bluuebunny/crossref_metadata_2025_split huggingface dataset:
TDS Study of Potassium Adsorption on Al(111) and fivefold Al-Pd-Mn
Authors: Wehner Barbara I. , Anderegg James W. , Jenks Cynthia J. , Ross Amy R. , Lograsso Thomas A. , Diehl Renee D. , Thiel Patricia A. 
Published: April 2011

AbstractWe have used thermal desorption spectroscopy to carry out a comparative study of potassium adsorption on Al(111) and on the fivefold Al-Pd-Mn surface. Potassium adsorption on the quasicrystal was found to be different than on Al(111). The potassium monolayer desorbed from fivefold Al-Pd-Mn at lower temperatures than from Al(111). Potassium is known to form a dense monolayer on Al(111), with an ideal coverage of 0.33, but for the monolayer on fivefold Al Pd Mn we find that the saturation coverage is only one twelfth.
Surfactant-Mediated Growth of Epitaxial Films on Quasiperiodic Surfaces
Authors: Shimoda Masahiko , Guo Junqing , Sato Taku J. , Tsai An Pang 
Published: April 2011

AbstractWe have succeeded for the first time in inducing epitaxial growth of metal films on quasiperiodic surfaces. Depositions of Au onto the tenfold surface of a decagonal Al-Ni-Co quasicrystal were originally attempted to create a quasicrystal of a single element as an epitaxial film. Although the desired film was not obtained on the clean surface, a multiply twinned AuAl2 crystalline layer with a (110)-oriented surface was formed with the aid of an In pre-deposition layer. The presence of pre-deposited In also worked as a surfactant for the case of Au-deposition onto the fivefold surface of an icosahedral Al-Pd-Mn quasicrystal and promoted the formation of an ordered film of Au-Al alloy. X-ray photoelectron diffraction images from this ordered film show that the alloy has an icosahedral structure as a long-range order, suggesting the formation of a quasicrystalline film.
About the Metal-Insulator Transition in Quasicrystals
Authors: Delahaye J. , Berger C. , Grenet T. , Fourcaudot G. 
Published: April 2011

AbstractElectronic properties (conductivity and density of states) of quasicrystals present strong similarities with disordered semiconductor based systems on both sides of the Mott-Anderson metal-insulator (MI) transition. We revisit the conductivity of the i-AlCuFe and i-AlPdMn phases, which has temperature and magnetic field dependence characteristic of the metallic side of the transition. The i-AlPdRe ribbon samples can be on either side of the transition depending on their conductivity value. In all these i-phases, the density of states at the Fermi level EF is low. Its energy dependence close to EF is similar to disordered systems close to the MI transition where it is ascribed to effects of interactions between electrons and disorder.
Beyond the Usefulness of Quasicrystals
Authors: Dubois J.M. 
Published: April 2011

AbstractFor more than a decade, quasicrystals were considered to exhibit only fundamental interest in so far that they have raised basic questions regarding the organization and stability of condensed matter. As well, they addressed the mechanisms of wave propagation in aperiodic solids. In more recent years, they turned to become useful materials in various mechanical devices, in solar absorbers or in heat insulation coatings. Nowadays, the science of quasicrystals, and especially the relevant high-dim crystallography techniques, have issued quite useful concepts and methods that prove useful in neighboring domains of condensed matter physics, of mechanics, of low temperature physics, etc. Hence, this article puts more emphasis on a few of the new subjects that quasicrystals science has helped us to study rather than on the few possible breakthroughs of quasicrystalline materials identified yet on the market.
Interralation Between Hume-Rothery Mechanism, Hybridization and Covalent Bonds in Aluminum- and Boron-based Icrosahedral Approximants and Quasicrystals
Authors: Kimura Kaoru , Kirihara Kazuhiro , Fujumori Masaaki , Nakayama Takahiro , Takata Masaki , Sakata Makoto 
Published: April 2011

AbstractMetallic-covalent bonding conversion in icosahedral clusters of Al and B by small changes of the structure was demonstrated by molecular orbital calculations. According to the electron density distribution obtained using the maximum entropy method and the Rietveld method, the bonding conversion phenomenon occurs even in cluster solids such as some Al- and B-based icosahedral approximant phases (Al12Re, α-AlMnSi, α-rhombohedral boron). The multiple-shell atomic structure, the electrical and optical conductivity are compared for metal doped β-rhombohedral boron and AlLiCu or AlPdRe icosahedral quasicrystal. Photoemission and electron energy loss spectroscopy investigations for V doped β-rhombohedral have been discussed. Conclusions are the following two. It is difficult to distinguish a Hume-Rothery, i.e. structure-induced, pseudogap, and a covalent bonding, i.e. hybridization, pseudogap for materials with a highly symmetric Brillouin zone and a strong potential for valence electrons. Because hybridization is necessary not only for covalent bonds but also for metallic ones, it is better to use the covalent bonding pseudogap than the hybridization pseudogap.
Stable Icosahedral Quasicrystals in the Cd-Based Alloys
Authors: Guo J. Q. , Abe E. , Tsai A. P. 
Published: April 2011

