Advanced Materials Research Vols. 299-300

Abstract: The structural and magnetic properties of arc-melted alloys of Gd₅Si₂Ge_2-xZn_x in vacuum were investigated by powder x-ray diffraction and Vibrating Sample Magnetometer. When the addition amount of Zn substituted for Ge is less than or equal to 0.05, the alloys have monoclinic Gd₅Si₂Ge₂-type phase structure, the magnetic entropy change of Gd₅Si₂Ge_2-xZnx alloys rapidly increase, When x=0.05, the alloy has the excellent magnetic entropy change (|S_M|). When the addition amount of Zn substituted for Ge is more than 0.05, the alloys have the orthorhombic Gd₅Si₄-type phase structure, the magnetic entropy change of Gd₅Si_2-xGe_2-xZn_x alloys rapidly decreases. The Curie temperature (T_c) of Gd₅Si₂Ge_2-xZnx alloys linearly increases and the peak of |S_M| is broader with the Zn amount substituted for Ge in Gd₅Si₂Ge_2-xZn_x alloys in x range from 0-0.15.

Abstract: Li-doped ZnO thin films were grown on quartz substrates by radio frequency magnetron sputtering and In-situ annealing. The structural, electrical and optical properties of Li-doped ZnO films strongly depend on the annealing oxygen pressure. XRD and AFM analysis indicate that the ZnO films possess a good crystallinity with c-axis orientation, uniform thickness and dense surface. Optical transmission spectra show a high transmittance (~85%) in the visible region. Hall measurement demonstrates that ZnO films have p-type conduction with a Hall mobility of 5.0 cm²/Vs, resistivity of 0.97Ωcm and carrier concentration of 1.60×10¹⁷cm^-3 when annealing oxygen pressure is 1Pa.

Abstract: In this paper, porous NiTi alloy prepared by powder metallurgy method was oxidized at high temperature. The effect of oxidation temperature and time on quality of oxidation layer of porous NiTi was studied. The component and morphology of oxidation layer before and after oxidation at high temperature were analyzed by XPS and SEM. The behavior of Ni ion release of porous NiTi alloy was observed. The results showed uniform and thick oxidation layer was formed on the surface of porous NiTi alloy after oxidation at 550°C for 1h. XPS analysis showed the oxidation layer mainly composed of TiO₂, and the thickness of the film was about 180nm higher than that before oxidation. The research on the behavior of Ni ion release showed the Ni release after oxidation can be significantly reduced at simulated body fluid due to TiO₂ layer.

Abstract: In Er³⁺/Yb³⁺ codoped Na₂O-ZnO-PbO-GeO₂-TeO₂ (NZPGT) glasses, effective ~1.5mm infrared (IR) emission was investigated under 980nm excitation. Judd-Ofelt intensity parameters Wt (t = 2, 4, 6) had been calculated to be 6.78´10-20, 1.54´10-20, and 1.17´10-20cm2, respectively. The IR emission full width at half maximum (FWHM) is 73nm, and the maximum stimulated emission cross-section (se) is derived to be 7.53×10-21cm2. A figure of merit (FOM) as the product FWHM´se is adopted to evaluate the gain bandwidth. The comparison of FOM in different glasses indicated that Er³⁺/Yb³⁺ codoped NZPGT glasses were potential materials in developing broadband optical amplifier.

Abstract: Precursor In(OH)₃ was synthesized by ultrasonic method with carbamide and indium salt, and was performed microwave radiation, then nano amorphous In₂O₃ was obtained. The structural and morphology of precursor and In₂O₃ were characterized by TG-DTA, XRD, TEM, etc. The results show that the In₂O₃ is nano amorphous with average grain size 12nm by microwave method. This paper discovered that nano amorphous In₂O₃ has good photocatalysis when we used it to degrade acidic black dye.

Abstract: A co-precipitation method for synthesizing Gd2O2S:(Yb3+,Er3+) nano-particles was developed, using the commercially available Gd2O3, Er2O3, Yb2O3, H2SO4 and NaOH as the starting materials. XRD analysis shows that the precursor can be transformed into single phase Gd2O2S nano-particles by calcining at 900 °C for 1 hour in hydrogen atmosphere. TEM observation shows that the Gd2O2S particles are quasi-spherical in shape and well dispersed, with a mean particle size of about 20-30 nm. Under 980nm infrared light excitation, the strongest emission bands of Gd2O2S:Er3+ nano-particles located at green region centered at 525 nm and 550 nm, attributing to the 2H11/2→4I15/2 and 4S3/2→4I15/2 transitions of Er3+ ions, respectively. The quenching concentration of Er3+ ions is 5 mol%. The up-conversion luminescent intensity increases obviously for Yb3+ and Er3+ co-doped Gd2O2S:(Yb3+,Er3+) nano-particles.

Abstract: Nb and Se elements were encapsulated in a quartz ampoules (Ø8×100mm), Then heated to 750°C and keep the quartz ampoules at corresponding temperature for 1h. Nanowires of NbSe₂ were obtained. This method is simple and minimizes the pollution. The nanostructure was investigated by XRD、EDAX、SEM、TEM and HRTEM. The results show that the nanostructures have outer diameters in the 40~200nm range, with lengths in excess of several hundred nanometers. Besides, growth process of nano- structure was discussed.

Abstract: It is very important for spheroidic metal cobalt powders production to control the morphology of cobalt oxalate powders precursor. The spheroidic cobalt oxalate powders were prepared by conventional precipitation when a pulsed electromagnetic field (PEMF) was introduced. Scanning electron microscopy (SEM) images and X-ray powder diffraction (XRD) were used to characterize morphologies and phase structures of the cobalt oxalate powders. The research results show that a pulsed electromagnetic field (PEMF) play a key role in the process of preparation of spheroidic cobalt oxalate powders. In addition, a possible morphology control mechanism was preliminarily discussed based on the effects of PEMF on the process of growth of cobalt oxalate particles.

Abstract: By using the sol-gel method, TiO₂ thin films and Ge doped TiO₂ composite thin films were fabricated onto quartz substrates. XRD, XPS and UV-vis were used to characterize the phase structure, the atomic chemical states and optical absorption of these composite TiO₂ thin films. XRD results indicate that diffraction peak of anatase is observed in samples. XPS result reveals that there is Ge crystal in Ge doped films which were prepared by sol-gel method, and Ge exists as elemental Ge and GeO₂ in the films. The composite TiO₂ thin films by sol-gel method exhibits the absorption shift to visible region due to Ge doped TiO₂ thin films.

Abstract: This paper studies the electric-pulse applied in the solidification process of the FeMnSiCrNi shape memory alloy, by applying different pulse frequency and polarity on the FeMnSiCrNi shape memory alloy to improve the shape memory effects. The results show : electric-pulse was conducive to FeMnSiCrNi alloys grain refinement, the alloy can improve the shape memory effect of Compression deformation, the absolute shape recovery rate is improved from 2% to 3.2% which is not treated by the electric-pulse ; when the liquid metal was connected with the anode of the pulse, it is easy to get the columnar grain structure and the column spacing is smaller; when the liquid metal was connected with the cathode of the pulse, the column spacing is larger; Columnar grain is conducive to FeMnSiCrNi alloy specimens compressed shape recovery, it has the smaller column spacing, yet the shape recovery rate is higher; equiaxed is favor in bending back, columnar crystals impede the bending response.