bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electronic Properties of Icosahedral Mg-Ai-Zn Alloys
Authors: Baxter David V. , Ström-Olsen J. O. 
Published: March 2011

AbstractThe resistivity and magnetic susceptibility of icosahedral Mg32(Al1-xZnx)49 have been measured for compositions between x=0.5 and x=0.69. Both quantities exhibit a stronger compositional dependence than do the same properties of the similar metallic glass Mg1-xZnx. The resistivity at low temperatures displays the classic behaviour as a function of temperature and magnetic field associated with the phenomenon of weak localization, and we are able to use this fact to measure the absolute resistivity in a way which is independent of sample geometry.
On the Glass Formation in Systems Forming Icosahedral Quasicrystals
Authors: Bendersky Leonid A. , Ridder Stephen D. 
Published: March 2011

AbstractRapidly solidified micron and submicron size droplets of Al-14 a/o Mn have been used to study the possibility of glass formation and nucleation behavior of icosahedral phase. Homogeneous nucleation of icosahedral phase is assumed, based on the high grain density (>1015 mm−3). Extremely low nucleation resistance of icosahedral phase can be understood when possible topological similarities between liquid and icosahedral quasicrystal structures are considered. Configurationally frozen liquid in Al-Mn and similar alloy systems is questionable, implying that Al-Mn “glass” probably has a microquasicrystalline structure.
Surface Crystallization of Metal-Metalloid-Glasses
Authors: Küster Uwe , Punge-Witteler Barbara 
Published: March 2011

AbstractPreferential crystal nucleation and growth may occur at surfaces because of a decrease in surface energy, a greater ease of diffusion and stress relaxation or a change in surface composition. Segregation as well as selective oxidation are assumed to possess the strongest influence on surface crystallization.Crystal nucleation and growth at both surfaces of melt-spun ribbons has been studied systematically in a number of Ni-B and Co-B glasses by means of quantitative light and electron microscopy. Crystal diameter distributions indicate a transient type heterogeneous nucleatior mode for surface crystallization. The results will be compared wi th crystallization in the bulk.
Icosahedral Symmetry and Magnetism
Authors: McHenry M. E. , O– R. C. 
Published: March 2011

AbstractWe examine the implications of icosahedral symmetry on electronic structure and especially magnetic properties in alloys. From simple geometric and synmetry arguments to detailed electronic structure calculations it is clear that icosahedral symmetry carries important consequences for magnetism in a wide range of alloys. Enhanced local magnetic moments, reduced anisotropies and new magnetic domain structures are predicted. We also propose a course of further study focussed on producing a strongly magnetic quasicrystalline phase and we describe interesting new metastable Co-Er phases produced in the preliminary phase of this investigation.
On Dominant Factors for C-Axis Orientation of Co-Cr Films in Sputter-Deposition
Authors: Nakagawa S. , Niimura Y. , Naoe M. 
Published: March 2011

AbstractCo-Cr thin film with the excellent c-axis orientation is required as the media for ultra high density perpendicular recording. There are two dominant factors that affect the c-axis orientation. One is the process condition such as argon gas pressure and targets-substrate distance L which change the kinetic energies of arriving atoms on substrate. The concept of mean collision number was introduced to get better understanding the relation between c-axis orientation and kinetic energy of particles. In this study, Facing Targets Sputtering (FTS) system was used because of its superiority as the plasma free sputtering. And the other is the interfacial effect between the substrate and the deposited film. In order to investigate the Interfacial effect, it has been performed to prepare the CoCr(500Å)/CoCr(500Å) double layer. By controlling the argon gas pressure, thin layers with different c-axis orientation can be easily obtained. When the c-axis well oriented 1st layer was used as the under layer, good c-axis orientation of 2nd layer was obtained even at the high argon gas pressure at which c-axis orientation in the single layer is poor. However, this improvement of c-axis orientation did not continue with the increase of the thickness of 2nd layer. It was clarified that there was the critical thickness in the 2nd layer affected by the c-axis orientation of under layer. As a result, it was concluded that the process condition was the superior dominant factor for c-axis orientation.
Effects of Elastic Anisotropy on the Anomalous Yield Behavior of Cubic Ordered Alloys
Authors: Yoo M. H. 
Published: March 2011

