bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nanocrystalline Soft Magnetic Fe-M-B (M = Zr, Hf, Nb) “NANOPERM,” Fe-M-O (M = Zr, Hf, Rare Earth) Alloys and Their Applications
Authors: Makino A. , Inoue A. , Masumoto T. 
Published: April 2011

ABSTRACTNew soft magnetic nanocrystalline materials in Fe-M-B (M = Zr, Hf, Nb) and Fe-M-O (M = Zr, Hf, rare earth) systems have been fabricated by use of partial crystallization of melt-spun amorphous phase and sputtering-induced partial crystallization, respectively. These alloys have a mixed structure of nanoscale a-Fe grains and an amorphous phase containing large amount of M, B and M, O, respectively. This structural property should be a dominant factor for achieving good soft magnetic properties in both alloys. The Fe85.5Zr2Nb4B8.5 ribbon exhibits a high mag- netic flux density (Bs) of 1.64 T and a high permeability of 60,000 at 1 kHz as well as a very low core loss of 0.09 W/kg at B = 1.4 T and 50 Hz. The soft magnetic Fe-M-O films with high O content of 10-35 at.% maintain high permeability up to the high frequency above 100 MHz be- cause of higher electrical resistively of 6 to 23 µΩm than those of other conventional soft mag- netic alloy films. The Fe-M-B ribbons "NANOPERM" should be more suitable for low frequen- cy transformers. The Fe-M-O films are useful for high frequency applications such as thin-film inductors and transformers for micro switching converters for portable electric equipment.
Soft Magnetic Properties and Structure of Nanocrystalline Alloys Based on Finemet
Authors: Todd I. , Davies H.A. , Gibbs M.R.J. , Kendall D. , Major R.V. 
Published: April 2011

ABSTRACTThe effects of partial substitution of Al for Fe in Fe73.5-xAlxSi13B9Nb3Cu1, nano composite alloys both on the a.c. magnetic properties such as permeability and core loss, saturation magnetostriction and core loss are presented. The observed improvements in material properties are discussed in relation to the nanocrystallite and residual glass component chemistry.
Effect of Cu On Microstructural Evolution of Nanocrystalline Soft and Hard Magnetic Materials
Authors: Hono K. , Ping D. H. , Hirosawa S. 
Published: April 2011

ABSTRACTThe nanocrystallization processes in Fe-Si-B-Nb-Cu and Fe-Nd-B(-Cu-Nb) amorphous alloys have been studied by transmission electron microscopy (TEM) and a three dimensional atom probe (3DAP). Cu additions are effective in refining the nanocrystalline microstructures of both alloys, because Cu atom clusters formed prior to the crystallization reaction serve as heterogeneous nucleation sites for the primary crystals. However, the clustering behaviors of Cu atoms in these two alloy systems are different, i.e., Cu completely dissolves in the Nd2Fe1 4B phase in the final microstructure of the Nd4.5Fe75.8B18.5Cu0.2Nb1 alloy, whereas CL' clusters grow to fcc-Cu particles in the Fe73.5Si13.5B9Nb3Cu1 alloy. The nanocrystallization processes in these two alloys clarified by the 3DAP results are compared.
Lorentz Microscopy and Electron Holography of Nanocrystalline Magnetic Materials
Authors: Graef Marc De 
Published: April 2011

ABSTRACTThis paper employs an analytical model for the phase shifts imparted on a beam electron by a spherical particle with a uniform magnetization. Model image simulations of Fresnel and Foucault type Lorentz microscopy contrast are presented. Estimates of a lower particle size limit for which no magnetic information can be extracted from the images are given and compared to similar estimates for the electron holography observation method. It is concluded that conventional Lorentz methods have a lower particle size limit of around 30 nm (for cobalt particles), while electron holography can be used to even smaller sizes.
Pvd Growth of Fcc Metal Films on Single Crystal Si and Ge Substrates
Authors: Westmacott K.H. , Hinderberger S. , Radetic and U. Dahmen T. 
Published: April 2011

