bluuebunny/crossref_metadata_2025_split huggingface dataset:
Micromechanical Simulations on Hygro-Mechanical Properties of Bio-fiber Plastic Composites
Authors: Xue Yibin , Wang Kunpeng 
Published: April 2011

AbstractThe hygro-mechanical properties of bio-fiber composites comprise two aspects: the coupling between moisture diffusion and mechanical deformations and the coupling of moisture contents and the constitutive behaviors. Bio-fiber is hydrophilic, which absorbs water promptly when environmental moisture content increases; as the moisture content in the fiber increases, its mechanical properties decrease. This paper presents a series of micromechanical simulations to predict the hygro-mechanical behaviors of woodfiber-reinforced plastic composites considering the effects of fiber arrangements on the stress-strain relations and moisture-expansions on three progressively constructed constitutive configurations: 1) the fiber is elastic orthotropic and expandable under moisture variations; the plastic matrix is elastic isotropic and insensitive to environmental moisture variations, and the interface between fiber and matrix is perfectly bounded; 2) the plastic matrix is hyperelastic and expresses a certain degree of damage as deformation progresses; and 3) the interface has a pseudo adhesive layer that obeys Smith and Ferrante's universal binding law implemented as a cohesive zone model in the micromechanical simulation. In configuration II, micromechanical simulations demonstrate significant reductions in the nominal elastic modulus of composites when a nonlinear elastic model for the polymer matrix is assumed. The prediction for stress-strain relationship is found to be comparable to the experimental measurements. A cohesive model in configuration III is introduced to evaluate the possible moisture degradation to the fiber-matrix interface, which results in a reduction in elastic modulus and failure strength of the composite s, as observed in experiments. The cohesive zone model parameters as a function of moisture content in the composites requires more attention in model correlation and guarantee more direct experimental observations.
Study of the Crystal Structure and Phase Transition of Li2NH System
Authors: Yang Jinbo , Lamsal J. , Cai Q , Yelon W B , James W J 
Published: April 2011

AbstractNeutron diffraction at different temperatures has been used to study the crystal structure and possible phase transitions of Li2NH. It was found that the crystal structure and phase transition are related to the synthesis methods. A phase transition from the low temperature phase 16-350 K to the high temperature phase above 370 K has been confirmed for the ケ-Li2NH sample prepared by reacting Li3N with LiNH2. The Li2NH (β-Li2NH) prepared by decomposition of LiNH2 shows only the high temperature phase. The reaction of LiH+LiNH2 at 300°C for 12 h under vacuum produces some Li2NH (γ-Li2NH) with partially unreacted LiNH2 and LiH as impurities. There is no phase transition in the temperature range from 16 K to 400 K for the - and β-Li2NH phases.ケ-Li2NH exhibits a higher reversible hydrogen storage capacity and faster kinetics. The structural differences among the lithium imides may lead to different reaction mechanisms for hydrogen absorption/desorption in the Li-N-H system.
Oxide ion conduction of yttria-stabilized zirconia films deposited by atomic layer deposition
Authors: Chao Cheng-Chieh , Huang Hong , Park Joon Seok , Prinz Fritz B. 
Published: April 2011

AbstractYttria-stabilized zirconia (YSZ) is one of the most common electrolytes in high temperature solid oxide fuel cell (SOFCs). We utilize atomic layer deposition (ALD) to fabricate the electrolyte of SOFC, which may potentially improve several fundamental characteristics of SOFC. Recently, our group demonstrated that ultra-thin ALD YSZ SOFSs can deliver high power density at low temperatures [1]. These SOFCs demonstrated not only reduction of Ohmic loss, but also enhancement of surface kinetics.The focus of this work is to investigate the surface and bulk conduction characteristics of YSZ films produced by ALD. In plane conductivity was measured as a function of film thickness and temperature dependence. YSZ thin films were deposited on standard 4 ” quartz substrates with thicknesses ranging from 8 nanometers to 55 nanometers. Micro-electrodes were patterned on top of the ALD YSZ layer by standard photolithography process. The impedances of the YSZ thin films with different thicknesses were measured. We have observed higher conductivities for thinner films which were attributed to higher oxide ion conductivity in the vicinity of the surface, and similar phenomenon was observed with YSZ films produced by electron beam evaporation [2].
Hydrogenation Of The Titanium Aluminides
Authors: Kazantseva Nataiya , Mushnikov Nikolai V , Popov Alexandr G , Sasonova Valentina A , Teren'ev Pavel B 
Published: April 2011

