bluuebunny/crossref_metadata_2025_split huggingface dataset:
Finite Element Simulations of the Deformation of BCC Aggregates Using a Crystal Plasticity Model - Local Orientation Effects
Authors: Arizmendi D. , Raphanel J. L. 
Published: April 2011

AbstractOne has simulated by a finite element computation, the tensile plastic deformation of bcc aggregates with the same initial crystallographic texture but a different spatial distribution of orientations. The computations show fairly large differences between the simulations in terms of axial strain fields: one aggregate presents an homogeneous field, while another one localizes the strain in a narrow band. This “macroscopic effect” is then analyzed at the smaller scale of the crystallite by comparing local re-orientations, glide activity and stress levels. The influence of neighboring grains and of the “local”texture is thus shown. This is an effect that polycrystalline models (Taylor or self-consistent models) cannot account for.
Crack Propagation in Freshwater and Saline Ice
Authors: Donovan Patrick J. , Arakawa Masahiko , Petrenko Victor 
Published: April 2011

AbstractCrack propagation in columnar saline and freshwater ice has been investigated with high-speed photography, acoustic emission detection and the resistance method. High-speed photography was found to be a single reliable technique. The resistance method proved effective for freshwater ice samples, but not for saline ice samples due to the presence of conductive fluid inclusions. Acoustic emissions pinpointed the moment of crack initiation, but did not correspond to the crack propagation time. Crack velocity has been characterized over a temperature range of -5°C to -30 °C for freshwater and saline ice. Freshwater ice exhibited an overall average velocity of 198 m/s, and did not vary with temperature. Crack velocity in saline ice demonstrated temperature dependence, increasing from an average of 86 m/s in the -5°C to -20°C range, to 131 m/s at -30°C. The crack velocity was also shown to have a general dependence on fracture toughness K' of the material, however, the microstructural variation between samples is also shown to influence significantly the crack behavior in both saline and freshwater ice. Nonuniform crack tip advance and crack reorientation were observed as crack slowing mechanisms in freshwater ice, while in saline ice fracture crack tip blunting on voids greatly reduced average crack velocities.
Void Shape and Distribution Effects on Coalescence in Elastic-Plastic Solids
Authors: Pardoen T. , Hutchinson J.W. 
Published: April 2011

AbstractAn extended Gurson model incorporating the effects of the void shape and distribution on the growth and coalescence is proposed. The emphasis is placed on void coalescence, which is modeled as a transition from diffuse plasticity around the void to transverse localized plastic yielding in the intervoid ligament. Selected results showing the importance of correctly accounting for the void coalescence stage, as well as for the void shape and distribution effects, are presented and discussed.
Atomistic Modeling of Void Growth and Coalescence in Ni+H
Authors: Somerday B.P. , Pattillo P.D. , Horstemeyer M.F. , Baskes M.I. 
Published: April 2011

AbstractFinite strain rate atomistic simulations were conducted on Ni and Ni+H lattices containing voids to better understand the dislocation-scale mechanisms of void growth and coalescence and how hydrogen affects these damage processes. Void growth is governed by dislocations that nucleate at the void surface to transport mass away from the void as well as dislocations arriving at the void from the lattice exterior to deposit vacancies and accommodate void-surface expansion. Hydrogen can retard void growth when large local hydrogen concentrations impede dislocation nucleation and propagation at the void surface. The formation of hydrogen gas molecules in the void interior does not necessarily aid void growth. Pressure in small voids may be mitigated by the mutual interaction of hydrogen molecules and the interaction of molecules with the void surface.
A Model for Calculating Substrate Curvature During Coalescence of PT Islands on an Amorphous Substrate
Authors: Phillips M. A. , Ramaswamy V. , Clemens B. M. , Nix W. D. 
Published: April 2011