ABSTRACTEpitaxial films of the fcc metals Al, Au, Ag and Ni were grown by physical vapor deposition on Si and Ge (111), (110) and (100) substrates at different deposition temperatures. The epitaxial relationships and morphological features of these films were characterized by transmission electron microscopy and diffraction in plan view and cross section. Ag formed single crystal films on all substrates at all temperatures. Au and Al could be grown as bicrystals, and under some conditions, Al and Ni grew as tricrystal films. The morphological effects of diffusion at the metal/substrate interface are ascribed to diffusion induced grain boundary migration.
Investigations On In Situ Nanocrystallization And Magnetic Properties For Amorphous Fe78Si9B13 Ribbons
Authors: Sun Xiangeheng , Cabral-Prieto A. , Yacaman M. Jose , Sun Wensheng 
Published: April 2011

ABSTRACTThe amorphous state of ferromagnetic Fe78Si9B13 (Metglas 2605S-2) and its nanocrystallization were investigated by in situ transmission electron microscope (TEM), Xray diffraction (XRD), Mossbauer spectroscopy (MS), differential scanning calorimeters (DSC) and magnetic moment measurements. The Mössbauer spectrum exhibited an essentially symmetric hyperfine field pattern of 259KOe in as-quenched amorphous state at room temperature. The Curie and crystallization temperature were determined to be Tc=708K and Tx= 803K, respectively. The Tx value was in good agreement with DSC measurement results. The occupied fraction of the nanocrystalline phases of α-Fe(Si) and Fe2B at in situ optimum annealing temperature was about 57% and 43%, respectively. It is notable that the magnetization of the amorphous phase decreases more rapidly with increasing temperature than those of nanocrystalline ferromagnetism, suggesting the presence of the distribution of exchange interaction in the amorphous phase or high metalloid contents.
Dislocation Multiplication in the Early Stage of Deformation in MO Single Crystals
Authors: Hsiung L. M. , Lassila D. H. 
Published: April 2011

AbstractInitial dislocation structure in annealed high-purity Mo single crystals and deformation substructure in a crystal subjected to 1% compression have been examined and studied using transmission electron microscopy (TEM) techniques in order to investigate dislocation multiplication mechanisms in the early stage of plastic deformation. The initial dislocation density is in a range of 106 σ 107 cm−2, and the dislocation structure is found to contain many grown-in superjogs along dislocation lines. The dislocation density increases to a range of 108 σ 109 cm−2, and the average jog height is also found to increase after compressing for a total strain of 1%. It is proposed that the preexisting jogged screw dislocations can act as (multiple) dislocation multiplication sources when deformed under quasi-static conditions. The jog height can increase by stress-induced jog coalescence, which takes place via the lateral migration (drift) of superjogs driven by unbalanced line-tension partials acting on link segments of unequal lengths. The coalescence of superjogs results in an increase of both link length and jog height. Applied shear stress begins to push each link segment to precede dislocation multiplication when link length and jog height are greater than critical lengths. This “dynamic” dislocation multiplication source is suggested to be crucial for the dislocation multiplication in the early stage of plastic deformation in Mo.
Properties of the Deformation Microstructure in Al-Rich γ-TiAl Deformed by Ordinary Dislocations
Authors: Grjégori Fabienne , VeyssiÈRe Patrick 
Published: April 2011

AbstractIn the near vicinity of the [021] load orientation, γ-TiAl deforms via ordinary dislocations (Burgers vector b = 1/2<110]). As for deformation by <110] dislocations, the flow stress shows a peak at about 600°C. Results of an extensive microstructural investigation aimed at identifying the origin of this mechanical anomaly are presented. The analysis was conducted on single crystals oriented for single slip. It confirmed that ordinary dislocations tend to align themselves along the screw direction. This preferential line direction becomes gradually accentuated as the deformation temperature is raised up to the peak temperature. This effect is accompanied by a strong tendency towards forming cusps, but there is indication that the immobilisation along the screw direction takes place prior to dislocation pinning. In the vicinity of the peak temperature, screw dislocations gather in the form of bundles. No clear correlation is found between the temperature dependence of the flow stress and that of the density of pinning points. The relationship between these microstructural findings and the occurrence of a flow stress anomaly is discussed.
Deformation of Al-Rich γ-TiAl by <110] Dislocations Over the Domain of Flow Stress Anomaly
Authors: Grégori Fabienne , Veysslère Patrick 
Published: April 2011

