bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of Retention Phenomena of Micron-Size Electrical Domains in Pzt Thin Films
Authors: Hong Seungbum , Shin Hyunjung , Pak Y. Eugene , No Kwangsoo 
Published: April 2011

AbstractThe retention phenomena of purposely aligned micron-size domains (defined as “bits”) in Pb(Zr,Ti)O3 thin films were characterized by atomic force microscopy (AFM) combined with a lock-in amplifier. It is found that the retention loss occurs by “region by region” showing local variation of the rate of the loss. Furthermore, the total retention loss can be successfully described by an extended exponential decay, which implies a narrow distribution of the relaxation times of the domains. This probably comes from the fact that the micron-size bits consist a few hundreds of domains. Along with the characterization, the effects of the bit size and the poling time per unit area on the retention characteristics were investigated. Based on our observations, it is concluded that the retention time is proportional to both the poling time per unit area and the bit size. This trend is successfully explained by a kinetic model developed by our group.
Excitation Spectra in the Time-Dependent Density-Functional Theory with Gradient Correction
Authors: Uimezawa Naoto , Saito Susumu 
Published: April 2011

ABSTRACTWe study tile optical absorption spectra of Na clusters using the time-dependent density-functional theory with gradient correction. A jellium-sphere background model, which is free from basis-set incompleteness error and is suitable for the comparison of various theoretical methods, is adopted. For energies of surface-plasinon excitations governing profiles of photoabsorption spectra with huge oscillator strengths., the gradient correction by van Leeiiwen and Baerends with correct asymptotic behavior of the effective potential is found to show considerable improvement over the time-dependent local-density approximation.
Optical Absorption and Electronic Excitations in Hydrogenated Silicon Clusters
Authors: Vasiliev Igor , Öĝüt Serdar , Chelikowsky James R. 
Published: April 2011

ABSTRACTThe study of electronic excitations in hydrogen terminated silicon clusters is important for understanding the optical properties of confined systems such as quantum dots and porous silicon. Here we calculate the excitation energies and absorption spectra for SinHm clusters using linear response theory within the time-dependent local density approximation (TDLDA). We find the computed excitation energies and photoabsorption gaps agree with available experimental data. The TDLDA optical absorption spectra exhibit a substantial blue shift with respect to the spectra calculated within the time-independent local density approximation. This trend is consistent with other theoretical calculations for excited state properties, such as the Bethe-Salpeter technique.
Phase Coarsening as a Relaxation Phenomenon
Authors: Marsh S. P. 
Published: April 2011

AbstractPhase coarsening, also known as Ostwald ripening, is generally treated as a growth phenomenon in which the average particle size increases during isothermal aging. However, coarsening is a relaxation process driven by a reduction in the excess interfacial energy of a two-phase structure. This viewpoint introduces a single temporal offset parameter that relates the experimental clock to the asymptotic time scale. Analysis of ripening as a relaxation phenomenon permits accurate determination of the kinetics that is less sensitive to particle morphology. Implications of this approach on measurement and interpretation of ripening kinetics will be discussed.
Optimizing The Metalloid Content in Bulk Metallic Glasses
Authors: Jin O. , Schwarz R. B. , Alamgir F. M. , Jain H. 
Published: April 2011

AbstractWe have studied the effect of phosphorus content on the formation and properties of bulk Pd-Cu-P and Pd-Ni-P metallic glasses. It was found that the molar volumes of the Pd-Ni-P bulk glasses plotted as a function of P content follow a straight line whereas those for the Pd-Cu-P glasses follow two straight lines of different slopes, intersecting at a critical P concentration. The transition in molar volume behavior is attributed to a change in the alloy's short-range order with increasing P content. The origin of this structural change is discussed based on x-ray photoelectron spectroscopy (XPS) measurements.
A Self-Similar Solution for the Growth Rate of a Compound Layer in Thin-Film Binary Diffusion Couples
Authors: Zhang Huifang , Wong Harris 
Published: April 2011

AbstractThe diffusion controlled growth of a compound phase AnB between two thin films of material A and B is studied with the nonlinear Kirkendall effect included. Previous models of the growth rate do not solve the diffusion equation, and thus do not fully utilize the predictive capability. This paper describes a self-similar transformation that reduces the nonlinear, time-dependent diffusion equation with two free boundaries into a nonlinear ordinary differential equation, which is solved numerically by a shooting method. It is found that the intrinsic diffusion coefficients of A and B in AnB can be determined from the positions of the interfaces without using the concentration profile. This provides a simpler method for measuring intrinsic diffusion coefficients.
Characterization of the Early Stages of Phase Separation by Atom probe Tomography
Authors: Miller M. K. 
Published: April 2011