AbstractPrevious work using in-situ curvature measurement has shown a correlation between stress and microstructure during the early stages of thin film growth. The model presented here can be used to predict the curvature change of the substrate during part of this growth process. Curvature, and thus film stress, is measured in-situ during growth of sputter-deposited Pt on amorphous substrates. The average film stress is observed to be slightly compressive initially, followed by a change towards a tensile maximum, after which the stress becomes compressive again. Plan view TEM micrographs of Pt films of thicknesses up to 35 Å show the evolution of microstructure from isolated islands to a coalesced film. This evidence suggests that the tensile regime is due to island coalescence. The model calculates the curvature induced in a substrate during the tensile excursion associated with island coalescence, where discontinuous islands are modeled as a series of cracks in an otherwise continuous film. Quantitative measurements of island size and areal fraction covered are extracted from the TEM micrographs and used to predict the curvature during coalescence. The predicted stresses are shown to compare favorably with the measured stresses.
Influence of Grain Boundary Structure on Liquid Metal Penetration Behavior
Authors: Ren Liping , Bahr D.F. , Hoagland R.G. 
Published: April 2011

AbstractThe penetration of Ga along Al grain boundaries under stress-free conditions is investigated in the present study. In-situ SEM observations indicate that the penetration rate of Ga along Al grain boundaries at room temperature ranged from 6.4 to 9.2 μm/s, which is similar to the rate of diffusion in the liquid state. For a specific high energy grain boundary, the grain boundary misorientation is determined from the TEM diffraction Kikuchi pattern, and a molecular statics simulation method was employed to investigate grain boundary structure. A comparison of the structure of this high energy boundary is made with the Σ11(131)[101] tilt grain boundary that is not penetrated by Ga in the absence of the applied stress. The results indicate that the grain boundary plane void structure in the high energy grain boundary may provide void channels for Ga monolayer penetration. In addition, penetration behavior investigated under different length scales supports this model.
The Cellular Automaton Simulation of Microstructural Evolution During Deformation Processing of Metals
Authors: Davies Chris H.J. 
Published: April 2011

AbstractThe computer simulation of the evolution of microstructure during deformation processing is a desirable but elusive goal. In order to be effective, models must be tied to deformation parameters (temperature, strain rate, strain), and grain size distributions and recrystallisation kinetics must be predicted with high accuracy if the evolution of microstructure is to be tracked through several passes. This paper examines the cellular automaton (CA) simulation technique which has the potential to enable the modeller to accomplish these goals.Aspects of the CA approach examined are the three dimensional representation of microstructure and its evolution and the incorporation of texture representation into simulations.Also investigated will be the limitations of the technique, in terms of the error that can be expected when different boundary conditions are imposed on a simulation.Although at a rudimentary stage of investigation, the interfacing of CA simulations to deformation simulations (eg, finite element) will be examined. The paper concludes with a discussion of the challenges facing the implementation of CA simulations in industrial process models.
Transmission Electron Microscopy Study of Gold-Coated Iron Core-Shell and Au/Fe/Au Onion-Like Nanoparticles Synthesized using Reverse Micelles
Authors: Zhou W.L. , Carpenter E.E. , Sims J. , Kumbhar A. , O'Connor C.J. 
Published: April 2011

ABSTRACTGold-coated iron core-shell structure and Au/Fe/Au onion-like nanoparticles synthesized using reverse micelles were characterized by transmission electron microscopy (TEM). The average nanoparticle size of the core-shell structure is about 8 nm, with about 6 nm diameter core and 2 nm shell. The gold shell structure can be resolved from both high resolution electron microscopy (HREM) image and energy dispersive X-ray spectrum (EDS). Even though the gold and iron electron diffraction rings overlap a little bit, they can still be identified due to the slight mismatch of the diffraction rings. The Au/Fe/Au onion-like nanoparticles were also observed. The nanoparticles were formed with about 6 nm diameter gold core, 1 nm iron interlayer and 2 nm gold shell. The shell structure coated on the core appeared unhomogeneous, however, in both cases the iron core and interlayer iron shell stay air-stable.
Nanocomposites in the Systems Fe1−xO-Fe3O4 and MgO-MgFe2O4 Produced by Mechanical Alloying
Authors: Huerta A. , Calderon H. A. , Yee-Madeira H. , Umemoto M. , Tsuchiya K. 
Published: April 2011

ABSTRACTWtastite-magnetite and magnesia-magnesioferrite nanocrystalline ceramics have been prepared by mechanical milling and spark plasma sintering. As-milled powders have a nanocrystal-line structure in both systems. Low energy milling gives rise to an increasingly higher volume fraction of wfistite as a function of milling time in the Fe1−xO-Fe3O4 system. Similar results are obtained in the MgO-MgFe2O4 system with increasingly larger amounts of MgFe2O4 produced by milling. Composites of magnetic particles (Fe3O4 or MgFe2O4) in a nonconductive matrix (FeO or MgO, respectively) are found in the sintered samples. Measurement of magnetic properties can be used to determine conclusively the nature of the developed phases and the effect of grain size.
Steady State Phase Diagram of Cu-Ag Under Ball Milling: An XRD and APFIM Study
Authors: Wu F. , Bellon P. , Melmed A.J. , Lusby T.A. 
Published: April 2011

