bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Microwave Power on Thermal Annealing Behaviors of Hydrogenated Amorphous Silicon
Authors: Wu Ping-Jung , Chen I-Chen , Lee Chien-Chieh , Chang Jenq-Yang , Li Tomi T. , Su Chiung-Chieh
Published: March 2011

In this study, we have investigated the recrystallization behaviors of hydrogenated amorphous silicon (a-Si:H) films by post-growth thermal annealing as a function of microwave power using electron cyclotron resonance chemical vapor deposition (ECRCVD). The crytallinity of annealed a-Si:H films depends on the porosity of the as-deposited thin films. We suggested that the film with high porosity has lowest crystallinity due to strong oxygen diffusion and formation of SiOx inside the film.
On the Electrical Characterization of Grain Boundaries in Multicrystalline Silicon
Authors: Chen Jiahe , Cornagliotti Emanuele , Hieckmann Ellen , Behrendt Simone , Weber Joerg , Simoen Eddy , Poortmans Jef
Published: March 2011

Impurity decoration of grain boundaries (GB) introduces deep levels and enhances their recombination activity. In this study we use the standard DLTS technique to investigate the influence of the GB structure on the electrical properties of mc-Si. The detected DLTS spectra have an opposite signal compared to the usually known majority carrier peaks of deep levels, but standard DLTS analysis can yield trap energies and capture cross sections. By comparing the properties between GB and intra-grain regions with similar minority carrier lifetime, it is considered that the DLTS signals might be due to traps generated in the extended defects present both at GBs and grains. It is observed that ∑3 GB has deep level traps at the same energy level as ∑9 GB, while the trap concentration in the former one is lower than the latter. Furthermore, a phosphorous gettering treatment can reduce the recombination activities both in the grains and at the GBs.
Plasmon Effect in Si Solar Cells Coated with a Thin Polymer Film Containing Silver or Gold Nanoparticles
Authors: Tanaka Yuki , Hachimura Hironori , Mishima Takayoshi , Ihara Manabu
Published: March 2011

To apply surface plasmon effects to Si solar cells, thin polymer films containing nanoparticles of silver and gold were fabricated using the spin-coating method. Advantages of this method are that it is simple, and that there is no possibility to produce additional crystal defects as surface recombination centers. Thin polymer films showed an absorption peak, anti-reflection effect and the haze ratio increase. In particular, thin polymer films containing gold nanoparticles were promising for improving Si solar cells, because the film had the longest peak wavelength and the lowest reflectance (3.84% at 800 nm), overall haze ratio increase caused by localized surface plasmon. Enhancement ratio in photocurrent conversion efficiency was 12% for single-crystal Si solar cells after being spin-coated with a thin polymer film containing gold nanoparticles. Enhancement ratio of the external quantum efficiency was 22% at the peak wavelength, caused by anti-reflection due to scattering by metal nanoparticles.
Porous Germanium Layers by Electrochemical Etching for Layer Transfer Processes of High-Efficiency Multi-Junction Solar Cells
Authors: Garralaga Rojas Enrique , Hensen Jan , Carstensen Juergen , Föll Helmut , Brendel Rolf
Published: March 2011

We demonstrate reproducible formation of mesoporous germanium layers suitable for solar energy applications by electrochemical etching in highly concentrated electrolytes. For long anodization times or thick layer formation a porosity gradient is observed leading eventually to high porosity regions and cavity formation at the bottom of the porous layer. A 30 min annealing step at a temperature of 575 ºC in hydrogen atmosphere allows for reorganization and subsequent lift-off. The mean surface roughness increases from 0.31 nm for unprocessed Ge up to 7.85 nm for reorganized Ge as measured by atomic force microscopy. µ-Raman confocal spectroscopy analysis confirms that etching and annealing do not affect the crystalline structure.
The Circle-Grid Electrode on Concentrated GaAs Solar Cells Efficiency
Authors: Chung Chen-Chen , Yu Hung-Wei , Hsu Li-Han , Kuo Chien-I , Quan Nguyen-Hong , Chiu Yu-Sheng , Chang Edward Yi
Published: March 2011

The relationship between front contact pattern of GaAs single-junction solar cell with conversion efficiency at different concentration ratios is studied in this paper. Five different front circle-grid patterns were designed and patterned on the in-house fabricated single junction GaAs solar cells. At high light concentration ratio, the cell efficiency is strongly dependent on the series resistance of the electrode. At the same time, the thermal effect should also be taken into consideration, especially when a device is operating under high concentration ratio. Therefore, the aim of this work is to find a suitable front contact pattern for a GaAs single-junction solar cell to increase the conversion efficiency under high concentration solar radiation. It is found that the device with proper pattern design geometrical shadowing factor of 7.1% has the best cell efficiency of 27.05% at CR>100x, AM1.5G.
Syntheses of Fluorene/Carbazole-Thienothiadiazole Copolymers for Organic Photovoltaics
Authors: Výprachtický Drahomír , Kmínek Ivan , Pavlačková Petra , Cimrová Věra
Published: March 2011

