Advanced Materials Research Vols. 415-417

Abstract: Nanocomposite films of poly (9,9-dioctylfluorene) (PFO)/Al₂O₃ have been prepared by blending the conjugated polymer solution with alumina nanoparticle dispersion in common organic solvent and investigated in terms of the optical property. A blue shift of the photoluminescence (PL) spectrum for the as fabricated PFO/Al₂O₃ nanocomposite film was observed as compared to the results obtained from the bulk PFO film, the maximum of the PL emission peaks occurs at 442 nm in the bulk film while after the incorporation of the alumina nanoparticles the maximum appears at 420 nm in the spectrum for PFO/Al₂O₃ nanocomposite film. The dependence of fluorescence blue shift of PFO on the concentration of Al₂O₃ was investigated. The isolation of the conjugated polymer chains by the flat rafts of alumina nanoparticles was shown to play a key role for the obtained blue shift.

Abstract: We reported characteristics of OLEDs with the metallocene compounds as cathode interfacial layer between the organic layer and the cathode electrode. The brightness and efficiency of OLEDs with the metallocene compound cathode interfacial layer exhibited higher performance than those of OLEDs without it. The enhancements are attributed to an improved balance of hole and electron due to increased electron injection at the organic layer and the cathode.

Abstract: A novel solution-processable spirosilafluorene oligomer is synthesized by palladium- catalyzed Stille coupling reaction from 2,2',7,7'-tetrabromospirosilafluorene, 2-(4-biphenyl)- 7-tributyltin-9,9-dioctylfluorene. The oligomer is soluble in common organic solvents and is highly photoluminescent. The electrochemical, optical, photoluminescent (PL) property of the oligomer was studied.

Abstract: The GaInAsSb-AlGaAsSb double quantum well lasers with an emission wavelength around 2.1μm, shown high quantum efficiency and high power conversion efficiency at continuous-wave power output. The threshold current density and the external quantum efficiency of the device were 130mA/cm² and 36.1%, respectively. The 15% maximum power conversion efficiency (PCE) were achieved from laser operating about 2.1μm wavelength.

Abstract: Single spinel phase nanocrystalline ferrite (Ni_0.5Zn_0.5)_1-XCo_xFe₂O₄was prepared using the spraying co-precipitation method. The coercivity of prepared (Ni_0.5Zn_0.5)_1-XCo_xFe₂O₄ increases with an increasing content of cobalt. The enhancement of the saturation magnetization was observed up to the maximum value of 102.1emu/g as x was 0.5. This can be attributed to the substitution of the Ni₂₊ and Zn₂₊ ions with Co₂₊ ions. This changed the net magnetic moment between the sublattices of structure.

Abstract: PLD(pulsed laser deposition) method was used to prepare amorphous GeS₂-Ga₂S₃-CdS chalcogenide film. Obvious SHG(second harmonic generation) was observed in electron beam irradiated film by Maker fringe method. According to Raman spectra, we discussed the mechanism of SHG and ascribed the origination of SHG to the local electric field generation under electron beam and uneven charge distribution. With the increase of accelerating voltage and the extension of irradiation time, the SHG intensity increased and reached the maximum, which is due to the enhancement of breakage of glassy isotropy with gradually increased incident electron energy and the finite population of electric dipoles leading to the saturation of SH intensity.

Abstract: Tris(8-hydroxyquinoline) bismuth complex has been synthesized with a facile method in a mixed solvent system containing bismuth nitrate and 8-hydroxyquinolineat at room temperature. The molecular formula of the products is speculated by the C, H and N element analysis and thermal gravimetric analysis, and FTIR was also utilized to measure the structure, which further confirms the molecular formula of the products. The observation of FESEM and TEM shows that the morphology of tris(8-hydroxyquinoline) bismuth complexes is rod-like structure. The results of photoluminescence emission indicate that inorganic element plays key roles in the luminescence property. According to the results, we found that the photoluminescence of tris-(8-hydroxyquinoline) bismuth is stronger than that of 8-hydroxyquinoline.

Abstract: The fluorescent and photovoltaic properties of derivatives of selected substituted meso-phenylporphyrins were studied. It was found that the fluorescent intensity could be enhanced by the electron-donating substituent but weakened by the electron-withdrawing subsituent. The photovoltaic properties and charge transfer process of the compounds were investigated by surface photovoltage spectroscopy (SPS) techniques, which revealed that all the compounds are p-type semiconductors. The spectral bands of all porphyrins could be ascribed to π→π* transitions. Comparing with the fluorescent spectral showed that the stronger the fluorescence intensity of porphyrin was, the weaker the surface photovoltage intensity of it was.

Abstract: It is necessary to know the heat transfer intensity for predicting temperature distribution in the hot strip rolling process. The HTC (heat transfer coefficient) was usually obtained by the experiments and mathematical model. In this paper the HTC prediction was discussed based on the measured or target temperature by the proposed finite element method (FEM). The temperature evolution and HTC in the hot strip rolling process according to a certain plant were analyzed by the iteration calculation. The result shows that the HTC between strip and work roll was much more than the value in the air cooling and water cooling process. Furthermore, the HTC value is lower in the air cooling process compared with that of water cooling. The maximum and minimum value of HTC were about 1.5×10⁵ (W/m².K) and 80(W/m².K) respectively. The temperature in the rough rolling according to the predicted HTC has been solved and the calculated results have a good agreement to the meausred value. Therefore, the research could be used to control the temperature distribution accurately and optimize the parameters.

Abstract: Abstract. A series of liquid crystalline polysiloxanes were synthesized by cholesteric LC monomer and nematic LC monomer. The chemical structures and liquid-crystalline properties of the monomers and polymers were characterized by various experimental techniques including Fourier transform infrared (FTIR), proton nuclear magnetic resonance spectra (1H-NMR), differential scanning calorimetry (DSC), thermogravimetric analyses (TGA) , X-ray diffraction measurements (XRD) and polarizing optical microscopy (POM). All the liquid crystalline polymers showed liquid crystalline properties with wide mesophase temperature ranges. For the polymers bearing only of one nematic LC monomer, it showed nematic phase, while others showed cholesteric phase. With increase the content of nematic LC monomer in the polymers from P1 to P7, the glass transition temperature and the isotropic temperature increased on heating circles. Reflection spectra of cholesteric mesophase of the series of polymers showed that the reflected wavelength shifted to long wavelength with increase content of nematic LC monomer in the polymers in the polymer systems, suggesting that helical pitch (P) become long.