AbstractThe flow stress of Al-rich γ-TiAl peaks at a temperature located between about 600°C and 1000°C. We present mechanical data on samples oriented so as to deform on a <011]{111} system in single slip. These data are complemented by TEM observations in samples strained at selected temperatures (RT, 400°C, 600°C and 800°C). The present paper addresses (i) properties of dislocation organisation, (ii) the dissociation mode of <110] dislocations, (iii) locking properties of <110] dislocations and (iv) the formation of faulted dipoles.
A Systematic Investigation of Strain Relaxation, Surface Morphology and Defects in Tensile and Compressive InGaAs/InP Layers
Authors: Ferrari C. , Lazzarini L. , Salviati G. , Natali M. , Berti M. , De Salvador D. , Drigo A.V. , Rossetto G. , Torzo G. 
Published: April 2011

AbstractThe results of a systematic investigation by transmission electron microscopy (TEM), cathodoluminescence (CL), Rutherford backscattering (RBS), X-ray diffraction and topography and scanning force microscopy (SFM) techniques on several InGaAs/InP compressive and tensile strained layers covering the misfit range from −2.3 to 1.5×10−2 and grown by the metal organic vapor phase epitaxy (MOVPE) technique are reported. In compressively strained films the same dependence for the residual strain vs the film thickness as for the InGaAs/GaAs is found whereas a different strain release rate and different extended defects are found in tensile stressed InGaAs alloy. In particular in tensile stressed samples, grooves, planar defects and cracks are present in addition to the interfacial network of misfit dislocations. The correlation between the observed planar defects and the mechanisms of strain relaxation in the case of tensile strained layers is discussed.
X-Ray Microbeam Diffraction Mapping of Different Texture Scales Important in Fatigue Cracking or in Large Deformations
Authors: Stock S.R. , Rek Z.U. 
Published: April 2011

AbstractPolychromatic synchrotron x-ray microbeam diffraction allows one to record Laue patterns simultaneously from all of the grains within the column of material irradiated. This paper describes 3-D texture mapping in polycrystalline Al and Cu samples. Transmission methods for determining the depths of diffracting volumes are outlined. The focus is on how the texture scale between micro- (i.e., individual grain orientations) and macro-texture defines fatigue crack paths in Al-Li 2090 T8E41: very large volumes of near single crystal material lead to large asperity formation, and at least forty volume percent of the material consists of these volumes. Results on grain subdivision in Cu after large deformations are also briefly reviewed.
Microstructurally Induced Ductile Deformation Mechanisms and Grain-Boundary Effects in Polycrystalline Aggregates
Authors: Ashmawi W. M. , Zikry M. A. 
Published: April 2011

AbstractDislocation-density based multiple-slip constitutive formulations and specialized computational schemes are introduced to account for large-strain ductile deformation modes in polycrystalline aggregates. Furthermore, new kinematically based interfacial grain-boundary regions and formulations are introduced to account for dislocation-density transmission, absorption, and pile-ups that may occur due to grain-boundary misorientations and properties.
Self-Affine Measurements on the Fracture Surface of Plastic Materials by AFM
Authors: Reyes E. , Guerrero C. , González V. , Hinojosa M. 
Published: April 2011

AbstractThe self-aff'me behavior of fracture surfaces of polymeric materials was qualitatively and quantitatively studied. SEM images of fracture surfaces of both polypropylene and polystyrene show Chevron marks at several magnifications. In addition, for polystyrene the mirror and Hackle zones were also observed. For quantitative analysis, the average roughness exponent, ζ, of height profiles generated by AFM images, was estimated by applying the variable bandwidth method. Values of ζ=0.788 and ζ=0.810 were obtained for polypropylene and polystyrene, respectively. These results are in very good agreement with the claimed universal exponent of 0.8 reported in the literature for other non-polymeric materials. By choosing the AFM appropriate operating conditions, measurements of roughness on plastic material surfaces could be performed.
Atomistic Simulations of Dislocation-Interface Interactions in the Cu-Ni Multilayer System
Authors: Rao Satish I. , Hazzledine Peter M. 
Published: April 2011

AbstractMultilayered Cu-Ni has a peak yield strength four orders of magnitude higher than either Cu or Ni because the multitude of interfaces obstruct glissile dislocations. The barrier strengths of the interfaces may be traced to four mismatches across an interface: modulus, lattice parameter, chemical and slip geometry. This paper describes sample embedded atom method (EAM) simulations of dislocations crossing interfaces, designed to separate the effects of the four mismatches. The results confirm some classical calculations and emphasize the importance of three new effects (i) an interface-chemical effect in which dislocations are trapped by core spreading in the interface, (ii) a coherency-chemical effect caused by coherency strains changing effective stacking fault energies and (iii) a coherency-modulus effect in which coherency strains change elastic moduli (and hence the Koehler stress) significantly.
Structure and Stability of Grain Boundaries in Molybdenum with Segregated Carbon Impurities
Authors: Janisch R. , Ochs T. , Merkle A. , Elsässer C. 
Published: April 2011

