bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and Properties of Li-Mn-O-F Compounds as Cathode in Li-Ion Batteries
Authors: Liu Hanxing , Hu Chen , Xia Junlei , Zhao Shixi , Ouyang Shixi
Published: April 2011

In present study LiMn2O4-xFxwere prepared by the sol-gel method. X-ray diffraction (XRD) and scanning electron microscope (SEM ) were employed to detect the microstructure of the reaction products. It were found perfect crystal particles were obtained, and its' size were uniform in 1∼2 μ m. The specific capacity and cycleability were measured basing on battery program control test system. The results shown the substitution of F for O increased the specific capacity of the material at the cost of the cycleability due to more Mn3+and less Mn4+existed in the material. The exist of Mn3+would reduce cycleability of cathode material due to the Jahn-Teller effect which were caused by the deformation of the crystal structure.
Preparation and Characterization of Pb2SnF6, The First Lead(II)-TIN(II) Fluoride that is a Superstructure of A-PbF2
Authors: Calandrino Raimondo , Collin Anthony , Dénés Georges , Logiou Morgane , Cecilia Madamba M.
Published: April 2011

All the known phases in the PbF2/SnF2 system have structures derived from the fluorite-type β-PbF2, and are either disordered, and therefore cubic, or ordered with lattice distortion and superstructures. In addition, they are the highest performance fluoride-ion conductors, with PbSnF4 being the very best. In this work, a new phase, Pb2SnF6 has been prepared and characterized. Contrary to the other lead(II) tin(II) fluorides known up to date, the structure of Pb2SnF6 is a superstructure of a-PbF2, instead of β-PbF2, with a large (4 × 4) bidimensional supercell. Pb2SnF6 is prepared by the reaction of a-PbF2 with an aqueous solution of SnF2.
Exploration of Cation Substitution in the Layered Compound CrWN2
Authors: Scott Weil K. , Kumta Prashant N. , Grins Jekabs
Published: April 2011

A series of derivative compounds based on the layered parent phase CrWN2 have been synthesized using a complexed precursor synthesis route. X-ray diffraction analyses demonstrate that both the chromium and tungsten display mutual substitution for one another and can also undergo considerable extensive replacement by a wide variety of cation species without significantly altering the original layered structure of the parent dinitride compound. The precursor approach employed here appears to offer a ready technique for exploring compositional phase space in layered nitrides of this type.
Epitaxial Stabilization in Thin Films of Oxides
Authors: Kaul A. , Gorbenko O. , Graboy I. , Novojilov M. , Bosak A. , Kamenev A. , Antonov S. , Nikulin I. , Mikhaylov A. , Kartavtzeva M.
Published: April 2011

This paper is a survey of recent author's results obtained by the authors. It shows that many oxides can be obtained as thin epitaxial films in spite of their thermodynamic instability in bulk state at the film deposition conditions. This new synthetic approach, named epitaxial stabilization, is based on free energy gain due to structural coherence at the film/substrate interface. The epitaxial stabilization can be effectively used to enlarge the spectrum of new functional materials.
High Quality Erbium-Doped Bismuth Based Oxide Film for Planar Waveguide Amplifier Prepared by Sputtering
Authors: Suzuki S. , Kondo Y. , Nagashima T. , Sugimoto N. , Ebisawa J. , Ito S.
Published: April 2011

High quality Bi2O3 based Er-doped films for planar waveguide amplifier have been deposited by sputtering from sintered targets. It was found that both the amount of residual water and the Er concentration in films mainly affected a lifetime of the fluorescence at 1530nm. By optimizing these parameters, we have obtained films with a lifetime over 3msec, as the same as that of bulk glass prepared by the melting method.
Electrochemical Properties of Blockcopolymer Templated Mesoporous Silicates with Heteropolyacids clusters
Authors: Yun Hui Suk , Kuwabara Makoto , Zhou Hao Shen , Honma Itaru
Published: April 2011

In this paper, we have studied a method of loading 12-tungstophosphoric acid (H3PW12O40; PWA) into blockcopolymer templated (designated EO20PO70EO20; Pluronic P-123) mesoporous SiO2 framework without a disordering of mesostructure and without remarkable decrease of specific surface area through one-step condensation process. A precursor solution is initially prepared by TEOS (tetraethoxysilane) hydrolyzed with templating polymer (eg. triblock copolymer), and then mixed directly with PWA to condense mesoporous silicate products that incorporate PWA clusters in the framework. Heteropolyanions are possibly incorporated in the framework silicates. Electrochemical properties of these PWA impregnated mesoporous silicates were studied as electrode materials of Li ion battery as well as solid proton conductors.
Electrical Conductivity Prediction in Langasite for Optimized Microbalance Performance at Elevated Temperatures
Authors: Seh Huankiat , Tuller Harry , Fritze Holger
Published: April 2011

