bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Analysis and Crystallographic Model of Plastic Deformation after a Change of Loading Path in Mild Steel Polycrystals
Authors: Hoc T. , Rey C. 
Published: April 2011

AbstractStrain localization in mild steel submitted to a sequential loading paths is investigated at macroscopic, mesoscopic and microscopic scales. The experimental results demonstrate that the morphology of the localization and the nominal load-displacement curves depend on the microstructural anisotropy. A crystalline model using a finite element code is proposed. The anisotropy is described by a hardening matrix whose terms correspond to dislocation-dislocation interactions and depend on the evolution of the dislocation densities on the activated slip systems during the sequential tests. The strain localization predicted by this model fits with the experimental observation and allows us to assume that localization is correlated to the saturation on the activated slip systems.
Complementary Experimental Techniques for Multi-Scale Modeling of Plasticity
Authors: Levine L. E. , Long G. G. , Black D. R. 
Published: April 2011

AbstractSome recently-developed experimental techniques, such asin situultra-small-angle Xray scattering (USAXS), have demonstrated a capability for measuring aspects of dislocation structure evolution that are inaccessible to other experimental methods. However, no single technique can provide the entire range of information required by theoretical and computational researchers. It is only through the synergy of several experimental techniques (such as USAXS, transmission electron microscopy, and X-ray diffraction imaging) that much of the required quantitative information can be obtained. Ultimately, the development of additional new experimental techniques will also be required.
Nano-Sized Semiconducting Oxide Powders for Thick Film Gas Sensors: From Powder Processing to Environmental Monitoring Devices
Authors: Traversa Enrico , Carotta Maria Cristina , Martinelli Giuliano 
Published: April 2011

ABSTRACTThis paper reports the study of semiconducting oxides to develop gas sensors in thick-film form for use in atmospheric pollutant monitoring devices. The investigation was achieved with the following steps: selection of the suitable oxides and of their most appropriate processing method to obtain nano-sized powders, fabrication using screen-printing technology of thick-film sensors from these powders, and electrical measurements in laboratory and in the field. Chemical routes such as sol-gel techniques and thermal decomposition of heteronuclear complexes have been used to prepare nano-sized powders of n-type (TiO2) and p-type (LaFeO3 and SmFeO3) semiconducting oxides. Thick-film gas sensors have been produced by screen-printing technology. Pastes have been prepared and printed on laser precut 96% alumina substrates, each 2×2 mm element being provided with a heater, comb-type Au contacts and a Pt-100 resistor for controlling the operating temperature. The firing of the films has been performed in conditions able to keep grain size at nanometer level. Electrical responses to some major polluting gases (CO, NO, NO2 and O3) have been tested in laboratory and in the field, and compared with results of the analytical techniques approved by the international standards.
Synthesis and Characterization of Mn Doped CdS Quantum Dots from a Single Source Precursor
Authors: Malik M. Azad , O'Brien Paul , Revaprasadu N. 
Published: April 2011

ABSTRACTCdS and Mn-doped CdS capped with TOPO (tri-n-octylphosphineoxide) have been prepared by a single source route using bis(methylhexyldithiocarbamato)cadmium(II) and manganese dichloride as precursors. The nanoparticles obtained show quantum size effects in their optical spectra with the CdS nanoparticles exhibiting near band-edge luminescence. The PL spectrum of the doped CdS nanoparticles have an emission maximum at 585 nm attributed to the 4T1-6A1 electronic transition of Mn in a tetrahedral site. However the PL spectrum changes over time (weeks) and gave a deep trap emission. The Selected Area Electron Diffraction (SAED) and X-ray diffraction (XRD) pattern show both CdS and the Mn doped CdS particles to be of the hexagonal phase. Transmission Electron Microscopy (TEM) and High Resolution TEM show well-defined images of nanosize particles with clear lattice fringes. ESR spectra and ICP results confirm the presence of Mn in the CdS nanoparticles.
Synthesis and Characterization of Strongly Fluorescent CdTe Nanocrystal Colloids
Authors: Mikulec Frederic V. , Bawendi Moungi G. 
Published: April 2011