AbstractThe positive temperature dependence of yield stress in certain L12 and B2 alloys, e.g. Ni3Al and β′-CuZn, is analyzed on the basis of the nature of dislocation dissociations predicted by anisotropic elasticity theory. In the case of Ni3Al, the torque due to the tangential component of the elastic interaction between two superpartials is a major driving force for either the cross-slip pinning model or the force couplet model. The corresponding torque term is relatively unimportant in the B2 structure. The core transformation of individual superpartials may be important for the anomalous increase of yield stress in β′-CuZn.
The Segregation of Boron and Its Effect on the Fracture of An Ni3Si Based Alloy
Authors: Oliver W. C. , White C. L. 
Published: March 2011

AbstractIt is now well established that microalloying additions of B to Ni3Al drastically reduce low temperature grain boundary fracture and consequently increase the ductility of this intermetallic compound. One possible explanation for such effects involves the relationship between boron segregation to grain boundaries and free surfaces, and the resulting effect of such segregation on the cohesive energy of the grain boundaries. This study involves the extension of these concepts to an alloy based on Ni3Si. Auger spectroscopy has been carried out on fractured grain boundaries, grain interiors, and free surfaces to determine how B segregates in Ni3(Si,Ti). The consequences of the segregation of B on the cohesive energy of grain boundaries in Ni3Si based alloys are discussed.
High Temperature Ordered Intermetallic Alloys
Authors: Pope D. P. 
Published: March 2011

AbstractThis paper is intended to be a general introduction to this conference and is therefore not a review of the state of our current knowledge. Instead, it will address questions like the following: Why are intermetallic compounds interesting? What alloys are being studied, and which are being ignored? Since most research work is now being performed on L12 alloys, with by far the greatest emphasis on Ni3Al, the balanceof the paper will concentrate on strengthening mechanisms and mechanisms of ductility control in Ni3Al, pointing out the interesting questions and controversies which arose during this conference.The conclusions to be drawn from this paper are that ordered intermetallic alloys are very valuable materials for high temperature use, but engineers probably must become more sophisticated in the use of materials with limited ductilities at low temperatures before intermetallics will gain widespread usage. Furthermore, additional research needs to be performed on more complex intermetallic compounds than L12 since L12 compounds, as a group, do not have particularly high melting temperatures. However,since alloys with complex structures, e.g. Laves phases, are well known for their brittleness at low temperatures, it is all the more important that the properties of such alloys be studied and methods found to improve their ductilities.
SiC Reinforced Aluminide Composites
Authors: Brindley Pamela K. 
Published: March 2011

AbstractThe tensile properties of SiC fiber, Ti Al+Nb and SiC/Ti3Al+Nb composite have been determined from 300 to 1365K. The Composite results compared favorably to rule-of-mixtures (ROM) predictions in the intermediate temperature regime of 475 to 700K. Deviations from ROM are discussed. Composite tensile results were compared on a strength/density basis to wrought superalloys and found to be superior. Fiber-matrix compatibility was characterized for the composite at 1250 and 1365K for 1 to 100 hours.
Calculation of the Defect and Interface Properties of Ni3Al
Authors: Foiles Stephen M. 
Published: March 2011

AbstractThe structure and energetics of point defects, surfaces and grain boundaries in Ni3A1 are investigated using the Embedded Atom Method. The approach is shown to reproduce the experimental phase diagram of the Ni-Al system and the elastic properties of Ni3AL. The vacancy and anti-site defect energies are calculated and used to predict the vacancy concentration as a function of bulk composition. The preferred geometries and energies of the low index surfaces are also computed. The equilibrium structure of certain ideal grain boundaries are computed by Monte Carlo computer simulations as a function of bulk composition. It is found that the boundaries act as a sink for anti-sitedefects and the degree of ordering at the boundaries is strongly affected by the bulk composition. The cohesive energy of grain boundaries in Ni3A1 is computed and is found to be comparable to that for pure Ni.
Antiphase Domain Boundary Tubes in Ordered Alloys
Authors: Hazzledine P.M. , Hirsch Peter 
Published: March 2011

