bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magnetic properties of melt-textured DyBCO single domains
Authors: Vanderbemden Philippe , Ausloos Marcel , Cloots Rudi 
Published: April 2011

ABSTRACTThis communication aims at reporting the superconducting properties of several bulk melt- processed DyBa2Cu3O7−x samples determined by using various measuring techniques. The original single domain material was first cut into 9 similar cubic samples which have been characterized by AC susceptibility, flux profiles and DC magnetization. The results indicate good quality melt- processed (RE)BCO materials with Tc ≈ 89 K. Next, the effect of post oxygen annealing treatments on these samples was studied. The influence of the non-uniformity of the oxygen content on the magnetic property anisotropy is discussed. Finally, additional magnetic measurements were carried out by using a couple of parallel pick-up coils wound on the same sample. From the results we conclude that geometric effects have to be taken into account in order to extract the critical current density from the magnetic properties.
Microtexture Mapping of Elecrtron Backscattered Diffraction in (Bi,Pb)2Sr2Ca2Cu3O10 Superconductor Tapes
Authors: Li Sean , Tan Thiam Teck 
Published: April 2011

ABSTRACTGrain boundaries is believed to act as weak-links limiting the critical current density (Jc) of bulk high-Tcsuperconductors. The weak-link problem can be greatly reduced by elimination or minimization of the large-angle grain boundaries. It has been reported that the Jc distribution in the transverse cross-section of (Bi,Pb)2Sr2Ca2Cu3O10+x (Bi2223) superconductor tapes follows a parabolic relationship, with the lowest currents occurring at the center of the tapes. The Jc distribution is proposed to be strongly dependent on the local crystallographic orientation distribution of the Bi2223 oxides. However, the local three dimensional crystallographic orientation distribution of Bi2223 crystals in (Bi,Pb)2Sr2Ca2Cu3O10+×superconductor tapes has not been experimentally determined yet. In this work, Electron Backscattered Diffraction technique was employed to map the crystallographic orientation of the crystals in Bi2223 superconductor tapes. From this, the misorientation of grain boundaries and also their distribution are obtained. Through crystallographic orientation mapping, the relationship of the crystallographic orientation distribution, the boundary misorientation distribution and the fabrication parameters may be understood. This can be used to optimize the fabrication processes thus increasing the critical current density in Bi2223 superconductor tapes.
Homogeneity area of Bi2Sr2CaCu2O8 - based solid solutions with substitution of alkaline earth elements by Nd and La
Authors: Veresov A.G. , Knotko A.V. , Korolyov D.V. , Garshev A.V. , Putlayev V.I. 
Published: April 2011

ABSTRACTCreation of precipitates in bulk matrix to act as pinning centres is a prospective way to improve critical current density in high temperature superconductors. It is possible to generate such precipitates via partial decomposition of the supersaturated solid solution derived from a superconducting phase. To control this process one should go by a knowledge of stability field for these solutions. The objective of present work was determination of the homogeneity area of Bi2Sr2Ca1−xRxCu2O8+d and Bi2Sr2−xCaRxCu2O8+d (R = Nd, La). Semi-quantitative XRD analysis was used to evaluate phase composition of specimens quenched from various temperatures. It was found that solubility limits of Nd and La in Bi-2212 for cases of alkaline earth element substitution by rare earth elements with smaller ionic radii (substitution Ca by Nd; Sr by Nd and La) were the same (values of x are about 0.8). These limits are determined by fraction of Cu+ ions in lattice site attributed to Cu2+. In case of substitution of Ca by La stability area of 2212 was found to be much narrower (values of x about 0.3) compared to other substitutions. One ca n deduce this fact from the difference of Ca2+ and La3+ ionic radii.
A Neutron Powder Diffraction Study of the Ferromagnetic Superconductor RuSr2(Gd1.3Ce0.7)Cu2O10-σ
Authors: Knee Christopher S. , Weller Mark T. 
Published: April 2011

