Pure Fe-Cr alloys with a Cr-content between zero and 60 wt% have been investigated with respect to their thermal expansion from room temperature to 1100°C and their corrosion resistance in air and humidified hydrogen up to 1300'C. The thermal expansion coefficient of the ferritic Fe-Cr steels is close to that of the supports used in the manufacture of thin-electrolyte cells. The corrosion resistance in air and humidified hydrogen appears to be best for a Cr content around 20 wt%. In addition, a ceria coating is found to reduce significantly the scale growth. Preliminary results for a Fe78Cr22 foil indicates that an electrical contact resistance less than 3 mQcm2 can be obtained between the alloy and a Ni/YSZ anode.

Electrical properties of yttria-stabilised zirconia/alumina (YSZ/AI2O3) composites were tentatively foreseen by simulating their complex impedance spectra. A digital image-based model was developed to describe the electrical conduction process in polycrystalline mono- or multi-phase materials. The microstructure of each polycrystalline sample was reconstructed using the Voronoi tessellation technique (in fact, ad hoc modifications with respect to the original algorithm were introduced) and it was then converted into a threedimensional electrical network according to a set of well-defined rules. The network was solved via an iterative procedure for different frequency values and successively the Nyquist plot generated The complex impedance spectra of different composites were simulated considering the alumina content (5,10 and 15 %wt) as a parameter; both the bulk and grain boundary electrical conductivity were calculated and the Arrhenius plots obtained. Experimental and simulated results were compared and discussed.

For the first time Li+ cations have been localized within the perovskite structure of the fast Liconductor La0 5Li0.5TiO3 from neutron powder diffraction data. Li cations are fourfold oxygen coordinated, located in the middle of the almost square windows determined by every four TiO6 octahedra, far away from the 12-fold coordinated La vacancy sites that, nevertheless, take part of the path for Li motion across the solid. The large multiplicity of the sites where Li reside (1/6 occupied) accounts for the huge ionic conductivity of this promising Li-conducting material.

The high temperature cubic phase of Ba2 nr2O5 shows large ion conductivity. It is interestingto examine, if the cubic phase can be stabilized in the low temperature region (920 C) by making solid solution of another element. In the present study, we investigated the ion conductivity and the crystal structure of Ba2(In2-x.Mx)O5 system by substituting In site for element M such as Sc, Y, La, Ce, Nb, Ta etc. By substituting 3 mole % Nb for In, the transition temperature decreased by about 300 C. High temperature X-ray diffraction analysis shows the crystal structure changes from orthorhombic to cubic at this transition temperature. The effective elements which decreased the transition temperature were pentavalent or tetra valent elements such as Nb or Si ,Ce. The substitution In site for 20 mole percentage Nb stabilizes the cubic structure down to room temperature. Considering the transport number, the tetravalent element doping is very effective to stabilize the cubic phase of Ba2In2O5 without lose of excellent characteristic of pure Ba2ln2O5.

In order to achieve commercial utilization, oxygen separation membranes and solid oxide fuel cells must be able to maintain their mechanical integrity over acceptable life-time periods. This imposes a need for characterization of mechanical behavior of the materials used under operating conditions (high temperature and low stress), in order to identify mechanisms that lead to mechanical degradation during operation. In this study, a series of compressive creep tests on rectangular specimens of SrCO0.8Feo.2O3-x of different grain sizes (2.4 to 6.8 microns) is performed in air, covering a temperature range of 850 to 975 °C and stress range of 10–20 and 40–50 MPa. In the high stress range the material has been found to render temperature dependent stress exponents (2.2 to 2.9) and high steady-state strain rates. In the low stress range the stress exponent has been found to be dose to unity (1.1 to 1.3) indicating diffusion controlled creep. The activation energy appears to assume two different values depending on operating temperature region, 457 kJ/mole below 925 OC and 268 kJ/mole above 925 OC. These values, being much higher than that for oxygen diffusion (<100 kJ/mole) indicate cation diffusion controlled creep. The shift in the value of activation energy indicates a shift in the slowest moving (rate-controlling) species between A and B cation sites. The inverse grain size exponent has been found to be dose to unity.

