bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ferroelectric nanocomposite with high dielectric constants
Authors: Pham Mai T.N. , Boukamp B.A. , Bouwmeester H.J.M. , Blank D.H.A. 
Published: April 2011

ABSTRACTComposites between ferroelectric material and a dispersed metal phase are of great interest due to the improvement in dielectric properties for such applications as high capacitance capacitors, non-volatile memory, ect. Using a colloidal method, Pt particles with a size of 3–5 nm were dispersed homogeneously in a PZT (PbZr0.53Ti0.43O3) matrix. No unwanted reaction phase between PZT and Pt during sintering at 1150 °C could be detected by X-ray diffraction. Electrical properties were investigated by impedance spectroscopy measurement. The effective dielectric constant increased remarkably as a power function of Pt volume content and can be described by the percolation theory. At 25 vol.% of Pt the dielectric constant of the composite is 4 times larger than that of pure PZT. The temperature dependence of the electrical properties is also influenced by the metallic phase fraction.
Synthesis and Sintering of (K,Na)NbO3 Based Ceramics
Authors: Malic Barbara , Jenko Darja , Bernard Janez , Cilensek Jena , Kosec Marija 
Published: April 2011

ABSTRACTStoichiometric K0.5Na0.5NbO3 solid solution(KNN) was prepared by solid-state synthesis from alkaline carbonates and niobium oxide. Thermal decomposition of the powder mixture occurs upon heating to 700 °C followed by crystallization of the perovskite phase. After sintering at 1100 °C, 2h the stoichiometric KNN reaches 94 % of theoretical density. Dielectric constant of stoichiometric KNN is 620, and the losses 0.03.
Contrasting Structural Behavior in the Aurivillius Phase Ferroelectrics Bi4Ti3O12, BaBi4Ti4O15 and Ba2Bi4Ti5O18
Authors: Lightfoot Philip , Snedden Alan , Blake Susan M. , Knight Kevin S. 
Published: April 2011

ABSTRACTThe crystal structures of the Aurivillius phase ferroelectrics Bi4Ti3O12, BaBi4Ti4O15 and Ba2Bi4Ti5O18, containing perovskite-like layers consisting of three, four and five adjacent TiO6 octahedra, respectively, have been analysed using high-resolution powder neutron diffraction data. At 2K the structure of Bi4Ti3O12 can be successfully modelled in the orthorhombic space group B2cb, with no evidence of the monoclinic distortion in the ferroelectric phase suggested by previous single crystal studies. At 298K BaBi4Ti4O15 shows a subtle orthorhombic distortion, but without the octahedral tilting seen in related ferroelectric phases, and is refined in space group F2mm. At 298 K Ba2Bi4Ti5O18 adopts a tetragonal polar phase (I4mm), thus displaying a third type of polar distortion within this family. It is suggested that these differences arise from a ‘tolerance factor’ type mechanism whereby the increasing content of the large Ba2+ cation causes a shift from underbonding at the perovskite A-site to underbonding at the perovskite B-site resulting in a change in the mechanism of ferroelectricity from A-site displacements to B-site displacements, akin to the mechanism in BaTiO3.
Structure, magnetization and Mössbauer study of nanostructured Ni0.5Zn0.5Fe2O4 ferrite powders
Authors: Ge Shihui , Zhang Zongtao , Wu Mingzhong , Zhang Y.D. , Yang D. P. , Budnick J. I. , Hines W. A. 
Published: April 2011

ABSTRACTNanostructured ferrites possess more advantages than the conventional ferrite materials and have been a research focus recently. In this work, a series of nanostructured Ni0.5Zn0.5Fe2O4 were synthesized by a citrate reaction method followed by calcining at various temperatures with the goal of obtaining pure phase Ni0.5Zn0.5Fe2O4 nanoparticle while keeping the size small. X-ray diffraction, transmission electron microscopy, SQUID magnetometry and Mössbauer spectroscopy (ME) have been employed to characterize the crystal structure, phase homogeneity, particle size, the conditions for reaction completion, and the magnetic properties. The results show that the saturation magnetization Ms at both 10K and 300K increase with increasing calcination temperature Tca, but particle size also increases with Tca. Three factors, the incomplete reaction for ferrite phase formation, the surface effect and superparamagnetic behavior, are found to be responsible for low Ms values at lower Tca. Based on a detailed analysis of nanostructure and magnetic properties in ferrites, the optimal conditions for synthesizing nanostructured Ni0.5Zn0.5Fe2O4 have been established.
Ag Ion-Exchange Reactions of Cu2P3I2 and Cu2P1.8As1.2I2
Authors: Jayasekera Buddhimathie , Brock Stephanie L. 
Published: April 2011

