Electrochemical Fabrication of Metallic Nanowires and Metal Oxide Nanopores

A nuclear track etched polycarbonate membrane filter with numerous cylindrical nanopores was applied as a nanoporous template for growing metallic nanowires. Nickel, cobalt, and iron nanowires were electrodeposited into the cylindrical nanopores. Cathodic polarization curves were measured to determine an optimum condition for growing nanowires. The shape of nanowires was observed using scanning electron microscope (SEM) and the crystal structure was analyzed using transmission electron microscopy (TEM). Diameter and length of nanowires corresponded to those of nanopores and each nanowire was composed of a single crystal. Anodized aluminum oxide films were also fabricated as a novel nanoporous template. The pore length and diameter was controlled changing anodizing conditions. Ordering behavior of nanopores array in an anodized aluminum oxide film was also investigated to make a novel nanoporous template with a highly ordered honeycomb array of nanopores.     

Surface wetting phenomena of plasma polymer-coated sheets of poly(l-lactic acid)/poly(butylene succinate)

Water-repellent surfaces were fabricated on blend sheets of poly(l-lactic acid)/poly(butylene succinate) with various blending ratios by the successive processing; (1) plasma etching, followed by (2) the hydrophobic plasma polymer coating. Rough morphology was formed effectively on the mosaic structured surface of blend sheets via the oxidative etching, and advanced water repellency was achieved after the thin membrane coating was synthesized with a hydrophobic plasma polymer coating by use of hexamethyldisiloxane or hexamethyldisilazane. High water repellency is expressed through the columnar hair-like structured model, where the air-water surface interaction in the voids is taken into account.     

Enhancement of turbulent jet diffusion flame blowout limits by annular counterflow

The effects of a proposed combustion technique, named as annular counterflow, on the enhancement of jet diffusion flame blowout limits were investigated by a series of experiments conducted for the present study. Annular counterflow was formed in a concentric annulus, in which fuel jet was ejected from a nozzle and air was sucked into an outer cylinder encompassing the nozzle. Three fuel nozzles and outer cylinders of different sizes were utilized to perform the experiments. Schlieren technique and normal video filming were employed for the visualization of diverse flame morphologies triggered by the said flow. Gas samplings were taken and scrutinized by the use of a gas chromatograph. Results showed that the blowout limits can be enhanced dramatically by an increase in volume flow rates of air‐suction. Mixing enhancement is achieved with frequent and strong outward ejection of fluids from the cold jet when this technique is applied. The blowout limits are further extended when the diameter of outer cylinders becomes smaller and/or that of the fuel nozzle becomes larger. The base widths of lifted flames were found to be narrower in the interim of annular counterflow application. The rates of increase in flame lift‐off heights and base widths along with an increase in fuel flow velocities become sluggish when the volume flow rates of air are increased. The amount of fuel that was sucked into the outer cylinder was found to be negligible and trivial. A model based on annular and coaxial jet was developed to predict the lifted flame base width and blowout limits. The coincidence between the prediction and experimental results unambiguously validates that the momentum of air‐suction dominates the beneficial effect. Copyright © 2001 John Wiley & Sons, Ltd.     

Fatigue crack propagation behavior in four-points bending specimens with multiple parallel edge notches at regular intervals

Fatigue crack propagation tests were performed using specimens with multiple parallel edge notches at regular intervals. Fatigue pre-cracks of uniform length were successfully introduced by eccentric tension-compression loading. Fatigue crack propagation tests were carried out under four-points bending loading. Obtained crack propagation behavior was simulated by using newly developed stress intensity factor equations for multiple parallel edge cracks with alternately different lengths. Simulated results showed a good agreement with the experiment for specimens with relatively broad crack intervals, while for specimens with narrow crack intervals showed a different tendency from the experiment when crack lengths became long.     

Characteristics of porous polymer composite columns prepared by radiation cast-polymerization

Porous polymer composite columns having porous structure were prepared by radiation cast-polymerization of hydrophilic monomers at low temperature and their characteristics were studied. The porosity of the polymer increased with decreasing monomer concentration. The elution time of water in the polymer column increased with increasing monomer concentration and with decreasing irradiation temperature. The elution time was dependent on the degree of hydration of the polymer. The polymer with a degree of hydration of 0.2 to 0.4 gave the minimum elution time. The elution time decreased with the addition of porous inorganic substances.     