AbstractAn atom probe tomography characterization of the early stages of phase separation in the FeCu-Ni system has been performed. The development of the copper-enriched regions into copper precipitates has been investigated during isothermal ageing at 573 K and 673 K for times up to 10,000 h. The formation and growth of the secondary precipitates in the nickel based superalloy, Alloy 718, have been determined during isothermal ageing at 873 K. These secondary precipitates were found to be a mixture of the L12-ordered γ' phase and the DO22-ordered γ” phase.
Solid Solutions (PbI2)x – (BiI3)1-x
Authors: Dmitriev Yu.N. , Bennett P.R. , Cirignano L.J. , Gupta T.K. , Klugerman M. , Shah K.S. 
Published: April 2011

AbstractSystem (PbI2)x – (BiI3)1-x of two layered semiconductors PbI2 and BiI3 with various composition were synthesized and grown both as bulk single crystals (by vertical Bridgman method) and films (by thermal vacuum deposition). Grown composites were tested by different techniques (X-ray difflaction analysis, optical transmission, I – V measurements, response to X-ray pulse excitation). Property versus composition showed nonlinear behavior of measured parameters. The structural model of ordered structures formation in this system, which was based upon local electrical neutrality of unit cells, was worked out. It has been experimentally demonstrated that a formation of ordered structures is possible within (PbI2)x-(BiI3)1-x system, which is consistent with the suggested model. The possibility of crystal structures formation as ordered sets of BiI3 and PbI2 layers was also checked.
Investigation of Electronic Surface States and its Correlation to Surface Modifications in Femtosecond UV-Laser Treated n(100) GaAs
Authors: Railkar T. A. , Malshe A. P. , Brown W. D. , Hullavarad S. S. , Bhoraskar S. V. 
Published: April 2011

AbstractGallium arsenide (GaAs) is an important III-V semiconductor, due to its applicability to several high-end and consumable electronic devices. However, GaAs, unlike silicon (Si), does not have a stable native oxide that can stabilize and protect the surface from further oxidation and degradation. In this paper, we report the use of femtosecond laser-based modification of the GaAs surface, leading to its stabilization against oxidation, the use of ultrafast laser-based processing and its effectiveness compared to conventional laser treatment. One of the prominent advantages of ultrafast lasers include an almost non-existent heat affected zone (HAZ). The surface stabilizing and passivating effects were confirmed by depth-profiling x-ray photoelectron spectroscopic (XPS) measurements, atomic force microscopy (AFM) measurements, and a surface sensitive spectroscopic technique called thermally stimulated exoelectron emission (TSEE) measurements.
Nonlinear Ripple Formation in Sputter Erosion
Authors: Barabási A.-L. , Kahng B. , Jeong H. , Park S. 
Published: April 2011

AbstractWe investigate the morphological features of sputter eroded surfaces, demonstrating that while at short times ripple formation is described by the linear theory, after a characteristic time the nonlinear terms determine the surface morphology. We also show that the morphological transitions induced by the nonlinear effects can be detected by monitoring the surface width and the erosion velocity.
Environmental Scanning Electron Microscopy as a Tool to Study Shrinkage Microcracks in Cement-Based Materials
Authors: Bisschop J. , Mier J.G.M. Van 
Published: April 2011

AbstractIn this paper a method is described to observe shrinkage microcracks on ‘wet’ specimen cross-sections of cement-based materials with Environmental Scanning Electron Microscopy (ESEM). A sample cooling device which can be used in the ESEM chamber was built to control the relative humidity above a microscope sample. The accuracy of measuring relative humidity is determined to be 5% at a sample temperature of 3°C. A microscope sample preparation method and a pump-down sequence of the ESEM-chamber, both without any drying of the sample, are described. Preliminary results show that in the studied mortar the visibility of shrinkage microcracks on a ‘wet’ specimen cross-section is low due to closure of microcracks by swelling of the cement paste.
Epitaxy and Atomic Structure Determination of Au/TiO2Interfaces by Combined EBSD and HRTEM
Authors: Cosandey F. , Stadelmann P. 
Published: April 2011