ABSTRACTWe present a synthesis of colloidal CdTe nanocrystals whose absolute room temperature quantum yields are routinely above 60%. The preparation is based on the trioctylphosphine oxide (TOPO) method reported by Murray, with a more stalbe tellurium precursor now used as the chalcogenide source. The photoluminescence is continuously tunable over the range 590-760 nm and is as narrow as 135 meV (45 nm) FWHM. No deep trap luminescence is detected for the diameter range 4-11 nm. CdTe nanocrystals are characterized by UV/vis absorption, photoluminescence emission, transmission electron microscopy, and powder X-ray diffraction.
Size Effect in Germanium Nanostructures Fabricated by Pulsed Laser Deposition
Authors: Hassan K.M. , Sharma A.K. , Narayan J. , Muth J.F. , Teng C.W. , Kolbas R.M. 
Published: April 2011

ABSTRACTWe have fabricated Ge nanostructures buried in AlN and Al2O3 matrices grown on Si(111) and sapphire substrates by pulsed laser deposition. Our approach involved three-dimensional island growth of low band-gap material followed by a layer of wide band-gap material. The nanodots were uniformly distributed in between alternating layers of AlN or Al2O3. It was observed that these nanodots exhibit crystalline structure when grown at 300-500 °C. The average size of Ge islands was determined to be ∼5-15 nm, which could be varied by controlling laser deposition and substrate parameters. The Raman spectrum showed a peak of the Ge-Ge vibrational mode downward shifted upto 295 cm− which is caused by quantum confinement of phonons in the Ge-dots. The photoluminescence of the Ge dots (size ∼15nm) was blue shifted by ∼0.266 eV from the bulk Ge value of 0.73 eV at 77 K, resulting in a distinct peak at ∼1.0 eV. The spectral positions of both E1 and E2 transitions in the absorption spectra at room temperature and 77K shift toward higher energy as the Ge dot size decreases. The interpretation of these behaviors in terms of quantum confinement is discussed in this work, and the importance of pulsed laser deposition in fabricating novel nanostructures is emphasized
Functionalisation of CdSe and GaAs Quantum Dots
Authors: Nørager Sebastian J. , Lazell Michael , O'Brien Paul 
Published: April 2011

ABSTRACTIn this communication we report the preliminary results of in-situ functionalisation, of Q-CdSe and Q-GaAs using thiols, (HSC12H25), dithiols, (HSC9H18SH), pyridine derivatives (4-ethylpyridine, 4-butylpyridine) and carboxylic acids (mercaptopropionic acid).The functionalisation of the capping group provides a potential route to the assembly of 2D arrays and supperlattices. Anchorage of the nanocrystals to surfaces for use in devices, such as solar cells and Grätzel type cells is also discussed.
Sputtering Effects and Two Dimensional Arrangement of Nanoparticles in Insulators Under High Flux Cu Implantation
Authors: Kishimoto N. , Lee C.G. , Umeda N. , Takeda Y. , Gritsyna V.T. 
Published: April 2011

ABSTRACTApplication of negative heavy ions, alleviating surface charging on insulators, enables us to conduct low-energy and high-flux implantation, and leads to a well-defined tool to fabricate near-surface nanostructures. Negative Cu ions of 60 keV, at high doses, have generated nanocrystals in amorphous(a-)SiO2 with a size (∼10 nm) suitable for nonlinear optical devices. The kinetic processes, inside the solid and at the surface, are studied by cross-sectional TEM and tapping AFM, respectively. In a-SiO2, nanoparticles spontaneously grow with dose rate, being controlled by the surface tension and radiation-induced diffusion. Furthermore, the nanospheres give rise to a two-dimensional (2D) arrangement around a given dose rate. The 2D-distribution occurs in coincidence with enhanced sputtering where a considerable Cu fraction sublimates from the surface. The dose-rate dependence of nanoparticles indicates that the surface-sputtering process influences the intra-solid process and contributes to the 2D-distribution. A self-assembling mechanism for 2D-arrangement of nanospheres is discussed taking into account contribution of the surface sputtering.
Preparationand Properties of Colloidal Particles. Silica on Yttrium Iron Garnet
Authors: Godoi R.H.M. , Jafelicci M. , Portillo Joaquim 
Published: April 2011

ABSTRACTVarious properties of particles can be altered by coating them with a layer of different chemical composition. Yttrium iron garnet (YIG) particles has been coated with silica for control of their sintering, corrosion resistance, and stabilization of magnetic properties. This silica cover was obtained by hydrolysis of tetraethylorthosilicate (TEOS) in 2-propanol. This material was characterized by transmission (TEM) electron microscopy, (XEDS) X-ray energy-dispersive spectrometry, (XPS) X-ray photoemission spectroscopy and (VSM) vibrating sample magnetometry. YIG was heterocoagulated by silica as indicated by TEM micrographies. XPS measurements indicated that only binding energy for silicon and oxygen was found on the silica shell, which confirms that the YIG was covered. The values of the saturation magnetization differ from the heterocoagulated system to well-crystallized YIG.
Composite Nanowires from Ion Beam Modification of Si Nanowires
Authors: Zhou X. T. , Peng H. Y. , Shang N. G. , Wang N. , Bello I. , Lee C. S. , Lee S. T. 
Published: April 2011