ABSTRACTThe temperature dependence of the crystal structure of the ferromagnetic superconductor RuSr2(160Gd1.3Ce0.7)Cu2O10-σ, which orders magnetically at TC ∼ 180 K and exhibits a Tc ∼ 30 K, has been investigated by time-of-flight neutron powder diffraction. In this system superconductivity is believed to occur in the CuO2 layers while the magnetic order is associated with the Ru moments. The tetragonal structure evolves from that of YBa2Cu3O7-σ by inserting a fluorite-type Gd1.3Ce0.7O2 layer instead of the Y ion and replacing the chain copper site with RuO6 octahedra. Rietveld analysis reveals that the basal oxygens of the RuO6 octahedra are displaced within the xy-plane to accommodate physically reasonable Ru-O in-plane bonds. These displacements are consistent with rotations of the octahedra by ∼ 15° around the c-axis. Data were collected at 40 K, 70 K, 100 K, 130 K, 150 K, 170 K 190 K and 230 K but no large structural response associated with the ferromagnetic transition is observed. A small level of oxygen deficiency within the (Gd/Ce)2O2−x, fluorite layer (x = 0.1) is detected leading to a refined stoichiometry of RuSr2(Gd1.3Ce0.7)Cu2O9.9.
Improvement in Fabrication of Hg-1223 Superconductor by Te-Doping
Authors: Yau K.K. , Lam C.C. , Shen L.J. , Li S.H. 
Published: April 2011

ABSTRACTThe sealed quartz tube method is one of the usual methods used for sintering mercury-based copper oxide superconductors. By this method, precursor pellets are inserted into the quartz tube together with certain mass ratio to the reagent sample pellets for controlling the mercury vapour pressure. A certain amount of excess HgO is required to ensure the fabricated sample to have the desired composition. In our research, it was found that if a small amount of TeO2 is added and mixed with the pulverized precursor after first calcination, Hg-1223 superconductors can be fabricated without using the precursor pellet and no excess HgO is required. Thus, the fabrication process can be simplified. As mercury and its oxide are toxic, if no excess Hg is involved, it is safe and good for the laboratory-environment. In this research, some amounts of 0.10 and 0.18 wt% (weigh percentage) of TeO2 were added into the precursor, it is shown that the critical temperature of the fabricated samples is comparable to that of the undoped Hg-1223 samples. For 0.10 wt% of TeO2, the Tc of the as-synthesized sample is about 116.7 K whereas the annealed Te-doped Hg-1223 is about 134.2 K. For 0.18 wt% of TeO2, the Tc of the as- synthesized and annealed samples are 115.8 K and 134.6 K, respectively. The phase structure of samples fabricated in this research has been analyzed by the X-ray diffraction technique. It shows that the Hg-1223 phase is dominated.
Synthesis And Magnetic Properties Of Block Copolymer-CoFe2O4 Nanoclusters
Authors: Ahmed Sufi R. , Kofinas Peter 
Published: April 2011

ABSTRACTThe overall goal of this research is to explore techniques for the development of novel binary magnetic oxide nanoclusters uniformly distributed within a polymer matrix. These CoFe2O4 nanoclusters were synthesized at room temperature, and are confined within the self-assembled nanoscale structure exhibited by block copolymers templates. The diblock copolymers were synthesized by ring opening metathesis polymerization of norbornene and norbornene trimethylsilane and the binary magnetic oxide was introduced through a nanoreaction scheme using wet chemical methods. Transmission electron micrographs of microtomed thin sections of these nanocomposites show that the metal oxide nanoclusters are ellipsoidal in shape and are uniformly distributed within the polymer matrix. A SQUID magnetometer was used to study the magnetic properties of the polymeric nanocomposites at applied fields up to 5 Tesla and at a temperature range between 300 °K and 5 °K. Mössbauer spectroscopy was used to study the structure of the nanoconfined metal oxide, and confirmed the synthesis of CoFe2O4 nanoclusters exhibiting an inverse spinel structure. This study provided a better understanding of the nucleation, growth and distribution of metal oxide nanoclusters within block copolymers and indicated ways to control the magnetic properties of polymeric based nanocomposite materials. The development of such binary metal oxide - block copolymer nanocomposites is targeting the functionalization of such nanostructures into magnetic device technologies.
Advanced Nanocomposite Polymer Films for Bimorphic Gas Sensors
Authors: Gerlach G. , Guenther M. , Suchaneck G. , Sahre K. , Eichhorn K.-J. , Deineka A. , Jastrabik L. 
Published: April 2011