AbstractWe have studied the effects of deposition conditions on the epitaxial orientation of Au or TiO2(110) and on the atomic structure of Au/TiO2interfaces by combined EBSD and HRTEM. Two experimental conditions were explored consisting of deposition of a 12 nim Au film at 300K followed by annealing at 770K and direct deposition of a 12 nm Au film at 770K. Deposition at 300K followed by annealing at 770K give rise to a (111)Au//(110)TiO2epitaxial orientation relationship, while direct deposition at 700K temperature give rise to an epitaxial orientation relationship given by (112)Au//(110)TiO2. For both orientations, two epitaxial variants are observed which are twin related. The (112)Au//(110)TiO2orientation has been found to minimize the interfacial lattice misfit while maximizing the number of Au-Ti bonds across the interface.
STEM Analysis of the Segregation of Bi to Σ19a Grain Boundaries in Cu
Authors: Sigle W. , Chang L.-S. , Gust W. , Rühle M. 
Published: April 2011

AbstractCu bicrystals were doped with different amounts of Bi and annealed at various temperatures. The segregation at the grain boundary (GB) was analyzed by energy dispersive X-ray analysis (EDX) in the scanning transmission electron microscope (STEM). It is found that with both increasing temperature and increasing Bi content the amount of faceting of the GB increases, finally reaching complete faceting. This final state is distinguished by brittle behavior. By analyzing the shape of pores at the GB we found that the Cu surface energy anisotropy is probably increased by Bi surface segregation.
Atomic and Electronic Structure Analysis of Σ=3, 9 and 27 Boundary, and Multiple Junction in β-SiC
Authors: Tanaka K. , Kohyama M. 
Published: April 2011

AbstractThe atomic structures of σ=3, 9 and 27 boundaries, and multiple junctions in β-SiC were studied by high-resolution electron microscopy (HREM). Especially, the existence of the variety of structures of σ=3 incoherent twin boundaries and σ=27 boundary was shown by HREM. The structures of σ=3, 9 and 27 boundary were explained by structural unit models. Electron energy-loss spectroscopy (EELS) was used to investigate the electronic structure of grain boundaries. The spectra recorded from bulk, {111}σ=3 coherent twin boundary (CTB) and {1211}σ=3 incoherent twin boundary (ITB) did not show significant differences. Especially, the energy-loss corresponding to carbon 1s-to Φ* transition was not found. It indicates that C atoms exist at grain boundary on the similar condition of bulk
The Effect of Different Oxidizing Atmospheres on the Initial Kinetics of Copper Oxidation as Studied In Situ UHV-TEM
Authors: Bharadwaj Mridula D. , Gupta Anu , Gibson J. Murray , Yang Judith C. 
Published: April 2011

AbstractEffect of moisture on the oxidation of copper was studied using in situ UHV-TEM. The ultra high vacuum condition is required for minimum contamination effects. The initial observations show that the water vapor reduces the oxide as well as reduces the rate of oxidation if both oxygen gas and water vapor are simultaneously used. Based on these observations, we have speculated on the role of moisture in the solid state reactions involved in copper oxidation
Multi-and Single-Walled Boron Nitride Nanotubes Produced From Carbon Nanotubes by a Substitution Reaction
Authors: Golberg D. , Bando Y. , Han W. , Bourgeois L. , Kurashima K. , Sato T. 
Published: April 2011

ABSTRACTBoron nitride (BN) multi-walled (MWNT) or single-walled (SWNT) nanotubes were synthesized from carbon MWNT and SWNT templates, respectively, under heating of C nanotubes together with boron trioxide in a flowing nitrogen atmosphere. B and N atom substitution for C atoms in the nanotubular shells during C oxidation by the B2O3 vapor in the N2 flow is thought to underlie the formation mechanism. Structural and chemical BN MWNT/SWNT analyses were performed by means of high-resolution electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS), respectively. In particular, BN MWNT shell structure and defects, and electron irradiation stability were studied. Finally, the prospects of using the substitution technique for the synthesis of other advanced nanostructures made of BN (nanorods, nanoplates and nanocones) are discussed.
Twisting of Single-Walled Carbon Nanotube Bundles
Authors: Qin Lu-Chang , Iijima Sumio 
Published: April 2011

