bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure–Property Relationship of Solution-Spun Ppbt/Peek and Ppbt/Nylon 6,6 Composite Fibers
Authors: Gabriel Carmen A. , Farris Richard J. , Malone Michael F. 
Published: March 2011

ABSTRACTPrevious work investigated the processing/structure/property relationships for solution spun composite fibers of rodlike poly(p-phenylene benzobisthiazole) [PPBT] with nylon 6,6 [N66] and poly(ether ether ketone) [PEEK] [1]. Evidence that these composite fibers were effectively reinforced by a network-like structure of PPBT was given. In the present investigation, the morphology and properties of wet, as-spun, and heattreated PPBT/nylon 6,6 and PPBT/PEEK composite fibers are contrasted to gain insight into the structure/property relations which result from these post-spinning processes. It is concluded that heat-treatment is simply a means of perfecting the network structure, thereby enhancing the tensile properties of the composite fibers.
“In-Situ Network” Composite Fibers of Pbzt/Nylon
Authors: Hwang C. Robin , Malone Michael F. , Farris Richard J. , Martin David C. , Thomas Edwin L. 
Published: March 2011

ABSTRACTA novel method of preparing PBZT/nylon composite fibers by infiltrating nylon into pure PBZT fiber is described. The pure PBZT fiber formed a microfibrillar network structure during coagulation, which is effective in reinforcing the matrix in the “in-situ network” composite fibers (designated IC). These new composite fibers exhibit nearly indistinguishable mechanical properties as those of “molecular” composite fibers (MC) prepared from isotropic solutions before and after tension heat-treatment (E = 44 GPa, σ = 430 MPa, ε = 1.2 %, σc = 250 MPa, G = 1.75 GPa) for PBZT/nylon weight ratios equal to unity.The fine structure of pure PBZT and its composite fibers spun from isotropic solutions was characterized using techniques based on nitrogen adsorption, small-angle X-ray scattering, scanning and transmission electron microscopies. The structure of both type of composites was found to be a microfibrillar network of PBZT in a matrix of amorphous nylon. The average diameters of the PBZT microfibrils were in the range of 10 to 20 nm for the IC and 4 nm for the MC.
Processing, Properties and Structure of Bulk Poly(P-Phenylene Benzobisthiazole)/Poly(Ether Ether Ketone) Molecular Composites
Authors: Wang C. S. , Bai S. J. 
Published: March 2011

ABSTRACTThe wet-state-consolidation process was used to fabricate bulk rigid-rod/thermoplastic molecular composites of poly(p-phenylene benzobisthiazole) and poly(ether ether ketone). The composites were molded into bar-shaped specimens. The morphology of those specimens was studied throughout the entire process using X-ray scattering and scanning electron microscopy to correlate processing conditions and properties. The mechanical properties of the bulk composites were comparable to those of other rigid-rod/thermoplastic molecular composite systems.
Theoretical Predictions of Nonlinear Optical Properties of Molecules and Polymers
Authors: Goldfarb Ivan J. , Reale Hector , Wierschke Scott , Medrano Jorge A. 
Published: March 2011

ABSTRACTThe prediction of nonlinear optical properties of molecules and polymers is an important goal toward which a considerable effort has been recently applied. It entails the calculation of the polarizability and first and second hyperpolarizability tensor, for the systems under study, using their quantum wavefunctions. In principle several approaches are possible. The wavefunctions themselves can be calculated at the ab initio or semi-empirical levels of approximation and then the calculations can proceed via the sum over states (SOS) or the finite field (FF) formalisms.Since we intend to calculate large systems we decided on the semi-empirical MNDO/AMI approaches for the calculation of the wavefunction. We also used the FF approach and numerical methods for finding the necessar) derivatives. The comparison between calculated and available experimental results is very encouraging. We also calculated the tensors for considerably large molecules, providing the first theoretical prediction of these values. The effect of different substituents on a given structure and the result of doping, were also studied. The polarizabilities of some oligomers as functions of the number of repeat units were calculated to assess the convergence properties. Because of the required periodicity of the perturbations, calculations cannot be made for infinite polymers in the same fashion as for small molecules. This problem is currently being addressed.
Theoretical Studies of the Physical Properties of Rodlike and Related Polymers
Authors: Welsh W. J. , Mark J. E. , Yang Y. , Das G. P. 
Published: March 2011

