bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photoelectrochemical Deposition of Metal Patterns on Semiconductors
Authors: Rose Timothy L. , Micheels Ronald H. , Longendorfer David H. , David Rauh R. 
Published: March 2011

ABSTRACTMicroscopic metal patterns may be produced on p-type semiconductors using a maskless photoelectrochemical procedure in which electroplating is induced by minority carriers in illuminated portions of a semiconductor electrode. Resolution exceeding l0μ has been achieved for deposits of Au on p-GaAs and Cu on p-Si. “Electroless” imaging and negative photoelectrochemical imaging are also discussed.
Analysis of Laser-Enhanced Adsorption/Desorption Processes on Semiconductor Surfaces via Electronic Surface State Excitation
Authors: Murphy William C. , Beri A. C. , George Thomas F. , Lin Jui-Teng 
Published: March 2011

ABSTRACTElectronic surface states in semiconductors often lie between the valence and conduction bands and give rise to charge densities confined to the surface region. Laser radiation of frequency less than the energy gap can excite electrons from delocalized valence band states to these localized surface states leading to large changes in the charge distribution at the surface. Selective enhancement of adsorption/desorption processes involving ionic or polar adspecies can result from such a charge redistribution. Using a onedimensional model for silicon, the cross-section for the laser-induced electronic transition to surface states is shown to be large. The interaction energy of an adspecies with the surface changes significantly with direct excitation of surface states in a semiconductor. For a one-dimensional metal, however, direct transitions between bulk and surface states are not allowed, but phonon-mediated transitions coupled with laser radiation lead to substantial charge transfer as for semiconductors.
Rheology of Blends of a Rodlike Polymer (PBO) and its Flexible Chain Analog
Authors: Sullivan V. J. , Berry G. C. 
Published: March 2011

ABSTRACTRheological properties of isotropic solutions of rodlike poly(p-phenylene benzbisoxazole), PBO, flexible chain poly(2,5-benzoxazole), ABPBO, and their miscible blends in solution are described. Measurements include steady state properties (the viscosity and recoverable compliance as functions of shear rate), transient properties (the recoverable compliance), and dynamic mechanical properties (the loss and storage compliances as functions of frequency). The relaxation spectrum of the blends is broader than that for the rodlike chain, and tends to occur at longer times, reflecting a viscosity enhancement that occurs with the blends. The measured zero shear viscosities for rod and blend solutions are compared with predictions based on the model of Doi and Edwards.
The Ordered Bicontinuous Double Diamond Structure in Binary Blends of Diblock Copolymer and Homopolymer.
Authors: Winey Karen I. , Thomas Edwin L. 
Published: March 2011

ABSTRACTWe report the observation of the ordered bicontinuous double diamond (OBDD) structure in binary blends of poly(styrene-isoprene) diblock copolymer and homopolystyrene. The overall polystyrene volume fraction range is 64 - 67 PSvol% for the OBDD structure in binary blends of a lamellar diblock (SI 27/22) and a homopolymer (14.0 hPS). This composition range is approximately within the polystyrene volume fraction range established for pure diblock copolymers in the strong segregation regime having the OBDD structure. Ordered lamellae are observed at approximately 65 PSvol% when the homopolystyrene molecular weight is greater than the molecular weight of the polystyrene block of the copolymer. This observation is discussed in terms of the decreased degree of mixing between the homopolymer and the corresponding block and the resultant effect on the interfacial curvature.
Morphological Consequences of Catalytic Hydrogenation of Polymers in the Bulk
Authors: Gilliom Laura R. , Schaefer Dale W. , Mark James E. 
Published: March 2011

ABSTRACTWhen suitable catalysts are molecularly dispersed in polymers, the polymers can be modified without added solvent. This paper describes studies on the morphology of samples of trans-l,4-polybutadiene and syn-1,2-polybutadiene which have been partially deuterated in the bulk. The development of a peak in the SANS data for the 1,2-polybutadiene suggests the formation of small domains upon deuteration. Possible explanations for this observation, including chemical and physical heterogeneity, are evaluated. Results of SAXS and thermal measurements are also considered.
Synthetic Control of Molecular Structure in Organic Aerogels
Authors: Pekala Richard W. 
Published: March 2011

ABSTRACTOrganic aerogels have been formed from the aqueous, sol-gel polymerization of resorcinol with formaldehyde. These materials are transparent and have continuous porosity with cell/pore sizes of less than 1000 Å. Their microstructure is composed of interconnected colloidal-like particles with diameters of 30-200 Å. The particle size, cell size, surface area, and density of the aerogels are predominantly controlled by the catalyst concentration used in gel preparation.
Interfacial Segregation Effects in Mixtures of Homopolymers with Copolymers.
Authors: Wakharkar Vijay S. , Russell Thomas P. , Deline Vaughn R. 
Published: March 2011

