bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization of Photovoltaic Devices from Layered PTEBS and Nanocrystalline TiO2
Authors: Qiao Qiquan , C. Kerr William , Beck James , Corrigan Eric , M. McLeskey James
Published: November 2006

Sodium poly[2-(3-thienyl)-ethoxy-4-butylsulfonate] or PTEBS has been explored previously for use in the fabrication of photovoltaic cells. PTEBS is a water-soluble polythiophene and the use of this polymer would allow safe, environmentally friendly processing as well improved reproducibility. In this study, solar cells based on layered PTEBS and TiO2 nanocrystalline films were investigated. The variation of the TiO2 thickness on the spin coating speed and suspension concentration was studied. Multiple spin coatings were used to make layers thicker than 3.5 μm. The photovoltaic samples with the TiO2 thickness in the range of 180 nm ~ 8.08 μm have been fabricated to investigate the dependence of the efficiency and open circuit voltage on the TiO2 thickness. The optimum TiO2 thickness was found to be around 4 ~ 4.5 μm. The maximum efficiency of 0.15% was obtained at the TiO2 thickness of 4.17 μm in this experiment. The initial investigation of dependence of the device characteristics on the PTEBS thickness was also explored.
Effects of Substrates on Dye-Sensitized Solar Cell Performance Using Nanocrystalline TiO2
Authors: Ngamsinlapasathian Supachai , Kitiyanan Athapol , Fujieda Takuya , Yoshikawa Susumu
Published: November 2006

The effects of conducting glasses on photovoltatic properties of dye-sensitized solar cells using nanocrystalline TiO2 were studied. The ITO substrate showed low ability to withstand heat during the sintering process, leading to an increase in sheet resistance. The heat stability of ITO conducting glass was improved by depositing metal oxide such as ATO, AZO, and SnO2, on ITO layer. The IPCE spectra of thin MP-TiO2 cell were higher than that of thick P25 cell in the region between 400-475 nm but lower than that of thick P25 cell in the red region, because the thickness of MP-TiO2 film was not enough to scatter the light leading to low absorbed spectra in red region. IPCE spectra can be improved by using the cell made from blend MP- TiO2 with P25. The efficiency of the MP-TiO2+P25 cells using ITO/SnO2 conducting substrate remarkably increased comparing with that of the cells using ITO.
Toward a 3-D Nanostructured Battery
Authors: Martin Charles R. , Sides Charles Robert , Xu Fan
Published: November 2006

Nanostructured Li-ion battery electrodes were created by methods based on template-synthesis. A nanofiber V2O5 cathode, a nanocomposite LiFePO4/carbon cathode, and a porous honeycomb carbon anode were characterized structurally and electrochemically. These electrodes show dramatically improved ability to deliver specific capacity (mAh g^-1) at extreme discharge conditions compared to microstructured control electrodes. The synthesis and characterization of these electrodes is discussed in the context of the goal of a three-dimensional (3-D) nanostructured battery.
Performance of PEFC Formed by Using Pt-Loaded Activated Carbon with CF3SO3H in Cathode
Authors: Maruyama Jun , Abe Ikuo
Published: November 2006

Enhancement of oxygen reduction at a catalyst layer formed from a Pt-loaded activated carbon (Pt/AC) with adsorbed CF3SO3H compared to that from Pt/carbon black (Pt/C) was recently found using rotating disk electrodes (RDE). In this study, we verified the enhancement at fuel cells formed by using Pt/AC in the cathode catalyst layer. At the relative humidity of 100%, the PEFC formed from Pt/AC showed better performance than that formed from the Pt/C in the cathodes. The adsorption of CF3SO3H onto Pt/AC further improved the performance. This tendency was in agreement with the results of the RDE measurements. At the relative humidity of 25%, although the hydrophilicity of the catalysts affected the kinetics of oxygen reduction and the cell resistance, the same tendency of the PEFC performance was observed. The results suggest the usefulness of Pt-loaded activated carbon with CF3SO3H for improvement of PEFC performance.
Leveraging Metal-Support Interactions to Improve the Activity of PEMFC Cathode Catalysts
Authors: Swider-Lyons Karen , Teliska Margaret , Baker Wendy , Bouwman Peter , Pietron Jeremy
Published: November 2006

The oxygen reduction reaction (ORR) at proton exchange membrane fuel cell (PEMFC) cathodes requires a relatively large amount of Pt to catalyze. Our goal is to reduce the Pt loading in PEMFC cathodes using catalysts modified by metal support interactions (MSIs), an approach commonly used in heterogeneous catalysis. We illustrate the benefits of MSIs by showing that the activity of Pt is improved by supporting it on hydrous tantalum phosphate. More dramatically, oxygen reduction on Au in changed from a 2- to 4-electron reaction simply by supporting the metal on hydrous tin oxide. The changes to the catalysis of Pt and Au are attributed to electronic and chemical effects imparted by the supports.
Fullerenes and Their Composites for Proton Conducting Membranes in Polymer Electrolyte Fuel Cells
Authors: DeSousa Ryan , Venkatesan Arun , Tasaki Ken , Wang Hengbin , Gasa Jeffrey
Published: November 2006

The effect of fullerene derivatives on the low humidity conductivity of Nafion® is discussed. Composites of Nafion with fullerene and poly-hydroxyfullerene (PHF) as additives are fabricated using solution casting techniques. The extraction of the additives from these composites was studied using UV-Vis spectroscopy. These composites show an excellent stability to extraction of the additive. Some of these composites show improved low humidity conductivity over recast nafion.
Fullerene Composite Membranes for Low Humidity Operation of Polymer Electrolyte Fuel Cells : Part III
Authors: Wang Hengbin , Venkatesan Arun , Tasaki Ken , Stucky Galen , Wudl Fred , DeSousa Ryan , Gasa Jeffrey
Published: November 2006

