bluuebunny/crossref_metadata_2025_split huggingface dataset:
Exafs Evidence For Atom Location In Icosahedral TiZrNi And Hydrogenated TiZrNi Quasicrystals
Authors: Sadoc A. , Kim J. K. , Kelton K.F. 
Published: April 2011

AbstractWe present results from the first extended X-ray absorption fine-structure studies in a Ti/Zrbased quasicrystal. The icosahedral Ti53Zr27Ni20 phase and an icosahedral Ti45Zr38Ni17 phase that also contains 1.7 hydrogen atoms for each metal atom were investigated. Experiments performed above the Ti, Ni and Zr K absorption edges have allowed to identify different types of atomic subshells around the Ti, Ni and Zr atoms. Significant differences are observed between these two quasicrystalline alloys, suggesting preferential sites for the hydrogen atoms.
Discerning Phason Coherency In Quasicrystalline Systems
Authors: Naumis G. G. , Wang Chumin , Barrio R. A. 
Published: April 2011

AbstractPhason disorder is expected to modify the neutron and x-ray scattering spectra of quasicrystals. However, it is not clear yet if phasons are coherent modes in real space, or if they should be considered as local random defects. In this work, a comparative study of different sorts of phasons is performed, and their effects on the dynamical structure factor of Fibonacci chains are analyzed in detail. The results show that coherent and random phasons can be distinguished for high values of the momentum transfer. Finally, it is observed that a random phason produced in the quasicrystal's hyper-space leads to a coherent phason field in real quasicrystalline lattice.
A Decagonal A170Mn17Pd13 Quasicrystal Structure With A Non-Centrosymmetric 5D Space Group
Authors: Yamamoto Akiji , Weber Steffen 
Published: April 2011

AbstractA single-crystal X-ray analysis revealed that a decagonal Al70Mn17Pd13 has a noncentrosymmetric structure with the 5-dimensional (5D) space group P105mc. The structure refinement based on a 5D cluster model gave Rw= 0.119 (R = 0.167) for 1428 independent reflections and a reasonable chemical composition of Al69.1Mn18.5Pd12 4.
Melting And Solidification Behaviour Of Lead Particles Embedded In Quasicrystalline Matrices
Authors: Singh Alok , Tsai A. P. 
Published: April 2011

AbstractComposites of nanoparticles of lead were prepared by embedding into Al-Cu-V and Al- Cu-Fe icosahedral, and Al-Cu-Co decagonal phase alloys by means of rapid solidification. The microstructure of these composites, the orientation relationships and the interfaces formed between the particles and the matrix has been studied by transmission electron microscopy. The melting and solidification behaviour of the lead particles in these matrices has been studied by differential scanning calorimetry. The microstructure and the nature of the particle-matrix interface has been related to the melting/solidification behaviour of the particles in the matrix.
Phase Diagram Determination For Modifications Of The D Phase In The Al-AlCo-AINi System
Authors: Lück R. , Scheffer M. , Gödecke T. , Ritschj S. , Beelif C. 
Published: April 2011

AbstractAn extensive investigation into the At-AICo-AlNi ternary subsystem is presented. Observations have used the techniques of differential thermal analysis, magnetothermal analysis, dilatometry, metallography, X-ray diffraction, transmission electron microscopy, and high-resolution electron microscopy. Representative graphic documentation, as liquidus projection surface, isothermal sections, temperature-concentration section, and reaction scheme are presented. 11 phases from the binaries Al-Co and Al-Ni and the three ternary phases Y2 (Co2NiAl9), X and the decagonal phase D were found at room temperature. The decagonal phase is formed from the melt peritectically via a critical tie line and its primary formation area dominates at the liquidus projection surface. 45 three-phase regions are present according to the reaction scheme.Several phase variants in the area of the decagonal phase were detected by transmission electron microscopy. Phase fields of the variants were determined from samples quenched from their respective temperatures. In-situ experiments on transformations of variants were performed by dilatometric measurements. The subdivision of the D phase area into the fields of the variants is discussed.
Leed Investigations Of A Cubic AL-PD-MN (110) Alloy
Authors: Heinzig M. W. , Warren O. L. , Shen Z. , Jenks C. J. , Lograsso T. A. , Thiel P. A. 
Published: April 2011

