bluuebunny/crossref_metadata_2025_split huggingface dataset:
Monoliths for Partial Oxidation Catalysis
Authors: Schmidt L. D. , Dietz A. 
Published: April 2011

ABSTRACTMonolith catalysts are effective for partial oxidation reactions at high temperatures at contact times between 10−4and 10−2sec. We summarize results for three reactions: (1) syngas by direct oxidation of CH4, (2) olefins by oxidative dehydrogenation of alkanes, and (3) HCN by ammoxidation of CH4, and we consider what features of monoliths create optimal selectivity with high conversions. Monoliths used are noble metal films coated on ceramic foams, extruded ceramics, ceramic fibers, and woven Pt-10%Rh gauze catalysts. Effects of metals and geometries of the ceramics are ceramics are compared to show how these factors influence activity and selectivity.
Sol-Gel Strategies for Controlled Porosity Ceramic Materials: Thin Film and Bulk
Authors: Brinker C. Jeffrey , Sehgal Rakesh , Raman Narayan K. , Prakash Sai S. , Delatire Laurent 
Published: April 2011

ABSTRACTUsing sol-gel processing techniques it is possible to vary the condensation pathway over wide ranges to form primary species ranging in structure from oligomers to polymers to particles. The porosity of the corresponding dry gels depends on the size and structure of the primary species, the organization of these structures, often by aggregation, to form a gel, and the collapse of the gel by drying. This paper reviews these ideas in the context of forming thin film or bulk specimens. Several strategies are introduced to control porosity on length scales of interest for catalysis and catalytic membrane reactors: 1) aggregation of fractals; 2) management of capillary pressure; 3) surface derivatization; 4) relative rates of condensation and evaporation; 5) the use of organic templates and 6) sintering. These strategies are contrasted with the more traditional particle packing approach to preparing controlled porosity materials.
Effect of Prehydrolysis on the Textural and Catalytic Properties of Titania-Silica Aerogels
Authors: Miller James B. , Johnston Scott T. , Ko Edmond I. 
Published: April 2011

ABSTRACTA sol-gel based preparation of a mixed oxide allows considerable control over the extent of component mixing. When the reactivities of the alkoxide precursors are evenly matched, a homogeneously mixed sample can be produced; a large reactivity difference results in a segregated mixed oxide product. We have prepared and characterized two sets of mixed titania-silica aerogels, each covering the entire composition range. One set was made using silicon precursor prehydrolysis to minimize the reactivity difference and promote homogeneous component mixing; the second set was made without prehydrolysis.
Nickel Catalyzed Conversion of Activated Carbon into Porous Silicon Carbide
Authors: Moene R. , Schoonman J. , Makkee M. , Moulijn J. A. 
Published: April 2011

ABSTRACTHigh surface area silicon carbide (SiC) of 31 m2/g has been synthesized by the catalytic conversion of activated carbon. The thermal stability in non-oxidizing environments is shown to be excellent; no significant sintering has been observed after ageing in nitrogen for 4 hours at 1273 K. The presence of 2v% steam or the use of air results in SiC oxidation into SiO2 and considerable sintering at 1273 K. Air oxidation of SiC is shown to cause substantial SiC conversion, viz. 60 % after 10 hours at 1273 K. Complete conversion is achieved at 1080 K in about 100 days. This rate of oxidation agrees with reports on the oxidation of non-porous Acheson SiC and Chemical Vapour Deposited SiC coatings. The use of SiC based catalysts is, therefore, limited to (1) high temperature gas phase reactions operating in the absence of oxidizing constituents (O2 or H2O) and (2) liquid phase processes at demanding pH. Syntheses of highly dispersed and highly loaded Ni/SiC catalysts are feasible by applying an ion-exchange technique, resulting in supported nickel particles of 4 nm.
Synthesis of Graphite Intercalation Compounds with Donor Species
Authors: GuÉrard Daniel , Nalimova Vera A. 
Published: April 2011

AbstractFor 15 years, the chemistry of the intercalation of donors species into graphite has beenlargely developed and a great number of new phases were discovered : over 100 if one takes into account the various stages and stacking, which involves different properties of the compounds for a given intercalate. Four new systems and synthesis methods were developed : intercalation of metallic alloys containing an alkali metal, ionic species (alkali metal hydrides, hydroxides and, even chlorides), alkali metals with oxygen (by addition to the metal of a small quantity of its peroxide M2O2), intercalation under high pressure of the alkali metal. Those new syntheses, still in progress, lead to compounds in which the first stages exhibit a fairly high intercalate/carbon ratio : from LiC2 to MC4 (M = Na, K, Rb or Cs) instead of LiC6 or MC8 obtained by classical methods.The increase of this ratio confers them interesting properties and possibilities of application, especially in the field of new materials for primary or secondary batteries.
The Carbon-Lithium Negative Electrode for Lithium-Ion Batteries in Polymer Electrolyte
Authors: Yazami R. , Deschamps M. 
Published: April 2011

