bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optical Microanalysis of Small Semiconductor Structures
Authors: Murphy D. V. , Brueck S. R. J. 
Published: March 2011

ABSTRACTRaman spectroscopy is a powerful tool for evaluating semiconductor crystal characteristics with a diffraction–limited spatial resolution of approximately 0.5 μm, comparable to device structure dimensions. Examples are presented of the use of Raman scattering to measure stress variations across Sion-insulator and Si-on-sapphire stripes with dimensions down to 2 μm and, to probe the spatial variation in the effectiveness of annealing of a Si layer deposited over metal device structures. Detailed measurements of the variation in the Raman spectra of thin crystalline Si films, with thicknesses down to 3.0 nm, are discussed. Measurements made on roughened Si surfaces are presented which show that surface morphology on a submicron spatial scale results in enhanced Raman intensities.
Light Scattering Studies of the State of Dispersion in Molecular Composites
Authors: Hsiao Benjamin S. , Stein Richard S. , Addad Silvie Cohen 
Published: March 2011

ABSTRACTPolymer solutions comprising stiff-chain polyester and flexible polysulfone were examined via light scattering techniques. Results were analyzed using the Stein-Wilson extension of the Debye-Bueche theory, in which the correlation lengths due to orientation fluctuations and mean-squared fluctuations of the molecular anisotropy were obtained. For a molecular dispersion, the correlation length is small and a function of concentration; as the anisotropy is attributed to the rod molecules. Aggregation of rods is associated with an increase in the magnitude and size of the density fluctuations, and a change in anisotropy fluctuations is dependent on the degree of orientation correlation of the rods in the aggregate. Blends prepared by solution casting were studied by a small-angle light scattering method. Results thus far demonstrate that aggregates are present in most of the rod/coil composites prepared.
The Synthesis, Structure and Property Behavior of Inorganic-Organic Hybrid Network Materials Prepared by The Sol Gel Process
Authors: Wilkes G.L. , Brennan A.B. , Huang Hao-Hsin , Rodrigues David , Wang Bing 
Published: March 2011

ABSTRACTThe synthesis, structure/property behavior of inorganic-organic hybrid network materials prepared by the sol gel process have been chronologically reviewed with emphasis on those systems prepared in the authors laboratory. Specific features of reactions as well as the nature of reactants are included. The morphological features of these “ceramer” systems formed have many features in common even though the reactants may be quite different. The mechanical properties of the final materials in conjunction with SAXS have proven beneficial in establishing the basics of their morphological texture. Finally, it is demonstrated how microwave radiation in some cases, can serve as an efficient way in processing the ceramer systems.
Pbzt Microcomposites with Advanced Thermoplastic Matrices
Authors: Sanford W. Michael , Prilutski Gerard M. 
Published: March 2011

ABSTRACTThermoplastic microcomposites offer the potential for better economics and improvements in composite processing, and possibly performance, over conventional ‘string-and-glue’ composites. The early development of molecular composite technology focused on polyamide matrix polymers; however, for many aerospace applications higher use temperatures and greater solvent resistance than that of conventional polyamide matrices will be required. This paper describes work performed under contract to the U.S. Air Force to develop PBZT (poly p-phenylene benzobisthiazole)/thermoplastic molecular composites with high performance matrix resins into a viable technology.A scaleable process has been defined based on a novel technology developed by Du Pont. Advantages of this process include better economics, superior processing performance, and improved MC fiber tensile properties versus prior art. Using this process we have obtained rule-of-mixtures properties in our microcomposite fibers with matrix polymers offering use temperatures from 330 to 600°F. Consolidation of PBZT/PEKK fibrous preforms into uniaxial panels up to 1011 × 1511 has been demonstrated and material propperty evaluation and data base development are in progress. Uniaxial property levels achieved to date for all systems compare favorably with conventional ‘string-and-glue’ PBZT/epoxy composites although as with other organic fiber reinforcements, compressive and shear performance may be limiting factors in MC applications.
Small Angle Neutron Scattering Studies of Blends of Protonated Linear Polystyrene with Crosslinked Deuterated Polystyrene
Authors: Briber Robert M. , Bauer Barry J. 
Published: March 2011

