bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and Al K-Edge Xanes Investigation of Mesostructured Aluminophosphates
Authors: Twemann M. , Fröba M. , Wong J. 
Published: April 2011

AbstractWe report on the synthesis of lamellar mesostructured aluminophosphate composites which contain variable relative amounts of aluminium oxide species in the core regions of the lamellae; this is investigated quantitatively by Al K-edge XANES spectroscopy. Templating is achieved by the utilisation of monododecyl phosphate surfactant. If no phosphorous source (such as H3PO4) is used for the synthesis, the phosphate head groups of the surfactant become incorporated into the inorganic network to form similar lamellar aluminophosphate structures. Thus, the surfactant serves as both template and reactant.
Processing and Properties of Amorphous Manganese Dioxide Formed by Sol-Gel Procedures
Authors: Xu Jun John , Passerini Stefano , Owens Boone B. , Smyrl William H. 
Published: April 2011

ABSTRACTSol-gel derived amorphous manganese dioxide (a-MnO2) showed extremely high reversible lithium intercalation capacity. The composition and structure of the material were modified by heating at different temperatures. Cycling performance of the modified samples suggests that lowering the water content in the material is beneficial, while introducing crystallinity is detrimental, to its cyclability. A novel double-solvent-exchange process was tried for the processing of the material. Preliminary results indicated significant improvement in the reversibility of the insertion/release cycles.
π-Stacking in Conjugated Polymers and Oligomers: A Structural and Spectroscopic Study
Authors: Curtis M. David , Blanda Wendy , Politis Jeffrey K. , Francis Anthony H. , Lee Jihoon , Kampf Jeff W. , Gonzalez-Ronda Lebzylisbeth , Martin David C. 
Published: April 2011

ABSTRACTRegioregular, alkyl-substituted poly(heteroaromatics) tend to crystallize in π-stacked structures as opposed to the herringbone pattern characteristic of non-substituted, planar aromatic molecules, e.g. sexithiophene. π-Stacking, favored by the crystallization of the sidechains, induces planarity in the conjugated backbone. The increased planarity causes a large (50-100 nm) shift in λmax (abs.) compared to the solution phase in which the backbone is twisted out of coplanarity, π-Stacking is a form of ground state aggregation that causes “fine structure” on the absorption peak. Excitation into the aggregate states rapidly leads to the formation of excimers as shown by the excitation spectra. In -stacked polymers, photoluminescence is almost entirely from the excimer states.
Low Cost Filled Thermostable Ionomer Membrane for P.E.M.F.C.
Authors: Poinsignon C. , Amodio I. , Foscallo D. , Sanchez J.Y. 
Published: April 2011

ABSTRACTA filled ionomeric membrane was achieved by dispersing phosphatoantimonic acid H3Sb3P2014, ×H20 (H3) in a Sulfonated PolySulfone (SPS) solution [1]. Water up-take is higher for filled than unfilled membrane as well as Protonic conductivity which is larger than that expected from the overall calculated concentration in charge carriers : a conductivity value of 0.135 S.cm−1 was gained at 50°C under 1003% Relative Humidity (HR) for a 1.6 meq.g−1 cationic exchange capacity (cec) SPS filled with 8% in H3 against 0.06S.cm−1 for an unfilled one. Mechanical measurements on the wet membrane shows the plasticizing effect of sulfonation, water and of the filler content which simultanously reinforced the cohesion of the membrane.
How Unique are the Microstructure and the Electrical Properties of Nanocrystalline Ceramics?
Authors: Knauth P. , Tuller H. L. 
Published: April 2011

ABSTRACTA literature overview on microstructural and electrical properties of nanocrystalline ceramics is given. Space charge effects in nanosystems, especially thin-films and colloidal particles, are discussed from a theoretical point of view. Some common features of nanocrystalline ceramics are pointed out: nanoparticles present few extended lattice imperfections and the densification process begins at distinctly lower temperatures than that of coarse-grained ceramics. A significant decrease of grain boundary resistance occurs due to grain-size dependent dopant segregation, which leads also to an important increase of the apparent solubility of dopants in nanocrystalline materials. A number of studies confirm the theoretically expected reduction of the point defect formation enthalpy at interface sites, giving rise to significantly larger nonstoichiometry and electronic conductivity of nanocrystalline materials. Increased ionic conductivity has been found only in a limited number of cases, some of which remain controversial.
Mechanism of Cation Doping by the Soed 2 Method
Authors: Kamada K. , Matsumoto Y. 
Published: April 2011