AbstractAn Al-Pd-Mn cubic alloy having a bulk chemical composition somewhat analogous to that of the icosahedral Al-Pd-Mn quasicrystal is studied. Our goal is to compare the surface structure and properties of the cubic alloy with those of the quasicrystalline alloy. In this paper, we report the first observations for the (110) surface of the cubic alloy using (primarily) low energy electron diffraction (LEED). The surface is prepared by sputtering and annealing in ultrahigh vacuum (UHV). In addition to the substrate LEED pattern, at least three superstructures evolve sequentially with annealing temperature.
Preparation And Properties Of Solar Selective Absorbers Based On AlCuFe AND AlCuFeCr Thin Films: Industrial Aspects
Authors: Eisenhammer T. , Nolte H. , Assmann W. , Dubois J. M. 
Published: April 2011

AbstractSolar selective absorbers for thermal energy applications can be realized with films of quasicrystal forming alloys. Absorbers were produced by sputtering thin films of AlCuFe and AlCuFeCr. Alumina and floatglass were used as dielectric antireflective coatings, which are necessary for the required optical properties. For applications, several aspects are of importance: high solar absorptance and low thermal emittance have to be achieved. Moreover, the coatings have to show good adhesion and stability with respect to oxidation in air at elevated temperatures and exposure to humidity and condensation of water. The present study emphasizes these aspects, especially degradation stability, for coatings deposited on technical copper foils with large roughness. Oxidation stability is achieved easily, while humidity stability depends strongly on the choice of materials. The combination AlCuFeCr/floatglass turned out to be stable, while the combination AlCuFe/alumina is destroyed rapidly.
Electrically switchable reflection gratings in polymer dispersed liquid crystals
Authors: Natarajan L. V. , Sutherland R. L. , Tondiglia V. P. , Siwecki S. , Pogue R. , Schmitt M. , Brandelik D. , Epling B. , Berman G. , Wendel C. , Ritter M. , Stallings M. , Bunning T. J. 
Published: April 2011

ABSTRACTElectrically switchable volume reflection holograms were written by inhomogeneous illumination of a prepolymer syrup containing a nematic liquid crystal and a multifunctional acrylate monomer. Switchable holograms are diffractive optics structures and the diffraction efficiency can be controlled by the application of an electric field. Reflection gratings with grating spacing varying between 0.16-0.27 µm were made during the phase separation of liquid crystals from the fast curing prepolymer syrup. The reflection efficiency of the holograms were electrically modulated with the applied field of ∼10-15V/µm. Real time study of the grating formation revealed that the maximum efficiency is reached in ∼15 seconds. The shrinkage of the host polymer during grating formation resulted in the blue shift of the reflection notch. The response time of the grating in an electric field is ∼50 µs. Low voltage scanning electron microscope studies showed the presence of discrete nematic droplet domains of sizes 30-60 nm in liquid crystal rich region.
The Optical and Morphological Properties of Fluorinated Polymer Dispersed Liquid Crystals
Authors: Schulte M.D. , Clarson S.J. , Natarajan L.V. , Tondiglia V.P. , Bunning T.J. 
Published: April 2011

ABSTRACTPolymer dispersed liquid crystal (PDLC) films with a partially fluorinated polymer matrix were investigated. The optical and morphological properties of fluorinated PDLC's were different from non-fluorinated films. The incremental addition of a fluorine-substituted monofunctional methacrylate monomer to a pentaacrylate-based standard PDLC formulation resulted in significant improvement in contrast ratio. In addition, results suggest that fluorine decreased compatibility between the polymer and liquid crystal phases. Scanning electron microscopy (SEM) was employed to elucidate morphological differences between fluorinated host matrices and non-fluorinated control films.
New Wholly-Aromatic Thermotropic Polyesters with Controlled Flexibility
Authors: Nagvekar Devdatt S. , Mather Patrick T. , Jeon Hong G. , Tan Loon-Seng 
Published: April 2011