The performance of the langasite-based crystal microbalance is limited due to reductions in its resistivity at high temperatures and reduced oxygen partial pressures. In this work, we utilize a recently developed defect model to predict the dependence of the ionic and electronic contributions to the total conductivity of langasite on temperature, oxygen partial pressure and acceptor and donor dopants. These results are used to select the type and concentrations of dopants expected to provide extended operating conditions for langasite-based gas sensors and crystal microbalances.
High-Temperature Potentiometric NO2 and CO Sensors Based on Stabilized Zirconia with Oxide Sensing Electrodes
Authors: Di Bartolomeo E. , Grilli M. L. , Kaabbuathong N. , Traversa E.
Published: April 2011

This paper reports the efforts made in our laboratory to develop electrochemical sensors that might detect NO2 and CO at high temperatures for On Board Diagnostic (OBD) application. The non-Nernstian behaviour of zirconia-based electrochemical NO2 sensors with various oxides as sensing electrodes was studied in the temperature range 450–700°C. Both pellets and tape-casted layers (150 μm of thickness) of yttria-stabilized zirconia (YSZ) were used for fabrication of the sensors. Pt electrodes were painted on both sides of the pellets or as two parallel fingers on one face of the layers. One of the Pt electrodes was covered with a thick-film oxide electrode. Various oxides were tested as sensing electrodes, either p- or n-type semiconductors, including WO3 and LaFeO3. The role of ionic conductivity of the oxide electrodes was investigated using Sr-doped perovskite-type oxides, such as LaxSr1-xFeO3, a mixed ionic-electronic conductor. The sensors were tested as potentiometric and amperometric devices. The performance of these devices was promising: fast and stable responses to different NO2 concentrations (20–1000 ppm in synthetic air) were observed at high temperatures. The role of the metallic electrodes is also studied. The sensing mechanism of the sensors is discussed.
Thin Film Stoichiometry Determination by High Temperature Microbalance Technique
Authors: Fritze H. , Seh H. , Schneider O. , Tuller H. L. , Borchardt G.
Published: April 2011

The 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

Composite 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

Results 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

We 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

The 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

In 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

In 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

A 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

The 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

We 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

Strontium 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

An 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

Consolidation 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

The 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

Die 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

Many 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

It 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

The 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

The 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

Since 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.
Formation Of Single-Wall Carbon Nanotubes Forrest Assemblies On Metal Surfaces
Authors: Chattopadhyay Debjit , Galeska Izabela , Papadimitrakopoulos Fotios
Published: April 2011

Learning how to purify and manipulate single wall carbon nanotubes (SWNTs) presents a unique challenge in material science. The processing-related difficulties of these long nano-fibers stem from their high aspect ratio, rigidity and the profound hydrophobic attractions along their tubular walls. Shortening them into discrete segments, with lengths from tens to hundreds of nanometers, presents a viable methodology to alleviate the shape-induced intractability. In addition, the metal-assisted self-organization of these nanosized objects into nano-forest geometries with dense perpendicular surface grafting, demonstrates that such nanosized objects hold significant promise for the development of nanoscale devices. This paper will present an extensive characterization of the topological characteristics of these assemblies, along with their surface coverage, growth characteristics and height fluctuation on iron hydroxide substrates.
Electric field and Charged Molecules Mediated Self-Assembly for Electronic Devices
Authors: Lee Sang Woo , McNally Helen A. , Bashir Rashid
Published: April 2011

In this paper we present techniques, utilizing dielectrophoresis and electrohydrodynamics, which can possibly be used for assembling devices suspended in a solution onto a binding site on a substrate. We explored the concepts using micro-scale negatively charged polystyrene beads and rectangular silicon blocks. Dielectrophoretic forces on devices in buffer solutions were examined as a function of frequency of the applied AC signal. The observed results can be explained by taking in account electro-thermal and AC electroosmotic effects. The study described in the paper can be used for placing and assembling micro and nano-electronic devices and objects at specific sites on various substrates, in combination with bio-inspired biological binding techniques such as DNA hybridization, antigen-antibody interactions, and ligand-receptor (avidin-biotin) interactions.
Covalently-linked Adducts of Single-walled Nanotubes with Biomolecules: Synthesis, Hybridization, and Biologically-Directed Surface Assembly
Authors: Baker Sarah E. , Lasseter Tami L. , Smith Lloyd M. , Hamers Robert J.
Published: April 2011

