Synthesis of Ti-based bulk quasicrystal by shock compression

We attempted to produce a Ti₄₅Zr₃₈Ni₁₇ bulk icosahedral (i) quasicrystal by a shock compression technique, in which a single-stage powder gun discharges a flyer plate that consolidates the target powders. The results were also compared with those by a conventional hot-pressing. The powder mixtures for the shock compression were blended by two kinds of methods; that is, gently mixing in a vial, and mechanically alloying by a planetary ball mill. A large bulk i-phase sample, with a Ti₂Ni crystal phase, was synthesized from mechanically alloyed powders after shock compression at a higher flyer velocity, although the conventional hot-pressing at 3 MPa synthesized only the Ti₂Ni phase. For the gently mixed powders, no reaction occured even after shock compression. High-pressure and high-temperature produced during shock compression, and milling process were key factors to obtain the i-phase. The Vickers hardness and the wetting contact angle with pure water under an atmospheric pressure for the bulk sample containing the i-phase were about 7 GPa and about 70°, respectively.     

Bi-Cu film deposition in aqueous solutions

The relatively uniform bismuth-copper film was electrodeposited between −15 and −20 mV in the sulfate electrolyte containing 4 mmol/L bismuth ion and 2 mmol/L copper ion. Only copper was electrodeposited at −5 mV. The dendritic bismuth-copper film was electrodeposited under −20 mV. The cathodic current became constant between −20 and −400 mV. Therefore, bismuth-copper electrodeposition changes from charge transfer controlling to diffusion controlling at −20 mV. On the other hand, the uniform bismuth-copper film was electrodeposited between −5 and −35 mV in the methanesulfonate electrolyte containing 4 mmol/L bismuth ion and 2 mmol/L copper ion. The dendritic bismuth-copper film was electrodeposited under −35 mV. The potential region for good electrodepositon in methanesulfonate electrolyte is wider than that in sulfate electrolyte. Therefore, it is easy to control electrodeposition conditions by using methanesulfonate electrolyte.     

Development of fabrication process for Ag/polydiacetylene (core/shell) hybridized nanocrystals

Core/shell hybridized nanocrystals composed of Ag nanoparticle core and polydiacetylene shell were fabricated successfully by means of “co-reprecipitation/microwave irradiation method”. The hybridized nanocrystals were characterized using transmission electron microscopy (TEM) observation and UV–vis absorption spectroscopy. UV–vis spectral measurements revealed that polydiacetylene shell was the red phase while π-conjugated backbone is distorted. Detailed mechanism of formation of the red phase was discussed.     

Back surface reflectors with periodic textures fabricated by self-ordering process for light trapping in thin-film microcrystalline silicon solar cells

Back surface reflectors (BSRs) with grating structures have been developed to enhance light trapping in thin-film hydrogenated microcrystalline Si (μc-Si:H) solar cells. As a grating structure, a periodic honeycomb-like dimple pattern with a period of ～450 nm has been fabricated on Al substrates by a self-ordering process using anodic oxidation of Al. The clear diffraction effect has been confirmed on the patterned Al from the angle-dependent reflection. From quantum efficiency measurements, we found that the periodically patterned BSR can confine the incident light more effectively than the random textured BSR, especially at longer wavelengths.     

Temperature Dependence of the Raman Spectrum in Lithium Oxide Single Crystal

Temperature dependence of the Raman spectrum of lithium oxide single crystal has been measured over a temperature range of 80 to 1073 K. The frequency shift and the line width of the Raman spectrum in lithium oxide were about 531 and 4.5 cm^-1 at 80 K, respectively. At 1073 K, the frequency shift and the line width attained the values of 464 and 112 cm^-1, respectively. The strong temperature dependence of the frequency shift and line width was compared with data from some crystals with a fluorite structure.     

Protein modelling using a chimera reference protein derived from exons

Bovine pancreatic /S-trypsin (PDB ID-code: 1TPO) which is registeredin the Brookhaven Protein Data Bank (PDB) consists of four exons.The results of homology searches for each exon in the PDB showedthat homologous proteins were tonin (PDB ID-code: 1TON), ratmast cell protease (PDB ID-code: 3RP2_A), kaffikrein A (PDBID-code: 2PKA_B) and kallikrein A (2PKA_B) respectively. Thus,for the three-dimensional structure prediction of 1TPO, a chimeraprotein was constructed from the three proteins mentioned aboveand the 3-D structure prediction was performed using this chimerareference protein. The modelled structure of 1TPO was energeticallyoptimized by molecular mechanics and molecular dynamics simulationand was compared with its X-ray crystal structure registeredin the PDB. The root mean square deviations (r.m.s.d.) of mainchain atoms and the neighbouring active site (5 sphere fromHis57, AsplO2 and Serl95) between the modelled structure andthe X-ray structure were 1.66 and 0.94 respectively. Porcinepancreatic elastase (PDB ID-code: 3EST) which is registeredin the PDB was used as the reference protein and the modelledstructure from 3EST was also compared with the X-ray data. Ther.m.s.d. of main chain atoms and that of the active site were2.14 and 1.18 respectively. These results dearly support thepropriety of this method using the chimera reference protein.     

Photo-induced graft copolymerization of methyl methacrylate on oxidized poly(vinyl alcohol) fiber

Photo-induced graft copolymerization of methyl methacrylate on oxidized poly(vinyl alcohol) fiber was investigated. Oxidation of the fiber sample with sodium hypochlorite or periodic acid led the radical formation by photo-irradiation to intensify markedly. ESR spectra of the irradiated oxidized sample proved that a considerable amount of triplet component radical was contained in it, whereas the unoxidized sample mostly indicated a singlet. The spectra found in the irradiated unoxidized sample was assigned to two radicals, I and II, and for the oxidized sample, to III and IV. The spectrum for I must be a singlet, and a triplet for II, III, and IV. Among the last three, II was less stable toward heat. As the oxidized sample has a high activity for photoinitiation, the radicals of III and IV are presumed to be the sites of graft copolymerization:      

Flexural properties of moldings of rigid polyurethane made by reaction injection molding

Flexural properties of moldings made by Reaction Injection Molding (RIM), which are structural foams consisting of high density skin and low density core, were investigated by three-point bending tests. Two failure modes were observed in bending tests of the moldings made by RIM, and they are classified as follows according to the density ratio of skin layer to core layer: the opposite side of the skin layer to which load was subjected failed by tensile stress: and the same side of the skin layer to which load was subjected failed by compressive stress, causing wrinkling or buckling. Then the conventional composite beam theory was applied to the former failure mode and Hoff s buckling theory to the latter, and equations were derived to predict the flexural properties of the structural foams, which involved buckling from the flexural properties of solid construction. In addition, it has been shown that there exists a density distribution that maximizes the flexural strength of the moldings made by RIM with a given overall density. The results obtained here should be useful to the optimum structural design of moldings made by RIM.