bluuebunny/crossref_metadata_2025_split huggingface dataset:
The High Temperature Deformation Behavior of A Cr2Nb Ordered Intermetallic System
Authors: Vignoul G. E. , Sanchez J.M. , Tien J. K. 
Published: March 2011

ABSTRACTA basic characterization of the deformation behavior of Cr2Nb by microindention at ambient and elevated temperatures (up to 1400 °C) was undertaken. The microhardness of this system was seen to decrease with increasing temperature, from 1040 MPa at 25°C to 322 MPa at 1400 °C. Further, the microindention creep behavior of this system was studied by varying time on load at T = 1000 and 1200°C. Analysis of the data showed that m = 24 and Qapp = 477.61 kJ/mole. These unusually high values are indicative of the existence of an effective resisting stress against creep. When the data was fit against a microindention creep deformation law which was modified to incorporate an effective resisting stress term, it was determined that m = 4.5, Qcreep = 357 kJ/mole and the resisting stress term σr = 300 MPa.
A Comparative Study of Short Range Order in Fe-Cr and Fe-V Alloys Around Equiatomic Composition
Authors: Turchi P.E.A. , Sluiter M. , Stocks G. M. 
Published: March 2011

ABSTRACTConfigurational energies have been calculated for equiatomic Fe-Cr and Fe-V alloys possessing the high temperature bcc crystalline structure, within a first principles electronic band structure approach. In agreement with experimental facts, a tendency towards order, with a B2 ordered structure of CsCI type, is found for FeV whereas phase separation characterizes FeCr. These results suggest that the nature of short range order in the high temperature bcc solid solution is not the primary driving force for describing the structural transformation from bcc to sigma which takes place in both alloys upon decreasing temperature.
Recent Advances in Gamma Titanium Aluminide Alloys
Authors: Kim Young-Won (Y-W.) 
Published: March 2011

ABSTRACTGamma titanium aluminide alloys of current interest are two-phase alloys consisting of γ-TiAl phase as the matrix and a α2-Ti3Al phase as the second phase. The properties of these alloys depend on alloy composition, processing, microstructure, and their combination. Two major microstructural constituents are gamma grains and lamellar grains, the latter of which contain alternate layers of gamma (γ) and alpha-2 (α2) thin plates. The relative amounts and distribution of these two constituents are the main factors controlling mechanical properties. This paper reviews our current understanding of the composition/microstructure/property relationships. An extended discussion will be made on the fundamental aspects of the formation of lamellar structure during cooling and the evolution of microstructure occurring during thermomechanical treatments.
Effect of Interstitials on the Phase Stability of Selected Intermetallics
Authors: Kassem M. A. , Koch C. C. 
Published: March 2011

ABSTRACTThe possibility of modifying the complex crystal structure of selected refractory metal aluminides and silicides of AB3 stoichiometry by interstitial alloying additions was investigated. The compounds Nb3Si, V3Si, Mo3Si, Cr3Si, and Nb3Al were alloyed with oxygen or carbon up to about 20 atomic %. Alloying with oxygen or carbon in V3 Au was studied as a model for the A15 to Ll2 (or L'l2) structural change induced by interstitial alloying. Oxygen and carbon stabilized the perovskite, L'l2, structure in V3Au. Oxygen stabilized a L12 phase in Nb3Si while carbon induced a hexagonal structure phase. No L12 or L'12 phases were stabilized with the addition of oxygen or carbon in V3Si, Mo3Si, Mo3A1, Cr3Si, or Nb3Al. The Pettifor structural map for AB3 compounds was used to predict the structural changes in these compounds on alloying of oxygen or carbon.
Development Of Fe3Si Alloys
Authors: Langhong Lou , Tianxiang Zhang , Yaoxiao Zhu 
Published: March 2011

