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Sample records for polar intermetallic phase

  1. Electrocrystallization: A Synthetic Method for Intermetallic Phases with Polar Metal-Metal Bonding.

    PubMed

    Tambornino, Frank; Sappl, Jonathan; Pultar, Felix; Cong, Trung Minh; Hübner, Sabine; Giftthaler, Tobias; Hoch, Constantin

    2016-11-07

    Isothermal electrolysis is a convenient preparation technique for a large number of intermetallic phases. A solution of the salt of a less-noble metal is electrolyzed on a cathode consisting of a liquid metal or intermetallic system. This yields crystalline products at mild reaction conditions in a few hours. We show the aptness and the limitations of this approach. First, we give an introduction into the relevance of electrolytic synthesis for chemistry. Then we present materials and techniques our group has developed for electrocrystallization that are useful for electrochemical syntheses in general. Subsequently, we discuss different phase formation eventualities and propose basic rationalization concepts, illustrated with examples from our work. The scope of this report is to present electrocrystallization as a well-known yet underestimated synthetic process, especially in intermetallic chemistry. For this purpose we adduce literature examples (Li3Ga14, NaGa4, K8Ga8Sn38), technical advice, basic concepts, and new crystal structures only available by this method: Li3Ga13Sn and CsIn12. Electrocrystallization has recently proven especially helpful in our work concerning synthesis of intermetallic phases with polar metal-metal bonding, especially Hg-rich amalgams of less-noble metals. With the term "polar metal-metal bonding" we describe phases where the constituting elements have large electronegativity difference and yet show incomplete electron transfer from the less-noble to the nobler metal. This distinguishes polar intermetallic phases from classical Zintl phases where the electron transfer is virtually complete. Polar metallic phases can show "bad metal behavior" and interesting combinations of ionic and metallic properties. Amalgams of less-noble metals are preeminent representatives for this class of intermetallic phases as Hg is the only noble metal with endothermic electron affinity and thus a very low tendency toward anion formation. To illustrate both

  2. Synthesis, Structure and bonding Analysis of the Polar Intermetallic Phase Ca2Pt2Cd

    SciTech Connect

    Samal, Saroj L.; Corbett, John D.

    2012-08-14

    The polar intermetallic phase Ca2Pt2Cd was discovered during explorations of the Ca-Pt-Cd system. The compound was synthesized by high temperature reactions, and its structure refined by single-crystal X-ray diffraction as orthorhombic, Immm, a = 4.4514(5), b = 5.8415(6), c = 8.5976(9) Å, Z = 2. The structure formally contains infinite, planar networks of [Pt2Cd]4– along the ab plane, which can be described as tessellation of six and four-member rings of the anions, with cations stuffed between the anion layers. The infinite condensed platinum chains show a substantial long–short distortion of 0.52 Å, an appreciable difference between Ca2Pt2Cd (26 valence electrons) and the isotypic but regular Ca2Cu2Ga (29 VE). The relatively large cation proportion diminishes the usual dominance of polar (Pt–Cd) and 5d–5d (Pt–Pt) contributions to the total Hamilton populations.

  3. More statistics on intermetallic compounds - ternary phases.

    PubMed

    Dshemuchadse, Julia; Steurer, Walter

    2015-05-01

    How many different intermetallic compounds are known so far, and in how many different structure types do they crystallize? What are their chemical compositions, the most abundant ones and the rarest ones? These are some of the questions we are trying to find answers for in our statistical analysis of the structures of the 20,829 intermetallic phases included in the database Pearson's Crystal Data, with the goal of gaining insight into some of their ordering principles. In the present paper, we focus on the subset of 13,026 ternary intermetallics, which crystallize in 1391 different structure types; remarkably, 667 of them have just one representative. What makes these 667 structures so unique that they are not adopted by any other of the known intermetallic compounds? Notably, ternary compounds are known in only 5109 of the 85,320 theoretically possible ternary intermetallic systems so far. In order to get an overview of their chemical compositions we use structure maps with Mendeleev numbers as ordering parameters.

  4. Nonstoichiometry of Al-Zr intermetallic phases

    SciTech Connect

    Radmilovic, V.; Thomas, G.

    1994-06-01

    Nonstoichiometry of metastable cubic {beta}{prime} and equilibrium tetragonal {beta} Al-Zr intermetallic phases of the nominal composition Al{sub 3}Zr in Al-rich alloys has been extensively studied. It is proposed that the ``dark contrast`` of {beta}{prime} core in {beta}{prime}/{sigma}{prime} complex precipitates, in Al-Li-Zr based alloys, is caused by incorporation of Al and Li atoms into the {beta}{prime} phase on Zr sublattice sites, forming nonstoichiometric Al-Zr intermetallic phases, rather than by Li partitioning only. {beta}{prime} particles contain very small amounts of Zr, approximately 5 at.%, much less than the stoichiometric 25 at.% in the Al{sub 3}Zr metastable phase. These particles are, according to simulation of high resolution images, of the Al{sub 3}(Al{sub 0.4}Li{sub 0.4}Zr{sub 0.2}) type. Nonstoichiometric particles of average composition Al{sub 4}Zr and Al{sub 6}Zr are observed also in the binary Al-Zr alloy, even after annealing for several hours at 600{degree}C.

  5. Transient liquid phase bonding of intermetallics

    NASA Astrophysics Data System (ADS)

    Guan, Yimin

    The present work was undertaken to examine the applicability of transient liquid phase bonding to structural intermetallics. This research was based on an investigation of the mechanisms governing microstructural development in the joint and adjacent substrates during the joining process. The bonding systems investigated included polycrystalline NiAl/Cu/Ni, polycrystalline NiAl/Cu/superalloys (Martin-Marietta (MM)-247, Inconel (IN) 718 and Nimonic 90), single-crystal NiAl (with 1.5 at % Hf) joined to MM-247 using different filler metals (Cu foil, powder filler metal and electro-plated thin Cu film), and martensitic NiAl joined with martensitic NiTi using Cu foil and specially designed powder filler metals. In polycrystalline NiAl/Cu/Ni bonds, the mechanism of isothermal solidification is considered. Changes in the microstructure of the bond centerline due to element redistribution are discussed. The precipitation of both L1sb2 type gammasp' and B2 type beta phase at the joint centerline is investigated. The formation of martensitic L1sb0 type NiAl is also examined. The mechanical properties of the joints are investigated using shear strength and microhardness tests. In TLP bonding of polycrystalline NiAl with MM-247, both the epitaxial growth of the beta phase NiAl into the joint and the formation of non-epitaxial beta-phase layers are considered. The formation of second-phases, including the gammasp' phase, carbides, and sigma-phase intermetallics is also examined. Bond-line and adjacent substrate microstructures for the NiAl/Cu/MM-247 bonds are correlated with joint mechanical properties determined by room temperature shear testing. Single-crystal NiAl (1.5 at % Hf)/Cu/MM-247 joints are examined and compared with polycrystalline NiAl/Cu/MM247 joints. The effect of Hf on the microstructure of joints is investigated. The influence of different filler metals (i.e., wide-gap powder filler metal and electro-plated thin film filler metal) on the joining process is also

  6. BaHg2TI2. An Unusual Polar Intermetallic Phase with Strong Differentiation between the Neighboring elements Mercury and Thallium

    SciTech Connect

    Dai, Jing-Cao; Gupta, Shalabh; Gourdon, Olivier; Kim, Hyun-Jeong; Corbett, John D.

    2009-05-21

    High yields of the novel BaHg{sub 2}Tl{sub 2} are achieved from reactions of the appropriate cast alloys at 400 C. (Isotypic SrHg{sub 2}Tl{sub 2} also exists.) The tetragonal barium structure (P4{sub 2}/mnm, a = 10.606 {angstrom}, c = 5.159 {angstrom}) was refined from both single-crystal X-ray and neutron powder diffraction data in order to ensure the atom site assignments although distances and calculated atom site population also support the results. The Hg and Tl network atoms are distinctive in their functions and bonding. Parallel chains of Hg hexagons and of Tl tetrahedra along c are constructed from polyhedra that share opposed like edges, and these are in turn interconnected by Hg?Tl bonds. Overall, the number of Tl?Tl bonds per cell exceeds the Hg?Hg type by 20:12, but these are {approx} 1:2 each in bonding according to their average -ICOHP values (related to overlap populations). Barium is bound within a close 15-atom polyhedron, 12 atoms of which are the more electronegative Hg. LMTO-ASA calculations show that scalar relativistic effects are particularly important for Hg 5d?6s mixing in Hg?Hg and Hg?Tl bonding, whereas relatively separate Tl 6s and 6p states are more important in Tl?Tl interactions. The 6p states of Hg and Tl and 5d of Ba define a dominant conduction band around E{sub F}, and the phase is metallic and Pauli-like paramagnetic. The thallium characteristics here are close to those in numerous alkali-metal?Tl cluster systems. Other active metal?mercury phases that have been studied theoretically are all distinctly electron-richer and more reduced, and without appreciable net 5d, 6s contributions to Hg?Hg bonding.

  7. BaHg2Tl2. An Unusual Polar Intermetallic Phase with Strong DifferentiationBetween the Neighboring Elements Mercury and Thallium

    SciTech Connect

    Dai, Jing-Chao; Gupta, Shalabh; Gourdon, Olivier; Proffen, Th.; Corbett, John D

    2009-01-01

    High yields of the novel BaHg2Tl2 are achieved from reactions of the appropriate cast alloys at ~ 400 C. (Isotypic SrHg2Tl2 also exists.) The tetragonal barium structure (P42/mnm, a = 10.417, c = 4.952 ) was refined from both single crystal X-ray and neutron powder diffraction data in order to ensure the atom site assignments although distances and atom site potentials all also supportive of the results. The Hg and Tl network atoms are distinctive in their functions and bonding. Parallel chains of Hg hexagons and of Tl tetrahedra along c are constructed of like polyhedra that share opposed like edges, and these are in turn interconnected by Hg Tl bonds. Overall, Tl Tl bonds per cell exceed Hg Hg by 20:12 although these are ~1:2 in bonding according to the −ICOHP (≈ overlap population) values. Barium is bound within a close 15-atom polyhedron, 12 of which are the more electronegative Hg. LMTO-ASA calculations show that scalar relativistic effects are particularly important for Hg (5d-6s mixing in Hg Hg and Hg Tl bonding), whereas relatively separate (lower) 5d and 6s states of Tl are more important in Tl Tl interactions, appropriate to the 6s2 6p1 ground state for the atom. The highest occupied states define a dominantly 6p band, and the phase is metallic and Pauli-like paramagnetic. Binary active metal mercury systems that have been studied theoretically all have distinctly higher electron populations per mercury.

  8. Intermetallic R-phase in maraging steels of the Fe-Cr-Ni-Co-Mo system

    NASA Astrophysics Data System (ADS)

    Tarasenko, L. V.; Titov, V. I.

    2006-07-01

    Concentration and temperature conditions of formation of intermetallic R-phase in margining steels of the Fe-Cr-Ni-Co-Mo system are studied with the help of methods of physicochemical phase analysis and x-ray diffraction analysis. The role of chemical elements in the formation of the multicomponent R-phase is determined. A hypothesis employing the Kasper dimensional principle is suggested for multicomponent intermetallics formed in steels.

  9. Griffiths phase behaviour in a frustrated antiferromagnetic intermetallic compound

    PubMed Central

    Ghosh, Krishanu; Mazumdar, Chandan; Ranganathan, R.; Mukherjee, S.

    2015-01-01

    The rare coexistence of a Griffiths phase (GP) and a geometrically frustrated antiferromagnetism in the non-stoichiometric intermetallic compound GdFe0.17Sn2 (the paramagnetic Weiss temperature θp ~ −59 K) is reported in this work. The compound forms in the Cmcm space group with large structural anisotropy (b/c ~ 4). Interestingly, all the atoms in the unit cell possess the same point group symmetry (Wycoff position 4c), which is rather rare. The frustration parameter, f = |θp|/TN has been established as 3.6, with the Néel temperature TN and Griffiths temperature TG being 16.5 and 32 K, respectively. The TG has been determined from the heat capacity measurement and also from the magnetocaloric effect (MCE). It is also shown that substantial difference in GP region may exist between zero field and field cooled measurements - a fact hitherto not emphasized so far. PMID:26515256

  10. Thermal Stability of Intermetallic Phases in Fe-rich Fe-Cr-Ni-Mo Alloys

    NASA Astrophysics Data System (ADS)

    Yang, Ying; Tan, Lizhen; Busby, Jeremy T.

    2015-09-01

    Understanding the thermal stability of intermetallic phases in Fe-rich Fe-Cr-Ni-Mo alloys is critical to alloy design and application of Mo-containing austenitic steels. Coupled with thermodynamic modeling, the thermal stability of intermetallic Chi and Laves phases in two Fe-Cr-Ni-Mo alloys was investigated at 1273 K, 1123 K, and 973 K (1000 °C, 850 °C, and 700 °C) for different annealing times. The morphologies, compositions, and crystal structures of the precipitates of the intermetallic phases were carefully examined by scanning electron microscopy, electron probe microanalysis, X-ray diffraction, and transmission electron microscopy. Two key findings resulted from this study. First, the Chi phase is stable at high temperature, and with the decreasing temperature it transforms into the Laves phase that is stable at low temperature. Secondly, Cr, Mo, and Ni are soluble in both the Chi and Laves phases, with the solubility of Mo playing a major role in the relative stability of the intermetallic phases. The thermodynamic models that were developed were then applied to evaluating the effect of Mo on the thermal stability of intermetallic phases in type 316 and NF709 stainless steels.

  11. Numerical simulations of creep in ductile-phase toughened intermetallic matrix composites

    SciTech Connect

    Henshall, G.A.; Strum, M.J.

    1994-04-07

    Analytical and finite element method (FEM) simulations of creep in idealized ductile-phase toughened intermetallic composites are described. For these strong-matrix materials, the two types of analyses predict similar time-independent composite creep rates if each phase individually exhibits only steady-state creep. The composite creep rate becomes increasingly higher than that of the monolithic intermetallic as the stress exponent of the intermetallic and the volume fraction and creep rate of the ductile phase increase. FEM analysis shows that the shape of the ductile phase does not affect the creep rate but may affect the internal stress and strain distributions, and thus damage accumulation rates. If primary creep occurs in one or both of the individual phases, the composite also exhibits primary creep. In this case, there can be significant deviations in the creep curves computed by the analytical and FEM models. The model predictions are compared with data for the Nb5Si3/Nb system.

  12. Intermetallic Phase Formation in Explosively Welded Al/Cu Bimetals

    NASA Astrophysics Data System (ADS)

    Amani, H.; Soltanieh, M.

    2016-08-01

    Diffusion couples of aluminum and copper were fabricated by explosive welding process. The interface evolution caused by annealing at different temperatures and time durations was investigated by means of optical microscopy, scanning electron microscopy equipped with energy dispersive spectroscopy, and x-ray diffraction. Annealing in the temperature range of 573 K to 773 K (300 °C to 500 °C) up to 408 hours showed that four types of intermetallic layers have been formed at the interface, namely Al2Cu, AlCu, Al3Cu4, and Al4Cu9. Moreover, it was observed that iron trace in aluminum caused the formation of Fe-bearing intermetallics in Al, which is near the interface of the Al-Cu intermetallic layers. Finally, the activation energies for the growth of Al2Cu, AlCu + Al3Cu4, Al4Cu9, and the total intermetallic layer were calculated to be about 83.3, 112.8, 121.6, and 109.4 kJ/mol, respectively. Considering common welding methods ( i.e., explosive welding, cold rolling, and friction welding), although there is a great difference in welding mechanism, it is found that the total activation energy is approximately the same.

  13. Gas-phase modification of rare-earth intermetallic compounds

    SciTech Connect

    Skomski, R.; Coey, J.M.D. )

    1993-04-01

    Recent work concerning the interstitial modification of permanent magnet alloys based on rare-earth iron intermetallic compounds is reviewed. The crystal structure of the new materials is discussed, then the thermodynamic and statistical aspects of the low-temperature interstitial modification process are considered. Finally, reaction kinetics and thermal stability of the new compounds are discussed and future prospects assessed.

  14. Iron intermetallic phases in the Al corner of the Al-Si-Fe system

    NASA Astrophysics Data System (ADS)

    Khalifa, W.; Samuel, F. H.; Gruzleski, J. E.

    2003-03-01

    The iron intermetallics observed in six dilute Al-Si-Fe alloys were studied using thermal analysis, optical microscopy, and image, scanning electron microscopy/energy dispersive X-ray, and electron probe microanalysis/wavelength dispersive spectroscopy (EPMA/WDS) analyses. The alloys were solidified in two different molds, a preheated graphite mold (600°C) and a cylindrical metallic mold (at room temperature), to obtain slow (}0.2 °C/s) and rapid (}15 °C/s) cooling rates. The results show that the volume fraction of iron intermetallics obtained increases with the increase in the amount of Fe and Si added, as well as with the decrease in cooling rate. The low cooling rate produces larger-sized intermetallics, whereas the high cooling rate results in a higher density of intermetallics. Iron addition alone is more effective than either Si or Fe+Si additions in producing intermetallics. The alloy composition and cooling rate control the stability of the intermetallic phases: binary Al-Fe phases predominate at low cooling rates and a high Fe:Si ratio; the β-Al5FeSi phase is dominant at a high Si content and low cooling rate; the α-iron intermetallics (e.g., α-Al8Fe2Si) exist between these two; while Si-rich ternary phases such as the δ-iron Al4FeSi2 intermetallic are stabilized at high cooling rates and Si contents of 0.9 wt pct and higher. Calculations of the solidification paths representing segregations of Fe and Si to the liquid using the Scheil equation did not conform to the actual solidification paths, due to the fact that solid diffusion is not taken into account in the equation. The theoretical models of Brody and Flemings[44] and Clyne and Kurz[45] also fail to explain the observed departure from the Scheil behavior, because these models give less weight to the effect of solid back-diffusion. An adjusted 500°C metastable isothermal section of the Al-Si-Fe phase diagram has been proposed (in place of the equilibrium one), which correctly predicts the

  15. The preparation of the Ti-Al alloys based on intermetallic phases

    NASA Astrophysics Data System (ADS)

    Kosova, N.; Sachkov, V.; Kurzina, I.; Pichugina, A.; Vladimirov, A.; Kazantseva, L.; Sachkova, A.

    2016-01-01

    This article deals with a method of obtaining materials in the Ti-Al system. Research was carried out in accordance with the phase diagram of the system state. It was established, that both single-phase and multiphase systems, containing finely dispersed intermetallic compositions of phases Ti3Al, TiAl and TiAl3, are formed. Additionally, it was found that the pure finely dispersed (coherent-scattering region (CSR) up to 100 nm) intermetallic compound TiAl3 is formed at molar ratio of Ti:Al = 1:3. Experimentally proved the possibility of produce the complex composition of alloys and intermetallic compounds and products based on them.

  16. Phase-Controlled Polarization Modulators

    NASA Technical Reports Server (NTRS)

    Chuss, D. T.; Wollack, E. J.; Novak, G.; Moseley, S. H.; Pisano, G.; Krejny, M.; U-Yen, K.

    2012-01-01

    We report technology development of millimeter/submillimeter polarization modulators that operate by introducing a a variable, controlled phase delay between two orthogonal polarization states. The variable-delay polarization modulator (VPM) operates via the introduction of a variable phase delay between two linear orthogonal polarization states, resulting in a variable mapping of a single linear polarization into a combination of that Stokes parameter and circular (Stokes V) polarization. Characterization of a prototype VPM is presented at 350 and 3000 microns. We also describe a modulator in which a variable phase delay is introduced between right- and left- circular polarization states. In this architecture, linear polarization is fully modulated. Each of these devices consists of a polarization diplexer parallel to and in front of a movable mirror. Modulation involves sub-wavelength translations of the mirror that change the magnitude of the phase delay.

  17. Superplasticity and hot rolling of two-phase intermetallic alloy based on TiAl

    SciTech Connect

    Imayev, R.; Shagiev, M.; Salishchev, G.; Imayev, V.; Valitov, V.

    1996-03-15

    The recent investigations of superplasticity (SP) in intermetallic alloys indicate that these materials exhibit lower indices of SP (the relative elongation to rupture) at high enough homologous temperatures and low strain rates compared to conventional alloys. This behavior inhibits application of SP effects in intermetallics. The results of two-phase titanium alloys indicate that the combination of a high stable microstructure with a submicron grain size is necessary to realize the effect of SP at relatively high strain rates. The aim of the present work is to examine the SP behavior of a Ti-46at.%Al intermetallic alloy (TiAl + Ti{sub 3}Al) with micro- and submicron grain sizes and to apply obtained results in hot rolling.

  18. Polar Intermetallics Pr5Co2Ge3 and Pr7Co2Ge4 With Planar Hydrocarbon-Like Metal Clusters

    DOE PAGES

    Lin, Qisheng; Aguirre, Kaiser; Saunders, Scott M.; ...

    2017-06-19

    Planar hydrocarbon-like metal clusters may foster new insights linking organic molecules with conjugated π-π bonding interactions and inorganic structures in terms of their bonding characteristics. However, such clusters are uncommon in polar intermetallics. Herein, we report two polar intermetallic phases, Pr5Co2Ge3 and Pr7Co2Ge4, both of which feature such planar metal clusters, viz., ethylene-like [Co2Ge4] clusters plus the concatenated forms and polyacene-like [Co2Ge2]n ribbons in Pr5Co2Ge3, and 1,2,4,5-tetramethylbenzene-like [Co4Ge6] cluster in Pr7Co2Ge4. Just as in the related planar organic structures, these metal-metalloid species are dominated by covalent bonding interactions. Both compounds magnetically order at low temperature with net ferromagnetic components: Pr5Co2Ge3more » via a series of transitions below 150 K; and Pr7Co2Ge4 via a single ferromagnetic transition at 19 K. Spin-polarized electronic structure calculations for Pr7Co2Ge4 reveal strong spin-orbit coupling within Pr and considerable magnetic contributions from Co atoms. This work suggests that similar structural chemistry can emerge for other rare earth-late transition metal-main group systems.« less

  19. Experimental and theoretical investigations of the polar intermetallics SrPt3Al2 and Sr2Pd2Al

    NASA Astrophysics Data System (ADS)

    Stegemann, Frank; Benndorf, Christopher; Touzani, Rachid St.; Fokwa, Boniface P. T.; Janka, Oliver

    2016-10-01

    SrPt3Al2, a CaCu5 relative (P6/mmm; a = 566.29(3), c = 389.39(3) pm; wR2 = 0.0202, 121 F2 values, 9 parameters), and Sr2Pd2Al, isostructural to Ca2Pt2Ge (Fdd2; a = 1041.45(5), b = 1558.24(7), c = 604.37(3) pm; wR2 = 0.0291, 844 F2 values, 25 parameters) have been prepared from the elements. The crystal structures have been investigated by single crystal X-ray diffraction. Structural relaxation confirmed the electronic stability of SrPt3Al2, while orthorhombic Sr2Pd2Al might be a metastable polymorph as it is energetically competitive to its monoclinic variant. Both compounds are predicted to be metallic conductors as their density-of-states (DOS) are non-zero at the Fermi level. COHP bonding analysis coupled with Bader effective charge analysis suggest that the title compounds are polar intermetallic phases in which strong Pt-Al and Pd-Al covalent bonds are present, while a significant electron transfer from Sr atoms to the [Pt3Al2]δ- or [Pd2Al]δ- network is found.

  20. Chemical Frustration. A Design Principle for the Discovery of New Complex Alloy and Intermetallic Phases, Final Report

    SciTech Connect

    Fredrickson, Daniel C

    2015-06-23

    Final technical report for "Chemical Frustration: A Design Principle for the Discovery of New Complex Alloy and Intermetallic Phases" funded by the Office of Science through the Materials Chemistry Program of the Office of Basic Energy Sciences.

  1. A New Thermodynamic Parameter to Predict Formation of Solid Solution or Intermetallic Phases in High Entropy Alloys (Postprint)

    DTIC Science & Technology

    2015-11-02

    AFRL-RX-WP-JA-2016-0345 A NEW THERMODYNAMIC PARAMETER TO PREDICT FORMATION OF SOLID SOLUTION OR INTERMETALLIC PHASES IN HIGH ENTROPY...Interim 22 September 2014 – 21 September 2015 4. TITLE AND SUBTITLE A NEW THERMODYNAMIC PARAMETER TO PREDICT FORMATION OF SOLID SOLUTION OR...simple thermodynamic criterion is proposed to predict the presence or absence of equilibrium intermetallic phases in a high entropy alloy at a given

  2. Metastable phase formation in Be-Nb intermetallic compounds

    SciTech Connect

    Brimhall, J.L.; Charlot, L.A.; Bruemmer, S.M.

    1990-11-01

    Amorphous structures or metastable crystalline phases are produced in sputter-deposited Beryllium-Niobium (Be-Nb) alloys (5-15 at. % Nb) depending on the substrate temperature. The metastable phases transform to the stable Be{sub 12}Nb, Be{sub 17}Nb{sub 2}Nb phases on annealing at temperatures >800{degree}C. No Be{sub 5}Nb phase was found and the Be{sub 17}Nb{sub 2} phase is stable to low temperature. The Be{sub 12}Nb phase appeared to have a stoichiometric range of about 5.5 to 7.7 at. % Nb. The formation of the metastable phases is consistent with current models and theories. 17 refs., 1 fig., 2 tabs.

  3. Thermal oxidation of the intermetallic phases Al8Mo3 and AlMo3

    NASA Astrophysics Data System (ADS)

    Oster, Michael; Tapp, Joshua; Hagenow, Alexander; Möller, Angela

    2017-07-01

    The thermal oxidation reactions of the intermetallic phases Al8Mo3 and AlMo3 were investigated and analyzed by ex-situ powder-x-ray diffraction (XRD), difference thermal analysis (DTA), thermogravimetry (TGA), and infrared spectroscopy (IR). The initial oxidation reactions in air were found to yield Al2O3 and AlMo3 in the case of Al8Mo3 (Tonset =725 °C), and MoO3 as well as Al8-xMo3 (Tonset =435 °C) for the pure intermetallic phase AlMo3, respectively. Thus, both intermetallic phases are coexisting in an equilibrium within a temperature range of 300 °C under oxidizing conditions. The formation of β-Al2(MoO4)3 followed the second oxidizing process of the respective minority component at elevated temperatures. Decomposition and evaporation of the volatile MoO3 yielded α-Al2O3 as the residue at 1000 °C.

  4. Preparation of nanocrystalline metal oxides and intermetallic phases by controlled thermolysis of organometallic coordination polymers

    NASA Astrophysics Data System (ADS)

    Rehbein, Marcus; Epple, Matthias; Fischer, R. Dieter

    2000-06-01

    Organometallic coordination polymers of the super-Prussian blue type [(Me 3Sn) nM(CN) 6] (Me=CH 3; n=3, 4; M=Fe, Co, Ru) were subjected to thermolysis in different atmospheres (air, argon, hydrogen/nitrogen). In air, oxides were found: Fe 2O 3/SnO 2 (crystalline and nanocrystalline), Co 2SnO 4 and RuO 2. In argon and in hydrogen, the intermetallic phases FeSn 2, CoSn 2, Ru 3Sn 7 and Fe 3SnC were obtained. A detailed mechanistic study was carried out using thermogravimetry (TG), X-ray diffraction (XRD), X-ray absorption spectroscopy (EXAFS) at Fe, Co, Ru and Sn K-edges, infrared spectroscopy (IR) and elemental analysis. Below 250°C, Me 3SnCN and (CN) 2 are released, whereas above 250°C oxidation or pyrolysis leads to the corresponding oxides or intermetallic phases. Polymeric cyanides containing at least two metals have turned out to be suitable precursors to prepare well-defined oxides and intermetallic phases at comparatively low temperature.

  5. In situ XPS study of methanol reforming on PdGa near-surface intermetallic phases

    PubMed Central

    Rameshan, Christoph; Stadlmayr, Werner; Penner, Simon; Lorenz, Harald; Mayr, Lukas; Hävecker, Michael; Blume, Raoul; Rocha, Tulio; Teschner, Detre; Knop-Gericke, Axel; Schlögl, Robert; Zemlyanov, Dmitry; Memmel, Norbert; Klötzer, Bernhard

    2012-01-01

    In situ X-ray photoelectron spectroscopy and low-energy ion scattering were used to study the preparation, (thermo)chemical and catalytic properties of 1:1 PdGa intermetallic near-surface phases. Deposition of several multilayers of Ga metal and subsequent annealing to 503–523 K led to the formation of a multi-layered 1:1 PdGa near-surface state without desorption of excess Ga to the gas phase. In general, the composition of the PdGa model system is much more variable than that of its PdZn counterpart, which results in gradual changes of the near-surface composition with increasing annealing or reaction temperature. In contrast to near-surface PdZn, in methanol steam reforming, no temperature region with pronounced CO2 selectivity was observed, which is due to the inability of purely intermetallic PdGa to efficiently activate water. This allows to pinpoint the water-activating role of the intermetallic/support interface and/or of the oxide support in the related supported PdxGa/Ga2O3 systems, which exhibit high CO2 selectivity in a broad temperature range. In contrast, corresponding experiments starting on the purely bimetallic model surface in oxidative methanol reforming yielded high CO2 selectivity already at low temperatures (∼460 K), which is due to efficient O2 activation on PdGa. In situ detected partial and reversible oxidative Ga segregation on intermetallic PdGa is associated with total oxidation of intermediate C1 oxygenates to CO2. PMID:22875996

  6. Technetium Incorporation into C14 and C15 Laves Intermetallic Phases

    SciTech Connect

    Buck, Edgar C.; Schemer-Kohrn, Alan L.; Wierschke, Jonathan B.

    2013-01-23

    Laves-type intermetallics have been observed to be the dominant phases in a series of alloy compositions being designed for the immobilization technetium in a metallic waste form. The dominant metals in the alloy compositions were Fe-Mo and Fe-Mo-Zr. Alloy composition, Fe-Mo-Zr, also contained Pd, Zr, Cr, and Ni. Both non-radioactive rhenium-containing and radioactive technetium-bearing alloy compositions were investigated. In the Fe-Mo series, phases were observed Fe2Mo (C14 Laves phase) and ferrite in agreement with predictions. Both Tc and Re resided predominantly in the Laves phase. In the Fe-Mo-Zr system, the phases included hexagonal C14 with the composition (Fe,Cr)2Mo, cubic C15 phase with a (Fe,Ni)2Zr composition, and the hcp phase Pd2Zr.

  7. Pressure-Induced Phase Transition and Mechanical Properties of Mg2Sr Intermetallics

    PubMed Central

    Yan, Haiyan; Han, Xingming; Zheng, Baobing

    2016-01-01

    A pressure-induced phase transition of Mg2Sr intermetallics from the low-pressure C14-type phase to an orthorhombic phase (space group Cmcm, Z = 4) at a high pressure of 21.0 GPa was firstly predicted using first-principles calculations combined with unbiased swarm structure searching techniques. The phase transition was identified as a first-order nature with a volume drop of 4.7%, driven by the softening of elastic behavior at high pressure. Further phonon calculations indicate that the newly predicted orthorhombic phase is dynamically stable at high pressure and ambient pressure. The mechanical properties including the elastic anisotropy of this orthorhombic phase were thus fully studied at ambient pressure. The elastic anisotropy behavior of this orthorhombic phase was investigated by the distributions of elastic moduli. The evidence of the bonding nature of Mg–Sr was also manifested by density of states (DOS) and electronic localization function (ELF) calculations. PMID:28774023

  8. Irradiation induced structural change in Mo2Zr intermetallic phase

    DOE PAGES

    Gan, J.; Keiser, Jr., D. D.; Miller, B. D.; ...

    2016-05-14

    The Mo2Zr phase has been identified as a major interaction product at the interface of U-10Mo and Zr. Transmission electron microscopy in-situ irradiation with Kr ions at 200 °C with doses up to 2.0E+16 ions/cm2 was carried out to investigate the radiation stability of the Mo2Zr. The Mo2Zr undergoes a radiation-induced structural change, from a large cubic (cF24) to a small cubic (cI2), along with an estimated 11.2% volume contraction without changing its composition. The structural change begins at irradiation dose below 1.0E+14 ions/cm2. Furthermore, the transformed Mo2Zr phase demonstrates exceptional radiation tolerance with the development of dislocations without bubblemore » formation.« less

  9. The Role of Phase Stability in Ductile, Ordered B2 Intermetallics

    SciTech Connect

    Morris, James R; Ye, Y. Y.; Krcmar, Maja; Fu, Chong Long

    2007-01-01

    We discuss the underlying atomistic mechanism for experimentally observed large tensile ductility in various strongly ordered B2 intermetallic compounds. First-principles calculations demonstrate that all of the compounds exhibit little energy differences between the B2, B27 and B33 phases. These calculations relate observations of ductility in YAg, YCu and ZrCo to shape-memory materials including NiTi. One transformation pathway between the B2 and B33 phases establishes a connection between this phase competition, and stacking faults on the {l_brace}011{r_brace}B2 plane. The low energy of such a stacking fault will lead to splitting of the b=<100> dislocations into b/2 partials, observed in ZrCo, TiCo, and in the B19' phase of NiTi. Calculations demonstrate that this pathway is competitive with the traditional pathway for NiTi.

  10. Intermetallic phase detection in lead-free solders using synchrotron x-ray diffraction

    NASA Astrophysics Data System (ADS)

    Jackson, Gavin J.; Lu, Hua; Durairaj, Raj; Hoo, Nick; Bailey, Chris; Ekere, Ndy N.; Wright, Jon

    2004-12-01

    The high-intensity, high-resolution x-ray source at the European Synchrotron Radiation Facility (ESRF) has been used in x-ray diffraction (XRD) experiments to detect intermetallic compounds (IMCs) in lead-free solder bumps. The IMCs found in 95.5Sn3.8Ag0.7Cu solder bumps on Cu pads with electroplated-nickel immersion-gold (ENIG) surface finish are consistent with results based on traditional destructive methods. Moreover, after positive identification of the IMCs from the diffraction data, spatial distribution plots over the entire bump were obtained. These spatial distributions for selected intermetallic phases display the layer thickness and confirm the locations of the IMCs. For isothermally aged solder samples, results have shown that much thicker layers of IMCs have grown from the pad interface into the bulk of the solder. Additionally, the XRD technique has also been used in a temperature-resolved mode to observe the formation of IMCs, in situ, during the solidification of the solder joint. The results demonstrate that the XRD technique is very attractive as it allows for nondestructive investigations to be performed on expensive state-of-the-art electronic components, thereby allowing new, lead-free materials to be fully characterized.

  11. Growth of new ternary intermetallic phases from Ca/Zn eutectic flux

    SciTech Connect

    Stojanovic, Milorad Latturner, Susan E.

    2007-03-15

    The eutectic 7.3:2.7 molar ratio mixture of calcium and zinc metal melts at 394 deg. C and was explored as a solvent for the growth of new intermetallic phases for potential use as hydrogen storage materials. The reaction of nickel in this molten mixture produces two new phases-the CaCu{sub 5}-related structure CaNi{sub 2}Zn{sub 3} (P6/mmm, a=8.9814(5) A, c=4.0665(5) A) and a new cubic structure Ca{sub 21}Ni{sub 2}Zn{sub 36} (Fd-3m, a=21.5051(4) A). Palladium-containing reactions produced CaPd{sub 0.85}Zn{sub 1.15} with the orthorhombic TiNiSi structure type (Pnma, a=7.1728(9) A, b=4.3949(5) A, c=7.7430(9) A). Reactions of platinum in the Ca/Zn mixture produce Ca{sub 6}Pt{sub 3}Zn{sub 5}, with an orthorhombic structure related to that of W{sub 3}CoB{sub 3} (Pmmn, a=13.7339(9) A, b=4.3907(3) A, c=10.7894(7) A). - Graphical abstract: The calcium/zinc eutectic is a useful synthesis medium for the growth of new intermetallic phases. Addition of group 10 transition metals to this flux produces ternary phases CaNi{sub 2}Zn{sub 3}, Ca{sub 21}Ni{sub 2}Zn{sub 36}, CaPd{sub 0.85}Zn{sub 1.15}, and Ca{sub 6}Pt{sub 3}Zn{sub 5}. The nickel-centered zinc icosahedron surrounded by a pentagonal dodecahedron of calcium atoms is found in Ca{sub 21}Ni{sub 2}Zn{sub 36}.

  12. Self-Supported Mesostructured Pt-Based Bimetallic Nanospheres Containing an Intermetallic Phase as Ultrastable Oxygen Reduction Electrocatalysts.

    PubMed

    Kim, Ho Young; Cho, Seonghun; Sa, Young Jin; Hwang, Sun-Mi; Park, Gu-Gon; Shin, Tae Joo; Jeong, Hu Young; Yim, Sung-Dae; Joo, Sang Hoon

    2016-10-01

    Developing highly active and stable cathode catalysts is of pivotal importance for proton exchange membrane fuel cells (PEMFCs). While carbon-supported nanostructured Pt-based catalysts have so far been the most active cathode catalysts, their durability and single-cell performance are yet to be improved. Herein, self-supported mesostructured Pt-based bimetallic (Meso-PtM; M = Ni, Fe, Co, Cu) nanospheres containing an intermetallic phase are reported, which can combine the beneficial effects of transition metals (M), an intermetallic phase, a 3D interconnected framework, and a mesoporous structure. Meso-PtM nanospheres show enhanced oxygen reduction reaction (ORR) activity, compared to Pt black and Pt/C catalysts. Notably, Meso-PtNi containing an intermetallic phase exhibits ultrahigh stability, showing enhanced ORR activity even after 50 000 potential cycles, whereas Pt black and Pt/C undergo dramatic degradation. Importantly, Meso-PtNi with an intermetallic phase also demonstrated superior activity and durability when used in a PEMFC single-cell, with record-high initial mass and specific activities. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Influence of the Heterogeneous Nucleation Sites on the Kinetics of Intermetallic Phase Formation in Aged Duplex Stainless Steel

    NASA Astrophysics Data System (ADS)

    Melo, Elis Almeida; Magnabosco, Rodrigo

    2017-09-01

    The aim of this work is to study the influence of the heterogeneous nucleation site quantity, observed in different ferrite and austenite grain size samples, on the phase transformations that result in intermetallic phases in a UNS S31803 duplex stainless steel (DSS). Solution treatment was conducted for 1, 24, 96, or 192 hours at 1373 K (1100 °C) to obtain different ferrite and austenite grain sizes. After solution treatment, isothermal aging treatments for 5, 8, 10, 20, 30, or 60 minutes at 1123 K (850 °C) were performed to verify the influence of different amounts of heterogeneous nucleation sites in the kinetics of intermetallic phase formation. The sample solution treated for 1 hour, with the highest surface area between matrix phases, was the one that presented, after 60 minutes at 1123 K (850 °C), the smaller volume fraction of ferrite (indicative of greater intermetallic phase formation), higher volume of sigma (that was present in coral-like and compact morphologies), and chi phase. It was not possible to identify which was the first nucleated phase, sigma or chi. It was also observed that the phase formation kinetics is higher for the sample solution treated for 1 hour. It was evidenced that, from a certain moment on, the chi phase begins to be consumed due to the sigma phase formation, and the austenite/ferrite interface presents higher S V for all solution treatment times. It was also observed that intermetallic phases form preferably in austenite-ferrite interfaces, although the higher occupation rate occurs at triple junction ferrite-ferrite-ferrite. It was verified that there was no saturation of nucleation sites in any interface type nor triple junction, and the equilibrium after 1 hour of aging at 1123 K (850 °C) was not achieved. It was then concluded that sigma phase formation is possibly controlled by diffusional processes, without saturation of nucleation sites.

  14. Phase stability and elasticity of C15 transition-metal intermetallic compounds

    SciTech Connect

    Chu, F.; Mitchell, T.E.; Chen, S.P.; Sob, M.; Siegl, R.; Pope, D.P.

    1995-03-01

    First-principle quantum mechanical calculations based on the local-density-functional theory have been performed to study the electronic, physical and metallurgical properties of C15 intermetallics MV{sub 2} (M = Zr, Hf, or Ta). The elastic constants of C15 HfV{sub 2} + Nb were measured by the resonant ultrasound spectroscopy technique. The phase stability of C15 HfV{sub 2} + Nb was studied by specific heat measurements and by transmission electron microscopy in a low temperature specimen holder. The total energies and their lattice volume dependence were used to obtain the equilibrium lattice constants and bulk modulus. The band structures at the X-point near the Fermi level were employed to understand the anomalous temperature dependence of shear modulus of the C15 intermetallics. It was found that the double degeneracy with a linear dispersion relation of electronic levels at the X-point near the Fermi surface is mainly responsible for the C15 anomalous elasticity. The density of states at the Fermi level, N(E{sub F}), and the Fermi surface geometry were obtained to understand the low temperature phase instability of C15 HfV{sub 2} and ZrV{sub 2} and the stability of C15 TaV{sub 2}. It was proposed that the large N(E{sub F}) and Fermi surface nesting are the physical reasons for the structural instability of the C15 HfV{sub 2} and ZrV{sub 2} at low temperatures. The relation between anomalous elasticity and structural instability of C15 HfV{sub 2} and ZrV{sub 2} is also discussed.

  15. Effect of Intermetallic Compound Phases on the Mechanical Properties of the Dissimilar Al/Cu Friction Stir Welded Joints

    NASA Astrophysics Data System (ADS)

    Khodir, S. A.; Ahmed, M. M. Z.; Ahmed, Essam; Mohamed, Shaymaa M. R.; Abdel-Aleem, H.

    2016-11-01

    Types and distribution of intermetallic compound phases and their effects on the mechanical properties of dissimilar Al/Cu friction stir welded joints were investigated. Three different rotation speeds of 1000, 1200 and 1400 rpm were used with two welding speeds of 20 and 50 mm/min. The results show that the microstructures inside the stir zone were greatly affected by the rotation speed. Complex layered structures that containing intermetallic compound phases such as CuAl2, Al4Cu9 were formed in the stir zone. Their amount found to be increased with increasing rotation speed. However, the increasing of the rotation speed slightly lowered the hardness of the stir zone. Many sharp hardness peaks in the stir zones were found as a result of the intermetallic compounds formed, and the highest peaks of 420 Hv were observed at a rotation speed of 1400 rpm. The joints ultimate tensile strength reached a maximum value of 105 MPa at the rotation speed of 1200 rpm and travel speed of 20 mm/min with the joint efficiency ranged between 88 and 96% of the aluminum base metal. At the travel speed of 50 mm/min, the maximum value of the ultimate tensile strength was 96 MPa at rotation speed of 1400 rpm with the joint efficiency ranged between 79 and 90%. The fracture surfaces of tensile test specimens showed no evidence for the effect of the brittle intermetallic compounds in the stir zones on the tensile strength of the joints.

  16. Structural properties, phase stability, elastic properties and electronic structures of Cu-Ti intermetallics

    NASA Astrophysics Data System (ADS)

    Chen, Shuai; Duan, Yong-Hua; Huang, Bo; Hu, Wen-Cheng

    2015-11-01

    The structural properties, phase stabilities, anisotropic elastic properties and electronic structures of Cu-Ti intermetallics have been systematically investigated using first principles based on the density functional theory. The calculated equilibrium structural parameters agree well with available experimental data. The ground-state convex hull of formation enthalpies as a function of Cu content is slightly symmetrical at CuTi with a minimal formation enthalpy (-13.861 kJ/mol of atoms), which indicates that CuTi is the most stable phase. The mechanical properties, including elastic constants, polycrystalline moduli and anisotropic indexes, were evaluated. G/B is more pertinent to hardness than to the shear modulus G due to the high power indexes of 1.137 for G/B. The mechanical anisotropy was also characterized by describing the three-dimensional (3D) surface constructions. The order of elastic anisotropy is Cu4Ti3 > Cu3Ti2 > α-Cu4Ti > Cu2Ti > CuTi > β-Cu4Ti > CuTi2. Finally, the electronic structures were discussed and Cu2Ti is a semiconductor.

  17. Growth of intermetallic phases in Al/Cu composites at various annealing temperatures during the ARB process

    NASA Astrophysics Data System (ADS)

    Hsieh, Chih-Chun; Shi, Ming-Shou; Wu, Weite

    2012-02-01

    The purpose of this study is to discuss the effect of annealing temperatures on growth of intermetallic phases in Al/Cu composites during the accumulative roll bonding (ARB) process. Pure Al (AA1100) and pure Cu (C11000) were stacked into layered structures at 8 cycles as annealed at 300 °C and 400 °C using the ARB technique. Microstructural results indicate that the necking of layered structures occur after 300 °C annealing. Intermetallic phases grow and form a smashed morphology of Al and Cu when annealed at 400 °C. From the XRD and EDS analysis results, the intermetallic phases of Al2Cu (θ) and Al4Cu9 (γ2) formed over 6 cycles and the AlCu (η2) precipitated at 8 cycles after 300 °C annealing. Three phases (Al2Cu (θ), Al4Cu9 (γ2), and AlCu (η2)) were formed over 2 cycles after 400 °C annealing.

  18. Kinetic Stabilization of Ordered Intermetallic Phases as Fuel Cell Anode Materials

    SciTech Connect

    Liu, Yi; Lowe, Michael A.; DiSalvo, Francis J.; Abruña, Héctor D.

    2010-08-16

    The influence of fuel molecules on the stability of the ordered intermetallic PtBi and PtPb phases has been extensively studied by synchrotron-based in situ X-ray grazing incidence diffraction under active electrochemical control. Cycling the potential to increasingly positive values resulted in little change to the surface composition and crystalline structure when specific fuel molecules (such as formic acid for PtBi and formic acid or methanol for PtPb) were oxidized at the intermetallic electrode surface. This was demonstrated by the absence of diffraction peaks due to Pt domains that would be generated by the leaching out of the less noble metal. This phenomenon has been rationalized as a competition process between the oxidation of fuel molecules at the electrode surface and corrosion and damage of the surface due to the electrochemical treatment. For example, PtBi electrodes, which exhibit excellent catalytic activity toward the oxidation of formic acid, could be kinetically stabilized to such a corrosion/degradation process in the presence of formic acid even at relatively positive potentials. An analogous effect was observed for PtPb in the presence of methanol as fuel. In the absence of fuel molecules (formic acid for PtBi and formic acid and/or methanol for PtPb), various surface layers were generated by different electrochemical pretreatments in the presence of only a supporting electrolyte. Crystalline oxidized bismuth species (such as Bi2O3) with an ~50 nm domain size were formed on the PtBi electrode surface by holding the potential at +1.00 V or beyond for at least 30 min. On the other hand, platinum nanopaticles with an ~5 nm crystalline domain size were formed when cycling the potential to higher values. In the case of PtPb, the only detected corrosion product was PbSO 4, whose diffraction peaks were utilized to qualitatively analyze the lead leaching-out and dissolution processes. No crystalline lead oxide species

  19. Discovery and characterization of magnetism in sigma-phase intermetallic Fe-Re compounds

    SciTech Connect

    Cieślak, J. Dubiel, S. M.; Tobola, J.; Reissner, M.

    2014-11-14

    Systematic experimental studies (vibrating sample magnetometry) supported by theoretical calculations (electronic structure by spin self-consistent Korringa-Kohn-Rostoker Green's function method) were performed on a series of intermetallic sigma-phase Fe{sub 100−x}Re{sub x} (x = 43–53) compounds. All investigated samples exhibit magnetism with an ordering temperature ranging between ∼65 K for x = 43 and ∼23 K for x = 53. The magnetism was revealed to be itinerant and identified as a spin-glass (SG) possibly having a re-entrant character. The SG was found to be heterogeneous, viz., two regimes could be distinguished as far as irreversibility in temperature dependence of magnetization is concerned: (1) of a weak irreversibility and (2) of a strong one. According to the theoretical calculations, the main contribution to the magnetism comes from Fe atoms occupying all five sub lattices, while Re atoms have rather small magnetic moments. However, the calculated average magnetic moments highly (ferromagnetic ordering model) or moderately (antiparallel ordering model) overestimate the experimental data.

  20. Data on a Laves phase intermetallic matrix composite in situ toughened by ductile precipitates.

    PubMed

    Knowles, Alexander J; Bhowmik, Ayan; Purkayastha, Surajit; Jones, Nicholas G; Giuliani, Finn; Clegg, William J; Dye, David; Stone, Howard J

    2017-10-01

    The data presented in this article are related to the research article entitled "Laves phase intermetallic matrix composite in situ toughened by ductile precipitates" (Knowles et al.) [1]. The composite comprised a Fe2(Mo, Ti) matrix with bcc (Mo, Ti) precipitated laths produced in situ by an aging heat treatment, which was shown to confer a toughening effect (Knowles et al.) [1]. Here, details are given on a focused ion beam (FIB) slice and view experiment performed on the composite so as to determine that the 3D morphology of the bcc (Mo, Ti) precipitates were laths rather than needles. Scanning transmission electron microscopy (S(TEM)) micrographs of the microstructure as well as energy dispersive X-ray spectroscopy (EDX) maps are presented that identify the elemental partitioning between the C14 Laves matrix and the bcc laths, with Mo rejected from the matrix into laths. A TEM selected area diffraction pattern (SADP) and key is provided that was used to validate the orientation relation between the matrix and laths identified in (Knowles et al.) [1] along with details of the transformation matrix determined.

  1. Ba 5Ti 12Sb 19+x, a polar intermetallic compound with a stuffed γ-brass structure

    NASA Astrophysics Data System (ADS)

    Bie, Haiying; Mar, Arthur

    2009-11-01

    The polar intermetallic compound Ba 5Ti 12Sb 19+x ( x⩽0.2) has been synthesized by reaction of the elements. Single-crystal X-ray diffraction analysis revealed that it adopts a new structure type (Ba 5Ti 12Sb 19.102(6), space group P43¯m, Z=2, a=12.4223(11) Å, V=1916.9(3) Å 3). The set of Ba and Sb sites corresponds to the structure of Cu 9Al 4, a γ-brass type with a primitive cell. A complex three-dimensional framework of Ti atoms, in the form of linked planar Ti 9 clusters, is stuffed within the γ-brass-type Ba-Sb substructure. Notwithstanding its relationship to the γ-brass structure, the compound does not appear to conform to the Hume-Rothery electron concentration rules. Band structure calculations on an idealized Ba 5Ti 12Sb 19 model suggest that the availability of bonding states above the Fermi level is responsible for the partial occupation, but only to a limited degree, of an additional Sb site within the structure. Magnetic measurements indicated Pauli paramagnetic behaviour.

  2. Crystal structure and chemical bonding of novel Li-containing polar intermetallic compound La11Li12Ge16

    NASA Astrophysics Data System (ADS)

    Jung, Yaho; Nam, Gnu; Jeon, Jieun; Kim, Youngjo; You, Tae-Soo

    2012-12-01

    A novel Li-containing polar intermetallic compound La11Li12Ge16 has been synthesized using the high-temperature reaction method and characterized by both powder and single-crystal X-ray diffractions. The title compound crystallized in the orthorhombic crystal system (space group Immm, Z=2, Pearson symbol oI78) with fifteen crystallographically unique atomic positions in the asymmetric unit, and the lattice parameters are refined as a=4.5244(4) Å, b=6.9932(6) Å, and c=53.043(5) Å. The complex crystal structure of the title compound can be described as a 2:1 intergrowth of two closely related compounds: La2Li2Ge3 (Ce2Li2Ge3-type) and La3Li4Ge4 (Zr3Cu4Si4-type) acting like “building-blocks” along the c-axis. Six La sites are categorized into three distinct types based on the local coordination environment showing the coordination numbers of 12-14. Three unique Li sites are placed in the centers of local tetrahedra formed by four Ge atoms which eventually construct Ge2 dimers or 1-dimensional cis-/trans-Ge chains. Theoretical investigations using the tight-binding linear muffin-tin orbital (LMTO) method provide rationales for an improved structural stability and for unique local coordination geometries established by anionic elements including [LiGe4] tetrahedra, cis-/trans-Ge chain and Ge2 dimers.

  3. Effect of chromium on the formation of intermetallic phases in hot-dipped aluminide Cr-Mo steels

    NASA Astrophysics Data System (ADS)

    Cheng, Wei-Jen; Wang, Chaur-Jeng

    2013-07-01

    Cr-Mo steels with different chromium contents were coated by hot-dipping into molten baths containing pure aluminum and Al-10 wt.% Si for 180 s. The effect of chromium content in the steels on the formation of the intermetallic phases in the aluminide coatings was studied. The results show that all the aluminide coatings can be distinguished into an outer pure aluminum or Al-Si topcoat and an inner intermetallic layer. The intermetallic layers, resulting from the steels hot-dipped in pure aluminum, have the same phase constitution, an outer minor FeAl3 and an inner major Fe2Al5. In the aluminide coatings on the steels with 0 and 2.25 wt.% chromium after hot-dipping in Al-10 wt.% Si, the intermetallic layers were composed of an outer layer of τ5(H)-Al7(Fe,Cr)2Si and an inner one of FeAl3/τ1-(Al,Si)5Fe3/Fe2Al5, while a small amount of polyhedral τ5(H)-Al7(Fe,Cr)2Si and plate-shaped τ6-Al4FeSi were observed in the Al-Si topcoats. In the aluminide coatings on the steels with 5 and 9 wt.% chromium after hot-dipping in Al-10 wt.% Si, the intermetallic layers were composed of only a τ5(H)-Al7(Fe,Cr)2Si phase. A large amount of scattered granular τ5(C)-Al7(Fe,Cr)2Si and a small amount of plate-shaped τ4-Al3FeSi2 and τ6-Al4FeSi were also found in the Al-Si topcoats. When the chromium content reached 5 wt.%, the amount of steel, which dissolved when samples were hot-dipped in Al-10 wt.% Si, increased. Also, the rate of dissolving went up as chromium content went up. The increase of dissolution is because the interdiffusion between steels and Al-10 wt.% Si bath was enhanced by the formation of scattered granular τ5(C)-Al7(Fe,Cr)2Si, which was stabilized by chromium.

  4. X-ray nano-diffraction study of Sr intermetallic phase during solidification of Al-Si hypoeutectic alloy

    SciTech Connect

    Manickaraj, Jeyakumar; Gorny, Anton; Shankar, Sumanth; Cai, Zhonghou

    2014-02-17

    The evolution of strontium (Sr) containing intermetallic phase in the eutectic reaction of Sr-modified Al-Si hypoeutectic alloy was studied with high energy synchrotron beam source for nano-diffraction experiments and x-ray fluorescence elemental mapping. Contrary to popular belief, Sr does not seem to interfere with the Twin Plane Re-entrant Edge (TPRE) growth mechanism of eutectic Si, but evolves as the Al{sub 2}Si{sub 2}Sr phase during the eutectic reaction at the boundary between the eutectic Si and Al grains.

  5. Intermetallic and metal-rich phases in the system Li-Ba-In-N

    NASA Astrophysics Data System (ADS)

    Smetana, Volodymyr; Vajenine, Grigori V.; Kienle, Lorenz; Duppel, Viola; Simon, Arndt

    2010-08-01

    Three new intermetallic phases, BaLi 2.1In 1.9, BaLi 1.12In 0.98, and BaLi 1.06In 1.16 and two subnitrides Li 35In 45Ba 39N 9 and LiIn 2Ba 3N 0.83 have been synthesized and their crystal structures have been determined. According to single crystal X-ray diffraction data BaLi 2.1In 1.9 and BaLi 1.12In 0.98 crystallize with hexagonal symmetry (BaLi 2.1In 1.9: P6 3/ mmc, a=10.410(2), c=8.364(2) Å, Z=6, V=785.0(2) Å 3) and BaLi 1.12In 0.98: P6/ mmm, a=17.469(1), c=10.6409(7) Å, Z=30, V=2813.5(8) Å 3), while BaLi 1.06In 1.16 has a rhombohedral structure ( R-3 c, a=18.894(3), c=85.289(17) Å, Z=276, V=26368(8) Å 3). BaLi 2.1In 1.9 is isostructural with the known phase BaLi 4. The phase BaLi 1.12In 0.98 is structurally related to Na 8K 23Cd 12In 48, while BaLi 1.06In 1.16 is isostructural with Li 33.3Ba 13.1Ca 3. A sample containing structurally similar BaLi 1.12In 0.98 and BaLi 1.02In 1.16 was also investigated by transmission electron microscopy. Li 35In 45Ba 39N 9 and LiIn 2Ba 3N 0.83 crystallize with tetragonal ( I-42 m, a=15.299(2), c=30.682(6) Å, Z=2, V=7182(2) Å 3) and cubic ( Fd-3 m, a=14.913(2) Å, Z=8, V=3316.7(7) Å 3) symmetry, respectively. While the first-mentioned subnitride belongs to the Li 80Ba 39N 9 structure type, the second extends the structural family of Ba 6In 4.78N 2.72. The structural features of the new compounds are discussed in comparison to the known phases and the results of total energy calculations.

  6. Crystal structure, chemical bonding and magnetism studies for three quinary polar intermetallic compounds in the (Eu(1-x)Ca(x))9In8(Ge(1-y)Sn(y))8 (x = 0.66, y = 0.03) and the (Eu(1-x)Ca(x))3In(Ge(3-y)Sn(1+y)) (x = 0.66, 0.68; y = 0.13, 0.27) phases.

    PubMed

    Woo, Hyein; Jang, Eunyoung; Kim, Jin; Lee, Yunho; Kim, Jongsik; You, Tae-Soo

    2015-04-22

    Three quinary polar intermetallic compounds in the (Eu(1-x)Ca(x))9In8(Ge(1-y)Sn(y))8 (x = 0.66, y = 0.03) and the (Eu(1-x)Ca(x))3In(Ge(3-y)Sn(1+y)) (x = 0.66, 0.68; y = 0.13, 0.27) phases have been synthesized using the molten In-metal flux method, and the crystal structures are characterized by powder and single-crystal X-ray diffractions. Two orthorhombic structural types can be viewed as an assembly of polyanionic frameworks consisting of the In(Ge/Sn)4 tetrahedral chains, the bridging Ge2 dimers, either the annulene-like "12-membered rings" for the (Eu(1-x)Ca(x))9In8(Ge(1-y)Sn(y))8 series or the cis-trans Ge/Sn-chains for the (Eu(1-x)Ca(x))3In(Ge(3-y)Sn(1+y)) series, and several Eu/Ca-mixed cations. The most noticeable difference between two structural types is the amount and the location of the Sn-substitution for Ge: only a partial substitution (11%) occurs at the In(Ge/Sn)4 tetrahedron in the (Eu(1-x)Ca(x))9In8(Ge(1-y)Sn(y))8 series, whereas both a complete and a partial substitution (up to 27%) are observed, respectively, at the cis-trans Ge/Sn-chain and at the In(Ge/Sn)4 tetrahedron in the (Eu(1-x)Ca(x))3In(Ge(3-y)Sn(1+y)) series. A series of tight-binding linear muffin-tin orbital calculations is conducted to understand overall electronic structures and chemical bonding among components. Magnetic susceptibility measurement indicates a ferromagnetic ordering of Eu atoms below 5 K for Eu1.02(1)Ca1.98InGe2.87(1)Sn1.13.

  7. SrZn{sub 2}Sn{sub 2} and Ca{sub 2}Zn{sub 3}Sn{sub 6} - two new Ae-Zn-Sn polar intermetallic compounds (Ae: alkaline earth metal)

    SciTech Connect

    Stegmaier, Saskia; Faessler, Thomas F.

    2012-08-15

    SrZn{sub 2}Sn{sub 2} and Ca{sub 2}Zn{sub 3}Sn{sub 6}, two closely related new polar intermetallic compounds, were obtained by high temperature reactions of the elements. Their crystal structures were determined with single crystal XRD methods, and their electronic structures were analyzed by means of DFT calculations. The Zn-Sn structure part of SrZn{sub 2}Sn{sub 2} comprises (anti-)PbO-like {l_brace}ZnSn{sub 4/4}{r_brace} and {l_brace}SnZn{sub 4/4}{r_brace} layers. Ca{sub 2}Zn{sub 3}Sn{sub 6} shows similar {l_brace}ZnSn{sub 4/4}{r_brace} layers and {l_brace}Sn{sub 4}Zn{r_brace} slabs constructed of a covalently bonded Sn scaffold capped by Zn atoms. For both phases, the two types of layers are alternatingly stacked and interconnected via Zn-Sn bonds. SrZn{sub 2}Sn{sub 2} adopts the SrPd{sub 2}Bi{sub 2} structure type, and Ca{sub 2}Zn{sub 3}Sn{sub 6} is isotypic to the R{sub 2}Zn{sub 3}Ge{sub 6} compounds (R=La, Ce, Pr, Nd). Band structure calculations indicate that both SrZn{sub 2}Sn{sub 2} and Ca{sub 2}Zn{sub 3}Sn{sub 6} are metallic. Analyses of the chemical bonding with the electron localization function (ELF) show lone pair like basins at Sn atoms and Zn-Sn bonding interactions between the layers for both title phases, and covalent Sn-Sn bonding within the {l_brace}Sn{sub 4}Zn{r_brace} layers of Ca{sub 2}Zn{sub 3}Sn{sub 6}. - Graphical abstract: Crystal structures of the new Ae-Zn-Sn polar intermetallic phases SrZn{sub 2}Sn{sub 2} and Ca{sub 2}Zn{sub 3}Sn{sub 6}. Highlights: Black-Right-Pointing-Pointer New polar intermetallic phases SrZn{sub 2}Sn{sub 2} and Ca{sub 2}Zn{sub 3}Sn{sub 6}. Black-Right-Pointing-Pointer Obtained by high temperature reactions of the elements. Black-Right-Pointing-Pointer Single crystal XRD structure determination and DFT electronic structure calculations. Black-Right-Pointing-Pointer Closely related crystal and electronic structures. Black-Right-Pointing-Pointer Metallic conductivity coexisting with lone pairs and covalent bonding

  8. Studies of magnetostriction and spin polarized band structures of rare earth intermetallics

    NASA Technical Reports Server (NTRS)

    Wallace, W. E.

    1979-01-01

    Anisotropic magnetostriction measurements of R6Fe23, R = (Tb, Dy, Ho, and Er) were carried out from 77 K to room temperature. Magnetic fields up to 2.1 Tesla were applied. All the compounds exhibited large magnetostrictions at 77 K, the largest effect being obtained for Tb6Fe23. Saturation magnetostriction values for the compounds were also determined for 77 K and room temperature. Results of the temperature dependence of magnetostriction for Er6Fe23 are in good agreement with Callen and Callen's single ion theory. Therefore, the main sources of magnetostriction in this compound is the Er ion. The spin-up and spin-down electronic energy bands, the density of states and the magnetic moments of YCo5, SmCo5, and GdCo5 were calculated by the spin polarized augmented plane wave technique. The calculations obtained show the origin of the moment, provide good estimates of its magnitude and variation, and the reasons for those variations. They also show the important role of partial charge transfer and of d-d electronic coupling. Calculations for LaNi5 and GdNi5 systems are discussed.

  9. A Review of the Influence of Production Methods and Intermetallic Phases on the Creep Properties of AZ91

    NASA Astrophysics Data System (ADS)

    Roodposhti, Peiman Shahbeigi; Sarkar, Apu; Murty, Korukonda Linga

    A review on the creep properties of AZ91 magnesium alloys is presented with a major emphasis on the influence of production methods that include steel mold casting, die casting and Thixoforming. Various creep characteristics such as the stress exponent and activation energy along with their resistance to creep for the alloys produced via different methods are compared. Role of intermetallic phases resulting from various alloying additions such as Si, Sb, Bi, Ca and rare earth elements on different creep mechanisms (grain boundary sliding and dislocation glide/climb) are also evaluated.

  10. Polar intermetallic compounds of the silicon and arsenic family elements and their ternary hydrides and fluorides

    SciTech Connect

    Leon-Escamilla, E.A.

    1996-10-17

    An investigation has been made on the effects of hydrogen and fluoride in the solid state chemistry of alkaline-earth and divalent rare-earth metal pnictide (Pn) and tetrelide (Tt) phases A{sub 5}(Pn,Tt,){sub 3}Z{sub x}, where A = Ca, Sr, Ba, Sm, Eu, Yb; Pn = As, Sb, Bi; Tt = Si, Ge, Sn, Pb and Z = H, F. Several trivalent rare-earth-metal pnictides, RE{sub 5}Pn{sub 3} (RE = Y, La, Gd, Tb, Dy, Ho, Er, Tm) and alkaline-earth-metal trielides, A{sub 5}Tr{sub 3}Z{sub x} (Tr = Ga, In, Tl) have been included in an effort to complete observed structural trends. Two main experimental techniques were followed throughout this work, (a) reactions in absence of hydrogen or under continuous high vacuum, and (b) reactions with binary metal hydrides, AH{sub x}, in closed containers. The results demonstrate that all the phases reported with the {beta}-Yb{sub 5}Sb{sub 3}-type structure in the A{sub 5}Pn{sub 3} systems are hydrogen-stabilized compounds. Reactions in absence of hydrogen lead to compounds with the Mn{sub 5}Si{sub 3}-type structure. The structure type {beta}-Yb{sub 5}Sb{sub 3} (= Ca{sub 5}SB{sub 3}F) was found to be characteristic of ternary systems and inaccurately associated with phases that form in the Y{sub 5}Bi{sub 3}-type. A new series of isomorphous Zintl compounds with the Ca{sub 16}Sb{sub 11}-type structure were prepared and studied as well. All the alkaline-earth-metal tetrelides, A{sub 5}Tt{sub 3}, that crystallize in the Cr{sub 5}B{sub 3}-type structure can be interstitially derivatized by hydrogen or fluoride. Binary and ternary compounds were characterized by Guinier powder patterns, single crystal X-ray and powder neutron diffraction techniques. In an effort to establish property-structure relationships, electrical resistivity and magnetic measurements were performed on selected systems, and the results were explained in terms of the Zintl concepts, aided by extended Hueckel band calculations.

  11. Contrasts in Structural and Bonding Representations among Polar Intermetallic Compounds. Strongly Differentiated Hamilton Populations for Three Related Condensed Cluster Halides of the Rare-Earth Elements

    SciTech Connect

    Gupta, Shalabh; Meyer, Gerd; Corbett, John D.

