bluuebunny/crossref_metadata_2025 huggingface dataset:
An atmospheric pressure static reactor – ion trap mass spectrometer for studying gas-phase reactions
Authors: Wedian Fadel , Atkinson Dean B.
Published: October 2010

The design and operation of an atmospheric pressure static reactor coupled to an ion trap mass spectrometer is described. The reactor is designed for studying gas-phase reactions that are important in atmospheric chemistry. The system provides a simple and robust method for identifying the products of gas-phase reactions. Results for the reaction of O3with 2,3-dimethyl-2-butene (tetramethylethylene, TME) are demonstrated as a proof of the principle for the performance of the static reactor. All of the previously reported major primary products of the reaction were observed, and the yields of two compounds (acetone and hydroxyacetone) were quantified, in excellent agreement with previous work. Several minor species were also observed, demonstrating the potential for this method to investigate the product channels for less well-studied atmospherically relevant reactions.
Temperature and density effects on the absorption maximum of solvated electrons in sub- and super-critical methanol
Authors: Yan Y. , Lin M. , Katsumura Y. , Muroya Y. , Yamashita S. , Hata K. , Meesungnoen J. , Jay-Gerin J.-P.
Published: October 2010

The optical absorption spectra of the solvated electron ([Formula: see text]) in sub- and super-critical methanol are measured by both electron pulse radiolysis and laser photolysis techniques, at temperatures in the range 220–270 °C. Over the density range studied (~0.45–0.59 g/cm3), the position of the absorption maximum ([Formula: see text]) of [Formula: see text] is found to shift only slightly to the red with decreasing density. In agreement with our previous work in water, at a fixed pressure, [Formula: see text] decreases monotonically with increasing temperature in passing through the phase transition at Tc(239.5 °C). By contrast, at a fixed density, [Formula: see text] exhibits a minimum as the solvent passes above the critical point into the supercritical state. These behaviors are discussed in terms of microscopic arguments based on the changes that occur in the methanol properties and methanol structure in the sub- and super-critical regimes. The effect of the addition of a small amount of water to the alcohol on the optical absorption energy of [Formula: see text] is also investigated.
BIANCHI TYPE I MAGNETIZED DUST FILLED UNIVERSE IN LYRA GEOMETRY
Authors: BALI RAJ , CHANDNANI NARESH K. , DHANKA JAGDISH PRASAD
Published: October 2010

Bianchi Type I dust filled universe in the frameworks of Lyra geometry in the presence of magnetic field is investigated. To get the deterministic model of the universe, we have also assumed that the eigenvalue [Formula: see text] of shear tensor [Formula: see text] is proportional to the expansion (θ) in the model. This leads to A = (BC)nwhere A, B and C are metric potentials and n is a constant. The physical and geometrical aspects of the model related with astronomical observations are also discussed.
THE STUDIES OF THERMAL ANNEALING ON Pt/AlGaN GROWN ON Si(111) BY PLASMA-ASSISTED MOLECULAR BEAM EPITAXY (PA-MBE)
Authors: MOHD YUSOFF M. Z. , HASSAN Z. , CHIN C. W. , THAHAB S. M. , ABU HASSAN H.
Published: October 2010

The application of thermal annealing at various annealing temperatures (473–1073 K) has been shown to significantly modify surface morphology of platinum ( Pt ) metal contacts on AlGaN / GaN / AlN heterostructure grown on silicon by plasma-assisted molecular beam epitaxy (PA-MBE). Structural analysis of the AlGaN / GaN samples used for the Pt Schottky contacts fabrication were performed by using high resolution X-ray diffraction (HR-XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The Pt metal contacts were then deposited on the samples followed by current–voltage (I–V) characterization. Thermally-treated samples showed significant decrease in current compared with untreated samples. From the I–V measurements, the Schottky barrier height (SBH) and ideality factor (n) were calculated. We found that the lowest value of SBH obtained was 0.526 eV at 873 K annealing temperature. Unfortunately, there are no values for the SBH and ideality factor at 1073 K annealing temperature. The SEM analysis has shown some island formation at high annealing temperature due to the difference of surface energies between thin metal films and AlGaN that causes dewetting. We suggest that the reason for the barrier height reduction is due to the metal island formation on the samples.
DISCRETIZATION OF STATIONARY SOLUTIONS OF SPDE'S BY EXTERNAL APPROXIMATION IN SPACE AND TIME
Authors: OGROWSKY A. , SCHMALFUSS B.
Published: October 2010

We consider a stochastic partial differential equation with additive noise satisfying a strong dissipativity condition for the nonlinear term such that this equation has a random fixed point. The goal of this article is to approximate this fixed point by space and space-time discretizations of a stochastic differential equation or more precisely, a conjugate random partial differential equation. For these discretizations external schemes are used. We show the convergence of the random fixed points of the space and space-time discretizations to the random fixed point of the original partial differential equation.
DETECTING DETERMINISM IN TIME SERIES WITH ORDINAL PATTERNS: A COMPARATIVE STUDY
Authors: AMIGÓ J. M. , ZAMBRANO S. , SANJUÁN M. A. F.
Published: October 2010