ABSTRACTThin films of aromatic polymers such as polyimide (PI) and polyethersulfone (PES) find an extensive use in aerospace and electronic applications, in particular, as sensitive to moisture and gas uptake layers for bimorphic sensors. In this work, a complex investigation of the film composition, microstructure and physical properties of ion beam modified polymer films was carried out to optimize the moisture uptake. To modify thin films of polyimide and polyethersulfone 50, 130 and 180 keV boron ions with irradiation doses between 1013 and 1016 B+/cm2 were implanted. It could be shown, that partly destruction of chemical bonding under ion bombardment leads to the creation of new amorphous and graphite-like structures, which increase the modified surface film conductivity by several orders of magnitude and enhances the sensitivity of these nanocomposite films to moisture uptake.
The Significance of Percolation on the Dynamics of Polymer Chains Bound to Carbon Black
Authors: Nakatani Alan I. , Ivkov Robert , Papanek Peter , Jackson Catheryn L. , Yang Henry , Nikiel Leszek , Gerspacher Michel 
Published: April 2011

A critical need in the fundamental understanding of reinforcement in filled polymers is the characterization of the polymer-filler interface and the dynamics of the polymer in this interfacial regime. In carbon black filled polymers, one of the central themes in the mechanism of reinforcement is that of “bound” polymer. Understanding the dynamics of this bound polymer may be key to arriving at an understanding of reinforcement mechanisms in filled polymers. The interactions between polymers and filler surfaces are also key in the development of more advanced nanocomposite materials.We have previously utilized inelastic neutron scattering methods to examine the variation of bound polymer dynamics as a function of carbon black type for a single, initial carbon black concentration. An apparent change in the distribution in backbone motions was observed in the bound polymer compared with the pure polymer. In this study, we extend our prior work to examine the bound polymer dynamics as a function of the type of carbon black and the initial concentration of carbon black. The results suggest that two types of dynamic behavior are observed as a function of the initial carbon black concentration. This critical cutoff concentration may be related to the percolation threshold of the carbon black and suggests that quantifying the amount of bound polymer is insufficient for understanding the relationship between mechanical behavior and bound polymer content.
New Technique for Determining Mechanical Property of Polymer/Metal Interface
Authors: Du T. , Liu M. , Seghi S. , Hsia K. J. , Economy J. , Shang J. K. 
Published: April 2011

ABSTRACTA new experimental technique for determining mechanical properties of the polymer-metal interface was developed by replacing conventional mechanical testing machine with a piezoelectric actuator. Using this technique, fatigue crack growth behavior of epoxy/aluminum interface was studied as a function of electric field, crack length and cyclic frequency. The crack growth rate was found to depend on the magnitude of the applied electric field and decrease with testing frequency.
Carbon Metamorphoses in a Medium with Varying Ionic Concentration
Authors: Bouda V. , Chladek J. 
Published: April 2011

ABSTRACTCarbon black in a polymer melt was used to model self-organized processes. A gradual growth of ionic concentration in the polymer melt induced a complex behavior, including a rapid increase in AC conductivity after a time delay. Colloid theory can provide an effective interpretation. The metamorphoses of the carbon black assembly include soft axial order generation, soft lateral order generation, axial condensation, and lateral condensation of carbon black particles, respectively. Similar processes are expected to be effective in generating complex carbonaceous organic structures in natural water.
Order To Disorder Transition at The Polymer-Air Interface for Hydrophobic Octadecyl Side Chain Copolymers
Authors: Gautam Keshav S. , Dhinojwala Ali 
Published: April 2011

ABSTRACTMolecular orientation of octadecyl alkyl side chains at the poly (vinyl octadecyl carbamates-co-vinyl acetate) polymer-air interface has been studied using surface sensitive sum frequency generation (SFG) spectroscopy. At 280C, below the side chain crystalline transition temperature, the SFG spectra show strong methyl vibrations indicating ordered alkyl side chains at the polymer-air interface. In the liquid state (980C), the SFG spectra show higher contributions from the methylene vibrations indicating higher gauche defects at the interface. This surface order to disorder transition is gradual and spans over a broad temperature range (50-900C), where the bulk is in the smectic liquid crystalline state.
Structure of Carbon Blacks
Authors: Zerda T. W. , Qian J. , Pantea C. , Ungar T. 
Published: April 2011