ABSTRACTSmall angle neutron scattering (SANS) has been used to study the scattering function and thermodynamics of blends of linear protonated polystyrene (PSH) and crosslinked deuterated polystyrene (PSD). Two series of samples were synthesized. In both cases the samples were made by dissolving the linear PSH in deuterated (d8) styrene monomer containing a small amount of divinyl benzene as a crosslinker which was then polymerized to form the PSD network around the linear PSH chains. The samples were all made at a concentration of 50/50 by weight PSD/PSH. A special effort was made to keep the samples single phase so that SANS could be used to study the thermodynamics of the system and compare with theory. This entailed working at relatively low crosslink densities (<1 mole % crosslink units). Series 1 is a set of samples with the same crosslink density varying the length of the linear chain. Series 2 is a set of samples containing the same length linear chain varying the crosslink density systematically. By extrapolating S(q) obtained from SANS to q=O the zero angle scattering, S(O), was obtained. S(O) is inversely proportional to the second derivative of the free energy with respect to composition, ∂2 (Δf/kT)/∂ø2. Assuming additivity of the free energies of mixing and elasticity, the portion of the zero angle scattering due to elasticity is calculated.
Interpenetrating Polymer Networks and Related Topological Isomers
Authors: Frisch Harry L. 
Published: March 2011

ABSTRACTWe have studied the phase compatibility of simultaneous interpenetrating polymer networks poly (2,6–dimethyl–l,4–phenylene oxide) with a number of other polymer networks as a function of their solubility parameters. Even when the blends of the corresponding linear chain polymers are immiscible their interpenetrating polymer networks can be miscible in all proportions. We have also prepared the corresponding pseudo (or semi) interpenetrating polymer networks where one component is linear and in one system the polymeric catenanes. All these systems generally show microphase separation.
Mechanical Properties and Structure of Melamine Formaldehyde/Poly(Vinyl Alcohol) Molecular Composites
Authors: Gong Kecheng , Zhang Xinghua 
Published: March 2011

ABSTRACTThe mechanical properties and structure of melamine formaldehyde (MF)/poly(vinyl alcohol) (PVA) composites were studied in this paper. When PVA content was less than a certain value(about 20 weight %), both flexible strength and impact resistance were improved obviously. While the impact resistance improvement remained the previous trend the flexible strength didn't increase so rapidly as before when the PVA content was more than 20%. The morphology and reactivity of the prepolymer powder and the morphology of the finished specimens were investigated by means of microscope, infrared spectrum and transmission electron microscope(TEM). The results indicated that molecular composite structure was formed in this two-component system. The well-distributed PVA in this system was beneficial to the formation of the molecular composite structure. That could explain the effects of PVA on the mechanical properties and showed that the molecular composite structure are favourable for making full use of the macromolecular potentiality.
Inorganic-Organic Composites by Sol-Gel Techniques
Authors: Schmidt Helmut 
Published: March 2011

ABSTRACTThe sol-gel process opens the possibility of combining inorganic and organic units to new hybrid polymers. Organic units can be used for structural modification of the inorganic backbone, for creating new functions within an inorganic network and for building up organic polymeric chains. The materials show interesting perspectives with respect to structural (surface hardness, strength) and functional properties (e. g. diffusion, photocuring, incorporation of dyes, optical properties). A review over structural and functional properties of sol-gel derived inorganic-organic polymers (ORMOCERs = organically modified ceramics) is given.
On the Scale of Diffusion Lengths Observable by Neutron Reflection: Application to Polymers.
Authors: Karim A. , Mansour A. , Felcher G.P. 
Published: March 2011

ABSTRACTA systematic approach has been applied to neutron reflectivity data to study interdiffusion across an interface. It is shown that with this technique it is possible to probe interface broadening from ∼10Å to upward of 200 Å, the upper limit being already within the range of observation of other techniques such as Rutherford backscattering spectrometry (RBS), forward recoil spectrometry (FRES) and secondary ions massspectroscopy (SIMS). As example is analyzed the interdiffusion of a bilayered polymer system: a deuterated polystyrene (d-PS) layer on protonated polystyrene (h-PS).
Biaxial Extrusion of Polyimide Larc—tpi and Larc—tpi Blends
Authors: Haghighat R. Ross , Elandjian Lucy , Lusignea Richard H. 
Published: March 2011

