Key Engineering Materials Vols. 434-435

Abstract: The 0.98(Na0.5K0.5)NbO3–0.02Ba(Zr0.04Ti0.96)O3 ceramics have been prepared following the conventional mixed oxide process. X-ray diffraction analysis revealed that, during sintering, all of the Ba(Zr0.04Ti0.96)O3 diffuses into the lattice of (Na0.5K0.5)NbO3 to form a solid solution, in which a orthorhombic phase with a perovskite structure was found In order to improve the sinterability of the ceramics, Bi2O3 additions were used as a sintering aid. The electromechanical coupling coefficients of the planar mode kp and the thickness mode kt reach 0.3 and 0.55, respectively, at the sintering of 1100oC for 5 h. For 0.98NKN-0.02BZT ceramics by doping 0.5 wt.% Bi2O3, the electromechanical coupling coefficients of the planar mode kp and the thickness mode kt reach 0.21 and 0.57, respectively. The ratio of thickness coupling coefficient to planar coupling coefficient is 2.7.

Abstract: ZnS is one of the most important semiconductors with wide direct band-gap (3.68 eV) and it is widely used as electroluminescence, flat panel display and cathode ray luminous materials. Uniform ZnS optical thin films were deposited on Si (111) substrates by a vacuum evaporation method. The influences of evaporation temperature, deposition time and the distances between substrates and evaporation sources on the phases and morphologies of the ZnS thin films were investigated. The as-prepared thin films were characterized by X-ray diffraction and atomic force microscopy. Results show that the as-prepared thin films are composed of sphalerite ZnS with a little wurtzite phase. The obtained thin films exhibit an oriented epitaxial growth along (111) direction. The evaporation temperature has a great effect on the phases and morphologies of ZnS thin films. Uniform ZnS thin films can be achieved at the evaporation temperature of 1200°C for 30 min. The crystallization of ZnS thin films improves with the increase of evaporation time.

Abstract: The ZnO films were fabricated by chemical oxidation of metallic Zn in a 5% N, N-dimethyl- formamide (DMF) aqueous solution at 95°C for 24h. After modified with octadecyltrichlorosilane (OTS), a superhydrophobic ZnO film was obtained. The superhydrophobic film turned into a superhydrophilic one after UV irradiation, which can be recovered through being placed in the dark.

Abstract: The oriented La modified PZT thin films were prepared on Pt/Ti/SiO2/Si substrate by the LB technique. The pre-sintering temperatures and the annealing temperatures for La modified PZT were determined by TG-DTA curves and XRD detect results. XRD detection of PZT and PZT with different La amount illustrated the crystal constructions and the effects by modification. The AFM observation of PLZT thin films with organic acid indicated that the LB technique could obtain smooth and flat film with the deposition of PLZT particles within nanometers on substrate. The detection results of the electrical properties indicated that the modification of La had great influence on the electric properties of LB thin film. PLZT thin film by annealing at 650°C had better dielectric constant of 569.2 and dielectric loss of 0.4915 at 5 kHz. And the amount of La of 2% in mass gave the piezoelectric constant of 14pC/N.

Abstract: The structure and principle of an optical scanner actuated by PZT films have been presented in this paper. FEA software (ANSYS9.0) has been used to analyze the modal and harmonic characteristics of the scanner to acquire its dynamic characteristic and deformation, on which we base to optimize its structure. Finally, its resonance frequency and displacement were measured through experiment to testify its feasibility. It shows that the piezoelectric scanner can realize two-dimensional scanning at high frequency, and it can be fabricated conveniently because of its simple structure.

Abstract: In this paper, the improvements in luminance and efficiency have been demonstrated in a white polymer light-emitting device (PLED) with the structure of ITO/ poly (N-vinylcarbazole) (PVK): 1,1,4,4- tetraphenyl-1,3-butadiene (TPB):5,6,11,12-tetrapheny lanpthacene (rubrene) /LiF(1 nm)/Ca(10 nm)/Al(100 nm). The luminance of the white PLED is up to 4940 cd/m2 at 17 V. The current efficiency and Commission Internationale d’Eclairage (CIE) coordinates is 1.66 cd/A and (0.325, 0.326), respectively. The enhancement of the luminance and efficiency can be attributed to an improved hole-injection ability and balance carrier recombination through two ways: (1) enhancing the hole-injection from ITO by using O2 plasma treatment, and (2) balance the recombination of hole and electron by produce a buffer layer with σ-bonded segments of polymer between the ITO and the polymer layer. Besides, orange-emitting rubrene provides that direct recombination of holes and electrons occurred on the dopant molecules and trapping significantly enhanced the luminance and efficiency.

Abstract: Monodispersed gold nanocubes of highly uniform size were fabricated by a simple electrochemical method. The lengths of the edges of the gold nanocubes were about 30 nm. The growth solution was prepared from two cationic surfactant solutions as micelle templates with added acetone solvent. The primary surfactant was hexadecyltrimethylammonium bromide (CTAB) and the co-surfactant was tetradodecylammonium bromide (TTAB).

Abstract: In this investigation, the effect of the thickness in the flexible organic light-emitting diode (FOLED) is studied. The larger luminance and luminance efficiency, 1160 cd/m2 and 2.71 lm/W, can be obtained at NPB thickness of 45 nm with the Alq3 thickness of 35 nm. The luminance dramatically rises when the Alq3 thickness is 45 nm at bias voltage of 19 V. The highest luminance is up to 2190 cd/m2. The extreme characteristic of FOLED may be useful to an organic electrically pumped laser.

Abstract: Perovskite-type oxides catalyst are of interest for various application such as auto-thermal reforming (ART), catalytic wet air oxidation (CWOA) and piezoelectric (PZT). In this paper, La1-xCexNiO3 (x= 0-0.4) perovskite-type oxides have been prepared b sol-gel process using PVA. The precursor was mixed metal ion and PVA with a mole ratio of 1:1 and 1:2. The decomposition during the calcinations process was evaluated by thermogravimetric analysis and differential thermal analysis. Phase of synthesized materials were characterized with X-ray diffraction. Morphological analysis and elemental composition of catalysts was determined by Scanning electron microscope and energy dispersion spectroscopy. The characterization results show that highly crystalline and homogeneous phase of these perovskite oxides were successfully synthesized by the sol-gel method via PVA as a complexing agent.

Abstract: Zinc-doped TiO2 nanotube arrays were fabricated by immersing TiO2 nanotube arrays in zinc-containing solution for hours. And subsequent heat-treatment was crucial for Zn2+ coming into the crystal lattice of TiO2 nanotubes. TEM analysis was used as main technique to investigate the structure of zinc-doped TiO2 nanotubes, and found that the Zn2+ ions only combine into the lattice of TiO2 nanotubes. This kind of doping can change the valence structure in the surface of TiO2 nanotube array. The obtained zinc-doped TiO2 nanotube arrays have potential application in photocatalysis.