ABSTRACTSecondary Ion Mass Spectroscopy (SIMS) has been used to study the surface and interfacial segregation of diblock copolymers in mixtures of the copolymer in the homopolymer. Symmetric, diblock copolymers of polystyrene (PS) and poly(methyl methacrylate) (PMMA), in either the PS or the PMMA homopolymers were investigated. In mixtures of the copolymer with the PS homopolymer, systematic surface enrichment of the copolymer as well as segregation of the copolymer to the polymer/Si interface or in the case of bilayered filmsto the polymer/polymer interface occurs with annealing treatments. These segregation effects persist over a large range of homopolymer molecular weights with changes in the kinetics of the segregation process being predominant.
Mechanically Induced Silica-Siloxane Mixtures. Structure of the Adsorbed Layer and Properties of the Network Structure
Authors: Cohen—addad J.P. 
Published: March 2011

ABSTRACTProperties specific to silica—siloxane mixtures are analysed and discussed. The effect of polymer adsorption is interpreted from the Gaussian statistics of chains: the amount of adsorbed polymer Qr is proportional to the square root of the chain molecular weight. The kinetics of adsorption is described as a process of surface saturation. It is discussed as a function of the silica concentration. The effect of swelling of the mixtures is interpreted within the statistical framework proposed by Flory for ordinary gels.
Deformation Behavior of Polymer Gels in Electric Field
Authors: Kurauchi Toshio , Shiga Tohru , Hirose Yoshiharu , Okada Akane 
Published: March 2011

ABSTRACTThe deformation of poly(acrylic acid)—co—(acrylamide) gels and poly(vinyl alcohol)—poly(acrylic acid) gels under an electric field was investigated. Bending of these ionic gels was induced by an electic field. Using this deformation, we constructed a prototype of a robot hand having soft fingers, and an artificial fish able to swim.
Nylon 6–Clay Hybrid
Authors: Okada Akane , Kawasumi Masaya , Usuki Arimitsu , Kojima Yoshitsugu , Kurauchi Toshio , Kamigaito Osami 
Published: March 2011

ABSTRACTζ-Caprolactam was polymerized in the interlayer spacing of montmorillonite, a clay mineral, yielding a nylon 6-clay hybrid (NCH) 1).X-ray and TEM measurements revealed that each template of the silicate, which is 10 Å thick, was dispersed in the nylon 6 matrix and that the repeat unit increased from 12 Å in unintercalated material to 21 Å in the intercalated material.Thus NCH, is a “polymer based molecular composite” or “nanometer composite”. NCH, when injection-molded, shows excellent properties as compared to nylon 6 in terms of tensile strength, tensile modulus and heat resistance. Heat distortion temperature increased from 65 °c for nylon 6 to 152 °c for NCH, containing 4 wt% (1.6 vol%) of clay mineral.
Reinforcement of Elastomers by The In-Situ Generation of Filler Particles
Authors: Mark James E. , Schaefer Dale W. 
Published: March 2011

ABSTRACTThe goal of primary interest in these investigations was the development of novel methods for filling elastomeric networks. The techniques developed employ thein-situgeneration of reinforcing fillers such as silica or a glassy polymer such as polystyrene either after, during, or before network formation. The reaction involves decomposition of organometallic compounds, using a variety of catalysts and precipitation conditions, or freeradical polymerization of a suitable monomer. The effectiveness of the technique is gauged by stress-strain measurements carried out on these elastomeric composites to yield values of the maximum extensibility, ultimate strength, and energy of rupture. Also of interest are calorimetric studies of the networks, to determine their crystallizability. Information on the filler particles themselves is obtained from density determinations, electron microscopy, and scattering measurements.
Structure of Microphase-Separated Silica/Siloxane Molecular Composites
Authors: Schaefer Dale W. , Mark James E. , Mccarthy David , Jian Li , Sun C. -C. , Farago Bela 
Published: March 2011

ABSTRACTThe structure of several classes of silica/siloxane molecular composites is investigated using small-angle x-ray and neutron scattering. These filled elastomers can be prepared through different synthethic protocols leading to a range of fillers including particulates with both rough and smooth surfaces, particulates with dispersed interfaces, and polymeric networks. We also find examples of bicontinuous filler phases that we attribute to phase separation via spinodal decomposition. In-situ kinetic studies of particulate fillers show that the precipitate does not develop by conventional nucleation-and-growth. We see no evidence of growth by ripening whereby large particles grow by consumption of small particles. Rather, there appears to be a limiting size set by the elastomer network itself. Phase separation develops by continuous nucleation of particles and subsequent growth to the limiting size. We also briefly report studies of polymer-toughened glasses. In this case, we find no obvious correlation between organic content and structure.
Nmr Imaging of Silica-Silicone Composites
Authors: Garrido Leoncio , Ackerman Jerome L. , Mark James E. 
Published: March 2011