HC60(CN)3 and C60(PEG)5 was synthesized by cyanide addition and atom transfer radical addition respectively. Fullerene- Nafion composite membranes with high quality were fabricated by a novel solution cast procedure. The composite membranes show enhanced proton conductivity at low humidity compare to recast Nafion made under the same condition. The membrane structure-property relationship was investigated by optical microscopy, SAXD and water uptake studies.
PTFE-Based High-Temperature Proton-Conducting Membrane
Authors: Peled Emanuel , Reichman Shaul , Ulus Avi
Published: November 2006

The demand for a Solid Polymer Electrolyte Membrane (SPEM) for fuel-cell systems, capable of withstanding temperatures above 130{degree sign}C, decreasing the electrode-catalyst loadings and reducing poisoning by carbon monoxide, has prompted this study. A novel, low-cost, highly conductive, nanoporous proton-conducting membrane (NP-PCM) based on a polytetrafluoroethylene (PTFE) backbone has been developed. It comprises a non-conductive nano- size ceramic powder, PTFE binder and an aqueous acid. Impregnation of the ceramic powder into the membrane substrate was carried out by sol-gel synthesis. The preparation procedures were studied and the membrane was characterized with the use of: PSD, SEM, EDS, DSC, FTIR and electrochemical methods. A non-optimized direct-methanol fuel cell (DMFC) with a 137 μm-thick membrane was assembled. It demonstrated 133 mW.cm-2 at 80oC, 0.05 atm. dry air (1.9 stoich). Future study will be directed to optimizing the Membrane-Electrode-Assembly (MEA) preparation process and testing of both DMFCs and H2-FCs at high temperatures.
Electrochemical Impedance Spectroscopy of Direct Methanol Fuel Cell
Authors: Hsueh Kan-Lin , Lai Chien-Ming , Hwang Chiou-Ping , Wu Fu-Chi , Tsai Li-Duan , Peng Alex Yu-Min , Lin Jing-Chie
Published: November 2006

Direct methanol fuel cells (DMFCs) are attractive for several transportation and portable applications. The performance of DMFCs was usually measured by I-V curves, it is not sufficient to understand the detailed characteristics of membrane electrode assembly (MEA) and to differentiate the effects of each layer on MEA. Therefore, it is very interest to investigate the characterization of MEA using electrochemical impedance spectroscopy. In present work, we successful discriminated that the contribution of each layer on MEA and developed a new equivalent circuit with interfacial properties for analysis of electrochemical impedance spectroscopy.
Ethanol-Tolerant Oxygen Reduction Reaction (ORR) Cathodes for Direct Ethanol Fuel Cell Applications
Authors: Savadogo O. , Varela F.J. Rodriguez
Published: November 2006

The catalytic activity of the ruthenium catalysts dispersed onto carbon powder for the ORR in an acid medium with and without ethanol was studied. It was found that the Ru/C catalyst cathode exhibited a high tolerance to ethanol and has a high degree of selectivity for the ORR in the presence of ethanol. Thus, its catalytic activity towards the ORR is not significantly affected by the presence of ethanol. The onset potential of the ORR on Ru/C increases very slightly by 60, 62 and 68 mV for the electrolytes containing 0.5M H2SO4 with respectively 0.125M, 0.250M and 0.500M C2H5OH solutions. This reduction of the onset potential of the ORR activity of the Ru/C catalyst from its value without ethanol to its value in the presence of the ethanol is about ten times smaller than those on Pt-based catalysts (i.e. an increase of 590 mV in onset potential of the ORR with a Pt/C catalyst in a 0.5M H2SO4 + 0.125M C2H5OH solution). Furthermore, when tested as cathode material in a DEFC, the Ru/C catalyst presented notable current density vs. fuel cell voltage characteristics at 80 and 90{degree sign}C.
Experiments Toward Fundamental Validation of PEM Fuel Cell Models
Authors: Yan Qiangu , Toghiani H. , Liu Q. Y. , Wu J. X.
Published: November 2006

Detailed experimental parameters are controlled and measured under widely varying operating conditions. In addition to polarization curves, feed gas flow rates, temperatures, pressure drop, and relative humidity are all measured accurately. Performance of a polymer electrolyte fuel cell (PEFC) was studied using steady-state polarization curves and electrochemical impedance spectroscopy (EIS) techniques. The effects of relative humidity, temperature, pressure and feed gas stoichiometry on fuel cell performance were investigated. It was found that the humidity of both the anode and cathode inlet gases had a significant effect on fuel cell performance. The experimental results showed that a decrease in the cathode humidity has a more detrimental effect on cell performance than a comparable decrease in the anode humidity. The obtained results will be used to define conditions of optimal hydration of the membrane. Based on the performance and resistance measurements, optimal humidification can be achieved. The polarization curves of the cell at different operating temperatures showed that fuel cell performance was improved with increasing temperature from 65 to 75{degree sign}C. The fuel cell performance also improved as the operating pressure was increased from 1 atm to 4 atm. The resistance of the working fuel cell showed that the membrane resistance increased as the feed gas relative humidity (RH) decreased. The experimental results were compared with the results of a CFD mathematical model. These experimental data will provide a baseline for validation of fuel cell models.
Effects of Temperature Difference on Water Management in PEMFCs
Authors: Zaffou Rachid , Yi Jung , Kunz Russell , Fenton James
Published: November 2006