The Suzuki coupling reaction was utilized for the syntheses of conjugated polymers with alternating conjugated electron-rich donor unit and conjugated electron-deficient acceptor unit in the same polymer backbone. The conjugated copolymers based on fluorene-thienothiadiazole and carbazole-thienothiadiazole structural units were synthesized. Organic multistep synthesis was applied for the preparation of tailored monomers, namely of the 4,6-bis[5`-bromo-3`-(2-ethylhexyl)thien-2`-yl]thieno[3,4-c][1,2,5]-thiadiazole (aromatic dihalocompound) and of the 9-(2-ethyl-hexyl)-2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)carba-zole (aromatic diboronic acid ester). These low-band gap materials were utilized as active layers in organic solar cells; see the second contribution (E8-1625) from our laboratory on 218th ECS meeting.
Low-Band Gap Donor-Acceptor Copolymers Containing Thienothiadiazole Units for Photovoltaics
Authors: Cimrová Věra , Kmínek Ivan , Pavlačková Petra , Výprachtický Drahomír
Published: March 2011

Optical, electrochemical and photovoltaic properties of novel donor-acceptor copolymers containing dithienylthienothiadiazole derivatives and 9,9-bis(2-ethylhexyl)fluorene or 2,5-diisopentoxybenzene units were studied. The copolymers exhibited long-wavelength absorption, and possess small optical bandgap in the range of 1.1 - 1.4 eV depending on copolymer units and alkyl side-chain nature and length. They exhibited ambipolar redox properties and electrochromism. Photovoltaic devices with bulk heterojunction made of blends of copolymers and fullerene derivatives were prepared. Effects of side-chain nature and length on photophysical properties are discussed.
Corrosion Resistance of Metallic Substrates for the Fabrication Dye-Sensitized Solar Cells
Authors: Reynolds Gavin J. , Watson Trystan M. , Williams Geraint , Worsley David
Published: March 2011

A novel method of monitoring corrosion activity when an iodide/ triiodide dye-sensitized solar cell redox electrolyte is placed in contact with a range of metallic substrates is described. Corrosion of the metallic substrate results from anodic dissolution of the metallic surface coupled with cathodic reduction of triiodide (I3-) to colorless iodide ions in solution. In the work described here, UV/Vis spectrophotometry in reflectance mode is used in conjunction with encapsulation cells which incorporate a 25 microns thick electrolyte layer, prepared using a range of polished metallic substrates. The corrosion rate is quantified by monitoring changes in the absorption spectra with respect to time. Of the metals evaluated, only titanium was wholly resistant to corrosion and did not show evidence of reaction with the electrolyte for periods of up to 3 months. Other metals such as zinc reacted within seconds and complete and irreversible loss of I3- was observed after only a few minutes.
Ultrafast TiO2 Sintering of Metal Mounted Dye-Sensitized Solar Cells
Authors: Watson Trystan M. , Mabbett Ian , Worsley David
Published: March 2011

A primary challenge to the industrial uptake of Dye-sensitized solar cells on metals is the ability to speed up process steps to facilitate rapid roll to roll production. One critical step is the sintering of the TiO2 layer typically taking up to one hour at 500°. Here, an ultrafast near infrared (NIR) heating method is presented which directly heats metal substrates to very high temperatures. NIR is used to heat 1mm thick titanium metal coupons onto which 1cm2 commercial TiO2 pastes have been deposited within 12.5 seconds giving assembled dye-sensitized solar cell efficiencies which are equivalent or better in terms of efficiency to cells prepared using a convection oven for 30 minutes.
Electrochemical Characterization of the Dye-Sensitized Solar Cells
Authors: Ha Seonbaek , Ramanathan Mayandi , Ramani V. , Prakash Jai
Published: March 2011

Dye-Sensitized Solar cells (DSSC) has had considerable interest to be a promising solar energy conversion device. In order to improve the performance and long term stability of the DSSC, it is essential to understand the characteristics of DSSC. Various electrochemical experiments were conducted to evaluate DSSC characteristics. Variation in internal interfaces and/or components of DSSC due to exposure time, light intensity and ambient temperature were monitored. Different illumination conditions affected open circuit voltage, short circuit current and fill factor. Change in behavior of DSSC was observed when test conditions were switched from open circuit voltage conditions to potential cycling conditions. Electrochemical impedance spectroscopy (EIS) was selected to scrutinize the interfacial charge transfer resistance variation. Equivalent circuit model for EIS results illustrated that charge transfer resistance at Pt counter electrode was mainly affected by both Voc conditions and potential scanning with same irradiation intensity in the aging study.
Estimation of Organic Tandem Solar Cell Power Conversion Efficiency via Optical Simulation Methods
Authors: Boland Patrick M. , Foe Kurniawan , Gu Diefeng , Baumgart Helmut , Lee Keejoo , Namkoong Gon
Published: March 2011

Organic tandem solar cells were investigated using modeling and simulation methods to determine the optimal structural design and to predict device efficiencies. Each tandem structure comprised two subcells composed of varying combinations of low- and high-bandgap donor polymers and acceptor fullerene materials. The subcell employing the low-bandgap polymer, poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT), was combined with either C61- or C71-based acceptor fullerene ([6,6]-phenyl C61/71 butyric acid methyl ester) (PC61/71BM). Similarly, a subcell employing the high-bandgap polymer, poly (3-hexylthiophene) (P3HT), was modeled after including either PC61BM or PC71BM components. The mutual effects of both subcells in tandem were analyzed to determine such parameters as current density, open circuit voltage, fill factor, and power conversion efficiency. Our results indicate that appropriate spatial ordering of the subcells can allow achievement of device efficiencies exceeding 9%.
Distribution of the Retained Less-Noble Element in Dealloyed Materials
Authors: Artymowicz Dorota , Coull Zoe , Bryk Mariusz , Newman Roger
Published: March 2011