AbstractThe hydrogen absorption properties of the Ti-Al-Nb system intermetallics subjected by ball milling were studied. It was found that the hydrogenation of the titanium aluminides during ball milling in hydrogen atmosphere could occur at room temperature without any special requirements to the quality of hydrogen. The crystal structure of the hydrides and phase transformations were also studied.
Mechanism of Hydrogen Storage on Reduced Carbon Single-Walled Nanotubes
Authors: Curtis Calvin J , Gennett Thomas , Engtrakul Chaiwat , O'Neill Kevin , Ellis Jamie E. , Heben Michael J. 
Published: April 2011

AbstractCarbon single-walled nanotubes (SWNTs) have been studied extensively as hydrogen storage materials. Herein, a novel hydrogen sorbtion behavior was observed for alkali metal reduced SWNTs and the mechanism of hydrogen binding in these materials has now been elucidated. SWNTs prepared by laser vaporization and purified by oxidation were reduced with Na in combination with naphthalene in tetrahydrofuran (THF) solution. The product, initially formulated as (Na+)xSWNTx-, was dark colored and insoluble in all common solvents examined. Temperature programmed desorption studies showed that hydrogen amounting to 3.5-4.2% w/w was released between 200 and 500°C from the Na-reduced material. This is consistent with hydrogenation of the reduced nanotubes to form C-H bonds with a C2H empirical formula. It appears that SWNT radical anions produced by reaction with sodium deprotonate THF to form hydrogenated nanotubes and the THF cleavage products ethylene and sodium enolate, as confirmed by isotope labeling. A structure consisting of pairs of lines of C-H units that spiral about the long tube axis with a coverage of 50% of the tube carbons is proposed.
RECENT PROGRESS IN SECOND-GENERATION HTS WIRE TECHNOLOGY AT SUPERPOWER
Authors: Chen Yimin , Xiong Xuming , Xie Yiyuan , Qiao Yunfei , Zhang Xun , Rar Andrei , Martchevskii Maxim , Schmidt Robert , Lenseth Kenneth , Herrin John , Hazelton Drew , Selvamanickam Venkat 
Published: April 2011

AbstractWe report recent progress in 2G-HTS wire technology at Superpower Inc. The throughputs of 4mm-wide tape have reached 750m/h for sputtering AlO3+Y2O3 base layer, 360m/h for IBAD MgO template, 345m/h for sputtering Homo-epi MgO+LMO buffer, 180m/h for MOCVD REBCO. Critical current (Ic) of 813A/cm-width at 77K and self-field has been achieved on 1 meter length of 12mm-wide tape in which the thickness of GdYBCO film is 3.3 microns. Ic in a magnetic field has been significantly improved through composition modification, doping and MOCVD condition optimization. Ic of 185.6A/cm-width at 77K and 1Tesla has been obtained. For Ic on long lengths, 314A/cm-width on 202m, 221A/cm-width on 610m and 170A/cm-width on 935m have been achieved. A coil of 19.1mm diameter we made with our 2G wires generated 26.8T magnetic field in the magnet. A 30m-long cable made with nearly 10,000 meters of Superpower 2G wires showed excellent overall performance and has been installed and energized in the power grid.
Microporous Carbon-halide Nanocomposites Electrodes for Symmetric and Asymmetric Capacitor
Authors: Barpanda Prabeer , Fanchini Giovanni , Amatucci Glenn G 
Published: April 2011

AbstractMicroporous carbon containing little mesoporosity was chemically modified through a vapor phase iodation treatment in an effort to improve the electrochemical performance of activated carbon system commonly utilized in symmetric and asymmetric capacitors. This new carbon system has been studied with respect to their structural, morphological and electrochemical properties and contrasted to the mesoporous carbon based nanocomposites.
Record Conductivity for P-Type Transparent Conductors in Polycrystalline Thin Films of a Sulfide-Fluoride
Authors: Frantz Jesse , Sanghera Jasbinder S. , Qadri Syed B. , Aggarwal Ishwar D. 
Published: April 2011