ABSTRACTElectrochemical cation doping into the YBCO ceramics has been carried out using SOED 2 method (electro-bi-injection). The SOED 2 method consists of the Anode/M-β”-A1203/Ceramics/YSZ/Cathode electrolysis system, where the metal cation M and oxygen anion are simultaneously injected into the oxide ceramics so that electrical neutrality is maintained in the ceramics. YBa2Cu3Oy superconductor was used as the ceramics to be doped. In general, graded doping occurred at a relatively high temperature, because the migration rate of the oxygen anion is close to that of the metal cation in the grain boundaries of the ceramics at high temperature. As a result, the metal cation was graded on the anode side of the YBCO ceramics. The doping situation depended on the electrolysis temperature, the valence of the doped cation. The mechanism of the electro-bi-injection is discussed.
Oxygen Ion Conductivities of Rhombohedral Phases in the Ba-Sr-Bi Oxide System
Authors: Gökcen O.A. , Kim S. , Meen J.K. , Elthon D. , Jacobson A.J. 
Published: April 2011

ABSTRACTThe rhombohedral phase of the Ba-Bi-O system is known to be a good oxygen ion conductor. Previous studies on conductivity of that system have shown that there is a sudden increase in conductivity at the β2-β1 polymorphic transition. Therefore, the high temperature β2 phase is a very good anionic conductor with values up to 10−1-100 S/cm. In the Ba-Sr-Bi-O system, the rhombohedral phase that contains Ba and Sr coexists with BaBiO3. Several specimens of the rhombohedral phase with different [Ba]-[Sr] ratios were synthesized. Electron microprobe analysis was used to determine the chemical composition of each specimen and to ensure that it consisted of a monophasic assemblage. Results of X-ray powder diffraction experiments confirmed that each sample has a rhombohedral unit cell. Oxygen ion conductivities of these materials were measured using the 2-probe AC Impedance technique over the 320-730°C temperature range. In each case, a sudden increase in conductivity indicates temperature range of the polymorphic transition. Exchange of the smaller cation Sr for Ba makes the transition temperature increase almost in a linear manner. Conductivities of all β2 polymorphs at a given temperature are very similar to conductivities of Ba-Bi-O and Sr-Bi-O β2 polymorphs. Conductivities of all β1 polymorphs are also similar. Apparently, the nature of the alkaline earth present has only slight influence on conductivities of these phases.
Hydrothermal Synthesis and Properties of Ce1−xMxO2-δ(M = La, Bi, Sm, Pr, Tb) Solid Solutions
Authors: Greenblatt M. , Shuk P. , Huang W. , Dikmen S. , Croft M. 
Published: April 2011

ABSTRACTA systematic study of hydrothermally prepared Ce1−x,MxO2−δ, (M= Sm, Bi, Pr, Tb; x= 0-0.30) solid solutions, promising materials for application in solid oxide fuel cells and oxygen membranes is presented. Ultrafine particles of uniform crystallite dimension, ∼ 20 nm can be formed in 30 min. under hydrothermal conditions (260°C, 10 MPa). The small particle size (20-50 nm) of the hydrothermally prepared materials allows sintering of the samples into highly dense ceramics at 900-1350°C, significantly lower temperatures than 1600-1650°C required for samples prepared by solid state techniques. The solubility limit of Bi2O3, in CeO2, was determined to be around 20 mol. %. The maximum conductivity, σ600°C ∼ 4.4 × 10−3 S/cm with Ea = 1.01 eV, and σ600°C = 5.7 × 10−3 S/cm with Ea ≈ 0.9 eV was found at x= 0.20 and x= 0.17 for Bi and Sm, respectively. In the Ce-Pr/Tb oxide systems, in addition to the high oxide ion conductivity, electronic conductivity occurs through the hopping of small polarons by a thermally activated mechanism (electron hopping from the Pr3+/Tb3+ to a neighboring Pr4+/Tb4+ ion).
Development of Mixed-Counducting Ceramics For Gas Separation Applications
Authors: Balachandran U. , Ma B. , Maiya P.S. , Dusek J.T. , Picciolo J.J. , Guan J. , Dorris S.E. , Liu M. 
Published: April 2011

