bluuebunny/crossref_metadata_2025 huggingface dataset:
ON CERTAIN INEQUALITIES ABOUT ARITHMETIC FUNCTIONS WHICH USE THE EXPONENTIAL DIVISORS
Authors: MINCULETE NICUŞOR
Published: May 2012

The purpose of this paper is to present several inequalities for the arithmetic functions σ(e) and τ(e). Among these, we have the following: [Formula: see text], for all n ≥ 6, [Formula: see text], for all n ≥ 1. We also prove that if the number [Formula: see text] is an e-perfect number, then it has at least one exponent ai equal with 2.
PROLIFERATION AND COLLECTIVE MIGRATION OF SMALL CELL GROUPS RELEASED FROM CIRCULAR PATCHES
Authors: MAREL A.-K. , ALBEROLA A. PIERA , RÄDLER J. O.
Published: May 2012

Collective cell migration is a key element in morphogenesis, cancer formation and wound healing. The multicellular dynamics of epithelial cell layers were studied in experiment and theory over the last years. Yet little is known about cell patches of finite size that should lead over from single cell behavior to collective motion. Here we study the migration and proliferation of small assemblies of epithelial cells (5-23 cells initially). Cells are released at defined time using removable poly(ethylene glycol)-dimethlacrylate (PEG-DMA) stencils with circular apertures, wherein cells were seeded. Using time-lapse microscopy we determine cell number, cell patch area and shape of multiple patches in parallel. We confirm exponential growth in cell number but find the area of the patches expanding faster than exponential in the early phase. The area is, however, well-described if cell proliferation is superimposed by elastic area dilation assuming that the cell groups were initially compressed. The elastic relaxation time is of the same order as the measured doubling time. Furthermore, analysis of the center-of-mass movement of the patches reveals bursts of directed motion, which coincide with asymmetric cell growth. In these cases the contours of the patches seem to result from a tug-of-war like scenario of opposing leader cells.
The Influence of PEO113-b-PS780 Vesicles on the Corrosion Performance of Carbon Steel in Simulated Pore Solution
Authors: Hu Jie , Koleva Dessi A. , Van Breugel Klaas
Published: May 2012

This study presents the results from a preliminary investigation on the corrosion behavior of carbon steel in cement extract (CE) in the presence of very low concentration (0.0024 wt. %) polymeric nano-aggregates (PEO113-b-PS780 vesicles). Two types of vesicles were studied: vesicles with a CaO-containing core and vesicles with an "empty" core. The results from the electrochemical measurements (Electrochemical Impedance Spectroscopy (EIS) and Potentio-dynamic Polarization (PDP)) indicate that the presence of the CaO-containing vesicles lead to a significantly increased corrosion resistance of the steel, but no pronounced effect was observed for the "empty" vesicles. However, steel surface analysis indicates that the presence of both vesicles type results in a more homogeneous and compact product layer.
Detection of Acetone on Human Breath Using Cyclic Voltammetry
Authors: Motsegood Perry , Leddy Johna
Published: May 2012

A cyclic voltammetric measurement protocol for acetone concentration collected in the vapor phase and measured in solution is demonstrated for acetone concentrations across the human physiological range, 1 μM to 10 mM at platinum electrodes in 0.5 M H2SO4. Effects arise through adsorption of acetone from the gas phase onto a platinum surface and hydrogen in acidic solution within the voltammetric butterfly region. The protocol is demonstrated to yield breath acetone concentration on a human subject within the physiological range and consistent with ketone urine test strip.
Voltammetry of 4-Hydroxybiphenyl
Authors: Haque Inam U. , Rashid Ashi , Tariq Muqaddas
Published: May 2012

The electrochemical oxidation of 4-hydroxybiphenyl was studied at the glassy carbon disk electrode using cyclic, normal pulse and differential pulse voltammetry in a solvent mixture. 4-Hydroxybiphenyl exhibited a well-defined, irreversible peak in 1:1 acetonitrile-water mixture containing 0.2 M sodium perchlorate at glassy carbon (0.125 cm2) electrode. In pulse voltammetry a linear relationship was obtained between the anodic peak current and concentration of 4-hydroxybiphenyl. The work needs optimization for the quantitative determination of 4-hydroxybiphenyl.
Effect of Addition of Alkali Metal Fluoride to a Molten NH4F-HF System on Current Efficiency for NF3 Formation and Nickel Anode Consumption
Authors: Shiono Tomoyuki , Iida Yuki , Omori Hiroyuki , Saito Morihiro , Inaba Minoru , Tasaka Akimasa
Published: May 2012

The current efficiency for NF3 formation and the current loss caused by Ni dissolution were investigated in electrolysis of the NH4F·2HF melts with and without alkali metal fluorides such as CsF, KF, and LiF. The addition of CsF to the melt was most effective for increasing the NF3 current efficiency. In contrast, the addition of KF to the melt decreased the current efficiency for NF3 formation and increased the current loss caused by Ni dissolution. The SEM observation and XRD analysis revealed that the oxidized layer formed on nickel in the melt containing LiF or CsF was composed of NiF2 with highly oxidized nickel fluoride. On the other hand, the oxidized layer in the melt containing KF was composed of only KNiF3, and was very brittle. Therefore, it is concluded that KF is detrimental to the nickel anode and highly oxidized nickel fluoride may relate to the NF3 current efficiency.
(Olin Palladium Award of the Electrochemical Society) The Use of Renewable Energy in the Form of Methane via Electrolytic Hydrogen Generation
Authors: Hashimoto Koji , Kumagai Naokazu , Izumiya Koichi , Takano Hiroyuki , Kato Zenta
Published: May 2012