    2010-10-01

    The crystal and electronic structures of three related R{sub 3}TnX{sub 3} phases (R = rare-earth metal, Tn = transition metal, X = Cl, I) containing extended mixed-metal chains are compared and contrasted: (1) Pr{sub 3}RuI{sub 3} (P2{sub 1}/m), (2) Gd{sub 3}MnI{sub 3} (P2{sub 1}/m), and (3) Pr{sub 3}RuCl{sub 3} (Pnma). The structures all feature double chains built of pairs of condensed R{sub 6}(Tn) octahedral chains encased by halogen atoms. Pr{sub 3}RuI{sub 3} (1) lacks significant Ru-Ru bonding, evidently because of packing restrictions imposed by the large closed-shell size of iodine. However, the vertex Pr2 atoms on the chain exhibit a marked electronic differentiation. These are strongly bound to the central Ru (and to four I), but very little to four neighboring Pr in the cluster according to bond populations, in contrast to Pr2-Pr 'bond' distances that are very comparable to those elsewhere. In Gd{sub 3}MnI{sub 3} (2), the smaller metal atoms allow substantial distortions and Mn-Mn bonding. Pr{sub 3}RuCl{sub 3} (3), in contrast to the iodide (1), can be described in terms of a more tightly bound superstructure of (2) in which both substantial Ru-Ru bonding and an increased number of Pr-Cl contacts in very similar mixed-metal chains are favored by the smaller closed-shell contacts of chlorine. Local Spin Density Approximation (LSDA) Linearized Muffin-Tin Orbital (LMTO)-ASA calculations and Crystal Orbital Hamilton Population (COHP) analyses show that the customary structural descriptions in terms of condensed, Tn-stuffed, R-R bonded polyhedral frameworks are poor representations of the bonding in all. Hamilton bond populations (-ICOHP) for the polar mixed-metal R-Tn and the somewhat smaller R-X interactions account for 75-90% of the total populations in each of these phases, together with smaller contributions and variations for R-R and Tn-Tn interactions. The strength of such R-Tn contributions in polar intermetallics was first established or anticipated by

  12. Phase Stability of Intermetallic Compound Ce3Al in Mechanical Milling

    NASA Astrophysics Data System (ADS)

    Zhang, Yan-ping; Takeya, Hiroyuki; Sakurai, Kenji

    2017-09-01

    For many years, cerium-aluminum systems have been extensively studied because of their unusual magnetic behavior. As the atomic radii of cerium and aluminum differ greatly from each other, a solid solution is not obtained because of the Hume-Rothery rule. Therefore, intermetallic compounds are usually studied, and structural stability is crucial for further discussion of their physical properties. The present article reports on high-energy ball milling of the intermetallic compound Ce3Al at room temperature. It has been found that non-equilibrium supersaturated Ce solid solution was formed during the milling. The solubility of aluminum was estimated as 5 to 13 at. pct from the peak shifts of the X-ray diffraction pattern. The structural changes in the initial stages of the milling were also studied.

  13. Polarization Imager Technology. Phase I

    DTIC Science & Technology

    2007-11-02

    orientation axes (e.g., with a polarizing filter). Resolving image irradiance at three (3) unique orientations is sufficient for unique measurement. Using...an orientation reference and resolving the electric field at relative 0’, 450, 900, if the image irradiances obtained at each pixel are respectively...with the video rate of the camera. See Figure 2. The unpolarized component is not effected . Each TN liquid crystal is binary in the sense that it either

  14. Intermetallic nanoparticles

    DOEpatents

    Singh, Dileep; Yusufoglu, Yusuf; Timofeeva, Elena; Routbort, Jules

    2015-07-14

    A process for preparing intermetallic nanoparticles of two or more metals is provided. In particular, the process includes the steps: a) dispersing nanoparticles of a first metal in a solvent to prepare a first metal solution, b) forming a reaction mixture with the first metal solution and a reducing agent, c) heating the reaction mixture to a reaction temperature; and d) adding a second metal solution containing a salt of a second metal to the reaction mixture. During this process, intermetallic nanoparticles, which contain a compound with the first and second metals are formed. The intermetallic nanoparticles with uniform size and a narrow size distribution is also provided. An electrochemical device such as a battery with the intermetallic nanoparticles is also provided.

  15. Intermetallic nanoparticles

    DOEpatents

    Singh, Dileep; Yusufoglu, Yusuf; Timofeeva, Elena; Routbort, Jules L.

    2017-01-03

    A process for preparing intermetallic nanoparticles of two or more metals is provided. In particular, the process includes the steps: a) dispersing nanoparticles of a first metal in a solvent to prepare a first metal solution, b) forming a reaction mixture with the first metal solution and a reducing agent, c) heating the reaction mixture to a reaction temperature; and d) adding a second metal solution containing a salt of a second metal to the reaction mixture. During this process, intermetallic nanoparticles, which contain a compound with the first and second metals are formed. The intermetallic nanoparticles with uniform size and a narrow size distribution is also provided. An electrochemical device such as a battery with the intermetallic nanoparticles is also provided.

  16. Intermetallic nanoparticles

    SciTech Connect

    Singh, Dileep; Yusufoglu, Yusuf; Timofeeva, Elena; Routbort, Jules L.

    2015-11-20

    A process for preparing intermetallic nanoparticles of two or more metals is provided. In particular, the process includes the steps: a) dispersing nanoparticles of a first metal in a solvent to prepare a first metal solution, b) forming a reaction mixture with the first metal solution and a reducing agent, c) heating the reaction mixture to a reaction temperature; and d) adding a second metal solution containing a salt of a second metal to the reaction mixture. During this process, intermetallic nanoparticles, which contain a compound with the first and second metals are formed. The intermetallic nanoparticles with uniform size and a narrow size distribution is also provided. An electrochemical device such as a battery with the intermetallic nanoparticles is also provided.

  17. Exploring phase stability, electronic and mechanical properties of Ce–Pb intermetallic compounds using first-principles calculations

    SciTech Connect

    Tao, Xiaoma; Wang, Ziru; Lan, Chunxiang; Xu, Guanglong; Ouyang, Yifang; Du, Yong

    2016-05-15

    The phase stability, electronic and mechanical properties of Ce–Pb intermetallics have been investigated by using first-principles calculations. Five stable and four metastable phases of Ce–Pb intermetallics were verified. Among them, CePb{sub 2} has been confirmed as HfGa{sub 2}-type structure. For Ce{sub 5}Pb{sub 3}, the high pressure phase transformation from D8{sub m} to D8{sub 8} with trivalent Ce has been predicted to occur at P=1.2 GPa and a high temperature phase transformation has been predicted from D8{sub m} to D8{sub 8} with tetravalent Ce at 531.5 K. The calculated lattice constants of the five stable phases are in good agreement with experimental values. The electronic density of states, charge density and electron localization function of Ce{sub 3}Pb have been calculated, which indicated that the Ce and Pb show ionic behavior. The polycrystalline bulk modulus, shear modulus, Young's modulus, and Poisson's ratio are also estimated from the calculated single crystalline elastic constants. All of the calculated elastic constants satisfy mechanical stability criteria. The microhardness and mechanical anisotropy are predicted. The anisotropic nature of the Ce–Pb intermetallic compounds are demonstrated by the three-dimensional orientation dependent surfaces of Young's moduli and linear compressibility are also demonstrated. The longitudinal, transverse and average sound velocities and the Debye temperatures are also obtained in this work. The Ce{sub 3}Pb has the largest Debye temperature of 192.6 K, which means the Ce{sub 3}Pb has a highest melting point and high thermal conductivity than other compounds. - Graphical abstract: The convex hull plots of the enthalpies of formation for Ce–Pb binary systems calculated at 0 K. - Highlights: • The five stable and four metastable phases in the Ce–Pb binary system were predicted. • The crystal structure of CePb{sub 2} has been confirmed as HfGa{sub 2}-type.

  18. Multiscale modeling of the influence of Fe content in a Al-Si-Cu alloy on the size distribution of intermetallic phases and micropores

    NASA Astrophysics Data System (ADS)

    Wang, Junsheng; Li, Mei; Allison, John; Lee, Peter D.

    2010-03-01

    A multiscale model was developed to simulate the formation of Fe-rich intermetallics and pores in quaternary Al-Si-Cu-Fe alloys. At the microscale, the multicomponent diffusion equations were solved for multiphase (liquid-solid-gas) materials via a finite difference framework to predict microstructure formation. A fast and robust decentered plate algorithm was developed to simulate the strong anisotropy of the solid/liquid interfacial energy for the Fe-rich intermetallic phase. The growth of porosity was controlled by local pressure drop due to solidification and interactions with surrounding solid phases, in addition to hydrogen diffusion. The microscale model was implemented as a subroutine in a commercial finite element package, producing a coupled multiscale model. This allows the influence of varying casting conditions on the Fe-rich intermetallics, the pores, and their interactions to be predicted. Synchrotron x-ray tomography experiments were performed to validate the model by comparing the three-dimensional morphology and size distribution of Fe-rich intermetallics as a function of Fe content. Large platelike Fe-rich β intermetallics were successfully simulated by the multiscale model and their influence on pore size distribution in shape castings was predicted as a function of casting conditions.

  19. Formation of intermetallic phases in AlSi7Fe1 alloy processed under microgravity and forced fluid flow conditions and their influence on the permeability

    NASA Astrophysics Data System (ADS)

    Steinbach, S.; Ratke, L.; Zimmermann, G.; Budenkova, O.

    2016-03-01

    Ternary Al-6.5wt.%Si-0.93wt.%Fe alloy samples were directionally solidified on-board of the International Space Station ISS in the ESA payload Materials Science Laboratory (MSL) equipped with Low Gradient Furnace (LGF) under both purely diffusive and stimulated convective conditions induced by a rotating magnetic field. Using different analysis techniques the shape and distribution of the intermetallic phase β-Al5SiFe in the dendritic microstructure was investigated, to study the influence of solidification velocity and fluid flow on the size and spatial arrangement of intermetallics. Deep etching as well as 3-dimensional computer tomography measurements characterized the size and the shape of β-Al5SiFe platelets: Diffusive growth results in a rather homogeneous distribution of intermetallic phases, whereas forced flow promotes an increase in the amount and the size of β-Al5SiFe platelets in the centre region of the samples. The β-Al5SiFe intermetallics can form not only simple platelets, but also be curved, branched, crossed, interacting with dendrites and porosity located. This leads to formation of large and complex groups of Fe-rich intermetallics, which reduce the melt flow between dendrites leading to lower permeability of the mushy zone and might significantly decrease feeding ability in castings.

  20. Kinetics of the Formation of Intermetallic Phases in HP-Type Heat-Resistant Alloys at Long-Term High-Temperature Exposure

    NASA Astrophysics Data System (ADS)

    Kondrat'ev, Sergey Yu.; Anastasiadi, Grigoriy P.; Petrov, Sergey N.; Ptashnik, Alina V.

    2017-01-01

    The kinetics of formation and morphology of the intermetallic phases in the structure of heat-resistant as-cast HP40NbTi alloys in the course of long high-temperature exposure have been studied with the help of light and electron microscopy, electron microprobe, and X-ray diffraction. During exposure of 2 to 1000 hours at 1423 K (1150 °C), intermetallic phase with conditional formula Cr7Ni5Si3N3FeNb is formed in the alloy. The analysis of the kinetics of intermetallic phase's growth for an impact assessment of certain metal substitutional elements (niobium, chromium, silicon) on the size of the formed particles was performed. Formation and growth of the intermetallic phases with high silicon content in the alloy structure on the boundaries between niobium and chromium carbides (NbC and M23C6) and matrix γ-phase provide a diffusion barrier for oxygen in oxidizing environment. This may create partial protection against oxidation of hardening carbide phases in the structure and promote increasing of the serviceability of the HP series alloys under operating conditions in the petrochemical industry.

  1. Phase and texture evolution in solution deposited lead zirconate titanate thin films: Formation and role of the Pt3Pb intermetallic phase

    NASA Astrophysics Data System (ADS)

    Nittala, Krishna; Mhin, Sungwook; Dunnigan, Katherine M.; Robinson, Douglas S.; Ihlefeld, Jon F.; Kotula, Paul G.; Brennecka, Geoff L.; Jones, Jacob L.

    2013-06-01

    Solution deposition is widely used for the fabrication of lead zirconate titanate (PZT) thin films on platinized silicon substrates. However, phase and texture evolution during the crystallization process is not well understood, particularly due to the difficulty in tracking changes in the thin films in situ during heating. In this work, we characterized phase and texture evolution in situ during heating and crystallization of PZT thin films using high-energy X-ray diffraction. Films were pyrolyzed at either 300 °C or 400 °C and heated at various rates between 0.5 °C/s and ˜150 °C/s. For films that were pyrolyzed at 300 °C, the most rapid heating rates first induced strong intensities from a transient Pt3Pb phase. The Pt3Pb phase inherited the texture of the pre-existing platinum layer. Combined with other observations, the results suggest the conversion of the platinum to the intermetallic phase near the interface due to the interdiffusion of lead. In all experimental variations, the pyrochlore phase was observed to form concurrently with the disappearance of the Pt3Pb phase after which the perovskite phase ultimately crystallized. For films that were pyrolyzed at 400 °C, the Pt3Pb phase was not observed at any of the heating rates; instead, the pyrochlore phase was first observed, followed by the perovskite phase. Independent of the pyrolysis temperature or observation of Pt3Pb, a 111-dominant crystallographic texture formed in the perovskite phase when crystallized using fast heating rates. These results demonstrate that 111 textures in solution-derived PZT thin films are not correlated with the observation of Pt3Pb or other intermetallic or transient phases.

  2. Prediction of intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Burkhanov, Gennady S.; Kiselyova, N. N.

    2009-06-01

    The problems of predicting not yet synthesized intermetallic compounds are discussed. It is noted that the use of classical physicochemical analysis in the study of multicomponent metallic systems is faced with the complexity of presenting multidimensional phase diagrams. One way of predicting new intermetallics with specified properties is the use of modern processing technology with application of teaching of image recognition by the computer. The algorithms used most often in these methods are briefly considered and the efficiency of their use for predicting new compounds is demonstrated.

  3. Structural, electronic and elastic properties of RERu2 (RE=Pr and Nd) Laves phase intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Shrivastava, Deepika; Sanyal, Sankar P.

    2016-05-01

    We have performed the first-principles calculations to study the structural, electronic and elastic properties of RERu2 (RE = Pr and Nd) Laves phase intermetallic compounds using full-potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT) within the generalized gradient approximation (GGA) for exchange and correlation potential. The optimized lattices constant are in reasonable agreement with available experimental data. The electronic properties are analyzed in terms of band structures, total and partial density of states, which confirm their metallic character. The calculated elastic constants infer that these compounds are mechanically stable in C15 (MgCu2 type) structure and found to be ductile in nature.

  4. Structural, electronic and elastic properties of RERu{sub 2} (RE=Pr and Nd) Laves phase intermetallic compounds

    SciTech Connect

    Shrivastava, Deepika Sanyal, Sankar P.

    2016-05-06

    We have performed the first-principles calculations to study the structural, electronic and elastic properties of RERu{sub 2} (RE = Pr and Nd) Laves phase intermetallic compounds using full-potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT) within the generalized gradient approximation (GGA) for exchange and correlation potential. The optimized lattices constant are in reasonable agreement with available experimental data. The electronic properties are analyzed in terms of band structures, total and partial density of states, which confirm their metallic character. The calculated elastic constants infer that these compounds are mechanically stable in C15 (MgCu{sub 2} type) structure and found to be ductile in nature.

  5. Quantum many-body intermetallics: Phase stability of Fe3Al and small-gap formation in Fe2VAl

    NASA Astrophysics Data System (ADS)

    Kristanovski, Oleg; Richter, Raphael; Krivenko, Igor; Lichtenstein, Alexander I.; Lechermann, Frank

    2017-01-01

    Various intermetallic compounds harbor subtle electronic correlation effects. To elucidate this fact for the Fe-Al system, we perform a realistic many-body investigation based on a combination of density functional theory with dynamical mean-field theory in a charge self-consistent manner. A better characterization and understanding of the phase stability of bcc-based D 03-Fe3Al through an improved description of the correlated charge density and the magnetic energy is achieved. Upon replacement of one Fe sublattice with V, the Heusler compound Fe2VAl is realized, known to display bad-metal behavior and increased specific heat. Here we document a charge-gap opening at low temperatures in line with previous experimental work. The gap structure does not match conventional band theory and is reminiscent of (pseudo)gap characteristics in correlated oxides.

  6. Crystal structure and chemical bonding of novel Li-containing polar intermetallic compound La{sub 11}Li{sub 12}Ge{sub 16}

    SciTech Connect

    Jung, Yaho; Nam, Gnu; Jeon, Jieun; Kim, Youngjo; You, Tae-Soo

    2012-12-15

    A novel Li-containing polar intermetallic compound La{sub 11}Li{sub 12}Ge{sub 16} has been synthesized using the high-temperature reaction method and characterized by both powder and single-crystal X-ray diffractions. The title compound crystallized in the orthorhombic crystal system (space group Immm, Z=2, Pearson symbol oI78) with fifteen crystallographically unique atomic positions in the asymmetric unit, and the lattice parameters are refined as a=4.5244(4) A, b=6.9932(6) A, and c=53.043(5) A. The complex crystal structure of the title compound can be described as a 2:1 intergrowth of two closely related compounds: La{sub 2}Li{sub 2}Ge{sub 3} (Ce{sub 2}Li{sub 2}Ge{sub 3}-type) and La{sub 3}Li{sub 4}Ge{sub 4} (Zr{sub 3}Cu{sub 4}Si{sub 4}-type) acting like 'building-blocks' along the c-axis. Six La sites are categorized into three distinct types based on the local coordination environment showing the coordination numbers of 12-14. Three unique Li sites are placed in the centers of local tetrahedra formed by four Ge atoms which eventually construct Ge{sub 2} dimers or 1-dimensional cis-/trans-Ge chains. Theoretical investigations using the tight-binding linear muffin-tin orbital (LMTO) method provide rationales for an improved structural stability and for unique local coordination geometries established by anionic elements including [LiGe{sub 4}] tetrahedra, cis-/trans-Ge chain and Ge{sub 2} dimers. - Graphical abstract: Reported is a novel ternary Li-containing polar intermetallic compound La{sub 11}Li{sub 12}Ge{sub 16}. The complex crystal structure can be viewed as a simple combination of two closely related known compounds acting as 'building-blocks', La{sub 2}Li{sub 2}G{sub 3} and La{sub 3}Li{sub 4}Ge{sub 4}, in a 2:1 stoichiometric ratio. Highlights: Black-Right-Pointing-Pointer A novel Li-containing polar intermetallic compound La{sub 11}Li{sub 12}Ge{sub 16} was synthesized. Black-Right-Pointing-Pointer The complex crystal structure was easily explained as

  7. Test data for the calculation of powder paterns for intermetallic phases

    SciTech Connect

    Calvert, L.D.; Mueller, M.H.; Wallace, P.L.; Huang, J.A.; Kaduk, J.A.; Dann, J.N.; Roberts, A.C

    1996-09-01

    Powder diffraction patterns are often calculated from structural parameters to assist in the identification of materials. To ensure that powder pattern calculations are correct, it is useful to have data to test the computer program doing the calculations. this paper contains test data for each of the crystallographic point groups and 63 of the 230 space groups. An important feature of the data is that many tests involve two high-symmetry structures (sodium and magnesium) that are set in successively lower-symmetry space groups. Thus, the calculated powder intensities for sodium, for example, are identical whatever the setting is. Though the data were chosen to be especially useful for the calculation of the powder patterns of metals and intermetallic compounds, the data have wider utility.

  8. Section 2: Phase transformation studies in mechanically alloyed Fe-Nz and Fe-Zn-Si intermetallics

    SciTech Connect

    Jordan, A.; Uwakweh, O.N.C.; Maziasz, P.J.

    1997-04-01

    The initial stage of this study, which was completed in FY 1995, entailed an extensive analysis characterizing the structural evolution of the Fe-Zn intermetallic system. The primary interest in these Fe-Zn phases stems from the fact that they form an excellent coating for the corrosion protection of steel (i.e., automobile body panels). The Fe-Zn coating generally forms up to four intermetallic phases depending on the particular industrial application used, (i.e., galvanization, galvannealing, etc.). Since the different coating applications are non-equilibrium in nature, it becomes necessary to employ a non-equilibrium method for producing homogeneous alloys in the solid-state to reflect the structural changes occurring in a true coating. This was accomplished through the use of a high energy/non-equilibrium technique known as ball-milling which allowed the authors to monitor the evolution process of the alloys as they transformed from a metastable to stable equilibrium state. In FY 1996, this study was expanded to evaluate the presence of Si in the Fe-Zn system and its influence in the overall coating. The addition of silicon in steel gives rise to an increased coating. However, the mechanisms leading to the coating anomaly are still not fully understood. For this reason, mechanical alloying through ball-milling of pure elemental powders was used to study the structural changes occurring in the sandelin region (i.e., 0.12 wt % Si). Through the identification of invariant reactions (i.e., eutectic, etc.) the authors were able to explore the sandelin phenomenon and also determine the various fields or boundaries associated with the Fe-Zn-Si ternary system.

  9. The Phase Composition of Triton's Polar Caps.

    PubMed

    Duxbury, N S; Brown, R H

    1993-08-06

    Triton's polar caps are modeled as permanent nitrogen deposits hundreds of meters thick. Complex temperature variations on Triton's surface induce reversible transitions between the cubic and hexagonal phases of solid nitrogen, often with two coexisting propagating transition fronts. Subsurface temperature distributions are calculated using a two-dimensional thermal model with phase changes. The phase changes fracture the upper nitrogen layer, increasing its reflectivity and thus offering an explanation for the surprisingly high southern polar cap albedo (approximately 0.8) seen during the Voyager 2 flyby. The model has other implications for the phase transition phenomena on Triton, such as a plausible mechanism for the origin of geyser-like plume vent areas and a mechanism of energy transport toward them.

  10. The phase composition of Triton's polar caps

    NASA Technical Reports Server (NTRS)

    Duxbury, N. S.; Brown, R. H.

    1993-01-01

    Triton's polar caps are modeled as permanent nitrogen deposits hundreds of meters thick. Complex temperature variations on Triton's surface induce reversible transitions between the cubic and hexagonal phases of solid nitrogen, often with two coexisting propagating transition fronts. Subsurface temperature distributions are calculated using a two-dimensional thermal model with phase changes. The phase changes fracture the upper nitrogen layer, increasing its reflectivity and thus offering an explanation for the surprisingly high southern polar cap albedo (approximately 0.8) seen during the Voyager 2 flyby. The model has other implications for the phase transition phenomena on Triton, such as a plausible mechanism for the origin of geyser-like plume vent areas and a mechanism of energy transport toward them.

  11. TEM study of the martensitic phases in the ductile DyCu and YCu intermetallic compounds [The martensitic phase transformation in ductile DyCu and YCu intermetallic compounds

    DOE PAGES

    Cao, G. H.; Oertel, C. -G.; Schaarschuch, R.; ...

    2017-05-03

    DyCu and YCu are representatives of the family of CsCl-type B2 rare earth intermetallic compounds that exhibit high room temperature ductility. Structure, orientation relationship, and morphology of the martensites in the equiatomic compounds DyCu and YCu are examined using transmission electron microscopy (TEM). TEM studies show that the martensite structures in DyCu and YCu alloys are virtually identical. The martensite is of orthorhombic CrB-type B33 structure with lattice parameters a = 0.38 nm, b = 1.22 nm, and c = 0.40 nm. (021¯) twins were observed in the B33 DyCu and YCu martensites. The orientation relationship of B33 and B2more » phases is (111¯)[112]B33 || (110)[001]B2. The simulated electron diffraction patterns of the B33 phase are consistent with those of experimental observations. TEM investigations also reveal that a dominant orthorhombic FeB-type B27 martensite with lattice parameters a = 0.71 nm, b = 0.45 nm, and c = 0.54 nm exists in YCu alloy. (11¯ 1) twins were observed in the B27 YCu martensite. As a result, the formation mechanism of B2 to B33 and B2 to B27 phase transformation is discussed.« less

  12. Innovative processing to produce advanced intermetallic materials. Phase 1 final report

    SciTech Connect

    Loutfy, R.O.

    1989-09-01

    The program demonstrates the technical feasibility of synthesizing submicron titanium aluminide in a thermal rf plasma. Micron and submicron spherical titanium aluminide particles are produced in argon, hydrogen, and argon/hydrogen plasmas from the reaction of TiCl4(g), and Al(g). The ratio of Ti and Al is varied to produce the compounds Ti3Al, TiAl, and TiAl3. Microalloying with boron and macroalloying with niobium is demonstrated. Ti3Al whiskers can be produced, as well as other intermetallics of niobium aluminide, nickel aluminide, and molybdenum disilicide in the plasma synthesis process. Since submicron particles are produced, they have a high surface area and are sensitive to oxidation if not treated with a fugitive protective coating or utilized in a nonoxidizing atmosphere. Ti3Al particles are consolidated and utilized as a matrix for TiC and AlN composites. The submicron AlTi3 has significantly higher strength at room temperature than reported for commercial Ti3Al-11Nb alloy and useable strength is maintained up to 1000 C. The elongation is about the same as for commercial material because of possible oxide contamination in powder handling. However, dimpling and nacking is evident in the fracture surface, which suggests true room temperature ductility. Titanium aluminides have the potential to replace superalloys and become the dominant material for aerospace engines, air frames and skins for hypersonic vehicles.

  13. Theoretical screening of intermetallic ThMn12-type phases for new hard-magnetic compounds with low rare earth content

    PubMed Central

    Körner, Wolfgang; Krugel, Georg; Elsässer, Christian

    2016-01-01

    We report on theoretical investigations of intermetallic phases derived from the ThMn12-type crystal structure. Our computational high-throughput screening (HTS) approach is extended to an estimation of the anisotropy constant K1, the anisotropy field Ha and the energy product (BH)max. The calculation of K1 is fast since it is based on the crystal field parameters and avoids expensive total-energy calculations with many k-points. Thus the HTS approach allows a very efficient search for hard-magnetic materials for which the magnetization M and the coercive field Hc connected to Ha represent the key quantities. Besides for NdFe12N which has the highest magnetization we report HTS results for several intermetallic phases based on Cerium which are interesting as alternative hard-magnetic phases because Cerium is a less ressource-critical element than Neodymium. PMID:27098547

  14. The polarization phase difference of orchard trees

    NASA Technical Reports Server (NTRS)

    Wang, James R.; Mo, Tsan

    1990-01-01

    An image obtained by the Jet Propulsion Laboratory's airborne L-band polarimeter (SAR) over an agricultural area near Fresno, California, was analyzed for the signatures of polarization phase difference (PPD). The PPD of orchard trees was found to be distinctly different from that of bare fields or fields covered with other crops. Thus the PPD signatures obtained from a polarimeter may be useful in the understanding of the radar remote sensing of the earth's surface.

  15. The polarization phase difference of orchard trees

    NASA Technical Reports Server (NTRS)

    Wang, James R.; Mo, Tsan

    1990-01-01

    An image obtained by the Jet Propulsion Laboratory's airborne L-band polarimeter (SAR) over an agricultural area near Fresno, California, was analyzed for the signatures of polarization phase difference (PPD). The PPD of orchard trees was found to be distinctly different from that of bare fields or fields covered with other crops. Thus the PPD signatures obtained from a polarimeter may be useful in the understanding of the radar remote sensing of the earth's surface.

  16. Study of fatigue and fracture behavior of NbCr{sub 2}-based alloys and intermetallic materials: Phase stability in NbCr{sub 2} Laves phase alloys

    SciTech Connect

    Zhu, J.H.; Liaw, P.K.; Liu, C.T.

    1996-08-01

    Phase stability in NbCr{sub 2}-based transition-metal Laves phases is studied in this paper, using data from binary X-Cr, Nb-X, and ternary Nb-Cr-X phase diagrams. It was shown that when the atomic size ratios are kept identical, the average electron concentration factor (e/a = the average number of electrons per atom outside the closed shells of the component atoms) is the determinate factor in controlling the phase stability of NbCr{sub 2}-based transition-metal Laves phases. The e/a ratios for different Laves phase structures were determined as follows: with e/a < 5.76, the C15 structure is stabilized; at an e/a range of 5.88-7.53, the C14 structure is stabilized; with e/a > 7.65, the C15 structure was stabilized again. A further increase in the electron concentration factor (e/a > 8) leads to the disordering of the alloy. The electron concentration effect on the phase stability of transition-metal A{sub 3}B intermetallic compounds and Mg-based Laves phases is also reviewed and compared with the present observations in transition-metal Laves phases.

  17. Primordial Inflation Polarization Explorer (Phase 3)

    NASA Astrophysics Data System (ADS)

    Kogut, Alan

    This is the Lead Proposal for the investigation "Primordial Inflation Polarization Explorer (Phase 3)". We propose to complete and fly the Primordial Inflation Polarization Explorer (PIPER) to measure the polarization of the cosmic microwave background (CMB) and search for the imprint of gravitational waves produced during an inflationary epoch in the early universe. Detection of the inflationary signal would have profound consequences for both cosmology and high-energy physics. Not only would it establish inflation as a physical reality, it would provide a direct, model-independent determination of the relevant energy scale, shedding light on physics at energies twelve orders of magnitude beyond those accessible to direct experimentation in particle accelerators. The recent detection of CMB polarization by the BICEP2 instrument brings new urgency to the field. The BICEP2 detection at degree angular scales is consistent with inflation, but the amplitude is a factor of two higher than upper limits set by unpolarized data. A critical test is the rise in power at large angular scales predicted by inflation. Detecting this rise would confirm the signal's inflationary origin, fulfilling a long quest for cosmology while providing new insight into physics at the highest energies. PIPER is the only suborbital instrument capable of measuring CMB polarization on the large angular scales needed to test an inflationary origin for the BICEP2 detection. PIPER is a balloon-borne instrument, optimized to detect the inflationary signal on large angular scales. It consists of two co-aligned telescopes cooled to 1.5 K within a large liquid helium bucket dewar. A variable-delay polarization modulator (VPM) on each telescope chops between linear and circular polarization to isolate the polarized signal while rejecting the much brighter unpolarized emission. Four 32 x 40 element detector arrays provide background-limited sensitivity. A series of flights from mid-latitude sites will map

  18. Primordial Inflation Polarization Explorer (Phase 2)

    NASA Astrophysics Data System (ADS)

    Kogurt, Alan; Bennett, Charles

    This is the Lead Proposal for the proposed investigation "Primordial Inflation Polarization Explorer (Phase 2)" We propose to fly the Primordial Inflation Polarization Explorer (PIPER) to measure the polarization of the cosmic microwave background (CMB) and search for the imprint of gravitational waves produced during an inflationary epoch in the early universe. Such a signal is expected to exist: the simplest inflation models predict tensor-to-scalar ratio 0.01 < r < 0.16 corresponding to detectable amplitudes in the range 30--100 nK. Detection of the inflationary signal would have profound consequences for both cosmology and high-energy physics. Not only would it establish inflation as a physical reality, it would provide a direct, model- independent determination of the relevant energy scale, shedding light on physics at energies twelve orders of magnitude beyond those accessible to direct experimentation in particle accelerators. PIPER is a balloon-borne instrument optimized to detect the inflationary signal on large angular scales. It consists of two co-aligned telescopes cooled to 1.5 K within a large liquid helium bucket dewar. A variable-delay polarization modulator (VPM) on each telescope chops between linear and circular polarization to isolate the polarized signal while rejecting the much brighter unpolarized emission. PIPER's innovative architecture combines cryogenic optics with kilo-pixel detector arrays to provide unprecedented sensitivity to CMB polarization. The fast modulation between linear and circular polarization takes advantage of the lack of astrophysical circular polarization to eliminate common sources of systematic error. The sensitivity and control of systematic errors in turn enable measurements over most of the sky from mid-latitude launch sites; long-duration Antarctic flights are not required. With sensitivity r < 0.007 at 95% CL, PIPER will either detect the inflationary signal or rule out nearly all large-field inflation models

  19. Fabrication and Investigation of Intermetallic Compound-Glassy Phase Composites having Tensile Ductility

    DTIC Science & Technology

    2012-08-09

    with Mg-Y-Cu BGA, MgY phase also has a cP2 B2 structure), Mg-Y-Ag (AgMg phase also has a cP2 B2 structure and is ductile) and Y-Cu-Zn and some other...result were obtained is connected with cP2 TiNi phase which demonstrates martensitic transformations. Choice of alloys and sample preparation...1. The tentative compositions at which bulk glassy phase formation and possible formation of cP2 crystal-glassy composites are Cu-Y (starting from

  20. Thermal stability of intermetallic phases in Fe-rich Fe-Cr-Ni-Mo alloys

    DOE PAGES

    Yang, Ying; Tan, Lizhen; Busby, Jeremy T.

    2015-06-12

    Understanding the stability of precipitate phases in the Fe-rich Fe-Cr-Ni-Mo alloys is critical to the alloy design and application of Mo-containing Austenitic steels. Coupled with thermodynamic modeling, stability of the chi and Laves phases in two Fe-Cr-Ni-Mo alloys were investigated at 1000, 850 and 700 °C for different annealing time. The morphologies, compositions and crystal structures of the matrix and precipitate phases were carefully examined by Scanning Electron Microscopy, Electron Probe Microanalysis, X-ray diffraction and Transmission Electron Microscopy. The two key findings resulted from this work. One is that the chi phase is stable at high temperature and transformed intomore » the Laves phase at low temperature. The other is that both the chi and Laves phases have large solubilites of Cr, Mo and Ni, among which the Mo solubility has a major role on the relative stability of the precipitate phases. The developed thermodynamic models were then applied to evaluating the Mo effect on the stability of precipitate phases in AISI 316 and NF709 alloys.« less

  1. Thermal stability of intermetallic phases in Fe-rich Fe-Cr-Ni-Mo alloys

    SciTech Connect

    Yang, Ying; Tan, Lizhen; Busby, Jeremy T.

    2015-06-12

    Understanding the stability of precipitate phases in the Fe-rich Fe-Cr-Ni-Mo alloys is critical to the alloy design and application of Mo-containing Austenitic steels. Coupled with thermodynamic modeling, stability of the chi and Laves phases in two Fe-Cr-Ni-Mo alloys were investigated at 1000, 850 and 700 °C for different annealing time. The morphologies, compositions and crystal structures of the matrix and precipitate phases were carefully examined by Scanning Electron Microscopy, Electron Probe Microanalysis, X-ray diffraction and Transmission Electron Microscopy. The two key findings resulted from this work. One is that the chi phase is stable at high temperature and transformed into the Laves phase at low temperature. The other is that both the chi and Laves phases have large solubilites of Cr, Mo and Ni, among which the Mo solubility has a major role on the relative stability of the precipitate phases. The developed thermodynamic models were then applied to evaluating the Mo effect on the stability of precipitate phases in AISI 316 and NF709 alloys.

  2. New method for computer analysis of complex intermetallic compounds and nanocluster model of the samson phase Cd{sub 3}Cu{sub 4}

    SciTech Connect

    Blatov, V. A.; Ilyushin, G. D.

    2010-12-15

    A new method is proposed for the computer analysis of crystal structures of complex intermetallic compounds (with more than 1000 atoms per unit cell) using a developed algorithm of the complete decomposition of the 3D graph of the structure into nanocluster substructures. This method has been implemented in the TOPOS software package and approved successfully in an analysis of the complex Cu{sub 3}Cd{sub 4} structure (Samson phase). Cu{sub 3}Cd{sub 4} structure models were used to establish a structural relationship between nanoclusters in this intermetallic compound and nanoclusters in other complex crystal structures: ZrZn{sub 22}, Ru{sub 7}Mg{sub 44}, NaCd{sub 2}, and Mg{sub 2}Al{sub 3}.

  3. Processing, phase equilibria and environmental degradation of molybdenum (silicom,aluminum)(2) intermetallic compound

    NASA Astrophysics Data System (ADS)

    Eason, Paul Duane

    The Mo(Si,Al)2 C40 compound was chosen for investigation as a possible high temperature structural material. To produce the C40 phase, several processing routes were explored with emphasis on obtaining microstructure/property relationships (i.e. control of grain size and minimization of secondary phases). To facilitate processing of single phase material, the phase equilibria of the Mo-Si-Al ternary system were reevaluated with respect to the phases adjacent to the C40 compound. An anomalous environmental degradation appeared to be the primary obstacle to further study of the compound and was investigated accordingly. Several processing routes were assessed for the production of dense, nearly single-phase Mo(Si,Al)2. Hot powder compaction was chosen as the method of sample production as is the case with many refractory silicide based materials. Therefore, variations in the processing techniques came from the choice of precursor materials and methods of powder production. Mechanical alloying, arc-melting and comminution, and blending of both elemental and compound powders were all employed to produce charges for hot uniaxial pressing. The final compacts were compared on the basis of density, grain size and presence of secondary phases. Establishment of a Mo-Si-Al ternary isothermal phase diagram at 1400°C was performed. Multiphase alloy compositions were selected to identify the phase boundaries of the C40, C54, T1 and Mo3Al8 phase fields, as well as to verify the existence of the C54 phase at 1400°C. The alloys were equilibrated by heat treatment and analyzed for phase identification and quantitative compositional information. The environmental degradation phenomenon was approached as a classical "pest" with an emphasis of study on grain boundary chemistry and atmospheric dependence of attack. Both Auger spectroscopy and electron microscopy revealed carbon-impurity-induced grain boundary segregation responsible for the embrittlement and material loss. Means of

  4. Structure of Intermetallic Phases in Al-free Galvannealed Zinc Coatings

    NASA Astrophysics Data System (ADS)

    Zmrzlý, M.; Fiala, J.; Schneeweiss, O.; Houbaert, Y.

    2005-07-01

    Galvannealed coatings of thickness of (20 40) µm were prepared on the ultra low carbon (ULC) steel substrate. Metalography analysis was carried out to obtain the phase composition of coatings. Coatings were then transfered onto a polyacrylate foil. Transmission spectra yielding all the positions of iron within the coating thickness were measured. The doublet of zeta phase occured only after short annealing times, lower annealing temperatures and longer dipping times. Parameters of three sites of delta phase were observed to approach equilibrium values at higher annealing temperatures and longer annealing times. These changes are ascribed to diffusion transformations in the coatings during annelaing.

  5. Solid-State Phase Equilibria and Intermetallic Compounds of the Si-V-Zr Ternary System

    NASA Astrophysics Data System (ADS)

    Pan, Yanfang; Ye, Haimei; Chen, Xiaoxian; Jiang, Wenping; Yang, Wenchao; Zhan, Yongzhong

    2016-12-01

    Phase relations in the Si-V-Zr ternary system at 973 K (700 °C) were experimentally investigated using X-ray powder diffraction and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. The isothermal section at 973 K (700 °C) is governed by seventeen three-phase regions, thirty-two two-phase regions, and sixteen single-phase regions. Ten binary compounds and one ternary compound (SiVZr) were confirmed. There are two new ternary compounds found in this work for the first time. One of them (Si4V3Zr2) was found in the stoichiometric composition around V 38 pct, Si 50 pct, and Zr 12 pct. The existence of another one (V17Si12Zr3) was observed while analyzing the XRD results of large quantities of equilibrated samples in the region around 54 at. pct V, 33 at. pct Si, and 13 at. pct Zr.

  6. Solid state phase equilibria and intermetallic compounds of the Al-Cr-Ho system

    SciTech Connect

    Pang, Mingjun; Zhan, Yongzhong; Du, Yong

    2013-02-15

    The solid state phase equilibria of the Al-Cr-Ho ternary system at 500 Degree-Sign C were experimentally investigated. The phase relations at 500 Degree-Sign C are governed by 14 three-phase regions, 29 two-phase regions and 15 single-phase regions. The existences of 10 binary compounds and 2 ternary phases have been confirmed. Al{sub 11}Cr{sub 2}, Al{sub 11}Cr{sub 4} and Al{sub 17}Ho{sub 2} were not found at 500 Degree-Sign C. Crystal structures of Al{sub 9}Cr{sub 4} and Al{sub 8}Cr{sub 4}Ho were determined by the Rietveld X-ray powder data refinement. Al{sub 9}Cr{sub 4} was found to exhibit cubic structure with space group I4-bar 3m (no. 217) and lattice parameters a=0.9107(5) nm. Al{sub 8}Cr{sub 4}Ho crystallizes in ThMn{sub 12} structure type with space group I4/mmm (no. 139) and lattice parameters a=0.8909(4) nm, c=0.5120(5) nm. It is concluded that the obtained Al{sub 4}Cr phase in this work should be {mu}-Al{sub 4}Cr by comparing with XRD pattern of the hexagonal {mu}-Al{sub 4}Mn compound. - Graphical abstract: The solid state phase equilibria of the Al-Cr-Ho ternary system at 500 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Al-Cr-Ho system has been investigated. Black-Right-Pointing-Pointer Al{sub 9}Cr{sub 4} has cubic structure with space group I4-bar 3m. Black-Right-Pointing-Pointer Al{sub 8}Cr{sub 4}Ho crystallizes in ThMn{sub 12} type with space group I4/mmm. Black-Right-Pointing-Pointer Al{sub 4}Cr phase is {mu}-type at 500 Degree-Sign C.

  7. Electrical, magnetic, and thermal properties of the δ-FeZn10 complex intermetallic phase

    NASA Astrophysics Data System (ADS)

    Jazbec, S.; Koželj, P.; Vrtnik, S.; Jagličić, Z.; Popčević, P.; Ivkov, J.; Stanić, D.; Smontara, A.; Feuerbacher, M.; Dolinšek, J.

    2012-08-01

    We report the electrical, magnetic, and thermal properties of the δ-FeZn10 phase in the zinc-rich domain of the Fe-Zn system. The δ-FeZn10 phase possesses high structural complexity typical of complex metallic alloys: a giant unit cell comprising 556 atoms, polyhedral atomic order with icosahedrally coordinated environments, fractionally occupied lattice sites, and statistically disordered atomic clusters that introduce intrinsic disorder into the structure. Structural disorder results in suppression of the electrical and heat transport phenomena, making δ-FeZn10 a poor electrical and thermal conductor. Structural complexity results in a complex electronic structure that is reflected in the opposite signs of the thermoelectric power and the Hall coefficient. The δ-FeZn10 phase is paramagnetic down to the lowest investigated temperature of 2 K with a significant interspin coupling of antiferromagnetic type. Specific heat indicates the formation of short-range-ordered spin clusters at low temperatures, very likely a precursor of a phase transition to a collective magnetic state that would take place below 2 K. The magnetoresistance of δ-FeZn10 is sizeable, amounting to 1.5% at 2 K in a 9-T field. The electrical resistivity exhibits a maximum at about 220 K, and its temperature dependence could be explained by the theory of slow charge carriers, applicable to metallic systems with weak dispersion of the electronic bands, where the electron motion changes from ballistic to diffusive upon heating.

  8. Irradiation induced structural change in Mo2Zr intermetallic phase

    SciTech Connect

    Gan, J.; Keiser, Jr., D. D.; Miller, B. D.; Eriksson, N.; Sohn, Y. H.; Kirk, M.

    2016-05-14

    The Mo2Zr phase has been identified as a major interaction product at the interface of U-10Mo and Zr. Transmission electron microscopy in-situ irradiation with Kr ions at 200 °C with doses up to 2.0E+16 ions/cm2 was carried out to investigate the radiation stability of the Mo2Zr. The Mo2Zr undergoes a radiation-induced structural change, from a large cubic (cF24) to a small cubic (cI2), along with an estimated 11.2% volume contraction without changing its composition. The structural change begins at irradiation dose below 1.0E+14 ions/cm2. Furthermore, the transformed Mo2Zr phase demonstrates exceptional radiation tolerance with the development of dislocations without bubble formation.

  9. Irradiation induced structural change in Mo2Zr intermetallic phase

    SciTech Connect

    Gan, J.; Keiser, Jr., D. D.; Miller, B. D.; Eriksson, N.; Sohn, Y. H.; Kirk, M.

    2016-05-14

    The Mo2Zr phase has been identified as a major interaction product at the interface of U-10Mo and Zr. Transmission electron microscopy in-situ irradiation with Kr ions at 200 °C with doses up to 2.0E+16 ions/cm2 was carried out to investigate the radiation stability of the Mo2Zr. The Mo2Zr undergoes a radiation-induced structural change, from a large cubic (cF24) to a small cubic (cI2), along with an estimated 11.2% volume contraction without changing its composition. The structural change begins at irradiation dose below 1.0E+14 ions/cm2. Furthermore, the transformed Mo2Zr phase demonstrates exceptional radiation tolerance with the development of dislocations without bubble formation.

  10. Digital polarization holography advancing geometrical phase optics.

    PubMed

    De Sio, Luciano; Roberts, David E; Liao, Zhi; Nersisyan, Sarik; Uskova, Olena; Wickboldt, Lloyd; Tabiryan, Nelson; Steeves, Diane M; Kimball, Brian R

    2016-08-08

    Geometrical phase or the fourth generation (4G) optics enables realization of optical components (lenses, prisms, gratings, spiral phase plates, etc.) by patterning the optical axis orientation in the plane of thin anisotropic films. Such components exhibit near 100% diffraction efficiency over a broadband of wavelengths. The films are obtained by coating liquid crystalline (LC) materials over substrates with patterned alignment conditions. Photo-anisotropic materials are used for producing desired alignment conditions at the substrate surface. We present and discuss here an opportunity of producing the widest variety of "free-form" 4G optical components with arbitrary spatial patterns of the optical anisotropy axis orientation with the aid of a digital spatial light polarization converter (DSLPC). The DSLPC is based on a reflective, high resolution spatial light modulator (SLM) combined with an "ad hoc" optical setup. The most attractive feature of the use of a DSLPC for photoalignment of nanometer thin photo-anisotropic coatings is that the orientation of the alignment layer, and therefore of the fabricated LC or LC polymer (LCP) components can be specified on a pixel-by-pixel basis with high spatial resolution. By varying the optical magnification or de-magnification the spatial resolution of the photoaligned layer can be adjusted to an optimum for each application. With a simple "click" it is possible to record different optical components as well as arbitrary patterns ranging from lenses to invisible labels and other transparent labels that reveal different images depending on the side from which they are viewed.

  11. Intermetallic Compounds

    NASA Astrophysics Data System (ADS)

    Takagiwa, Y.; Matsuura, Y.; Kimura, K.

    2014-06-01

    We have focused on the binary narrow-bandgap intermetallic compounds FeGa3 and RuGa3 as thermoelectric materials. Their crystal structure is FeGa3-type (tetragonal, P42/ mnm) with 16 atoms per unit cell. Despite their simple crystal structure, their room temperature thermal conductivity is in the range 4-5-W-m-1-K-1. Both compounds have narrow-bandgaps of approximately 0.3-eV near the Fermi level. Because their Seebeck coefficients are quite large negative values in the range 350-<-| S 373K|-<-550- μV-K-1 for undoped samples, it should be possible to obtain highly efficient thermoelectric materials both by adjusting the carrier concentration and by reducing the thermal conductivity. Here, we report the effects of doping on the thermoelectric properties of FeGa3 and RuGa3 as n and p-type materials. The dimensionless figure of merit, ZT, was significantly improved by substitution of Sn for Ga in FeGa3 (electron-doping) and by substitution of Zn for Ga in RuGa3 (hole-doping), mainly as a result of optimization of the electronic part, S 2 σ.

  12. Spin-polarized structural, electronic and magnetic properties of intermetallic Dy 2Ni 2Pb from computational study

    NASA Astrophysics Data System (ADS)

    Arbouche, Omar; Azzaz, Yahia; Bendaoud, Hanifi; Belgoumène, Berrzoug; Driz, Mohamed; Abid, Hamza

    2012-03-01

    We report a first-principles study of structural, electronic and magnetic properties of ternary plumbides (rare earth-transition metal-Plumb) Dy 2Ni 2Pb crystallizes with the orthorhombic structure of the Mn 2AlB 2 type (space group Cmmm), were studied by means of the full-relativistic version of the full-potential augmented plane wave plus local orbital method within the frame work of spin-polarized density functional theory (SP-DFT). The electronic exchange-correlation energy is described by generalized gradient approximation (GGA). We have calculated the lattice parameters, bulk modulii and the first pressure derivatives of the bulk modulii, total densities of states and magnetic properties. The calculated total magnetic moment is found to be equal to 9.52 μB.

  13. Polarization phase shifting interferometric technique for phase calibration of a reflective phase spatial light modulator

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, Somparna; Sarkar, Sanjukta; Bhattacharya, Kallol; Hazra, Lakshminarayan

    2013-03-01

    Calibration of phase in spatial light modulators is a prerequisite for applications where a prespecified phase distribution needs to be implemented over the surface of the modulator. The present work proposes a full-field polarization phase shifting interferometric technique, based on the Twyman-Green interferometer, for the purpose.

  14. Relativistic Effects and Gold Site Distributions: Synthesis, Structure, and Bonding in a Polar Intermetallic Na6Cd16Au7

    SciTech Connect

    Samal, Saroj L.; Corbett, John D.

    2011-07-05

    Na{sub 6}Cd{sub 16}Au{sub 7} has been synthesized via typical high-temperature reactions, and its structure refined by single crystal X-ray diffraction as cubic, Fm{bar 3}m, a = 13.589(1) {angstrom}, Z = 4. The structure consists of Cd{sub 8} tetrahedral star (TS) building blocks that are face capped by six shared gold (Au2) vertexes and further diagonally bridged via Au1 to generate an orthogonal, three-dimensional framework [Cd{sub 8}(Au2){sub 6/2}(Au1){sub 4/8}], an ordered ternary derivative of Mn{sub 6}Th{sub 23}. Linear muffin-tin-orbital (LMTO)-atomic sphere approximation (ASA) electronic structure calculations indicate that Na{sub 6}Cd{sub 16}Au{sub 7} is metallic and that {approx}76% of the total crystal orbital Hamilton populations (-ICOHP) originate from polar Cd-Au bonding with 18% more from fewer Cd-Cd contacts. Na{sub 6}Cd{sub 16}Au{sub 7} (45 valence electron count (vec)) is isotypic with the older electron-richer Mg{sub 6}Cu{sub 16}Si{sub 7} (56 vec) in which the atom types are switched and bonding characteristics among the network elements are altered considerably (Si for Au, Cu for Cd, Mg for Na). The earlier and more electronegative element Au now occupies the Si site, in accord with the larger relativistic bonding contributions from polar Cd-Au versus Cu-Si bonds with the neighboring Cd in the former Cu positions. Substantial electronic differences in partial densities-of-states (PDOS) and COHP data for all atoms emphasize these. Strong contributions of nearby Au 5d{sup 10} to bonding states without altering the formal vec are the likely origin of these effects.

  15. X-ray Fluorescence Investigation of Ordered Intermetallic Phases as Electrocatalysts towards the Oxidation of Small Organic Molecules

    SciTech Connect

    Liu, Yi; Lowe, Michael A.; Finkelstein, Ken D.; Dale, Darren S.; DiSalvo, Francis J.; Abruña, Héctor D.

    2010-10-13

    The composition of ordered intermetallic nanoparticles (PtBi and PtPb) has been quantitatively studied by in situ X-ray fluorescence (XRF) during active electrochemical control in solutions of supporting electrolyte and small organic molecules (SOMs). Because the Pt Lβ1,2 lines and the Bi Lα1,2 lines are only separated by 200 eV, an energy-dispersive detector and a multiple-channel analyzer (MCA) were used to record the major fluorescent emission lines from these two elements. The molar ratios of platinum to the less-noble elements (Bi, Pb) in the nanoparticles dramatically changed as a function of the applied upper limit potentials (Eulp) in cyclic voltammetric (CV) characterization. Similar to previous investigations for bulk intermetallic surfaces, the less-noble elements leached out from the surfaces of the intermetallic nanoparticles. For PtBi nanoparticles, the ratios of fluorescence intensities of Pt/Bi in the samples were 0.42, 0.96, and 1.36 for Eulp=+0.40, +0.80, and 1.20 V, respectively, while cycling the potential from -0.20 V to the Eulp value for 10 cycles. The leaching-out process of the less-noble elements occurred at more negative Eulp values than expected. After cycling to relatively positive Eulp values, nonuniform PtM (M=Bi of Pb) nanoparticles formed with a Pt-rich shell and intermetallic PtM core. When the supporting solutions contained active fuel molecules in addition to the intermetallic nanoparticles (formic acid for PtBi, formic acid and methanol for PtPb), kinetic stabilization effects were observed for Eulp=+0.80 V, in a way similar to the response of the bulk materials. It was of great importance to quantitatively explore the change in composition and structure of the intermetallic nanoparticles under active electrochemical control. More importantly, this approach represents a simple, universal, and multifunctional method for the study of multi

  16. Some statistics on intermetallic compounds.

    PubMed

    Dshemuchadse, Julia; Steurer, Walter

    2015-02-02

    It is still largely unknown why intermetallic phases show such a large variety of crystal structures, with unit cell sizes varying between 1 and more than 20 000 atoms. The goal of our study was, therefore, to get a general overview of the symmetries, unit cell sizes, stoichiometries, most frequent structure types, and their stability fields based on the Mendeleev numbers as ordering parameters. A total of 20829 structures crystallizing in 2166 structure types have been studied for this purpose. Thereby, the focus was on a subset of 6441 binary intermetallic compounds, which crystallize in 943 structure types.

  17. Improving hot corrosion resistance of two phases intermetallic alloy α2-Ti3Al/γ-TiAl with enamel coating

    NASA Astrophysics Data System (ADS)

    Pambudi, Muhammad Jajar; Basuki, Eddy Agus; Prajitno, Djoko Hadi

    2017-01-01

    TiAl intermetallic alloys have attracted great interest among aerospace industry after successful utilization in low pressure turbine blades of aircraft engine which makes dramatic weight saving up to 40% weight saving. However, poor oxidation and corrosion resistance at temperatures above 800°C still become the drawbacks of this alloys, making the development of protective coatings to improve the resistance is important. This study investigates the hot corrosion behavior of two phases intermetallic alloy α2-Ti3Al/γ-TiAl with and without enamel coating using immersion test method in molten salt of 85%-wt Na2SO4 and 15%-wt NaCl at 850°C. The results show after 50 hours of hot corrosion test, bare alloy showed poor hot corrosion resistance due to the formation of non-protective Al2O3+TiO2 mixed scale at the surface of the alloy. Improvement of hot corrosion resistance was obtained in samples protected with enamel coating, indicated by significant decreasing in mass change (mg/cm2) by 98.20%. Enamel coating is expected to has the capability in suppressing the diffusion of oxygen and corrosive ions into the substrate layer, and consequently, it improves hot corrosion resistance of the alloy. The study showed that enamel coatings have strong adherent to the substrate and no spallation was observed after hot corrosion test. Nevertheless, the dissolution of oxides components of the enamel coating into the molten salts was observed that lead enamel coating degradation. This degradation is believed involving Cl- anion penetration into the substrate through voids in the coating that accelerates the corrosion of the two phases α2-Ti3Al/γ-TiAl alloy. Even though further observations are needed, it appears that enamel coating could be a promising protective coating to increase hot corrosion resistance of TiAl intermetallic alloys.

  18. Polarization-multiplexed plasmonic phase generation with distributed nanoslits.

    PubMed

    Lee, Seung-Yeol; Kim, Kyuho; Lee, Gun-Yeal; Lee, Byoungho

    2015-06-15

    Methods for multiplexing surface plasmon polaritons (SPPs) have been attracting much attention due to their potentials for plasmonic integrated systems, plasmonic holography, and optical tweezing. Here, using closely-distanced distributed nanoslits, we propose a method for generating polarization-multiplexed SPP phase profiles which can be applied for implementing general SPP phase distributions. Two independent types of SPP phase generation mechanisms - polarization-independent and polarization-reversible ones - are combined to generate fully arbitrary phase profiles for each optical handedness. As a simple verification of the proposed scheme, we experimentally demonstrate that the location of plasmonic focus can be arbitrary designed, and switched by the change of optical handedness.

  19. Phase Diversity and Polarization Augmented Techniques for Active Imaging

    DTIC Science & Technology

    2007-03-01

    Phase Diversity and Polarization Augmented Techniques for Active Imaging DISSERTATION Peter M. Johnson, Captain, USAF AFIT/DS/ENG/07-05 DEPARTMENT OF...Force, Department of Defense, or the United States Government. AFIT/DS/ENG/07-05 Phase Diversity and Polarization Augmented Techniques for Active Imaging...must be used. To facilitate this, a multi-frame active phase diversity imaging (APDI) algorithm is derived and demonstrated for the statistics of

  20. Metasurface Polarization Optics: Independent Phase Control of Arbitrary Orthogonal States of Polarization.

    PubMed

    Balthasar Mueller, J P; Rubin, Noah A; Devlin, Robert C; Groever, Benedikt; Capasso, Federico

    2017-03-17

    We present a method allowing for the imposition of two independent and arbitrary phase profiles on any pair of orthogonal states of polarization-linear, circular, or elliptical-relying only on simple, linearly birefringent wave plate elements arranged into metasurfaces. This stands in contrast to previous designs which could only address orthogonal linear, and to a limited extent, circular polarizations. Using this approach, we demonstrate chiral holograms characterized by fully independent far fields for each circular polarization and elliptical polarization beam splitters, both in the visible. This approach significantly expands the scope of metasurface polarization optics.

  1. Polyclusters and substitution effects in the Na-Au-Ga system: remarkable sodium bonding characteristics in polar intermetallics.

    PubMed

    Smetana, Volodymyr; Miller, Gordon J; Corbett, John D

    2013-11-04

    A systematic exploration of Na- and Au-poor parts of the Na-Au-Ga system (less than 15 at. % Na or Au) uncovered several compounds with novel structural features that are unusual for the rest of the system. Four ternary compounds Na1.00(3)Au0.18Ga1.82(1) (I), NaAu2Ga4 (II), Na5Au10Ga16 (III), and NaAu4Ga2 (IV) have been synthesized and structurally characterized by single crystal X-ray diffraction: Na1.00(3)Au0.18Ga1.82(1)(I, P6/mmm, a = 15.181(2), c =9.129(2)Å, Z = 30); NaAu2Ga4 (II, Pnma, a = 16.733(3), b = 4.3330(9), c =7.358(3) Å, Z = 4); Na5Au10Ga16 (III, P6(3)/m, a = 10.754(2), c =11.457(2) Å, Z = 2); and NaAu4Ga2 (IV, P2(1)/c, a = 8.292(2), b = 7.361(1), c =9.220(2)Å, β = 116.15(3), Z = 4). Compound I lies between the large family of Bergman-related compounds and Na-poor Zintl-type compounds and exhibits a clathrate-like structure containing icosahedral clusters similar to those in cubic 1/1 approximants, as well as tunnels with highly disordered cation positions and fused Na-centered clusters. Structures II, III, and IV are built of polyanionic networks and clusters that generate novel tunnels in each that contain isolated, ordered Na atoms. Tight-binding electronic structure calculations using linear muffin-tin-orbital (LMTO) methods on II, III, IV and an idealized model of I show that all are metallic with evident pseudogaps at the Fermi levels. The integrated crystal orbital Hamilton populations for II-IV are typically dominated by Au-Ga, Ga-Ga, and Au-Au bonding, although Na-Au and Na-Ga contributions are also significant. Sodium's involvement into such covalency is consistent with that recently reported in Na-Au-M (M = Ga, Ge, Sn, Zn, and Cd) phases.

  2. Elliptically polarizing adjustable phase insertion device

    DOEpatents

    Carr, Roger

    1995-01-01

    An insertion device for extracting polarized electromagnetic energy from a beam of particles is disclosed. The insertion device includes four linear arrays of magnets which are aligned with the particle beam. The magnetic field strength to which the particles are subjected is adjusted by altering the relative alignment of the arrays in a direction parallel to that of the particle beam. Both the energy and polarization of the extracted energy may be varied by moving the relevant arrays parallel to the beam direction. The present invention requires a substantially simpler and more economical superstructure than insertion devices in which the magnetic field strength is altered by changing the gap between arrays of magnets.

  3. Evaluation of polarized terahertz waves generated by Cherenkov phase matching.

    PubMed

    Akiba, Takuya; Akimoto, Yasuhiro; Suizu, Koji; Miyamoto, Katsuhiko; Omatsu, Takashige

    2014-03-10

    We report terahertz (THz) wave generation by satisfying Cherenkov phase-matching condition in both s and p polarizations. A dual-wavelength optical parametric oscillator is constructed from two potassium titanium oxide phosphate crystals pumped by a frequency-doubled Nd:YAG laser. By rotating the orientation of both a lithium niobate crystal (LiNbO3) and the polarization of the pump waves, the polarization of the THz wave changes. Due to the difference in the refractive index and absorption, the output power for p polarization is one tenth that for s polarization. A tuning range from 0.2 to 6.5 THz is obtained for s polarization, and from 0.2 to 4.2 and 5.4 to 6.9 THz for p polarization. The extraction efficiency is improved by changing the angle of prism for p polarization, and a large phase change occurs at total internal reflection. Consequently, p-polarized THz waves are optimal for spectroscopic applications.

  4. Metasurface Polarization Optics: Independent Phase Control of Arbitrary Orthogonal States of Polarization

    NASA Astrophysics Data System (ADS)

    Balthasar Mueller, J. P.; Rubin, Noah A.; Devlin, Robert C.; Groever, Benedikt; Capasso, Federico

    2017-03-01

    We present a method allowing for the imposition of two independent and arbitrary phase profiles on any pair of orthogonal states of polarization—linear, circular, or elliptical—relying only on simple, linearly birefringent wave plate elements arranged into metasurfaces. This stands in contrast to previous designs which could only address orthogonal linear, and to a limited extent, circular polarizations. Using this approach, we demonstrate chiral holograms characterized by fully independent far fields for each circular polarization and elliptical polarization beam splitters, both in the visible. This approach significantly expands the scope of metasurface polarization optics.

  5. Elliptically polarizing adjustable phase insertion device

    DOEpatents

    Carr, R.

    1995-01-17

    An insertion device for extracting polarized electromagnetic energy from a beam of particles is disclosed. The insertion device includes four linear arrays of magnets which are aligned with the particle beam. The magnetic field strength to which the particles are subjected is adjusted by altering the relative alignment of the arrays in a direction parallel to that of the particle beam. Both the energy and polarization of the extracted energy may be varied by moving the relevant arrays parallel to the beam direction. The present invention requires a substantially simpler and more economical superstructure than insertion devices in which the magnetic field strength is altered by changing the gap between arrays of magnets. 3 figures.

  6. Photonic radio-frequency phase shifter based on polarization interference.

    PubMed

    Chen, Han; Dong, Yi; He, Hao; Hu, Weisheng; Li, Lemin

    2009-08-01

    An rf photonic phase shifter based on polarization interference is presented, and the theoretical fundamentals of the design are explained. This phase shifter provides broad operational bandwidth and a full 360 degrees phase-shift tuning range with a single external electrical control. A prototype of the rf photonic phase shifter with a frequency of 26.75 GHz and 360 degrees tuning range is experimentally demonstrated.

  7. The Pancharatnam-Berry phase in polarization singular beams

    NASA Astrophysics Data System (ADS)

    Kumar, Vijay; Viswanathan, Nirmal K.

    2013-04-01

    Space-variant inhomogeneously polarized field formed due to superposition of orthogonally polarized Gaussian (LG00) and Laguerre-Gaussian (LG01) beams results in polarization singular beams with different morphology structures such as lemon, star and dipole patterns around the C-point in the beam cross-section. The Pancharatnam-Berry phase plays a critical role in the formation and characteristics of these spatially inhomogeneous fields. We present our experimental results wherein we measure the variable geometric phase by tracking the trajectory of the component vortices in the beam cross-section, by interfering with selective polarization states and by tracking different latitudes on the Poincaré sphere without the effect of a dynamic phase.

  8. Polarization phase-shifting cyclic Jamin shearing interferometer

    NASA Astrophysics Data System (ADS)

    Wang, Lijuan; Liu, Liren; Sun, Jianfeng; Zhou, Yu; Dai, Enwen; Wu, Yapeng

    2012-10-01

    In the inter-satellite laser communication, the laser beam transmitted from the optical terminals is required to be highly collimated and its divergence approaches diffraction-limit. For testing the diffraction-limit wavefront, a polarization phase-shifting cyclic Jamin shearing interferometer is proposed. It is composed of a Jamin plate with a PBS film coated on its front surface, a right-angle prism reflecting beams two times, a shearing plate shearing beams by its rotation and a polarization phase shifter. The laser beam to be test is incident on the Jamin plate and gives rise to two interference beams with mutually perpendicular polarization directions by the PBS film. The two beams falls on the right-angle prism before or after passing through the shearing plate. With reflection of the right-angle prism, a cyclic Jamin shearing interferometric light path is formed. Two emitted beams go into the polarization phase shifter to obtain phase-shifting interferograms. In this interferometer, the cyclic interferometric light path can eliminate error of the surface profile of the optical element and the effect of environment. The interferometer has polarization phase shifting function and its fringe visibility is high. Therefore the interferometer can obtain high accuracy with variable shearing amount. In experiments, phase-shifting interferograms are obtained and the usefulness of the interferometer is verified.

  9. Polarization Phase-Shift Interferometry: A Simple Laboratory Setup

    NASA Astrophysics Data System (ADS)

    Vannoni, Maurizio; Trivi, Marcelo; Molesini, Giuseppe

    2008-04-01

    An interferometry experiment is proposed, working on a Twyman-Green optical configuration. The interferogram is acquired with a digital camera and processed. Using polarization components the interferogram is phase-shifted and four different interferograms are acquired. The experiment is proposed as an introduction to modern phase-shift interferometry, using concepts and laboratory equipment at the level of undergraduate optics courses.