ABSTRACTMixed-conducting oxides are used in many applications, including fuel cells, gas separation membranes, sesors, and electrocatalysis. This paper describes mixed-conducting ceramic membranes that are being developed to selectively remove oxygen and hydrogen from gas streams in a nongalvanic mode of operation (i.e., with no electrodes or external power supply). Because of its high combined electronic/ionic conductivity and significant oxygen permeability, the mixed-coducting Sr-Fe-Co oxide (SFC) has been developed for high-purity oxygen separation and/or partial oxidation of methane to synthesis gas, i.e., syngas, a mixture of carbon monoxide and hydorgen. The electronic and ionic conductivities of SFC were found to be comparable in magnitude are presented as a function of temperature. The oxygen flux through dense SFC tubes during separation of oxygen from air is compared with the oxygen flux during methane conversion.Unlike SFC, in which the ionic and electronic conductivities are nearly equivalent, BaCe0.80Y0.20O3 (BCY) exhibits protonic conductivity that is significantly higher that its electronic coductivity. To enhance the electronic conductivity and increase hydrogen permeation, metal powder was combined with the BCY to form a cermet membrane. Nongalvanic permeation of hydrogen through the cermet memebrane was demonstrated and characterized as a function of membrane thickness. A sintering aid was developed to avoid interconnected porosity in and improve the mechanical properties of the cermet membrane.
Surface Oxygen Exchange Kinetics and Oxygen Diffusion Rates in Ysz Single Crystals
Authors: Joos N.I. , van der Heide P.A.W. , Liu J.R. , Christoffersen R. , Chu W.K. , Mims C.A. 
Published: April 2011

ABSTRACTIsotope exchange with C18O2 followed by depth profiling analysis was used to study surface exchange and bulk diffusion of oxygen in single crystal ((100) surface orientation) yttria-stabilized zirconia (YSZ) in the temperature range 250°C - 350°C. The depth profiles, which were obtained using 18O(ρ,α)15N nuclear reaction analysis (NRA) and secondary ion mass spectrometry (SIMS), reveal both the bulk oxygen diffusion coefficients (D) and surface exchange coefficients (k). Bulk oxygen diffusion coefficients are consistent with an extrapolation to lower temperature of previously published results with an activation energy of 114 kJ/mol (1.2 eV). The surface exchange rates, however, depend strongly on the gas exchange species. Much higher exchange rates are observed with C18O2 than with 18O2 (over four orders of magnitude when compared to an extrapolation to lower temperatures of previously published results) with a measured activation energy of 152 kJ/mol (1.6 eV). This faster surface exchange rate enabled measurable 18O tracer profiles to be generated at lower temperatures than previously reported, further contributing to the understanding of YSZ material properties and bringing to light a possible order/disorder transition similar to that previously observed at 650°C.
Commercial Graphites for Li-Ion Battery Applications
Authors: Siapkas D.I. , Hatzikraniotis E. , Mitsas C.L. , Terzidis D. , Zorba T. , Moumouzias G. , Papadopoulos I. 
Published: April 2011

ABSTRACTIn this work we have examined different types of synthetic graphites (SFG and KS types) that have different morphology and particle sizes. In our analysis we examined the incremental capacity (dC/dV), which shows a series of peaks that correspond to potential plateaus. This approach enable us to identify the processes involved (formation of SEI, Li+ intercalation or de-intercalation, etc.). Our analysis was mainly concentrated on the first lithiation, in an attempt to specify the origin of the capacity loss related to each type of synthetic graphite.
Novel Design and Fabrication of Thermal Battery Cathodes Using Thermal Spray
Authors: Ye Hui , Strock Chris , Xiao T. Danny , Strutt Peter R. , Reisner David E. , Guidotti Ronald A. , Reinhardt Frederick W. 
Published: April 2011

ABSTRACTLi-Alloy/FeS2 thermal batteries are the predominant thermal battery chemistry today. Conventional electrodes are fabricated by cold pressing of powders. A better means of providing thin electrodes would dramatically increase volumetric and gravimetric energy densities and cost efficiency of thermal batteries. In this study, experiments were conducted on fabricating the cathode via high-velocity oxygen-fuel (HVOF) and dc-arc plasma thermal spray technique. The deposited films were characterized by cross-section examination using Scanning Electron Microscopy (SEM) and X-ray Diffraction. The thermal decomposition of pyrite was suppressed by a proprietary additive. The electrochemical test results showed that pyrite cathodes prepared by dc-arc plasma spraying with additives demonstrated better performance compared traditional pressed-powder electrodes.
Molybdenum and Vanadium Oxide Polycrystalline Films: Properties and Application to Lithium Microbatteries
Authors: Yebka B. , El-Farh L. , Julien C. , Nazri G.A. 
Published: April 2011

