Superstructure and mechanical properties of nylon 66 microfiber prepared by carbon dioxide laser‐thinning method

Nylon 66 microfibers were obtained by a carbon dioxide (CO₂) laser‐thinning method. A laser‐thinning apparatus used to continuously prepare microfibers consisted of spools supplying and winding the fibers, a continuous‐wave CO₂‐laser emitter, a system supplying the fibers, and a traverse. The diameter of the microfibers decreased as the winding speed increased, and the birefringence increased as the winding speed increased. When microfibers, obtained through the laser irradiation (at a power density of 8.0 W cm^?2) of the original fiber supplied at 0.23 m min^?1, were wound at 2000 m min^?1, they had a diameter of 2.8 μm and a birefringence of 46 × 10^?3. The draw ratio calculated from the supplying and winding speeds was 8696×. Scanning electron microscopy showed that the microfibers obtained with the laser‐thinning apparatus had smooth surfaces not roughened by laser ablation that were uniform in diameter. To study the conformational transition with winding speed, the changes in trans band at 936 cm^?1 and gauche band at 1136 cm^?1 were measured with a Fourier transform infrared microscope. The trans band increased as the winding speed increased, and the gauche band decreased. Young's modulus and tensile strength increased with increasing winding speed. The microfiber, which was obtained at a winding speed of 2000 m min^?1, had a Young's modulus of 2.5 GPa and tensile strength of 0.6 GPa. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 802–807, 2006     

High temperature zone‐drawing of nylon 66 microfiber prepared by CO2 laser‐thinning

A high temperature zone‐drawing method was applied to a nylon 66 microfiber, obtained by using CO₂ laser‐thinning, to develop its mechanical properties. The microfiber used for the high temperature zone‐drawing was prepared by winding at 150 m min^?1 the microfiber obtained by irradiating the laser at 4.0 W cm^?2 to an original fiber with a diameter of 50 μm, and had a diameter of 9.6 μm and a birefringence of 0.019. The high temperature zone‐drawing was carried out in two steps; the first drawing was carried out at a temperature of 230°C at supplying and winding speeds of 0.266 and 0.797 m min^?1, the second at 250°C at supplying and winding speeds of 0.266 and 0.425 m min^?1, respectively. The diameter of the microfiber decreased, and its birefringence increased stepwise with the processing. The high temperature zone‐drawn microfiber finally obtained had a diameter of 4.2 μm, a birefringence of 0.079, total draw ratio of 4.8, tensile modulus of 12 GPa, and tensile strength of 1.0 GPa. The wide‐angle X‐ray diffraction photograph of the drawn microfiber showed the existence of highly oriented crystallites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 42–47, 2006     

On the scaling-up of a two-stage air blown entrained flow coal gasifier

A two-stage air blown entrained flow gasifier is being developed in Japan for the IGCC process. However, its scale-up up faces significant difficulties because of ash/slag deposition problems. The ash/slag deposition in the gasifier depends on both the ash properties and entrainment produced by the swirling gas flow. Therefore, the flow hydrodynamics are critical issues for the control of the ash behavior. In this paper, a comprehensive simulation model is used to examine the effects of the gasifier geometry and jet configuration on the flow hydrodynamics in order to control the ash deposition on the gasifier walls. A swirl number for the multi-stage injection swirling gas flow is defined and proved to be the most important hydrodynamic scaling law for the entrained flow gasifier.     

Enhanced performance of organic light-emitting diodes by inserting wide-energy-gap interlayer between hole-transport layer and light-emitting layer

We demonstrated that driving voltages, external quantum efficiencies, and power conversion efficiencies of organic light-emitting diodes (OLEDs) are improved by inserting a wide-energy-gap interlayer of (4,4′-N,N′-dicarbazole)biphenyl (CBP) between a hole-transport layer of N,N-di(naphthalen-1-yl)-N,N′-diphenyl-benzidine (α-NPD) and a light-emitting layer of tris(8-hydroxyquinoline)aluminum. By optimization of CBP thicknesses, the device with a 3-nm-thick CBP layer had the lowest driving voltage and the highest power conversion efficiency among the OLEDs. We attributed these improvements to enhancement of a carrier recombination efficiency and suppression of exciton–polaron annihilation. Moreover, we found that the degradation of the OLEDs is caused by decomposition of CBP molecules and excited-state α-NPD molecules.     

Plastic deformation and creep damage evaluations of type 316 austenitic stainless steels by EBSD

The inspection method of plastic and/or creep deformations has been required as the quantitative damage estimation procedure for structural components especially used in electric power plants. In this study, the method using electron backscatter diffraction (EBSD) was applied to the deformation and damage evaluation of austenitic stainless steels strained by tension or compression at room temperature and also tested in creep at high temperature. It was found that the value of Grain Average Misorientation (GAM) which showed the average misorientation for the whole observed area including over several dozen grains, was a very useful parameter for quantifying the microstructural change as either the plastic or creep strain increased. The unique linear correlation was obtained between GAM and plastic strain in tension and compression. For creep damage evaluation, the difference of grain average misorientation from the value of the unstrained specimen (ΔGAM) showed an excellent correlation with the inelastic strain below strain at which the tertiary creep began.     

