bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thin Film Stoichiometry Determination by High Temperature Microbalance Technique
Authors: Fritze H. , Seh H. , Schneider O. , Tuller H. L. , Borchardt G. 
Published: April 2011

ABSTRACTThe in-situ determination of small mass changes of thin films became feasible with the availability of high temperature stable microbalances. With this technique, changes of the mechanical properties of thin films deposited on piezoelectric resonators are investigated at temperatures above 500 °C by monitoring the resonance behavior of the resonators. The results are valuable for fundamental understanding of the ionic and electronic transport processes in ceramic materials and for applications such as high temperature gas sensors.This work correlates the electrical and the mechanical properties of TiO2-x at different oxygen partial pressures. TiO2-x films are deposited onto high temperature resonators by laser ablation and characterized by the high temperature microbalance technique as well as electrical impedance spectroscopy at 600 °C.The oxygen partial pressure dependent resonance behavior cannot be attributed solely to mass changes of the TiO2-x film. Changes of the film's mechanical stiffness have to be taken into consideration to explain the resonance behavior. The simultaneous electrical impedance measurements indicate a n-type conduction behavior of the TiO2-x films.
Increasing the Operating Temperature of Nafion Membranes with Addition of Nanocrystalline Oxides for Direct Methanol Fuel Cells
Authors: Baglio Vincenzo , Blasi Alessandra Di , Arico' Antonino S. , Antonucci Vincenzo , Antonucci Pier Luigi , Fiory Francesca Serraino , Licoccia Silvia , Traversa Enrico 
Published: April 2011

ABSTRACTComposite Nafion membranes containing various amounts of TiO2 (3%, 5% and 10%) were prepared by using a recast procedure for application in high temperature Direct Methanol Fuel Cells (DMFCs). The electrochemical behaviour was compared to that of a membrane-electrode assembly (MEA) based on a bare recast Nafion membrane. All the MEAs containing the Nafion-titania membranes were able to operate up to 145°C, whereas the assembly equipped with the bare recast Nafion membrane showed the maximum performance at 120°C. A maximum power density of 340 mW cm-2 was achieved at 145°C with the composite membrane in the presence of oxygen feed, whereas the maximum power density with air feed was about 210 mW cm-2.
Polymer Relaxational Dynamics Associated With Ionic Conduction in Confined Geometry
Authors: Zanotti J.-M. , Smith L. J. , Giannelis E. , Levitz P. , Price D. L. , Saboungi M.-L. 
Published: April 2011

ABSTRACTResults of a quasi-elastic incoherent neutron scattering study of the influence of confinement on polyethylene oxide (PEO) and (PEO)8Li+[(CF3SO2)2N]- (or (POE)8LiTFSI) dynamics are presented. The confining media is Vycor, a silica based hydrophilic porous glass. We observe a strong slowing down of the bulk polymer dynamics under presence of Li salt. The confinement also affects dramatically the apparent mean-square displacement of the polymer. As supported by DSC measurements, the PEO melting transition at 335 K is strongly attenuated under confinement, suggesting that confinement modifies the global structure of the system, increasing the fraction of amorphous PEO by respect to crystalline phase. Local relaxational PEO dynamics is successfully described by the DLM (Dejean-Laupretre-Monnerie) model usually used to interpret NMR spin-lattice relaxation time data. The scattering vector dependence of the correlation times deduced from inelastic neutron scattering data is found to obey a power-law dependence. DSC and preliminary ionic conduction measurements are also presented.
Discussion about non-Arrhenius behavior of high Li-ion conductor, (La,Li)TiO3
Authors: Katsumata Tetsuhiro , Inaguma Yoshiyuki , Baba Satoshi , Hiraki Ko-ichi , Takahashi Toshihiro 
Published: April 2011

ABSTRACTWe investigated the dielectric properties of La0.53Na0.41-xLixTiO3 (x<0.26) and 7Li NMR for La0.53Na0.34Li0.17TiO3 (x=0.17). As results, relaxation process were observed at 40 K and 225 K for La0.53Na0.34Li0.17TiO3 (x=0.17). The activation energy of the dielectric relaxation at 40 K is in accordance with the that obtained by NMR measurement. On the other hand, the activation energy of the relaxation at 225 K accords with that of the Li ion conduction in the low temperature region for (La,Li)TiO3. These results indicate that different transport mechanisms intrinsically exist in (La,Li)TiO3 and one of reasons for the non-Arrhenius behavior of (La,Li)TiO3 is that the transport mechanism mainly related to the dc conductivity varies with the temperature.
Space Charge Layers in Polycrystalline Cerium Oxide
Authors: Tschöpe Andreas 
Published: April 2011

