bluuebunny/crossref_metadata_2025_split huggingface dataset:
COMBINATORIAL SYNTHESIS AND REACTIVITY SCREENING OF ELECTRO-OXIDATION CATALYST GRADIENTS
Authors: Jayaraman Shrisudersan , Hillier Andrew C. 
Published: April 2011

ABSTRACTCombinatorial methods represent an appealing experimental method for the discovery of heterogeneous catalysts. One can efficiently identify candidate materials or sample vast regions of composition space using a combination of dense catalyst libraries and high-throughput reactivity screening techniques. This is particularly appealing for the discovery of novel catalysts for low temperature fuel cells where multi-component systems have shown improved performance. For example, the poison tolerance of typical anode catalysts can be improved by the addition of oxophilic components such as ruthenium, molybdenum, tin or osmium. Consequently, a vast composition space must be sampled in order to identify catalyst compositions or regions of composition space with greater activity. Combinatorial methods represent a practical means to speed-up the catalyst discovery process. In this manuscript, we demonstrate a novel method for combinatorial catalyst discovery based upon the synthesis and reactivity mapping of catalyst composition gradients. Samples consisting of uniform variations in surface composition of metals catalysts (Pt-M1 and Pt-M1−M2, where M1, M2 = Ru, Mo, Sn or Os) are fabricated using a gel-transfer technique. A concentration gradient of source metal ions is produced in a swollen polymer gel and then transferred onto a surface by electrodeposition to create a continuous composition gradient. An in situ reactivity-mapping tool based on the scanning electrochemical microscope is used to interrogate these catalyst gradients for the hydrogen oxidation reaction in the presence of adsorbed carbon monoxide.
Synthesis and Screening of Materials Libraries of Buried Compound Semiconductors by Ion Beam Implantation
Authors: Großhans I. , Karl H. , Stritzker B. 
Published: April 2011

ABSTRACTA combinatorial approach was employed to ion beam synthesis and optical analysis of buried II-VI compound CdSe semiconductor nanocrystals. Typically standard ion implantation setups are designed in a way to create a laterally homogenous dose distribution of the implanted ion species. In order to achieve intentional lateral variations of the implanted doses a special implanter endstation was constructed. Computer controlled apertures in front of the wafer cover up in succession parts of a 4 in. wafer, so that a lateral pattern of distinct dose combinations of the implanted elements Cd and Se was generated. The obtained materials library consists of 1:1 stoichiometric, but also off-stoichiometric dose ratios. After implantation the wafers passed through a rapid thermal heat treatment, where the implanted material forms buried semiconductor nanocrystals. Photoluminescence spectra of the elements of the materials library were screened in rapid succession in an optical cryostat into which the whole wafer was mounted and cooled down. The obtained spectra were compared and key-parameters determined which control the photoluminescence properties. In this contribution will be shown, that slight variations of the dose ratio significantly alter the optical properties and that new efficient photoluminescent materials and processing parameters can be found. In this way, also other complex interdependencies of physical and chemical parameters in the field of multiple element ion beam implantation might be efficiently investigated.
Combinatorial material library synthesis from insoluble oxide suspension using a drop-on-demand inkjet delivery system
Authors: Chen Lei , Huang Sungxiang , Bao Jun , Liu Chihui , Liu Wenhan , Gao Chen 
Published: April 2011

AbstractA combinatorial synthesis method was developed by ejecting insoluble oxide suspensions using a drop-on-demand inkjet delivery system. The insoluble oxide suspensions with ultrafine/nano particles were prepared by grinding the oxide power in water using a high-energy ball mill. Using luminescent materials as model systems, it was established that the technique is very well suited to combinatorial synthesis of insoluble oxides.
Design, Use and Results from Combinatorial Steady-State Reactors for the Optimization of Highly Selective Heterogeneous Catalysts in Liquid Systems
Authors: Spivack James L , Webb Jimmy , Flanagan William P , Sabourin Cheryl , May Ralph , Hassib Lamyaa 
Published: April 2011