ABSTRACTA variety of ion exchange techniques for Cu2P3I2 and its mixed pnictogen analog Cu2P1.8As1.2I2 have been studied. Ag2P3I2 is an existing material, previously prepared from Cu2P3I2 by ion exchange of Ag+ for Cu+ in aqueous medium. This method is compared to non-aqueous (ionic liquid) and solid state routes for ion exchange. Additionally, the new compound Ag2P1.8As1.2I2 with cell parameters a = 15.838(17) Å, b = 13.684(10) Å, c = 15.580(17) Å and β = 117.63(7)°, has been prepared by reaction of Cu2P1.8As1.2I2 with AgNO3 in aqueous solution.
Heterogeneous Design: Concentration Fields Determination with the Unique Crystallization Schemes and Microstructures
Authors: Lutsyk Vasily I. , Vorob'eva Vera P. 
Published: April 2011

ABSTRACTNew approach to calculation of microstructure by means of the one-phase regions borders equations is proposed. Projections of all geometrical elements of phase diagram to the concentration simplex divide it to fields with unique crystallization schemes. All crystallization stages for the given concentration field are simulated and as a result the all elements of microstructure is designed and origin of every phase is shown.
New Method of Preparation of Superionic BaSnF4
Authors: Dénès Georges , Muntasar Abdualhafed , Retrif Tony 
Published: April 2011

ABSTRACTThe first preparation of superionic BaSnF4, BaSnF4(ssr), was carried out in 1975 by direct reaction at high temperature between appropriate amounts of BaF2 and SnF2 under inert conditions in sealed copper tubes. In the present work, BaSnF4(aq2) was synthesized for the first time by the wet method. X-ray powder diffraction and Mössbauer spectroscopy were used to characterize the products, and show that BaSnF4(aq2) and BaSnF4(ssr) are the same material.
Synthesis of Metal-doped Cryptomelane Nanomaterials using Cross-linking Reagents
Authors: Liu Jia , Cai Jun , Shen Xiongfei , Suib Steven L. , Aindow Mark 
Published: April 2011

ABSTRACTThree cross-linking reagents (PVA, glycerol and glucose) have successfully been used to synthesize non-doped and metal-doped nanosized cryptomelane materials via a solid-state preparation method. The 2×2 tunnel structure of cryptomelane was formed at 500 °C. FT-IR data show that no cross-linking reagent residues were found in the products after the reactions were complete at 800 °C. The metal dopants used were Fe, Ag, Co, Cu, Ni, and Zn. XRD data show that Fe and Co cations can be doped into the materials without the formation of additional phases. The tunnel structures of the nanosized materials exhibit long-range along the b axis, as indicated by transmission electron microscopy data. High-resolution scanning electron microscopy studies show that morphologies of the products are nanorods or nanofibers, depending on the cross-linking reagents used in the preparation. Thermogravimetric analyses indicate that these nanomaterials are thermally stable to 700 °C.
Design Of New Oxide Ceramic Materials And Nanocomposites With Mixed Conductivity By Using Mechanical Activation Route.
Authors: Zyryanov Vladimir V. , Uvarov Nikolai F. , Kostrovskii Vitalii G. , Sadykov Vladislav A. , Kuznetsova Tatiana G. , Rogov V. A. , Zaikovskii V. I. , Frolova Y.V. , Alikina G. M. , Litvak G. S. , Burgina E. B. , Moroz E. M. , Neophytides S. 
Published: April 2011

ABSTRACTSome perovskite –like Fe (Co) -containing and fluorite-like Bi –containing solid solutions considered as promising materials for high oxygen flux membranes application have been synthesized by the mechanochemical activation route. Structural/microstructural features of those systems characterized by TEM, XRD, IR, and Raman spectroscopy are compared with the data on their mixed conductivity and oxygen mobility. Some properties of nanocomposites comprised of those materials and such oxides as Fe2O3, BaTiO3, BaBiO3 etc are elucidated as well. Densification of those powdered samples by sintering in the 700–1400 K temperature range is accompanied by annealing of metastable phases generating “core-shell” nanocomposites with oxygen transport properties different from those of traditional materials.
Hydrothermal Synthesis of a Microporous Organic-Inorganic Hybrid Framework [Fe0.28V0.72OH0.8(NH4)0.2(C8H4O4)] · 0.53(C8H6O4)
Authors: Whitfield Tabatha R. , Wang Xiqu , Jacobson Allan J. 
Published: April 2011