Ultrafine particles of the ZrO2-SiO2 system prepared by the spray-ICP technique

Ultrafine powders of the ZrO₂-SiO₂ system prepared by spraying aqueous mixed solutions of ZrO(NO₃)₂·2H₂O and silicone oil into an ultrahigh temperature inductively coupled plasma (the spray-ICP technique) have been investigated in connection with particle growth and phase change caused by heat treatment. The prepared powders were composed of roundish ultrafine particles 10 to 20 nm in size, and their components were tetragonal ZrO₂ (t-ZrO₂) and amorphous SiO₂ (a-SiO₂).a-SiO₂ alone did not crystallize below 1400° C, though the particles grew above 900° C.t-ZrO₂ converted to monoclinic ZrO₂ (m-ZrO₂) above 400° C, also followed by particle growth. On the other hand composite powders oft-ZrO₂ anda-SiO₂ exhibited no particle growth below 1200° C. Above 1200° Ct-ZrO₂ converted tom-ZrO₂, and its amount decreased with an increase in SiO₂ content. At 1400° C particle growth occurred, and the round particles of ZrO₂ were dispersed in ana-SiO₂ glass medium. These results indicate that ZrO₂ and SiO₂ mutually block particle growth, and that SiO₂ contributes to the quenching oft-ZrO₂ by keeping the particles of ZrO₂ within the critical particle size oft-ZrO₂.     

An Intrinsically Fluorescent Recognition Ligand Scaffold Based on Chaperonin Protein and Semiconductor Quantum‐Dot Conjugates

Genetic engineering of a novel protein–nanoparticle hybrid system with great potential for biosensing applications and for patterning of various types of nanoparticles is described. The hybrid system is based on a genetically modified chaperonin protein from the hyperthermophilic archaeon Sulfolobus shibatae. This chaperonin is an 18‐subunit double ring, which self‐assembles in the presence of Mg ions and ATP. Described here is a mutant chaperonin (His‐β‐loopless, HBLL) with increased access to the central cavity and His‐tags on each subunit extending into the central cavity. This mutant binds water‐soluble semiconductor quantum dots, creating a protein‐encapsulated fluorescent nanoparticle. The new bioconjugate has high affinity, in the order of strong antibody–antigen interactions, a one‐to‐one protein–nanoparticle stoichiometry, and high stability. By adding selective binding sites to the solvent‐exposed regions of the chaperonin, this protein–nanoparticle bioconjugate becomes a sensor for specific targets.     

Adsorption properties of amphiphilic polyoxyalkylenated dimethylpolysiloxane derivatives on keratin

Adsorption properties of two types of dimethylpolysiloxane backbone derivatives, perfluoroalkyl polyoxyethylenated dimethylpolysiloxane (FPD) and polyoxyethylenated dimethylpolysiloxane (PD), onto keratin surfaces were investigated. Both polymers are amphiphilic, since they possess hydrophilic polyoxyethylene groups. FPD contains a perfluoroalkyl group that provides both water-and oil-repellent properties, whereas PD lacks these groups. Adsorption properties of these polymers onto keratin surfaces are considered a good index to evaluate these compounds as nonionics used in hair-coating agents, since keratin is a major component of hair. FPD was more likely to be adsorbed and less likely to be eliminated from the keratin surface than PD. Once FPD had been adsorbed onto the keratin surface, it was very slowly washed from the surface when it was immersed in stationary water, whereas PD polymers were quickly washed from the keratin surface. Even in running water, rapid elimination of FPD was not observed. The strong resistance to loss of FPD after washing with a large quantity of water may be due to the water-repellent nature of the perfluoroalkyl groups. As a comparison, FPD adsorption onto a glass surface was also investigated. The affinity to the glass surface was found to be less than to the keratin surface.     

Synthesis of zirconium diboride platelets from mechanically activated ZrCl4 and B powder mixture

ZrB₂ platelets were prepared by mechanochemical processing a zirconium (IV) chloride–boron mixture with subsequent annealing from 800 °C to 1200 °C. The phases present were identified by X-ray diffraction. The size and morphology of the synthesized ZrB₂ powders were characterized by scanning electron and transmission electron microscopy. At 800 °C, ZrO₂ was detected in absence of ZrB₂. At or above 1000 °C, ZrCl₄–B converted to ZrB₂. Moreover, at 1200 °C, ZrCl₄–B completely converted to ZrB₂ without trace quantities of residual ZrO₂. The synthesized ZrB₂ consisted of platelets with a diameter of 0.1–2.1 μm and a thickness of 40–200 nm.