AbstractA reactor was designed, built and successfully operated that allowed the simultaneous running of 96 independent reactions at steady-state. Since the problem involved the attainment of 98% in selectivity from a starting point of 93%, very precise reproducibility in selectivity was required. Because selectivity varies with time in a batch reactor, and since commercial reactors for this process are continuous, continuous reactors operated at steady-state were required. Longterm standard deviation in selectivity of <0.2% was attained. Information feedback from so many reactors allowed study of variation in catalyst composition, liquid retention times, space velocity, temperature and other variables to be accomplished in relatively short time. Comparison between heterogeneous and homogeneous catalysis in the same reactors gave insight into the underlying mechanisms determining activity and selectivity. Results from 200 uL reactors scaled very well to laboratory and pilot plant sizes.
Combinatorial Catalysis Survey concerning Proton Exchange Membrane Fuel Cell Technology – As a Part of “MATERIOMICS” –
Authors: Yamada Yusuke , Ueda Atsushi , Shioyama Hiroshi , Mathew Thomas , Ioroi Tsutomu , Yasuda Kazuaki , Akita Tomoki , Ichikawa Satoshi , Tanaka Koji , Kohyama Masanori , Kobayashi Tetsuhiko 
Published: April 2011

ABSTRACTOur efforts to combine the combinatorial technology and microstructure analysis to develop catalysts for proton exchange membrane fuel cell (PEMFC) technology have been described. This offers the realization of “materiomics” in comprehensive material research. Catalyst technologies are indispensable for wide use of PEMFC, which are regarded as the low emission and highly efficient energy conversion device for the next generation. We have applied the combinatorial method for the hydrogen production and/or purification of catalysts, and anode catalyst investigations. The catalyst library consisting of precious metals loaded on various metal oxides was tested for water gas shift reaction and steam reforming of methanol and/or DME. Various metal oxides added to platinum loaded on carbon were screened for anode catalysts. The microstructure of each catalyst was analyzed by employing scanning electron and/or transmission electron microscopy. This paper mainly describes the catalysis screening results of above reactions that form a part of “materiomics”.
Recursive Image Charge Approach for Quantitative Characterization of Dielectric Thin Film Library Using Scanning Tip Microwave Near-field Microscopy
Authors: Gao Chen , Hu Bo , Huang Mengming , Zhang Pu , Liu Wen-han 
Published: April 2011

ABSTRACTWe developed a recursive image charge approach for quantitative characterizations of dielectric thin films using the scanning tip microwave near-field microscope. With this method, frequency shift of the microscope as functions of the dielectric constant and the thickness of a film can be effectively computed in a recursive way. We believe that this approach can promote the high-throughput characterization of the dielectric libraries.
Order-disorder transition in the Cd-Ca cubic approximant
Authors: Widom M. , Mihalkovič M. 
Published: April 2011

ABSTRACTRecent experiments discovered an order-disorder transition occuring at low temperatures in large unit 1/1 cell cubic approximants of the stable Cd-based binary alloy quasicrystals. The transition is related to correlations among orientational degrees of freedom whose separations are around 12 Å. We analyze the interactions between the degrees of freedom using ab-initio calculations for Cd-Ca alloys and derive an equivalent antiferromagnetic Ising model which shows a similar phase transition. However, the calculated transition temperature is higher than observed experimentally, indicating that the actual structure and its order-disorder transition are more complex than originally proposed. A side-benefit of our study is the discovery of a canonical-cell decoration model for the Cd-Ca icosahedral phase.
Structural Evolution of Cold Rolled Multi-Layers in the Al-Cu-Fe Ternary System
Authors: Park J. S. , Fleury E. , Kim J. H. , Chang H. J. , Kim W. T. , Kim D. H. 
Published: April 2011

ABSTRACTSamples with a target composition of Al62.5Cu25Fe12.5 (at.%) have been produced from the repeated cold rolling and folding (R&F) process of Al, Cu and Fe elemental foils. Upon early increments of the R&F cycle, the mechanically-induced process led to the fragmentation of the initial foils, which resulted in the dispersion of elemental Fe layers through the refined Al and Cu layers. After 40 R&F cycles the Al2Cu phase was detected, while Fe did not contribute to the formation of compounds. Thermal analyses suggested that the formation and dissolution of the Al2Cu and Al7Cu2Fe phases are critical steps for the synthesis of the i-phase during post-R&F treatment. Annealing between 650° and 750°C enabled the formation of the stable i-phase and resulted in high values of the microhardness.
Electrocodeposited Quasicrystalline Coatings for Non-Stick Wear Resistant Cookware
Authors: Minevski Zoran , Tennakoon Charles L. , Anderson Kelvin C. , Nelson Carl J. , Burns Frederick C. , Sordelet Daniel J. , Haering Chad W. , Pickard Don W. 
Published: April 2011