AbstractAPB tubes have been observed in both a B2 and an L12 ordered alloy by means of weak beamtransmission electron microscopy. The tubes are attached to near—edge dislocations, either to single superdislocations or to superdipoles. The majority appearto have been formed by cross slip of screw dislocations. A computer model of the cross slip process in B2 alloys is described. The tubes formed by cross slip drag on edge dislocations and are capable in principle of explaining the extra work hardening shown by ordered over disordered crystals. The temperature and orientation dependence of the work hardening are similar to those of the proof stress which is also thought to be controlled by cross slip. This new mechanism of work hardening is shown to give order of magnitudeagreement with experiment.
Impurities in SiO2: Atomic States of Phosphorus and Arsenic
Authors: Rhodes H. E. , Apai G. 
Published: March 2011

ABSTRACTWe have studied the atomic states of arsenic (As) and phosphorus (P) in SiO2 using X-ray photoelectron spectroscopy (XPS). Silicon dioxide implanted with As or P shows multiple XPS core level peaks corresponding to the impurity atoms located in two distinct atomic sites. The binding energies of the two arsenic 3d core levels occur at 45.8 and 42.3 eV and the two phosphorus 2p core levels occur at 134.7 and 130.3 eV. When the implanted oxides are annealed in an oxygen ambient between 900°C and 950°C, only the highbinding- energy peaks of P and As are observed. This identifies the highbinding- energy core level peaks as being associated with the impurity (P or As) on silicon sites. Annealing in nitrogen at 950° C results in an increase in the low-binding-energy signal. The low-binding-energy peaks are associated with the impurity (P or As) bonded to silicon neighbors. The relative amounts of dopants in silicon and oxygen sites depend on ambient purity and processing details. Reference to previous work shows that the presence of As or P on silicon sites in SiO2 corresponds to a fast diffusing state whereas As or P on oxygen sites corresponds to a slow diffusing state [1].
Grain Boundary Dislocations in GaAs
Authors: Smith D.A. , Krakow W. 
Published: March 2011

ABSTRACTA preliminary survey of the dislocation structures of grain boundaries in Bridgman grownpolycrystalline GaAs suggests that many of the phenomena observed in grain boundaries inface centered cubic metals, silicon and germanium also occur in boundaries of a polar semiconductor. Our experiments show that low angle grain boundaries are comprised of crystal lattice dislocations and deviations from coincidence orientations are accommodated bysecondary dislocations; specifically, in twins, the a-fringe technique reveals that there are multiple structures where the different domains are separated by partial grain boundary dislocations.
Grazing Incidence X-Ray Scattering Study of Surface Defects
Authors: Liang K. S. , Eisenberger P. 
Published: March 2011

ABSTRACTGrazing incidence x-ray scattering is emerging to become an important structural probe for surface and interface studies, especially in conjunction with the development of high brilliant synchrotron sources. In this paper, we give a brief review of the experimental principle and examples of how the technique can be applied to study surface defects.
Detection of Near-Surface 52Cr Segregation in Irradiated 51V(Cr) By Rbs
Authors: Rehn L. E. , Baldo P. M. 
Published: March 2011

ABSTRACTIrradiation at elevated temperatures of V(Cr) alloys is known to create a near-surface layer of nonequilibrium Cr enrichment. Highly reproducible RBS spectra were accumulated from a V-15%Cr alloy irradiated at 750°C, and from unirradiated portions of the same specimen. Differences between these spectra are used to demonstrate the high sensitivity of conventional RBS techniques for determining near-surface segregation behavior. Sensitivities obtained utilizing differences in the acquired spectra are much higher than those typically assumed for RBS measurements. Using 1.8 MeV 4He, and conventional RBS equipment and scattering geometries, segregation of < two atomic layers of 52Cr in 51V- 15at.%Cr over a depth of ∼5 nm has been observed.
A Comparison of Small Angle Neutron Scattering and X-Ray Diffraction Studies of Cobalt Precipitates in A Cu-0.95 at. % Co Alloy
Authors: Spooner S. , Iida S. , Larson B. C. 
Published: March 2011

ABSTRACTA detailed comparison of small-angle scattering (SANS) and large angle x-ray diffraction methods of characterization of precipitates was undertaken. Cobalt-rich precipitates on the order of 50 Å developed after a 17 hour anneal at 570°C were studied in a single crystal sample with SANS and with diffuse x-ray scattering near the (400)Bragg peak. Each scattering data set was analyzed independently in terms of a distribution of precipitate sizes; a detailed comparison is made of the size distribution obtained. A small interparticle interference effect is seen.
Arups Studies of the Interaction of Co with the Interface States for Strained-Layer Cu on Ru 0001)
Authors: Houston J. E. , Peden C. H. F. , Feibelman P. J. , Hamann D. R. 
Published: March 2011