  10. Phase, amplitude, and polarization microscopy with a sampling field sensor.

    PubMed

    Tumbar, Remy

    2008-07-01

    I describe an improved implementation of a previously reported interferometric device, the sampling field sensor (SFS) [Appl. Opt.47, B32-B43 (2008)]. It provides X, Y, and XY shearing interferometric information simultaneously (space multiplexed) with amplitude and polarization information while using time-multiplexed phase shifting. Its simple common-path configuration makes it compact and vibration insensitive, as demonstrated by the ~lambda/125 phase estimation repeatability that was below the coherent noise floor (estimated at ~lambda/50). The SFS may be viewed as an efficient, robust and accurate full-field optical-digital interface, easy to integrate with traditional imaging systems. This is demonstrated by using the sensor as the focal plane array of a transmitted-light microscope in a straightforward setup using an illumination path polarization phase shifter. This work is focused on a qualitative demonstration and presents phase, amplitude, and polarization images of different types of human cheek cells and Caenorhabditiselegans larvae.

  11. Electric field driven mesoscale phase transition in polarized colloids

    NASA Astrophysics Data System (ADS)

    Khusid, Boris; Elele, Ezinwa; Lei, Qian

    2016-11-01

    A mesoscale phase transition in a polarized suspension was reported by Kumar, Khusid, Acrivos, PRL95, 2005 and Agarwal, Yethiraj, PRL102, 2009. Following the application of a strong AC field, particles aggregated head-to-tail into chains that bridged the interelectrode gap and then formed a cellular pattern, in which large particle-free domains were enclosed by particle-rich thin walls. Cellular structures were not observed in numerous simulations of field induced phase transitions in a polarized suspension. A requirement for matching the particle and fluid densities to avoid particle settling limits terrestrial experiments to negatively polarized particles. We present data on the phase diagram and kinetics of the phase transition in a neutrally buoyant, negatively polarized suspension subjected to a combination of AC and DC. Surprisingly, a weak DC component drastically speeds up the formation of a cellular pattern but does not affect its key characteristic. However, the application of a strong DC field destroys the cellular pattern, but it restores as the DC field strength is reduced. We also discuss the design of experiments to study phase transitions in a suspension of positively polarized, non-buoyancy-matched particles in the International Space Station. Supported by NASA's Physical Science Research Program, NNX13AQ53G.

  12. Polarization effects in reconfigurable liquid crystal phase holograms

    NASA Astrophysics Data System (ADS)

    Komarčević, Miloš; Manolis, Ilias G.; Wilkinson, Timothy D.; Crossland, William A.

    2005-01-01

    An improved configuration for achieving true polarization insensitive reconfigurable phase holograms for optical switches using homogeneously aligned nematic liquid crystal devices is presented. Previous experimental results have been analyzed and explained using numerical modeling of the nematic liquid crystal orientation and associated optical modulation. Twisting of the liquid crystal optical axis from the optimal 45° orientation from the quarter waveplate is shown to degrade the polarization insensitive performance. The alternative direction of surface alignment perpendicular to the long pixel edge eliminates the twist of the director during switching. True polarization insensitivity is predicted with our model for this mode of operation.

  13. About a linear polarization of comets: The phase-angle dependences of polarization degree

    NASA Astrophysics Data System (ADS)

    Shestopalov, D. I.; Golubeva, L. F.

    2017-05-01

    The ground-based astronomic observations of comet cannot provide a proper phase angle coverage that is needed to estimate with a reasonable accuracy all of the attributes of comet polarization phase curve. To find the best approximation to the phase polarization dependences observed for comets, we apply a simple empiric formula that has already shown good results when operating with asteroid and lunar polarimetric curves (Shestopalov, 2004; Shestopalov and Golubeva, 2015). From the set of comets present in DBCP (Kiselev et al., 2006), we selected 20, for which the calculation of regular polarimetric curves (i.e. the phase angle - polarization dependences with a low level of nonsteady activity) was possible. Within the phase angle coverage area for these 20 comets, a potential user can reproduce 82 best-fitting polarimetric phase curves in various spectral domains. Then we analyzed the properties of negative and positive polarization of the comets. The interrelation between the averaged polarimetric slope h at the inversion angle and wavelength was found. In general, the parameters of negative branch vary slightly from one comet to another. We found a close correlation between the maximum polarization degree Pmax and the slope of the segment of polarimetric curve bounded by phase angles of 30° and 50°. This finding allowed to adduce the evidence in support of the idea voiced by Chernova et al. (1993) about two types of comet with high and low Pmax. Moreover, we have found direct correlation between the maximum polarization degree of comets and their dust-to-gas ratio. The latter is actually a visual proof of assumptions voiced many years ago about a mutual effect of gas and dust on observed polarization of comets (see, for instance, a historical review in Kiselev et al., 2015). Thus, the polarimetric effect of resonant fluorescence should be completely eliminated from the phase-dependent polarization curve of comet in order to correctly interpret the physical

  14. Formation of Intermetallic Phases in Al-Sc Alloys Prepared by Molten Salt Electrolysis at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Wang, Zengjie; Guan, Chunyang; Liu, Qiaochu; Xue, Jilai

    Molten salts electrolysis method to prepare Al-RE alloys has attracted increasing attention recently. CaCl2 and Na3AlF6 were the most often used melts for this purpose. In this work, Al-Sc alloys prepared by electrolytic deposition process in both CaCl2 and Na3AlF6 melts were investigated, respectively. It was found that Sc distributes almost uniformly and Sc contents increase with increasing current intensity in both melts. Current efficiency was measured for comparison among various current densities applied. The alloy products were analyzed using XRD and SEM, where the formation behaviors of Al-Sc intermetallics were investigated in details. The experimental and theoretical results demonstrate that Al3Sc and Al0.968Sc0.032 are the major precipitates in the Al-Sc alloys prepared by molten electrolysis. The results are useful for selection and optimization of the molten salts compositions and the parameters of electrolysis operation.

  15. Polarization selective phase-change nanomodulator

    PubMed Central

    Appavoo, Kannatassen; Haglund Jr., Richard F.

    2014-01-01

    Manipulating optical signals below the diffraction limit is crucial for next-generation data-storage and telecommunication technologies. Although controlling the flow of light around nanoscale waveguides was achieved over a decade ago, modulating optical signals at terahertz frequencies within nanoscale volumes remains a challenge. Since the physics underlying any modulator relies on changes in dielectric properties, the incorporation of strongly electron-correlated materials (SECMs) has been proposed because they can exhibit orders of magnitude changes in electrical and optical properties with modest thermal, electrical or optical trigger signals. Here we demonstrate a hybrid nanomodulator of deep sub-wavelength dimensions with an active volume of only 0.002 µm3 by spatially confining light on the nanometre length scale using a plasmonic nanostructure while simultaneously controlling the reactive near-field environment at its optical focus with a single, precisely positioned SECM nanostructure. Since the nanomodulator functionality hinges on this near-field electromagnetic interaction, the modulation is also selectively responsive to polarization. This architecture suggests one path for designing reconfigurable optoelectronic building blocks with responses that can be tailored with exquisite precision by varying size, geometry, and the intrinsic materials properties of the hybrid elements. PMID:25346427

  16. Polarization selective phase-change nanomodulator

    SciTech Connect

    Appavoo, Kannatassen; Haglund Jr., Richard F.

    2014-10-27

    Manipulating optical signals below the diffraction limit is crucial for next-generation data-storage and telecommunication technologies. Although controlling the flow of light around nanoscale waveguides was achieved over a decade ago, modulating optical signals at terahertz frequencies within nanoscale volumes remains a challenge. Since the physics underlying any modulator relies on changes in dielectric properties, the incorporation of strongly electron-correlated materials (SECMs) has been proposed because they can exhibit orders of magnitude changes in electrical and optical properties with modest thermal, electrical or optical trigger signals. Here we demonstrate a hybrid nanomodulator of deep sub-wavelength dimensions with an active volume of only 0.002 µm3 by spatially confining light on the nanometre length scale using a plasmonic nanostructure while simultaneously controlling the reactive near-field environment at its optical focus with a single, precisely positioned SECM nanostructure. Since the nanomodulator functionality hinges on this near-field electromagnetic interaction, the modulation is also selectively responsive to polarization. Lastly, this architecture suggests one path for designing reconfigurable optoelectronic building blocks with responses that can be tailored with exquisite precision by varying size, geometry, and the intrinsic materials properties of the hybrid elements.

  17. Polarization selective phase-change nanomodulator

    DOE PAGES

    Appavoo, Kannatassen; Haglund Jr., Richard F.

    2014-10-27

    Manipulating optical signals below the diffraction limit is crucial for next-generation data-storage and telecommunication technologies. Although controlling the flow of light around nanoscale waveguides was achieved over a decade ago, modulating optical signals at terahertz frequencies within nanoscale volumes remains a challenge. Since the physics underlying any modulator relies on changes in dielectric properties, the incorporation of strongly electron-correlated materials (SECMs) has been proposed because they can exhibit orders of magnitude changes in electrical and optical properties with modest thermal, electrical or optical trigger signals. Here we demonstrate a hybrid nanomodulator of deep sub-wavelength dimensions with an active volume ofmore » only 0.002 µm3 by spatially confining light on the nanometre length scale using a plasmonic nanostructure while simultaneously controlling the reactive near-field environment at its optical focus with a single, precisely positioned SECM nanostructure. Since the nanomodulator functionality hinges on this near-field electromagnetic interaction, the modulation is also selectively responsive to polarization. Lastly, this architecture suggests one path for designing reconfigurable optoelectronic building blocks with responses that can be tailored with exquisite precision by varying size, geometry, and the intrinsic materials properties of the hybrid elements.« less

  18. Dynamic phase measurements based on a polarization Michelson interferometer employing a pixelated polarization camera

    NASA Astrophysics Data System (ADS)

    Serrano-Garcia, David I.; Otani, Yukitoshi

    2017-02-01

    We implemented an interferometric configuration capable of following a phase variation in time. By using a pixelated polarization camera, the system is able to retrieve the phase information instantaneously avoiding the usage of moving components and the necessity of an extra replication method attached at the output of the interferometer. Taking into account the temporal stability obtained from the system, a spatial-temporal phase demodulation algorithm can be implemented on frequency domain for the dynamic phase measurement. Spatial resolution is analyzed experimentally using a USAF pattern, and dynamic phase measurements were done on air and water medium variations due to a jet flame and a living fish as a biological sample, respectively.

  19. Polarization-sensitive optical coherence tomography using continuous polarization modulation with arbitrary phase modulation amplitude

    NASA Astrophysics Data System (ADS)

    Lu, Zenghai; Kasaragod, Deepa K.; Matcher, Stephen J.

    2012-03-01

    We demonstrate theoretically and experimentally that the phase retardance and relative optic-axis orientation of a sample can be calculated without prior knowledge of the actual value of the phase modulation amplitude when using a polarization-sensitive optical coherence tomography system based on continuous polarization modulation (CPM-PS-OCT). We also demonstrate that the sample Jones matrix can be calculated at any values of the phase modulation amplitude in a reasonable range depending on the system effective signal-to-noise ratio. This has fundamental importance for the development of clinical systems by simplifying the polarization modulator drive instrumentation and eliminating its calibration procedure. This was validated on measurements of a three-quarter waveplate and an equine tendon sample by a fiber-based swept-source CPM-PS-OCT system.

  20. Polarization Phase-Compensating Coats for Metallic Mirrors

    NASA Technical Reports Server (NTRS)

    Balasubramanian, Kunjithapatham

    2006-01-01

    A method of compensating for or minimizing phase differences between orthogonal polarizations of light reflected from metallic mirrors at oblique incidence, as, for example, from weakly curved mirrors, is undergoing development. The method is intended to satisfy a need to maintain precise polarization phase relationships or minimum polarization differences needed for proper operation of telescopes and other scientific instruments that include single or multiple mirrors. The basic idea of the method is to optimally coat mirrors with thin engineered layers of materials that introduce phase differences that, as nearly precisely as possible, are opposite of the undesired phase differences arising in reflection with non-optimum coatings. Depending on the specific optical system, the method could involve any or all of the following elements: a) Optimization of a single coat on all the mirrors in the system. b) Optimization of a unique coat for each mirror such that the polarization phase effects of the coat on one mirror compensate, to an acceptably high degree over an acceptably wide wavelength range, for those of the coat on another mirror. c) Tapering the coat on each mirror. Optimization could involve the choice of a single dielectric coating material and its thickness, or design of a more complex coat consisting of multiple layers of different dielectric materials and possibly some metallic materials. Such designs and coatings are particularly significant and needed for obtaining very high quality of wavefront required in high-contrast imaging instruments such as the NASA Terrestrial Planet Finder Coronagraph.

  1. Phase-shifting digital holography with a phase difference between orthogonal polarizations.

    PubMed

    Nomura, Takanori; Murata, Shinji; Nitanai, Eiji; Numata, Takuhisa

    2006-07-10

    Phase-shifting digital holography with a phase difference between orthogonal polarizations is proposed. The use of orthogonal polarizations can make it possible to record two phase-shifted holograms simultaneously. By combining the holograms with the distributions of a reference wave and an object wave, the complex field of the object's wavefront can be obtained. Preliminary experimental results are shown to confirm the proposed method.

  2. Effects of intermetallic phases on the electrochemical properties of rapidly-solidified Si-Cr alloys for rechargeable Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Ha, Jeong Ae; Jo, In Joo; Park, Won-Wook; Sohn, Keun Yong

    2016-09-01

    The microstructures and the electrochemical properties of rapidly-solidified Si-Cr alloys of various compositions were investigated in order to elucidate the effects of intermetallic phases on the cyclic energy capacity of the materials. Rapidly-solidified ribbons of the alloys were prepared by using a melt-spinning process, which is one of the most efficient rapid-solidification processes. The ribbons were fragmented by using a ball-milling process to produce powders of the alloys. To examine the electrochemical characteristics of the alloys, we mixed each of the alloy powders with Ketjenblack®, a conductive material, and a binder dissolved in deionized water and used it to form electrodes. The electrolyte used was 1.5-M LiPF6 dissolved in ethyl carbonate/dimethyl carbonate/fluoroethylene carbonate. The microstructures and the phases of the alloys were analyzed by using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction analyses. The obtained results showed that the microstructures of the rapidly-solidified Si-Cr alloys were composed of Si and CrSi2 phases. Fine Si particles with diameters of 50 - 100 nm were observed in an eutectic constituent while the sizes of the primary Si and CrSi2 phases were relatively larger at 500 - 900 nm. The specific energy capacities ( C) of the Si-Cr alloys decreased linearly with increasing volume fraction ( f) of the CrSi2 phase as follows: C = -1,667 f + 1,978 after the 50th cycle. The Columbic efficiency after the 3rd cycle increased slightly with increasing volume fraction of the CrSi2 phase; this was effective in improving the cycling capacity of the Si particles.

  3. Chemistry of intermetallic hydrides

    SciTech Connect

    Reilly, J.J.

    1991-01-01

    Certain intermetallic hydrides are safe, convenient and inexpensive hydrogen storage compounds. A particular advantage of such compounds is the ease with which their properties can be modified by small changes in alloy composition or preparation. This quality can be exploited to optimize their storage properties for particular applications, e.g. as intermetallic hydride electrodes in batteries. We will be concerned herein with the more important aspects of the thermodynamic and structural principles which regulate the behavior of intermetallic hydrogen systems and then illustrate their application using the archetype hydrides of LaNi5, FeTi and Mg alloys. The practical utility of these classes of materials will be briefly noted.

  4. New roles for icosahedral clusters in intermetallic phases: micelle-like segregation of Ca-Cd and Cu-Cd interactions in Ca10Cd27Cu2.

    PubMed

    Hadler, Amelia B; Harris, Nicholas A; Fredrickson, Daniel C

    2013-11-20

    Despite significant progress in the structural characterization of the quasicrystalline state, the chemical origins of long- and short-range icosahedral order remain mysterious and a subject of debate. In this Article, we present the crystal structure of a new complex intermetallic phase, Ca10Cd27Cu2 (mC234.24), whose geometrical features offer clues to the driving forces underlying the icosahedral clusters that occur in Bergman-type quasicrystals. Ca10Cd27Cu2 adopts a C-centered monoclinic superstructure of the 1/1 Bergman approximant structure, in which [110] layers of Bergman clusters in the 1/1 structure are separated through the insertion of additional atoms (accompanied by substantial positional disorder). An examination of the coordination environments of Ca and Cu (in the ordered regions) reveals that the structure can be viewed as a combination of coordination polyhedra present in the nearest binary phases in the Ca-Cd-Cu compositional space. A notable feature is the separation of Ca-Cd and Cu-Cd interactions, with Bergman clusters emerging as Ca-Cd Friauf polyhedra (derived from the MgZn2-type CaCd2 phase) encapsulate a Cu-Cd icosahedron similar to those appearing in Cu2Cd5. DFT chemical pressure calculations on nearby binary phases point to the importance of this segregation of Ca-Cd and Cu-Cd interactions. The mismatch in atomic size between Cu and Cd leads to an inability to satisfy Ca-Cu and Ca-Cd interactions simultaneously in the Friauf polyhedra of the nearby Laves phase CaCd2. The relegation of the Cu atoms to icosahedra prevents this frustration while nucleating the formation of Bergman clusters.

  5. Synthesis of general polarization transformers. A geometric phase approach

    NASA Astrophysics Data System (ADS)

    Bhandari, Rajendra

    1989-07-01

    Using a generalized form of Jordan's formulation of the geometric phase problem it is shown that a single gadget capable of realising an arbitrary element of the polarization transformation group SU (2) can be constructed using two half-wave plates and two quarter-wave plates. For special transformations, simpler, practical gadgets are proposed.

  6. Relating polarization phase difference of SAR signals to scene properties

    NASA Technical Reports Server (NTRS)

    Ulaby, Fawwaz T.; Dobson, Myron C.; Mcdonald, Kyle C.; Senior, Thomas B. A.; Held, Daniel

    1987-01-01

    This paper examines the statistical behavior of the phase difference Delta-phi between the HH-polarized and VV-polarized backscattered signals recorded by an L-band SAR over an agricultural test site in Illinois. Polarization-phase difference distributions were generated for about 200 agricultural fields for which ground information had been acquired in conjunction with the SAR mission. For the overwhelming majority of cases, the Delta-phi distribution is symmetric and has a single major lobe centered at the mean value of the distribution Delta-phi. Whereas the mean Delta-phi was found to be close to zero degrees for bare soil, cut vegetation, alfalfa, soybeans, and clover, a different pattern was observed for the corn fields; the mean Delta-phi increased with increasing incidence angle Theta = 35 deg. The explanation proposed for this variation is that the corn canopy, most of whose mass is contained in its vertical stalks, acts like a uniaxial crystal characterized by different velocities of propagation for waves with horizontal and vertical polarization. Thus, it is hypothesized that the observed backscatter is contributed by a combination of propagation delay, forward scatter by the soil surface, and specular bistatic reflection by the stalks. Model calculations based on this assumption were found to be in general agreement with the phase observations.

  7. Polarization Mechanisms in Phase II Poly(Vinylidene Fluoride) Films.

    DTIC Science & Technology

    1981-11-12

    34 OdRO a mnk W) Poly(Vinylidene Fluoride), x-rays, piezelectricity, polarization, poling FAWWRmCT ffls~ -ew nam 9 Uf"Oo me..Mv £*mM NOWsA Unoriented...phase II films were poled with fields up to 3.2 MV/cm at room o) temperature. A determination of the piezoelectric strain coefficient provided a measure...sT. VW OtU.4LF-41U.4" ". . -. I u CIImVP CLAI IaICATIOM OV- VPI PU.I (Ul... O111 111..41 the poling field and different polarization mechanisms appear

  8. First principles investigation of the mechanical, thermodynamic and electronic properties of FeSn5 and CoSn5 intermetallic phases under pressure

    NASA Astrophysics Data System (ADS)

    Sun, Wenming; Liu, Jing; Wang, Hong; Zhang, Zhenwei; Zhang, Liang; Bu, Yuxiang

    2017-02-01

    For guidance for developing Fe/Co-Sn-based anode materials for lithium-ion batteries, the mechanical, thermodynamic and electronic properties of FeSn5 and CoSn5 intermetallic phases under pressures ranging from 0 to 30 GPa have been investigated systematically using first-principles total-energy calculations within the framework of the generalized gradient approximation. The pressure was found to have significant effects on the mechanical, thermodynamic and electronic properties of these compounds. In the selected pressure range, CoSn5 has a more negative formation enthalpy than FeSn5. Based on the calculated elastic constants, the bulk modulus, shear modulus, and Young's modulus were determined via the Viogt-Reuss-Hill averaging scheme. The variations of specific heats at constant volume for FeSn5 and CoSn5 in a wide pressure (0 - 30 GPa) and temperature (0 - 1000 K) range are also predicted from phonon density of states calculation. The calculated results suggested that both FeSn5 and CoSn5 are mechanically stable at pressure from 0 to 30 GPa. FeSn5 is dynamically stable at pressure up to, 30 GPa, at least, however, CoSn5 is dynamically stable no higher than 15 GPa.

  9. Polarization phase-shifting lateral shearing interferometer with two polarization beam splitter plates

    NASA Astrophysics Data System (ADS)

    Gu, Liyuan; Liu, Lei; Hu, Shiyu; Zeng, Aijun; Huang, Huijie

    2017-08-01

    We proposed a compact and simple polarization phase-shifting lateral shearing interferometer using two polarization beam splitter plates (PBSP). This interferometer is composed of two PBSP, a quarter-wave plate, an analyzer and a CCD camera. With the two PBSP positioned in appropriate spatial positions, optical path difference compensation is achieved, which allows for the implement of aplanatic and common-path shearing interferometer. Therefore, the system possesses significant advantages of simple structure, compact and strong anti-interference ability. The effectiveness of the interferometer is demonstrated by simulations and experiments.

  10. Progress report on DOE research project [Thermodynamic and kinetic behavior of systems with intermetallic and intermediate phases

    SciTech Connect

    Tsakalakos, T.; Semenovskaya-Khachaturyan, S.; Khachaturyan, A.G.

    2000-12-13

    A theoretical investigation was made of the coherent displacive phase transformation between two equilibrium single-phase states producing several orientation variants of the product phase. The research was focused on a behavior of coherent systems (martensitic systems, metal and ceramic, and ferroelectric systems) with defects. The computer simulation demonstrated that randomly distributed static defects may drastically affect the thermodynamics, kinetics, and morphology of the transformation. In particular, the interaction of the transformation mode with the defects may be responsible for appearance of two new fields in the phase diagram: (i) the two-phase field describing the tweed microstructure, which consists of the retain parent phase and the variants of the product phase and (ii) the single-phase field describing the tweed microstructure, which consists of the variants of the product phase. These new fields can be attributed to the pre-transitional states observed in some of th e displacive transformations. The microstructure evolution resulting in formation of the thermoelastic equilibrium is path dependent. This unusual behavior is expected in systems with a sharp dependence of the transition temperature on the defect concentration.

  11. Numerical generation of a polarization singularity array with modulated amplitude and phase.

    PubMed

    Ye, Dong; Peng, Xinyu; Zhao, Qi; Chen, Yanru

    2016-09-01

    A point having no defined polarized ellipse azimuthal angle (circularly polarized) in a space-variant vector field is called a polarization singularity, and it has three types: Lemon, Monstar, and Star. Recently, the connection of polarization singularities has been performed. Inspired by this, we conduct a numerical generation of a polarization singularity array. Our method is based on two orthogonal linearly polarized light beams with modulated amplitude and phase. With appropriate distribution functions of amplitudes and phases we can control the polarized states of polarization singularities, which offer a possibility to simulate a polarization singularity array.

  12. Laboratory polarized phase curve measurement of airless body analog materials

    NASA Astrophysics Data System (ADS)

    Jiang, Te; Chen, Lei; Yang, Yazhou; Zhang, Hao; Liu, Yan; Ma, Pei; Zheming, Jianxiong

    2017-06-01

    When Sun light is incident on surfaces of airless bodies the reflected radiation is often found to be more polarized in the direction perpendicular to the scattering plane than in the parallel direction at small phase angle. This so-called negative polarization effect may be quantitatively characterized by several parameters of the polarized phase curve (PPC) such as the minimum degree of polarization (DOP) (Pmin), the inversion angle where the DOP changes its sign (alpha_inv), and the slope of the PPC near alpha_inv (h). Currently these parameters are believed to be complementary to spectroscopic data in revealing asteroid surface compositions and physical properties. Because of the paucities of laboratory experiments on analog materials, there are many open questions in interpretations of observational data. For example, earlier studies show that bare rocks, fine dust and rubble piles are located in different regions in the parameter space spanned by Pmin and alpha_inv, while recent observational results tend to support the idea that the locations are more related to surface mineralogy and chemical compositions; the compositions of F asteroids and the Barbarians with smallest and largest inversion angles. How much information on space weathering can polarization provide? To answer these questions, we have set up a three wavelength light scattering system to measure analog materials with different physical properties. The system can measure the Mueller matrices of packed surfaces from 2 to 135 deg. phase angle. We present measurement results on typical pure minerals with refractive indices varying from 1.4 to 2.4, both in bulk and grains, to understand the effects of refractive index on Pmin, alpha_inv and h. Olivine and pyroxene grains and their mixtures, both original and irradiated by a 1064 nm pulse laser at different energy levels in a vacuum chamber, are used to simulate asteroid surface materials with varying degrees of space weathering. Their reflectance

  13. Tunable and wideband microwave photonic phase shifter based on a single-sideband polarization modulator and a polarizer.

    PubMed

    Pan, Shilong; Zhang, Yamei

    2012-11-01

    A novel microwave photonic phase shifter based on a single-sideband (SSB) polarization modulator (PolM) and a polarizer is proposed and demonstrated. In the SSB-PolM, two SSB intensity-modulated signals with a phase difference of π along two orthogonal polarization directions are generated. With the polarizer to combine the two signals, the phase of the optical microwave signal can be tuned from -180 to 180 deg by simply adjusting the polarization direction of the polarizer, whereas the amplitude keeps unchanged. An experiment is carried out. A full-range tunable phase shift in the frequency range of 11-43 GHz is achieved. The flat power response, power independent operation, and high stability of the proposed microwave photonic phase shifter is also confirmed.

  14. Suppression of the antiferroelectric phase during polarization cycling of an induced ferroelectric phase

    SciTech Connect

    Liu, Xiaoming; Tan, Xiaoli

    2015-08-17

    The ceramic Pb{sub 0.99}Nb{sub 0.02}[(Zr{sub 0.57}Sn{sub 0.43}){sub 0.92}Ti{sub 0.08}]{sub 0.98}O{sub 3} can exist in either an antiferroelectric or a ferroelectric phase at room temperature, depending on the thermal and electrical history. The antiferroelectric phase can be partially recovered from the induced ferroelectric phase when the applied field reverses polarity. Therefore, polarization cycling of the ferroelectric phase in the ceramic under bipolar fields at room temperature is accompanied with repeated phase transitions. In this letter, the stability of the recovered antiferroelectric phase upon electrical cycling of the ceramic is investigated. Ex-situ X-ray diffraction reveals that bipolar cycling suppresses the antiferroelectric phase; this is indirectly supported by piezoelectric coefficient d{sub 33} measurements. It is speculated that the accumulated charged point defects during polarization cycling stabilize the polar ferroelectric phase. The findings presented are important to the fundamental studies of electric fatigue and field-induced phase transitions in ferroelectrics.

  15. An elliptically-polarizing undulator with phase adjustable energy and polarization

    NASA Astrophysics Data System (ADS)

    Lidia, Steve; Carr, Roger

    1994-08-01

    We present a planar helical undulator designed to produce elliptically-polarized light. Helical magnetic fields may be produced by a variety of undulators with four parallel cassettes of magnets. In our design, all cassettes are mounted in two planes on slides so that they may be moved parallel to the electron beam. This allows us to produce X-rays of left- or right-handed elliptical or circular polarization as well as horizontal or vertical linear polarization. In model calculations, we have found that by sliding the top pair of rows with respect to the bottom pair, or the left pair with respect to the right pair, we retain the polarization setting but change the magnetic field strength, and hence the X-ray energy. This allows us to select both energy and polarization by independent phase adjustments alone, without changing the gap between the rows. Such a design may be simpler to construct than an adjustable-gap machine. We present calculations that model its operation and its effects on an electron beam.

  16. Large phase shift via polarization-coupling cascading.

    PubMed

    Huo, Juan; Chen, Xianfeng

    2012-06-04

    Herein, we propose a phenomenon of "polarization-coupling (PC) cascading" generated in MgO doped periodically poled lithium niobate crystal (PPMgLN). PC cascading contributes to the effective electro-optical (EO) Kerr effect that is several orders of magnitude stronger than the classical ones. Experiment of Newton's rings demonstrates the large phase accumulation during the PC cascaded processes, and the experimental data is identical with the theoretical simulation.

  17. Stress-induced phase transformation and pseudo-elastic/pseudo-plastic recovery in intermetallic Ni-Al nanowires.

    PubMed

    Sutrakar, Vijay Kumar; Mahapatra, D Roy

    2009-07-22

    Extensive molecular dynamics (MD) simulations have been performed in a B2-NiAl nanowire using an embedded atom method (EAM) potential. We show a stress induced [Formula: see text]-centered-tetragonal (BCT) phase transformation and a novel temperature and cross-section dependent pseudo-elastic/pseudo-plastic recovery from such an unstable BCT phase with a recoverable strain of approximately 30% as compared to 5-8% in polycrystalline materials. Such a temperature and cross-section dependent pseudo-elastic/pseudo-plastic strain recovery can be useful in various interesting applications of shape memory and strain sensing in nanoscale devices. Effects of size, temperature, and strain rate on the structural and mechanical properties have also been analyzed in detail. For a given size of the nanowire the yield stress of both the B2 and the BCT phases is found to decrease with increasing temperature, whereas for a given temperature and strain rate the yield stress of both the B2 and the BCT phase is found to increase with increase in the cross-sectional dimensions of the nanowire. A constant elastic modulus of approximately 80 GPa of the B2 phase is observed in the temperature range of 200-500 K for nanowires of cross-sectional dimensions in the range of 17.22-28.712 A, whereas the elastic modulus of the BCT phase shows a decreasing trend with an increase in the temperature.

  18. Polarization-induced phase noise in fiber optic Michelson interferometer with Faraday rotator mirrors

    NASA Astrophysics Data System (ADS)

    Wu, Yuefeng; Li, Fang; Zhang, Wentao; Xiao, Hao; Liu, Yuliang

    2008-11-01

    Polarization-induced phase noise in Michelson interferometer with imperfect Faraday rotator mirrors was investigated. This kind of noise generates from the rotation angle errors of Faraday rotator mirrors and external polarization perturbation. The conversion factor κ, representing the magnitude conversion ability from polarization-noise to polarization induced phase-noise, have been theoretically evaluated and experimentally investigated.

  19. Stochastic Radiative Transfer in Polar Mixed Phase Clouds

    NASA Astrophysics Data System (ADS)

    Brodie, J.; Veron, D. E.

    2004-12-01

    According to recent research, mixed phase clouds comprise one third of the overall annual cloud cover in the Arctic region. These clouds contain distinct regions of liquid water and ice, which have a different impact on radiation than single-phase clouds. Despite the prevalence of mixed phase clouds in the polar regions, many modern atmospheric general circulation models use single-phase clouds in their radiation routines. A stochastic approach to representating the transfer of shortwave radiation through a cloud layer where the distribution of the ice and liquid is governed by observed statistics is being assessed. Data from the Surface Heat Budget of the Arctic (SHEBA) program and the Atmospheric Radiation Measurement (ARM) program's North Slopes of Alaska Cloud and Radiation Testbed site will be used to determine the characteristic features of the cloud field and to evaluate the performance of this statistical model.

  20. Synthesis and characterization of Fe-Ti-Sb intermetallic compounds: Discovery of a new Slater-Pauling phase

    NASA Astrophysics Data System (ADS)

    Naghibolashrafi, N.; Keshavarz, S.; Hegde, Vinay I.; Gupta, A.; Butler, W. H.; Romero, J.; Munira, K.; LeClair, P.; Mazumdar, D.; Ma, J.; Ghosh, A. W.; Wolverton, C.

    2016-03-01

    Compounds of Fe, Ti, and Sb were prepared using arc melting and vacuum annealing. Fe2TiSb , expected to be a full Heusler compound crystallizing in the L 21 structure, was shown by XRD and SEM analyses to be composed of weakly magnetic grains of nominal composition Fe1.5TiSb with iron-rich precipitates in the grain boundaries. FeTiSb, a composition consistent with the formation of a half-Heusler compound, also decomposed into Fe1.5TiSb grains with Ti-Sb rich precipitates and was weakly magnetic. The dominant Fe1.5TiSb phase appears to crystallize in a defective L 21 -like structure with iron vacancies. Based on this finding, a first-principles DFT-based binary cluster expansion of Fe and vacancies on the Fe sublattice of the L 21 structure was performed. Using the cluster expansion, we computationally scanned >103 configurations and predict a novel, stable, nonmagnetic semiconductor phase to be the zero-temperature ground state. This new structure is an ordered arrangement of Fe and vacancies, belonging to the space group R 3 m , with composition Fe1.5TiSb , i.e., between the full- and half-Heusler compositions. This phase can be visualized as alternate layers of L 21 phase Fe2TiSb and C 1b phase FeTiSb, with layering along the [111] direction of the original cubic phases. Our experimental results on annealed samples support this predicted ground-state composition, but further work is required to confirm that the R 3 m structure is the ground state.

  1. Mars Polar Cap During Transition Phase Instrument Checkout

    NASA Technical Reports Server (NTRS)

    2006-01-01

    During the last week of September and the first week or so of October 2006, scientific instruments on NASA's Mars Reconnaissance Orbiter were turned on to acquire test information during the transition phase leading up to full science operations. The mission's primary science phase will begin the first week of November 2006, following superior conjunction. (Superior conjunction is where a planet goes behind the sun as viewed from Earth.) Since it is very difficult to communicate with a spacecraft when it is close to the sun as seen from Earth, this checkout of the instruments was crucial to being ready for the primary science phase of the mission.

    Throughout the transition-phase testing, the Mars Color Imager (MARCI) acquired terminator (transition between nighttime and daytime) to terminator swaths of color images on every dayside orbit, as the spacecraft moved northward in its orbit. The south polar region was deep in winter shadow, but the north polar region was illuminated the entire Martian day. During the primary mission, such swaths will be assembled into global maps that portray the state of the Martian atmosphere -- its weather -- as seen every day and at every place at about 3 p.m. local solar time. After the transition phase completed, most of the instruments were turned off, but the Mars Climate Sounder and MARCI have been left on. Their data will be recorded and played back to Earth following the communications blackout associated with conjunction.

    Combined with wide-angle image mosaics taken by the Mars Orbiter Camera on NASA's Mars Global Surveyor at 2 p.m. local solar time, the MARCI maps will be used to track motions of clouds.

    This image is a composite mosaic of four polar views of Mars, taken at midnight, 6 a.m., noon, and 6 p.m. local Martian time. This is possible because during summer the sun is always shining in the polar region. It shows the mostly water-ice perennial cap (white area), sitting atop the north polar layered

  2. Mars Polar Cap During Transition Phase Instrument Checkout

    NASA Technical Reports Server (NTRS)

    2006-01-01

    During the last week of September and the first week or so of October 2006, scientific instruments on NASA's Mars Reconnaissance Orbiter were turned on to acquire test information during the transition phase leading up to full science operations. The mission's primary science phase will begin the first week of November 2006, following superior conjunction. (Superior conjunction is where a planet goes behind the sun as viewed from Earth.) Since it is very difficult to communicate with a spacecraft when it is close to the sun as seen from Earth, this checkout of the instruments was crucial to being ready for the primary science phase of the mission.

    Throughout the transition-phase testing, the Mars Color Imager (MARCI) acquired terminator (transition between nighttime and daytime) to terminator swaths of color images on every dayside orbit, as the spacecraft moved northward in its orbit. The south polar region was deep in winter shadow, but the north polar region was illuminated the entire Martian day. During the primary mission, such swaths will be assembled into global maps that portray the state of the Martian atmosphere -- its weather -- as seen every day and at every place at about 3 p.m. local solar time. After the transition phase completed, most of the instruments were turned off, but the Mars Climate Sounder and MARCI have been left on. Their data will be recorded and played back to Earth following the communications blackout associated with conjunction.

    Combined with wide-angle image mosaics taken by the Mars Orbiter Camera on NASA's Mars Global Surveyor at 2 p.m. local solar time, the MARCI maps will be used to track motions of clouds.

    This image is a composite mosaic of four polar views of Mars, taken at midnight, 6 a.m., noon, and 6 p.m. local Martian time. This is possible because during summer the sun is always shining in the polar region. It shows the mostly water-ice perennial cap (white area), sitting atop the north polar layered

  3. A comparative first-principles study of martensitic phase transformations in TiPd2 and TiPd intermetallics.

    PubMed

    Krcmar, M; Morris, James R

    2014-04-02

    Martensitic phase transformations in TiPd2 and TiPd alloys are studied employing density-functional, first-principles calculations. We examine the transformation of tetragonal C11b TiPd2 to the low-temperature orthorhombic phase (C11b → oI6), and the transformation of cubic B2 TiPd under orthorhombic (B2→B19) and subsequent monoclinic transformations (B19→B19') as the system is cooled. We employ a theoretical approach based on a phenomenological Landau theory of the structural phase transitions and a mean-field approximation for the free energy, utilizing first-principles calculations to obtain the deformation energy as a function of strains and to deduce parameters for constructing the free energy. The predicted transition temperature for the TiPd2 C11b → oI6 transition is in good agreement with reported experimental results. To investigate the TiPd B2→B19 transformation, we employ both the Cauchy-Born rule and a soft-mode-based approach, and elucidate the importance of the coupling between lattice distortion and atomic displacements (i.e. shuffling) in the formation of the final structure. The calculated B2→B19 transition temperature for TiPd alloy agrees well with the experimental results. We also find that there exists a very small but finite (0.0005 eV/atom) energy barrier of B19 TiPd under monoclinic deformation for B19→B19' structural phase transformation.

  4. Solid-state transformation of Fe-rich intermetallic phases in Al–5.0Cu–0.6Mn squeeze cast alloy with variable Fe contents during solution heat treatment

    SciTech Connect

    Lin, Bo; Zhang, Weiwen; Zhao, Yuliang; Li, Yuanyuan

    2015-06-15

    The Al–5.0 wt.% Cu–0.6 wt.% Mn alloys with a variable Fe content were prepared by squeeze casting. Optical microscopy (OM), Deep etching technique, scanning electron microscopy(SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to examine the solid-state transformation of Fe-rich intermetallics during the solution heat treatment. The results showed that the Chinese script-like α-Fe, Al{sub 6}(FeMn) and needle-like Al{sub 3}(FeMn) phases transform to a new Cu-rich β-Fe (Al{sub 7}Cu{sub 2}(FeMn)) phase during solution heat treatment. The possible reaction and overall transformation kinetics of the solid-state phase transformation for the Fe-rich intermetallics were investigated. - Graphical abstract: Display Omitted - Highlights: • The α-Fe, Al{sub 6}(FeMn) and Al{sub 3}(FeMn) phases change to the β-Fe phases. • Possible reactions of Fe phases during solution heat treatment are discussed. • The overall fractional transformation rate follows an Avrami curve.

  5. Condensation phase of the Martian south polar cap

    NASA Technical Reports Server (NTRS)

    Capuano, J.; Reed, M.; James, P. B.

    1992-01-01

    One type of database that can be useful in limiting models of the Mars surface-atmosphere system is the time dependent boundary of CO2 frost for the polar caps. Data acquired by the thermal infrared sensors on spacecraft are not limited by the lighting problems that hamper visual observations. The surface temperature of solid CO2 is limited by Clapeyron's equation as a function of the local partial pressure of CO2 gas. The growth was studied of the Martian south polar cap using the Viking IRTM dataset. These data are available in five bands, four of which should correspond to surface radiation in clear conditions; the 20 micron data was examined in the first phase.

  6. Shaping of attosecond pulses by phase-stabilized polarization gating

    SciTech Connect

    Sansone, G.; Benedetti, E.; Caumes, J. P.; Stagira, S.; Vozzi, C.; Nisoli, M.; Poletto, L.; Villoresi, P.; Strelkov, V.; Sola, I.; Elouga, L. B.; Zaier, A.; Mevel, E.; Constant, E.

    2009-12-15

    We demonstrate that the characteristics of the high-order harmonic spectra generated by few-cycle carrier-envelope phase-stabilized pulses can be finely adjusted by controlling the time-dependent ellipticity. The experimental measurements show evidence for the generation of single, pairs, and trains of attosecond pulses by controlling the time window of linear polarization of the driving pulses. The influence of the carrier-envelope phase on the generation process in different confinement configurations is interpreted and analyzed using a nonadiabatic stationary phase model. We show that the xuv emission depends critically on particular aspects of the fundamental electric field that allows us to steer the electron trajectories on the time scale of tens of attoseconds.

  7. Edge states and phase diagram for graphene under polarized light

    DOE PAGES

    Wang, Yi -Xiang; Li, Fuxiang

    2016-03-22

    In this paper, we investigate the topological phase transitions in graphene under the modulation of circularly polarized light, by analyzing the changes of edge states and its topological structures. A full phase diagram, with several different topological phases, is presented in the parameter space spanned by the driving frequency and light strength. We find that the high-Chern number behavior is very common in the driven system. While the one-photon resonance can create the chiral edge states in the π-gap, the two-photon resonance will induce the counter-propagating edge modes in the zero-energy gap. When the driving light strength is strong, themore » number and even the chirality of the edge states may change in the π-gap. The robustness of the edge states to disorder potential is also examined. We close by discussing the feasibility of experimental proposals.« less

  8. Edge states and phase diagram for graphene under polarized light

    SciTech Connect

    Wang, Yi -Xiang; Li, Fuxiang

    2016-03-22

    In this paper, we investigate the topological phase transitions in graphene under the modulation of circularly polarized light, by analyzing the changes of edge states and its topological structures. A full phase diagram, with several different topological phases, is presented in the parameter space spanned by the driving frequency and light strength. We find that the high-Chern number behavior is very common in the driven system. While the one-photon resonance can create the chiral edge states in the π-gap, the two-photon resonance will induce the counter-propagating edge modes in the zero-energy gap. When the driving light strength is strong, the number and even the chirality of the edge states may change in the π-gap. The robustness of the edge states to disorder potential is also examined. We close by discussing the feasibility of experimental proposals.

  9. Anisotropy in the paramagnetic phase of RAl/sub 2/ cubic intermetallic compounds (R = Tb, Dy, and Er)

    SciTech Connect

    del Moral, A.; Ibarra, M.R.; Abell, J.S.; Montenegro, J.F.D.

    1987-05-01

    In this paper it is shown that the anisotropy in the paramagnetic phase is a useful characteristic when used to single out high-rank susceptibility tensor components in the paramagnetic regime of cubic crystals. Application of this technique to RAl/sub 2/ compounds (R = Tb,Dy,Er) allows the determination of longitudinal and transverse (in the form of linear combinations) fourth- and sixth-rank paramagnetic susceptibilities. The use of the fourth-rank longitudinal susceptibility allows quadrupolar pair interactions in these compounds to be probed.

  10. Control of beta phase in an EPM-processed intermetallic compound based on Ti-Al-Mn-Mo

    SciTech Connect

    Lee, T.K.; Hwang, S.K.; Nam, S.W.; Kim, N.J.

    1997-06-01

    Gamma TiAl alloys have been under considerable research in recent years because of their good specific strength and the high resistance to creep and oxidation at elevated temperatures. Since the first report on their promising high temperature properties the gamma alloys have been continuously improved and their merits are highly valued now. Among the methods to produce the gamma alloys, EPM (Elemental Powder Metallurgy) method drew attention due to its amenability to the cost-effective near-net shape processing. In the EPM method alloying reaction is basically the exothermic reactions between elemental powders. A practical drawback of using this reaction as a sole method of alloying is the Kirkendall pores generated by the difference in the diffusivities of each alloying element. Therefore high temperature deformation process is added to seal the pores and consolidate the alloying reaction. In the previous attempt, the authors used hot extrusion to consolidate the TiAl compound containing Mn and Mo for improved mechanical properties. The Mo addition and the inherent characteristics of EPM, however, raised a question about the presence of {beta} phase that may cause undesirable effect on high temperature mechanical properties. In the present work, the authors attempted to answer this question from the stand point of finding a practical control method of {beta} phase and optimizing the microstructure.

  11. Polarization-phase tomography of biological fluids polycrystalline structure

    NASA Astrophysics Data System (ADS)

    Dubolazov, A. V.; Vanchuliak, O. Ya.; Garazdiuk, M.; Sidor, M. I.; Motrich, A. V.; Kostiuk, S. V.

    2013-12-01

    Our research is aimed at designing an experimental method of Fourier's laser polarization phasometry of the layers of human effusion for an express diagnostics during surgery and a differentiation of the degree of severity (acute - gangrenous) appendectomy by means of statistical, correlation and fractal analysis of the coherent scattered field. A model of generalized optical anisotropy of polycrystal networks of albumin and globulin of the effusion of appendicitis has been suggested and the method of Fourier's phasometry of linear (a phase shift between the orthogonal components of the laser wave amplitude) and circular (the angle of rotation of the polarization plane) birefringence with a spatial-frequency selection of the coordinate distributions for the differentiation of acute and gangrenous conditions have been analytically substantiated. Comparative studies of the efficacy of the methods of direct mapping of phase distributions and Fourier's phasometry of a laser radiation field transformed by the dendritic and spherolitic networks of albumin and globulin of the layers of effusion of appendicitis on the basis of complex statistical, correlation and fractal analysis of the structure of phase maps.

  12. Weldability of intermetallic alloys

    SciTech Connect

    David, S.A. )

    1990-01-01

    Ordered intermetallic alloys are a unique class of material that have potential for structural applications at elevated temperatures. The paper describes the welding and weldability of these alloys. The alloys studied were nickel aluminide (Ni[sub 3]Al), titanium aluminide (Ti[sub 3]Al), and iron aluminide.

  13. Stable Topological Superfluid Phase of Ultracold Polar Fermionic Molecules

    SciTech Connect

    Cooper, N. R.; Shlyapnikov, G. V.

    2009-10-09

    We show that single-component fermionic polar molecules confined to a 2D geometry and dressed by a microwave field may acquire an attractive 1/r{sup 3} dipole-dipole interaction leading to superfluid p-wave pairing at sufficiently low temperatures even in the BCS regime. The emerging state is the topological p{sub x}+ip{sub y} phase promising for topologically protected quantum information processing. The main decay channel is via collisional transitions to dressed states with lower energies and is rather slow, setting a lifetime of the order of seconds at 2D densities approx10{sup 8} cm{sup -2}.

  14. Simultaneous phase, amplitude, and polarization control of femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Lindinger, A.; Weber, S. M.; Plewicki, M.; Weise, F.

    2012-12-01

    We present a serial pulse shaper design which allows us to shape the phase, amplitude, and polarization of fs laser pulses independently and simultaneously. The capabilities of this setup are demonstrated by implementing a method for generating parametrically tailored laser pulses. This method is applied on the ionization of NaK molecules by feedback loop optimization, employing a temporal sub pulse encoding. Moreover, we introduce and characterize a further development of this common path pulse shaper scheme for full control of all light field parameters.

  15. Phase modulation in polarization beating quasi-phase-matching of high-order-harmonic generation

    NASA Astrophysics Data System (ADS)

    Diskin, Tzvi; Kfir, Ofer; Fleischer, Avner; Cohen, Oren

    2015-09-01

    Polarization beating quasi-phase-matching (PB QPM) in high-harmonic generation (HHG) is currently understood as a purely-intensity-modulation quasi-phase-matching (QPM) technique. In PB QPM, the driver ellipticity oscillates during propagation, modulating the HHG conversion efficiency since the single-atom HHG yield decreases rapidly with increasing ellipticity of the driving laser. We show that PB QPM is in fact based on both intensity and phase modulations. Unfortunately, in PB QPM the intensity and phase contributions oppose each other, resulting in significant reduction in the QPM efficiency.

  16. Polarization-Fizeau interferometer enabling phase measurement with reduced uncertainty

    NASA Astrophysics Data System (ADS)

    Fütterer, G.

    2017-06-01

    A Fizeau interferometer is significantly less sensitive to vibrations and air turbulence than other types of interferometers. This is due to the common path of the reference wave front and the object wave front. A common path arrangement offers the opportunity to reduce systematic errors of the measured phase of the surface under test (SUT). That is why Fizeau type interferometers are most commonly used to test e.g. plane surfaces, spheres or aspheres. A reduced uncertainty of the measured phase distribution can be obtained if the reference surface is placed close to the SUT. Multiple beam reflections will produce interference fringes, which are not sinusoidal. Furthermore, the discrete intensity distribution depends on the reflectance of the reference surface and the reflectance of the SUT. Some surfaces to be tested show significant variations of the local reflectance, e.g. lithographic masks with 0.05 <= r(x,y) <= 0.95. Thus, the inherent potential of phase shifting algorithms cannot be used. A modification of the reference surface can be applied. An on-axis polarization beam splitter, which is placed in the plane of the reference surface, separates the two surfaces, which are imaged onto the detector. Thus, true two beam interference can be obtained. The potential of phase shifting algorithms can be used. The interference contrast is high, even if large local variations of r(x,y) are present. In addition, high speed operation is enabled. The embodiment of a modified Fizeau type interferometer will be described.

  17. Effect of Stress-Induced Phase Transformation on the Fracture Toughness of Fe3Al Intermetallic Reinforced with Yttria-Partially Stabilized Zirconia Particles

    NASA Astrophysics Data System (ADS)

    Amiri Talischi, Lima; Samadi, Ahad

    2017-10-01

    In this study, fracture toughness and microhardness of Fe3Al intermetallic reinforced with yttria-partially stabilized zirconia (Y-PSZ) particles were investigated. Fe3Al/Y-PSZ composites containing up to 20 wt pct of Y-PSZ were fabricated by hot pressing of powder mixtures. It is found that the microhardness and fracture toughness of Fe3Al intermetallic increase by adding Y-PSZ particles. The maximal levels of fracture toughness and microhardness correspond to Fe3Al-10 wt pct Y-PSZ composite with the fracture toughness of 23.1 MPa√m and the microhardness of 645 HV. The improvement in fracture toughness could be related to the stress-induced structural transformation of zirconia particles from tetragonal to monoclinic which causes crack deflection and prevents crack propagation.

  18. A tunable and wideband microwave photonic phase shifter based on dual-polarization modulator

    NASA Astrophysics Data System (ADS)

    Peng, Zhengxue; Wen, Aijun; Gao, Yongsheng; Tu, Zhaoyang

    2017-01-01

    A microwave photonic phase shifter based on dual-polarization Mach-Zehnder modulator (DPol-MZM) is proposed and experimentally demonstrated in this paper. A polarization multiplexed double sideband (DSB) signal is produced by a DPol-MZM. An optical bandpass filter (OBPF) follows after the DPol-MZM to filter out the optical carrier and one sideband. The polarization multiplexed signal is converted into a linear polarization light by a polarizer (Pol), and then beat at a photodiode (PD) to obtain the phase shifted signal. Experiments are carried out, and a continuous phase shift from -180° to 180° over a wide microwave frequency range of 10-33 GHz can be achieved by changing the polarization state using a polarization controller (PC). We also studied the spurious free dynamic range (SFDR) in the experiments. The features of this proposed phase shifter are large operation bandwidth, full-range 360° phase shift, and simple structure.

  19. Polarization evolution of radially polarized partially coherent vortex fields: role of Gouy phase of Laguerre-Gauss beams.

    PubMed

    Martínez-Herrero, R; Prado, F

    2015-02-23

    In the framework of the paraxial approximation, we derive the analytical expressions for describing the effect of the Gouy phase of Laguerre-Gauss beams on the polarization evolution of partially coherent vortex fields whose electric field vector at some transverse plane exhibits a radially polarized behavior. At each transverse plane, the polarization distribution across the beam profile is characterized by means of the percentage of irradiance associated with the radial or azimuthal components. The propagation laws for these percentages are also presented. As an illustrative example, we analyze a radially polarized partially coherent vortex beam.

  20. Microstructural Evolution and Compressive Properties of Two-Phase Nb-Fe Alloys Containing the C14 Laves Phase NbFe2 Intermetallic Compound

    NASA Astrophysics Data System (ADS)

    Li, K. W.; Wang, X. B.; Wang, W. X.; Li, S. M.; Gong, D. Q.; Fu, H. Z.

    2016-02-01

    Microstructural evolution and compressive properties of two-phase Nb-Fe binary alloys based on the C14 Laves phase NbFe2 were characterized at both the hypo- and hypereutectic compositions. The experimental results indicated that the microstructures of the two alloys consisted of fully eutectics containing Fe and NbFe2 phases at the bottom of the ingots corresponding to the largest solidification rates. With the decrease of solidification rate, the microstructures developed into primary Fe (NbFe2) dendrites plus eutectics in the middle and top parts of the ingots. The microstructural evolutions along the axis of the ingots were analyzed by considering the competitive growth between the primary phase and eutectic as well as using microstructure selection models based on the maximum interface temperature criterion. Furthermore, the compressive properties of the two alloys were measured and the enhancements were explained in terms of the second Fe phase and halo toughening mechanisms.

  1. Polarization-independent rapidly responding phase grating based on hybrid blue phase liquid crystal

    NASA Astrophysics Data System (ADS)

    Lin, Yi-Ting; Jau, Hung-Chang; Lin, Tsung-Hsien

    2013-02-01

    This work demonstrates a polymer-stabilized blue phase (PSBP) liquid crystal phase grating, which is made of hybrid PSBPs with two different Kerr constants. The Kerr constant of a PSBP is related to the morphology of the polymer network which can be controlled by the phase separation temperature. Owing to the non-patterned electrode and the optical isotropy of the PSBP, the diffraction effect can be completely switched off when the voltage is absent. The diffraction intensity increases when a uniform applied electrical field induces the phase difference in the hybrid PSBP. The phase grating is completely independent of the polarization of the incident light. Furthermore, the response time to switching is in the sub-millisecond range.

  2. Propagation of polarized light in opals: Amplitude and phase anisotropy

    SciTech Connect

    Baryshev, A. V. Dokukin, M. E.; Merzlikin, A. M.; Inoue, M.

    2011-03-15

    The interaction of linearly polarized light with photonic crystals based on bulk and thin-film synthetic opals is studied. Experimental transmission spectra and spectra showing the polarization state of light transmitted through opals are discussed. A change in polarization is found for waves experiencing Bragg diffraction from systems of crystallographic planes of the opal lattice. It is shown that the polarization plane of the incident linearly polarized wave at the exit from photonic crystals can be considerably rotated. In addition, incident linearly polarized light can be transformed to elliptically polarized light with the turned major axis of the polarization ellipse. Analysis of polarization states of transmitted light by using the transfer-matrix theory and homogenization theory revealed good agreement between calculated and experimental spectra.

  3. Mixed-phased particles in polar stratospheric ice clouds

    NASA Astrophysics Data System (ADS)

    Bogdan, Anatoli; Molina, Mario J.; Loerting, Thomas

    2010-05-01

    Keywords: polar stratospheric clouds (PSCs), ozone depletion, differential scanning calorimeter. The rate of chlorine activation reactions, which lead to ozone depletion in the winter/spring polar stratosphere (Molina, 1994), depends on the phase state of the surface of polar stratospheric cloud (PSC) ice crystals (McNeil et al., 2006). PSCs are thought to consist of solid ice and NAT (nitric acid trihydrate, HNO3× 3H2O) particles and supercooled HNO3/H2SO4/H2O droplets. The corresponding PSCs are called Type II, Ia, and Ib PSCs, respectively (Zondlo et al., 1998). Type II PSCs are formed in the Antarctic region below the ice frost point of 189 K by homogeneous freezing of HNO3/H2SO4/H2O droplets (Chang et al., 1999) with the excess of HNO3. The PSC ice crystals are thought to be solid. However, the fate of H+, NO3-, SO42- ions during freezing was not investigated. Our differential scanning calorimetry (DSC) studies of freezing emulsified HNO3/H2SO4/H2O droplets of sizes and compositions representative of the polar stratosphere demonstrate that during the freezing of the droplets, H+, NO3-, SO42- are expelled from the ice lattice. The expelled ions form a residual solution around the formed ice crystals. The residual solution does not freeze but transforms to glassy state at ~150 K (Bogdan et al., 2010). By contrast to glass-formation in these nitric-acid rich ternary mixtures the residual solution freezes in the case of sulphuric-acid rich ternary mixtures (Bogdan and Molina, 2009). For example, we can consider the phase separation into ice and a residual solution during the freezing of 23/3 wt% HNO3/H2SO4/H2O droplets. On cooling, ice is formed at ~189 K. This is inferred from the fact that the corresponding melting peak at ~248 K exactly matches the melting point of ice in the phase diagram of HNO3/H2SO4/H2O containing 3 wt % H2SO4. After the ice has formed, the glass transition occurs at Tg ≈ 150 K. The appearance of the glass transition indicates that the

  4. Polarization independent blue phase liquid crystal gratings based on periodic polymer slices structure

    NASA Astrophysics Data System (ADS)

    Yan, Jing; Li, Qing; Hu, Kai

    2013-10-01

    A polarization independent switchable phase grating based on polymer stabilized blue phase liquid crystal is proposed. A high efficiency of the phase grating has been achieved because of the sharp rectangular phase profile which shows good agreement with the simulation results. The diffraction efficiency of the 1st order is 38%, the response time is in the submillisecond range, and the phase grating is independent of the polarization of the incident light. The voltage-induced hysteresis characteristics are also investigated.

  5. Spatiotemporal polarization gradients in phase-bearing light

    SciTech Connect

    Lembessis, V. E.; Babiker, M.

    2010-03-15

    It is shown how the interference of two circularly polarized laser beams endowed with orbital angular momentum can give rise to spatial and temporal polarization gradients, displaying axial as well as angular symmetry properties. Illustrations are given with reference to circularly polarized Laguerre-Gaussian beams as typical light beams carrying orbital angular momentum.

  6. Recent advances in ordered intermetallics

    SciTech Connect

    Liu, C.T.

    1992-12-31

    This paper briefly summarizes recent advances in intermetallic research and development. Ordered intermetallics based on aluminides and silicides possess attractive properties for structural applications at elevated temperatures in hostile environments; however, brittle fracture and poor fracture resistance limit their use as engineering materials in many cases. In recent years, considerable efforts have been devoted to the study of the brittle fracture behavior of intermetallic alloys; as a result, both intrinsic and extrinsic factors governing brittle fracture have been identified. Recent advances in first-principles calculations and atomistic simulations further help us in understanding atomic bonding, dislocation configuration, and alloying effects in intermetallics. The basic understanding has led to the development of nickel, iron, and titanium aluminide alloys with improved mechanical and metallurgical properties for structural use. Industrial interest in ductile intermetallic alloys is high, and several examples of industrial involvement are mentioned.

  7. Recent advances in ordered intermetallics

    SciTech Connect

    Liu, C.T.

    1994-12-31

    Ordered intermetallic alloys based on aluminides and silicides offer many advantages for structural use at high temperatures in hostile environments. Attractive properties include excellent oxidation and corrosion resistance, light weight, and superior strength at high temperatures. The major concern for structural use of intermetallics was their low ductility and poor fracture resistance at ambient temperatures. For the past 10 years, considerable effort was devoted to R&D of ordered intermetallic alloys, and progress has been made on understanding intrinsic and extrinsic factors controlling brittle fracture in intermetallic alloys based on aluminides and silicides. Parallel effort on alloy design has led to the development of a number of ductile and strong intermetallic alloys based on Ni{sub 3}Al, NiAl, Fe{sub 3}Al, FeAl, Ti{sub 3}Al, and TiAl systems for structural applications.

  8. Potentiodynamic polarization effect on phase and microstructure of SAC305 solder in hydrochloric acid solution

    NASA Astrophysics Data System (ADS)

    Zaini, Nurwahida Binti Mohd; Nazeri, Muhammad Firdaus Bin Mohd

    2016-07-01

    The corrosion analysis of SAC305 lead free solder was investigated in Hydrochloric acid (HCl) solution. Potentiodynamic polarization was used to polarize the SAC305. The effect of polarization on the phase and microstructure were compared to as-prepared SAC305 solder. Potentiodynamic polarization introduces mixed corrosion products on the surface of SAC305 solder. The XRD analysis confirms that the mixed corrosion products emerged on the surface after polarization by formation of SnO and SnO2 of which confirmed that dissolution of Sn was dominant during polarization. Microstructure analysis reveal the presence of gap and porosities produced limits the protection offered by the passivation film.

  9. SrAu4In4 and Sr4Au9In13: Polar Intermetallic Structures with Cations in Augmented Hexagonal Prismatic Environments

    SciTech Connect

    Palasyuk, A.; Dai, J.C.; Corbett, J.

    2008-03-11

    The title compounds were synthesized via high-temperature reactions of the elements in welded Ta tubes and characterized by single-crystal X-ray diffraction analyses and band structure calculations. SrAu{sub 3.76(2)}In{sub 4.24} crystallizes in the YCo{sub 5}In{sub 3} structure type with two of eight network sites occupied by mixtures of Au and In: Pnma, Z = 4, a = 13.946(7), b = 4.458(2), c = 12.921(6) {angstrom}. Its phase breadth appears to be small. Sr{sub 4}Au{sub 9}In{sub 13} exhibits a new structure type, P{sub 6}m2, Z = 1, a = 12.701(2), c = 4.4350(9) {angstrom}. The Sr atoms in both compounds center hexagonal prisms of nominally alternating In and Au atoms and also have nine augmenting (outer) Au + In atoms around their waists so as to define 21-vertex Sr{at}Au{sub 9}M{sub 4}In{sub 8} (M = Au/In) and Sr{at}Au{sub 9}In{sub 12} polyhedra, respectively. The relatively larger Sr content in the second phase also leads to condensation of some of the ideal building units into trefoil-like cages with edge-shared six-member rings. One overall driving force for the formation of these structures can be viewed as the need for each Sr cation to have as many close neighbors as possible in the more anionic Au-In network. The results also depend on the cation size as well as on the flexibility of the anionic network and an efficient intercluster condensation mode as all clusters are shared. Band structure calculations (LMTO-ASA) emphasize the greater strengths (overlap populations) of the Au-In bonds and confirm expectations that both compounds are metallic.

  10. Molecular-level comparison of alkylsilane and polar-embedded reversed-phase liquid chromatography systems.

    PubMed

    Rafferty, Jake L; Siepmann, J Ilja; Schure, Mark R

    2008-08-15

    Stationary phases with embedded polar groups possess several advantages over conventional alkylsilane phases, such as reduced peak tailing, enhanced selectivity for specific functional groups, and the ability to use a highly aqueous mobile phase. To gain a deeper understanding of the retentive properties of these reversed-phase packings, molecular simulations were carried out for three different stationary phases in contact with mobile phases of various water/methanol ratios. Two polar-embedded phases were modeled, namely, amide and ether containing, and compared to a conventional octadecylsilane phase. The simulations show that, due to specific hydrogen bond interactions, the polar-embedded phases take up significantly more solvent and are more ordered than their alkyl counterparts. Alkane and alcohol probe solutes indicate that the polar-embedded phases are less retentive than alkyl phases for nonpolar species, whereas polar species are more retained by them due to hydrogen bonding with the embedded groups and the increased amount of solvent within the stationary phase. This leads to a significant reduction of the free-energy barrier for the transfer of polar species from the mobile phase to residual silanols, and this reduced barrier provides a possible explanation for reduced peak tailing.

  11. Global Observation of Substorm Growth Phase Processes in the Polar Caps

    NASA Technical Reports Server (NTRS)

    Brittnacher, M.; OFillingim, M. O.; Chua, D.; Wilber, M.; Parks, G. K.; Germany, G. A.; Spann, J. F.

    1998-01-01

    Global images of the polar cap region during the substorm growth phase by the Polar Ultraviolet Imager reveals evidence of the processes which are not completely explained by current models. In particular, it was found that size of the polar cap region increases during the growth phase even if the interplanetary magnetic field has no southward component. Three phenomena were observed to produce an increase in the size of the polar cap: (1) motion of the auroral oval to lower latitude, (2) thinning of the auroral oval, and (3) reduction of intense aurora[ precipitation in the polar region. Correlation of image intensities with in situ particle measurements from the FAST satellite are being conducted to study the three growth phase phenomena; and to help identify the source regions of the particles, the mechanisms involved in producing the auroral structures and what may be reducing the polar cap precipitation during the substorm growth phase.

  12. Quorum polarity and the dynamics of the zooming bionematic phase

    NASA Astrophysics Data System (ADS)

    Kessler, John O.

    2005-03-01

    Many species of bacteria are peritrichously flagellated, i.e. the long, helical, rapidly rotating flagella that propel them emerge out of motors that appear randomly distributed over the body of the bacterial cell. The organism considered here is Bacillus subtilis. The cell body is a rod approximately 4 μm long, 0.7μm in diameter; flagella are 3 or 4 times longer than the body. Swimming cells are pushed by the flagella, bundled into a braid of rotating helices. When the bacteria self concentrate into an approximately close-packed assemblage, rapidly moving (zooming) domains of aligned bacterial rods continually form and break apart. PIV measurements show that correlation times are seconds, lengths are hundreds of micrometers, transport of passive tracers is superdiffusive.Below a threshold concentration there is no collective dynamic. A theory of this zooming bionematic phase will be presented, together with measurements and video sequences. The theory considers hydrodynamic cell-cell and collective interactions, the collectively generated flow of the suspending water relative to the cells, and the dynamics of helix bundle flipping, yielding quorum polarity within a given zooming domain. Quorum sensing of signalling molecules and molecular transport generally are pertinent microbiological applications.

  13. Full-Polarization 3D Metasurface Cloak with Preserved Amplitude and Phase.

    PubMed

    Yang, Yihao; Jing, Liqiao; Zheng, Bin; Hao, Ran; Yin, Wenyan; Li, Erping; Soukoulis, Costas M; Chen, Hongsheng

    2016-08-01

    A full-polarization arbitrary-shaped 3D metasurface cloak with preserved amplitude and phase in microwave frequencies is experimentally demonstrated. By taking the unique feature of metasurfaces, it is shown that the cloak can completely restore the polarization, amplitude, and phase of light for full polarization as if light was incident on a flat mirror. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Polarization-sensitive optical coherence tomography measurements with different phase modulation amplitude when using continuous polarization modulation

    NASA Astrophysics Data System (ADS)

    Lu, Zenghai; Kasaragod, Deepa K.; Matcher, Stephen J.