ABSTRACTPolydimethylsiloxane (PDMS) model networks reinforced by in situ precipitated SiO2, and polymer-modified silica glasses were obtained following the usual sol-gel methods. The conditions were chosen to increase the probability of observing inhomogeneities: (i) bulky samples, and (ii) limited reaction times. These composites were characterized by measuring bulk spin-lattice (T1) and spin-spin (T2) relaxation times and using 1H NMR two-dimensional Fourier transform (2DFT) spin echo imaging techniques. The T1 and T2 maps show clear and significant variations of NMR signal intensity throughout the sample due to nonuniform hydrolysis of the tetraethylorthosilicate (TEOS) in the specimens.
Luminescence Measurement of Fused Silica in the Presence of Excimer Laser Radiation
Authors: Kuzuu Nobu , Komatsu Yohshikazu , Murahara Masataka 
Published: March 2011

AbstractExicimer laser induced luminsecence characteristics of type III fused silica was investigated. The luminescence characteristics in the ultraviolet wavelength region are strongly depending on the intensity of red luminescence at 650 nm. A sample without red luminescence shows a strong emission band at 280 nm. We found that the 280 nm band is corresponds to a absorption band at 225 nm. To clearfy the nature of the 280 nm band, we studied the difference of luminescence of samples which had been kept on heating under various atmosphares, i.e., N2, O2, He, H2, and air. By these results we suspect that the 280 nm band is related to hydrogen atom which are weakly bounded to the glass network.
Synthesis and Characterisation of Heavy Metal Fluoride Glasses and Fibres
Authors: France Paul W , Carter S F , Moore M W , Williams J R 
Published: March 2011

AbstractThe fabrication of optical fibres based on fluoride glasses has required the development of novel preparation techniques. Some of these techniques are based on methods used to prepare multicomponent oxide glass fibres although some have been developed specially for fluoride glasses. This paper will review such processes as glove-box melting, reactive atmosphere processing, and rapid quenching; show how these have been used to prepare fluoride glass fibres with losses down to 2.6 dB/km at 2.6 μm; and discuss remaining problems with the glass.
Proton Effects in KTiOPO4
Authors: Morris P. A. , Crawford M. K. , Roelofs M. G. , Bierlein J. D. , Gallagher P. K. , Gashurov G. , Loiacono G. M. 
Published: March 2011

AbstractEvidence supporting the temperature dependent defect mechanism of nonstoichiometry on the potassium and oxygen sublattices in KTP is presented. The primary compensating defects for the formation of vacant potassium sites in typical flux grown KTP are vacant oxygen sites. Protons (OH-) are the principal defect compensating for the formation of vacant potassium sites in high temperature hydrothermal KTP. A model of the ionic conductivity in high temperature hydrothermal KTP is proposed in which specific protons participate in cooperative motion over a limited distance with the potassium vacancies migrating along the “channels” in the structure in the Z-direction. The higher activation energy measured for ionic conductivity in flux grown KTP (0.5 eV) relative to high temperature hydrothermal (0.3 eV) is suggested to be due to the energy required to dissociate from a defect complex, such as a (VO - VK). The correlation of ionic conductivity to damage susceptibility appears to be due to the levels of compensating defects for vacant potassium sites in KTP, which are related to the concentrations of Ti3+ formed in the crystals. Further study is ongoing to understand the specific mechanisms involved in the ionic conductivity and damage in KTP grown by the flux and hydrothermal techniques.
Fluid Dynamic Instabilities in Drawn Fibers
Authors: Thompson Charles , Mulpur Arun 
Published: March 2011

AbstractThe nonlinear stability analysis of viscoelastic fibers is presented. The molten fiber is modeled as a Maxwellian viscoelastic fluid and the zeroth order equations governing its behavior given. Linear stability analysis is performed to determine the influence of winder speed and impedance as well as viscosity and elasticity. The results of numerical solution of the nonlinear equations are given.
Deposition of Hermetic Carbon Coatings on Silica Fibers
Authors: Huff R. G. , DiMarcello F. V. , Hart A. C. , Walker K. L. 
Published: March 2011