Detecting determinism in univariate and multivariate time series is difficult if the underlying process is nonlinear, and the noise level is high. In a previous paper, the authors proposed a method based on observable ordinal patterns. This method exploits the robustness of admissible ordinal patterns against observational noise, and the super-exponential growth of forbidden ordinal patterns with the length of the patterns. The new method compared favorably to the Brock–Dechert–Scheinkman independence test when applied to time series projected from the Hénon attractor and contaminated with Gaussian noise of different variances. In this paper, we extend this comparison to higher fractal dimensions by using noisy orbits on the attractors of the Lorenz map, and the time-delayed Hénon map. Finally, we make an analysis that enlightens the robustness of admissible ordinal patterns in the presence of observational noise.
Pt-Decorated Pd/C Catalysts for Methanol-Tolerant Oxygen Reduction Reaction
Authors: He Wei , Kang Y. Y. , Li Zhilin , Zhang Xiaogang , Zhou Zhiqing , Yang Hui
Published: October 2010

The Pt-decorated Pd/C catalysts were prepared by two consecutive steps, synthesizing Pd/C catalyst and then decoration of Pt via a polyol reduction. It is believed that Pt was deposited onto the Pd surface through conformal epitaxial growth. A series of Pt-decorated Pd/C catalysts were characterized by XRD, TEM and electrochemical methods. The CO stripping voltammograms of the Pt-decorated Pd/C catalysts exhibit two CO oxidation peaks, indicative of two active sites for CO oxidation. An activity evaluation of the oxygen reduction reaction (ORR) on as-prepared Pt-decorated Pd/C catalysts with a rotating disk electrode (RDE) technique revealed that the maximum ORR mass activity was observed for a Pd:Pt atomic ratio of 7:1, and meanwhile bimetallic catalysts exhibited good methanol tolerance during the ORR.
Novel Metastable Pd-Ru Catalysts for Electrooxidation of Formic Acid
Authors: Kedzierzawski Piotr , Mikołajczuk Anna , Borodziński Andrzej , Mierzwa Bogusław , Stobiński Leszek
Published: October 2010

Pd catalysts are very active towards formic acid oxidation, but are being gradually poisoned, mainly by formic acid impurities. Pt-Ru catalysts are stable, but considerably less active than Pd. The Pd-Ru materials are expected to combine high activity and stability. In the present work, such alloys were obtained by high-energy ball milling and by a rapid co-reduction of Pd and Ru salts. Using mechanical alloying we have obtained single phase a fcc solid solution of Ru in Pd (xRu=0.5). The new catalysts appeared to be more stable and about two times more active in the electrooxidation of formic acid than a commercial high surface Pd black. Catalysts obtained by co-reduction of Pd2+ and Ru3+ ions consisted of two phases: hex solid solution of Pd in Ru and fcc solid solution of Ru in Pd. This catalyst was less stable and had a slightly lower activity than the commercial Pd black.
From Polymeric Systems, through Composites to Hybrid Networks: Evolution of Electrolytes for Modern Electrochemical Power Sources
Authors: Siekierski Maciej S. , Wieczorek Władysław
Published: October 2010

The aim of presented work is to present the possibilities of the polymeric electrolyte modifications leading to its practical application in lithium containing batteries. These approaches include synthesis of new polymeric matrices, synthesis of new doping salts and formation of composites. Three main goals are to be achieved by these means. Firstly the improvement of overall ionic conductivity is needed to increase the battery high power performance. Secondly, the improvement of the electrode-electrolyte interface stability is a key to improve the long term performance of the electrochemical system. Finally, the improvement of the cation transference number is important for the low internal polarization of the battery.
Composite Film Cathodes of Nanobeam V2O5 and Conductive Polymer for Lithium Batteries
Authors: Song Hahn-Mok , Kim Youna , Ta Quang-Thao , Yeo In-Hyeong , Cho Won Il , Mho Sun-il
Published: October 2010

Flexible composite films of nanobeam V2O5 and conductive polymer have been grown using the facile electrochemical polymerization method, which involves the application of anodic polymerization potential to the substrate electrode with the dispersed nanobeam V2O5 in solutions containing monomer - pyrrole or EDOT. For the case of pyrrole: V2O5 nanobeams can be thoroughly coated with polypyrrole, by taking advantage of the oxidative catalytic action of V2O5 in pyrrole polymerization. For the case of EDOT: since the advantage of V2O5 oxidative catalytic action is not applicable to PEDOT, it had been copolymerized with a surfactant p-TSA to achieve thorough and smooth coating of V2O5 nanobeams. Thus produced conductive polymers have shown to connect the isolated V2O5 nanobeam structures and provide valid electrical conductive networks for the cathode electrodes. These polymers enhanced the accessibility and diffusability of Li+ ions, thereby enabled V2O5/PPy and V2O5/PEDOT nanobeam composite film cathodes to have excellent cycling stability.
Development of New Thin-Film Electrolyte Composed of Layered Compound NaCo2O4 as Alkaline Fuel Cell
Authors: Matsuda Motofumi , Murota Tadatoshi , Takahashi Hiroki , Takeguchi Tatsuya , Ueda Wataru
Published: October 2010

In this work, we developed a thin-film anion-conducting electrolyte composed of NaCo2O4. The NaCo2O4 powder was slurried with poly vinylidene difluoride (PVDF) and N-methyl pyrrolidone (NMP). The slurry was painted on the punched metal base or meshed metal base by the doctor blade method, followed by calcination at 600{degree sign}C for 5 h. In making NaCo2O4 film, the shape of the base greatly affected the cell performance. The cell consisting of a thin-film electrolyte on punched base showed higher performance than that on meshed base, since meshed base is difficult to be packed densely with NaCo2O4 slurry.
Nonprecious Metal Electrocatalysts for Alkaline Fuel Cells
Authors: Nakamura Ayaka , Takahashi Hiroki , Takeguchi Tatsuya , Yamanaka Toshiro , Wang Qi , Uchimoto Yoshiharu , Ueda Wataru
Published: October 2010