ABSTRACTThe nature of the steady state reached during ball milling of CuxAg1−x powders (x=35 to 75) is studied as a function of the milling temperature (85K≤T≤503K). The characterization of the powders is performed by using x-ray diffraction, differential calorimetry and atom probe field ion microscopy. A steady-state phase diagram is built. Three-phase coexistence is shown to generally take place at intermediate milling temperatures. Atom probe data reveals that the solid solution stabilized by low milling temperature is nearly random, where as milling at elevated temperatures results in the decomposition of the elements at a lengthscale of 20∼30 nm.
Synthesis and Characterization of CdSe/CdS Core-Shell and CdSe/CdS Composites
Authors: Malika M. Azad , O'Brien Paul , Revaprasaduac N. 
Published: April 2011

ABSTRACTHighly mono-dispersed CdSe/CdS core-shell and CdSe/CdS composites have been prepared by a novel route involving thermolysis in TOPO using Cd(Se2CNMe(nHex))2 and Cd(S2CNMe(nHex))2. The absorption band edge (652 nm, 1.90 eV) of the CdSe-CdS core-shell structure is red shifted (22 nm, 0.0 17 eV) as compared to the CdSe nanoparticles (630 nm, 1.96 eV) whereas the absorption spectrum of the CdSe-CdS composites shows the absorption band edge at (584 nm, 2.12 eV), blue shifted (46 nm, 0.037 eV) as expected. Photoluminescence (PL, λex = 400 nm) of both the core-shell (622 nm) and the composites (588 nm) show values close to band edge emission. A sharper emission maximum with a considerable increase of intensity is observed for core-shell structure as compared to that of CdSe whereas the composite showed a broader emission maximum. The TEM images of the CdSe/CdS core-shell nanoparticles show crystalline, spherical particles with the average size of 53 Å (±7 %), a increase of 8 Å than the average size of CdSe (45 Å) nanoparticles, with a narrow size distribution. The High Resolution Transmission Electron Microscopy (HRTEM) showed lattice spacing intermediate between those for CdSe and CdS as is observed by Selected Area Electron Diffraction (SAED) and X-ray patterns (hexagonal phase). As expected no interface can be observed by HRTEM between CdSe core and CdS shell. The TEM image of the CdSe-CdS composites show particles with an average size of 48.7 Å (±10%).
Effect of Vapor Pressure of H2O on the Formation of Nano-Crystalline TiO2 Ultrafine Powders
Authors: Lee K. R. , Kim S. J. , Song J. S. , Park S. 
Published: April 2011

ABSTRACTMono-dispersed TiO2 ultrafme particles with diameters 40-400nm were obtained from aqueous TiOCl2 solution with 0.67M Ti4+ concentration prepared diluting TiCl4 by homogeneous precipitation process in the ranges of 17-230°C. With the spontaneous hydrolysis of TiOCl2, which means the natural decrease of pH value in the aqueous solution, all mono-dispersed precipitates were crystallized with the anatase or rutile TiO2 phase. TiO2 precipitate with the pure rutile phase was fully formed at the temperatures below 65 °C, not involving the evaporation of H2O, and above 155 °C, which were available by suppressing it. TiO2 precipitate with rutile phase including a small amount of the anatase phase started to be formed in the intermediate temperatures above 70 °C showing the full formation of the anatase above 95 °C under the free evaporation of H2O. However, in the case of completely suppressing H2O evaporation at the temperatures above 70°C, TiO2 precipitate with anatase phase was fully transformed into the precipitate with the rutile phase by the vapor pressure of H2O. Therefore, the formation of TiO2 precipitates with the rutile phase around room temperature would be caused due to the existence of the capillary pressure between the agglomerated needle-shaped particles or the ultrafme clusters, together with the slow reaction rate.
CVD of Carbide Multi-Phased Coatings
Authors: Versprille K.E. , Ji Hua Xia , Amato-Wierda C.C. , Ramsey P.J. , Wierda D.A. 
Published: April 2011