    2012-01-01

    We demonstrate theoretically and experimentally that the phase retardance and relative optic-axis orientation of a sample can be calculated without prior knowledge of the actual value of the phase modulation amplitude when using a polarization-sensitive optical coherence tomography system based on continuous polarization modulation (CPM-PS-OCT). We also demonstrate that the sample Jones matrix can be calculated at any values of the phase modulation amplitude in a reasonable range depending on the system effective signal-to-noise ratio. This has fundamental importance for the development of clinical systems by simplifying the polarization modulator drive instrumentation and eliminating its calibration procedure. This was validated on measurements of a three-quarter waveplate and an equine tendon sample by a fiber-based swept-source CPM-PS-OCT system.

  15. Synthesis, structure, and bonding in K12Au21Sn4. A polar intermetallic compound with dense Au20 and open AuSn4 layers

    SciTech Connect

    Li, Bin; Kim, Sung-Jin; Miller, Gordon J.; and Corbett, John D.

    2009-10-29

    The new phase K{sub 12}Au{sub 21}Sn{sub 4} has been synthesized by direct reaction of the elements at elevated temperatures. Single crystal X-ray diffraction established its orthorhombic structure, space group Pmmn (No. 59), a = 12.162(2); b = 18.058(4); c = 8.657(2) {angstrom}, V = 1901.3(7) {angstrom}{sup 3}, and Z = 2. The structure consists of infinite puckered sheets of vertex-sharing gold tetrahedra (Au{sub 20}) that are tied together by thin layers of alternating four-bonded-Sn and -Au atoms (AuSn{sub 4}). Remarkably, the dense but electron-poorer blocks of Au tetrahedra coexist with more open and saturated Au-Sn layers, which are fragments of a zinc blende type structure that maximize tetrahedral heteroatomic bonding outside of the network of gold tetrahedra. LMTO band structure calculations reveal metallic properties and a pseudogap at 256 valence electrons per formula unit, only three electrons fewer than in the title compound and at a point at which strong Au-Sn bonding is optimized. Additionally, the tight coordination of the Au framework atoms by K plays an important bonding role: each Au tetrahedra has 10 K neighbors and each K atom has 8-12 Au contacts. The appreciably different role of the p element Sn in this structure from that in the triel members in K{sub 3}Au{sub 5}In and Rb{sub 2}Au{sub 3}Tl appears to arise from its higher electron count which leads to better p-bonding (valence electron concentrations = 1.32 versus 1.22).

  16. Parallel-quadrature phase-shifting digital holographic microscopy using polarization beam splitter

    NASA Astrophysics Data System (ADS)

    Das, Bhargab; Yelleswarapu, Chandra S.; Rao, D. V. G. L. N.

    2012-11-01

    We present a digital holography microscopy technique based on a parallel-quadrature phase-shifting method. Two π/2 phase-shifted holograms are recorded simultaneously using polarization phase-shifting principle, slightly off-axis recording geometry, and two identical CCD sensors. The parallel phase-shifting is realized by combining circularly polarized object beam with a 45° degree polarized reference beam through a polarizing beam splitter. DC term is eliminated by subtracting the two holograms from each other and the object information is reconstructed after selecting the frequency spectrum of the real image. Both amplitude and phase object reconstruction results are presented. Simultaneous recording eliminates phase errors caused by mechanical vibrations and air turbulences. The slightly off-axis recording geometry with phase-shifting allows a much larger dimension of the spatial filter for reconstruction of the object information. This leads to better reconstruction capability than traditional off-axis holography.

  17. Parallel-quadrature phase-shifting digital holographic microscopy using polarization beam splitter.

    PubMed

    Das, Bhargab; Yelleswarapu, Chandra S; Rao, Dvgln

    2012-11-01

    We present a digital holography microscopy technique based on parallel-quadrature phase-shifting method. Two π/2 phase-shifted holograms are recorded simultaneously using polarization phase-shifting principle, slightly off-axis recording geometry, and two identical CCD sensors. The parallel phase-shifting is realized by combining circularly polarized object beam with a 45° degree polarized reference beam through a polarizing beam splitter. DC term is eliminated by subtracting the two holograms from each other and the object information is reconstructed after selecting the frequency spectrum of the real image. Both amplitude and phase object reconstruction results are presented. Simultaneous recording eliminates phase errors caused by mechanical vibrations and air turbulences. The slightly off-axis recording geometry with phase-shifting allows a much larger dimension of the spatial filter for reconstruction of the object information. This leads to better reconstruction capability than traditional off-axis holography.

  18. Parallel-quadrature phase-shifting digital holographic microscopy using polarization beam splitter

    PubMed Central

    Das, Bhargab; Yelleswarapu, Chandra S; Rao, DVGLN

    2012-01-01

    We present a digital holography microscopy technique based on parallel-quadrature phase-shifting method. Two π/2 phase-shifted holograms are recorded simultaneously using polarization phase-shifting principle, slightly off-axis recording geometry, and two identical CCD sensors. The parallel phase-shifting is realized by combining circularly polarized object beam with a 45° degree polarized reference beam through a polarizing beam splitter. DC term is eliminated by subtracting the two holograms from each other and the object information is reconstructed after selecting the frequency spectrum of the real image. Both amplitude and phase object reconstruction results are presented. Simultaneous recording eliminates phase errors caused by mechanical vibrations and air turbulences. The slightly off-axis recording geometry with phase-shifting allows a much larger dimension of the spatial filter for reconstruction of the object information. This leads to better reconstruction capability than traditional off-axis holography. PMID:23109732

  19. First-principles studies of Ni-Ta intermetallic compounds

    SciTech Connect

    Zhou Yi; Wen Bin; Ma Yunqing; Melnik, Roderick; Liu Xingjun

    2012-03-15

    The structural properties, heats of formation, elastic properties, and electronic structures of Ni-Ta intermetallic compounds are investigated in detail based on density functional theory. Our results indicate that all Ni-Ta intermetallic compounds calculated here are mechanically stable except for P21/m-Ni{sub 3}Ta and hc-NiTa{sub 2}. Furthermore, we found that Pmmn-Ni{sub 3}Ta is the ground state stable phase of Ni{sub 3}Ta polymorphs. The polycrystalline elastic modulus has been deduced by using the Voigt-Reuss-Hill approximation. All Ni-Ta intermetallic compounds in our study, except for NiTa, are ductile materials by corresponding G/K values and poisson's ratio. The calculated heats of formation demonstrated that Ni{sub 2}Ta are thermodynamically unstable. Our results also indicated that all Ni-Ta intermetallic compounds analyzed here are conductors. The density of state demonstrated the structure stability increases with the Ta concentration. - Graphical abstract: Mechanical properties and formation heats of Ni-Ta intermetallic compounds are discussed in detail in this paper. Highlights: Black-Right-Pointing-Pointer Ni-Ta intermetallic compounds are investigated by first principle calculations. Black-Right-Pointing-Pointer P21/m-Ni{sub 3}Ta and hc-NiTa{sub 2} are mechanically unstable phases. Black-Right-Pointing-Pointer Pmmn-Ni{sub 3}Ta is ground stable phase of Ni{sub 3}Ta polymorphs. Black-Right-Pointing-Pointer All Ni-Ta intermetallic compounds are conducting materials.

  20. An optically controlled phased array antenna based on single sideband polarization modulation.

    PubMed

    Zhang, Yamei; Wu, Huan; Zhu, Dan; Pan, Shilong

    2014-02-24

    A novel optically controlled phased array antenna consisting a simple optical beamforming network and an N element linear patch antenna array is proposed and demonstrated. The optical beamforming network is realized by N independent phase shifters using a shared optical single sideband (OSSB) polarization modulator together with N polarization controllers (PCs), N polarization beam splitters (PBSs) and N photodetectors (PDs). An experiment is carried out. A 4-element linear patch antenna array operating at 14 GHz and a 1 × 4 optical beamforming network (OBFN) is employed to realize the phased array antenna. The radiation patterns of the phased array antenna at -30°, 0° and 30° are achieved.

  1. Advanced ordered intermetallic alloy deployment

    SciTech Connect

    Liu, C.T.; Maziasz, P.J.; Easton, D.S.

    1997-04-01

    The need for high-strength, high-temperature, and light-weight materials for structural applications has generated a great deal of interest in ordered intermetallic alloys, particularly in {gamma}-based titanium aluminides {gamma}-based TiAl alloys offer an attractive mix of low density ({approximately}4g/cm{sup 3}), good creep resistance, and high-temperature strength and oxidation resistance. For rotating or high-speed components. TiAl also has a high damping coefficient which minimizes vibrations and noise. These alloys generally contain two phases. {alpha}{sub 2} (DO{sub 19} structure) and {gamma} (L 1{sub 0}), at temperatures below 1120{degrees}C, the euticoid temperature. The mechanical properties of TiAl-based alloys are sensitive to both alloy compositions and microstructure. Depending on heat-treatment and thermomechanical processing, microstructures with near equiaxed {gamma}, a duplex structure (a mix of the {gamma} and {alpha}{sub 2} phases) can be developed in TiAl alloys containing 45 to 50 at. % Al. The major concern for structural use of TiAl alloys is their low ductility and poor fracture resistance at ambient temperatures. The purpose of this project is to improve the fracture toughness of TiAl-based alloys by controlling alloy composition, microstructure and thermomechanical treatment. This work is expected to lead to the development of TiAl alloys with significantly improved fracture toughness and tensile ductility for structural use.

  2. Ag–Pt compositional intermetallics made from alloy nanoparticles

    DOE PAGES

    Pan, Yung -Tin; Yan, Yuqi; Shao, Yu -Tsun; ...

    2016-09-07

    Intermetallics are compounds with long-range structural order that often lies in a state of thermodynamic minimum. They are usually considered as favorable structures for catalysis due to their high activity and robust stability. However, formation of intermetallic compounds is often regarded as element specific. For instance, Ag and Pt do not form alloy in bulk phase through the conventional metallurgy approach in almost the entire range of composition. Herein, we demonstrate a bottom-up approach to create a new Ag–Pt compositional intermetallic phase from nanoparticles. By thermally treating the corresponding alloy nanoparticles in inert atmosphere, we obtained an intermetallic material thatmore » has an exceptionally narrow Ag/Pt ratio around 52/48 to 53/47, and a structure of interchangeable closely packed Ag and Pt layers with 85% on tetrahedral and 15% on octahedral sites. This rather unique stacking results in wavy patterns of Ag and Pt planes revealed by scanning transmission electron microscope (STEM). Finally, this Ag–Pt compositional intermetallic phase is highly active for electrochemical oxidation of formic acid at low anodic potentials, 5 times higher than its alloy nanoparticles, and 29 times higher than the reference Pt/C at 0.4 V (vs RHE) in current density.« less

  3. Microstructure and electrochemical characterization of laser melt-deposited Ti{sub 2}Ni{sub 3}Si/NiTi intermetallic alloys

    SciTech Connect

    Dong Lixin Wang Huaming

    2008-11-15

    Corrosion and wear resistant Ti{sub 2}Ni{sub 3}Si/NiTi intermetallic alloys with Ti{sub 2}Ni{sub 3}Si as the reinforcing phase and the ductile NiTi as the toughening phase were designed and fabricated by the laser melt-deposition manufacturing process. Electrochemical behavior of the alloys was investigated using potentiodynamic polarization testing and electrochemical impedance spectroscopy in an NaOH solution. The results showed that the alloys have outstanding corrosion resistance due to the formation of a protective passive surface film of Ni(OH){sub 2} as well as the high chemical stability and strong inter-atomic bonds inherent to Ti{sub 2}Ni{sub 3}Si and NiTi intermetallics. The Ti{sub 2}Ni{sub 3}Si content has a significant influence on the microstructure of the alloys but only a slight effect on electrochemical corrosion properties.

  4. Materials Processing and Microstructure Control in High Temperature Ordered Intermetallics.

    DTIC Science & Technology

    2007-11-02

    an integrated approach that couples processing with microstructure control as guided by the operative phase equilibria has been used to identify...several promising intermetallic alloys. The experimental efforts have focused on three areas involving a coordination of phase equilibria information with

  5. Tunable giant exchange bias in the single-phase rare-earth-transition-metal intermetallics YM n12 -xF ex with highly homogenous intersublattice exchange coupling

    NASA Astrophysics Data System (ADS)

    Xia, Yuanhua; Wu, Rui; Zhang, Yinfeng; Liu, Shunquan; Du, Honglin; Han, Jingzhi; Wang, Changsheng; Chen, Xiping; Xie, Lei; Yang, Yingchang; Yang, Jinbo

    2017-08-01

    A tunable giant exchange bias effect is discovered in a family of bulk intermetallic compounds YM n12 -xF ex . Experimental data demonstrate that the exchange bias effect originates from global interactions among ferromagnetic and antiferromagnetic sublattices but not the interfacial exchange coupling or inhomogeneous magnetic clusters. A giant exchange bias with a loop shift of up to 6.1 kOe has been observed in YM n4.4F e7.6 compound. In a narrow temperature range, the exchange bias field shows a sudden switching-off whereas the coercivity shows a sudden switching-on with increasing temperature. This unique feature indicates that the intersublattice exchange coupling is highly homogenous. Our theoretical calculations reveal this switching feature, which agrees very well with the experiments and provides insights into the physical underpinnings of the observed exchange bias and coercivity.

  6. Focusing light through scattering media by full-polarization digital optical phase conjugation

    PubMed Central

    Shen, Yuecheng; Liu, Yan; Ma, Cheng; Wang, Lihong V.

    2016-01-01

    Digital optical phase conjugation (DOPC) is an emerging technique for focusing light through or within scattering media such as biological tissue. Since DOPC systems are based on time reversal, they benefit from collecting as much information about the scattered light as possible. However, existing DOPC techniques record and subsequently phase-conjugate the scattered light in only a single polarization state, limited by the operating principle of spatial light modulators. Here, we develop the first full-polarization DOPC system which records and phase-conjugates scattered light along two orthogonal polarizations. When focusing light through thick scattering media, such as 2 mm and 4 mm thick chicken breast tissue, our full-polarization DOPC system on average doubles the focal peak-to-background ratio achieved by single-polarization DOPC systems and improves the phase conjugation fidelity. PMID:26977651

  7. Polarization sensitive phase-shifting Mirau interferometry using a liquid crystal variable retarder.

    PubMed

    Bouchal, Petr; Čelechovský, Radek; Bouchal, Zdeněk

    2015-10-01

    We present all-optical motionless arrangement for polarization sensitive phase-shifting (P-S) interferometry, where the phase shifts are accurately implemented by a liquid crystal variable retarder (LCVR). The LCVR is used as a polarization selective device capable of introducing a computer-controlled phase retardance between signal and reference waves with orthogonal linear polarizations. The proposed optical P-S is deployed in a polarization adapted common-path Mirau interferometer. Application of the method to a setup using the Michelson interference objective or Linnik interference module is also outlined. The accuracy of the quantitative phase reconstruction is examined theoretically, and a possibility to reduce the optical path difference error below 1/200 wavelength is demonstrated experimentally. Benefits and application potential of the polarization P-S interferometry supported by versatile liquid crystal devices are also discussed.

  8. Focusing light through scattering media by full-polarization digital optical phase conjugation.

    PubMed

    Shen, Yuecheng; Liu, Yan; Ma, Cheng; Wang, Lihong V

    2016-03-15

    Digital optical phase conjugation (DOPC) is an emerging technique for focusing light through or within scattering media such as biological tissue. Since DOPC systems are based on time reversal, they benefit from collecting as much information about the scattered light as possible. However, existing DOPC techniques record and subsequently phase-conjugate the scattered light in only a single-polarization state, limited by the operating principle of spatial light modulators. Here, we develop the first, to the best of our knowledge, full-polarization DOPC system that records and phase-conjugates scattered light along two orthogonal polarizations. When focusing light through thick scattering media, such as 2 mm and 4 mm-thick chicken breast tissue, our full-polarization DOPC system on average doubles the focal peak-to-background ratio achieved by single-polarization DOPC systems and improves the phase-conjugation fidelity.

  9. Single-shot polarization-imaging digital holography based on simultaneous phase-shifting interferometry.

    PubMed

    Tahara, Tatsuki; Awatsuji, Yasuhiro; Shimozato, Yuki; Kakue, Takashi; Nishio, Kenzo; Ura, Shogo; Kubota, Toshihiro; Matoba, Osamu

    2011-08-15

    We propose single-shot digital holography which is capable of simultaneously capturing both the information of multiple phase-shifted holograms and the distribution of the polarization. In this technique, a single image sensor records both the information required for phase-shifting interferometry and that of the polarization states of objects using an array of polarizers. The essence of the technique is the capability of imaging the distribution of the polarization of three-dimensional objects with a single-shot exposure by using the space-division multiplexing of holograms. The validity of the proposed technique was confirmed by the preliminary experiments. © 2011 Optical Society of America

  10. A polar-embedded C30 stationary phase: preparation and evaluation.

    PubMed

    Zhang, Mingliang; Mai, Wenpeng; Zhao, Liang; Guo, Yong; Qiu, Hongdeng

    2015-04-03

    A novel polar-embedded C30 stationary phase has been synthesized and characterized. The polar carbamate group was generated homogeneously in situ by the catalytic reaction between isocyanate and primary alcohol. The simple one-pot synthetic strategy provided an efficient and effective strategy for modification of silica spheres. Efficiency, selectivity and silanol activity of the resulting column were characterized in detail with different classes of analytes that included Standard Reference Materials (SRM) 870, SRM 869b and SRM 1647e, alkylbenzene congeners, as well as polar-substituted aromatics. The polar-embedded C30 stationary phase was found to exhibit excellent shape selectivity.

  11. MECHANICAL BEHAVIOR OF INTERMETALLIC COMPOUNDS.

    DTIC Science & Technology

    AGING(MATERIALS), AGING(MATERIALS), INTERMETALLIC COMPOUNDS, VANADIUM ALLOYS, COBALT ALLOYS, NICKEL ALLOYS, MECHANICAL PROPERTIES, TEMPERATURE, TIME ... CRYSTAL STRUCTURE, MICROSTRUCTURE, HARDNESS, TRANSFORMATIONS, ELECTRICAL RESISTANCE, MEASUREMENT, MICROSCOPY, ALLOYS, METALLOGRAPHY, X RAY DIFFRACTION.

  12. One-shot phase-shifting phase-grating interferometry with modulation of polarization: case of four interferograms.

    PubMed

    Rodriguez-Zurita, Gustavo; Meneses-Fabian, Cruz; Toto-Arellano, Noel-Ivan; Vázquez-Castillo, José F; Robledo-Sánchez, Carlos

    2008-05-26

    An experimental setup for optical phase extraction from 2-D interferograms using a one-shot phase-shifting technique able to achieve four interferograms with 90 degrees phase shifts in between is presented. The system uses a common-path interferometer consisting of two windows in the input plane and a phase grating in Fourier plane as its pupil. Each window has a birefringent wave plate attached in order to achieve nearly circular polarization of opposite rotations one respect to the other after being illuminated with a 45 degrees linear polarized beam. In the output, interference of the fields associated with replicated windows (diffraction orders) is achieved by a proper choice of the windows spacing with respect to the grating period. The phase shifts to achieve four interferograms simultaneously to perform phase-shifting interferometry can be obtained by placing linear polarizers on each diffraction orders before detection at an appropriate angle. Some experimental results are shown.

  13. Self-referenced rectangular path cyclic interferometer with polarization phase shifting.

    PubMed

    Sarkar, S; Ghosh, N; Chakraborty, S; Bhattacharya, K

    2012-01-01

    A polarization phase shifting interferometer using a cyclic path configuration for measurement of phase nonuniformities in transparent samples is presented. A cube beam splitter masked by two linear polarizers is used to split the source wavefront into two counter propagating linearly polarized beams that pass through the sample. At the output of the interferometer, the two orthogonally polarized beams are rendered circularly polarized in the opposite sense through the use of a quarter wave plate. Finally, phase shifting is achieved by rotating a linear polarizer before the recording plane. In a rectangular path interferometer, although the two counter propagating wavefronts are laterally folded with respect to each other in the interferometer arms, the beams finally emerge mutually unfolded at the output of the interferometer. This phenomenon is utilized to create a reference if the sample is introduced in one lateral half of the beam in any one of the interferometer arms. The polarization phase shifting technique is used to generate four phase-shifted interferograms, which are utilized to evaluate the phase profile of the phase sample. Experimental results presented validate the proposed technique.

  14. Observation of ferroelectric phase and large spontaneous electric polarization in organic salt of diisopropylammonium iodide

    NASA Astrophysics Data System (ADS)

    Saripalli, Ravi K.; Swain, Diptikanta; Prasad, Siva; Nhalil, Hariharan; Bhat, Handady L.; Guru Row, Tayur N.; Elizabeth, Suja

    2017-03-01

    In this manuscript, we explore diisopropylammonium iodide (DPI) for its ferroelectric properties and phase transitions. DPI showed two phase transitions which were identified by differential scanning calorimetry and dielectric and nonlinear optical measurements. From detailed structural studies it was found that the first transition at 369 K is from orthorhombic P212121 to monoclinic P21. The polar P21 phase is ferroelectric as evidenced by the pyroelectric data and has a very high value of spontaneous polarization (Ps = 33 μC cm-2), which is probably the highest among other reported bulk organic ferroelectrics. The second transition at 415 K is identified as polar monoclinic P21 space group to non-polar monoclinic P21/m. Thus, DPI has a high Curie temperature of 415 K. The large spontaneous polarization and high Curie temperature make DPI technologically important.

  15. Effect of the spiral phase element on the radial-polarization (0, 1) ∗ LG beam

    NASA Astrophysics Data System (ADS)

    Machavariani, G.; Lumer, Y.; Moshe, I.; Jackel, S.

    2007-03-01

    Radially-polarized beams can be strongly amplified without significant birefringent-induced aberrations. However, radially-polarized beam is a high-order beam, and therefore has to be transformed into a fundamental Gaussian beam for reduction the beam-propagation factor M2. In effort to transform the radially-polarized beam to a nearly-Gaussian beam, we consider effect of a spiral phase element (SPE) on the Laguerre-Gaussian (LG) (0, 1)∗ beam with radial polarization, and compare this with the case when the input beam is a LG (0, 1)∗ beam with spiral phase and uniform or random polarization. The LG (0, 1)∗ beam with radial polarization, despite its identity in intensity profile to the beam with spiral phase, has distinctly different properties when interacting with the SPE. With the SPE and spatial filter, we transformed the radially-polarized (0, 1)∗ mode with M2 = 2.8 to a nearly-Gaussian beam with M2 = 1.7. Measured transformation efficiency was 50%, and the beam brightness P/(M2)2 was practically unchanged. The SPE affects polarization state of the radially-polarized beam, leading to appearance of spin angular momentum in the beam center at the far-field.

  16. Phase separation in a polarized Fermi gas with spin-orbit coupling

    SciTech Connect

    Yi, W.; Guo, G.-C.

    2011-09-15

    We study the phase separation of a spin-polarized Fermi gas with spin-orbit coupling near a wide Feshbach resonance. As a result of the competition between spin-orbit coupling and population imbalance, the phase diagram for a uniform gas develops a rich structure of phase separation involving topologically nontrivial gapless superfluid states. We then demonstrate the phase separation induced by an external trapping potential and discuss the optimal parameter region for the experimental observation of the gapless superfluid phases.

  17. Quantum phase diagram of Polar Molecules in 1D Double Wire Systems

    NASA Astrophysics Data System (ADS)

    Chang, Chi-Ming; Wang, Daw-Wei

    2007-03-01

    We study the quantum phase transitions of fermionic polar molecules loaded in a double wire potential. By tuning the magnitude and direction of external electric field we observed many interesting quantum phases in different parameter range, including an easy-plane spin density wave, a triplet superconducting phase, and a truly long range order of easy-axis ferromagnetic phase in strong interacting regime. We also discuss how these exotic quantum phases can be measured in the existing experimental techniques.

  18. Geometric-Phase Polarization Fan-out Grating Fabricated with Deep-UV Interference Lithography

    NASA Astrophysics Data System (ADS)

    Wan, Chenhao; Lombardo, David; Sarangan, Andrew; Zhan, Qiwen

    2017-06-01

    We report the design, fabrication and testing of a highly efficient polarization fan-out grating for coherent beam combining working at 1550 nm. The grating design exploits the geometric-phase effect. Deep-UV interference lithography is used to fabricate the designed grating. Such a polarization fan-out grating demonstrates several advantages that are ideal for laser beam combining.

  19. Radiation-induced amorphization of intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Lam, N. Q.; Sabochick, M. J.; Okamoto, P. R.

    1994-06-01

    In the present paper, important results of our recent computer simulation of radiation-induced amorphization in the ordered compounds CuTi and Cu4Ti3 are summarized. The energetic, structural, thermodynamic and mechanical responses of these intermetallics during chemical disordering, point-defect production and heating were simulated, using molecular dynamics and embedded-atom potentials. From the atomistic details obtained, the critical role of radiation-induced structural disorder in driving the crystalline-to-amorphous phase transformation is discussed.

  20. In-line phase retarder and polarimeter for conversion of linear to circular polarization

    SciTech Connect

    Kortright, J.B.; Smith, N.V.; Denlinger, J.D.

    1997-04-01

    An in-line polarimeter including phase retarder and linear polarizer was designed and commissioned on undulator beamline 7.0 for the purpose of converting linear to circular polarization for experiments downstream. In commissioning studies, Mo/Si multilayers at 95 eV were used both as the upstream, freestanding phase retarder and the downstream linear polarized. The polarization properties of the phase retarder were characterized by direct polarimetry and by collecting MCD spectra in photoemission from Gd and other magnetic surfaces. The resonant birefringence of transmission multilayers results from differing distributions of s- and p-component wave fields in the multilayer when operating near a structural (Bragg) interference condition. The resulting phase retardation is especially strong when the interference is at or near the Brewster angle, which is roughly 45{degrees} in the EUV and soft x-ray ranges.

  1. Reactions of intermetallic clusters

    SciTech Connect

    Farley, R.W.; Castleman, A.W. Jr. )

    1990-02-01

    Reaction of bismuth--alkali clusters with closed-shell HX acids provides insight into the structures, formation, and stabilities of these intermetallic species. HC1 and HI are observed to quantitatively strip Bi{sub {ital x}}Na{sub {ital y}} and Bi{sub {ital x}}K{sub {ital y}}, respectively, of their alkali component, leaving bare bismuth clusters as the only bismuth-containing species detected. Product bismuth clusters exhibit the same distribution observed when pure bismuth is evaporated in the source. Though evaporated simultaneously from the same crucible, this suggests alkali atoms condense onto existing bismuth clusters and have negligible effect on their formation and consequent distribution. The indistinguishibility of reacted and pure bismuth cluster distributions further argues against the simple replacement of alkali atoms with hydrogen in these reactions. This is considered further evidence that the alkali atoms are external to the stable bismuth Zintl anionic structures. Reactivities of Bi{sub {ital x}}Na{sub {ital y}} clusters with HC1 are estimated to lie between 3{times}10{sup {minus}13} for Bi{sub 4}Na, to greater than 4{times}10{sup {minus}11} for clusters possessing large numbers of alkali atoms. Bare bismuth clusters are observed in separate experiments to react significantly more slowly with rates of 1--9{times}10{sup {minus}14} and exhibit little variation of reactivity with size. The bismuth clusters may thus be considered a relatively inert substrate upon which the alkali overlayer reacts.

  2. Ultrahigh temperature intermetallic alloys

    SciTech Connect

    Brady, M.P.; Zhu, J.H.; Liu, C.T.; Tortorelli, P.F.; Wright, J.L.; Carmichael, C.A.

    1998-11-01

    A new family of Cr-Cr{sub 2}Ta intermetallic alloys based on Cr-(6--10)Ta (at.%) is under development for structural use in oxidizing environments in the 1,000-1,300 C (1,832--2,372 F) temperature range. Development objectives relate to high temperature strength and oxidation resistance and room temperature fracture toughness. The 1,200 C (2,192 F) strength goals have been met: yield and fracture strengths of 275 MPa (40 ksi) and 345 MPa (50 ksi), respectively, were achieved. Progress in attaining reasonable fracture toughness of Cr-Cr{sub 2}Ta alloys has been made; current alloys exhibit room-temperature values of about 10--12 MPa{radical}m (1.1 MPa{radical}m = 1 ksi{radical}in.). Oxidation rates of these alloys at 950 C (1,742 F) in air are in the range of those reported for chromia-forming alloys. At 1,100 C (2,012 F) in air, chromia volatility was significant but, nevertheless, no scale spallation and positive weight gains of 1--5 mg/cm{sup 2} have been observed during 120-h, 6-cycle oxidation screening tests. These mechanical and oxidative properties represent substantial improvement over Cr-Cr{sub 2}Nb and Cr-Cr{sub 2}Zr alloys previously developed.

  3. Measurement of relative phase distribution of onion epidermal cells by using the polarization microscope

    NASA Astrophysics Data System (ADS)

    Shin, In Hee; Lee, Ji Yong; Lee, Seungrag; Lee, Dong Ju; Kim, Dug Young

    2007-02-01

    Bio-cells and tissues have intrinsic polarization characteristics, which are changed by external stimulus and internal metamorphosis in cells and tissues and some of the bio-cells and tissues have intrinsic birefringence characteristics, which are also changed by external stimulus and internal metamorphosis in cells and tissues. In this paper, we have developed the polarization microscope for measurement of relative phase which results from birefringence characteristics of materials with improved linear polarizing method and have measured relative phase distribution of onion epidermal cells. From the measurement of the relative phase distribution of onion epidermal cells, decrease of relative phase distribution of onion epidermal cells was investigated as the elapse of time. In decrease of relative phase distribution, relative phase of cell membrane in onion epidermal cells decreased radically as compared with that of cytoplasm because decline of function in cell membrane that takes charge of matter transfer in onion epidermal cells has occurred.

  4. Characterisation of stationary phases in subcritical fluid chromatography with the solvation parameter model. III. Polar stationary phases.

    PubMed

    West, C; Lesellier, E

    2006-03-31

    In this third paper, varied types of polar stationary phases, namely silica gel (SI), cyano (CN)- and amino-propyl (NH2)-bonded silica, propanediol-bonded silica (DIOL), poly(ethylene glycol) (PEG) and poly(vinyl alcohol) (PVA), were investigated in subcritical fluid mobile phase. This study was performed to provide a greater knowledge of the properties of these phases in SFC, and to allow a more rapid and efficient choice of polar stationary phase in regard of the chemical nature of the solutes to be separated. The effect of the nature of the stationary phase on interactions between solute and stationary phases and between solute and carbon dioxide-modifier mobile phases was studied by the use of a linear solvation energy relationship (LSER), the solvation parameter model. The retention behaviour observed with sub/supercritical fluid with carbon dioxide-methanol is close to the one reported in normal-phase liquid chromatography with hexane. The hydrogen bond acidity and basicity, and the polarity/polarizability favour the solute retention when the molar volume of the solute reduces it. As with non-polar phases, the absence of water in the subcritical fluid allows the solute/stationary phase interactions to play a greater part in the retention behaviour. As expected, the DIOL phase and the bare silica display a similar behaviour towards acidic and basic solutes, when interactions with basic compounds are lower with the NH2 phase. On the CN phase, all interactions (hydrogen bonding, dipole-dipole and charge transfer) have a nearly equivalent weight on the retention. The polymeric phases, PEG and PVA, provide the most accurate models, possibly due to their better surface homogeneity.

  5. SYNTHESIS AND CHARACTERIZATION OF NEW INTERMETALLIC COMPOUNDS

    SciTech Connect

    Professor Monica Sorescu

    2003-05-07

    This six-month work is focused mainly on the properties of novel magnetic intermetallics. In the first project, we synthesized several 2:17 intermetallic compounds, namely Nd{sub 2}Fe{sub 15}Si{sub 2}, Nd{sub 2}Fe{sub 15}Al{sub 2}2, Nd{sub 2}Fe{sub 15}SiAl and Nd{sub 2}Fe{sub 15}SiMn, as well as several 1:12 intermetallic compounds, such as NdFe{sub 10}Si{sub 2}, NdFe{sub 10}Al{sub 2}, NdFe{sub 10}SiAl and NdFe{sub 10}MnAl. In the second project, seven compositions of Nd{sub x}Fe{sub 100-x-y}B{sub y} ribbons were prepared by a melt spinning method with Nd and B content increasing from 7.3 and 3.6 to 11 and 6, respectively. The alloys were annealed under optimized conditions to obtain a composite material consisting of the hard magnetic Nd{sub 2}Fe{sub 14}B and soft magnetic {alpha}-Fe phases, typical of a spring magnet structure. In the third project, intermetallic compounds of the type Zr{sub 1}Cr{sub 1}Fe{sub 1}T{sub 0.8} with T=Al, Co and Fe were subjected to hydrogenation. In the fourth project, we performed three crucial experiments. In the first experiment, we subjected a mixture of Fe{sub 3}O{sub 4} and Fe(80-20 wt%) to mechanochemical activation by high-energy ball milling, for time periods ranging from 0.5 to 14 hours. In the second experiment, we ball-milled Fe{sub 3}O{sub 4}:Co{sup 2+} (x=0.1) for time intervals between 2.5 and 17.5 hours. Finally, we exposed a mixture of Fe{sub 3}O{sub 4} and Co(80-20 wt%) to mechanochemical activation for time periods ranging from 0.5 to 10 hours. In all cases, the structural and magnetic properties of the systems involved were elucidated by X-ray diffraction (XRD), Moessbauer spectroscopy and hysteresis loop measurements. The four projects resulted in four papers, which are currently being considered for publication in Intermetallics, IEEE Transactions on Magnetics, Journal of Materials Science Letters and Journal of Materials Science. The contributions reveal for the first time in literature the effect of

  6. Creation of Sub-diffraction Longitudinally Polarized Spot by Focusing Radially Polarized Light with Binary Phase Lens.

    PubMed

    Yu, An-Ping; Chen, Gang; Zhang, Zhi-Hai; Wen, Zhong-Quan; Dai, Lu-Ru; Zhang, Kun; Jiang, Sen-Lin; Wu, Zhi-Xiang; Li, Yu-Yan; Wang, Chang-Tao; Luo, Xian-Gang

    2016-12-12

    The generation of a sub-diffraction longitudinally polarized spot is of great interest in various applications, such as optical tweezers, super-resolution microscopy, high-resolution Raman spectroscopy, and high-density optical data storage. Many theoretical investigations have been conducted into the tight focusing of a longitudinally polarized spot with high-numerical-aperture aplanatic lenses in combination with optical filters. Optical super-oscillation provides a new approach to focusing light beyond the diffraction limit. Here, we propose a planar binary phase lens and experimentally demonstrate the generation of a longitudinally polarized sub-diffraction focal spot by focusing radially polarized light. The lens has a numerical aperture of 0.93 and a long focal length of 200λ for wavelength λ = 632.8 nm, and the generated focal spot has a full-width-at-half-maximum of about 0.456λ, which is smaller than the diffraction limit, 0.54λ. A 5λ-long longitudinally polarized optical needle with sub-diffraction size is also observed near the designed focal point.

  7. Creation of Sub-diffraction Longitudinally Polarized Spot by Focusing Radially Polarized Light with Binary Phase Lens

    PubMed Central

    Yu, An-ping; Chen, Gang; Zhang, Zhi-hai; Wen, Zhong-quan; Dai, Lu-ru; Zhang, Kun; Jiang, Sen-lin; Wu, Zhi-xiang; Li, Yu-yan; Wang, Chang-tao; Luo, Xian-gang

    2016-01-01

    The generation of a sub-diffraction longitudinally polarized spot is of great interest in various applications, such as optical tweezers, super-resolution microscopy, high-resolution Raman spectroscopy, and high-density optical data storage. Many theoretical investigations have been conducted into the tight focusing of a longitudinally polarized spot with high-numerical-aperture aplanatic lenses in combination with optical filters. Optical super-oscillation provides a new approach to focusing light beyond the diffraction limit. Here, we propose a planar binary phase lens and experimentally demonstrate the generation of a longitudinally polarized sub-diffraction focal spot by focusing radially polarized light. The lens has a numerical aperture of 0.93 and a long focal length of 200λ for wavelength λ = 632.8 nm, and the generated focal spot has a full-width-at-half-maximum of about 0.456λ, which is smaller than the diffraction limit, 0.54λ. A 5λ-long longitudinally polarized optical needle with sub-diffraction size is also observed near the designed focal point. PMID:27941852

  8. Creation of Sub-diffraction Longitudinally Polarized Spot by Focusing Radially Polarized Light with Binary Phase Lens

    NASA Astrophysics Data System (ADS)

    Yu, An-Ping; Chen, Gang; Zhang, Zhi-Hai; Wen, Zhong-Quan; Dai, Lu-Ru; Zhang, Kun; Jiang, Sen-Lin; Wu, Zhi-Xiang; Li, Yu-Yan; Wang, Chang-Tao; Luo, Xian-Gang

    2016-12-01

    The generation of a sub-diffraction longitudinally polarized spot is of great interest in various applications, such as optical tweezers, super-resolution microscopy, high-resolution Raman spectroscopy, and high-density optical data storage. Many theoretical investigations have been conducted into the tight focusing of a longitudinally polarized spot with high-numerical-aperture aplanatic lenses in combination with optical filters. Optical super-oscillation provides a new approach to focusing light beyond the diffraction limit. Here, we propose a planar binary phase lens and experimentally demonstrate the generation of a longitudinally polarized sub-diffraction focal spot by focusing radially polarized light. The lens has a numerical aperture of 0.93 and a long focal length of 200λ for wavelength λ = 632.8 nm, and the generated focal spot has a full-width-at-half-maximum of about 0.456λ, which is smaller than the diffraction limit, 0.54λ. A 5λ-long longitudinally polarized optical needle with sub-diffraction size is also observed near the designed focal point.

  9. Structural size effects of intermetallic compounds on the mechanical properties of Mo-Si-B alloy: An experimental investigation

    NASA Astrophysics Data System (ADS)

    Byun, Jong Min; Bang, Su-Ryong; Park, Chun Woong; Suk, Myung-Jin; Kim, Young Do

    2016-01-01

    In general, size, shape and dispersion of phases in alloys significantly affect mechanical properties. In this study, the mechanical properties of Mo-Si-B alloys were experimentally investigated with regards to the refinement of intermetallic compound. To confirm the size effect of the intermetallic compound phases on mechanical properties, two differently sized intermetallic compound powders consisting Mo5SiB2 and Mo3Si were fabricated by mechano-chemical process and high-energy ball milling. A modified powder metallurgy method was used with core-shell intermetallic powders where the intermetallic compound particles were the core and nano-sized Mo particles which formed by the hydrogen reduction of Mo oxide were the shells, leading to the microstructures with uniformly distributed intermetallic compound phases within a continuous α-Mo matrix phase. Vickers hardness and fracture toughness were measured to examine the mechanical properties of sintered bodies. Vickers hardness was 472 Hv for the fine intermetallic compound powder and 415 Hv for the coarse intermetallic compound powder. The fracture toughness was 12.4 MPa·√m for the fine IMC powders and 13.5 MPa·√m for the coarse intermetallic compound powder.

  10. Solid phase extraction cleanup for non-polar and moderately polar molecular markers of PM 2.5 sources

    NASA Astrophysics Data System (ADS)

    Turlington, John M.; McDow, Stephen R.

    2010-06-01

    A solid phase extraction cleanup step substantially improved analytical efficiency and data quality for measurements of non-polar and moderately polar organic molecular marker concentrations in airborne particulate matter. Rapid gas chromatography column deterioration was evident after very few samples in the absence of a cleanup step, resulting in the need for frequent recalibration. High molecular weight polycyclic aromatic hydrocarbons, were among the species most strongly impacted by the deterioration, exhibiting deviations as high as 30-40% from expected calibration verification standard values after only a few injections. Column deterioration and calibration verification failure were eliminated by introducing a solid phase extraction step prior to analysis and a total of 58 samples were analyzed with no unacceptable deviation of calibration verification standards from target values

  11. Effects of birefringence on Fizeau interferometry that uses a polarization phase-shifting technique.

    PubMed

    Zhao, Chunyu; Kang, Dongyel; Burge, James H

    2005-12-10

    Interferometers that use different states of polarization for the reference and the test beams can modulate the relative phase shift by using polarization optics in the imaging system. Thus the interferometer can capture simultaneous images that have a fixed phase shift, which can be used for phase-shifting interferometry. As all measurements are made simultaneously, the interferometer is not sensitive to vibration. Fizeau interferometers of this type have an advantage compared with Twyman-Green-type systems because they are common-path interferometers. However, a polarization Fizeau interferometer is not strictly common path when both wavefronts are transmitted by an optic that suffers from birefringence. The two polarized beams see different phases owing to birefringence; as a result, an error can be introduced in the measurement. We study the effect of birefringence on measurement accuracy when different polarization techniques are used in Fizeau interferometers. We demonstrate that measurement error is reduced dramatically and can be eliminated if the reference and test beams are circularly polarized rather than linearly polarized.

  12. Laser polarization and phase control of up-conversion fluorescence in rare-earth ions

    PubMed Central

    Yao, Yunhua; Zhang, Shian; Zhang, Hui; Ding, Jingxin; Jia, Tianqing; Qiu, Jianrong; Sun, Zhenrong

    2014-01-01

    We theoretically and experimentally demonstrate the up-conversion fluorescence control via resonance-mediated two-photon absorption in rare-earth ions by varying both the laser polarization and phase. We show that both the laser polarization and phase can control the up-conversion fluorescence, and the up-conversion fluorescence intensity is decreased when the laser polarization changes from linear through elliptical to circular. We also show that the laser polarization will affect the control efficiency of the up-conversion fluorescence by varying the laser phase, and the circular polarization will reduce the control efficiency. Furthermore, we suggest that the control efficiency by varying the laser polarization and the effect of the laser polarization on the control efficiency by varying the laser phase can be artificially manipulated by controlling the laser spectral bandwidth. This optical control method opens a new opportunity to control the up-conversion fluorescence of rare-earth ions, which may have significant impact on the related applications of rare-earth ions. PMID:25465401

  13. Magnesium silicide intermetallic alloys

    NASA Astrophysics Data System (ADS)

    Li, Gh.; Gill, H. S.; Varin, R. A.

    1993-11-01

    Methods of induction melting an ultra-low-density magnesium silicide (Mg2Si) intermetallic and its alloys and the resulting microstructure and microhardness were studied. The highest quality ingots of Mg2Si alloys were obtained by triple melting in a graphite crucible coated with boron nitride to eliminate reactivity, under overpressure of high-purity argon (1.3 X 105 Pa), at a temperature close to but not exceeding 1105 °C ± 5 °C to avoid excessive evaporation of Mg. After establishing the proper induction-melting conditions, the Mg-Si binary alloys and several Mg2Si alloys macroalloyed with 1 at. pct of Al, Ni, Co, Cu, Ag, Zn, Mn, Cr, and Fe were induction melted and, after solidification, investigated by optical microscopy and quantitative X-ray energy dispersive spectroscopy (EDS). Both the Mg-rich and Si-rich eutectic in the binary alloys exhibited a small but systematic increase in the Si content as the overall composition of the binary alloy moved closer toward the Mg2Si line compound. The Vickers microhardness (VHN) of the as-solidified Mg-rich and Si-rich eutectics in the Mg-Si binary alloys decreased with increasing Mg (decreasing Si) content in the eutectic. This behavior persisted even after annealing for 75 hours at 0.89 pct of the respective eutectic temperature. The Mg-rich eutectic in the Mg2Si + Al, Ni, Co, Cu, Ag, and Zn alloys contained sections exhibiting a different optical contrast and chemical composition than the rest of the eutectic. Some particles dispersed in the Mg2Si matrix were found in the Mg2Si + Cr, Mn, and Fe alloys. The EDS results are presented and discussed and compared with the VHN data.

  14. Anomalous oxidation of intermetallics

    SciTech Connect

    Berztiss, D.A.; Pettit, F.S.; Meier, G.H.

    1995-07-01

    MoSi{sub 2}, {beta}-NiAl and TiAl with Cr additions are of interest for high temperature applications in oxidizing environments, where an oxide layer such as SiO{sub 2} or Al{sub 2}O{sub 3} should form to protect the base material. At elevated temperatures (600--1,700 C), a protective SiO{sub 2} layer forms on MoSi{sub 2}, while near 500 C pesting and/or accelerated oxidation could disintegrate the material to powder as Mo and Si oxidize to form a complex, thick, non-protective oxide layer. Use of {gamma}-TiAl is limited by poor oxidation resistance, whereby layered mixed oxides of TiO{sub 2} and Al{sub 2}O{sub 3} form. With the addition of Cr from 4 to 34 at%, results are varied: protective Al{sub 2}O{sub 3} formation, mixed oxide formation as with TiAl or more rapid oxidation than TiAl. NiAl is currently used as a diffusion coating on Ni-based superalloys and is being considered for use as a structural material itself because of its excellent oxidation resistance, i.e. forming {alpha}-alumina above 1,000 C. Recent work indicates that pure NiAl oxidized under low oxygen partial pressures in a contained atmosphere develops nonprotective oxide scales similar to accelerated oxidation of MoSi{sub 2}. This study explores the parameters defining protective behavior of these intermetallics and attempts to describe and explain anomalies at low temperatures and pressures.

  15. Oligonuclear molecular models of intermetallic phases: a case study on [Pd2Zn6Ga2(Cp*)5(CH3)3].

    PubMed

    Bollermann, Timo; Molon, Mariusz; Gemel, Christian; Freitag, Kerstin; Seidel, Rüdiger W; von Hopffgarten, Moritz; Jerabek, Paul; Frenking, Gernot; Fischer, Roland A

    2012-04-16

    The synthesis, characterization, and theoretical investigation by means of quantum-chemical calculations of an oligonuclear metal-rich compound are presented. The reaction of homoleptic dinuclear palladium compound [Pd(2)(μ-GaCp*)(3)(GaCp*)(2)] with ZnMe(2) resulted in the formation of unprecedented ternary Pd/Ga/Zn compound [Pd(2)Zn(6)Ga(2)(Cp*)(5)(CH(3))(3)] (1), which was analyzed by (1)H and (13)C NMR spectroscopy, MS, elemental analysis, and single-crystal X-ray diffraction. Compound 1 consisted of two C(s)-symmetric molecular isomers, as revealed by NMR spectroscopy, at which distinct site-preferences related to the Ga and Zn positions were observed by quantum-chemical calculations. Structural characterization of compound 1 showed significantly different coordination environments for both palladium centers. Whilst one Pd atom sat in the central of a bi-capped trigonal prism, thereby resulting in a formal 18-valence electron fragment, {Pd(ZnMe)(2)(ZnCp*)(4)(GaMe)}, the other Pd atom occupied one capping unit, thereby resulting in a highly unsaturated 12-valence electron fragment, {Pd(GaCp*)}. The bonding situation, as determined by atoms-in-molecules analysis (AIM), NBO partial charges, and molecular orbital (MO) analysis, pointed out that significant Pd-Pd interactions had a large stake in the stabilization of this unusual molecule. The characterization and quantum-chemical calculations of compound 1 revealed distinct similarities to related M/Zn/Ga Hume-Rothery intermetallic solid-state compounds, such as Ga/Zn-exchange reactions, the site-preferences of the Zn/Ga positions, and direct M-M bonding, which contributes to the overall stability of the metal-rich compound.

  16. Quantum phase gate and controlled entanglement with polar molecules

    SciTech Connect

    Charron, Eric; Keller, Arne; Atabek, Osman; Milman, Perola

    2007-03-15

    We propose an alternative scenario for the generation of entanglement between rotational quantum states of two polar molecules. This entanglement arises from dipole-dipole interaction, and is controlled by a sequence of laser pulses simultaneously exciting both molecules. We study the efficiency of the process, and discuss possible experimental implementations with cold molecules trapped in optical lattices or in solid matrices. Finally, various entanglement detection procedures are presented, and their suitability for these two physical situations is analyzed.

  17. Insights into the retention mechanism of neutral organic compounds on polar chemically bonded stationary phases in reversed-phase liquid chromatography.

    PubMed

    Ali, Zahid; Poole, C F

    2004-10-15

    The solvation parameter model is used to characterize the retention properties of a 3-aminopropylsiloxane-bonded (Alltima amino), three 3-cyanopropylsiloxane-bonded (Ultrasphere CN, Ultremex-CN and Zorbax SB-CN), a spacer bonded propanediol (LiChrospher DIOL) and a multifunctional macrocyclic glycopeptide (Chirobiotic T) silica-based stationary phases with mobile phases containing 10 and 20% (v/v) methanol-water. The low retention on the polar chemically bonded stationary phases compared with alkylsiloxane-bonded silica stationary phases arises from the higher cohesion of the polar chemically bonded phases and an unfavorable phase ratio. The solvated polar chemically bonded stationary phases are considerably more hydrogen-bond acidic and dipolar/polarizable than solvated alkylsiloxane-bonded silica stationary phases. Selectivity differences are not as great among the polar chemically bonded stationary phases as they are between the polar chemically bonded phases and alkylsiloxane-bonded silica stationary phases.

  18. Polar intermetallic compounds as catalysts for hydrogenation reactions: synthesis, structures, bonding, and catalytic properties of Ca(1-x)Sr(x)Ni4Sn2 (x=0.0, 0.5, 1.0) and catalytic properties of Ni3Sn and Ni3Sn2.

    PubMed

    Hlukhyy, Viktor; Raif, Fabian; Claus, Peter; Fässler, Thomas F

    2008-01-01

    The potential of polar intermetallic compounds to catalyze hydrogenation reactions was evaluated. The novel compounds CaNi4Sn2, SrNi4Sn2, and Ca(0.5)Sr(0.5)Ni(4)Sn(2) were tested as unsupported alloys in the liquid-phase hydrogenation of citral. Depending on the reaction conditions, conversions of up to 21.0 % (253 K and 9.0 MPa hydrogen pressure) were reached. The binary compounds Ni3Sn and Ni3Sn2 were also tested in citral hydrogenation under the same conditions. These materials gave conversions of up to 37.5 %. The product mixtures contained mainly geraniol, nerol, citronellal, and citronellol. The isotypic stannides CaNi4Sn2, Ca(0.5)Sr(0.5)Ni4Sn2, and SrNi4Sn2 were obtained by melting mixtures of the elements in an arc-furnace under an argon atmosphere. Single crystals were synthesized in tantalum ampoules using special temperature modes. The novel structures were established by single-crystal X-ray diffraction. They crystallize in the tetragonal space group I4/mcm with parameters: a=7.6991(7), c=7.8150(8) A, wR2=0.034, 162 F(2) values, 14 variable parameters for CaNi4Sn2; a=7.7936(2), c=7.7816(3) A, wR2=0.052, 193 F(2) values, 15 variable parameters for Ca(0.5)Sr(0.5)Ni4Sn2; and a=7.8916(4), c=7.7485(5) A, wR2=0.071, 208 F(2) values, 14 variable parameters for SrNi4Sn2. The Ca(1-x)Sr(x)Ni(4)Sn(2) (x=0.0, 0.5, 1.0) structures can be represented as a stuffed variant of the CuAl2 type by the formal insertion of one-dimensional infinite Ni-cluster chains [Ni4] into the Ca(Sr)Sn2 substructure. The Ni and Sn atoms form a three-dimensional infinite [Ni4Sn2] network in which the Ca or Sr atoms fill distorted octagonal channels. The densities of states obtained from TB-LMTO-ASA calculations show metallic character for both compounds.

  19. Origin of Ferroelectricity in a Family of Polar Oxides: The Dion-Jacobson Phases

    NASA Astrophysics Data System (ADS)

    Benedek, Nicole

    2014-03-01

    The discovery of octahedral rotation-induced ferroelectricity has expanded the opportunities for designing materials in which the polarization is coupled to (and therefore makes possible the electric field control of) other properties, e.g. magnetism, orbital order, metal-insulator transitions. Recent work has elucidated the microscopic mechanism of octahedral rotation-induced ferroelectricity in two families of layered perovskites: AA'B2O6 double perovskites and Ruddlesden-Popper (RP) phases. However, there are many other families of layered perovskites - are there octahedral rotation-induced polar materials among them also? We use symmetry arguments, crystal chemical models and first-principles calculations to elucidate the microscopic origin of ferroelectricity in the Dion-Jacobson (DJ) phases. Although ``on paper'' the phenomenology of the DJ phases appears identical to that of polar double perovskites and RP phases, the crystal chemical details regarding how the polar state emerges are different. We link trends in the magnitude of the induced polarizations to changes in structure and composition and discuss possible phase transition scenarios. Our results add surprising new richness to theories of how polar structures emerge in layered perovskites.

  20. Developments in rare earth intermetallics

    SciTech Connect

    Kirchmayr, H.R.

    1984-09-01

    The magnetic properties of rare earth intermetallics have been the subject of numerous investigations in recent years. However, while the preparation of new intermetallic compounds and the determination of their properties have been the prime concern in former years, more recently the analysis and theoretical explanation of the available data has become most important. Furthermore single crystals have now become available, which permit new experiments. Also many investigations on pseudo-binary systems have permitted the systematic determination of the primary magnetic properties. After a summary of the magnetic properties of intermetallics where the B-moment is zero and nonzero, some examples of pseudobinary systems and especially applications of R-3d multicomponent systems as the basis for advanced permanent magnets are discussed. Finally RE-3d alloys with metalloids and non-metals are discussed with emphasis on the newly developed R-Fe-B permanent magnets.

  1. A wideband 360° photonic-assisted microwave phase shifter using a polarization modulator and a polarization-maintaining fiber Bragg grating.

    PubMed

    Li, Wangzhe; Zhang, Weifeng; Yao, Jianping

    2012-12-31

    A novel approach to implementing a wideband microwave photonic phase shifter by a joint use of a polarization modulator (PolM) and a polarization-maintaining fiber Bragg grating (PM-FBG) is proposed and experimentally demonstrated. A microwave signal to be phase shifted is applied to the PolM. Two phase-modulated signals along the two principal axes of the PolM are generated and sent to the PM-FBG. The phase-modulated signals have a static but complementary phase shift introduced by the dc bias applied to the PolM. Due to the birefringence of the polarization-maintaining (PM) fiber, the PM-FBG has two spectrally separated and orthogonally polarized reflection bands. By employing the PM-FBG to reflect one first-order sideband along one polarization direction and one optical carrier along the other polarization direction, and send them back to the PolM, a second-time phase modulation is imposed to the sideband and the optical carrier. By sending the two signals to a polarizer and beating them at a photodetector, a phase shifted microwave signal is obtained. Since the PolM is used twice, a low dc bias voltage would lead to a large phase shift. A full 360° microwave photonic phase shifter over a frequency range of 30-40 GHz is experimentally demonstrated. The spurious free dynamic range (SFDR) of the phase shifter is also studied.

  2. Slope measurement of a phase object using a polarizing phase-shifting high-frequency Ronchi grating interferometer.

    PubMed

    Toto-Arellano, Noel-Ivan; Martínez-García, Amalia; Rodríguez-Zurita, Gustavo; Rayas-Álvarez, Juan Antonio; Montes-Perez, Areli

    2010-11-20

    An interferometric method to measure the slope of phase objects is presented. The analysis was performed by implementing a polarizing phase-shifting cyclic shear interferometer coupled to a 4-f Fourier imaging system with crossed high-frequency Ronchi gratings. This system can obtain nine interference patterns with adjustable phase shifts and variable lateral shear. In order to extract the slope of a phase object, it is only analyzed using four patterns obtained in a single shot, and applying the classical method of phase extraction.

  3. What the Polar Cap Tells Us about the Substorm Growth Phase

    NASA Technical Reports Server (NTRS)

    Brittnacher, M. J.; Fillingim, M. O.; Chua, D.; Wilber, M.; Parks, G. K.; Germany, G. A.; Spann, James F., Jr.

    1998-01-01

    The polar cap region in the 30 to 60 minute period prior to the onset of the auroral substorm has been examined using global images from the Polar Ultraviolet Imager (UVI) to look for observational evidence of processes related to the substorm growth phase. In particular, the area of the polar cap has been measured to determine changes in its size in relation to the orientation of the interplanetary magnetic field (IMF). It was found that the size of the polar cap region increases during the growth phase even if the IMF has no southward component. Three phenomena have been observed to produce the increase in the size of the polar cap: (1) motion of the auroral oval to lower latitude, (2) thinning of the auroral oval, and (3) reduction of intense auroral precipitation in the polar cap region. The first phenomenon has been considered to be a result of the growth of the tail lobe magnetic field and the second is related to the thinning of the plasma sheet. Both of these have been supported by in situ observational evidence and are consistent with current models of substorm development. However, the third phenomenon appears to be unrelated to the first two and does not appear to be the result of opening of the polar cap flux tubes to the solar wind IMF. This reduction of auroral precipitation provides evidence of a growth phase process, or change in auroral precipitation processes, that is not explained by current substorm models.

  4. Polarization of the C. elegans zygote proceeds via distinct establishment and maintenance phases

    PubMed Central

    Cuenca, Adrian A.; Schetter, Aaron; Aceto, Donato; Kemphues, Kenneth; Seydoux, Geraldine

    2006-01-01

    SUMMARY Polarization of the C. elegans zygote along the anterior-posterior axis depends on cortically enriched (PAR) and cytoplasmic (MEX-5/6) proteins, which function together to localize determinants (e.g. PIE-1) in response to a polarizing cue associated with the sperm asters. Using time-lapse microscopy and GFP fusions, we have analyzed the localization dynamics of PAR-2, PAR-6, MEX-5, MEX-6 and PIE-1 in wild-type and mutant embryos. These studies reveal that polarization involves two genetically and temporally distinct phases. During the first phase (establishment), the sperm asters at one end of the embryo exclude the PAR-3/PAR-6/PKC3 complex from the nearby cortex, allowing the ring finger protein PAR-2 to accumulate in an expanding ‘posterior’ domain. Onset of the establishment phase involves the non-muscle myosin NMY-2 and the 14-3-3 protein PAR-5. The kinase PAR-1 and the CCCH finger proteins MEX-5 and MEX-6 also function during the establishment phase in a feedback loop to regulate growth of the posterior domain. The second phase begins after pronuclear meeting, when the sperm asters begin to invade the anterior. During this phase (maintenance), PAR-2 maintains anterior-posterior polarity by excluding the PAR-3/PAR-6/PKC3 complex from the posterior. These findings provide a model for how PAR and MEX proteins convert a transient asymmetry into a stably polarized axis. PMID:12588843

  5. Quantum Theory of a Polarization Phase Gate in an Atomic Tripod Configuration

    SciTech Connect

    Rebic, S.; Vitali, D.; Ottaviani, C.; Tombesi, P.; Artoni, M.; Cataliotti, F.; Corbalan, R.

    2005-08-15

    We present the quantum theory of a polarization phase gate that can be realized in a sample of ultracold rubidium atoms driven into a tripod configuration. The main advantages of this scheme are its relative simplicity and inherent symmetry. It is shown that conditional phase shifts of order {pi} can be attained.

  6. Phase boundary of spin-polarized-current state of electrons in bilayer graphene

    NASA Astrophysics Data System (ADS)

    Yan, Xin-Zhong; Ma, Yinfeng; Ting, C. S.

    2016-06-01

    Using a four-band Hamiltonian, we study the phase boundary of spin-polarized-current state (SPCS) of interacting electrons in bilayer graphene. The model of spin-polarized-current state has previously been shown to resolve a number of experimental puzzles in bilayer graphene. The phase boundaries of the SPCS with and without the external voltage between the two layers are obtained in this work. An unusual phase boundary where there are two transition temperatures for a given carrier concentration is found at finite external voltage. The physics of this phenomenon is explained.

  7. Low-complexity and phase noise tolerant carrier phase estimation for dual-polarization 16-QAM systems.

    PubMed

    Gao, Yuliang; Lau, Alan Pak Tao; Yan, Shuangyi; Lu, Chao

    2011-10-24

    A low-complexity feed-forward carrier phase estimation (CPE) technique is presented for dual-polarization (DP)-16-QAM transmission systems. By combining QPSK partitioning, maximum likelihood (ML) detection and phase offset estimation between signals in different polarizations, simulation and experimental results for a 200 Gb/s DP-16-QAM system demonstrate similar linewidth tolerance to the best feed-forward CPE reported to date while the computational complexity is at least three times lower compared with other simplified feed-forward CPE techniques.

  8. Long Astral Microtubules and RACK-1 Stabilize Polarity Domains during Maintenance Phase in Caenorhabditis elegans Embryos

    PubMed Central

    Ai, Erkang; Poole, Daniel S.; Skop, Ahna R.

    2011-01-01

    Cell polarity is a very well conserved process important for cell differentiation, cell migration, and embryonic development. After the establishment of distinct cortical domains, polarity cues have to be stabilized and maintained within a fluid and dynamic membrane to achieve proper cell asymmetry. Microtubules have long been thought to deliver the signals required to polarize a cell. While previous studies suggest that microtubules play a key role in the establishment of polarity, the requirement of microtubules during maintenance phase remains unclear. In this study, we show that depletion of Caenorhabditis elegans RACK-1, which leads to short astral microtubules during prometaphase, specifically affects maintenance of cortical PAR domains and Dynamin localization. We then investigated the consequence of knocking down other factors that also abolish astral microtubule elongation during polarity maintenance phase. We found a correlation between short astral microtubules and the instability of PAR-6 and PAR-2 domains during maintenance phase. Our data support a necessary role for astral microtubules in the maintenance phase of cell polarity. PMID:21533050

  9. The Thermodynamic Stability of Multiple Phases In The Particulate Material of Aerosols Containing Both Polar and Non-polar Compounds

    NASA Astrophysics Data System (ADS)

    Erdakos, G. B.; Pankow, J. F.

    Organic compounds can comprise a significant portion of ambient aerosol particulate material (PM ). Current models of organic aerosol formation based on absorptive gas/particle partitioning theory have frequently assumed each aerosol particle to be one liquid phase. This assumption is not always correct. Moreover, it will affect the predicted equilibrium composition of modeled aerosols. There are important cases when multiple phases can be present in ambient aerosol PM. We examine two scenarios in which multiple liquid phases may be possible: 1) particles form when a volatile organic compound (VOC) yields oxidized products which condense with some wa ter and 2) particles formed by the first scenario acquire long- chained hydrocarbons (HCs) and plant-wax related compounds . Both (1) and (2) result in particles that contain compounds having a range of polarities, with particles formed by (2) containing a wider range. We test a number of these types of aerosol systems for the stability of two liquid phases with distinct compositions. Each system involves the oxidation of a different VOC, so that the overall aerosol particle composition, whether stable as one or two liquid phases, will vary from system to system. For the systems tested, particles composed of VOC oxidation products and water were found to have one stable liquid phase, while particles which also contain long-chained HCs and plant-wax related compounds, accounting for 10% of the total organic carbon, were found to have two distinct stable liquid phases.

  10. Spin filtering and quantum phase transition in double quantum dots attached to spin-polarized leads.

    PubMed

    Wang, Wei-zhong

    2011-05-20

    We study the spin filtering and quantum phase transition (QPT) in double quantum dots attached to spin-polarized leads. For spin-independent leads, we observe a Kosterlitz-Thouless transition between the local triplet and doublet. For spin-polarized leads, the above QPT becomes first order, and Kondo splitting, gate-controlled spin reversal and a perfect spin filtering are observed. The breaking of spin-rotation SU(2) symmetry and the interdot transport mediated by the conduction electron are responsible for the fully spin-polarized conductance. Because spin-polarized leads suppress the Kondo effect, in order to obtain a large conductance with perfect spin filtering, one should choose leads with small spin polarization, such as Rashba spin-orbital coupling leads.

  11. Dynamical Piezoelectric and Magnetopiezoelectric Effects in Polar Metals from Berry Phases and Orbital Moments

    NASA Astrophysics Data System (ADS)

    Varjas, Dániel; Grushin, Adolfo G.; Ilan, Roni; Moore, Joel E.

    2016-12-01

    The polarization of a material and its response to applied electric and magnetic fields are key solid-state properties with a long history in insulators, although a satisfactory theory required new concepts such as Berry-phase gauge fields. In metals, quantities such as static polarization and the magnetoelectric θ term cease to be well defined. In polar metals, there can be analogous dynamical current responses, which we study in a common theoretical framework. We find that current responses to dynamical strain in polar metals depend on both the first and second Chern forms, related to polarization and magnetoelectricity in insulators as well as the orbital magnetization on the Fermi surface. We provide realistic estimates that predict that the latter contribution will dominate, and we investigate the feasibility of experimental detection of this effect.

  12. Polarization fields and phase space densities in storage rings: Stroboscopic averaging and the ergodic theorem

    NASA Astrophysics Data System (ADS)

    Ellison, James A.; Heinemann, Klaus

    2007-10-01

    A class of orbital motions with volume preserving flows and with vector fields periodic in the “time” parameter θ is defined. Spin motion coupled to the orbital dynamics is then defined, resulting in a class of spin-orbit motions which are important for storage rings. Phase space densities and polarization fields are introduced. It is important, in the context of storage rings, to understand the behavior of periodic polarization fields and phase space densities. Due to the 2π time periodicity of the spin-orbit equations of motion the polarization field, taken at a sequence of increasing time values θ,θ+2π,θ+4π,…, gives a sequence of polarization fields, called the stroboscopic sequence. We show, by using the Birkhoff ergodic theorem, that under very general conditions the Cesàro averages of that sequence converge almost everywhere on phase space to a polarization field which is 2π-periodic in time. This fulfills the main aim of this paper in that it demonstrates that the tracking algorithm for stroboscopic averaging, encoded in the program SPRINT and used in the study of spin motion in storage rings, is mathematically well-founded. The machinery developed is also shown to work for the stroboscopic average of phase space densities associated with the orbital dynamics. This yields a large family of periodic phase space densities and, as an example, a quite detailed analysis of the so-called betatron motion in a storage ring is presented.