AbstractBarium copper sulfur fluoride thin films with a face-centered cubic phase in the Fm3m space group were synthesized via RF magnetron sputtering. The results of a detailed optical and electronic characterization of the films are presented. As-deposited, they exhibit degenerate p-type conductivity at room temperature of approximately 260 S/cm – higher than that of any previously reported p-TC. Their conductivity after post-deposition processing increases to as high as 800 S/cm. The films exhibit bandgaps ranging from 1.45-1.75 eV. They are typically deposited with a substrate temperature between room temperature and 100°C, making them suitable for deposition on plastic as well as glass or crystalline substrates. It was found that a silica protective layer reduces degradation in film transparency that is caused by exposure to air.
Nano-scale Investigation of Light Scattering at Randomly Textured Light Trapping Structures for Thin-film Silicon Solar Cells
Authors: Bittkau Karsten , Beckers Thomas , Rockstuhl Carsten , Fahr Stephan , Lederer Falk , Carius Reinhard 
Published: April 2011

AbstractWe report on nano-scale optical effects of amorphous silicon layer conformally deposited on randomly textured zinc oxide layers on glass substrates investigated by near-field scanning microscopy. Such textured layers are used in thin-film photovoltaic devices to enhance light trapping. Experimental results are compared to theoretical data, obtained from large scale finite-difference time-domain simulations. Light localization on the surface of the textured interface and a focusing of light by the structure further away are observed. The measurements are compared with simulations, which provide additional insight into the light intensity distribution inside the solar cell on a nm-scale. It will be shown how this information can be used to optimize light trapping in thin-film solar cells using an amorphous silicon solar cell as an example.
Optical developments for silicon thin film solar cells in the substrate configuration
Authors: Soderstrom Thomas , Haug Franz-Joseph , Niquille Xavier , Cubero Oscar , Perregaux Stéphanie , Ballif Christophe 
Published: April 2011

AbstractIn the nip or substrate configuration thin film silicon solar cells, the choice of front TCO contact is critical because there is a trade off between its transparency which influences the current in the solar cell and its conductivity which influences the series resistance. Here, we investigate the optical behavior of two different TCO front contacts, either a 70 nm thick, nominally flat ITO or a 2 μm thick rough LPCVD ZnO. The back contact consists of LP-CVD ZnO with random texture. First we investigate the influence of the rough and flat front TCOs in μc-Si:H and a-Si:H solar cells. With the back contact geometries used in this work, the antireflection properties of ITO are effective at providing as much light trapping as the rough LP-CVD ZnO. In the second part, we demonstrate that total of 25 to 26 mA/cm2is achievable in nip micromorph tandem cells and show short circuit current up to 11.7 mA/cm2 using an SIO based intermediate reflector.
Shape-Controllable Surface Texturization for Crystalline Silicon Solar Cells
Authors: Im Jong-San , Jeon Jin-Wan , Lim Koeng Su 
Published: April 2011

AbstractThis paper describes a new method to make surface textures for photovoltaic application. Using this method, we can make textures having various shapes. The first step is to make photo-resist (PR) molds using the polymer dispersed liquid crystal (PDLC) film. The second step is to transfer the PR molds to silicon by inductively coupled plasma etching process. The final step is a solar cell fabrication process. The structure of the solar cell is simple Al Grid/c-Si/Al back contact. The solar cells show the increase of the short circuit current (Jsc) comparing to the planar cells. By this texturing method, we can get solar cells having various textures which we want to make.
Microscopic Theory of Coupled Quantum Well Structures in Photovoltaics
Authors: Aeberhard Urs , Morf Rudolf 
Published: April 2011

AbstractWe use our recently developed microscopic approach to a quantum theory of photovoltaic processes in nanostructures [1]to investigate geometry effects in quantum well photovoltaics, focussing on the role of asymmetry and inter-well coupling in double quantum well (DQW) systems. For that purpose, the IV and power characteristics for DQW systems with different asymmetry and degree of coupling are calculated numerically in the vicinity of the maximum power point. In order to assess the transport properties of a specific QW structure, we isolate these from the effects of absorption by normalizing to the absorptivity. The results obtained from this procedure reveal the escape regime dominating at room temperature and confirm previous experimental observations.
Loss Mechanisms in Photovoltaic Fluorescent Collectors
Authors: Proenneke Liv , Rau Uwe 
Published: April 2011

AbstractMonte-Carlo simulations calculate the photon collection of fluorescent collectors in photovoltaic systems. We focus on two collector geometries: solar cells mounted at the collector sides, and solar cells covering the back of the collector. A mirror covers the bare back sides of both systems. On top lies optionally a photonic structure, which acts as an energy selective filter. Ideal systems in their radiative limits are compared to systems where loss mechanisms in the dye, at the mirror, or the filter are included. The examination of loss mechanisms in photovoltaic systems with fluorescent collectors enables us to estimate quality limitations of the used materials and components.
MeV Si Ions Bombardment Effects on SiO2/SiO2-ZrNiSn Nano-layered Thermoelectric Generator
Authors: Budak S. , Guner S. , Muntele C. , ILA D. 
Published: April 2011