Electrolytic dealloying of a solid-solution alloy is usually understood to involve a relatively large content of more-noble element in the alloy (e.g. 25%), from which starting point it is natural that dealloying will produce a connected nanoporous structure. But it has been known for a long time, since the work of H.W. Pickering, that starting alloys such as Cu-10 at%Au can be dealloyed to produce fully connected Au-rich dealloyed layers, at least to a certain thickness. Clearly not all the Cu could have been removed during this process, and Pickering demonstrated not only that the dealloyed material retained much of its Cu, but that there was a compositional gradient, or at least a range of dealloyed compositions, within the material. In the present work we have used a 95Ag-5Au (at%) alloy and have attempted to correlate the dealloying behaviour (ligament size in the nanoporous layer; true surface area) with Kinetic Monte Carlo simulations of the dealloying process. The results are analogous, with some areas for further quantitative development. A related behaviour in stainless steels is discussed.
Corrosion Mechanism of Refractory Immersed in Molten Slag
Authors: Sunayama Hiroyuki , Hiramatsu Yuichi , Kawahara Masayasu
Published: March 2011

The corrosion test was carried out by using the rotating cylinder in the CaO-SiO2-FeO-CaF2 slag at 1673K for the commercial sintered MgO, MgO-C and MgO-Cr2O3 brick. The severe corrosion was observed for the MgO-C refractory. The mass transfer through the boundary layer must be accelerated by the movement of CO bubbles formed as a result of oxidation of C which reacted with FeO in the molten slag. The cause of the severe corrosion accompanied by H2 bubbles formation was confirmed by using a naphthalene cylinder. The dragging matter in the wake behind the small resin ball of 6 mm diameter rising up in NaCl solution was observed. Formation of the slightly soluble product, Cr2O3FexO, around the refractory and the Cr2O3 suspension in the molten slag played the major role in the appearance of high corrosion resistance.
PEMFC Oscillatory Behavior on a Pd-Pt/C Electrocatalyst
Authors: Lopes Pietro P. , Varela Hamilton , Ticianelli Edson A.
Published: March 2011

We have recently reported the emergence of spontaneous sustained potential oscillation in a PEMFC system fed with H2/CO on a Pd-Pt electrocatalyst anode. When compared to previously observed oscillation in the PtRu anode, the oscillations in the former case where characterized by features such as lower frequency and higher amplitude. Herein we report a numerical study of this system and discuss the results in terms of the reaction mechanism, in connection with the data for PtRu. We found that the main oscillatory features could be linked to the material adsorptive and oxidative properties by combining CO stripping voltammetry, steady and oscillatory state data and kinetic simulation of the electrochemical reactions taking place at the PEMFC anode. We show that not only PtRu can prompt the emergence of such behavior, but also that some degradation aspects must be considered before making benefit from the higher power output generated in the oscillatory regime.
Pattern Formation during Anodic Etching of Semiconductors
Authors: Föll Helmut , Carstensen Juergen
Published: March 2011

The current burst model asserts that current flow through anodically dissolving semiconductor electrodes is localized in space and time. The only relevant parameters of the model are probability functions for current "on" and "off". Interactions between current bursts in space and time account quantitatively, or at least qualitatively, for a wealth of pattern formation phenomena observed on semiconductor electrodes that are classified as oscillations in time and space (= pore formation). The paper reviews these electrode oscillations in the light of the current burst model.
Electrodeposition of Cu-Ag Film in Cyanide-Based Electrolyte
Authors: Lee Hyo June , Kim Myung Jun , Lim Taeho , Park Kyung Ju , Kim Jae Jeong , Kwon Oh Joong
Published: March 2011

Electromigration is considered a major concern of the decrease of Cu line reliability. Thus Copper-silver, a promising material for the next generation of interconnect in the aspect of electromigration resistance,has been studied. Electrodeposition in cyanide-based electrolyte was chosen as a Cu-Ag film formation method in this study. To carry out the electrodeposition, a linear sweep voltammetry was conducted to find an optimum reduction potential. Then, the Cu-Ag film was deposited with a static potential method. Film properties were investigated varying an applied potential, pH and electrolyte composition. High quality Cu-Ag film was obtained under the condition of - 1.6 V and pH 6.6. The composition of the film could be controlled by varying Ag concentration.
Thermal Desorption Spectroscopic Study of Hydrogen in Electrodeposited Ni-P Films
Authors: Takemoto Tatsuya , Fukumuro Naoki , Yae Shinji , Matsuda Hitoshi
Published: March 2011

The objective of this study is to reveal the atomistic state of hydrogen in electrodeposited Ni-P films by thermal desorption spectroscopy. Two peaks corresponding to the desorption of hydrogen occupying regular interstitial sites and the break-up of vacancy-hydrogen (Vac-H) clusters were observed in electrodeposited pure Ni film. With an increase in phosphorus content, the crystallinity of electrodeposited Ni-P films decreased and the hydrogen desorption from the interstitial sites and Vac-H clusters disappeared. The amount of diffusible hydrogen increased abruptly with the increase in the amorphous phase in Ni-P film.
Influence of Si Surface Condition on Electroless Displacement Deposition of Pt Particles
Authors: Takami Koji , Yae Shinji , Yamagishi Kenji , Fukumuro Naoki , Matsuda Hitoshi
Published: March 2011

