bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dielectric Properties of Various Ranks of Coal and Numerical Modeling Under Electromagnetic Irradiation
Authors: Chatterjee I. , Misra M. 
Published: March 2011

ABSTRACTThe dielectric properties of different ranks of Argonne Premium coal samples have been measured using an automated network analyzer system in the frequency range 0.3MHz to 3GHz. These measurements indicate that the inherent moisture present in the various ranks ofcoal has dielectric properties which are different from that of free water. The dielectric properties were also observed to increase with the moisture content as well as with the amount of oxygen present in the coal sample. A mixture model was successfully used topredict these dielectric properties.The measured dielectric properties have been incorporated into numerical calculations ofthe distribution of absorbed energy in coal irradiated with electromagnetic waves. The numerical technique used is the Method of Moments. Subsequently, the temperature distribution obtained in the coal is evaluated using a Finite Difference technique to solve the heat conduction equation. These calculations should prove very useful in the microwave drying of coal where it is difficult to monitor the temperature using probes.
Technique for Measuring the Dielectric Properties of Minerals as a Function of Temperature and Density at Microwave Heating Frequencies
Authors: Salsman Johanna B. 
Published: March 2011

ABSTRACTAs part of the research effort on investigating the effects of microwave energy absorption on the chemical and physical properties of minerals and ores, the Bureau of Mines, Tuscaloosa Research Center has developed a technique of measuring the dielectric constant and loss tangent of minerals at the common microwave heating frequencies. The objective was to establish a reliable data base to aid in predicting the effects of microwave heating on minerals.In this phase of microwave research, the Bureau measured the dielectric properties of powdered minerals with medium to high electrical conductivities (a ≥ 0.02 Mho/m) in the frequency range of 300 MHz to 3 GHz using an open-ended coaxial line probe connected to an HP 8753A network analyzer. Since the minerals were prepared as powders, techniques were used to relate the measured dielectric properties of the powdered minerals to the dielectric properties of the mineral at Its theoretical or natural density. Also, these measurements were performed as a function of temperature, from 25° to 325° C.The measured values of the dielectric constants and loss tangents using this method were accurate within ±5 percent. This report describes the method of measurement and discusses the results of the Bureau's investigations into dielectric properties of minerals.
Geometrical Arrangement of Magnetosomes in Magnetotactic Bacteria
Authors: Shih W.-H. , Sarikaya M. , Shih W. Y. , Aksay I. A. 
Published: March 2011

AbstractIn 1975, Blakemore discovered the freshwater magnetotactic bacterium Aquaspirillum magnetotacticum which navigates along the magnetic-field direction. Electron microscopic work showed that the magnetotactic bacteria contain magnetosomes which are intracytoplasmic membrane-bound particles of magnetite, Fe3 O4. The magnetosomes are within the single-domain size range (∼500 Å) of Fe3O4. The magnetosomes within cells are often arranged in one or more chains with the chain axis more or less parallel to the axis of motility of the cell. A detailed study of the magnetic properties of magnetotactic bacteria can be found in the paper by Moskowitz.
Advances in Self-Limiting Growth of Wide Bandgap II–VI Semiconductors
Authors: Konagai M. , Takemura Y. , Nakanishi H. , Takahashi K. 
Published: March 2011

ABSTRACTRecent advances in understanding the ALE (atomic layer epitaxy) growth of ZnSe, ZnS and ZnTe are reviewed. The Ideal ALE growth is obtained in the substrate temperature range of 250–350°C for ZnSe. In the ALE growth of ZnSe and ZnTe, a unique self-limiting mechanism is observed, in which the deposition rate saturates at 0.5 monolayer per cycle. Furthermore, applications of ALE of II–VI compounds to the growth of strained layer superlattices are also reviewed.
Atomic Layer Controlled Substitutional Doping With Lithium in ZnSe
Authors: Zhu Ziqiang , Kawashima Mitsuo , Yao Takafumi 
Published: March 2011

ABSTRACTThe detailed observation of dynamical behaviors of reflection high energy electron diffraction (RHEED) patterns during the adsorption processes of Li, Se and Zn is carried out. It is found that the RHEED intensity variation reflects the Li surface coverage during Li adsorption process on a Secovered surface. This fact enables one to control quantitatively the doping of Li “in situ”. A new method for atomic-layer controlled substitutional doping of ZnSe layers with lithium is proposed based on the RHEED investigations. The method allows the incorporation of Li dopants on Zn-sites of ZnSe by monitoring the RHEED patterns and intensities, and is expected to suppress the compensation by Li interstitials. Photoluminescence spectrum shows the growth of high quality p-type layers.
Growth of ZnSe and ZnSSe at Low Temperature with Aid of Atomic Hydrogen and Alternate Gas Supply
Authors: Gotoh Jun , Shirai Hajime , Hanna Jun-ichi , Shimizu Isamu 
Published: March 2011