ABSTRACTComposite nanowires with typical diameters of 30-100nm, which consisted of Si, β-SiC, amorphous carbon were converted from Si nanowires by ion beam deposition. The Si nanorods were exposed to broad low energy ion beams. The low energy hydrocarbon, argon and hydrogen ions, generated in a Kaufman ion source, reacted with Si nanowires and formed the composite nanowires. It has been assumed that the reaction pathway to form the composite nanowires were driven by both thermal diffusion and kinetic energic of interacting particles.
Supersonic Cluster Beam Synthesis of Nanophase Materials
Authors: Milanil P. , Iannotta S. , Biasioli F. , Piseri P. , Barborini E. 
Published: April 2011

ABSTRACTWe present the characterization of supersonic cluster beam deposition as a viable technique for the synthesis of nanostructured materials. Stable and intense cluster beams can be obtained with a pulsed microplasma cluster source. This technique has been applied to produce TiNi nanostructured thin films on various substrates at room temperature. The morphology and the structure of the film are strongly influenced by the precursor clusters. Films characterized by crystallite sizes of a few tens of nanometers can be grown without recrystallization by thermal annealing. The stoichiometry of the original TiNi alloy is maintained.
Magnetic Entropy Change of Nanocomposites Composed of a Silver Matrix and Grains of Iron-Oxide Or -Nitride
Authors: Yamamoto T. A. , Tanaka M. , Shiomi K. , Nakayama T. , Nishimaki K. , Nakagawa T. , Numazawa T. , Katsura M. , Niihara K. 
Published: April 2011

ABSTRACTMagnetocaloric effect of nanocomposites composed of iron-oxide or iron-nitride grains dispersed in a silver matrix was studied by calculating magnetic entropy change ΔS induced by a change in applied magnetic field H. These nanocomposites were synthesized by the inert gas condensation technique and nitridation by heat treatment in an ammonia gas stream. Average sizes of the iron-containing grains were 10-35 nm. Magnetic phases in the materials were Fe3O4 or γ -Fe2O3 for the oxide-composites and γ-Fe4N or ε -Fe3N for the nitride-composites. Values of the ΔS were obtained by applying a thermodynamic Maxwell's relation, (∂S / ∂H)T = (∂M / ∂T)H, to data set of magnetization M measured at various temperatures T. They clearly indicated significant enhancement due to the nanostructure as predicted.
Nanocomposites nc-TiN/a-Si3N4/a- and nc-TiSi2 with Hardness Exceeding 100 GPa and High Fracture Toughness
Authors: Vepřiek S. , Niederhofer A. , Moto K. , Nesládek P. , Männling H. , Bolom T. 
Published: April 2011

ABSTRACTIn course of further development of our generic concept for the design of novel superhard nanocomposites [1,2] we have recently developed new multi-phase ultrahard nano-composite coatings with Vickers mirohardness of 80 to 105 GPa which is in the range of natural diamond. The coatings show a high elastic recovery of up to 90% upon a relatively large indentation deformation. The hardness measured by the depth sensing technique agree with those calculated from the area of the remaining pseudoplastic deformation. The very high apparent fracture toughness is illustrated by the absence of any radial cracks upon in-dentation with a large load of I N into 10.3 p.m thick film [3]. The unusual combination of high hardness, elastic recovery and apparent fracture toughness was attributed to the ample possibility of cracks deflection, meandering and termination during loading and cracks closure upon unloading [1,2,4]. The suggested nanostructure of the coatings has been elucidated on a basis of a complex analysis by means XRD, EDX, ERD, XPS and HR TEM.
Vanadium Oxide Nanotubes with Diamine Templates
Authors: Krumeich F. , Muhr H.-J. , Niederberger M. , Bieri F. , Reinoso M. , Nesper R. 
Published: April 2011