ABSTRACTBundles of single-walled carbon nanotubes produced by laser ablation are often seen twisted in morphology, forming nanoropes which would better suit the function for improvement of structural stability in mechanical applications. The rope-like configuration is explained with a model that relates the twisting morphology to the helicity difference between the neighboring nanotubes. This selfassembly phenomenon is attributed to the fact that a twisted structure has lower total energy compared with the raft-like parallel bundles when the helicities of neighboring nanotubes are different.
Nanomechanical Properties of Amorphous Carbon and Carbon Nitride Thin Films Prepared by Shielded Arc Ion Plating
Authors: Tajima N. , Saze H. , Sugimura H. , Takai O. 
Published: April 2011

ABSTRACTHydrogen free amorphous carbon (a-C) and carbon nitride (a-C:N) were synthesized by means of shielded arc ion plating in which a shielding plate was inserted between a target and a substrate in order to reduce macroparticle deposition onto the substrate. Using a graphite target as a cathode, thin films of a-C and a-C:N were prepared in an arc discharge plasma of argon or nitrogen gas, respectively, at a pressure of 1 Pa. Based on nanoindentation, mechanical properties of these films were studied in relation to substrate bias voltage (Vs). The a-C films prepared at Vs ranging from -50 to -200 V consisted of diamond-like phase and showed hardness higher than 20 GPa with its maximum of 35 GPa at Vs = -100 V. However, hardness of the films deposited at Vs < 300 V was less than 7 GPa indicating that the films were converted to graphite-like phase due to excessive ion impact in Ar plasma. Wear resistance of the a-C films was closely related to their hardness. Namely, a harder a-C film was more wear resistant. On the contrary, hardness of the a-C:N films was less dependent on Vs. It remained in the range of 10 to 15 GPa and was much lower than the maximum hardness of the a-C films. Nevertheless, the wear resistance of the a-C:N films was comparable to or much better than the a-C films. In particular, the a-C:N film prepared at Vs = -300 V was so wear resistant that the film showed no apparent wear when rubbed with a diamond tip less than 100 nm in tip-diameter at a contact force of 20μN. The presence of β-C3N4like phase characterized by a N1 s XPS peak at 400.5 eV has found to be crucial for high wear resistance of the a-C:N films
Poly(SNS) Electrochemical Synthesis and Processability
Authors: Otero T. F. , Villanueva S. , Brillas E. , Carrasco J. 
Published: April 2011

AbstractThe flow of an anodic current density of 0.5 mA. cm−2 through a 5 mmol/l solution of 2,5-di-(2-thienyl)pyrrole (SNS), in acetonitrile, gives dark-violet and uniform polymer films coating the platinum electrode in presence of different electrolytes. The process is named either electropolymerization or electrogeneration.
Electrochemical Investigation of 2, 2′-Dlaminobenzyloxydisulfide
Authors: Su Y. Z. , Gong K. C. 
Published: April 2011

AbstractA new conducting polymer, poly(2, 2′-diaminobenzyloxydisulfide), has been proposed as a positive material suitable for secondary lithium batteries. With the aim of better understanding the process of polymerization and depolymerization of 2,2′-diaminobenzyloxydisulfide(DABO). The redox behavior, kinetic reversibility and adsorption of DABO have been investigated at platinum electrode in acetonitrile/tetrahydrofuran solution by using linear sweep voltammetry, the cyclic sweep voltammetry and the rotating disk electrode technique. These experiments clearly showed the reaction is chemically reversible but kinetically slow at ambient temperature and charge transfer is the rate-determining step, but chemical dimerizaton is at equilibrium. The results are common to many organic disulfides. Furthermore, the striking observation from cyclic voltammograms is the smaller separation of the anodic and cathodic peak owing to the specific structure of DABO, compared with other organic disulfides. This results indicates the redox reaction of DABO is higher kinetically reversible and poly (DABO) positive material is expected to deliver higher power output or energy efficiency.
Polymer-Gel Phase-Transition as the Mechanism of Muscle Contraction
Authors: Pollack Gerald H. 
Published: April 2011