AbstractWe have deposited 50 nano-layers of 710 nm of SiO2/SiO2+ZrNiSn with a periodic structure consisting of alternating layers where each layer is about 14 nm thick. The purpose of this research is to generate nanolayers of nanostructures of ZrNiSn with SiO2 as host and as buffer layer using a combination of co-deposition and MeV ion bombardment taking advantage of the energy deposited in the MeV ions track to nucleate nanostructures. The performance of the thermoelectric materials and devices is shown by a dimensionless figure of merit, ZT = S2σT/ĸ, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature and ĸ is the thermal conductivity. ZT can be increased by increasing S, increasing σ, or decreasing ĸ. The electrical and thermal properties of the layered structures were studied before and after bombardment by 5 MeV Si ions at seven different fluences ranging from 1014 to 1015 ions/cm2 in order to form nanostructures in layers of SiO2 containing few percent of ZrNiSn. Rutherford Backscattering Spectrometry (RBS) was used to monitor elemental analysis of the film.
Chemical Modification on Hierarchically Structured ZnO Films for Energy Conversion Efficiency Enhancement of Dye-Sensitized Solar Cells
Authors: Zhang Qifeng , Jenekhe Samson A , Cao Guozhong 
Published: April 2011

AbstractWe report the synthesis of ZnO aggregates in the presence of lithium salt and the enhancement on the energy conversion efficiency of dye sensitized solar cells when the photoelectrode films consist of as-synthesized ZnO aggregates. The conversion efficiency for ZnO film consisting of aggregates synthesized with lithium involvement is significantly improved up to 5.8%, which is 32% higher than that of 4.4% obtained for pure ZnO film. Such an enhancement can be attributed to the effect of lithium-induced changes on the morphology and crystallinity of aggregates, the optical absorption of films, and the surface chemistry of ZnO, which provides the film with decreased electron trapping and increased refractive index, and enhances the electronic coupling between the dye molecules and ZnO.
Sulfur Nanoparticles Synthesis and Characterization from H2S Gas, Using Novel Biodegradable Iron Chelates in Aqueous Surfactant Systems
Authors: Deshpande Aniruddha Subhash , Khomane Ramdas B. , Vaidya Bhalchandra K. , Joshi Renuka M. , Harle Arti S. , Kulkarni Bhaskar D. 
Published: April 2011

AbstractSulfur nanoparticles were synthesized from hazardous H2S gas by desulfurization based on liquid redox process [1]. The use of novel biodegradable iron chelates, in particular, FeCl3-malic acid chelate system has been extensively studied in various aqueous surfactant systems of Tween 80, SDS, CTAB for catalytic oxidation of H2S gas at ambient conditions of temperature, pressure and neutral pH. The structural features of sulfur nanoparticles have been characterized by XRD, TEM, and DLS measurements. XRD analysis indicates the presence of Metal-sulfur (JCPDS-08247). TEM analysis shows that the morphology of sulfur nanoparticles synthesized in aqueous surfactant system of Tween 80 is nearly uniform in size of 12nm average particle size, in SDS surfactant system shows 15nm average particle size, where as sulfur nanoparticles synthesized in CTAB shows average particle size of 7nm. The DLS result shows the mono-dispersity of the sulfur nanoparticles in the aqueous surfactant systems. The described process serves mainly two objectives; (a) waste utilization for preparation of commercially important nano-sulfur product and (b) reduction in environmental pollution. 1. G. Nagal, Chem. Eng. 104, 125 (1997).
Ambient-temperature Conditioning as a Probe of Double-C Transformation Mechanisms in Pu-2.0 at. % Ga
Authors: Jeffries Jason R , Blobaum Kerri J. M. , Wall Mark A. , Schwartz Adam J. 
Published: April 2011

