Improving the mechanical properties of isosorbide copolycarbonates by varying the ratio of comonomers

Polycarbonates were synthesized by transesterification polymerization of isosorbide, bisphenol A, and diphenyl carbonate in the presence of n‐BuSn(?O)OH as the catalyst. The polymers were prepared by varying the ratio of the two monomers. The polymers exhibited good thermal stability, rigidity, and strength. The storage moduli for the polymers were 2.6 to 3.2 GPa at 25°C and increased with increasing isosorbide content. The dynamic mechanical analysis indicated that the storage moduli (E′) of the polymers are constant to higher temperatures than that of bisphenol A polycarbonate. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Atomic-scale cellular model and profile simulation of Si etching: Formation of surface roughness and residue

Formation mechanisms for profile anomalies such as surface roughness and residue have been investigated numerically and experimentally for Si etching in Cl₂/O₂ plasmas. The numerical simulation employed an atomic-scale cellular model (ASCeM) based on the Monte Carlo algorithm, which reproduced the feature profile evolution experimentally observed during etching at increased O₂ concentrations. A comparison between simulation and experiment indicated that the local surface oxidation induces surface roughness at the bottom of the feature during etching; then, synergistic effects between surface oxidation and ion scattering in microstructural features on roughened surfaces increase the surface roughness, which in turn causes a number of significant residues or micropillars on bottom surfaces of the feature. In practice, in roughened microstructural features, geometrical shadowing effects for neutral oxygen suppress the surface oxidation at the local feature bottom, where the energetic ion incidence is increased owing to ion scattering on sidewalls of the local feature.     

Required limiting impedance and capacity of fault current limiter installed in customer system with synchronous generator

We investigated the required limiting impedance and capacity of a fault current limiter (FCL) installed at an incoming feeder of a customer system with a synchronous generator in a utility distribution system. It was assumed that two types of FCL were installed, i.e. a resistive type (R‐type) FCL and an inductive type (L‐type) FCL. A fault current out of the customer system and a voltage in the customer system were calculated following a three‐phase, short‐circuit fault occurrence. It was found that the required type of FCL and the required limiting impedance depended on the rated capacity of the generator in order to obtain the suppression of the fault current under 0.1 kA_S and to maintain of customer voltage between 85 and 100% of the nominal voltage (6.6 kV). The capacity of FCL consisting of the smallest limiting impedance is discussed. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Dynamic characteristics of spiral groove bearing spindles: comparison between rotating‐shaft and fixed‐shaft designs

In this paper, two types of spiral groove bearing (SGB) spindles, a rotating‐shaft spindle and a fixed‐shaft spindle, are analysed, and the dynamic characteristics of these two types of spindles are tested and compared. The effects of lubricants on the dynamic characteristics and power consumption of the spindles are considered. It is found that the dynamic characteristics of the fixed‐shaft spindle are much better in terms of non‐repeatable run out than those of the rotating‐shaft spindle. The lubricants are found to have significant effects on both the dynamic characteristics and power consumption of the spindles. Copyright © 2006 John Wiley & Sons, Ltd.     

Si-C-O glass-like compound/exfoliated graphite composites for negative electrode of lithium ion battery

Two low molecular weight silicone compounds, a cyclic type having vinyl groups and a chain-type having Si-H bonds, a catalyst for curing, and a catalyst regulator were mixed. The mixture was impregnated into exfoliated graphite (EG) by sorption, and cured in air at 200 °C. By this process cross-linked silicone coatings were formed on graphite flakes. The composites of Si-C-O glass-like compounds and EG were synthesized by heat treatment of this precursor at 1000-1400 °C for 1 h in argon. The composites formed at 1000-1300 °C were amorphous by XRD and had practically the same chemical composition: Si 44-45, C 27-29, O 25-26, H < 0.5, all in mass%. The ²⁹Si MAS-NMR spectra indicated that the compound formed at 1000 °C was mainly composed of siloxane bonds and amorphous silica, whereas in the compound formed at 1300°C, Si-C bonds and amorphous silica were predominant. The insertion/extraction characteristics of lithium ions for the electrode prepared with composite:poly(vinylidene fluoride) = 90:10 mass% were examined in 1 mol L⁻¹ LiClO₄ solution of ethylene carbonate:diethyl carbonate = 50:50 vol%. High, 650-700 mA h g⁻¹, capacities and steady cycle performance at 50 mA g⁻¹ were achieved with the composites formed at 1250-1300 °C. Capacities of the composites formed at 1200 °C and lower were initially higher but decreased with increasing number of cycles. The composites formed at 1350 °C showed good cycle performance but the capacity was about 500 mA h g⁻¹ due to the formation of β-SiC. Except for the first cycle, the capacity-potential characteristics were similar to those of hard carbons and the coulomb efficiency was 95-100%. For all the composites the capacity was larger than that of graphite (372 mA h g⁻¹) in the range of 50-200 mA g⁻¹. Due to the large insertion capacity of the first cycle, the efficiency was low (60-70%) at first. By short-circuiting the working electrode to the lithium foil counter electrode for a certain period, the irreversible capacity of the first cycle was almost eliminated. It indicates that direct doping of lithium ions into composites is a promising way to increase the efficiency of the first cycle.     

