bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polybenzimidazoles/Phosphoric Acid Solid Polymer Electrolytes: Mechanical and Electrical Properties
Authors: Litt M. , Ameri R. , Wang Y. , Savinell R. , Wainwright J. 
Published: April 2011

ABSTRACTPoly (2,2'-(m-phenylene) 5,5'-bibenzimidazole), PBI and poly (2,5-benzimidazole), ABPBI, were cast into films and doped with phosphoric acid. Their mechanical properties were studied as a function of inherent viscosity and phosphoric acid content. The commercial PBI with an I. V. of 0.8 to 0.9 had relatively low elongation at break. It was fractionated; the higher the inherent viscosity the higher the modulus and elongation. At low phosphoric acid doping the modulus rose because a crystalline phase developed, and then dropped as more phosphoric acid was added. A second doping method produced films with high crystallinity and higher conductivity (0.02-.03 vs. 0.06-.08 S/cm) but poorer elongation than those made by doping a cast film in phosphoric acid. In order to get higher molecular weight films that could have better mechanical properties, we decided to polymerize 3,4-diaminobenzoic acid to ABPBI, an AB polymer for which I. V.'s of∼16 have been reported. After learning how to purify and polymerize the monomer, I. V.'s of 6–8 were easily obtained. Conductivities of the doped ABPBI films were as high as those of the best PBI films. With their high viscosities, the ABPBI films were much tougher and had better elongation than the doped PBI films.
A Comparative Study of Ionic Association in Poly(Ethylene Oxide)- MCF3SO3 Systems (M=Lithium and Sodium)
Authors: Frech Roger , Rhodes Christopher P. , York Shawna S. 
Published: April 2011

ABSTRACTA comparative infrared spectroscopic study of the local vibrational potential energy environment of the CF3SO3 (triflate) anion in the poly(ethylene oxide)-lithium triflate and poly(ethylene oxide)-sodium triflate systems is presented. Analysis of the crystalline stoichiometric compounds in the two systems identifies significant differences in the ionic association. Comparison of the relative percentages of the anionic species in the PEO-NaTf system at various concentrations suggests that crystalline compound formation may proceed through intermediate structures. A symmetry-based vibrational analysis is applied to the crystalline compounds.
Conductivity and Morphology of Hybrid Electrolytes Based on Blends of Pvdf With PEO-co-PPO Copolymers
Authors: Wang H.P. , Kejha J. B. , Yarovoy Y.K. , Wunder S.L. 
Published: April 2011

ABSTRACTHybrid film electrolytes with high room temperature conductivity have been prepared by casting solutions of PVDF-HFP copolymers with PEO-PPO block copolymers and PEO oligomers followed by activation of the polymer blend films in electrolyte solutions. The morphology and conductivity of these solid electrolytes were studied as a function of concentration, molecular weight and sequence order (in the case of PPO-co-PEO-co-PPO or PEO-co-PPO-co-PEO) of the PEO and PEO-PPO copolymers, and also of the casting solvent and evaporation rate of the casting solvent. Structural studies of PVDF-HFP/PEO and PVDF- HFP/PPO-co-PEO blend films (SEM, DSC) before activation with lithium salt electrolyte may indicate the occurrence of spinodal decomposition in the films during slow evaporation of the casting solvent. As a result of spinodal decomposition, an interpenetrating bi-continuous phase may evolve with microphase separation between PVDF-HFP and PPO-PEO phases, in which the PVDF phase provides mechanical support and the PPO-PEO phase pfovides a conductive path.
Study of Polyethers/Lii Systems by Addition of Alumina Ceramic Powders Prepared by Two Synthesis Methods
Authors: Ribeiro R. A. , Silva G. G. , Mohallem N. D. S. 
Published: April 2011