AbstractSeveral types of carbonaceous materials are evaluated as negative electrodes for lithium storage in polymer electrolyte based cells operated at 100ºC. The corresponding faradaic efficiencies of the spherical cycle and the achieved reversible first capacity and rate capacity will be given. A meso carbon yielded a higher capacity than the theoretical 372 mAh/g. This is tentatively explained by the necessary enhancement of the carbon/polymer interfacial properties through the formation of C-Li-O bonding at the carbon surface and by the possible formation of multilayers of lithium on the external a,b planes of disordered carbons. The formation of the passivating layer on the carbon surface will be described.A lithium-ion type battery using coke and LiNiO2 as the negative and positive leads and POE-LiCIO4 was operated at 100ºC and cycled galvanostatically. Good reversible capacity was attained with the LiNiO2 electrode.
Transition Metal Oxides for Rocking-Chair Cells
Authors: Thackeray M. M. , Ferg E. , Gummow R. J. , Kock A. De 
Published: April 2011

AbstractTransition metal oxides have been evaluated extensively in the past as cathode materials for lithium cells. The major emphasis of recent research has been to develop lithium-ion or rockingchair cells that are assembled in the discharged state with a lithiated transition metal oxide cathode and a carbon anode. Although these cells are significantly safer to use than lithium cells with metallic lithium anodes, the possibility of depositing lithium at the surface of the carbon particles at the top of charge or at high rates of charge cannot be discounted. This paper discusses some recent developments in fabricating rocking-chair cells with transition metal oxide host structures as both anode and cathode, the anode providing a relatively low voltage vs. lithium and the cathode a relatively highvoltage vs. lithium. These cells avoid the reduction and oxidation of lithium during charge and discharge and, therefore, reduce the safety hazards of lithium cells. Improved safety is gained, however, at the expense of cell voltage and specific energy.
MorphÒlogy and Properties of Vanadium Oxide Xerogels and Aerogels
Authors: Katz B. , Liu W. , Salloux K. , Chaput F. , Dunn B. , Farrington G.C. 
Published: April 2011

AbstractThe high redox potential and ion insertion properties of vanadium pentoxide have made this material a viable cathode for secondary lithium batteries. The use of sol-gel methods to synthesize vanadium pentoxide and other transition metal oxides has been well studied as the technique represents a relatively simple approach for preparing thin films and powders. Although it is well known that sol-gel processing may be used to prepare high surface area aerogels, the research on transition metal oxides has been largely limited to xerogels. The present paper compares the properties, structures and morphologies of vanadate xerogels and aerogels.
Monte Carlo Study of Dispersive Transport in Glassy Electrolytes
Authors: Knödler D. , Pendzig P. , Dieterich W. 
Published: April 2011

AbstractA lattice-gas model is presented, where ions are diffusing in an energy landscape due to immobile, randomly placed counterions. All Coulombic interactions are taken into account.By Monte Carlo simulations we obtain the ac-conductivity, which shows strong dispersion in the form of power-laws. In a separate study we investigate a restricted model, where long-range diffusion is suppressed. These calculations suggest that the response at high frequencies can be interpreted in terms of highly correlated, local motions of dipolar character. Conductivity exponents n1 near unity or even exceeding unity arefound in that regime. We discuss the relationship of these results to experiments on ionic transport in alkali-doped network glasses.
Point Defects and Protonic Conduction in A3B'B”2O9 Compounds
Authors: Du Yang , Nowick A.S. 
Published: April 2011

AbstractWe have investigated the defect structure and protonic transport properties of nonstoichiometric complex perovskite-type compounds of the type A3B'1+xNb2-xO9-δ. where A and B' are both divalent ions. Protons are incorporated by treatment in H2O vapor and their presence is manifested by the appearance of an OH band in the IR spectra, as well as by the large increase in electrical conductivity to produce excellent protonic conductors, with lower activation energies. A non-classical isotope effect, in which the Arrhenius plots for D+ and H+ cross over, can be explained by a modification of the classical ART hopping theory.
Point Defects and Cation Diffusion in Cobaltous Oxide
Authors: Aggarwal Sanjeev , Dieckmann RÜdiger 
Published: April 2011