ABSTRACTDuring the growth of the first monolayer, Cu has been shown to form in 2d islands pseudomorphic to the Ru 0001) surface under a tensile strain of -6%. The chemical behavior of such films has been found to be unlike that of either of the pure elements both from the standpoint of catalytic activity and molecular adsorption properties. In addition, these strainedlayer films have unique electronic properties. Specifically, we have identified a set of interface and surface states near the K point in the surface Brillioun zone. Here are shown new results concerning the behavior of the interface states with respect to CO adsorption. Specifically, CO is found to attenuate all Cu/Ru ARUPS structures except those due to the antibonding components of the interface states and these components move to higher binding energy with CO coverage. An analysis of these results, based on the properties of the interface states, indicates that there is negligible direct interaction between the CO orbitals and the metal d states. The increased bonding that is seen for CO on Cu/Ru compared to CO on Cu is suggested to result from an enchanced polarizability of the Cu 4s states due to the proximity of the Ru substate.
The Characterization of Thin Platinum Films on Alumina
Authors: Altman E. I. , Gorte R. J. 
Published: March 2011

ABSTRACTIndustrial metal catalysts are usually in the form of small metal particles supported on a porous oxide. The typical size of these metal particles ranges between 1.0 and 10.0 nm and it is well known that the particle size and the oxide substrate can affect the catalytic properties of the metal for some important reactions[1]. Previous work with adsorption on small particles has indicated that desorption temperatures[2–4] and the ability to dissociate CO[5,6] can also be affected by the particle size. To further investigate these size and substrate effects, we have examined the adsorption properties of several simple gases on small Pt particles supported on alumina using temperature programmed desorption (TPD). We will show that the desorption curves for CO, H2, and NO on these particles are very similar to curves measured on single crystals.
Potassium Adsorption on Pt(111) and its Effect on Co Chemisorption
Authors: Greenlief C. Michael , Radloff Patricia L. , Akhter Sohail , White J. M. 
Published: March 2011

ABSTRACTTemperature programmed desorption (TPD) and secondary ion mass spectrometry (SIMS) have been used to study the chemisorption properties of carbon monoxide on potassium predosed Pt. SIMS cluster ions (such as K+, K2+, KO+ and KCO+) were monitored to probe, K-CO interactions. Large changes in the SIMS yields are observed as the potassium coverage is varied. The SIMS results are correlated with previous work function change and TPD studies. Temperature programmed secondary ion mass spectrometry of potassium-containing ions indicates a local interaction between potassium and CO molecules.As typically observed on transition metal surfaces, two different CO TPD states are observed. The lower temperature state shifts to higher temperatures with increasing potassium coverage and to lower temperatures with increasing CO exposure. The high temperature CO state builds in with increasing potassium coverage and is accompanied by simultaneous potassium desorption. Evidence for the occurrence of both long-range (indirect) and short-range (direct) potassium effects on adsorbed CO is presented.
Oxygen Adsorption on and Oxidation of NiAl Surfaces
Authors: Zehner D. M. , Gruzalskia G. R. 
Published: March 2011

ABSTRACTOxygen adsorption on and the eventual oxidation of the (100), (110), and (111) surfaces of NiAl was studied extensively using a variety of surface sensitive techniques. While the initial rate of uptake at 22°C varied significantly with orientation and surface composition, in all cases it was possible to form an overlayer region containing the equivalent of several monolayers of oxygen. No ordered overlayers were observed. Information about the chemical bonding was obtained from changes in core-level binding energies. Examination of the Al 2p region showed evidence for two different oxide environments, depending on surface treatment. Comparison of these results with those for both Ni and Al clearly shows effects due to alloying.
Second Harmonic Generation from Alkali Thin Films on AG(110)
Authors: Song K. J. , Heskett D. , Urbach L. , Dai H. L. , Plummer E. W. 
Published: March 2011