ABSTRACTThis review focuses on a new type of para-catenated aromatic polymer being used in the preparation of high-performance films and fibers of exceptional strength, thermal stability, and environmental resistance, including inertness to essentially all common solvents. Polymers of this type include the cis- and trans-poly(p-phenylene benzobisoxazole) (PBO), the cis- and trans-forms of the corresponding poly(pphenylene benzobisthiazole) (PBT), and the structurally similar poly(5,5ʹ-bibenzoxazole-2.2ʹ-diyl-l,3-phenylene) (AAPBO) and poly(2,5-benzoxazole) (ABPBO) and their sulfurcontaining analogues. Because of their rigidity, these polymers become highly oriented in solution and some display liquid crystalline behavior. The purpose of this paper is to summarize the authorsʹ theoretical work on the structures, conformational energies, intermolecular interactions, electronic properties, electrical conductivity, and electrooptical properties of these chains, including, in some cases, the so-called articulated forms and the protonated forms known to exist in strong acids. The emphasis is on how such studies provide a molecular understanding of the unusual properties and processing characteristics of this new class of materials.
Electric Properties of Ladder Type Polymers BBB and BBL
Authors: Belaish I. , Rettori C. , Davidov D. , Mclean M.R. , Dalton L. , Nalwa H. 
Published: March 2011

ABSTRACTWe report on ESR and electric conductivities of BBB and BBL ladder polymers with emphasis on the former. Both the ESR and the electrical conductivities are strongly anisotropic suggesting that the polymer backbones are plannar. The ESR data implies the existence of two different types of spin species. The hyperfine spectrum of one of these species is analyzed in terms of a Spin Hamiltonian and anisotropic transferred hyperfine interaction with the 14N nuclei (I = 1). We found that “annealing” the BBB and BBL films to high temperatures, To, increase the spin susceptibility for To ≤ 850K (BBB). However annealing to To ≥ 900K results in a dramatic reduction in the spin susceptibility and dramatic incise in the conductivity. The room temperature in-plane conductivity of annealed samples at To ≥ 900K exceeds σ = 1 Ω−1 cm−1. This high intrinsic conductivity is probably associated with the formation of cross-linked condensed aromatic structure. The 'phase transition” temperature to this structure is higher by 50K for BBB compared to BBL. The conductivity versus temperature of annealed samples (700K ≤ To) can be described by the onisotropic version of Mott's law for variable range hopping. We demonstrate that the anisotropic conductivity is due to the anisotropic localization lengths (ξ∥ and ξ⊥) of the wave function of the localized states.
Structural Changes in Fast Ion Conducting Chloride Doped Potassium Borate Glasses
Authors: Fusco F.A. , Massot M. , Oueslati M. , Haro E. , Tuller H.L. , Balkanski M. 
Published: March 2011

AbstractThe effects of halide substitution on ionic conductivity in potassium borate glasses are different from those observed in their Li and Na analogs. Physical property and Raman spectroscopy results suggest that this behavior is associated with differences in the glass network structure induced by the presence of different interstitial alkali cations.
Raman Spectroscopy and Structural Disorder in Gd2(ZrxTi1−x)2O7
Authors: Oueslati M. , Balkanski M. , Moon P.K. , Tuller H.L. 
Published: March 2011

AbstractRaman measurements on the Gd2(ZrxTi1−x)2O7, solid solution show increasing peak widths as the composition is varied from Gd2Ti2O7, to Gd2Zr2,O7. The increase in peak width is interpreted as reflecting an increase in structural disorder with increasing x in this pyrochlore structure material. Structural disorder occurs readily in such oxides by the formation of cation anti-site defects and anion frenkel defects. We have previously observed that this leads to a marked increase in oxygen ion conduction with increasing x. Preliminary results also indicate that certain peaks in the Raman spectra are characteristic of the end members of the solid solution and may occur at the same frequency independent of composition. The Raman results are discussed in relation to earlier x-ray diffraction and ionic conductivity data obtained in this group.
Studying Ionic Conductivity with Diffraction Techniques an Application to laF3
Authors: Belzner Andreas , Schulz Heinz 
Published: March 2011