  13. Observation of polarization conflict caused by geometrical phase in a twisted nematic liquid crystal cell.

    PubMed

    Vasnetsov, M V; Pas'ko, V A; Kasyanyuk, D S

    2011-06-01

    We analyze the optical effects associated with an adiabatic rotation of a plane of polarization in a twisted nematic liquid crystal. The experimental verification was performed with a cell with linear rubbing of a front surface and circular rubbing of a rear surface. The expectations of the liquid crystal's orientation defect origin along the line of the maximum tension and a polarization conflict caused by geometrical phase are confirmed. © 2011 Optical Society of America

  14. Generation of Bright Phase-matched Circularly-polarized Extreme Ultraviolet High Harmonics

    DTIC Science & Technology

    2014-12-08

    molecular decay dynamics2, the direct measurement of quantum phases (for example, Berry’s phase and pseudo- spin ) in graphene and topological insulators3,4 and...Lett. 12, 3900–3904 (2012). 4. Xu, S.-Y. et al. Hedgehog spin texture and Berry’s phase tuning in a magnetic topological insulator. Nature Phys. 8, 616...Mauger, F., Bandrauk, A. D., Kamor, A., Uzer, T. & Chandre, C. Quantum - classical correspondence in circularly polarized high harmonic generation. J. Phys

  15. Prediction of retention in reversed-phase liquid chromatography by means of the polarity parameter model.

    PubMed

    Lázaro, Elisabet; Izquierdo, Pere; Ràfols, Clara; Rosés, Martí; Bosch, Elisabeth

    2009-07-03

    The polarity parameter model previously developed: log k=(log k)(0) + p(P(m)(N) - P(s)(N)) has been successfully applied to study several chromatographic systems involving new generation RPLC columns (Luna C18, Resolve C18, XTerra MSC18, and XTerra RP18). In this model the retention of the solutes (log k) is related to a solute parameter (p), a mobile phase parameter (P(m)(N)) and two chromatographic system parameters [P(s)(N) and (log k)(0)]. The studied systems have been characterized with different acetonitrile-water and methanol-water mobile phases, using a set of 12 neutral solutes of different chemical nature. The polarity parameter model allows prediction of retention of any solute in any mobile phase composition just using the retention data obtained in one percentage of organic modifier and the polarity parameters established in the characterization of the chromatographic systems. This model also allows the solute polarity data transference between RPLC characterized systems, so it is possible to predict the retention in various RPLC systems working experimentally with just one of them. Moreover, the global solvation parameter model has also been applied to the same chromatographic systems using a wide set of solutes in order to compare its predictive ability with the one of the polarity parameter model. The results clearly show that both models predict retention with very similar accuracy but the polarity parameter model requires much less preliminary experimental measurements to achieve equivalent results than the global solvation approach.

  16. B phase with polar distortion in superfluid {sup 3}He in “ordered” aerogel

    SciTech Connect

    Dmitriev, V. V. Senin, A. A.; Soldatov, A. A.; Surovtsev, E. V.; Yudin, A. N.

    2014-12-15

    The properties of the low-temperature superfluid phase of {sup 3}He in “nematically ordered” aerogel in which strands are almost parallel to one another are investigated by nuclear magnetic resonance methods. Such a strong anisotropy of the aerogel affects the phase diagram of {sup 3}He and the structure of superfluid phases. A theoretical model of the B phase with polar distortion is developed. It is shown that this model successfully describes the observed properties of the low-temperature phase.

  17. Role of quantum fluctuations in the hexatic phase of cold polar molecules.

    PubMed

    Lechner, Wolfgang; Büchler, Hans-Peter; Zoller, Peter

    2014-06-27

    Two-dimensional crystals melt via an intermediate hexatic phase, which is characterized by an anomalous scaling of spatial and orientational correlation functions and the absence of an attraction between dislocations. We propose a protocol to study the effect of quantum fluctuations on the nature of this phase with a model system of strongly correlated ultracold polar molecules. Dislocations can be located in experiment from local energy differences which induce internal stark shifts in the molecules. We present a criterion to identify the hexatic phase from the statistics of the end points of topological defect strings and find a hexatic phase, which is dominated by quantum fluctuations, between the crystal and superfluid phases.

  18. Phase control of six-wave mixing from circularly polarized light

    NASA Astrophysics Data System (ADS)

    Zhang, Yunzhe; Liu, Zhe; Wang, Hang; Li, Shuoke; Zhang, Weitao; Yi, Wenhui; Zhang, Yanpeng

    2016-08-01

    We investigate the phase control of six-wave mixing (SWM) in atomic system with multi-Zeeman levels theoretically and experimentally. With the relative phase varying, the switch between bright and dark state can appear in probe transmission signal. Then we demonstrate the evolution of six-wave mixing generated in bright and dark states by scanning the frequency detuning of the dressing field at different polarized probe field. Meanwhile, by utilizing the strong dressing effect of circular polarized light, we observe pure dark state switched to pure bright state in terms of energy level splitting, and compare different phases under different detuning of circularly polarized light. Theoretical calculations are in well agreement with the experimental observations.

  19. Influence of perturbative phase noise on active coherent polarization beam combining system.

    PubMed

    Ma, Pengfei; Zhou, Pu; Wang, Xiaolin; Ma, Yanxing; Su, Rongtao; Liu, Zejin

    2013-12-02

    In this manuscript, the influence of perturbative phase noise on active coherent polarization beam combining (CPBC) system is studied theoretically and experimentally. By employing a photo-detector to obtain phase error signal for feedback loop, actively coherent polarization beam combining of two 20 W-level single mode polarization-maintained (PM) fiber amplifiers are demonstrated with more than 94% combining efficiency. Then the influence of perturbative phase noise on active CPBC system is illustrated by incorporating a simulated phase noise signal in one of the two amplifiers. Experimental results show that the combining efficiency of the CPBC system is susceptible to the frequency or amplitude of the perturbative phase noise. In order to ensure the combining efficiency of the unit of CPBC system higher than 90%, the competence of our active phase control module for high power operation is discussed, which suggests that it could be worked at 100s W power level. The relationship between residual phase noise of the active controller and the normalized voltage signal of the photo-detector is developed and validated experimentally. Experimental results correspond exactly with the theoretically analyzed combining efficiency. Our method offers a useful approach to estimate the influence of phase noise on CPBC system.

  20. Enhancement of polar crystalline phase formation in transparent PVDF-CaF2 composite films

    NASA Astrophysics Data System (ADS)

    Lee, Sang Goo; Ha, Jong-Wook; Sohn, Eun-Ho; Park, In Jun; Lee, Soo-Bok

    2016-12-01

    We consider the influence of calcium fluoride (CaF2) nanoparticles on the crystalline phase formation of poly(vinylidene fluoride) (PVDF) for the first time. The transparent PVDF-CaF2 composite films were prepared by casting on PET substrates using N,N-dimethylacetamide (DMAc) as a solvent. It was found that CaF2 promoted the formation of polar crystalline phase of PVDF in composites, whereas nonpolar α-phase was dominant in the neat PVDF film prepared at the same condition. The portion of polar crystalline phase increased in proportional to the weight fraction of CaF2 in the composite films up to 10 wt%. Further addition of CaF2 suppressed completely the α-phase formation. Polar crystalline phase observed in as-cast composite films was a mixture of β- and γ-polymorph structures. It was also shown that much ordered γ-phase could be obtained through thermal treatment of as-cast PVDF-CaF2 composite film at the temperatures above the melting temperature of the composite films, but below that of γ-phase.

  1. Polarization-independent and high-diffraction-efficiency Fresnel lenses based on blue phase liquid crystals.

    PubMed

    Lin, Chi-Huang; Wang, Yu-Yin; Hsieh, Cheng-Wei

    2011-02-15

    A polarization-independent and high-diffraction-efficiency Fresnel lens is developed based on blue phase liquid crystals (BPLCs). The optically isotropic characteristic of BPLCs is used to produce a polarization-independent Fresnel lens. The small optical phase shift of BPLCs that is induced by the Kerr effect is sufficient for the BPLC Fresnel lens to have high theoretical and experimental diffraction efficiencies of 41% and ∼34%, respectively. An electrically erasable memory effect in the focusing diffraction at an electric field E>4.44 V/μm is observed. The electro-optical properties of the BPLC Fresnel lens are analyzed and discussed.

  2. Phase sensitivity to temperature of the guiding mode in polarization-maintaining photonic crystal fiber.

    PubMed

    Song, Jingming; Sun, Kang; Li, Shuai; Cai, Wei

    2015-08-20

    The propagating phase changing of a polarization-maintaining photonic crystal fiber (PM-PCF) caused by temperature variation is theoretically studied, as well as compared with conventional PANDA fiber. As to verifying numerical analysis, a platform based on a Michelson interferometer for phase versus temperature measurement was built for both kinds of fiber. Experiments show that PM-PCF has similar temperature sensitivity with conventional polarization-maintaining fiber. With optimized PM-PCF design (thinner coating layer and coating material with smaller thermal expansion coefficient), the sensitivity could be further reduced to about 80% of the present level.

  3. Tight Focusing Properties of Phase Modulated Radially Polarized Laguerre Bessel Gaussian Beam

    NASA Astrophysics Data System (ADS)

    Prabakaran, K.; Sangeetha, P.; Karthik, V.; Rajesh, K. B.; Musthafa, A. M.

    2017-05-01

    We propose a new approach for generating a multiple focal spot segment of subwavelength size, by tight focusing of a phase modulated radially polarized Laguerre Bessel Gaussian beam. The focusing properties are investigated theoretically by vector diffraction theory. We observe that the focal segment with multiple focal structures is separated with different axial distances and a super long dark channel can be generated by properly tuning the phase of the incident radially polarized Laguerre Bessel Gaussian beam. We presume that such multiple focal patterns and high intense beam may find applications in atom optics, optical manipulations and multiple optical trapping.

  4. Substantial Cd-Cd bonding in Ca6PtCd11: a condensed intermetallic phase built of pentagonal Cd7 and rectangular Cd4/2Pt pyramids.

    PubMed

    Gulo, Fakhili; Samal, Saroj L; Corbett, John D

    2013-09-03

    The novel intermetallic Ca6PtCd11 is orthorhombic, Pnma, Z = 4, with a = 18.799(2) Å, b = 5.986(1) Å, c = 15.585(3) Å. The heavily condensed network contains three types of parallel cadmium chains: apically strongly interbonded Cd7 pentagonal bipyramids, linear Cd arrays, and rectangular Cd4/2Pt pyramids. All of the atoms have 11-13 neighbors. Calculations by means of the linear muffin-tin orbitals method in the atomic spheres approximation indicate that some Cd-Cd interactions correspond to notably high Hamilton populations (1.07 eV per average bond) whereas the Ca-Ca covalent interactions (integrated crystal orbital Hamiltonian population) are particularly small (0.17 eV/bond). (Pt-Cd interactions are individually greater but much less in aggregate.) The Ca-Ca separations are small, appreciably less than the single bond metallic diameters, and unusually uniform (Δ = 0.14 Å). The Cd atoms make major contributions to the stability of the phase via substantial 5s and 5p bonding, which include back-donation of Cd 5s, 5p and Pt 5d into Ca 3d states in the principal bonding modes for Ca-Cd and Ca-Pt. Bonding Ca-Ca, Ca-Cd, and Cd-Cd states remain above EF, and some relative oxidation of Ca in this structure seems probable. Ca6PtCd11 joins a small group of other phases in which Cd clustering and Cd-Cd bonding are important.

  5. Phase transition observations and discrimination of small cloud particles by light polarization in expansion chamber experiments

    NASA Astrophysics Data System (ADS)

    Nichman, Leonid; Fuchs, Claudia; Järvinen, Emma; Ignatius, Karoliina; Florian Höppel, Niko; Dias, Antonio; Heinritzi, Martin; Simon, Mario; Tröstl, Jasmin; Wagner, Andrea Christine; Wagner, Robert; Williamson, Christina; Yan, Chao; Connolly, Paul James; Dorsey, James Robert; Duplissy, Jonathan; Ehrhart, Sebastian; Frege, Carla; Gordon, Hamish; Hoyle, Christopher Robert; Bjerring Kristensen, Thomas; Steiner, Gerhard; McPherson Donahue, Neil; Flagan, Richard; Gallagher, Martin William; Kirkby, Jasper; Möhler, Ottmar; Saathoff, Harald; Schnaiter, Martin; Stratmann, Frank; Tomé, António

    2016-03-01

    Cloud microphysical processes involving the ice phase in tropospheric clouds are among the major uncertainties in cloud formation, weather, and general circulation models. The detection of aerosol particles, liquid droplets, and ice crystals, especially in the small cloud particle-size range below 50 μm, remains challenging in mixed phase, often unstable environments. The Cloud Aerosol Spectrometer with Polarization (CASPOL) is an airborne instrument that has the ability to detect such small cloud particles and measure the variability in polarization state of their backscattered light. Here we operate the versatile Cosmics Leaving OUtdoor Droplets (CLOUD) chamber facility at the European Organization for Nuclear Research (CERN) to produce controlled mixed phase and other clouds by adiabatic expansions in an ultraclean environment, and use the CASPOL to discriminate between different aerosols, water, and ice particles. In this paper, optical property measurements of mixed-phase clouds and viscous secondary organic aerosol (SOA) are presented. We report observations of significant liquid-viscous SOA particle polarization transitions under dry conditions using CASPOL. Cluster analysis techniques were subsequently used to classify different types of particles according to their polarization ratios during phase transition. A classification map is presented for water droplets, organic aerosol (e.g., SOA and oxalic acid), crystalline substances such as ammonium sulfate, and volcanic ash. Finally, we discuss the benefits and limitations of this classification approach for atmospherically relevant concentrations and mixtures with respect to the CLOUD 8-9 campaigns and its potential contribution to tropical troposphere layer analysis.

  6. Polarization effects and phase equilibria in high-energy-density polyvinylidene-fluoride-based polymers.

    PubMed

    Ranjan, V; Yu, L; Nakhmanson, Serge; Bernholc, Jerry; Nardelli, M Buongiorno

    2010-09-01

    Using first-principles calculations, the phase diagrams of polyvinylidene fluoride (PVDF) and its copolymers under an applied electric field are studied and phase transitions between their nonpolar alpha and polar beta phases are discussed. The results show that the degree of copolymerization is a crucial parameter controlling the structural phase transition. In particular, for tetrafluoroethylene (TeFE) concentration above 12%, PVDF-TeFE is stabilized in the beta phase, whereas the alpha phase is stable for lower concentrations. As larger electric fields are applied, domains with smaller concentrations (< or = 12%) undergo a transition from the alpha to the beta phase until a breakdown field of approximately 600 MV m(-1) is reached. These structural phase transitions can be exploited for efficient storage of electrical energy.

  7. Generation of phase-coded microwave signals using a polarization-modulator-based photonic microwave phase shifter.

    PubMed

    Zhang, Yamei; Pan, Shilong

    2013-03-01

    A scheme for the generation of phase-coded microwave signals using an electrically tunable photonic microwave phase shifter is proposed and demonstrated. The photonic phase shifter is based on a single-sideband polarization modulator (PolM), and the tuning of the phase shifter is implemented by a second PolM. By introducing an RF signal to the first PolM and an electrical coding signal to the second PolM, a phase-coded microwave signal with binary phase codes or polyphase codes is achieved. An experiment is performed. The simple and flexible operation, high coding rate, large frequency range, excellent transmission performance, and high stability of the system is confirmed.

  8. Ferroelectric order in liquid crystal phases of polar disk-shaped ellipsoids

    NASA Astrophysics Data System (ADS)

    Bose, Tushar Kanti; Saha, Jayashree

    2014-05-01

    The demonstration of a spontaneous macroscopic ferroelectric order in liquid phases in the absence of any long range positional order is considered an outstanding problem of both fundamental and technological interest. Recently, we reported that a system of polar achiral disklike ellipsoids can spontaneously exhibit a long searched ferroelectric nematic phase and a ferroelectric columnar phase with strong axial polarization. The major role is played by the dipolar interactions. The model system of interest consists of attractive-repulsive Gay-Berne oblate ellipsoids embedded with two parallel point dipoles positioned symmetrically on the equatorial plane of the ellipsoids. In the present work, we investigate in detail the profound effects of changing the separation between the two symmetrically placed dipoles and the strength of the dipoles upon the existence of different ferroelectric discotic liquid crystal phases via extensive off-lattice N-P-T Monte Carlo simulations. Ferroelectric biaxial phases are exhibited in addition to the uniaxial ferroelectric fluids where the phase biaxiality results from the dipolar interactions. The structures of all the ferroelectric configurations of interest are presented in detail. Simple phase diagrams are determined which include different polar and apolar discotic fluids generated by the system.

  9. Photoinduced topological phase transition and spin polarization in a two-dimensional topological insulator

    NASA Astrophysics Data System (ADS)

    Chen, M. N.; Su, W.; Deng, M. X.; Ruan, Jiawei; Luo, W.; Shao, D. X.; Sheng, L.; Xing, D. Y.

    2016-11-01

    A great deal of attention has been paid to the topological phases engineered by photonics over the past few years. Here, we propose a topological quantum phase transition to a quantum anomalous Hall (QAH) phase induced by off-resonant circularly polarized light in a two-dimensional system that is initially in a quantum spin Hall phase or a trivial insulator phase. This provides an alternative method to realize the QAH effect, other than magnetic doping. The circularly polarized light effectively creates a Zeeman exchange field and a renormalized Dirac mass, which are tunable by varying the intensity of the light and drive the quantum phase transition. Both the transverse and longitudinal Hall conductivities are studied, and the former is consistent with the topological phase transition when the Fermi level lies in the band gap. A highly controllable spin-polarized longitudinal electrical current can be generated when the Fermi level is in the conduction band, which may be useful for designing topological spintronics.

  10. Stability of superfluid phases in the 2D spin-polarized attractive Hubbard model

    NASA Astrophysics Data System (ADS)

    Kujawa-Cichy, A.; Micnas, R.

    2011-08-01

    We study the evolution from the weak coupling (BCS-like limit) to the strong coupling limit of tightly bound local pairs (LPs) with increasing attraction, in the presence of the Zeeman magnetic field (h) for d=2, within the spin-polarized attractive Hubbard model. The broken symmetry Hartree approximation as well as the strong coupling expansion are used. We also apply the Kosterlitz-Thouless (KT) scenario to determine the phase coherence temperatures. For spin-independent hopping integrals (t↑=t↓), we find no stable homogeneous polarized superfluid (SCM) state in the ground state for the strong attraction and obtain that for a two-component Fermi system on a 2D lattice with population imbalance, phase separation (PS) is favoured for a fixed particle concentration, even on the LP (BEC) side. We also examine the influence of spin-dependent hopping integrals (mass imbalance) on the stability of the SCM phase. We find a topological quantum phase transition (Lifshitz type) from the unpolarized superfluid phase (SC0) to SCM and tricritical points in the h-|U| and t↑/t↓-|U| ground-state phase diagrams. We also construct the finite temperature phase diagrams for both t↑=t↓ and t↑≠t↓ and analyze the possibility of occurrence of a spin-polarized KT superfluid.

  11. Measurement of displacement and distance with a polarization phase shifting folded Twyman Green interferometer.

    PubMed

    Chatterjee, Sanjib; Kumar, Y Pavan

    2015-11-20

    A Sagnac interferometer (SI), consisting of a polarization beam splitter (PBS), along with two equally spaced plane mirrors that are inclined at 45° to each other, is transformed into a folded Twyman Green interferometer (TGI) by placing a mirrored parallel plate (MPP) into the hypotenuse arm of the SI. The converging input beam produced by a telescope objective (TO) is split into reflected (s-polarized) and transmitted (p-polarized) components by the PBS. The p- and s-polarized focal spots are made to fall on the mirrored end surfaces of the parallel plate (PP). The retroreflected p- and s-polarized beams become collimated after passing through the TO. A linear shift of the PP in either (longitudinal) direction alters the positions of the p- and s-polarized focal spots and results in a set of converging and diverging spherical wavefronts that interfere to form concentric circular fringes. We applied polarization phase-shifting interferometry to obtain the optical path difference (OPD) variation of the interference field. The displacement is calculated from the OPD variation. A validation experiment has been carried out by introducing known shifts to the PP. The setup can be used for displacement as well as distance measurement.

  12. Low-Temperature Synthesis Routes to Intermetallic Superconductors

    SciTech Connect

    Schaak, Raymond E

    2008-01-08

    Over the past few years, our group has gained expertise at developing low-temperature solution-based synthetic pathways to complex nanoscale solids, with particular emphasis on nanocrystalline intermetallic compounds. Our synthetic capabilities are providing tools to reproducibly generate intermetallic nanostructures with simultaneous control over crystal structure, composition, and morphology. This DOE-funded project aims to expand these capabilities to intermetallic superconductors. This could represent an important addition to the tools that are available for the synthesis and processing of intermetallic superconductors, which traditionally utilize high-temperature, high-pressure, thin film, or gas-phase vacuum deposition methods. Our current knowledge of intermetallic superconductors suggests that significant enhancements could result from the inherent benefits of low-temperature solution synthesis, e.g. metastable phase formation, control over nanoscale morphology to facilitate size-dependent property studies, robust and inexpensive processability, low-temperature annealing and consolidation, and impurity incorporation (for doping, stoichiometry control, flux pinning, and improving the critical fields). Our focus is on understanding the superconducting properties as a function of synthetic route, crystal structure, crystallite size, and morphology, and developing the synthetic tools necessary to accomplish this. This research program can currently be divided into two classes of superconducting materials: intermetallics (transition metal/post transition metal) and metal carbides/borides. Both involve the development and exploitation of low-temperature synthesis routes followed by detailed characterization of structures and properties, with the goal of understanding how the synthetic pathways influence key superconducting properties of selected target materials. Because of the low-temperature methods used to synthesize them and the nanocrystalline morphologies

  13. Analysis of polar peptides using a silica hydride column and high aqueous content mobile phases.

    PubMed

    Yang, Yuanzhong; Boysen, Reinhard I; Kulsing, Chadin; Matyska, Maria T; Pesek, Joseph J; Hearn, Milton T W

    2013-09-01

    The retention behavior of a set of polar peptides separated on a silica hydride stationary phase was examined with a capillary HPLC system coupled to ESI-MS detection. The mobile phases consisted of formic acid or acetic acid/acetonitrile/water mixtures with the acetonitrile content ranging from 5 to 80% v/v. The effects on peptide retention of these two acidic buffer additives and their concentrations in the mobile phase were systematically investigated. Strong retention of the peptides on the silica hydride phase was observed with relatively high-organic low-aqueous mobile phases (i.e. under aqueous normal-phase conditions). However, when low concentrations of acetic acid were employed as the buffer additive, strong retention of the peptides was also observed even when high aqueous content mobile phases were employed. This unique feature of the stationary phase therefore provides an opportunity for chromatographic analysis of polar peptides with water-rich eluents, a feature usually not feasible with traditional RP sorbents, and thus under conditions more compatible with analytical green chemistry criteria. In addition, both isocratic and gradient elution procedures can be employed to optimize peptide separations with excellent reproducibility and resolution under these high aqueous mobile phase conditions with this silica hydride stationary phase.

  14. Amplitude and phase variations of the chandler wobble from 164-yr polar motion series

    NASA Astrophysics Data System (ADS)

    Malkin, Z. M.; Miller, N. O.

    2011-10-01

    This paper is aimed at investigation of the Chandler wobble (CW) at the 164-year interval to search for the major CW amplitude and phase variations. The CW signal was extracted from the IERS polar motion series using digital filtering. The CW amplitude and phase variations were examined by means of several methods which yield very similar results. Results of our analysis have shown that, besides the well-known CW phase jump in the 1920s, two other large phase jumps have been found in the 1850s and 2000s, all three contemporarily with a sharp decrease in the CW amplitude.

  15. Security authentication using phase-encoded nanoparticle structures and polarized light.

    PubMed

    Carnicer, Artur; Hassanfiroozi, Amir; Latorre-Carmona, Pedro; Huang, Yi-Pai; Javidi, Bahram

    2015-01-15

    Phase-encoded nanostructures such as quick response (QR) codes made of metallic nanoparticles are suggested to be used in security and authentication applications. We present a polarimetric optical method able to authenticate random phase-encoded QR codes. The system is illuminated using polarized light, and the QR code is encoded using a phase-only random mask. Using classification algorithms, it is possible to validate the QR code from the examination of the polarimetric signature of the speckle pattern. We used Kolmogorov-Smirnov statistical test and Support Vector Machine algorithms to authenticate the phase-encoded QR codes using polarimetric signatures.

  16. A method to calibrate phase fluctuation in polarization-sensitive swept-source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Lu, Zenghai; Kasaragod, Deepa K.; Matcher, Stephen J.

    2011-06-01

    A phase fluctuation calibration method is presented for polarization-sensitive swept-source optical coherence tomography (PS-SS-OCT) using continuous polarization modulation. The method consists of the generation of a continuous triggered tone-burst waveform rather than an asynchronous waveform by use of a function generator and the removal of the global phases of the measured Jones matrices by use of matrix normalization. This could remove the use of auxiliary optical components for the phase fluctuation compensation in the system, which reduces the system complexity. Phase fluctuation calibration is necessary to obtain the reference Jones matrix by averaging the measured Jones matrices at sample surfaces. Measurements on an equine tendon sample were made by the PS-SS-OCT system to validate the proposed method.

  17. Polarization conversion based on plasmonic phase control by an ultra-thin metallic nano-strips

    NASA Astrophysics Data System (ADS)

    Wei, Helei; Hu, Dejiao; Deng, Yunsheng; Wu, Xuannan; Xiao, Xiao; Hou, Yidong; Wang, Yunjiao; Shi, Ruiying; Wang, Deqiang; Du, Jinglei

    2016-12-01

    Ultra-thin metallic nano-strips (thinner than skin depth) can lead to anomalous reflection for a transverse magnetic (TM) incidence of some wave-lengths, due to the phase modulation of localized surface plasmon resonance. Based on the principle above, we proposed a method of polarization modulation using ultra-thin metallic nano-strips. When irradiating nano-strips vertically by light with a given polarized angle, we can utilize the phase difference of the TM transmission and transverse electric (TE) transmission near anomalous reflection region to modulate transmission polarization. We have designed and fabricated the ultra-thin metallic nano-strips with the function of quarter-wave plate, the attained transmission Stokes parameter S3 is 0.95. The nano-strips is easy to design and fabricate, also compatible with other optics devices, hence has the potential applications in integrated optics field.

  18. Method to calibrate phase fluctuation in polarization-sensitive swept-source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Lu, Zenghai; Kasaragod, Deepa K.; Matcher, Stephen J.

    2011-07-01

    We present a phase fluctuation calibration method for polarization-sensitive swept-source optical coherence tomography (PS-SS-OCT) using continuous polarization modulation. The method uses a low-voltage broadband polarization modulator driven by a synchronized sinusoidal burst waveform rather than an asynchronous waveform, together with the removal of the global phases of the measured Jones matrices by the use of matrix normalization. This makes it possible to average the measured Jones matrices to remove the artifact due to the speckle noise of the signal in the sample without introducing auxiliary optical components into the sample arm. This method was validated on measurements of an equine tendon sample by the PS-SS-OCT system.

  19. Mid-infrared polarization devices based on the double-phase modulating dielectric metasurface

    NASA Astrophysics Data System (ADS)

    Guo, Zhongyi; Tian, Lihua; Shen, Fei; Zhou, Hongping; Guo, Kai

    2017-06-01

    Metasurfaces are composed of the subwavelength structures, which can be used to manipulate the phase, amplitude and polarization of transmitted or reflected electromagnetic waves. Here, we propose an all-dielectric metasurface working in mid-infrared (mid-IR) range, in which the transmitted phase can almost span over the entire 2π range for both X-polarization and Y-polarization simultaneously just by tailoring the geometric sizes of the silicon (Si) nanobricks, while the transmitted amplitude can be maintained at high values without significant variations. We have successfully realized the beam deflector, beam splitter and the focusing lenses based on the designed metasurfaces at a wavelength of 4.5 µm. Our work paves the way toward establishing low-loss dielectric-based mid-IR devices and extends the modulating dimension of the metasurfaces.

  20. Microemulsions with an ionic liquid surfactant and room temperature ionic liquids as polar pseudo-phase.

    PubMed

    Zech, Oliver; Thomaier, Stefan; Bauduin, Pierre; Rück, Thomas; Touraud, Didier; Kunz, Werner

    2009-01-15

    In this investigation we present for the first time microemulsions comprising an ionic liquid as surfactant and a room-temperature ionic liquid as polar pseudo-phase. Microemulsions containing the long- chain ionic liquid1-hexadecyl-3-methyl-imidazolium chloride ([C16mim][Cl]) as surfactant, decanol as cosurfactant, dodecaneas continuous phase and room temperature ionic liquids (ethylammonium nitrate (EAN) and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim

  1. Diagnostic efficiency of Mueller-matrix polarization reconstruction system of the phase structure of liver tissue

    NASA Astrophysics Data System (ADS)

    Zabolotna, Natalia I.; Pavlov, Sergii V.; Radchenko, Kostiantyn O.; Stasenko, Vladyslav A.; Wójcik, Waldemar; Kussambayeva, Nazym

    2015-12-01

    The application field of using the Mueller-matrix polarizing reconstruction system of phase structure of biological layer for optical-anisotropic parameters differentiation of histological sections of healthy and rat's liver with hepatitis were investigated. Comparison of system informativity with known systems on indexes of sensitivity, specificity and balanced accuracy were performed.

  2. Anomalous temperature dependence of gas chromatographic retention indices of polar compounds on nonpolar phases

    NASA Astrophysics Data System (ADS)

    Zenkevich, I. G.; Pavlovskii, A. A.

    2016-05-01

    The character of the temperature dependences of the retention indices RI( T) of polar sorbates on nonpolar stationary phases was found to depend on the dosed amounts of sorbates, but not on column overloading. A physicochemical model was suggested to explain the observed anomalies in RI( T).

  3. ANALYTIC MODELS FOR ALBEDOS, PHASE CURVES, AND POLARIZATION OF REFLECTED LIGHT FROM EXOPLANETS

    SciTech Connect

    Madhusudhan, Nikku; Burrows, Adam E-mail: burrows@astro.princeton.edu

    2012-03-01

    New observational facilities are becoming increasingly capable of observing reflected light from transiting and directly imaged extrasolar planets. In this study, we provide an analytic framework to interpret observed phase curves, geometric albedos, and polarization of giant planet atmospheres. We compute the observables for non-conservative Rayleigh scattering in homogeneous semi-infinite atmospheres using both scalar and vector formalisms. In addition, we compute phase curves and albedos for Lambertian, isotropic, and anisotropic scattering phase functions. We provide analytic expressions for geometric albedos and spherical albedos as a function of the scattering albedo for Rayleigh scattering in semi-infinite atmospheres. Given an observed geometric albedo our prescriptions can be used to estimate the underlying scattering albedo of the atmosphere, which in turn is indicative of the scattering and absorptive properties of the atmosphere. We also study the dependence of polarization in Rayleigh scattering atmospheres on the orbital parameters of the planet-star system, particularly on the orbital inclination. We show how the orbital inclination of non-transiting exoplanets can be constrained from their observed polarization parameters. We consolidate the formalism, solution techniques, and results from analytic models available in the literature, often scattered in various sources, and present a systematic procedure to compute albedos, phase curves, and polarization of reflected light.

  4. Behaviour of the isothermal retention indices of n-alkylbenzenes on stationary phases of different polarity.

    PubMed

    Santiuste, José María; Quintanilla-López, Jesús Eduardo; Takács, Jószef M; Lebrón-Aguilar, Rosa

    2012-01-27

    Isothermal retention indices (I) of benzene, toluene, ethylbenzene, n-propylbenzene and n-butylbenzene were determined at 323-423 K on twelve WCOT capillary columns covering a broad stationary phase polarity spectrum. These I values have been tested carrying out a comparison with the NIST database values. The effect of the stationary phase polarity on I values was studied. But for the poly(3,3,3-trifluoropropylmethyl siloxane) column, a good linear correlation was found. At each temperature, the dependence on I of the alkyl chain length (z) attached to the ring of the n-alkylbenzenes was linear and of similar magnitude for the stationary phases of low to middle polarity, but lower for the more polar ones. Moreover, an important influence of the column temperature on the slope of the I vs. z plots was observed for the only non polysiloxane-type stationary phase studied, i.e., poly(ethylene glycol), due to its higher chain stiffness. Finally, different expressions describing the effect of the temperature on the retention index have been compared. I values of the n-alkylbenzenes in the 323-423 K range increase with increasing column temperature according to the Antoine-type (I=α+β(γ+T)(-1)) and the extended (I=a+bT(-1)+clnT) models. No significant differences were observed between them, except for the poly[70% bis(3-cyanopropyl) 30% dimethyl silphenylene-siloxane] column, for which the Antoine-type model was slightly better.

  5. Quantum mixed phases of a two-dimensional polarized degenerate Fermi gas in an optical cavity.

    PubMed

    Feng, Yanlin; Zhang, Kuang; Fan, Jingtao; Mei, Feng; Chen, Gang; Jia, Suotang

    2017-09-05

    The coupling of ultracold fermions to a high-finesse optical cavity can result in novel many-body phenomena, and has attracted significant interests at present. Here we consider a realization of the Fermi-Dicke model with controllable parameters, based on a two-dimensional polarized degenerate Fermi gas coupled to an optical cavity. We analytically investigate the ground-state properties of such system under the mean-field approximation. We find the system can exhibit a rich phase diagram depending on the fermion-photon coupling strength and the atomic resonant frequency. Contrasting to the bosonic counterpart, a first-order quantum phase transition between the superradiant phase and the normal phase featuring two Fermi surfaces can occur for the weak atomic resonant frequency, and there is a unique mixed phase where this normal phase and the superradiant phase coexist. The experimental detection of our results is also discussed.

  6. On Helium 1083 nm Line Polarization during the Impulsive Phase of an X1 Flare

    NASA Astrophysics Data System (ADS)

    Judge, Philip G.; Kleint, Lucia; Sainz Dalda, Alberto

    2015-12-01

    We analyze spectropolarimetric data of the He i 1083 nm multiplet (1s2s{}3{S}1-1s2p{}3{P}2,1,0o) during the X1 flare SOL2014-03-29T17:48, obtained with the Facility Infrared Spectrometer (FIRS) at the Dunn Solar Telescope. While scanning active region NOAA 12017, the FIRS slit crossed a flare ribbon during the impulsive phase, when the helium line intensities turned into emission at ≲twice the continuum intensity. Their linear polarization profiles are of the same sign across the multiplet including 1082.9 nm, intensity-like, at ≲5% of the continuum intensity. Weaker Zeeman-induced linear polarization is also observed. Only the strongest linear polarization coincides with hard X-ray (HXR) emission at 30-70 keV observed by RHESSI. The polarization is generally more extended and lasts longer than the HXR emission. The upper J = 0 level of the 1082.9 nm component is unpolarizable thus, lower-level polarization is the culprit. We make non-LTE radiative transfer calculations in thermal slabs optimized to fit only intensities. The linear polarizations are naturally reproduced, through a systematic change of sign with wavelength of the radiation anisotropy when slab optical depths of the 1082.9 component are ≲1. Neither are collisions with beams of particles needed, nor can they produce the same sign of polarization of the 1082.9 and 1083.0 nm components. The He i line polarization merely requires heating sufficient to produce slabs of the required thickness. Widely different polarizations of Hα, reported previously, are explained by different radiative anisotropies arising from slabs of different optical depths.

  7. Simultaneous separation of hydrophobic and polar bases using a silica hydride stationary phase.

    PubMed

    Yang, Yuanzhong; Matyska, Maria T; Boysen, Reinhard I; Pesek, Joseph J; Hearn, Milton T W

    2013-04-01

    In this study, the retention behavior of selected hydrophobic and polar bases on a minimally modified silica hydride phase was investigated. From these results and the associated retention plots, significant differences in the chromatographic dependencies of these two classes of basic compounds were evident. The polar bases exhibited strong retention with mobile phases of high organic solvent content, but displayed weak retention with mobile phases of high water content. In contrast, the hydrophobic bases showed "U-shape" retention dependencies, indicative of the interplay of both RP and normal-phase retention characteristics. These studies have demonstrated that hydrophobic and polar bases can be simultaneously separated on the same column either under typical RP-like or aqueous normal-phase-like conditions, respectively, with distinctive selectivity. Finally, the effects of temperature on the RP and aqueous normal phase modality of separations with these analytes were investigated, where discrete changes in retention behavior were also observed. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Limonene in Arizona liquid systems used in countercurrent chromatography. II Polarity and stationary-phase retention.

    PubMed

    Faure, K; Bouju, E; Doby, J; Berthod, A

    2014-09-01

    The previous article in this series described the physico-chemical properties and chemical compositions of the two phases of the limonene-ethyl acetate-ethanol-water biphasic liquid system. This system was designed to be a "green" version of the so-called Arizona (AZ) scale of heptane-ethyl acetate-methanol compositions in which the heptane-ethyl acetate volume ratio is exactly the same as the methanol-water ratio. The first major difference between the standard and "green" AZ systems is the difference in upper and lower phase densities. The higher density of limonene compared with heptane greatly reduces the density difference of the "green" system: half the compositions have a density difference lower than 0.06 g mL(-1), precluding their use in hydrodynamic CCC columns. The other major difference is the phase polarity. The better distribution of ethanol between the upper organic and lower aqueous phases of the "green" AZ scale renders them more polar than their counterparts in standard heptane-based compositions. The test solutes aspirin and coumarin have higher distribution constants in the "green" AZ compositions. It is revealed that a hydrostatic column is suitable for use with all "green" compositions, with very good phase retention and limited driving pressure at high flow rates. A hydrodynamic column only functioned at limited flow rates with polar compositions of sufficient phase-density difference. The CCC chromatograms obtained with different compositions and columns are shown, and their peak position and sharpness discussed.

  9. Intermetallic-Based High-Temperature Materials

    SciTech Connect

    Sikka, V.K.

    1999-04-25

    The intermetallic-based alloys for high-temperature applications are introduced. General characteristics of intermetallics are followed by identification of nickel and iron aluminides as the most practical alloys for commercial applications. An overview of the alloy compositions, melting processes, and mechanical properties for nickel and iron aluminizes are presented. The current applications and commercial producers of nickel and iron aluminizes are given. A brief description of the future prospects of intermetallic-based alloys is also given.

  10. A novel terahertz device with multi-function of polarization and switch based on phase transition of VO2

    NASA Astrophysics Data System (ADS)

    Gu, Wen-hao; Chang, Sheng-jiang; Fan, Fei

    2016-11-01

    A terahertz (THz) polarizer and switch structure is proposed based on the phase transition of vanadium dioxide (VO2). When VO2 is in the insulation phase, the resonance frequencies of the proposed structure are 1.49 THz and 1.22 THz for the x- and y-polarization, respectively. It can perform as a THz polarizer with extinction ratios of 52.5 dB and 17 dB for the y- and x-polarization, respectively; When VO2 transforms into metallic phase, the resonance frequency for x-polarization wave shifts from 1.49 THz to 1.22 THz, while that remains still for the y-polarization component. It means that the structure can work as a polarization-dependent THz switch with a high extinction ratio of 32 dB.

  11. Monte Carlo simulation of antiphase boundaries and growth of antiphase domains in Al5Ti3 phase in Al-rich γ-TiAl intermetallics

    NASA Astrophysics Data System (ADS)

    Kulkarni, U. D.; Hata, S.; Nakano, T.; Mitsuhara, M.; Ikeda, K.; Nakashima, H.

    2011-08-01

    Predominantly two kinds of antiphase boundaries (APBs) form in Al5Ti3, which is an Al-rich ordered derivative of the γ-TiAl (L10) phase. This phase can be viewed as a periodic arrangement of lean rhombs and squares on the Ti-rich (002) planes of the tetragonal L10. Energies of the two types of APBs were varied in a Monte Carlo simulation by suitably changing the pair interaction parameters. APBs of both types form boundaries of Al5Ti3 antiphase domains (APDs), which coarsen with time. An important observation in this regard is that mostly facetted APBs form at lower ageing temperatures, whereas curved APBs appear to form at relatively higher ageing temperatures. The findings of this work suggest that there exists a critical temperature, akin to the roughening transition temperature for crystals, that marks the transition from facetted to curved APBs.

  12. New icosahedral nanoclusters in crystal structures of intermetallic compounds: Topological types of 50-atom deltahedra D50 in samson phases β-Mg2Al3 and ɛ-Mg23Al30

    NASA Astrophysics Data System (ADS)

    Blatov, V. A.; Ilyushin, G. D.

    2012-12-01

    A database of intermetallic compounds has been compiled using the TOPOS program package. This database includes 514 topological types, containing 12- and 13-atom icosahedral i clusters. An isolated group of 1649 i clusters is described by 14 point groups and their maximum symmetry D 3 d (bar 3 m) and T h ( m bar 3) is established, respectively, in 47 and 25 types of crystal structures. A structural analysis of the outer quasispherical shells showed that local 63-atom i configurations 1@12@50, which contain 50 atoms in the second layer, are implemented in 8 out of 19 cases. Examples of new topologically different types of 50-atom D50 deltahedra in the Samson phases ɛ-Mg23Al30 and β-Mg2Al3 are presented. Four topologically different sites with coordination numbers of 5, 6, 6, or 7 are established in the ɛ shell and seven sites with coordination numbers of 5, 5, 6, 6, 6, 6, or 7 are found in the β shell. The inner i clusters for the β-Mg2Al3 structure (with the symmetry bar 3 m) and the ɛ-Mg23Al30 structure (with the symmetry bar 3) have a similar chemical composition, i.e., Mg7Al6 and Mg6Al7, and their 50-atom shells are chemically identical to 18Mg + 32Al. The configurations found supplement the series of known two-layer icosahedral Bergman and Mackay clusters in the form of deltahedra with 32- and 42-atom shells.

  13. Kilohertz generation of high contrast polarization states for visible femtosecond pulses via phase-locked acousto-optic pulse shapers

    SciTech Connect

    Seiler, Hélène; Walsh, Brenna; Palato, Samuel; Kambhampati, Patanjali; Thai, Alexandre; Forget, Nicolas; Crozatier, Vincent

    2015-09-14

    We present a detailed analysis of a setup capable of arbitrary amplitude, phase, and polarization shaping of broadband visible femtosecond pulses at 1 kHz via a pair of actively phase stabilized acousto-optic programmable dispersive filters arranged in a Mach-Zehnder interferometer geometry. The setup features phase stability values around λ/225 at 580 nm as well as degrees of polarization of at least 0.9 for any polarization state. Both numbers are important metrics to evaluate a setup's potential for applications based on polarization-shaped femtosecond pulses, such as fully coherent multi-dimensional electronic spectroscopy.

  14. Generation of bright phase-matched circularly-polarized extreme ultraviolet high harmonics

    NASA Astrophysics Data System (ADS)

    Kfir, Ofer; Grychtol, Patrik; Turgut, Emrah; Knut, Ronny; Zusin, Dmitriy; Popmintchev, Dimitar; Popmintchev, Tenio; Nembach, Hans; Shaw, Justin M.; Fleischer, Avner; Kapteyn, Henry; Murnane, Margaret; Cohen, Oren

    2015-02-01

    Circularly-polarized extreme ultraviolet and X-ray radiation is useful for analysing the structural, electronic and magnetic properties of materials. To date, such radiation has only been available at large-scale X-ray facilities such as synchrotrons. Here, we demonstrate the first bright, phase-matched, extreme ultraviolet circularly-polarized high harmonics source. The harmonics are emitted when bi-chromatic counter-rotating circularly-polarized laser pulses field-ionize a gas in a hollow-core waveguide. We use this new light source for magnetic circular dichroism measurements at the M-shell absorption edges of Co. We show that phase-matching of circularly-polarized harmonics is unique and robust, producing a photon flux comparable to linearly polarized high harmonic sources. This work represents a critical advance towards the development of table-top systems for element-specific imaging and spectroscopy of multiple elements simultaneously in magnetic and other chiral media with very high spatial and temporal resolution.

  15. Linear polarization of binaries II. Phase function : wQ~(?)Q~? (??)

    NASA Astrophysics Data System (ADS)

    Barman, S. K.

    2000-12-01

    This paper presents a method of calculating linear polarizations in close binaries whose surfaces are distorted due to tidal and rotational forces. Limb-darkening effect has been taken into account. Particles of different sizes are embedded in the outer atmosphere. The law of differential rotation of the primary is considered in analytic form: ??=3D b1 + b2 w2 + b3 w4, where b1, b2 and b3 are constants and w is the distance of a point P (r,?,?) from the axis of rotation of the primary. The atmosphere is assumed to be non-grey, plane-parallel and the phase function is wQ~(?)Q~? (??). Calculations are done with respect to rest frame fixed at the centre of the primary star for several functions as : mass-ratio (q) between the secondary and the primary, polar radius (rp) of the primary, wave-length (?) of the incident light, radius of a particle (1) and angle of inclination (?) with respect to the line of sight. It is noticed that polarization increases with an increase of the radius rp steadily; polarization increases with an increase of the radius of the particle (1), polarization increases with an increase of the mass-ratio q. The method of solution has been applied to several late type binaries to calculate disk integrated linear polarization of light emitted by them. When the mass-ratio q = 0, the general problem reduces to the calculation for a rotationally distorted single (primary) star.

  16. Quasi-amorphous inorganic thin films: non-crystalline polar phases.

    PubMed

    Wachtel, Ellen; Lubomirsky, Igor

    2010-06-18

    Quasi-amorphous thin films of BaTiO3, SrTiO3, and BaZrO3 are the only known examples of inorganic, non-crystalline, polar materials. The conditions under which they are formed and the origin of their polarity set these materials apart from other classes of inorganic materials. The most important feature of the quasi-amorphous phase is that the polarity is the result of the orientational ordering of local bonding units but without any detectable spatial periodicity. This mechanism is reminiscent of that observed in ferroelectric polymers and permits compounds that do not have polar crystalline polymorphs, such as SrTiO3 and BaZrO3, to form polar non-crystalline solids. In the present report, we provide an overview of the essential features of these materials including preparation, structure, and chemical composition. The report also reviews our current level of understanding and offers some guidelines for further development and application of non-crystalline inorganic polar materials.

  17. Phase-controllable spin wave generation in iron garnet by linearly polarized light pulses

    SciTech Connect

    Yoshimine, Isao; Iida, Ryugo; Shimura, Tsutomu; Satoh, Takuya; Stupakiewicz, Andrzej; Maziewski, Andrzej

    2014-07-28

    A phase-controlled spin wave was non-thermally generated in bismuth-doped rare-earth iron garnet by linearly polarized light pulses. We controlled the initial phase of the spin wave continuously within a range of 180° by changing the polarization azimuth of the excitation light. The azimuth dependences of the initial phase and amplitude of the spin wave were attributed to a combination of the inverse Cotton-Mouton effect and photoinduced magnetic anisotropy. Temporally and spatially resolved spin wave propagation was observed with a CCD camera, and the waveform was in good agreement with calculations. A nonlinear effect of the spin excitation was observed for excitation fluences higher than 100 mJ/cm{sup 2}.

  18. Detection of two identical frequency vibrations by phase discrimination in polarization-OTDR

    NASA Astrophysics Data System (ADS)

    Wang, Feng; Pan, Yun; Zhang, MingJiang; Cao, Chunqi; Zhang, Xuping

    2017-04-01

    In this paper, a new detection method for two identical frequency vibrations along optic fiber is proposed, by discrimination of their phase relationship in polarization optical time-domain reflectometer (POTDR). A vibration on fiber would modulate its index and birefringence, then it can consequently change the state of polarization (SOP) of the scattering signal. However, multiple simultaneous vibrations at different positions would result in random fluctuating SOP of the scattering signal, which make them very difficult to be identified. In our proposed method, the phase of the vibration signal along the fiber is obtained by Fast Fourier Transform. Therefore, two vibration events with the same frequency could be distinguished effectively by using the pattern of the phase distribution. The principle of the method is analyzed in detail. Both simulation and experiment results are presented to demonstrate the validity and limitation of this method. It could be widely used for safety monitoring of long distance perimeters, electrical transmission line, and so on.

  19. A high-power microwave circular polarizer and its application on phase shifter.

    PubMed

    Shao, Hao; Hu, Yongmei; Chang, Chao; Guo, Letian

    2016-04-01

    A high-power waveguide dual circular polarizer was theoretically designed and proof-of-principle was experimentally tested. It consists of two incident rectangular waveguides with a perpendicular H-plane junction, one circular waveguide with a pair of trapezoidal grooves coupled in E-plane at the top, a spherical crown located at the bottom, and an iris at the perpendicular junction of two rectangular waveguides. When wave incidents at one of the two separated rectangular waveguides, it, respectively, generates a left-hand circular polarized wave or a right-hand circular polarized wave in the circular waveguide. By adding a dumbbell-like metal plug driven with a high speed servomotor, a movable short circuit is formed along the circular waveguide to adjust the output RF phase of the rectangular port, realizing a high-speed high-power phase shifter. The C-band high power microwave (HPM) experiments were carried out, and the power capacity of the HPM polarizer and phase shifter was demonstrated to reach gigawatt level.

  20. Zn13(CrxAl1-x)27 (x = 0.34-0.37): a new intermetallic phase containing icosahedra as building units

    SciTech Connect

    Thimmaiah, Srinivasa; Han, Mi-Kyung; Miller, Gordon J.

    2011-03-13

    The title compounds Zn{sub 13}(Cr{sub x}Al{sub 1-x}){sub 27} (x = 0.34-0.37) were obtained by melting the pure elements at 923 K, and followed by a heat treatment at 723 K in a tantalum container. According to single crystal structural analysis, the title compounds crystallize in the rhombohedral system, adopting a new structure type (R-3m, a = 7.5971(8), c = 36.816(6), for crystal I). Single crystal X-ray structural analysis reveals a statistical mixing of Cr/Al in their crystallographic positions. Single crystal and powder X-ray diffraction as well as energy dispersive X-ray analyses suggested the title phase to have a narrow homogeneity range. The substructure of Zn{sub 13}(Cr{sub x}Al{sub 1-x}){sub 27} shows close resemblance with the Mn{sub 3}Al{sub 10} structure type. A bonding analysis, through crystal orbital Hamiltonian populations (COHPs), of 'Cr{sub 9}Al{sub 18}Zn{sub 13}' as a representative composition indicated that both homo- and heteronuclear interactions are important for the stability of this new phase.

  1. Chromatic dispersion and polarization mode dispersion monitoring for multi-level intensity and phase modulation systems.

    PubMed

    Wang, Yan; Hu, Song; Yan, Lianshan; Yang, Jeng-Yuan; Willner, Alan E

    2007-10-17

    We demonstrate chromatic dispersion (CD) and polarization mode dispersion (PMD) monitoring techniques via simulation and experiment for 2- and 4-level intensity-modulated as well as phase-modulated optical systems. Degree of polarization (DOP) measurement for monitoring PMD up to 100-ps and clock tone measurement for monitoring CD up to 720-ps/nm are demonstrated in 10-Gsymbol/s non-return-to-zero (NRZ) and return-to-zero (RZ) systems. Analysis on dynamic range and monitoring window shows that careful consideration and characterization are necessary when applying these monitoring techniques to multi-level systems.

  2. Core polarization effects in the Hartree--Fock--random phase approximation schemes

    SciTech Connect

    Lipparini, E.; Stringari, S.

    1987-02-01

    Core polarization effects in odd nuclei are investigated in the framework of the Hartree--Fock and random phase approximation schemes. The results of the particle vibration coupling model are recovered by linearizing the equations of motion in the interaction Hamiltonian between the external and the core particles. The formalism is used to study the renormalization of diagonal and off-diagonal M1 matrix elements. It is found that M1 polarization effects exhibit a very strong dependence on the range of the force. Copyright 1987 Academic Press, Inc.

  3. Generation of High Efficiency Longitudinally Polarized Beam using High NA Lens Axicon and Dedicated Phase Filter

    SciTech Connect

    Rajesh, K. B.; Mohankumar, R.; Prathibajanet, C. Amala; Pillai, T. V. S.; Jaroszewicz, Z.

    2011-10-20

    We propose to use pure phase filter in combination with high NA lens axicon to achieve high efficient longitudinally polarized beam with a subwavelength spot size and large depth of focus using hyper geometric Gaussian beam. Using this system, the spot size is reduced to 0.392 {lambda} and the depth of focus is increased to 7 {lambda}. The efficiency of such system is found to be 87%. This high efficient longitudinally polarized beam generated by hyper geometric Gaussian beam is useful for most of the near-field optics applications.

  4. Experimental phase-covariant cloning of polarization states of single photons

    SciTech Connect

    Cernoch, Antonin; Bartu ring skova, Lucie; Jezek, Miroslav; Fiurasek, Jaromir; Dusek, Miloslav; Soubusta, Jan

    2006-10-15

    The experimental realization of optimal symmetric phase-covariant 1{yields}2 cloning of qubit states is presented. The qubits are represented by polarization states of photons generated by spontaneous parametric down-conversion. The experiment is based on the interference of two photons on a custom-made beam splitter with different splitting ratios for vertical and horizontal polarization components. From the measured data we have estimated the implemented cloning transformation using the maximum-likelihood method. The result shows that the realized transformation is very close to the ideal one and the map fidelity reaches 94%.

  5. Method for making devices having intermetallic structures and intermetallic devices made thereby

    DOEpatents

    Paul, Brian Kevin; Wilson, Rick D.; Alman, David E.

    2004-01-06

    A method and system for making a monolithic intermetallic structure are presented. The structure is made from lamina blanks which comprise multiple layers of metals which are patternable, or intermetallic lamina blanks that are patternable. Lamina blanks are patterned, stacked and registered, and processed to form a monolithic intermetallic structure. The advantages of a patterned monolithic intermetallic structure include physical characteristics such as melting temperature, thermal conductivity, and corrosion resistance. Applications are broad, and include among others, use as a microreactor, heat recycling device, and apparatus for producing superheated steam. Monolithic intermetallic structures may contain one or more catalysts within the internal features.

  6. Method for making devices having intermetallic structures and intermetallic devices made thereby

    DOEpatents

    Paul, Brian Kevin; Wilson, Richard Dean; Alman, David Eli

    2004-01-06

    A method and system for making a monolithic intermetallic structure are presented. The structure is made from lamina blanks which comprise multiple layers of metals which are patternable, or intermetallic lamina blanks that are patternable. Lamina blanks are patterned, stacked and registered, and processed to form a monolithic intermetallic structure. The advantages of a patterned monolithic intermetallic structure include physical characteristics such as melting temperature, thermal conductivity, and corrosion resistance. Applications are broad, and include among others, use as a microreactor, heat recycling device, and apparatus for producing superheated steam. Monolithic intermetallic structures may contain one or more catalysts within the internal features.

  7. Flat polarization-controlled cylindrical lens based on the Pancharatnam-Berry geometric phase

    NASA Astrophysics Data System (ADS)

    Piccirillo, Bruno; Florinda Picardi, Michela; Marrucci, Lorenzo; Santamato, Enrico

    2017-05-01

    The working principle of ordinary refractive lenses can be explained in terms of the space-variant optical phase retardations they introduce, which reshape the optical wavefront curvature and hence affect the subsequent light propagation. These phases, in turn, are due to the varying optical path length followed by light at different transverse positions relative to the lens center. A similar lensing behavior can, however, be obtained when the optical phases are introduced by an entirely different mechanism. Here, we consider the ‘geometric phases’ that arise from the polarization transformations occurring in anisotropic optical media, named after Pancharatnam and Berry. The medium anisotropy axis is taken to be space-variant in the transverse plane and the resulting varying geometric phases give rise to the wavefront reshaping and lensing effect, which however also depends on the input polarization. We describe the realization and characterization of a cylindrical geometric-phase lens that is converging for a given input circular-polarization state and diverging for the orthogonal one, which provides one of the simplest possible examples of optical elements based on geometric phases. The demonstrated lens is flat and only a few microns thick (not including the supporting substrates); moreover, its working wavelength can be tuned and the lensing can be switched on and off by the action of an external control electric field. Other kinds of lenses or more general phase elements inducing different wavefront distortions can be obtained by a similar approach. Besides their potential for optoelectronic technology, these devices offer good opportunities for introducing college-level students to an advanced topic of modern physics, such as the Berry phase, with the help of interesting optical demonstrations.

  8. Polarity, selectivity and performance of hydrophilic organic/salt-containing aqueous two-phase system on counter-current chromatography for polar compounds.

    PubMed

    Liu, Dan; Hong, Zhilai; Gao, Mingzhe; Wang, Zhixin; Gu, Ming; Zhang, Xiaozhe; Xiao, Hongbin

    2016-05-27

    The essential attributes of a solvent system for separation polar compounds on CCC are polarity, selectively and performance. Here, hydrophilic organic/salt-containing aqueous two-phase system (HO/S TPS) was evaluated as an alternative solvent system for CCC separation of polar compounds. Polarity measurements based on Rohrschneider-Snyder parameter was developed as quantitative assessing the polarity of HO/S TPS and comparing with an organic/aqueous system. All investigated 1-butanol/ethanol/saturated ammonium sulfate solution/water (BEAsWat) and 1-butanol/ethanol/saturated dipotassium hydrogen phosphate solution/water (BEDhpWat) systems with polarity values of organic phase from 4.5 to 6.8, were more polar than chloroform/methanol/water (1/1/1). The considerable water content of BEAsWat and BEDhpWat (0/1/1/1/) was 45.4 and 42.6% (w%) of hydrophilic organic phase, and 66.4 and 51.2% (w%) of salt-containing aqueous phase, respectively, closed to conventional aqueous two-phase system. Therefore, the polarity of HO/S TPS is in the middle of organic/aqueous and aqueous two-phase system. The LogKC values of twenty four polar compounds as model mixture confirmed that the polarities of HO/S TPSs were matched to that of the polar compounds and shown to be a very selective technique capable of separating positional isomers. Moreover, BEAsWat and BEDhpWat systems can be easily retained in CCC column with suitable elution mode. The hydrodynamic behavior reversion of HO/S TPS on hydrodynamic CCC was observed and was tentatively explained based on the density difference. Finally, caffeoylquinic acid isomers and dihydroxybenzoic acid isomers were successfully separated with HO/S TPS on CCC, respectively. Those results demonstrate that HO/S TPS on CCC is a performant and stable way to separate polar compounds from natural products.

  9. 1.14 Tb/s DP-QPSK WDM polarization-diverse optical phase conjugation.

    PubMed

    Stephens, M F C; Tan, M; Phillips, I D; Sygletos, S; Harper, P; Doran, N J

    2014-05-19

    Optical phase conjugation (OPC) of a polarization-multiplexed comb of 10x114Gb/s DP-QPSK signals has been demonstrated for the first time, occupying a spectral bandwidth of >1 THz (~9 nm). The nonlinear element employed for the OPC was highly nonlinear fiber (HNLF) optimized for the suppression of stimulated Brillouin scattering (SBS) and configured in a bi-directional loop offering polarization diversity. Pump power (each way about the loop) and input signal power to the OPC subsystem were optimized at 29.7 dBm and + 3 dBm respectively producing a Q(2) penalty of ≤ 0.9 dB over all conjugate wavelengths, polarizations and output OSNR (up to 20 dB).

  10. Phase-resolved Spectroscopy of the Intermediate Polars -- TV Col and V1223 Sgr

    NASA Astrophysics Data System (ADS)

    Long, K.

    The cataclysmic variables called intermediate polars are characterized by magnetic fields that rip material from an accretion disk and funnel it to a WD that is not phase-locked to the binary period of the system. This is a proposal to use FUSE to conduct a time-resolved spectroscopic study to dissect the emission of two long-period intermediate polars, V1223 Sgr and TV Col, with very different inclination angles. These, along with the short-period high-inclination IP EX Hya (already observed with FUSE), comprise the only IPs with accurate distances derived from HST astrometry. We will isolate emission from the photosphere of the WD, the magnetically dominated accretion curtain, and the accretion stream. Having characterized the emission sources, we will explore the physical conditions in these same regions, and develop an integrated picture of these two intermediate polars.

  11. Thermomechanical processing of plasma sprayed intermetallic sheets

    DOEpatents

    Hajaligol, Mohammad R.; Scorey, Clive; Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier; Lilly, Jr., A. Clifton; German, Randall M.

    2001-01-01

    A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3% Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

  12. Vortex phase-induced changes of the statistical properties of a partially coherent radially polarized beam.

    PubMed

    Guo, Lina; Chen, Yahong; Liu, Xianlong; Liu, Lin; Cai, Yangjian

    2016-06-27

    Partially coherent radially polarized (PCRP) beam was introduced and generated in recent years. In this paper, we investigate the statistical properties of a PCRP beam embedded with a vortex phase (i.e., PCRP vortex beam). We derive the analytical formula for the cross-spectral density matrix of a PCRP vortex beam propagating through a paraxial ABCD optical system and analyze the statistical properties of a PCRP vortex beam focused by a thin lens. It is found that the statistical properties of a PCRP vortex beam on propagation are much different from those of a PCRP beam. The vortex phase induces not only the rotation of the beam spot, but also the changes of the beam shape, the degree of polarization and the state of polarization. We also find that the vortex phase plays a role of resisting the coherence-induced degradation of the intensity distribution and the coherence-induced depolarization. Furthermore, we report experimental generation of a PCRP vortex beam for the first time. Our results will be useful for trapping and rotating particles, free-space optical communications and detection of phase object.

  13. Space-bandwidth extension in parallel phase-shifting digital holography using a four-channel polarization-imaging camera.

    PubMed

    Tahara, Tatsuki; Ito, Yasunori; Xia, Peng; Awatsuji, Yasuhiro; Nishio, Kenzo; Ura, Shogo; Kubota, Toshihiro; Matoba, Osamu

    2013-07-15

    We propose a method for extending the space bandwidth (SBW) available for recording an object wave in parallel phase-shifting digital holography using a four-channel polarization-imaging camera. A linear spatial carrier of the reference wave is introduced to an optical setup of parallel four-step phase-shifting interferometry using a commercially available polarization-imaging camera that has four polarization-detection channels. Then a hologram required for parallel two-step phase shifting, which is a technique capable of recording the widest SBW in parallel phase shifting, can be obtained. The effectiveness of the proposed method was numerically and experimentally verified.

  14. Massive spalling of intermetallic compounds in solder-substrate reactions due to limited supply of the active element

    NASA Astrophysics Data System (ADS)

    Yang, S. C.; Ho, C. E.; Chang, C. W.; Kao, C. R.

    2007-04-01

    Massive spalling of intermetallic compounds has been reported in the literature for several solder/substrate systems, including SnAgCu soldered on Ni substrate, SnZn on Cu, high-Pb PbSn on Cu, and high-Pb PbSn on Ni. In this work, a unified thermodynamic argument is proposed to explain this rather unusual phenomenon. According to this argument, two necessary conditions must be met. The number one condition is that at least one of the reactive constituents of the solder must be present in a limited amount, and the second condition is that the soldering reaction has to be very sensitive to its concentration. With the growth of intermetallic, more and more atoms of this constituent are extracted out of the solder and incorporated into the intermetallic. As the concentration of this constituent decreases, the original intermetallic at the interface becomes a nonequilibrium phase, and the spalling of the original intermetallic occurs.

  15. A Low-Noise Delta-Sigma Phase Modulator for Polar Transmitters

    PubMed Central

    Zhou, Bo

    2014-01-01

    A low-noise phase modulator, using finite-impulse-response (FIR) filtering embedded delta-sigma (ΔΣ) fractional-N phase-locked loop (PLL), is fabricated in 0.18 μm CMOS for GSM/EDGE polar transmitters. A simplified digital compensation filter with inverse-FIR and -PLL features is proposed to trade off the transmitter noise and linearity. Experimental results show that the presented architecture performs RF phase modulation well with 20 mW power dissipation from 1.6 V supply and achieves the root-mean-square (rms) and peak phase errors of 4° and 8.5°, respectively. The measured and simulated phase noises of −104 dBc/Hz and −120 dBc/Hz at 400-kHz offset from 1.8-GHz carrier frequency are observed, respectively. PMID:24719578

  16. A low-noise delta-sigma phase modulator for polar transmitters.

    PubMed

    Zhou, Bo

    2014-01-01

    A low-noise phase modulator, using finite-impulse-response (FIR) filtering embedded delta-sigma (ΔΣ) fractional-N phase-locked loop (PLL), is fabricated in 0.18 μ m CMOS for GSM/EDGE polar transmitters. A simplified digital compensation filter with inverse-FIR and -PLL features is proposed to trade off the transmitter noise and linearity. Experimental results show that the presented architecture performs RF phase modulation well with 20 mW power dissipation from 1.6 V supply and achieves the root-mean-square (rms) and peak phase errors of 4° and 8.5°, respectively. The measured and simulated phase noises of -104 dBc/Hz and -120 dBc/Hz at 400-kHz offset from 1.8-GHz carrier frequency are observed, respectively.

  17. Suppressors made from intermetallic materials

    SciTech Connect

    Klett, James W; Muth, Thomas R; Cler, Dan L

    2014-11-04

    Disclosed are several examples of apparatuses for suppressing the blast and flash produced as a projectile is expelled by gases from a firearm. In some examples, gases are diverted away from the central chamber to an expansion chamber by baffles. The gases are absorbed by the expansion chamber and desorbed slowly, thus decreasing pressure and increasing residence time of the gases. In other examples, the gases impinge against a plurality of rods before expanding through passages between the rods to decrease the pressure and increase the residence time of the gases. These and other exemplary suppressors are made from an intermetallic material composition for enhanced strength and oxidation resistance at high operational temperatures.