ABSTRACTComposites of alumina ceramic powders prepared by co-precipitation and sol-gel methods with Lithium Iodide based polymer electrolytes are described. The polyether matrices Poly(ethylene oxide) (PEO) and block copolymer Poly(propylene glycol-ethylene glycolpropylene glycol) (Triblock) with Lil in a ratio [O]:[Li] = 20:1 are used with up to 17 wt% of α-A1203 (medium grain size). Differential Scanning Calorimetry (DSC) studies show that Tg values for PEO based composites are higher whereas those for Triblock based composites are lower than the Tg value of the polymer/salt system.Conductivity measurements as a function of temperature show that there is no significant change in conductivity above the melting points for the electrolytes after α-A1203 powder addition (σ approximately 10−3 S.cm−l at 100°C), whereas better mechanical properties are observed for the ceramic reinforced samples. An increase in conductivity is obtained for the Triblock based composites near room temperature as a consequence of the lower melting point of these materials (26°C) in comparison to the PEO based composites (54°C).
Intercalation of Sodium-Potassium Alloys Into Graphite
Authors: Antoine L. , Gachon J.C. , Guerard D. 
Published: April 2011

ABSTRACTThe intercalation, at room temperature, of the sodium-potassium eutectic into graphite is performed, in a glove box under purified argon. It leads to a high alkali metal content powder. The annealing under vacuum, at 200°C for two days leads to a pure first stage compound whose formula is NaK2C12 with a color and a structure close to that of KC8. This phase is unstable and decomposes slowly in a mixture of KC8 and free alloy. However, this free alloy, which is liquid at room temperature, remains as inclusions between the graphene layers and the compound remains as a powder which can be useful for some applications when one needs large quantities of an alkali metal “solid” at room temperature, e.g. for gas purification (it reacts with oxygen and with moisture), for rapid and intense heat provider (it burns in air and the carbon is also participating to the heating), for ionic polymerization catalyst…
Mixed Ionic-Electronic Conduction of Na-Beta-Alumina Under the Conditions of a Potentiometric CO2Sensor
Authors: Näfe H. , Gollhofer S. , Aldinger F. 
Published: April 2011

ABSTRACTIt is shown that, on employing a practically relevant type of a potentiometric solid state CO2sensor comprising Na-beta-alumina as solid electrolyte and Na2CO3as gas sensitive electrode, the voltage response may be remarkably affected by electronic transference. This is in contradiction to what is commonly stated in the literature about the measuring properties of such a type of a sensor. On the other hand, the observation of a non-negligible amount of electronic conduction confirms previous findings on the behaviour of Na-beta-alumina under the conditions of a CO2sensor.
New Mixed Conductors Based on Doped Layered Perovskites
Authors: Navas Carlos , Tuller Harry L. , Loye Hans-Conrad zur 
Published: April 2011

ABSTRACTA series of doped Ruddlesden-Popper phases, of general formula Sr3Ti2−xMxO7−δ (M=Al, Ga, Co), were synthesized and their electrical conductivity characterized as a function of temperature and oxygen partial pressure. For fixed-valent dopants, p-type conductivity predominates at p(O2)>10−5 atm, followed by a p(O2)-independent electrolytic regime, and n-type electronic conductivity at very low p(O2). The electrolytic regime exhibits activation energies in the range 1.7-1.8 eV. Doping with transition metals such as Co results in a very significant increase in total conductivity with a p-type conductivity at high p(O2). Furthermore, an apparent ionic regime at intermediate p(O2) is observed, characterized by high conductivity (>10−2 S/cm at 700 °C) and low activation energy (0.7 eV). This interpretation is consistent with iodometric measurements as interpreted by a defect chemical model. Other measurements are in progress to confirm this conclusion.
Investigation of Tin-Graphite Composite Anodes for Rechargeable Lithium Ion Battery
Authors: Dayalan E. 
Published: April 2011

ABSTRACTTwo tin-graphite composite electrodes (27.8 % and 44.4 % tin) were evaluated for their use as high capacity anodes in rechargeable lithium ion cells. The initial charge capacities of these two electrodes were 520 mAh/g and 590 mAh/g, respectively. Cyclic voltammetry and charge-discharge cycling studies point to the alloy formation reaction between tin and lithium being the main contributing factor to the increased capacity. The capacity of these electrodes decreases with cycling but maintains considerably higher capacity than graphite electrode with same number of cycles. The development of optimized tin-graphite composite electrodes with much higher capacity than graphite electrodes looks promising.
Xps and Voltammetry Studies of Redox Behavior of Lacrl1−NixO3Electrodes
Authors: Vovk Greg , Chen Xiaohua , Mims Charles A. 
Published: April 2011