ABSTRACTThe partial phase diagram of the Fe-Mn-Si system at 900°C was obtained by electron microprobe measurement. In addition, the effect of carbon on these equilibrium were also studied. Depending on these, a series of Fe-Mn-Si-C alloys with the matrix of Fe3Si were designed. It was found that they all have some plasticity and can satisfy the engineering requirement. Moreover, after appropriate heat treatment, all these alloys have good corrosion resistance in sulphuric acid with various concentrations.
Microstructure of Rapidly Solidified Nb3Al-X Ribbons
Authors: Yasuda Ken , Fujiwara Tetsuo , Kodama Hideyo , Suwa Masateru 
Published: March 2011

ABSTRACTNb-Al and Nb-Al-X(X is Cr,Ti or Zr) ternary alloys ribbons, with compositions around the A15 (Nb3Al) structure, a candidate intermetallic as an advanced high temperature material, were rapidly solidified by an arc melt spin process. The rapid solidification structure of these tri-niobium aluminide alloys and the relationship between formed phases and compositions of ribbons are investigated.
Hot Extrusion of A Ti-Al-Nb-Mn Alloy
Authors: Seetharaman V. , Malas J. C. , Lomibard C. M. 
Published: March 2011

ABSTRACTForward extrusion of a gamma-TiAl alloy (Ti-49.5A1-2.5Nb-l.lMn) was investigated, with special reference to the role of preheat temperature, ram velocity, and can material. Cylindrical billets were sealed in evacuated cans, soaked at extrusion temperatures ranging from 1050 to 1350°C for 2 hr and then extruded through streamlined dies held at 260°C. Microstructural features of the extruded billets which evolved under steady-state conditions were characterized. In conjunction with these observations, a coupled (thermal-deformation) finite-element analysis procedure was used to predict the local distributions of strain, strain rate, temperature, and stress present during extrusion. The microstructures of the extruded products are compared with those obtained in samples subjected to isothermal constant-strain-rate compression tests.
Oxidation Behavior of Gamma-Titanium Aluminide Alloys
Authors: Mckee Douglas W. , Huang Shyhchin C. 
Published: March 2011

ABSTRACTThe oxidation behavior of a number of gamma-TiAl alloys with ternary additions has been studied for extended periods during rapid thermal cycling to temperatures of up to 1000°C in flowing air. Under these conditions, binary alloys, such as Ti-48a/oAl and Ti-52a/oAl form flaking scales with sub-scale embrittlement, although the initial oxidation rate decreases with increasing aluminum content. Ternary Ti-Al-Cr and Ti-Al-Ta alloys with up to 4 a/o Cr or Ta also show a tendency to form spalling scales at these temperatures. On the other hand, the addition of niobium or tungsten results in a dramatic improvement in oxidation resistance at 850 °C, although at 1000°C even these alloys begin to spall after an induction period of several hundred hours.
Oxidation Behavior of Ni Aluminides Using X-ray Absorption Spectroscopy
Authors: Greegor R.B. , Lytle F.W. 
Published: March 2011

ABSTRACTXAS was used to investigate the oxidation behavior of Ni3Al aluminides with and without the addition of Cr. At 450 C the Cr formed a Cr2O3 like oxide layer which inhibited the oxidation of the Ni at the surface. Ni oxidation did occur in the sample without Cr at 450 C. At higher temperatures the Ni at the surface oxidized to NiO, but in the bulk no oxidation of the Ni was observed whether Cr was present or not. When no Cr was present a minimum was observed at 700 C in the fraction of oxidized Ni. The Cr (8at.%) did not cluster and substituted for Ni or Al in the Ni3Al aluminide.
The Methods of Investigation of Complex Dielectric Permittivity of Layer Polymers Containing Conductive Inclusions
Authors: Kalachev A.A. , Kukolev I.V. , Matitsin S.M. , Novogrudskiy L.N. , Rozanov K.N. , Sarychev A.K. , Seleznev A.V. 
Published: March 2011