A quantitative investigation has been carried out to examine the effect of through-plane temperature gradients on water transport across the membrane-electrode assembly (MEA) of a Proton Exchange Membrane (PEM) fuel cell. The presence of a temperature gradient across the cell was found to cause a significant amount of water to transport through the MEA in the direction towards the colder side; the water transport rate increased with temperature and temperature gradient. This study reveals the importance of thermo-osmosis in PEM fuel cells (PEMFCs) and the need to consider the through-plane temperature profile in water management design and operation in PEMFCs.
Investigation of Carbon Nanofibers as Catalyst Support for Fuel Cell Electrodes
Authors: Wallnofer Eva , Baumgartner Wolfgang , Schaffer Thomas , Besenhard Juergen Otto , Hacker Viktor
Published: November 2006

Cathodes for fuel cells with platinum as catalyst supported on tubular carbon nanofibers (CNFs) were investigated for the oxygen reduction reaction. CNFs should find a promising application field in fuel cell technology, due to their electrical and structural properties. CNFs were plated with platinum particles by an electroless plating method. CNF-based electrodes were produced by a sedimentation method. Polarization curves were measured in half cell tests, and physical characterization was carried out by scanning electron microscopy. It was shown that the fibers are capable of providing the required porosity with low binder content and an excellent electrical conductivity, as well as a good performance with low catalyst loading. The fibers allowed a reduction of the binder content in the electrode to prevent covering of catalyst with binder. With an optimization of the thickness of the electrode, the catalyst is lowered by 40 % without a significant loss of performance.
Electrocatalyst Stability In PEMFCs And The Role Of Fuel Starvation And Cell Reversal Tolerant Anodes
Authors: Ralph Thomas R. , Hudson Sarah , Wilkinson David P.
Published: November 2006

Gross fuel starvation at the anode of a proton exchange membrane fuel cell (PEMFC) can result in cell reversal. High positive anode potentials are reached to sustain the current by water oxidation and carbon corrosion at the Pt based anode electrocatalysts. The membrane electrode assembly (MEA) is irreversibly damaged and the flow field plates and stack material in electrical contact with the MEA can be corroded. One of the best approaches to minimise the impact of fuel starvation is to build cell reversal tolerance into the MEA.Moving to more corrosion resistant carbon supports, adding Teflon to the anode catalyst layer to retain water, and deploying a water oxidation electrocatalyst in the anode significantly improved the cell reversal tolerance of the MEA.
A Model for SO2 Impurity in Air Fed to a Proton Exchange Membrane Fuel Cell
Authors: Wang Wentao , Lee W. K. , Van Zee John W.
Published: November 2006

Transient data of SO2 in air are presented to understand the effect of SO2 on the fuel cell performance. An empirical relationship between steady state voltage loss and the concentration of SO2 in air was found for the Gore Select® membrane. A poisoning mechanism was proposed for SO2 in air.
Enhanced Stability of PtCo catalysts for PEMFC
Authors: Ball Sarah C. , Theobald Brian , Thompsett David , Hudson Sarah
Published: November 2006

In this work it is shown that PtCo/C catalysts give a 2x mass activity enhancement in oxygen reduction activity, compared to Pt/C. Through the use of Pt and PtCo catalysts of varying surface area, clear evidence of a particle size effect on oxygen reduction activity was found. Investigation of the effects of cathode potential cycling in both wet electrolyte cells (1M H2SO4) and as small MEAs revealed high metal surface area stability and stable oxygen performance over 10,000 cycles for the PtCo/C alloys compared to Pt/C. TEM analysis of MEA cross-sections after cycling show clear evidence of Pt migration towards and into the PEMFC membrane for Pt/C cathodes, whilst PtCo/C materials show minimal deterioration. The larger crystallite sizes present in PtCo particles therefore confer higher stability to cycling and resistance to dissolution, whilst use of an alloy produces high mass activity, despite a lower metal surface area compared to Pt/C.
Fuel Cell Catalyst Particle Size Growth Characterized by X-Ray Scattering Methods
Authors: Garzon F. H. , Davey John , Borup Rodney
Published: November 2006

X-ray diffraction experiments coupled with whole profile pattern refinement and Warren Averbach data analysis methods were used to quantify Pt electrode crystallite growth in polymer membrane fuel cell cathode samples. Both X-ray data analysis methods produced similar results for average particle sizes. The cycling of cathodes to cell potentials above 1 volt greatly increases the loss of Pt cathode surface area by Pt grain growth. The fuel cell anode catalysts exhibit little to no growth after potential cycling experiments. Changes in Pt to carbon peak integrated intensity ratios indicate carbon corrosion is occurring upon cycling to high potentials.
Aspects of PEMFC Degradation
Authors: Burlatsky Sergei F. , Atrazhev Vadim , Cipollini Ned , Condit David , Erikhman Nikolai
Published: November 2006

Two important aspects for understanding membrane degradation in PEM fuel cells are Pt dissolution, migration and precipitation from the electrodes into the membrane and chemical attack of the membrane by hydroxyl radicals. Transmission electron microscopy was used to detect and quantify the distribution of Pt particles in Nafion membrane after accelerated cyclic testing. Quantum chemical calculations revealed that hydroxyl radicals that chemically degrade the membrane can be directly generated at low and high potentials as opposed to indirectly generated through peroxide intermediate.
Outstanding Student/Post-doc Presentation Award Recipient: Factors Accelerating Membrane Degradation Rate and the Underlying Degradation Mechanism in PEMFC
Authors: Mittal Vishal , Kunz Russell , Fenton James
Published: November 2006