AbstractThe LaF3-structure has been reinvestigated using diffraction data measured with twinned crystals.LaF3 is fluoride ion conductor with essentially 3-dimensional conductivity. The conduction perpendicular to the c-axis is shown to occur on paths which include all three sets of fluorine positions in the structure and which connect symmetrically non-equivalent nearest neighbor positions only. This is confirmed by determination of anharmonic temperature factors. The temperature dependence of the harmonic thermal parameters indicates that thermal vibrations are described rather than static disorder. The magnitude of the temperature factors of fluorine is consistent with an intrinsic activation energy of 0.8 eV for fluorine conduction.
Structural Investigations on Scandium Substituted Nasicons. Order Disorder Effects
Authors: Clearfield A. , Hinson P.G. , Rudolf P.R. , Squattrito P.J. 
Published: March 2011

AbstractNeutron diffraction data were used to refine the structures of three scandium substituted NASICONS: Na2 ZrSc(PO4)3, R3c Na2.5 Zr1.8 Sc0.2 Si1.7 O12 R3c and Na2.7. Zr1.0 Sc0.2Si1.5 P1.5O12, C2/c. The phosphate (compound 1) exhibited oxygen disorder. The second compound exhibited a similar type of oxygen disorder but also an interstitial Na+ position. The oxygen disorder in compound 2 apparently results from the position of the interstitial Nae whereas it is suggested that the Sc site in Na2 ZrSC(PO4)3 is slightly removed from that of the Zr position, requiring a shift of phosphate groups. In contrast the monoclinic phase does not exhibit oxygen disorder and all the sodium ions reside within the cavities.
Solid State NMR Studies of Ionically Conductive Non-Oxide Chalcogenide Glasses
Authors: Eckert Hellmut , Zhang Zhengming , Kennedy J. H. 
Published: March 2011

AbstractThe utility of 29Si, 31 p, and 6.7 Li MAS-NMR at 7.05 T to provide structural information in non-oxide chalcogenide glasses is discussed in connection with experimental results obtained on the systems Li2 S-SiS2, Li2 S-SiS2 -P2S5, and Li2 S-P2 S5-B2 S329Si MAS-NMR data indicate that the principles governing glass formation in these systems are fundamentally different from those applicable to stoichiometry-analog oxide glasses. 31p MAS-NMR can be used to identify microphase-separation in glasses containing two network former constituents. The use of the rare isotope 6 Li instead of 7 Li offers the advantage of significantly improved spectroscopic resolution, enabling the presentation of the first comprehensive lithium NMR chemical shift scale in the solid state.
Ion Association in Polymer Electrolytes; A Raman Study of Poly (Propylene Oxide) Based Complexes
Authors: Kakihana M. , Schantz S. , Torell L.M. , Borjesson L. 
Published: March 2011

AbstractRaman spectra of a series of PPO-LiClO4 and PPO-NaCF3SO3 complexes have been obtained for different temperatures and salt concentrations to study the various ion associations of the dopant salt. It was found that ion-ion interactions dramatically influenced the internal symmetric stretching modes ν1 of the anions. Splitting of ν1 into a multicomponent band was observed. The intensity profile of the band was found to change rapidly with salt concentration and temperature. A three component band analysis led to the identification of dissociated ions, ion pairs and multiple ion aggregates, respectively. Increased ion association with increased temperature and/or salt concentration was observed for both LiCIO4- and NaCF3SO3- complexes. It is likely to initiate the phase separation and salt precipitation observed in many salt-polymer complexes at higher temperatures. Considerably stronger ion-ion interaction was observed in the NaCF3SO3-system than in the LiCIO4-complex, which may explain the lower conductivities reported for PPO-NaCF3SO3 electrolytes. The drastic conductivity drop observed in both systems at higher salt concentrations can however only partly be due to a decreased concentration of “free” ions, the major effect being attributed to decreased ion mobility.
Ion Transport Through Polyperfluorosulfonic Acid Membranes.
Authors: Nguyen T. , Guante J. , Vanderborgh N. 
Published: March 2011