  18. A reconfigurable parity-time symmetric meta-atom for polarization and phase control (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Baum, Brian; Dionne, Jennifer; Alaeian, Hadiseh; Jankovic, Vladan; Lawrence, Mark

    2016-09-01

    Metasurfaces offer exotic optical properties, which often originate from carefully designed material geometries. With locked geometries, these metasurfaces are difficult or impossible to change post-fabrication. Here, we theoretically explore a nano-scale coaxial structure capable of adjustably manipulating the polarization, phase, and spatial distribution of light through the introduction of parity-time (PT) symmetric perturbations. Coaxial waveguides possess degenerate modes, corresponding to different orbital angular momentum (OAM) states. The degeneracy of OAM modes can be lifted through the introduction of any non-zero amount of gain and loss into the structure in a way that matches the azimuthal periodicity of the degenerate mode pair. New hybrid complex conjugate modes are created which lose their pure OAM nature and are either amplifying or lossy. We confirm this behavior using both a Hamiltonian formulation and degenerate perturbation theory, and propose this selective excitation and absorption scheme as a new method of filtering for mode division multiplexing in on-chip nanophotonic systems. In addition to the creation of new hybrid modes, we show that these PT-symmetric perturbations in coaxial apertures are capable of converting incident circularly polarized light into linearly polarized light with unity efficiency. Further, due to the localization of field intensity within the gain sections, it is possible to rotate linear polarization and induce up to a pi-phase shift. We describe how our PT-symmetric coaxial aperture could function as a reconfigurable meta-atom for phase, amplitude, and polarization controlled meta-surfaces, and discuss routes toward unity-efficiency, reconfigurable holography.

  19. Light beams with general direction and polarization: Global description and geometric phase

    NASA Astrophysics Data System (ADS)

    Nityananda, R.; Sridhar, S.

    2014-02-01

    We construct the manifold describing the family of plane monochromatic light waves with all directions, polarizations, phases and intensities. A smooth description of polarization, valid over the entire sphere S2 of directions, is given through the construction of an orthogonal basis pair of complex polarization vectors for each direction; any light beam is then uniquely and smoothly specified by giving its direction and two complex amplitudes. This implies that the space of all light beams is the six dimensional manifold S2×C2∖{0}, the (untwisted) Cartesian product of a sphere and a two dimensional complex vector space minus the origin. A Hopf map (i.e. mapping the two complex amplitudes to the Stokes parameters) then leads to the four dimensional manifold S2×S2 which describes beams with all directions and polarization states. This product of two spheres can be viewed as an ordered pair of two points on a single sphere, in contrast to earlier work in which the same system was represented using Majorana's mapping of the states of a spin one quantum system to an unordered pair of points on a sphere. This is a different manifold, CP2, two dimensional complex projective space, which does not faithfully represent the full space of all directions and polarizations. Following the now-standard framework, we exhibit the fibre bundle whose total space is the set of all light beams of non-zero intensity, and base space S2×S2. We give the U(1) connection which determines the geometric phase as the line integral of a one-form along a closed curve in the total space. Bases are classified as globally smooth, global but singular, and local, with the last type of basis being defined only when the curve traversed by the system is given. Existing as well as new formulae for the geometric phase are presented in this overall framework.

  20. Composite optical fiber polarizer with ternary copolymer overlay for large range modulation of phase difference

    NASA Astrophysics Data System (ADS)

    Cui, Minxin; Tian, Xiujie; Zou, Gang; Zhu, Bing; Zhang, Qijin

    2017-04-01

    In this work, a ternary copolymer composed of (E)-2-(4-((4-isocyanophenyl) diazenyl) phenoxy) ethyl methacrylate (2-CN), methacrylisobutyl polyhedral oligomeric silsesquioxane (MAPOSS) and 2,2,2-trifluoroethyl methacrylate (TFEMA) is synthesized and used as the overlay for composite optical fiber, in which cage-like POSS component and fluorine-containing component are used to reduce refractive index, and azobenzene component is used to finely manipulate the refractive indices in two orthogonal directions through photo-induced orientation under irradiation of polarized light. Before irradiation, the refractive index of terpolymer (1.4503) is slightly higher than that of the core material (1.4489) of commercial silica single-mode fiber, which is obtained by optimizing the amount of each monomer. After the irradiation of 435 nm polarized light, refractive indices of the overlay in two orthogonal directions decrease, and two values have been finely manipulated so that one is higher and another is lower than the refractive index of the fiber core by optimizing irradiation time. In this way, a radial loss type fiber polarization modulator is obtained. By changing the polarization direction of the irradiation at 435 nm, the polarization of propagating light at 1550 nm in the fiber can also be modulated continuously. The maximum change of phase difference is about 300°, making the device useful as a quarter-wave plate or a half-wave plate.

  1. LIMITS ON OPTICAL POLARIZATION DURING THE PROMPT PHASE OF GRB 140430A

    SciTech Connect

    Kopac, D.; Mundell, C. G.; Arnold, D. M.; Steele, I. A.; Kobayashi, S.; Lamb, G. P.; Smith, R. J.; Virgili, F. J.; Japelj, J.; Gomboc, A.; Guidorzi, C.; Dichiara, S.; Harrison, R. M.; Melandri, A.; Castro-Tirado, A. J.; Gorosabel, J.; Sánchez-Ramírez, R.; Oates, S. R.; Jelínek, M.

    2015-11-01

    Gamma-ray burst GRB 140430A was detected by the Swift satellite and observed promptly with the imaging polarimeter RINGO3 mounted on the Liverpool Telescope, with observations beginning while the prompt γ-ray emission was still ongoing. In this paper, we present densely sampled (10-s temporal resolution) early optical light curves (LCs) in 3 optical bands and limits to the degree of optical polarization. We compare optical, X-ray, and gamma-ray properties and present an analysis of the optical emission during a period of high-energy flaring. The complex optical LC cannot be explained merely with a combination of forward and reverse shock emission from a standard external shock, implying additional contribution of emission from internal shock dissipation. We estimate an upper limit for time averaged optical polarization during the prompt phase to be as low as P < 12% (1σ). This suggests that the optical flares and early afterglow emission in this GRB are not highly polarized. Alternatively, time averaging could mask the presence of otherwise polarized components of distinct origin at different polarization position angles.

  2. Polarization properties of cubic blue phases of a cholesteric liquid crystal

    NASA Astrophysics Data System (ADS)

    Orzechowski, Kamil; Sierakowski, Marek W.; Sala-Tefelska, Marzena; Joshi, Pankaj; Woliński, Tomasz R.; De Smet, Herbert

    2017-07-01

    In this paper, we have experimentally investigated polarization properties of the blue phase of a cholesteric liquid crystal in polycrystalline cells with different alignment layers. Experiments were carried out by various temperatures and wavelengths within the spectral range covering Bragg reflection. It was conclusively demonstrated that the change of polarization state of transmitted light through polycrystalline BP-cell is mainly due to Bragg reflection, while optical activity is relatively small. Besides, the linear birefringence was not observed, as expected. It was shown that the ellipticity of the outgoing polarization state can change from almost linear (1.33%) to elliptic (7.33%), depending on sample orientation, with negligible changing of optical rotatory power (for BP I at 470 nm). The results indicate that also polycrystalline BPLC structure, although locally anisotropic, is macroscopically isotropic showing non-negligible optical activity only for resonant wavelengths, although being much lower than that in a typical cholesteric phase. It was also shown that different alignment layers in BP-cell may shift Bragg reflection spectral range, so influencing the outgoing polarization state for particular wavelength.

  3. Intermetallic Nanocrystals: Syntheses and Catalytic Applications.

    PubMed

    Yan, Yucong; Du, Jingshan S; Gilroy, Kyle D; Yang, Deren; Xia, Younan; Zhang, Hui

    2017-02-24

    At the forefront of nanochemistry, there exists a research endeavor centered around intermetallic nanocrystals, which are unique in terms of long-range atomic ordering, well-defined stoichiometry, and controlled crystal structure. In contrast to alloy nanocrystals with no elemental ordering, it is challenging to synthesize intermetallic nanocrystals with a tight control over their size and shape. Here, recent progress in the synthesis of intermetallic nanocrystals with controllable sizes and well-defined shapes is highlighted. A simple analysis and some insights key to the selection of experimental conditions for generating intermetallic nanocrystals are presented, followed by examples to highlight the viable use of intermetallic nanocrystals as electrocatalysts or catalysts for various reactions, with a focus on the enhanced performance relative to their alloy counterparts that lack elemental ordering. Within the conclusion, perspectives on future developments in the context of synthetic control, structure-property relationships, and applications are discussed.

  4. Effect of Mn and Fe on the Formation of Fe- and Mn-Rich Intermetallics in Al-5Mg-Mn Alloys Solidified Under Near-Rapid Cooling.

    PubMed

    Liu, Yulin; Huang, Gaoren; Sun, Yimeng; Zhang, Li; Huang, Zhenwei; Wang, Jijie; Liu, Chunzhong

    2016-01-29

    Mn was an important alloying element used in Al-Mg-Mn alloys. However, it had to be limited to a low level (<1.0 wt %) to avoid the formation of coarse intermetallics. In order to take full advantage of the benefits of Mn, research was carried out to investigate the possibility of increasing the content of Mn by studying the effect of cooling rate on the formation of Fe- and Mn-rich intermetallics at different content levels of Mn and Fe. The results indicated that in Al-5Mg-Mn alloy with low Fe content (<0.1 wt %), intermetallic Al₆(Fe,Mn) was small in size and amount. With increasing Mn content, intermetallic Al₆(Fe,Mn) increased, but in limited amount. In high-Fe-containing Al-5Mg-Mn alloys (0.5 wt % Fe), intermetallic Al₆(Fe,Mn) became the dominant phase, even in the alloy with low Mn content (0.39 wt %). Cooling rate played a critical role in the refinement of the intermetallics. Under near-rapid cooling, intermetallic Al₆(Fe,Mn) was extremely refined. Even in the high Mn and/or high-Fe-containing alloys, it still demonstrated fine Chinese script structures. However, once the alloy composition passed beyond the eutectic point, the primary intermetallic Al₆(Fe,Mn) phase displayed extremely coarse platelet-like morphology. Increasing the content of Fe caused intermetallic Al₆(Fe,Mn) to become the primary phase at a lower Mn content.

  5. Vibration energy harvesting based on stress-induced polarization switching: a phase field approach

    NASA Astrophysics Data System (ADS)

    Wang, Dan; Wang, Linxiang; Melnik, Roderick

    2017-06-01

    Different from the traditional piezoelectric vibration energy harvesting, a new strategy based on stress-induced polarization switching has been proposed in the current paper. Two related prototypes are presented and the associated advantages and drawbacks have been discussed in detail. It has been demonstrated that, with the assistance of a bias electric field, the robustness of the energy harvesters is improved. Furthermore, the real-space phase-field model has been employed to study the nonlinear hysteretic behavior involved in the proposed energy harvesting process. A substantially larger electric current associated with the stress-induced polarization switching has been demonstrated when compared with that with piezoelectric effect. In addition, the effects of bias electric potential, bias resistance, mechanical boundary conditions, charge leakage and electrodes arrangements have also been investigated by the phase-field simulation, which provides a guidance for future real implementations.

  6. Polarization maintaining fiber magnetic sensor based on the digital phase generated carrier technology

    NASA Astrophysics Data System (ADS)

    Zhang, Xueliang; Meng, Zhou; Hu, Zhengliang; Yang, Huayong; Song, Zhangqi; Hu, Yongming

    2008-12-01

    A polarization maintaining fiber (PMF) magnetic field sensor based on a digital phase generated carrier (PGC) technology is presented. A magnetic sensor constructed with two magnetostrictive strips attached on the sensing fiber is joined in the sensing arm of a fiber Michelson interferometer. The fiber optic interferometric system is made of all PMF, which inhibits the polarization-induced signal fading. The light source is a fiber laser which can be modulated directly. The PGC metnod is used to demodulate magnetic field signal avoiding phase induced interferometric signal fading, and ensure the sensing partto be all fiber structure. A fiber optic magnetic field sensor with appreciate size for the fiber optic hydrophone towed array is obtained, which can be used to sense the enviromental magnetic field along the sensing direction.This sensor is a good choice for the directional angle measurement through sensing the Earth magnetic field in the array shape measurement of a fiber optic hydrophone towed array.

  7. Visualizing the phenomena of wave interference, phase-shifting and polarization by interactive computer simulations

    NASA Astrophysics Data System (ADS)

    Rivera-Ortega, Uriel; Dirckx, Joris

    2015-09-01

    In this manuscript a computer based simulation is proposed for teaching concepts of interference of light (under the scheme of a Michelson interferometer), phase-shifting and polarization states. The user can change some parameters of the interfering waves, such as their amplitude and phase difference in order to graphically represent the polarization state of a simulated travelling wave. Regarding to the interference simulation, the user is able to change the wavelength and type of the interfering waves by selecting combinations between planar and Gaussian profiles, as well as the optical path difference by translating or tilting one of the two mirrors in the interferometer setup, all of this via a graphical user interface (GUI) designed in MATLAB. A theoretical introduction and simulation results for each phenomenon will be shown. Due to the simulation characteristics, this GUI can be a very good non-formal learning resource.

  8. Image encryption using polarized light encoding and amplitude and phase truncation in the Fresnel domain.

    PubMed

    Rajput, Sudheesh K; Nishchal, Naveen K

    2013-06-20

    In this paper, an image encryption scheme based on polarized light encoding and a phase-truncation approach in the Fresnel transform domain is proposed. The phase-truncated data obtained by an asymmetric cryptosystem is encrypted and decrypted by using the concept of the Stokes-Mueller formalism. Image encryption based on polarization of light using Stokes-Mueller formalism has the main advantage over Jones vector formalism that it manipulates only intensity information, which is measurable. Thus any intensity information can be encrypted and decrypted using this scheme. The proposed method offers several advantages: (1) a lens-free setup, (2) flexibility in the encryption key design, (3) use of asymmetric keys, and (4) immunity against special attack. We present numerical simulation results for gray-scale and color images in support of the proposed security scheme. The performance measurement parameters relative error and correlation coefficient have been calculated to check the effectiveness of the scheme.

  9. Phase of the quantum harmonic oscillator with applications to optical polarization

    NASA Technical Reports Server (NTRS)

    Shepard, Scott R.

    1993-01-01

    The phase of the quantum harmonic oscillator, the temporal distribution of a particle in a square-well potential, and a quantum theory of angles are derived from a general theory of complementarity. Schwinger's harmonic oscillator model of angular momenta is modified for the case of photons. Angular distributions for systems of identical and distinguishable particles are discussed. Unitary and antiunitary time reversal operators are then presented and applied to optical polarization states in birefringent media.

  10. Unscented Kalman filters for polarization state tracking and phase noise mitigation.

    PubMed

    Jignesh, Jokhakar; Corcoran, Bill; Zhu, Chen; Lowery, Arthur

    2016-09-19

    Simultaneous polarization and phase noise tracking and compensation is proposed based on an unscented Kalman filter (UKF). We experimentally demonstrate the tracking under noise-loading and after 800-km single-mode fiber transmission with 20-Gbaud QPSK and 16-QAM signals. These experiments show that the proposed UKF outperforms both conventional blind tracing algorithms and a previously proposed extended Kalman filter, at the cost of higher complexity. Additionally, we propose and test modified Kalman filter algorithms to reduce computational complexity.

  11. Bright Phase-Stable Broadband Fiber-Based Source of Polarization-Entangled Photon Pairs

    DTIC Science & Technology

    2007-10-24

    distribution 2, and quantum - state teleportation 3. For example, it is now well known that two parties, each sharing half of an entangled photon pair...FUNDING NUMBERS Bright Phase-Stable Broadband Fiber-Based Source of MURI Center for Photonic Quantum Information Systems: ARO/ARDA Program Polarization...wide range of quantum -information applications. 14. SUBJECT TERMS 15. NUMBER OF PAGES single photon source, microstructure fiber, photon correlation

  12. Theoretical energy release of thermites, intermetallics, and combustible metals

    SciTech Connect

    Fischer, S.H.; Grubelich, M.C.

    1998-06-01

    Thermite (metal oxide) mixtures, intermetallic reactants, and metal fuels have long been used in pyrotechnic applications. Advantages of these systems typically include high energy density, impact insensitivity, high combustion temperature, and a wide range of gas production. They generally exhibit high temperature stability, and possess insensitive ignition properties. In this paper, the authors review the applications, benefits, and characteristics of thermite mixtures, intermetallic reactants, and metal fuels. Calculated values for reactant density, heat of reaction (per unit mass and per unit volume), and reaction temperature (without and with consideration of phase changes and the variation of specific heat values) are tabulated. These data are ranked in several ways, according to density, heat of reaction, reaction temperature, and gas production.

  13. Systematics of Mössbauer hyperfine parameters in Np intermetallics

    NASA Astrophysics Data System (ADS)

    Kalvius, G. M.; Gal, J.; Asch, L.; Potzel, W.

    1992-05-01

    Data for intermetallic compounds of neptunium obtained with the 60 keV Mössbauer resonance of237Np are reviewed. Measurements of temperature, pressure and field dependencies are available. The main questions addressed are: (a) the degree of delocalization of 5f-electrons, (b) the formal charge state of Np, and (c) the influence of the ligand on the neptunium electronic structure. For this purpose, we present an evaluation of systematic behavior concerning mainly the hyperfine field and isomer shift in the cubic Laves phase materials NpX2, the NaCl-type monochalcogenides and monopnictides, and intermetallics with AuCu3 and ThCr2Si2 structures. Analogies to corresponding rare-earth compounds will be pointed out.

  14. Superplastic ceramics and intermetallics and their potential applications

    SciTech Connect

    Wadsworth, J.; Nieh, T.G.

    1994-11-01

    Recent advances in the basic understanding of superplasticity and superplastic forming of ceramics and intermetallics are reviewed. Fine-grained superplastic ceramics, including yttria-stabilized tetragonal zirconia polycrystal, Y- or MgO-doped Al{sub 2}O{sub 3} Hydroxyapatite, {beta}-spodumene glass ceramics, Al{sub 2}0{sub 3}-YTZP two-phase composites, SiC-Si{sub 3}N{sub 4} and Fe-Fe{sub 3}C composites, are discussed. Superplasticity in the nickel-base (e.g., Ni{sub 3}Al and Ni{sub 3}Si) and titanium-base intermetallics (TiAl and T1{sub 3}Al), is described. Deformation mechanisms as well as microstructural requirements and effects such as grain size, grain growth, and grain-boundary phases, on the superplastic deformation behavior am addressed. Factors that control the superplastic tensile elongation of ceramics are discussed. Superplastic forming, and particularly biaxial gas-pressure forming, of several ceramics and intermetallics are presented with comments on the likelihood of commercial application.

  15. Layered Structures and Disordered Polyanionic Nets in the Cation-Poor Polar Intermetallics CsAu 1.4 Ga 2.8 and CsAu 2 Ga 2.6

    DOE PAGES

    Smetana, Volodymyr; Steinberg, Simon; Mudring, Anja-Verena

    2016-12-27

    Gold intermetallics are known for their unusual structures and bonding patterns. Two new compounds have been discovered in the cation-poor part of the Cs–Au–Ga system. We obtained both compounds directly by heating the elements at elevated temperatures. Structure determinations based on single-crystal X-ray diffraction analyses revealed two structurally and compositionally related formations: CsAu1.4Ga2.8 (I) and CsAu2Ga2.6 (II) crystallize in their own structure types (I: Rmore » $$\\bar{3}$$, a = 11.160(2) Å, c = 21.706(4) Å, Z = 18; II: R$$\\bar{3}$$, a = 11.106(1) Å, Å, c = 77.243(9) Å, Z = 54) and contain hexagonal cationic layers of cesium. Furthermore, this is a unique structural motif, which has never been observed for the other (lighter) alkali metals in combination with Au and post transition elements. The polyanionic part is characterized in contrast by Au/Ga tetrahedral stars, a structural feature that is characteristic for light alkali metal representatives, and disordered sites with mixed Au/Ga occupancies that occur in both structures with a more significant disorder in the polyanionic component of CsAu2Ga2.6. Examinations of the electronic band structure for a model approximating the composition of CsAu1.4Ga2.8 have been completed using density-functional-theory-based methods and reveal a deep pseudogap at EF. Bonding analysis by evaluating the crystal orbital Hamilton populations show dominant heteroatomic Au–Ga bonds and only a negligible contribution from Cs pairs.« less

  16. Layered Structures and Disordered Polyanionic Nets in the Cation-Poor Polar Intermetallics CsAu 1.4 Ga 2.8 and CsAu 2 Ga 2.6

    SciTech Connect

    Smetana, Volodymyr; Steinberg, Simon; Mudring, Anja-Verena

    2016-12-27

    Gold intermetallics are known for their unusual structures and bonding patterns. Two new compounds have been discovered in the cation-poor part of the Cs–Au–Ga system. We obtained both compounds directly by heating the elements at elevated temperatures. Structure determinations based on single-crystal X-ray diffraction analyses revealed two structurally and compositionally related formations: CsAu1.4Ga2.8 (I) and CsAu2Ga2.6 (II) crystallize in their own structure types (I: R$\\bar{3}$, a = 11.160(2) Å, c = 21.706(4) Å, Z = 18; II: R$\\bar{3}$, a = 11.106(1) Å, Å, c = 77.243(9) Å, Z = 54) and contain hexagonal cationic layers of cesium. Furthermore, this is a unique structural motif, which has never been observed for the other (lighter) alkali metals in combination with Au and post transition elements. The polyanionic part is characterized in contrast by Au/Ga tetrahedral stars, a structural feature that is characteristic for light alkali metal representatives, and disordered sites with mixed Au/Ga occupancies that occur in both structures with a more significant disorder in the polyanionic component of CsAu2Ga2.6. Examinations of the electronic band structure for a model approximating the composition of CsAu1.4Ga2.8 have been completed using density-functional-theory-based methods and reveal a deep pseudogap at EF. Bonding analysis by evaluating the crystal orbital Hamilton populations show dominant heteroatomic Au–Ga bonds and only a negligible contribution from Cs pairs.

  17. Electrochemical properties of the passive film on bulk Zr-Fe-Cr intermetallic fabricated by spark plasma sintering

    NASA Astrophysics Data System (ADS)

    Bai, Yakui; Ling, Yunhan; Lai, Wensheng; Xing, Shupei; Ma, Wen

    2016-12-01

    Although Zr-based second phase particles (SPPs) are important factors influencing corrosion resistance of zircaloy cladding materials, the corrosion behavior of SPPs has not been investigated by means of electrochemical method so far. In order to clarify the role of SPPs commonly existed in zircaloy, bulk Zr-based intermetallics were firstly fabricated by spark plasma sintering (SPS) at temperatures 1373 K and an applied pressure of 60 MPa in this work. Both the natural passive film on surface and oxidation behavior of intermetallic has been investigated in this work. X-ray diffraction (XRD) pattern showed that as-prepared intermetallic of crystal structure belongs to Laves phase with AB2 type. Electrochemical measurement of passive film on surface of bulk Zr-based intermetallic exhibited significant difference with that of zirconium. Potentiodynamic measurements results revealed that intermetallic exhibited higher corrosion potential and lower corrosion current density than that of pure zirconium, implying that Zr-based second phase will act as cathode when they are included in zirconium matrix. Meanwhile, significant improvement of Zr-Fe-Cr intermetallic on the water chemistry corrosion resistance was demonstrated comparing with Zr-Fe and Zr-Cr binary intermetallics.

  18. The chemical phenol extraction of intermetallic particles from casting AlSi5Cu1Mg alloy.

    PubMed

    Mrówka-Nowotnik, G; Sieniawski, J; Nowotnik, A

    2010-03-01

    This paper presents a chemical extraction technique for determination of intermetallic phases formed in the casting AlSi5Cu1Mg aluminium alloy. Commercial aluminium alloys contain a wide range of intermetallic particles that are formed during casting, homogenization and thermomechanical processing. During solidification, particles of intermetallics are dispersed in interdendritic spaces as fine primary phases. Coarse intermetallic compounds that are formed in this aluminium alloy are characterized by unique atomic arrangement (crystallographic structure), morphology, stability, physical and mechanical properties. The volume fraction, chemistry and morphology of the intermetallics significantly affect properties and material behaviour during thermomechanical processing. Therefore, accurate determination of intermetallics is essential to understand and control microstructural evolution in Al alloys. Thus, in this paper it is shown that chemical phenol extraction method can be applied for precise qualitative evaluation. The results of optical light microscopy LOM, scanning electron microscopy SEM and X-ray diffraction XRD analysis reveal that as-cast AlSi5Cu1Mg alloy contains a wide range of intermetallic phases such as Al(4)Fe, gamma- Al(3)FeSi, alpha-Al(8)Fe(2)Si, beta-Al(5)FeSi, Al(12)FeMnSi.

  19. Phase-retrieval algorithm for dual-polarization imaging in a ground-penetrating synthetic aperture radar satellite

    NASA Astrophysics Data System (ADS)

    Hunt, Bobby R.; Gough, Peter T.

    1997-12-01

    There are several important remote sensing applications where the development of Ground Penetrating Synthetic Aperture Radar (GPENSAR) is the logical approach, e.g., searching for buried military facilities, minefield mapping, survey of underground pipelines. Penetration of sufficient soil depth for useful results require a SAR to operate at VHF/UHF frequencies, e.g., 200 - 300 MHz. At these frequencies a satellite SAR will encounter substantial distortion in the double passage of the SAR signal through the ionosphere. One of the ionospheric distortions is equivalent the phase aberrations caused in imaging through the turbulent atmosphere, and the problem of phase retrieval for the GPENSAR becomes a necessity. For GPENSR there are imaging concepts that exploit dual polarization radiation of the SAR pulse. The phase retrieval problem then becomes one of compensation for the phase aberrations induced in each of the polarization components returned to the satellite receiver. We discuss the use of the two polarizations to cancel the ionospheric phase aberrations. Unfortunately, the resulting signal has only relative phase of the two polarizations. We discuss an algorithm for the retrieval of the absolute phase. The algorithm is based on an optimization approach. Although phase retrieval by optimization is difficult because of local minima, the retrieval of absolute phase in the dual polarization case is substantially less difficult, because the two polarizations constrain the solution sufficiently to eliminate many local minima.

  20. Profiling of polar metabolites in biological extracts using diamond hydride-based aqueous normal phase chromatography.

    PubMed

    Callahan, Damien L; De Souza, David; Bacic, Antony; Roessner, Ute

    2009-07-01

    Highly polar metabolites, such as sugars and most amino acids are not retained by conventional RP LC columns. Without sufficient retention low concentration compounds are not detected due ion suppression and structural isomers are not resolved. In contrast, hydrophilic interaction chromatography (HILIC) and aqueous normal phase chromatography (ANP) retain compounds based on their hydrophilicity and therefore provides a means of separating highly polar compounds. Here, an ANP method based on the diamond hydride stationary phase is presented for profiling biological small molecules by LC. A rapid separation system based upon a fast gradient that delivers reproducible chromatography is presented. Approximately 1000 compounds were reproducibly detected in human urine samples and clear differences between these samples were identified. This chromatography was also applied to xylem fluid from soyabean (Glycine max) plants to which 400 compounds were detected. This method greatly increases the metabolite coverage over RP-only metabolite profiling in biological samples. We show that both forms of chromatography are necessary for untargeted comprehensive metabolite profiling and that the diamond hydride stationary phase provides a good option for polar metabolite analysis.

  1. Sonochemical formation of intermetallic coatings

    SciTech Connect

    Sweet, J.D.; Casadonte, D.J. Jr.

    1994-11-01

    An energy-dispersive X-ray (EDX) study of the agglomerates produced during the sonication of a series of mixed-metal powders in decane indicates that metal particles are both fused by the action of ultrasound and develop coatings which are intermetallic in nature. The principal mechanism of these effects is believed to be interparticle collision caused by the rapid movement of particles of less than 50 {mu}m diameter which are propelled by shockwaves generated at cavitation sites. By examination of mixed-metal systems including Ni/Co, Al/Ni, Al/Co, Ni/Mg, and Cu/Mo with substantially different tribological characteristics, it has been determined that the coatings are generated by both adhesive wear and direct impact. The fusion of Cu and Mo is particularly intriguing, as these two metals are immiscible below 1000{degrees}C. This indicates the enormous impact temperatures produced in sonically induced collisions. The mechanisms of intermetallic coatings produced via ultrasound are discussed. 26 refs., 4 figs.

  2. Characterizing polarized illumination in high numerical aperture optical lithography with phase shifting masks

    NASA Astrophysics Data System (ADS)

    McIntyre, Gregory Russell

    The primary objective of this dissertation is to develop the phase shifting mask (PSM) as a precision instrument to characterize effects in optical lithography related to the use of polarized partially coherent illumination. The intent is to provide an in-situ characterization technique to add to the lithographer's tool-kit to help enable the stable and repeatable mass production of integrated circuits with feature sizes approaching 1/6th the wavelength of light being used. A series of complex-valued mathematical functions have been derived from basic principles and recent advances in photomask fabrication technology have enabled their implementation with four-phase mask making. When located in the object plane of an imaging system, these test functions serve to engineer a wavefiront that interacts with one particular optical effect, creating a measurable signal in the image plane. In most cases, these test patterns leverage proximity effects to create a central image intensity and are theoretically the most sensitive to the desired effect. Five novel classes of test patterns have been developed for in-situ characterization. The first two classes, The Linear Phase Grating (LPG) and Linear Phase Ring (LPR), both serve to characterize illumination angular distribution and uniformity by creating signals dependent on illumination angular frequency. The third class consists of the Radial Phase Grating (RPG) and Proximity Effect Polarization Analyzers (PEPA), which each create a polarization-dependent signal by taking advantage of the image reversal of one polarization component at high numerical aperture (NA). PSM Polarimetry employs a series of these patterns to form a complete polarization characterization of any arbitrary illumination scheme. The fourth and fifth classes employ sub-resolution interferometric reference probes to coherently interact with proximity effect spillover from a surrounding pattern. They measure the effective phase and transmission of the

  3. Phase Diagram of Two-Dimensional Polar Condensates in a Magnetic Field

    SciTech Connect

    James, A. J. A.; Lamacraft, A.

    2011-04-08

    Spin-1 condensates in the polar (antiferromagnetic) phase in two dimensions are shown to undergo a transition of the Ising type, in addition to the expected Kosterlitz-Thouless (KT) transition of half-vortices, due to the quadratic Zeeman effect. We establish the phase diagram in terms of temperature and the strength of the Zeeman effect using Monte Carlo simulations. When the Zeeman effect is sufficiently strong, the Ising and KT transitions meet. For very strong Zeeman field the remaining transition is of the familiar integer KT type.

  4. Energy exchange between orthogonally polarized waves by cascaded quasi-phase-matched processes

    NASA Astrophysics Data System (ADS)

    Johnston, B. F.; Dekker, P.; Saltiel, S. M.; Withford, M. J.; Kivshar, Y. S.

    2008-01-01

    By identifying appropriate quasi-phase-matching (QPM) conditions in z-cut congruent lithium niobate, we demonstrate simultaneous QPM of type-I (ooe) and higher order type-0 (eee) second-harmonic-generation, which share a common second harmonic wave. We demonstrate this experimentally at 1064nm, and show that cascading between these processes occurs. The cascading can result in energy exchange between the cross-polarized fundamentals, indicative of an equivalent 3rd order process. The nonlinear phase shifts and transfer functions resulting from this cascading are explored numerically.

  5. Spin-polarized noble gases: A playground for geometric quantum-phase studies in magnetic resonance

    NASA Astrophysics Data System (ADS)

    Wäckerle, G.; Appelt, S.; Mehring, M.

    1998-02-01

    We report on geometric (Berry) phase experiments performed with the Stuttgart nuclear magnetic resonance gyroscope utilizing highly polarized noble-gas atoms as sensor nuclei for spatial rotations. Due to the long nuclear spin-relaxation times in the gas phase and the different spin-level schemes of the different isotopes of xenon, 129Xe (I = {1}/{2}) in a rotating magnetic field and 131Xe (I = {3}/{2}) in a rotating electric field gradient, the regime of adiabatic changes to nondegenerate levels can experimentally be extended to the nonadiabatic regime for both nondegenerate and degenerate levels, which is of interest in the field on non-Abelian gauge kinematics.

  6. Spalling of Cu3Sn intermetallics in high-lead 95Pb5Sn solder bumps on Cu under bump metallization during solid-state annealing

    NASA Astrophysics Data System (ADS)

    Jang, Jin-Wook; Ramanathan, Lakshmi N.; Lin, Jong-Kai; Frear, Darrel R.

    2004-06-01

    We report the spalling of Cu3Sn intermetallics in high-lead 95Pb5Sn solder bumps on Cu under bump metallization (UBM) during solid state annealing. Upon reflow, the Cu3Sn intermetallics formed on Cu UBM. However, after solid state annealing at 170 °C, the Cu3Sn intermetallics spalled off from Cu UBM and the Pb phase filled the gap between the Cu3Sn intermetallics and Cu UBM. This is primarily explained by the loss of chemical adhesion between the Cu3Sn intermetallics and Cu UBM due to no additional chemical reaction. Thermodynamic principles are used to interpret the spalling phenomenon and the analysis showed that the interfacial free energy without spalling is greater than that with spalling after solid-state annealing. Spalling of the Cu3Sn intermetallics initiated at an open interface such as the edge of Cu UBM and finally extended to the flat interface at a slower rate.

  7. Polarization induced Z2 and Chern topological phases in a periodically driving field

    NASA Astrophysics Data System (ADS)

    Pi, Shu-Ting; Savrasov, Sergey

    2016-03-01

    Z2 and Chern topological phases such as newly discovered quantum spin Hall and original quantum Hall states hardly both co–exist in a single material due to their contradictory requirement on the time–reversal symmetry (TRS). We show that although the TRS is broken in systems with a periodically driving field, an effective TRS can still be defined provided the ac–field is linearly polarized or certain other conditions are satisfied. The controllable TRS provides us a route to manipulate contradictory phases by tuning the polarization. To demonstrate the idea, we consider a tight-binding model that is relevant to several monolayered materials as a benchmark system. Our calculation shows not only topological Z2 to Chern phase transition occurs but rich Chern phases are also observed. In addition, we also discussed the realization of our proposal in real materials, such as spin-orbit coupled graphene and crystal Bismuth. This opens the possibility of manipulating various topological phases in a single material and can be a promising approach to engineer new electronic states of matter.

  8. Identification and Misidentification of Arctic Mixed Phase Clouds By Polarization Lidar

    NASA Astrophysics Data System (ADS)

    Stillwell, R. A.; Neely, R.; Thayer, J. P.; Shupe, M.

    2016-12-01

    The measurement of liquid only (LO) and mixed phase (MP) clouds in the Arctic is a critical building block to understanding larger problems such as the regional energy and mass budgets over the Greenland ice sheet. Measurement of polarization properties by lidar allows for the identification of MP clouds and the vertical partitioning of cloud phase. However, the measurement of cloud phase is tightly linked to other macrophysical cloud properties such as cloud base height and optical thickness due to limits imposed by the observing lidar system's dynamic range. Measurements made by the Clouds Aerosols Polarization and Backscatter Lidar (CAPABL) located at Summit Camp, Greenland (72o35'46.4"N, 38o25'19.1"W, 3200 m asl) will be shown to demonstrate this systematic bias in polarimetric lidar cloud phase retrievals. In observations from CAPABL taken over several months, we found that biases of up to 2 km in the median liquid cloud height estimate can occur between analog and photon counting signal analyses. This relates to false phase identification between the two signal approaches where photon counting analysis is more likely to misidentify liquid clouds as ice clouds. These measurements will be compared to co-located microwave radiometer, Doppler radar spectral width, and radiosonde data which are part of the Integrated Characterization of Energy Clouds Atmospheric State and Precipitation at Summit (ICECAPS) program to compare and contrast the quantitative error caused by limited lidar dynamic range.

  9. Polarization induced Z2 and Chern topological phases in a periodically driving field.

    PubMed

    Pi, Shu-Ting; Savrasov, Sergey

    2016-03-11

    Z2 and Chern topological phases such as newly discovered quantum spin Hall and original quantum Hall states hardly both co-exist in a single material due to their contradictory requirement on the time-reversal symmetry (TRS). We show that although the TRS is broken in systems with a periodically driving field, an effective TRS can still be defined provided the ac-field is linearly polarized or certain other conditions are satisfied. The controllable TRS provides us a route to manipulate contradictory phases by tuning the polarization. To demonstrate the idea, we consider a tight-binding model that is relevant to several monolayered materials as a benchmark system. Our calculation shows not only topological Z2 to Chern phase transition occurs but rich Chern phases are also observed. In addition, we also discussed the realization of our proposal in real materials, such as spin-orbit coupled graphene and crystal Bismuth. This opens the possibility of manipulating various topological phases in a single material and can be a promising approach to engineer new electronic states of matter.

  10. Polarization induced Z2 and Chern topological phases in a periodically driving field

    PubMed Central

    Pi, Shu-Ting; Savrasov, Sergey

    2016-01-01

    Z2 and Chern topological phases such as newly discovered quantum spin Hall and original quantum Hall states hardly both co–exist in a single material due to their contradictory requirement on the time–reversal symmetry (TRS). We show that although the TRS is broken in systems with a periodically driving field, an effective TRS can still be defined provided the ac–field is linearly polarized or certain other conditions are satisfied. The controllable TRS provides us a route to manipulate contradictory phases by tuning the polarization. To demonstrate the idea, we consider a tight-binding model that is relevant to several monolayered materials as a benchmark system. Our calculation shows not only topological Z2 to Chern phase transition occurs but rich Chern phases are also observed. In addition, we also discussed the realization of our proposal in real materials, such as spin-orbit coupled graphene and crystal Bismuth. This opens the possibility of manipulating various topological phases in a single material and can be a promising approach to engineer new electronic states of matter. PMID:26965181

  11. Corrosion behavior of binary titanium aluminide intermetallics

    SciTech Connect

    Saffarian, H.M.; Gan, Q.; Hadkar, R.; Warren, G.W.

    1996-08-01

    The corrosion behavior of arc-melted binary titanium aluminide intermetallics TiAl, Ti{sub 2}Al, and TiAl{sub 3} in aqueous sodium sulfate and sodium chloride solutions was measured and compared to that of pure Ti and Al. Effects of electrolyte composition (e.g., sulfate [0.25 M SO{sub 4}{sup 2}{sup {minus}}], chloride [0.1 to 1.0 M Cl{sup {minus}}], and pH [3 to 10]) were examined. Anodic polarization of titanium aluminides in aqueous SO{sub 4}{sup 2}{sup {minus}} solutions was similar (showing passive behavior), but no pitting or pitting potential (E{sub pit}) was observed. In aqueous NaCl, however, titanium aluminides were susceptible to pitting, and E{sub pit} decreased with increasing Al content (i.e., Ti{sub 3}Al had the highest E{sub pit} and, therefore, a greater resistance to pitting, followed by TiAl and TiAl{sub 3}). For TiAl, E{sub pit} was slightly dependent upon pH or Cl{sup {minus}} concentration. Pit morphology and E{sub pit} values were quite different for TiAl compared to Ti{sub 3}Al. TiAl showed numerous small pits, whereas Ti{sub 3}Al exhibited fewer but larger and deeper pits. The larger pit density for TiAl was associated with Al-rich interdendrite regions. One interesting feature of the anodic polarization curves for Ti{sub 3}Al was a small anodic peak frequently observed at {approximately}1.4 V{sub SCE} to 1.8 V{sub SCE}. Results suggested this peak was associated with pit initiation, since pitting initiated concurrently with the peak or immediately afterward.

  12. Electron Density Determination, Bonding and Properties of Tetragonal Ferromagnetic Intermetallics

    SciTech Connect

    Wiezorek, Jorg

    2016-09-01

    The project developed quantitative convergent-beam electron diffraction (QCBED) methods by energy-filtered transmission electron microscopy (EFTEM) and used them in combination with density functional theory (DFT) calculations to study the electron density distribution in metallic and intermetallic phases with different cubic and non-cubic crystal structures that comprise elements with d-electron shells. The experimental methods developed here focus on the bonding charge distribution as one of the quantum mechanical characteristics central for understanding of intrinsic properties and validation of DFT calculations. Multiple structure and temperature factors have been measured simultaneously from nano-scale volumes of high-quality crystal with sufficient accuracy and precision for comparison with electron density distribution calculations by DFT. The often anisotropic temperature factors for the different atoms and atom sites in chemically ordered phases can differ significantly from those known for relevant pure element crystals due to bonding effects. Thus they have been measured from the same crystal volumes from which the structure factors have been determined. The ferromagnetic ordered intermetallic phases FePd and FePt are selected as model systems for 3d-4d and 3d-5d electron interactions, while the intermetallic phases NiAl and TiAl are used to probe 3d-3p electron interactions. Additionally, pure transition metal elements with d-electrons have been studied. FCC metals exhibit well defined delocalized bonding charge in tetrahedral sites, while less directional, more distributed bonding charge attains in BCC metals. Agreement between DFT calculated and QCBED results degrades as d-electron levels fill in the elements, and for intermetallics as d-d interactions become prominent over p-d interactions. Utilizing the LDA+U approach enabled inclusion of onsite Coulomb-repulsion effects in DFT calculations, which can afford improved agreements with QCBED results

  13. Na-Au intermetallic compounds formed under high pressure at room temperature

    NASA Astrophysics Data System (ADS)

    Takemura, K.; Fujihisa, H.

    2011-07-01

    High-pressure powder x-ray diffraction experiments have revealed that sodium and gold react at room temperature and form Na-Au intermetallic compounds under high pressure. We have identified four intermetallic phases up to 60 GPa. The first phase (phase I) is the known Na2Au with the tetragonal CuAl2-type structure. It changed to the second phase (phase II) at ˜0.8 GPa, which has the composition Na3Au with the trigonal Cu3As-type or hexagonal Cu3P-type structure. Phase II further transformed to phase III at 3.6 GPa. Phase III has the same composition, Na3Au, with the cubic BiF3-type structure. Finally, phase III changed to phase IV at ˜54 GPa. Phase IV gives broad diffraction peaks, indicating large structural disorder.

  14. A simple method for the synthesis of a polar-embedded and polar-endcapped reversed-phase chromatographic packing with low activity of residue silanols.

    PubMed

    Liu, Hai-yan; Li, Zhi-yong; Liu, Dan; Xue, Ying-wen; Shi, Zhi-guo

    2016-04-22

    Octadecyl bonded silica (ODS) is the most popular packing for reversed-phase chromatography. However, it generally demonstrates bad resolution for polar analytes because of the residue silanols and its poor stability in aqueous mobile phase. To address the problem, a new reversed-phase packing containing both polar-embedded and polar-endcapped moieties was proposed. It was prepared by a very simple method, in which the epoxide addition reaction of 3-glycidoxypropyltrimethoxysilane with 1-octadecanethiol proceeded simultaneously with the reaction of silane coupling onto silica particles. By controlling the molecular ratio of 3-glycidoxypropyltrimethoxysilane to 1-octadecanethiol higher than 1.0 (1.56 for the present study), both polar-embedded and polar-endcapped moieties were achieved onto the packing. The performance of the packing was evaluated in detail. The results demonstrated that neutral, acidic and basic analytes were well separated on the packing. The column efficiency for phenanthrene was 34,200 theoretical plates per meter. In addition, four nucleotides can be separated in 100% phosphate buffered saline solution with good reproducibility, which indicates the packing has good stability in aqueous mobile phase. Amitriptyline, a typical basic analytes, was eluted out with relatively symmetric peak shape (asymmetry factor of 1.36), which implies that the packing has not suffered from the negative effect of residue silanols significantly. Good stability in buffer solution of pH ranging from 2.0 to 10.0 was also documented for the packing.

  15. Polarization phase-shifting double-shearing interferometer for the test of the diffraction-limited wavefront

    NASA Astrophysics Data System (ADS)

    Wang, Lijuan; Liu, Liren; Luan, Zhu; Sun, Jianfeng; Zhou, Yu

    2007-09-01

    In the inter-satellite laser communication, the laser wavefront reaches the diffraction limit. For the test of the diffraction-limited wavefront, we have developed a Jamin double-shearing interferometer of which the detectable wave-front height is in the order of 0.1 wavelengths. Based on this interferometer, a polarization phase-shifting double-shearing interferometer is proposed to improve the performance. The existing Jamin double-shearing interferometer is consists of two Jamin plates to form lateral shearing and four wedge plates to divide the aperture. The polarization phase shifter is composed of three polarizers, a quarter-wave plate and an analyzer. The first polarizer is placed in front of the first Jamin plate. The second and third polarizers are placed behind the wedge plates and their transmission axes are parallel and perpendicular to the incident plane of the Jamin plates, respectively. The fast axis of the quarter-wave plate has an angle of 45 degrees to the transmission axis of the second and third polarizers. By rotating the analyzer, the phase-shift interferogram is obtained. In the interferometer, the polarization phase shifter is simple to be inserted and the phase shifting is easy to realize. The interferometer is kept as an equal optical path system and still suits wavefront testing of the low coherent light. In experiments, phase-shifting interferograms are obtained and the usefulness of the interferometer is verified.

  16. Structure Defect Property Relationships in Binary Intermetallics

    NASA Astrophysics Data System (ADS)

    Medasani, Bharat; Ding, Hong; Chen, Wei; Persson, Kristin; Canning, Andrew; Haranczyk, Maciej; Asta, Mark

    2015-03-01

    Ordered intermetallics are light weight materials with technologically useful high temperature properties such as creep resistance. Knowledge of constitutional and thermal defects is required to understand these properties. Vacancies and antisites are the dominant defects in the intermetallics and their concentrations and formation enthalpies could be computed by using first principles density functional theory and thermodynamic formalisms such as dilute solution method. Previously many properties of the intermetallics such as melting temperatures and formation enthalpies were statistically analyzed for large number of intermetallics using structure maps and data mining approaches. We undertook a similar exercise to establish the dependence of the defect properties in binary intermetallics on the underlying structural and chemical composition. For more than 200 binary intermetallics comprising of AB, AB2 and AB3 structures, we computed the concentrations and formation enthalpies of vacancies and antisites in a small range of stoichiometries deviating from ideal stoichiometry. The calculated defect properties were datamined to gain predictive capabilities of defect properties as well as to classify the intermetallics for their suitability in high-T applications. Supported by the US DOE under Contract No. DEAC02-05CH11231 under the Materials Project Center grant (Award No. EDCBEE).

  17. Coexistence of probe conformations in lipid phases-a polarized fluorescence microspectroscopy study.

    PubMed

    Urbančič, Iztok; Ljubetič, Ajasja; Arsov, Zoran; Strancar, Janez

    2013-08-20

    Several well-established fluorescence methods depend on environment-sensitive probes that report about molecular properties of their local environment. For reliable interpretation of experiments, careful characterization of probes' behavior is required. In this study, bleaching-corrected polarized fluorescence microspectroscopy with nanometer spectral peak position resolution was applied to characterize conformations of two alkyl chain-labeled 7-nitro-2-1,3-benzoxadiazol-4-yl phospholipids in three model membranes, representing the three main lipid phases. The combination of polarized and spectral detection revealed two main probe conformations with their preferential fluorophore dipole orientations roughly parallel and perpendicular to membrane normal. Their peak positions were separated by 2-6 nm because of different local polarities and depended on lipid environment. The relative populations of conformations, estimated by a numerical model, indicated a specific sensitivity of the two probes to molecular packing with cholesterol. The coexistence of probe conformations could be further exploited to investigate membrane organization below microscopy spatial resolution, such as lipid rafts. With the addition of polarized excitation or detection to any environment-sensitive fluorescence imaging technique, the conformational analysis can be directly applied to explore local membrane complexity.

  18. Field-driven mesoscale phase transition in polarized colloids in microgravity

    NASA Astrophysics Data System (ADS)

    Khusid, Boris; Elele, Ezinwa

    2014-11-01

    An unexpected phase transition in a polarized suspension was reported by Kumar, Khusid, Acrivos, PRL 95, 258301, 2005 and Agarwal, Yethiraj, PRL 102, 198301, 2009. Following the field application, particles aggregated head-to-tail into chains that bridged the interelectrode gap and then formed a cellular pattern, in which large-scale particle-free voids were enclosed by particle-rich thin walls. Surprisingly, the size of particle-free domains scales linearly with the gap thickness but is insensitive to the particle size and the field strength and frequency. Cellular structures were not observed in simulations of equilibrium in a polarized suspension (Richardi, Weis, J. Chem. Phys. 135, 124502, 2011; Almudallal, Saika-Voivod, PRE 84, 011402, 2011). Nonequilibrium simulations (Park, Saintillan, PRE 83, 041409, 2011) showed cellular-like structures but at a particle concentration much higher than in experiments. A requirement for precise matching of densities between particles and a fluid to avoid gravity effects limits terrestrial experiments to negatively polarized particles. We will present data on positively polarized non-buoyancy-matched particles and the development of experiments in the International Space Station needed to evaluate gravity contribution. Supported by NASA's Physical Science Research Program, NNX13AQ53G.

  19. Ground state searches in fcc intermetallics

    SciTech Connect

    Wolverton, C.; de Fontaine, D.; Ceder, G.; Dreysse, H.

    1991-12-01

    A cluster expansion is used to predict the fcc ground states, i.e., the stable phases at zero Kelvin as a function of composition, for alloy systems. The intermetallic structures are not assumed, but derived regorously by minimizing the configurational energy subject to linear constraints. This ground state search includes pair and multiplet interactions which spatially extend to fourth nearest neighbor. A large number of these concentration-independent interactions are computed by the method of direct configurational averaging using a linearized-muffin-tin orbital Hamiltonian cast into tight binding form (TB-LMTO). The interactions, derived without the use of any adjustable or experimentally obtained parameters, are compared to those calculated via the generalized perturbation method extention of the coherent potential approximation within the context of a KKR Hamiltonian (KKR-CPA-GPM). Agreement with the KKR-CPA-GPM results is quite excellent, as is the comparison of the ground state results with the fcc-based portions of the experimentally-determined phase diagrams under consideration.

  20. Ground state searches in fcc intermetallics

    SciTech Connect

    Wolverton, C.; de Fontaine, D. ); Ceder, G. ); Dreysse, H. . Lab. de Physique du Solide)

    1991-12-01

    A cluster expansion is used to predict the fcc ground states, i.e., the stable phases at zero Kelvin as a function of composition, for alloy systems. The intermetallic structures are not assumed, but derived regorously by minimizing the configurational energy subject to linear constraints. This ground state search includes pair and multiplet interactions which spatially extend to fourth nearest neighbor. A large number of these concentration-independent interactions are computed by the method of direct configurational averaging using a linearized-muffin-tin orbital Hamiltonian cast into tight binding form (TB-LMTO). The interactions, derived without the use of any adjustable or experimentally obtained parameters, are compared to those calculated via the generalized perturbation method extention of the coherent potential approximation within the context of a KKR Hamiltonian (KKR-CPA-GPM). Agreement with the KKR-CPA-GPM results is quite excellent, as is the comparison of the ground state results with the fcc-based portions of the experimentally-determined phase diagrams under consideration.

  1. Method of making sintered ductile intermetallic-bonded ceramic composites

    DOEpatents

    Plucknett, K.; Tiegs, T.N.; Becher, P.F.

    1999-05-18

    A method of making an intermetallic-bonded ceramic composite involves combining a particulate brittle intermetallic precursor with a particulate reactant metal and a particulate ceramic to form a mixture and heating the mixture in a non-oxidizing atmosphere at a sufficient temperature and for a sufficient time to react the brittle intermetallic precursor and the reactant metal to form a ductile intermetallic and sinter the mixture to form a ductile intermetallic-bonded ceramic composite. 2 figs.

  2. A Laboratory Study on the Phase Transition for Polar Stratospheric Cloud Particles

    NASA Technical Reports Server (NTRS)

    Teets, Edward H., Jr.

    1997-01-01

    The nucleation and growth of different phases of simulated polar stratospheric cloud (PSC) particles were investigated in the laboratory. Solutions and mixtures of solutions at concentrations 1 to 5 m (molality) of ammonium sulfate, ammonium bisulfate, sodium chloride, sulfuric acid, and nitric acid were supercooled to prescribed temperatures below their equilibrium melting point. These solutions were contained in small diameter glass tubing of volumes ranging from 2.6 to 0.04 ml. Samples were nucleated by insertion of an ice crystal, or in some cases by a liquid nitrogen cooled wire. Crystallization velocities were determined by timing the crystal growth front passages along the glass tubing. Solution mixtures containing aircraft exhaust (soot) were also examined. Crystallization rates increased as deltaT2, where deltaT is the supercooling for weak solutions (2 m or less). The higher concentrated solutions (greater than 3 m) showed rates significantly less than deltaT2. This reduced rate suggested an onset of a glass phase. Results were applied to the nucleation of highly concentrated solutions at various stages of polar stratospheric cloud development within the polar stratosphere.

  3. Dipole-Oriented Molecular Solids Can Undergo a Phase Change and Still Maintain Electrical Polarization

    DOE PAGES

    Cassidy, Andrew; Jørgensen, Mads R. V.; Rosu-Finsen, Alexander; ...

    2016-10-02

    It has recently been demonstrated that nanoscale molecular films can spontaneously assemble to self-generate intrinsic electric fields that can exceed 108 V/m. These electric fields originate from polarization charges in the material that arise because the films self-assemble to orient molecular dipole moments. This has been called the spontelectric effect. Such growth of spontaneously polarized layers of molecular solids has implications for our understanding of how intermolecular interactions dictate the structure of molecular materials used in a range of applications, for example, molecular semiconductors, sensors, and catalysts. In this paper, we present the first in situ structural characterization of amore » representative spontelectric solid, nitrous oxide. Infrared spectroscopy, temperature-programmed desorption, and neutron reflectivity measurements demonstrate that polarized films of nitrous oxide undergo a structural phase transformation upon heating above 48 K. A mean-field model can be used to describe quantitatively the magnitude of the spontaneously generated field as a function of film-growth temperature, and this model also recreates the phase change. Finally, this reinforces the spontelectric model as a means of describing long-range dipole–dipole interactions and points to a new type of ordering in molecular thin films.« less

  4. Dipole-Oriented Molecular Solids Can Undergo a Phase Change and Still Maintain Electrical Polarization

    SciTech Connect

    Cassidy, Andrew; Jørgensen, Mads R. V.; Rosu-Finsen, Alexander; Lasne, Jérôme; Jørgensen, Jakob H.; Glavic, Artur; Lauter, Valeria; Iversen, Bo B.; McCoustra, Martin R. S.; Field, David

    2016-10-02

    It has recently been demonstrated that nanoscale molecular films can spontaneously assemble to self-generate intrinsic electric fields that can exceed 108 V/m. These electric fields originate from polarization charges in the material that arise because the films self-assemble to orient molecular dipole moments. This has been called the spontelectric effect. Such growth of spontaneously polarized layers of molecular solids has implications for our understanding of how intermolecular interactions dictate the structure of molecular materials used in a range of applications, for example, molecular semiconductors, sensors, and catalysts. In this paper, we present the first in situ structural characterization of a representative spontelectric solid, nitrous oxide. Infrared spectroscopy, temperature-programmed desorption, and neutron reflectivity measurements demonstrate that polarized films of nitrous oxide undergo a structural phase transformation upon heating above 48 K. A mean-field model can be used to describe quantitatively the magnitude of the spontaneously generated field as a function of film-growth temperature, and this model also recreates the phase change. Finally, this reinforces the spontelectric model as a means of describing long-range dipole–dipole interactions and points to a new type of ordering in molecular thin films.

  5. Enhanced ferroelectric polarization and possible morphotrophic phase boundary in PZT-based alloys

    SciTech Connect

    Parker, David S.; Singh, David; McGuire, Michael A.; Herklotz, Andreas; Ward, Thomas Zac

    2016-05-16

    We present a combined theoretical and experimental study of alloys of the high performance piezoelectric PZT (PbZr0.5Ti0.5O3) with BZnT (BiZn0.5Ti0.5O3) and BZnZr (BiZn0.5Zr0.5O3), focusing on atomic displacements, ferroelectric polarization, and elastic stability. From theory we find that the 75-25 PZT-BZnT alloy has substantially larger cation displacements, and hence ferroelectric polarization than the PZT base material, on the tetragonal side of the phase diagram. We also find a possible morphotrophic phase boundary in this system by comparing displacement patterns and optimized c/a ratios. Elastic stability calculations find the structures to be essentially stable. Lastly, experiments indicate the feasibility of sample synthesis within this alloy system, although measurements do not find significant polarization, probably due to a large coercive field.

  6. Enhanced ferroelectric polarization and possible morphotrophic phase boundary in PZT-based alloys

    DOE PAGES

    Parker, David S.; Singh, David; McGuire, Michael A.; ...

    2016-05-16

    We present a combined theoretical and experimental study of alloys of the high performance piezoelectric PZT (PbZr0.5Ti0.5O3) with BZnT (BiZn0.5Ti0.5O3) and BZnZr (BiZn0.5Zr0.5O3), focusing on atomic displacements, ferroelectric polarization, and elastic stability. From theory we find that the 75-25 PZT-BZnT alloy has substantially larger cation displacements, and hence ferroelectric polarization than the PZT base material, on the tetragonal side of the phase diagram. We also find a possible morphotrophic phase boundary in this system by comparing displacement patterns and optimized c/a ratios. Elastic stability calculations find the structures to be essentially stable. Lastly, experiments indicate the feasibility of sample synthesismore » within this alloy system, although measurements do not find significant polarization, probably due to a large coercive field.« less

  7. Dipole-Oriented Molecular Solids Can Undergo a Phase Change and Still Maintain Electrical Polarization

    SciTech Connect

    Cassidy, Andrew; Jørgensen, Mads R. V.; Rosu-Finsen, Alexander; Lasne, Jérôme; Jørgensen, Jakob H.; Glavic, Artur; Lauter, Valeria; Iversen, Bo B.; McCoustra, Martin R. S.; Field, David

    2016-10-02

    It has recently been demonstrated that nanoscale molecular films can spontaneously assemble to self-generate intrinsic electric fields that can exceed 108 V/m. These electric fields originate from polarization charges in the material that arise because the films self-assemble to orient molecular dipole moments. This has been called the spontelectric effect. Such growth of spontaneously polarized layers of molecular solids has implications for our understanding of how intermolecular interactions dictate the structure of molecular materials used in a range of applications, for example, molecular semiconductors, sensors, and catalysts. In this paper, we present the first in situ structural characterization of a representative spontelectric solid, nitrous oxide. Infrared spectroscopy, temperature-programmed desorption, and neutron reflectivity measurements demonstrate that polarized films of nitrous oxide undergo a structural phase transformation upon heating above 48 K. A mean-field model can be used to describe quantitatively the magnitude of the spontaneously generated field as a function of film-growth temperature, and this model also recreates the phase change. Finally, this reinforces the spontelectric model as a means of describing long-range dipole–dipole interactions and points to a new type of ordering in molecular thin films.

  8. Extrinsic Fabry-Perot interferometric sensor using a polarization-switched phase interrogator

    NASA Astrophysics Data System (ADS)

    Xia, Ji; Wang, Fuyin; Yang, Yangyang; Xiong, Shuidong; Luo, Hong; Wei, Wenjian

    2016-10-01

    In this paper, a phase variation tracking method for the extrinsic Fabry-Perot interferometric (EFPI) voice sensing system is designed and experimentally demonstrated through a polarization-switched unit based on the combination of polarization-maintaining fiber Bragg grating (PMFBG). The measurements at two operation wavelengths are firstly achieved in one total-optical path, which eliminates the imbalance of optical power from the external disturbances, optical source fluctuation, different detecting response of photoelectric detector and different background noise. Two operation wavelengths reflected from a PMFBG for interference phase tracking are switched via an electro-optic modulator at a high switching speed of 10 kHz. Besides, an ellipse fitting-differential cross multiplication (EF-DCM) algorithm is proposed and illustrated for interrogating the variation of EFPI cavity gap length of the EFPI voice sensor effectively. Preliminary experimental results have proven that the polarization-switched system based on the EF-DCM algorithm could find potential applications in the fields of marine acoustic, medical science measurements, etc.

  9. Enhanced ferroelectric polarization and possible morphotrophic phase boundary in PZT-based alloys

    SciTech Connect

    Parker, David S.; Singh, David; McGuire, Michael A.; Herklotz, Andreas; Ward, Thomas Zac

    2016-05-16

    We present a combined theoretical and experimental study of alloys of the high performance piezoelectric PZT (PbZr0.5Ti0.5O3) with BZnT (BiZn0.5Ti0.5O3) and BZnZr (BiZn0.5Zr0.5O3), focusing on atomic displacements, ferroelectric polarization, and elastic stability. From theory we find that the 75-25 PZT-BZnT alloy has substantially larger cation displacements, and hence ferroelectric polarization than the PZT base material, on the tetragonal side of the phase diagram. We also find a possible morphotrophic phase boundary in this system by comparing displacement patterns and optimized c/a ratios. Elastic stability calculations find the structures to be essentially stable. Lastly, experiments indicate the feasibility of sample synthesis within this alloy system, although measurements do not find significant polarization, probably due to a large coercive field.

  10. Existence of polar switching in the nematic and orthogonal smectic phases in novel four-ring bent-core compounds

    NASA Astrophysics Data System (ADS)

    Turlapati, Srikanth; Khan, Raj Kumar; Ghosh, Sharmistha; Tadapatri, Pramod; Pratibha, R.; Rao, Nandiraju V. S.

    2016-11-01

    Bent-core liquid crystals have set the first example of forming polar superstructures from achiral molecules. Polar switching studies in smectic phases have revealed several exciting sub-phases which have never been observed in rod-like liquid crystals. In this study, mesomorphic and polar switching properties of three bent-core compounds belonging to a homologous series have been investigated using polarizing optical microscopy (POM), differential scanning calorimetry, XRD studies, electro-optics, and dielectric spectroscopy. These achiral, unsymmetrical four-ring bent-core liquid crystals with a polar fluoro substituent at one end and n-alkoxy chain at the other terminal end possess azo, ester, and imine linkages between the four phenyl rings and different lateral substituents. The compounds 16-F and 18-F exhibit orthogonal smectic phase with antiferroelectric polar order, and additionally, the compound 16-F exhibits a short range nematic phase with a polar order. The compound 7-F exhibits broad enantiotropic nematic mesomorphism without appearance of any smectic ordering at low temperature. The smectic and nematic phases were identified by their optical textures observed by POM. Distinct polarization current peaks under triangular wave voltage are observed for all the compounds in the entire mesophase range. Relaxation phenomena corresponding to polar associations of the molecules are observed in dielectric spectroscopy. The cybotactic nature of the nematic phase is established by the XRD and electro-optic studies of 16-F. Although it is rather difficult to form mesophase when the number of aromatic rings is reduced from five, we have successfully demonstrated the bent-core compounds with four-ring which exhibit orthogonal smectic phases as well as nematic mesomorphism with unusual cybotactic signature.

  11. Environmental Effects in Advanced Intermetallics

    SciTech Connect

    Liu, C.T.

    1998-11-24

    This paper provides a comprehensive review of environmental embrittlement in iron and nickel aluminizes. The embrittlement involves the interaction of these intermetallics with moisture in air and generation of atomic hydrogen, resulting in hydrogen-induced embrittlement at ambient temperatures. Environmental embrittlement promotes brittle grain-boundary fracture in Ni{sub 3}Al alloys but brittle cleavage fracture in Fe{sub 3}Al-FeAl alloys. The embrittlement strongly depends on strain rate, with tensile-ductility increase with increasing strain rate. It has been demonstrated that environmental embrittlement can be alleviated by alloying additions, surface modifications, and control of grain size and shape. Boron tends to segregate strongly to grain boundaries and is most effective in suppressing environmental embrittlement in Ni{sub 3}Al alloys. The mechanistic understanding of alloy effects and environmental embrittlement has led to the development of nickel and iron aluminide alloys with improved properties for structural use at elevated temperatures in hostile environments.

  12. Evolution of Fragmented Fe-Intermetallic Compounds in the Semi-Solid State of Al-Mg-Si-Fe Alloys by Deformation Semi-Solid Forming Process

    NASA Astrophysics Data System (ADS)

    Phongphisutthinan, Chakkrist; Tezuka, Hiroyasu; Kobayashi, Equo; Sato, Tatsuo

    Fe-intermetallic compounds are commonly considered as a harmful phase in the recycled aluminum alloys. The Deformation Semi-Solid Forming (D-SSF) process has advantages to modify these harmful compounds into more favorable particles by thermo-mechanical deformation and subsequently heating to the semi-solid state. The evolution of fragmented Fe-intermetallic compounds of the Al-Mg-Si-Fe alloy was investigated during heating to various semi-solid temperatures. The fragmented Fe-intermetallic compound was transformed into the polyhedral shape in the initial stage and subsequently spheroidized shape at the low semi-solid temperatures between 580-610°C. At temperatures higher than 613°C, fragmented Fe-intermetallic compounds completely melt into the liquid phase with long holding time. The Fe-intermetallic compounds are stable as solid phase at low semi-solid temperature and metastable at high semi-solid temperature.

  13. Phase dynamics in vertical-cavity surface-emitting lasers with delayed optical feedback and cross-polarized reinjection

    NASA Astrophysics Data System (ADS)

    Javaloyes, J.; Marconi, M.; Giudici, M.

    2014-08-01

    We study theoretically the nonlinear polarization dynamics of vertical-cavity surface-emitting lasers in the presence of an external cavity providing delayed optical feedback and cross-polarized reinjection. We show that, far from the laser threshold, the dynamics remains confined close to the equatorial plane of a Poincaré sphere with a fixed radius. It entails that the evolution of the system is described by two phase variables: the orientation phase of the quasilinear polarization and the optical phase of the field. We explore the complex modal structure given by the double reinjection configuration and how it evolves between the cases of single cross-polarized reinjection and single optical feedback, hence disclosing the relationship with the Lang-Kobayashi model. We also reinterpret the square-wave switching observed by J. Mulet et al. [Phys. Rev. A 76, 043801 (2007), 10.1103/PhysRevA.76.043801] in terms of phase kinks.

  14. Measuring CP-violating phases through studying the polarization of the final particles in μ → eee

    NASA Astrophysics Data System (ADS)

    Farzan, Yasaman

    2009-06-01

    It is shown that the polarizations of the final particles in μ+ →e+e-e+ provide us with information on the CP-violating phases of the effective Lagrangian leading to this Lepton Flavor Violating (LFV) decay.