ABSTRACTAnin-situXPS and voltammetry investigation of the redox properties of LaCrj1-xNixO3(x = 0.4, 1) was carried out by incorporating the materials as one electrode in an electrochemical cell (LaCr1xNixO3|YSZ|Pd:PdO), which was directly mounted on a heated sample stage in an ultra high vacuum (UHV) chamber. Under a 0.7V cathodic bias, the perovskites reduce from formal oxidation state of Ni3+to Ni2+. This reduction is accompanied by wholesale shifts of the Cr and O core level binding energies, in keeping with the delocalized electronic states in the material. The adsorption properties of the surfaces are affected by the redox state of the surfaces; increased CO2adsorption is observed on the reduced (and therefore more basic) surface.
Mixed Conducting and Cathodic Properties of Zirconia-Nio Mixture
Authors: Park Y. M. , Choi G. M. 
Published: April 2011

AbsractStabilized zirconia-NiO mixture was chosen as a representative of ionic-electronic composite and the effect of mixture composition on the mixed conducting properties were studied. The measurements of oxygen partial-pressure dependence of conductivity and Hebb-Wagner polarization enabled to determine the electronic contribution to the total conduction in a wide composition range. In ion conduction region, electronic conductivity increased continuously with NiO content. The overpotentials of screen-printed YSZ-NiO electrode on YSZ electrolyte were measured and found to decrease with increasing NiO content and thus with the estimated electronic conductivity of porous electrode.
Iron Oxides as Anodic Materials in Li Rechargeable Batteries
Authors: Duncan M. J. , Nazar L. F. 
Published: April 2011

ABSTRACTThe open framework material, CaFe204 and the isostructural solid solution phases, LiyCa1−(x+y)/2SnxFe2−xO4, where 0<y<x and O<x<0.6 have been evaluated as promising anodic materials in Li-ion batteries. These materials can be discharged to low potential, the end member CaFe2O4 attaining a discharge capacity of 800 mAh/g at a cutoff voltage of 50 mV. The capacity is enhanced on substitution of Fe3+, for Sn4+ in the framework (920 mAh/g for the composition, Li0.6Ca0.4Sn0.6Fe1.404). On introducing Sn into the structure the reversible capacity is also substantially increased compared with the parent material. Although there is a large irreversible component to the redox process during first discharge-charge, the materials can sustain a stable reversible capacity of >600 mAh/g within the voltage window of 3.0-0.005 V. The profile of the electronic density plots suggest there is no phase separation to Li/Sn alloy phases on reduction, but rather a lithium-rich, oxygen deficient Sn/Fe/oxide matrix is formed.
Titanium Dioxide and Apatite Coated Fibrous Ceramics Photocatalyst
Authors: Nonami Torn , Kato Shinji , Taoda Hiroshi 
Published: April 2011

AbstractA TiO2 and apatite coated fibrous ceramics photocatalyst filter has been developed. This filter has a function to absorb and decompose bacteria and various other materials. TiO2 was coated on the surface of the fibrous ceramics by a sol-gel method, then the filter was soaked in a pseudo-body solution containing excessive phosphate ion for 1 day at 37°C. In this research, it is recognized that this filter has absorbed and decomposed colon bacillus, methylene blue and acetaldehyde effectively.
Growth Characteristics of Au/SiO2 Nanocomposites
Authors: Jaeger M. D. , Soltis R. E. , Thomas J. A. , Hangas J. , Chen A. E. , Logothetis E. M. 
Published: April 2011

AbstractThis paper describes experimental studies of the growth morphology of Au/SiO2 nanocomposites consisting of nanometer-sized metal particles imbedded in a metal oxide, formed by the sequential deposition of metal and metal-oxide layers by RF sputtering. The materials work is aimed at the development of novel resistive-type exhaust gas constituent sensors. Using digitized images from a transmission electron microscope and an automated particle counting routine, we have measured the particle size distributions for films with varying layer thicknesses and deposition conditions. We find strong dependence of the particle size and overall composite structure on the Au and SiO2 layer thicknesses, in agreement with previous work.[1] We also identified four microstructure classes which can occur.
Structural Defects In Cerium Oxide Catalytic Support Studied by Pulsed Neutron Diffraction
Authors: Mamontov E. , Egami T. , Brezny R. 
Published: April 2011

