Advanced Materials Research Vols. 105-106

Abstract: Ceramic filter material was developed mainly with coal fly ash and used as an absorbent for Cr(VI) removal. This material was characterized through physico-chemical analysis with scanning electron microscope (SEM), energy dispersive X-ray spectrometry (EDS) and mercury porosimeter. Then static adsorption experiment was carried out to study adsorption characteristics of Cr(VI) on this filter material. SEM patterns indicated this material had enormous specific surface area and high porosity. EDS results showed this material was mainly composed of O, Si, C, Al, Mg, Fe, Ca and K in various compounds. Total pore area and porosity above 1.5 nm were 66.8 m2/g and 60.1% respectively. The main parameters affecting Cr(VI) adsorption were dosage and contact time. 200 g/l dosage of this filter material could remove more than 90% of Cr(VI) to solution with 20 mg/l initial concentration. Adsorption isotherm accorded with both Langmuir and Freundlich model. The study proved this ceramic filter material was a good adsorbent with high adsorption capacity to Cr(VI).

Abstract: In this study, 2.5 dimensional quartz fibers reinforced fused silica (2.5D SiO2f/SiO2) composites were prepared by in-situ solidification vacuum-assisted liquid-phase infiltration method using Si-sol and tetraethoxysilane. Composites’ tensile strength and compressive strength were tested by universal testing machine, and the microstructures of the specimen were observed by scanning electron microscopy (FEI Sirion 200). The ultimate sintering temperature was chosen by the differential thermal analysis of tetraethoxysilane gel and the effect of sintering temperature on the composites’ tensile strength. Densification behavior, mechanical properties and microstructures of the composites were investigated. The results show that tetraethoxysilane infiltration process is an efficient route for the preparation of SiO2f/SiO2 composites, after two cycles when the weight was no longer increased using Si-Sol infiltration, the density of SiO2f/SiO2 composites increases from 1.63 to 1.74g/cm3, while the tensile strength and compressive strength, respectively, increase from 31.2 to 52.7MPa and 59.0 to 129.7 MPa. And the interface de-bonding and distinct fibers pull-out of the fracture faces show that it is non-brittle fracture. The enhanced mechanism of tetraethoxysilane infiltration was also analyzed in this paper.

Abstract: A new strategy involving the introduction of the common cationic surfactant cetyltrimethyl ammonium bromide (CTAB) for the cathodic electrodeposition of ZnO electrodes from Zn(NO3) solutions by cyclic voltammetry has been developed. Frizzily lamellar and porous ZnO films were obtained. The deposited films were characterized by X-ray diffraction (XRD) in the range of low-angle and wide-angle, X-ray photoelectron Spectroscopy (XPS), scanning electron microscopy (SEM), and UV-Vis transmittance spectroscopy. The role of the CTAB was also discussed. Under the optimal contents of CTAB, the XRD pattern shows that the as-synthesized ZnO is lamellar nanostructure and SEM image demonstrates that porous and frizzyly lamellar ZnO crystals are formed; XPS spectra of as-deposited film shows that the electrodeposition mainly consists of Zn and O and the Optical transmittance spectra of ZnO film indicates that optical transmittance is low and gradually decreases with the wavelength lessening in the visible light region. Mechanisms are proposed for the electrochemical deposition and the beneficial role of CTAB.

Abstract: La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) tubular membranes with relative density more than 95% were prepared using plastic extrusion method, and their oxygen permeation properties were characterized in steady state. It was found that the permeation properties were influenced apparently by the sintering temperature for the resulting LSCF membranes. The as prepared LSCF membrane sintered at 1300oC had a permeation rate by 5~6 times higher than that sintered at 1250oC. The XRD results showed that the as prepared LSCF membrane sintered at 1250oC had the content of impurity more than that sintered at 1300oC. Namely the reasonable elevation of sintering temperature can reduce the impurity in LSCF membranes, which was produced during green process, and the effect of impurity reduction can improve the transport capability of LSCF membranes made by plastic extrusion.

Abstract: A molecular dynamics model was performed to study the proton transport of Nafion series membrane which is often used in low temperature fuel cells. The simulations intents to investigate the microstructure and the phenomenon of the proton transport processing. The model includes all-atom of main and side chains. The force field includes intermolecular Coulomb and Lennard-Jones terms and intra-molecular terms for harmonic bond stretch potentials, harmonic angle bend potentials and cosine terms for the torsions. The simulations were carried out in two cube systems at different temperature where water content differed from 5 and 10 water molecules per acid group in the polymer, respectively. The results showed that proton transport affected with water content by analyses of snap- shots of the MD simulation, the radial distribution functions between the sulfur atoms of SO3− groups, between the oxygen atoms of H3O+ ions, between oxygen atoms of water molecules and Nafion atoms at various stages.

