Advanced Materials Research Vols. 347-353

Abstract: A simple method for preparing nanoscale copper ferrite particles with narrow distribution and uniform size was developed by auto-combusting the precursor using copper nitrate, iron nitrate, and malic acid as raw materials. The constituents and the thermal decomposition process of the precursor were studied by Fourier transform infrared (FT-IR), thermogravimetry-differental thermal analysis (TG-DTA) and X-ray diffraction (XRD). The results showed that the carboxyl and nitrate ion take part in the reaction during the auto-combustion process. The precursor decomposed completely at about 199 °C, to yield single phase product. Transmission electron microscopy (TEM) indicated that the average size of the as-burnt sample was about 90 nm.

Abstract: CdS films were prepared by R.F. magnetron sputtering method. The effects of vapor CdCl₂ treatment on the properties of CdS films were studied. The vapor CdCl₂ thermal treatment at different temperature was employed in a CSS device, using CdCl₂ powder as evaporant. The structural and optical properties of CdS films were investigated by x-ray diffraction (XRD), PL spectra, and transmittance spectra, respectively. The results revealed that the CdS films had a structure of hexagonal wurtzite with a preferential orientation of the (002) plane. A better crystal quality and larger grain size, which are good for the solar cell application, were observed in the CdS samples annealed with CdCl2_{Subscript text}.

Abstract: Based on the single-layer thin film theory, we calculated transmittance of ITO thin film. The reflectivity arrive a maximum or a minimum according to whether the refractive index of film is greater or smaller than the refractive index of the glass substrate. we obtain the same maximum of transparence which is above 95% and the minimum value which decrease to 76.5% with the increase of refractive index.

Abstract: In this paper, nickel nanopowder was prepared by liquid phase reduction method, where nickel acetate and hydrazine hydrate was used as nickel source and reducing agent, respectively. The resulting Ni nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM). The results showed that nickel acetate can be effectively reduced by hydrazine hydrate. The as-prepared nickel nanoparticles are in spherical shape, with size ranging from 100 to 200nm and good dispersion. By changing the reaction conditions, the morphology and size of nickel particles can be controlled. The synthesized nickel nanopowders meet the general requirements of nickel powder that would be used for conductive paste, which can be prepared for nickel-based conductive paste. This method has some advantages such as inexpensive, non-pollution to environment; it can be used for industry.

Abstract: Using the first principle method based on density functional theory (DFT), we have studied the stability, structure, and electronic properties in (2 2), (3, 3), (4 4), (5 5), (6 6) armchair and (4 0), (5 0), (6 0) zigzag GaN nanotubes (GaN-NTs). In addition, the radius of N, Ga atoms, buckling separations, band gap and binding energy of (3 3) and (4 0) GaN-NTs in c-axis strain are investigated. We also explore the modification of density of states due to the strain along c-axis orientation. It is found that the strain can change conductive properties of (3 3) and (4 0) GaN-NTs.

Abstract: The current distribution on the grid and plate in lead-acid batteries was determined mathematically by using the equivalent circuit method. The grids used in lead-acid batteries are the general lead grids and the 3-D networks grids, respectively. The calculated current distribution on the grid and plate of three-dimension networks lead-acid battery is more uniform than that of general lead-acid battery. To make the current distribution nearly uniform, extended current tabs located between two plate electrodes were proposed, and a sandwich networks plate was formed.

Abstract: The layered LiNi_0.5Mn_0.5O₂ used as a cathode material for lithium-ion batteries was synthesized from precursor Ni_0.5Mn_0.5CO₃ prepared via a carbonate co-precipitation method. The precursor Ni_0.5Mn_0.5CO₃ was synthesized by the addition of KHCO₃ to an aqueous solution of Ni, Mn sulphates. The powder LiNi_0.5Mn_0.5O₂ was characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Spherical LiNi_0.5Mn_0.5O₂ with well development layered structure was obtained by the carbonate co-precipitation method. The LiNi_0.5Mn_0.5O₂ samples adopted the α-NaFeO₂ structure with a space group R-3m. Galvanostatic charge-discharge behavior of the LiNi_0.5Mn_0.5O₂ cathodes delivered a initial charge and discharge capacity of 144.4 mAh/g and 140.2 mAh/g, respectively in the voltage range 2.5-4.5V at a discharge rate of 0.02A/g. The capacity showed no dramatic capacity fading during 50 cycles.

Abstract: A new simple electrode based on a blended cathode as a practicable method for industrial application was introduced to improve the capacities of LiFePO4 cathodes. Here, the effects of physical blending with a small amount of Li₃V₂(PO₄)₃ on the electrochemical performance of LiFePO₄ were studied. The influence of blended ratios on the capacity of LiFePO₄ was examined by galvanostatic charge and discharge test. The results showed that the discharge capacity of LiFePO₄/Li₃V₂(PO₄)₃ was increased from 146 mAh/g to 156 mAh/g by adding 20 wt.% Li₃V₂(PO₄)₃ and the mixture cathode exhibited excellent capacity retention (93.4% after 12 cycles) compared with prismatic ones. Moreover, the rate performance of LiFePO₄ was also improved greatly by adding Li₃V₂(PO₄)₃. The beneficial effects of adding Li₃V₂(PO₄)₃ were found to be related to an improvement of the rate performance of LiFePO₄ cathode, which was ascribed to the better electron conductivity of Li₃V₂(PO₄)₃.

Abstract: Si/C composites were synthesized by using graphite and glucose as carbon source. The samples were characterized by X-ray diffractometer (XRD) and field emission scanning electron microscope(SEM). The electrochemical charge/discharge test was used to evaluate capacity and cycling stability of the composites. The first discharge and charge capacity of SGC composite using graphite and glucose as carbon source were 1661mAh/g and 1259.1 mAh/g, and the first coulombic efficiency was 75.8%. After 20 cycles, the capacity of SGC composite was 380 mAh/g and the coulombic efficiency remained over 98%.

Abstract: Spinel Li4Ti5O12 nanostructures were synthesized by hydrothermal treatment of hydrogen titanate at 150 oC and further calcinated at 400~750 oC. Their physicochemical features were characterized by TG/DSC, XRD and TEM techniques. Results showed that the Li4Ti5O12 phase with its crystal size of tens of nanometers was likely produced by the reaction between Li2TiO3 and orthorhombic TiO2 upon thermal treatment, and such reaction would be exothermic.