Advanced Materials Research Vols. 311-313

Abstract: A kind of carbon nanotube/expanded graphite (EG/CNT) was used as counter electrodes for the DSSCs following five different weight ratios of 1:0, 1:1, 1:2, 2:1, and 0:1. The impedance spectra and J-V curves were recorded using the Zahner Zennium CIMPS system based on an IM6x electrochemical workstation. The dynamic parameters of the cells were discussed with the intensity-modulated photo current spectroscopy (IMPS) and the intensity modulated photo voltage spectroscopy (IMVS) using white light-emitting diode (75w/m², 604nm, LED) as the light source.

Abstract: In this paper, the effects of Bi₂O₃ addition on the electrical and physical properties of 0.98(Na0.5K0.5)NbO3-0.02(Na0.5Bi0.5)TiO3 were investigated. The 0.98(Na_0.5K_0.5)NbO₃ -0.02(Na_0.5Bi_0.5)TiO₃ [0.98NKN-0.02NBT] ceramics with the addition of 0~0.5 wt% Bi₂O₃ have been prepared following the conventional mixed oxide process. X-ray diffraction analysis revealed that, during sintering, all of the (Na_0.5Bi_0.5)TiO₃ diffuse into the lattice of ((Na_0.5Bi_0.5))NbO₃ to form a solid solution, in which a orthorhombic phase with a perovskite structure was found. For 0.98NKN-0.02NBT ceramics by doping 0.1 wt% Bi₂O₃, the poled dielectric constant (K33^T) and the electromechanical coupling coefficients of the planar mode k_p reach 684 and 0.38, respectively, after sintering at 1100 °C for 3 h. Our results show that 0.98NKN-0.02NBT with the addition of 0.1 wt% Bi₂O₃ is a good lead-free piezoelectric ceramic.

Abstract: Flow characteristic of the desalted water influenced by three inlet structures in different diameter nomal tube, equal diameter nomal tube and tangential tube inlet of the jacketed tube in high-pressure tubular reactor was investigated based on computational fluid dynamics. The results show that the desalted water flow forms a region where the flow velocity is close to zero in the different diameter nomal tube structure and temperature of the desalted water in this region raises notablely. It is also found that the peaks of the shear stress occur at wall inside near inlet of the jacket. The other structures avoid in large extent advent of the former two phenomena and obviously reduce the shear stress value at wall. From the results, the second inlet structure is better than the third and the third better than the first.

Abstract: Silicon dioxide films; radio-frequency magnetron sputtering; annealing temperature Abstract. Silicon dioxide (SiO₂) films are fabricated on single crystal silicon substrate by radio-frequency magnetron sputtering (RFMS) technique and annealed in electric furnaces at 800°C and 1180°C to form uniform, transparent and compact silica. The surface morphology and roughness of the films are characterized by an atomic force microscopy (AFM). X-ray diffraction (XRD) is employed to analyze the crystalline of the thin films. The chemical composition after annealing is analyzed using X-ray photoelectron spectroscopy (XPS).

Abstract: Pure titanium plates as anode and mixture of solutions containing 0.2M Sr(OH)₂ and 0.2M NaOH as electrolyte, titanium plates were microarc-oxidated for 10 minutes. X-Ray Diffraction (XRD) analysis indicated that SrTiO₃ film was successfully deposited. The MAO film is composed mainly of tetragonal SrTiO₃ phases and found to possess high dielectric constant of 371.0 at the frequency of 1 kHz. Scanning Electron Microscopy (SEM) and portable roughness tester were used to characterize the surface morphology and roughness values(Ra), The influences of electrolyte concentration, current density and frequency on the surface morphology of SrTiO₃ film were investigated in detail . several rules were drawn from the results. A kinetics expression was established for the growth of film thickness and agreed well with the experimental results.

Abstract: The structural and optical properties of C-doped and C-F colonel Zoo compounds are investigated by using a first principle method with the plane wave pseudopotential calculations, based on the density functional theory(DFT), within generalized-gradient approximation (GGA). We discuss the structural properties by comparison with C-Al and C-Ga doped systems and the calculated results demonstrate that the c/a is smaller than C doped ZnO when incorporating F into the system and C-F codoping causes a smaller lattice mismatch compared with the C-Al codoped ZnO. Moreover, we focus on the complex dielectric function in order to investigate the optical properties. By analysing the results, we remark that the absorption edge shift the lower energy region(red shift) when incorporating C-F into ZnO compound.

Abstract: A set of ZnO films of different thickness have been deposited on sapphire substrates using molecular beam epitaxy (MBE) by varying the growth time and the effect of film thickness on the structural, electrical and optical properties have been investigated. The X-ray diffraction (XRD) results indicate that the full width at half maximum (FWHM) of the (002) diffraction peak is decreased as the film thickness increasing, and the stress along c-axis is stable. Scanning electron microscope (SEM) measurement shows that the grains become more uniform as the film grows thicker and the film surface present distinct hexagon shape as the film is grown up to a thickness of 500nm. The optical absorbance, Hall mobility and photoluminescence (PL) intensity are increased in accordance with the thickness of the film.

Abstract: ZnS films were prepared on silicon (Si) and glass substrates by radio-frequency (RF) magnetron sputtering method. The effect of annealing treatment on the structural and optical properties of ZnS films was studied. The results showed that annealing treatment was helpful in improving the crystalline quality of the ZnS films, and the bandgap was about 3.61eV and 3.49eV for films with and without annealing, respectively. A ZnS/ Si heterojunction diode was fabricated successfully by depositing ZnS films on p-type single-crystalline Si substrates. The electrical and optical property of the device was reported.

Abstract: The NdFe magnetic absorbing materials were prepared by rapid solidification and high-energy ball milling method. The effect of high-energy ball milling on particle morphology, organizational structure and microwave absorbing properties of NdFe magnetic absorbing materials were analyzed with the aid of X-ray diffractometer, scanning electron microscope and vector network analysis. The results show that the Nd2Fe17 and α-Fe phase are refined, the particles become smaller and thinner; the span-ratio of the particles increases along with time during the process of high-energy ball milling; and meanwhile, the frequency of absorbing peak reduces. The absorbing bandwidth broadens as the increase of the time of ball milling, except that of 48h.The minimum reflectance of the powder decreases from -22dB to - 44dB under the circumstances that the time of high energy ball milling reaches 48h and the thickness of the microwave absorbing coating is 1.5mm. But it rebounds to about - 6dB when the time of ball milling reaches 72h.

Abstract: A convenient one-pot process to synthesize 2-(1H-imidazo[4,5-b]phenazin-2-yl) phenol derivatives 3a-e with substitute (s) X (X = H, CH3O, CH2OH, Cl, Br) via the reaction of 2-hydroxy aromatic aldehydes with phenazine-2,3-diamines in the presence of manganese(III) acetate at room temperature in 80-85% yield was developed. Meanwhile, the ultraviolet absorption and the fluorescent spectra of these o-hydroxy derivatives of 1H-imidazo[4,5-b] phenazin were measured in methanol. Compared with the dual emission characteristics of 2-(2-hydroxy-phenyl) benzimidazole derivatives, only one fluorescence band with a peak wavelength of 540nm was observed and that the Stokes shifts were around 136-140 nm for 3a-e.