AbstractStable icosahedral quasicrystals have been found in ternary Cd65Mg20RE15 (RE=Y, Gd, Tb, Dy, Ho, Er, Tm, Lu, Yb and Ca) and binary Cd85Ca15 and Cd84Yb16 alloys. These icosahedral quasicrystals have a primitive quasilattice. Their quasilattice parameters range from 0.5571 to 0.5731 nm. Formation mechanism of the quasicrystals is discussed.
Unraveling the Structure of Decagonal Approximants by “Brute Force” Deconvolution of the Experimental Autocorrelation Function
Authors: Estermann Michael A. , Lemster Katja , Steurer Walter 
Published: April 2011

AbstractMethods for theab initiostructure analysis of periodic approximant phases from single- crystal X-ray diffraction data are presented. These methods are particularly suited to complex approximant structures with large unit cells and strong pseudosymmetry (where routine X-ray structure solution tools fail) and are based on the “brute-force” deconvolution of the experimentally measured autocorrelation function. This function is obtained directly by a simple Fourier transform of the measured X-ray diffraction intensities. Sub-optimal diffraction data from twinned, nanodomain and polycrystalline specimens can be processed despite the inevitable lack of information due to reflection overlap and limited resolution. The deconvolution process allows complex approximant structures to be unraveled without prior knowledge about the structure-building motifs. Examples are presented for the systems Al-Co-Ni and Al-Co-(Ta).
High Temperature Plastic Behaviour of Icosahedral AlCuFe Quasicrystals.
Authors: Fikar Jan , Bonneville Joël , Baluc Nadine , Guyot Pierre 
Published: April 2011

AbstractIcosahedral AlCuFe poly-quasicrystalline specimens were deformed in constant strain rate compression tests at temperatures ranging between 300K - 1020K. Below nearly 0.7 Tm (Tm is the melting temperature) the specimens were brittle. Above the brittle-to-ductile transition temperature, after the elastic stage the stress-strain curves exhibit a marked yield-point followed by a stage of strain softening only. Transient creep tests were performed at different given stress/strain levels after interrupting the constant strain-rate deformation tests. After the transient tests, the flow strength of the specimens was investigated anew at constant strain rate. The results are interpreted in the framework of a dislocation model, where two effects opposing dislocation movement are considered: firstly, the usual elastic dislocation interaction, yielding a work-hardening contribution, and, secondly, a friction stress specific to the quasiperiodic lattice, leading to a softening effect.
Low Temperature Plastic Behaviour of Icosahedral AlCuFe Quasicrystals
Authors: Fikar Jan , Bonneville Joël , Rabier Jacques , Baluc Nadine , Proult Anne , Cordier Patrick , Stretton Iona 
Published: April 2011

AbstractThe mechanism by which dislocations move in the icosahedral quasicrystalline structure, i.e., glide or climb, is still an open question. In order to check whether pure dislocation glide occurs in this quasi-periodic structure, low temperature deformation tests have been performed under confining pressure conditions. These experimental techniques, which superimpose a shear stress on an isostatic component, enable the brittle-to-ductile transition temperature to be shifted to temperatures at which diffusion processes can be assumed to be negligible. Such techniques have been applied to deform plastically AlCuFe poly-quasicrystals at low and intermediate temperatures, using both gas and solid-confining media. Mechanical data as well as microstructural observations associated with this low temperature deformation range are reported. The first results provide new insights into the deformation mechanisms that control plasticity in the icosahedral quasicrystalline phase.
Estimation of Back Stress Produced by Dislocation Interaction in Icosahedral Al-Pd-Mn
Authors: Hirai Hisatoshi , Kitahara Akira , Yoshida Fuyuki , Nakashima Hideharu 
Published: April 2011

