Advanced Materials Research Vols. 476-478

Abstract: The measurements of magneto-impedance,, have been performed, at the frequency f = 1 MHz, on amorphous and nanocrystalline wires under the application of torsion stress ( = 0-125 rad/m). At , exhibit single-peak due to the axial easy direction of the wires. The torsion-impedance,, is defined as the impedance change with at the condition of the axial field H = 0. We found that at the low torsion , shows a maximum at = 0.87 and 5.23 rad/m for the amorphous and the nanocrystalline samples, respectively; with increasing ,of the amorphous wire decreases monotonously and tends to the saturation, but of the nanocrystalline sample shows two more peaks at = 70.65 and 104.67rad/m. These results have been discussed considering the modification of domain structure by the applied torsion.

Abstract: The development works on high temperature lead free solder are mostly discussed nowadays. To replace the current high temperature lead free solders, further research need to be done. A great deal of effort has been put into the development of lead free solder alloys. Bi (Bismuth) and Sb (Antimony) solder system proved as one of the promising candidates for electronic assembly. Melting temperature of three Bi-Sb solder alloys studied in this research enhanced their potential as the alternative solder candidates for high temperature lead free solder. At interface, Cu3Sb IMC layer was formed for 95Bi-5Sb solder alloy. Spallation of Cu3Sb IMC layer took placed with the results of Cu3Sb IMC also found in the solder bulk. Analysis of 97.5Bi-2.5Sb solder alloy classified as no metallurgical reaction at the interface and only the mechanical joining existed at the interface. The dissolution of Cu from subtrate affected the formation of Cu rich phase and the unstable Bi-Cu rich phase phenomena act as the isothermal product found in solder bulk. Mechanical grain boundary grooving observed in 98.5Bi-1.5Sb solder alloys at interface. Different compositions of Bi-Sb solder alloys resulted in different types of microstructures at interface and in solder bulk after reflow.

Abstract: The biomorphic ZnO were prepared with zinc nitrate using radish slices as the biotemplate. Microstructure, morphology and optical properties of the ZnO were studied using XRD, FTIR, FE-SEM and PL spectra. It is found that ZnO are wurtzite structure, the average diameter and length are 0.5μm and 2μm, respectively. There are a large number of small particles on the grain surface, the size of small particles is about100nm. The PL spectra of the biomorphic ZnO consists of two peaks centered at 394nm and 448nm, and the 394nm peak exhibits an obvious red shift compared with hexageonal cone-shaped ZnO.

Abstract: Computing sound field from an arbitrary radiator is of interest in acoustics, with many significant applications, one that includes the design of classical projectors and the noise prediction of underwater vehicle. To overcome the non-uniqueness of solution at eigenfrequencies in the boundary integral equation method for structural acoustic radiation, wave superposition method is introduced to study the acoustics. In this paper, the theoretical backgrounds to the direct boundary element method and the wave superposition method are presented. The wave superposition method does not solve the Kirchoff-Helmholtz integral equation directly. In the approach a lumped parameter model is estabiled from spatially averaged quantities, and the numerical method is implemented by using the acoustic field from a series of virtual sources which are collocated near the boundary surface to replace the acoustic field of the radiator. Then the sound field over the of a pulsating sphere is calculated. Finally, comparison between the analytical and numerical results is given, and the speed of solution is investigated. The results show that the agreement between the results from the above numerical methods is excellent. The wave superposition method requires fewer elements and hence is faster, which do not need as high a mesh density as traditionally associated with BEM.

Abstract: The number and molecular structures of the alpha-brominated 2,5-dimethylterephthalonitrile (DMT) derivatives and the dependences of the yields of derivatives on the reaction time were systematicaly investigated by means of NMR spectroscopy, MS and chromatography. The alpha-brominated DMT derivatives were comprised of 2-bromomethyl-5-methylterephthalonitrile (1), 2,5-bis(bromomethyl)terephthalonitrile (2), 2-(1,1-dibromo)methyl-5-methylterephthalonitrile (3) and 2-bromomethyl-5-(1,1-dibromo)methylterephthalonitrile (4). More than 90 % of DMT mainly transformed swiftly into 1 during the first two-hour alpha-bromination reacting, and nearly half of monobromination compound 1 converts into multibromination compounds 2, 3 and 4 in the ensuing reacting. N-bromosuccinimide (NBS) was not utterly exhausted until the reacting lasted 16 hours. The selection law in the alpha-bromination-reaction of DMT, and the close affinity between the yields of the alpha-bromination products and the reaction time were originally revealed.