It is desirable to develop non-precious metal electrocatalysts for alkaline fuel cell (AFC). In this present work, Fe-Co-Ni/C anode catalysts were prepared by impregnating method and reduced at 900{degree sign}C under a flow of H2 for 9 h. Alloy formation was confirmed by XRD. The maximum power density of 37 mW cm-2 was obtained for the cell with the Fe-Co-Ni/C anode catalyst. The NaCo2O4/C cathode catalysts were prepared by dry-up method. The maximum power density, 27 mW cm-2 was obtained for the cell with the NaCo2O4/C cathode catalyst. Though both Fe-Co-Ni/C and NaCo2O4/C catalysts leave much room for improvement, these results indicate that non-precious metal can be used as electrocatalyst for fuel cells.
Engineered Tungsten Oxy-Nitride Thin Film Materials for Photocatalytical Water Splitting Fabricated by MOCVD
Authors: Cwik Stefan , Milanov Andrian P. , Gwildies Vanessa , Thiede Tobias , Vidyarthi Vinay , Savan Alan , Meyer Robert , Becker Hans-Werner , Rogalla Detlef , Ludwig Alfred , Fischer Roland , Devi Anjana
Published: October 2010

The growth of tungsten oxynitride thin films by metalorganic chemical vapor deposition (MOCVD) was achieved using an all nitrogen coordinated tungsten imido-amidinato precursor in the presence of oxygen as the reactive gas. In particular the influence of CVD process parameters on the structure, morphology and composition of the films was studied by scanning electron microscopy (SEM), Rutherford backscattering spectroscopy (RBS), nuclear reaction analysis (NRA) and X-ray diffraction XRD. It was possible to tune the content of the nitrogen of the films which could be an advantage in terms of functional properties of the tungsten oxide based materials.
Impedance Monitoring of the Anodic Dissolution of PANi during the V2O5 Deposition Step for the PANi/V2O5 Composite Film Preparation
Authors: Park Kyung-Il , Dinh Hung-Cuong , Kim Joo-Sung , Yeo In-Hyeong , Mho Sun-il
Published: October 2010

Vanadium pentoxide / polyaniline (V2O5/PANi) composite films were prepared by a two-step electrochemical method for the cathode material application in lithium batteries. As a first step the PANi film was potentiodynamically grown in an acid solution containing aniline monomer, and secondly vanadium oxide was oxidatively deposited on the polyaniline film in a temperature controlled VOSO4 solution. The increased anodic current efficiency in the hot VOSO4 solution results in high contents of V2O5 in the composite films. The in-situ electrochemical impedance spectra for the second step of V2O5-deposition at the PANi-film electrodes were measured. The impedance increases as the oxidative deposition of V2O5 proceeds. Polyaniline film is also oxidized during the second V2O5-deposition step in the high temperature acidic solutions, which result in the polyaniline being overoxidized to a less conductive form.
Flame Plasma Electrochemical Sensor for Airborne Particulates: The Case of Pollen
Authors: Sarantaridis Dimitris , Caruana Daren J.
Published: October 2010

A novel method for the detection of airborne particulates, such as pollen, is proposed. It utilizes the plasma and built-in amplification properties of flames through combustion and ionization in the gas phase. We present high-speed potentiometry and imaging results in situ a H2/O2/N2 flame for the combustion of single Bermuda grass and black walnut pollen grains. It is shown that these can be effectively detected, giving signals in the order of 1 V and useful voltage patterns that can potentially enable differentiation between species. The most likely contributing mechanisms to the overall measured voltage are finally discussed giving an insight into the processes involved.
Electrodeposition of Polypyrrole-Biotin Films by Square Wave Cyclic Voltammetry
Authors: Pham Nam Thang , Tavares Ana C. , Dao Le
Published: October 2010

PPy-DBS-Biotin films were prepared by square wave cyclic voltammetry. The film composition was determined by FTIR and the morphology by scanning electron microscopy. The impact of the occlusion of Biotin in the electrochemical behavior of the PPy film was evaluated by cyclic voltammetry and electrochemical impedance spectroscopy. The presence of Biotin on the PPy film surface after continuous cycling was evaluated by x-ray photoelectron spectroscopy.
Nanoporous Gold: A Novel Catalyst with Tunable Properties
Authors: Wittstock Arne , Biener Jürgen , Bäumer Marcus
Published: October 2010

Nanoporous gold materials (np-Au) can be generated by selective corrosion of e.g. Au-Ag alloys. The resulting monolithic gold struc¬ture consists of a 3 dimensional network of ligaments in the range of a few tens of nanometers. Due to its homogeneous porosity (> 70 %) gas molecules can penetrate the material and adsorb on its entire surface. This can be used for catalytic application. On the one hand the strongly curved ligament-surface containing a large proportion of low coordinated gold atoms provides specific adsorption sites for gas molecules. On the other hand small Ag residues, leftovers from the corrosion process, enhance the reactivity of the surface with regard to activation of molecular oxygen. The influence of Ag on the activity and selectivity is exemplarily discussed for the oxidation of CO and methanol. By controlling the amount of residual Ag the catalytic performance of the np-Au material can be tuned.
High Power Planar Sodium-Nickel Chloride Battery
Authors: Lu Xiaochuan , Coffey Greg , Meinhardt Kerry , Sprenkle Vincent , Yang Zhenguo , Lemmon John P.
Published: October 2010