AbstractWe studied the structure of coarse and nano-scale powders of CeO2 using pulsed neutron scattering. The diffraction data were analyzed using Rietveld refinement, and were also Fourier-transformed to obtain the pair-distribution function (PDF). The Frenkel type oxygen defects consisting of vacancies in the oxygen sublattice and oxygen ions in the octahedral interstitial sites of the fluorite structure were observed in cerium oxide for the first time. The interstitial oxygen ions were found to recombine with vacancies when the sample underwent thermal treatment at 1073 K. We suggest that these defects are directly involved in the oxygen storage mechanism of ceria used in automotive catalytic converters.
Palladium Supported on Alumina Catalysts Prepared by MOCVD and Impregnation Methods
Authors: Garcia G. , Vargas J.R. , Valenzuela M.A. , Rebollar M. , Acosta D. 
Published: April 2011

AbstractConventional MOCVD method has been explored to prepare Pd supported catalysts. Pd and PdO phases were found on the surface of the support. Small Pd particles about 1 to 3 nm and dispersions up to 19%were obtained by MOCVD. TPR results indicated that several surface Pd compounds are reduced. At temperatures below 25°C, PdO, the main compound, is completely converted to metallic Pd which forms hydrides. At higher temperatures, between 500 to 800°C, the reduction peaks could be attributed to Pd-support interactions and a strong support dehydroxylation. All catalysts were inactive in benzene hydrogenation and a significant conversion was only detected a temperatures above 100 °C. This was explained by the reduced accessibility of Pd sites imposed by the carbon contamination and by the Pd-Al2O3interactions.
High-Surface - Area Framework Zirconium Phosphates as Catalysts of Hexane Isomerization and Dehydroaromatization: Synthesis and Properties
Authors: Sadykov Vladislav A. , Pavlova S. N. , Zabolotnaya G. V. , Kochubey D. I. , Maximovskaya R. I. , Zaikovskii V. I. , Kriventsov V. V. , Tsybulya S. V. , Burgina E. B. , Paukshtis E. A. , Volodin A. M. , Fenelonov V. B. , Kuznetsova N. N. , Lunin V. V. , Chaikina M. V. , Agrawal Dinesh , Roy Rustum 
Published: April 2011

AbstractMechanochemical activation of solid inorganic precursors and sol-gel routes followed by hydrothermal treatment in the presence of surfactants were used to synthesize highly dispersed NZP-type complex zirconium phosphates. Genesis of samples real structure and its impact on the surface properties and catalytic performance in the reactions of hexane isomerization and dehydroaromatization have been studied.
Osteoblast Attachment on Biomaterials as a Function of Surface Charge
Authors: Marcolongo M. , Dinardo N. J. , Hickok N. , Tuan R. , Pourezzaei K. , Beard R. , Brennan D. , Heipp P. , Phan T. 
Published: April 2011

AbstractBioactive materials such as calcium phosphate ceramics and bioactive glasses enhance bone tissue formation and then bond to bone tissue. In our work, we question what particular surface feature or features of bioactive materials are responsible for the bone tissue response. In this study we have uncoupled surface charge from surface chemistry, energy, and topography and have examined osteoblast adhesion to titanium surfaces of varying surface charge. We have shown that a negative surface charge promotes osteoblast adhesion by approximately 60% over a neutral surface and that conversely, a positive surface charge inhibits osteoblast adhesion by about 20%. Continued examination of surface characteristics that control cellular responses are warranted with the eventual goal of applying those desirable surface characteristics to any structural biomaterial for bone implant or tissue engineering applications.
Functionalized Copolymers and Their Composites with Polylactide And Hydroxyapatite
Authors: Jin S. , Gonsalves K. E. 
Published: April 2011

AbstractSynthetic copolymers poly(E-caprolactone-co-vinylphosphonic acid) (P(MDOVPA) and poly(E-caprolactone-co-dimethylvinylphosphoester) (P(MDOVPE)) were used to prepare composites with polylactide (PLac) and hydroxyapatite (HAp). The P(MDOVPA) was used as filler in PLac films, as it has pendant functional groups P(O)(OH)2, providing nucleation sites for the deposition of HAp in simulated body fluid. HAp growth on PLac-P(MDOVPA) film was observed by XRD. The incorporation of hydrophilic P(MDOVPE) into PLac increased the hydrophilicity of the blend. Synthetic HAp was also used to make multi-layered, alternating organic-inorganic composites with porous PLac-P(MDOVPE) blends.
Towards a Tissue Engineered Bladder Wall Patch: The Scaffold
Authors: Hilborn J. G. , Laurent A. , Mathieu H.-J. , Bisson I. , Frey P. 
Published: April 2011