Encapsulation of glucose oxidase (GOD) in polyelectrolyte complexes of chitosan–carrageenan

The purpose of this study was to investigate the potential ability of carrageenan (κ-, ι-, λ-) and chitosan to form a controlled-release system for glucose oxidase (GOD). GOD was encapsulated in chitosan/carrageenan complexes at charge ratios (+/?) of 3 and 5 in mildly acidic solution. The encapsulation efficiency and activity of the loaded GOD were investigated. Among the different complexes prepared, chitosan/κ-carrageenan complex showed high encapsulation efficiencies of 79% and 62.5% at charge ratios of 3 and 5, respectively. The order of encapsulation efficiency decreases toward chitosan/λ-carrageenan complex (κ > ι > λ). After treatment with chitosanase and pepsin solutions, the activity of encapsulated glucose oxidase (GOD) was preserved for all complexes. The chitosan/κ-carrageenan complex was able to preserve 80.2% of GOD activity in pH 1.2 solution, 73.3% in chitosanase solution and 66.4% in pepsin solution. Controlled release of GOD was observed when the complexes were treated with different physiological and enzyme solutions; the complex of chitosan/κ-carrageenan had the lowest release rate of GOD. The simple preparation of chitosan/carrageenan complexes and their ability to protect protein integrity under acidic conditions make them a promising drug delivery system for the oral administration of peptides and proteins.     

Enhancement of the actuation performance of dielectric triblock copolymers modified with additives

To enhance actuation performance without prestrain, an elastomeric acrylic triblock copolymer, poly(methyl methacrylate)‐block‐poly(n‐butyl acrylate)‐block‐poly(methyl methacrylate), was modified with two kinds of additives, oligomeric poly(n‐butyl acrylate) and the plasticizer dibutyl sebacate. An actuator modified with those additives showed about 6% strain, whereas the unmodified actuator showed only 1% strain for the same applied electric field without prestrain. In addition, actuation was attained at lower critical electric field strength (625 and 1000 V mm^?1 for modified and unmodified actuators, respectively). Upon increasing the amounts of the additives, the electrically induced actuation velocity and degree of deformation increased. These results are explained by the dielectric and mechanical properties of the elastomers. The dielectric constants for elastomers modified with dibutyl sebacate were larger than those for elastomers modified with oligomeric poly(n‐butyl acrylate). The initial tensile stresses of both of the modified elastomers were much smaller than that of unmodified elastomer. The results provide a route to enhancing actuation performance of dielectric elastomers without prestrain. Copyright © 2011 Society of Chemical Industry     

Consolidation of Al2O3–GdAlo3 eutectic powder prepared from induction-melted solid and strength at high temperatures

A eutectic powder of Al₂0₃–GdA10₃ was melted using a Mo crucible by induction heating. The melt was slowly solidified, resulting in a eutectic solid with coarse Al₂0₃ and GdAl0₃ phases. The eutectic solid was ground and sieved into 3–44 µm and 64–124 µm particles. The powders were consolidated to produce a eutectic composite by spark plasma sintering. Mechanical properties of the consolidated eutectic composite were measured at room temperature. High temperature strength was obtained at temperatures up to 1673 K. Superplastic deformation of the eutectic composite was not observed on stress–strain curves at 1673 K, but did occur in the case of a conventional composite at 1573 K.     

Catechol derivatives inhibit the fibril formation of amyloid-β peptides

The inhibition of fibril formation of amyloid β proteins (Aβ) would be attractive therapeutic targets for the treatment of Alzheimer's disease (AD). Dopamine (DA) and other catechol derivatives were used as inhibitory factors for Aβ fibril formation. The fibril formation of Aβ was monitored by Thioflavin T fluorescence, a transmission electron microscopy (TEM) and a total internal reflection fluorescence microscopy (TIRFM). Catechol and its derivatives showed the dose-dependent inhibitory effects on the spontaneous Aβ fibril formation. The inhibitory activity depended on the chemical structure of catechol derivatives both in the presence and absence of the liposome a model of biomembrane. Formation of catechol quinone-conjugated-Aβ adduct by a Schiff-base is a key step for the inhibition effect of Aβ fibril formation.     

Permeation properties of hydrogen and water vapor through porous silica membranes at high temperatures

Silica and cobalt‐doped silica membranes that showed a high permeance of 1.8 × 10^?7 mol m^?2 s^?1 Pa^?1 and a H₂/N₂ permeance ratio of ～730, with excellent hydrothermal stability under steam pressure of 300 kPa, were successfully prepared. The permeation mechanism of gas molecules, focusing particularly on hydrogen and water vapor, was investigated in the 300–500°C range and is discussed based on the activation energy of permeation and the selectivity of gaseous molecules. The activation energy of H₂ permeation correlated well with the permeance ratio of He/H₂ for porous silica membranes prepared by sol–gel processing, chemical vapor deposition (CVD), and vitreous glasses, indicating that similar amorphous silica network structures were formed. The permeance ratios of H₂/H₂O were found to range from 5 to 40, that is, hydrogen (kinetic diameter: 0.289 nm) was always more permeable than water (0.265 nm). © 2010 American Institute of Chemical Engineers AIChE J, 2011