Beta-gallia-rutile (BGR) intergrowths possess one-dimensional tunnels that are suitable hosts for small-to-medium cations, thereby making them potential candidates for ion conductors, ion separators, battery electrodes, and chemical sensors. The BGR intergrowths are a series of homologous compounds expressed generically as Ga4Mn-4O2n-2, where n is an integer; and M is a tetravalent cation that forms a rutile-type oxide. In an attempt to identify materials with high tunnel densities and higher contents of a reducible M4+ cation, we are mapping the compositional stability regions of intergrowths expressed as Ga4–4xIn4xSn(n-4)(1-y)Ti(n-4)yO2n-2 where n = 6, 7 and 9 and 0.15 < x < 0.30 and 0 < y < 1.0. Polycrystalline samples were prepared by solid-state reaction at 1250 – 1400 °C and characterized by X-ray diffraction. Factors that affect phase stability are discussed.

Gd-doped ceria (Ce0.80Gd0.20O1.90) obtained by several nanopowder synthesis processes are compared structurally, morphologically and electrochemically. The powders have been sintered into pellets and investigated by ac-impedance measurements. The electrochemical properties of the electrolytes have been correlated to the structural morphology of the sintered pellets. When the intergrain region exhibits an elevated interdiffusion, the observation of the grain boundaries becomes difficult while the electrochemical properties are improved. Acrylamide polymerization and oxalic co-precipitation techniques showed the best properties.

Ordered-mesoporous Al2O3 was synthesized by the sol-gel method using neutral surfactants as templates. The pore size can be controlled over the range of 2.8∼12.5 nm by using different surfactant copolymers and by different synthetic conditions. By utilizing cyclohexane as a co-solvent, mesoporous Al2O3 having relatively mono-dispersed particle size was obtained. Composites composed of the synthesized mesoporous Al2O3 and the lithium ion conductor (LiI) was prepared. The dc electrical conductivity of 50LiI ·50(mesoporous Al2O3) was 2.6×10-4 S cm-1 at room temperature, which is more than 100 times higher than that of pure LiI. The pore size dependence of the conductivity of LiI-mesoporous Al2O3 composite was examined. A systematic dependence of conductivity upon pore size was observed, in which the conductivity increased with decreasing the pore size.

An analysis of RMC structure models of ion conducting glasses in terms of our bond softness sensitive bond-valence method enables us to identify the conduction pathways for a mobile ion as regions of sufficiently low valence mismatch. The strong correlation between the volume fraction F of the “infinite pathway cluster” and the transport properties yields a prediction of both the absolute value and activation energy of the dc ionic conductivities directly from the structural models. Separate correlations for various types of mobile cations can be unified by employing the square root of the cation mass as a scaling factor. From the application of this procedure to RMC models of mixed alkali glasses, the mixed alkali effect, i.e. the extreme drop of the ionic conductivity when a fraction of the mobile ions is substituted by another type of mobile ions may be attributed mainly to the blocking of conduction pathways by unlike cations. The high efficiency of the blocking can be explained by the reduced fractal dimension of the pathways on the length scale of individual ion transport steps.

The preparation of new anodic materials for lithium-ion batteries is possible by ball-milling within liquid media. Those powders can be as diverse as: highly anisometric graphite particles (geometrical anisotropy around 100), graphite-maghemite (γ Fe2O3) composites and graphite-intercalation compounds with high lithium contents (e.g. LiC3 is obtained by ball-milling of Li + 2C powders). These phases are the first superdense graphite-lithium compounds stable under ambient pressure and lead to a capacity of 1 Ah/g as primary battery and 370 mAh/g as secondary one. The synthesis and characterizationschemical analysis, XRD, pycnometry, TEM, SEM, 7Li NMR, magnetic measurements) are presented for each materials as well as the electrochemical behavior.

Nanoparticul ate Pt50Ru50 supported on a carbon black (CB) were prepared by an impregnation method and the effect of the nano and microstructure towards the electrocatalytic oxidation of methanol and carbon monoxide were evaluated. The in-house prepared PtRu nanoparticles were well-alloyed and finely dispersed on CB, as revealed by XRD and FESEM. FESTEM-EDX analysis of isolated PtRu single nanoparticles indicated that although the majority of the binary particles had a metal composition in accordance to the nominal ratio, some compositional deviation was observed. The activity towards electrocatalytic oxidation of methanol and preadsorbed carbon monoxide is discussed based on the nano and microstructure.

Liquid fuel combustion chemical vapor deposition technique was successfully used for YSZ thin film processing. The nucleation rates were obtained for the samples processed at different temperatures and total-metal-concentrations in the liquid fuel. An optimum substrate temperature was found for the highest nucleation rate. The nucleation rate was increased with the total-metal-concentration. Structural evolution of the thin film in the early processing stage was studied with regard to the formation of nuclei, crystallites and final crystals on the films. The films were found to be affected by high temperature annealing. The crystals and the thin films were characterized with scanning electron microscopy.