Abstract: Highly ordered macro- and meso- porous carbon materials were prepared in a facile nanocasting approach using colloidal crystals silica and SBA-15 as starting template, respectively. The synthesized macroporous carbon templated from colloidal silica shows a honeycomb-like morphology and three-dimensionally interconnected networks of macrospores of about 400 nm in diameter. The resulting mesoporous carbon derived from SBA-15 templates exhibits high specific area (1206m²/g), large pore volume (1.097cc/g) and uniform pore size distribution (3.64 nm). These carbon materials were employed to aerobic oxidation of glucose as support of Au NPs catalyst. 2wt% Au NPs/mesoporous carbon shows high catalytic activity due to highly dispersion of Au NPs resulting from the confinement effects of mesoporous carbon.

Abstract: The difference of heartwood and sapwood is one of the problems in discrinmant analysis of wood species. The effect of heartwood and sapwood on discrinmant analysis of wood species by near infrared spectroscopy was investigated in this paper. Three models in turn calibrated by sapwood samples, heartwood samples and mix samples of sapwood and heartwood of Chinese fir and eucalyptus were applied to discriminate wood species of unknown samples. The results showed sapwood and heartwood can influence the discriminant efficiency of wood species by near infrared spectroscopy coupled with PLS discriminant analysis but the influence was limited. In order to improve the accuracy, stability and reliability of the model, the model should be calibrated by samples which covered the characters of unknown samples.

Abstract: As the core part of a reactor, a spiral pipe structure working under loads of high temperature and high pressure was designed and researched by using CAE method. The properties of high temperature resistance, high-pressure resistance and corrosion resistance play a crucial role for the reactor whether working well or not. Spiral structure was designed for a core component of this reactor in order to increase the staying time that the medium stays in the pipe. The performances of this spiral structure under its working conditions were calculated and analyzed. The changes of performance of the spiral structure caused by changing of elastic modulus of material under high temperature was studied; because the structure has very large length radius ratio, operation of elements meshing is difficult when using FEM method, in order to solving this problem, the methods of establishing elements modal for this kind of structure was proposed in this paper.

Abstract: Eleven europium complexes doped other metal ions with 2,3 - pyrazine dicarboxylic acid had been synthesized and characterized by elemental analyses, rare earth EDTA titration, IR, UV and fluorescence spectra. They were EuL1.5•5H2O, Eu0.5Ln0.5 L1.5•5H2O (Ln3+=La3+, Y3+, Gd3+), EuML2.5•8H2O (M2+= Mg2+, Ca2+, Sr2+, Ba2+, Co2+, Ni2+, Zn2+). Doped metal ions could enhanced the fluorescence of Eu3+ complex, and the order of the fluorescence enhancement was Zn2+>La3+>Gd3+>Y3+; Mg2+> Sr2+>Ca2+>Ba2+. And doped with Co2+ and Ni2+ made the Eu3+ luminescence quenched, which the luminous intensity was almost zero.

Abstract: In the protecting inert gas, Fe nanoparticles were successfully prepared by confined arc plasma method. The particle size, microstructure and morphology of the particles by this process were characterized via X-ray powder diffraction (XRD), Brunauer–Emmett–Teller (BET) adsorption equation, transmission electron microscopy (TEM) and the corresponding selected area electron diffraction (SAED). The experiment results indicate that the samples by this process distributed uniform with spherical chain shapes, the crystal structure is body centered cubic (BCC) structure as same as the bulk materials, the particle size distribution ranging from 20 to 70 nm, with an average particle size about 39 nm obtained by TEM and confirmed by XRD and BET results. The specific surface area is 17.5 m2/g.