Extrapolation of world energy consumption from 1990 to 2008 will result in the complete exhaustion of world reserves of oil, natural gas, uranium and coal until 2040, 2046, 2048 and 2054, respectively. For the survival of all people in the whole world, intermittent and fluctuating electricity generated from renewable energy should be supplied in the form of usable fuel to all people in the whole world. We are proposing global carbon dioxide recycling. Electricity generated from renewable energy will be converted to hydrogen by seawater electrolysis. Hydrogen, for which no infrastructures of transportation and combustion exist, will be converted to methane by the reaction with carbon dioxide captured from chimney. We created energy-saving cathodes for hydrogen production, anodes for oxygen evolution without chlorine formation in seawater electrolysis and catalysts for methanation of carbon dioxide, and built the pilot plants of industrial scale. The practical application is in progress.
Evaluation of a LiSi/Cu3V2O8 Thermal Battery
Authors: Dai Jinxiang , Lai Monique , McKee Jeremy
Published: May 2012

In this paper, thermal cells/batteries with LiSi/Cu3V2O8 chemistry have been studied. The cell open circuit voltage at 500oC is >3.0V and working voltage at 99mA/cm2 current density is over 2.5V. Cu3V2O8 cathode is able to deliver 376 mAh/g specific capacity corresponding to 5.9 electron transfer per formula. A 30V thermal battery has also been assembled and evaluated. The battery is able to work at 340 mA/cm2 constant current density (>10C rate) and 990mA/cm2 pulse current density (>30C rate).
Intermediate-Temperature Alkaline Methanol Fuel Cell
Authors: Jiang Junhua , Aulich Ted
Published: May 2012

An intermediate-temperature alkaline methanol fuel cell (ITAMFC) based on significantly accelerated electrode reactions and minimized CO-poisoning of catalysts in alkaline media and in an intermediate-temperature range of 80 to 200 oC has been successfully developed. In this temperature range, electrochemical oxidations of both methanol and CO at Pt-group elemental-based catalysts are rather facile and silver shows high activity for oxygen reduction reaction which is comparable to that of Pt. The ITAMFC using carbon-supported platinum as both anode and cathode catalysts demonstrates high performance which is characterized by a peak power density of around 100 mW cm-2 at 120 oC. Moreover, it has been observed that it is possible to replace Pt catalysts using less-expensive Pd catalyst at the anode side and Ag catalyst at the cathode side without sacrificing performance. Therefore, the ITAMFC is a novel promising fuel cell technology with improved performance and/or decreased cost.
A Microbial Fuel Cell for Starch Oxidation
Authors: Ghosh Subhodip , Chatterjee Someswar , Chatterjee Moitrayee , Ghosh Susanta , Basumallick Indra Narayan
Published: May 2012

A new type of Microbial Fuel Cell (MFC) employing fish bladder as proton exchange membrane has been reported. Yeasts were impregnated on to nano gold supported carbon felt and used as anode of a lab model cell with dilute aqueous solution of starch in buffer solutions (pH 7.2) as fuel. The Cell generates an open circuit potential of 0.185 V vs. SCE at 298 K. Experimental data shows feasibility of power generation using immobilized yeast on to gold nano surface and using a natural proton exchange membrane like fish bladder.
The Correlation of the Anodic and Cathodic Open Circuit Potential (OCP) and Power Generation in Microbial Fuel Cells (MFCs)
Authors: Santoro Carlo , Agrios Alexander G. , Li Baikun , Cristiani Pierangela
Published: May 2012

The overall open circuit potential (OCP) and short circuit potential of anodes and cathodes and the power generation in air-cathode membraneless single chamber microbial fuel cells (SCMFCs) were investigated in this study. Two SCMFCs with different anode areas (10 and 40 cm2) were tested in 8 weeks of experiments. At the beginning of the tests, the anodes were well colonized and the cathodes were in a clean condition. Anodic OCPs remained stable throughout the experiments while the cathodic OCPs decreased dramatically in the first week. The overall OCP of SCMFCs followed the cathodic OCP trend. The power generation of SCMFCs dropped dramatically in the first 3 weeks and then remained stable. The short circuit potential indicated that the performance of SCMFCs was mostly limited by the cathodic process of oxygen diffusion to the platinum.
Carbonate Fuel Cell Matrix and Electrolyte Developments
Authors: Hilmi Abdelkader , Yuh Chao-Yi , Farooque Mohammad
Published: May 2012

The carbonate fuel cell matrix and electrolyte are important components for performance and life stability. Significant improvements were achieved in the areas of matrix pore structure, manufacturing and electrolyte chemistry. These efforts have enabled extending cell life and reducing cost. The optimization of electrolyte composition showed 40 mV performance improvement at low temperatures and >55% reduction of NiO dissolution compared to baseline design. Investigations on electrolyte compositions, electrolyte additives and stable matrix materials continue to further enhance cell life
Micromechanisms of Capacity Fade in Silicon Anode for Lithium-Ion Batteries
Authors: Pal Siladitya , Damle Sameer , Patel Siddharth , Dutta M. K. , Kumta Prashant N. , Maiti Spandan
Published: May 2012

Large volume change and associated stress generation is known to cause failure of the silicon thin film anode used for Lithium-ion batteries after a few cycles. Experimental observations suggest that plastic deformation of the underlying Cu substrate and degradation of the active/inactive interface are the primary reasons responsible for the capacity fade. The goal of the present study is to examine the interplay between these mechanisms using a computational mechanics approach. In the present study, a novel multi-physics finite element framework has been developed to simulate the lithiation and de-lithiation induced failure of amorphous Si (a-Si) thin film on Cu foil. The numerical framework is based on the finite deformation of the active silicon wherein diffusion of lithium occurs, plastic deformation of the Cu foil, and debonding of the active/inactive interface. The effect of substrate property, interfacial energy and kinetics of interface degradation has been examined.
Battery Characteristics of Nanocrystalline V2O5 and Conductive Polymer Composite Film Cathodes
Authors: Yoo Dah-Yeon , Hong Soon-Kie , Song Hahn-Mok , Yeo In-Hyeong , Mho Sun-il
Published: May 2012