ABSTRACTA set of methods for measure complex dielectric permittivity of layer materials at microwaves is suggested. These methods allow one to measure dielectric permittivity of composite materials in with the mean size of inhomogeneities is comparable with the wavelength and materials with high dielectric permittivity.
Third – Order Nonlinear Optical Properties of Polysilane Films
Authors: Kaatz P.G. , Patterson G.D. , Kim H.K. , Frey H. , Matyjaszewski K. 
Published: March 2011

ABSTRACTResults are presented from third harmonic generation, (THG), experiments on a number of polysilane films. The polymers studied include poly(di-n-hexylsilylene) PDHS, and copoly(di-n-hexyl, hexylmethylsilylene) PDHS / PHMS. These polymers exhibit positive thermochromism, where the transition temperature and spectral properties are dependent on the copolymer ratio. The nonlinear susceptibility, , in the low temperature phase of the polymer increases by approximately 4 − 5 times that of the high temperature phase where the absorption maximum decreases by ∼ 60 nm. The polymers are prepared as neat, solid films on fused silica substrates. Thickness and refractive index measurements of these polymers were made by UV-VIS-NIR spectroscopy.
Structure and Optical Property of Polymers Obtained by Solid-State Polymerization of a Tetraacetylene Compound
Authors: Okada Shuji , Matsuda Hiro , Masaki Atsushi , Nakanishi Hachiro , Hayamizu Kikuko 
Published: March 2011

ABSTRACTThe polydiacetylene having diacetylenic substituents has been prepared by γ-ray irradiated solid-state polymerization of 15, 17, 19, 21- hexatriacontatetrayne. It has been found that the polymer can be converted into the di(polydiacetylene), i.e., a new type of the fused-ring polymer of conjugated 10π-electron system, by the subsequent heat-treatment in the solid-state.
Doped Polymers as Third-Order Nonlinear-Optical Materials
Authors: Kuzyk Mark. G. , Paek U. C. , Dirk Carl W. , Andrews Mark P. 
Published: March 2011

ABSTRACTRecently, there has been much interest in doped polymeric materials owing to their suitability for optical device applications.[1] While most of this effort has been centered on poled polymers and their applications to electrooptics, doped polymers are beginning to emerge as a promising material class for all-optical device applications. In this contribution, we discuss the status of doped polymers as third-order optical materials. Particular attention is focused on those properties that make doped polymers attractive as device materials such as optical nonlinearity and loss and their suitability for nonlinear-optical fiber devices.
Photocross-Linked Second Order Nonlinear Optical Polymers
Authors: Chen Y. M. , Mandal B. K. , Lee J. Y. , Miller P. , Kumar J. , Tripathy S. 
Published: March 2011

ABSTRACTWe report a novel method to obtain stable second order nonlinear optical (NLO) properties in polymeric thin films. Photocross-linking between the NLO active molecules and a photoreactive polymer is achieved by UV irradiation subsequent to poling. The thin film exhibits a nonlinear coefficient d33of 16.5 pm/V at a doping level of 20% by weight of NLO active molecules and possesses quite stable second order nonlinear optical properties
Determination of Linear and Nonlinear Optical Properties of a Polymer Thin Film
Authors: Koerkamp H.M.M. Klein , Hoekstra T.H. , Driessen A. , Popma Th.J.A. , Mohlmann G.R. , Horsthuis W.H.G. , Akzo E.W.P. Erdhuisen 
Published: March 2011

ABSTRACTThe second- and third-order nonlinear susceptibilities χ(2) and χ(3) of a polymer thin film are determined for three wavelengths (543.Snm, 632.8nm and 1523nm) using a method based on the linear and quadratic electro-optic effect. The frequency dependences of χ(2) and χ(3), deduced from a simple two-level electron-spring model, are consistent with our experimental results. Using this frequency dependence the intensitydependent refractive index, determined by nonlinear grating coupling, is transformed to a χ(3) value for the quadratic electro-optic effect. This value is in good agreement with our experiments. The layer structure used is simple and consists basically of a polymer layer sandwiched between thin metal electrodes.
Nonlinear Optical Properties of Ladder Polymers and Their Model Compound
Authors: Jenekhe Samson A. , Roberts Michael , Agrawal Ashwini K. , Meth Jeffrey S. , Vanherzeele Herman 
Published: March 2011

