Advanced Materials Research Vol. 510

Abstract: The laser welding with filling wire (LWFW) could not only keep the advantages of laser beam welding (LBW), but also reduce the assembled accuracy before butt-welding and improve the weld quality significantly. In present work, the microstructure and mechanical properties of 6061 aluminum alloy sheet by LWFW have been studied. The results show that the main microstructure characteristics of joint by LWFW are columnar microstructure near the fusion zone and the equiaxed dendritic grains in the center of the weld. And the boundaries of those grains become unclear after the heat treating. A large quantity of ageing strengthening particles precipitate dispersedly during the process of the heat treating, which cause that the average microhardness value of joint by LWFW could be improved significantly after the heat treating. The ultimate strength and the yield strength of 0.2% of the joints could reach the level of the base metal after the heat treating, while the elongation after fracture of the joints could reach 83.3% of the base metal. The tensile fracture presents typical ductile rupture. Therefore, the LWFW is an effective method for 6061 aluminum alloy.

Abstract: Removed due to double publication.

Abstract: By means of mechanical properties test and microstructure observation,the relationship between mechanical properties ,microstructure graph of core-shell Ni/TiO₂ group particles concentration of EMR and different electric field, magnetic field or electric-magnetic field have been researched. It is found that with increasing of particles concentration, the properties are increased. But there is a critical range value, too high or too low particles concentrations are harmful to properties and microstructure. The best particles concentration of Ni/TiO₂ particles is about 30%. In the same field with increasing concentration, particles chain of electrorheological fluid under certain electric field become more strong,brawnier and interweaved each other.

Abstract: Phosphors Zn₂Si_1+xO_4+2x: Mn²⁺(0x0.5) were synthesized through sol-gel process and their photoluminescence in UV and VUV region were investigated. At 254 nm excitation, the phosphor gives intense green emission (527 nm) and the luminescence intensity was enhanced with the increasing of x. At 147 nm excitation, the optimum luminescence intensity occurred at x = 0.1 and the absorption of host became blue shift slightly, which could be related with the absorption of excess SiO₂. The sample Zn₂Si_1.1O_4.2 had the highest emission intensity and it is 40% higher than that of Zn₂SiO₄:Mn²⁺.

Abstract: Aim at the different characteristics from general fuel-cell vehicles of extended-range electric vehicles (E-REVs) with a fuel-cell stack as the Range Extender (RE), an energy management strategy based on minimum power loss algorithm is presented, which considers the efficiency of the fuel-cell stack and the charging and discharging efficiency of battery. The strategy is realized by neural network, simulated with the E-REV model, which is set up with ADVISOR. And a longer driving range is obtained.

Abstract: A series of NaYF₄: Yb³⁺, Er³⁺ nanoparticles with different doping concentration were successfully prepared by the combination of coprecipitation and hydrothermal methods using sodium citrate as chelator. Upconversion luminescence can be observed in all of the samples at room temperature. Fixed the Er³⁺ concentration with 1 mol% unchanged, the effect of the Yb³⁺ concentration on the upconversion luminescence of NaYF₄: Yb³⁺, Er³⁺ samples were studied when the doped Yb³⁺ concentrations were 0 mol%, 1 mol%, 2 mol%, 5 mol%, 10 mol% and 20 mol%, respectively. As increasing the Yb³⁺ concentration, the total intensity of the upconversion luminescence of the samples is increasing while the ratio of red to green emission increases firstly and then decreases. The maximum ratio value is 22.1 when the Yb³⁺ concentration is 10 mol%. It is found that the cross relaxation and cooperative sensitization effect are the reasons for the phenomenon above.

Abstract: An intense broadband 1.53-μm emission with a full width at half-maximum of 51.2 nm and peak emission cross-section of 8.58×10^-21 cm² of Er³⁺-doped Ga₂O₃-GeO₂-Bi₂O₃-R₂O (R= Na⁺, K⁺) glass have been obtained upon 980 nm diode-laser excitation. Effects of alkali metal ions on the thermal stability and spectroscopic properties of Er³⁺-doped Ga₂O₃-GeO₂-Bi₂O₃ glass have been investigated. It is found that the incorporation of Na⁺ replacing K⁺ into Er³⁺-doped Ga₂O₃-GeO₂-Bi₂O₃ glass can effectively improve the 1.53-μm emission and deduce upconversion luminescence .The results show that Ga₂O₃-GeO₂-Bi₂O₃-Na₂O glass might be an attractive host material for their application in C-band optical fiber amplifiers.

Abstract: Fine cemented carbide in the diameter of less than 1 μm is obtained activated tungsten oxide. The samples are characterized by laser particle size analyze, electron microscope and sclerometer. The experimental results show that the size of tungsten particles and tungsten carbide prepared with activated tungsten becomes small remarkably, and coarse tungsten particles decrease. The properties of cemented carbide prepared with activated tungsten oxide are better than those of cemented carbide made with blue tungsten oxide. Especially, the hardness of cemented carbide prepared with activated tungsten oxide increases by about 7 %.

Abstract: In this work, the core-shell FePt@Fe₃O₄ nanowires and nanoparticles as a new hard-soft composite magnetic materials were synthetized by reduction of platinum acetyl acetonate and iron pentacarbonyl together in the presence of oleic acid and oleyl amine stabilizers by polyol process. As-synthesized FePt nanowires and nanoparticles with 0.5-3 nm Fe₃O₄ shell were preparated by controlled addition of excess of Fe (CO)₅ into the reaction mixture and air oxidation. The phase analysis, structure, and magnetic properties were determined by X-ray diffraction (XRD), High resolution transmission electron microscope (HRTEM), Scanning electron microscope (SEM) and vibrating sample magnetometer (VSM) techniques.

Abstract: This paper investigates the evolution of the deformation mechanisms in a homogenized Mg-10Gd-2Y-0.5Zr alloy ingot compressed at 300-500 °C and 0.1-20 s^-1. It can be found that the basal slip and mechanical twinning are the major deformation mechanisms in the alloy compressed at 300 and 0.1-20 s^-1. Increasing the testing temperature to 350 °C, basal slip, non-basal slip and mechanical twinning control the plastic deformation of the alloy compressed at 0.1-20 s^-1. When the testing temperatures increase further to 400-500 °C, the mechanical twinning is replaced gradually by the local shear bands which are formed by dynamic recrystallization (DRX) grains (referred as transformation bands). The transformation bands have the trend to form the typical DRX microstructure with increasing the temperatures (might be caused by increasing testing temperatures or strain rates). Besides, the transformation bands can also be found in the sample compressed at 350 °C and 20 s^-1 when the temperature in the deformation alloy is high enough to activate non-basal slip and form DRX grains at local zone.