Quasicrystal
Mostrando 1-11 de 11 artigos, teses e dissertações.
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1. Multistage Phase Decomposition Behavior and Kinetics for Zr65Ni30Pd5 Ternary Amorphous Alloy
We have examined heating-induced phase decomposition and its kinetics for Zr65Ni30Pd5 amorphous alloy in an argon atmosphere. The amorphous phase decomposes through three stages in the order of amorphous → icosahedral quasicrystal (I-Q) + amorphous → approximant cubic Zr2(Ni,Pd) → tetragonal Zr2Ni + tetragonal Zr2Pd phases. The approximant crystalline
Mat. Res.. Publicado em: 20/01/2020
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2. Directional Coupler Based on a Photonic Quasi-Crystal Fiber with Extended Cores
Abstract In this paper, an optical coupler composed by a photonic quasi-crystal fiber (PQCF) with two cores is proposed. The structure is obtained by immersion of a quasi-periodic arrangement of air holes replicated twelve-fold in a conventional fiber optical constituted of pure silica. The cores are generated from defects caused due to absence of two air ho
J. Microw. Optoelectron. Electromagn. Appl.. Publicado em: 2018-06
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3. Enhancement of Mechanical Properties of Aluminum and 2124 Aluminum Alloy by the Addition of Quasicrystalline Phases
A structural and mechanical characterization of pure aluminum and 2124 T6 aluminum alloy reinforced with quasicrystalline phases of composition Al65Cu20Fe15 and Al70.5Pd21Mn8.5 (%at.) were performed. The quasicrystalline phases were synthesized by arc melting and then milled to produce powder of the alloys, which were then mechanical mixed with the starting
Mat. Res.. Publicado em: 25/08/2016
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4. Chromatic Dispersion of an Optical Fiber Based on Photonic Quasicrystals with Twelve-Fold Symmetry and its Application as Directional Coupling
Abstract Optical fibers composed by photonic quasicrystals it is based on aperiodic structures characterized by at least two different symmetrical patterns from the base matrix. In this work, an optical fiber composed by quasi-periodic and symmetric matrix was analyzed using the finite element method in conjunction with cylindrical perfectly matched layers.
J. Microw. Optoelectron. Electromagn. Appl.. Publicado em: 2015-12
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5. Hydrogen absorption study of ti-based alloys performed by melt-spinning
The hydrogen absorption and desorption of Ti53Zr27Ni20 icosahedral quasicrystal (ICQ) and Ti50Ni50 shape memory alloy (SMA) melt-spun ribbons was studied. Samples were exposed to hydrogen gas at 623 K and 4 MPa for 1000 minutes. The total capacity of hydrogen obtained for Ti53Zr27Ni20 and Ti50Ni50 was 3.2 and 2.4 wt. % respectively. The Thermal Desorption Sp
Mat. Res.. Publicado em: 02/04/2013
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6. The formation of quasicrystal phase in Al-Cu-Fe system by mechanical alloying
In order to obtain quasicrystalline (QC) phase by mechanical alloying (MA) in the Al-Cu-Fe system, mixtures of elementary Al, Cu and Fe in the proportion of 65-20-15 (at. %) were produced by high energy ball milling (HEBM). A very high energy type mill (spex) and short milling times (up to 5 hours) were employed. The resulting powders were characterized by X
Mat. Res.. Publicado em: 22/05/2012
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7. PRODUCTION OF AlCuFe QUASICRYSTAL ALLOY BY HIGH ENERGY MILLING / Produção da liga quasicristalina do sistema AlCuFe por moagem de alta energia
Os quasicristais, cujas estruturas apresentam simetria não cristalográfica, vem atraindo considerável interesse devido as suas propriedades estruturais, eletrônicas e magnéticas, bem como a interação entre elas, vem sendo investigadas. Em geral, os quasicristais são bons isolantes elétricos e térmicos, são muito duros, resistentes à fricção e a
Publicado em: 2009
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8. Analysis of pulsed-neutron powder diffraction patterns of the icosahedral quasicrystals Pd3Siu and AlCuLiMg (three alloys) as twinned cubic crystals with large units.
The low-Q peaks on three pulsed-neutron powder patterns (total, U differential, and Pd differential) of the icosahedral quasicrystal Pd3SiU have been indexed on the basis of an assumed cubic structure of the crystals that by icosahedral twinning form the quasicrystal. The primitive unit cube is found to have edge length 56.20 A and to contain approximately 1
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9. Icosahedral and decagonal quasicrystals of intermetallic compounds are multiple twins of cubic or orthorhombic crystals composed of very large atomic complexes with icosahedral point-group symmetry in cubic close packing or body-centered packing: Structure of decagonal Al6Pd
A doubly icosahedral complex involves roughly spherical clusters of atoms with icosahedral point-group symmetry, which are themselves, in parallel orientation, icosahedrally packed. These complexes may form cubic crystallites; three structures of this sort have been identified. Analysis of electron diffraction photographs of the decagonal quasicrystal Al6Pd
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10. Five-fold symmetry in crystalline quasicrystal lattices
To demonstrate that crystallographic methods can be applied to index and interpret diffraction patterns from well-ordered quasicrystals that display non-crystallographic 5-fold symmetry, we have characterized the properties of a series of periodic two-dimensional lattices built from pentagons, called Fibonacci pentilings, which resemble aperiodic Penros
The National Academy of Sciences of the USA.
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11. Icosahedral quasicrystals of intermetallic compounds are icosahedral twins of cubic crystals of three kinds, consisting of large (about 5000 atoms) icosahedral complexes in either a cubic body-centered or a cubic face-centered arrangement or smaller (about 1350 atoms) icosahedral complexes in the β-tungsten arrangement
The twofold-axis electron-diffraction photographs of icosahedral quasicrystals are of three kinds, reflecting three different structures of the cubic crystals that by icosahedral twinning form the quasicrystals. The first kind, represented by Al13Cu4Fe3, contains two very large icosahedral complexes, each of about 4680 atoms, in the body-centered arrangement