AbstractThe segregation of interstitial impurities to symmetrical tilt grain boundaries (STGB) in bodycentered cubic transition metals is studied by means of ab-initio electronic-structure calculations based on the local density functional theory (LDFT). Segregation energies as well as changes in atomic and electronic structures at the ΣE5 (310) [001] STGB in Mo caused by segregated interstitial C atoms are investigated. The results are compared to LDFT data obtained previously for the pure Σ5 (310) [001] STGB in Mo. Energetic stabilities and structural parameters calculated ab initio for several crystalline Molybdenum Carbide phases with cubic, tetragonal or hexagonal symmetries and different compositions, MoCx, are reported and compared to recent high-resolution transmission electron microscopy (HRTEM) observations of MoCx, intergranular films and precipitates formed by C segregation to a Σ5 (310) [001] STGB in a Mo bicrystal.
Crystallographic Texture and Yield Behavior of Al-Cu-Li (2195) Plate
Authors: Crosby K.E. , Mirshams R.A. , Pang S.S. 
Published: April 2011

AbstractExisting experimental texture analysis capabilities allow testing of theories on plasticity using polycrystal models. Aluminum-lithium alloys, which are particularly suited for aerospace applications due to excellent strength to weight ratio, typically possess pronounced texture. Al- Cu-Li (2195) thick plates were deformed by cold rolling to various thickness reductions. The plates exhibit a texture gradient through the plate thickness accompanied by a variation in yield strength values. The difference in yield strength values is related to the texture variation in terms of the texture components (ideal crystallographic orientations) identified from experimental measurements. A modified Taylor-based polycrystal plasticity model developed by Kocks and his colleagues is used to predict yield surfaces by incorporating texture data. Results of this investigation show that the texture intensities measured at certain ideal orientations increase or decrease with increasing deformation. These textural changes influence the value and anisotropy of the yield strength of the alloy.
Atomic-Scale Design for Enhanced Low Temperature Twinning in ZrCr2-Based Laves Phases
Authors: Kim W.-Y. , Luzzi D.E. 
Published: April 2011

AbstractRecently, we have designed and produced several transition metal Laves phases with low-temperature compressive ductility. These improved alloys demonstrate that manipulation of atomic-scale structure can have a drastic effect on meso-scale deformation behavior. To gain a basic understanding of the role of atomic-scale substitutions on the room temperature mechanical properties, a systematic investigation of the Laves ZrCr2-based alloy system alloyed with Hf, Nb, Ta and Ti was conducted and is reported here. Extensive room temperature ductility was obtained in the Hf-alloyed ternary Laves phase alloy system. Mechanical twinning is found to be the predominant deformation mode at room temperature in this alloy system. It is emphasized that Hf substitution in the Zr sublattice of ZrCr2 may play the most prominent role in changing the local electronic structure resulting in easier twinning.
Electrochemical Atomic-Layer Epitaxy: Electrodeposition of III-V and II-VI Compound Semiconductors
Authors: Wade Travis L. , Flowers Billy H. , Vaidyanathan Raman , Mathe Kenneth , Maddox Clinton B. , Happek Uwe , Stickney John L. 
Published: April 2011

ABSTRACTElectrochemical atomic-layer epitaxy (EC-ALE) is an approach to electrodepositing thin-films of compound semiconductors. It takes advantage of underpotential deposition (UPD), deposition of a surface limited amount (a monolayer or less) of an element at a potential less negative than bulk deposition, to form a thin-film of a compound--one atomic layer at a time. Ideally, the 2-D growth mode should promote epitaxial deposition.Many II-VI and a few III-V compounds have been formed by EC-ALE. TI-VI films such as CdSe, CdS, and CdTe have been successfully formed. In addition, deposition of III-V compounds of InAs and InSb are being explored, along with initial studies of GaAs deposition. Depositions of the I-VI systems are better understood so this report will focus on the III-V's, particularly InAs and InSb.Building compounds an atomic layer at a time lends electrochemical-ALE to nanoscale technology. Deposited thickness ranged from a few nanometers to a few hundred. The films are typically characterized by atomic-force microscopy (AFM), X-ray diffraction (XRD), electron microprobe analysis (EPMA) and ellipsometry. InAs deposits are also characterized by infrared reflection absorption.
Electrical Properties of Nanocrystalline Tungsten Trioxide
Authors: Hoel A. , Kish L.B. , Vajtai R. , Niklasson G.A. , Granqvist C.G. , Olsson E. 
Published: April 2011

