bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phase Transformation Hysteresis in a Plutonium Alloy System: Modeling the Resistivity during the Transformation
Authors: Haslam Jeffery J. , Wall Mark A. , Johnson David L. , Mayhall David J. , Schwartz Adam J. 
Published: April 2011

AbstractWe have induced, measured, and modeled the β - α' martensitic transformation in a Pu-Ga alloy by a resistivity technique on a 2.8-mm diameter disk sample. Our measurements of the resistance by a 4-probe technique were consistent with the expected resistance obtained from a finite element analysis of the 4-point measurement of resistivity in our round disk configuration. Analysis by finite element methods of the postulated configuration of α' particles within model σ grains suggests that a considerable anisotropy in the resistivity may be obtained depending on the arrangement of the α' lens shaped particles within the grains. The resistivity of these grains departs from the series resistance model and can lead to significant errors in the predicted amount of the α' phase present in the microstructure. An underestimation of the amount of α' in the sample by 15%, or more, appears to be possible.
Effects of grain size distribution on Cole-Cole plots of polycrystalline spinels
Authors: Gutiérrez-Amador M. P. , Valenzuela R. 
Published: April 2011

AbstractSpinel ferrites of composition Ni0.5Zn0.5Fe2O4 were prepared by coprecipitation. Different grain size and grain size distributions were obtained by various heat treatments. Their electrical properties were investigated by impedance spectroscopy in the temperature range 25-200°C and in the frequency range of 5Hz-13MHz. A decrease in resistivity was observed as grain size increased, which can be explained by an increase in the mean free path of electrons. Cole-Cole plots showed two well-resolved semicircles for samples with a narrow grain size distribution. As the width of the distribution increased, the semicircles exhibited a deformation and eventually became unresolved. These results are interpreted on the basis of a distribution of time-constant of the impedance response, associated with the grain size distribution.
Charge-Based Deep Level Transient Spectroscopy of Semiconducting and Insulating Materials
Authors: Polyakov V.I. , Rukovishnokov A.I. , Rossukanyi N.M. , Druz B. 
Published: April 2011

AbstractThe opportunity of the charge-based deep level transient spectroscopy (Q-DLTS) for study of the structures based on wide bandgap semiconducting and insulating materials such as diamond and Al2O3 was demonstrated. Using our isothermal Q-DLTS method with rate window (tm)scanning we obtained information about concentration, activation energy and capture cross-section of the native and extrinsic electrical active defects - trapping centers (TC) in slightly boron-doped polycrystalline diamond, diamond single-crystal and in the structures Al2O3 film on NiFe and Si substrates. In comparison with widely used capacitance-based deep level transient spectroscopy, Q-DLTS gives one possibility to investigate the structures in which a capacitance does not depend on the charge state of the surface and bulk traps.
Influence of Substrate Annealing Temperature upon Deep Levels in n-Type 4H SiC
Authors: Kordesch Martin E. , Perjeru Florentina , Woodin R. L. 
Published: April 2011

AbstractThe evolution of deep levels that depend upon annealing temperature is investigated for n-type 4H SiC-Ni Schottky barriers. Several samples, cut from the same wafer, have been left unheated or annealed at 400°C, 700°C and 900°C, in air. Deep level transient spectroscopy (DLTS) has been used to investigate deep levels in all four sets of samples. Electron traps with activation energies EC-ET = 0.19 to 0.5 eV are observed, as well as a hole trap in the sample annealed at 900°C at energy ET-EV = 0.14 eV.
Capacitance Spectroscopy of n-i-n and p-i-p GaAs Sandwich Structures with Nanoscale As Clusters in the i-Layers
Authors: Chaldyshev V.V. , Brunkov P.N. , Chernigovskii A. V. , Moskalenko A. , Bert N.A. , Konnikov S. G. , Preobrazhenskii V. V. , Putyato M. A. , Semyagin B. R. 
Published: April 2011