ABSTRACTThe effect of space charge layers in polycrystalline cerium oxide was analyzed by comparing experimental results of grain size-dependent electrical conductivity with theoretical models. Modeling included the calculation of space charge segregation of acceptor ions and of the effective electrical conductivity of polycrystalline cerium oxide in both the macroscopic and mesoscopic range of grain sizes. It is shown that an L-3 power law for the electronic conductivity in the nm-regime is characteristic for the equilibrium space charge model and different from the scaling behavior of alternative models. The origin of space charge potential was investigated by numerical calculation of the electrical potential in a two-phase model. It was found, that a positive excess charge at grain boundaries of cerium oxide is caused by an enhanced oxygen deficiency at the grain boundary core. The influence of acceptor ion doping in the dilute limit and of non-equilibrium distribution of acceptor ions on electrical conductivity was also studied.
Microstructure, nanochemistry and transport properties of Y-doped zirconia and Gd-doped ceria
Authors: Petot-Ervas G. , Petot C. , Raulot J. M. , Kusinski J. , Sproule I. , Graham M. 
Published: April 2011

ABSTRACTIn this work we have shown the influence of the microstructure and nanochemistry on the transport properties of Y2O3-(9mol%) stabilized zirconia and Gd2O3 (10 mol%)-doped ceria. Zirconia (YSZ) samples show transport properties (DO, σgb) which increase with the grain size, while they decrease in ceria (GSC). This difference was attributed to the presence of glassy grain boundary precipitates in YSZ. On the other hand, it was shown that kinetic demixing processes during cooling, at the end of sintering, play an important role on the grain boundary properties of these oxides.
Impedance spectroscopy and direct current measurements of YSZ films
Authors: Petrovsky T. , Anderson H. U. , Petrovsky V. 
Published: April 2011

ABSTRACTIn this study the electrical properties of thin films of Ysubstituted zirconia were investigated. The films were prepared using a polymer precursor technique and investigated in the temperature region 250 to 900°C. It was shown, that impedance spectroscopy (IS) and direct current (DC) conductivity measurements results are in good agreement for the films measured in plane for temperatures greater than 400°C. Due to the high resistance resulting from a planar geometry, the DC measurements were found preferable at temperatures <600°C.Since in planar geometry the films represent a high resistance to the measurement circuit, it is important to minimize sources of electrical leakage, so different sample holders and substrates were investigated. A sapphire substrate and sample holder design using separated alumina single bore tubing for each electrode provided the lowest electrical leakage.The experimental results showed that electrical behavior of all of the films produced at low annealing temperatures (less than 400°C) was similar regardless of Y content. These films have relatively low conductivity and an activation energy of about 1.5eV. The influence of different Y content started to appear after annealing above 600°C.The results of the film conductivity measurements were compared with those for the bulk samples of Y stabilized zirconia prepared from 200nm powder by tape casting. These samples were measured by IS in plane and through the tape. It was shown that electrical properties of bulk and thin film material were similar.
New Iron (III) Hydroxyl-Phosphate with Rod-packing Structure as Intercalation Materials
Authors: Song Yanning , Zavalij Peter Y. , Stanley Whittingham M. 
Published: April 2011

ABSTRACTA new iron hydroxyl-phosphate, H2Fe14/3(PO4)4(OH)4 has been synthesized under hydrothermal conditions. In this compound, perpendicular chains formed by the face-sharing FeO6 form rod-packing structure. Only about 60% of the chain sites are occupied by iron atoms; other metals, such as manganese, nickel, zinc, can be incorporated into the chain either by filling in the vacancies and/or replacing some of the iron atoms. Reversible insertion and extraction of lithium into this compound shows it to be an excellent cathode material. At current density of 0.1 mA/cm2, 90 % of the theoretical capacity (176 mAh/g) can be obtained. The utilization was reduced to about 70 % on a ten-fold increase of current density. The electrochemical behavior is attributed to the 3-dimensional rod packing structure, where lithium can move freely even at high current densities inside the 3-dimensional framework without altering the host structure. Two of the protons in the lattice may be exchanged by lithium giving Li2Fe14/3(PO4)4(OH)4. These lithium atoms are not removable in electrochemical cycling and similar electrochemical property was found for these two compounds, suggesting an ion-exchange process for the lithiation.
Preparation and Oxygen Permeability of Gd-Doped Ceria and Spinel-Type Ferrite Composites
Authors: Takamura Hitoshi , Kawai Masashi , Okumura Katsutoshi , Kamegawa Atsunori , Okada Masuo 
Published: April 2011