ABSTRACTSingle crystals of a novel organic-inorganic framework [Fe0.28V0.72OH0.8(NH4)0.2(C8H4O4)] · 0.53(C8H6O4), 1, have been prepared by hydrothermal synthesis in the presence of an oxidizing agent. The structure was solved by single crystal X-ray diffraction: space group Pnma, a = 17.6956 (19) Å, b = 6.8745 (7) Å, c = 11.9303(12) Å. The three dimensional framework is constructed from Fe/V-O chains that are cross-linked by 1,4-benzene dicarboxylate (BDC) anions forming large one-dimensional channels. As synthesized, the compound contains additional dicarboxylate groups occupying disordered positions in the channels that can be removed by heating. The chemical reactivity of 1 and its magnetic properties are reported. The new phase is closely related to analogous Cr (III) and V(III) phases recently reported by Férey and co-workers.
Structural and Physical Property Trends of the Hyperstoichiometric Series, La2Ni(1-x)CoxO4+δ
Authors: Amow G. , Whitfield P. S. , Davidson J. , Hammond R. P. , Munnings C. , Skinner S. 
Published: April 2011

ABSTRACTMembers of the Ruddlesden-Popper system, La2Ni(1-x)CoxO4+δ (0.00 ≤ × ≤ 1.00), were synthesized and studied for their potential use as cathodes for solid-oxide fuel cells. An unusual structural trend has been noted across the series, which appears to correlate with the oxygen-hyperstoichiometry observed. Details of the structural variance by x-ray and neutron diffraction, as well as selected physical properties for this system will be presented.
Bond valence analysis of ion transport in reverse Monte Carlo models of mixed alkali glasses
Authors: Adams Stefan , Swenson Jan 
Published: April 2011

ABSTRACTAn analysis of RMC structure models of ion conducting glasses in terms of our bond softness sensitive bond-valence method enables us to identify the conduction pathways for a mobile ion as regions of sufficiently low valence mismatch. The strong correlation between the volume fraction F of the “infinite pathway cluster” and the transport properties yields a prediction of both the absolute value and activation energy of the dc ionic conductivities directly from the structural models. Separate correlations for various types of mobile cations can be unified by employing the square root of the cation mass as a scaling factor. From the application of this procedure to RMC models of mixed alkali glasses, the mixed alkali effect, i.e. the extreme drop of the ionic conductivity when a fraction of the mobile ions is substituted by another type of mobile ions may be attributed mainly to the blocking of conduction pathways by unlike cations. The high efficiency of the blocking can be explained by the reduced fractal dimension of the pathways on the length scale of individual ion transport steps.
Li mobility in (Li,Na)yLa0.66-y/3TiO3 perovskites (0.09<y≤0.5). A model system for the percolation theory.
Authors: Sanz J. , Rivera A. , León C. , Santamaría J. , Várez A. , V'yunov O. , Belous A. G. 
Published: April 2011

ABSTRACTThe dependence of ionic transport on structure and composition of perovskites LiyLa0.66-y/3TiO3 (0.09 ≤ y ≤ 0.5) and Li0.5-xNaxLa0.5TiO3 (0 ≤ x ≤ 0.5) has been analyzed by means of Neutron Diffraction, NMR and Impedance Spectroscopy. In the first series, ion conductivity displays a non-Arrhenius behavior, decreasing activation energy at increasing temperatures. Li mobility is accompanied by a considerable increase of Li thermal factor deduced from ND data. In the second series, local lithium mobility decrease monotonously with the sodium content at room temperature; however, long-range dc conductivity decreases sharply at x = 0.2 more than six orders of magnitude. This decrease on dc conductivity is discussed in terms of a three-dimensional percolation theory of vacant Asites. In this model, the number of vacant sites is controlled by the amount of Na and La of the perovskite.
Preparation and Characterization of Anatase (Tio2) Nanoceramics
Authors: Weibel A. , Bouchet R. , Knauth P. 
Published: April 2011

ABSTRACTWe have systematically investigated the influence of various parameters (pressure, temperature, time, sample size) on the hot pressing process of TiO2nanoceramics. This study is backed by thermodilatometric experiments and microscopic observations of the microstructure. Impedance spectra of TiO2nanoceramics with different porosity are also presented.
The Syntheses and Characterization of Layered LiNi1-y-zMnyCozO2 Compounds
Authors: Katana Ngala J. , Chernova Natasha A. , Matienzo Luis , Zavalij Peter Y. , Stanley Whittingham M. 
Published: April 2011