AbstractWe attempted to calculate the breakaway stress σb of dislocation from attractive junction made by reaction of dislocations. Assuming that the force f acting on the unit length of dislocation with the Burgers vector B under a shear stress τa is f τ∣b˝∣ where b˝ is the phonon component of B, and that the elastic energy per unit length of dislocation W is approximated by W = G(∣b˝∣2 + c2 ∣b˔∣2) where G is the shear modulus, b˔ the phason component of B and c2 a coefficient of about 3.1 × 10−3. Using the values G = 48.4 GPa at 1070 K, the Taylor factor M = 3 and the measured dislocation density of 1.8 × 1013 m−2, we calculated σb for 21 possible dislocation reactions. Picking up the most possible dislocation reactions, σb distributed between 50 and 80 MPa, and the average of them was 64 MPa. This result strongly suggested the possibility that the main part of the internal stress of the high-temperature deformation of icosahedral Al-Pd-Mn is explained by σb.
Influence of Chemical Disorder, Magnetic Field and Phason Flipd on the Localization of Electronic States in a Regular Icosahedral Quasicrystal
Authors: Vekilov Yu.Kh. , Isaev E.I. , Arslanov S.F. 
Published: April 2011

AbstractThe influence of substitutional chemical disorder, magenetic field and phasons, on the electronic spectrum and wave functions of icosahedral quasicrystals is investigated by means of tight-biding approximation and level statistic method. The results show that the localization of electronic states in an ideal quasictystal exists due to their coherent interfernce at the Fremi level which is caused by the symmetry and aperiodic long-range order.
Diffraction Study of The Transformation of an Al-Cu-Fe Atomized Powder Upon Annealing at 500°C
Authors: Weisbecker P. , Bonhomme G. , Cael A. , Zhang L. , Dubois J.M. 
Published: April 2011

AbstractUsing powder X-ray diffraction, we have studied the transformation of an atomized powder of nominal composition Al62Cu25.5Fe12.5 upon annealing at 500°C in air or in vacuum. The initial mixture of icosahedral and B2 cubic phases transforms within 2 hours into a nearly pure icosahedral compound. We observe however that a small amount of residual cubic phase is still present after annealings as long as 65 hours. Furthermore, the initial cubic phase splits in two components, a CsCl-type and a disordered bcc cubic phase. By comparison of the heat treatments in air and in vacuum, we point out that oxygen atoms diffuse into the icosahedral lattice.
Local Atomic Structures in Amorphous and Quasicrystalline Zr70Ni10Pt20and Zr80Pt20Alloys by the Anomalous X-ray Scattering Method
Authors: Matsubara Eiichiro , Nakamura Takahiro , Sakurai Masaki , Imafuku Muneyuki , Sato Shigeo , Saida Jyunji , Inoue Akihisa 
Published: April 2011

AbstractLocal atomic structures around Zr and Pt in a quasicrystalline Zr80Pt20alloy, and amorphous and quasicrystalline Zr70Ni10Pt20alloys have been determined by the anomalous x-ray scattering (AXS) method. A distinct prepeak observed in an intensity profile of the amorphous Zr70Ni10Pt20alloy indicates existence of strong chemical short-range order (CSRO) clusters in the amorphous phase. Total coordination numbers around Zr and Pt in a nearest neighbor region in both alloys have been evaluated. The values around Pt are almost equal to 12 in the amorphous and quasicrystalline states suggest formation of icosahedral clusters around Pt. Some of crystalline structures formed from the quasicrystalline phases by annealing consist of icosahedral clusters of Zr and Ni atoms, or polyhedral clusters of Zr and Pt atoms similar with icosahedral clusters. The present result appears to support that the phase transformation from the amorphous to the crystal through the quasicrystal is explained by the icosahedral CSRO clusters in the amorphous and quasicrystalline states.
Study of the Electrical Resistivity Change upon Phase Transformation in Zr-Based Metallic Glass
Authors: Komatsu Keiko , Tamura Ryuji , Takeuchi Shin , Shibuya Tadaharu 
Published: April 2011

AbstractIn order to gain insight into the influences of formation of an icosahedral phase in Zr-based metallic glasses on the physical properties, thermal and electrical properties of Zr70Ni10Pd20 metallic glass were investigated. From DSC analyses, activation energies for the phase transition from an amorphous to an icosahedral phase and from the icosahedral to a crystalline (Zr2Ni) phase were estimated to be 3.42 and 3.07 eV, respectively. The effect of the phase transformations on the electrical resistivity was successfully observed; the resistivity clearly exhibits an increase and a decrease corresponding to the transitions from the amorphous to the icosahedral phase and from the icosahedral to the crystalline Zr2Ni phase, respectively. It is concluded that the increase of the resistivity upon the precipitation of the icosahedral phase is due to an increase of the volume fraction of the icosahedral grains, which possess higher resistivity.
Structural Study of Fe-Based Glassy Alloys with a Large Supercooled Liquid Region
Authors: Imafuku M. , Sato S. , Nakamura T. , Koshiba H. , Matsubara E. , Inoue A. 
Published: April 2011

