Synthesis and electronic property of platinum nanowire and nanoparticle in mesoporous silica template

Platinum nanowires and nanoparticles were selectively synthesized in mesoporous silicas FSM-16 and HMM-1. The nanowires are 3 nm in diameter and several hundred nm to μm in length with high crystallinity. Pt nanowires and nanoparticles can be isolated by dissolving silica matrix with HF. The Pt wires extracted from organosilica HMM-1 have a nanonecklace structure, while the wires from siliceous FSM-16 have a nanorod structure. The extracted Pt nanoparticles (3 nm in size) on HOPG show the Coulomb staircase phenomena in STM/STS analysis. The mechanism for formation of the Pt nanowires is based on the migration of Pt ions in the mesoporous channels.     

Sintering Kinetics at Isothermal Shrinkage: II, Effect of Y2O3 Concentration on the Initial Sintering Stage of Fine Zirconia Powder

The shrinkage behavior of fine zirconia powders containing 2.9 and 7.8 mol% Y₂O₃ was investigated to clarify the effect of Y₂O₃ concentration on the initial sintering stage. The shrinkage of powder compact was measured under both conditions of constant rates of heating (CRH) and constant temperatures. CRH measurements revealed that when the Y₂O₃ concentration of fine zirconia powder increased, the starting temperature of shrinkage shifted to a high temperature. Isothermal shrinkage measurements revealed that the increase in Y₂O₃ concentration causes the shrinkage rate to decrease. The values of activation energy ( Q ) and frequency-factor term (β₀) of diffusion at initial sintering were estimated by applying the sintering-rate equation to the isothermal shrinkage data. When the Y₂O₃ concentration increases, both Q and β₀ of diffusion increase. It is, therefore, concluded that the increase in Y₂O₃ concentration of fine zirconia powder decreases the shrinkage rate because of increasing Q of diffusion at the initial stage of sintering.     

Estimation of the Surface Energy of Polymer Solids

The methods to estimate the surface tension of polymer solids using contact angles have been reviewed in the first part. They are classified into the following three groups depending on the theories or the equations applied: (1) the methods using the Young's equation alone, (2) the methods using the combined equation of Young and Good-Girifalco, and (3) the methods using the equations of work of adhesion. Some notes and comments are given for each method and results are compared with each other. The two-liquids method for rather high energy surface is also introduced.

Next, some new possibilities to evaluate the surface tension of polymer solids are presented by our new contact angle theory in consideration of the friction between a liquid drop and a solid surface. The advancing and receding angles of contact (θ _a and θ _r ) are explained by the frictional tension γ_F and accordingly two kinds of the critical surface tension γ_C (γ_Ca and γ_Cr ) are given.

This work has shown that one of the recommendable ways to evaluate γ_S is either the maximum γ_LV cos θ_a or the maximum γ_C using the advancing contact angle θ_a alone, and another way is the arithmetic or the harmonic mean of the γ_Ca and γ_Cr . A depiction to determine the γ_C such as ln(1 + cos θ₀ ) vs. γ_LV with cos θ₀ = (cos θ₀ + cos θ_r )/2 has also been proposed.     

Influence of the conditions of storage and cooking on growth,invasion and survival of Salmonella enteritidis in eggs

Basal studies for the confirmation of sanitary rules in the kitchen were performed, focusing on preventing an outbreak of food poisoning due to eggs contaminated with Salmonella Enteritidis (SE), using hen and quail eggs. SE did not grow at 5 degrees C but grew markedly at 25 degrees C in eggs. The invasion and growth of SE were marked under very humid conditions regardless of whether the eggshell was damaged. The invasion of SE into egg also occurred when eggs were taken in and out of the refrigerator. Moreover, SE was spread immediately to all non-contaminated eggs when SE-contaminated eggs were cracked into a bowl with non-contaminated eggs. In homemade mayonnaise containing 15% vinegar, sterilization took several hours to occur. On a stainless-steel bowl, SE survived for 2 weeks or more. These findings suggest that it is necessary to pay attention to secondary contamination.     

Dielectric properties of Permalloy granular composite materials

Dielectric and electrical properties of Permalloy granular composite materials have been studied considering the application to left-handed meta-materials. Surface oxidized Permalloy particles have high surface electrical resistance; the eddy current effect in the composite structure is suppressed. The electrical conductivity of compacted Permalloy particles increases with increasing temperature and indicates the semiconductive layer formation on the particle. The low frequency ac electrical conductivity of Permalloy composite materials shows a drastic increase in the particle content between 50 and 60 vol.%. Electrical permittivity spectra of Permalloy composites show a non-metallic characteristic and the enhancement of permittivity is observed with increase of Permalloy particle content.     

Toughening of cyanate ester resin by N‐phenylmaleimide–N‐(p‐hydroxy)phenyl‐maleimide–styrene terpolymers and their hybrid modifiers

N‐Phenylmaleimide–N‐(p‐hydroxy)phenylmaleimide–styrene terpolymer (HPMS), carrying reactive p‐hydroxyphenyl groups, was prepared and used to improve the toughness of cyanate ester resins. Hybrid modifiers composed of N‐phenylmaleimide–styrene copolymer (PMS) and HPMS were also examined for further improvement in toughness. Balanced properties of the modified resins were obtained by using the hybrid modifiers. The morphology of the modified resins depends on HPMS structure, molecular weight and content, and hybrid modifier compositions. The most effective modification of the cyanate ester resin was attained because of the co‐continuous phase structure of the modified resin. Inclusion of the modifier composed of 10 wt% PMS (M_w 136 000 g mol^?1) and 2.5 wt% HPMS (hydroxyphenyl unit 3 mol%, M_w 15 500 g mol^?1) led to 135% increase in the fracture toughness (K_IC) for the modified resin with a slight loss of flexural strength and retention of flexural modulus and glass transition temperature, compared with the values for the unmodified resin. Furthermore, the effect of the curing conditions on the mechanical and thermal properties of the modified resins was examined. The toughening mechanism is discussed in terms of the morphological and dynamic viscoelastic behaviour of the modified cyanate ester resin system. © 2001 Society of Chemical Industry     

Lateral Inhomogeneity in the Electronic Structure of a Conjugated Poly(3‐hexylthiophene) Thin Film

How annealing influences the morphology of a highly regioregular poly(3‐hexylthiophene) (RR‐P3HT) film at the substrate interface as well as the lateral inhomogeneity in the electronic structure of the film are elucidated. Whereas previous studies have reported that high‐molecular‐weight (MW) RR‐P3HT films tend to show low crystallinity even after annealing, it is found that high‐MW RR‐P3HT does show high crystallinity after annealing at high temperature for a long time. Photoemission electron microscopy (PEEM), X‐ray photoemission spectroscopy, and ultraviolet photoemission spectroscopy results clearly resolve a considerable lateral inhomogeneity in the morphology of RR‐P3HT film, which results in a variation of the electronic structure depending on the local crystallinity. The PEEM results show how annealing facilitates crystal growth in a high‐MW RR‐P3HT film.