ABSTRACTIn this work, we present the synthesis and characterization of a new series of wholly-aromatic copolyesters derived from the condensation of various weight fractions of 4,4'-(o- phenylenedioxy)dibenzoic acid (OPDB) and substituted terephthalic acid (BTA) with 2-phenylhydroquinone (PHQ). The Higashi method, involving tosyl chloride and pyridine as solvent, was employed to yield polymer with significant molecular weight. These polymers are intended to enable accessible clearing transition and to control the balance of stiffness and toughness in melt-spun fibers systematically. We report the synthetic details along with characterization of quiescent phase behavior and morphology.
Effect of Composition on The Morphology and Electro-Optical Properties of Physically Crosslinked Liquid Crystals
Authors: Schneider A. , Geppert S. , Spontak R.J. , Gronski W. , Finkelmann H. 
Published: April 2011

ABSTRACTAddition of an ABA triblock copolymer to a midblock-selective solvent can, depending on copolymer/blend composition and the magnitude of block-block and block-solvent interactions, result in the formation of a physical network that is stabilized by aggregates of the incompatible A-block. In this work, an ABA copolymer with a nematic side-chain liquid crystal midblock is added to a low-molar-mass nematic liquid crystal (LC) in an effort to produce a comparable copolymer network and bind the LC matrix. This nanostructured system, designated a physically crosslinked liquid crystal (PCLC), may not suffer as much from the constraint-induced LC anchoring problems associated with conventional polymer-dispersed liquid crystals (PDLCs). Results presented here demonstrate that hierarchical phase behavior must be carefully considered in the design of PCLCs.
Relation Between Molecular and Macroscopic Properties of Nematic Liquid Crystals
Authors: Ferris Kim F. , Exarhos Gregory J. , Risser Steven M. 
Published: April 2011

ABSTRACTWhile many liquid crystal studies have focused on static structural and electronic properties, dynamic factors such as molecular anisotropy, partial ordering and structural fluctuations have hindered descriptions linking liquid crystalline properties at the molecular level with the macroscopic level properties (as measured experimentally). In this paper, we examine the transition from molecular to bulk properties for the nematogen 5-alkyl-cyanobiphenyl (5CB), using both molecular dynamics and quantum mechanical calculations. We perform molecular dynamics simulations on a collection of molecules in the nematic phase, sample the trajectory to create a representative collection of structures, and perform electronic structure calculations on the sampled structures.
Light Transmission-Light Scattering Reverse Mode Switching of (Liquid Crystalline Polymer/Liquid Crystal)Composite System
Authors: Kikuchi Hirotsugu , Kibe Shigeru , Yamane Hirokazu , Kajiyama Tisato 
Published: April 2011

ABSTRACTConventional (polymer/liquid crystal) composite films exhibit the normal mode electro-optical switching, that is, the light scattering-light transmission switching upon electric field OFF-ON states, respectively. The “reverse mode” electro-optical switching, that is, the light transmission-light scattering switching upon electric field OFF-ON states, respectively, has been investigated for a novel type of composite system being composed of a side chain type liquid crystalline polymer(LCP) and low molecular weight liquid crystals(LCs). The polarizing optical microscopic observation and X-ray diffraction study revealed that the two types of smectic-like short range ordering were present in the (LCP/LCs) composite system in a nematic state. It was confirmed from electric capacitance measurements of the homogeneous alignment cell that these phases with different smectic-like short range orderings each exhibited a different value of threshold voltage. Although the homogeneous alignment cell of the (LCP/LCs) composite system was in a light transmitting state in the absence of an electric voltage, the cell turned into a light scattering state upon the application of an electric voltage of 5-15 V for the cell of 14 µm thick (0.4−1.1 MV" m−1). The reversible change from the light scattering state to the transmission state was observed after removing the electric voltage. The light scattering state of the (LCP/LCs) composite system upon the application of electric voltage might be due to the appearance of optically heterogeneous structure induced by the different values of the threshold voltage between the two types of smectic-like phases with different short range orderings. These phases might be in a phase-separated state with an optical dimension (several hundred nm). The reversible “reverse mode” electro-optical switching was realized for the (LCP/LCs) composite system in a nematic state in which the two types of smectic-like short range orderings were separately formed in an optical size level.
X-Ray Diffraction and Reflectometry Investigation of Interdiffusion In Sputtered Niobium-Tungsten Bilayers
Authors: Welzel U. , Lamparter P. , Mittemeijer E. J. 
Published: April 2011