ABSTRACTLynntech, Inc has successfully researched and demonstrated a unique method for the manufacture of quasicrystalline (QC) coatings that utilizes the process of electrocodeposition. The purpose of this study was to optimize the physical-mechanical properties of the QC coatings. All metal substrates were aluminum alloy Al-3004 and codeposition was performed using Al65Cu23Fe12 QC powders in nickel plating solutions. X-ray diffraction spectroscopy was performed in order to verify the attachment of quasicrystals to the aluminum alloy substrate and coated samples displayed identical spectra to those of raw QC powders. The average contact angle θ was 117.2° for electrocodeposited QC coatings. Friction was monitored during pin-on-disk wear tests and QC coated samples had coefficients of friction as low as 0.01 and an average value of 0.05 with samples showing no visible wear scar. Lynntech's electrocodeposited quasicrystalline coatings withstand high temperatures and exhibit low wear and friction characteristics with a low surface energy making them ideal for cookware, as well as various other applications such as bearings, landing gear and engine parts, where thermal and mechanical conditions are prime importance.
Thermoelectric properties of the Al-TM-Si (TM = Mn, Re) 1/1-cubic approximant
Authors: Takeuchi Tsunehiro , Otagiri Toshio , Sakagami Hiroki , Mizutani Uichiro 
Published: April 2011

ABSTRACTThe electrical resistivity, thermoelectric power, and thermal conductivity were investigated for the Al71.6-xMn 17.4Six and Al71.6-xRe 17.4Six (7 ≤ x ≤ 12) 1/1-cubic approximants. A large thermoelectric power ranging from -40 to 90 μV/K and a low thermal conductivity less than 3 W/K·cm were observed at room temperatures. The electrical resistivity at room temperature for these approximants was kept below 4,000 μΩcm, that is much smaller than that in the corresponding quasicrystals. As a result of the large thermoelectric power, the low thermal conductivity, and the low electrical resistivity, large dimensionless figure of merit ZT = 0.10 (n-type) and 0.07 (p-type) were achieved for the Al71.6Re17.4Si11 and Al71.6Mn17.4Si11 at room temperature, respectively.
Constitutive model of quasicrystal plasticity: Strain-rate and temperature dependence
Authors: Heggen Marc , Feuerbacher Michael 
Published: April 2011

ABSTRACTA constitutive model describing the plasticity of icosahedral quasicrystals [1] was applied to icosahedral Al-Pd-Mn over a wide range of experimental deformation conditions. The model incorporates the evolution of two microstructural parameters: The first, as in crystals, is the dislocation density; the second is a quasicrystal-specific order parameter that accounts for deformation-induced disordering and thermally activated reordering of the quasicrystal structure. Significant strain-rate dependence was found which can be understood by the interactive evolution of these two microstructural parameters. The present work shows that the constitutive model comprehensively describes the features of quasicrystal plasticity over a wide range of experimental conditions.
Low temperature deformation mechanisms of icosahedral AlPdMn quasicrystals.
Authors: Texier Michael , Bonneville Joël , Proult Anne , Rabier Jacques , Thilly Ludovic 
Published: April 2011

ABSTRACTConfining pressure techniques, that superimpose a shear stress on an isostatic component, allowed us to plastically deform AlPdMn specimens at temperatures below the brittle-to-ductile transition temperature obtained using conventional uniaxial deformation tests at usual strain-rates. Microstructural observations associated with these low deformation temperatures are reported. They provide new insights on the elementary deformation mechanisms that control plasticity in this non-periodic structure.
Influence of Al on Quasicrystal Formation in Zr-Ti-Nb-Cu-Ni-Al Metallic Glasses
Authors: Scudino Sergio , Eckert Jürgen , Kühn Uta , Breitzke Hergen , Lüders Klaus , Schultz Ludwig 
Published: April 2011