ABSTRACTX-ray diffraction, Raman spectroscopy, and neutron scattering were used to characterize structure of carbon blacks. Different grades, N990, N774, N299, N134, and N110, untreated, after heat treatment and compressed at 2.5 GPa have been investigated. The average sizes of the crystallites obtained by X-ray diffraction agree with those estimated from Raman spectra. The distribution functions of crystallite sizes were evaluated from X-ray diffraction using the recently developed method. Heat treatment results in increased vertical and lateral sizes of graphitic crystallites. Postproduction pressure treatment has little effect on the average sizes of the crystallites, however, it affects the crystallite size distribution function. The magnitude of strain within the crystallites is affected by applied pressure. The relative concentration of amorphous carbon blacks estimated from Raman spectra decreases with increasing temperature but not with increased pressure. It is suggested that the initial growth is associated with alignment of the existing graphitic planes and later by incorporating aromatic carbon into the crystallites.
High Thermal Conductivity Shape-Stabilized Phase Change Materials
Authors: Xiao Min , Sun Luyi , Huang Chengya , Zhang Yonghua , Gong Kecheng 
Published: April 2011

ABSTRACTIn this paper, shape-stabilized phase change materials (PCMs) based on paraffin and thermoplastic elastomer poly(styrene-butadiene-styrene) are prepared. The shape-stabilized PCMs can keep the same shape in a solid state even when their temperature is above the melting point of the paraffin. They exhibit same phase transition characteristics as paraffin and up to 80% of the latent heat of paraffin. Thermal conductivity of the shape-stabilized PCMs is increased significantly by the introduction of expanded graphite (EG). The time for complete solidification and complete melting of the composite P(80)/S(20)/EG(3) is two ninths and two fifths of paraffin, respectively.
The Synthesis of Silicon-containing Polyester Directly from SiO2 and Characterization of Its Structure
Authors: Song Jianhua , Sun Luyi , Liu Anhua , Gong Kecheng 
Published: April 2011

ABSTRACTA new approach to the synthesis of a novel silicon-containing polyester by noncarbothermal method directly from SiO2 was studied. At first, a high reactive pentacoordinate organic silicon compound (KSi(OCH2CH2O)2(OCH2CH2OH)) was prepared by the reaction of the fumed silica with ethylene glycol (EG) and KOH. Then, a novel double hydroxy tetracoordinate silicon monomer (OCH2CH2O)Si(OCH2CH2OH)(OCH2CH2OCH2CH2OH) was synthesized by the reaction of ClCH2CH2OH with reactive pentacoordinate silicon compound. Finally, a silicon-containing polyester was synthesized by low temperature solution condensation between tetracoordinate silicon compound and p-phthaloyl chloride in dimethyl sulfoxide (DMSO). The product was characterized by FTIR, TG, GPC, etc. The IR spectra of polyester exhibited a characteristic strong absorption band for ester carbonyl in the 1722.2cm-1. IR spectra also showed absorption at 1124.6cm-1 due to the O-Si-O group. TG analysis showed its good thermal stability. GPC analysis showed that the number average molecular weight of this siliconcontaining polyester was about ninety thousand.
Small Angle Scattering and the Structure and Dynamics of Filled and Unfilled Rubbers
Authors: Geissler Erik , Hecht Anne-Marie , Rochas Cyrille , Horkay Ferenc , Bley Françoise , Livet Frédéric , Sutton Mark 
Published: April 2011

ABSTRACTRandom cross-linking in rubbers produces local variations in the elasticity of the network. These variations, whose characteristic size lies in the range 1-100 nm, are revealed when the rubber is swollen in a low molecular weight solvent, owing to the competition between the osmotic pressure of the solvent and the local elastic constraints, which affects the local polymer concentration. Such concentration fluctuations can be measured by small angle X-ray or neutron scattering (SAXS or SANS) as well as by dynamic light scattering.In filled elastomers, the filler modifies the distribution of the polymer and of the elastic constraints. Swelling these systems in a solvent in which the deuteron/proton ratio can be varied permits the different components in the scattering function of the polymer and of the filler to be separated. Observations on silica particles in a poly(dimethyl siloxane) (PDMS) rubber yield measurements not only of the surface area of the particles but also of the fraction of the surface area occupied by the polymer. Analysis of the dynamic light scattering response of these systems gives confirmation of the validity of the procedure.Coherent X-ray scattering measurements, combined with dynamic light scattering measurements of the filled uncross-linked polymer melts in the absence of solvent reveal that the structural relaxation process that follows an external mechanical perturbation is a diffusioncontrolled process.
Chitosan/Calcium Phosphate Scaffolds for Bone Tissue Engineering
Authors: Zhang Yong , Zhang Miqin 
Published: April 2011