Sodium-beta batteries (NBBs), which are typically constructed on a thick tubular electrolyte and operate at relatively high temperatures, have a number of disadvantages such as high capital cost and performance/safety issues that limit market penetration of the technology. In this work we report a new generation NBB that utilizes a planar design. The planar design allows for a thinner electrolyte that reduces the area of specific resistance and may be operated at reduced temperatures. The lower operating temperatures would alleviate adverse temperature effects that impact cycle life and overall cost. We here present recent progress generated from planar NBB button cells, including initial cell performance, cathode design and chemistry.
An Adaptable Lithium-Ion Battery Model
Authors: Parfitt Claire E. , Crofts William E. , Buckle Rachel
Published: October 2010

We present here a complete model of a Sony 18650HC lithium-ion battery developed in MATLAB/Simulink, which is adaptable to other lithium-ion cell chemistries and can be implemented into a full power system model. The model accounts for varying current rates, temperature dependencies and internal cell characteristics under both charge and discharge conditions and is primarily based on characterisation tests of the 18650HC cell with the addition of standard thermal equations and electrical relationships. The model can be adapted to fit other types of lithium-ion cell chemistries when the characterisation profile for that chemistry is created using our testing procedures. Comparisons between the model and experiments conducted on test cells have shown very accurate results and the adaptability of the model has been proven. This allows us to test and model newer cell technologies for which commercial data may not yet be available.
In Situ Analysis of Pb Electrodeposition on Polycrystalline Cu Using Ellipsometry
Authors: Wang Yanru , Li Wenpo , Liao Shiguo
Published: October 2010

In this study, electrodeposition of Pb on polycrystalline Cu surface has been investigated by cyclic voltammetry (CV). Simultaneous in real time ellipsometry (SE) have been performed to study the characterization and morphological evolution of the Pb layer. The results demonstrated that the rate at which deposition thickness is increasing is going up and revealed that thin Pb deposition layer has already acquired at all the polarization process. So the Cu substrate is not optically ignored during the total polarization process.
Electrode Reconstruction by FIB/SEM and Microstructure Modeling
Authors: Joos Jochen , Rüger Bernd , Carraro Thomas , Weber André , Ivers-Tiffée Ellen
Published: October 2010

Polarization losses within solid oxide fuel cell electrodes are strongly related to microstructure characteristics and composition. High-resolution microstructure analysis is a sensible method to understand and improve electrode performance. This study presents the application of a dual-beam focused ion beam/scanning electron microscope (FIB/SEM) for the three-dimensional (3D) reconstruction of a high performance LSCF-cathode. Error sources arising from FIB slicing and SEM sequencing are identified and methods of correction are presented. The corrected reconstruction data representing altogether a volume of ~ 2800µm3 are the basis for the calculation of the microstructure parameters (i) surface area, (ii) volume/porosity fraction and (iii) tortuosity. These parameters constitute the basis to calculate cathode performance via simplified microstructure models (1-3). Furthermore we present a detailed 3D finite element method (FEM) model to calculate the tortuosity from the accurately reconstructed 3D FIB/SEM data. This model has been extended to calculate electrode performance (ASRcat) from the 3D reconstruction.
Electrochemical Characterization of Ni/(Sc)YSZ Electrodes
Authors: Ramos Tânia , Thydén Karl , Mogensen Mogens
Published: October 2010

Investigations of Ni/(Sc)YSZ cermets for solid oxide cells (SOCs) were performed by electrochemical impedance spectroscopy (EIS), under varying experimental conditions and upon redox cycling, using three different designs of symmetric cells. The deconvolution and fitting of the obtained impedance spectra was performed using a combination of distribution of relaxation times (DRT) and complex non-linear least squares fitting routine (CNLS). The exhibited behaviours allowed the attribution of each contribution to a specific process, and correlated with production methods and microstructural parameters. Initial degradation results for both Ni/ScYSZ and Ni/YSZ based anodes under very high steam content are also reported.
Molybdate Based Ceramic Negative-Electrode Materials for Solid Oxide Cells
Authors: Graves Christopher , Sudireddy Bhaskar R. , Mogensen Mogens
Published: October 2010

Novel molybdate materials with varying Mo valence were synthesized as possible negative-electrode materials for solid oxide cells. The phase, stability, microstructure and electrical conductivity were characterized. The electrochemical activity for H2O and CO2 reduction and H2 and CO oxidation was studied using simplified geometry point-contact electrodes. Unique phenomena were observed for some of the materials - they decomposed into multiple phases and formed a nanostructured surface upon exposure to operating conditions (in certain reducing atmospheres). The new phases and surface features enhanced the electrocatalytic activity and electronic conductivity. The polarization resistances of the best molybdates were two orders of magnitude lower than that of donor-doped strontium titanates. Many of the molybdate materials were significantly activated by cathodic polarization, and they exhibited higher performance for cathodic (electrolysis) polarization than for anodic (fuel cell) polarization, which makes them especially interesting for use in electrolysis electrodes.
Structural, Chemical, and Electronic State on La0.7Sr0.3MnO3 Dense Thin-Film Surfaces at High Temperature: Surface Segregation
Authors: Jalili Helia , Chen Yan , Yildiz Bilge
Published: October 2010