AbstractCarbon coated optical fibers have recently been shown to have excellent resistance to both static fatigue and hydrogen induced losses. The deposition technique used to form the carbon coating strongly affects the coating's ability to resist these degradation mechanisms. The system developed by AT&T utilizes an atmospheric CVD chamber in which a hydrocarbon has is pyrolyzed on the fiber surface. The heat retained in the fiber from the fiber forming process is used to drive the reaction, and high draw speeds are typically used to attain the ˜900°C temperature required to deposit the hermetic form of the carbon coating. Deposition rates of ˜1μm/sec are required to produce the ˜500 Å coating.
Superconducting and Normal State Properties of Organic Metals β- (Bedt-Ttf)2X
Authors: Tokumoto M. , Kinoshita N. , Murata K. , Bando H. , Anzai H. 
Published: March 2011

ABSTRACTRecent progress on the superconducting and normal state properties characteristic to the organic metals β-(BEDT-TTF)2X are presented. Out of a systematic study on the β-(BEDT-TTF)2X salts, including β-(BEDT-TTF)2trihalide mixed crystals, with the superconducting transition temperature (Tc) varying from 8 K to below 1 K, empirical rules for various factors governing the Tc in this class of organic metals have been extracted. In addition to the low- and high-Tc states, with Tc=l K and 8 K, respectively, a new superconducting state with Tc=2 K was found in α-(BEDT-TTF)2I3. A particular attention is paid for the correlation between Tc and resistivity. In addition, a correlation between Tc and the anisotropy of coherence length is also considered.
Thin Film Formations of Charge Transfer Complexes with Metallic Properties by Vacuum Deposition Method
Authors: Yudasaka M. , Hironaga K. , Yamochi H. , Nakanishi K. , Saito G. 
Published: March 2011

ABSTRACTThin films of a charge transfer complex, hepta-(tetrathiafulvalene) pentaiodide ( TTF7I5, TTF:I0-71 ), were prepared by double source evaporation of TTF and iodine. Crystalline films of TTF:I0-7i were obtained when substrate temperatures were kept between 0°C and 25°C. Orientation alignment of the crystalline films were affected by supply rate of iodine. By controlling the substrate temprature and the supply rate of iodine, highly oriented crystalline films were grown on mica substrates. It showed strong dichroism and anisotropic electrical propert ies.
Synthesis, Crystal Structure and Spectroscopic Studies of New Charge Transfer Compounds Obtained by Reaction of TTF and the Polyoxoanion [Mo6O19]2−
Authors: Bellitto C. , Attanasio D. , Bonamico M. , Fares V. , Imperatori P. , Patrizio S. 
Published: March 2011

ABSTRACTTwo different tetrathiafulvalene radical cation salts of the [M06O19]2−polyoxoanion have been isolated and characterized. Compound 1 corresponds to the chemical formula (TTF)3[Mo6019]. The crystal structure shows a ID stack of the donor TTF molecule, and each stack fits into channels formed by the anions. Within the stack a chain of trimers is identified, the inter-trimeric distance being 3.51 Å. The I.R., electronic and XPS spectra suggest the compound to be a mixed-valence salt. The electrical conductivity at room temperature is σ = 10−4Ω−1cm−1Compound 2 corresponds to the chemical+formula (TTF)2[M06019] . The compound consists of isolated (TTF+•)2dimers, interspersed with the polyoxoanions. In agreement with this crystal structure the compound is a diamagnetic insulator.
Synthesis of Bulk High Spin Density Charge Transfer Complexes for Organic Magnets
Authors: Chiang Long Y. , Upasani Ravindra B. , Goshorn D. P. , Tindall P. 
Published: March 2011

ABSTRACTWe describe a synthetic approach to the preparation of high spin density organic solid as a probe to organic ferromagnetism utilizing an external doping process to achieve a molecular sequence of alternate donors and acceptors in different spin states for, in principle, the ground state ferrimagnets. In contrast to the irreversibility of electron oxidations of many triaminobenzene derivatives, we found that, by substituting three hindered diisopropylamino groups on benzene, stable monocationic TDIAB radicals can be obtained. In the case of HDMAB its cationic radicals can be stabilized in a strong acid medium. The observed bulk spin densities of 0.18 — 0.23 spins 1/2 per donor molecule in TDIAB-PF6 and HDMAB-PF6 solids are significant comparing to the diamagnetic properties normally obtained in solids of simple cationic salts of planar organic donor molecules. The results imply that a small degree of molecular spin separation due to the steric effect can readily increase sharply the paramagnetic spin density of solids. We also found that the introduction of arsenic pentafluoride into molecular crystals disintegrates the long range order of crystal without rearranging the molecular stacking sequence in HMT complexes. Arsenic pentafluoride serves as not only the oxidant, but also the physical molecular separator. That results in a molecular spin separation of triplet dicationic HMT spins from each other at high doping level. This concept of molecular spin separation explains the observation of static magnetic data with an observed high spin density of many doped HMT charge transfer complexes. Without the molecular spin separation, the segregated-stack complexes, such as HMT-(AsF5.5)3.4 and HMT-DDQ-(AsF5.5)4.1, should instead give a low net bulk spin density with no triplet resonance after the intermolecular spin exchanges resemble to those observed in the case of HMT+2(CIO4)2 crystals.
Bridged Macrocyclic Transition Metal Complexes, a New Type of Semiconducting Materials
Authors: Hanack Michael , Hirsch A. , Lange A. , Rein M. , Renz G. , Vermehren P. 
Published: March 2011