  15. Hierarchical Phased Array Antenna Focal Plane for Cosmic Microwave Background Polarization and Sub-mm Observations

    NASA Astrophysics Data System (ADS)

    Lee, Adrian

    We propose to develop planar-antenna-coupled superconducting bolometer arrays for observations at sub-millimeter to millimeter wavelengths. Our pixel architecture features a dual-polarization, log-periodic antenna with a 5:1 bandwidth ratio, followed by a filter bank that divides the total bandwidth into several broad photometric bands. We propose to develop an hierarchical phased array of our basic pixel type that gives optimal mapping speed (sensitivity) over a much broader range of frequencies. The advantage of this combination of an intrinsically broadband pixel with hierarchical phase arraying include a combination of greatly reduced focal-plane mass, higher array sensitivity, and a larger number of spectral bands compared to focal-plane designs using conventional single-color pixels. These advantages have the potential to greatly reduce cost and/or increase performance of NASA missions in the sub-millimeter to millimeter bands. For CMB polarization, a wide frequency range of about 30 to 400 GHz is required to subtract galactic foregrounds. As an example, the multichroic architecture we propose could reduce the focal plane mass of the EPIC-IM CMB polarization mission study concept by a factor of 4, with great savings in required cryocooler performance and therefore cost. We have demonstrated the lens-coupled antenna concept in the POLARBEAR groundbased CMB polarization experiment which is now operating in Chile. That experiment uses a single-band planar antenna that gives excellent beam properties and optical efficiency. POLARBEAR recently succeeded in detecting gravitational lensing B-modes in the CMB polarization. In the laboratory, we have measured two octaves of total bandwidth in the log-periodic sinuous antenna. We have built filter banks of 2, 3, and 7 bands with 4, 6, and 14 bolometers per pixel for two linear polarizations. Pixels of this type are slated to be deployed on the ground in POLARBEAR and SPT-3G and proposed to be used on a balloon by EBEX

  16. Opaque optics thickness measurement using a cyclic path optical configuration setup and polarization phase shifting interferometry.

    PubMed

    Kumar, Y Pavan; Chatterjee, Sanjib

    2012-03-20

    Thickness measurement of an opaque optics using a cyclic path optical configuration (CPOC) setup and polarization phase shifting interferometry (PPSI) is presented. The CPOC setup is used to simultaneously focus two orthogonally polarized counterpropagating converging beams at its hypotenuse arm. The opaque optics is placed at the hypotenuse arm of the CPOC setup such that one of its surfaces reflects back one of the counterpropagating focusing beams. Because of the thickness of the opaque optics, the other focusing beam suffers a longitudinal shift in the beam focus. Applying PPSI, the longitudinal shift in the beam focus which is twice the thickness of the opaque optics is determined. The results obtained for a silicon plate of thickness 0.660 mm with a measurement uncertainty of 0.013 mm are presented. © 2012 Optical Society of America

  17. Barkhausen-like antiferromagnetic to ferromagnetic phase transition driven by spin polarized current

    NASA Astrophysics Data System (ADS)

    Suzuki, Ippei; Naito, Tomoyuki; Itoh, Mitsuru; Taniyama, Tomoyasu

    2015-08-01

    We provide clear evidence for the effect of a spin polarized current on the antiferromagnetic to ferromagnetic phase transition of an FeRh wire at Co/FeRh wire junctions, where the antiferromagnetic ground state of FeRh is suppressed by injecting a spin polarized current. We find a discrete change in the current-voltage characteristics with increasing current density, which we attribute to the Barkhausen-like motion of antiferromagnetic/ferromagnetic interfaces within the FeRh wire. The effect can be understood via spin transfer, which exerts a torque to the antiferromagnetic moments of FeRh, together with non-equilibrium magnetic effective field at the interface. The conclusion is reinforced by the fact that spin unpolarized current injection from a nonmagnetic Cu electrode has no effects on the antiferromagnetic state of FeRh.

  18. Strain-induced phase transition and electron spin-polarization in graphene spirals

    PubMed Central

    Zhang, Xiaoming; Zhao, Mingwen

    2014-01-01

    Spin-polarized triangular graphene nanoflakes (t-GNFs) serve as ideal building blocks for the long-desired ferromagnetic graphene superlattices, but they are always assembled to planar structures which reduce its mechanical properties. Here, by joining t-GNFs in a spiral way, we propose one-dimensional graphene spirals (GSs) with superior mechanical properties and tunable electronic structures. We demonstrate theoretically the unique features of electron motion in the spiral lattice by means of first-principles calculations combined with a simple Hubbard model. Within a linear elastic deformation range, the GSs are nonmagnetic metals. When the axial tensile strain exceeds an ultimate strain, however, they convert to magnetic semiconductors with stable ferromagnetic ordering along the edges. Such strain-induced phase transition and tunable electron spin-polarization revealed in the GSs open a new avenue for spintronics devices. PMID:25027550

  19. A polarization independent phase gradient metasurface for spoof plasmon polaritons coupling

    NASA Astrophysics Data System (ADS)

    Wu, Chenjun; Cheng, Yongzhi; Wang, Wenying; He, Bo; Gong, Rongzhou

    2016-02-01

    A polarization-independent phase-gradient metasurface (PGM) is proposed, and theoretically as well as experimentally investigated, for realizing spoof surface plasmon polariton (SPP) coupling. The designed PGM is a periodic array comprising a dielectric substrate sandwiched between a metallic split cross structure and a continuous metallic film. The numerical results for the designed PGM indicate that normally incident electromagnetic waves can be efficiently coupled into spoof SPPs, since the additional wave vector generated by the designed PGM is greater than that of the incident waves. Both simulations and experiments demonstrate that the designed PGM, as a spoof SPP coupler, is insensitive to polarization, and highly efficient under normally incident X-band radiation.

  20. Barkhausen-like antiferromagnetic to ferromagnetic phase transition driven by spin polarized current

    SciTech Connect

    Suzuki, Ippei; Naito, Tomoyuki; Itoh, Mitsuru; Taniyama, Tomoyasu

    2015-08-24

    We provide clear evidence for the effect of a spin polarized current on the antiferromagnetic to ferromagnetic phase transition of an FeRh wire at Co/FeRh wire junctions, where the antiferromagnetic ground state of FeRh is suppressed by injecting a spin polarized current. We find a discrete change in the current-voltage characteristics with increasing current density, which we attribute to the Barkhausen-like motion of antiferromagnetic/ferromagnetic interfaces within the FeRh wire. The effect can be understood via spin transfer, which exerts a torque to the antiferromagnetic moments of FeRh, together with non-equilibrium magnetic effective field at the interface. The conclusion is reinforced by the fact that spin unpolarized current injection from a nonmagnetic Cu electrode has no effects on the antiferromagnetic state of FeRh.

  1. Momentum analyticity of transverse polarization tensor in the normal phase of a holographic superconductor

    NASA Astrophysics Data System (ADS)

    Yin, Lei; Ren, Hai-cang; Lee, Ting Kuo; Hou, Defu

    2016-08-01

    We explore the momentum analyticity of the static transverse polarization tensor of a 2+1 dimensional holographic superconductor in its normal phase, aiming at finding the holographic counterpart of the singularities underlying the Friedel oscillations of an ordinary field theory. We prove that the polarization tensor is a meromorphic function with an infinite number of poles located on the complex momentum plane off real axis. With the aid of the WKB approximation these poles are found to lies asymptotically along two straight lines parallel to the imaginary axis for a large momentum magnitude. The similarity between the holographic Green's function and that of an weakly coupled ordinary field theory (e.g., 2+1 dimensional QED) regarding the location of the momentum singularities offers further support to the validity of the gauge/gravity duality.

  2. Ultracold Polar Molecules: New Phases of Matter for Quantum Information and Quantum Control

    DTIC Science & Technology

    2013-06-01

    Devil’s staircase” where Mott solids appear at rational fillings of the lattice.   Studied 1D  fermionic  and bosonic gases with repulsive power‐law...superfluid transition in single‐component  fermionic  gas in a trap with dipole  moments polarized in perpendicular layers, finding that many‐body effects...Zoller, Bilayer superfluidity of fermionic polar molecules: Many‐Body effects, Phys. Rev. A 83, 043602 (2011).  2012 Phase   1) N. Henkel, F. Cinti, P

  3. Liquid-solid directional composites and anisotropic dipolar phases of polar nanoregions in disordered perovskites.

    PubMed

    Parravicini, Jacopo; DelRe, Eugenio; Agranat, Aharon J; Parravicini, Gianbattista

    2017-07-13

    Using temperature-resolved dielectric spectroscopy in the range of 75-320 K we have inspected the solid-like and liquid-like arrangements of nanometric dipoles (polar nanoregions) embedded in sodium-enriched potassium-tantalate-niobate (KNTN), a chemically-substituted complex perovskite crystal hosting inherent substitutional disorder. The study of order versus direction is carried out using Fröhlich entropy measurements and indicates the presence of four long-range symmetry phases, two of which are found to display profoundly anisotropic features. Exotic phases are found for which the dipoles at one fixed temperature manifest a liquid reorientational response along one crystal axis and a solid-like behavior along another axis. The macroscopic anisotropy observed in the sequence of different phases is found to match a microscopic order-disorder sequence typical of nominally pure perovskites. Moreover, experimental demonstration of the onset of a frozen state above transitions is provided.

  4. Apparatus and method for phase fronts based on superluminal polarization current

    DOEpatents

    Singleton, John [Los Alamos, NM; Ardavan, Houshang [Cambridge, GB; Ardavan, Arzhang [Cambridge, GB

    2012-02-28

    An apparatus and method for a radiation source involving phase fronts emanating from an accelerated, oscillating polarization current whose distribution pattern moves superluminally (that is, faster than light in vacuo). Theoretical predictions and experimental measurements using an existing prototype superluminal source show that the phase fronts from such a source can be made to be very complex. Consequently, it will be very difficult for an aircraft imaged by such a radiation to detect where this radiation has come from. Moreover, the complexity of the phase fronts makes it almost impossible for electronics on an aircraft to synthesize a rogue reflection. A simple directional antenna and timing system should, on the other hand, be sufficient for the radar operators to locate the aircraft, given knowledge of their own source's speed and modulation pattern.

  5. Three-dimensional displacement measurement for diffuse object using phase-shifting digital holography with polarization imaging camera.

    PubMed

    Kiire, Tomohiro; Nakadate, Suezou; Shibuya, Masato; Yatagai, Toyohiko

    2011-12-01

    The amount of displacement of a diffused object can be measured using phase-shifting digital holography with a polarization imaging camera. Four digital holograms in quadrature are extracted from the polarization imaging camera and used to calculate the phase hologram. Two Fourier transforms of the phase holograms are calculated before and after the displacement of the object. A phase slope is subsequently obtained from the phase distribution of division between the two Fourier transforms. The slope of the phase distribution is proportional to the lateral displacement of the object. The sensitivity is less than one pixel size in the lateral direction of the movement. The longitudinal component of the displacement can be also measured separately from the intercept on the phase axis along the phase distribution of the division between two Fourier transforms of the phase holograms. © 2011 Optical Society of America

  6. Microstructure and Mechanical Properties of the Ti-45Al-5Fe Intermetallic Alloy

    NASA Astrophysics Data System (ADS)

    Nazarova, T. I.; Imayev, V. M.; Imayev, R. M.

    2015-10-01

    Microstructure including changes in the phase composition and mechanical compression properties of the Ti-45Al-5Fe (at.%) intermetallic alloy manufactured by casting and subjected to homogenization annealing are investigated as functions of the temperature. The initial alloy has a homogeneous predominantly lamellar structure with relatively small size of colonies of three intermetallic phases: γ(TiAl), τ2(Al2FeTi), and α2(Ti3Al) in the approximate volume ratio 75:20:5. Compression tests have revealed the enhanced strength at room temperature and the improved hot workability at 800°C compared to those of TNM alloys of last generation.

  7. Environmental embrittlement in ordered intermetallic alloys

    SciTech Connect

    Liu, C.T.; Stoloff, N.S.

    1992-12-31

    Ordered intermetallics based on aluminides and silicides possess many promising properties for elevated-temperature applications; however, poor fracture resistance and limited fabricability restrict their use as engineering material. Recent studies have shown that environmental embrittlement is a major cause of low ductility and brittle fracture in many ordered intermetallic alloys. There are two types of environmental embrittlement observed in intermetallic alloys. One is hydrogen-induced embrittlement occurring at ambient temperatures in air. The other is oxygen-induced embrittlement in oxidizing atmospheres at elevated temperatures. In most cases, the embrittlements are due to a dynamic effect involving generation and penetration of embrittling agents (i.e., hydrogen or oxygen ) during testing. Diffusion of embrittling agents plays a dominant role in fracture of these intermetallic alloys. This chapter summarizes recent progress in understanding and reducing environmental embrittlement in these alloys.

  8. New twisted intermetallic compound superconductor: A concept

    NASA Technical Reports Server (NTRS)

    Coles, W. D.; Brown, G. V.; Laurence, J. C.

    1972-01-01

    Method for processing Nb3Sn and other intermetallic compound superconductors produces a twisted, stabilized wire or tube which can be used to wind electromagnetics, armatures, rotors, and field windings for motors and generators as well as other magnetic devices.

  9. Broadband Polarization-Independent Perfect Absorber Using a Phase-Change Metamaterial at Visible Frequencies

    NASA Astrophysics Data System (ADS)

    Cao, Tun; Wei, Chen-Wei; Simpson, Robert E.; Zhang, Lei; Cryan, Martin J.

    2014-02-01

    We report a broadband polarization-independent perfect absorber with wide-angle near unity absorbance in the visible regime. Our structure is composed of an array of thin Au squares separated from a continuous Au film by a phase change material (Ge2Sb2Te5) layer. It shows that the near perfect absorbance is flat and broad over a wide-angle incidence up to 80° for either transverse electric or magnetic polarization due to a high imaginary part of the dielectric permittivity of Ge2Sb2Te5. The electric field, magnetic field and current distributions in the absorber are investigated to explain the physical origin of the absorbance. Moreover, we carried out numerical simulations to investigate the temporal variation of temperature in the Ge2Sb2Te5 layer and to show that the temperature of amorphous Ge2Sb2Te5 can be raised from room temperature to > 433 K (amorphous-to-crystalline phase transition temperature) in just 0.37 ns with a low light intensity of 95 nW/μm2, owing to the enhanced broadband light absorbance through strong plasmonic resonances in the absorber. The proposed phase-change metamaterial provides a simple way to realize a broadband perfect absorber in the visible and near-infrared (NIR) regions and is important for a number of applications including thermally controlled photonic devices, solar energy conversion and optical data storage.

  10. Broadband polarization-independent perfect absorber using a phase-change metamaterial at visible frequencies.

    PubMed

    Cao, Tun; Wei, Chen-wei; Simpson, Robert E; Zhang, Lei; Cryan, Martin J

    2014-02-04

    We report a broadband polarization-independent perfect absorber with wide-angle near unity absorbance in the visible regime. Our structure is composed of an array of thin Au squares separated from a continuous Au film by a phase change material (Ge2Sb2Te5) layer. It shows that the near perfect absorbance is flat and broad over a wide-angle incidence up to 80° for either transverse electric or magnetic polarization due to a high imaginary part of the dielectric permittivity of Ge2Sb2Te5. The electric field, magnetic field and current distributions in the absorber are investigated to explain the physical origin of the absorbance. Moreover, we carried out numerical simulations to investigate the temporal variation of temperature in the Ge2Sb2Te5 layer and to show that the temperature of amorphous Ge2Sb2Te5 can be raised from room temperature to > 433 K (amorphous-to-crystalline phase transition temperature) in just 0.37 ns with a low light intensity of 95 nW/μm(2), owing to the enhanced broadband light absorbance through strong plasmonic resonances in the absorber. The proposed phase-change metamaterial provides a simple way to realize a broadband perfect absorber in the visible and near-infrared (NIR) regions and is important for a number of applications including thermally controlled photonic devices, solar energy conversion and optical data storage.

  11. Effect of poly(ethylene glycol) on phospholipid hydration and polarity of the external phase.

    PubMed

    Arnold, K; Pratsch, L; Gawrisch, K

    1983-02-09

    The hydration properties of phosphatidylcholine (PC)/water dispersions on the addition of poly(ethylene glycol) were studied by means of 2H-NMR. The quadrupole splittings and their temperature dependences correspond to measurements of PC/water dispersions at low water content. It is concluded that the bound water is partly extracted by poly(ethylene glycol) but the binding properties of the water in the inner hydration shell of about five water molecules are not changed. The ability of some phospholipid/water dispersions to undergo phase transitions to nonlamellar structures upon dehydration is discussed. Dipalmitoylphosphatidylcholine (DPPC) and egg phosphatidylcholine do not form nonlamellar structures on addition of purified poly(ethylene glycol), as was demonstrated by means of 31P-NMR. Poly(ethylene glycol) decreases the polarity of the aqueous phase and the partition of hydrophobic molecules between the membrane and the external phase is changed. This was demonstrated using the excimer fluorescence of pyrene in a ghost suspension. It is suggested that the changes in polarity and hydration on the addition of poly(ethylene glycol) can contribute to the alterations in the membrane surface observed under conditions of membrane contact and fusion.

  12. Polarization state demodulation of channeled imaging spectropolarimeter by phase rearrangement calibration method

    NASA Astrophysics Data System (ADS)

    Li, Qiwei; Zhang, Chunmin; Yan, Tingyu; Wei, Yutong

    2016-11-01

    The basic principle of channeled Fourier-transform imaging spectropolarimeter (CFTISP) is outlined. The two mainstream techniques existing for performing polarization state demodulation are analyzed, which show uncertainty that may not be suitable for CFTISP based on lateral shear interferometer. A modified demodulation method for Stokes parameters is described. The method separate the phase of the sign and the high-order retarders' retardations from the total phase acquired from the fast Fourier transform of the interferogram, which will not cause the amplitude error from the reference beam. Furthermore, the retardations and the residual phase error in each band introduced by instrument can be seen directly in this method. The effectiveness of this method is experimentally demonstrated with four known input states of polarization, and the results are satisfactory. The RMS error of each Stokes parameters is also presented, which demonstrates that the low spectral signal-to-noise ratio can increase the RMS error by nearly a factor of 2-5 for the individual Stokes parameters. The comparison of reconstructed results by four methods further demonstrates the effectiveness of the proposed method.

  13. Broadband Polarization-Independent Perfect Absorber Using a Phase-Change Metamaterial at Visible Frequencies

    PubMed Central

    Cao, Tun; Wei, Chen-wei; Simpson, Robert E.; Zhang, Lei; Cryan, Martin J.

    2014-01-01

    We report a broadband polarization-independent perfect absorber with wide-angle near unity absorbance in the visible regime. Our structure is composed of an array of thin Au squares separated from a continuous Au film by a phase change material (Ge2Sb2Te5) layer. It shows that the near perfect absorbance is flat and broad over a wide-angle incidence up to 80° for either transverse electric or magnetic polarization due to a high imaginary part of the dielectric permittivity of Ge2Sb2Te5. The electric field, magnetic field and current distributions in the absorber are investigated to explain the physical origin of the absorbance. Moreover, we carried out numerical simulations to investigate the temporal variation of temperature in the Ge2Sb2Te5 layer and to show that the temperature of amorphous Ge2Sb2Te5 can be raised from room temperature to > 433 K (amorphous-to-crystalline phase transition temperature) in just 0.37 ns with a low light intensity of 95 nW/μm2, owing to the enhanced broadband light absorbance through strong plasmonic resonances in the absorber. The proposed phase-change metamaterial provides a simple way to realize a broadband perfect absorber in the visible and near-infrared (NIR) regions and is important for a number of applications including thermally controlled photonic devices, solar energy conversion and optical data storage. PMID:24492415

  14. Processing - Property Relationship in Advanced Intermetallics

    DTIC Science & Technology

    1994-07-01

    AD-A285 262 - IlE I !!III Illl iIII c.,. Processing- Property Relationship I in Advanced Intermetallics Final Report For Period March 4,1991 through...through 03-03-94 4. TITLE AND SUBTITLE 5. FUNDING NUMBERS Processing- Property Relationship in Advanced Intermetallics; 4. AUTHOR(S) D.A. Hardwick and P.L...2 M echanical Properties ......................................................................... 9 3 C

  15. Resonant ultrasound spectroscopy: Elastic properties of some intermetallic compounds

    SciTech Connect

    Chu, F.; Thoma, D.J.; He, Y.; Maloy, S.A.; Mitchell, T.E.

    1996-09-01

    A novel nondestructive evaluation method, resonant ultrasound spectroscopy (RUS), is reviewed with an emphasis upon defining the elastic properties of intermetallic phases. The applications and advantages of RUS as compared to other conventional elastic constant measurement methods are explained. RUS has been employed to measure the elastic properties of single crystal and/or polycrystalline intermetallics, such as Laves phases (C15 HfV{sub 2} and NbCr{sub 2}), Nb-modified titanium aluminides, and transition metal disilicides (C11{sub b} MoSi{sub 2}, C40 NbSi{sub 2} and TaSi{sub 2}). For Laves phases, the elastic properties of HfV{sub 2}-based C15 phases show various anomalies and those of C15 NbCr{sub 2} do not. For Nb-modified titanium aluminides, the elastic properties of O-phase alloys are investigated as a function of alloying content. For transition metal disilicides, single crystal elastic constants of MoSi{sub 2}, NbSi{sub 2}, and TaSi{sub 2} are obtained and compared. Based on the experimentally determined elastic properties, the characteristics of interatomic bonding in these materials are examined and the possible impact of the elastic properties on mechanical behavior is discussed.

  16. Cycle of phase, coherence and polarization singularities in Young's three-pinhole experiment.

    PubMed

    Pang, Xiaoyan; Gbur, Greg; Visser, Taco D

    2015-12-28

    It is now well-established that a variety of singularities can be characterized and observed in optical wavefields. It is also known that these phase singularities, polarization singularities and coherence singularities are physically related, but the exact nature of their relationship is still somewhat unclear. We show how a Young-type three-pinhole interference experiment can be used to create a continuous cycle of transformations between classes of singularities, often accompanied by topological reactions in which different singularities are created and annihilated. This arrangement serves to clarify the relationships between the different singularity types, and provides a simple tool for further exploration.

  17. Dispersion characterization of group birefringence in polarization-maintaining fiber using a Kerr phase-interrogator

    NASA Astrophysics Data System (ADS)

    Lu, Yang; Baker, Chams; Bao, Xiaoyi

    2015-07-01

    We present a new approach to characterize dispersion of group birefringence in a long polarization-maintaining fiber (PMF). Two sinusoidal optical signals are respectively launched into fast and slow axes of a PMF under test. Wavelength dependent group-delay difference between two sinusoidal optical signals induced by group birefringence in the PMF is measured using a Kerr phase-interrogator, and dispersion of group birefringence is characterized from the group-delay difference. Measurements of wavelength dependent group birefringence and group birefringence dispersion for a 459.4-m Panda PMF are experimentally demonstrated.

  18. All dielectric reflective metasurface for controlling phase and polarization by using silicon nanoblocks

    NASA Astrophysics Data System (ADS)

    Kim, Youngsoo; Lee, Young Jin; Hong, Seokhyeun; Moon, Kihwan; Kwon, Soon-Hong

    2017-09-01

    We suggest all dielectric metasurfaces composed of silicon (Si) nanoblock array. We can control the phase and polarization of light reflected the metasurface by changing Mie scattering of each Si block. The Mie scattering is easily adjusted by changing structure parameters of Si block width and height. In single Si nanoblock, the magnetic dipole resonance mode was diminished when decreasing its height. In this study, for making 2-dimensional metasurface, we analyze the scattering cross-section by changing width and height of Si nanoblock with finite-difference time-domain method.

  19. Self-consistent relativistic random-phase approximation with vacuum polarization

    SciTech Connect

    Haga, A.; Toki, H.; Tamenaga, S.; Horikawa, Y.; Yadav, H.L.

    2005-09-01

    We present a theoretical formulation for the description of nuclear excitations within the framework of a relativistic random-phase approximation whereby the vacuum polarization arising from nucleon-antinucleon fields is duly accounted for. The vacuum contribution to the Lagrangian is explicitly described as extra new terms of interacting mesons by means of the derivative expansion of the effective action. It is shown that the self-consistent calculation yields zero eigenvalue for the spurious isoscalar-dipole state and also conserves the vector-current density.

  20. Circularly polarized carrier-envelope-phase stable attosecond pulse generation based on coherent undulator radiation.

    PubMed

    Tóth, Gy; Tibai, Z; Nagy-Csiha, Zs; Márton, Zs; Almási, G; Hebling, J

    2015-09-15

    In this Letter, we present a new method for generation of circularly polarized attosecond pulses. According to our calculations, shape-controlled, carrier-envelope-phase stable pulses of several hundred nanojoule energy could be produced by exploitation of the coherent undulator radiation of an electron bunch. Our calculations are based on an existing particle accelerator system (FLASH II in DESY, Germany). We investigated the energy dependence of the attosecond pulses on the energy of electrons and the parameters of the radiator undulator, which generate the electromagnetic radiation.

  1. Study of polarization properties of fiber-optics probes with use of a binary phase plate.

    PubMed

    Alferov, S V; Khonina, S N; Karpeev, S V

    2014-04-01

    We conduct a theoretical and experimental study of the distribution of the electric field components in the sharp focal domain when rotating a zone plate with a π-phase jump placed in the focused beam. Comparing the theoretical and experimental results for several kinds of near-field probes, an analysis of the polarization sensitivity of different types of metal-coated aperture probes is conducted. It is demonstrated that with increasing diameter of the non-metal-coated tip part there occurs an essential redistribution of sensitivity in favor of the transverse electric field components and an increase of the probe's energy throughput.

  2. Deformation twinning in ordered alloys transformation induced ductility in intermetallics. Final report

    SciTech Connect

    Goo, E.

    1992-09-01

    Intermetallics, which are ordered alloys, have excellent high temperature strength. Unfortunately a universal problem facing intermetallics is the lack of ductility. This program attempted to look at some novel solutions for enhancing ductility in intermetallics. Deformation twinning has been demonstrated in TiNi to be responsible for its ductility. This was a surprising result since twinning was not believed to occur readily in ordered alloys. Furthermore the twinning occurred on a (114) plane which had not been previously observed. Research into determining the mechanisms for twinning in ordered alloy and understanding how twinning enhances the ductility of intermetallic was studied. Martensitic transformations in many intermetallics also provides a possible means of enhancing ductility. The detwinning of martensite twins or transformation induced martensite provides a mechanism for accommodating large strains. It is known that a metastable martensitic phase may be created by quenching a non-stoichiometric NiAl alloy. This presents the potential of substantial ductility in NiAl. Investigation of the martensitic phase transformation and its effect on the ductility of NiAl alloys was investigated.

  3. Deformation twinning in ordered alloys transformation induced ductility in intermetallics. [TiNi; NiAl

    SciTech Connect

    Goo, E.

    1992-09-01

    Intermetallics, which are ordered alloys, have excellent high temperature strength. Unfortunately a universal problem facing intermetallics is the lack of ductility. This program attempted to look at some novel solutions for enhancing ductility in intermetallics. Deformation twinning has been demonstrated in TiNi to be responsible for its ductility. This was a surprising result since twinning was not believed to occur readily in ordered alloys. Furthermore the twinning occurred on a (114) plane which had not been previously observed. Research into determining the mechanisms for twinning in ordered alloy and understanding how twinning enhances the ductility of intermetallic was studied. Martensitic transformations in many intermetallics also provides a possible means of enhancing ductility. The detwinning of martensite twins or transformation induced martensite provides a mechanism for accommodating large strains. It is known that a metastable martensitic phase may be created by quenching a non-stoichiometric NiAl alloy. This presents the potential of substantial ductility in NiAl. Investigation of the martensitic phase transformation and its effect on the ductility of NiAl alloys was investigated.

  4. Formation of Intermetallic Compounds During Explosive Welding

    NASA Astrophysics Data System (ADS)

    Greenberg, Bella A.; Ivanov, Mikhail A.; Pushkin, Mark S.; Inozemtsev, Alexei V.; Patselov, Alexander M.; Tankeyev, Anatoliy P.; Kuzmin, Sergey V.; Lysak, Vladimir I.

    2016-11-01

    Transition states between traditional, i.e., plain and wavy, shapes of the interface during explosive welding were studied. A sequence of the transition states was found for the studied copper-titanium and copper-tantalum joints. Some transition states are common for the joints under study, while others are only typical of the copper-titanium joints, due to sufficiently high solubility of original elements. A transition state has been found, during which cusps, even though they are solid phase, look like splashes on the water. The key role of these splashes is that they evidence the lower boundary of the `weldability window.' The study found certain self-organization processes of the cusps that cause them to turn into a quasi-wavy shape of the interface, and then, as the welding mode is intensified, into a wavy shape. The role of intermetallic compounds was analyzed, due to which a wave only consists of cusps in case mutual solubility of original metals is sufficiently high.

  5. Laser scanning confocal microscope with programmable amplitude, phase, and polarization of the illumination beam.

    PubMed

    Boruah, B R; Neil, M A A

    2009-01-01

    We describe the design and construction of a laser scanning confocal microscope with programmable beam forming optics. The amplitude, phase, and polarization of the laser beam used in the microscope can be controlled in real time with the help of a liquid crystal spatial light modulator, acting as a computer generated hologram, in conjunction with a polarizing beam splitter and two right angled prisms assembly. Two scan mirrors, comprising an on-axis fast moving scan mirror for line scanning and an off-axis slow moving scan mirror for frame scanning, configured in a way to minimize the movement of the scanned beam over the pupil plane of the microscope objective, form the XY scan unit. The confocal system, that incorporates the programmable beam forming unit and the scan unit, has been implemented to image in both reflected and fluorescence light from the specimen. Efficiency of the system to programmably generate custom defined vector beams has been demonstrated by generating a bottle structured focal volume, which in fact is the overlap of two cross polarized beams, that can simultaneously improve both the lateral and axial resolutions if used as the de-excitation beam in a stimulated emission depletion confocal microscope.

  6. Geometric phase coded metasurface: from polarization dependent directive electromagnetic wave scattering to diffusion-like scattering

    NASA Astrophysics Data System (ADS)

    Chen, Ke; Feng, Yijun; Yang, Zhongjie; Cui, Li; Zhao, Junming; Zhu, Bo; Jiang, Tian

    2016-10-01

    Ultrathin metasurface compromising various sub-wavelength meta-particles offers promising advantages in controlling electromagnetic wave by spatially manipulating the wavefront characteristics across the interface. The recently proposed digital coding metasurface could even simplify the design and optimization procedures due to the digitalization of the meta-particle geometry. However, current attempts to implement the digital metasurface still utilize several structural meta-particles to obtain certain electromagnetic responses, and requiring time-consuming optimization especially in multi-bits coding designs. In this regard, we present herein utilizing geometric phase based single structured meta-particle with various orientations to achieve either 1-bit or multi-bits digital metasurface. Particular electromagnetic wave scattering patterns dependent on the incident polarizations can be tailored by the encoded metasurfaces with regular sequences. On the contrast, polarization insensitive diffusion-like scattering can also been successfully achieved by digital metasurface encoded with randomly distributed coding sequences leading to substantial suppression of backward scattering in a broadband microwave frequency. The proposed digital metasurfaces provide simple designs and reveal new opportunities for controlling electromagnetic wave scattering with or without polarization dependence.

  7. Geometric phase coded metasurface: from polarization dependent directive electromagnetic wave scattering to diffusion-like scattering.

    PubMed

    Chen, Ke; Feng, Yijun; Yang, Zhongjie; Cui, Li; Zhao, Junming; Zhu, Bo; Jiang, Tian

    2016-10-24

    Ultrathin metasurface compromising various sub-wavelength meta-particles offers promising advantages in controlling electromagnetic wave by spatially manipulating the wavefront characteristics across the interface. The recently proposed digital coding metasurface could even simplify the design and optimization procedures due to the digitalization of the meta-particle geometry. However, current attempts to implement the digital metasurface still utilize several structural meta-particles to obtain certain electromagnetic responses, and requiring time-consuming optimization especially in multi-bits coding designs. In this regard, we present herein utilizing geometric phase based single structured meta-particle with various orientations to achieve either 1-bit or multi-bits digital metasurface. Particular electromagnetic wave scattering patterns dependent on the incident polarizations can be tailored by the encoded metasurfaces with regular sequences. On the contrast, polarization insensitive diffusion-like scattering can also been successfully achieved by digital metasurface encoded with randomly distributed coding sequences leading to substantial suppression of backward scattering in a broadband microwave frequency. The proposed digital metasurfaces provide simple designs and reveal new opportunities for controlling electromagnetic wave scattering with or without polarization dependence.

  8. Geometric phase coded metasurface: from polarization dependent directive electromagnetic wave scattering to diffusion-like scattering

    PubMed Central

    Chen, Ke; Feng, Yijun; Yang, Zhongjie; Cui, Li; Zhao, Junming; Zhu, Bo; Jiang, Tian

    2016-01-01

    Ultrathin metasurface compromising various sub-wavelength meta-particles offers promising advantages in controlling electromagnetic wave by spatially manipulating the wavefront characteristics across the interface. The recently proposed digital coding metasurface could even simplify the design and optimization procedures due to the digitalization of the meta-particle geometry. However, current attempts to implement the digital metasurface still utilize several structural meta-particles to obtain certain electromagnetic responses, and requiring time-consuming optimization especially in multi-bits coding designs. In this regard, we present herein utilizing geometric phase based single structured meta-particle with various orientations to achieve either 1-bit or multi-bits digital metasurface. Particular electromagnetic wave scattering patterns dependent on the incident polarizations can be tailored by the encoded metasurfaces with regular sequences. On the contrast, polarization insensitive diffusion-like scattering can also been successfully achieved by digital metasurface encoded with randomly distributed coding sequences leading to substantial suppression of backward scattering in a broadband microwave frequency. The proposed digital metasurfaces provide simple designs and reveal new opportunities for controlling electromagnetic wave scattering with or without polarization dependence. PMID:27775064

  9. Laser scanning confocal microscope with programmable amplitude, phase, and polarization of the illumination beam

    NASA Astrophysics Data System (ADS)

    Boruah, B. R.; Neil, M. A. A.

    2009-01-01

    We describe the design and construction of a laser scanning confocal microscope with programmable beam forming optics. The amplitude, phase, and polarization of the laser beam used in the microscope can be controlled in real time with the help of a liquid crystal spatial light modulator, acting as a computer generated hologram, in conjunction with a polarizing beam splitter and two right angled prisms assembly. Two scan mirrors, comprising an on-axis fast moving scan mirror for line scanning and an off-axis slow moving scan mirror for frame scanning, configured in a way to minimize the movement of the scanned beam over the pupil plane of the microscope objective, form the XY scan unit. The confocal system, that incorporates the programmable beam forming unit and the scan unit, has been implemented to image in both reflected and fluorescence light from the specimen. Efficiency of the system to programmably generate custom defined vector beams has been demonstrated by generating a bottle structured focal volume, which in fact is the overlap of two cross polarized beams, that can simultaneously improve both the lateral and axial resolutions if used as the de-excitation beam in a stimulated emission depletion confocal microscope.

  10. Polarization independent electro-optical waveguides with liquid crystals in isotropic phase

    NASA Astrophysics Data System (ADS)

    Costache, Florenta; Blasl, Martin; Bornhorst, Kirstin

    2015-02-01

    Electro-optically induced waveguides can be used in fiber optic networks for optical power control and the distribution of optical signals transmitted over optical fibers. Reliable operation is ensured with this type of waveguides due to their non-mechanical principle of operation. Their polarization dependent behavior caused by field-induced birefringence effects may limit however their practical applications. We report on a method to reduce the polarization dependent loss in electro-optically induced waveguides with a core made of liquid crystals in isotropic phase. The concept design enables a controlled adjustment of the electric field distribution, which is responsible for inducing and shaping the optical mode, by employing an optimized electrode arrangement. In this new waveguide structure, the TM and TE modes coexist spatially and are guided in a similar way. In order to demonstrate this concept, straight and bending waveguides in 1×1 and 1×2 light input to output configurations have been designed and fabricated. The electrode arrangement and single mode waveguide geometry were optimized using FEM simulations. Bulk silicon micromachining was used to fabricate these waveguides. In particular, the manufactured device consisted of two processed silicon substrates with a liquid crystal layer enclosed in between. Devices tested with varying driving voltage have revealed comparable transmitted power for both TE and TM modes. Very low polarization dependent losses over a more than 20 dB wide dynamic attenuation range have been obtained.

  11. Spin-polarized hydrogen and its isotopes: A rich class of quantum phases (Review Article)

    NASA Astrophysics Data System (ADS)

    Bešlić, I.; Vranješ Markić, L.; Boronat, J.

    2013-10-01

    We review the recent activity in the theoretical description of spin-polarized atomic hydrogen and its isotopes at very low temperatures. Spin-polarized hydrogen is the only system in nature that remains stable in the gas phase even in the zero temperature limit due to its small mass and weak interatomic interaction. Hydrogen and its heavier isotope tritium are bosons, the heavier mass of tritium producing a self-bound (liquid) system at zero temperature. The other isotope, deuterium, is a fermion with nuclear spin one making possible the study of three different quantum systems depending on the population of the three degenerate spin states. From the theoretical point of view, spin-polarized hydrogen is specially appealing because its interatomic potential is very accurately known making possible its precise quantum many-body study. The experimental study of atomic hydrogen has been very difficult due to its high recombination rate, but it finally led to its Bose-Einstein condensate state in 1998. Degeneracy has also been observed in thin films of hydrogen adsorbed on the 4He surface allowing for the possibility of observing the Berezinskii-Kosterlitz-Thouless superfluid transition.

  12. Forming metal-intermetallic or metal-ceramic composites by self-propagating high-temperature reactions

    DOEpatents

    Rawers, James C.; Alman, David E.; Petty, Jr., Arthur V.

    1996-01-01

    Industrial applications of composites often require that the final product have a complex shape. In this invention intermetallic or ceramic phases are formed from sheets of unreacted elemental metals. The process described in this invention allows the final product shape be formed prior to the formation of the composite. This saves energy and allows formation of shaped articles of metal-intermetallic composites composed of brittle materials that cannot be deformed without breaking.

  13. Unravelling the effects of mobile phase additives in supercritical fluid chromatography. Part I: Polarity and acidity of the mobile phase.

    PubMed

    West, Caroline; Melin, Jodie; Ansouri, Hassna; Mengue Metogo, Maïly

    2017-04-07

    The mobile phases employed in current supercritical fluid chromatography (SFC) are usually composed of a mixture of pressurized carbon dioxide and a co-solvent. The co-solvent is most often an alcohol and may contain a third component in small proportions, called an additive (acid, base or salt). The polarity of such mobile phase compositions is here re-evaluated with a solvatochromic dye (Nile Red), particularly to assess the contribution of additives. It appears that additives, when employed in usual concentration range (0.1% or 20mM) do not modify the polarity in the immediate environment of the probe. In addition, the combination of carbon dioxide and an alcohol is known to form alkoxylcarbonic acid, supposedly conferring some acidic character to SFC mobile phases. Direct measurements of the apparent pH are impossible, but colour indicators of pH can be used to define the range of apparent pH provided by carbon dioxide-alcohol mixtures, with or without additives. Five colour indicators (Thymol Blue, Bromocresol Green, Methyl Red, Bromocresol Purple, and Bromothymol Blue) were selected to provide a wide range of aqueous pKa values (from 1.7 to 8.9). UV-vis absorption spectra measured in liquid phases of controlled pH were compared to those measured with a diode-array detector employed in SFC, with the help of chemometric methods. Based on these observations, it is concluded that the apparent pH range in carbon dioxide-methanol mobile phases is close to 5. Increasing the proportion of methanol (in the course of a gradient elution for instance) causes decreasing apparent pH. Strong acids can further decrease the apparent pH below 1.7; strong bases have little influence on the apparent pH, probably because, in this range of concentrations, they are titrated by alkoxylcarbonic acid or form ion pairs with alkoxycarbonate. However, bases and salts could stabilize the acidity in the course of gradient runs.

  14. A birefringent polarization modulator: Application to phase measurement in conoscopic interference patterns.

    PubMed

    Veiras, F E; Garea, M T; Perez, L I

    2016-04-01

    Conoscopic interferometry for crystal characterization is a very well-known technique with increasing applications in different fields of technology. The advantage of the scheme proposed here is the introduction of a polarization modulator that allows the recovery of the phase information contained in conoscopic interferograms. This represents a real advantage since the most relevant physical information of the sample under study is usually contained in the phase of the fringe pattern. Moreover, this technique works successfully even when there are no visible fringes. The setup employed is a simple conoscopic interferometer where the elements under study correspond to two birefringent crystal slabs and a commercial mica wave plate. It allows the crystals to be characterized and the wave plate retardance to be measured as a function of the angle of incidence. The modulator itself consists of a single tiltable crystal plate which, by means of phase shifting techniques, permits the recovery of a phase map for each sample. It is inexpensive and it can be easily calibrated, so it works with a wide range of phase shifting interferometry algorithms. We show that our scheme is easily adaptable to algorithms that require either a low or high amount of interferograms.

  15. Valley polarized quantum Hall effect and topological insulator phase transitions in silicene

    PubMed Central

    Tahir, M.; Schwingenschlögl, U.

    2013-01-01

    The electronic properties of silicene are distinct from both the conventional two dimensional electron gas and the famous graphene due to strong spin orbit interaction and the buckled structure. Silicene has the potential to overcome limitations encountered for graphene, in particular the zero band gap and weak spin orbit interaction. We demonstrate a valley polarized quantum Hall effect and topological insulator phase transitions. We use the Kubo formalism to discuss the Hall conductivity and address the longitudinal conductivity for elastic impurity scattering in the first Born approximation. We show that the combination of an electric field with intrinsic spin orbit interaction leads to quantum phase transitions at the charge neutrality point, providing a tool to experimentally tune the topological state. Silicene constitutes a model system for exploring the spin and valley physics not accessible in graphene due to the small spin orbit interaction. PMID:23355947

  16. Generation of a flat optical frequency comb based on a cascaded polarization modulator and phase modulator.

    PubMed

    Chen, Cihai; He, Chao; Zhu, Dan; Guo, Ronghui; Zhang, Fangzheng; Pan, Shilong

    2013-08-15

    A scheme to generate a flat optical frequency comb (OFC) with a fixed phase relationship between the comb lines is proposed and experimentally demonstrated based on a cascaded polarization modulator (PolM) and phase modulator. Because the PolM introduces more controllable parameters compared with the conventional intensity modulator, 9, 11, and 13 comb lines can be generated with relatively low RF powers, or 15, 17, and 19 comb lines can be obtained if high RF powers are applied. The experimentally generated 9, 11, and 13 OFCs have a flatness of 1, 1.3, and 2.1 dB, respectively. The scheme requires no DC bias to the modulators, no optical filter, and no frequency divider or multiplier, which is simple and stable.

  17. An experimental study of growth and phase change of polar stratospheric cloud particles

    NASA Technical Reports Server (NTRS)

    Hallett, John; Teets, Edward

    1992-01-01

    This report describes the progress made on understanding phase changes related to solutions which may comprise Polar Stratospheric Clouds. In particular, it is concerned with techniques for investigating specific classes of metastability and phase change which may be important not only in Polar Stratospheric Clouds but in all atmospheric aerosols in general. While the lower level atmospheric aerosol consists of mixtures of (NH4)(SO4)2, NH4HSO4, NaCl among others, there is evidence that aerosol at PSC levels is composed of acid aerosol, either injected from volcanic events (such as Pinatubo) or having diffused upward from the lower atmosphere. In particular, sulfuric acid and nitric acid are known to occur at PSC levels, and are suspected of catalyzing ozone destruction reactions by adsorption on surfaces of crystallized particles. The present study has centered on two approaches: (1) the extent of supercooling (with respect to ice) and supersaturation (with respect to hydrate) and the nature of crystal growth in acid solutions of specific molality; and (2) the nature of growth from the vapor of HNO3 - H2O crystals both on a substrate and on a pre-existing aerosol.

  18. Polarization discrimination in a phase-sensitive optical time-domain reflectometer intrusion-sensor system.

    PubMed

    Juarez, Juan C; Taylor, Henry F

    2005-12-15

    A distributed sensor system for detecting and locating intruders based on a phase-sensitive optical time-domain reflectometer (phi-OTDR) that utilizes polarization discrimination is described. The sensing element is a single-mode telecommunications fiber in a 3 mm diameter cable buried along a monitored perimeter in a 20-46 cm deep, 10 cm wide trench in clay soil. Light pulses from a continuous-wave Er fiber Fabry-Perot laser with a narrow (< 3 kHz) instantaneous linewidth and low (a few Kilohertz per second) frequency drift are injected into one end of the fiber, and the orthogonal polarizations of the backscattered light are monitored with separate receivers. Localized phase changes in the optical carrier are sensed by subtraction of a phi-OTDR trace from an earlier stored trace. In field tests with a monitored length of 12 km, detection of intruders on foot as far as 4.5 m from the cable line was consistently achieved.

  19. Preparation and evaluation of a lysine-bonded silica monolith as polar stationary phase for hydrophilic interaction pressurized capillary electrochromatography.

    PubMed

    Huang, Guihua; Lian, Qiuyan; Zeng, Wencan; Xie, Zenghong

    2008-09-01

    A silica-based monolith as polar stationary phase was described for hydrophilic interaction pressurized capillary electrochromatography (HI-pCEC). The polar monolithic column was prepared by on-column reaction of lysine with epoxy groups on a gamma-glycidoxypropyltrimethosysilane-modified silica monolith. The stationary phase yielded strong hydrophilic interaction due to the slightly polar hydroxyl groups, and the strong polar lysine ligand with amino groups and carboxylic groups contained on the surface of the monolith. In order to evaluate the hydrophilic character of lysine ligand, the chromatographic behaviors of epoxy monolith (before lysine bonded) and diol monolith (hydroxyl groups contained) were also investigated. Two groups of comparative experiment were developed in terms of the separation of typical neutral non-polar and polar compounds performed in a mobile phase of aqueous-acetonitrile solution. Results showed that the lysine monolith was much more hydrophilic than the diol monolith, which presented less hydrophobic than the epoxy monolith. For further study on its hydrophilic character, the lysine monolith was demonstrated in the HI-pCEC mode for the separations of various polar compounds such as phenols, nucleic acid bases and nucleosides.

  20. Operational modes of a ferroelectric LCoS modulator for displaying binary polarization, amplitude, and phase diffraction gratings.

    PubMed

    Martínez-García, Antonio; Moreno, Ignacio; Sánchez-López, María M; García-Martínez, Pascuala

    2009-05-20

    We analyze the performance of a ferroelectric liquid crystal on silicon display (FLCoS) as a binary polarization diffraction grating. We analyze the correspondence between the two polarization states emerging from the displayed grating and the polarization and intensity of the diffracted orders generated at the Fourier diffraction plane. This polarization-diffraction analysis leads, in a simple manner, to configurations yielding binary amplitude or binary phase modulation by incorporating an analyzer on the reflected beam. Based on this analysis, we present two useful variations of the polarization configuration. The first is a simplification using a single polarizer, which provides equivalent results for amplitude or phase modulation as the more general operational mode involving two polarizers. The second variation is proposed to compensate the reduction of the diffraction efficiency when the operating wavelength differs from the design one (for which the FLCoS liquid-crystal layer acts as a half-wave plate). In this situation we show how the ideal grating performance can be recovered in spite of the phase-shift mismatch originated by chromatic dispersion. In all cases, we provide experimental results that verify the theoretical analyses.

  1. Dislocation sources in ordered intermetallics

    SciTech Connect

    Yoo, M.H.; Appel, F.; Wagner, R.; Mecking, H.

    1996-09-01

    An overview on the current understanding of dislocation sources and multiplication mechanisms is made for ordered intermetallic alloys of the L1{sub 2}, B2, and D0{sub 19} structures. In L1{sub 2} alloys, a large disparity of edge/screw segments in their relative mobility reduces the efficiency of a Frank-Read Type multiplication mechanism. In Fe-40%Al of the B2 structure, a variety of dislocation sources are available for <111> slip, including ones resulting from condensation of thermal vacancies. In NiAl with the relatively high APB energy, <100> dislocations may result from the dislocation decomposition reactions, the prismatic punching out from inclusion particles, and/or steps and coated layers of the surface. Internal interfaces often provide sites for dislocation multiplication, e.g., grain boundaries, sub-boundaries in Ni{sub 3}Ga, NiAl and Ti{sub 3}Al, and antiphase domain boundaries in Ti{sub 3}Al. As for the crack tip as a dislocation source, extended SISFs trailed by super-Shockley partials emanating form the cracks in Ni{sub 3}Al and Co{sub 3}Ti are discussed in view of a possible toughening mechanism.

  2. Aircraft Measurements of Aerosol Phase Matrix Elements by the Polarized Imaging Nephelometer (Invited)

    NASA Astrophysics Data System (ADS)

    Dolgos, G.; Martins, J.; Espinosa, R.; Dubovik, O.; Beyersdorf, A. J.; Ziemba, L. D.; Hair, J. W.

    2013-12-01

    Aerosols have a significant impact on the radiative balance and water cycle of our planet through influencing atmospheric radiation. Remote sensing of aerosols relies on scattering phase matrix information to retrieve aerosol properties with frequent global coverage, the assumed phase matrices must be validated by measurements. At the Laboratory for Aerosols, Clouds and Optics (LACO) at the University of Maryland, Baltimore County (UMBC) we developed a new technique to directly measure the aerosol phase function (P11), the degree of linear polarization of the scattered light (-P12/P11), and the volume scattering coefficient (SCAT). We designed and built a portable instrument called the Polarized Imaging Nephelometer (PI-Neph), shown in Figure 1 (a). The PI-Neph successfully participated in dozens of flights of the NASA Development and Evaluation of satellite ValidatiOn Tools by Experimenters (DEVOTE) project and the Deep Convective Clouds and Chemistry (DC3) project and the January and February deployment of the Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (Discover-AQ) mission. The ambient aerosol enters the PI-Neph through an inlet and the sample is illuminated by laser light (wavelength of 532 nm); the scattered light is imaged by a stationary wide field of view camera in the scattering angle range of 2° to 178° (in some cases stray light limited the scattering angle range to 3° to 176°). Data for P11, P12, and SCAT were taken every 12 seconds, example datasets from DEVOTE of P11 times SCAT are shown on Figure 1 (b). The talk will highlight results from the three field deployments and will show microphysical retrievals from the scattering data. The size distribution and the average complex refractive index of the ambient aerosol ensemble can be retrieved from the data by an algorithm similar to that of AERONET, as illustrated in Figure 1 (c). Particle sphericity can potentially be

  3. Anisotropic lattice response induced by a linearly-polarized femtosecond optical pulse excitation in interfacial phase change memory material

    NASA Astrophysics Data System (ADS)

    Makino, Kotaro; Saito, Yuta; Fons, Paul; Kolobov, Alexander V.; Nakano, Takashi; Tominaga, Junji; Hase, Muneaki

    2016-01-01

    Optical excitation of matter with linearly-polarized femtosecond pulses creates a transient non-equilibrium lattice displacement along a certain direction. Here, the pump and probe pulse polarization dependence of the photo-induced ultrafast lattice dynamics in (GeTe)2/(Sb2Te3)4 interfacial phase change memory material is investigated under obliquely incident conditions. Drastic pump polarization dependence of the coherent phonon amplitude is observed when the probe polarization angle is parallel to the c-axis of the sample, while the pump polarization dependence is negligible when the probe polarization angle is perpendicular to the c-axis. The enhancement of phonon oscillation amplitude due to pump polarization rotation for a specific probe polarization angle is only found in the early time stage (≤2 ps). These results indicate that the origin of the pump and probe polarization dependence is dominantly attributable to the anisotropically-formed photo-excited carriers which cause the directional lattice dynamics.

  4. Characterization of phase-shifted Brillouin dynamic gratings in a polarization maintaining fiber

    NASA Astrophysics Data System (ADS)

    Zhou, Dengwang; Dong, Yongkang; Xu, Pengbai; Teng, Lei; Zhang, Hongying; Lu, Zhiwei

    2016-11-01

    We numerically calculate and experimentally investigate the characterization of phase-shifted Brillouin dynamic gratings (PS-BDGs) in a polarization maintaining fiber (PMF). A phase-shifted point is induced into the middle of a conventional BDG through phase-modulating one of the two pump pulse, generating a PS-BDG thanks to the stimulated Brillouin scattering (SBS). When the frequency difference between a high frequency pump1 pulse with 1ns and π-1ns and a low frequency pump2 pulse with 100ps is equal to the Brillouin frequency shift of the PMF, a transient PS-BDG with a 3dBbandwidth of 354MHz of the notch spectrum is simulated based on the coupled-wave equations of BDG. By increasing the repetition rate up to 250MHz, an enhanced PS-BDG with a deep notch depth is obtained since the residual acoustic wave of the former SBS process is enhanced by the optical waves of the latter SBS process. Then a proof-of-concept experiment is built to verify the transient PS-BDG and the results show that the notch feature is consistent with the simulation results and the notch frequency of the PS-BDG can be changed by tuning the phase shift Δϕ . The proposed PS-BDGs have important potential applications in optical fiber sensing, microwave photonics, all-optical signal processing and RoF (radio-over-fiber) networks.

  5. Unusual physical properties in B phase of polar bent-core thioester compound

    NASA Astrophysics Data System (ADS)

    Wróbel, S.; Burakowski, Z.; Chruściel, J.; Czerwiec, J.; Marzec, M.; Ossowska-Chruściel, M. D.; Wantusiak, B.

    2012-04-01

    Bent-core compound, 4-chloro-1,3-phenylene bis{4-[(n-undecyloxybenzoyl)-sulfanyl]benzoate}, has been studied by dielectric spectroscopy, DSC calorimetry, and electro-optic methods. As found, the spontaneous polarization of the B phase is by one order of magnitude smaller than for B 2 phases of nOSOR series studied by us before. Its temperature dependence is characteristic for B 1 phase, observed for shorter homologues of nOSORs. Measurements of the complex electric permittivity were carried out in the frequency range from 40 to 15 MHz using gold-coated electrodes. Electro-optic studies have been done applying AWAT HG 1.9 µm cells with strongly rubbed polymer layers. Such cells facilitate inhomogeneous planar alignment, which under strong electric field transforms into a mono-domain exhibiting switching behavior. Dielectric and electro-optic data of bent-core compounds will be discussed taking into account molecular structure and phase structure as well.

  6. Ab Initio Investigation on Structural, Elastic and Electronic Properties of η-Phase Cu4.5Ni1Au0.5Sn5 and Cu5Ni1Sn4.5In0.5 Intermetallic Compounds

    NASA Astrophysics Data System (ADS)

    Li, Xuezheng; Ma, Yong; Zhou, Wei; Wu, Ping

    2017-10-01

    The structural, elastic and electronic properties of quaternary intermetallic compounds η-Cu4.5Ni1Au0.5Sn5 and η-Cu5Ni1Sn4.5In0.5 are investigated by an ab initio method. The calculated heat of formation determines preferential occupancy sites for Ni, Au and In atoms which lead to thermodynamically stable compounds. Variation of lattice constants reveals that the change of atomic bonding has a directional discrepancy in η-Cu4.5Ni1Au0.5Sn5; the polycrystalline moduli obtained from single-crystal elastic stiffness show an increase after both Ni/Au and Ni/In additions. Also, the anisotropy of Young's modulus and shear modulus is significantly weakened in η-Cu4.5Ni1Au0.5Sn5. The density of states and maps of charge density distribution suggest that the atomic bonding in the quaternary intermetallic compounds is strengthened by the addition of Ni and Au but weakened by the addition of In.

  7. Four-dimensional key design in amplitude, phase, polarization and distance for optical encryption based on polarization digital holography and QR code.

    PubMed

    Lin, Chao; Shen, Xueju; Li, Baochen

    2014-08-25

    We demonstrate that all parameters of optical lightwave can be simultaneously designed as keys in security system. This multi-dimensional property of key can significantly enlarge the key space and further enhance the security level of the system. The single-shot off-axis digital holography with orthogonal polarized reference waves is employed to perform polarization state recording on object wave. Two pieces of polarization holograms are calculated and fabricated to be arranged in reference arms to generate random amplitude and phase distribution respectively. When reconstruction, original information which is represented with QR code can be retrieved using Fresnel diffraction with decryption keys and read out noise-free. Numerical simulation results for this cryptosystem are presented. An analysis on the key sensitivity and fault tolerance properties are also provided.

  8. Polarized Imaging Nephelometer for Field and Aircraft Measurements of Aerosol Phase Function

    NASA Astrophysics Data System (ADS)

    Dolgos, G.; Martins, J.

    2012-12-01

    Aerosols have a significant impact on the radiative balance and water cycle of our planet through influencing atmospheric radiation. Remote sensing of aerosols relies on scattering phase matrix information to retrieve aerosol properties with frequent global coverage. At the Laboratory for Aerosols, Clouds and Optics (LACO) at the University of Maryland, Baltimore County we developed a new technique to directly measure the aerosol phase function and the degree of linear polarization of the scattered light (two elements of the phase matrix). We designed and built a portable instrument called the Polarized Imaging Nephelometer (PI-Neph). The PI-Neph successfully participated in dozens of flights of the NASA Development and Evaluation of satellite ValidatiOn Tools by Experimenters (DEVOTE) project and the Deep Convective Clouds and Chemistry (DC3) project. The ambient aerosol enters the PI-Neph through an inlet and the sample is illuminated by laser light (wavelength of 532 nm); the scattered light is imaged by a stationary wide field of view camera in the scattering angle range of 2° to 178°. (In some cases stray light limited the scattering angle range to 3° to 176°). The PI-Neph measurement of phase function and the AERONET (AErosol RObotic NETwork) retrievals have already been compared in some cases when the aircraft spiraled over AERONET sites, for example at NASA's Wallops Flight Facility, on October 18 2011, as shown in Figure 1. The differences between the PI-Neph and the AERONET retrievals can be attributed to differences between the ambient size distribution and the one sampled inside the aircraft. The data that is resolved with respect to scattering angle is used to compute the volume scattering coefficient. The above mentioned October 18 flight data showed good agreement between the PI-Neph measurements of volume scattering coefficient and the parallel TSI integrating nephelometer measurements. On average the TSI measurements were 1.02 times the PI

  9. Dual-polarization phase shift processing with the Python ARM Radar Toolkit

    NASA Astrophysics Data System (ADS)

    Collis, S. M.; Lang, T. J.; Mühlbauer, K.; Helmus, J.; North, K.

    2016-12-01

    Weather radars that measure backscatter returns at two orthogonal polarizations can give unique insight into storm macro and microphysics. Phase shift between the two polarizations caused by anisotropy in the liquid water path can be used as a constraint in rainfall rate and drop size distribution retrievals, and has the added benefit of being robust to attenuation and radar calibration. The measurement is complicated, however, by the impact of phase shift on backscatter in the presence of large drops and when the pulse volume is not filled uniformly by scatterers (known as partial beam filling). This has led to a signal processing challenge of separating the underlying desired signal from the transient signal, a challenge that has attracted many diverse solutions. To this end, the Python-ARM Radar Toolkit (Py-ART) [1] becomes increasingly important. By providing an open architecture for implementation of retrieval techniques, Py-ART has attracted three very different approaches to the phase processing problem: a fully variational technique, a finite impulse response filter technique [2], and a technique based on a linear programming [3]. These either exist within the toolkit or in another open source package that uses the Py-ART architecture. This presentation will provide an overview of differential phase and specific differential phase observed at C- and S-band frequencies, the signal processing behind the three aforementioned techniques, and some examples of their application. The goal of this presentation is to highlight the importance of open source architectures such as Py-ART for geophysical retrievals. [1] Helmus, J.J. & Collis, S.M., (2016). The Python ARM Radar Toolkit (Py-ART), a Library for Working with Weather Radar Data in the Python Programming Language. JORS. 4(1), p.e25. DOI: http://doi.org/10.5334/jors.119[2] Timothy J. Lang, David A. Ahijevych, Stephen W. Nesbitt, Richard E. Carbone, Steven A. Rutledge, and Robert Cifelli, 2007: Radar

  10. Smart Solution Chemistry to Sn-Containing Intermetallic Compounds through a Self-Disproportionation Process.

    PubMed

    Zhang, Yuelan; Li, Liping; Li, Qi; Fan, Jianming; Zheng, Jing; Li, Guangshe

    2016-09-26

    Developing new methods to synthesize intermetallics is one of the most critical issues for the discovery and application of multifunctional metal materials; however, the synthesis of Sn-containing intermetallics is challenging. In this work, we demonstrated for the first time that a self-disproportionation-induced in situ process produces cavernous Sn-Cu intermetallics (Cu3 Sn and Cu6 Sn5 ). The successful synthesis is realized by introducing inorganic metal salts (SnCl2 ⋅2 H2 O) to NaOH aqueous solution to form an intermediate product of reductant (Na2 SnO2 ) and by employing steam pressures that enhance the reduction ability. Distinct from the traditional in situ reduction, the current reduction process avoided the uncontrolled phase composition and excessive use of organic regents. An insight into the mechanism was revealed for the Sn-Cu case. Moreover, this method could be extended to other Sn-containing materials (Sn-Co, Sn-Ni). All these intermetallics were attempted in the catalytic effect on thermal decompositions of ammonium perchlorate. It is demonstrated that Cu3 Sn showed an outstanding catalytic performance. The superior property might be primarily originated from the intrinsic chemical compositions and cavernous morphology as well. We supposed that this smart solution reduction methodology reported here would provide a new recognition for the reduction reaction, and its modified strategy may be applied to the synthesis of other metals, intermetallics as well as some unknown materials.

  11. Electric Current Enhanced Point Defect Mobility in Ni3Ti Intermetallic

    SciTech Connect

    Anselmi-Tamburini, U; Asoka-Kumar, P; Garay, J E; Munir, Z A; Glade, S C

    2004-02-05

    The effect of the application of a DC current on the annealing of point defects in Ni{sub 3}Ti was investigated by positron annihilation spectroscopy (PAS). An increased rate of point defect annealing is observed under the influence of a current and is attributed to a 24% decrease in the mobility activation energy. The results are interpreted in terms of the electron wind effect and the complex nature of diffusion in ordered intermetallic phases. This work represents the first direct evidence of the role of the current on the mobility of point defects in intermetallic systems.

  12. The oxidation of Ni-rich Ni-Al intermetallics

    NASA Technical Reports Server (NTRS)

    Doychak, Joseph; Smialek, James L.; Barrett, Charles A.

    1988-01-01

    The oxidation of Ni-Al intermetallic alloys in the beta-NiAl phase field and in the two phase beta-NiAl/gamma'-Ni3Al phase field has been studied between 1000 and 1400 C. The stoichiometric beta-NiAl alloy doped with Zr was superior to other alloy compositions under cyclic and isothermal oxidation. The isothermal growth rates did not increase monotonically as the alloy Al content was decreased. The characteristically ridged alpha-Al2O3 scale morphology, consisting of cells of thin, textured oxide with thick growth ridges at cell boundaries, forms on oxidized beta-NiAl alloys. The correlation of scale features with isothermal growth rates indicates a predominant grain boundary diffusion growth mechanism. The 1200 C cyclic oxidation resistance decreases near the lower end of the beta-NiAl phase field.

  13. Atomic interaction of the MEAM type for the study of intermetallics in the Al-U alloy

    NASA Astrophysics Data System (ADS)

    Pascuet, M. I.; Fernández, J. R.

    2015-12-01

    Interaction for both pure Al and Al-U alloys of the MEAM type are developed. The obtained Al interatomic potential assures its compatibility with the details of the framework presently adopted. The Al-U interaction fits various properties of the Al2U, Al3U and Al4U intermetallics. The potential verifies the stability of the intermetallic structures in a temperature range compatible with that observed in the phase diagram, and also takes into account the greater stability of these structures relative to others that are competitive in energy. The intermetallics are characterized by calculating elastic and thermal properties and point defect parameters. Molecular dynamics simulations show a growth of the Al3U intermetallic in the Al/U interface in agreement with experimental evidence.

  14. Chemistry and Properties of Complex Intermetallics from Metallic Fluxes

    SciTech Connect

    Kanatzidis, Mercouri G.

    2015-03-28

    This project investigated the reaction chemistry and synthesis of new intermetallic materials with complex compositions and structures using metallic fluxes as solvents. It was found that the metallic fluxes offer several key advantages in facilitating the formation and crystal growth of new materials. The fluxes mostly explored were liquid aluminum, gallium and indium. The main purpose of this project was to exploit the potential of metallic fluxes as high temperature solvent for materials discovery in the broad class of intermetallics. This work opened new paths to compound formation. We discovered many new Si (or Ge)-based compounds with novel structures, bonding and physicochemical properties. We created new insights about the reaction chemistry that is responsible for stabilizing the new materials. We also studied the structural and compositional relationships to understand their properties. We investigated the use of Group-13 metals Al, Ga and In as solvents and have generated a wide variety of new results including several new ternary and quaternary materials with fascinating structures and properties as well as new insights as to how these systems are stabilized in the fluxes. The project focused on reactions of metals from the rare earth element family in combination with transition metals with Si and Ge. For example molten gallium has serves both as a reactive and non-reactive solvent in the preparation and crystallization of intermetallics in the system RE/M/Ga/Ge(Si). Molten indium behaves similarly in that it too is an excellent reaction medium, but it gives compounds that are different from those obtained from gallium. Some of the new phase identified in the aluminide class are complex phases and may be present in many advanced Al-matrix alloys. Such phases play a key role in determining (either beneficially or detrimentally) the mechanical properties of advanced Al-matrix alloys. This project enhanced our basic knowledge of the solid state chemistry

  15. Spectral and polarization properties of a ‘cholesteric liquid crystal—phase plate—metal’ structure

    NASA Astrophysics Data System (ADS)

    Vetrov, S. Ya; Pyatnov, M. V.; Timofeev, I. V.

