bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of Silicon Nitride Whiskers by Microwave Heating
Authors: Gedevanishvili S. , Cherian K. , Agrawal D. , Roy R. 
Published: April 2011

AbstractWhiskers of silicon nitride were synthesized by heating silicon powder compacts, silicon single crystal and polycrystalline silicon in microwave in the presence of flowing forming gas or nitrogen. Various gas compositions and form of silicon used resulted in different whisker morphologies. Silicon powder as starting material leads to the formation of needle-like whiskers while silicon single crystal and polycrystalline silicon led to the formation of wool-like and web-like structures respectively. Length of the whiskers apparently depends on the holding time at the optimum temperature ~1350°C; whiskers up to 250 micrometers in length may be grown in 30 minutes. Microstructural data suggest that the silicon nitride whiskers form through gas-solid reaction and vapor-solid mechanism.
Lone Pair Interactions in Zintl Phases and Intermetallic Compounds: Influence on Electronic Properties in Stannides and Plumbides
Authors: Fässler Thomas F. 
Published: April 2011

AbstractThe phases K6Sn23Bi2, K6Sn25, NaSn5, BaSn3, BaSn5, and K5Pb24 depict the structural transition from Zintl phases with localized chemical bonds to typical intermetallic compounds which may even have superconducting properties. The question of the nature of the chemical bond in these compounds is studied with the help of quantum mechanical calculations. Tight binding band structure calculations and real space representations using the Electron Localization Function (ELF) show that free electron pairs play a crucial role for the description of the chemical bond in polar intermetallic compounds. Interactions between lone pairs have a dominant influence on the electronic structures. The coincident appearance of quasi-molecular localized states in form of lone pairs and disperse delocalized bands at the Fermi level EF is discussed with respect to a ‘chemical view’ of the superconductivity observed for BaSn3, BaSn5, and K5Pb24.
Cryosol Synthesis of Nanocomposite Materials
Authors: Kalinin S.V. , Vertegel A.A. , Tretyakov Yu.D. 
Published: April 2011

AbstractFormation of nanocomposites in the course of hydrolytic polycondensation processes is investigated. Depending on the order of particle-formation and matrix-formation steps three possible synthetic strategies are studied. The freeze-drying technique is used for dehydration of the gel precursor to avoid the redistribution of a soluble component. Heat treatment or chemical modification of the cryogel yields the desired nanomaterial.
Robust Microporous Molecular Frameworks Which Retain Structural Integrity Upon Template Loss
Authors: Kepert C. J. , Rosseinsky M. J. , Hesek D. , Beer P. D. 
Published: April 2011

AbstractRetention of the void space upon loss of the solvent template is directly demonstrated using single-crystal X-ray diffraction for molecular frameworks constructed using both hydrogen and co-ordinate bonds. While the co-ordination polymer remains rigid upon desolvation, the extra flexibility in the hydrogen-bonded framework, due both to the large number of redundant hydrogen-bonding donor and acceptor groups and the possibility of significant φ-φ stacking interactions within the framework, lead to a significant structural and symmetry change while retaining significant void volume. Molecular modelling techniques are used to understand and predict the guest uptake chemistry of these host frameworks.
Graphite Intercalation Compounds Prepared in Hydrofluoric Acid
Authors: Zhang X. , Lerner M.M. 
Published: April 2011

AbstractThe graphite intercalation compounds CxC8F17SO3 · yF and CxN(SO2CF3)2 are readily prepared under ambient conditions in 48 % hydrofluoric acid, using the oxidant K2MnF6. The product compositions are evaluated by mass uptake, TGA, and elemental analysis. PXRD peak position and peak width analyses indicate that the stable product CxC8F17SO3 · yF is obtained after 50 h. (x ≅ 18, y ≅ 4) and is comprised of a solid solution of stage 2 and 3. This material can be obtained within 1 h. at 50 °C. The addition of up to 83 vol. % conc. HNO3 or 17 % fuming H2SO4 produces a stage 2 intercalation compound within hours. Stage 2 CxN(SO2CF3)2 (x = 37) is obtained within 15 minutes under ambient condition in HF. The anion orientations for these GICs are evaluated by structural refinement. Larger anions containing –SO2CnF2n+1 substitutents can also be intercalated, although the reaction rates are very slow.
Study of The Hydrothermal Synthesis of Gallium Phosphates Using in Situ Time-Resolved X-Ray Diffraction
Authors: Walton R.I. , Loiseau T. , Francis R.J. , O'Hare D. , Férey G. 
Published: April 2011