The evolution of the surface topographic and electronic structure and chemical state of the La0.7Sr0.3MnO3 (LSMO) thin films were probed using Scanning Tunneling microscopy and X-ray photoelectron spectroscopy to identify the structural nature of surface segregation of Sr on LSMO. The films had a layer-by-layer structure with a step height of 3.9 Aå, close to the lattice parameter of LSMO. Up to 500oC in oxygen, the topography and the step heights remained the same, statistically within 2-4%, implying that no phase separation took place on the top layers. The low oxygen pressures, down to 10E-10 mbar at 500-580oC promoted segregation of Sr by 12-20% on the A-site. Our results suggests two possible structures for Sr segregation; the replacement of La by Sr on the AO-surface of the LSMO which retains a perovskite termination, or a separate AO-oxide phase nucleating on the defected lower layers.
Preparation and Characterization of Fast Ion Conducting Lithium Thio-Germanate Thin-Films Grown by RF Magnetron Sputtering
Authors: Seo Inseok , Martin Steve W.
Published: October 2010

In this study, amorphous lithium thio-germanate thin-films were prepared as electrolytes for lithium rechargeable batteries by RF sputtering deposition in Ar atmospheres. For the first time, new high quality lithium germanium sulfide, nLi2S + GeS2(n = 1, 2, and 3) thin-films have been successfully made by RF sputtering and synthesized as new solid state electrolytes. Although these materials are unstable in air the starting materials, target materials, and thin-films were thoroughly characterized by XRD, Raman, SEM, XPS, and impedance spectroscopy using special setups to prevent contamination. Thin-films did not show any cracks and pits on the surface and the ionic conductivities of the thin-films are ~1000 times higher than reported values for oxide thin-films. In this way, this work may provide a new way for developing new thin-film electrolytes for solid state lithium ion batteries.
Ba0.5Sr0.5Co0.8Fe0.2O3-δ for Oxygen Separation Membranes
Authors: Müller Philipp , Dieterle Levin , Müller Erich , Störmer Heike , Gerthsen Dagmar , Niedrig Christian , Taufall Simon , Wagner Stefan F. , Ivers-Tiffée Ellen
Published: October 2010

The crystal structure and chemical composition of Ba0.5Sr0.5Co0.8Fe0.2O3-δ bulk samples and powders were studied after heat treatments between 700 ° C and 1000 ° C. X-ray diffractometry (XRD) and in addition transmission electron microscopy (TEM) combined with energy dispersive X-ray spectroscopy (EDXS) was applied to analyze the properties of individual grains. Besides the cubic perovskite phase a hexagonal phase and an additional, not yet clearly identified phase was found at temperatures below 900 ° C.
Properties of Scandia-Doped Zirconia Synthesized by the Polymeric Precursor and the Polyacrylamide Techniques
Authors: Muccillo Reginaldo , Costa Gustavo C.
Published: October 2010

Zirconia-10 mol% scandia powders were synthesized by the polyacrylamide and the polymeric precursor techniques. The state of agglomeration of the powder particles was analyzed by laser scattering, the structural phases by X-ray diffraction, and the morphology by scanning electron microscopy. Transparent gels and polymeric resins were obtained by the polyacrylamide and the polymeric precursor techniques, respectively. The resulting ceramic powders, fully stabilized in the cubic fluorite structure, had high surface area. The electrical behavior of sintered pellets, using powders synthesized by both techniques, was analyzed by the impedance spectroscopy technique. The content of organics used in the syntheses was related to the state of agglomeration of the ceramic powders which, by its turn, was responsible for the different electrical behavior of the sintered pellets.
Effect of Processing Methodology on Microstructure and Ionic Conductivity of Yttria-Stabilized Zirconia
Authors: Muccillo Eliana N. , Muccillo Reginaldo
Published: October 2010

In this study, different methodologies were used for preparing commercial zirconia-8 mol% yttria sintered specimens. Powder compacts were conformed by uniaxial or by a combination of uniaxial and cold isostatic pressing. The sintering of powder compacts was carried out by the two-step sintering process and the results were compared to those of conventionally sintering specimens. The use of combined pressing procedures and two-step sintering process allowed for obtaining sintered specimens with high densities, small grain sizes and with minor differences in the electrical conductivity, which should improve the mechanical properties without compromising the electrical behavior at high temperatures.
A 0-Dimensional Stationary Model for Anode-Supported Solid Oxide Fuel Cells
Authors: Leonide André , Hansmann Simon , Ivers-Tiffée Ellen
Published: October 2010

We present a zero dimensional stationary model which precisely predicts the current-voltage-characteristics of anode supported SOFC single cells over a wide range of operating conditions. The different kinds of electrode polarization resistances are separated from experimental impedance data by means of a detailed equivalent circuit model developed specifically for the analyzed cell type. The activation losses are modeled by the Butler-Volmer equation, whereas the loss contributions from gas diffusion polarizations are calculated from Fick's law. The partial pressure and temperature dependency of the cathodic and anodic exchange current density could be determined by a fit of semi empirical power law model equations. The exponents c and d for the CO and CO2 partial pressure dependency of the anodic exchange current density are determined independently of each other. This paper presents the modeling results for a wide range of operation parameters as well as their experimental verification.
Evaluating H2O Electrolysis on Ceria with Thin-Film Electrodes
Authors: DeCaluwe Steven , Zhang Chunjuan , Eichhorn Bryan W. , Jackson Gregory S.
Published: October 2010