This paper presents an advanced design and fabrication concept for a solid oxide fuel cell (SOFC). The concept is based on a laminate repeat unit comprised of a thin electrolyte, cermet anode, metallic gas flow fields, and a metallic bipolar plate. The laminate is sintered in a singlestep process in a controlled atmosphere, and the cathode is applied and sintered in situ during the initial heating of the cell (or stack). Observations about the types of cracks that formed in the electrolyte during the sintering process guided the development of the sintering protocol to yield the desired product. Cells with power densities exceeding 250 mW/cm2 have been tested.

Miniature and microscale fuel processors that incorporate novel catalysts and microtechnology-based designs are discussed. The novel catalyst allows for methanol reforming at high gas hourly space velocities of 50,000 hr-1 or higher while maintaining a carbon monoxide levels at 1% or less. The microtechnology-based designs extremely compact and lightweight devices. The miniature fuel processors, with a volume less than 25 cm3, a mass less than 200 grams, and thermal efficiencies of up to 83%, nominally provide 25 to 50 watts equivalent of hydrogen, which is ample for the portable power supplies described here. With reasonable assumptions on fuel cell efficiencies, anode gas and water management, parasitic power loss, the energy density was estimated at 1700 Whr/kg. These processors have been demonstrated with a CO cleanup method and a fuel cell stack. The microscale fuel processors, with a volume of less than 0.25 cm3 and a mass of less than 1 gram, are designed to provide up to 0.3 watt equivalent of power with efficiencies over 20%.

Composite Nafion membranes containing various amounts of TiO2 (3%, 5% and 10%) were prepared by using a recast procedure for application in high temperature Direct Methanol Fuel Cells (DMFCs). The electrochemical behaviour was compared to that of a membrane-electrode assembly (MEA) based on a bare recast Nafion membrane. All the MEAs containing the Nafion-titania membranes were able to operate up to 145°C, whereas the assembly equipped with the bare recast Nafion membrane showed the maximum performance at 120°C. A maximum power density of 340 mW cm-2 was achieved at 145°C with the composite membrane in the presence of oxygen feed, whereas the maximum power density with air feed was about 210 mW cm-2.

We present a detailed study of the O2-LiCoO2 phase used as positive electrode in lithium batteries. This phase is a metastable form of LiCoO2 and is prepared by ionic exchange from P2-Na0.70CoO2. The O2-LiCoO2 system presents interesting fundamental problems as it exhibits several phase transformations upon lithium deintercalation that imply either CoO2 sheet gliding or lithium/vacancy ordering. Two unusual structures are observed: T#2 and O6. The T#2 phase was characterized by X-ray, neutron and electron diffraction, whereas the O6 phase was only characterized by XRD.

In order to better understand the structures and the driving forces responsible for the phase transformations involved in lithium deintercalation, we combine our experimental study of this system with a theoretical approach. The voltage-composition curve at room temperature is calculated using Density Functional Theory combined with Monte Carlo simulations, and is qualitatively in good agreement with the experimental voltage curve over the complete lithium composition range. Pseudopotential and thermodynamic calculations both show that two tetrahedral sites have to be considered for Li in the T#2 structure. The calculated voltage curve thus exhibits a two-phase O2/T#2 region that indicates that this phase transformation is driven by the entropy maximization and not by a non-metal to metal transition. We also predict two ordered phases for Li1/4CoO2 (O2) and Li1/3CoO2 (O6) and show that the formation of the O6 phase is not related to Li staging or Co3+/Co4+ charge ordering.

Lithium sodium sulfate (LiNaSO4) belongs to a group of simple inorganic salts exhibiting fast-cation conducting high-temperature phases with rotationally disordered anions. The analysis of a combination of quasielastic neutron scattering and high-frequency (10 MHz to 60 GHz) conductivity measurements in the high-temperature phase of LiNaSO4 reveals an unusual cation conduction mechanism: the Haven ratio, HR = D*/Dσ, turns out to be considerably larger than one. This behavior, to our knowledge detected for the first time in a typical fast ion conductor, can be traced back to a charge correlation factor clearly smaller than unity, indicating that charge transport is less effective than tracer transport in this material.

Novel carbon materials with nanometer dimensions are of potentially significant importance for a number of advanced technological applications. Within this report we describe the results for the electrochemical characterization of a series of single walled carbon nanotube (SWNT) metal supported catalysts as cathodes for basic fuel cell systems. Compared to the typical carbon black electrocatalysts, the nanotube supported platinum catalyst resulted in up to a 140% improvement in the efficiency for a proton exchange membrane (PEM) fuel cell.