Electric double-layer capacitors(EDLC) based on charge storage at the interface between a high surface area activated carbon electrode and an electrolyte solution are characterized by their long cycle life and high power density in comparison with batteries. However, energy density of electric double-layer capacitors obtained at present is at most 1Wh/kg at a power density of 600W/kg and smaller compared with that of batteries, which limits the applications of the capacitor. Therefore, new capacitors which show larger energy density than that of electric-double layer capacitors are proposed. The new capacitors are hybrid capacitors consisting of activated carbon cathode, Li-doped graphite anode and an organic electrolyte. Maximum voltage applicable to the cell becomes over 4.OV which is larger than that of the electric double-layer capacitor. As a result, discharged energy density of the cell becomes 4Wh/kg at a power density of 600W/kg.

Electrochemical Double Layer Capacitors (EDLC) for high energy and power density applications, based on glassy carbon (GO) electrodes, are being developed in our laboratory. In the context of this project, GC sheets were oxidized and investigated with Small Angle X-ray Scattering (SAXS), Electrochemical Impedance Spectroscopy (EIS) and Nitrogen Gas Adsorption (BET). During oxidation an active film with open pores is built on the surface of the GC. Upon oxidation, the internal volumetric surface area of the active film decreases, whereas the volumetric electrochemical double layer capacitance increases. We show that this effect is correlated with the opening, the growth and the coalescence of the pores.

Electrochemical capacitors (ultracapacitors) are being developed for hybrid vehicles as candidate power assist devices for the fast response engine and for other energy storage systems that can utilize the high power densities available from these devices. Ultracapacitors show promise toward being able to accept high regenerative pulses and high power delivery capabilities while exhibiting very high cycle life. This paper will present recent test data from two U.S. Department of Energy (DOE) supported ultracapacitor projects designed to meet the fast response engine requirements. Constant-current and constant-power test results will be presented that have been acquired from recent prototype capacitors supplied by SAFT America, Inc. (ten devices), and Maxwell Energy Products, Inc. (two devices). The SAFT capacitors are rated at 0.5 V to 3 V with capacitance ratings ranging from 135 F to 138 F. Capacitor cells rated at 2.3 V and 101.4 F were also evaluated that were produced by Maxwell Energy Products, Inc. Both sets of devices used proprietary carbon electrodes with non-aqueous electrolytes in their design. From the constant-current discharge tests, the discharge current dependence of the capacitance, equivalent series resistance, and RC-time constant were determined as well as the capacitors’ voltage dependence of the capacitance. Constant-power discharge tests permitted the specific energy as a function of the specific power to be determined, and also the discharge/charge round trip efficiency as a function of the magnitude of the constant-power discharge.

Redox reactions and structural changes of a poly(2,2′-dithiodianiline) [poly(DTDA)], a conducting polymer interconnected with disulfide (S-S) bonds, in acid aqueous solution of various pH values are discussed. We proposed the poly(DTDA) as a proton-exchange type of energy storage material. The cyclic voltammograms (CVs) for poly(DTDA) showed a reproducible redox couples for repeated (10,3-104cycles. To investigate the structure of the poly(DTDA) for each potential and the pH value, a plot of E° vs. pH values obtained from the results of CVs (Pourbaix diagram) was formed and discussed.