Membrane degradation and failure is one of the factors limiting the overall durability of the polymer electrolyte membrane fuel cell. The fluoride emission rate (FER), which was calculated from the fuel cell effluent water analysis, was used to quantify the membrane degradation. The FER was found to decrease with an increase in load in the range from open circuit voltage (OCV) to 150 mA/cm2. Since at OCV no current is drawn from the fuel cell the effect of location of Pt/C catalyst on the FER was evaluated by having only one layer of catalyst applied to the membrane. The membrane degradation rate was found to be very high at OCV irrespective of whether the catalyst is present at the anode, cathode or in the membrane (catalyst layer sandwiched between 2 membranes). Effect of Pt/C catalyst exposure to oxygen is shown to have a significant effect on the FER at OCV.
Ruthenium Crossover in DMFCs Operating with Different Proton Conducting Membranes
Authors: Zelenay Piotr , Kim Yu Seung , Bashyam Rajesh , Choi Jong-Ho
Published: November 2006

Ruthenium crossover in alternative membranes with low water/methanol permeability was investigated using carbon monoxide stripping voltammetry. Voltammograms indicate that ruthenium crossover occurs in such membranes to a similar degree as in the Nafion®. We found substantial ruthenium crossover took place at an initial stage of direct-methanol fuel cell (DMFC) operation. In this paper, we demonstrate a pre- treatment method for the Pt-Ru anode designed to substantially reduce ruthenium crossover and its effect on long-term DMFC performance. Measured shifts in stripping peak potentials for the Pt-Ru anode and Pt cathode indicate that ruthenium crossover continues to take place over the life test duration, but without any significant impact on cathode performance. This leads to a conclusion that the crossover phenomenon is likely to involve at least two different Ru species. Those that are most detrimental to DMFC performance can be removed from the anode via the pre-treatment proposed in this study.
Performance of DMFC with TiN Coated Aluminum Bipolar/End Plates
Authors: Padhy Biswa R. , Reddy Ramana G. , Ada Earl
Published: November 2006

Bipolar/end plate is an important component of DMFC, which has intricate flow field design machined on it and carries 80-85 % weight of the whole stack. Emphasizing more on issues like weight, fabrication cost and availability, Al-6061 was selected as a material for bipolar plate. Long term stability test was carried out for 100 hrs on DMFC with Al-6061 end plates at 70 {degree sign}C and 200 kPa and a constant open circuit voltage of 0.614 V was achieved. MEA was characterized by SEM, EDS, and XPS. The aluminum from the end plates were leached and 23 % by weight fraction of MEA surface was found as aluminum. To avoid the dissolution of Al-6061 end plate, it was coated with TiN using spray technique. Experiments were carried out using TiN coated endr plates. There was no dissolution product found on MEA by EDS analysis and OCV of 0.56 V was received.
Durability of Membrane-Electrode Interface under DMFC Operating Conditions
Authors: Kim Yu Seung , Pivovar Bryan
Published: November 2006

In this study, interfacial degradation under DMFC operating conditions was systematically investigated using series of alternative sulfonated poly(sulfone) membranes. In-situ cell high frequency resistance measurement indicated that membrane dimensional stability was the key parameter for interfacial delamination. Based on this result, less water swollen sulfonated poly(sulfone) membranes were prepared by introducing fluorine and other polar groups such as benzonitirle or phenyl phosphine oxide in the backbone of poly (sulfone) copolymer. Long-term fuel cell performance of an interface-optimized poly (sulfone) membrane showed a stable interfacial resistance and an excellent cell performance for 3,000h under continuous DMFC operation at fixed voltage of 0.5 V.
Epitaxial Growth of Ag on Au(111) by Monolayer Restricted Galvanic Displacement
Authors: Dimitrov Nikolay , Vasilic Rastko
Published: November 2006

The development of a new method for epitaxial growth of metals in solution by galvanic displacement of layers pre-deposited by underpotential deposition (UPD) is discussed and experimentally illustrated. Cyclic Voltammetry and Scanning Tunneling Microscopy are employed to carry out and monitor a quasi-perfect , two-dimensional growth of up to 35 monolayers (MLs) of Ag on Au(111) by repetitive galvanic displacement of underpotentially deposited Tl and Pb monolayers. A comparative study emphasizes the displacement stoichiometry as an efficient tool for thickness control during the deposition process and as a key parameter that affects the deposit morphology. The excellent quality of layers deposited by monolayer-restricted galvanic displacement is manifested by a steady UPD voltammetry and ascertained by a flat and uniform surface morphology maintained during the entire growth process. An X-ray Photoelectron Spectroscopy analysis finds no traces of Pb in the Ag deposit.
An Examination of Co and Fe Core Nanoparticles with a Protecting Shell
Authors: Podlaha Elizabeth J. , Henry Lawrence , Guo Zhanhu
Published: November 2006

The displacement reactions of Cu(II) in a citrate electrolyte with sulfobetaine stabilized colloidal cobalt and iron nanoparticles were compared. While a core-shell structure was obtained with a Co core and a Cu shell, Fe nanoparticles were completely displaced by Cu(II) and resulted in a Cu nanoparticle. To create a shell structure around Fe, an annealing step was used to decompose the sulfobetaine in a H2 environment to a carbon shell around the Fe core. The carbon shell was found to effectively protect the iron core from oxidation in acidic solution.
Solid-State Electrochemical Sensor for Monitoring Mg in Al Refining Process
Authors: Kale Girish M. , Jacob K. T. , Wang Ling , Hong Yanruo
Published: November 2006

Novel solid-state electrochemical sensors have been designed using the Mg2+ cation conductors incorporating novel solid- state reference electrodes for in-line monitoring of Mg in molten Al during the refining process and also for in-line monitoring of Mg content in molten Al in the alloying process. In this paper we report the preparation of Mg2+ ion conductors, MgAl2O4 and MgZr4(PO4)6, by the solid state ceramic synthesis route, measurement of their electrical properties using ac-impedance spectroscopy and application of the above cation conductors for designing novel electrochemical sensors for monitoring Mg dissolved in molten Al. The activation energy for Mg2+ ion conduction in MgAl2O4 is 2.08 eV and in MgZr4(PO4)6 is 1.7 eV, respectively. The sensors have been found to respond rapidly to change in Mg content in molten aluminium around 1000 K.
Hydrothermal Synthesis of Vanadium Oxide Nanorods by Surfactant-Assisted Method
Authors: Pavasupree Sorapong , Suzuki Yoshikazu , Yoshikawa Susumu , Ngamsinlapasathian Supachai
Published: November 2006