ABSTRACTBiaxial films of polyimide LARC—TPI and LARC—TPI/liquid crystal polymer Xydar®were extruded directly from the melt for the first time via an innovative new extrusion technique. Three types of films, neat LARC—TPI, LARC—TPI/lO wt percent and 30 wt percent blends were processed as a part of this NASA funded program. This new process offers an alternative technique to costly post—processing stretching of both solution cast and sheet extruded films. The post—processing step is often required to enhance certain properties. Processability was greatly enhanced by incorporating Xydar. The coefficient of thermal expansion was reduced from 34 ppm/ºC for the neat LARC—TPI to 15 ppm/º C for the 10 wt percent Xydar blend and ultimately down to I to 3 ppm/º C for the 30 wt percent blend films in the direction of extrusion. The maximum improvementin stiffness was realized by incorporating 10 wt percent Xydar (2.8 GPa up to 4.9 GPa). Tensile strength, however, experienced a drop as a result of Xydar addition, probably caused by inefficient mixing of the two phases.
Polymer-Derived Si3N4/BN Composites
Authors: Schmidt Wayde R. , Hurley William J. , Sukumar Vijay , Doremus Robert H. , Interrante Leonard V. 
Published: March 2011

ABSTRACTPartially crystalline silicon nitride, with a specific surface area greater than 200 m2/g, is obtained by the pyrolysis of an organometallic, polymeric precursor under NH3 to 1000 °C. Additional heating to 1400 °C under N2 produces alpha-Si3N4. The addition of up to 15% h-BN was found to affect the coarsening characteristics of amorphous silicon nitride by promoting surface area reduction and suppressing crystallinity. By combining Si3N4 and BN molecular and polymeric precursors prior to ceramic conversion, or incorporating Si, N, and B into a single preceramic polymer, the relative proportion and crystallinity of the ceramic phases can be controlled in the resulting Si3N4/BN composites.
The Physical Properties of Microcellular Composite Foams
Authors: Nyitray Alice M. , Williams Joel M. , Onn David , Witek Adam 
Published: March 2011

ABSTRACTRecently we reported on a method of preparing microcellular composite foams. In this procedure an open-celled polystyrene foam is prepared by the polymerization of a high-internal-phase water-in-oil emulsion containing styrene, divinylbenzene, surfactant, free-radical initiator and water. After drying, the cells of the polystyrene foam are then filled with other materials such as aerogel or resoles. The physical properties of these materials e.g., surface area, density, thermal conductivity, and compressive strength will be presented.
Investigation of Differential Induced Attenuation of Orthogonal Axes in Polarization Maintaining Fibers
Authors: Gingerich M. E. , Hickey S. J. , Harrington C. C. , Marrone M. J. , Friebele E. J. , Looney L. D. , Onstott J. R. 
Published: March 2011

AbstractRecent studies have indicated that the birefringent-inducing stress of polarization-maintaining (PM) fibers decreases the long term, permanent loss induced by ionizing radiation and that light polarized along the two orthogonal axes of PM fibers may be attenuated differently by exposure to irradiation sources. This paper reports the results of specific studies of this differential attenuation induced in a series of PM fibers by both steady state and transient irradiations. It has been found that the response to ionizing radiation depends on the materials properties of the fiber, i.e. the core and clad dopants and/or degree of stress, and that the magnitude of the differential attenuation is small relative to the total or one-axis incremental loss.
Photoluminescence Induced by 6.4 eV Photons in High Purity Silica
Authors: Tsai T. E. , Lin H. B. 
Published: March 2011

Abstractphotoluminescence in the visible range in high purity silica rods at room temperature was studied using 6.4 eV photons as the excitation source. Electron spin resonance (ESR) was used to monitor the induced paramagnetic centers. Broad luminescence bands at 2.7 eV, 2.2 eV and 1.9 eV were observed. The relative intensities of these bands were found to be intensity dependent. The fluence dependence of these bands were also studied. The results are discussed in relationship to the excitonic mechanism for defect generation in silica.
Effect of Compositional Variations and Processing on the Optical Scattering of Zblan Glass
Authors: Neeves A. E. , Reed W. A. , Chui-Sabourin M. , Bruce A. J. 
Published: March 2011

