bluuebunny/crossref_metadata_2025 huggingface dataset:
Viscous Flow of a Liquid Over a Rotating Surface With Gas Drag
Authors: Gardner G. C.
Published: October 2011

Differential equations are set up to describe the viscous flow of a liquid on a rotating surface with a shear stress exerted by a flowing gas stream along the surface and normal to the radial direction. Such a problem is met in the low-pressure stages of a steam turbine. The equations are solved first for a uniform flux of liquid onto the surface along a radial boundary R > R0, where R is the radial position and R0 is constant. It is then shown that absence of liquid flowing in along the radial boundary for R < R0 casts what is called a “flow shadow” and that two solutions of the equations are required, one for the “shadow flow” and one for the “main flow” region. The solutions are extended to the case where the shear stress exerted by the gas varies in a manner described by a simple power function of the distance along the surface, x, normal to the radial direction. All these solutions can be represented on a single graph showing streamlines and the shadow boundary. In conclusion, it is demonstrated that the two solutions for the main and shadow flows are special cases of a more general solution in which flow in along the radial boundary at x = 0 varies as 1−R0R1/32
On Unsteady Heat Transfer of Combined Free and Forced Convection in Circular Tubes
Authors: Tao L. N.
Published: October 2011

The unsteady heat-transfer problems of combined free and forced convection of a fully developed laminar flow of a heat-generating fluid in a circular tube with constant axial temperature gradient at the wall are investigated. The general solution with arbitrary time-dependent pressure gradient, heat generation, and wall temperature is established by the application of the “generalized Duhamel’s theorem.” Two specific cases are then studied. The results indicate that this type of transient problem has a time-variation of an oscillatory type with decaying amplitude. This time-variation is different from that of forced convection or of combined free and forced convection with constant axial wall temperature.
Stresses in a Linear Incompressible Viscoelastic Cylinder With Moving Inner Boundary
Authors: Shinozuka M.
Published: October 2011

A method is developed to find the stresses and strains in an incompressible viscoelastic hollow cylinder with moving inner radius contained by an elastic case and subject to internal pressure under the assumption of a state of plane strain. Stresses and strains are computed for a material with deviatoric stress-strain relations characteristic of a standard solid. The numerical computation is carried out with the aid of an IBM digital computer 1620 and is intended to illustrate the effects of the thickness of the cylinder, of the rate of increase of the internal pressure, and of the strength of the reinforcement provided by the elastic shell.
Breathing Vibrations of a Partially Filled Cylindrical Tank—Linear Theory
Authors: Chu Wen-Hwa
Published: October 2011

An accurate linear hydrodynamic theory (incompressible) is presented for breathing vibrations of a liquid column with an assumed mode shape. It yields the natural frequencies of liquid sloshing as well as the pressure distribution. A simplified frequency prediction for the partially filled cylindrical shell is derived from the Donnell-Yu equation with an apparent mass correction. Comparison with some available experiments show good agreement for breathing vibrations with the fundamental longitudinal mode.
Powered-Flight Trajectories of Rockets Under Constant Transverse Thrust
Authors: Zee Chong-Hung
Published: October 2011

The second-order nonlinear differential equations of motion in the case of a rocket in drag-free powered-flight under constant transverse (normal to the focal radius) thrust are solved by series expansion developed to the seventh power of the independent variable “time.” The coefficients of the powers of time are in terms of given boundary conditions. The truncation errors of the series are estimated, hence the accuracy for any practical problem based on the analysis presented in this paper could be well established. The case of constant transverse thrust acceleration, which may be conceived as a special case of the present analysis, is also solved.
Finite Twisting and Expansion of a Hole in a Rigid/Plastic Plate
Authors: Nordgren R. P. , Naghdi P. M.
Published: October 2011

This paper is concerned with the finite twisting and expansion of an annular rigid/plastic plate in the state of plane stress. The plate, bounded by two concentric circles one of which may extend to infinity, is subjected in its plane to the combined action of pressure on the inner boundary and a couple due to circumferential shear. A detailed solution which includes the effect of isotropic work hardening is obtained with the use of Tresca’s yield function and its associated flow rules and the corresponding solution with the use of Mises’ yield function and its associated flow rules is also discussed. Numerical results are given which illustrate the influence of twisting on the expansion of a hole in an infinite plate.
On the Bending of Circular Cylindrical Shells by Equal and Equally Spaced End Radial Shear Forces and Moments
Authors: Seide Paul
Published: October 2011

The effect of discontinuous circumferential end loading of a circular cylinder by equal and equally spaced radial shear forces and moments is investigated by means of Donnell’s equations. Large nonuniform bending effects are found for combinations of circumferential load coverage and cylinder geometry for which an assumption of uniform loading might intuitively be expected to be adequate.
Dynamic Stability of a Pendulous Missile Suspension System
Authors: Chobotov V.
Published: October 2011

The stability criteria for a missile on a pendulous support are derived for the case of parametrically excited motions of the support. The suspension system is described by two linear second-order differential equations with a periodic coefficient. The analysis is carried out by means of the first method of Liapunov. The results are somewhat modified, however, to obtain greater generality without which the technique is too laborious to be useful.
On a Class of Oscillations in the Finite-Deformation Theory of Elasticity
Authors: Knowles J. K.
Published: October 2011