Vanadium oxides nanorods with high crystallinity and high surface area were synthesized by hydrothermal method using laurylamine hydrochloride, metal alkoxide and acetylacetone. The samples characterized by XRD, nitrogen adsorption isotherm, SEM, TEM, and SAED. Uniformly sized VO2 nanorods had widths about 40-80 nm and lengths reaching up to 1 μm. V2O5 rodlike structured with the widths about 100-500 nm and the length of 1-10 μm were obtained by calcination at 400 oC for 4 h. This synthesis method provides a new simple route to fabricate 1-D nanostructured metal oxides under mild conditions.
Investigation of Temperature Induced Structural Transformations in Tungsten Oxide (WO3) Thin Films
Authors: Chintalapalle Ramana V. , Utsunomiya Satoshi , Julien C. M. , Becker Udo
Published: November 2006

Tungsten oxide (WO3) thin films were produced by pulsed laser depositon and the effect of temperature on their structure studied. Characterization of PLD WO3 thin films as a function of growth temperature using X-ray diffraction (XRD) and Raman spectroscopy (RS) indicated that the films grown at room temperature were nearly stoichiometric and amorphous. The structural order improves with the increase in temperature. WO3 thin films formed at temperatures {greater than or equal to} 400 oC were non- stoichiometric with oxygen deficiency. The amorphous to polycrystalline (monoclinic) structural transition occurs at a growth temperature of 300 oC.
Isolation, Spectroscopic Characterization, and Study of Island Formation of Two Isomers of the Metallofullerene Nd@C82
Authors: Porfyrakis Kyriakos , Leigh David , Owen James , Lee Seung , Kanai Mito , Morley Gavin , Ardavan Arzhang , Dennis John , Pettifor David , Briggs Andrew
Published: November 2006

Two types of the metallofullerene Nd@C82 have been isolated and characterized. HPLC was used to isolate Nd@C82(I, II). The two isomers were characterized by mass spectrometry and UV-Vis- NIR absorption spectroscopy. Nd@C82(I) was found to be similar in structure to the main isomer of other lanthanofullerenes such as La@C82. We assign Nd@C82(I) to have a C2v cage symmetry. Nd@C82(II) showed a markedly different UV-Vis-NIR absorption spectrum to Nd@C82(I). Its spectrum is in good agreement with that of the minor isomer of metallofullerenes such as Pr@C82. We therefore assign Nd@C82(II) to have a Cs cage symmetry. In contrast to other metallofullerenes, both isomers appear to be equally abundant. Their molecular orbital structures have been studied by a combination of scanning tunnelling microscopy (STM) and density functional theory (DFT). Matching filled and empty-states STM images to DFT calculations allowed us to distinguish directly between the two isomers on a substrate.
Sputtering Deposition Parameters and Their Interactions in Amorphous Tungsten Oxide Thin Film as Electrochromic Electrode
Authors: Widjaja Edy J. , Delporte Gerdy , Larsson Anna-Lena
Published: November 2006

Amorphous tungsten oxide (a-WO3) thin films were deposited as electrochromic electrodes on ITO coated glass substrates via reactive DC magnetron sputtering from metallic tungsten target. A two-level full-factorial design-of-experiment (DoE) was carried out with the following variables: 1) sputter target power density, 2) total pressure, 3) oxygen to argon flow ratio and 4) deposition time. Characterizations via lithium intercalation in potentiostatic mode were conducted in a wet electrochemical cell. Our work shows that parameters interaction should be considered in optimizing WO3 thin film for electrochromic applications. Work based on a factorial design reduces the number of experiments and allows reaching near-optimized region with small amount of effort.
Jubelee Letter
Authors: Janik-Czachor Maria
Published: November 2006

Abstract not Available.
Corrosion-Resistant Bulk Amorphous Ni-Cr-Ta-Mo-Nb-5P Alloys in Concentrated Hydrochloric Acids
Authors: Hashimoto Koji , Shinomiya Hiroyuki , Nakazawa Akito , Kato Zenta , El-Moneim Ahmed A. , Niizeki Yoshio , Asami Katsuhiko
Published: November 2006

Amorphous bulk Ni-Cr-Mo-22at%Ta-14at%Nb-P alloys resistant to concentrated hydrochloric acids was prepared by copper-mold casting. The amorphous alloys of single phase, such as (1- 4Cr)-1Mo-7P and (1-2.5)Cr-(1-2)Mo-4P alloys did not show detectable corrosion weight loss after immersion in 12 M HCl for 168 h. These alloys were spontaneously passive in concentrated hydrochloric acids due to presence of stable air- formed films, in which chromium was particularly rich in addition to enrichment of tantalum and niobium. The high corrosion resistance of the homogenous alloys of single phase was interpreted in terms of the presence of bi-layer structure film consisting of the outer stable triple oxyhydroxide, Cr1- xTaxNbyOzOH3+2x+2y-2z, and the inner MoO2 layer acting as the effective diffusion barrier.
Data Mining of Experimental Corrosion Data Using Neural Network
Authors: Kamrunnahar Mst , Urquidi-Macdonald Mirna
Published: November 2006