The displacement reaction, which is the immersion of Si wafers into a metal-salt solution containing HF, has been applied to prepare catalytic fine metal particles for metal-assisted HF etching, photoelectrochemical solar cells, and autocatalytic plating. The particle density of Pt particles deposited by displacement reaction on n-Si was different based on the solution used for Si chemical oxidation prior to the deposition. Particle density correlates not with the electrical state density at the SiOx/Si interface but with the contact angle of pure water and the microroughness of the oxidized n-Si surface. A model of the deposition process of Pt particles on an oxidized n-Si surface is proposed.
Sensitivity Analysis of Some Key Gas Diffusion Layer Parameters in PEM Fuel Cells
Authors: Kulkarni Abhay , Wang Xia
Published: March 2011

The gas diffusion layer(GDL) plays a very important role in the overall functioning of PEM Fuel Cells. Through the GDL, reactant gas is delivered to the catalyst layer and product water is removed from the catalyst layer. It is known from different experiments and numerical studies that the GDL has highly anisotropic property. In this study, a non-isothermal two dimensional fuel cell model is developed taking into account the anisotropic nature of the GDL by introducing the in-plane and through-plane characteristics for permeability, thermal conductivity and electrical conductivity. The statistical sensitivity analysis is then performed to determine the most influential parameter which affects the performance of fuel cell. The governing equations are solved using the commercial software COMSOL Multiphysics. The standard analysis of variance (ANOVA) method is used to do the sensitivity analysis. It shows that the porosity and through-plane permeability are the most influential GDL parameters on the performance of fuel cells.
New Electrochemical Hydrogen Production System from Ammonia Borane
Authors: Shimada Motoki , Baba Toyohiro , Chiku Masanobu , Higuchi Eiji , Inoue Hiroshi
Published: March 2011

Electrochemical hydrogen production from ammonia borane, which is a promising hydrogen storage material with the theoretical hydrogen content of 19.6 wt%, was investigated. A cyclic voltammogram of ammonia borane at a Pt electrode in methanol containing 0.5 mol L-1 LiClO4 demonstrated that the current for the oxidation of ammonia borane began to increase at ca. -0.3 V vs. Ag/AgCl. In potentiostatic electrolyses at -0.1 and 0.1 V, hydrogen gas was produced by electrochemical methanolysis of ammonia borane at the Pt working electrode and reduction of methanol at the Ni counter electrode. The current density for hydrogen production at the Pt working electrode was beyond 100 %. This seems to be because hydrogen ions produced by electrochemical oxidation of ammonia borane worked as a catalyst for the methanolysis.
Effect of Electrochemical Parameters on the Morphology and Ca/P Ratios of Deposited Apatite Coatings on Metal and Alloy Substrates
Authors: DeLeon Vallerie , Golden Teresa D.
Published: March 2011

Calcium phosphates were electrochemically deposited on stainless steel, titanium, and copper metal substrates with modified simulated body fluid of pH adjusted from 4 to 10 at 25 - 65 °C while maintaining cathodic potentials at -1.2 to -1.8 V (vs. SCE). The coatings were characterized by powder x-ray diffraction, scanning electron microscopy, and linear polarization corrosion method. X-ray diffraction show depositions in electrolytic solutions of pH below 8 contain hydroxyapatite along with a significant amount of impurities; however at pH 10 the deposit primarily consists of hydroxyapatite with little impurity, ideal for orthopedic implants. As the pH increases the morphology changes as shown with scanning electron microscopy, from an amorphous to a dense crystalline phase. Linear polarization and Tafel plot show surgical stainless steel has the most improvement in anticorrosion when coated with hydroxyapatite.
Contact Probe Card with Large Overdrive
Authors: Kimoto Gunsei , Watanabe Takehiro , Matsusaka Souta , Kuroda Takaharu , Saito Mikiko
Published: March 2011

In this paper, we present a new contact probe card with an insulating resin film that can achieve large overdrive. The probe pins were manufactured using Be-Cu through etching and silkscreen polyimide printing. It was confirmed that the probes have a long life expectancy because they act within the thresholds of elastic deformation. The proposed assembly technology allows us to achieve highly accurate probe units with a narrow pitch and a probe thickness of only 28 μm.
Distinguishing Li+ Charge Transfer Kinetics at 1. NCA/Electrolyte and Graphite/Electrolyte Interfaces and 2. NCA/Electrolyte and LFP/Electrolyte Interfaces in Li-ion Cells
Authors: Jow T. R. , Marx Michelle , Allen Jan
Published: March 2011

In examining the Li+ charge transfer kinetics at the graphite anode and the lithium nickel cobalt aluminum oxide, LiNi0.80Co0.15Al0.05O2 (NCA), cathode in a complete cell, we found that the activation energy, Ea, for the charge transfer at the graphite/electrolyte interface is about 68 kJ/mol, which is consistent with the recently reported values. However, the Ea for the charge transfer at the NCA/electrolyte interface is about 50 kJ/mol, which is lower than that at the graphite anode. With desolvation as the predominate step for limiting the kinetics and both of the electrodes were subject to the same electrolyte, the difference in Ea suggests that the Ea is influenced greatly with respect to the nature of electrode materials and their associated SEIs. This is further confirmed by the examination of the LiFePO4 (LFP)/electrolyte and the graphite/electrolyte interfaces using a LFP/graphite complete cell.
Modified Solid Electrolyte Interphase of Silicon Nanowire Anodes for Lithium-Ion Batteries
Authors: Xu Wanli , Vegunta Sri S. , Flake J. C.
Published: March 2011