This paper treats the large-amplitude radial oscillations of a perfectly elastic, incompressible cylindrical tube of infinite length due to suddenly applied pressures on its lateral surfaces. The motion is studied for materials with essentially arbitrary strain-energy density. Sufficient conditions for periodic motions and a formula for the period of oscillation are given in terms of the strain energy. The results are specialized to the case of a rubberlike material of Mooney type, and asymptotic formulas are given for the case of a thin shell and for the case of small applied pressure.
A Two-Phase Boundary Layer and Its Drag-Reduction Characteristics
Authors: Sparrow E. M. , Jonsson V. K. , Eckert E. R. G.
Published: October 2011

Consideration is given to coexisting gas and liquid boundary layers which occur when a gas is injected at the surface of a flat plate into a free-stream liquid flow. It is postulated that the gas forms a continuous film over the plate surface. The problem can be formulated exactly within the framework of laminar boundary-layer theory. Solutions have been carried out for a range of values of blowing velocity and of a fluid property parameter (ρμ) L / (ρμ)g. It is demonstrated that the drag forces associated with the two-phase boundary layer are much smaller than those for the single-phase liquid flow. For example, for a blowing velocity which is 0.001 of the free-stream velocity and a gas Reynolds number of 105, the over-all drag calculation yields a value which is 0.0205 of the single-phase drag force. The effect of evaporation at the gas-liquid interface is analyzed and found to be small at temperatures which are not too close to saturation.
Homogeneous Stress States in Helicoidal Shells
Authors: Cicala P.
Published: October 2011

The fundamental differential sets are presented for the various classes of stress states originated in a right helicoidal shell by loading along helixes or straight generators.
The Effect of Spacewise Lumping on the Solution Accuracy of the One-Dimensional Diffusion Equation
Authors: Murray W. D. , Landis Fred
Published: October 2011

Numerical or semidiscrete analog approximations to the diffusion equation must be formulated for solutions with automatic computing equipment. The present paper is devoted to the evaluation of truncation errors inherent in the spacewise difference formulation of the equation under general boundary conditions. A general method of analysis is developed and the error between the semidiscrete solution and the exact solution of the partial differential equations is evolved by matrix algebra and the Laplace transform. The method is illustrated by example showing the errors in the case of a symmetrically heated slab subject to temperature boundary conditions expressed as polynomials in time.
Symmetrical Bending of Circular Plates of Constant Radial Bending Stress
Authors: Lee J. P.
Published: October 2011

Bending of simply supported circular plates of constant radial bending stress subjected to uniformly distributed loading is investigated by solving a nonlinear integrodifferential equation. Boundary conditions are satisfied by joining the central portion of the plates of variable thickness to an annular rim along the boundary with uniform thickness. Usual assumptions for bending of thin plates of small deflections are assumed valid.
The Elastic, Plastic Bending of a Simply Supported Plate
Authors: Eason G.
Published: October 2011

In this paper the problem of the elastic, plastic bending of a circular plate which is simply supported at its edge and carries a constant load over a central circular area is considered. The von Mises yield condition and the associated flow rule are assumed and the material of the plate is assumed to be nonhardening, elastic, perfectly plastic, and compressible. Stress fields are obtained in all cases and a velocity field is presented for the case of point loading. Some numerical results are given comparing the results obtained here with those obtained when the Tresca yield condition is assumed.
The Stresses in an Elastoplastic Bar Subjected to a Sudden Change of Surface Temperature
Authors: Parkes E. W.
Published: October 2011

An analysis is given for the stress history in an elastoplastic bar subjected to a sudden change of surface temperature. The type of behavior is found to depend on the ratio of thermal strain (αV) to yield strain (σy/E). For EαV/σy < 1, the stresses are entirely elastic. For 1 < EαV/σy < 2.04 there are two transient zones of compressive yielding. For 2.04 < EαV/σy < 4.4 there are two transient zones of compressive yielding and two enduring zones of tensile yielding. For EαV/σy > 4.4 there are two transient zones of compressive yielding, one transient zone of tensile yielding, and two enduring zones of tensile yielding. The investigation is restricted to the range 0 ⩽ EαV/σy ⩽ 5 and the particular case EαV/σy → ∞. Detailed solutions are given for EαV/σy = 1, 2, 3, 4, 5, and ∞.
Torque and Cavitation Characteristics of Butterfly Valves
Authors: Sarpkaya Turgut
Published: October 2011

The present study deals with torque and cavitation characteristics of idealized two-dimensional and axially symmetrical butterfly valves. Theoretical results obtained for the two-dimensional case are compared with the ones obtained experimentally and by a relaxation technique. Based on the results of the two-dimensional case, an approximate solution is presented for the more general and practical case of three-dimensional butterfly valves. The results are in good agreement with the actual flow tests.
On the Stability of Rotation of a Rotor With Rotationally Unsymmetric Inertia and Stiffness Properties
Authors: Crandall S. H. , Brosens P. J.
Published: October 2011

The stability of uniform rotation of a rigid body about a principal axis of inertia is analyzed for the case where there is a diametral inertia inequality and there is an elastic restoring mechanism with a diametral stiffness inequality which rotates with the body. This model is an idealization for systems such as a two-bladed propeller rotating on a flexible shaft whose stiffness characteristics are not rotationally symmetric. It is found that many such systems possess unstable speed ranges. The instability may be due to either type of asymmetry alone or due to the interaction of the two. Quantitative analytical results are obtained which relate the unstable speed range to the gyroscopic coupling, the inertia inequality, the stiffness inequality, and the relative orientation of the principal axes of inertia with respect to the principal axes of stiffness. Three-dimensional stability surfaces are plotted to give a qualitative overview of the interplay of the various parameters.
Resistance Gene Transfer during Treatments for Experimental Avian Colibacillosis
Authors: Dheilly Alexandra , Le Devendec Laëtitia , Mourand Gwenaëlle , Bouder Axelle , Jouy Eric , Kempf Isabelle
Published: October 2011