A supervised Neural Network (NN) method was used to predict the corrosion behavior (general and localized corrosion) and in turn, the life of metals and alloys over extended periods of time in specific environments, such that the developed NN model learns the underlying laws that map the alloy characteristics and environments to the alloy's corrosion behavior. The approach used in this work is the mining of existing experimental databases for both DC and AC corrosion experiments on metallic glasses, and grade-2 Titanium. The data mining results allow us to categorize and prioritize certain parameter sets (e.g. pH, temperature, time, electrolyte & metal compositions) that impact the alloy's corrosion rate and electrochemical potential. The developed NN models were tested by validating the predicted life of metals/alloys against available experimental data. The NN models were then used to predict future corrosion rates for user-specified environmental conditions and time frames.
Electrochemical Noise Study on Galvanic Corrosion of Aluminum Alloy in Chloride Environments- Effect of Oxide Film Structure
Authors: Sakairi Masatoshi , Shimoyama Yukiya , Takahashi Hideaki
Published: November 2006

Four different types of anodic films, barrier type, porous type anodized in (COOH)2 solution, porous type anodized in H2SO4 solution and composite type, were formed on pure aluminum and aluminum alloy specimens. The effect of anodic oxide film structure on galvanic corrosion of aluminum and its alloys was measured by electrochemical noise technique. During incubation period (before localized corrosion started), both current and potential slightly changed with time. After localized corrosion started, those changed suddenly with time with fluctuation. The composite type anodic oxide film formed on pure aluminum and 6061 alloys showed the longest incubation period than other types of anodic oxide films formed on these specimens. However, anodic oxide treatment did not increase corrosion resistance of 2017 alloy.
Conventional and Pulse Cathodic Protection of Reinforced Concrete: Electrochemical Approach and Microstructural Investigations
Authors: Koleva Dessislava A. , Hu Jing , van Breugel Klaas , Boshkov Nikolai , de Wit Hans
Published: November 2006

An improved cathodic protection (CP), based on pulse regime was investigated in reinforced concrete, compared to conventional CP. Both regimes used CP current in the range of 2 to15 mA/m2. A voltage-to-current converter maintained the pulse current, the latter adjusted with duty cycle of 12% to 50 % and frequency of 500 Hz to 1 kHz. The efficiency of the improved CP was evaluated by means of electrochemical methods and microstructural investigation of the bulk concrete matrix, the steel/paste interface and the steel surface. The combination of techniques provides a detailed understanding of the electrochemical phenomena associated with corrosion and protection processes. The pulse CP achieves sufficient protection of the steel reinforcement and is less detrimental to the bulk concrete matrix. In this sense, pulse CP is able to minimize the negative side effects and to ensure better performance and protection in reinforced concrete.
Effect of Electrode Potential on Solution Chemistry Inside a Crevice
Authors: Shinohara Tadashi , Fukaya Yuichi
Published: November 2006

A mathematical model to calculate the solution chemistry inside a corroding crevice was developed based on mass transfer. Distributions of concentrations of ions, pH and electrode potential were obtained for Type 304 and 316 stainless steels in 3% NaCl solution at 80{degree sign}C. The highest pH values at corroding areas did not depend on electrode potential, and were equal to the depassivation pH, pHd. On the other hand, the lowest pH values, pHmin, increased with decreasing electrode potential, and were equal to pHd at the repassivation potential, ER. So, it was confirmed that ER is the critical potential for crevice corrosion, because below this potential, pH values inside crevices are higher than pHd and crevice corrosion cannot continue to progress.
New Nanocrystalline Manganese-Molybdenum-Tin Oxide Anodes for Oxygen Evolution in Seawater Electrolysis
Authors: Hashimoto Koji , El-Moneim Ahmed A. , Kumagai Naokazu , Asami Katsuhiko
Published: November 2006

IrO2/Ti supported g-MnO2 type Mn-Mo-Sn oxide electrodes were prepared by electrodeposition from MnSO4-Na2MoO4-SnCl4 solutions of pH -0.1~0.5 at 600 Am-2 and 90oC for 60~90 min. The electrodes consist of Mn3+, Mn4+, Mo6+ and Sn4+ in the form of nanocrystalline single phase triple oxide. The performance of electrodes for oxygen evolution reaction during electrolysis of 0.5 M NaCl of pH 8.7 was examined at 1000 Am-2. Anodic deposition in 0.2 M Mn2+-0.003 M Mo6+-0.006 M Sn4+ electrolyte of pH -0.1 for 60 min guaranteed the stable electrode performance of 100 and 94% oxygen evolution efficiencies before and after electrolysis for more than seven months. Durability of the electrode was further improved by repeated deposition.
Screen-Printed Dense Yttria-Stabilized-Zirconia Electrolytes for Anode-Supported Solid Oxide Fuel Cells.
Authors: White Briggs M. , Grilli Maria Luisa , Traversa E. , Roncari Edoardo , Pittalis Francesco , Wachsman E. D. , Sanson Alessandra
Published: November 2006

Further cost reductions are necessary for the commercialization of solid oxide fuel cells (SOFCs). The economically sensible methods of screen-printing and tape casting were used to fabricate green films that were subsequently sintered producing 5 cm x 5 cm planar Yittria- stabilized-Zirconia (YSZ)-based SOFCs. An anode-interlayer was also included in the cell design that increased interfacial bonding between the electrolyte and anode. The SOFCs were characterized using scanning electron microscopy and pressure drop measurements. The YSZ electrolytes were gas- tight and dense. These cells showed a maximum power density of 0.14 W/cm2 when tested using a methane-water vapor fuel source at 800{degree sign}C.
NO2 Sensor Using Sc2O3-ZrO2 Solid Electrolyte and CuO + CuCr2O4 Sensing Electrode
Authors: Kale Girish M. , Xiong Weizhen
Published: November 2006