Organic disulfide compounds has been proposed as a new class of high-energy storage material. Poly(2,2'-diaminobenzyloxydisulfide), a novel conducting polymer having O-S-S-O bond joined two moieties of anilines, is synthesized both chemically and electrochemically as a new positive storage material. It exhibits conductivity in the region of 10-3 S cm-1 by the fourprobe method and the O-S-S-0 bonds in it are confirmed by Fourie Transform Raman Spectroscopy(FT-RS) and Fourie Transform Infrared Spectroscopy(FT-IR). The poly(2,2'- diaminobenzyloxydisulfide) films are formed by electropolymerization from a AN/THF solution containing 0. IM LiClO4, 0. IM HCl and 0.05 M 2,2'-diaminobenzyloxydisulfide monomer on Pt electrode under continuous cycling between -0.30V and 1.20V vs Ag/AgCl(sat. KCI) at scanning rate 50mv s-1. The cyclic voltammetry shows its electrochemical behaviour is similar to polyaniline. The redox peak current of the cyclic voltammograms increase with increasing of the cyclic numbers.

Transition metal nitrides and carbonitride materials were fabricated via sol-gel technology. The transition metal amides were sythesized by two methods: chemical route and electrolysis. The transition metal amides were then further polymerized, sintering to high temperature in an inert or reduced atmosphere. Transition metal nitrides and carbonitrides powders with surface area up to 160 m2/g were obtained. The resultant electrode material showed high specific capacitance as crystalline ruthenium oxide.

Nanoparticulate MnO2 thin films fabricated by the sol-gel process have been shown to be an outstanding novel electrode material for Ultracapacitors. The average specific capacitance of sol-gel-derived MnO2 thin-films on nickel substrates as determined by cyclic voltammetry ranged from 566 to 698 F/g. These films also exhibited good cycling stability within the potential range of 0.0-0.9V (vs SCE) in unbuffered aqueous electrolyte. Both CV and XPS studies showed that MnO2 films have remained chemically and structurally intact after 1,500 cycles. The XRD spectra and SEM micrographs showed that the microstructure of MnO2 thin films are highly porous, and poorly crystalline or amorphous in nature. The high specific capacitance of MnO2 may be predominantly due to pseudocapacitance associated with homogenous and reversible redox reactions of proton insertion into and out of the MnO2 lattice. Any variation in the microstructure and thickness of films might affect proton mobility within the oxide matrix and thereby affecting their cycling behaviors. Further optimization of the cycling behaviors is envisaged with better microstructural and thickness control of these sol-gelderived nanoparticulate MnO2 thin films.

Polymer gel electrolytes consisting of poly(vinylidene fluoride) (PVdF), tetraethylammoniumtetrafluoroborate (TEABF4), and propylene carbonate (PC) as a plasticizer have been investigatedfor electric double layer capacitors. The PVdF gel electrolytes showed high ionic conductivity (ca.6 mS cm-1 at 298 K). To assemble model capacitors with the PVdF gel electrolytes and activatedcarbon fiber cloth electrodes, a pair of the fixed electrodes was soaked in a precursor solutioncontaining PC, PVdF, and TEABF4 , followed by evaporation of the PC solvent in a vacuumoven. The resulting gel electrolytes were in good contact with the electrodes. The modelcapacitors with the PVdF gel electrolytes showed a large value of capacitance and high coulombicefficiency in operation voltage ranges of 1–2 and 1–3 V. It is worth noting that the capacitors withthe PVdF electrolytes showed long voltage retention in a self-discharge test. These goodcharacteristics of our gel capacitors were comparable to those of typical double layer capacitorswith a liquid organic electrolyte containing PC and TEABF4; rather, the voltage retentivity of thePVdF gel capacitors was much superior to that of the capacitors with the organic electrolyte.

Impedance measurements are performed on Pd/Y8Z composites. At 500 'C a 2- 108 times enhancement of the permittivity of the composite at a Pd composition near the percolation threshold for electronic conductivity relative to Y8Z at room temperature is obtained. At high frequencies, the enhancement decreases to a value comparable to geometric capacity of the composite as the double-layer capacity diminishes. At relatively low temperatures the capacity of Y8Z, due to ionic polarisability, increases with temperature.