Synthesis of Nanowire TiO2 Thin Films by Hydrothermal Treatment and their Photoelectrochemical Properties

Nanowire TiO₂ thin films were successfully prepared on Ti metal substrates by hydrothermal treatment of calcined Ti foils in 10 M NaOH. The nanowire TiO₂ thin films exhibited much larger surface area and higher photoelectrochemical performance than the TiO₂ thin films prepared on Ti metal substrates by the calcination of Ti foil. These nanowire films were shown to act as an efficient photoanodes for the photoelectrochemical water splitting reaction.     

A memory‐in‐pixel reflective‐type LCD using newly designed system and pixel structure

A 7.03‐in. extended graphics array reflective LCD prototype has been developed by using memory‐in‐pixel (MIP) technologies with a newly designed system and pixel structure. The MIP system comprising a MIP backplane and a display driver has been optimized to reduce power consumption. The MIP backplane has specific circuits that allow accessing row drivers randomly, and the display driver manages which row should be accessed. Thus, the system is capable of showing a mixture of still and moving images, resulting in low power consumption. A dithering block embedded in the display driver enables to select an appropriate dithering algorithm according to the types of images and the position on the screen. In addition, the novel pixel structure, “three divided patterns”, has been designed to improve image quality and to provide visibility in dark environments. The latter is based on a novel approach; interpixel area is used for an aperture to transmit light from the backlight, and the fringe field from adjacent pixel electrodes is used to control LC directions. The feature of the pixel structure is also effective for obtaining equivalent gamma between reflective and transmissive images.     

Detailed analyses of key phenomena in core disruptive accidents of sodium-cooled fast reactors by the COMPASS code

A five-year research project has been initiated in 2005 to develop a code based on the MPS (Moving Particle Semi-implicit) method for detailed analysis of key phenomena in core disruptive accidents (CDAs) of sodium-cooled fast reactors (SFRs). The code is named COMPASS (Computer Code with Moving Particle Semi-implicit for Reactor Safety Analysis). The key phenomena include (1) fuel pin failure and disruption, (2) molten pool boiling, (3) melt freezing and blockage formation, (4) duct wall failure, (5) low-energy disruptive core motion, (6) debris-bed coolability, and (7) metal–fuel pin failure. Validation study of COMPASS is progressing for these key phenomena. In this paper, recent COMPASS results of detailed analyses for the several key phenomena are summarized. Simulations of GEYSER and THEFIS experiments were performed for dispersion and freezing behaviors of molten materials in narrow flow channels. In particular, the latter experiment using melt–solid mixture is also related to fundamental behavior of low energy disruptive core. CABRI-TPA2 experiment was simulated for boiling behavior of molten core pool. Expected mechanism of heat transfer between molten fuel and steel mixture was reproduced by the simulation. Analyses of structural dynamics using elastoplastic mechanics and fracture criteria were performed for SCARABEE BE+3 and CABRI E7 experiments. These two analyses are especially focused on thermal and mechanical failure of steel duct wall and fuel pin, respectively. The present results demonstrate COMPASS will be useful to understand and clarify the key phenomena of CDAs in SFRs in details.     

Physical properties of 2-hydroxyethyl methacrylate-grafted silk fibers

This paper deals with the physical properties of silk fibers grafted with 2-hydroxyethyl methacrylate (HEMA). Both tensile strength and elongation measured in the dry and wet states gradually decreased with increasing weight gain. The initial modulus of the grafted silk fibers in the dry state sharply increased in the weight gain range of 0–16%, then decreased to a lower value than the reference untreated sample. The refractive indices parallel and perpendicular to the fiber axis decreased, though the former showed a steeper slope. Accordingly, birefringence and isotropic refractive index also decreased, suggesting a lower degree of crystallinity and molecular orientation of grafted silk fibers. DSC, TMA, and TGA curves of the HEMA-grafted silk fibers indicated an increased higher thermal stability of silk fibers due to the HEMA grafting. The dynamic mechanical measurements showed that the thermally induced molecular movement of both amorphous and crystalline domains of silk fibers was enhanced by HEMA grafting. X-ray diffraction curves, however, implied that the crystalline structure of the silk fibroin remained unchanged regardless of HEMA polymerization. The introduction of HEMA polymer in silk fibers was evidenced by the infrared spectra, exhibiting the absorption bands characteristic of either the grafted HEMA polymer and the fibroin molecules with ordered β structure. © 1993 John Wiley & Sons, Inc.     