AbstractThe thermal stability and local atomic structures of glassy Fe70M10B20 (M = Hf, Zr, Nb, W and Cr) alloys were analyzed by DSC, ordinary X-ray diffraction and AXS measurements. The random network of the trigonal prism-like structure of (Fe,M)3B with edge-sharing, was identified in all the Fe70M10B20 (M = Hf, Zr, Nb, W and Cr) alloys in spite of the wide variety of thermal stability upon heating. Several unique primary precipitated crystalline phases, such as Fe23B6 type and Fe-M phases, were observed in the alloys exhibiting a high thermal stability. These crystallization reactions require relatively long range rearrangements of the constituents and hence the thermal stability of the glassy phase increases, leading to the appearance of a large supercooled liquid region upon heating. These phenomena may be originated from the difference in the chemical affinity and the atomic size mismatch between M and Fe or B.
Plastic Deformation of Bulk Amorphous Alloys
Authors: Xing L.Q. , Hufnagel T.C. , Ramesh K.T. 
Published: April 2011

AbstractWe have studied plastic deformation, including “serrated flow,” of bulk metallic glasses under quasi-static uniaxial compression. The deformation response is essentially elastic-perfectly plastic, but the “plastic” deformation actually consists of sections of elastic loading separated by abrupt load drops. The load drops are due to the formation of shear bands, which represent the primary mechanism of plastic deformationIn Zr-Ti-Cu-Ni-Al bulk metallic glasses, fracture occurs after about 1-2% plastic strain, but in Zr-Ta-Cu-Ni-Al metallic glass the plastic strain to failure can be as large as 6-7%. The difference appears to be due a strong tendency for the shear bands in this alloy to branch. The branching presumably reduces the stress concentration on the shear bands, retarding the onset of fracture. No evidence is seen for the formation of crystalline phases in this alloy.
Correlation Between Resistivity Characteristics and Electronic Structure Parameters of the Ni-Pd-P Amorphous Alloys
Authors: Babich Mykola , Nakonechna Olesya , Semen'ko Mykhailo , Zakharenko Mykola , Yeremenko Gennagy , Yavari Alain R. 
Published: April 2011

AbstractThe temperature dependencies of resistivity of the Ni-Pd-P-based amorphous alloys (P content was varied from 14 to 23 at. %) have been measured in a wide temperature range using the standard four-probe method. The temperature coefficients of resistivity (TCR) have been calculated. TCR value is decreased with P content increasing and becomes negative for Ni46Pd31P23 alloy. On the other hand, TCR value is increased with Pd content increasing while P content is not changed. Such behavior could be attributed to the electronic transfer effect from Ni to Pd and from P to Ni. These lead to the Fermi level shift to d-band edge and to the increasing influence of the Mott's localized state. The peculiarities caused by structural relaxation processes have been observed at the temperature range of 550 – 620 K. The relaxation process was shown to consist at least of two stages. The kinetics of the crystallization process has been analyzed using the Kissinger method.
Structure and Soft Magnetic Properties of Bulk Fe-Al-Ga-P-C-B-Si Glassy Alloys Prepared by Consolidating Glassy Powders
Authors: Inoue Akihisa , Yoshida Shoji , Mizushima Takao , Makino Akihiro 
Published: April 2011

AbstractWith the aim of developing a bulk glassy Fe-based alloy with good soft magnetic properties by the powder metallurgy technique, we have applied the pulse current sintering technique to a Fe70Al5Ga2P9.65C5.75B4.6Si3 glassy alloy powder with a large supercooled liquid region of 60K before crystallization. The existence of the supercooled liquid region was found to enable us to form a bulk glassy alloy with a very high relative density of 99%. The resulting bulk glassy alloy exhibits good soft magnetic properties, i.e., 1.17T for flux density at a field of 800A/m, 12.0A/m for coercive force and 8000 for maximum permeability which are much superior to those for the bulk amorphous Fe-Si-B alloy prepared by the same sintering method. The much better soft magnetic properties for the multicomponent Fe-based bulk alloy are attributed to the combination of the high relative density and the unique amorphous structure with the features of high packing density and long-range homogeneous atomic configurations. The first success of forming the bulk amorphous alloy with good soft magnetic properties by the powder metallurgy technique is expected to enable us to use as practical soft magnetic materials.
Exafs and Exelfs Study of the Structure of Pd-Ni-P Bulk Metallic Glasses
Authors: Alamgir Faisal M. , Jain Himanshu , Williams David B. , Hug Gilles , Schwarz Ricardo B. , Jin Ou 
Published: April 2011