ABSTRACTBridged quasi onedimensional macrocyclic transition metal complexes [MacM(L)]nusing phthalocyanine (Pc), tetrabenzoporphyrine (TBP), 1,2 -and 2,3-naphthalocyanines (1,2-; 2,3-Nc) as macrocycles (Mac) with M = e.g. Fe, Ru, Co and L = e.g. pyrazine (pyz), 1,4-diisocyanobenzene (dib), tetrazine (tz) exhibit interesting electrical properties. Regardless of the size of the bridging ligand after either chemical or electrochemical doping stable semiconducting compounds [MacM(L)Xy]n(X = e.g. I, BF4-, CIO4-…) are formed. For the first time the complete characterization of a soluble oligomer [MacM(L)]n(Mac = R4PC, M = Ru, L = dib) by1H-NMR spectroscopy is reported. Some of these shish kebab complexes e.g. [PcM(tz)]n, (M = Fe, Ru) or [MacMCN]n; (Mac = Pc, TBP; M = Co, Fe) exhibit good semiconducting properties without additional external doping. Whether or not these compounds are intrinsic semiconductors will be discussed. The synthesis of oligomeric bridged mixed valence compounds [PcM3+LPсM2+L]n(M = e.g. Fe) is another target of our work. We report here about first attempts to synthesize these oligomers.
Charge Transfer Complex of Hexakis (Alkylthio) Benzene with Tetrafluorotetracyanoquinodimethane (tEDTB)2 TCNQF4
Authors: Chasseau D. , Alleaume M. , Bravic G. , Lapouyade R. , Morand J. P. , Amiell J. , Delhaes P. 
Published: March 2011

ABSTRACTIn order to evaluate the potentiality of organic donor molecules for molecular organic ferromagnets, with in principle C3 molecular symmetry, as in the hexakis (alkylthio) benzene, we have prepared single crystals of the charge transfer complex of tris [ethylene dithio] benzene (tEDTB) with TCNQF4, which have been subsequently oxidized with bromine and arsenic pentafluoride gas. The stoichiometry of this complex is 2:1 and it crystallizes in the triclinic system, space group P1 with the following cell parameters: a=11.515, b=11.044, c=10.460 A, α=111.50°, β=122.50°, γ=93.82°. The crystal structure consists of columns of alternating donor dyads and acceptors monads (DDADDA). The degree of charge transfer is estimated to be 0.2-0.3 from the methods based on bond lengths. While (tEDTB)2- TCNQF4 does not give a significant ESR spectrum, after treatment with the bromine or AsF5 gas, a single intense line, centered around the free electron g value, appears without any evidence of either a ground or an excited triplet state.
The Polyanilines: a Novel Class of Conducting Polymers
Authors: Macdiarmid Alan G. , Epstein Arthur J. 
Published: March 2011

ABSTRACTThe synthesis of polyaniline in its fully oxidized, fully reduced and selected average intermediate oxidation states is described together with the synthesis of a self-protonic acid doped polyaniline. The processing of polyaniline films and fibers by thermal stretching to give conductivities up to ∼100 S/cm is reported. Both doped and undoped polyaniline fibers have tensile strengths approaching those of commercial polymers.
Infrared Reflection-Absorption Study of the Aniline Electropolymerization on Stainless Steel
Authors: Gaillard F. , Bouyssoux G. , Kumar S.N. 
Published: March 2011

ABSTRACTPolyaniline (PANI) films were grown on 304 L steel and studied by FTIR spectrometry. The spectra of the films formed carry evidence for quinonic/aromatic alternating structure involving head-to-tail coupling. The coupling is quite independent of the thickness of the polymeric layer. The quinonic/aromatic ratio can be varied when the film is subjected to further dedoping treatments (electrochemical reduction or KOH immersion).