AbstractThe effects of compositional modifications, specifically oxide and p-block fluoride additions, and melt processing, via “on-situ oxidation”, have been investigated on bulk samples of ZBLAN glasses. Molecular light scattering in the Mie and Rayleigh regime has been measured as a function of scattering angle at wavelengths between 0.6 and 2.6 μm. From an analysis of the angular scattering of both vertically and horizontally polarized beams the Rayleigh ratios and dissymmetry factors are determined as a function of wavelength. The average size of the scattering sites can be estimated in the range of 0.02 and 2.0 μm. Relatively high oxide substituted ZBLAN glasses exhibit light scattering losses only moderately higher than the ZBLAN base glass, and do not show any evidence of gross phase separation or precipitation. InF3 containing samples also exhibit scattering comparable to the ZBLAN base glass. The scattering of ZBLAN at 2.6 μm is larger than the scattering predicted by extrapolating data taken at 0.647 μm using a λ−4 dependence. This added scattering may interpreted as due to either a wavelength independent contribution or a result of a difference in the wavelength dependence of the dispersion between the host and the scattering center.
Thermochemistry of the Amorphous System SiO2-GeO2: Comparision of Flame Hydrolysis Materials to High Temperature Fused Glasses
Authors: Maniar P. D. , Navrotsky A. , Draper C. W. 
Published: March 2011

AbstractEnergetics and structure of germania doped silica prepared from high temperature melts and by flame hydrolysis were investigated using transposed temperature drop and solution calorimetry. Heat contents (H973-H298) are similar for first and second drops for the flame hydrolysis preforms reflecting the effect of temperature of deposition (1073 K) in creating a relaxed structure which is not easily rearranged. Heats of solution, at 973 K in molten lead borate, of fused glasses along the SiO2-GeO2 binary show ideal heats of mixing between the endmembers. This'indicates that fused glasses behave in a simple manner, with ideal substitution of Ge for Si in the tetrahedral framework. Flame hydrolysis samples (preform and annealed glasses) also show ideal heats of mixing. This suggests that the flame hydrolysis materials are energetically very similar to their bulk-melted counterparts. This insensitivity of energetics to preparation conditions is consistent with our previous studies on silica prepared at various temperatures [1].
Design Parameters for Multimode Fluoride Fibers: Effects of Coating and Bending on Loss
Authors: Busse L. E. , Aggarwal I. D. 
Published: March 2011

AbstractNumerical calculations of losses due to polymer coatings and macrobending have been made for step index multimode fluoride fibers. To avoid such losses, fiber core and cladding diameters and numerical aperture must be chosen carefully.
New Stable Iodide Glasses in the Cd-As-I and Cd-As-Ge-I Systems
Authors: Heo Jong , Sigel George H. 
Published: March 2011

AbstractIodide glasses presently being investigated suffer from their poor glass forming abilities, thermal instabilities and general lack of chemical durability. Glasses in the Cd-As-I and Cd-As-Ge-I systems are investigated in this study for the purpose of developing water-resistant, thermally stable iodide glasses and optical fibers. Differential scanning calorimetry(DSC) showed that glasses in these systems have glass transition temperature(Tg) values above 300°C. Devitrification of glasses during cooling and reheating can be suppressed by incorporating small amount of Ge atoms into ternary Cd-As-I glasses. They are transparent up to 14μm in the infrared region with excellent durability against liquid water at 90°C.
Crystallization Studies of Glassy Te-Se-Br Thin Films
Authors: Adam J. L. , Ortiz C. , Salem J. R. , Zhang X. H. 
Published: March 2011

AbstractWe have studied the effect of laser irradiation on Te-Se-Br thin films. The major effects were found to be dominated by changes in composition because of the complete loss of Br and variable loss of Se. These losses are measured by EIDS and are reasonable in view of the temperatures obtained from a heat flow calculation. The remaining Te-Se material can be made crystalline under specific conditions of laser pulse length and laser power (which determine the cooling rate). We have been able to establish that the crystallization starts with surface filamentary growth exhibiting fractal network formation. With higher laser energy it tends to coalesce to form three dimensional crystals.
Low-Loss GI Plastic Optical Fiber and Novel Optical Polymers
Authors: Koike Yasuhiro , Ohtsuka Yasuji 
Published: March 2011

AbstractA low-loss GI plastic optical fiber in which the attenuation of transmission was about 130 dB/km at 650 nm wavelength was successfully obtained by a new interfacial-gel copolymerization technique. Novel optical functional polymer glasses, such as birefringence-free copolymers for any degree of orientation and optically active amorphous polymers which act as polarization modulators, were synthesized and characterized.
Silica-Based Single-Mode Waveguides and Their Applications to Integrated-Optic Devices
Authors: Takato Norio , Sugita Akio 
Published: March 2011