Covalently-linked adducts of single-walled carbon nanotubes (SWNTs) with biomolecules have been fabricated. Results are presented here for DNA-SWNT and for biotin-SWNT adducts. DNA-SWNT adducts are shown to be biochemically accessible and to exhibit high selectivity, favoring hybridization with complementary vs. non-complementary DNA sequences. Biotin-SWNT adducts were also prepared and used to direct the assembly of nanotubes onto a biotinylated glass surface.
Electrochemical detection of non-labeling DNA using electronic array
Authors: Lee H. Y. , Park J. W. , Choi Y. S. , Kannno T. , Tanaka Hiro. , Tanaka Hide. , Kawai T.
Published: April 2011

Our system is the electrochemical approaches include the detection of hybridization from nonlabeling nucleic acids to protein-bound nucleic acids using soluble mediators with K4Fe(CN)6 solutions. In order to generate bio-functional surfaces, the streptavidin(SAv)-biotin system is used. A 50 % change of redox peak current after hybridization measured with 50 ?M concentration of target DNA. We suggest that this result comes from the efficient electron transport through the SAv-biotin interaction. Our electrochemical detection system showed good reproducibility on a chip with non-labeling DNA hybridization detection.
Semi-Empirical Study of a pH-Switchable [2] Rotaxane
Authors: Frankfort Laura , Sohlberg Karl
Published: April 2011

Semi-empirical (AM1) electronic structure calculations are reported on a pH-switchable [2] rotaxane whose synthesis was reported in [Angew. Chem. Int. Ed, 36 (1997) 1904] . The [2] rotaxane possesses two cationic binding sites, with different affinities toward dibenzo [24] crown-8 (the ring component of the [2] rotaxane) depending upon the pH of the system. The computational results capture this pH-sensitive bistability, the key device-like characteristic of the rotaxane.
Design and Performance of Polymeric Ultra-thin Substrates for use as Embedded Capacitors: Comparison of Unfilled and Filled Systems with Ferroelectric Particles
Authors: Andresakis John , Yamamoto Takuya , Pramanik Pranabes , Buinno Nick
Published: April 2011

As CPUs increase in performance, the numbers of passive components on the surface of the boards are increasing dramatically. To reduce the number of components, as well as improve the electrical performance (i.e. reduce inductance), designers are increasingly embedding capacitive layers in the Printed Circuit Board (PCB).

The majority of the products in use today utilize reinforced epoxy laminates. These products are relatively easy to handle and provide good electrical performance, but a need exists for even better performance than a fiberglass-reinforced product can produce.

Other materials are being developed that are thinner (and thus increase capacitance and reduce inductance), but either have problems with dielectric breakdown strength, handling or only marginal improvements over the reinforced epoxy material. A need exists for an ultra-thin (less than 25 micron) material that not only provides improved electrical performance, but can be readily manufactured using standard PCB processing.

We will discuss the design criteria we used for developing our family of products, as well as the results. The design of the conductor (copper foil) has been determined to be as critical as the properties of the dielectric (polymer). Examination of the effect of loading the polymer with High Dk ferroelectric particles will also be examined.

The products have been through both internal and external testing and are compared to existing and developing capacitor materials. We will describe the electrical as well as the processing characteristics in detail, and how these types of products can greatly improve performance of high-speed systems
Solidly Mounted Bulk Acoustic Wave Filters
Authors: Loebl H. P. , Metzmacher C. , Milsom R. F. , Tuinhout A. , Lok P. , van Straten F.
Published: April 2011

Selective RF filters based on solidly mounted thin film bulk acoustic wave resonator filters (SMR filters) are of great interest for mobile and wireless applications in the GHz frequency range. They are small in size, robust and can be integrated on silicon. The SMR configuration comprises a textured piezoelectric layer of AlN or ZnO sandwiched between two electrodes, and an acoustic reflector, which confines the acoustic energy in the resonator region. The bulk acoustic wave (BAW) resonators are exited in the thickness extensional mode. In these paper examples of BAW resonators and filters for the frequency range between 1 and 8 GHz are shown. It will become clear that precise control of AlN film growth is very important. Modelling the resonator performance using a 1-dimensional electro acoustical model allows the extraction of important thin film parameters and thus simulation of the filter performance. Limitations of the 1-D model are discussed.
Investigation of Highly c-axis Oriented AlN Thin Film Re-growth
Authors: Martin F. , Muralt P. , Dubois M.-A.
Published: April 2011