ABSTRACTHigh quality ZnSe films were successfully grown on GaAs(100) at low temperatures, 200 °C or lower by Hydrogen Radical-enhanced Chemical Vapor Deposition (HRCVD). Defects were makedly eliminated by the following factors: selection of source materials; avoidance of ion bombardment; and suppression of formation of adducts by alternate gas supply. Strained-layer superlattice (SLS) consisting of ZnSe as the well and ZnS0. 1Se0.9 as the barrier was made by this technique. Emission line attributed to the free exciton was dominantly observed in the SLS.
Synthesis and Optical Characterization of New NLO-Active Polyurethanes and a Silver Colloidal Suspension in a Select Polyurethane
Authors: Kitlplchal P. , LaPeruta R. , Korenowskl G. M. , Wnek G. E. 
Published: March 2011

ABSTRACTNLO-active polyurethanes were developed and optically characterized. We synthesized polyurethanes possessing large hyperpolarlzabilities, which are covalently attached or crosslinked to the polymer backbone. At ambient temperature the d33 values for poled polyurethanes were measured shortly after poling and 6 months later. The second-order nonllnearlty of the poled, crosslinked polyurethane is extremely stable decreasing slightly over 6 months. Also, using a polyurethane bearing a tricyanovinyl moiety as the host, we developed a nonlinear optical silver nanoparticle composite system. A third-order susceptibility was measured for the composite and was determined to be larger than that from the sum of its components. A chemical enhancement mechanism is speculated to be contributing to the large optical nonlinearities.
Materials Requirements for Electro-Optic Polymers (for electronic systems applications)
Authors: Lytel Rick , Lipscomb George F. 
Published: March 2011

ABSTRACTThe field of electro-optic (EO) polymer materials for integrated optics has been developing rapidly during the past several years. Recent advances include the formulation of poled crosslinked epoxies and guest-host polyimides exhibiting thermal stability at temperatures significantly higher than that previously achieved with thermoplastic acrylate chemistry. These developments are an essential first step toward achieving practical materials exhibiting stability to manufacture, assembly, and end-use in modern electronic systems applications.Despite these developments, there is still much basic research to be performed to achieve a practical EO polymer material system. A polymer material system for integrated optics consists of a set of three compatible materials: cladding polymers, passive core polymers, and active core polymers. The three materials should ideally be derived from the same base polymer so that the layers of the entire waveguide structure have nearly identical thermal, mechanical, chemical, electrical, and optical properties. In an ideal syst', the active core material would consist of passive materials highly loaded with aligned nonlinear optical moieties exhibiting large hyperpolarizabilities and suitable size and shape for thermal stability.This paper provides a detailed review of the material requirements for EO polymer waveguide devices in electronic systems and points to new areas of research required for practical systems.
Dynamic Mechanical Behavior of Photo-Crosslinkable Nonlinear Optical Polymers
Authors: Marturunkakul S. , Lee J. Y. , Sengupta S. K. , Kumar J. , Tripathy S. K. 
Published: March 2011

ABSTRACTAn easily processable photocrosslinking guest-host system with stable second order nonlinear optical properties using polyvinylcinnamate as a host polymer has been developed1–2. Samples were made as free standing films from photo-crosslinkable polyvinylcinnamate and different concentration levels of 3-cinnamoyloxy-4-[4-(N, N'-diethylamino)-2-cinnamoyloxy phenyl azo] nitrobenzene. Photo-crosslinking was carried out by ultraviolet radiation at the major wavelengths viz. 297 and 313 nm subsequent to corona poling. Dynamic mechanical properties of these polymer films were investigated. The changes in the storage and loss moduli, as well as relaxation behavior of the system upon crosslinking and poling are discussed.
Study of the Solid State Properties of an Organic Superconductor
Authors: Fainchtein Raul , D'arcangelo S. T. , Yangt S. S. , Cowant D. O. 
Published: March 2011

