Advanced Materials Research Vols. 1004-1005

Abstract: KBe₂BO₃F₂ (KBBF) crystal is a sole important and practical ultraviolet nonlinear optical material. It can realize the output of vacuum ultraviolet laser below 200nm with the method of phase-matching. However, it is difficult to grow a practical crystal size with the general growth methods such as fluxed melts, hydrothermal or prism-coupling technique because of the layering growth habit. A reduced-pressure melts growth method was presented to grow bulk KBBF crystal and how to achieve the high quality raw material for growth is a critical factor. In this paper, the influences of syntheses methods of raw material and experiment conditions were discussed, and the best syntheses method was selected.

Abstract: Yellow light-emitting heteroleptic iridium complex with 2-(4-bromophenyl) -1H-benzo [d] imidazole as cylcometalated ligand and 5,5'-dimethyl-2,2'-dipyridyl as the ancillary ligand was synthesized and characterized by ¹H NMR, elemental analysis and IR. The poly (methyl methacrylate)(PMMA) and poly (ethyl acrylate carbazole)(PEAK) doped with the complex were prepared by solution method. The photoluminescent properties of the complex and polymers were studied. The results show that the complex exhibits yellow luminescence with the emission peak of 562nm and CIE coordinates of (0.439, 0.502) upon 365nm excitation. The polymers transfer effectively intermolecular energy to the iridium complex, which results in effective yellow emission for the doped polymers.

Abstract: Investigation of crystal structure, dielectric, magnetic and local ferroelectric properties of the diamagnetically substituted (1-x)BiFeO₃-xBi (Ti_0.5Ni_0.5)O₃ solid solutions samples have been carried out. The solid solutions have been found to possess a rhombohedrally distorted perovskite structure described by the space group R3c. Compared with pure BiFeO₃ compound, both ferroelectric and magnetic properties are much improved by solid solution with Bi (Ti_0.5Ni_0.5)O₃ with saturation hysteresis loops observed. Among all the samples, the x=0.1 samples shows the optimal ferromagnetism with M_r~0.56531emμ/g and the optimal ferroelectricity with P_r~5.767μC/cm2 at room temperature.

Abstract: The thermal problems of high power LEDs could be solved effectively and the stability of the device could be also improved, employing metal substrates for high power LEDs. In this paper,high power GaN based blue LEDs on metal substrates were successfully prepared by transferring GaN-based LED epitaxial film on Si (111) substrates to the Cu/Cr composite substrates employing electroplating method. The forward voltage of the as-prepared LEDs was 3.4 V, when the forward operating current was 350 mA, which was similar with the level of market products. The corresponding voltage could reach 25 V when reverse current was 10 μA, better than the level of market products. It showed good anti-saturation property when forward current varied from 0 mA to 1200 mA. The stability of wavelength vs current was also favourable, which the peak wavelength shifted to long wavelength about 1nm in the test range of 10 mA to 1200 mA.

Abstract: The ingot of Sm-Fe alloy was prepared by vacuum melting. After a process of coarse crushing, it was made into Sm-Fe ribbons by melt-spinning. By analysis of XRD and SEM, it was confirmed that the ribbons composed of fine Sm₂Fe₁₇ columnar grains with almost the same orientation can be obtained under the condition of 5~7m/s surface rotating velocity of Cu wheel, suitable nozzle size, injection pressure, temperature and composition of the Sm-Fe melt to regulate cooling rate and crystallization. The achievement of the ribbons lays a foundation for preparing anisotropic Sm₂Fe₁₇N_x magnetic powders by rapid quenching.

Abstract: The β (β′′)-Al₂O₃ powder is prepared by solid phase reaction method, which is sintered inside the powder in MoSi₂ electric resistance furnace at 1600°C after isostatic pressing. The experimental result shows that the addition of Li₂O can greatly decrease the resistivity of β (β′′)-Al₂O₃ electrolyte and when the mass fraction of Li₂O is 0.8~0.9%, the resistivity of β (β′′)-Al₂O₃ electrolyte can reach 4~5(Ω•cm)^-1_.

Abstract: A 1-D chain-like POM - based organic-inorganic hybrid compound with the chemical formula of [Ni (en)₂]{[Ni (en)₂]₂[Mo₈V₈O₄₀(VO₄)]}[(NH₂)₂(C₂H₄)₂NH]₂·2H₂O (en = ethylenediamine) (1) has been hydrothermally synthesized and structurally characterized by the elemental analysis, and single crystal X-ray diffraction. Compound 1 consists of the bi-supported tetra-capped Keggin-type {[Ni (en)₂]₂[Mo₈V₈O₄₀(VO₄)]}^2- building blocks and [Ni (en)₂]²⁺ metal organic cationic moieties are connected together to form 1-D chain through covelent-bonding interactions, which is further linked into 3-D supramolecular networks . The degradation of methylene blue (MB) under UV irradiation with 1 as the heterogeneous photocatalyst has been investigated, showing a good photocatalytic property of 1 for MB degradation.

Abstract: Antimony doped tin oxide (ATO) is an oxide material with well electrical conductivity. The composite material of Ti based ATO is prepared with Ti particles (45 μm) according to the thermal decomposition method. The resistivity of the material has been analyzed with a measurement device under 1.7 MPa in particles form. The factors influencing the resistivity were studied and optimized in this work. In order to minimize the resistivity of the material, the optimum conditions are putted forward as: mass ratio of coating solution 15% (SbCl₃ to SnCl₄⋅5H₂O), repeating coating process 20 times (coating with the solution and then dried at 100 °C), sintering at 450 °C for 15 min. Under the optimum experimental conditions, the resistivity of the composite particles is 232 Ω·m. Furthermore, ATO coating improved the properties of the composite material in the oxidation resistance.

Abstract: The AC loss calculation is crucial for the thermal analysis of the High Temperature Superconducting (HTS) magnet. Generally, the critical state model is used to calculate the AC loss value of the HTS conductor with Finite Element Method (FEM). The mesh of the model have a large impact both on the convergence and the accuracy in calculation processes. In this paper, we investigate the effect of different meshes on the AC loss calculation of HTS conductors using a second generation tape model. Both triangular and quadrangle element with fix number of elements and predefined distribution type meshes have been used. The results illustrates that quadrangle with geometric sequence is the best choice when calculating the AC loss in HTS tape.

Abstract: Spherical submicron SiO2 particles have been coated with luminescent Lu2O3: Eu3+ layers by a Pechini sol-gel process, resulting in the formation of SiO2@Lu2O3: Eu3+ core-shell particles(300, 500 nm). The obtained core–shell phosphors have perfect spherical shape with narrow size distribution, smooth surface and non-agglomeration. The thickness of shells could be easily controlled by changing the number of deposition cycles (50 nm for four deposition cycles). Under the excitation of ultraviolet, the Eu3+ ion mainly shows its characteristic emissions in the core-shell particles from Lu2O3: Eu3+) shells. The PL intensity of Eu3+ increases with the number of coating cycles.