AbstractAccumulation of electrons and holes in GaAs layers, that contained As clusters and were sandwiched between n- and p-type buffer GaAs layers, was revealed by capacitance-voltage measurements. As a result of majority-carrier accumulation, expansive depletion regions are formed in the adjoining buffer layers. Simulation of the capacitance-voltage characteristics, based on a numerical solution of the Poisson equation, shows that the accumulated charge density is ∼1 × 1012 cm−2, which is comparable with the concentration of As nanoclusters determined by transmission electron microscopy. The levels where the electrons or holes are accumulated lie close but above the GaAs midgap. A strong difference in the emission rates of the accumulated electrons and holes has been revealed.
Microwave Transient Photoconductivity Studies in Porous Semiconductors
Authors: Porteanu Horia-Eugen , Konstantinova Elisaveta , Kytin Vladimir , Loginenko Oleg , Timoshenko Victor , Dittrich Thomas , Koch Frederick , München T.U. 
Published: April 2011

AbstractThe dynamics of the photogenerated carriers in porous silicon and TiO2 anatase was studied at 35 GHz by measuring the change in time of the conductivity s and dielectric constanter. Localization of carriers leads to a positive change ofer, while quasifree carriers to a negative change. Size reduction in Si shortens the recombination time as long as the surface traps are not significant. Magnetic field investigations show opposite variation of conductivity in poroussilicon compared with TiO2.
Electrochemical Porosimetry
Authors: Song Hyun-Kon , Lee Kun-Hong 
Published: April 2011

AbstractWe have developed the electrochemical porosimetry analyzing microstructures of porous electrodes, which can give geometric information most meaningful in electrochemical systems. The methodology is based on the transmission line model with pore size distribution (TLM-PSD) that relates electrochemical impedance data with microstructural information. Pore length (lp), as well as pore size distribution, can be obtained by fitting the TLM-PSD to the experimental impedance data of a porous electrode. This geometric information was validated for the microporous, mesoporous and macroporous samples by comparing with the data obtained from conventional porosimetry. It was also shown that the electrochemical porosimetry could be used as a nondestructive probe to investigate the construction of electrochemical devices.
Microstructure and Damage of the Interlaminar Interface of Carbon Fiber Polymer-Matrix Composites, Monitored by Contact Electrical Resistivity Measurement
Authors: Wang Shoukai , Guerrero Victor H. , Kowalik Daniel P. , Chung D.D.L. 
Published: April 2011

AbstractThe microstructure and damage of the interlaminar interface of continuous carbon fiber polymer-matrix structural composites were monitored during dynamic changes in temperature, humidity and stress by contact electrical resistivity measurement. The stress was compressive, in the direction perpendicular to the interface. Temperature, humidity and stress had reversible effects on the resistivity, due to the effects on the interfacial microstructure, such as the extent of contact between fibers of adjacent laminae. These parameters had irreversible effects on the resistivity, due to relaxation and damage of the interface. The effects differed between composites with thermoplastic and thermoset matrices. The reversible effects allow the use of the contact resistivity as an indicator of temperature, humidity and stress.
A Percolation Equation for Modeling Experimental Results for Continuum Percolation Systems
Authors: McLachlan D.S. , Chiteme C. , Heiss W.D. , Wu Junjie 
Published: April 2011

AbstractThe standard percolation equations or power laws, for dc and ac conductivity (dielectric constant) are based on scaling ansatz, and predict the behaviour of the first and second order terms, above and below the percolation or critical volume fraction (øc), and in the crossoverregion. Recent experimental results on ac conductivity are presented, which show that these equations, with the exception of real σm above øc and the first order terms in the crossover region, are only valid in the limit σi/σc = 0, where for an ideal dielectric σi=ωε0εr.A single analytical equation, which has the same parameters as the standard percolation equations, and which, for ac conductivity, reduces to the standard percolation power laws in the limit σi(ωε0εr)/σc = 0 for all but one case, is presented. The exception is the expression for real σm below øc, where the standard power law is always incorrect. The equation is then shown to quantitatively fit both first and second order dc and ac experimental data over the entire frequency and composition range. This phenomenological equation is also continuous, has the scaling properties required at a second order metal-insulator and fits scaled first order dc and ac experimental data. Unfortunately, the s and t exponents that are necessary to fit the data to the above analytical equation are usually not the simple dimensionally determined universal ones and depend on a number of factors.
Electrical Conductivity of Ionic and Electronic Mixture
Authors: Choi Gyeong Man , Kim Joon Hee , Park Young Min 
Published: April 2011