AbstractA new method for surface functionalization of inherently reactive polymers such as polyesters has been developed. It is based on the direct nucleophilic attack on the ester group in the polyethyleneterephtalate backbone by the acid moiety of polyacrylic acid (PAA) catalyzed by titaniumisopropoxide. The PAA grafted surfaces were characterized by X-ray photoelectron spectroscopy to demonstrated the presence of a thin grafted layer rendering the substrates hydrophilic. Subsequent acid group activation using N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide hydrochloride allowed for in-situ collagen immobilization rendering the surfaces cell adhesive. Human smooth muscle and urothelial cells successfully seeded these surfaces, reaching confluence after 7 days.
Sintering Behavior and Mechanical Properties of Hydroxyapatite-Zirconia Composites
Authors: Silva Viviane V. , Domingues Rosana Z. 
Published: April 2011

AbstractThe elaboration of composite materials has been considered one possibility to improve mechanical properties of bioactive phases based on hydroxyapatite used for medical implants. Ceramic and polymeric materials have been tested as the other phase. The aim of this study is to evaluate the sintering behavior and the mechanical properties (compressive strength, modulus of resiliency and microhardness) of hydroxyapatite-zirconia (ZH) composites prepared by precipitation method. Powders of hydroxyapatite-zirconia (ZH) composites, with 40 vol % of zirconia content, and pure hydroxyapatite (HA) as well as pure ZrO2- CaO (ZO) were sintered at 900, 1100 and 1200°C in air at a pressure of 700 MPa for 3 hours, using uniaxial pressing. The products obtained at 1100 and 12000 C are dense, with density values over 91% of the theoretical ones. Experimental results indicated that the sinterization process can be described as admitting a bi-modal structure for ZH composites consisting of a sphere of ZO embedded into a matrix of HA. In this structure the matrix is consider to sinter faster. Intermediate values (between those of pure phases of HA and ZO) of compressive strength and modulus of resiliency were found for ZH composites, suggesting that these composites have potential applications as implant materials.
Peptide Coated Titanium Rods Show Increased Bone Formation in a Rat Femur Model
Authors: Ferris D.M. , Moodie G.D. , Dimond P.M. , Ehrlich M.G. , Valentini R.F. 
Published: April 2011

AbstractIn vitro, groups have demonstrated that peptide modified surfaces influence short and long term cell responses like attachment, shape and function via cell receptors known as integrins. These receptors translate information to the nucleus via sets of complex signaling pathways. Little is known about the ability of these surfaces to influence the inherently complex in vivo environment, however. The present study was designed to evaluate the quality and quantity of new bone formed in response to gold coated titanium rods modified with the peptide sequence Arg-Gly-Asp-Cys (RGDC). Quantitative histomorphometric analysis of histologic sections perpendicular to the implant long axis showed a thicker (P < 0.01) shell of new bone formed in response to peptide modified implants (26.2 microns ± 1.9 vs. 20.5 microns ± 2.9) as early as 2 weeks. Mechanical pull-out testing conducted at 4 weeks revealed the average pull-out force of peptide modified rods was 38% greater than gold control rods. The significant difference in the thickness of new bone formed around the implant was maintained at 4 weeks (32.7 microns ± 4.6 vs. 22.6 microns ± 4.0). These results demonstrate the feasibility of developing peptide coated biomaterials designed to elicit a host response at the cell receptor level.
Development of Vascular Substitutes
Authors: Nerem Robert M. 
Published: April 2011

AbstractA long-term objective of many involved in blood vessel research is the development of a small diameter vascular substitute which can be used in coronary bypass graft surgery. If these efforts are to be successful, there are critical functional characteristics which must be achieved. In recent years many of those interested have turned their attention to tissue engineering, and over the past decade some progress has been reported. The results of some of these efforts are briefly reviewed here. Included is the strategy of the Georgia Tech team and recent results which demonstrate that in vitro mechanical stimulation of smooth muscle cell-seeded tubular collagen constructs induces a remodeling with the result that the associated material properties are considerably enhanced.