AbstractThis research involves synthesis and characterization of biodegradable 3-dimensional polymer/calcium phosphate hybrid matrices as scaffolds for bone tissue regeneration. The scaffolds are comprised of chitosan and calcium phosphates [β-tricalcium phosphate (β-TCP), invert glass] and have combined optimum mechanical and biological properties of the two materials. Chitosan is a biocompatible and biodegradable polymer, and has rich hydroxyl groups for surface modification. Calcium phosphate crystals and invert glass are used as powder fillers to reinforce the scaffolds and increase bioactivity of the scaffolds. The scaffolds are fabricated using a thermally induced phase separation technique. The principal advantages of this technique are its low cost, low shrinkage levels, low sintering temperatures, and its ability to produce a variety of microstructures of various shapes and sizes. The osteoblast-like MG63 cells are seeded on the scaffolds to study the attachment and proliferation of the cells. The hydroxyl groups on the scaffolds are used to graft arginine-glycine-aspartate (RGD) peptides for promoting bone cell attachment and new tissue formation.
Development of Biodegradable Polymer Scaffolds Using Co-Extrusion
Authors: Washburn Newell R. , Simon Carl G. , Karim Alamgir , Amis Eric J. 
Published: April 2011

AbstractA methodology for the preparation of porous scaffolds for tissue engineering using co-extrusion is presented. Poly(ε-caprolactone) is blended with poly(ethylene oxide) in a twin-screw extruder to form a two-phase material with micrometer-sized domains. Selective dissolution of the poly(ethylene oxide) with water results in a porous material. This method of polymer extrusion permits the preparation of scaffolds having continuous void space and controlled characteristic length scales without the use of potentially toxic organic solvents. A range of blend volume fractions results in co-continuous networks of polymer and void spaces. Annealing studies demonstrate that the characteristic pore size may be increased to larger than 100 μm. The mechanical properties of the scaffolds are characterized by a compressive modulus on the order of 1 MPa at low strains and approximately 10 MPa at higher strains. The results of osteoblast seeding suggest it is possible to use co-extrusion to prepare polymer scaffolds without the introduction of toxic contaminants.
Design and Characterization of New Ti-Ag and Ti-Ag-Sn Alloys for Cranio-Maxillo-Facial Prostheses Made by Three-Dimensional Printing
Authors: Hong Sang-Bum , Eliaz Noam , Leisk Gary G. , Sachs Emanuel M. , Latanision Ronald M. , Allen Samuel M. 
Published: April 2011

Abstractnew Ti-5Ag and Ti-5Ag-35Sn (wt.%) alloys were designed and synthesized by threedimensionalprinting (3DP). The identification of an appropriate binder, densificationtechnique, and densification parameters for fabricating cranio-maxillo-facial prostheses wasundertaken using microscopic observations, x-ray diffraction tests, microhardness testing, linearshrinkage and wettability measurements. Moreover, electrochemical tests and surface analysiswere used to evaluate the corrosion resistance and passivation behavior of the materials ofinterest. Silver nitrate was found to be an appropriate inorganic reactive binder for atomizedtitanium powder. The optimal temperature for densification of as-printed parts using sinteringwas determined for Ti-Ag alloys. In addition, the type of infiltrant material and use ofhomogenization in liquid-Sn infiltration was explored for Ti-Ag-Sn alloys. While the Ti-Agalloy exhibited superior corrosion and mechanical behavior to the Ti-Ag-Sn alloy, the lattershowed better dimensional stability.
Design, Synthesis, and Characterization of Hydroxyapatite Particulates
Authors: Chen Chun-Wei , Byrappa Kullaiah , Oakes Charles S. , Sushanek Wojciech , Riman Richard E. , Senna Mamoru , Brown Kelly , TenHuisen Kevor S. , Janas Victor F. 
Published: April 2011

AbstractNew hydrothermal technology for the preparation of hydroxyapatite designer particulates has been developed. Phase diagrams were constructed for the pH dependent equilibrium between monetite and HA from 50 to 200°C. Thermodynamic calculations were completed using temperature dependent functions for the relevant solution phase and solid-liquid equilibria and solute species activity coefficients. Model accuracy was evaluated through experiment at 50, 100, and 200°C and pHs between 2.2 and 8.9. The thermodynamic calculations and experimental results are in good agreement. Stoichiometric, crystalline HA has also been prepared by heterogeneous reaction of Ca(OH)2 powder and aqueous (NH4)2HPO4 at room temperature using mechanochemical-hydrothermal methods. This method appears to have very good reproducibility in terms of crystallinity and chemical composition.