Abstract: Ni/YSZ cermet is the most widely used anode material for solid oxide fuel cell. In this paper, the NiO/YSZ green body was prepared by gel-tape casting, using 15%wt. starch as pore-forming agent, in the mixed polyvinyl alcohol and acrylamide systems. Ni/YSZ anode material was obtained after sintered at 1450°C for 2h and reduced at 800°C in H2 atmosphere for 4h. The anode porosity, XRD, TGA and microstructures were measured. YSZ formed a continuous network structure and Ni particles were dispersed homogeneously in the YSZ network. It is suitable to fabrication of anode material for solid oxide fuel cell.

Abstract: La0.7Sr0.15Ca0.15Co1-yFeyO3-δ(LSCCF)powders with 0.2y0.5 for the applications as the cathode materials in intermediate temperature solid oxide fuel cell(ITSOFC) were synthesized by glycine-nitrates-process(GNP) using metal-nitrates and glycine as the raw materials. The process, crystal structure and particles morphology of the powders calcined at 600°C,800°C,1000°C for 3h were characterized by IR,XRD and SEM. The experimental results show that co-doped Ca2+ and Sr2+ replacing some La3+ in A site and Fe3+ replacing some Co3+ in B site didn’t influence the formation of perovskite structure and the powders calcined at 800°C for 3h were high pure single perovskite state. The electrical conductivity of LSCCF samples sintered at 1200°C for 3h,was measured as a function of temperature from 100°C to 800°C by the four-probe DC method in air.As a result, the conducting mechanism of LSCCF is p-type small polaron hopping process, and the electrical conductivity are all higher than 100 S/cm. But the electrical conductivity of LSCCF samples increase with Fe3+ content decrease.

Abstract: Double-perovskite Sr2Fe1-xScxMoO6- (x = 0, 0.05, 0.1, 0.2, 0.3, 0.4) powders have been synthesized by sol-gel citrate method. Initial powders were calcined in different temperature and atmosphere (air, H2(4vol%)/Ar), then analyzed by using the methods of X-ray, scanning electron microscopy (SEM), as well as thermal analysis. It is found that the formation of perovskite structure is related to the content of Sc, pH value, calcination temperature and sintering atmosphere. Especially, a pure perovskite structure almost completely formed after three hours sintering in atmosphere of H2(4vol%)/Ar. Although the formation of perovskite structure also happened in the air atmosphere, at the same time the SrMoO4 structure formed undesirably as a result of oxidization of Mo.

Abstract: ZrOCl2•6H2O and Y(NO3)3 were used as raw materials to fabricated Y2O3 stabilized ZrO2(YSZ) nanopowders by hydrothermal method. The addition of Y2O3, different precipitants, different hydrothermal temperatures and times were studied. XRD and TEM were employed to characterize phase compositions, grain sizes and lattice parameters of the as-prepared YSZ nanopowders. The results show that less than 10nm and well crystallized cubic YSZ were obtained under a certain experimental conditions. Different precipitants affect the formation of precursors and final products. The addition of NaOH is benefit to the growth of YSZ crystals with the max grain size and the minimum lattice distortion among the three kinds of precipitants. Amorphous YSZ powders are obtained at lower hydrothermal temperature of 150°Cfor longer treating time of 6h. However, when the hydrothermal temperature is elevated at 180°C, well crystallized YSZ powders are prepared only treated for 2h.

Abstract: The precursor of Mn0.75Ni0.25CO3 is prepared by carbonate co-precipitation method. And the cathode material 0.5Li2MnO3•0.5LiMn0.5Ni0.5O2 is synthesized with two stages calcining temperatures T1 and T2. T1 represents 400°C, 500°C, 600°C and T2 is selected at 750°C, 850°C, 950°C respectively. XRD Patterns shows that the cathode material has the integrated structures of Li2MnO3 and LiMO2, and it has better crystallization during the rise of calcined temperature at 950°C. The electrochemical performances tests indicates that the initial discharge specific capacity are greater than 220mAh/g at the current density 0.2 mA/cm2 in 2.5-4.6V at room temperature. When cathode material is calcined at 750°C, its discharge specific capacity even reach to 248mAh/g, but the cathode material has more perfect general electrochemical properties during calcined temperature at 950°C.