Solid electrolyte interphase (SEI) plays a significant role in maintaining reversible capacities by protecting silicon anodes of lithium-ion batteries from chemical reactions with electrolyte and mechanical failures. In this work, silicon nanowires were functionalized and applied as anode material for lithium-ion batteries to study the effects of modified SEI via surface functionalization. The results from cyclicvoltammetry, charge/discharge and SEI characterizations (XPS, FTIR, and AFM) showed that by modifying the silicon surface the capacity retention varied significantly within 15 consecutive cycles; electrochemically and chemically grafted monolayer prevent silicon from reaction with electrolyte, while impedes lithium insertion so as to compromise lithium storage in silicon; by introducing coupling agent, such as trimethoxymethylsilane to form Si-O-Si cross-linking, the anode capacity retention was greatly improved by forming a chemically and mechanically stable SEI on silicon.
Effect of Flame-Retarding Additives on Surface Chemistry of Electrodes in Li-Ion Batteries
Authors: Nam Nguyen Dang , Park In Jun , Kim Jung-Gu , Kim H. S. , Moon S. I.
Published: March 2011

This study examined the properties of 1 wt.% vinylene carbonate, vinyl ethylene carbonate, and diphenyloctyl phosphate additive electrolytes as a promising way of beneficially improving the surface and cell resistance of Li-ion batteries. The additive electrolytes were dominant both in surface formation and internal resistance. In particular, electrochemical impedance spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy confirmed that diphenyloctyl phosphate is an excellent additive to the electrolyte in the Li-ion batteries due to the improved co-intercalation of the solvent molecules.
Hazards Associated with High Voltage High Capacity Lithium-Ion Batteries
Authors: Jeevarajan Judith A.
Published: March 2011

The results of the tests conducted at NASA-JSC indicate that lithium-ion cells, when used in high voltage and high capacity configurations, have to be designed with stringent monitoring and control. The limitations with cell-level controls are described in detail in this paper.
Nanostructured Lithium-Aluminum Alloy Electrodes for Lithium-Ion Batteries
Authors: Hudak Nicholas , Huber Dale
Published: March 2011

Electrodeposited aluminum films and template-synthesized aluminum nanorods are examined as negative electrodes for lithium-ion batteries. The lithium-aluminum alloying reaction is observed electrochemically with cyclic voltammetry and galvanostatic cycling in lithium half-cells. The electrodeposition reaction is shown to have high faradaic efficiency, and electrodeposited aluminum films reach theoretical capacity for the formation of LiAl (1 Ah/g). The performance of electrodeposited aluminum films is dependent on film thickness, with thicker films exhibiting better cycling behavior. The same trend is shown for electron-beam deposited aluminum films, suggesting that aluminum film thickness is the major determinant in electrochemical performance regardless of deposition technique. Synthesis of aluminum nanorod arrays on stainless steel substrates is demonstrated using electrodeposition into anodic aluminum oxide templates followed by template dissolution. Unlike nanostructures of other lithium-alloying materials, the electrochemical performance of these aluminum nanorod arrays is worse than that of bulk aluminum.
Iron Oxide Nanotubes Incorporated with Fluoride Anions for Enhanced Li-Ion Intercalation
Authors: Raja Krishnan S. , Misra Mano
Published: March 2011

Ordered arrays of fluoride incorporated iron oxide nanotubes were synthesized by a simple electrochemical anodization technique. An iron foil was anodized at 50 - 60 V in ethylene glycol solution containing 0.3 wt% NH4F and 1.5 vol% distilled water for 15 - 30 minutes. During the anodization process, oxygen anions were partially substituted with fluoride anions. The self-ordered, vertically oriented, and free-standing iron oxide based nanotubes showed enhanced Li-ion storage capacity, and faster kinetics for Li-ion diffusion. The fluoride incorporation in the oxide was believed to expand the lattice, thereby increasing the ability of the lattice to accommodate enhanced lithium ion intercalation. Furthermore, increased conductivity was noted because of adsorption of carbonaceous species on the nanotubes while anodization and subsequent incorporation of carbon in the Fe-O-F lattice structure after thermal annealing. The proposed configuration of nanotubes showed a reversible nominal capacity > 700 mAh/g.
Microstructure Reconstruction and Direct Evaluation of Li-Ion Battery Cathodes
Authors: Liu Fuqiang , Siddique N.A.
Published: March 2011

High-capacity Li-ion batteries are among the best candidates for next generation, clean, and potentially fossil fuels independent electric vehicles. One of the major challenges in Li-ion batteries is to improve mass transport across multiple phase interfaces within complex electrode structures. The goal of this work is to study the role of interfacial interaction in Li-ion battery electrodes through physical microstructure reconstruction and direct evaluation. It has been found that macro electrochemical properties of the numerically reconstructed electrodes depend critically on nanoscale physical characteristics of electrode components and their interfacial interactions. This work also revealed the localized nanoscale electrode complexity and transport processes in great details, which are currently impossible to investigate experimentally or by alternative models.
Materials and Corrosion Research in the Yucca Mountain Project
Authors: Rebak Raul B.
Published: March 2011

There is a current nuclear energy renaissance around the world, mainly in Asia. However, after 60 years of using nuclear power, the issue of nuclear waste still needs to be solved. All the countries currently addressing the issue of nuclear wastes are considering disposing them in stable geologic formations. Most repositories designs in Europe are considering materials such as carbon steel and copper for the container. The US repository in Yucca Mountain is currently on hold waiting for new recommendations from the Blue Ribbon Commission. A robust corrosion and materials testing program was carried out over the last 20 years at universities and National Laboratories to support the Yucca Mountain Project. For example, the intensive corrosion and electrochemical research helped understanding of how the different variables affect the resistance of C-22 to localized corrosion. Even if the repository of Yucca Mountain is not materialized, the knowledge gained on the corrosion behavior of materials is permanent.
Stress Corrosion Cracking of Pure Copper under Possible Nuclear Fuel Waste Management Conditions
Authors: Ikeda Brian M. , Litke Cindy D. , Kwong Gloria
Published: March 2011