ABSTRACTWe report on the growth of molybdenum and vanadium oxide films, i.e., MOO3, V205, and V6013, and their application as positive electrodes in lithium microbatteries. We have characterized various polycrystalline samples and studied how their structural and electrical properties are affected by the different preparation conditions. The highest quality films were grown on silicon substrate maintained at 250°C and annealed at 300°C. It is shown that the growth conditions play an important role in the electrochemical properties of the film. Both thermodynamic and kinetic parameters are strongly dependent on film morphology and stoichiometry. Microbatteries fabricated with cathodes formed at moderate temperature have shown a volumetric capacity about 80 μAh/μm/cm2. The cells exhibit a monotonous discharge profile indicating that the cathode materials remain single phase even for a large degree of intercalation.
Propylene Combustion on Lanthanum Perovskites
Authors: Zenteno R. , Vicente L. , Viveros T. 
Published: April 2011

AbstractThe catalytic activity of lantane perovskytes in the combustion of propylene was studied. The catalysts were LaFeO3, LaNiC3, LaCoO3, La2-xSrxNiO4and La1-xSrxCoO3where x is the amount of Sr substitution. Below 400°C the only products are CO2and H2O, and above 400°C besides the total oxidation products, acroleine, acetaldehyde acetone and other partial oxidation products were obtained. The substitution of La by Sr improves the catalytic behaviour.
Preparing Monodispersed Hydrogel Microspheres and Microcapsules
Authors: Senuma Y. , Lowe Ch. , Zweifel Y. , Hilborn J. G. , Marison I. 
Published: April 2011

AbstractOur spinning disk atomization (SDA) can, relative to other existing techniques, produce micronsized particles of very narrow size distribution. The aim of this work is to present this technology for the production of alginate microspheres. We have atomized and gelled aqueous alginate solutions into very narrowly dispersed microspheres with sizes ranging from 300 to 600 μm. Here the interest is to design particles of a given size with a narrow size distribution and to show a new method of encapsulation using the SDA. The viscosity and flow rate contributions in the drop formation is qualitatively analyzed to show how it affects the droplet size. In addition, a technique for high degree of encapsulation will be presented. As an example, yeast has been used as a model system. The production of yeast loaded microspheres will show the potential of the technique for biotechnology applications. Such alginate beads could potentially serve as carriers for acitive substances or cells in large scale bioreactors.
Ultrasound -Triggered Drug Delivery with Contrast Imaging: Effect of Microencapsulation Method
Authors: Wheatley M.A. , El-Sherif D. , Basude R. , Shimp R. , Narayan P. 
Published: April 2011

AbstractA method for preparation of hollow, biodegradable polymeric microcapsules for use as contrast agents is described, and strategies for their use in concomitant imaging and drug delivery are outlined. Compared with X-ray or magnetic resonance imaging, diagnostic ultrasound is a safe, relatively inexpensive imaging technique, which allows the physician to view real-time images. Contrast agents are being developed which will greatly enhance the contrast of the received image, when injected into the patients blood stream. We have developed hollow polymeric CA based upon the ability to microencapsulate a solid core of ammonium carbonate which is then removed by decomposition and freeze-drying. The polymer poly D,L(lactide-co-glycolide) (PLGA) was chosen for it's FDA approval, and because it has the most rapid in vivo degradation of the α-hydroxy acid series. Spray dried and solvent extraction samples were used to test the concept of concomitant drug delivery and imaging. The method of fabrication had an important effect on the drug loading by adsorption, and on the amount of drug that was released when the capsules were insonated with ultrasound in the medical imaging range. Both were greater for spray dried samples. Both frequency and pressure of insonation also influenced release. The most dramatic increase in release was after 5 minutes for the 10 Mhz low (1.25 MPa) pressure insonation, which showed 316% greater release than control, a total of 1.89 mg.
Fiber Based Tissue Engineered Scaffolds for Musculoskeletal Applications:in VitroCellular Response
Authors: Laurencin Cato T. , Ko Frank K. , Borden Mark D. , Cooper James A. , Li Wan-Ju , Attawia Mohamed A. 
Published: April 2011

