Method for patterning various nanomaterials: electrochemical deposition of patterned Ni thin films and their utilization as a strippable mask

We report an interesting approach for preparing micropatternings of nanomaterials, such as carbon nanotubes and TiO(2) nanoparticles. In the method, exfoliation of electrodeposited Ni thin films was the key process. After patterning indium thin oxide (ITO) plates with an insulating photoresist by conventional photolithography, Ni was electrodeposited on only the exposed ITO areas. The resulting substrates were evenly covered with nanomaterials by a drop cast method. By exfoliating the electrodeposited Ni thin films from the substrates, patterned nanomaterial films were formed.     

Electrical conductivity of calcium phosphate ceramics with various Ca/P ratios

Calcium orthophosphate powders with various Ca/P ratios were prepared by a wet process, employing CaCO₃ and H₃PO₄ as starting materials. After they were calcined and pressed to form pellets, they were fired at various temperatures ranging from 800 to 1200 °C. The samples at various stages were examined by X-ray diffraction and SEM, The a.c. electrical conductivity was measured for a series of samples. For some of the samples, the d.c. electrical conductivity and electromotive force were also measured. The samples showed relatively high conductivity (4×10^–5 S cm^–1 at 800 °C). With respect to the tricalcium orthophosphate with nearly stoichiometric composition, the predominant charge carrier at 800 °C was presumed to be an ion although it is not identified at the moment.     

Influence of Oxidation Temperature and Cr Content on the Adhesion and Microstructure of Scale on Low Cr Steels

Descalability of steels during hot rolling processes is essential in order to maintain the surface quality of steel products, because the remaining scale can be impressed into the steel, producing surface defects. Therefore, a quantitative evaluation of scale adhesion at high temperature is needed in order to find suitable heating conditions for hot rolling processes that promote the formation of scale that easily detach. Round bar shape specimens of low Cr steels were oxidized in a fuel combustion environment, and then compressed at high temperature to detach the scale. The area fraction of the remaining scale was evaluated by image analysis. Under a thick outer oxide scale, a thin continuous inner oxide layer, which consisted of Cr and Si oxides, strongly adhered to the substrate, resulting in poor descalability. On the other hand, if this inner scale changed into a discontinuous layer with a porous FeO layer beneath, the descalability improved. It was found that scales with greater descalability formed on steels containing less Cr and for oxidation at higher temperatures.     

Promotion of H2 production from ethanol steam reforming by zeolite basicity

The effect of the basicity of zeolite as a metallic catalyst substrate on ethanol steam reforming reaction was investigated. Catalysts with various basicities were prepared using an ion exchange process with aqueous solutions including Na⁺, K⁺ and Cs⁺ after an impregnation process of Ni on Na-Y zeolite (referred to as Ni/Na-Y, Ni/K-Y and Ni/Cs-Y, respectively). Infrared spectroscopy indicated that the OH bonds of ethanol molecules adsorbed on zeolites were weakened with increasing zeolite basicity. H₂ production at 300 °C increased in the order of Ni/Cs-Y > Ni/K-Y > Ni/Na-Y, and selectivity for a high production ratio of H₂ to C₂H₄ was significantly promoted by exchanging Na⁺ for K⁺ or Cs⁺. H₂ production at 500 °C was also enhanced by the zeolite basicity; however, degradation of catalytic activity was mainly caused by carbon deposition on the three samples at this temperature. Ni/Cs-Y, with higher H₂ production than Ni/Na-Y, also exhibited higher resistance to carbon deposition. Increase of the zeolite basicity was effective for selective acceleration of the dehydrogenation reaction with ethanol, inhibition of coke deposition, and the promotion of H₂ production.     

Study of Electron Orbits for Formation of Toroidal Closed Flux Surface by ECH

Electron orbits under the external vertical field (BV) and the self poloidal field of the toroidal plasma current in a toroidal geometry are investigated by using analytic model fields in order to search for the conditions of occurence of appropriate confinement asymmetry of fast electrons along the field lines. This asymmetry e±ciently and quickly generates a toroidal current, which may close the field lines in ECH-started plasmas. It is analytically shown that the characteristics of confinement asymmetry depend on the product of the major radius and the strength of the external vertical field. The results suggest that in large devices BV should be lowered and also some artificial means to speed up the pitch angle scattering for the fast electrons at a higher energy range are beneficial to generate the toroidal current in order to close the filed lines.     

