Bismuth-activated luminescent materials for broadband optical amplifier in WDM system

New broadband near infrared luminescence covering the whole work windows (1260-1625 nm) of the current wavelength division multiplexing (WDM) system was found from bismuth-activated M2O-Al2O3-SiO2 (M = Li, Na) and Li2O-Ta2O5-SiO2 glasses at room temperature in the case of 808 nm-laser excitation. But the near infrared luminescence mechanism of the bismuth-activated glasses is not well understood up to now. The figure-of-merits of bandwidth and gain of the glasses are better than those of Er3+-doped silicate glasses and Ti3+ doped sapphire, implying they are the promising gain-medium candidates for the broadband amplifiers and the widely tunable laser sources. (c) 2007 Elsevier B.V. All rights reserved.

Effect of immersion in various media on the sorption, solubility, elution of unreacted monomers, and flexural properties of two model dental composite compositions

Immersion in various media has different effect on the properties of dental composites, such as sorption, solubility, elution of unreacted monomers, flexural strength, and flexural elastic modulus. In the present work, the effect of immersion in various media and the relationship between the variation of these properties and the components of dental composite were investigated.

Numerical Simulation of Reactive Extrusion Processes for Activated Anionic Polymerization

In order to deal with the complicated relationships among the variables of the reactive extrusion process for activated anionic polymerization, a three-dimensional equivalent model of closely intermeshing co-rotating twin screw extruders was established. Then the numerical computation expressions of the monomer concentration, the monomer conversion, the average molecular weight and the fluid viscosity were deduced, and the numerical simulation of the reactive extrusion process of Styrene was carried out. At last, our simulated results were compared with Michaeli's simulated results and experimental results. (C) 2007 Elsevier B.V. All rights reserved

Preparation and characterization of a novel solid solution of aluminum in tungsten carbide by mechanically activated high-temperature reaction

In this work, a novel substitutional solid solution (W0.8Al0.2)C was synthesized by mechanically activated high-temperature reaction. X-ray diffraction was used for phase identification during the whole reaction process. Environment scanning electronic microscopy-field emission gun and energy dispersive x-ray were used to investigate the microstructure and the quantitative material composition of the specimen. (W(0.8)A(10.2))C was found to crystallize in the WC-type, and the cell parameters were a = 2.907(1) angstrom and c = 2.837(1) angstrom. The hardness of (W0.8Al0.2)C was tested to be 19.3 +/- 1 GPa, and the density was 13.19 +/- 0.05 g cm(-3).

The optical spectroscopic properties of rare earth-activated barium orthophosphate in VUV-Vis range

The optical properties of rare earth ions-activated barium orthophosphate phosphors, Ba-3(PO4)(2):RE (RE = Ce3+, Sm3+, Eu3+, Eu2+, and Tb3+), were investigated in vacuum ultraviolet (VLTV)-Vis range. A band-band transition Of PO43- in Ba-3(PO4)(2) is observed in the region of 150-170 nm. The partial reduction of Eu3+ to Eu2+ was observed and confirmed by luminescent spectra under the VUV-UV excitation. It is proposed that the electronegative defects that formed by aliovalent substitution of Eu3+ on the Ba2+ site in the host are responsible for the reduction process.

Synthesis of nanometric-size magnesium nitride by the nitriding of pre-activated magnesium powder

Magnesium nitride (Mg3N2) was synthesized by the reaction of magnesium in the highly reactive form (Mg*) with nitrogen at 450 degrees C under normal pressure. The effect of doping with nickel dichloride on the nitridation of Mg* was investigated. Differential thermal analysis (DTA) of Mg* systems and transmission electron microscopy (TEM) measurement of the product formed were carried out. TEM measurement showed that the particle size of the Mg3N2 synthesized was in the nanometric range. The dependence of nitridation of the NiCl2-doped Mg* on temperature was investigated at temperatures ranging from 300 to 500 degrees C. The nitridation of NiCl2-doped Mg* could occur even at temperature as low as 300 degrees C. (C) 1999 Kluwer Academic Publishers.

Effects of Microstructural Heterogeneity on the Spallation Behavior of Materials

It is of utmost importance to understand the spallation behaviour of heterogeneous materials. In this paper, a driven nonlinear threshold model with stress fluctuation is presented to study the effects of microstructural heterogeneity on continuum damage evolution. The spallation behavior of heterogeneity material is analyzed with this model. The heterogeniety of mesoscopic units is characterized in terms of Weibull modulus m of strength distibution and stress fluctuation parameter k. At high stress, the maximum damage increases with m; while at low stress, the maximum damage decreases. In addition, for low stress, severe stress fluctuation causes higher damage; while for high stress, causes lower damage.