Solid-state planar NO2 sensor using scandia-stabilised zirconia (8mol%Sc2O3-ZrO2) solid electrolyte and seven different oxide sensing electrodes have been tested in NO2 containing gaseous atmosphere in the range of 10 ppm to 500 ppm NO2 between 520 oC to 660 oC. Among the sensors incorporating seven different kinds of oxide sensing electrode, the sensor with CuO + CuCr2O4 mixed-oxide electrode has been found to respond consistently and rapidly to change in concentration of NO2 in the oxygen rich gas mixture at 660 ºC. A logarithmic relationship between the measured electromotive force (EMF) and NO2 concentration from 100 to 500 ppm has been observed at 660 ºC whereas a linear relationship between EMF and NO2 concentration has been observed below 30 ppm at the same temperature of measurement. The sensor exhibited negligible cross-sensitivity to CO and CH4 in the gas stream at 660 oC. A possible sensing mechanism has been discussed.
Non-Nernstian Planar Sensors Based on YSZ with an Nb2O5 Electrode: Discussion on Sensing Mechanism
Authors: Chevallier Laure , Di Bartolomeo Elisabetta , Grilli Maria Luisa , Mainas Marina , White Briggs M. , Wachsman E. D. , Traversa E.
Published: November 2006

Solid electrolyte based sensors have been widely studied for the detection of CO/ HC and NOx at high temperature. Nevertheless, the discussion about the sensing mechanism of non-nernstian electrochemical gas sensors, with a semiconducting sensing electrode, is still open. In this work, a study of the influence of the metallic electrode under the semiconducting metal oxide Nb2O5 on the sensor response was performed. Planar sensors based on tape-cast YSZ layers were fabricated. Two Pt or Au finger electrodes were deposited in a parallel arrangement on a single side of YSZ. One of these electrodes was covered with Nb2O5 thick film. In order to better understand the sensing mechanism, the electrical measurements were correlated with catalytic measurements performed on both sensing and reference electrodes
Bi2Ru2O7 Pyrochlore Electrodes for Bi2O3 Based Electrolyte for IT-SOFC Applications
Authors: Esposito Vincenzo , Luong Bac , Di Bartolomeo Elisabetta , Wachsman E. D. , Traversa E.
Published: November 2006

Bismuth ruthenate pyrochlore (Bi2Ru2O7: BRO) was tested as a cathode in several bismuth oxide-based electrolyte cells. Erbium oxide stabilized bismuth oxide (ESB) (Bi2O3)0.8 (Er2O3) 0.2, Bi2V0.9Me0.1O5.35 (BIMEVOX10, Me = Co, Cu, Zn), and Bi2Ru2O7 (BRO) were synthesized via solid state reaction. ESB and BIMEVOX powders were pressed and sintered into dense pellets while BRO was deposited and sintered as porous electrodes onto ESB and BIMEVOX dense pellet surfaces. Morphologies and phases of the materials were characterized by Field Emission Scanning Electron Microscope and x-ray diffraction, respectively. Electrochemical performances of BRO/ESB and BRO/BIMEVOX symmetric cells were tested using Electrochemical Impedance Spectroscopy (EIS) at 200-700 {degree sign}C in air. High polarization for BIMEVOX cells was observed, while ESB cells showed a promising behaviour. Different electrochemical performances of BRO electrodes, with ESB or BIMEVOX, indicated that the phases formed at electrodes/electrolyte interface controlled the cell polarization process.
Intermediate Temperature Polymer Electrolyte Membranes via Inorganic Cross-Linking of Hybrid Polymers
Authors: Marani Debora , Di Vona Maria Luisa , Ahmed Zakarya , Bellitto Serafina , Trombetta Marcella , Traversa E. , Licoccia Silvia
Published: November 2006

Commercial polyphenylsulfone was reacted with SiCl4 to afford a hybrid polymer and sulfonated to different degrees using sulphuric acid or ClSO3Si(CH3)3. Polymers having different degrees of sulfonation and different inorganic content were cross-linked via the formation of Si-O-Si bonds. The products were characterized by ATR/FTIR spectroscopy demonstrating the formation of covalent bonds between the organic and inorganic components and the absence of dispersed inorganic silicon. The physicochemical properties of the hybrids were suitable for the preparation of membranes which showed adequately high conductivity values to make them suitable candidates for application in PEMFCs.
Intermediate Temperature Electrochemical Reactor for NOx Decomposition
Authors: Hamamoto Koichi , Fujishiro Y. , Awano Masanobu
Published: November 2006

We attempted to fabricate new electrochemical cells for NOX decomposition using high oxygen ion conducting materials with a multilayer cathode operable in the intermediate temperature. Thermal measurements of the cells were carried out to clarify the correlation between the oxygen ion conductivity of the solid electrolyte and the NOX decomposition properties. The NO decomposition by the electrochemical cell with a NiO-ScCeSZ catalytic layer started at around 325{degree sign}C and it was shown that the starting temperature and the efficiency of the NOx decomposition are attributed to the oxygen ion conductivity of the electrolyte.
Applications of Metal Surface Modification in Microdevice Fabrication
Authors: Zhang Gang
Published: November 2006

EFAB{trade mark, serif} is a multilayer electrochemical microfabrication technology for the manufacture of truly 3-demensional (3-D) metal microdevices. Metal surface modification techniques can be applied to not only the EFAB process but also EFAB products. This paper first briefly introduces the applications of surface modification techniques in EFAB and then reports and discusses a surface treatment method for extending the use life of copper instant-masks (Cu-IM) used for instant-mask plating in EFAB. In this surface treatment process a copper substrate is immersed in a benzotriazole (BTA) solution to form a protective film on the copper substrate prior to the application of a patterned insulator layer. This protective film increases the delamination resistance of insulator layers on Cu-IMs in copper plating baths. Therefore the use life of Cu-IMs can be extended.
The Effects of CPC Coatings on the Corrosion/Fatigue Behavior of AA7075-T6
Authors: Kelly Robert , Cui Fushuang , Galyon Sarah E.
Published: November 2006