ABSTRACTThe third order nonlinear optical properties of thin films of polybenzimidazobenzophenanthroline ladder (BBL) and semi–ladder (BBB) polymers and their model compound cis–BBB were investigated by picosecond, third harmonic generation. The χ(3) (−3ω, ω ω, ω) spectrum of BBL, BBB, and cis-BBB was obtained in the wavelength range 1.0–2.4µm and shown to exhibit a three–photon peak at respectively 1.695, 1.695, and 1.50 µm. The magnitude of the three–photon enhanced χ(3) was 6.40×10−11, 3.15×10−11, and 0.77×10−11 esu, respectively, for BBL, BBB, and cis–BBB. The results show that the χ(3) of BBL and BBB is enhanced by a factor of 50 and 17, respectively, relative to the model compound cis–BBB at 1.05µm.
Asymmetrical Diphenylpolyene Pendant Polymers for Nonlinear Optical Activity
Authors: Sapochak Linda S. , Polis David W. , Dalton Larry R. , Spangler Charles W. 
Published: March 2011

ABSTRACTRecent activity in the development of nonlinear optical (NLO) materials with high second order susceptibilities has prompted the development of a wide variety of pendant polymers which possess desirable properties for device development, including high Tg minimal relaxation of the poled matrix, and high laser damage threshold. Ideal candidates for such systems are asymmetrically substituted oligomers of polyacetylenes such as dimethylaminonitrostilbene (DANS) and corresponding higher order oligomers. We report here a preliminary study of the synthesis of asymmetrically substituted donor/acceptor diphenyl-capped polyenes and thienylene vinylene oligomers attached as pendant moieties on polyvinylphenol (PVP) for second harmonic generation.
Broadband Microwave Dielectric Properties of Polymers
Authors: Robertson W. M. , Pastol Y. , Arjavalingam G. , Halbout J.-M. , Kopcsay G. V. 
Published: March 2011

ABSTRACTThe recently developed coherent microwave transient spectroscopy (COMITS) technique is capable of determining the complex dielectric properties of materials over a broad frequency range (15–140 GHz), in a single experiment. COMITS is based on the radiation and detection of picosecond duration electromagnetic transients by optoelectronically pulsed antennas. The essential features of the COMITS technique are described and representative results on dielectric and conducting polymers are presented.
Adam-Gibbs Formulation of Nonlinear Enthalpy Relaxation
Authors: Hodge Ian M. 
Published: March 2011

AbstractThe Adam-Gibbs (AG) expression linking relaxation times with configurational entropy gives an excellent account of the nonlinearity observed in enthalpy relaxation of amorphous polymeric, inorganic, and simple molecular materials near and below Tg. Data analyses yield zero entropy temperatures that are comparable with available Kauzmann values. The AG formulation, when coupled with a few plausible ancillary assumptions, predicts correlations between the Arrhenius parameters x, Δh*, and the KWW exponent β that are observed experimentally. It is suggested that the AG primary activation energy, Δμ, is the single causative factor that generates these correlations.
New NMR Methods that Probe the Structure of Glasses
Authors: Tycko Robert , Dabbagh Gary 
Published: March 2011

AbstractTwo-dimensional NMR methods allow a determination of the relative orientations of nearby molecules in polycrystalline and noncrystalline solids. We describe these methods and present applications to the determination of the crystal structures of two forms of polycrystalline methanol and to the investigation of short range molecular orientational ordering in methanol glass and in atactic PMMA.
Permeation of Selected Organic Compounds Through Untreated and Barrier-Treated High-Density Polyethylene
Authors: Kathios Daniel J. , Ziff Robert M. 
Published: March 2011