Composite films of nanocrystalline V2O5 embedded in a conducting polymer, poly-3,4-ethylenedioxythiophene (PEDOT), were grown using an electrochemical polymerization method. The nanobeam-shaped V2O5 and PEDOT composite film cathodes have high capacities, excellent rate capabilities and cycling stabilities: the specific capacity was 269 mAhg-1 and the degradation rate was only 8% after 100 consecutive cycles at 1 C rate. The charge transfer resistances (Rct) for the nanobeam-V2O5/PEDOT composite film cathodes were smaller than that for the nanobeam-V2O5 powder cathode, in the electrochemical impedance measurements. The diffusion coefficient (DLi+) in the nanobeam-V2O5 crystallines was calculated to be approximately 4.6 x 10-8, and the values of DLi+ for each of α-, ε-, and δ-LixV2O5 crystalline phases, reversibly formed in the composite films during the discharging and charging processes, were able to be estimated in the range of (2.1~9.8) x 10-10.
Single-Step Bacterial Detection by Simultaneous Synthesis and Integration of Gold Nanoparticles and Its Application in Intracellular Delivery
Authors: Badwaik Vivek D. , Dakshinamurthy Rajalingam
Published: May 2012

Bacterial infections are one of the most common concerns among environmental and clinical settings. Detection of such pathogenic bacteria, in a rapid and a sensitive manner is a key requirement. Herein, we report the detection of bacterial contamination through simultaneous nanoparticle formation on the cell surface. In this approach, gold nanoparticles (GNPs) were synthesized and integrated simultaneously on the surface of analyte bacteria, imparting visual readout. The synthesized GNPs were examined by several different analytical techniques including transmission electron microscopy (TEM). The results indicated that the particles were stable; near spherical in shape with an average diameter of 25 ± 5 nm. The histological changes in bacteria which were observed through TEM analysis indicated the successful intracellular delivery of nanoparticles.
The High Performance Nanorod Pd/WO3/Silicon Carbide/Silicon (P-I-N) Diode for Carbon Monoxide Gas Sensing Operation
Authors: Juang Feng-Renn , Fang Yean-Kuen , Ke Jian-Cun
Published: May 2012

The nanorod Pd/WO3/SiC/Si p-i-n diode prepared on p+ type (100) Si substrate for carbon monoxide (CO) sensing applications was studied. The SiC material was used to enhance operating temperature, and the nanorod structure was designed to improve sensing performance of the device. The developed p-i-n diode exhibited a high relative response ratio of ~445% to 100 ppm CO ambient under condition of 300oC and -3V bias. The response ratio was better than the reported WO3 based resistive type CO sensors of 15 % and 8 %, respectively on Si and Al2O3 substrates. Thus, the Pd/WO3/SiC/Si p-i-n diode had the potential to develop a low cost high performance CO sensor.
Mild HEV Performance at Micro Hybrid Cost - A Low Voltage Lead-Acid Approach
Authors: Cooper Allan , Morris Guy , Neumann Michael , Kellaway Michael
Published: May 2012

The Advanced Lead Acid Battery Consortium (ALABC) has since 2000 been demonstrating valve-regulated lead-acid (VRLA) batteries in hybrid electric vehicles and has shown that advanced designs can cope with this duty cycle with good reliability (1). This demonstration work has been done by converting existing vehicles and thus all work to date has utilized Japanese mild hybrids. The European market is coming at hybridization from a different direction, with the introduction of low-cost micro-hybrid stop/start systems, such as the BMW EfficientDynamics (2), in order to meet CO2 regulations. Recently Controlled Power Technologies (CPT) has been promoting an alternative way of achieving mild hybrid performance (3), which would meet projected CO2 regulations, at a fraction of the cost of the current Japanese approach. This new system would operate with advanced VRLA batteries at 12V or 48V and provides an opportunity for lead-acid to be at the leading edge of hybrid technology.
The Beneficial Role of Carbon in the Negative Plate of Advanced Lead-Carbon Batteries
Authors: Monahov Boris
Published: May 2012

Lead-acid batteries have short cycle life in hybrid electric vehicles due to negative plate sulphation occurring at high-rate partial-state-of-charge cycling. It has been found experimentally that the problem can be solved by adding carbon to the negative plate. The types of carbon added, and the methods for their application are reviewed in this study. Special attention is devoted to the physical and chemical properties of carbon and to their importance for battery performance. Some methods for designing carbon electrodes (solid carbon and carbon powder) for electrochemical studies of carbon are described along with some initial test results like open circuit potential data and voltammograms in the negative plate potential region and in the region of hydrogen evolution. The available theoretical models explaining the mechanism of the influence of carbon on the power performance of lead-carbon batteries are also discussed.
Electrochemical Principles as Applied to Grid Corrosion in Lead-Acid Batteries
Authors: Misra Sudhan S.
Published: May 2012