AbstractThe deviation from stoichiometry, δ, in Co1-δO was measured in-situ as a function of oxygen activity at temperatures between 1000 and 1400 ºC, using ahigh resolution microbalance. The experiments were conducted over the entire Co1-δO phase stability region at atmospheric pressure. The experimental results were analyzed with regard to the point defect structure and also in comparison with mass and charge transport data. Contrary to prior belief, it was found that the average mobility of the cationic defects and holes varied with their respective concentration.
Improved Oxide Ion Electrolytes
Authors: Feng Man , Goodenough John B. 
Published: April 2011

AbstractSystematic experiments on anion-deficient ABO3-δ perovskites are reviewed with a view to the development of a strategy for the design of improved oxide-ion electrolytes. Ba0.6 La0.4 1nO2.7 is shown to be competitive with the best yttria-stabilized zirconia and La0.9 Sr0.1 Ga0.8Mg0.202.85 to be a superior oxide-ion electrolyte suitable for fuel-cell applications.
Bi2Sr2M'2M”O11.5 [(M' = Nb, Ta) and (M” = Al, Ga)], Synthesis and Characterization of Oxygen-Deficient Aurivillius Phases
Authors: Kendall Kurt R. , Navas Carlos J. , Zur Loye Hans-Conrad 
Published: April 2011

AbstractOxygen-deficient layered bismuth oxides, Bi2Sr2M'2M”O11.5 [(M' = Nb, Ta) and (M” = Al, Ga)] were synthesized. Powder X-ray diffraction and transmission electron microscopy were usedto characterize the new materials' structures. The ionic conductivity was measuredusing impedance spectroscopy which indicated the existence of multiple conductive states in the new oxygen-deficient materials. Arrhenius plots of the conductivity showed discontinuities which were attributed to transitions between different conductive states. At 800ºC, Bi2Sr2Nb2GaO11.5 and Bi2Sr2Nb2A1O1.5, have ionic conductivities of 2.0×10−2 S/cm and 1.2×10−2 S/cm, respectively. Differential thermal analysis showed phase transitions in the oxygen-deficient materials. These transitionsoccurred at temperatures similar to those at which discontinuities were observed in the Arrhenius plots of the conductivity and are attributed to oxygen vacancy order/disorder transitions. The transference number was calculated for some of the samples by measuring both the EMF and the conductivity as a function of oxygen partial pressure. Under atmospheric conditions the new materials are predominantly ionic conductors.
Defect Spinels in the System Li—Mn—O. Chemistry and Lithium Insertion
Authors: Cras F. Le , Bloch D. , Anne M. , Strobel P. 
Published: April 2011

AbstractSpinel phases Li-Mn-C with Li/Mn ratios between 0.35 and 0.8 were synthesized. The relationships between composition, manganese valence, vacancy fraction and electrochemical capacity are described using a new composition-valence phase diagram. Electrochemical performances in lithium batteries are compared. The best materials showed constant capacit> 140 Ah/kg in the range 3.5/2 V in liquid electrolyte batteries up to 20 cycles, without the usual capacity drop observed in stoichiometric LiMn204.
Ionic Conductivities of Lithium Phosphorus Oxynitride Glasses, Polycrystals and Thin Films
Authors: Wang B. , Bates J. B. , Chakoumakos B. C. , Sales B. C. , Kwak B. S. , Zuhr R. A. , Robertson J. D. 
Published: April 2011

AbstractVarious lithium phosphorus oxynitrides have been prepared in the form of glasses, polycrystals, and thin films. The structures of these compounds were investigated by X-ray and neutron diffraction, X-ray photoelectron spectroscopy (XPS), and high-performance liquid chromatography (HPLC). The ac impedance measurements indicate a significant improvement of ionic conductivity as the result of incorporation of nitrogen into the structure. In the case of polycrystalline Li2.88PO3.73N0.14 with the γ-Li3PO4 structure, the conductivity increased by several orders of magnitude on small addition of nitrogen. The highest conductivities in the bulk glasses and thin films were found to be 3.0 × 10-7 and 8.9 × 10-7 S-cm-1 at 25°C, respectively.
Synthesis and Lithium Intercalation Properties of a Layered Lithiated Manganese Oxide with Rancieite Type
Authors: Leroux F. , Guyomard D. , Piffard Y. 
Published: April 2011