AbstractThe permeation rates of alkanes, alcohols, and aromatic hydrocarbons through untreated, fluorinated, and sulfonated high-density polyethylene (HDPE) were measured at a variety of temperatures and solvent compositions. The results were then analyzed to separate the individual contributions that solubility and diffusion make to the overall permeation rate. These results are discussed in terms of the chemical characteristics of the permeating constituents, and the barrier treatments on the HDPE surface.
Application of a Classical Force Field for Polyvinylchloride Derived from Ab initio Calculations.
Authors: Ludovice Peter J. , Jaffe Richard L. , Yoon Do Y. 
Published: March 2011

AbstractAb initio calculations were used to characterize the inter- and intramolecular energy surfaces for polyvinylchloride (PVC) model compounds and a classical force field was fit to these energy surfaces. This new force field will be used in molecular mechanics and stochastic dynamics simulations to analyze the atomic level morphology of PVC.
Strong and Fragile Behavior in Liquid Polymers
Authors: Angell C. A. , Monnerie L. , Torell L. M. 
Published: March 2011

AbstractIn the light of the strong and fragile classification of simple liquids we review some of the relaxation data for some well-known polymers to see the extent to which a similar pattern may be manifested. Relaxation time data rather than viscosity data are used in the polymer case to avoid complications from long chain effects on the Vogel-Fulcher equation pre exponent. A combination of light scattering and 13C NMR data seem to provide the most reliable guide to the microviscosity of interest to the classification. A pattern similar to that for viscous liquids is recovered with polyisobutylene, the “strongest” chain polymer and bisphenol polycarbonate, the most fragile. The extent to which correlations of other properties with fragility, found in the non-polymeric liquids cases, will carry over to the polymer case is still being evaluated, though the work of Hodge on the analysis of the more complicated problem of non-linear thermal relaxation, suggests the carry over may be extensive.
Thermal Treatment of Hg Containing I-VI Semiconductors by Annealing in a Mercury Bath (AMEBA)
Authors: Kalish R. , Uzan-Saguy C. 
Published: March 2011

ABSTRACTAn extremely simple and inexpensive technique (AMEBA) for the thermal treatment of Hg containing specimens which permits short or long time annealing in a Hg rich atmosphere is described. It is based on the immersion of the sample, properly protected by proximity caps in, or above, a hot mercury bath. The sample assembly is such that it permits Hg vapors, but not the liquid, to reach the specimen's surface.The usefulness of AMEBA in improving the electrical and structural properties of as-grown Hg1-xCdxTe (x = 0.21) and in removing ion implantation related damage as well as electrically activating B implants in various p-type HgCdTe samples is demonstrated. All the data presented show that AMEBA treatment yields results which are comparable or superior to those obtainable by convensional annealing methods.
Ohmic Contacts on N-Type Hg0.4Cd0.6Te.
Authors: Leech Patrick W. , Reeves Geoffrey K. , Kibel Martyn H. 
Published: March 2011

ABSTRACTThe electrical characteristics of In, Sn, Au and Pt contacts on n-type Hg0.4Cd0.6Te formed in the presence and absence of prior In2+ implantation have been examined. Measurements of specific contact resistance made using a Transmission Line Model have shown that the unimtlanted In/Hg0.4Cd0.6 and Sn/Hg0.4Cd0.6 junctions gave values of pc = 3.0x10−3 to 4.0x10−3 ohm.cm2. Auger sputter profiles of the asdeposited In/Hg0.4Cd0.6 and Sn/Hg0.4Cd0.6 interfaces have shown a significant in-diffusion of the metal overlayer. The influence of shallow In2+ implantation prior to metallization was an increase in pc which occurred above a dose of 1013 ions/cm2. In contrast, Pt and Au formed Schottky barrier diodes on n-type Hg0.4Cd0.6 with øb=0.69eV for Pt and øb=0.79eV for Au. With prior In2+ implantation, both Pt and Au contacts exhibited an ohmic behaviour with pc= 2x10−1 ohm.cm2. These results have significance in the fabrication of devices for 1.0 -2.5μm optical communications.
Photoluhi Nescence of Inas/InAsPSb and InAs/Heterojunctions
Authors: Baranov A.N. , Bresler M.S. , Gusev O.B. , Moiseev K.D. , Sherstnev V.V. , Yakovlev Yu. P. , Yassievich I.N. , Ioffe A. F. 
Published: March 2011