ABSTRACTWe have synthesized cooper(I)di[bis(ethylenedithiolo)terathiafulvalene] bis(isothiocyanato), [(BEDT-TTF)2]+[Cu(NCS)2]using standard electrochemical methods. Single crystal samples of the compound were obtained and were found to have superconducting transition temperatures of 10.4 K, using DC conductivity measurements. [(BEDT-TTF)2+[Cu(NCS)2] shows a region between room temperature and 90 K which appears to be“semiconducting”To characterize the structure of the samples we used Scanning Tunneling Microscopy (STM). STM supplied real-space images of the sample surface in accordance to its electronic structure. Ravy observed diffuse streaks between Bragg spots in his X-ray data of [(BEDT-TTF)2+[Cu(NCS)2]−, which he attributes to a stacking fault at every fourth repetition of the anion in the crystal structure [1]. STM shows no evidence for such disorder in [−(BEDT-TTF)2]+[Cu(NCS)2]−of the type proposed, and in fact illustrates direct evidence to the contrary. An intensity modulation in the STM data supports the possibility of a charge density wave commensurate with the lattice. This interpretation is consistent with the calculated Fermi surface which allows nesting of the wave vector and may explain the peculiar behavior of the temperature dependency of the conductivity data in the normal region.
Superpolaron Model of Metallic Polyacetylene
Authors: Takahashi A. , Yamamoto S. , Fukutome H. 
Published: March 2011

ABSTRACTWe develop a new model for heavily doped metallic polyacetylene. An electron and a hole injected in a doped chain make localized defects called superpolarons (SP's) in the electronic order parameters (OP) in a charged soliton lattice. The SP's can make quantum intrachain translational motion and interchain transfer via dopant ions. They are stabilized by their quantum motions and SP pairs are spontaneously produced in a high doping regime. The SP's are Fermions and can be a Fermi liquid in the doping regime. Some metallic properties of the Fermi liquid of the SP' s are studied.
Synthesis of Heterocyclic Monomers Designed to Produce Conducting Polymer with Specific Redox Requisites and to Evaluate Stereochemical Factors Influencing the Conductivity
Authors: Berlin Anna , Brenna Elisabetta , Pagani Giorgio. A. , Sannicolo Franco , Zotti Gianni , Schiavon Gilberto 
Published: March 2011

ABSTRACTAccording to the “spacer” strategy we have previously proposed the monomers candidate for providing conductive polymers endowed with special properties should contain the polymerogenic rings (pyrrole or thiophene), as terminal units, linked to a central π-conjugatively active frame; we describe how it is possible in this way to control the redox potentials E of the polymers derived from such monomers. This control is beneficial because it is possible to increase the E° value of polypyrrole-type systems and decreases the E° value of polythiophene-type systems. Also, the “spacer”may be further functionalised and, being remote from the polymerisation site, cannot alter the conductivity characteristics typical of the polymer derived from the parent heterocycle (pyrrole or thiophene): such a functionalisation may provide the final, tailored, conductive polymer with special properties (e.g. solubility). If the central ring, acting as a spacer, is formed linking two positions of a di-heterocycle with a saturated chain, it is possible to partially control the twist angle between the heterocyclic units. Crystal and molecular structures have shown that dipyrrole units further linked through the nitrogen atoms are quite sensitive to the central ring size. With respect to the conductivity of unsubstituted polypyrrolc, the conductivity of the polymers derived from such monomers is dependent from the twist angle between the rings. This result is relevant to describe conditions of conjugation between the heterocyclic units of a monomer required to produce upon doping a conductive polymer.
Fabrication of an Electrically Conducting Full-Interpenetrating Polymer Network
Authors: Wang Yading , Rubner M. F. 
Published: March 2011

ABSTRACTFull-interpenetrating polymer networks (IPN) comprised of a styrene crosslinked polythiophene derivative and a crosslinked polystyrene network were synthesized and characterized. The IPNs were prepared by first crosslinking the pendant groups of a vinyl derivatized polythiophene with styrene monomer and then polymerizing and crosslinking styrene monomer in a swollen gel of the crosslinked polythiophene network. The doped forms of these full-IPNs reached conductivities as high as 0.5 S/cm. Conductivity stability studies showed that the IPNs are more stable than the as-prepared conjugated polymer at 40 °C but somewhat less stable at 80 °C.
Investigation of Polymer Relaxation after Deformation by Positron Annihilation
Authors: Tishin Sergey A. , Tsapovestsky Mihail I. , Tishin Vladimir A. , Kestelman Vladimir N. 
Published: March 2011