We are developing a fuel-cell-integrated system for enhancing the effectiveness of an air-bleed for CO-tolerance of hydrogen and reformate PEM fuel cells, with minimal increase in stack cost or specific volume. This is called the reconfigured anode (RCA) system [1]. We report here on properties of several potential catalysts for this system. The materials were characterized by X-ray powder diffraction (XRD), energy dispersive X-ray spectrometry (EDS), and thermal analysis techniques. Surface area was determined using the Brunauer-Emmett-Teller (BET) technique. The XRD results were interpreted using full-profile analysis. In ongoing work, reactivity with CO is being quantified under various conditions, using gas chromatographic (GC) analysis. The results are discussed in terms of effects of the presence of an RCA catalyst on fuel cell performance, using a small air-bleed.

Platinum supported on nanoporous carbon (NPC) is promising candidate for using as electrodes in proton exchange membrane fuel cells. Performance of the anode of a fuel cell is markedly influenced by the efficiency of the splitting of hydrogen atoms by platinum and the transference of the produced protons to the carbon support (spillover process). Consequently a better understanding of these elemental processes could prompt the improvement of the materials used. With this aim, a series of Pt/NPC samples varying the metallic content were studied by electron spin resonance (ESR) under controlled gas environment. This spectroscopic tool is especially suitable for the investigation of processes that involve transference of electrons. In the present case, all materials studied, including bare carbon, showed a very narrow signal (Hpp=1.5–3 gauss) at g=2.0028±0.0002 after activation in vacuum at 500–C. In the case of the pure carbon and for the samples with lower platinum content (lower than 0.2 wt%) signals are significantly asymmetric, and their intensity is scarcely affected by the introduction of hydrogen up to 500°C. In contrast the spin concentration experiences a significant increment when the samples with platinum loading comes in contact with hydrogen at temperatures in the 300–500°C range. Although the centres originating these signals are located in the carbon matrix, the present results emphasize the importance of platinum for hydrogen activation and electron transference.

We have systematically investigated the influence of various parameters (pressure, temperature, time, sample size) on the hot pressing process of TiO2 nanoceramics. This study is backed by thermodilatometric experiments and microscopic observations of the microstructure. Impedance spectra of TiO2 nanoceramics with different porosity are also presented.

The subsolidus phase relationships in the In2O3-WO3 system at 800 – 1400°C were studied by X-ray diffraction. Two binary oxide phases – In2(WO4)3 and In6WO12 – are stable in air over the temperature range of 800 – 1200°C. Preferential volatilization of WO3 prevented the determination of phase equilibria above 1300°C.

Strontium and magnesium doped lanthanum gallate (LSGM) is a promising electrolyte material for intermediate temperature range (650–800°C) solid oxide fuel cell (SOFC) applications. Formation of unwanted phases and Ga loss at high temperatures (1100–1500°C) during synthesis and under low oxygen partial pressures during operation are major hurdles that stand in LSGM's way of full utilization. Using a polymeric precursor synthesis method, the feasibility of producing SOFC electrolyte material LSGM is investigated. The method involves complexing each constituent metal ion by the carboxyl and/or hydroxyl group of the citric acid and/or polyvinyl alcohol (PVA) in aqueous solution. The facility of this method compared with the traditional solid state reaction method was shown by synthesis of single phase and pure LSXM (X= Fe, Cr) oxides at reasonable temperatures (800°C). The X-ray diffraction patterns of LSFM and LSCM are also reported here for the first time.

This paper reports the efforts made in our laboratory to develop electrochemical sensors that might detect NO2 and CO at high temperatures for On Board Diagnostic (OBD) application. The non-Nernstian behaviour of zirconia-based electrochemical NO2 sensors with various oxides as sensing electrodes was studied in the temperature range 450–700°C. Both pellets and tape-casted layers (150 μm of thickness) of yttria-stabilized zirconia (YSZ) were used for fabrication of the sensors. Pt electrodes were painted on both sides of the pellets or as two parallel fingers on one face of the layers. One of the Pt electrodes was covered with a thick-film oxide electrode. Various oxides were tested as sensing electrodes, either p- or n-type semiconductors, including WO3 and LaFeO3. The role of ionic conductivity of the oxide electrodes was investigated using Sr-doped perovskite-type oxides, such as LaxSr1-xFeO3, a mixed ionic-electronic conductor. The sensors were tested as potentiometric and amperometric devices. The performance of these devices was promising: fast and stable responses to different NO2 concentrations (20–1000 ppm in synthetic air) were observed at high temperatures. The role of the metallic electrodes is also studied. The sensing mechanism of the sensors is discussed.

Nanocrystalline CeO2 thin films were synthesized by Plasma-Enhanced Chemical Vapor Deposition using Ce(dpm)4 as precursor. Film growth was accomplished at 150–300°C either in Ar or in Ar-O2 plasmas on SiO2 and Si(100) with the aim of studying the effects of substrate temperature and O2 content on coating characteristics. Film microstructure as a function of the synthesis conditions was investigated by Glancing Incidence X-Ray Diffraction (GIXRD) and Transmission Electron Microscopy (TEM), while surface morphology was analyzed by Atomic Force Microscopy (AFM). Surface and in-depth chemical composition was studied by X-ray Photoelectron Spectroscopy (XPS) and Secondary Ion Mass Spectrometry (SIMS).