ABSTRACTThe effect of Al on the crystallization behavior of (Zr0.616Ti0.087Nb0.027Cu0.15Ni0.12)100–xAlx melt-spun glassy ribbons with x = 7.5, 5, 2.5 and 0 was investigated by differential scanning calorimetry, x-ray diffraction and transmission electron microscopy. The devitrification of the ribbons is characterized by the formation of a metastable quasicrystalline phase during the first stage of the crystallization process even for the alloy with x = 0. Therefore, Al is not essential for quasicrystal formation in the present alloys. However, it affects the properties of the amorphous as well as of the quasicrystalline phase. With decreasing Al content, the temperature range of stability of the quasicrystalline phase increases whereas the thermal stability of the amorphous phase decreases together with a slight decrease of the extension of the supercooled liquid region. Thus, it is concluded that although the addition of Al improves the stability of the glassy phase, it has no beneficial effect on the formation of quasicrystals.
Local Structural Variations in Al72Ni20Co8 Decagonal Quasicrystals
Authors: Yan Yanfa , Pennycook S. J. 
Published: April 2011

ABSTRACTWe investigate local structural variations in Al72Ni20Co8 quasicrystals using first principles density-functional total-energy calculations. We find that local chemical fluctuation can cause large structural variations on the central rings of the 2-nm clusters. Such structure variations may result in ambiguities at the central rings in high-resolution electron microscopy images of Al72Ni20Co8 decagonal quasicrystals.
Orientation relationship between metallic thin films and quasicrystalline substrates.
Authors: Fournée V. , Rossa A. R. , Lograsso T. A. , Thiel P. A. 
Published: April 2011

ABSTRACTWe present experimental results on the structure of Ag thin films grown on high-symmetry surfaces of both quasicrystals and approximants. For coverages above ten monolayers, Ag form fcc nanocrystals with (111) plane parallel to the surface plane. Depending on the substrate surface symmetry, the Ag nanocrystals exist in one, two or five different orientations, rotated by a multiple of 2π/30. The orientation relationship between crystalline films and substrates appears to be determined by the following principles: high atomic density rows of the adsorbate are aligned along high atomic density rows of the substrate.
Cleavage Planes of Icosahedral Quasicrystals: A Molecular Dynamics Study
Authors: Rösch Frohmut , Rudhart Christoph , Gumbsch Peter , Trebin Hans-Rainer 
Published: April 2011

ABSTRACTThe propagation of mode I cracks in a three-dimensional icosahedral model quasicrystal has been studied by molecular dynamics techniques. In particular, the dependence on the plane structure and the influence of clusters have been investigated. Crack propagation was simulated in planes perpendicular to five-, two- and pseudo-twofold axes of the binary icosahedral model.Brittle fracture without any crack tip plasticity is observed. The fracture surfaces turn out to be rough on the scale of the clusters. These are not strictly circumvented, but to some extent cut by the dynamic crack. However, compared to the flat seed cracks the clusters are intersected less frequently. Thus the roughness of the crack surfaces can be attributed to the clusters, whereas the constant average heights of the fracture surfaces reflect the plane structure of the quasicrystal. Furthermore a distinct anisotropy with respect to the in-plane propagation direction is found.
Effects of Positive Feedback on Crystallization Kinetics and Recalescence
Authors: Bossuyt Sven , Lindsay Greer A. 
Published: April 2011

ABSTRACTIn bulk metallic glasses cooled at nearly the critical cooling rate for glass formation, nucleation is observed to be spatially localized; nanocrystals are clustered together in spherical regions. This implies that a positive feedback mechanism locally increases the nucleation rate in the vicinity of other nucleation events. Linear stability analysis and computer simulation of differential equations describing crystal nucleation and growth are used to theoretically examine the plausibility of different potential feedback mechanisms. It is shown that interactions between different crystallizing phases can lead to counter-intuitive composition dependence of the crystallization kinetics in the case of non-polymorphic crystallization.
Modifications of the phase selection during the crystallization of amorphous Al-Y-Fe
Authors: Boucharat N. , Rösner H. , Hebert R. J. , Perepezko J. H. , Wilde G. 
Published: April 2011