ABSTRACTTungsten oxide is a material of significant interest for applications in several areas. It can, for example, be used as the electrochromic film in smart windows. Tungsten trioxide nanoparticles were produced using an advanced gas evaporation unit in which the tungsten was oxidized in low pressure ambient air. The tungsten trioxide particles were formed via vapor condensation and were deposited by gas deposition technique to avoid coagulation effects. The average size of the primary particles was around 5 nm, depending on the heating power and the pressure. The particles exhibited a body centred cubic structure. The impedance spectrum of particle deposits showed resonance and negative capacitance effects. The correlation between fabrication conditions, structure and impedance spectrum is discussed.
Solar Cell Contacts Using Nano-Sized Dispersions
Authors: Schulz Doug , Ribelin R. , Wu X. , Jones K.M. , Matson R.J. , Curtis C.J. , Gessert T. , Ginley D.S. 
Published: April 2011

ABSTRACTNano-sized dispersions have been employed as precursor inks for the spray deposition of contacts to both Si and CdTe materials. In the case of Si, nano-sized Al particles (nano-Al) were dispersed and spray deposited onto p-type Si. Annealing above the eutectic temperature causes alloy formation yielding a p+ layer with p ∼ 10−4 Ω•cm. For CdTe, nano-sized Te particles (nano-Te) were dispersed and sprayed onto CdTe/CdS/SnO2/glass heterostructures. Contact to the CdTe layer occurred during a 30 min anneal in He (T = 215 to 255 °C). These solar cells were finished by spin-coating the Te layer with Ag paint and subsequently annealing in air (100 °C / 1 h). This approach produces solar cells with open circuit voltages (Voc) from 720 to 800 mV, short circuit current densities (Jsc) from 18 to 20 mA/cm2 and efficiencies up to 10.3%. The performance of these cells was similar to those produced using the standard NREL contact.
Structure of Polycrystalline Silicon Films by Glow-Discharge Decomposition using SiH4/H2/SiF4 at Low Temperature
Authors: Tsuchida R. , Syed M. , Inokuma T. , Kurata Y. , Hasegawa S. 
Published: April 2011

ABSTRACTFor poly-Si films prepared by a plasma-enhanced chemical vapor deposition, we examined the changes in the local structure caused by adding H2 and/or SiF4 in the SiH4 feed gases and by changing supplied rf power values. The conditions of low rf power supply, low H2 addition, and SiF4 addition allow formation of films with microcrystalline or nanocrystalline structures. In addition, the H2 or SiF4 addition was found to be effective in promotive growth of <111> or <110> grains, respectively. In such low crystallized films, it was suggested that high-angle boundary would be formed, leading to a decrease in the density of SiH2 and Si dangling bonds, and to an increase in g values.
Magnetic Hardening of Mechanichally Alloyed SmFe11−xCoxTi
Authors: Bessais L. , Djega-Mariadassou C. 
Published: April 2011

ABSTRACTMechanical alloying of ternary SmFe11−xCoxTi (x = 0, 0.5, 1, 1.5, 2) alloys was carried out under an Ar atmosphere. Milled samples were annealed for 30 min in a vacuum at different temperatures Ta from 650 °C to 1150 °C. The effects of heat treatment, on structure and magnetic property changes, have been investigated by means of x-ray diffraction using the Rietveld method, Mössbauer spectroscopy and differential sample magnetometer. Tetragonal ThMn12-type structure is observed for samples annealed at Ta > 900 °C. For 650<Ta<800 °C the TbCu7 type phase was identified as the major phase. Between these two regions a mixture of TbCu7 and ThMn12-type nanocrystalline phases is obtained with a maximum of the coercive field Hc (Hc > 5kOe). The Mössbauer spectra relative to the hexagonal phase show sextuplets broadened by the statistical occupancies of the iron sites. An enhancement of the magnetic properties results from the Co substitution.