AbstractThe thesis offered here is that the muscle-contraction mechanism is similar to the mechanism of contraction in many artificial muscles. Artificial muscles typically contract by a phasetransition. Muscle is thought to contract by a sliding-filament mechanism in which one set of filaments is driven past another by the action of cyclically rotating cross-bridges—much like the mechanism of rowing. However, the evidence is equally consistent with a mechanism in which the filaments themselves contract, much like the condensation of polymers during a phasetransition. Muscle contains three principal polymer types organized neatly within a framework. All three can shorten. The contributions of each filament may be designed to confer maximum strength, speed and versatility on this biological machine. The principles of natural contraction may be useful in establishing optimal design principles for artificial muscles.
Giant Electrostrictive Response in Poly(vinylidene-fluoride hexafluoropropylene) copolymer
Authors: Lu Xiaoyan , Schirokauer Adriana , Scheinbeim Jerry 
Published: April 2011

AbstractIn the present study, the strain response of a new class of copolymers of PVF2 is investigated. Electrostrictive strains were measured in poly(vinylidene-fluoride hexafluoropropylene), P(VF2-HFP), using a capacitance method (air-gap capacitor), as a function of electric field. Three different thermal treatments (ice water quenched, air quenched and slow cooled) were given to samples of composition 5% and 15% HFP. Strains greater than 4 % were observed in the 5% HFP ice water quenched P(VF2-HFP) copolymer. Values of elastic modulus were lower for the quenched 5 % films than for the slow cooled ones, and in both cases they were higher than previously studied polyurethane elastomers and poly(vinylidene-fluoride trifluoroethylene) copolymers. Key words: Electrostrictive Polymer, Poly(vinylidene-fluoride hexafluoropropylene) copolymer, Ferroelectic, X-ray, DSC.
Superplasticity in Nb3Al/Nb In Situ Composites
Authors: Hanada S. , Fang W. 
Published: April 2011

AbstractMicrostructures of a binary Nb-15.8at%Al alloy ingot were controlled by isothermal forging and heat treatment to produce equiaxed, fine grains of Nb3Al and Nb solid solution (Nb33). Nb3Al/Nb33 two phase alloy (in-situ composite) is found to exhibit superplasticity especially when one of the constituent phases, Nb33, is supersaturated. During superplastic deformation Nb33 transforms to Nb3Al, and Al content in Nb33 decreases. After superplastic deformation the microstructure consisting of equiaxed grains is left unchanged, although a slight grain growth is observed. It is suggested that stress induced by grain boundary sliding is effectively accommodated through dislocation glide and climb in the soft Nb33
A Superplasticity Theory based on Dynamic Grain Growth
Authors: Mayo M.J. , Seidensticker J.R. 
Published: April 2011

AbstractThe linear relation between dynamic grain growth rate and strain rate appears to be constant across all superplastic materials—regardless of whether the system examined is metallic or ceramic, and regardless of the stress exponent exhibited during deformation. The simplicity and universality of the dynamic grain growth law suggest it might be useful as a foundation for a theory for superplasticity. One attempt at such a theory is presented. It is argued that stress leads to the development of anisotropic grain shapes that then require recovery through directionally biased grain growth events. Once this mathematical relationship between stress and grain growth rate is developed, it is inserted into the existing dynamic grain growth - strain rate law to arrive at a phenomenological law for superplasticity.
Cavity Nucleation in AL 5083 Alloys
Authors: Chandra N. , Chen Z. 
Published: April 2011

AbstractIn this paper we address the controversial issue of nucleation of cavities in Al 5083 alloys. We focus on the origin of cavities during the manufacture of these alloys into SPF (superplastic forming) sheet form. Experimental observations on the pre-existing cavities in this alloy are made using optical and electron microscopy. The effects of rolling direction and state of stress during superplastic deformations on the formation of cavities are also discussed. Numerical simulations of the sheet manufacturing process are carried out to understand the effect of hard phase/matrix, mechanical properties and interfacial strength on the origin of cavities. Based on the numerical results, a simplified model relating the process, material parameters and the cavity nucleation is presented.
Processing by Equal-Channel Angular Pressing: Potential for Achieving Superplasticity
Authors: Furukawa Minoru , Nemoto Minoru , Horita Zenji , Langdon Terence G. 
Published: April 2011

AbstractEqual-channel angular (ECA) pressing is a processing procedure whereby a very severe plastic strain is imposed on a sample without any change in the cross-sectional dimensions of the material. This processing method leads to a substantial grain refinement, producing grains which are within the submicrometer or even the nanometer scale. This paper discusses the potential for using this method to prepare materials for superplasticity. The results demonstrate that it is possible to achieve superplastic deformation in selected materials subjected to ECA pressing and, in addition, there is the possibility of extending the superplastic region so that it occurs at very rapid strain rates.