AbstractLow-loss silica-based single-mode waveguides are fabricated on Si substrates by flame hydrolysis deposition and reactive ion etching. The waveguide loaded with a thin film heater operates as a phase shifter due to the refractive index dependence on temperature. The phase shifter can afford optical switching and/or tuning functions for silica-based integrated-optic devices. The waveguides have large stress-induced birefringence due to the difference in thermal expansion coefficients between SiO2 and Si. Waveguide birefringence control techniques are proposed for constructing various polarization insensitive and sensitive devices.
Continuous Casting of Particulate Silica Gels
Authors: Rabinovich E. M. , Jackson K. A. , Kopylov Nonna A. 
Published: March 2011

AbstractA feasibility study of continuous casting of particulate silica sols has been conducted. The process consists in measured pumping of the sol and a gelling agent into a heated mold where the sol gels. The gel is continuously pushed out of the cylindrical mold by the pressure of the pumped sol. Gel rods of 2.5 cm diameter, up to 150 cm long, were prepared by this method. Temperature dependence of the gelation was studied, and activation energies of the process were determined.
Optical Absorption and Emission in Rare Earth Heavy Metal Fluoride Glasses
Authors: Pafchek R. , Aniano J. , Snitzer E. , Sigel G. H. 
Published: March 2011

AbstractTrivalent thulium is a 4-level laser system which operates in the 1.47μm spectral region. A tunable amplifier at this wavelength is of great interest since it falls in one of the telecommunication windows. For lasing action to occur the relatively long lived 3F4 lower laser level must be quenched to eliminate the self-terminating behavior of thulium. Rosenblatt et al. co-doped Tm and Th into a ZBLAN host to quench the 3F4 lower laser level.[1] Co-doping with Ho offers the possibility of more efficient laser operation, but it must be established whether Ho can effectively quench the lower level of Tm. This preliminary study indicated appreciable energy transfer occurred from the 3F4 level of Tm to the 5I7 level of Ho which decreased the lower laser level lifetime by as much as two orders of magnitude. The subsequent decay of the Ho ions is an issue requiring further investigation.
Chemical Reactions at Glass/Liquid Interfaces
Authors: Ferris Kim F. , Sosa C. P. , Pederson L. R. 
Published: March 2011

AbstractElectronic structure calculations were performed on model silicate complexes in the presence of a perturbing dielectric field. Solid state dielectric effects were represented by an electrostatic representation of surrounding molecular subunits, which were developed from quantum mechanical electron density distributions. Only minor changes in the molecular geometry of the surface silicate model were noted; however, significant intramolecular charge redistribution and intermolecular interaction energy changes occur in the presence of the perturbing field. Molecular probes of surface absorption show a differential stabilization of donor and acceptor interactions for hydrogen bonding species.
Pressure Dependence of the Structural and Electronic Properties of Organic Superconductors
Authors: Chasseau D. , Gaultier J. , Houbib H. , Rahal M. , Ducasse L. , Kurmoo M. , Day P. 
Published: March 2011

ABSTRACTThe pressure dependence (≤12 × 102 MPa) of the cell parameters of (TMTSF)2 - C104 and κ - (BEDT-TTF)2 - Cu(NCS)2 has been measured at room temperature. The magnitudes of the principal compressibilities calculated and the bulk modulus (B) do not vary all over the experimental pressure range for (TMTSF)2 - C104, while ki decrease slightly for κ - (ET)2 - Cu(NCS)2 and its Dulk modulus strongly increases. The directions of the principal compressibilities strongly varywith pressure for the former salt; in the latter case, the projections of the directions of the smallest and of the largest principal compressibilities remain parallel and perpendicular to the long molecular axis respectively whereas the intermediate is along the monoclinic b axis.The crystal structures have been refined at 4 × 102 ,6 × 102 and 9.5 × 102 MPa (R = 0.05) for (TMTSF)2 - C104 and at 7 × 102 MPa (R = 0.095) for κ - (ET)2 - Cu(NCS)2. The transfer integrals have been calculated for the two compounds. In (TMTSF)2 - C104, both normal and transverse overlaps strongly increase with pressure; the dimerization is reduced under pressure and the two largest transverse interactions become identical. In κ - (ET)2 - Cu(NCS)2, the intra-dimer interaction strongly increases whereas the variations of the inter-dimer interactions may be very different.