AbstractThe hydrothermal crystallisation (130-180 °C) of three-dimensional open-framework gallium and aluminium oxyfluoro-phosphates with the ULM-3 and ULM-4 structures have been studied in situ for the first time. The in situ energy-dispersive X-ray diffraction method has allowed the formation of the crystalline products to be observed under hydrothermal conditions The integrated areas of the strongest Bragg reflections has allowed quantitative kinetic data to be extracted. The effect of temperature, phosphorus source, templating agent have been investigated. The nature of phosphorus source in the reaction mixture has been found to affect dramatically the course of reaction for certain combinations of amine and temperature. Previously unobserved transient crystalline phases have been seen during the production of ULM-3 gallium phosphates when P2O5 or polyphosphoric acid are used. The formation of these intermediates affects the kinetics of product growth. In the case of the aluminium ULM-3 materials reaction always proceeds via a crystalline intermediate whatever phosphorus source is used. The ULM-4 framework materials are found to always crystallise directly with no evidence for any intermediates. Kinetic data for each system have been modelled using standard solid-state chemistry expressions, and these calculations indicate the reactions to be diffusion controlled.
Redox Processes in Polynary Copper Oxides and Copper Oxide / Mesoporous Silica Composites
Authors: Reller A. , Ebbinghaus S. , Köhn R. , Fröba M. , Sazama U. , Fortunato P. 
Published: April 2011

AbstractDynamic redox processes in different complex copper oxides and oxide / mesoporous silica composites are characterized. In the spinel-type CuxMn3.xO4 the atomic and electronic structures are described with respect to the reversible process Cu2+ + Mn3+ ⇒ Cu3+ + Mn4+, the crucial dynamic equilibrium for the catalytic oxidation of CO to CO2 at ambient temperatures. A comparison with the perovskite-type LaCu1-xMnxO3-δ is presented. In the K2NiF4-type La2-xSrxCu1-yRuyO4-δ the electronic structure is characterized with respect to the equilibrium Cu2+ + Ru5+ ⇒ Cu3+ + Ru4+. Analogous redox processes are characterized in composite compounds made up of copper oxides inserted in mesoporous MCM-type silica. Due to their structural order in the nanoscopic range, the investigation of these materials required multiple, complementary characterization methods, i.e. X-ray diffractometry, thermal analysis, scanning and transmission electron microscopy, magnetic measurements, XPS, and particularly X-ray absorption spectroscopy (EXAFS / XANES) measurements.
The Hydrothermal Synthesis of KzMnO2 in the Presence of Citric Acid
Authors: Sharma Pramod K. , Moore Gregory J. , Whittingham M. Stanley 
Published: April 2011

ABSTRACTKxMnO2 exhibits a layered structure that provides attractive properties as a cathode material for secondary Li batteries. Therefore, in the present study, our attention was paid to the hydrothermal preparation of highly homogenous KxMnO2 in presence of citric acid. Out X-ray diffraction and SEM studies indicated that the final product markedly change the phase and morphology on vary the concentration of citric acid. The prepared products have also studied with the help of TGA and DTA. EDS and DCP made the chemical analysis of the compounds. The impedance data of the materials were explained in terms of the compounds formed.
First Principles Calculations for Lithiated Manganese Oxides
Authors: Prasad R. , Benedek R. , Thackeray M. M. , Wills J. M. , Yang L. H. 
Published: April 2011

ABSTRACTFirst principles calculations within the local-spin-density-functional theory (LSDFT) framework are presented of densities of electronic states for MnO, LiMnO2 in the monoclinic and orthorhombic structures, cubic LiMn204 spinel and λ-MnO2 (delithiated spinel), all in antiferromagnetic spin configurations. The changes in energy spectra as the Mn oxidation state varies between 2+ and 4+ are illustrated. Preliminary calculations for Co-doped LiMnO2 are presented, and the destabilization of a monoclinic relative to a rhombohedral structure is discussed.
Sulfone Containing Clay Electrolytes and Their Potential for Li-Rechargeable Batteries
Authors: Moore Gregory J. , Whittingham M. Stanley 
Published: April 2011

ABSTRACTClays have been synthesized and several types of molecules have been intercalated into them to enhance their ionic conductivity. The clay has the molecular formula of Litaeniolite, Li(Mg2Li)Si4O10F2, and the inserted molecules include PEO and two varieties of sulfone, tetramethylene sulfone and ethylmethyl sulfone. These have been made in the interest of electrolytes in lithium secondary batteries in order to produce a truly solid state cell. The products have been thoroughly characterized by x-ray diffraction to verify the uptake of the molecules into the layers, thermal analysis to observe the stabilization of the intercalated molecules, along with impedance measurements to test their conductivity.
Direct Observation of Xrd Redox Processes in TMO'S
Authors: Björk H. , Gustafsson T. , Thomas J.O. 
Published: April 2011