This study investigated the effect of nitrite/chloride and ammonia/chloride concentrations, on the stress corrosion cracking (SCC) behaviour of oxygen free phosphorous doped (OFP) copper. Constant extension rate tests (CERTs) were performed at room temperature using a compact tension specimen. The findings are summarized as follow: A 1:1 ratio of nitrite to chloride suppressed SCC, as did an overabundance of chloride. The susceptibility of OFP copper to SCC in a deaearated 0.1 mol•L 1 nitrite solution appeared to decrease and the steady-state potential values became more negative with increasing chloride concentration. A 1:1 ratio of ammonia to chloride suppressed SCC, as did an overabundance of chloride. The addition of chloride in concentrations ≤0.5 mol•L 1 had little effect on the SCC behaviour. High chloride concentrations appeared to increase the uniform corrosion of OFP copper, which coincided with a blunting of the crack tip.
Acetyl Salicylic Acid (Aspirin) and Antioxidative Agents in Joshanda - a Herbal (Medicinal) Tea
Authors: Soomro Muhammad Tahir , Mohammad Mahboob , Aqeel Zeeshan
Published: March 2011

Joshanda**, a herbal medicine taken as tea, claimed to be a remedy for some ailments, was analyzed for acetyl salicylic acid and antioxidative property. HPLC analysis of Joshanda showed 18.3 ppm acetyl salicylic acid in it. Cyclic voltammetric analysis of Joshanda tea for its antioxidative property was done by using simple and novel electrochemical device recently developed and reported. It established the presence of some antioxidative agent(s) (antioxidants). The presence of these chemicals may render this herbal medicine (tea) beneficial for general health. **The name of the manufacturer of Joshanda Sample analyzed is classified.
The Effect of Nanoscale Metal / Metal Oxide Depositions on TiO2 Photo Catalysed PVC Photodegradation
Authors: Robinson Andrew J. , Worsley David
Published: March 2011

Most organic coatings are pigmented with Titanium Dioxide (TiO2) to increase their covering power. TiO2 can be photoactivated under UV irradiation causing the formation of free radicals leading to accelerated degradation of the polymeric coating and release of Carbon Dioxide (CO2). In commercial paint systems expensive Ultra Violet Absorbers (UVA's) and Hindered Amine Light Stabilisers (HALS) are used to control degradation. The application of thin film oxygen barriers to the surface of an organic coating could be a possible alternative. Various metal and metal oxide films have been applied to a model paint system and the effects upon stability studied using a novel closed-loop flat panel irradiation reactor measuring the CO2 evolution kinetics by FTIR spectroscopy.
Novel Strategy for Finding the Optimal Parameters of Ion Selective Electrodes
Authors: Jasielec Jerzy J. , Wierzba Bartłomiej , Grysakowski Bartosz , Sokalski Tomasz , Danielewski Marek , Lewenstam Andrzej
Published: March 2011

The detection limit (DL) of an analytical method determines the range of its applicability. For ion selective electrodes (ISE) used in potentiometric measurements, this parameter can vary by several orders of magnitude depending on the inner solution concentrations or the time of measurement. The detection limit of ISE can be predicted using the Nernst-Planck-Poisson model (NPP), as a general approach to the description of the time-dependent electro-diffusion processes. To find the optimal parameters, we need to formulate the inverse electro-diffusion problem. In this work, we combine the Nernst-Planck-Poisson model with the Hierarchical Genetic Strategy with real number encoding (HGS-FP). We use the HGS-FP method to approximate inner solution concentrations as well as the measuring time that provide a linear dependence of the membrane potential over the widest concentration range. We show that the HGS-FP method allows us to find the solution of the inverse problem. The presented calculations show a great future potential of the NPP method combined with the HGS-FP strategy.
Novel Electrochemiluminescent Platinum (II) Schiff-Base Complexes
Authors: Reid Ellen F. , Hogan Conor , Cook Vernon
Published: March 2011

A series of platinum (II) complexes with Schiff base ligands were synthesized and compared in terms of their photoluminescence, electrochemical and electrochemiluminescence (ECL) properties. Photochemical and electrochemical techniques were used to establish the relationship between the photophysical and redox properties. The emission wavelengths (λem) of theses complexes were found to be highly tuneable with shifts of up to 150 nm in the emission resulting from very minor changes in the ligand structure. All reported complexes exhibit intense ECL via both annihilation and co-reactant pathways. The ECL properties are considered in the light of the photochemical and electrochemical properties of each complex as well as the thermodynamics of the ECL reaction in each case. The findings provide useful insights into the favorable characteristics required for efficient ECL and the directions which should be explored in the search for new ECL luminophores.
Voltammetry of N-Bromosuccinimide in Hexafluoropropan-2-ol
Authors: Haque Inam U. , Akram Wajiha , Tariq Muqaddas , Khan Asim
Published: March 2011