Alloying constituents for lead alloys used for grids utilized in the manufacture of lead-acid batteries fall into two main categories: those with antimony and those without. The alloys without antimony can be further divided into those with calcium and those without, thus dividing the entire family of alloys into three main categories. This paper discusses the electrochemical principles that influence the progress of corrosion of these alloys in the lead-acid battery environment. Even as the alloy selected must meet the requirements of the application mode, it ultimately impacts the life expectancy of the battery. This review and discussion encompasses both the vented (or flooded) as well as the valve regulated lead acid (VRLA) battery types. Focus is on cast alloys in relationship to the grain structure and the inter-metallic phases present at the grain boundaries that lead to electrochemical disparity and corrosion, and the steps taken to control it.
Lead Acid-NiMH Hybrid Battery System Using Gel Electrolyte
Authors: Weng Guo-Ming , Li Chi Ying Vanessa , Chan Kwong-Yu
Published: May 2012

A hybrid battery system with gel electrolytes is proposed here to alleviate some limitations on conventional batteries, such as maintenance cost and acid stratification for the lead-acid battery, high self-discharge and short life cycles for high current discharge for nickel-metal hydride battery. This hybrid battery consists of a lead-acid positive electrode and a nickel-metal hydride negative electrode, operating in H2SO4-silica gel and KOH-potassium salt poly(acrylic acid) gel electrolytes via monopolar ion exchange membranes, respectively. The hybrid battery using gel electrolyte maintained stable discharge plateau at 2.27 V and longer discharge capacity than wet electrolyte system. This improved performance may be due to the gel electrolyte which can prevent acid stratification, reduce the corrosion rate of electrodes, and resolve the problem of salting-out in the central chamber for aqueous electrolyte system.
Evaluation of Blister Growth of High Performance Organic Coatings by Electrochemical Impedance Measurements
Authors: Ito Daisuke , Yokoyama Takashi , Okazaki Shinji
Published: May 2012

An organic coating is widely used as the way of corrosion prevention. The degradation of the coating appears in the form of blister. Therefore, the clarification of the occurrence phenomenon of blister is very important with the corrosion control. In this study, the blister growth of a high performance coating was quantitatively evaluated by an impedance measurement. To analyze the blister growth process, a new equivalent circuit model (Constant Phase Element, CPE) was proposed. The blister was created by the acceleration test which used a temperature gradient. As a result, the shape and the number of the blister strongly depended on the coating thickness. The impedance behavior of degraded coating did not agree with the equivalent circuit model using one CPE. On the other hand, the model containing the two CPE could express the experimental results and parameter value of this model is closely related to the occurrence of blisters.
Interesting Electronic Interaction between Polyaniline and Chloranil
Authors: Yano Jun , Okamoto Kazuyuki , Komaguchi Kenji , Harima Yutaka , Kitani Akira
Published: May 2012

Reduced polyaniline (PANI) showed a Nernstian response to dissolved chloranil (CHR), linear electrode potential-log[CHR] relationship. The anodic peak potential (Epa) of PANI in the cyclic voltammogram was directly proportional to log[CHR], i.e. linear Epa-log[CHR] relationship. These linear relationships and the fact that the new absorption shoulder was evident at around 450 nm in the UV-visible absorption spectra implied that PANI incorporated with CHR. The measurements of the electron spin resonance (ESR) spectra and the magnetic susceptibility (χg) of the PANI incorporating CHR revealed that the incorporation magnetized PANI. No magnetic hysteresis loop was observed for the PANI, and it showed no ferromagnetic property. However, it had an unusual paramagnetic property because χg was not inversely pro-portional to temperature. In addition, from the ESR spectra, the polaron species (cation radicals) of PANI are delocalized along the entire polymeric backbones.
Redox Potential Evolution of Nitric Species and Plutonium in HNO3-HNO2 System
Authors: Larabi-Gruet Nathalie , Buravand Emilie , Gwinner Benoit , Robin Raphael , Fauvet P.
Published: May 2012

In France, the reprocessing process of spent fuel is carried out using the Purex process. The first chemical step of this process is the dissolution of the spent fuel in aqueous concentrated nitric acid. This dissolution solution is composed of many oxidizing species and it is necessary to understand the chemistry of these species to apprehend the behavior of structural materials. The redox potential is a useful discriminate variable to differentiate the effect of each species. In this framework, only the effect of NO3-/HNO2 couple and PuO22+/Pu4+ couple were investigated. These species were chosen because one is the main couple of medium and the other has a high standard potential. Their influence was investigated from the Nernst's equation.
Two Common Electroanalytical Techniques - Cyclic Voltammetry and Impedance Capacitance Data from Cyclic Voltammetry
Authors: Vanýsek Petr
Published: May 2012

Steady state monitoring of electrochemical parameters in process control, for example, is recognized as very viable approach. An impedance detector can be used to monitor a property, perhaps at a set frequency. Cyclic voltammetry is much less practical for those applications, because of its non-steady state nature, but the method can be also incorporated in a general sensing scheme. In cyclic voltammetry the potential excursion is usually quite high, perhaps a volt or so, whereas in impedance, the excursion is small, maybe only ten millivolts. In many experimental situations the two methods can be combined. Often, some information, usually obtained from one method, is attempted to be obtained from the other method as well. This work compares the results obtained from the two methods.
The Distribution of Relaxation Times as Beneficial Tool for Equivalent Circuit Modeling of Fuel Cells and Batteries
Authors: Klotz Dino , Schmidt Jan Philipp , Kromp Alexander , Weber André , Ivers-Tiffée Ellen
Published: May 2012

In this work we present a method for the pre-identification of impedance measurements by the distribution of relaxation times (DRT). Several new features for parameter identification for electrochemical systems such as batteries and fuel cells are presented. The approach enables robust, accurate and consistent fit results for complex technically relevant systems with a large number of polarization processes involved in the impedance response.
AC Impedance Analysis of Electrorheological Fluids - Activated Biomedical Devices
Authors: Lvovich Vadim F. , Samorezov Sergey S.
Published: May 2012