ABSTRACTThe relaxation of polyimid films after the axial tension has been investigated by measuring life-time of positrons and angular correlation of annihilation photons. The nonmonotonic change of mean life-time while relaxing the free film has been found. Two range of changes of positron-sensitive properties can be seen: “rapid” relaxation for 4–5 hours (characterized by reducing life-time of short-lived component) and “slow” relaxation (characterized by reducing the intensity of long-lived component). The results of this investigation have been compared with those of measuring of sample density and dielectric losses. The possible explanations and the- changes of mechanizms of relaxation with the conditions of deformation and “the rest” of polymers are analyzed.
Molecular Precursors to Boron Nitride then Films: the Reactions of Diborane with Ammonia and with Hydrazine on Ru(0001)
Authors: Truong Charles M. , Rodriguez José A. , Wu Ming Cheng , Goodman D. W. 
Published: March 2011

AbstractThe coadsorption and reaction of diborane with ammonia and with hydrazine on Ru(0001) have been studied using X-ray photoelectron spectroscopy (XPS) and thermal desorption mass spectroscopy (TDS). Diborane is found to decompose to atomic boron and hydrogen upon adsorption at T>200K. Multilayers of diborane and ammonia, deposited at 90K on Ru(0001), react when annealed to 600K. The XPS results indicate that boron-nitrogen adlayers can be formed by this reaction. These boron-nitrogen films are boron-rich and.decompose at temperatures higher than 1100K. Our TDS studies reveal that hydrazine decomposes extensively to NH3, N2, N and H on Ru(0001). Due to its higher reactivity, boron-nitrogen films of B/N stoichiometric ratio near unity are obtained when hydrazine is used rather than ammonia. In our studies, these films were formed by either simultaneously dosing B2H6 and N2H4 at 450K or by coadsorption of the reactants at 90K and subsequent annealing to 450K. These studies have shown that diborane and hydrazine can be successfully used as molecular precursors in the low temperature deposition of boron nitride thin-films.
Advances in Modeling of the Chemical Vapor Infiltration Process
Authors: Starr Thomas L. 
Published: March 2011

AbstractThe technology of chemical vapor infiltration (CVI) has progressed dramatically over the past twenty-five years and stands now as the leading process for fabrication of high temperature structures using ceramic matrix composites. Modeling techniques also have advanced from extensions of catalyst theory to full 3-D finite element code with provision for temperature and pressure gradients. These modeling efforts offer insight into critical factors in the CVI process, suggest opportunities for further advances in process technology and provide a tool for integrating the design and manufacture of advanced components.Early modeling identified the competition between reaction and diffusion in the CVI process and the resulting trade-off between densification rate and uniformity. Modeling of forced flow/thermal gradient CVI showed how the evolution of material transport properties provides a self-optimizing feature to this process variation.“What-if” exercises with CVI models point toward potential improvements from tailoring of the precursor chemistry and development of special preform architectures.As a link between component design and manufacture, CVI modeling can accelerate successful application of ceramic composites to advanced aerospace and energy components.
Effects of Fiber Orientation and Overlapping on Knudsen, Transition, and Ordinary Regime Diffusion in Fibrous Substrates
Authors: Tomadakis Manolis M. , Sotirchos Stratis V. 
Published: March 2011

AbstractWe prescnt effective diffusion coefficients of gases in porous media whose structure can be represented as an assemblage of cylindrical fibers, such as the media used as substrates in chemical vapor infiltration. Structures consisting of non-, partially, or freely overlapping fibers of various orientation distributions are considered, and effective diffusion coefficients are computed by means of a Monte Carlo simulation scheme. In order to be able to examine the interrelation of ordinary, transition, and Knudsen diffusivities and tortuosities, computations are carried out over the whole diffusion regime, i.e., from bulk to Knudsen. Our simulation results are compared with variational bounds and experimcntal values of tortuosity of fibrous beds reported by other investigators.
MOCVD Growth of Copper and Copper Oxide Films from Bis-β-Diketonate Complexes of Copper. The Role of Carrier Gas on Deposit Composition.
Authors: Rees William S. , Caballero Celia R. 
Published: March 2011