ABSTRACTAccurate XRD, often in combination with ND, has long been used to study electron density features in crystalline compounds. The method is particularly successful for light-atom systems in which the valence-to-core electron ratio is high. The same method is clearly applicable to the study of (typically) lithium insertion/extraction processes in TMO compounds; the greatest hinder has been the availability of sufficiently large single crystals, which do not then disintegrate into micron-size particles during the reaction. The case of V6O13 is especially advantageous in this context, however: millimeter-size crystals can be grown by CVT methods, which do not then exhibit severe cracking on lithium insertion, probably as a result of the layer-like nature of the structure. A sequence of single-crystal phases have now been studied in this way (LixV6O13 for x= 0, 1.0, 2.0 and 3.0) following in situ electrochemical synthesis in the composite cathode of a <Li| PE |V6O13> half-cell. The resulting structures have been solved, and their associated electron-density distributions carefully analysed by so-called Hirshfeld deformation electron density refinement. The method would appear to provide meaningful information relating to oxidation state changes occurring on lithium-ion insertion.
Manganese Dioxides: Chemical-Structural Disorder, Electronic Properties, Electrochemical Activity and Proton Diffusivity
Authors: Poinsignon C.J. 
Published: April 2011

ABSTRACTSeveral synthetic and natural manganese dioxides (MD) are characterized in terms of chemical composition, structural disorder and electrochemical activity; semi conducting properties are examined on pressed powdered samples. The reactivity scale established between structural disorder and electrochemical reactivity is paralleled by semi conducting properties and proton diffusivity. Conductivity values of 0.15 S.cm−1for stoechiometric β-MnO2, 1.3 10−2, 2.5 10−2 and 3.7 10−2 S.cm−1 for the defect dioxides, respectively Synthetic-Ramsdellite, CMD and EMD are measured. Proton diffusivity study by EIS provides, for low reduction rate, diffusion coefficient D values varying from 10–15 cm2/s value to 10−16 for the best reactive forms EMD and CMD; for NMD and β-MD, D is respectively 10−16 and 10−21 cm2/s. Redox reversibility is obtained around 1.3V (vs Hg.HgO) for EMD for a one electron reduction in [KOH] <IM; at -0.4V for a 2 electrons reduction in 9M KOH for Bi modified NMD.
Reactivity of Carbonaceous Anodes Used in Lithium-ion Batteries, Part I: Correlation of Structural Parameters and Reactivity
Authors: Nazri G. A. , Yebka B. , Nazri M. , Curtis D. , Kinoshita K. , Derwin Dave 
Published: April 2011

ABSTRACTCarbonaceous anodes are the most practical elecrode for application in lithium-ion battery, mainly due to their low cost, flexibility for modification to achieve high energy capacity and high rate capability, abundance and environmentally uniquencess. Despite superior advantages of carbonaceous anodes vs other alternative anode and metallic lithium, there is considerable reactivity of lithiated graphite with organic electrolytes, which is a major safety concern. In this work, we report the nature of gaceous species generated on various carbonaceous anodes during initial charge-discharge cycling. The correlation between structural parameters of carbonaceous materials and their irreversible capacity loss have been investigated. Structural parameters have been studied using x-ray diffraction, Raman spectroscopy, and scanning and transmission electron microscopy. We have found a direct correlation between crystal morphology, degree of disorder, degree of graphitisation and the irreversible capacity loss. There is also a direct correlation between the irrversible capacity loss and the volume of gas generated during initial charge- disharge cycling. Results also show the importance of removing adsorbed and trapped gases in addition to removal of bonded impurities, such as functional groups from carbonaceous electrode before fabrication of batteries.Particular attention is given on thermal analysis for different graphite compounds and the influence of different parameters and conditions: nature of graphite in term of specific surface area, degree of graphitization and the length of microcristallites, degree of intercalation, nature of electrolytes on irreversible capacity loss and volume of gases generated during the initial charge-discharge cycles.
Spectroscopic and Transport Properties of Lithium Salts in Ethylene Carbonate Based Mixed Solvents for Lithium Batteries
Authors: Nazri M. , Nazri G. A. , Aroca R. 
Published: April 2011