AbstractMixed ionic-electronic conductors (MIECs) which have both ionic and electronic species as charge carriers have a wide range of applications, such as electrodes in fuel cells, electrocatalytic reactors, and gas separating membranes. They may have either electronic or ionic species as the majority charge carriers. In addition to the single-phase mixed conductors, they may be fabricated by mixing two different phases of materials. Although these composites have been less studied than the single phase MIECs, the combined properties are often superior to single phase MIECs, and properties not seen in an individual phase may appear in the composite phase.YSZ-based composite systems were chosen to test the effect of transition-metal-oxide (TMO) addition on the electronic conductivity of composite. To induce mixed conductivity, electronic-conducting TMOs such as NiO and Mn2O3 were added into YSZ above the solubility limit. While the solid solubility of NiO in YSZ is limited that of Mn2O3 is large.In this work, mixed conducting yttria (8 mol%) stabilized zirconia (YSZ) - TMO composites were prepared in full composition range and the electrical conductivity of the composites was measured by 4-probe d.c. conductivity. Electromotive force (emf) measurements of the galvanic cell, current-voltage (I-V) measurements in ion blocking condition and the oxygen-partial-pressure dependent conductivity have been used to determine the contribution of the ionic and electronic charge carriers on the conductivity. Thus the composition-dependent electrical properties were used to explain the percolation behavior of electronic charge carriers in ionic matrix.Although the total conductivity of dense YSZ-TMO composite was variable with TMO content, the partial-electronic conductivity increased and the ionic conductivity decreased. The composition-dependent conductivity was discussed.
Combinatorial Synthesis and Characterization of Zinc-Tin-Oxide Transparent Conductors
Authors: Perkins J.D. , Cueto J.A. del , Alleman J.L. , Warmsingh C. , Keyes B.M. , Gedvilas L.M. , Parilla P.A. , To B. , Readey D.W. , Ginley D.S. 
Published: April 2011

AbstractIn this work, we discuss the combinatorial deposition and analysis of transparent conducting oxides along the ZnO-SnO2 composition tie line. Libraries were deposited by co-sputtering from ZnO and Sn-metal targets. The production and analysis of Zn-Sn-O libraries has already produced significant results, confirming the properties of the 2:1 (Zn2SnO4) region and revealing a second region of interest, the 1:1(ZnSnO3) composition. Subsequent film growth of these stochiometries by pulsed laser deposition has confirmed the potential for both of these stochiometries. Work is currently underway to optimize both Zn2SnO4 and ZnSnO3. Planned future work includes a combinatorial investigation of ternary metal systems such as Zn-In-Sn-O.
Combinatorial Synthesis Approach for Optimizing Oxide/Si Interfaces for the Future Ulsi
Authors: Chikyow T. , Ahmet P. , Naruke T. , Nakajima K. , Okazaki N. , Hasegawa K. , Minami H. , Itaka K. , Koida T. , Song J.H. , Yoshimoto M. , Hasegawa T. , Kawasaki M. , Koinima H. 
Published: April 2011

AbstractA combinatorial material synthesis with temperature gradient heating system was employed to optimizing growth parameters for oxide growth on Si substrate. From the obtained results, it was found the dielectric property depends on the growth temperature as well as the composition. The interface structures were investigated by high resolution electron microscopy with a series of specimens fabricated by micro sampling method. The results showed that amorphous oxide region and SiO2 layer were formed at the interface. It was speculated that the amorphous oxide region contributed to the reduction of the dielectric property. To avoid the amorphous and SiO2 formation at the oxide/Si interface, a few kinds of intermediate layers were inserted and tested to find the possibility of abrupt interface formation.
On the Implementation of Neural Network Concept to Optimize Thermal Spray Deposition Process
Authors: Guessasma Sofiane , Montavon Ghislain , Coddet Christian 
Published: April 2011