AbstractThe 2D lithiated manganese oxide with Rancieite-type structure (lithium phyllomanganate), synthesized via a soft chemistry route (T≤60ºC) is hydrated at room temperature and can be dehydrated progressively by a thermal treatment. This compound and a series of samples obtained after annealing at different temperatures were characterized and studied for their electrochemical lithium intercalation properties. They are poorly crystallized, with however the advantage of a manganese oxidation state very close to 4, a mustto get high specific capacity. Their chemical characterization was achieved after gathering results obtained from complementary techniques such as AAS, redox titration, TGA and XPS measurements. Special care was taken for the chemical characterization of electrode compositions effectively used in the electrochemical cells.Electrochemical lithium intercalation was systematically studied for the series of samples, when starting in charge or in discharge after assembly of the Li battery. The electrochemical behavior is discussed in relation with the manganese average oxidation state and the interlayer water content. Materials of the series showing the larger specific capacities were further examined on the application point of view, for their reversibility, cyclability and high rate capability upon Li intercalation.This work shows that the anhydrous material which is obtained at 300ºC, with the composition Li0.42MnIII0.20MnIV0.8002.11, is a promising rechargeable layered manganese dioxide material.
Non-Crystallizing Molten Salt and Ionic Rubber Electrolytes with Wide Electrochemical Windows
Authors: Xu K. , Angell C. A. 
Published: April 2011

AbstractNew realizations of the type of ambient temperature lithium ion conducting electrolyte introduced at this symposium two years ago are given and a 5 volt electrochemical window, absent from the earlier examples, is demonstrated. The new systems satisfy the criteria for “ionic oils” though their conductivities, - 10-3 S cm-1, are smaller than desirable.
Xafs Studies of Polymer Electrolytes
Authors: Bandara H M N , Linford R G , Latham R J , Schlindwein D W S 
Published: April 2011

AbstractBecause of the procedures associated with the deconvolution of the data present in an EXAFS spectrum, the experimental XAFS spectra also include both the edge and XANES regions. It is possible to obtain additional structural and chemical information from the data associated with these regions of the XAFS spectrum and in this work we have re-examined the XAFS spectra for a series of polymer electrolytes. These spectra were originally recorded for EXAFS analysis. The XANES spectra for PEOn:CaBr2 electrolytes confirm that the behaviour of calcium polymer electrolytes appears to be very different from that of other divalent based electrolytes. We have also examined the edge features for PEO8:NiBr2 samples which were subject to different thermal histories and evidence for phase separation is presented.
Lithium-7 NMR Studies of Li1−xCoO2 Battery Cathodes
Authors: Ouyang B. , Cao X. , Lin H.W. , Slane S. , Kostov S. , Denboer M. , Greenbaum S.G. 
Published: April 2011

AbstractLithium-deficient cathode materials Li1-xCoO2 where x = 0.1, 0.4 and 0.6 were prepared electrochemically from the stoichiometric parent compound (x = 0.0).The materials were observed to be air-stable, and x-ray diffraction characterization yielded good agreement with the in situ studies of Dahn and co-workers, regarding changes in lattice parameters. In addition to both static and magic angle spinning (MAS) 7Li NMR, measurements, the samples were investigated by EPR and cobalt K-edge NEXAFS. The removal of Li is accompanied by compensating electrons from the Co d-orbitals, asevidenced by both shifts in the NEXAFS peak and the observation of EPR signals due to spins localized on the Co ions. These spins, in turn, result in dramatic 7Li chemical shifts (89 ppm for x = 0.6) and line broadening. Whereas MAS analysis of Li0.9CoO2 indicates two magnetically inequivalent Li sites, the spectra becometoo broad to resolve different sites for higher values of x. Finally NMR linewidth and spinlattice relaxation measurements as a function of temperature suggest a modest increase in Li+ ion mobility for Li-deficient samples as compared to the parent compound.
The Li-Ion Technology: Its Evolution From Liquid to Plastic
Authors: Tarascon J.M. , Schmutz C. , Gozdz A.S. , Warren P.C. , Shokoohi F.K. 
Published: April 2011

