Advanced Materials Research Vols. 712-715

Abstract: The structure of two-dimensional (2D) photonic crystals (PCs) with square lattice is proposed in this paper, and researches on characteristics of photonic band gap (PBG) are conducted using finite difference time domain (FDTD) method, then the effects of the dielectric constant and the radius of dielectric rods on band gap are analysed, dielectric rods in air (rods/air). The research results indicate that in the case of TE and TM polarization mode, the difference value of dielectric constant of medium and dielectric rods affects forming PBG.The band gap broadens with the difference value increasing. Whats more, the complete band gap (CBG) appears in range of large rods radius structure when dielectric constants of rods are smaller than that of medium.

Abstract: P+a-SiC/ I nc-Si/N+a-Si structure solar cells is simulated by AMPS-1D program package to characterize the new thin film solar cell. In order to analyze the characteristics of the device, the thickness of layer are considered. The results show that the thickness of layer and the value of layer have a great effect on the conversion efficiency. Our results suggest a high performance P a-SiC/ I nc-Si/N a-Si structure solar cells with high efficiency of 14.411% and fill factor of 0.738. The simulation result is potentially valuable in exploring gradual bandgap P+a-SiC/I nc-Si/N+a-Si structure solar cells with high performance.

Abstract: Li_4-xK_xTi₅O₁₂ (x=0.02, 0.04, 0.06) were prepared via a solution method. The electrochemical performances including charge-discharge, rate property and cyclic voltammety were also investigated. The structure of the samples were characterized by X-ray diffraction. The results revealed that Li_3.96K_0.04Ti₅O₁₂ was well. K⁺ doping did not change the electrochemical process, instead enhanced the electronic conductivity and ionic conductivity. The reversible capacity and cycling performance were effectively improved.

Abstract: The petroleum ether-insoluble fraction of Dagang vacuum residue (DVR-PEIF) was subject to catalytic hydrogenation in the presence of Y zeolite. Most of compounds detected with GC/MS in the PE-soluble fraction of products from DVR-PEIF are saturated hydrocarbons, including chain alkanes and cyclanes. Small amounts of olefins and heteroatom-containing compounds (HOs) were also identified.

Abstract: The aim of this study is to evaluate the effect of boric acid as an additive for gelled electrolytes. Cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and an equivalent circuit analysis were employed to study the electrochemical performance of the gelled electrolyte with the addition of varying amounts of boric acid. Scanning electron microscope (SEM) was employed to observe the grid corrosion in corrosion test. For moderate contents of boric acid, the electrode capacity improved, as well as the oxygen evolution profermance. However, the adverse effects of boric acid were found to include increased electrical resistance, decreased hydrogen evolution overpotential and promote the corrosion of the grid. The experimental results indicates that the optimum content was 0.4wt.%.

Abstract: The present of SiH₂Cl₂ (DCS) is a big problem because of its instability. The content of SiH₂Cl₂ should be controlled below somewhat concentration. Therefore, the present study is aimed at investigating the thermodynamic behavior of SiH₂Cl₂ in polysilicon production by Siemens process in order to provide effective theory for the production process. The effect of pressure (1-5atm), feeding ratio of H₂ to SiHCl₃ (2-50) and temperature (1000-1500K) have been studied in the paper. The results show that the productivity ratio of DCS increases with increasing pressure and increases firstly and then decreases with increasing feeding ratio or temperature. In a word, the pressure have biggest effect on productivity ratio of DCS compared to temperature and feeding ratio.

Abstract: Transparent conducting oxides (TCO) are commonly used in electrodes of dye-sensitized solar cells (DSSCs). The flexible DSSCs presented in this work was changed to be based on stainless steel (StSt) meshes and the mesoporous TiO₂ films were fabricated by electrophoretic deposition (EPD) method which consists of repetitive short-term depositions with intermediate drying. The optimum efficiency was found by changing the TiO₂ concentration of EPD solution and the potential difference between the electrodes. The experimental results show that the photovoltaic efficiency (η) of the DSSC with an active size of 1 cm² is 3.25% under an electric field of 60 V/cm and a TiO₂ concentration of EPD solution of 1.0wt%.

Abstract: Two aluminum hydride polymorphs (α-AlH₃ and β-AlH₃) were prepared by desolvation of AlH₃-etherate based on the organometallic synthesis method and the thermal properties of them were investigated using TG-DSC and ex situ XRD under heating and isothermal processes. The results suggest that the α polymorph is more stable than the β polymorph, and the decomposition of the less stable polymorph, β-AlH₃, occurs by an exothermic transformation to the α phase followed by the decomposition of α-AlH₃ into Al and H₂, with partial direct decomposition occurring in the process of phase transition at low temperatures (<100 C).

Abstract: The heat treatment technology of PAN based carbon felt used for sodium-sulfur battery was studied. The influence of different heat treatment technologies on element content of felt and the microstructure of graphitized felt was investigated by the element analysis, Raman spectroscopy. The relationship between element content and resistivity of felt was discussed. Results showed that the oxidation time was shorter, the oxygen content of the stabilized felt was lower, which resulted in higher carbon content of graphitized felt. Thus the higher degree of graphitization produced the more regular structure and the lower resistivity of the felt.

Abstract: A novel method was proposed to form porous silicon (PS) antireflection layers and thin SiO2 films at the same time by HF/H2O2 treatment of acid-textured pn+ multicrystalline silicon. Porous silicon structures formed inside the cavities and the porosity became large with an increase of the treated time resulting in a dramatical decrease of reflectance. The reflectance decreased to less than 5% within the wavelength range of 420-970 nm after 5 min HF/H2O2 treatment. Furthermore, the minority-carrier lifetime showed an increase of about 42% for a short treated time because of the formation of a thin silicon oxide layer resulting the reduction of dangling silicon bonds in the interface between PS/Si.