ABSTRACTThe layered compounds of formula LiNi0.4Mn0.6-yCoyO2, for y=0.2, 0.3, and 0.4 and LiNi0.7-yMn0.3CoyO2 for y=0.3, and 0.1 were synthesized at 800°C. X-ray powder diffraction indicates layered structure of R 3m symmetry similar to a-NaFeO2. Rietveld refinement data shows that Mn and Ni increase the tendency of transition metal ions to migrate into the interlayer sites relative to LiCoO2. Both magnetic susceptibility and XPS data support a 2+ oxidation state for Ni and 4+ and 3+ for Mn and Co, respectively. The layered compound LiNi0.4Mn0.4Co0.2O2 shows a high initial capacity of about 200mAh/g when cycled between 2.5V and 4.3 V at 20°C.
Preparation and Oxygen Permeability of La-Sr-Co-Fe Oxide Thin Films by a Chemical Solution Deposition Process
Authors: Kakuta Hirofumi , Iijima Takashi , Takamura Hitoshi 
Published: April 2011

ABSTRACTOxygen-ionic and electronic conductive thin films with the composition of La0.6Sr0.4Co0.5Fe0.5O3-α (LSCF) were prepared on a porous alumina substrate by a chemical solution deposition (CSD) process and their oxygen permeating flux densities were measured. Thickness of the LSCF layer on the substrate was about 0.4 μm. Oxygen flux density of the LSCF sample was found to be 0.6 μmol·cm-2·s-1, however, time-dependent degradation of oxygen flux was observed. The CeO2 barrier layer between the LSCF layer and the substrate was effective in order to improve time-dependent degradation of oxygen flux.
Oxide Ion Transport in Bismuth-Based Materials
Authors: Vannier Rose-Noëlle , Capoen Edouard , Pirovano Caroline , Steil César , Nowogrocki Guy , Mairesse Gaëtan , Chater Richard J. , Skinner Stephen J. , Kilner John A. 
Published: April 2011

ABSTRACTWhen used as ceramic membranes for the electrically driven separation of oxygen from air, BIMEVOX materials allow the production of high oxygen fluxes at moderate temperature, 300–600°C. However, 18O/16O Isotope Exchange Depth Profile Technique revealed low kinetics of oxygen transfer at the surface of these ceramics when studied under equilibrium. These kinetics were considerably enhanced when a current was applied. The same membranes were characterized under working conditions using X-ray synchrotron and neutron radiations. Their dynamical transformation under bias was confirmed and explained by a slight reduction of the BIMEVOX electrolyte under working conditions.
Study of the effect of hydrogen on Pt supported Nanoporous Carbon derived from Polyfurfuryl alcohol
Authors: Rajagopalan Ramakrishnan , Coronado Juan , Foley Henry C. , Vannice Albert 
Published: April 2011

ABSTRACTPlatinum supported on nanoporous carbon (NPC) is promising candidate for using as electrodes in proton exchange membrane fuel cells. Performance of the anode of a fuel cell is markedly influenced by the efficiency of the splitting of hydrogen atoms by platinum and the transference of the produced protons to the carbon support (spillover process). Consequently a better understanding of these elemental processes could prompt the improvement of the materials used. With this aim, a series of Pt/NPC samples varying the metallic content were studied by electron spin resonance (ESR) under controlled gas environment. This spectroscopic tool is especially suitable for the investigation of processes that involve transference of electrons. In the present case, all materials studied, including bare carbon, showed a very narrow signal (Hpp=1.5–3 gauss) at g=2.0028±0.0002 after activation in vacuum at 500–C. In the case of the pure carbon and for the samples with lower platinum content (lower than 0.2 wt%) signals are significantly asymmetric, and their intensity is scarcely affected by the introduction of hydrogen up to 500°C. In contrast the spin concentration experiences a significant increment when the samples with platinum loading comes in contact with hydrogen at temperatures in the 300–500°C range. Although the centres originating these signals are located in the carbon matrix, the present results emphasize the importance of platinum for hydrogen activation and electron transference.
In-situ x-ray absorption experiments with a PEM fuel cell in hydrogen and methanol operation mode
Authors: Buhrmester Th. , Roth C. , Martz N. , Fuess H. 
Published: April 2011

ABSTRACTIn-situ XAS studies have been carried out on PEM fuel cells in methanol and hydrogen operation. This has become possible due to a recently developed PEM fuel cell (single cell) equipped with inherent carbon fibre windows to allow x-ray studies in transmission geometry. The set-up chosen allows the in-situ monitoring of the structural changes of the Pt-Ru catalyst, utilised as electrode active material, during cell operation. The analysis of the white line intensities, edge shifts of the Pt-Lш edge and the XAFS signal, which was modelled for the first co-ordination shell around Platinum, exhibited no significant changes during operation in terms of the first neighbouring shell. Nevertheless, the white line intensity decreased comparing the ex-situ to in-situ measurements. From the latter, can be concluded that the catalyst is reduced during operation and further, the redox behaviour of the catalyst does not change the local environment of the Pt-centres in the first co-ordination shell to a measurable extend.
Simulation of Multi-component Charged Particle Systems
Authors: Retzlaff Ted , Shaw John G. 
Published: April 2011