ABSTRACTInterdiffusion in sputtered niobium(45nm)-tungsten(45nm) bilayers upon annealing at low temperatures (T<1000K) has been investigated using X-ray reflectometry and diffraction. The accompanying changes in macrostress and microstructure have been characterized by applying the X-ray diffraction sin2ψ T method and by qualitative evaluation of the diffraction line broadening, respectively. Annealing causes, besides interdiffusion, changes of macrostress and decrease of microstructural imperfection. Concentration profiles corresponding to diffusion lengths of only a few nanometers were determined by simulation of the measured reflectivity patterns. The values obtained for the diffusion coefficients are compared with corresponding values obtained by extrapolation from published data for bulk materials at much higher temperatures.
Modeling of Microstructure Development in Nanoscale Layered Systems
Authors: Pompe W. , Ullrich A. , Bobeth M. 
Published: April 2011

ABSTRACTThe composition evolution in nanoscale layered systems during annealing is considered within the framework of the Cahn-Hilliard theory. Starting from as-deposited multilayers with morphologically rough and chemically diffuse coherent interfaces, the sharpening of concentration profiles and the flattening of interphase boundaries have been simulated. Grain boundary grooving within multilayers was supposed to initiate break-throughs in individual layers and the subsequent morphological development has been analyzed. The simulations reveal a deterioration of the layered structure by the fusion of individual layers.
Microstructure Evolution During Solid-State Reactions in Polycrystalline Nb/Al and Ti/Ai Multilayer Thin-Films
Authors: Lucadamo G. , Barmak K. , Carpenter D. T. , Lavoie C. , Cabral C. , Michaelsen C. , Rickman J. M. 
Published: April 2011

ABSTRACTThe microstructural changes that occur during the reaction of sputter-deposited Nb/Al and Ti/Al multilayer thin-films with bilayer thicknesses ranging from 10 nm to 333 nm have been studied. The films were deposited with an overall stoichiometry of XAl3 (X = Nb,Ti) and subsequently annealed to different stages of the reaction in a differential scanning calorimeter (DSC). Data obtained from cross-sectional transmission electron microscopy (XTEM), and in situ synchrotron X-ray diffraction (XRD) experiments have provided evidence for a two-stage reaction mechanism for the formation of NbAl3. Microscopy results from a film with a bilayer period of 333 nm showed a microstructure that was consistent with two-dimensional growth in the plane of the interface. A uniform, 10 nm thick continuous layer of the product phase was formed followed by growth normal to the interface that initially consisted of larger, faceted grains. By the end of the reaction, an equiaxed NbAl3 grain structure was observed. High resolution elemental mapping using a scanning transmission electron microscope (STEM) revealed penetration of Nb into the Al layer and enhanced growth in regions where Al grain boundaries intersected the interface. Characterization of microstructure evolution in the Ti/Al system was complicated by the formation of two metastable structures consisting of cubic Ll2 followed by tetragonal DO23, and finally the equilibrium, tetragonal DO22 structure. However, the metastable phase transition temperatures were clearly isolated using the in situ XRD technique.
Evaluation of Young's Modulus and Yield Strength of Thin Film Structural Material Using Nanoindentation Technique
Authors: Son Dongil , Lee Yun-Hee , Ahn Jeong-Hoon , Kwon Dongil 
Published: April 2011

ABSTRACTAluminum films have wide applications in micromechanical devices such as micro sensors and actuators. Therefore, their mechanical properties are very important for reliability evaluation. However, there is no standardized method to evaluate the mechanical properties of the materials used in MEMS(microelectromechanical system) devices since the measured mechanical properties are influenced by many factors such as the surface condition of materials, intrinsic limit of the measurement device, etc. Hence, it was intended to evaluate the mechanical properties of thin film, which is important in its mechanical operation. Because MEMS devices are usually operated in the elastic range, Young's modulus and yield strength were evaluated by using a microcantilever beam technique. First, A1 cantilever beams were fabricated using the silicon bulk micromachining technology to have various film thicknesses. The load-displacement curves during beam bending by nanoindentation method were then obtained. The linear relationship of the curve in elastic range was utilized in deriving Young's modulus of the A1 film, which gave reproducible results regardless of film thickness. In the high load range, the deviation from the linear relation was detected, so that yield strength of A1 film could be evaluated. It was found that the yield strength increases with decreasing film thickness. By applying the misfit dislocation theory and the Hall-Petch relationship, the theoretical estimation could predict the trend of yield strength.
Influence of Cu Seed Deposition Temperature on Electroplated Cu Texture Formation in Damascene Structures
Authors: Jiang Qing-Tang , Mikkola Robert , Ortega Richard , Blaschke Volker 
Published: April 2011