Unique structural features and electrical properties of electrospun conjugated polymer poly(3-hexylthiophene) (P3HT) fibers

This study examines and compares the internal structure conjugated polymeric fibers fabricated by electrospinning with cast films. Despite rigidity of polymer chain and the inability of its molecular chains to entangle to form viscoelastic jets, regioregular poly(hexyl-3-thiophene) (P3HT) exhibited the remarkable capability to be electrospun when the solution was subjected to gelation. In order to investigate the influence of additional mechanical stretching on the fibers, P3HT was electrospun with the aid of a rotating disc collector. Structure of electrospun fibers was probed via characterization techniques such as differential scanning calorimetry (DSC), Fourier transform infrared and photoluminescence (PL) spectroscopies. The findings indicated internal structural modifications developed within P3HT fibers, as a consequence of additional mechanical stretching induced by the rotating collector. Polarized FTIR and PL spectroscopies suggested that the molecular chains were aligned along the fiber axis. Electrical conductivity of iodine doped P3HT electrospun fibers was between 3 × 10³ S/m and 6 × 10³ S/m.     

Improvement of fatigue properties of fillet lap joints by local TIG arc heating

Summary

The temper embrittlement affecting the HAZ of 2 1/4Cr-1Mo steel subjected to SR treatment and subsequent reheating is investigated with synthetic HAZ specimens and compared with the embrittlement observed in specimens tempered in the same temperature range without SR treatment (direct tempering). The synthetic HAZ specimens are de-embrittled on application of suitable SR treatment (975 K × 5 hours). Subsequent reheating at 775 to 925 K, however, produces four different types of embrittlement in the specimens. These are the second, third, fourth, and fifth types of embrittlement already identified in the direct-tempered specimens. The first type of embrittlement which occurs during direct tempering in the shortest time range does not appear after SR treatment. The second type (the short-term type), which occurs over a wide time-temperature range during direct tempering, only appears in a narrow range after SR treatment. The third and fourth types (the long-term types) occur just as intensively as during direct tempering. The fifth type (the high-temperature type) also appears after SR treatment. This suggests that embrittlement in the short-term range is to some extent suppressed by SR treatment, but the types of embrittlement arising in the long-term range and high-temperature range occur after SR treatment as well. The ‘step cooling process’ can be applied for short-term detection of temper embrittlement in this steel. However, there is considered to be little or no embrittlement promotion effect due to step cooling per se.     

Flexible ultraviolet detector with robust ZnO nanoparticle nanoassemblies on catechol-functionalized polysiloxane nanofilms

As a result of the vast Young's moduli difference between an inorganic semiconducting channel and flexible substrates, flexible optoelectronic devices readily lose their functionality through material delamination and local fracturing, which lead to short-circuiting of devices. For this study, we synthesized a catechol-containing polysiloxane (CFPS) adhesive and applied it to ZnO nanoparticle (NP) assembly on plastic substrates for flexible UV detector applications. The 30 nm thick CFPS adhesive can anchor 70 nm thick ZnO NPs strongly through a coordination bond, thereby forming an ultra-stable ZnO NP channel layer. A peeling test of ZnO NP layer was conducted using transparent tape (Scotch®; 3 M Inc.). The ZnO NPs were firmly immobilized, reflecting the outstanding mechanical stability of CFPS adhesives. A UV detector also exhibited stable photo-response performance even after a thousand iterations of bending with 3 mm curvature radii. The result indicates the polycyclosiloxane-based flexible device as promising for wearable detector applications.     

A Comparative Study of Organic Cobalt Complex Catalysts for Oxygen Reduction in Polymer Electrolyte Fuel Cells

Reduction of platinum catalysts loading is a central issue in polymer electrolyte fuel cells. As alternatives for platinum, some organic metal chelate compounds are tested as cathode catalysts, such as cobalt aza-complexes or cobalt complexes possessing aminophenyl moieties featured as Co-N₄ or Co-N₂O₂ chelate structures. The way of immobilization of catalysts on the graphite surface influences their stability as well as the performance of oxygen reduction. Heat-treated catalysts supported on graphite at 600°C show much better oxygen reduction abilities than as-received metal complexes. The original chemical structure of metal complexes affects crucially the catalytic ability, though initial structures of molecules are no more intact after the heat treatment. The catalytic activity of these complexes may originate from the central chelate unit CoN₄ on the carbon substrate, and this unit is assumed to constitute the basic coordination site for an oxygen molecule. Electropolymerized catalysts impart a high level of oxygen reduction ability, probably due to the improved molecular orientation for oxygen coordination and formation of good chelate sites on the graphite surface.     

Effects of a constricted nozzle on the arc phenomena in the TIG welding process

Effects of a constricted nozzle on the arc phenomena in the tungsten inert gas (TIG) welding process are investigated by numerical simulation. the obtained results show that the temperature and velocity of the arc plasma are increased by attaching an additional gas nozzle, which is called the "constricted nozzle". As a result, the iron vapour does not diffuse upward but is transported outward. In addition, the heat transfer to the base metal surface is enhanced.