An experiment was conducted in animal facilities to compare the impacts of four avian colibacillosis treatments—oxytetracycline (OTC), trimethoprim-sulfadimethoxine (SXT), amoxicillin (AMX), or enrofloxacin (ENR)—on the susceptibility of
Escherichia coli
in broiler intestinal tracts. Birds were first orally inoculated with rifampin-resistant
E. coli
strains bearing plasmid genes conferring resistance to fluoroquinolones (
qnr
), cephalosporins (
bla
CTX-M
or
bla
FOX
), trimethoprim-sulfonamides, aminoglycosides, or tetracyclines. Feces samples were collected before, during, and after antimicrobial treatments. The susceptibilities of
E. coli
strains were studied, and resistance gene transfer was analyzed. An increase in the tetracycline-resistant
E. coli
population was observed only in OTC-treated birds, whereas multiresistant
E. coli
was detected in the dominant
E. coli
populations of SXT-, AMX-, or ENR-treated birds. Most multiresistant
E. coli
strains were susceptible to rifampin and exhibited various pulsed-field gel electrophoresis profiles, suggesting the transfer of one of the multiresistance plasmids from the inoculated strains to other
E. coli
strains in the intestinal tract. In conclusion, this study clearly illustrates how, in
E. coli
, “old” antimicrobials may coselect antimicrobial resistance to recent and critical molecules.
Determining the Cause of Faults in the SAE 1018 Carbon Steel Used in Potable Water Pipelines by Means of Digital Image Processing
Authors: Bolaños Rodríguez Ernesto , Flores García Ernesto , Felipe Riveron Edgardo Manuel , Veloz Rodríguez Maria Aurora , Reyes Cruz Victor , Hernández-Ávila Juan
Published: October 2011

In this work the reason of the cracks found in SAE 1018 carbon steel pipelines used for potable water supply is determined. In order to accomplish it, some techniques of microanalysis using X-rays (SEM: Scanning Electron Microscopy) over some samples of faulty and normal pipes as well as the Digital Image Processing (DIP) of its microphotographs captured by means of SEM, were used. The obtained results prove that the low quality of the raw material and the steel manufacturing process were the reason of the cracks observed in the SAE 1018 carbon steel pipelines.
Water and Inhibitor Transport in Paint Films
Authors: Zhang Weilong , Jaworowski Mark R.
Published: October 2011

ASTM permeability cup method and capacitance technique were used to study water (vapor) transport processes in inhibitor-free, and praseodymium (Pr)-containing aerospace primer films. The water transport rate from the cup method was found much higher in inhibitor-free epoxy film than Pr-containing aerospace primer films when fully cured. The change in film capacitance, determined by electrochemical impedance spectroscopy (EIS), was quantitatively correlated with the total amount of in-plane water transported in primer films. The water diffusion coefficients derived from the permeability cup and capacitance data were in an order of magnitude of 10-8 ~ 10-7 -cm2/s, while the diffusion coefficient of inhibitor ion (Pr+3), calculated from the side-by-side diffusion cell measurements, was in an order of magnitude of 10-10 cm2/s, significantly lower than water transport within primer films. The effects of inhibitor ion (Pr+3) concentration, solution pH on inhibitor transport process were also studied. It was found that both Pr and Ca-containing pigments were dissolved (leached) more significantly in strong acidic (pH ~2) than in weak acidic (pH ~ 5.5) environments.
(Invited) Zinc Surface Morphological Variations and Ionic Mass Transfer Rates in Alkaline Solution
Authors: Arise I. , Homma Takayuki , McLarnon F. R. , Fukunaka Yasuhiro
Published: October 2011

The present simplified electrochemical model of a horizontal upward-facing Zn anode combined with a Ni(OH)2/NiOOH cathode thus reasonably simulates the time-dependent coupling phenomena between the electrode surface morphological variations and the ionic mass transfer rate inside the model-pore mesoporous microstructure that extends across the width of a Zn battery cell.
Effect of Surface Modification of HM-n-TiO2 and CM-n-TiO2 by Electrocatalytic Metal Islets on Photoelectrochemical Splitting of Water
Authors: Frites Mourad , Khan Shahed U.
Published: October 2011

In this study different metal (Ni, Pt, Co and Ru) islets were electrodeposited on the surface of hydrogen modified titanium oxide (HM-n-TiO2) and carbon modified titanium oxide (CM-n-TiO2) photoelectrodes. The effect of surface modification of these photoelectrodes on oxygen evolution reaction during photoelectrochemical splitting of water was studied in a basic electrolyte under solar simulated light illumination. The photo-electrocatalytic activity and surface morphology of these metal islet decorated HM-n-TiO2 and CM-n-TiO2 electrodes were characterized using potentiodynamic and scanning electron microscopic (SEM) measurements. Nickel metal islets showed enhanced photo-electrocatalytic effect on oxygen evolution reaction (OER) during water splitting on HM-n-TiO2 whereas ruthenium metal islets on carbon modified (CM)-n-TiO2 electrodes exhibited increased photo-electrocatalytic activity towards OER.
Preparation of DSSC Nanotitania Thin Film Photoanodes by Electrophoretic Deposition in an Aqueous Suspension
Authors: Parsi Benehkohal Nima , Demopoulos George P.
Published: October 2011

