyl and carbonyl groups to tan δ was significantly large, but the contribution of double bond groups was less significant. The tan δ was observed to decrease with a decrease of methyl group density although the overall contribution of methyl groups to tan δ was small. This suggests that tan δ is closely related to the secondary structure of polyethylenes, thus indicating the methyl groups seem to play an important role in the secondary structure.     

Boundary element method for electromagnetic scattering from cylinders

The computation of low frequency scattering of electromagnetic fields by solid/hollow dielectric or conducting cylinders using the boundary element method (BEM) is considered. A general computer program has been developed for both transverse electric and magnetic cases. Numerical examples are given for conducting circular cylinders, and solid and hollow dielectric cylinders. The computational accuracy is checked by comparing the results with the analytic solution or computing an error defined from the optical theorem. In addition some problems at an interior resonance of the scatterer are discussed. The method can be directly applied to more complicated geometries.     

A Promising Alternative to PEMFC Graphite Bipolar Plates: Surface Modified Type 304 Stainless Steel with TiN Nanoparticles and Elastic Styrene Butadiene Rubber Particles

In order to utilise inexpensive bipolar plates for proton exchange membrane fuel cells (PEMFC), a surface modification with TiN nanoparticles and elastic styrene butadiene rubber (SBR) particles has been applied to the most widely commercialised stainless steel of type 304 which did not satisfy the required properties in the bare form. The electro‐conducting agglomerates were electrophoretically deposited on the stainless steel bipolar plates. The surface modification greatly improved the corrosion resistance of the stainless steel as well as the interfacial contact resistance (ICR). As a result, the cell performance was significantly enhanced and become comparable to that with graphite bipolar plate during operation for 1,000 h. Ac‐impedance results indicated that the TiN–SBR coating was effective not only in reducing the ICR but also in retaining the resistance low throughout the operation. The hydrophobic character of the TiN–SBR coating on the stainless steel bipolar plates, which facilitated the removal of the formed water in the cathode side during the single cell operation, is also responsible for the enhanced cell performance. Therefore, the type 304 stainless steel bipolar plate modified with the electro‐conducting nanosized TiN – elastic SBR particles is suggested to be a promising substituent for the PEMFC graphite bipolar plate.     

Identification of species in Aspergillus section Flavi based on sequencing of the mitochondrial cytochrome b gene.

The partial sequences of the mitochondrial (mt) cytochrome b gene (402 bp) were determined for species of Aspergillus section Flavi. On the basis of identities of DNA sequences, 77 strains were divided into seven DNA types, from D-1 to D-7. The type strains of A. sojae, A. parasiticus, A. flavus and A. oryzae together, A. tamarii, and A. nomius were placed in DNA types D-1. D-2, D-4, D-5 and D-7, respectively. These species could be differentiated from each other. Furthermore, two other DNA types, D-3 and D-6 were found. DNA type D-3 was closely related to A. parasiticus (D-2) and included one strain that deposited as A. flatus var. flavus and produced aflatoxins B and G. DNA types D-6 included one strain named A. flavus and closely related to A. tamarii. The observations of conidial wall texture by SEM (Scanning Electron Microscopy) supported the relationships derived from the cytochrome b gene. The production of aflatoxins was also examined. Using the DNA sequence of cytochrome b gene, several strains were reidentified. The derived amino acids sequences were all the same in the studied strains. The mt cytochrome b gene is useful and reliable in distinguishing and identifying the species in Aspergillus section Flavi.