ABSTRACTThe deposition temperature of the PVD Cu seed layer has a critical impact on the subsequent electroplated Cu film. Sheet resistance transformation of electroplated Cu on 50°C seeded Cu was more than twice faster than on 150°C seeded Cu. X-ray pole figure analysis on a 3 mm × 3 mm dense array of 0.35 μm Cu damascene lines at spacing of 0.4 μm revealed significant grain orientation differences between directions parallel and perpendicular to the Cu lines. It was observed that for both seed process temperatures, the (111) pole figures showed a sharper texture parallel to the trench direction than to the perpendicular direction. After annealing at 450°C for 30 minutes, a (511) secondary orientation emerged and the (111) texture along the trench direction became even sharper. Perpendicular to the trench, the (111) texture split into two peaks after anneal, exhibiting near fiber texture. The deviation of the two splits from normal was 2.4° tilt towards the trench wall indicating strong interaction between trench sidewall and electrodeposited Cu inside the trench. The (111) pole figure analysis also revealed a 20% contribution of Cu growth directly from the side walls. Although the pole figure pattern of 150°C seeded sample resembles that of the 50°C seeded sample, the (111) fiber texture of a 50°C seeded sample was always stronger and sharper.
Room Temperature Self-Annealing of Electroplated and Sputtered Copper Films
Authors: Chen Michelle , Rengarajan Suraj , Hey Peter , Dordi Yezdi , Zhang Hong , Hashim Imran , Ding Peijun , Chin Barry 
Published: April 2011

ABSTRACTSelf-annealing properties of electroplated and sputtered copper films at room temperature were investigated in this study, in particular, the effect of copper film thickness, electrolyte systems used, as well as their level of organic additives for electroplating. Real-time grain growth was observed by transmission electron microscopy. Sheet resistance and X-ray diffraction measurements further confirmed the recrystallization of the electroplated copper film with time. The recrystallization of electroplated films was then compared with that of sputtered copper films.
Surface Microstructure and Magnetic Properties of Laser-Processed Granular Co-Ag Films
Authors: Agostinelli E. , Fiorani D. , Foglia S. , Kaciulis S. , Testa A. M. , Vittori-Antisari M. 
Published: April 2011

ABSTRACTCo-Ag films prepared by Pulsed Laser Deposition and showing GMR in the as deposited state, have been irradiated by excimer laser: the chemical and structural modification induced by such treatment have been studied by XPS and by atomic force and electron microscopies. The pulsed laser irradiation favors the nucleation of nanosized Co grains at Ag grain boundaries, resulting in an enhancement of the magnetoresistivity at low fields and low temperature. Indeed, after laser treatment, a doubled field sensitivity (δGMR/δH) at T=I0K, with respect to the untreated samples, has been observed. The correlation with the observed magnetic properties variations, is discussed.
Effects of Magnetic and Non-Magnetic Impurity Addition on Magnetoresistance Behavior of Lanthanum Manganite Thin Films
Authors: Pietambaram Srinivas V. , Kumar D. , Singh Rajiv K. , Lee C. B. 
Published: April 2011

ABSTRACTIn this paper, we report our studies on the growth, structural, magnetotransport and magnetic properties of La1−x,CaxMnO3: Co/Ag. Thin films of these materials were grown in situ on (100) LaAlO3 substrates using a pulsed laser deposition technique. Microstructural characterization carried out on these films show that the films are single phase, textured and smooth. The temperature dependence of resistance of the films in the 10 – 300 K range was examined in zero and applied field using four-probe technique and magnetization measurements were carried out using the quantum design superconducting quantum interference device (SQUID) magnetometer. The MR ratios of La0.7Ca0.3MMnO3, Ag added La0.7CaM0.3MnO3 and Co added La0.7CaM0.3MnO3 films were found to be 200%, 3.4 × 104% and 660% in 5 T and 21%, 435% and 30% in 0.1 T respectively. The enhanced MR ratio in the case of Ag added La0.7Ca0.3MMnO3 films is attributed to the increase in the oxygen content and in the case of Co added La0.7Ca0.3MMnO3, it can be attributed to the Co supplying some additional magnetic field.