Electrochemical behaviour of N-bromosuccinimide (NBS, mp 174 ºC) was investigated in 1,1,1,3,3,3-hexafluoropropan-2-ol (HFP) by cyclic and pulsed voltammetry at platinum electrode. The cyclic voltammetric response was characterized by an irreversible reduction peak at around 0.7 V vs. SCE, and an anodic peak at about 0.1 V on reverse sweep. The possible mechanism for electro-reduction of NBS was outlined. In case of normal pulse voltammetry, a well-defined sigmoid-shaped curve was obtained. An increase in step time resulted in a significant cathodic shift. Differential pulse voltammetric response was consistent with the normal pulse behaviour, and featured a single peak centered at about 0.88 V. Linear variation of summit current with pulse height was observed.
Effect of Supporting Electrolyte on Mass Transport through Nafion Films
Authors: Stewart Kathryn E. , Barrett Seth M. , Molden Erin K. , Zook-Gerdau Lois A.
Published: March 2011

The role supporting electrolyte plays on the transport of the redox probe tris(bipyridine)ruthenium(II) chloride through the ion exchange polymer Nafion® was examined using cyclic voltammetry, rotating disk voltammetry, and spectroscopic techniques. Variations in both the extraction coefficient (κ) and the diffusion coefficient (D) were observed as the supporting electrolyte was varied. The anion of the supporting electrolyte was not found to influence mass transport, but the cation significantly influenced both extraction and diffusion of the redox probe within the polymer. A series of monovalent (Li+, Na+, K+, Rb+) and divalent (Mg2+, Ca2+, Ba2+, Zn2+) cations were studied, as well as the trivalent cation La3+.
Study of High-Frequency Artifacts in EIS Measurements of Ti and its Alloys in Simulated Body Fluid
Authors: Zhou Xuan , Mohanty Pravansu
Published: March 2011

In electrochemical impedance spectroscopy which is commonly used to study the behavior of titanium and its alloy in simulated body fluid solution, high frequency artifacts are commonly observed. Two parameters that may augment the high frequency artifacts including the electrochemical cell design and the solution are investigated in this environment. The results suggest that the luggin capillary design of the cell can be the main reason responsible for high frequency artifacts. In order to reduce the effect of high frequency artifacts, two cell modification methods including use of auxiliary platinum wire and by-pass circuit, were selected. Both methods can greatly reduce the high frequency artifacts, but both methods increase the complexity of experiments. In addition, increasing the solution conductivity can reduce the artifacts in high frequency region too.
Improving the Production Process and Durability of Amperometric Biosensors for Detection of Cholesterol Using Gold Microelectrodes
Authors: McCaslin Tyler G. , Harper Alice C.
Published: March 2011

An amperometric biosensor for the quantification of cholesterol has been developed. The enzyme cholesterol oxidase (ChOx), expressed in Brevibacterium, was surface bound to a gold microelectrode modified with a self-assembled monolayer (SAM) of 11-mercaptoundecanoic acid (11-MUA) with ferrocene poly(allylamine) (FePAA) as an electron transfer mediator. The covalent matrix of SAM, mediator, and enzyme improves the kinetics of the redox reaction of cholesterol to cholest-4-en-3-one. The performance of the biosensor was assessed with cyclic voltammetry (CV) and shows to be an effective prototype for the development of a device to measure serum cholesterol in vivo.
Physicochemical and Electrochemical Characterization of Sulfate-Based Ionic Liquid
Authors: Wu Tzi-yi , Jou Li-Shian , Lin Yuan-Chung , Su Shyh-Gang , Sun I-Wen
Published: March 2011

In this study, various types of ionic liquid (IL) containing an alkyl sulfate group are synthesized and their physical and electrochemical properties are investigated. The various cations of alkylsulfate-containing ionic liquids are shown to greatly influence viscosity, density, and conductivity. The electrochemical and thermal stabilities of these ILs make them promising electrolytes for use in electrochemical devices.
Reversible Hydrogen Electrode Application as Indicator Electrode for Real Time Kinetic Study of Microbial H2 Production
Authors: Iñiguez Cesar , Zlatev Roumen , Stoytcheva Margarita , Valdez Benjamín , Magnin Jean-Pierre , Kiyota Sayuri
Published: March 2011

The Reversible Hydrogen Electrode (RHE) potential depends on the pH and the H2 pressure which determines the disolved hydrogen concentration according to the Henry law. RHE was applied as hydrogen sensor for real time bacterial hydrogen production rate evaluation employing the photosynthetic Rodobacter Capsulatus strain IR3 in 10 ml reactor containing RCV medium. The reliable determination of the produced H2 volume for determination of the process rate requires big reactor volumes since the H2 production rate is small, measured in mL/hour and the precise measurements of small gas volumes is very complicated. The RHE potential monitoring however allows real time determination of the generated H2 and hence the process rate without consumption of great reagent amounts.
(Ga,N) and (Cu,Ga) Co-Doped ZnO Films for Improving Photoelectrochemical Response for Solar Driven Hydrogen Production
Authors: Shet Sudhakar
Published: March 2011

In this study, Bandgap-reduced p-type ZnO thin films were synthesized through Cu and Ga co-doping. The ZnO:(Cu,Ga) films were synthesized by RF magnetron sputtering in O2 gas ambient at room temperature and then annealed at 500° in air for 2 hours. We found that the carrier concentration tuning does not significantly change the bandgap and crystallinity of the ZnO:Cu films. However, it can optimize the carrier concentration and thus dramatically enhance PEC response for the bandgap-reduced p-type ZnO thin films. The co-doped ZnO:(Ga,N) films were deposited by co-sputtering at room temperature, followed by post-annealing at 500°. We found that the ZnO:(Ga,N) films exhibited greatly enhanced crystallinity compared to ZnO:N films doped with pure N. Furthermore, the ZnO:(Ga,N) films showed much higher N-incorporation than ZnO:N films. As a result, the ZnO:(Ga,N) films showed significantly higher photocurrents than ZnO:N films.
Status of the U. S. Department Of Energy, Energy Efficiency and Renewable Energy's Fuel Cell Research and Development Efforts
Authors: Papageorgopoulos Dimitrios , Benjamin Thomas G. , Kopasz John P. , Podolski Walt
Published: March 2011