AbstractIn 1992, Bellcore researchers demonstrated the feasibility of a liquidelectrolyte Li-ion system based on the Li1 + xMn2O4/C redox couple which presents cost and environmental advantages over the LiCoO2/C system. However, neither of these systems are free of the risk of electrolyte leakage. To address this problem, we investigated various means of trapping the liquid electrolyte in a polymer matrix and developed the first practical plastic Li-ion battery. In this paper we compare the performance and scaleability of this technology to those of its liquid Li-ion counterpart. Based on the “hybrid polymer” concept, this battery exhibits excellent cycle life (more than 2500 cycles) and good rate capabilities (the battery can deliver 95% of its total capacity at a 1C discharge rate). This technology is compatible with various positive (LiMn2O4, LiCoO2 and LiNiO2) and negative (carbon, graphite) electrode materials.
Vapor Deposition of Thin-Film Y-Doped ZrO2 For Electrochemical Device Applications
Authors: Chung Brandon W. , Brosha Eric L. , Brown David R. , Garzon Fernando H. 
Published: April 2011

AbstractThe growth of high-quality, pin-hole free, ytrrium doped ZrO2 thin films is of great interest for a variety of electrochemical applications such as fuel cells and oxygen gas separation devices. In the work, we have grown polycrystalline thin films of ytrrium doped ZrO2 on thick porous Al2O3 substrates in multilayer La1-xSrxMEO3/YSZ/La1-xSrxMEO3 (ME = Mn, Co) configurations using a combination of single-target RF magnetron sputtering and electron beam physical vapor deposition techniques. The structure and morphology of these films have been studied using X-ray diffraction, and Scanning Electron Microscopy techniques. The ionic conductivity of the thin films has been measured using AC impedance analysis.
Image-Based Characterization of Fracture Surface Roughness
Authors: Abell A.B. , Lange D.A. 
Published: April 2011

AbstractAnalysis of images from SEM, optical and confocal microscopes provides insight into the roughness of fracture surfaces of cement-based materials. Several techniques including 3D surface reconstruction and 2-D vertical contour analysis are compared. Roughness parameters and fractal dimensions are computed to describe the degree of tortuosity of the fracture surface. The tortuosity of the surface (i.e. crack path) is an aspect that has not been adequately integrated into fracture mechanics models of cement-based materials. Topographic maps from confocal microscopy reveal orientation of the crack front throughout the fracture process, allowing analysis of mixed-mode character of nominally mode I fracture. These techniques allow quantification of microstructural parameters to be linked to material properties.
A Re-Evaluation of Hardened Cement Paste Microstructure Based on Backscatter Sem Investigations
Authors: Diamond Sidney , Bonen David 
Published: April 2011

AbstractBackscattered electron imaging of polished cement paste specimens permits a re-evaluation of structural details of hydrated cement paste at the gim level. The primarily microstructural units comprise a highly porous groundmass and large distinct grains (“phenograins”) set in it. The groundmass is composed of several kinds of fine particles, with a significant content of easily detected gross pores. Phenograins are primarily large clinker grains hydrating in-situ, but may be distinct deposits of CH, or may be mineral admixture grains. Detailed EDS analyses indicated that hydrating cement in phenograins has a highly consistent composition, interpreted as C-S-H with a small but regular incorporation of sub-jim CH and calcium monosulfoaluminate. Groundmass particles are highly variable in composition, but appear to consist of C-S-H with variable and occasionally major contents of other hydration products on a sub-μm scale. Incorporation of fly ash does not appear to change the basic microstructure, but silica fume incorporated with superplasticizer drastically modifies the character of the groundmass. Some attempts at quantification of these features by application of image analysis are briefly described.
Sem Observation of the Influence of Sucrose and Koh on Formation of Sulphoaluminate Hydrates of a Cement Clinker During the Early Hydration
Authors: Peiming Wang , Peifen Xia , Zhiyuan Chen 
Published: April 2011

AbstractThe morphology of early hydrates of a cement clinker was studied by SEM and EDS. The hydrates were formed on thin plates cut from the clinker and immersed in a solution containing Ca(OH)2, CaSO4·2H20, and varying amounts of sucrose and KOH. The results show the different influences of sucrose and of KOH on the formation of the hydrates, in particular on the crystallization of AFt. The sucrose plays a leading role, and altered the time of primary formation of AFt and its morphology. KOH did not. In CaSO4·2H20 saturated solution without sucrose, regardless of the presence or absence of Ca(OH)2, the foil -like hydrates, CxAHy are formed as the first result of reaction of C3A with water. Then CxAHy reacts with CaSO4·2H20 to form AFt. However, in the presence of sucrose the C3A reacts directly with CaSO4·2H20 to form AFt. It is supposed that sucrose acts as a catalyst for the formation of AFt crystals. During the early stage of cement hydration, AFt crystals appear to form by both topochemical and by through-solution reaction mechanisms.