AbstractThe architecture of an engineered scaffold is an important consideration in the design of a synthetic tissue replacement. We have begun to explore the use of heirarchical fiber scale design ranging from microscale nonwoven to 3-D integrated fiber bundles in orthopaedic tissue engineering applications. The use of heirarchical fiber and design includes the following advantages: 1) the ability to tailor a broad spectrum of substrates with a wide range of mechanical properties, and 2) the ability to create structures capable of supporting cell proliferation as well as the micro-diffusion of nutrients throughout the structure. Using the bioresorbable copolymer, poly(D,L-lactide-co-glycolide) [PLAGA], we have fabricated two matrices based on fiber technology: 1) a microfiber non-woven mesh composed of 50:50 PLAGA and 2) a 3-dimensional braided structure composed of 5:95 PLAGA. These structures were examined by scanning electron microscopy [SEM] in anin vitrocell culture environment. Matrices were seeded with two types of cells (osteoblasts from neonatal rat calvaria and fibroblasts from the BALB/C cell line) to determine the effect of matrix architecture on cellular morphology and proliferation. SEM analysis of the microfiber matrix indicated a highly porous, structure resulting from the random arrangement of the microfibers. PLAGA fibers appear to have a range in diameter from approximately 2-7 μm. The 3-D braided matrix was shown to have a organized fibrous structure resulting from the 3-D braiding process. Examination of the attachment and proliferation of cells on the matrices revealed that cell morphology and proliferation patterns were dependent on cell type and matrix geometry. SEM analysis also indicated that cells responded dynamically to changes in structure due to the onset of degradation.
Putting Cells on Biomaterials to Engineer Cell Behavior and Tissue Repair, Taste, Touch and Force
Authors: Curtis A.S.G. , Wilkinson C.D.W. 
Published: April 2011

AbstractCells react to topography on the micro and nanoscale with a variety of consequences. These reactions can be used to advantage in controlling cell behavior on the surfaces of prostheses. This short paper examines two of the possible causes of these reactions, namely diffusion effects caused by the shape of the substratum and stretch reception by the cells.
Application of Conductive Polymers in Bone Regeneration
Authors: Shastri V.P. , Rahman N. , Martin I. , Langer R. 
Published: April 2011

AbstractThe role of electromagnetism in the physiology of the human body and in the healing process is well accepted. Electroactive polymers, such as electrically conducting polymers, by virtue of their susceptibility to either electrical, mechanical, optical or thermal phenomena, could be utilized as an interface between the external world and the physiological environment1. In this study we have evaluated the utility of polypyrrole (PPy)-a conductive polymer, as an interactive substrate for inducing differentiation in bovine bone marrow stromal cells (BMSC). It was observed, the PPy is an excellent substrate for BMSC attachment, proliferation and differentiation. Furthermore, an application of an electrical stimulus (ES) to BMSC via PPy substrate was found to enhance the osteogenic commitment of these cells.
Synthesis and Swelling Behavior of Hydrogels Based on Grafted Chitosan
Authors: Yazdani-Pedram M. , Retuert J. 
Published: April 2011

AbstractThe grafting of poly (acrylic acid) and /or acrylamide onto biopolymer chitosan were carried in order to obtain hydrogel materials- The grafting reactions were carried out in a homogeneous aqueous phase by using potassium persulfate in combination with ferrous ammonium sulfate as redox initiator system in the case of acrylic acid and potassium persulfate alone in the case of acrylamide The percentage of grafting was found to depend on the relative amount of monomer to chitosan, initiator and ferrous ion concentration, volume of the aqueous phase as well as reaction time and reaction temperature. In the case of acrylic acid a maximum grafting of 1800% was obtained, whereas with acrylamide the optimum percentage of grafting attained was near 400%. Evidence of grafting was obtained from comparison of FTIR of the grafted and ungrafted chitosan as well as solubility characteristics and swelling behavior of the products. The swelling degree of the grafted chitosan samples was determined at two different pH values. The percentage of grafting influenced the degree of swelling of the grafted chitosan, in different manner depending on the nature of the grafted chains, where values as high as 40 was observed.
An Investigation of the Release Properties of a Cationic Drug From a Hydrophobic Polyanhydride Matrix as a Function of Dissolution Medium
Authors: Ginsburg E. J. , Stultz T. D. , Stephens D. A. , Robinson D. , Tian Y. , LIU R. M. , Gao X. , Li L. C. , Quick J. E. , Chang H.-C. 
Published: April 2011

AbstractThe dissolution of a drug delivery system consisting of gentamicin sulfate in a hydrophobic polyanhydride matrix has been examined. The in vitro release of gentamicin is a function of the composition of the dissolution medium, with slower release in pH 7.4 buffer than in unbuffered water. This is consistent with an anion exchange taking place under conditions in which carboxylate polymer chain-ends form a poorly soluble salt with gentamicin, and sulfate is released into solution. Results of additional experiments probing this model are digeussed.