Electrorheological fluids (ERFs) have been described as highly engineered variable-impedance fluids that possess rheological and electrical properties that demonstrate dramatic nonlinear change with an applied electric field. ERF is a two-phase composite colloidal suspension of electrically polarizable particles dispersed in insulating media. This article describes an application of low-voltage electrochemical impedance spectroscopy (EIS) to comparative characterization of four different ERFs and a prediction of their performance in ER-activated medical prosthetic devices. The ERF impedance response is interpreted in the context of a classical Debye relaxation model. EIS data analysis allows the determination of the electrical characteristics of polarizable particles and base fluid, an investigation of the preferred conduction mechanisms in the fluid, an evaluation of the potential for chemical agglomeration, and modification of the electrical properties of the ERF to achieve better fluid performance. The ERF performance improves significantly for highly concentrated suspensions of well-dispersed, small, closely packed particles. The recent introduction of nanoparticles-based ERF has created an opportunity for further development of fluids with transformationally superior performance.
Polysaccharide-Based Gel Electrolytes Containing Hydrophobic Ionic Liquids for Electric Double-Layer Capacitors
Authors: Yamagata Masaki , Soeda Kazunari , Ikebe Shota , Yamazaki Shigeaki , Ishikawa Masashi
Published: May 2012

Non-aqueous gel electrolytes based on polysaccharides (alginate or chitosan) with hydrophobic 1-ethyl-3-methylimidazolim tetrafluoroborate (EMImBF4) were prepared for electric double layer capacitors (EDLCs). The transparent colorless gel sheets have high mechanical strength and high retentivity of EMImBF4 enough to construct EDLC cells. According to charge/discharge measurements, the model EDLC cells with alginate- and chitosan-based gels show high discharge capacitance in spite of using a gel-state electrolyte, implying that high affinity of alginate for an activated carbon electrode leads to a decrease in the electrode/electrolyte interfacial resistance. A test cell with Alg/EMImBF4 maintains its coulombic efficiency over 99.8 % during 5,000 cycles.
Study of Carbon Based Solid State EDLCs at High Sweep Rates
Authors: Subramaniam C.K. , Cheralathan K.K. , Velayutham Guruviah , Bollepalli Sri
Published: May 2012

Study of carbon based solid state EDLCs at high sweep rates. C.K. Subramaniam, K. K. Cheralathan, G.Velayutham and Sri Bollepalli a Materials Division, School of Advanced Sciences, VIT University, Vellore, 632014, TN, INDIA. b Anabond Sainergy Fuel Cell India Pvt., Ltd., 288 Burma Colony, Perungudi Chennai 600096, INDIA. c Sainergy Tech, Inc., 869 Pickens Industrial Drive, Suite 11, Marietta, GA 30062,USA, Solid state carbon based Electrochemical Double Layer capacitors (EDLC) was assembled and cyclic voltammetry (CV) was studied at high sweep rates. The carbons used were Vulcan XC carbon with typical surface area of 260 m2/gm, templated mesoporous carbon, (CMK-3), typical surface area of 1260 m2/gm, and a blend of Vulcan XC carbon and mesoporous carbon (90:10 % by weight). Solid ionic polymers of perfluorosulphonic acid were used as electrolyte. CV was performed for scan rates as high as 800V/s. The polymer electrolyte membrane can support high scan rates.
Fabrication of a Transparent Supercapacitor Electrode Consisting of Mn-Mo Oxide/CNT Nanocomposite
Authors: Nakayama Masaharu , Okamura Keigo , Athouël Laurence , Crosnier Olivier , Brousse Thierry
Published: May 2012

We have fabricated nanocomposite electrode materials consisting of manganese-molybdenum mixed oxide and carbon nanotubes (CNTs) for supercapacitor application. The process involves electrophoretic deposition (EPD) of multi-walled CNTs onto an ITO electrode, followed by anodic deposition of Mn-Mo oxide from an aqueous MnSO4 solution with MoO4
2- anions. The composite electrodes with a variety of combinations of Mn-Mo oxide and CNTs were evaluated systematically with the aim of maximizing the capacitive properties of the oxide. Optimization led to a high specific capacitance of 408 F g-1 (2 mV s-1) with an area-normalized capacitance of 31 mF cm-2.
Temperature Dependence of Key Performance Indicators for Aqueous Supercapacitors Containing Nanostructured Birnessite
Authors: Roberts Alexander J. , Slade Robert C.
Published: May 2012

Birnessite has been made in a number of morphologies through variation of reaction conditions in a simple templated hydrothermal synthesis. After processing into electrodes and testing in hybrid supercapacitor cells, good cycleability and a range of specific capacitances were observed. The most promising material, a birnessite nanotube, was extensively electrochemically tested at elevated temperatures. An increase in specific capacitance from 340 to700 F g-1 was observed as the temperature was raised from 30 to 80ºC but with an accompanying increase in current leakage. There was a drop in specific capacitance with cycling at elevated temperatures and, with the aid of electrochemical impedance spectroscopy data, inferences have been drawn regarding the effects of both cycling and time spent at elevated temperatures.
Fabrication of a Hybrid Capacitor Composed of Vertically-Aligned Multilayered Manganese Oxide Film
Authors: Inoue Ryota , Nakayama Masaharu
Published: May 2012