This work has developed a rapid screening method for differentiating the performance of corrosion prevention compounds (CPC) in delaying the loss of fatigue life due to exposure to corrosive conditions. Fatigue samples were machined from extruded AA7075-T6, coated with CPC, and then a single line defect was created in the CPC within the gauge length of the sample. The samples were then exposed to solution for 30, 60, or 120 days. Upon removal, the samples were fatigued to failure. Three commercially available CPC were compared in terms of their effectiveness in delaying the loss of fatigue life. AV8 and LPS 3 were able to prevent the loss of fatigue life for exposures of greater than 30 and 120 days, respectively, whereas the Amlguard samples showed shortened fatigue lives after only 30 days exposure. The double layer capacitance was able to predict the ordinal ranking of the CPC performance.
Development and Characterization of Corrosion Resistant Coatings Using the Natural Biopolymer Chitosan
Authors: Kumar Girdhari , Buchheit Rudolph G
Published: November 2006

In the present study, chitosan was used as the basis for corrosion resistant coating. Chitosan suffers from two inherent weaknesses as a coating material namely high hydrophilicity and poor adhesive strength with Al 2024 T3 alloy. In the present study, chitosan structure was modified using epoxy functional silane and vanadate. Performance of coatings was tested using EIS, adhesion testing and salt spray testing. The best salt spray performance was observed in case of chitosan-(3-Glycidoxypropyl)-trimethoxysilane-vanadate coatings, which lasted 450 hours in salt spray chamber. UV/Visible measurements showed release of vanadate by chitosan increases with increasing solution pH. This property of chitosan provides self-healing characteristics to these coatings. When the solution pH is readjusted to a lower value, chitosan can re-adsorb released vanadate. FTIR spectra of chitosan gel showed adsorption of vanadate at protonated amine sites. Chitosan showed a maximum in the vanadate adsorption capacity in the pH 3 to 5 range.
Investigation into the Effects of Metallic Coating Thickness on the Corrosion Properties of Zn - Al Alloy Galvanizing Coatings
Authors: Worsley David A. , Penney David , Sullivan James H.
Published: November 2006

Galvalloy (4.5%Al/95.5%Zn) coatings were produced on a continuous coil coating line with varying metallic coating thickness from 7.8μm (120gm-2) to 48μm (325gm-2). Coating thickness was controlled by adjusting the air knives. A higher volume fraction of the primary zinc phase was observed metallographically for the thinner coatings. The faster cooling initiates greater steel coating interfacial nucleation of solid primary zinc phase. The scanning vibrating electrode technique (SVET) was used to measure the cut-edge corrosion properties. It was found that increasing the coating thickness resulted in a decrease in the level of zinc removed from over a 24-hour experiment in 5% NaCl solution. The same trend was also observed in external zinc runoff measurements. The increasing corrosion observed at lower coating weights results from greater undercutting and self-corrosion of these coatings that are further away from a eutectic composition and the presence of crevice corrosion due to zinc dendrite interconnectivity.
Electroless Plated CoWB and COWPB Films for Copper Cap Applications
Authors: Mathew Varughese , Michaelson Lynne , Garcia Sam , Acosta Eddie , Werho Dennis , Gregory Richard , Jiang Zhi-Xiong , Kim Kiwoon
Published: November 2006

Electroless plated CoWB and CoWPB films were studied for copper cap applications in semiconductor device processing. Both films were found to be polycrystalline but introduction of phosphorus made the CoWPB film less crystalline than CoWB. Films were stable for four cycles of thermal annealing with each cycle consisting of a 2 hour anneal at 400åC. Cu diffused through thin cap films after one thermal cycle but for subsequent cycles no significant increase in copper concentration was observed. It appeared that the solubility limit of Cu in cobalt is reached limiting further diffusion of Cu after the first cycle at this annealing temperature. Electrical data collected for 3.9m snake and comb test structures with CoWB and CoWPB showed less than one order of magnitude increase in leakage and less than a 1.5 % change in resistance.
AirGaps for Ultra Low-k Interconnects Fabricated with Hardened Sacrificial Polymer
Authors: Kohl Paul A. , Park Seongho , Krotine Jeff , Allen Sue Ann
Published: November 2006

Polymers based on norbornene have been used for low-k dielectric materials, advanced photoresists, and as sacrificial materials in the formation buried air-gaps. In this study, the hardness of thin films of butylpolynorbornene - triethoxysilylpolynorbornene copolymer was enhanced by exposure to electron beam radiation. The effect of electron energy, dose, and temperature on the thermal and mechanical properties of the irradiated copolymer films was investigated using dynamic thermal gravimetric analysis and nanoindentation. The hardness of the copolymer thin films was increased by electron beam irradiation; however, the thermal stability was degraded.
Low Temperature ALD MoN for Applications in Nanoscale Devices
Authors: Zeng Wanxue , Wang Xiaodong , Meiere Scott H. , Eisenbraun Eric
Published: November 2006

A low temperature plasma enhanced atomic layer deposition (ALD) process has been developed for the growth of ultra thin MoN films. An optimized process was identified by performing a systematic study of film growth rate as a function of Mo precursor pulse and purge times, N2 and H2 pulse time and heater temperature. Subsequent chemical and microstructural analysis shows that the as-deposited MoN film has a stoichiometric composition, a resistivity of 1280 mW, an atomically smooth surface and amorphous structure. Copper diffusion barrier performance measurements show that MoN films between 2.5 and 15 nm thick could prevent copper diffusion after a 1-hour anneal at 600{degree sign}C.