ABSTRACTThe preparation and oxygen permeability of composites of Ce0.8Gd0.2O2-ö (GDC) and spinel-type ferrites, MFe2O4 (M = Co and Mn) have been investigated. The composites of GDC -x vol% MFe2O4, where x ranged from 5 to 65, were prepared by a citrate-based liquid-mix technique. The composites were found to be almost fully densified by sintering at 1300 °C for 2 h. From TEM observations, the grain size of GDC and spinel-type phases was found to be less than 0.5 μm. In the case of M = Co, GDC - 25 vol% CoFe2O4 with a membrane thickness of 1.0 mm exhibited an oxygen flux density of 0.21 μmol·cm-2·s-1 under the P(O2) difference between He (20 sccm) and air at 1000 °C. Under reducing atmosphere of Ar-5%H2, the oxygen flux density of this composite increased up to 1.3 μmol·cm-2·s-1. Moreover, under Ar-10%CH4 gas flow, GDC - 15 vol% MnFe2O4 with a membrane thickness of 0.24 mm exhibited the oxygen flux density of 2 and 7 μmol·cm- · s- at 800 and 1000 °C, respectively.
Characterization of Potential Catalysts for Carbon Monoxide Removal from Reformate Fuel for PEM Fuel Cells
Authors: Adcock Peter A. , Brosha Eric L. , Garzon Fernando H. , Uribe Francisco A. 
Published: April 2011

ABSTRACTWe are developing a fuel-cell-integrated system for enhancing the effectiveness of an air-bleed for CO-tolerance of hydrogen and reformate PEM fuel cells, with minimal increase in stack cost or specific volume. This is called the reconfigured anode (RCA) system [1]. We report here on properties of several potential catalysts for this system. The materials were characterized by X-ray powder diffraction (XRD), energy dispersive X-ray spectrometry (EDS), and thermal analysis techniques. Surface area was determined using the Brunauer-Emmett-Teller (BET) technique. The XRD results were interpreted using full-profile analysis. In ongoing work, reactivity with CO is being quantified under various conditions, using gas chromatographic (GC) analysis. The results are discussed in terms of effects of the presence of an RCA catalyst on fuel cell performance, using a small air-bleed.
Synthesis of LaSrXMg-Oxide with X=Ga, Fe, or Cr
Authors: Oncel Cinar , Gulgun Mehmet A. 
Published: April 2011

ABSTRACTStrontium and magnesium doped lanthanum gallate (LSGM) is a promising electrolyte material for intermediate temperature range (650–800°C) solid oxide fuel cell (SOFC) applications. Formation of unwanted phases and Ga loss at high temperatures (1100–1500°C) during synthesis and under low oxygen partial pressures during operation are major hurdles that stand in LSGM's way of full utilization. Using a polymeric precursor synthesis method, the feasibility of producing SOFC electrolyte material LSGM is investigated. The method involves complexing each constituent metal ion by the carboxyl and/or hydroxyl group of the citric acid and/or polyvinyl alcohol (PVA) in aqueous solution. The facility of this method compared with the traditional solid state reaction method was shown by synthesis of single phase and pure LSXM (X= Fe, Cr) oxides at reasonable temperatures (800°C). The X-ray diffraction patterns of LSFM and LSCM are also reported here for the first time.
Structure and Electrochemical Behavior of Plasma-Sprayed LSGM Electrolyte Films
Authors: Zhang H. , Ma X. , Dai J. , Hui S. , Roth J. , Xiao T.D. , Reisner D.E. 
Published: April 2011