Undoped ceria with its facile redox at high-temperatures has potential as an effective material for electrolysis. This study explores the electrochemical performance of thin-film ceria electrodes for H2O electrolysis at 700 °C. The electrochemical characterization is complemented by in situ XPS measurements, which show that the highly reduced ceria surface increases in degree of reduction with electrolysis voltage. Results also show that H2O electrolysis is enhanced with increased H2 partial pressure. Analysis of electrochemical impedance spectra and voltammetric measurements show that the electrolysis reactions depend strongly on H2 pressure. These trends, which are not readily explained by simple surface kinetic models, do indicate that increased ceria surface reduction by the presence of H2 product enhances activity for H2O electrolysis. The results were used to create a microkinetic model to assess surface and subsurface processes in ceria for H2O electrolysis.
Electrochemical Study of Pt(111)-Cs Surfaces Prepared in Ultra-High Vacuum
Authors: Drnec Jakub , Harrington David
Published: October 2010

Cesium adsorbed on a Pt(111) surface is studied in 0.5 M HClO4. When the surface is extensively cleaned in UHV by Ar+ sputtering, adsorbed Cs completely dissolves in the solution and the cyclic voltammetry is the same as for clean Pt(111). Standard UHV cleaning procedures leave a surface that is more reactive: Cesium is detected on the surface after cycling the potential between -0.03 and 1.6 V, and the cyclic voltammogram shows a shift of the surface oxidation to more negative potentials.
Influence of Electrochemical Conditions on CoCrMo Behavior in Simulated Body Fluid by Step Polarization Technique
Authors: Igual Muñoz Anna , Valero Vidal Carlos
Published: October 2010

Corrosion processes occurring at implant surfaces, the role of oxide films in the corrosion process, alloy biocompatibility and the electrochemical response of alloys to mechanical or electrical transients are all important in the behaviour and success of implant alloys. Most transition metal alloys used in medicine (i.e. Titanium, CoCrMo alloys, stainless steels) have a passive film which spontaneously forms on the surface of the alloy and it provides a kinetic barrier to corrosion reactions. Oxide film structure and morphology are susceptible to the potential which exists across the alloy-solution interface. The present study presents an electrochemical technique based on the application of a potential step and measuring the current transient response to the step in potential. Electrochemical Impedance Spectroscopy (EIS) was carried out in order to provide information concerning the electrical character of the interface. The current density response and the properties of the interface (biomaterial/body fluid) depends on the solution chemistry and the way potential is achieved.
Microstructural Characterization of Reinforced Mortar after Corrosion and Cathodic Prevention in the Presence of Core-Shell Micelles
Authors: Koleva Dessi
Published: October 2010

This work reports on the microstructural properties of reinforced mortar after chloride-induced corrosion and two regimes of cathodic prevention. Additionally, the impact of a very low concentration polymeric nano-aggregates (core-shell micelles from PEO113-b-PS218), admixed in the mortar mixture is discussed. The study reveals that a very low concentration of 0.006 wt.% micelles exerts significant alterations in the bulk matrix on one hand, and increases chloride threshold levels on the other. Both prevention regimes are effectively performing in terms of corrosion protection. When electrical current flow (both steady and pulse) is involved, the micelle-containing matrix behaves close to control cases. Therefore the presence of micelles does not increase current demand; cathodic polarization is well achieved and the long term application of Cathodic Prevention in such systems is expected to have superior performance
Electrochemical Performance of Low-Carbon Steel in Alkaline Model Solutions Containing Hybrid Aggregates
Authors: Koleva Dessi , Hu Jie , De Wit J. H. W. , Boshkov Nikolai , Radeva Ts. , Milkova V. , Van Breugel Klaas
Published: October 2010

This work reports on the electrochemical performance of low-carbon steel electrodes in model alkaline solutions in the presence of 4.9.10-4 g/l hybrid aggregates i.e. cement extract, containing PDADMAC (poly (diallyl, dimethyl ammonium chloride) / PAA (Poly (acrylic acid)/ PDADMAC over a CaO core. The main objective was to determine if the addition of hybrid aggregates will lead to increased corrosion resistance of the steel surface layers, generally formed in the hereby investigated environmental medium. Further, it was expected that when chlorides are involved, as corrosion accelerating factor, the presence of hybrid aggregates will delay corrosion initiation and therefore lead to increased corrosion resistance. This investigation forms part of a novel approach to control steel corrosion in reinforced concrete, using self-healing mechanisms. The results from this study denote for indeed superior corrosion performance of steel in chloride-free and chloride containing alkaline solution, when hybrid aggregates are involved. The mechanisms are related to increased barrier effects of the formed layer and CaO release from the core of the aggregates.
The Role of Alumina in Aluminum Corrosion and Passivation
Authors: Skrovan John , Troczynski Tom , Alfantazi A.
Published: October 2010

The self passivation of aluminum in water generally prevents the generation of hydrogen from an aluminum-water reaction in conditions preferred for portable systems. However the corrosion rate of aluminum powders and thin foils is seen to greatly increase when in contact with alumina powder. This allows commercially useful amounts of hydrogen to be generated at moderate temperatures and neutral pH regions. Data is presented to support the claim that proton availability from the alumina surface is responsible for the increased hydrogen evolution rates, and hydrogen capture tests show passivation no longer stops the corrosion reaction.
High-Pressure Electrochemical Hydrogen Purification Process Using a High-Temperature Polybenzimidazole (PBI) Membrane
Authors: Jiang Junhua , Aulich Ted , Collings Micheal E. , Sohn Chang W.
Published: October 2010