Aqueous-based electrophoretic deposition (EPD) of titania nanoparticles (Evonic's P25) for the fabrication of mesoporous electrodes for dye-sensitized solar cells is investigated. Poor film adhesion and cracking arising from the electrolysis of water and interstitial water evaporation during drying were largely overcome via the judicious selection of EPD operating current but more importantly the addition of zinc nitrate in a 5 vol.% isopropanol-water suspension. As a result, a composite nanostructured TiO2-ZnO film was fabricated. Photoelectrochemical characterization indicates that formation of ZnO causes suppression of electron leakage from substrate to electrolyte and additionally prolongs photoelectron lifetime. A 5.01% conversion efficiency was obtained under 1 sun illumination (100 mW•cm−2) of a 13 µm thick single transparent layer. Fabrication of multilayer film by repeated cycles of EPD found to increase the conversion efficiency to 5.52% for the same total film thickness due to better overall film construction.
Microstructural and Optical Properties of Electrodeposited CdSnSe Thin Films
Authors: Mahalingam Thaiyan , Dhanasekaran Vickraman , Chu Jinn Peter , Kim Taekyu , Kim Yong Deak
Published: October 2011

The deposition potentials effects on the structural, morphological and optical properties of the CdSnSe films are studied. X-ray diffraction (XRD) patterns revealed a mixer of cubic and orthogonal phases for the grown CdSnSe thin films. The refractive index, extinction coefficient, dielectric constant and thereby the optical band gap of the films are calculated from transmittance spectral data recorded in the range 400-1200 nm by UV-Vis-NIR Spectrometer. The optical band gap energy of CdSnSe thin films is found to be in the range of 1.23-1.25 eV. Morphological studies revealed nano-rod shaped grains occupied over the entire surface of the film with average grain size of 150 nm. The influence of deposition potential on the microstructural properties of CdSnSe is plausibly explained.
Characterization of Single Bath Electrodeposited Cu2ZnSnSe4 Thin Films
Authors: Hu Shao-Yu , Lee Wen-Hsi , Su Yin-Hsien
Published: October 2011

Cu2ZnSnSe4 (CZTSe), a chalcopyrite-like semiconductor, which has high optical absorption and p-type electrical conductivity, provide a low-cost mass production solution with abundant and cheap materials, Zn and Sn. In previous researches, CZTSe was produced from co-evaporated or sputtered precursors. In this study, electrodeposition, a non-vacuum and low-cost process, was used to grow CZTSe films. The films were grown by one-step cathodic electrodeposition in single electrolyte bath, which contained CuCl2, ZnCl2, SnCl2, and were deposited onto Mo coated glass substrates at room temperature. The CZTSe thin films have been obtained after annealing the as-deposited thin CZT films with powder of Se. The reduction potentials of each element in the electrolyte were determined by linear scan voltammetry (LSV) method. The film properties were characterized by field-emission scanning electron microscopy (FE-SEM) amd EDS.
The Role of Surface Carbon in Oxidation of Ethylene and Toluene on Platinum-Ceria Anodes for Solid Oxide Fuel Cells
Authors: Medvedev Valentin , Adler Stu , Stuve Eric M.
Published: October 2011

Surface reactions of ethylene and toluene on a Pt-modified, samarium-doped ceria (Pt/CSO) anode were examined as a function of hydrocarbon to oxygen ratio and cycling of oxy- gen ion current through the electrolyte. Reaction conditions were temperatures of 540 °C (C2H4) and 730 °C (C7H8), hydro- carbon partial pressures of 0.001-0.04 Torr, and oxygen partial pressures of 0.1 Torr (anode) and 5 Torr (cathode). A gen- eral result is that reactions of both ethylene and toluene are strongly sensitive to surface carbon. A step change in oxygen ion current results in electrochemical enhancements of up to 80 and catalytic enhancements as high as 3. Cycling of oxygen ion currents leads to enhanced catalytic activity that remained for 1 hour or more after cycling was terminated. Enhance- ment was sensitive to the ratio of hydrocarbon to oxygen and attributed to a combination of carbon removal and redox ki- netics in the ceria anode.
Topmost Atomistic Li Structures and Native Point Defects in the Li (001) Surface
Authors: Park Min Sik , Doo Seok-Gwang
Published: October 2011

To elucidate the atomic scale mechanism of the dendrite growth in the Li metal anode under the electrochemical condition, the formations of native point defects and topmost atomistic Li structures in the surface of Li metal were studied by using the first-principles calculation. In the (001) surface, vacancies are dominant and mainly confined in the surface, and moreover, the vacancy clustering is not favorable. Li interstitials near the surface always migrate to the top of the surface. Such native point defects without clustering effects near the surface, therefore, cannot be the initial step of dendrite growth. On the surface, the formations of atomistic Li structures with low coordination numbers, such as bridge-, tetrahedron-, pyramid-types and c-directional chain structures, were studied. It is found that the local electric potentials deviation of ~1V can initiate filamentary type dendrite growths in the electrochemical charging process of rechargeable batteries.
Effect of Li2CO3 Deposition on Electrochemical Cycling-Induced Graphite Damage
Authors: Bhattacharya Sandeep , Riahi A. Reza , Alpas Ahmet
Published: October 2011