The properties of AlN films grown on a first set of differently treated AlN films have been studied by XRD, XPS, AFM, in-plane stress and interferometry. All films were deposited by dc pulsed sputtering at 300°C. The first set of films consisted of smooth, pure c-axis oriented AlN monolayers with narrow rocking curve width and excellent piezoelectric coefficient grown on platinized substrate in a large thickness range of 35–2000 nm. Subsequently, a 1000 nm AlN layer has been added. The use of a strongly alkaline developer during intermediate lithography steps and the time elapsed between the two steps of AlN re-growth were found to degrade the overall quality of the films. It's been shown that the alkaline developer etches down, increases the roughness and contaminates the surface of the AlN monolayer with mainly oxides and hydroxides while the exposure of the films to air develops a native oxide layer. By reducing the air exposure time and by the use of RF plasma cleaning prior to the re-growth process, a good piezoelectric coefficient can be recovered.
Surface Oxide Evolution on Al-Si Bond Wires
Authors: Qin Wentao , Doyle Ray , Scharr Tom , Shah Mahesh , Kottke Mike , Werho Dennis , Theodore N. David
Published: April 2011

Al-Si wires are often used to make contact to bond-pads of semiconductor chips and devices. During operation in certain types of devices the wires typically reach relatively high temperatures. Under such circumstances, the oxidation could lead to a decrease of wire conductivity. It is of interest therefore to understand the oxidation behavior of the bond wires, particularly at elevated temperatures. In the current study, Al-Si wires were characterized as received from the supplier, and after thermal annealing at 240°C and 300°C. The surface oxides were found to evolve from a single-layer oxide to a double-layer oxide with varying chemistry. Oxide thicknesses were substantially lower than the wire diameter, even after 3000 hours of annealing. Therefore oxidation of the Al-Si wires has an insignificant impact on their electrical conductivity.
Stress evolution in integrated SrBi2Ta2O9 ferroelectric layers
Authors: Lisoni J. G. , Wafer K. , Johnson J. A. , Goux L. , Schwitters M. , Paraschiv V. , Maes D. , Haspeslagh L. , Caputa C. , Zambrano R. , Wouters D. J.
Published: April 2011

In our integration scheme, a “pseudo-3D” capacitor cell is used where the TiAlN\Ir\IrO2\Pt bottom electrode is patterned before SBT deposition. In order to understand how this system behaves mechanically, we have investigated the evolution of the stress of blanket Sr1-xBi2+yTa2O9 (x, y < 0.5) layers deposited on this pre-patterned bottom electrode stack. SBT was deposited by metal organic vapor deposition (MOCVD) between 405 °C and 440 °C. The stresses were monitored by the change in the radius of curvature of the wafer at the subsequent processing steps: deposition of electrodes and SBT, crystallization and recovering annealing, and after removal of Pt top electrode, SBT and bottom electrode layers by dry etching. The stress conditions observed for the different planar layers as a function of the SBT deposition temperature was correlated to the TiAlN lateral oxidation length observed in the etched structure after the SBT crystallization step.
Ferro- and piezoelectric properties of Bi4−xPrxTi3O12 polycrystalline thick films with Ps-vector orientation
Authors: Matsuda Hirofumi , Ito Sachiko , Iijima Takashi
Published: April 2011

To reveal the complete performance of intrinsic ferroelectriciy-related properties in single crystalline bismuth-layer-structured displacive ferroelectrics in film form on Si, the crucial roles of both orientation control technology by lattice matching from the atomic arrangement of substrate layer and configuration of the volume fraction of 90°-domain during cooling process were demonstrated. 1.2 μm-thick and Pr3+-substituted Bi4-xPrxTi3O12 (BPT, x =0.0, 0.3, 0.5, 0.7) films were grown on Ir(111)/Ti/SiO2/Si(001) substrates by chemical solution deposition (CSD) method with preferred orientation along the major component of Ps vector. BPT film of x =0.3 exhibited superb ferroelectric properties of remanent polarization 2Pr=92 μC/cm2, saturation polarization Psat=50 μC/cm2, and coercive field 2Ec=184 kV/cm. The film also showed uniform piezoelectric response with an effective piezoelectric coefficient of AFM-d33=36 pm/V. During the decomposition of precursor solutions, IrO2 layers were formed at the surface of Ir layers and promoted a/b-axes orientation. During the cooling process after grain growth, in addition, the differential thermal expansion and residual strain between film and substrate introduced bidirectional lateral stress into BPT film and might eliminate the 90°-domain walls dividing a-and b-domains through the relaxation by domain formation at the Curie temperature TC. Consequently the polar-axis orientation was distinctively grown along the film normal and the conjugate non-polar-axis was grown in-plane.
Parametric Studies on Suppression of Secondary Phases in LiNbO3 Thin Films Deposited by Pulsed Laser Deposition
Authors: Son Ji-Won , Orlov Sergei S. , Phillips Bill , Hesselink Lambertus
Published: April 2011