Buserite-type layered manganese oxide was prepared on Pt substrate by anodic deposition of birnessite intercalated with tetrabutyl ammonium cations and the following ion-exchange with Ni2+ ions. The resulting Ni-intercalated buserite was subjected to repetitive potential steps between +0.8 and 0.0 V in an Na2SO4 aqueous electrolyte. During the repetitive steps, the electrochemical activity of the film was enhanced drastically with increasing the step number and interval. This behavior was accompanied by an irreversible morphological transformation of the MnO2 film. The structure thus formed exhibited a specific capacitance of 225 F g-1 at a scan rate of 2 mV s-1 in Na2SO4 electrolyte. Furthermore, we fabricated a hybrid cell based on the optimized MnO2 film and activated carbon as the positive and negative electrodes, respectively. It can be cycled reversibly in the voltage region of 0.0 to +1.8 V and exhibits an energy density of 1.1 Wh kg-1.
Development of High-Voltage Electrolytic-Electrochemical Solid Polymer Electrolyte-Based Capacitors for Implantable Defibrillators
Authors: Dweik Badawi , Rasimick Brian J. , Moulai Marjon H. , Wu Man
Published: May 2012

Implantable defibrillators require compact, high-voltage capacitors. One category of capacitors suitable for the application is electrolytic-electrochemical hybrid capacitors. This study investigated replacing the liquid electrolyte of these capacitors with a solid-ionomer polymer such as perfluorsulfonic acid polymers or sulfonated-poly(dimethylphenylene oxide). Such a change eliminates the use of corrosive liquids and allows for several cells in series to be packaged together. A single cell operating at 200 V with an energy density of 6.0 J/cc was produced. A three-cell capacitor stack capable of operating at 700 V was produced. Capacitors were evaluated using electrochemical impedance spectrography and charge/discharge cycling. Data showed that there is no major performance penalty associated with the use of solid electrolytes.
Molecular Theory of Solvation and Electrical Double Layer in Nanoporous Carbon Electrodes
Authors: Kovalenko Andriy
Published: May 2012

Electrical double layer (EDL) in a nanoporous electrode is very different from a planar electrochemical capacitor. The statistical-mechanical, Replica RISM-KH-VM molecular theory for electrolyte solution sorbed in disordered nanoporous materials provides full microscopic details of the solvation structure and thermodynamics and electrochemical properties averaged over the thermal motion of sorbed solution and over quenched morphology of host nanoporous material. The method reveals the molecular mechanisms and driving forces of sorption of electrolyte solution in a nanoporous carbon electrode which are drastically different from the electrical double layer in electrolyte solution at a planar electrode. These include nanoporous confinement morphology and external charge, size and chemical specificities of solvent and electrolyte, osmotic forces, the internal EDL at the surface of nanopores and the external EDL at the contact with bulk solution. The interplay of these factors determines the efficiency of an electrosorption cell and the specific capacitance of the electrochemical supercapacitor.
Electrochemical Double Layer Capacitance of Metallic and Semiconducting SWCNTs and Single Layer Graphene
Authors: Ervin Matthew H. , Mailly Benjamin , Palacios Tomas
Published: May 2012

The specific double layer capacitance that has been achieved with single wall carbon nanotubes (SWCNTs) is below that which is predicted from calculations based on the theoretical surface area of the CNTs and the intrinsic capacitance of the electrolyte. This paper investigates the specific capacitance of metallic (M-) and semiconducting (SC-) CNTs in order to determine if density of states (DOS)/quantum capacitance is a limiting factor in the capacitances achieved. In addition, a model system composed of a large-area single-layer graphene electrode on a nonconducting substrate has been used in order to put a lower bound on the ultimate double layer capacitance that should be achievable with CNT and graphene electrodes. We find that at the specific capacitances achieved here, the quantum capacitance of SWCNTs is not the limiting factor. In addition, the single-sided single-layer graphene electrode indicates that capacitances in excess of 550 F/g should be achievable.
Electrochemical Impedance Spectroscopy of a Porous Graphite Electrode Used for Li-Ion Batteries with EC/PC Based Electrolytes
Authors: Foss Carl Erik L. , Svensson Ann Mari , Sunde Svein , Vullum-Bruer Fride
Published: May 2012

Electrochemical impedance spectroscopy has been employed to investigate different electrolyte compositions used for lithium-ion batteries. Diffusion coefficients in ethylene carbonate (EC) was estimated to be in order of 10-7-10-11 cm2/s, depending on the state of charge (SOC), and propylene carbonate (PC) based electrolytes has been estimated to be in the order 10-10-10-11 cm2/s. Lithium bis(oxalato) borate (LiBOB) was used as an additive in the PC electrolytes to prevent exfoliation
Characterization of Pretreated Co(OH)2-Coated Ni(OH)2 Positive Electrode for Ni-MH Batteries
Authors: Otsuka Hazuki , Chiku Masanobu , Higuchi Eiji , Inoue Hiroshi
Published: May 2012

The transmission electron micrographs of the pretreated Co(OH)2-coated Ni(OH) showed that metallic Co nanoparticles were formed on the positive active material surface during the pretreatment as on the pretreated Co(OH)2 electrode. The UV-Vis spectroscopy and ICPS also exhibited that the metallic Co nanoparticles effectively suppress the loss of Co(OH)2 from the active material surface due to the suppress of its dissolution. From the comparison of the XRD patterns after charging for the pretreated and untreated positive electrodes, the state of charge or the valence of Ni ions for the former was not influenced by the depth of the active material layer in contrast to that for the latter. This may be ascribed to that mosaic CoOOH with higher conductivity is formed on the pretreated positive active material, and it forms a dense and high conductive network on the surface of the Co(OH)2-coated Ni(OH)2 positive active material, improving the electrochemical performance of the pretreated positive electrode.
CF/PAni/MWNT Composites Material, A Novel Electrode to Supercapacitor
Authors: Almeida Dalva A. , Fonseca Carla Polo , Baldan Mauricio Ribeiro , Ferreira Neidenei Gomes
Published: May 2012

