Materials Science Forum Vols. 663-665

Abstract: A series of polyimide thin films were prepared successfully based on bis[3,5-dimethyl-4- (4-aminophenoxy)phenyl]methane （BDAPM）, 9,9-bis（4-（4-aminophenoxy）phenyl）fluorene (BAOFL) and different dianhydrides. And an interesting result of dielectric property for polyimide thin films was found that the polyimide thin film prepared with 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) exhibited high dielectric constants of 5.7 at 1MHz. Conversely, the other polyimides possessing fluorene groups showed low dielectric constants. The structures and the mechanical properties of polyimide films also proved the reason for results of dielectric properties.

Abstract: Crystal structure and microwave dielectric properties of Ca[(Li1/3Nb2/3) 0.92Zr0.08]O3−δ−xTiO2(0≤x≤0.2) ceramics were investigated. A single phase with orthorhombic perovskite structure was obtained at x=0.0~0.1. With an increasing of Ti4+ content, the Qf value decreased due to a decrease of the degree of B-site 1:2 ordering. However, the τf value firstly increased from-14.2ppm /°C to -6.6ppm/°C, and then moved to the negative direction. When x=0.05, the optimum microwave dielectric properties: εr=32.8, Qf =19460GHz and τf =−8.3 ppm/°C.

Abstract: By Applying Nonequilibrium Green’s Function Formalism Combined First-Principles Density Functional Theory, we Investigate the Electronic Transport Properties of Thiophene and Furan Molecules with Different Quantum Length. the Influence of HOMO-LUMO Gaps and the Spatial Distributions of Molecular Orbitals on the Electronic Transport through the Molecular Device Are Discussed in Detail. the Results Show that the Transport Behaviors Are Determined by the Distinct Electronic Structures of the Molecular Compounds. the Length Dependence of Molecular Conductance Exhibits its Diversity for Different Molecules.

Abstract: The silicon dioxide particles are coated by polyaniline (PANI) under low temperature, and the doped ion concentration in PANI was adjusted by ammonia with different pH. The dielectric properties of PANI/SiO2 eletrorheological (ER) fluids are measured by impedance analyzer. The results indicated that the dielectric increment and relaxation frequency of ER fluid were enhanced after surface modification of SiO2, which are positive to the ER effect. Moreover, the pH of ammonia can change the relaxation frequency of ER fluid, which can improve the response ability of ER fluid to electric field.

Abstract: The influence of metal ions on the peroxyoxalate chemiluminescence reaction was investigated. A number of metal ions showed the quenching effect of the chemiluminescence reaction of bis (3, 5, 6- trichloro-2-carbopentyloxy) oxalate with hydrogen peroxide in the presence of Rhodamine B as the fluorophore. Copper ion gave the highest quenching effect. The reason for the decrease in the chemiluminescence intensity by metal ions is probably a change in the conjugative structure of Rhodamine B due to combination of metal ions and Rhodamine B

Abstract: In order to acquire conductive film with high transparency, conductive polymer PEDT: PSS was mixed with some polar dopants and some surfactants. The coating fluid was acquired and coated on the PET film with different coating rods, and conductive film was gotten after drying at some temperature. The conductive mechanism of polymer after doping was introduced. Furthermore, the influenced factors of conductivity were discussed, including different dopants and surfactants as well as dried temperature. It was concluded that DMSO and EG were the best dopants, that surfactants including fluoride or silicon were suited for high conductivity. The sheet resistance of conductive film can be less than 300 Ω/□ when dried at 130 oC, at the same time the transparency at 550 nm is more than 83%. After measuring with AFM, the surface of film was sharp and the surface roughness is 7nm.

Abstract: The phosphoric acid-based geopolymers were synthesized using chemosynthetic Al2O3-2SiO2 and phosphoric acid at ambient temperature, curing for 28d at room temperature. The influence of the water from the geopolymer materials on the dielectric properties was investigated. The phase’s transformation was measured by XRD. The amorphous SiO2 from unreacted particles transformed to quartz crystal at 950 °C when exposure to 1350 °C, some mulite appeared, however, the dielectric properties change a little. After the geopolymer materials were heated at 350 °C, its dielectric loss could depress down to lower level of 10-3.

Abstract: The PANI/ITO conducting nanocomposites have been synthesized by in-situ polymerization. The obtained nanocomposites were characterized by X-ray diffraction pattern, scanning electron microscopy and Fourier transform infrared. Electrical conductivity measurements on the samples pressed into pellets showed that the maximum conductivity attained 2.0 ± 0.05 S/cm for PANI/ITO nanocomposites, at ITO doping concentration of 10 wt%. The results of the present work may provide a simple, rapid and efficient approach for preparing PANI/ITO nanocomposites.

Abstract: Li and Al codoped ZnO (LAZO) thin films have been prepared by sol-gel method. The electrical and structural properties of the LAZO films have been investigated. X-ray diffraction (XRD) results showed that the prepared LAZO films had a polycrystalline hexagonal wurtzite structure. X-ray photoelectron spectrometer (XPS) measurements indicated that our sol-gel prepared films were of high purity and codoped with Li and Al evidenced by peaks centered at 74.1 and 55.6 eV. The resulting LAZO films were p-type, and had a low resistivity in the range of 10-3~100 Ωcm, and high carrier concentration in the range of 1014~1018 cm-3.

Abstract: Activated carbon was fabricated by using phenolic resin as carbon source, PEG as organic template, KOH as activator. The samples were analyzed by N2 adsorption, scanning electron microscopy (SEM). Cyclic voltammetry and galvanostatic charge-discharge were used to characterize the electrochemical performance of the samples. The results showed that the specific surface area of the prepared sample (AC1) was 2469 m2/g, the pore size was mainly in the range of 1.0～4.0 nm. At a current density of 7.5 mA/cm2, a specific capacitance of 327F/g was achieved, the equivalent series resistance (ESR) was 0.8Ω. Supercapacitors based on the sample have low ESR and excellent power property. For comparison, commercial AC (AC2) was also studied.