We performed a parametric study to suppress secondary phases in lithium niobate thin films by using pulsed laser deposition (PLD). A KrF excimer laser (λ=248nm) was used as a PLD source and c-oriented sapphire was used as substrates, for waveguide applications. By reducing the growth rate and changing the ambient gas pressure respectively, we found that the main parameter suppressing a secondary phase is controlling the plume strength. To investigate the relation between film phases and the plume strength, extensive parametric studies were performed by changing the oxygen ambient pressure, the target to substrate distance, and also the Li content in the target. The surface morphologies of single phase films and Li-deficient phase mixed films are compared and related to the growth mechanism with a lattice misfit. Deposition parameters to achieve lower loss films are also discussed.
Lead deficient PST Thin Films on LSCO/SrTiO3by RF-Sputtering
Authors: Martínez E. , Blanco O. , Fundora A. , Siqueiros J. M.
Published: April 2011

We have investigated the structural, chemical and electrical properties of films with Pb0.6Sr0.4TiO3(PST60) nominal composition grown on well texturized LSCO/SrTiO3(STO) substrates by RF-Sputtering. The crystal structure and electrical properties of the PST60 films are remarkably influenced by the texture characteristics of the LSCO films. The structural and ferroelectric characteristics of PST60 thin films are determined to evaluate the potential of this heterostructure for non-volatile memory applications. Epitaxy of LSCO films was confirmed before depositing PST60 films on the above mentioned substrates through 4-Circle X-Ray Diffraction analysis (θ/2θ, ω and φ scans). The XRD analysis performed on the ferroelectric PST60 layer showed that the films are textured and entirely perovskite phase. LSCO and PST60, crystallize in the perovskite structure and their lattice parameters are well matched. This fact renders favorable structural and chemical conditions for the growth of PST60 on LSCO. The electrical performance of the Pt/PST60/LSCO/SrTiO3(001) capacitors was evaluated through Polarization-Voltage (P-V), Current-Voltage (I-V) and Fatigue measurements.
Ti-site Substitution Using the Higher-valent Cation for Enhancing the Ferroelectric Properties of Nd3+−substituted Bismuth Titanate Thin Films
Authors: Uchida Hiroshi , Koda Seiichiro , Matsuda Hirofumi , Iijima Takashi , Watanabe Takayuki , Funakubo Hiroshi
Published: April 2011

Ti-site substitution using the higher-valent cation was performed on ferroelectric thin films of neodymium-substituted bismuth titanate, (Bi,Nd)4Ti3O12(BNT), in order to improve its ferroelectric properties by compensating the space charge in BIT-based crystal. Ti-site-substituted BNT films, (Bi3.50Nd0.50)1-(x/12)(Ti3.00-xVx)O15(x= 0 ∼ 0.09), were fabricated on (111)Pt/Ti/ SiO2/(100)Si substrates using a chemical solution deposition (CSD) technique. V5+-substitution enhanced the remanent polarization of BNT film without change in the coercive field. V5+-substitution also exhibited the possibilities for improving the endurance against leakage current and fatigue degradation.
Preparation, Microstructure and Physical Characteristics of Ferroelectric Pb5Ge3O11 Thin Films for Memory Application
Authors: Liu Y. X. , Caragianis-Broadbridge C. , Lehman A. H. , McGuinness J. , Ma T. P.
Published: April 2011

We report sol-gel process of Pb5Ge3O11 (PGO) as well as the microstructure and physical properties of ferroelectric PGO films for memory applications. The PGO sol was prepared from lead acetate hydrate, germanium isopropoxide, and di(ethylene glycol) ethyl ether. The reactions taking place during the sol-gel process were examined in detail. Diethanolamine (DEA) was added to help maintain the desired species ratio and prevent germanium oxide precipitation. The preferred orientation of the PGO thin films was well controlled by the heating and reflux procedures in the sol-gel preparation process. Additionally, to examine the impact of postdeposition processing, selected samples were oxygen annealed at temperatures ranging from 450–650°C. The samples were characterized with X-ray diffraction (XRD), non-contact (planview) atomic force microscopy (NC-AFM). The resulting data indicate that the microstructure and physical properties of PGO films depend strongly on the precursor preparation as well as the post deposition annealing temperature.