AbstractWater transport rates through Dow experimental polyperfluorosulfonic acid membranes were investigated by using dynamic thermogravimetry. A mathematical model was developed to describe water transport rates within the membrane. Values for the diffusion coefficient of water in membrane samples of the same equivalent weight but of three different thicknesses, 265, 4.0, and 7.0 mil, were obtained for temperatures of 60, 80, and 90° C. Results show that the diffusion coefficient of water increases with water content and temperature.
Electrical Properties of Poly(Vinyl Alcohol) Complexed with Phosphoric Acid
Authors: Gong Ke-Cheng , Shou-Cai Huang 
Published: March 2011

AbstractThe electrical properties of poly(vinyl alcohol) complexed with phosphoric acid have been studied. It is found that the conductivity increases with the concentration of the acid, and also increases with time if the sample is exposed to the air, which is interpreted in terms of glass transition temperature. A.C. impedance measurement and polarization experiment show that this proton-conducting polymer is a promising candidate for electrochromic display. It is also found that some plasticizers, such as glycerol and ethylene-glycol are effective for improving its conductivity.
Solid Electrolytes: Jump Relaxation and “Universal” Dynamic Response
Authors: Funke Klaus 
Published: March 2011

AbstractIn solid ionic conductors, the hopping motion of the mobile charged defects is strongly influenced by their mutual repulsive interaction. Therefore, their jump diffusion ist not a random process. Instead, correlated forward-backward hopping sequences are a common phenomenon, constituting the elementary steps of jump relaxation. The microscopic dynamics of the relaxation is described in a simple model which yields the frequency spectrum of the hopping motion. With the help of this function, it is possible to explain experimental spectra displaying the so-called “universal” dynamic response. In particular we reproduce the frequency dependent ionic conductivity of fast ion conductors and the arcs in their complex-conductivity and complex-permittivity planes. The model also explains the non-BPP-type behavior of spin-lattice relaxation times and the broad components of quasielastic neutron scattering spectra. Examples are presented and discussed.
Lithium Electrochemical Investigations of Crystalline Layered Compounds
Authors: Julien C. , Samaras I. , Saikh S.I. , Balkanski M. 
Published: March 2011

AbstractElectrochemical investigations on lithium insertion in crystalline layered chalcogenide compounds are presented. Systematic and precise studies of the voltage-composition relation were made in single crystals of InSe, In2Se3, MoS2, TiS2 and NiPS3. The stability of the intercalated phases is discussed on bases of electrochemical potential spectroscopy measurements and inverse derivative composition voltage is analysed using the lattice gas model. The chemical diffusion coefficient D and the Darken factor Kt are deduced from the galvanostatic discharge curves of the lithium-solid solution electrode cells. All parameters have been measured as a function of lithium composition.
Plasmon-Phonon Coupling in Li Intercalated InSe
Authors: Burret P.A. , Julien C. , Jouanne M. , Balkanski M. 
Published: March 2011

AbstractThe layered semiconductor InSe which is a potential insertion cathode for thin film batteries can be intercalated with lithium which act as donor in the host. Chemical intercalation in n-butyllithium, leads to a drastic increase of the free carrier density in the host material, InSe single crystal.The variation of the free carrier density with intercalation shifts the plasma frequency into the region of the LO-mode vibrations and allows the observation of the plasmon-LO-phonons coupling by light scattering experiments. By varying the sample temperature, it is possible to follow the two branches of the curve ω(q) corresponding to the modes L+ and L-.
Developments in Rechargeable Mno2Electrodes for Lithium Batteries
Authors: Thackeray Michael M 
Published: March 2011

AbstractConsiderable efforts are in progress to develop rechargeable batteries as alternative systems to the nickel-cadmium battery. In this regard, several advances have been made in ambient-temperature lithium battery technology, and specifically in the engineering of rechargeable lithium/manganese dioxide cells. This paper reviews the current state of the art in rechargeable Li/MnO2battery technology; particular attention is paid to the structural features of various MnO2electrode materials which influence their electrochemical and cycling behaviour in lithium cells.
AC and DC Studies of Non-Exponential Relaxation Processes in Superionic Conductors: Correlation of Conductivity and NMR Studies
Authors: Angell C.A. , Martin S.W. 
Published: March 2011