ABSTRACTDiamine vanadium oxide nanotubes (DA-VOx-NTs) have been prepared in high yields applying two different synthesis routes, namely either a sol-gel reaction followed by a hydrothermal treatment or an exchange reaction. The first route is analogous to the well-known preparation of VOx-NTs containing monoamines: a vanadium(V) alkoxide is mixed with an α, ω- diamine (H2N[CH2]nNH2with 12≤n≤20), the resulting adduct is hydrolyzed, and, after aging, a hydrothermal treatment leads to the nanotubes in pure form. The exchange of the monoamine template in VOx-NTs against diamines represents an alternative access to DA-VOx-NTs. This reaction occurs readily and is also applicable for diamines with short CH 2 chains like, e.g., in ethylene diamine. The TEM characterization of the DA-VOx-NTs confirms the tubular morphology which is widely preserved in the products of the exchange reactions. The characteristic feature of as-synthesized DA-VOx-NTs is a thick tube wall with many VO, layers while the exchange products are tubes comprising thin walls or bent packs of layers.
Phase Transition and Control of Self-Assembled Mesostructured Vanadia/Surfactant Composites
Authors: Honma I. , Yagi Y. , Zhou H. S. , Endo A. , Miyayama M. , Kudo T. 
Published: April 2011

ABSTRACTThe mesostructured vanadia/surfactant composites are synthesized by self assembled processes and phase transition has been investigated. The lamellar mesostructure of the vanadia/surfactant has been shifted to monoclinic and hexagonal mesophase by low temperature annealing, possibly due to the change of the inorganic/surfactant ratio.
Optical Characterization of a Spheroidal Nanoparticle on a Substrate
Authors: Román-Velázquez Carlos E. , Noguez Cecilia , Barrera Rubén G. 
Published: April 2011

ABSTRACTWith the help of a spectral formalism recently formulated, we study the effects in the optical response of the material properties of a nanoparticle lying over a substrate. A spectral representation was formulated to calculate the optical response of spheroidal nanoparticles including multipolar effects. We present our results in terms of Differential Reflectance spectra that can be compared directly with measurements. We have found that multipolar contributions depend in the shape of the particle and type of substrate.
Hysteresis Loop Shifts in Magnetic Field Cooled FeOOH Nanoparticles
Authors: Seehra M.S. , Roy Paromita , Manivannan A. 
Published: April 2011

ABSTRACTMeasurements of the magnetization M as a function of temperature (5K - 300K) and applied magnetic field H (up to 50 kOe) in 30 Å particles of FeOOH are reported. M increases with decreasing T, peaking at TB = 65 K below which the ZFC (zero-field-cooled) and the FC (field-cooled) data separate. Hysteresis loop measured at 10 K for ZFC shows an open loop up to 40 kOe with coercivity = 2 kOe. For the FC case, the loop shifts and the loop-shift increases with the cooling field ItL, approaching saturation above Hc = 20 kOe. From the variation of M vs H above TB, a magnetic moment/particle μp = 300 μB is determined. These results suggest that the FeOOH nanoparticles have an antiferromagnetically ordered core with uncompensated surface spins yielding μp and the surface spins order in a spin-glass-like state below TB, possibly due to interparticle interactions.
Preparation of Nanocrystalline Bismuth-Containing Powders through Solution-Phase Reductions
Authors: Foos Edward E. , Berry Alan D. , Snow Arthur W. , Armistead J. Paul 
Published: April 2011

ABSTRACTIn an attempt to both prepare nanocrystalline bismuth and understand the fundamental chemistry behind the formation of this potentially interesting material, we have examined the reduction of BiCl3 in the presence of strongly coordinating solvents and ligands. These studies have resulted in the formation of bismuth powders with approximate average particle sizes of between 20 and 40 nm which exhibit large size distributions. The simultaneous reduction of both gold and bismuth precursors, done in an attempt to better control the final particle size, instead produces Au2Bi of comparable dimensions. There is no evidence that the ligands utilized in either of these systems remain bound to the final product. These nanocrystalline powders have been characterized through XRD and TEM, and full details of the synthesis are presented.
Temperature Dependence of the Electrical Resistivity in Nanocrystalline Gold Films Made by Advanced GaS Deposition
Authors: Ederth J. , Kiss L. B. , Niklasson G. A. , Granqvist C. G. , Olsson E. 
Published: April 2011