In this work, the binary and ternary composites composed respectively by carbon fiber/polyaniline(CF/PAni) and carbon fiber/multiwall carbon nanotubes/polyaniline (CF/PAni/MWCNT) were synthesized by oxidative polymerization. The composite materials were physically characterized by Scanning electron microscopy, by Raman spectroscopy and electrochemically by cyclic voltammetry. These hybrid composites were designed to be used as supercapacitors. By Raman spectroscopy, a higher conductivity for the CF/PAni/MWCNT composite was observed composite was observed .The highest specific capacitance was achieved to CF/PAni/MWCNT (400Fg-1) which is a good candidate to the supercapacitor electrode.
NO2 Gas Sensing Using a CF/PAni Composite as Electrode
Authors: Fonseca Carla Polo , Almeida Dalva A. , Baldan Mauricio Ribeiro , Ferreira Neidenei Gomes
Published: May 2012

Gas sensors based on CF/PAni composite electrodes were synthesized using the polymerization chemistry. These sensors were used for detection of toxic gases like NO2. Three different deposition times were used in the synthesis of the CF/PAni composite: 30, 60 and 90 min. The morphology and the structural characteristics of the composites were analyzed by scanning electron microscopy and Raman spectroscopy, respectively. Experiment results confirmed that the NO2 gas sensor using CF/PAni composite has good response characteristics to different NO2 gas concentrations. Furthermore, the NO2 gas sensor using CF/PAni-90 composite showed the best sensitivity. This behavior was attributed to its largest content of PAni on the carbon fiber, which induced to its largest surface area. This morphology favors the adsorption of gas molecules leading to the highest current variation with the oxidation process.
Electrochemically Fabricated Nickel-Tungsten Nanowires
Authors: Bairachna Tetiana , Fowle W. , Podlaha E. J.
Published: May 2012

Nickel-tungsten thin films and nanowires were electrodeposited from a non-ammonia, citrate electrolyte. Direct current deposition at room temperature in unstirred electrolyte conditions resulted in thin films with the tungsten content ranging between 41 to 58 wt % (18 to 30 at %) and faradaic current efficiency 7-63 %. The nanowires were deposited by both direct and pulse current into polycarbonate templates. TEM and SEM analyses showed that the nanowires were solid having length up to 6 µm. Treatment of the nanowires under 3 h of ultrasound in order to examine their mechanical robustness resulted in breaking the smaller diameter nanowires (35-40 nm), but not larger diameter ones (100-250 nm).
(Invited) Investigation of Early Degradation Processes at Coated Metals by AC-Scanning Electrochemical Microscopy
Authors: Santana Juan José , Souto Ricardo M. , González Sergio , Pähler Maike , Schuhmann Wolfgang
Published: May 2012

Alternating-current scanning electrochemical microscopy (AC-SECM) is employed to characterize the early stages of the degradation reactions occurring in metal-coating systems upon exposure to an aqueous environment. The spatial resolution of the technique results from the measurement of changes in the resistance of the thin electrolyte layer comprised between the tip and the surface of the coating due to variations in the tip-substrate distance. Resistance measurements are conducted at various frequencies of the AC perturbation signal effectively allowing topographic changes to be monitored as a function of time. Furthermore, AC-SECM can be used to determine the tip-substrate distance without the addition of redox mediators to the electrolyte, which might affect the chemical properties of the system. In this way, the effect of chloride ions from the aqueous phase to induce either the heterogeneous absorption of water by the coating, or its accumulation at the metal-substrate interface, has been imaged.
(Invited) Smart-Release Inhibition of Corrosion-Driven Organic Coating Delamination on Galvanized Steel Surfaces
Authors: Williams Geraint , Geary Steven , Loveridge Melanie , McMurray Hamilton N.
Published: May 2012

In-coating cation and anion-exchange pigments are studied with respect to their ability to inhibit corrosion-driven organic coating disbondment on the zinc surface of hot-dip galvanized (HDG) steel. The efficiency of inorganic smart-release cation-exchangers, including bentonite and zeolite based pigments containing stored Zn(ii) inhibitor are compared with an organic cation-exchange cross-linked polystyrene based system. In-situ scanning Kelvin probe experiments carried out on HDG samples coated pigment-containing model polymer organic films showed that only the bentonite system was capable of halting delamination over a 24 h holding period, despite having a cation exchange capacity of only one third of the other exchangers. The reasons for this are discussed in terms of the kinetics of underfilm ion-exchange process. A preliminary investigation of anion-exchange hydrotalcite-based pigments is also described. The inhibition efficiency is shown to be highly anion specific, with chromate and phosphate exchanged pigments providing the best protection against organic coating cathodic disbondment.
Electrochemical Corrosion Study of Protective Organic Thin Film Coating on Magnesium Alloy
Authors: Abdel-Fattah Tarek M. , Mahapatro Anil
Published: May 2012

Organic thin films on magnesium alloys could serve as a protection layer for controlled biodegradation and for subsequent tailored modification. In this report we demonstrate the preliminary invitro stability of octadecylphosphonic acid (ODPA) organic thin films on Magnesium (Mg) alloy using impedance spectroscopy. Impedance spectroscopy of Mg alloy before and after coating with ODPA organic thin films determined the surface corrosion resistance after film deposition.
Study of a Renewable Biomass Powered SOFC
Authors: Gong Yunhui , Chien Andrew C. , Mao Z. P. , Huang Kevin
Published: May 2012