ABSTRACTAn intermediate temperature solid oxide fuel cell (SOFC) electrolyte film of La0.8Sr 0.2Ga0.8Mg0.2O2.8 (LSGM) was fabricated using a plasma spray process. The microstructure and phase were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical behavior of the thermal sprayed LSGM film was investigated using electrochemical impedance spectroscopy (EIS). The study indicates that thermal spray can deposit a dense LSGM layer. It was found that the rapid cooling in the thermal process led to an amorphous or poor crystalline LSGM deposited layer. This amorphous structure has a significant effect on the performance of the cell. Crystallization of the deposited LSGM layer was observed during annealing between 500–600 °C. After annealing at 800 °C, the ionic conductivity of the sprayed LSGM layer can reach the same level as that of the sintered LSGM.
Detonation Consolidation of NiFe/SiO2 and Co/SiO2 nanocomposites
Authors: Ma Xinqing , Zhang Y. D. , Hui S. , Wu Mingzhong , Ge Shihui , Hines W. A. , Budnick J. I. , Cetegen B. M. , Semenov S. Y. 
Published: April 2011

ABSTRACTConsolidation of nanostructure magnetic particles is required not only for manufacturing bulk component, it is actually a fundamental requirement for obtaining novel magnetic properties from the material. Consolidation (assembly) of nanoparticles to full density without deteriorating their nanostructure (size and morphology) is a big challenge. Here we present the consolidation experiments of NiFe/SiO2 and Co/SiO2 nanocomposites via detonation consolidation. This approach is based on the explosive pressure created when an acetylene and oxygen mixture gas fires in a sample containing tube, the very high hypersonic propulsion force makes nanoparticles deposit onto the target. Depending on the powder morphology and operation conditions, the density of the consolidated sample can reach over 91% of the theoretical density of the bulk materials. X-ray diffraction experiments on the samples before and after consolidation indicate that the denotation consolidations can be optimized such that it does not cause any phase transition. However, a particle size increase was observed. Static magnetic studies carried out on the samples before and after detonation operation shows that the saturation magnetization does not. This indicates that the operation does not cause an oxidation of the nanopowders. These experiments show that detonation approach is a good candidate for consolidating magnetic nanoparticles.
On Probabilistic Distribution of Forces in Granular Materials: A Statistical Mechanics Approach
Authors: Ngan Alfonso H.W. 
Published: April 2011

ABSTRACTThe contact force distribution in stressed grain piles under simple compaction or gravity has been studied intensively in recent years. In the present investigation, by performing discrete element simulations, it is found that the contact force distribution in a stressed granular packing can be described by a generalized form the Second Law of Thermodynamics involving minimization of a free energy functional containing an energy and an entropy component. The relative importance of energy and entropy is controlled by a parameter known as the “mechanical temperature”.
Granule Structure Evolution during Powder Compaction
Authors: Walker William J. 
Published: April 2011

ABSTRACTDie compaction of granulated powder is a common forming process used in the ceramics industry. Glass spheres were used as a model system to investigate granule failure during die compaction. Since glass spheres are brittle, failure results in fragmentation. Particle size analysis of the resulting fragments demonstrates the statistical nature of granule failure during compaction, with some granules failing at very low applied pressures while a large fraction persist at even the highest applied loads. The results are discussed in terms of the Andreasen, Furnas and Dinger-Funk particle packing models for continuous size distributions.
Characterization of Booming Sands
Authors: Brantley Katherine S. , Hunt Melany L. , Brennen Christopher E. , Gao Steven S. 
Published: April 2011

ABSTRACTMany sand dunes – at least seven in the United States – make loud booming noises when they avalanche. Records of the sound are centuries old, but the cause remains a mystery. This study examines properties of both the sand and the sound.Properties of the sand reveal clues about the source of the booming. Sand must be extremely dry to boom, but low moisture content alone is not sufficient to facilitate booming. Although the mean grain diameters of both booming and silent dune sands range from 0.20 – 0.40mm, the booming samples have smaller standard deviations. However, synthetic sands with similar size distributions do not boom, so a narrow size distribution cannot be solely responsible for the booming. Studies of the roundness and sphericity of the grains are currently underway.Air microphone and geophone recordings of the booming indicate that the fundamental frequency varies between 80–105 Hz depending on the dunes. This is consistent with previous measurements. Laboratory recordings of the “burping” sound that booming sand makes when shaken in a jar reveal a broad peak between 150–300 Hz.
Shock (Blast) Mitigation by “Soft” Condensed Matter
Authors: Nesterenko Vitali F. 
Published: April 2011