ABSTRACTDuring the past several years, we developed a 3-D particle simulation software system to study particle transport problems that occur in research and design of electrophotographic or “laser” printers. Several particle systems have been simulated; they include various singlecomponent electrophotographic image formation systems, transport of charged micron-sized plastic particles through magnetically agitated granular bulk, and magnetic bead chain formation. The software has broader applications including granular hopper flow, and ion generation and tracking.The software can simulate the motion of tens of thousands of particles through bounded volumes, handling particle-particle and particle-boundary collisions. It tracks individual particle motion in non-uniform ensembles of multiple material types under the influence of various forces: electric and magnetic fields, adhesion, cohesion, air drag, friction, etc. It is easily extended to include other force laws. Excellent agreement has been obtained between simulated and experimental data. When accurate materials characterization experiments are available, the software provides valuable insight into the behavior of particle systems.
The Introductory Materials Science and Engineering Course
Authors: Callister William D. 
Published: April 2011

ABSTRACTThe introductory materials science and engineering course offered at the college/university level is, for many instructors, very difficult to design and to teach. This presentation discusses challenges for the course, as well as several problematic issues to include: course content, course organization, and course mechanics. The results of two surveys of engineering faculty are presented and discussed; these provide perspectives and lead to suggestions on how to manage these troublesome areas, and improve the quality of and student satisfaction in this course. Also discussed are commercially available software packages, and, in addition, a hybrid electronic-paper introductory materials textbook.
Nanoscale Organic Electronic Devices Formed by Lamination With Stamps
Authors: Zaumseil Jana , Someya Takao , Bao Zhenan , Loo Yueh-Lin , Baldwin Kirk , Cirelli Raymond , Rogers John A. 
Published: April 2011

ABSTRACTLamination of metal-coated elastomeric stamps against thin films of electroactive organics provides non-invasive, high resolution electrical contacts for investigations of charge transport in these materials. This approach uses the features of relief on the stamps to define, with nanometer resolution, the geometry and separation of electrodes that are formed by uniform evaporation of a thin metal film onto the stamp. Soft, room temperature contact of an element of this type with an organic semiconductor film on a gate dielectric and a gate yields a high performance top contact transistor with source/drain electrodes supported by the stamp. We review here our use of this approach to study the electrical properties of the organic semiconductor pentacene in thin film transistors structures. We also introduce a method for using the same techniques and structures to probe transport through organic monolayers.
Site-specific cross-sectioning of carbon nanotube-to-metal junctions for high spatial resolution chemical and structural analysis
Authors: Dovidenko K. , Abramson N. L. , Rullan J. 
Published: April 2011

AbstractIn this study, we have demonstrated successful site-specific cross-sectioning of carbon-nanotube - metal junctions which provided samples suitable for high resolution transmission electron microscopy and electron energy loss spectroscopy. For the cross-sectioning, we have suggested a modified technique based on combination of the Focused Ion Beam (FIB) lift-out and the conventional Ar+ ion milling techniques. Electron-transparent cross-sections of multiwall carbon nanotubes showing no significant surface amorphization or Ga contamination (typical artifacts of conventional FIB lift-out technique) were obtained. High-resolution transmission electron microscopy and electron energy loss spectroscopy of a multi-wall carbon nanotube cross-section have been carried out.
Ordered Structures in Ba(Cd1/3Ta2/3)O3 Microwave Ceramics: A Transmission Electron Microscopy Study
Authors: Sun J. , Liu S. J. , Newman N. , Smith David. J. 
Published: April 2011

ABSTRACTOrdered structures of Ba(Cd1/3Ta2/3)O3 ceramics with and without boron additive were investigated systemically by electron diffraction and high resolution transmission electron microscopy. The results showed a well-ordered structure of 1:2 with hexagonal symmetry for Ba(Cd1/3Ta2/3)O3 with boron additive. No significant changes in ordered structures were observed after long-period annealing. The 1:2 ordered domain structures (average domain size ∼18 nm) and high-density domain boundaries induced by ordering were observed for Ba(Cd1/3Ta2/3)O3 without boron additive sintered at relatively high temperature. The sintering process has a profound influence on the microstructure of Ba(Cd1/3Ta2/3)O3 ceramics.