ABSTRACTElectrolyte solutions formed by the addition of lithium hexafluorophosphate (LiPF6) and lithium perchlorate (LiC104) to solvents obtained by mixing ethylene carbonate (EC) with propylene carbonate (PC) and dimethyl carbonate (DMC) were studied. The temperature dependence of conductivity, infrared and Raman spectra of the EC-DMC and PC-EC-DMC solvent electrolytes are discussed. The experimental and theoretical studies of characteristic vibrations of DMC are reported.
Use of Mössbauer Spectroscopy for the Characterization of Order/Disorder Phenomena in Tin(II) Containing Ionic Conductors and for Making Predictions Regarding Possible Electron Contribution to the Conduction
Authors: Dénès Georges , Madamba M. Cecilia , Muntasar Abdualhafeed , Peroutka Alena , Tam Korzior , Zhu Zhimeng 
Published: April 2011

ABSTRACTMössbauer spectroscopy has been seldom used for the characterization of ionic conductors. However, since the introduction of divalent tin in MF2 fluorites (M = Sr, Pb and Ba) to form MSnF4, PbSn4F10 or the Pb1−xSnxF2 solid solution, all of which have structures closely related to the fluorite type, results in an enhancement of the fluoride ion conductivity by up to three orders of magnitude, and since 119 Sn is the second best Mössbauer nuclide, it seems that the Mössbauer technique could provide useful information about how tin(II) modifies the fluorite structure and leads to such a tremendous enhancement of the fluoride ion mobility. The MF2/SnF2 systems contain some number of materials that show order/disorder phenomena (between M and Sn, and also between different fluorine atoms) which make it difficult to understand them from diffraction data only. Mössbauer spectroscopy has been invaluable in helping understand the local structure at tin. By probing the valence electronic structure of tin, we can also make predictions on the possible long range mobility of the tin(II) non-bonded electron pair, which would make the material an electronic conductor or a mixed conductor.
Preparation and Electrical Conductivity of Bismuth-Doped Antimonic Acids
Authors: Ozawa K. , Sakka Y. , Amano M. 
Published: April 2011

ABSTRACTBismuth-doped antimonic acids with the empirical formula Sb2O5·xBi2O3·nH2O (0 ≤ x ≤ 0.2) were prepared by reacting an H2O3, aqueous solution with Sb(O-i-C3H7)3and Bi(O-i-C3H7)3. X-ray diffraction confirmed that the anhydrous composites, Sb2O·xBi2O3(0 ≤ x ≤ 0. 1), are a single cubic Sb2O5phase, where the cubic cell parameter increases linearly from 10.277 to 10.380 Å with the bismuth content x. The electrical conductivity of the polycrystalline disks for Sb2O5·xBi2O3·nH2O (0 ≤ x ≤ 0.1) was evaluated by an ac impedance method at 19.5 °C under various conditions of relative humidity. The conductivity of Sb2O5·xBi2O3·nH2O with x = 0.1 was found to be high (1.0 × 10−3Scm−1) even at a relative humidity of 68.3%. There was a stronger humidity dependence than that of Sb2O5·xBi2O3·nH2O with x = 0.
Ionic Conductivities and Microstructures of CeO2:Y203 Solid Electrolytes
Authors: Tian Chunyan , Chan Siu-Wai 
Published: April 2011

ABSTRACTIonic conductivities of solid CeO2:Y203 electrolytes were systematically investigated as a function of dopant concentration and sintering temperatures. The highest lattice conductivity occurred at 6–8% dopant concentration, and maximum grain boundary conductivity was observed at 10% dopant concentration. The sintering temperature was found to have a significant effect on the conductivities of the pellets. The samples sintered at lower temperatures (T≤140°C) showed higher grain boundary conductivity than those sintered at 150°C; this was found to be related to size-dependent-impurity segregation and precipitation at grain boundaries. The grain boundary conductivities as related to the microstructure are discussed by adopting different grain boundary models. Solute segregation and oxygen depletion at grain boundaries, which have been suggested to be responsible for the grain boundary resistivities in these samples, were examined by a microanalytical technique for small-grain-size samples.
Copper-Conducting Nasicon-Type CuTi2(PO4)3 Glass-Ceramics for Application to a Novel O2 Sensor
Authors: Yamamoto K. , Kasuga T. , NOGAMI M. 
Published: April 2011