AbstractAn examination of thermal chemical vapor deposit elemental composition by EDAX has been completed for material films grown from Cu(acac)2 and Cu(tmhd)2 (acac = pentane-2,4-dionate; tmhd = 2,2,6,6-tetramethylheptane-3,5-dionate), using both hydrous and anhydrous carrier gas steams each of reducing (H2), inert (H2), and oxidizing (O2) composition.
Deposition and Characterization of Metalorganic Chemical Vapor Deposition ZrO2 Thin Films Using Zr(Thd)4
Authors: Si Jie , Peng Chien H. , Desu Seshu B. 
Published: March 2011

AbstractExcellent quality ZrO2 thin films were successfully deposited on single crystal silicon wafers by metalorganic chemical vapor deposition (MOCVD) at reduced pressures using tetrakis(2,2,6,6—tetramethyl—3,5—heptanedionato) zirconium, [Zr(thd)4]. For substrate temperatures below 530°C, the film deposition rates were very small (≤ 1 nm/min). The film deposition rates were significantly affected by: (1) source temperature, (2) substrate temperature, and (3) total pressure. As—deposited films are stoichiometric (Zr/O = 1/2) and carbon free. Furthermore, only the tetragonal ZrO2 phase was identified in as—deposited films. The tetragonal phase transformed progressively into the monoclinic phase as the films were subjected to high temperature post—deposition annealing. The optical properties of the ZrO2 thin films as a function of wavelength, in the range of 200 nm to 2000 nm, are reported. The measured value of the dielectric constant of the as—deposited ZrO2 films is around 19 in the frequency range of 5 kHz to 1000 kHz.
Kinetic Characteristics of Si3N4 CVD
Authors: Lee W. Y. , Strife J. R. , Veltri R. D. 
Published: March 2011

AbstractThe CVD of Si3N4 from SiF4 and NH3 gaseous precursors was studied using a hotwall reactor in the temperature range of 1340 to 1490°C. The effects of temperature, time, flow rate, and SiF4/NH3 molar ratio on deposition rate and axial and radial deposition profiles were identified. The decomposition characteristics of pure NH3 and SiF4 were studied utilizing mass spectroscopy and compared to thermodynamic predictions.
Effects of Silicon Ion Implantation upon Thin Gate Oxide Integrity
Authors: Lee G. -S. , Park J. -G. , Choi S. -P. , Shin C. -H. , Sun Y. -B. , Kwak Y. -S. , Shin C. -K. , Smith W. L. , Hahn S. 
Published: March 2011

ABSTRACTIn this study, using oxide breakdown voltage and time-dependent-dielectric breakdown measurements, thermal wave modulated reflectance and chemical etching/optical microscopy, we investigated effects of Si ion implantation upon formation of D-defects and thin gate oxide integrity. Our data show that addition of Si ion implantation with a dose of up to 1013 ions/cm2 improves oxide integrity if the implantation is done at a certain step just before sacrificial oxidation in the Mb DRAM process. However, no improvement in oxide integrity is observed when the same implantation is done on the virgin wafer surfaces at the start of the same Mb DRAM process. We discuss our hypothesis that the improvement in oxide integrity is due to a reduction in the D-defect density in the near-surface region of the wafer.
In-Situ Quality Control of the Production of Semiconductor Devices by Microwave Photoconductivity Measurements
Authors: Swiatkowski C. , Sanders A. , Kunst M. , Seidelmann G. , Haffer C. , Emmelmann K. 
Published: March 2011

ABSTRACTThe application of transient photoconductivity measurements in the microwave frequency range to the characterization of semiconductors and semiconductor devices is analyzed. Quality control and in-situ optimization are discussed from a more general point of view and as a concrete example the optimization of the deposition of amorphous silicon films is presented.
Simulation of Sintering Experiments in Single-Mode Cavities
Authors: Chapman B. , Iskander M.F. , Smith R. L. , Andrade O. M. 
Published: March 2011

ABSTRACTThe use of single-mode cavities has been recognized as a viable technique for sintering and joining ceramics and for creating microwave plasma for materials processing. It is often reported, however, that tuning these cavities at lower and higher temperatures critically depends on the types of materials being processed, the variation of ε* as a function of temperature, the size and shape of samples, and the overall heating system configuration with and without insulation.In this paper we use the finite-difference time-domain technique to address the performance of the single-mode cavity heating system under a wide variety of heating conditions and system configurations. Specifically, practical issues such as limiting values of sample sizes, the dependence of optimal sample sizes on the complex permittivity of materials under test, the role of sample shape on enhancing uniformity of heating patterns, and various tradeoffs involved in utilizing various cavity modes and/or SiC rods as stimulus for heating large samples are evaluated.