AbstractWe have explored the short-range order around all three constituent atoms in (Pd-Ni)80P20 bulk metallic glasses (BMGs), a system that is a prototype for a whole class of BMG formers containing 80% transition metal and 20% metalloid. We have examined the changes in the nearest neighbor environments around the transition metals in (Pd-Ni)80P20 glasses using extended X-ray absorption fine structure (EXAFS) in comparison to their binary counterparts. We have done similar studies around the coordination of P using extended energy loss fine structure (EXELFS). The environment around the all the atoms in Pd60Ni20P20 and Pd30Ni50P20are very similar to those of the binary phosphides at the ends of the composition range. However, the (Pd-Ni)80P20 glasses are not simply solid solutions of the phases. The nearest neighbor distances of the metals are reduced in the ternary alloys with respect to those of the binary phosphides. The best glass former in this series, Pd40Ni40P20 is nearly isostructural to Pd30Ni50P20 but shows shorter distances at the 2nd and 3rd coordination shells, which we believe is due to more efficient packing in this glass. The metal environments in Pd40Ni40P20, on the other hand, are better described by a weighted average of those of Pd30Ni50P20 and Pd60Ni20P20.
Formation of Nanostructured Alloys by Liquid Phase Spinodal Decomposition
Authors: Guo W.H. , Kui H.W. 
Published: April 2011

AbstractA molten Pd82Si18 alloy, free of potent heterophase impurities and enclosed in a fused silica tube of conical shape, was quenched in water. Four regions classified according to their microstructures can be distinguished. They are: region I, amorphous; region II, a mixture of an amorphous nanostructure and a nanocrystal; region III, a mixture of two kinds of nanocrystals; region IV, spinodal networks; and region V, conventional eutectic structure. The detailed microstructures in each region are discussed.
Processing and Hard Magnetic Properties of Nanocrystalline Sm(Co,Zr)7 Magnet Powders
Authors: Tang H. , Zhou J. , Liu Y. , Sellmyer D.J. 
Published: April 2011

AbstractIsotropic nanocrystalline Sm(Co,Zr)7 permanent magnet powders of the TbCu7 type structure and with high coercivity and enhanced remanent magnetization has been synthesized by mechanically milling Sm12.5Co87.5-xZrx alloys (x = 0, 1, 2, 3) alloys and subsequently appropriate annealing. The mechanical-milling process of the alloys and the formation of nanostructured Sm(Co,Zr)7 magnet powders have been investigated with respect to hard magnetic properties. Hard magnetic properties are found to be strongly dependent upon the processing condition (like milling time, annealing temperature, etc.). Optimal coercivity Hci of value above 21 kOe has been obtained in Sm12.5Co85.5Zr2 magnet powders subjected to milling for 5 hr and annealing at 600°C for 20min. Optimal remanent magnetization Mr of 73.4 emu/g, remanence ratio Mr/Ms of 0.71, and maximum energy products (BH)max of over 13 MGOe have been realized in Sm12.5Co87.5-xZrx (x = 1, 2) magnet powders with grain size of 15-20 nm. The hard magnetic properties are ascribed to the nanosized Sm(Co,Zr)7 phase of the TbCu7 type structure with grain size of 10-20 nm. The enhancement of remanent magnetization may be contributed from the enhanced exchange-coupling interaction between nanosized grains.
Microstructures and Properties of Metal Reinforced Zr57Nb5Al10Cu15.4Ni12.6Bulk Metallic Glass Composites
Authors: Choi-Yim Haein , Conner Robert D. , Johnson William L. 
Published: April 2011

AbstractTo increase toughness of a metallic glass with the nominal composition Zr57Nb5Al10Cu15.4Ni12.6, it was used as the matrix in the composites reinforced with W fiber, W particles, and W/Re particles. Microstructures of the composites are studied by scanning electron microscopy and electron microprobe. Compression results are presented. Dynamic deformation behavior of the composites is studied in ballistic tests. The tests were performed firing composite rods into 6061 T651 aluminum target and 4130 steel targets. The composite rods failed by localized adiabatic shear banding and exhibited self-sharpening behavior.