ABSTRACTTiC and Ti-W-C films have been produced by chemical vapor deposition (CVD). A fractional factorial design was used to study the effects of deposition temperature, C:Ti input, H:Ti input, reactor pressure, and total mass flow on TiC film composition. Statistical models were developed for both titanium at.% and C:Ti in the film. It was found that the most significant affect on titanium at.% was the interaction of temperature, pressure and total mass flow. The most important affect on the C:Ti in the deposited film was the interaction C:Ti input, H:Ti, and total mass flow. Ti-W-C films have been deposited at 1050°C at various (TiCl4+W(CO)6)/CH4 inlet ratios ranging from 0.53 to 1.01. The characterization of the films revealed that the changes in deposition rate, crystallinity, film orientation, and morphology of various Ti-W-C compositions were affected by (TiCl4+W(CO)6)/CH4 inlet ratios.
Fiber Reinforced Epoxy Resin Composite Materials Using Carboxylate-Alumoxanes as Cross-Linking Agents
Authors: Vogelson Cullen T. , Koide Yoshihiro , Barrona Andrew R. 
Published: April 2011

ABSTRACTChemically functionalized alumina nanoparticles (carboxylate-alumoxanes) are used as the inorganic component of a new class of inorganic-organic hybrid materials. Lysine- or para- hydroxybenzoic acid-derivatized alumoxanes are readily prepared from the reaction of boehmite, [Al(O)(OH)]n, with the appropriate carboxylic acid. The peripheral organic hydroxides and amines of these carboxylate-alumoxanes either react directly with epoxide resins, such as the diglycidyl ether of bisphenol-A (DER 332), to form a hybrid material, or in the presence of an organic resin and hardener system to form a composite material. SEM and AFM show a uniform distribution of alumina nanoparticles within the resin matrix. The properties and cure times of the alumoxane hybrid and composite materials are distinct from both the pure resins and from a physical blend of the resins with traditional ceramic fillers. A significant increase in thermal stability and tensile strength is observed for both the hybrid and composite resin systems. In addition, both carbon fiber and carbon/Kevlar® matting have been successfully incorporated into the hybrid resin systems resulting in further property improvements.
Proton Conducting Organic/Inorganic Nanocomposite Polymer Electrolytic Membrane Synthesized by Sol-Gel Process
Authors: Honma I. , Nomura S. , Nakajima H. 
Published: April 2011

ABSTRACTIn this paper, new synthetic routes have been investigated for the preparation of Organic/inorganic nanocomposite polymer membranes consisting of SiO2 /PTMO(polytetramethylene oxide) hybrids and novel proton conducting materials. These materials have been synthesized through sol-gel processes in flexible, ductile, free-standing thin membrane form. The hybrid membrane has been found to be thermally stable up to 160 C and possesses proton conductivities of approximately 10−4 S/cm from a room temperature to 160 C.
Modified Sol-Gel Synthesis of Vanadium Oxide Nanocomposites Containing Surfactant Ions
Authors: Dobley Arthur , Zavalij Peter Y. , Whittingham M. Stanley 
Published: April 2011

ABSTRACTRecently, there has been much interest in creating new layered transition metal oxides. Vanadium oxides may be used as sorbents, catalysts, and cathodes in lithium batteries. The modified sol-gel technique allows for some control towards the final structure of the compound. Using this technique, a new layered vanadium oxide compound - I, containing the surfactant dodecylphosphate, has been synthesized. After the removal of the organic ligand a new compound - II is formed which might be hexagonal. The compounds were analyzed using XRD, TGA, SEM, and NMR. VO2PO3(OH)C12H25(H2O)n is the general formula of the layered product I with a layer spacing of about 40 angstroms. II appears to be hexagonal with a = 43Å. The synthesis, composition, and structure of these compounds are discussed.
Electroluminescence Devices with CdS and CdS:Mn Nanoparticles and Polymer Blends
Authors: Brugger Ch. , Tasch S. , Lal M. , Prasad P.N. , Leising G. 
Published: April 2011