AbstractNumerous processing parameters, up to fifty, characterize the plasma spray deposition process. A better quality control of the resulting deposits induces a better understanding of their effects on coating formation mechanisms. Numerical models can help to provide such an understanding. From a mathematical point of view, d.c. plasma spray deposition process is assimilated to a nonlinear problem in regards to its variables (operating parameters, environment, etc.). This paper develops a global approach based on an implicit describing of the mechanisms implementing Artificial Neural Networks (ANNs). The global concept and the protocols to implement are presented and developed for an example related to d.c. plasma spray process.
Designing Conducting Polymers with Genetic Algorithms
Authors: Giro R. , Cyrillo M. , Galvão D.S. 
Published: April 2011

AbstractWe have developed a new methodology to design conducting polymers with pre-specified properties using genetic algorithms (GAs). The methodology combines GAs with the Negative Factor Counting (NFC) technique. NFC is a powerful technique to obtain the eigenvalues of large matrices without direct diagonalization.We present the results for a case study of polyanilines, one of the most important families of conducting polymers. The methodology proved to be able of generating automatic solutions for the problem of determining the optimum relative concentration for binary and ternary disordered polyaniline alloys exhibiting metallic properties. The methodology is completely general and can be used to design new classes of materials.
Molecular Dynamics Simulations of Reactive Wetting
Authors: Webb Edmund B. , Grest Gary S. 
Published: April 2011

ABSTRACTThe wetting and spreading of liquid Ag drops on Cu (001) surfaces are studied with molecular dynamics simulations. As the liquid Ag drop spreads on the Cu surface, reactive wetting occurs in that a Ag/Cu alloy is formed. The results for the reactive wetting case are compared to a frozen substrate for which there is no alloying. At the highest temperature studied, T = 1300 K, the radius of the drop spreads faster than for the frozen substrate, indicating the driving force for spreading is greater when the liquid and solid mix. Lowering temperature in reactive systems results in behavior more similar to non-reactive systems due to suppressed mixing.
Growth of Nanosize and Colloid Particles by Controlled Addition of Singlets
Authors: Privman Vladimir 
Published: April 2011

ABSTRACTWe outline a theoretical framework for estimating the evolution of the particle size distribution in colloid and nanoparticle synthesis, when the primary growth mode is by externally controlled addition of singlet building blocks. The master equations, analyzed in the leading “non-diffusive” expansion approximation, are reduced to a set of easily numerically programmable relations that yield information on the time evolution of the particle size distribution.
Fibers of Bamboo and Hem Palm Tree
Authors: Amada Shigeyasu 
Published: April 2011

ABSTRACTBamboo is a typical composite material which is axially reinforced by very strong fibers. So that, the fibers play an important role for the bamboo structure. The elastic properties of the bamboo culm have been measured only by tensile test so far, which needs a large specimen. Recently ultra-sonic technique, which has a simple procedure and uses a small specimen, has been applied to woods as well as metals. This report reviews about the elastic properties of bamboo and Hemp palm fibers. The Young's modulus and Poisson's ratio of the bamboo fibers are measured by ultra-sonic method with a transmitting wave. On the other hand, the strength of the bamboo and Hemp palm fibers are measured by the tensile tests. Using the volume fraction of fibers in the specimen and mixture principle, the Young's modulus and strength of the fibers and parenchyma were obtained. The fiber has a high strength up to 1GPa and an strong anisotropic property because its axial Young's modulus has 7 times higher than the one in the transverse direction.
Production and Characterization of Yarns and Fabrics Utilizing Turkey Feather Fibers
Authors: Evazynajad Alimohammad , Kar Adnan , Veluswamy Sathpurushan , McBride Holly , George Brian R. 
Published: April 2011

ABSTRACTTurkey feather fibers were characterized and then converted into products such as yarn and nonwoven fabrics for a study into the feasibility of their use as textile products. Yarn containing blends of nylon and up to thirty percent turkey feather fibers were spun by combining novel techniques with commercial yarn spinning machinery. These yarns were tested for determination of their mechanical properties. As the percentage of turkey feather fibers increased, the tenacity and elongation of the yarns decreased while the modulus increased. These yarns were knitted into fabrics to determine their insulating properties. As the percentage of turkey feather fibers increased the insulating capabilities of the fabrics also increased. Recent research has focused on producing nonwoven fabrics containing turkey feather fibers utilizing various production methods for use as erosion control fabrics.
Electrostatic Synthesis and Characterization of Pb(ZrxTi1-x)O3 Micro/nano-fibers
Authors: Wang Yu , Serrano Santiago , Santiago-Aviles Jorge J. 
Published: April 2011