ABSTRACTNanocrystalline thin Au films with grain size 10 - 76 nm have been analyzed regarding the temperature dependence of the electrical resistivity. A sudden change in the power function, ρ α Tn, was found at ∼10 K, where n = 1.7 in the range 5 - 10 K and n = 3.3 in the range 10 - 15 K. This effect disappears after annealing at 773 K for 0.5 h in air at atmospheric pressure. After the annealing the grain size was ∼ 100 nm. This is an indication of interference between electron-phonon scattering and electron-grain boundary scattering in nanocrystalline materials at low temperatures.The temperature coefficient of resistivity, TCR, increased with increasing grain size at any temperature and the position of the maximum TCR was shifted towards lower temperatures with increasing grain size.
Microstructure and Mechanical Properties of Oxide Eutectic Fibers
Authors: Durbin S. D. , Yoshikawa A. , Hasegawa K. , Lee J.-H. , Epelbaum B. M. , Fukuda T. , Waku Y. 
Published: April 2011

ABSTRACTSome oxide eutectic materials, such as sapphire/YAG, display an intricate “Chinese script” microstructure which strongly influences properties such as mechanical strength. We used the micro pulling-down technique to grow fibers of a series of such materials at rates over 20 mm/min, giving a uniform microstructure with a characteristic size as low as 150 nm. Bulk and surface characteristics of this microstructure were investigated by electron and atomic force microscopy. Smaller microstructure size gave higher tensile strength at 1500°C. Annealing of the fibers produced some coarsening of the microstructure, but increased the strength at lower temperatures.
Structure and Stability of Nano-Scale Melt Spun Mg-Ca-Zn Alloys
Authors: Jardim P.M. , Solórzano I.G. , Sande J.B. Vander , You B.S. , Park W.W. 
Published: April 2011

ABSTRACTAlloys, with six different compositions in the system Mg-Ca-Zn were produced by melt spinning. The aging behavior of alloys was investigated by measuring the changes in microhardness after isochronal aging and the microstructure was analyzed by means of Transmission Electron Microscopy(TEM), Energy Dispersive X-ray Spectrometry (EDS), Scanning Transmission Electron Microscopy (STEM) and Scanning Electron Microscopy (SEM). All six compositions in the as-solidified condition show a difference in microstructure between the wheel contact side (zone A) and the free surface side (zone B) as a result of the differences in the solidification rate across the ribbons. One of the alloys was chosen to be more deeply investigated in this work as it exhibited grain boundary films and presented the highest peak hardness among the low Ca alloys. The comparison between the two microstructural zones in this alloy can aid in understanding of the phase transformation steps during cooling with a model which is proposed here.
Nano-Photoluminescence Studies of Self-Assembled Quantum Dots
Authors: Htoon H. , Yu Hongbin , Kulik D. , Keto J. W. , Baklenov O. , Holmes A. L. , Shih C. K. 
Published: April 2011

AbstractTwo simple and effective far-field-optics-based methods capable of isolating photoluminescence peaks of different individual self assembled quantum dots (SAQD's) with nanometer scale precision are presented. By using these methods, we performed the temperature and electric field dependent studies on the optical properties of SAQD's. We found temperature induced inter-dot carrier transfer among neighboring quantum dots (QD's) and observed the quantum confined stark effect (QCSE).
Kinetic Aspects of Island Nucleation Derived from Near Equilibrium Growth Experiments
Authors: Christiansen S. H. , Becker M. , Wawra H. , Albrecht M. , Strunk H. P. 
Published: April 2011

AbstractUsing liquid phase epitaxy from Bi solution, a by its nature a near equilibrium growth process, we study the kinetics of island formation in the heteroepitaxial system SiGe/Si(001) as dependent on growth temperature, growth rate and composition (which also determines the lattice misfit between layer and substrate). As a main result island formation can be described by classical nucleation theory, moreover, it can be described as any other crystallization process such as solid state crystallization of amorphous silicon or crystallization from a melt, provided that the limited size the islands can grow into is correctly considered. In consequence, after an incubation time period that depends on the growth temperature, islands nucleate and cover the substrate surface with time. The activation energy of island nucleation is 0.84±0.13eV. The coverage with islands depends only on the undercooling and is independent of the cooling rate in case near equilibrium growth conditions are maintained. In these cases the islands have the shape of truncated pyramids with four {111}– side facets and a base width λ that only depends on the misfit f (λ ∝ 1/f2). Deviations from the equilibrium growth stage at high growth rates (thus higher growth driving forces) result in the formation of a higher density of smaller islands with smaller facet angles. At higher growth rates, some kinetic influences begin to appear indicated by the additional appearance of shallower pyramids with four {115}– facet side faces.