ABSTRACTThe sensitivity of second harmonic generation at interfaces has been utilized to probe the spatial and frequency dependence of the local field generated near the surface of a nearly free electron metal by an externally imposed electromagnetic field. The longitudinal screening field was found to oscillate with a wavelength on the order of 10Å and to propagate into the bulk several layers deep.
Electronic and Vibrational Properties of Single Crystal Surfaces of NiAl
Authors: Lui S.-C. , Mundenar J. M. , Plummer E. W. , Mostoller M. E. , Nicklow R. M. , Zehner D. M. , Ford W. K. , Erskine J. 
Published: March 2011

ABSTRACTSurface and bulk electronic structure of the ordered NiAl alloy were measured using angle resolved photoelectron spectroscopy. The measured bulk d-bands (Ni like) were observed to be narrower than theoretically calculated d band widths which are 20 to 40% wider (depending upon what is used as a measure of the width). At least two surface states were observed on both the (110) and (111) surfaces. The nature of these surface states and their relationship to the bulk band structure is discussed. Dispersion of bulk phonons was measured by neutron scattering and fitted with a fourth nearest neighbor Born-von Karman model. Dipole active surface phonons on the (110) and (111) surfaces were observed by inelastic electron scattering and the frequencies also calculated assuming a truncated bulk surface. The calculated surface modes present a qualitative picture of the atomic displacement at each surface and also show that the surface phonon energy and intensity depends upon the structure of the surface.
Carbon Monoxide Adsorption on (111) and (110) Single-Crystal Nickel-Aluminum Alloy Surfaces
Authors: Mundenar J. M. , Gaylord R. H. , Lui S. C. , Plummer E. W. , Zehner D. M. , Ford W. K. , Sneddon L. G. 
Published: March 2011

ABSTRACTCarbon monoxide chemisorption on the (111) and (110) surfaces of a single-crystal NiAI alloy has been studied using several surface sensitive techniques, including work function change measurements, ultra-violet photoelectron, thermal desorption and electron energy loss spectroscopy. Results from these experiments indicate that the reactivity of these NiAI surfaces toward CO is distinctly different and that although the CO/NiAI (111) surface behaves more like CO adsorbed on pure nickel surfaces, the CO/NiAI (110) surface is neither like CO adsorbed on pure nickel nor aluminum surfaces. The local CO bonding sites, as probed with photoemission and electron energy loss spectroscopy, are similar on both NiAI surfaces.
New Preparation Method For Liquid Alloy Surfaces and Their Characterization by Electron Spectroscopy
Authors: Indlekofer G. , Oelhafen P. , Güntherodt H.- J. 
Published: March 2011

ABSTRACTSurface investigations of liquid metals in ultra-high vacuum are scarce as compared with solid state studies, mainly because of experimental difficulties of preparing atomically clean liquid surfaces. A new technique has been developed in order to prepare clean liquid metal surfaces. According to the characterization with electron spectroscopy it proved to be an effective way to obtain high purity liquid surfaces and hence offers the possibility to study a variety of metals and alloys in the liquid state.Information about the surface composition, segregation properties and its purity in the liquid state and the valence electron structure has been obtained by X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS, respectively). Exciting new insights in the electronic structure of various liquid alloys such as Au-Si, Cu-Sn, Ga-Sn and TI-Bi have been obtained from these measurements.
Ag Layers on Cu(110): Bonding, Structure, and Stability
Authors: Taylor T. N. , Hoffbauer M. A. , Borodovsky L. , Beery J. G. , Maggiore C. J. 
Published: March 2011

ABSTRACTThe atomic-level properties ( bonding, structure, composition ) and thermal stability of Ag overlayers on Cu(110) have been investigated using combined surface and high energy ion beam techniques. Analysis of the first Ag adatom layer with LEED shows that the Ag is initially confined to the [110] troughs and that further deposition results in a Ag(111) layer exhibiting c(2×4) symmetry. Rutherford backscattering analysis gives absolute coverages that are consistent with the surface science coverage determination. Thermal desorption of CO from the trough composite reveals a lower ( more Ag-like ) binding energy than that for clean Cu(110). Continuous films grown cold at thicknesses <115 Å are found to agglomerate above 500 K exposing a tenacious Ag-Cu interface like that formed by one monolayer deposition. Ion beam analysis has been employed to characterize the agglomerate coverage and depth distribution for these degraded films. Thin films grown 900Å thick exhibit much higher thermal stability, giving detectable interfacial degradation only after heating above 725 K.