The objective of this work is to explore a solution to utilize biomass carbon by a tubular solid oxide fuel cell integrated with an "in-situ" steam gasification reactor. Non-catalyzed and catalyzed coconut shell carbons were employed as solid fuels, which were directly converted to gaseous fuels to feed the SOFC operated at 800°. Single cells showed variable electrochemical performances according to the catalytic additives. Sample without catalysts exhibited low power density, while those with catalysts such as Fe2O3 and K2CO3 showed higher performances. The enhanced cell performance with catalysts was considered to be the result of increased conversation rate of carbon and consequently high fuel concentration supplied to SOFC.
(Invited) Electrolyzer for Waste to Energy Conversion
Authors: Pal Uday B. , Pati Soobhankar , Yoong K. J. , Gopalan Srikanth
Published: May 2012

Hydrogen and syngas can be produced from municipal solid waste to meet part of our energy demand. In this work, the performance of a novel, energy-efficient, solid oxide membrane (SOM) electrolyzer for the production of high purity hydrogen from steam and hydrocarbon waste such as plastics is analyzed. Energy analysis of the proposed electrolyzer shows that hydrogen can be generated at an efficiency of nearly 75%. Based on this study, design and electrode materials for commercially viable SOM electrolyzer is proposed.
Fast UV Luminescence of Pr3+-Doped Calcium Lutetium Whitlockite
Authors: Trevisani Mattia , Ivanovskikh Konstantin V. , Piccinelli Fabio , Speghini Adolfo , Bettinelli Marco
Published: May 2012

The double phosphate Ca9Lu(PO4)7 doped with 1 mol% of Pr3+ was prepared by solid-state reaction. The obtained material was characterized by powder X-ray diffraction (XRD). The luminescence spectroscopy and the excited state dynamics of this material were studied upon VUV excitation using synchrotron radiation. The sample has shown efficient 5d-4f emission upon direct VUV excitation of 5d levels. It was observed that energy transfer from host to Pr3+ 5d states is inefficient. The decay kinetic of the Pr3+ 5d-4f emission in this host lattice upon direct VUV excitation of 5d levels is characterized by a decay time of 17 ns with no significant rise after the excitation pulse. No significant temperature dependence of the decay time was observed within the range 8-300 K.
The Evolution of The Optical Spectra of (M,M′)TiO3: Pr3+ (M, M′: Ca2+, Zn2+, Sr2+)Phosphors
Authors: Kim Gunha , Lee Seung Jae , Kim Young Jin
Published: May 2012

(M,M′)TiO3:Pr3+ (M, M′: Ca2+, Zn2+, Sr2+) phosphors were prepared by a solid-state reaction method, and the luminescent properties were investigated. The PLE and PL spectra of Ca1-xSrxTiO3:Pr3+ powders exhibited the strong dependence on the Sr content, resulting in the maximum emission intensity at x = 0.1. The PLE spectra of (Ca0.5Sr0.5-yZny)TiO3:Pr3+ showed wide excitation bands with increasing Zn content. The red emission intensity of (Ca0.5Sr0.35Zn0.15)TiO3:Pr3+ was higher than that of the pure CaTiO3:Pr3+.
The Enhancement of the Green Emission of Na(Y,Al)F4:Yb3+/Er3+ Up-Conversion Phosphors
Authors: Kwon Seok Hun , Lee Jun Seong , Kim Young Jin
Published: May 2012

NaY0.78-xAlxF4:Yb3+/Er3+powders were prepared by a solvothermal method using the various chemical compositions of the reactants. The amount ratio of oleic acid to NaF (RO/N) and the reactant concentration strongly affected the structural and up-conversion luminescent properties. The morphology of the obtained NaYF4:Yb3+/Er3+ particle depended on RO/N, and the best green emission was obtained from the powders with the irregular hexagonal-shaped rods. The Al3+ doping (x = 0.01) caused the significant enhancement of the green emission by about 40%. It was possible to speculate that these phenomena correlated with the particle morphology and the modification of the crystal field surrounding the Yb3+/Er3+ ions.
Redox Flow Battery Simulations for Optimizing Separator Membrane Performance
Authors: Sing David C. , Michael Philip H. , Meyers Jeremy P.
Published: May 2012

The redox flow battery (RFB) is being developed as a large-scale energy storage system to facilitate the integration of highly variable alternative energy sources such as wind and solar into the electrical grid. Optimization of the RFB requires evaluation of new electrochemical materials, electrode and separator materials, geometrical parameters such as cell dimensions and electrode porosity, and the operating conditions such as current density and electrolyte flow. A flexible computationally efficient model of the Vanadium RFB has been developed to gain insight into energy losses mechanisms and methods to optimize cell efficiency. A membrane model has been developed which utilizes concentrated- solution theory to refine membrane transport coefficients used as input parameters for the full cell RFB model.
In Situ Single Electrode Studies of an All-Vanadium Redox Flow Battery
Authors: Aaron Douglas S. , Tang Zhijiang , Lawton Jamie S. , Papandrew Alexander P. , Zawodzinski Thomas A.
Published: May 2012

We use polarization curves and a dynamic hydrogen reference electrode (DHE) to study the effects of electrode material and state of charge on all-vanadium redox flow battery (VRB) performance. The current trend in studying these systems is to evaluate new materials or designs based on voltage, charge and power efficiency metrics. However, such characterization does not allude to which processes may be limiting performance or which electrode dominates performance loss. At moderate state of charge, the negative electrode dominated cell overpotential at all current densities. As state of charge increased, the overpotential was dominated less by the negative electrode. Thicker carbon paper showed better performance while partially wet-proofed carbon paper had a negative impact on performance compared to untreated carbon paper. Through improvements made to the design and materials, VRB power output increased from 77 mW/cm2 to 404 mW/cm2.