Graphite electrode surfaces were treated with aqueous solutions containing 0.50, 0.75, and 1.00 wt.% Li2CO3 (~1-2 microns). Li2CO3 deposits had positive effect on reducing graphite surface damage during cyclic voltammetry (CV) tests. Tests conducted at a scan rate of 2 mV s-1 revealed that only 14% of graphite surface exhibited damage features (cavities) when the surface had a high concentration (1.00 wt.%) of pre-deposited Li2CO3, compared to 20% damage on untreated graphite. A composite layer consisting of the solid electrolyte components and the pre-deposited Li2CO3 was formed during electrochemical cycling which controlled solvent and Li+ diffusion. While the extent of damage was decreased, a reduction in Li+ diffusion at high Li2CO3 concentrations also occurred. With 0.50 wt.% Li2CO3 deposited on graphite surface, a high current density was observed within the electrodes indicating enhanced diffusion of Li+ compared to untreated electrodes. However, this low concentration was unable to reduce graphite damage.
Phase Behavior and Solvation of Lithium Triflate γ-Butyrlactone
Authors: Foley Matthew P. , Seo Daniel M. , Boyle Paul D. , Henderson Wesley A. , De Long H. C. , Trulove Paul C.
Published: October 2011

Data describing the concentration and temperature dependent solvation and phase behavior of lithium trifluoromethanesulfonate (LiTf) in γ-butyrolactone (GBL) is presented. Differential scanning calorimetry (DSC), Raman spectroscopy and X-ray diffraction measurements are employed to elucidate the electrolyte interactions. DSC analysis show the presence of a crystallinity gap at concentrations between 2.56:1 and 5.00:1 GBL:LiTf (mole:mole) and a high melting solvate in more concentrated samples. Raman spectroscopic analysis indicates that the coordination of ions in the high melting solvate undergoes temperature dependent transitions. X-ray diffraction analysis showed that lithium triflate forms a 1:1 aggregated solvate having 6 ion pair coordinated by 6 solvent molecules. Taken together, data suggest ion transport in electrolytes is influenced by solvation.
Scanning Electrochemical Microscopy for Investigation of Multicomponent Bioelectrocatalytic Films
Authors: Dobrzeniecka Anna , Zeradjanin Aleksandar , Masa Justus , Stroka Jadwiga , Goral Monika , Schuhmann Wolfgang , Kulesza Pawel J.
Published: October 2011

Scanning electrochemical microscopy in the redox competition mode (RC-SECM) is proposed as an useful technique for local investigation of the electrocatalytic activity of different catalysts towards the oxygen reduction reaction (ORR) with simultaneous detection of the produced undesirable intermediate hydrogen peroxide. We have used cobalt porphyrin dispersed in a multiwalled carbon nanotubes (MWCNTs) matrix as a model electrocatalyst for the predominant two-electron reduction of oxygen to hydrogen peroxide. Furthermore, Prussian Blue or horseradish peroxidase were used as catalysts for the further reduction of hydrogen peroxide to water. The properties of each component of the film were examined along with their potential interactions with the other components. As a result an efficient electrocatalyst for oxygen reduction at physiological pH could be obtained.
Development of Conductive Mesoporous Structures from Chitosan
Authors: Sjoholm Kyle H. , Minteer Shelley D.
Published: October 2011

Chitosan, a biopolymer extracted from crab shells, was combined with silica spheres and cobalt chloride in concentrations ranging from 0 to 10 mM and cast onto Toray paper electrodes over a 1 cm2 area. The electrodes were then pyrollyzed via ohmic heating by passing current through the electrode for 5 minutes under an argon environment. The silica spheres were then removed to leave a porous scaffold, by soaking the electrodes in 30% KOH. Analysis of these mesoporous structures as possible cathode materials was done by microscopy and voltammetry.
Novel Hydrotalcite Composites Membranes for Alkaline Fuel Cells
Authors: Vieira Ribeiro Paulo Maria Joao , Tavares Ana
Published: October 2011

In this work, hydrotalcite (Mg6Al2(CO3)(OH)16•4H2O, HT-CO32-) and an hydrotalcite-like (HT-CO32--OH-) compounds were characterized and used in the fabrication of composite membranes for alkaline fuel cells. HT-CO32--OH- was prepared from commercial hydrotalcite through anion exchange. The materials were characterized by X-Ray Diffraction, Infrared Spectroscopy, CHNS Elemental Analysis, N2 sorption and Dynamic Vapor Sorption. Composite membranes were prepared by casting method using a styrene/ethylene/butylene copolymer as binder. Water up-take and OH- ion conductivity measurements were performed on two independent set of composite membranes. The partial exchange of carbonate by hydroxyl anions increases the water content in the clay gallery. Higher values of water up-take and ion conductivity were measured for the composite membranes containing the HT-CO32--OH- form.
Formation of Inverted-Pyramid Structure by Modifing Laser Processing Parameters and Acid Etching Time
Authors: Lin Je-Wei , Liu En-Ting , Wu Chien-Hung , Hsieh Ing-Jar , Chao Tien-Sheng
Published: October 2011

This paper is to investigate the possibility to fabricate the inverted-pyramid structure on silicon wafer base solar cell by using laser scribing technology. The UV spectrometer and SEM had also been used to observe the reflectance and microstructure of the wafer surface. In this experiment, a Q-switched Nd:YAG laser operating at wavelength of 1064nm is used to scribe on the p-type wafer surface to produce inverted-pyramid structure. In order to remove the laser damage, we used acid etching and Alkaline etching solutions to smooth the damage region and inverted pyramid structure formed, simultaneously.
Modification of Glassy Carbon Electrode with Pyridine
Authors: Agullo Julia , Morin Mario , Bélanger Daniel
Published: October 2011