ABSTRACTFast Cu+-conducting ceramics containing NASICON-type CuTi2(PO4)3 and Cu3 (PO4)2 phases, which three-dimensionally interlock with each other, has been successfully prepared by the controlled crystallization of glass in the Cu-Ti-P-O system. The electrical conductivity of the glass-ceramic was ∼3×10−4Scm−1 at 300°C. The obtained glass-ceramics was applied to an oxygen-concentration cell operating at low temperature such as 100°C. The electromotive force (EMF) of the sensor showed good Nemstian response. The mechanism for O2 sensing is discussed in terms of the redox reaction between Cu+ ion in the dense glass-ceramic and O2 gas.
Trivalent Ion Conduction in the Scandium Tungstate-Type Structure
Authors: Imanaka N. , Kobayashi Y. , Tamura S. , Fujiwara K. , Asano T. , Okazaki Y. , Adachi G. 
Published: April 2011

ABSTRACTThe realization of a trivalent ion conduction in solids was successful by selecting the Sc2(WO4)3-type structure from the consideration of the mobile trivalent cations and the structure which decreases the electrostatic interaction between the migrating trivalent ionic species and the framework structure as much as possible. Among the rare earth tungstates, Sc2(WO4)3 (σ600°C=6.5× 10−5 S'cm−1, Ea=44.1 kJ.mo−1) was found to hold the most suitable size for the trivalent ion migration in the relation between the mobile ion size and the lattice volume. The ion conducting characteristics of rare earths were studied by means of both the polarization and dc electrolysis techniques. The mobile species was demonstrated to be the trivalent ions in the Sc2(WO4)3-type structure. By the dc electrolysis, the mobile ion species was definitely identified to be the trivalent ions in the Sc2(WO4)3-type tungstates. In addition, the demonstration of a macroscopic Al3+ ion conduction in the tungstate structure was directly accomplished.
High Reflectivity Modulation Electrochromic Windows
Authors: Gerouki A. , Goldner R.B. 
Published: April 2011

ABSTRACTIn this paper we report the fabrication of high reflectivity modulation electrochromic Windows (ECW's) which have exhibited a colored state reflectivity of more than 50% for the wavelength range of 1 to 2.5 µm with an average bleached state reflectivity of 20%. The transmissivity of these ECW's in the colored state was less than 5% and in the bleached state it averaged 60%. The materials employed were tungsten oxide (nominally WO3) for the first electrochromic electrode, lithium cobalt oxide (nominally LiCoO2) for the second, complementary, electrochromic electrode, lithium phosphorus oxynitride (Lipon) for the ionic conductor (electrolyte), and indium tin oxide (ITO) and indium oxide (In2O3) for the two transparent electronic conductors. The predicted and measured reflectivity of the ECW's were influenced by the first transparent conductor (TM) in relation to its thickness and optical properties. Devices without a TC1 exhibited the highest reflectivity modulation, It was also concluded that two of the main limitations to the degree of reflectivity modulation attainable with the ECW's were lithium insertion into TC1 and electronic transport through the electrolyte.
Light Emitting Electrochemical Cells as Mixed Ionic Electronic Conductors
Authors: Riess I. , Cahen D. 
Published: April 2011

ABSTRACTPolymer electrochemical cells have been reported to emit light. The current and light output increase rapidly with voltage, apparently beyond 2V. The polymer is an ionic conductor as well as an electronic (electron/hole) conductor, i.e. a mixed ionic-electronic conductor (MIEC).The I-V relations are explained here to be those of an MIEC of a particular defect model placed between two ion blocking electrodes. This MIEC defect model assumes a large concentration of mobile ions and small concentrations of electrons and holes. A p and an n region are formed in the MIEC. However, there is no space charge within the MIEC and it stays neutral. The resulting I-V relations are exponential. A good fit to the experimental data is obtained when electrode over-potential and heating of the polymer under current are taken into consideration.
Pd, Pt and ZrO2-Pt Films Prepared by Mocvd and Their Electrochemical Properties
Authors: De Oca J.A. Montes , Vargas J.R. , Godinez J. 
Published: April 2011

ABSTRACTPd, Pt and ZrO2-Pt films were prepared by metal organic chemical vapor deposition (MOCVD) as electrodes for zirconia solid electrolyte and their electrochemical properties were examined by impedance spectroscopy. Carbon containing films (Pt-C and Pd-C) consisted of agglomerated fine particles (2-5 nm in diameter) exhibit higher electrode conductivities than that of conventional Pt paste electrodes at temperatures below 873 K. The sintering of the fine particles and/or oxidation of impurity carbon or Pd spoil their electrochemical performance. On the other hand, two-phase ZrO2-Pt films show promise as electrode material for zirconia electrolyte at low temperatures (below 973 K) because of their higher conductivity than Pt paste electrodes and their thermal stability.