ABSTRACTWe have investigated the photophysical properties of surface capped CdS and CdS:Mn nanoparticles in the form of spin coated thin films of the pure nanoparticles and nanoparticle -polymer blends. The organic capping reagent was p-thiocresol. Electroluminescence (EL) devices were fabricated and characterized by their current/voltage characteristics and EL emission performance. This is to our knowledge the first report on Mn doped CdS nanoparticles applied in EL devices with a single layer device structure (ITO/CdS:Mn/Al). Photoluminescence (PL) and PL excitation measurements were performed on CdS:Mn nanoparticles in pyridine dispersion and on thin films. The PL excitation spectrum shows a narrow peak at 390nm. Excitation at this wavelength yields a broad PL spectrum spanning from about 450 to 700nm, which is dominated by a strong emission band at 585nm. This emission is attributed to transitions involving Mn levels in previous works. The EL emission peak is shifted to the red compared to the PL emission spectra. The characteristics and performance of these new types of EL devices will be presented and discussed.
Synthesis of Passivated Metal Nanoparticles
Authors: Green Mark , O'Brien Paul 
Published: April 2011

ABSTRACTHere we report the synthesis of organically passivated nanoparticles of gold, chromium and nickel. The routes involve the reduction of a metal precursor in various Lewis base solvents, which appear to affect the final nanoparticle morphology. The preparation of highly monodispersed samples can lead to the potential for further manipulation of dots into ordered 2D and 3D arrays. These colloidal thin films and crystals have potential application in magnetic data storage devices.
Features of Fracture Surface and Grain Boundary Structure of Boride/Nitride Materials
Authors: Andrievski R.A. , Kalinnikov G.V. , Shtansky D.V. 
Published: April 2011

ABSTRACTNanostructured bulks and films of TiB2, TiN, AIN, Ti(B,N), and (Ti,Al)N prepared by high pressure sintering and nonreactive magnetron sputtering accordingly. Fracture surfaces and structure of grain boundaries have been investigated by high-resolution scanning and transmission electron microscopy as well as by atomic force microscopy. The revealing of transgranular fracture, homogeneous and inhomogeneous deformation, and the availability of dislocations and amorphous phases in structure are discussed.
Relationship Between Thermally Activated Atomic Diffusion Processes in Co-Cu Nanoscale Granular Films and Electric/Magnetic Properties
Authors: Spizzo F. , Ronconi F. , Vavassori P. , Bordin G. , Bisero D. , Pareti L. , Turilli G. 
Published: April 2011

ABSTRACTCo-Cu multilayer granular films deposited onto Si substrates have been submitted to thermal treatments in scanning mode. Their magnetisation and resistance have been studied after applying two different heating rates. The comparison between the experimental data measured before and after the treatment points out that the effect of the annealings depends strongly on the heating rate used. We also present XPS data collected as a function of depth to show how the different heating rate modify the composition and chemical environment produced by thermal treatments.
Understanding the Second Harmonic Generation of Light from Nanometal Composites
Authors: Sandrock M. L. , Foss Colby A. 
Published: April 2011

ABSTRACTWe have synthesized two sets of nanometal composites of different metal concentrations via electrodeposition of gold into porous aluminum oxide membranes Within each set, both centrosymmetric and non-centrosymmetric particles were produced whose linear and nonlinear optical effects were investigated.Because our method of template synthesis allows for the close examination of our composite materials in terms of shape, size. and symmetry, we can interpret the SHG response in terms of differences in local field enhancements of magnetic dipole and quadrupole modes.
Screen-Printed Dye-Sensitized Large Area Nanocrystalline Solar Cell
Authors: Gupta T.K. , Cirignano L.J. , Shah K.S. , Moy L.P. , Kelly D.J. , Squillante M.R. , Entine G. , Smestad G.P. 
Published: April 2011

ABSTRACTThe fabrication and testing of screen printed dye-sensitized large solar cell (15 cm × 15 cm) based on nanocrystalline TiO2 is described. It is the largest photo-electrochemical (PEC) cell that is based on the dye sensitization of thin (8-18 μm) films of TiO2 nanoparticles in contact with a non-aqueous liquid electrolyte. The cell has the potential to be a low cost, commercial, environmentally friendly, photovoltaic option. Surface as well as electrical characterization, of the nanostructured PEC cells have been performed. The efficiency of these large commercial cells are compared to the laboratory-made small PEC cells. Key words: Photoelectrochemical, solar cells, nanocrystalline, dye-sensitized