Glassy carbon electrodes were modified with pyridine by electrografting of the corresponding in situ generated diazonium cations. The diazonium cations formation from the 3-aminopyridine in acid media at room temperature was confirmed by UV spectroscopy. The presence of immobilized pyridine at the electrode surface was demonstrated by XPS measurements. The influence of the diazotization reaction conditions on the grafting process was investigated by determination of the blocking properties of the grafted layer by electrochemical impedance spectroscopy in presence of Fe(CN)63-/4- as redox probes. The best blocking properties of the grafted layer are obtained for a diazotization reaction of one min and 1 equivalent of sodium nitrite.
Planar Microfluxgates Using Electroplated NiFe Cores Aimed for the Monitoring of Cardiac Valves Prosthesis
Authors: Heimfarth Tobias , De Oliveira Amanda L. , Mulato Marcelo
Published: October 2011

Fluxgates are high sensitivity magnetometers. This work presents our efforts to produce microfluxgates using electrodeposited NiFe cores. Large form-factor parameters were adopted, but with all the miniaturization benefits like low price, low power consumption, usability in embedded systems, etc. We also focus on a specific application that is the monitoring of cardiac valves prosthesis.
Portable Electrochemical Sensor for Detection of Tricresyl-Phosphate
Authors: Yang Xiaoyun , Zitova Alice , Overfelt Ruel , Simonian Aleksandr
Published: October 2011

Tricresyl-phosphate, a toxic organophosphate, is added widely in jet engine oil, acting as a flame retardant and a plasticizer. On an aircraft where the air is circulated, TCP may enter the cabin and be a hazard to the health of passengers, if oil leakage occurs. Current analytical techniques to detect TCP such as GC-MS, HPLC, and TLC have disadvantages of complex and expensive instrument, trained operators needed. A new portable and easy operating analytical device is needed. In this work, we are describing a hand-held analytical device, for real-time detection of TCP in air. Chemical degradation was carried out in order to get electrochemically active chemical, the cresol. The analytical device is observed to detect cresol in high sensitivity, wide linear range, and high selectivity. The detection limit of TCP is 4 ppb in an air sample.
Electrochemical Synthesis of Green Rust and Its Modified Form Developed for Wastewater Treatment in Remote Areas
Authors: Gomes Jewel A. , Haider Md. Iftikher , Irwin George , Bernazzani Paul , McWhinney Hylton , Grady Tony , Cocke David
Published: October 2011

Green rust (GR) is an important intermediate in oxidative transformation of ferrous phase. It contains a mixture of ferrous and ferric hydroxides that belong to a family of layered double hydroxides. Anionic and cationic species can replace their corresponding parts in the layered structure and different species can also accumulate in between the layers. GR can play an important role in wastewater remediation, such as reduction and removal of toxic compounds. Unfortunately, GR is not stable in the oxidative atmosphere and thus cannot be efficiently used for wastewater treatment in remote areas. In this work, we prepared GR electrochemically and developed its stability by physical methods using acrylic resin, polyethylene sheet, and glycerin, and by chemical/electrochemical methods using aluminum and magnesium as dopants in its pyroaurite-type structure. Its efficiencies for wastewater treatment containing arsenic were also studied with both original and modified forms. Furthermore, these solids before and after treatment were characterized using Mössbauer, x-ray diffraction, scanning electron microscopy/energy dispersive x-ray analysis, x-ray photoelectron, and Fourier transform infrared spectroscopic techniques.
Gas-Phase Hybrid Sulfur Electrolyzer Stack
Authors: Stone Simon , McPheeters Clark , Staser John , Jayakumar Jai V. , Weidner John W.
Published: October 2011

Membrane-electrode assemblies (MEAs) were developed for the gas-phase Hybrid Sulfur electrolyzer, and the addition of a low-permeability anode prelayer (LPAP) significantly reduced the observed SO2 crossover rate under nominal 25-cm² electrolyzer operating conditions vs. untreated controls utilizing the same base membrane. An 80-cm² bipolar electrolyzer stack having common fluid manifolds was designed and fabricated. Preliminary stack testing indicates similar performance and efficiency to the small, single-cell electrolyzer, but that some corrosion was observed in the anolyte paths of the graphite composite bipolar plates. Follow-up experiments are discussed.
Nano-Link Based Ultra Low Power Micro Electronic Hotplates for Sensors and Actuators
Authors: Groenland Alfons W. , Wolters Rob A. , Kovalgin Alexey Y. , Schmitz Jurriaan
Published: October 2011

Ultra low-power electrical hotplates are presented based on Ohmic heating of a small conductive volume (link) sandwiched between two electrodes. The link is fabricated by etching a hole in the dielectric layer between the electrodes and subsequently filling it with TiN deposited via ALD. This results in a hollow vertical cylinder with the walls covered by a conductive (TiN) film with a thickness of 7-15 nm. Devices with micro- (D_link ~2-6 μm) and nano- (D_link ~100 nm) links were fabricated on silicon substrates and electrically characterized (I-V curves). The link temperature as a function of the applied power was estimated. Devices with a micro link reached a link temperature of ~250 ºC with a power consumption of 2.7 mW. Devices with a nanolink exhibited a link temperature of ~280 ºC by consuming only 5.5 μW.
The Effects of Fabrication Process on the Performance of a CMOS Based Capacitive Humidity Sensor
Authors: Saeidi Nooshin , Blake Alan , Colinge Cindy , Burke M. , Quinn A. J. , Demosthenous A. , Donaldson N.
Published: October 2011

Measuring the change in electrical properties of materials in the presence of moisture is a widely used method for humidity measurement. During the fabrication of a thin film humidity sensor, different layers of the device, as well as its moisture sensing film, undergo a series of commonly used manufacturing steps. Plasma treatment is one of these steps, primarily used for dry etching. However, exposing a moisture sensing film to plasma can modify physical and chemical properties of the film and affect sensor performance. We have examined the response of two humidity sensors fabricated using polyimide sensing film, one of them received plasma treatment during fabrication and the other did not. Despite the fact that the sensors were of similar design they exhibited different responses. Further investigations were conducted by examining the effects of plasma treatment on blanket polyimide films and the results are presented in this paper.
Optoelectronic Device with Dual Quantum Wells
Authors: Guo Der-Feng
Published: October 2011