ABSTRACTPb(Zr0.48Ti0.52)O3 (PZT) micro/nano-fibers and mats were synthesized from alkoxides using electrostatic deposition. The PZT micro/nano-fibers precursor, a mixture of zirconium npropoxide, titanium isopropoxide, and lead 2-ethylhexanoate, was deposited under the following conditions: tip-screen distance=15cm, voltage drop between tip and screen of 15kV. The deposited fibers and mats samples were sintered for half an hour at 400, 500, 600, 700, and 800°C, respectively. Sintered mats were characterized using x-ray diffraction (XRD), sintered fibers were characterized using optical microscope, scanning electron microscopes (SEM), Raman microscope, and scanning probe microscope (SPM). SEM revealed that micro/nano-fibers have diameters varying from a fraction of a micron to around 10 micrometer. XRD and Raman spectra indicated that the precursors begin to transform into intermediate phase Pb2Ti2O6 at 400°C, whose transformation into the perovskite phase starts at 600°C and ends at 800°C. Scanning probes microscope (SPM), operated in voltage-modulated dynamic contact mode, revealed the spontaneous polarization domains, with diameters ranging from 0.1 to 0.5 micron, in microfibers, confirming their piezoelectricity.
Acoustic Imaging of Microstructures of Carbon Fiber-Reinforced Composite Laminates
Authors: Liu Songping , Levin Vadim M. , Guo Enming 
Published: April 2011

ABSTRACTThe properties and homogeneity of a composite laminate are strongly dependent on structures and microstructures in it. The investigations have shown that the microstructures of carbon fiber-reinforced polymer composite laminates can be visualized by means of acoustic imaging techniques. The frequency of ultrasonic wave to be used is up to 50MHz. The composite laminates to be investigated include unidirectional carbon fiber-reinforced polymer composite laminates, bi-directional carbon fiber-reinforced polymer composite laminates and carbon fiber woven composite laminates. Very useful quantitative information about inside structures of the composites can be visualized in plan-section of the laminates in the depth directions by ultrasonic T-scan imaging technique. Typical results have been represented in this article.
Biopolymer-silica Hybrid Aerogels Containing Transition Metal Species; Structure, Properties, and Reactions
Authors: Hu Xiangjun , Ji Shuang , Risen William M. 
Published: April 2011

ABSTRACTNovel transition-metal containing hybrid biopolymer-silica aerogels have been synthesized as transparent monolithic structures. The compositions include Ru(III), Rh(III), Co(II), and Pd(II) species, silica and chitosan, and amine-group-containing biopolymer derived from chitin. Due to its aqueous solubility and hydrogen bonding properties, chitosan was homogeneously incorporated into the silica network. These aerogels have densities in the range of 0.25-0.30 g/cm3, BET surface areas in the range of 600-975 m2/g, and refractive indexes below 1.17 (at 632.8 nm). Infrared spectroscopy shows that chitosan is effectively introduced into the silica aerogels, and the transition metal ions can coordinate with the amine sites on chitosan. This combines the metal-ion interaction of chitosan with that of silica aerogels. Transmission electronic microscopy indicates that the particle sizes of silica are about 2 nm. Small angle neutron scattering (SANS) has been used to study the microstructure of these aerogels. A new Small-Particle Mass-Fractal model scattering function, derived from the Teixeira Mass-Fractal model scattering function, was used to fit the SANS data. It was found that chitosan helps to form an open aerogel structure. It supports a structural model in which there are primary particles that connect with each other closely to form clusters, and these clusters serve as a secondary structural unit to form the chitosan-reinforced aerogel network. It also indicates that chitosan reinforces the interparticle connections. The local environments, structures and chemistries of the transition metal ions have been explored. Of special interest in this regard are the magnetic properties of the Ru(III) containing materials, which are consistent with anti-ferromagnetic coupling, and the reactions of the Rh(III), Ru(III), and Pd(II) species with small gaseous molecules.