ABSTRACTIt is a common point that “soft” condensed matter (like granular materials or foams) can reduce damage caused by impact or explosion. It is attributed to their ability to absorb significant energy. This is certainly the case for quasistatic type of deformation at low velocity of impact widely used for packing of fragile devices. At the same time a mitigation of blast phenomena must take into account shock wave properties of “soft” matter which very often exhibit highly nonlinear, highly heterogeneous and dissipative behavior. This paper considers applications of “soft” condensed matter for blast mitigation using simplified approach, presents analysis of some anomalous effects and suggestions for future research in this exciting area.
Materials Science Education at Keio University: Adopting U.S. Instruction Practices in Japan
Authors: Itoh Kohei M. 
Published: April 2011

ABSTRACTThe undergraduate experience in Materials Science and Engineering (MSE) in Japan differs from that at U.S. institutions in several respects. While MSE programs at many U.S. universities exist as established departments, it is rare to find MSE departments in Japan. Therefore, materials science education in Japan is somewhat fractured as it is intermingled with other disciplines and spread across a variety of departments such as applied physics, chemical engineering, mechanical engineering, and bioengineering. Here, I will report on the challenges of materials science education in Japanese universities focusing on the Department of Applied Physics at Keio University as an example. The challenge is two-fold: 1) stimulating student interest in MSE before undergraduate students choose their home department/major at the conclusion of their first year and 2) providing a rigorous MSE curriculum that will prepare students for post-graduate education both domestically and abroad. For this purpose, we have adopted a U.S. teaching style comprising two 90-minute lectures per week (instead of the one customarily given in Japan), weekly homework assignments, discussion sessions with teaching assistants, and office hours. Although these are standard pedagogical practices in the U.S., they represent major changes in instruction and culture at Keio that have therefore been met with resistance from both some faculty members and students. I shall discuss how we have addressed these challenges and have stimulated student interest in MSE at Keio University.
Incorporating Materials Science into an Undergraduate Applied Physics Curriculum
Authors: Guerra-Vela Claudio , Zypman Fredy R. 
Published: April 2011

ABSTRACTThe Intermediate Physics laboratory is a pivotal course of the undergraduate physics curriculum. Besides its intrinsic importance for introducing modern physics experiments, this laboratory also plays an important role in addressing the needs of the future applied scientist and engineer using contemporary equipment for data acquisition and control. This laboratory course has a mix of standard (usually not directly addressing materials science questions) and newer experiments. Among the newer experiments, we have developed a kit for measuring the transverse and longitudinal Young and Shear modulus of a homemade concrete block by analyzing their standing modes of vibrations. The technique is similar to that of the C-215 American Society for Testing Materials (ASTM) Standard, but more appropriate for university educational setting, using ordinary student laboratory equipment and piezoelectric transducers. From these measurements, we also deduce Poisson's ratio. Students start measuring during the curing process of the concrete sample, something that it is not possible with the standard technique. However, our results have a precision comparable to that of the standard. Through the experiment, students learn about the properties of concrete. They make the samples following the C-192 ASTM standardized process, and review several concepts about waves such as wave equations, resonant modes of vibrations, dispersion relations, and standing modes.
The Junior Laboratory: A Place to Introduce Basics as Well as New Findings
Authors: Martínez-Miranda Luz J. , Wilson O. C. , Salamanca-Riba L. G 
Published: April 2011

ABSTRACTSince its establishment in 1997, the undergraduate program at the University of Maryland has successfully established laboratories where new findings are introduced and used to teach the basic concepts and basic experimental methods in Materials Science and Engineering. This presents the challenge of changing the materials, keeping in mind that the students are being introduced for the first time to many of the concepts. In the junior laboratory of materials, we have successfully changed three laboratories (optical microscopy, rectifying components and X-ray) and a demonstration (TEM) in order to introduce nanomaterials and biomaterials. These laboratories show that currently used techniques can aid in studying the new developments in materials and that most, if not all, the basic concepts can be applied in studying them. They also help the students look at the effects of the structure – processing – properties relationship that is basic to Materials Science and Engineering. We relate all laboratories to experiments and studies currently happening in materials science, even if we have not had the opportunity or the facilities to change it. The laboratory has been approved by ABET 2000.