Advanced Materials Research Vol. 815

Abstract: Magnetic properties of nanocrystalline Fe_73.5Cu₁Nb₃Si_15.5B₇ ribbons with anisotropy induced by stress-annealing at different temperatures have been investigated.The results show that the magnetic properties were improved with the increase of temperature and excellent DC bias property was obtained after annealing above 580°C due to the transverse strip domain structure.

Abstract: In this paper, we investigate numerically the negative refraction properties of a closed-ring pair (CRP) structure metamaterial under parallel incidence. The surface currents and magnetic-field distribution are demonstrated to the physical mechanism of the negative refraction of the CRP. It is found that the electric response is attributed to the plasma oscillation of electrons and resulting in negative permittvity. However, the magnetic response origins from the antsymmetric resonant mode, which is excited by the edges of up and down of the CRP structure. In addition, the electric field distribution based on wedge-shaped and parallelogram-shaped models and the backward wave propagation from the phase changes in the moving picture are shown to further confirm the negative refraction.

Abstract: The rare earth-cobalt compounds with CaCu₅-type structure were discovered to have outstanding permanent magnetic properties. The thermal stability of Y_1-xEr_xCo₅ (x = 0, 0.12, 0.24) was investigated by X-ray powder diffraction, differential thermal analysis and scanning electron microscopy with energy dispersive analysis. The influence of Er for Y on the decomposition of Y_1-xEr_xCo₅ was discussed. The substitution of Er for Y in the compound YCo₅ obviously enhanced the decomposition temperature and accelerated the decomposition reaction of the compounds Y_1-xEr_xCo₅ into (Y_1-xEr_x)₂Co₁₇ and (Y_1-xEr_x)₂Co₇.

Abstract: Thiourea-modified ZnO nanoparticles were prepared by the microwave-assisted method. The nanoparticles were characterized by X-ray diffraction (XRD), High-resolution transmission electron microscope (TEM), UV-Vis absorption spectroscopy (UV-Vis) and X-ray photoelectron spectroscopy (XPS). ZnO nanoparticles presented typical wurtzite structure. Microwave-assisted method and thiourea modifying reduced the particle size of ZnO corporately and the particle size of 2.0 mol% thiourea/ZnO was about 3 nm. The photocatalytic efficiency of thiourea-modified ZnO was influenced by the molar precent between thiourea and ZnO and 2.0 mol% thiourea/ZnO had the highest photocatalytic activity. The degradation rate of 30 mg/L C.I. Reactive Blue 4 could get to 85% in 50 min at room temperature when the concentration of 2.0 mol% thiourea/ZnO was 0.10 g/L.

Abstract: The external quantum efficiency of organic light-emitting diodes (OLEDs) was suppressed by the wave guide mode in the glass substrate and organic layers. In this paper, a mechanism is developed to simulate the optical luminous field for OLEDs based on inverted pyramid substrate structure. Monte Carlo method was used to optimize the structural parameters to enhance the external quantum efficiency of device by changing the substrate structure. A considerable enhancement in the extraction efficiency of the OLED is expected theoretically, and near 42% out-coupling efficiency was achieved in experiment without affecting the electroluminescent spectrum.

Abstract: The InGaN nanowires (NWs) have attracted intense attention for their huge potential in applications such as light emitting diodes, laser diodes and solar cells. Although lots of work are focused on improving their optical performance, little is known about the influence of the In distribution and the surface states on the microscopic light emission mechanism. In order to give an atomic level understanding, we investigate the electronic structures of the wurtziteGa-rich InGaN NWs with different In distributions using first-principles calculations. We find that the In-atoms are apt to distribute on the surface of the NWs and the short surface In-N chains can be easily formed. For the unsaturated NWs, several new bands are induced by the surface states, which can be modified by the surface In microstructures. The randomly formed surface In-N chains can highly localize the electrons/holes at the band edges and dominate the interband optical transition. For the saturated NWs, the band edges are determined by the inner atoms. Our work is useful to improve the performance of the InGaN NW-based optoelectronic devices.

Abstract: With HFHIPS as the substrate, through the double-screw extrusion processing technology of blending modification, add the titanium dioxide (TiO₂) and brightener (ZB) into the HFHIPS. Change the content of TiO₂ and ZB of the substrate respectively, study the influence of content on the HFHIPS Reflective materials with microstructure on surface, Including reflectivity, whiteness, impact strength and tensile strength. The results show that, when add the TiO₂ and ZB into the HFHIPS, reflectivity and whiteness were improved obviously. Reflectivity can reach 95.3%, at the same time, the intensity will not have a significant reduction; But when the content reaches a certain value, TiO₂ and ZB will cover each other, this will reduce the reflectivity and whiteness.

Abstract: General aspects of different gamma ray Compton scattering techniques are introduced. Comparison between the performances of different Compton spectrometers in terms of the parameters: resolution, statistical accuracy, and signal-to-noise ratio are presented. In addition to that, the most relevant parameters for further improvement in the quality of Compton profile measurements are suggested.

Abstract: The nonlinear absorption (NLA) properties of copper phthalocyanine (CuPc) acetone solution were investigated by femtosecond open-aperture (OA) Z-scan technique. The reverse saturable absorption (RSA) was observed, and it was found that the RSA effect was origin from three-photon absorption. Moreover, the influences of concentration and excitation laser power on the NLA of CuPc solution are studied. Results show that the RSA effect increases with the increase of sample concentration and excitation laser power. It indicates that the CuPc could be a promising candidate for optical limiting material.

Abstract: Luminescence of trivalent lanthanide ions (Ln³⁺) doped glasses is influenced by many factors. The emission enhancement of Ln³⁺ can be achieved either through an external approach or an internal adjustment. The external approaches mainly include application of metal nanoparticles, which changes the local structure, local filed and interaction with active ions. In this work, efforts to obtain luminescence enhancement in Ln³⁺ through introducing noble metals are reviewed. The merits of different processes are concluded.