A high-pressure electrochemical hydrogen purification system comprising a two-chamber electrochemical cell and fully automatic flow, pressure, and temperature control units has been successfully constructed. The electrochemical hydrogen purification process using a high-temperature polybenzimidazole membrane and Pt electrocatalysts has been investigated via polarization measurements and product analysis at elevated pressure. Measured linear potential-current curves demonstrate high electrode polarizations in simulated reformate gas containing hydrogen, carbon monoxide, and carbon dioxide. The adsorption of both CO and CO2 onto Pt electrocatalysts at increased pressure has been proposed to be responsible for the high electrode polarizations. The gas chromatography analysis of cathode products suggests that high-purity hydrogen could be obtained at the cathode side, albeit with a small amount of CO2 as impurity. Further research on the optimization of the high-pressure electrochemical purification process for minimized electrode polarizations and maximized hydrogen purity is under way in our lab.
Electrochemistry of Fe-Phenylenediamine Derived Cathode Catalysts Supported on Carbon
Authors: Gharaibeh Samar A. , Birss V. I.
Published: October 2010

The primary goal of this work has been to better understand the oxygen reduction (ORR) activity of a series of Fe-N-C catalysts, formed by mixing Fe chloride with o-phenylenediamine (PDA) followed by heat treatment (HT). It is shown that, for HT at less than 500oC, significant redox chemistry, typical of a o-PDA redox polymer, is revealed in fully deaerated acidic solutions. This redox chemistry disappears at higher HT temperatures, arguing that the ORR active site arises from the thermal decomposition product of the PDA surface polymer. By electrodepositing PDA, either from a solution of o-PDA or from one also containing Fe3+, followed by ORR studies, it is demonstrated that the presence of Fe in the PDA film serves to enhance the ORR activity.
Nitrogen Doped Carbon Nanotube Thin Films as Efficient Oxygen Reduction Catalyst for Alkaline Anion Exchange Membrane Fuel Cell
Authors: Higgins Drew C. , Chen Zhongwei
Published: October 2010

Nitrogen doped carbon nanotubes (N-CNTs) were synthesized from three different aliphatic diamine compounds. Ethylenediamine based N-CNTs (ED-CNTs) were found to have the highest nitrogen content and displayed significant oxygen reduction reaction (ORR) activity. ED-CNTs were fabricated into a thin, free standing film for use as cathode layer in an alkaline anion exchange membrane electrode assembly (MEA). These thin films displayed significantly higher performance in the alkaline MEA setup when compared with commercial carbon supported platinum (Pt/C). The increase in performance was attributed to the distinct structural properties of N-CNTs and enhanced electronic properties resulting from a high degree of nitrogen incorporation.
Fingerprints of Automotive Fuel Cell Degradation
Authors: Mayer Doug , Kundu Sumit , Elvidge Chris , Stumper Jürgen , Bessarabov Dmitri
Published: October 2010

Durability of fuel cell components is a challenge for commercialization of automotive fuel cells. Materials such as the cathode catalyst layer are subjected to a number of voltage stresses which can cause multiple failure modes such as carbon corrosion and Pt dissolution. This work examines three degradation cycles and attempts to de-convolute the amount of degradation from carbon corrosion. A 1.4V hold, 1.0-1.4V cycle, and a 0.6-1.4V cycle were examined. Performance and EPSA measurements were taken and CO2 release was monitored over time. A carbon corrosion fingerprint was created using 1.4V hold results and used to evaluate the contribution of the corrosion mechanism to performance degradation in the other cycles. The results indicate that the 1.0-1.4V cycle degrades primarily by carbon corrosion while the 0.6-1.4V cycle had a significant contribution from other mechanisms, including Pt dissolution.
Increasing and Decreasing Mass Transport Effects in the Oxidation of Small Organic Molecules
Authors: Seland Frode , Foss Carl Erik L. , Tunold Reidar , Harrington David
Published: October 2010

The local mass transport effect in the oxidation of small organic molecules on polycrystalline platinum was studied. A transient increase in RDE rotation rate caused an increase in methanol and ethanol oxidation current, in contrast to a reduced current in slower experiments with a sustained increase in rotation rate. Sweep hold experiments during the initial stages of the oxidation peak in the positive going scan, also showed an increase in oxidation current with increased rotation rate. This effect slowly turned off and resulted in a lower current density with time. The increased current density was explained in terms of a temporary increase in consumption of alcohol to soluble products, while a more competitive formation of strongly adsorbed species explained the reduced current with sustained rotation. Parallels between ethanol and methanol oxidation are drawn.
Spectroscopic Signatures of Photogenerated Radical Anions in Polymer-[C70]Fullerene Bulk Heterojunctions
Authors: Liedtke Moritz , Sperlich Andreas , Kraus Hannes , Deibel Carsten , Dyakonov Vladimir , Filippone Salvatore , Delgado Juan L. , Martín Nazario , Poluektov Oleg G.
Published: October 2010