An optoelectronic switch with both n- and p-type delta-doped (d-doped) quantum wells was investigated. The d-doped structures formed potential wells for the carrier accumulation and potential barriers for the carrier injection. Being possessed of d-doped sheets with different doping levels, the potential barriers were sequentially collapsed to produce a double negative-differential-resistance (NDR) phenomenon in the current-voltage (I-V) characteristics of the device due to the carrier accumulation in the potential wells. The device also showed an optical function related to the barrier heights controllable by incident light.
Fabrication and Modeling of a Novel SAW-Like Transducer Device Based on Branched Carbon Nanotubes
Authors: Darbari Sara , Abdi Yaser , Ebrahimi Aida , Doostani Narges , Mohajerzadeh Shamsoddin
Published: October 2011

A novel interdigital sensor and actuator device based on branched carbon nanotubes (B-CNTs) on silicon-based membranes with a high capacitance value is reported. The presence of B-CNTs leads to a high overlap between interdigital (ID) fingers and the resulted capacitance value. The formation of a sensor/actuator system is based on ID patterns on silicon-based membranes, and the branched carbon nano-structures have been grown selectively on the electrodes. The actuation behavior of the device has been investigated in a SAW-like sensor and actuator device which has been placed on a flexible membrane.
Elastostriction and Electrostriction in Piezoelectric Transducers Comprising Bulk PZT Ceramics
Authors: Wischke Martin , Dieterich Nils , Haller Daniel , Kroener Michael , Woias Peter
Published: October 2011

Piezoelectric materials are a key component in applications such as sensing, actuation and energy harvesting as they couple energy between the electrical and the mechanical domain. With increasing loads, the elastostriction and the electrostriction gain impact on the PZT transducer performance. A procedure to determine the nonlinear parameters is introduced and three different PZT ceramics are studied in comparison. The detailed investigation shows that the electrostriction is dominant in actuator applications, while the elastostriction is affecting sensor applications.
RRDE Study of ORR Kinetics on a Pd3Fe/C Electrocatalyst Annealed at Elevated Temperatures
Authors: Ramanathan Mayandi , Ramani Vijay , Prakash Jai
Published: October 2011

Carbon-supported Pd3Fe, annealed to 800°C, was synthesized and evaluated using a rotating ring disk electrode to probe oxygen reduction reaction kinetics and mechanism. Ring currents were measured at various disk potentials and at different rotation rates. Disk-to-ring current ratio was found to be different at lower rotation rates for various disk potentials and these results indicated oxygen reduction and hydrogen peroxide generation on Pd3Fe/C surface followed parallel reaction pathway. Extent of hydrogen peroxide generation on Pd3Fe/C surface was also compared to that of Pt/C and Pd/C. Diffusion corrected tafel plots were constructed for overpotentials up to 200 mV. Calculated tafel slope implies that the chemical step following the first electron transfer step is the rate-determining step.
LiNi0.33+δMn0.33+δCo0.33-2δO2 (0.025 ≤ δ ≤ 0.075) Cathode Materials for Li-Ion Batteries: Local Structure
Authors: Ben-Kamel Karim , Ben-Amor Ghazi , Amdouni Nouredine , Mauger Alain , Groult Henri , Julien Christian M.
Published: October 2011

Structural features of LiNixMnyCozO2 oxides (LNMCOs) have been studied as a function of the synthetic procedure and the composition. Materials were characterized by a set of methods including XRD, SEM, TEM, EDAX, BET, 7Li MAS-NMR and Raman experiments. TEM experiments show that the increase of cobalt content induces a change of particles morphology, form octahedron to spherical like shape with size range 200-350 nm. HRTEM image shows layered structure without dislocations.
Electrochemical Performance of Porous NiO Films as Anode Material for Lithium-Ion Batteries
Authors: Kim Tae Kwon , Chen Chunhui , Dhanabalan Abirami , Wang Chunlei
Published: October 2011

Electrochemical performance of porous NiO films was investigated as anodes for lithium ion batteries. Different porous morphologies of NiO films were fabricated by the electrostatic spray deposition (ESD) technique in different spray distances. Prepared porous NiO films were assembled in a half cell using lithium metal as a counter electrode and tested by cyclic voltammetry and galvanostatic charge/discharge. The test results showed that ESD derived porous NiO films exhibited highly reversible capacities and good cycle performance. The superior electrochemical performance might be attributed to their porous structures, which provide large electrode/electrolyte contact area. The porous structured NiO film electrodes could be promising anodes for use in high-energy density lithium ion batteries.
Electrochemical Investigation of Lithium Intercalation in MOCVD Derived Nanostructured Anatase/Rutile TiO2
Authors: Graczyk-Zając Magdalena , Lazar Ana Maria , Chaumont Denis , Sacilotti Marco , Riedel Ralf
Published: October 2011