Power generation of the touching Cu/Bi-Te/Cu composites under the periodically alternating temperature gradients

The thermo-emf ΔV of the touching p- and n-type Cu/Bi-Te/Cu composites with different thicknesses of t _Bi-Te and t _Cu was measured as a function of time by alternating the temperature difference ΔT at periods of T = 20, 60, 120, 240 and ∞ sec, where t _Bi-Te was varied from 0.1 to 2.0 mm and t _Cu from 0 to 4.0 mm. As a result, ΔV changes significantly with t _Bi-Te, t _Cu and T. The effective thermo-emf ΔV _eff increases significantly with an increase of 1/T and exhibited a local maximum at 1/T = 1/240 s⁻¹. The resultant | α | and the effective temperature difference ΔT _eff were increased significantly by optimizing t _Bi-Te and t _Cu at 1/T = 1/240 s⁻¹. The power generation ΔW _eff (= ΔV _eff²/4R _calc) estimated using the measured ΔV _eff and calculated R _calc also exhibited a local maximum at 1/240 s⁻¹ for an optimum combination of t _Bi-Te = 0.1 mm and t _Cu = 2.0 mm, so that the maxima ΔW _eff at 1/T = 1/240 s⁻¹ for the p- and n-type composites were 2.28 and 2.92 times higher than those obtained at 1/T = 0 s⁻¹. This significant increase in ΔW _eff is owing to both the increase in ΔT _eff and the increase in ZT due to the increase in |α|. The power generation was thus found to be enhanced significantly by imposing the alternating temperature gradients on touching Cu/Bi-Te/Cu composites.     

Novel hepatitis C virus protease inhibitors: thiazolidine derivatives

This study evaluated the inhibitory effects of thiazolidine derivatives on hepatitis C virus (HCV) protease and other human serine proteases. The inhibition efficacy was tested with a reversed-phase high-performance liquid chromatography (HPLC) assay system using a NS3-NS4A fusion protein as the HCV protease and a synthetic peptide substrate that mimics the NS5A-5B junction. Nine thiazolidine derivatives showed more than 50% inhibition at 50 microg/ml. The most potent derivative was RD4-6250, with 50% inhibition at a concentration of 2.3 microg/ml; this concentration was lower than those of other protease inhibitors reported previously. The most selective derivative was RD4-6205, with 50% inhibition at a concentration of 6.4 microg/ml, a lower concentration than those on other serine proteases (chymotrypsin, trypsin, plasmin, and elastase). These results suggest that the RD4-6205 skeleton is an important structure for inhibitory activity on the HCV protease NS3-NS4A.     

Environmentally friendly coloured materials: cellulose/titanium dioxide/inorganic pigment composite spherical microbeads prepared by viscose phase-separation method

In order to develop environmentally friendly coloured materials, cellulose composite spherical microbeads hybridised with titanium dioxide (TiO₂) particles and inorganic pigment were prepared by a phase-separation method using viscose and an aqueous solution containing sodium polyacrylate. Findings regarding the relationships between cellulose xanthate and the electronic characteristics of TiO₂ particles used in the cellulose/inorganic material composite sphering process are also reported. These findings suggest that the location of TiO₂ particles in cellulose microbeads is related to electrical repulsion between the xanthate (CSS⁻) group and TiO₂. The use of TiO₂ powder as colour pigment is limited, as its colour is white. The cellulose composite spherical microbeads covered with TiO₂ and Fe₂O₃ particles were developed by addition of iron oxide (Fe₂O₃). Their surfaces were viewed by laser microscope and using SEM images. These composite microbeads retained the photocatalytic property of TiO₂. Cellulose/TiO₂/Fe₂O₃ composite spherical microbeads with both colour function and photocatalytic properties were successfully prepared.     

Development of the Water Cooled Ceramic Breeder Test Blanket Module in Japan

The development of a Water Cooled Ceramic Breeder (WCCB) Test Blanket Module (TBM) is being performed as one of the most important steps toward DEMO blanket in Japan. For the TBM testing and evaluation toward DEMO blanket, the module fabrication technology development by a candidate structural material, reduced activation martensitic/ferritic steel, F82H, is one of the most critical items from the viewpoint of realization of TBM testing in ITER. In Japan, fabrication of a real scale first wall, side walls, a breeder pebble bed box and assembling of the first wall and side walls have succeeded. Recently, the real scale partial mockup of the back wall was fabricated. The fabrication procedure of the back wall, whose thickness is up to 90 mm, was confirmed toward the fabrication of the real scale back wall by F82H. Important key technologies are almost clarified for the fabrication of the real scale TBM module mockup. From the view point of testing and evaluation, development of the technology of the blanket tritium recovery, development of advanced breeder and multiplier pebbles and the development of the blanket neutronics measurement technology are also performed. Also, tritium production and recovery test using D-T neutron in the Fusion Neutronics Source (FNS) facility has been started as the verification test of tritium production performance. This paper overviews the recent achievements of the development of the WCCB TBM in Japan.     

Microwave dielectric properties and crystal structures of Mg0.7Al2.2O4 and Mg0.4Al2.4O4 ceramics with defect structures

Mg_0.7Al_2.2O₄ and Mg_0.4Al_2.4O₄ ceramics with cation vacancies were synthesized using the molten salt method, and the relationships between the microwave dielectric properties and crystal structures of these materials were investigated. The ²⁷Al NMR spectra of these ceramics indicate that the preferential occupation of tetrahedral sites by Al³⁺ cations was enhanced by the introduction of cation vacancies. The λ values of Mg_0.7Al_2.2O₄ and Mg_0.4Al_2.4O₄ ceramics fired at 1600°C, which correspond to the fraction of Al³⁺ cations in tetrahedral sites, were 0.37 and 0.60, respectively. Crystal structure refinements using the Rietveld method suggest that cation vacancies are preferentially located at octahedral sites in both ceramics. The ε_r and Q·f values of a Mg_0.7Al_2.2O₄ ceramic fired at 1600°C were 7.7 and 201 111 GHz, respectively, while those of a Mg_0.4Al_2.4O₄ ceramic fired at 1600°C were 7.5 and 232 301 GHz, respectively. These data demonstrate that the preferential occupation of tetrahedral sites by Al³⁺ cations following the introduction of cation vacancies enhances the Q·f value.