Synthesis of Eu-Doped CaAlSiN3 from Ammonometallates: Effects of Sodium Content and Pressure

We report the effects of synthesis pressure and sodium content in reactants on the lattice structure and photoluminescence properties of Eu-doped CaAlSiN₃, a red phosphor, synthesized by a low-temperature process (up to 800°C) from ammonometallates. The lattice parameters and average and anisotropic values of crystallite size and lattice strains were calculated by refining against X-ray diffraction data. These values are correlated with synthesis pressure and sodium content. The light emission was shown to be a result of a compromise between the effects of the lattice cell dimensions and the strains. The sample obtained at Na/Ca=2.0 under 100 MPa showed the best photoluminescence emission among all the produced samples. On the other hand, our analysis suggests the optimum pressure and Na/Ca ratio for a maximum light emission could be around 60 MPa and 2, respectively.     

Cellulose/polypropylene composites: Influence of the molecular weight and concentration of oxidatively degraded and maleated polypropylene compatibilizers on tensile behavior

To improve interactions between fibrous cellulose (FC) and polypropylene (PP), oxidatively degraded polypropylene (DgPP) and maleated polypropylene (MAPP) were studied as compatibilizers. Both compatibilizers had the same mechanism, using esterification between the OH group in FC and the reactive (γ‐lactone, acid, and maleic anhydride) groups in the compatibilizers. However, the adhesion style with the ester bond was considerably different because of the arrangements of the reactive groups. DgPP had reactive groups at the polymer chain end, and the tensile behavior of the FC/PP/DgPP composite exhibited comparatively ductile behavior. However, MAPP had inner reactive groups, and the tensile behavior of the FC/PP/MAPP composite was quite brittle. Observation of these fracture surfaces suggested that the adhesion performance of the interface between FC and PP was strongly influenced by the arrangements of the reactive group. In addition, the performance was influenced by the molecular weight of DgPP and by the content of maleic anhydride groups in MAPP. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The effect of one slow-fast strain cycle on the fatigue crack growth behavior of SUS 304 stainless steel at elevated temperature

Fatigue crack growth behavior of SUS 304 stainless steel when one slow-fast strain cycle was introduced to the fast-fast strain cycles was investigated at 600 °C. It was found that the fatigue crack growth rate in the fast-fast strain cycles was accelerated by the introduction of one slow-fast strain cycle. It was also found that there was a linear relationship between the size of the region where the acceleration occurred and the value of creepJ-integral range, ΔJ_C, which was produced just when one slow-fast strain cycle was introduced. To investigate the above acceleration, the longitudinal section through the specimen was observed. It was shown that the wedge-type cracks were produced at the grain boundaries and that they contributed to the above acceleration. Based on the results thus obtained, the predicting procedure of crack growth curve when one slow-fast strain cycle was introduced to the fast-fast strain cycles was proposed. As the result, it was shown that the predicted crack growth curve was in good agreement with the experimental one.     

Lower hybrid heating and current drive system for a tokamak reactor

A lower hybrid heating system has been designed for heating a tokamak reactor to ignition and for sustaining steady-state operation by driving the toroidal plasma current. The power spectrum from an active/passive waveguide grill is computed, and the resulting equilibrium current density profile is computed from a full electromagnetic WKB analysis of wave propagation in a cylinder. The corresponding toroidal current profile is a low-current equilibrium which is stable to various ideal modes at an economically acceptable beta. The electronic circuitry is designed to minimize the electric power required for current drive, and the resulting design appears to provide reliable operation in a reactor environment. The same system can drive current during reactor startup if some of the waveguides are modified slightly. A typical sequence of startup equilibria is calculated.     

New thermoplastic dual-coextrusion-coating system for optical-fibre drawing

A new thermoplastic dual-coextrusion-coating technique consisting of a soft thermoplastic rubber primary coating and a hard secondary coating has been proposed as an in-line coating system with fibre drawing. The use of a low linear-expansion-coefficient polymer as the hard secondary coating is a necessary condition for obtaining no microbending loss of the dual-coated fibres.     

Current views on the structure and crystallization of metallic glasses

An attempt has been made in this review to cover recent information on the structure of metallic glasses (amorphous metals) obtained by X-ray diffraction. Based on the experimental data, the partial structure factors of a binary metallic glass are given. Various characteristics such as crystallization processes, thermal effects and alloying effects are also discussed.     

Preparation of a silica gel–carbon black composite by the sol–gel process in the presence of polymer-grafted carbon black

This paper is concerned with the preparation of a silica gel–carbon black composite by the sol–gel process, which consists of tetraethoxysilane and polymer-grafted carbon black. Polymer-grafted carbon black was synthesized by three methods: (1) cationic polymerization of N-vinyl-2-pyrrolidone, (2) cationic ring-opening polymerization of 2-methyl-2-oxazoline, and (3) radical polymerization of glycidyl methacrylate followed by reaction of glycidyl groups in the grafted polymer chains with 3-aminopropyltriethoxysilane. The polycondensation of tetraethoxysilane proceeded under acidic conditions in the presence of polymer-grafted carbon black to give a deep black silica gel–carbon black composite. The more the content of untreated carbon black was increased, the more the gelation time was shortened. On the contrary, gelation was retarded by grafted polymer chains on the carbon black surface in the case of polymer-grafted carbon black. The scratch hardness of the resulting silica gel–carbon black composite was almost equal regardless of the carbon black content in the presence of untreated carbon black, whereas it was liable to decrease as the content of polymer-grafted carbon black increased. The solvent adsorption properties of the silica gel–polymer-grafted carbon black composite varied with the solubility of grafted polymer chains on the carbon black surface towards the immersion solvent. © 1998 Chapman & Hall     

Fabrication of Crack-Free C12A7 Nano-Ceramics Composite from Eutectic Glass in the C12A7–CaYAlO4 System

Crack formation in the C12A7 nano-composite during crystallization was successfully avoided by using the eutectic glass in the C12A7–CaYAlO₄ system. The crystal phases from the eutectic glass were identified to be C12A7 (major phase) and CaYAlO₄ (minor phase) by X-ray diffraction and high-resolution transmission electron microscope. It was indicated that origin of cracks upon crystallization of C12A7 glass was the volume expansion caused by crystallization of C12A7 in the glass and the cracking could be avoided by the volume shrinkage by crystallization of CaYAlO₄. By using a conventional molding technique, we have also succeeded to fabricate a bulk C12A7 composite with arbitrary shapes.