The U.S. Department of Energy (DOE) Fuel Cell Technologies Program, in the Office of Energy Efficiency and Renewable Energy (EERE), seeks to enable the widespread commercialization of fuel cells, through applied research and development (R&D) to overcome technical barriers, as well as through efforts to reduce institutional and market barriers. In support of this goal, DOE funds a broad range of fuel cell R&D activities with emphasis on materials, fuel cell stack components, balance of plant (BOP) subsystems, and integrated fuel cell systems targeting lower cost and enhanced durability. Fuel cell system cost estimates for transportation applications have illustrated that catalysts and system BOP are major cost drivers at high-volume production. Membranes are a cost driver at lower production volumes. The DOE has supported research to develop improved fuel cell catalysts and membranes and characterize and optimize transport phenomena to improve membrane electrode assembly (MEA) and stack performance.
SS 316L by Thermal Treatments
Authors: Wang Wen-Lin , Hsueh Kan-Lin , Chang Wen-Chen , Hsiao Li-Yin
Published: March 2011

Type 316L is molybdenum-bearing austenitic stainless steel which is more resistant to general corrosion and pitting/crevice corrosion than the conventional chromium-nickel austenitic stainless steels such as Type 304. The alloy also offers higher creep, stress-to-rupture and tensile strength at elevated temperatures and thus is considered to be good candidates for bipolar plate materials for the polymer electrolyte membrane fuel cell (PEMFC). While operating at high temperatures (>100°), the stainless steel can be easily passivated. The major concern for SS316L then would be the possibility of additional film growth and its possible effect on the interfacial contact resistance and the corrosion resistance. In this study, the contact resistance has been evaluated for SS316L samples pretreated at high temperatures for different periods of time. The surface morphology and the composition change of these samples were analyzed by high-resolution SEM/EDS. Also, the polarization curves of these heated samples in 0.5M sulfuric acid solution at 25° were measured by linear scanning voltammetry. The results showed that a stable passive film formed due to the thermal treatments. The interfacial contact resistance increased with heating time but not necessary with elevated temperatures.
Novel ABPBI/POSS Composite Membranes for High Temperature PEMFC Applications
Authors: Liu Qingting , Bao Xujin , Rogers Daniel M. , Zou Siqin
Published: March 2011

Novel organic-inorganic composite membranes involving poly(2,5-benzimidazole) (ABPBI) and polyhedral oligomeric silsesquioxane (POSS) were prepared via in-situ synthesis followed by phosphoric acid doping. The formation of composites was characterized by SEM, XRD and FTIR. The results of water uptake showed that POSS cores emerged extraordinary water absorbability. When doping in phosphoric acid solution, phosphoric acid absorption in composites was dominated by functional groups linked to POSS cores. The excellent proton conductivities i.e. above 0.1S/cm at 100~160oC achieved from anhydrous ABPBI/OA-POSS composite membranes with 241wt.% of phosphoric acid absorption, make them very good candidates as the membranes for high temperature polymer electrolyte membrane fuel cell (PEMFC) applications.
Accurate Determination of the Hydrogen-Water Viscosity in PEMFC
Authors: Huang Peter H.
Published: March 2011

Transport properties of viscosity of hydrogen-water vapor systems are needed for engineering applications in PEMFC system analysis and design. For instance, transport properties are needed up to 500 K for hydrogen fuel cell operation using PEMs. The properties may be conveniently represented as a function of the quantity of moisture by weight in grams of water per kilogram of dry hydrogen. The most recent values of viscosity of hydrogen based on a full quantum-mechanical formalism as well as the viscosity of water based on a new international formulation were used to calculate the effective viscosity of hydrogen-water mixture for constant pressures of 0.1 MPa, 0.5 MPa and 1 MPa, respectively, in the temperature range from 340 K to 500 K and in the range of water vapor concentrations from 100 grams of water vapor per kilogram of dry hydrogen to 100 kilograms of water vapor per kilogram of dry hydrogen. The results show that the effective viscosity of a hydrogen-water vapor mixture is not sensitive to the changes in ambient pressure in a PEMFC system. Their relative standard uncertainties are shown to be 0.2 % of the values with a coverage factor k = 2 (confidence level of 95 %).
Stainless Steel Bipolar Plates.- Double-Channel Serpentine Flow Field Design
Authors: Hidalgo Pablo E. , Rivas Sandra V. , Correa Fernando , Arredondo Gerardo , Castaneda Federico , Orozco German
Published: March 2011

The performances of two gas-channel designs of bipolar plates were investigated by numerical simulations and experimental in-cell tests. The experimental study examined the performances of two gas-channel geometries and materials under cathode and anode flooding conditions. Design 1 consisted in straight-parallel channels with graphite monopolar plates. On the other hand, Design 2 was made of a double-channel serpentine flow field pattern with stainless steel monopolar plates. Design 1 did not provide a uniform flow distribution over the gas diffusion layer, so liquid water was accumulated in certain regions. The flow velocity in Design 2 was higher and produced more uniform electrical current distributions than the straight-parallel channels design. This design, using 304 SS plates, diminished the effect of the electrical resistance related to the mass transfer rate.