AbstractThis paper considers the results of NMR relaxation studies of fast ion glasses in the light of variable frequency electrical conductivity measurements. We show that the low activation energy observed for relaxation processes studied at constant frequency below the temperature of the T1minimum is reproduced by the corresponding constant frequency conductivity measurements. Other characteristics of the constant frequency conductivity in this low activation energy regime, such as the unphysically low pre-exponent, match with the corresponding observations for NMR measurements. Since the activation energy observed at constant frequency in the frequency-dependent regime for conductivity depends on the characteristic departure from exponential relaxation for the conductivity process, we conclude that the NMR activation energy is likewise a simple consequence of the nonexponential character of ionic relaxation in the glass. In this case, the low activation energy attributed to processes probed by NMR relaxation is simply a misinterpretation since it is found, in the wide frequency range studies available to admittance bridge measurements, that all elements of the relaxation spectrum have essentially equal activation energies.
Influence Of Test Conditions On Water Permeability Of Concrete In aTriaxial Cell
Authors: Hooton R. Doug , Wakeley Lillian D. 
Published: March 2011

AbstractThe hydraulic conductivity of three concretes with a high ratio of water to cementitious solids (w/cs) was measured using a test device in which confining and driving pressures are controlled separately (triaxial, or Hassler cell). Test variables included: confining pressure (c), driving pressure (d), ratio of these two pressures (c/d), and sample length. The objective was to determine the effect of these variables on measured permeability (K).For these concretes, the driving pressure has a strong influence on K values, which generally are significantly higher at lower driving pressures. The c/d ratio controls K to a lesser extent, and not in a consistent direction. K increases as c/d increases for specimen lengths of 3X the maximum aggregate size or longer. For specimens the length of which is closer to the aggregate size, K values decrease with increasing c/d, making specimen length an important variable. Removal of entrapped air from the system and presaturation of the specimens also are important.
Air Permeability Measurement
Authors: Perraton Daniel , Carles-Gibergues André , Aitcin Pierre-Claude , Thenoz Bernard 
Published: March 2011

AbstractAir permeability was determined for concretes of variable porosity (w/c ratio of 0.33, 0.50, and 0.67). The reproducibility of the test and the ability to characterize the permeability of different concrete were evaluated. Results indicate that air permeability test gives suitable reproducibility with a margin of error of 10%, which tends to improve with increase in w/c ratio. The difference in air permeability of concretes with the w/c ratios investigated are distinguishable by this technique. Furthermore air permeability coefficients used were modified with equations derived in accordance to Darcy's law, and the resulting air permeabilities compared. Data calculated with an air permeability coefficient based on mean radius pore (corrected equation) appears to give a more realistic value with greater differentiation between the ranges. Values were determined on specimens after 28 days, maintained at room temperature (50% RH), then again after an additional 2 days at 60°C in a ventilated oven. Oven-dried specimens exhibit significantly greater air permeability.
Porosity/Diffusivity And Alkali-Silica Reaction
Authors: Moranville-Resocurd Micheline 
Published: March 2011

AbstractPhysical and chemical processes are responsible for the alkali-silica reaction in concrete. Physical processes include (i) migration of hydroxyl and alkali ions (ii) swelling by water imbibition of the alkali-silica gel produced, (iii) development of cracks. Chemical processes involve (i) neutralisation of acidic silanol groups and attack of siloxane bridges, both by OH- ions (ii) formation of an alkali silicate. These reactions result in a breakdown in the silica structure and diffusion of some silicate and impregnate the cement paste filling the capillary pores. The increase in permeability due to the opening and progression of cracks facilitates secondary chemical deteriorations like the formation of ettrinqite, carbonation and corrosion of steel reinforcement. Recent studies have emphasized the role of Ca(OH)2 preventing the dissolution or miqration of freed silica out of the structure. Only the removal of Ca(OH)2 is able to stop the expansion of concrete.The paper will present some new interpretations of alkali-silica reaction related to the diffusivity of various ions from the pore solution.
Pore Structure And Its Relationship To Properties Of Materials
Authors: Pereira C. J. , Rice R. W. , Skalny J. P. 
Published: March 2011

AbstractPore structure affects almost all the physical properties of materials and, thus, is important in engineering practice. Engineering desired physical properties by microstructural modification of the porosity and/or the solid phases has practical importance and, therefore, there is considerable research activity in developing relationships between the desired physical properties and the pore structure. The ability to vary the level of porosity, the pore size distribution, pore shape, and pore connectivity opens new opportunities for developing materials not only for conventional uses but also for novel applications such as electronics.