ABSTRACTPhotol uminescence of p-P InAs/InAsPSb and InAs/InAl AsSb heterojunctions grown by LPE method was studied at liquid helium temperature. The recombination spectra contained a new broad band lying between the substrate and the layer lines which was identified as an emission from the interface. This line is characterized by a strong blue shift when the excitation intensity increases. The intensities of bulk and interface lines show an unusual dependence on the pumping power. On the basis of experimental findings the interface line is attributed to emission from electrons confined at the interface due to reflection of elecctrons moving above the barrier.
The Growth Mechanisms of GaSb Epitaxial Film by MOCVD
Authors: Ueng H. Y. , Chen S. M. , Su Y. K. , Juang F. S. 
Published: March 2011

ABSTRACTThe growth reaction mechanism was experimentally investigated for TEGa and TMSb used for MOCVD GaSb epitaxial growth. The variations of growth rate, substrate temperature, the V/III ratio and the mole-fraction of III and V source gases, were detailly considered and investigated with regard to their effect on electrical and optical properties were measured during the epitaxial process. The experimental results were used to provide an inspection on defects interaction mechanisms and on the type of conductivity. Based on the investigation of growth mechanism, at 470°, a high quality GaSb epitaxial film 1 with 3 mobility, 634 cm2/V*sec and low hole concentration, 1.67x1016 cm−2 was obtained.
Mev Ion Beam Applications In III-V Semiconductors
Authors: Elliman R.G. , Ridgway M.C. , JOHNSON S.T. , Williams J.S. 
Published: March 2011

ABSTRACTThis paper reviews some key areas where MeV ion beams can be applied to III-V semiconductor materials. In particular, ion damage is assessed for various III-V materials in terms of implantation parameters, especially substrate temperature and dose rate. Implant isolation, involving the introduction of damage to remove carriers and achieve highlyresistive layers, is assessed for MeV irradiation. It is concluded that MeV ions can provide deep, uniform damage with a single-energy implant. Finally, improved epitaxy of amorphous InP with MeV ions is demonstrated.
Temperature Dependence of the Linewidth and Peak Position of the Intersubband Infrared Absorption in GaAs/Al0.3Ga0.7As Quantum Wells
Authors: Manasreh M. O. , Stutz C. E. , Evans K. R. , Szmulowicz F. , Fischer D. W. 
Published: March 2011

ABSTRACTThe linewidth and peak position (vo) of the intersubband transition (IT) in GaAs/Al0.3Ga0.7As multiple quantum wells are studied as a function of temperature using the infrared absorption technique. We find that electrons in the GaAs well are weakly coupled to the GaAs normal optical phonon mode. The total integrated area of IT absorption is found to be approximately constant in the samples that were doped in the well but temperature dependent in the samples that were doped in the barrier. We also find that vo increases as the temperature decreases. This blue shift is found to increase as the dopant concentration is increased. We calculated the absorption spectrum in a nonparabolic-anisotropic envelope function approximation including temperature dependent effective masses, nonparbolicity, conduction band offsets, the Fermi level, and lineshape broadening. Our results indicate that a large manybody correction, in particular an exchange interaction (Eexch) for the ground state, is necessary to account for the observed blue shift as the dopant concentration increases.