ABSTRACTThe effect of thermal treatments, plastic deformation and inoculation of quenched Al88Y7Fe5glasses with immiscible Pb and In on their crystallization behavior has been studied based on calorimetric and microstructural analyses. The results demonstrate the effect of the plastic deformation and of the inoculants to promote nanocrystallization. Moreover, the formation of a pronounced concentration gradient at the growing nanocrystal interface provides for the kinetic stability of the nanostructure and the modification of the phase evolution sequence of the crystallization reactions.
Metallic glass fluid flow during welding using self-propagating reactive multilayer foils
Authors: Swiston Albert J. , Weihs Timothy P. , Knio Omar M. , Hufnagel Todd C. 
Published: April 2011

ABSTRACTWe use a fluid mechanics model to analyze glass fluid flow during the welding of bulk metallic glasses with reactive multilayer foils acting as local heat sources. The resulting welded joints were shear tested, and fracture surfaces were analyzed by optical microscopy. Fracture surfaces of failed metallic glass joints show distinct regions of metal-metal veins that indicate effective metallurgical bonding. We observe a monotonic increase in the failure strength of the joints with the fraction of the joint composed of such veins. For the strongest joint tested (shear strength of 420 MPa), nearly 60% of the fracture surface is comprised of metal-metal veins. We have developed a qualitative fluid mechanics explanation of the welding process, in which shear stresses (due to pressure applied during joining) push the reactive foil from the joint interface and create the metal-metal veins. The welding process is more effective at higher joining pressure and greater foil thickness, leading to increased joint strength.
Thermodynamics of The Pd43Ni10Cu27P20 Bulk Metallic Glass Forming Alloy
Authors: Kuno Masahiro , Shadowspeaker Ludi A. , Schroers Jan , Busch Ralf 
Published: April 2011

ABSTRACTThe thermodynamics of the bulk metallic glass forming Pd43Ni10Cu27P20 alloy were investigated with differential scanning calorimetry (DSC). The specific heat capacity of the undercooled liquid with respect to the crystalline mixture was measured in the DSC simultaneously with the enthalpy of crystallization over the entire supercooled liquid region. The enthalpy, entropy, and Gibbs free energy change between the liquid and the crystalline mixture was determined from the specific heat capacity data. The calculated enthalpy function closely matched the enthalpies of crystallization that were measured in the DSC, which verifies the validity of the thermodynamic model used. A small Gibbs free energy difference between undercooled liquid and crystalline mixture was found for decreasing temperature in Pd43Ni10Cu27P20 when compared to other glass forming alloys. This reflects a small driving force for crystallization when undercooling this alloy and is the main contributing factor for its high glass forming ability.
The Thermal Shear-Transformation-Zone Theory: Homogeneous Flow and Superplasticity in Bulk Metallic Glasses
Authors: Falk Michael L. , Langer James S. , Pechenik Leonid 
Published: April 2011

ABSTRACTWe present an extended version of our earlier shear-transformation-zone theory of amorphous plasticity that takes into account thermally assisted molecular rearrangements. As in the previous low-temperature theory a transition is predicted between jammed and flowing states at a well defined yield stress. In the new theory the jammed state below the yield stress exhibits thermally assisted creep. The theory accounts for the experimentally observed strain-rate dependence of the viscosity of a bulk metallic glass. In particular it models the onset of superplastic behavior at high strain rates as the system approaches the yield stress. The theory also captures many of the details of the transient stress-strrain response of the metallic glass at temperatures near the glass transition.
High-density liquid-like component facilitates plastic flow in a model amorphous silicon system
Authors: Demkowicz Michael J. , Argon Ali S. 
Published: April 2011

ABSTRACTMolecular dynamics simulations show that plastic deformation behavior of model Stillinger-Weber amorphous Si is very sensitive to the density of the initial unstressed state. Low-density systems exhibit a pronounced yield phenomenon, strain softening, and a dramatic drop in pressure during deformation at constant volume. This behavior is explained by the interplay in every system of the prevailing solid-like and liquid-like components, with the latter being denser and more amenable to plastic flow.