MoO3 buffer layer effect on photovoltaic properties of interpenetrating heterojunction type organic solar cells

Photovoltaic cells, with a conducting polymer/fullerene (C₆₀) interpenetrating heterojunction structure fabricated by spin-coating a conducting polymer onto a C₆₀ thin film, have been investigated and demonstrated a high efficiency as solar cells based on organic materials. The photovoltaic properties of the solar cells with a structure of indium-tin-oxide (ITO)/C₆₀/poly(3-hexylthiophene) (PAT6)/Au have been improved by the insertion of a molybdenum trioxide (VI) (MoO₃) layer as a cathode buffer layer. In the solar cells with the structure of ITO/C₆₀/PAT6/MoO₃/Au, the energy conversion efficiency has been improved to 1.15% under AM1.5 (100 mW/cm²) illumination.     

Evaluation of surface characteristics of ground CVD-SiC using cast iron bond diamond wheels

The precision and efficient machining of CVD-SiC ceramic to required quality has not been well established yet. In this paper, a comparative study was conducted to investigate the special aspects in grinding of CVD-SiC ceramic, with ELID method or rotary dressing method. The stability of surface roughness, effects of material properties and dressing methods on grinding results, effects of material properties and dressing methods on surface stress state, and microscopic analysis of ground CVD ceramics by both methods were well analyzed. In addition, a wheel-workpiece interaction model was proposed for the two dressing methods.     

Study concerning production of lightning overvoltages on low‐voltage power distribution lines

In order to study lightning problems of low‐voltage power distribution lines, lightning overvoltage waveforms were observed inside the homes of customers. The cause of lightning overvoltages was examined from observation of striking points by still cameras. Lightning overvoltages of 62 waveforms were recorded by observation over a period of about 3 1/2 years. Observed waveforms can be classified into three types of single polarity (positive or negative), both polarities (which change from positive to negative or negative to positive), and pulsive waveform. The causes of these lightning overvoltages which were estimated from striking points are shown as follows: (1) Induced lightning overvoltages on low‐voltage distribution lines. (2)   Electric potential rise due to discharge of surge arresters or current of overhead ground wire. (3)   Shift of lightning overvoltages from high‐voltage side of transformer to low‐voltage side, which is due to electromagnetic induction. © 2000 Scripta Technica, Electr Eng Jpn, 130(4): 66–75, 2000     

Consideration of radiated electromagnetic waves from partial discharge based on half‐wave dipole antenna model

Partial discharge (PD) may take place due to residual defects like metallic particles in SF₆ gas‐insulated power apparatus such as GIS. However, the signal of PD occurring in SF₆ gas is very weak and susceptible to external noise in air. Moreover, because of the complicated mechanism of PD, the radiation property of electromagnetic waves from PD has not as yet been clarified. Therefore, it is hard to distinguish the PD signal in SF₆ gas from external noise. From the above points of view, we have been investigating the radiation mechanism of electromagnetic waves from PD. We measured the polarization characteristics of electromagnetic waves radiated from PD in comparison with those of half‐wave dipole antennas. The polarization characteristics of PD were explained by the theory of half‐wave dipole antenna, rather than that of an infinitesimal dipole antenna. Moreover, we compared the power spectrum for PD measured using a biconical antenna with that received from the half‐wave dipole antenna or infinitesimal dipole. It was found that the power spectrum for PD also corresponded to that for the half‐wave dipole antenna with a length of 50 cm. © 1999 Scripta Technica, Electr Eng Jpn, 126(4): 40–47, 1999     

Dependence of RF characteristics on ac bias current for large‐sized ferrites

A ferrite‐loaded radio‐frequency (RF) cavity with resonant frequency of several megahertz is commonly used for proton synchrotrons. The resonant frequency of the cavity is shifted upward during beam acceleration by increasing the bias current. Because the bias current is swept sinusoidally at a high repetition rate, the RF characteristics of ferrites deteriorate due to disappearance of the magnetic anisotropy induced by Co²⁺ and Co³⁺ ions. This paper presents test results of the RF characteristics for three ferrites with large diameters of over 500 mm. The tests were carried out on our ferrite test bench. The RF frequency and the ac bias current vary from 2 MHz to 3.3 MHz and from 0 A to 1000 A, respectively, at the maximum frequency of 75 Hz. As the frequency of the ac bias current became high, deterioration of the RF characteristics and an increase in the ac bias current were observed. Consequently, it was verified that an ac bias test with full RF power using the test bench was inevitable for designing an actual RF cavity. © 1999 Scripta Technica, Electr Eng Jpn 127(4): 1–8, 1999