Light induced polarons in solid films of polymer-fullerene blends were studied by applying photoluminescence (PL), photo induced absorption (PIA) techniques as well as electron spin resonance (ESR). The materials used were poly(3-hexylthiophene) (P3HT) and poly-[2-methoxy, 5-(2'-ethyl-hexyloxy) phenylene vinylene] (MEH-PPV) as donors. As acceptors we used [6,6]-phenyl-C61-butyric acid methyl ester ([C60]PCBM) and various soluble C70-derivates: [C70]PCBM, diphenylmethano[70]fullerene oligoether (C70-DPM-OE), C70-DPM-OE2, and two fullerene dimers, C70-C70 and C60-C70 (all shown in figure 1). In all blends containing C70 we found typical signatures which were absent if [C60]PCBM was used as acceptor. Light-induced ESR revealed signals at g>2.005, which we previously assigned to an electron localized on the C70 cage, the PIA measurements showed a new sub-bandgap absorption band at 0.92 eV, which we correspondingly ascribe to C70 radical anions formed in the course of photoinduced electron transfer from donor to acceptor.
Nanocarbon Synthesis Using Oxidized Diamond-Supported Metal Catalysts
Authors: Nakagawa Kiyoharu , Gamo Hidenori , Nishitani-Gamo Mikka , Ando Toshihiro , Oda Hirokazu
Published: October 2010

Nanocarbons could be obtained by the decomposition of light alkanes using oxidized diamond-supported Ni catalyst with high yields. This is the report to show that oxidized diamond can serve as an active catalytic support material for nanocarbon synthesis. Oxidized diamond is proposed as a novel catalytic means for the synthesis of nanocarbons, and it is suggested that oxidized diamond may catalyze unique reactions of importance in nanomaterial synthesis.
Nanostructures to Probe Electrocatalytic Reactions
Authors: Yagi Ichizo , Nomura Kamba , Notsu Hideo , Kimijima Ken'ichi , Hayashi Akari , Ohta Narumi
Published: October 2010

The electrochemical annealing of very flat Au thin film with adhesive Ti layer can modify its morphology to an island-like film, which is favorable for spectroscopies with the surface enhanced infrared absorption (SEIRA) method. The nanostructured Au/Ti bilayer can be also useful to detect adsorbates on commercial or developed catalysts deposited on its surface.
Adipogenic and lipolytic effects of chronic glucocorticoid exposure
Authors: Campbell Jonathan E. , Peckett Ashley J. , D'souza Anna M. , Hawke Thomas J. , Riddell Michael C.
Published: October 2010

Glucocorticoids have been proposed to be both adipogenic and lipolytic in action within adipose tissue, although it is unknown whether these actions can occur simultaneously. Here we investigate both the in vitro and in vivo effects of corticosterone (Cort) on adipose tissue metabolism. Cort increased 3T3-L1 preadipocyte differentiation in a concentration-dependent manner, but did not increase lipogenesis in adipocytes. Cort increased lipolysis within adipocytes in a concentration-dependent manner (maximum effect at 1–10 μM). Surprisingly, removal of Cort further increased lipolytic rates (∼320% above control, P < 0.05), indicating a residual effect on basal lipolysis. mRNA and protein expression of adipose triglyceride lipase and phosphorylated status of hormone sensitive lipase (Ser563/Ser660) were increased with 48 h of Cort treatment. To test these responses in vivo, Sprague-Dawley rats were subcutaneously implanted with wax pellets with/without Cort (300 mg). After 10 days, adipose depots were removed and cultured ex vivo. Both free fatty acids and glycerol concentrations were elevated in fed and fasting conditions in Cort-treated rats. Despite increased lipolysis, Cort rats had more visceral adiposity than sham rats (10.2 vs. 6.9 g/kg body wt, P < 0.05). Visceral adipocytes from Cort rats were smaller and more numerous than those in sham rats, suggesting that adipogenesis occurred through preadipocyte differentiation rather than adipocyte hypertrophy. Visceral, but not subcutaneous, adipocyte cultures from Cort-treated rats displayed a 1.5-fold increase in basal lipolytic rates compared with sham rats ( P < 0.05). Taken together, our findings demonstrate that chronic glucocorticoid exposure stimulates both lipolysis and adipogenesis in visceral adipose tissue but favors adipogenesis primarily through preadipocyte differentiation.
Cathelicidin LL-37 peptide regulates endothelial cell stiffness and endothelial barrier permeability
Authors: Byfield Fitzroy J. , Wen Qi , Leszczyńska Katarzyna , Kułakowska Alina , Namiot Zbigniew , Janmey Paul A. , Bucki Robert
Published: October 2010

LL-37 peptide is a multifunctional host defense molecule essential for normal immune responses to infection or tissue injury. In this study we assess the impact of LL-37 on endothelial stiffness and barrier permeability. Fluorescence microscopy reveals membrane localization of LL-37 after its incubation with human umbilical vein endothelial cells (HUVECs). A concentration-dependent increase in stiffness was observed in HUVECs, bovine aortic endothelial cells (BAECs), human pulmonary microvascular endothelial cells, and mouse aorta upon LL-37 (0.5–5 μM) addition. Stiffening of BAECs by LL-37 was blocked by P2X7 receptor antagonists and by the intracellular Ca2+chelator BAPTA-AM. Increased cellular stiffness correlated with a decrease in permeability of HUVEC cell monolayers after LL-37 addition compared with nontreated cells, which was similar to the effect observed upon treatment with sphingosine 1-phosphate, and both treatments increased F-actin content in the cortical region of the cells. These results suggest that the antiinflammatory effect of LL-37 at the site of infection or injury involves an LL-37-mediated increase in cell stiffening that prevents increased pericellular permeability. Such a mechanism may help to maintain tissue fluid homeostasis.