Novel SiC synthesis method applicable to SiC solid phase sintering

Most of the present production processes of SiC sintered bodies require some powder mixing using a mechanical milling process (ball milling, and so on). In this case, relatively long hours are required, and there is the problem of contamination during the preparation process. To avoid these problems, we developed a new process for obtaining a self-sinterable, stoichiometric SiC powder, whose precursor material is water-soluble; the precursor material was synthesized from aqueous silica and citric acid containing a small amount of aluminum compound. In order to obtain the stoichiometric SiC composition, the above aqueous precursor material was adequately cured in air (200°C-400°C); subsequently carbonization reaction (~800°C) in nitrogen atmosphere, carbothermal reduction (~1600°C) in argon atmosphere, and pressureless sintering (~1900°C) were performed. Among these processes, the curing process (cross-linking process) is very important for obtaining the equivalent composition (silica and carbon) for the subsequent carbothermal reduction. In this study, the adequate curing temperature and suitable preparation condition for the carbothermal reduction were investigated for the production of stoichiometric self-sinterable SiC powder. The pressureless sintered body achieved using the obtained SiC powder demonstrated a desirable trans-crystalline fracture behavior.     

Double-action bending for eliminating springback in hat-shaped bending of advanced high-strength steel sheet

The International Journal of Advanced Manufacturing Technology - This paper presents a novel technology called ‘double-action bending (DAB)’ to eliminate springback in hat-shape forming...     

Boiling heat transfer characteristics of a sulfuric-acid flow in thermochemical iodine–sulfur cycle

The Japan Atomic Energy Agency has been conducting research and development on the thermo-chemical iodine–sulfur (IS) process, which is one of the most attractive water-splitting hydrogen production methods that uses nuclear thermal energy. The sulfuric acid decomposer is one of the key components of the IS process. The boiling heat transfer coefficients of sulfuric acid solutions are required to design the sulfuric acid decomposer. These coefficients were measured in aqueous solutions where the mole fraction of H₂O ranged from 0.17 to 0.37 (heat flux range from 16.9 kW/m² to 5.6 kW/m²) and compared with the empirical correlations formulated for binary mixtures. A combination of the Stephan–Körner correlation, using the empirical constant A₀ = 2.00, and the Nishikawa–Fujita correlation was used to predict the experimental results with an accuracy of ±10%.     

Passive piezoelectric single-side MEMS DC current sensor with five parallel PZT plates applicable to two-wire DC electric appliances without using cord separator

A passive (power-less), non-contact macro-scale piezoelectric bimorph DC current sensor to satisfy the increasing needs of DC power supply for monitoring the electricity consumption by either one-wire or two-wire appliance cord was proposed at our laboratory previously. In present study however, a MEMS-scale piezoelectric single-side DC current sensor, comprised of five parallel PZT plates, was further proposed and micro-fabricated for preliminarily examination. A micro magnet was fixed by manipulator onto the PZT cantilever tip to the theoretically pinpointed position of the center plate. Different from the results of the macro-scale piezoelectric bimorph DC current sensor, impulsive piezoelectric output voltages accompanying with a gradual decrease in decay were detected when the applied DC electric current was varied from 0.5 to 2.5 A. A linear relationship between the detected peak value of the impulse output voltage and the applied DC electric current was also obtained but with a higher slope compared to the result of the macro-scale piezoelectric bimorph DC current sensor.     

Preparation of polyynes by liquid-phase laser ablation using different irradiation target materials and solvents

Polyynes were prepared from pellets of a perylene derivative, 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA), and graphite by liquid-phase laser ablation, using solvents of methanol, ethanol, 1-propanol, 1-butanol, t-butyl alcohol, n-hexane, and decalin. The amounts of polyynes produced from PTCDA strongly depended on the polarity of the solvent, while those from graphite did not. Polar functional groups of acid-anhydride side chains in PTCDA are believed to influence the amounts of C₂ radicals produced by laser ablation. The long-chain polyyne C₂₈H₂ was detected in a chromatogram of a solution obtained from a graphite pellet and solvent decalin.     

Effect of different features to drill-wear prediction with back propagation neural network

In this paper, a back propagation neural network (BPNN) has been applied to predict the corner wear of a high speed steel (HSS) drill bit for drilling on different workpiece materials. Specially defined static and dynamic features extracted by a wavelet packet transform (WPT) from the resultant force converted from thrust and torque together with the cutting conditions (workpiece material, spindle speed, drill diameter, feed rate) are used as inputs to train the network to obtain a better output, drill corner wear. Drilling experiments have been carried out over a wide range and, features newly defined and conventional ones, features extracted from different frequency bands are compared.     

An anaerobic bacterium isolated from Japanese spiny lobster Panulirus japonicus

Eight strains of bacteria which could not grow under aerobic conditions, were isolated from Japanese spiny lobster. All the strains were Gram-positive, non-sporeforming cocci, and grew well under anaerobic conditions. The strains required a decreased oxygen tension rather than an increased CO₂ tension. Catalase, oxidase, nitrate reductase and urease were not produced. The strains fermented glucose, cellobiose, trehalose and levulose. Indole and H₂S were not produced. Macromolecule substances including starch, esculin, casein, gelatin and chitin were not hydrolyzed. Lactic acid was the sole product from peptone-yeast extract-Fildes solution-glucose broth. Fermentable carbohydrates were not required. The strains could grow at 20 to 37°C, and required NaCl for growth. From the above results, the strains were identified as anaerobic (aerotolerant) Streptococcus sp.     

An analytical study of the effect of a support geometry on frequency shift and support loss of piezoelectric ring-shaped resonators for healthcare and environmental applications

Ring-shaped resonators with one support have been designed in this work. The ring-shaped resonator reacts with a mass perturbation to provide eigenstate or frequency shifts which could transfer to electrical signals by piezoelectric effect. The aforementioned ring-shaped resonator is mainly comprised with a multilayer of Pt/Ti/PZT/Pt/Ti/SiO₂ deposited on the silicon-on-insulator wafer and expected to be a contour mode. In order to estimate the sensitivity of the ring-shaped resonator against the mass perturbation, the theoretical analysis was conducted by ANSYS from two aspects including: (a) the effect of support geometry on frequency shift and support loss (from view point of vibration mode shape); and (b) the mass application methodology. It is found that low-amplitude vibration area is smaller at narrow support, and frequency shift of trapezoid support is higher than that of rectangle support.