In this paper we report on the lithium reversible storage in titanium dioxide (TiO2) prepared by metal-organic chemical vapor deposition (MOCVD). Electrochemical properties in terms of lithium reversible insertion depend on the deposited microstructure. For thick films deposited on silicon wafer electrochemical activity of the anatase type of TiO2 is registered in the potential range 1.8-2.1 V vs. Li. For thinner films the intercalation reaction takes place in two potential ranges: 1.8-2.1 V vs. Li and below 1.4 V vs. Li. The second electroactivity range is attributed to lithium insertion into rutile. We found that the decrease of the lower potential limit (0.5 V instead of commonly used 1 V) leads to an increase of the recovered capacity. In consequence the investigated MOCVD TiO2 demonstrates high reversible capacity of about 300 mAhg-1.
Synthesis and Characterization of Layered Vanadium Oxide Nanotubes for Rechargeable Lithium Batteries
Authors: McNulty David , Buckley D. Noel , O'Dwyer C.
Published: October 2011

A range of vanadium oxide nanotubes consisting of scrolled layers of primary amine functionalized xerogel have been produced by a hydrothermal treatment of a xerogel/amine mixture. The nanotubes consist of a hollow core flanked by parallel layers of scrolled vanadium oxide layers. The interlayer spacing is varied on the sub-nm scale by intercalated amines templates of various molecular lengths. High resolution transmission electron microscopy and X-ray diffraction were used to characterize the resulting nanotubes. When the molar ratio of xerogel:amine is 1:2, a maximum yield of nanotubes is produced and the interlayer spacing can be controlled. For a molar ratio of xerogel:amine of 2:1, the product contains a low yield of nanotubes and the corresponding interlayer spacing is independent of the length of the amine template. A comparison of measured interlayer distances with the actual physical length of the primary amine chains shows that interdigitation of the amines occurs.
Electrochemical Promotion of the Water-Gas Shift Reaction on Pt/YSZ
Authors: Souentie Stamatios , Lizarraga Leonardo , Valverde Jose-Luis , Vernoux Philippe
Published: October 2011

The effect of the electrochemical promotion of catalysis was investigated on the water-gas shift reaction over porous Pt catalyst electrodes interfaced with YSZ. The study was conducted in a fuel cell type electrochemical reactor operated at temperatures from 300°C to 400°C, under ratio values from 2.85 to 31. Positive potential application (+2.5 V), i.e. O2- species supply to the catalyst surface, caused a small decrease in the reaction rate, while negative potential application (-1.5 V) resulted in a pronounced rate increase, up to 200%, with apparent Faradaic efficiency values up to 110. The obtained increase of the rate upon negative polarization was attributed to the partial reduction of the YSZ surface and the stabilization of the adsorbed OH species at the vicinity of the Pt particles, but mainly to the weakening of the Pt-CO bond strength, upon Oδ- ion pumping from the catalyst surface, which results in Pt work function decrease.
Analysis of Aged Polymer Electrolyte Fuel Cell (PEFC) Components by Non Traditional Methods
Authors: Hiesgen Renate , Wehl Ines , Helmly Stefan , Friedrich K. Andreas , Schulze Mathias , Haug Andrea , Yuan Xiao-Zi , Wang Haijang
Published: October 2011

The ageing of microporous layers (MPL) of fuel cell gas diffusion layers has been quantitavely analyzed using a special atomic force microscopy technique, namely the so-called HarmoniX technique. From the change of mean adhesion force under dry and wet conditions an increased loss of polytetrafluoroethylene (PTFE) at the cathode was found. With ionic current measurement in tapping- and contact mode by AFM, activated Nafion was investigated before fuel cell operation with high resolution and individual ionic channels were imaged in one cluster. These measurements were compared to the current distribution of membranes after 1600 h of fuel cell operation under OCV. Distinct current levels were found which demonstrate the existence of an interpenetrating ionic network with different branches not directly connected at the surface. SEM/EDX investigations of the specially designed fuel cells indicate an important role of platinum in degradation of membranes.
Evaluation Model of Emitter Roughness Impact Responsible for Diamond Based Cold Emitter IV Characteristics Aberration
Authors: Kartashov Dmitry , Krasnikov Andrey , Matyushkin Igor , Orlov Sergey , Yanovich Sergey , Zaytsev Nikolay
Published: October 2011

Nanostructured diamond films deposited in microwave (MW) plasma enhanced chemical vapor deposition (CVD) process were evaluated as a potential material for cold emitters in autoemission microdiode and microtriode. Graphite-diamond composite film was chosen for further evaluation after initial feasibility study with unpatterned films. Autoemission currents were detected even at normal conditions without vacuum. Measured IV microdiode and microtriode characteristics showed certain aberration from linearity when plotted with Fowler-Northeim coordinates. A model based on consideration of gradual activation of emitting centers is proposed. Emitter surface roughness plays essential role and it is believed to be have the most sufficient impact on Fowler-Northeim IV curves linearity distortion.
(Invited) Synthesis of Unsymmetrically Meso-Substituted Porphyrins
Authors: Plunkett Shane , Senge Mathias O.
Published: October 2011

The continued development of new medicinal and industrial uses of highly substituted porphyrins, especially in the fields of photodynamic therapy, nonlinear optics and electron transfer systems, has led to a resurgent interest in developing new methodologies for porphyrin synthesis. The porphyrins in question, so called ABCD-type porphyrins, have mixed meso substituents, making them highly unsymmetric and thus not synthetically available through classical condensation routes. Synthetic strategies towards the formation of meso substituted porphyrins have been extensively researched over the last decade with various routes now available. While methods using mixed condensations are still preferred for systems with high symmetry, the number of possible products makes it an unviable route for the synthesis of the more useful non symmetric porphyrins. To this end novel syntheses of ABCD-type porphyrins have been developed using synthetic manipulations of pre-formed porphyrin scaffolds with various organolithium reagents and Pd-catalyzed metal couplings.