AbstractThe gallium-stabilized Pu-2.0 at. % Ga alloy undergoes a partial or incomplete low-temperature martensitic transformation from the metastable δ phase to the gallium-containing, monoclinic α′ phase near -100 °C. This transformation has been shown to occur isothermally and it displays anomalous double-C kinetics in a time-temperature-transformation (TTT) diagram, where two nose temperatures anchoring an upper- and lower-C describe minima in the time for the initiation of transformation. The underlying mechanisms responsible for the double-C behavior are currently unresolved, although recent experiments suggest that a conditioning treatment—wherein, following an anneal at 375 °C, the sample is held at a sub-anneal temperature for a period of time—significantly influences the upper-C of the TTT diagram. As such, elucidating the effects of the conditioning treatment upon the δ⟶α′ transformation can provide valuable insights into the fundamental mechanisms governing the double-C kinetics of the transition. Following a high-temperature anneal, a differential scanning calorimeter (DSC) was used to establish an optimal conditioning curve that depicts the amount of α′ formed during the transformation as a function of conditioning temperature for a specified time. With the optimal conditioning curve as a baseline, the DSC was used to explore the circumstances under which the effects of the conditioning treatment were destroyed, resulting in little or no transformation.
Enabling the Double-C Curve in Pu-Ga Alloy Time-Temperature-Transformation Diagrams
Authors: Jeffries Jason R. , Blobaum Kerri J. M. , Wall Mark A. , Schwartz Adam J. 
Published: April 2011

AbstractUnder ambient conditions, a Pu-2.0 at.% Ga alloy is retained in the metastable δ phase. Upon cooling to approximately -120 °C, the face-centered-cubic δ phase partially transforms to the metastable monoclinic α′ phase via a martensitic transformation. The kinetics of the δ⟶α′ transformation are reported to have double-C curve kinetics in a time-temperature-transformation (TTT) diagram, but the mechanisms responsible for this unusual behavior are not understood. Our work focuses on determining the underlying cause of the two noses. Optical microscopy has been used to investigate the role of “conditioning”—an isothermal hold at sub-anneal temperatures—on the δ⟶α′ transformation and to illuminate any disparities in transformation products. Conditioning was found to affect substantially the amount of transformation that occurs at particular points corresponding to both the upper- and lower-C of the TTT diagram.
Comparison of Aromatic Dithiophosphinic and Phosphinic Acid Derivatives for Minor Actinide Extraction
Authors: Harrup Mason K. , Peterman Dean R. , Greenhalgh Mitchell R. , Luther Thomas A. , Klaehn John 
Published: April 2011

AbstractA new extractant for the separation of actinide(III) and lanthanide(III), bis(o-trifluoromethylphenyl)phosphinic acid (O-PA) was synthesized. The synthetic route employed mirrors one that was employed to produce the sulfur containing analog bis(o-trifluoromethylphenyl)dithiophosphinic acid (S-PA). Multinuclear NMR spectroscopy was used for elementary characterization of the new O-PA derivative. This new O-PA extractant was used to perform Am(III)/Eu(III) separations and the results were directly compared to those obtained in identical separation experiments using S-PA, an extractant that is known to exhibit separation factors of ∼100,000 at low pH. The separations data are presented and discussed in terms comparing the nature of the oxygen atom as a donor to that of the sulfur atom in extractants that are otherwise identical.
Preliminary Study of Corrosion Mechanisms of Actinides Alloys: Calibration of FT-IR Spectroscopy
Authors: Magnien Véronique , Cadignan Marx , Faivret Olivier , Rosa Gaelle 
Published: April 2011

AbstractIn situ analyzes of gaseous atmospheres could be performed by FT-IR spectroscopy in order to study the corrosion reactions of actinides. Nevertheless experimental conditions and the nature of studied species have a strong effect on IR absorption laws. Thus a prior calibration of our set-up is required to obtain an accurate estimation of gas concentration. For this purpose, the behavior of several air pure gases has been investigated according to their concentration from IR spectra. Reproducible results revealed subsequent increases of the most significant peak areas with gas pressure and small deviations from Beer Lambert's law. This preliminary work allowed to determine precise absorption laws for each studied pure gas in our in situ experimental conditions. Besides our FT-IR set-up was well suitable to quantitative analysis of gaseous atmosphere during corrosion reactions. Finally the effect of foreign gas will be investigated through more complex air mixtures to obtain a complete calibration network.
A Model for the Study of Molecules Radiochemical Decomposition by Actinides Materials
Authors: Berlu Lilian , Rosa Gaëlle 
Published: April 2011

AbstractThe radiochemical decomposition of molecules in storage environment which could lead to the corrosion of container or the formation of dangerous gas mixtures is a critical problem for radioactive materials. The complexity of the chemical system makes numerical models suitable for the reproduction mechanisms and the prediction of phenomena. In this study, a mathematical model for the dose rate distribution in external medium surrounding an α emitter actinide material has been proposed. The model has been implemented in a Monte Carlo scheme. An evaluation of the dose rate in the surrounding medium as a function of the sample size was shown and a discussion of the expected reactivity was made.