    2016-01-01

    We investigate the localized surface modes in a structure consisting of the cholesteric liquid crystal layer, a phase plate, and a metal layer. These modes are analogous to the optical Tamm states. The nonreciprocal transmission of polarized light propagating in the forward and backward directions is established. It is demonstrated that the transmission spectrum can be controlled by external fields acting on the cholesteric liquid crystal and by varying the plane of polarization of the incident light.

  16. Solid-phase polarization matrixes for dynamic nuclear polarization from homogeneously distributed radicals in mesostructured hybrid silica materials.

    PubMed

    Gajan, David; Schwarzwälder, Martin; Conley, Matthew P; Grüning, Wolfram R; Rossini, Aaron J; Zagdoun, Alexandre; Lelli, Moreno; Yulikov, Maxim; Jeschke, Gunnar; Sauvée, Claire; Ouari, Olivier; Tordo, Paul; Veyre, Laurent; Lesage, Anne; Thieuleux, Chloé; Emsley, Lyndon; Copéret, Christophe

    2013-10-16

    Mesoporous hybrid silica-organic materials containing homogeneously distributed stable mono- or dinitroxide radicals covalently bound to the silica surface were developed as polarization matrixes for solid-state dynamic nuclear polarization (DNP) NMR experiments. For TEMPO-containing materials impregnated with water or 1,1,2,2-tetrachloroethane, enhancement factors of up to 36 were obtained at ∼100 K and 9.4 T without the need for a glass-forming additive. We show that the homogeneous radical distribution and the subtle balance between the concentration of radical in the material and the fraction of radicals at a sufficient inter-radical distance to promote the cross-effect are the main determinants for the DNP enhancements we obtain. The material, as well as an analogue containing the poorly soluble biradical bTUrea, is used as a polarizing matrix for DNP NMR experiments of solutions containing alanine and pyruvic acid. The analyte is separated from the polarization matrix by simple filtration.

  17. Microstructure Characterization and Wear-Resistant Properties Evaluation of an Intermetallic Composite in Ni-Mo-Si System.

    PubMed

    Huang, Boyuan; Song, Chunyan; Liu, Yang; Gui, Yongliang

    2017-02-04

    Intermetallic compounds have been studied for their potential application as structural wear materials or coatings on engineering steels. In the present work, a newly designed intermetallic composite in a Ni-Mo-Si system was fabricated by arc-melting process with commercially pure metal powders as starting materials. The chemical composition of this intermetallic composite is 45Ni-40Mo-15Si (at %), selected according to the ternary alloy diagram. The microstructure was characterized using optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS), and the wear-resistant properties at room temperature were evaluated under different wear test conditions. Microstructure characterization showed that the composite has a dense and uniform microstructure. XRD results showed that the intermetallic composite is constituted by a binary intermetallic compound NiMo and a ternary Mo₂Ni₃Si metal silicide phase. Wear test results indicated that the intermetallic composite has an excellent wear-resistance at room-temperature, which is attributed to the high hardness and strong atomic bonding of constituent phases NiMo and Mo₂Ni₃Si.

  18. Evidence of high densities and ion outflows in the polar cap during the recovery phase

    SciTech Connect

    Gallagher, D.L.; Menietti, J.D.; Burch, J.L.; Persoon, A.M.; Waite J.H. Jr.; Chappell, C.R.

    1986-03-01

    During the recovery phase of a large storm on October 14, 1981, instruments on board Dynamics Explorer 1 (DE 1) the Retarding Ion Mass Spectrometer (RIMS), the High Altitude Plasma Instrument (HAPI), and the Plasma Wave Instrument (PWI) detected unusually high plasma densities and ion flows in the polar cap. At the time of detection, DE 1 was located at a radial distance of about 3.5 earth radii, a magnetic local time near midnight, and between 70/sup 0/ and 80/sup 0/ invariant latitude. Total plasma density was found to be about 50 cm/sup -3/, an order of magnitude above median polar cap densities at the altitude of observation. In addition, highly collimated flows of hydrogen and oxygen are found flowing through a background hydrogen plasma. The O/sup +/ component of the plasma discussed is not directly identified but is inferred to be O/sup +/ through the combined analysis of data from three instruments. Results of the combined instrument analysis indicate that the detected plasma was composed of outflowing H/sup +/ with a density of 6-10 cm/sup -3/ with a temperature of about 0.15 eV; isotropic H/sup +/ with a density of about 15-20 cm/sup -3/; and outflowing and strongly convecting O/sup +/ with an average density of about 20 cm/sup -3/ and a temperature of about 0.26 eV. The flux of outflowing H/sup +/ and O/sup +/ are both about 10/sup 7/ cm/sup -2/ s/sup -1/. The data indicate that the O/sup +/ detected by HAPI seems to originate in the dayside ionosphere, while the H/sup +/ detected by RIMS has a source in the nightside polar cap.

  19. Photoinduced phase transfer of luminescent quantum dots to polar and aqueous media.

    PubMed

    Palui, Goutam; Avellini, Tommaso; Zhan, Naiqian; Pan, Feng; Gray, David; Alabugin, Igor; Mattoussi, Hedi

    2012-10-03

    We report a new strategy for the photomediated phase transfer of luminescent quantum dots, QDs, and potentially other inorganic nanocrystals, from hydrophobic to polar and hydrophilic media. In particular, we demonstrate that UV-irradiation (λ < 400 nm) promotes the in situ ligand exchange on hydrophobic CdSe QDs with lipoic acid (LA)-based ligands and their facile QD transfer to polar solvents and to buffer media. This convenient method obviates the need to use highly reactive agents for chemical reduction of the dithiolane groups on the ligands. It maintains the optical and spectroscopic properties of the QDs, while providing high photoluminescence yield and robust colloidal stability in various biologically relevant conditions. Furthermore, development of this technique significantly simplifies the preparation and purification of QDs with sensitive functionalities. Application of these QDs to imaging the brain of live mice provides detailed information about the brain vasculature over the period of a few hours. This straightforward approach offers exciting possibilities for expanded functional compatibilities and reaction orthogonality on the surface of inorganic nanocrystals.

  20. Polarized Raman scattering of epitaxial vanadium dioxide films with low-temperature monoclinic phase

    NASA Astrophysics Data System (ADS)

    Shibuya, Keisuke; Sawa, Akihito

    2017-07-01

    A polarized Raman scattering study was carried out on epitaxial VO2 thin films on MgF2(001) and (110) substrates to investigate the Raman symmetry and tensor elements of the phonon modes of the films in a low-temperature monoclinic phase. From the polarization angular dependence of the Raman intensity, we assigned the phonon modes at 137, 194, 310, 340, 499, 612, and 663 cm-1 to Ag symmetry and the phonon modes at 143, 262, 442, 480, 582, and 820 cm-1 to Bg symmetry. The angular-dependence measurements also revealed that two phonon modes with Ag and Bg symmetries are present at about 224 and 393 cm-1, although only a single peak was observed in the Raman spectra at around these wavenumbers. On the basis of the experimental results, we evaluated the Raman tensors of the identified phonon modes. From the Raman tensors, we found that the atomic displacements of the 194 and 340 cm-1 phonon modes are approximately perpendicular and parallel, respectively, to the V-V dimer direction. This is consistent with a previous theoretical prediction, i.e., these modes are attributable to the tilting motion and the stretching vibration of the V-V dimers, respectively.

  1. Broadband polarization-independent wide-angle and reconfigurable phase transition hybrid metamaterial absorber

    NASA Astrophysics Data System (ADS)

    Yahiaoui, Riad; Ouslimani, Habiba Hafdallah

    2017-09-01

    We report the simulation, fabrication, and experimental characterization of a single-layer broadband, polarization-insensitive and wide-angle near perfect metamaterial absorber (MA) in the microwave regime. The topology of the resonators is chosen in such a way that is capable of supporting simultaneously multiple plasmon resonances at adjacent frequencies, which lead to a broadband operation of the MA. Absorption larger than 80% at normal incidence covering a broad frequency range (between 7.4 GHz and 10.4 GHz) is demonstrated experimentally and through numerical simulations. Furthermore, the performance of the metamaterial absorber is kept constant up to an incident angle of 30°, for both TE and TM-polarizations. In addition, a hybrid model of the MA is proposed and implemented numerically in order to dynamically tune the absorption window. The hybrid MA is controlled by incorporating vanadium dioxide (VO2) temperature-driven metal-insulator phase transition material, which enables the transition from broadband (80% absorption and 3 GHz bandwidth) to narrowband (80% absorption and 0.7 GHz bandwidth) absorption window. Our proposed single-layer MA offers substantial advantages due to its low-cost and simplicity of fabrication. The results are very promising, suggesting a potential use of the MA in wide variety of applications including solar energy harvesting, biosensing, imaging, and stealth technology.

  2. Polarization effects on the electric properties of urea and thiourea molecules in solid phase

    SciTech Connect

    Santos, O. L.; Fonseca, T. L. Sabino, J. R.; Georg, H. C.; Castro, M. A.

    2015-12-21

    We present theoretical results for the dipole moment, linear polarizability, and first hyperpolarizability of the urea and thiourea molecules in solid phase. The in-crystal electric properties were determined by applying a supermolecule approach in combination with an iterative electrostatic scheme, in which the surrounding molecules are represented by point charges. It is found for both urea and thiourea molecules that the influence of the polarization effects is mild for the linear polarizability, but it is marked for the dipole moment and first hyperpolarizability. The replacement of oxygen atoms by sulfur atoms increases, in general, the electric responses. Our second-order Møller–Plesset perturbation theory based iterative scheme predicts for the in-crystal dipole moment of urea and thiourea the values of 7.54 and 9.19 D which are, respectively, increased by 61% and 58%, in comparison with the corresponding isolated values. The result for urea is in agreement with the available experimental result of 6.56 D. In addition, we present an estimate of macroscopic quantities considering explicit unit cells of urea and thiourea crystals including environment polarization effects. These supermolecule calculations take into account partially the exchange and dispersion effects. The results illustrate the role played by the electrostatic interactions on the static second-order nonlinear susceptibility of the urea crystal.

  3. Analysis of a shearography device using a Wollaston prism and polarization phase shifting

    NASA Astrophysics Data System (ADS)

    Sanchez, E.; Benedet, M. E.; Willemann, D. P.; Fantin, A. V.; Albertazzi, A. G.

    2016-08-01

    Speckle shear interferometry, or shearography, has been more and more frequently used in the industry for in-field nondestructive inspections of flaws in composite materials used in the aerospace and oil and gas industry. Nowadays new applications has emerged demanding the ability to operate in harsher environments. Bringing interferometric systems to harsh environments is not an easy task since they are very sensitive to many harsh environmental factors. Due to the quasi-equal-path property, shearography is an intrinsically robust interferometric technique that has been successfully used in the field, but there are still limits to overcome. Mechanical vibrations are probably the most challenging factor to cope in the field measurements. This work presents a potentially robust shear interferometer configuration. It uses a Wollaston prism as the shearing element rather than a traditional Michelson interferometer and polarizers to achieve the phase shift. The use of the Wollaston prism makes the optical setup more compact and robust, given that a rotating polarizer is the only movable part of the interferometer.

  4. Direct acceleration of electrons by a circular polarized laser pulse with phase modulation

    NASA Astrophysics Data System (ADS)

    Zhu, Lun-Wu; Sheng, Zheng-Mao; Yu, M. Y.

    2013-11-01

    Electron acceleration by transversely echelon phase-modulated (EPM) circularly polarized (CP) intense laser pulse is investigated. Solution of the relativistic electron equations of motion shows that the CP EPM light wave structure can disrupt the harmonic response of a trapped electron not only in the transverse direction but also in the direction of laser propagation. In each laser cycle, there can be a net gain in the electron's transverse momentum, which is promptly converted into the forward direction by the Lorentz force. As a result, the electron can be trapped and accelerated in the favorable phase of the laser for a rather long time. Its momentum gain then accumulates and can eventually reach high levels. It is also found that with the CP EPM laser, the net acceleration of the electron is not sensitive to its initial position and velocity relative to the phase of the laser fields, so that such a laser can also be useful for accelerating thermal electron bunches to high energies.

  5. Direct acceleration of electrons by a circular polarized laser pulse with phase modulation

    SciTech Connect

    Zhu, Lun-Wu; Sheng, Zheng-Mao; Yu, M. Y.

    2013-11-15

    Electron acceleration by transversely echelon phase-modulated (EPM) circularly polarized (CP) intense laser pulse is investigated. Solution of the relativistic electron equations of motion shows that the CP EPM light wave structure can disrupt the harmonic response of a trapped electron not only in the transverse direction but also in the direction of laser propagation. In each laser cycle, there can be a net gain in the electron's transverse momentum, which is promptly converted into the forward direction by the Lorentz force. As a result, the electron can be trapped and accelerated in the favorable phase of the laser for a rather long time. Its momentum gain then accumulates and can eventually reach high levels. It is also found that with the CP EPM laser, the net acceleration of the electron is not sensitive to its initial position and velocity relative to the phase of the laser fields, so that such a laser can also be useful for accelerating thermal electron bunches to high energies.

  6. Anthracenyl polar embedded stationary phases with enhanced aromatic selectivity. Part II: A density functional theory study.

    PubMed

    Mignot, Mélanie; Schammé, Benjamin; Tognetti, Vincent; Joubert, Laurent; Cardinael, Pascal; Peulon-Agasse, Valérie

    2017-09-11

    New polar embedded aromatic stationary phases (mono- and trifunctional versions) that contain an amide-embedded group coupled with a tricyclic aromatic moiety were developed for chromatographic applications and described in the first paper of this series. These phases offered better separation performance for PAHs than for alkylbenzene homologues, and an enhanced ability to differentiate aromatic planarity to aromatic tridimensional conformation, especially for the trifunctional version and when using methanol instead of acetonitrile. In this second paper, a density functional theory study of the retention process is reported. In particular, it was shown that the selection of the suitable computational protocol allowed for describing rigorously the interactions that could take place, the solvent effects, and the structural changes for the monofunctional and the trifunctional versions. For the first time, the experimental data coupled with these DFT results provided a better understanding of the interaction mechanisms and highlighted the importance of the multimodal character of the designed stationary phases: alkyl spacers for interactions with hydrophobic solutes, amide embedded groups for dipole-dipole and hydrogen-bond interactions, and aromatic terminal groups for π-π interactions. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Room-temperature electric polarization induced by phase separation in multiferroic GdMn2O5

    NASA Astrophysics Data System (ADS)

    Khannanov, B. Kh.; Sanina, V. A.; Golovenchits, E. I.; Scheglov, M. P.

    2016-02-01

    It was generally accepted until recently that multiferroics RMn2O5 crystallized in the centrosymmetric space group Pbam and ferroelectricity in them could exist only at low temperatures due to the magnetic exchange striction. Recent comprehensive structural studies [V. Baledent et al., Phys. Rev. Lett. 114, 117601 (2015)] have shown that the actual symmetry of RMn2O5 at room temperature is a noncentrosymmetric monoclinic space group Pm, which allows room temperature ferroelectricity to exist. However, such a polarization has not yet been found. Our electric polarization loop studies of GdMn2O5 have revealed that a polarization does exist up to room temperature. This polarization occurs mainly in restricted polar domains that arise in the initial GdMn2O5 matrix due to phase separation and charge carrier self-organization. These domains are selfconsistent with the matrix, which leads to the noncentrosymmetricity of the entire crystal. The polarization is controlled by a magnetic field, thereby demonstrating the presence of magnetoelectric coupling. The lowtemperature ferroelectricity enhances the restricted polar domain polarization along the b axis.

  8. Formation of mixed-phase particles during the freezing of polar stratospheric ice clouds.

    PubMed

    Bogdan, Anatoli; Molina, Mario J; Tenhu, Heikki; Mayer, Erwin; Loerting, Thomas

    2010-03-01

    Polar stratospheric clouds (PSCs) are extremely efficient at catalysing the transformation of photostable chlorine reservoirs into photolabile species, which are actively involved in springtime ozone-depletion events. Why PSCs are such efficient catalysts, however, is not well understood. Here, we investigate the freezing behaviour of ternary HNO₃-H₂SO₄-H₂O droplets of micrometric size, which form type II PSC ice particles. We show that on freezing, a phase separation into pure ice and a residual solution coating occurs; this coating does not freeze but transforms into glass below ∼150 K. We find that the coating, which is thicker around young ice crystals, can still be approximately 30 nm around older ice crystals of diameter about 10 µm. These results affect our understanding of PSC microphysics and chemistry and suggest that chlorine-activation reactions are better studied on supercooled HNO₃-H₂SO₄-H₂O solutions rather than on a pure ice surface.

  9. The structure and phase of cloud tops as observed by polarization lidar

    NASA Technical Reports Server (NTRS)

    Spinhirne, J. D.; Hansen, M. Z.; Simpson, J.

    1983-01-01

    High-resolution observations of the structure of cloud tops have been obtained with polarization lidar operated from a high altitude aircraft. Case studies of measurements acquired from cumuliform cloud systems are presented, two from September 1979 observations in the area of Florida and adjacent waters and a third during the May 1981 CCOPE experiment in southeast Montana. Accurate cloud top height structure and relative density of hydrometers are obtained from the lidar return signal intensity. Correlation between the signal return intensity and active updrafts was noted. Thin cirrus overlying developing turrets was observed in some cases. Typical values of the observed backscatter cross section were 0.1-5 (km/sr) for cumulonimbus tops. The depolarization ratio of the lidar signals was a function of the thermodynamic phase of cloud top areas. An increase of the cloud top depolarization with decreasing temperature was found for temperatures above and below -40 C.

  10. Angular phase shift in polarization-angle dependence of microwave-induced magnetoresistance oscillations

    NASA Astrophysics Data System (ADS)

    Liu, Han-Chun; Samaraweera, Rasanga L.; Mani, R. G.; Reichl, C.; Wegscheider, W.

    2016-12-01

    We examine the microwave frequency (f ) variation of the angular phase shift, θ0, observed in the polarization-angle dependence of microwave-induced magnetoresistance oscillations in a high-mobility GaAs/AlGaAs two-dimensional electron system. By fitting the diagonal resistance Rx x versus θ plots to an empirical cosine square law, we extract θ0 and trace its quasicontinuous variation with f . The results suggest that the overall average of θ0 extracted from Hall bar device sections with length-to-width ratios of L /W =1 and 2 is the same. We compare the observations with expectations arising from the "ponderomotive force" theory for microwave radiation-induced transport phenomena.

  11. Measurements of antenna polar diagrams and efficiencies using a phase-switched interferometer

    NASA Technical Reports Server (NTRS)

    Vincent, R. A.; Candy, B.; Briggs, B. H.

    1986-01-01

    It is desirable to know antenna polar patterns and efficiencies accurately. In the past, calibration measurements have been made using balloons and aircraft and more recently satellites. These techniques are usually very expensive. It is shown that under certain circumstances it is possible to use a simpler and inexpensive technique by connecting together the antenna under test with another antenna to form a phase switched interferometer as first described by Ryle (1952). The technique does require a suitable radio source which gives measurable powers when using small antennas and since dipoles have broad patterns, radio sources with similar right ascensions but different declinations to the primary source can be a problem. These problems can partly be overcome by filtering the interference pattern.

  12. Hydrogen in polar intermetallics: Syntheses and structures of the ternary Ca5Bi3D0.93, Yb5Bi3Hx, and Sm5Bi3H~1 by powder neutron or single crystal X-ray diffraction

    SciTech Connect

    Leon-Escamilla, E. Alejandro; Dervenagas, Panagiotis; Stasis, Constantine; Corbett, John D.

    2010-01-01

    The syntheses of the title compounds are described in detail. Structural characterizations from refinements of single crystal X-ray diffraction data for Yb{sub 5}Bi{sub 3}H{sub x} and Sm{sub 5}Bi{sub 3}H{sub 1} and of powder neutron diffraction data for Ca{sub 5}Bi{sub 3}D{sub 0.93(3)} are reported. These confirm that all three crystallize with the heavy atom structure type of {beta}-Yb{sub 5}Sb{sub 3}, and the third gives the first proof that the deuterium lies in the center of nominal calcium tetrahedra, isostructural with the Ca{sub 5}Sb{sub 3}F-type structure. These Ca and Yb phases are particularly stable with respect to dissociation to Mn{sub 5}Si{sub 3}-type product plus H{sub 2}. Some contradictions in the literature regarding Yb{sub 5}Sb{sub 3} and Yb{sub 5}Sb{sub 3}H{sub x} phases are considered in terms of adventitious hydrogen impurities that are generated during reactions in fused silica containers at elevated temperatures.

  13. Chemical effect on diffusion in intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Chen, Yi-Ting

    With the trend of big data and the Internet of things, we live in a world full of personal electronic devices and small electronic devices. In order to make the devices more powerful, advanced electronic packaging such as wafer level packaging or 3D IC packaging play an important role. Furthermore, ?-bumps, which connect silicon dies together with dimension less than 10 ?m, are crucial parts in advanced packaging. Owing to the dimension of ?-bumps, they transform into intermetallic compound from tin based solder after the liquid state bonding process. Moreover, many new reliability issues will occur in electronic packaging when the bonding materials change; in this case, we no longer have tin based solder joint, instead, we have intermetallic compound ?-bumps. Most of the potential reliability issues in intermetallic compounds are caused by the chemical reactions driven by atomic diffusion in the material; thus, to know the diffusivities of atoms inside a material is significant and can help us to further analyze the reliability issues. However, we are lacking these kinds of data in intermetallic compound because there are some problems if used traditional Darken's analysis. Therefore, we considered Wagner diffusivity in our system to solve the problems and applied the concept of chemical effect on diffusion by taking the advantage that large amount of energy will release when compounds formed. Moreover, by inventing the holes markers made by Focus ion beam (FIB), we can conduct the diffusion experiment and obtain the tracer diffusivities of atoms inside the intermetallic compound. We applied the technique on Ni3Sn4 and Cu3Sn, which are two of the most common materials in electronic packaging, and the tracer diffusivities are measured under several different temperatures; moreover, microstructure of the intermetallic compounds are investigated to ensure the diffusion environment. Additionally, the detail diffusion mechanism was also discussed in aspect of diffusion

  14. Development of intermetallic coatings for fusion power applications

    SciTech Connect

    Park, J.H.; Domenico, T.; Dragel, G.; Clark, R.

    1994-03-01

    In the design of liquid-metal cooling systems, corrosion resistance of structural materials and magnetohydrodynamic (MHD) force and its subsequent influence on thermal hydraulics and corrosion are major concerns. The objective of this study is to develop stable corrosion-resistant electrical insulator coatings at the liquid-metal/structural-material interface, with emphasis on electrically insulating coatings that prevent adverse MHD-generated currents from passing through the structural walls. Vanadium and V-base alloys are potential materials for structural applications in a fusion reactor. Insulator coatings inside the tubing are required when the system is cooled by liquid metals. Various intermetallic films were produced on V, V-t, and V-20 Ti, V-5Cr-t and V-15Cr-t, and Ti, and Types 304 and 316 stainless steel. The intermetallic layers were developed by exposure of the materials to liquid lithium of 3--5 at.% and containing dissolved metallic solutes at temperatures of 416--880{degrees}C. Subsequently, electrical insulator coatings were produced by reaction of the reactive layers with dissolved nitrogen in liquid lithium or by air oxidation under controlled conditions at 600--1000{degrees}C. These reactions converted the intermetallic layers to electrically insulating oxide/nitride or oxy-nitride layers. This coating method could be applied to a commercial product. The liquid metal can be used over and over because only the solutes are consumed within the liquid metal. The technique can be applied to various shapes because the coating is formed by liquid-phase reaction. This paper will discuss initial results on the nature of the coatings and their in-situ electrical resistivity characteristics in liquid lithium at high temperatures.

  15. Polar phase transitions and physical properties in fresnoite A2TiSi2O8 (A= Ba, Sr) by first principles calculations

    NASA Astrophysics Data System (ADS)

    Song, Nayoung; Momida, Hiroyoshi; Oguchi, Tamio; Kim, Bog G.

    2016-10-01

    Polar phase transitions of fresnoites, Ba2TiSi2O8 (BTS) and Sr2TiSi2O8 (STS) have been comparatively analyzed by the first principles calculations. We show that both BTS and STS have a polar structure with the space group P4bm as a ground state, and there is a fictitious phase transition in the tetragonal space group from the nonpolar P4/mbm meta-stable phase to the polar P4bm phase. From the analyses of the two atomic structures, we find that a noticeable issue in the phase transition is bond length changes of Si-O and Ti-O which break the inversion symmetry, resulting that one of vertices in the edge-shared Si-O and Ti-O polyhedron is detached in the polar phase. The structural phase transition between the polar and the nonpolar states are discussed in terms of electronic structures and structural symmetry mode analyses. We evaluate the size of spontaneous polarizations of BTS and STS in the polar P4bm phases, and the correlation analysis shows significant contributions of the detached polyhedrons to the strong polar property. We also show second harmonic generation susceptibilities of BTS and STS as a candidate for second-order nonlinear optics materials. Our quantitative studies can provide full understandings of atomic and electronic mechanisms of their polar phase and nonlinear optical properties.

  16. Thermal stability of sputtered intermetallic Al-Au coatings

    SciTech Connect

    Moser, M.; Mayrhofer, P. H.; Ross, I. M.; Rainforth, W. M.

    2007-09-15

    Recently, the authors have shown that single-phase Al{sub 2}Au coatings, prepared by unbalanced magnetron sputtering, exhibit a dense columnar structure and highest hardness and indentation moduli of 8 and 144 GPa, respectively, within the Al-Au films investigated. This study focuses on the thermal stability of Al{sub 2}Au with respect to films containing more Al and Au having Al/Au at. % ratios of 4.32 and 1.85, respectively. Single-phase Al{sub 2}Au has the highest onset temperature for recovery of 475 deg. C and recrystallization of 575 deg. C. Upon annealing Au- and Al-rich films, their stresses deviate from the linear thermoelastic behavior at temperatures (T) above 200 and 450 deg. C, respectively, due to pores and metallic phases present. Metastable Au within the as-deposited Au-rich film is consumed by the growing intermetallic AlAu and AlAu{sub 2} phases at T{>=}450 deg. C, which themselves melt at {approx}625 deg. C. Due to nanometer scale segregations of Al, encapsulated by Al{sub 2}Au in Al-rich coatings, their melting point is reduced by {approx}85 deg. C to 575 deg. C. Dynamic thermal analyses up to 1100 deg. C in synthetic air reveal the single-phase Al{sub 2}Au films with a superior thermal stability and only negligible oxidation. At 750 deg. C, the mass gain is {approx}1.5 mg/cm{sup 2} after 50 h isothermal exposure. Based on the investigations, the authors can conclude that single-phase intermetallic Al{sub 2}Au films have a high potential for oxidation protection of sensitive materials.

  17. Phonon coupling to dynamic short-range polar order in a relaxor ferroelectric near the morphotropic phase boundary

    DOE PAGES

    John A. Schneeloch; Xu, Zhijun; Winn, B.; ...

    2015-12-28

    We report neutron inelastic scattering experiments on single-crystal PbMg1/3Nb2/3O3 doped with 32% PbTiO3, a relaxor ferroelectric that lies close to the morphotropic phase boundary. When cooled under an electric field E∥ [001] into tetragonal and monoclinic phases, the scattering cross section from transverse acoustic (TA) phonons polarized parallel to E weakens and shifts to higher energy relative to that under zero-field-cooled conditions. Likewise, the scattering cross section from transverse optic (TO) phonons polarized parallel to E weakens for energy transfers 4 ≤ ℏω ≤ 9 meV. However, TA and TO phonons polarized perpendicular to E show no change. This anisotropicmore » field response is similar to that of the diffuse scattering cross section, which, as previously reported, is suppressed when polarized parallel to E but not when polarized perpendicular to E. Lastly, our findings suggest that the lattice dynamics and dynamic short-range polar correlations that give rise to the diffuse scattering are coupled.« less

  18. Phonon coupling to dynamic short-range polar order in a relaxor ferroelectric near the morphotropic phase boundary

    SciTech Connect

    John A. Schneeloch; Xu, Zhijun; Winn, B.; Stock, C.; Gehring, P. M.; Birgeneau, R. J.; Xu, Guangyong

    2015-12-28

    We report neutron inelastic scattering experiments on single-crystal PbMg1/3Nb2/3O3 doped with 32% PbTiO3, a relaxor ferroelectric that lies close to the morphotropic phase boundary. When cooled under an electric field E∥ [001] into tetragonal and monoclinic phases, the scattering cross section from transverse acoustic (TA) phonons polarized parallel to E weakens and shifts to higher energy relative to that under zero-field-cooled conditions. Likewise, the scattering cross section from transverse optic (TO) phonons polarized parallel to E weakens for energy transfers 4 ≤ ℏω ≤ 9 meV. However, TA and TO phonons polarized perpendicular to E show no change. This anisotropic field response is similar to that of the diffuse scattering cross section, which, as previously reported, is suppressed when polarized parallel to E but not when polarized perpendicular to E. Lastly, our findings suggest that the lattice dynamics and dynamic short-range polar correlations that give rise to the diffuse scattering are coupled.

  19. Phonon coupling to dynamic short-range polar order in a relaxor ferroelectric near the morphotropic phase boundary

    NASA Astrophysics Data System (ADS)

    Schneeloch, John A.; Xu, Zhijun; Winn, B.; Stock, C.; Gehring, P. M.; Birgeneau, R. J.; Xu, Guangyong

    2015-12-01

    We report neutron inelastic scattering experiments on single-crystal PbMg1 /3Nb2 /3O3 doped with 32% PbTiO3, a relaxor ferroelectric that lies close to the morphotropic phase boundary. When cooled under an electric field E ∥ [001] into tetragonal and monoclinic phases, the scattering cross section from transverse acoustic (TA) phonons polarized parallel to E weakens and shifts to higher energy relative to that under zero-field-cooled conditions. Likewise, the scattering cross section from transverse optic (TO) phonons polarized parallel to E weakens for energy transfers 4 ≤ℏ ω ≤9 meV. However, TA and TO phonons polarized perpendicular to E show no change. This anisotropic field response is similar to that of the diffuse scattering cross section, which, as previously reported, is suppressed when polarized parallel to E but not when polarized perpendicular to E . Our findings suggest that the lattice dynamics and dynamic short-range polar correlations that give rise to the diffuse scattering are coupled.

  20. Chemical bonding in equiatomic cerium intermetallics - The case of CeMgSn, CePdSn, and CeMgPb

    NASA Astrophysics Data System (ADS)

    Matar, Samir F.; Pöttgen, Rainer

    2015-10-01

    The electronic and magnetic structures and the properties of chemical bonding in isopointal CeMgSn and CePdSn (both phases belong to the family of TiNiSi related intermetallics, space group Pnma) and CeMgPb belonging to the family of CeScSi intermetallics, space group I4/mmm, have been investigated within the density functional theory (DFT). The charge analyses indicate negatively charged tin and lead leading to assign the compounds as stannides and plumbides, as also illustrated by the mapping of the electron localization function ELF. Calculations within spin-degenerate non-magnetic spin-polarized ferro- (SP-F) and SP-antiferromagnetic configurations led to assign a major role of Ce 4f states in the onset of ordered moments within SP-AF ground states from energy differences. Chemical bonding analyses from crystal orbital overlap populations revealed the strongest interactions for Ce-Sn in CeMgSn, Ce-Pb in CeMgPb, and Ce-Pd in CePdSn.

  1. Experimental investigations of phase error caused by electrode impedance in laboratory spectral induced polarization (SIP) measurements

    NASA Astrophysics Data System (ADS)

    Wang, C.; Ntarlagiannis, D.; Slater, L. D.; Seleznev, N. V.

    2016-12-01

    High frequency phase errors that plague spectral induced polarization (SIP) measurements are partly due to the effects of electrode impedance. Others have recently proposed an experimental correction procedure based on a simplified electrical model of the system under test. The application of the method is limited due to the dependence of the correction on the input capacitance (Ci) of SIP instruments. With this study, we evaluated the correction procedure with a new experimental set up, confirming the improved phase accuracy at high frequency. In addition, we propose an experimental method to calculate Ci based on the experimental set up used for each measurement. The method utilizes well characterized fluids, with known electrical properties, for the accurate estimation of Ci. Following this new procedure, Ci of the used set up was determined to be 6.30 ± 0.29 pF. High frequency errors were further suppressed when the calculated, versus the estimated, Ci was used. Correction results suggest that Ci is weakly dependent on sample properties. The correction procedure with the experimental determination of Ci significantly improves the quality of SIP measurements on unconsolidated sediments and rock cores.

  2. Polarization rotation of light propagating through a medium with efficient four-wave mixing and cross-phase modulation

    NASA Astrophysics Data System (ADS)

    Sahoo, Sushree S.; Bhowmick, Arup; Mohapatra, Ashok K.

    2017-03-01

    We have studied the rotation of an elliptically polarized light propagating through thermal rubidium vapor with efficient four-wave mixing (FWM) and cross-phase modulation (XPM). These nonlinear processes are enhanced by Zeeman coherence within the degenerate sub-levels of the two-level atomic system. The elliptically polarized light with small ellipticity is considered as the superposition of a strong-linearly-polarized pump beam and a weak-orthogonal-polarized probe beam. The interference of the probe and the newly generated light field due to degenerate FWM and their gain in the medium due to a large XPM induced by the pump beam leads to the rotation of the elliptical polarized light. A theoretical analysis of the probe propagation through the nonlinear medium was used to explain the experimental observation and the fitting of the experimental data gives the estimates of the third-order non-linear susceptibilities associated with FWM and XPM. Our study can provide useful parameters for the generation of efficient squeezed vacuum states and squeezed polarization states of light. Furthermore our study finds application in controlling the diffraction of a linearly-polarized light beam traversing the medium.

  3. Finite-Difference Time-Domain Analysis of Polarization-Dependent Transmission in Cholesteric Blue Phase II

    NASA Astrophysics Data System (ADS)

    Ojima, Masayoshi; Ogawa, Yasuhiro; Ozaki, Ryotaro; Moritake, Hiroshi; Yoshida, Hiroyuki; Fujii, Akihiko; Ozaki, Masanori

    2010-03-01

    The photonic band structure and circular-polarization dependence of the transmission properties of cholesteric blue phase II were analyzed using a finite-difference time-domain method based on a double-twist cylinder model. The polarization dependence of the calculated band structure was not recognized in the same manner as that in previous studies. However, it can be clearly observed that the calculated transmission spectra depend on the circular polarization; this result agrees well with experimental results. On the basis of the circular-polarization dependence of the transmission spectra in the case of a thick sample, it can be indicated that a total reflection band appears in the selective reflection band.

  4. The μ3 model of acids and bases: extending the Lewis theory to intermetallics.

    PubMed

    Stacey, Timothy E; Fredrickson, Daniel C

    2012-04-02

    A central challenge in the design of new metallic materials is the elucidation of the chemical factors underlying the structures of intermetallic compounds. Analogies to molecular bonding phenomena, such as the Zintl concept, have proven very productive in approaching this goal. In this Article, we extend a foundational concept of molecular chemistry to intermetallics: the Lewis theory of acids and bases. The connection is developed through the method of moments, as applied to DFT-calibrated Hückel calculations. We begin by illustrating that the third and fourth moments (μ(3) and μ(4)) of the electronic density of states (DOS) distribution tune the properties of a pseudogap. μ(3) controls the balance of states above and below the DOS minimum, with μ(4) then determining the minimum's depth. In this way, μ(3) predicts an ideal occupancy for the DOS distribution. The μ(3)-ideal electron count is used to forge a link between the reactivity of transition metals toward intermetallic phase formation, and that of Lewis acids and bases toward adduct formation. This is accomplished through a moments-based definition of acidity which classifies systems that are electron-poor relative to the μ(3)-ideal as μ(3)-acidic, and those that are electron-rich as μ(3)-basic. The reaction of μ(3) acids and bases, whether in the formation of a Lewis acid/base adduct or an intermetallic phase, tends to neutralize the μ(3) acidity or basicity of the reactants. This μ(3)-neutralization is traced to the influence of electronegativity differences at heteroatomic contacts on the projected DOS curves of the atoms involved. The role of μ(3)-acid/base interactions in intermetallic phases is demonstrated through the examination of 23 binary phases forming between 3d metals, the stability range of the CsCl type, and structural trends within the Ti-Ni system.

  5. Heats of formation in transition intermetallic alloys

    SciTech Connect

    Pasturel, A.; Colinet, C.; Hicter, P.

    1984-07-01

    The heats of formation in intermetallic alloys are calculated within a tight-binding scheme for the d band. The difference in bandwidth between the metals and the difference between their energy levels are two dominant effects in determination of the formation energy. The influence of charge transfer on alloy formation is studied.

  6. Crystal structure analysis of intermetallic compounds

    NASA Technical Reports Server (NTRS)

    Conner, R. A., Jr.; Downey, J. W.; Dwight, A. E.

    1968-01-01

    Study concerns crystal structures and lattice parameters for a number of new intermetallic compounds. Crystal structure data have been collected on equiatomic compounds, formed between an element of the Sc, Ti, V, or Cr group and an element of the Co or Ni group. The data, obtained by conventional methods, are presented in an easily usable tabular form.

  7. Surfaces of Intermetallics: Quasicrystals and Beyond

    SciTech Connect

    Yuen, Chad

    2012-01-01

    The goal of this work is to characterize surfaces of intermetallics, including quasicrystals. In this work, surface characterization is primarily focused on composition and structure using X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM) performed under ultrahigh vacuum (UHV) conditions.

  8. Global Positioning System phase fluctuations and ultraviolet images from the Polar satellite

    NASA Astrophysics Data System (ADS)

    Aarons, J.; Lin, B.; Mendillo, M.; Liou, K.; Codrescu, M.

    2000-03-01

    In a study designed to determine the temporal development of ionospheric irregularities in the auroral region in magnetic storm periods, different types of simultaneous observations were compared for the storms of January 10, April 10-11, and May 15, 1997. The data sets consisted of ultraviolet images (UVI) from the Polar satellite, phase fluctuations and total electron content (TEC) from Global Positioning Systems (GPS) recordings at a large number of sites, magnetometer observations and hemispheric power precipitation. The large-scale global or macroscale picture of the magnetic storm showed the importance of universal time in the development of irregularities. The hemispheric total power picture and the global indices such as Kp show this macroscale picture of the entire storm period. However, individual sites show differences in localized magnetic field variations and the development of irregularities; this we term the microscale. The storms of January 10 and May 15 show the importance of local magnetic time and local magnetic variations at the sites, while the storm of April 10-11 was dominated by the UT storm development. During the intense activity of the storms, total electron content shows minute-by-minute increases with the satellite moving to positions 6 km apart in the minute. The structured precipitation either directly produces irregularities or indirectly sets instability conditions for irregularity development in the auroral region. Good correlation was established for the three storms between UVI intensity and phase fluctuation development. The UVI Lyman-Birge-Hopfield-long (170 nm) emission is sensitive to 100-200 km precipitation. Phase fluctuation development undoubtedly arises from perturbations in the F region as well. Topside and bottomside soundings have shown the high occurrence of spread-F in the auroral region. The comparison of the data sets from these storms and from other studies indicates that the creation of irregularities develops

  9. Polar phase transitions in heteroepitaxial stabilized La0.5Y0.5AlO3 thin films

    NASA Astrophysics Data System (ADS)

    Liu, Shenghua; Zhang, Chunfeng; Zhu, Mengya; He, Qian; Chakhalian, Jak; Liu, Xiaoran; Borisevich, Albina; Wang, Xiaoyong; Xiao, Min

    2017-10-01

    We report on the fabrication of epitaxial La0.5Y0.5AlO3 ultrathin films on (001) LaAlO3 substrates. Structural characterizations by scanning transmission electron microscopy and x-ray diffraction confirm the high quality of the film with a ‑ b + c ‑ AlO6 octahedral tilt pattern. Unlike either of the nonpolar parent compound, LaAlO3 and YAlO3, second harmonic generation measurements on the thin films suggest a nonpolar–polar phase transition at T c near 500 K, and a polar–polar phase transition at T a near 160 K. By fitting the angular dependence of the second harmonic intensities, we further propose that the two polar structures can be assigned to the Pmc2 1 and Pmn2 1 space group, while the high temperature nonpolar structure belongs to the Pbnm space group.

  10. Surface morphology and optical properties of Eu3+ ions incorporated into N-polar GaN grown by organometallic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Fuji, Ryoken; Mitchell, Brandon; Koizumi, Atsushi; Inaba, Tomohiro; Fujiwara, Yasufumi

    2017-06-01

    N-polar GaN doped with Eu was grown by organometallic vapor phase epitaxy. Investigation of the surface morphology and photoluminescence properties indicated that Eu doping into N-polar GaN is more difficult than it is for Ga-polar GaN. The origin of this difficulty was also explored.

  11. Helicity-selective phase-matching and quasi-phase matching of circularly polarized high-order harmonics: towards chiral attosecond pulses

    NASA Astrophysics Data System (ADS)

    Kfir, Ofer; Grychtol, Patrik; Turgut, Emrah; Knut, Ronny; Zusin, Dmitriy; Fleischer, Avner; Bordo, Eliyahu; Fan, Tingting; Popmintchev, Dimitar; Popmintchev, Tenio; Kapteyn, Henry; Murnane, Margaret; Cohen, Oren

    2016-06-01

    Phase matching of circularly polarized high-order harmonics driven by counter-rotating bi-chromatic lasers was recently predicted theoretically and demonstrated experimentally. In that work, phase matching was analyzed by assuming that the total energy, spin angular momentum and linear momentum of the photons participating in the process are conserved. Here we propose a new perspective on phase matching of circularly polarized high harmonics. We derive an extended phase matching condition by requiring a new propagation matching condition between the classical vectorial bi-chromatic laser pump and harmonics fields. This allows us to include the influence of the laser pulse envelopes on phase matching. We find that the helicity dependent phase matching facilitates generation of high harmonics beams with a high degree of chirality. Indeed, we present an experimentally measured chiral spectrum that can support a train of attosecond pulses with a high degree of circular polarization. Moreover, while the degree of circularity of the most intense pulse approaches unity, all other pulses exhibit reduced circularity. This feature suggests the possibility of using a train of attosecond pulses as an isolated attosecond probe for chiral-sensitive experiments.

  12. Estimation of age based on tooth cementum annulations: A comparative study using light, polarized, and phase contrast microscopy.

    PubMed

    Kaur, Prabhpreet; Astekar, Madhusudan; Singh, Jappreet; Arora, Karandeep Singh; Bhalla, Gagandeep

    2015-01-01

    The identification of living or deceased persons using unique traits and characteristics of the teeth and jaws is a cornerstone of forensic science. Teeth have been used to estimate age both in the young and old, as well as in the living and dead. Gradual structural changes in teeth throughout life are the basis for age estimation. Tooth cementum annulation (TCA) is a microscopic method for the determination of an individual's age based on the analysis of incremental lines of cementum. To compare ages estimated using incremental lines of cementum as visualized by bright field microscopy, polarized microscopy, and phase contrast microscopy with the actual age of subject and to determine accuracy and feasibility of the method used. Cementum annulations of 60 permanent teeth were analyzed after longitudinal ground sections were made in the mesiodistal plane. The incremental lines were counted manually using a light, polarized and phase contrast microscopy. Ages were estimated and then compared with the actual age of individual. Analysis of variance (ANOVA), Student's t-test, the Pearson product-moment corre (PPMCC) and regression analysis were performed. PPMCC value r = 0.347, 0.542 and 0.989 were obtained using light, polarized and phase contrast microscopy methods respectively. It was concluded that incremental lines of cementum were most clearly visible under a phase contrast microscope, followed by a polarized microscope, and then a light microscope when used for age estimation.

  13. Polarization imaging of a 3D object by use of on-axis phase-shifting digital holography.

    PubMed

    Nomura, Takanori; Javidi, Bahram; Murata, Shinji; Nitanai, Eiji; Numata, Takuhisa

    2007-03-01

    A polarimetric imaging method of a 3D object by use of on-axis phase-shifting digital holography is presented. The polarimetric image results from a combination of two kinds of holographic imaging using orthogonal polarized reference waves. Experimental demonstration of a 3D polarimetric imaging is presented.

  14. Compensation algorithm for the phase-shift error of polarization-based parallel two-step phase-shifting digital holography.

    PubMed

    Tahara, Tatsuki; Ito, Kenichi; Kakue, Takashi; Fujii, Motofumi; Shimozato, Yuki; Awatsuji, Yasuhiro; Nishio, Kenzo; Ura, Shogo; Kubota, Toshihiro; Matoba, Osamu

    2011-03-01

    We propose an algorithm for compensating the phase-shift error of polarization-based parallel two-step phase-shifting digital holography, which is a technique for recording a spatial two-step phase-shifted hologram. Although a polarization-based system of the technique has been experimentally demonstrated, there had been the problem that the phase difference of two phase-shifted holograms had been changed by the extinction ratio of the micropolarizer array attached to the image sensor used in the system. To improve the performance of the system, we established and formulated an algorithm for compensating the phase-shift error. Accurate spatial phase-shifting interferometry in the system can be conducted by the algorithm regardless of phase-shift error due to the extinction ratio. By the numerical simulation, the proposed algorithm was capable of reducing the root mean square errors of the reconstructed image by 1/4 and 1/5 in amplitude and phase, respectively. Also, the algorithm was experimentally demonstrated, and the experimental results showed that the system employing the proposed algorithm suppressed the conjugate image, which slightly appeared in the image reconstructed by the system not employing the algorithm, even when the extinction ratio was 10:1. Thus, the effectiveness of the proposed algorithm was numerically and experimentally verified. © 2010 Optical Society of America

  15. Alumina as diffusion barrier to intermetallic formation in thermal interface materials made from indium and copper

    NASA Astrophysics Data System (ADS)

    Saleh, Ibrahim Khalifa

    Indium and copper react at wide range of temperatures to form intermetallic compounds that have different physical, mechanical and thermal properties. Liquid Phase Sintered indium-copper composite long-term performance as thermal interface material is adversely affected by the evolution of the intermetallic. In this study, i) the effect of intermetallic formation and growth on the performance of Liquid Phase Sintered copper-indium composite, ii) the effect of alumina as diffusion barrier between indium and copper, (iii) thermal stability and wettability between indium and alumina, iv) the indium and quartz wettability, v) indium and tungsten oxide wettability have been studied. Deleterious effect of the intermetallic formation and growth on the thermal and mechanical properties has been observed. 5nm of alumina deposited by Atomic Layer Deposition on flat copper surface has been optimized to prevent diffusion process between indium and copper at 120°C. 15nm of alumina prevented the reaction at 230°C. Instability of indium thin film thermally deposited on sapphire substrate was observed. Also, decrease in the sintering density of indium-alumina composite with increasing temperature was observed. The dewetting contact angle between liquid indium and sapphire was ˜127°. The wetting experiments between indium and different oxides showed that indium wets tungsten oxide and quartz..

  16. Effect of Mn and Fe on the Formation of Fe- and Mn-Rich Intermetallics in Al–5Mg–Mn Alloys Solidified Under Near-Rapid Cooling

    PubMed Central

    Liu, Yulin; Huang, Gaoren; Sun, Yimeng; Zhang, Li; Huang, Zhenwei; Wang, Jijie; Liu, Chunzhong

    2016-01-01

    Mn was an important alloying element used in Al–Mg–Mn alloys. However, it had to be limited to a low level (<1.0 wt %) to avoid the formation of coarse intermetallics. In order to take full advantage of the benefits of Mn, research was carried out to investigate the possibility of increasing the content of Mn by studying the effect of cooling rate on the formation of Fe- and Mn-rich intermetallics at different content levels of Mn and Fe. The results indicated that in Al–5Mg–Mn alloy with low Fe content (<0.1 wt %), intermetallic Al6(Fe,Mn) was small in size and amount. With increasing Mn content, intermetallic Al6(Fe,Mn) increased, but in limited amount. In high-Fe-containing Al–5Mg–Mn alloys (0.5 wt % Fe), intermetallic Al6(Fe,Mn) became the dominant phase, even in the alloy with low Mn content (0.39 wt %). Cooling rate played a critical role in the refinement of the intermetallics. Under near-rapid cooling, intermetallic Al6(Fe,Mn) was extremely refined. Even in the high Mn and/or high-Fe-containing alloys, it still demonstrated fine Chinese script structures. However, once the alloy composition passed beyond the eutectic point, the primary intermetallic Al6(Fe,Mn) phase displayed extremely coarse platelet-like morphology. Increasing the content of Fe caused intermetallic Al6(Fe,Mn) to become the primary phase at a lower Mn content. PMID:28787888

  17. In situ examination of moving crack tips in ordered intermetallics.

    SciTech Connect

    Heuer, J.; Lam, N. Q.; Okamoto, P. R.; Stubbins, J. F.

    1999-01-25

    Recent studies have shown that high stress concentrations at moving crack tips in the intermetallic compound NiTi can induce a crystalline-to-amorphous (C-A) transformation of the crack tip region. This stress-induced C-A transformation has a temperature dependence and crystallization behavior similar to those of ion irradiation-induced C-A transformation of NiTi. The present study examines if these similarities between stress- and irradiation-induced amorphization hold true for two other intermetallic compounds, CuTi and Ni{sub 3}Ti. In situ straining was performed in an intermediate-voltage transmission electron microscope. The presence or absence of an amorphous phase was determined by dark field imaging and selected area diffraction of crack tip regions. Crack tips in both CuTi and Ni{sub 3}Ti were found to remain crystalline upon fracture. The observed absence of stress-induced amorphization in Ni{sub 3}Ti is consistent with its known absence during irradiation, but the absence in CuTi differs from its known irradiation-induced amorphization behavior. Reasons for the similarity and difference are discussed.

  18. Spark plasma sintering of titanium aluminide intermetallics and its composites

    NASA Astrophysics Data System (ADS)

    Aldoshan, Abdelhakim Ahmed

    Titanium aluminide intermetallics are a distinct class of engineering materials having unique properties over conventional titanium alloys. gamma-TiAl compound possesses competitive physical and mechanical properties at elevated temperature applications compared to Ni-based superalloys. gamma-TiAl composite materials exhibit high melting point, low density, high strength and excellent corrosion resistance. Spark plasma sintering (SPS) is one of the powder metallurgy techniques where powder mixture undergoes simultaneous application of uniaxial pressure and pulsed direct current. Unlike other sintering techniques such as hot iso-static pressing and hot pressing, SPS compacts the materials in shorter time (< 10 min) with a lower temperature and leads to highly dense products. Reactive synthesis of titanium aluminide intermetallics is carried out using SPS. Reactive sintering takes place between liquid aluminum and solid titanium. In this work, reactive sintering through SPS was used to fabricate fully densified gamma-TiAl and titanium aluminide composites starting from elemental powders at different sintering temperatures. It was observed that sintering temperature played significant role in the densification of titanium aluminide composites. gamma-TiAl was the predominate phase at different temperatures. The effect of increasing sintering temperature on microhardness, microstructure, yield strength and wear behavior of titanium aluminide was studied. Addition of graphene nanoplatelets to titanium aluminide matrix resulted in change in microhardness. In Ti-Al-graphene composites, a noticeable decrease in coefficient of friction was observed due to the influence of self-lubrication caused by graphene.

  19. In situ examination of moving crack tips in ordered intermetallics

    SciTech Connect

    Heuer, J.K. |; Lam, N.Q.; Okamoto, P.R.; Stubbins, J.F.

    1999-08-01

    Recent studies have shown that high stress concentrations at moving crack tips in the intermetallic compound NiTi can induce a crystalline-to-amorphous (C-A) transformation of the crack tip region. This stress-induced C-A transformation has a temperature dependence and crystallization behavior similar to those of ion irradiation-induced C-A transformation of NiTi. The present study examines if these similarities between stress- and irradiation-induced amorphization hold true for two other intermetallic compounds, CuTi and Ni{sub 3}Ti. In situ straining was performed in an intermediate-voltage transmission electron microscope. The presence or absence of an amorphous phase was determined by dark field imaging and selected area diffraction of crack tip regions. Crack tips in both CuTi and Ni{sub 3}Ti were found to remain crystalline upon fracture. The observed absence of stress-induced amorphization in Ni{sub 3}Ti is consistent with its known absence during irradiation, but the absence in CuTi differs from its known irradiation-induced amorphization behavior. Reasons for the similarity and difference are discussed.

  20. Theoretical Energy Release of Thermites, Intermetallics, and Combustible Metals

    SciTech Connect

    Fischer, S.H.; Grubelich, M.C.

    1999-05-14

    Thermite mixtures, intermetallic reactants, and metal fuels have long been used in pyrotechnic applications. Advantages of these systems typically include high energy density, high combustion temperature, and a wide range of gas production. They generally exhibit high temperature stability and possess insensitive ignition properties. For the specific applications of humanitarian demining and disposal of unexploded ordnance, these pyrotechnic formulations offer additional benefits. The combination of high thermal input with low brisance can be used to neutralize the energetic materials in mines and other ordnance without the "explosive" high-blast-pressure events that can cause extensive collateral damage to personnel, facilities, and the environment. In this paper, we review the applications, benefits, and characteristics of thermite mixtures, intermetallic reactants, and metal fuels. Calculated values for reactant density, heat of reaction (per unit mass and per unit volume), and reaction temperature (without and with consideration of phase changes and the variation of specific heat values) are tabulated. These data are ranked in several ways, according to density, heat of reaction, reaction temperature, and gas production.

  1. Development of intermetallic-hardened abrasion-resistant weld hardfacing alloys

    SciTech Connect

    School, M.R.

    1986-01-01

    Chromium and cobalt are strategic materials in the US and both are major constituents in many weld hardfacing alloys. Substitution for these materials or alternatives to their use was a primary direction of this investigation which was conducted in conjunction with the US Bureau of Mines. Minimization of the use of strategic materials was the criteria guiding the development of intermetallic-hardened abrasion resistant weld hardfacing materials. Other criteria were that the new alloy contain a hard intermetallic compound in an FCC matrix, and that these intermetallic compounds be stable at room temperature. A survey of ternary systems was made and the Fe-Mo-Ni system was selected to provide a basis for alloy development. Fe-Mo-Ni alloys synthesized by arc-melting and similar alloys made by welding possessed similar microstructures, a (Fe, Ni){sub 7}Mo{sub 6} intermetallic plus austenite eutectic in an austenitic matrix. These materials exhibited poor abrasive resistance. Silicon additions to the alloy promoted formation of a Laves phase FeMoSi intermetallic which helped increase the abrasive wear resistance. Through a series of alloy chemistry iterations a final composition of Fe-20Mo-15Ni-5Si was selected. Heat treatment of this alloy at 550 to 650 C caused second phase precipitation in the matrix and raised the hardness about 14 points HRC to 50 HRC. The alloy's wear rate, measured with the pin-on-drum abrasive wear test, was 6.3 to 6.5 mg/m. However this was twice the wear rate observed in commercial high-carbon high-chromium alloys. Based on examination of the alloy microstructures, their chemistry, and an analysis of the Fe-Mo-Si phase system; directions for further research are to increase the molybdenum and silicon content to produce a Fe-20Mo-10Ni-15Si composition.

  2. The role of zinc on the chemistry of complex intermetallic compounds

    SciTech Connect

    Xie, Weiwei

    2014-01-01

    Combining experiments and electronic structure theory provides the framework to design and discover new families of complex intermetallic phases and to understand factors that stabilize both new and known phases. Using solid state synthesis and multiple structural determinations, ferromagnetic β-Mn type Co8+xZn12–x was analyzed for their crystal and electronic structures.

  3. Experimental verification of PSM polarimetry: monitoring polarization at 193nm high-NA with phase shift masks

    NASA Astrophysics Data System (ADS)

    McIntyre, Gregory; Neureuther, Andrew; Slonaker, Steve; Vellanki, Venu; Reynolds, Patrick

    2006-03-01

    The initial experimental verification of a polarization monitoring technique is presented. A series of phase shifting mask patterns produce polarization dependent signals in photoresist and are capable of monitoring the Stokes parameters of any arbitrary illumination scheme. Experiments on two test reticles have been conducted. The first reticle consisted of a series of radial phase gratings (RPG) and employed special apertures to select particular illumination angles. Measurement sensitivities of about 0.3 percent of the clear field per percent change in polarization state were observed. The second test reticle employed the more sensitive proximity effect polarization analyzers (PEPA), a more robust experimental setup, and a backside pinhole layer for illumination angle selection and to enable characterization of the full illuminator. Despite an initial complication with the backside pinhole alignment, the results correlate with theory. Theory suggests that, once the pinhole alignment is corrected in the near future, the second reticle should achieve a measurement sensitivity of about 1 percent of the clear field per percent change in polarization state. This corresponds to a measurement of the Stokes parameters after test mask calibration, to within about 0.02 to 0.03. Various potential improvements to the design, fabrication of the mask, and experimental setup are discussed. Additionally, to decrease measurement time, a design modification and double exposure technique is proposed to enable electrical detection of the measurement signal.

  4. Suppression of metastable-phase inclusion in N-polar (0001{sup ¯}) InGaN/GaN multiple quantum wells grown by metalorganic vapor phase epitaxy

    SciTech Connect

    Shojiki, Kanako Iwabuchi, Takuya; Kuboya, Shigeyuki; Choi, Jung-Hun; Tanikawa, Tomoyuki; Hanada, Takashi; Katayama, Ryuji; Matsuoka, Takashi; Usami, Noritaka

    2015-06-01

    The metastable zincblende (ZB) phase in N-polar (0001{sup ¯}) (−c-plane) InGaN/GaN multiple quantum wells (MQWs) grown by metalorganic vapor phase epitaxy is elucidated by the electron backscatter diffraction measurements. From the comparison between the −c-plane and Ga-polar (0001) (+c-plane), the −c-plane MQWs were found to be suffered from the severe ZB-phase inclusion, while ZB-inclusion is negligible in the +c-plane MQWs grown under the same growth conditions. The ZB-phase inclusion is a hurdle for fabricating the −c-plane light-emitting diodes because the islands with a triangular shape appeared on a surface in the ZB-phase domains. To improve the purity of stable wurtzite (WZ)-phase, the optimum conditions were investigated. The ZB-phase is dramatically eliminated with decreasing the V/III ratio and increasing the growth temperature. To obtain much-higher-quality MQWs, the thinner InGaN wells and the hydrogen introduction during GaN barriers growth were tried. Consequently, MQWs with almost pure WZ phase and with atomically smooth surface have been demonstrated.

  5. Role of nitridation on polarity and growth of InN by metal-organic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Dinh, Duc V.; Skuridina, D.; Solopow, S.; Pristovsek, M.; Vogt, P.; Kneissl, M.

    2013-08-01

    We report on metal-organic vapor phase epitaxy (MOVPE) of (0001)InN layers simultaneously grown on a-plane (112¯0) and c-plane (0001) sapphire substrates. The substrates were nitridated at temperatures from 500 °C to 1050 °C prior to the growth of c-plane InN layers. Nitridation determined the polarity, the crystallinity, and the surface morphology of the InN layers. Nitridation temperatures above 800 °C lead to N-polar InN layers, while nitridation temperatures from 700 °C to 750 °C produce mixed-polar InN layers, and nitridation temperatures from 500 °C to 650 °C produce In-polar InN layers. The roughness and crystallinity of the InN layers are correlated with the changes of polarity. The incorporation of nitrogen into the nitridation layers at different nitridation temperatures was measured. A strong N-Al bond signal after nitridation is correlated with N-polarity layers after overgrowth.

  6. Column selectivity in reversed-phase liquid chromatography. VI. Columns with embedded or end-capping polar groups.

    PubMed

    Wilson, N S; Gilroy, J; Dolan, J W; Snyder, L R

    2004-02-13

    A previous model of column selectivity for reversed-phase liquid chromatography (RP-LC) has been applied to an additional 21 columns with embedded or end-capping polar groups (EPGs). Embedded-polar-group columns exhibit a significantly different selectivity vs. non-EPG, type-B columns, generally showing preferential retention of hydrogen-bond donors, as well as decreased retention for hydrogen-bond acceptors or ionized bases. EPG-columns are also generally less hydrophobic (more polar) than are non-EPG-columns. Interestingly, columns with polar end-capping tend to more closely resemble non-EPG columns, suggesting that the polar group has less effect on column selectivity when used to end-cap the column versus the case of an embedded polar group. Column selectivity data reported here for EPG-columns can be combined with previously reported values for non-EPG columns to provide a database of 154 different columns. This enables a comparison of any two of these columns in terms of selectivity. However, comparisons that involve EPG columns are more approximate.

  7. Polar-phase indices of perioral muscle reciprocity during syllable production in Parkinson's disease.

    PubMed

    Chu, Shin Ying; Barlow, Steven M; Lee, Jaehoon; Wang, Jingyan

    2017-02-08

    This research characterised perioral muscle reciprocity and amplitude ratio in lower lip during bilabial syllable production [pa] at three rates to understand the neuromotor dynamics and scaling of motor speech patterns in individuals with Parkinson's disease (PD). Electromyographic (EMG) signals of the orbicularis oris superior [OOS], orbicularis oris inferior [OOI] and depressor labii inferioris [DLI] were recorded during syllable production and expressed as polar-phase notations. PD participants exhibited the general features of reciprocity between OOS, OOI and DLI muscles as reflected in the EMG during syllable production. The control group showed significantly higher integrated EMG amplitude ratio in the DLI:OOS muscle pairs than PD participants. No speech rate effects were found in EMG muscle reciprocity and amplitude magnitude across all muscle pairs. Similar patterns of muscle reciprocity in PD and controls suggest that corticomotoneuronal output to the facial nucleus and respective perioral muscles is relatively well-preserved in our cohort of mild idiopathic PD participants. Reduction of EMG amplitude ratio among PD participants is consistent with the putative reduction in the thalamocortical activation characteristic of this disease which limits motor cortex drive from generating appropriate commands which contributes to bradykinesia and hypokinesia of the orofacial mechanism.

  8. Nuclear quadrupole interaction of highly polarized gas phase 131Xe with a glass surface

    NASA Astrophysics Data System (ADS)

    Butscher, R.; Wäckerle, G.; Mehring, M.

    1994-05-01

    We report nuclear magnetic resonance (NMR) experiments on 131Xe (I=3/2) gas-phase atoms which exhibit nuclear quadrupole interaction with the surface of the sample cell. Nuclear quadrupole coupling constants and quadrupole relaxation rates are obtained from the time-domain signal of the freely precessing nuclear magnetization in weak magnetic fields. The nuclear spin species is polarized by spin-exchange collisions with optically pumped ground-state spins of Rb gas atoms. The Rb atoms also present in the sample are used as a magnetometer to probe the free-induction decay of the nuclear-spin ensemble. The temperature dependence of both the effective quadrupole splittings and the relaxation rates are explained by a model for the surface interactions of a Xe atom adsorbed on the glass surface. The desorption is thermally activated with an activation energy of EA=0.12 eV. The surface diffusion of an adsorbed atom is characterized by an activation energy ED for thermally activated hopping between neighboring surface sites. Both energies enter the spectral density function governing wall-induced nuclear quadrupole relaxation. Our experimental results lead to the conclusion that they are on the same order of magnitude.

  9. [Corrected Title: Solid-Phase Extraction of Polar Compounds from Water] Automated Electrostatics Environmental Chamber

    NASA Technical Reports Server (NTRS)

    Sauer, Richard; Rutz, Jeffrey; Schultz, John

    2005-01-01

    A solid-phase extraction (SPE) process has been developed for removing alcohols, carboxylic acids, aldehydes, ketones, amines, and other polar organic compounds from water. This process can be either a subprocess of a water-reclamation process or a means of extracting organic compounds from water samples for gas-chromatographic analysis. This SPE process is an attractive alternative to an Environmental Protection Administration liquid-liquid extraction process that generates some pollution and does not work in a microgravitational environment. In this SPE process, one forces a water sample through a resin bed by use of positive pressure on the upstream side and/or suction on the downstream side, thereby causing organic compounds from the water to be adsorbed onto the resin. If gas-chromatographic analysis is to be done, the resin is dried by use of a suitable gas, then the adsorbed compounds are extracted from the resin by use of a solvent. Unlike the liquid-liquid process, the SPE process works in both microgravity and Earth gravity. In comparison with the liquid-liquid process, the SPE process is more efficient, extracts a wider range of organic compounds, generates less pollution, and costs less.

  10. Robust aptamer sol-gel solid phase microextraction of very polar adenosine from human plasma.

    PubMed

    Mu, Li; Hu, Xiangang; Wen, Jianping; Zhou, Qixing

    2013-03-01

    Conventional solid phase microextraction (SPME) has a limited capacity to extract very polar analytes, such as adenosine. To solve this problem, aptamer conjugating sol-gel methodology was coupled with an SPME fiber. According to the authors' knowledge, this is the first reported use of aptamer SPME. The fiber of aptamer sol-gel SPME with a mesoporous structure has high porosity, large surface area, and small water contact angle. Rather than employing direct entrapment, covalent immobilization was the dominant method of aptamer loading in sol-gel. Aptamer sol-gel fiber captured a specified analyte from among the analog molecules, thereby, exhibiting an excellent selective property. Compared with commercial SPME fibers, this aptamer fiber was suitable for extracting adenosine, presenting an extraction efficiency higher than 20-fold. The values of repeatability and reproducibility expressed by relative standard deviation were low (9.4%). Interestingly, the sol-gel network enhanced the resistance of aptamer SPME to both nuclease and nonspecific proteins. Furthermore, the aptamer sol-gel fiber was applied in human plasma with LOQ 1.5 μg/L, which is an acceptable level. This fiber also demonstrates durability and regeneration over 20-cycles without significant loss of efficiency. Given the various targets (from metal ions to biomacromolecules and cells) of aptamers, this methodology will extend the multi-domain applications of SPME.

  11. Electric field-induced orthogonal polarization switching in morphotropic phase boundary Pb(0.57)Ba(0.43)Nb(2)O(6) (PBN57) single crystals.

    PubMed

    Guo, R; Bhalla, A S; Cross, L E

    1990-03-01

    Tungsten bronze crystals of Pb(0.57)Ba(0.43)Nb(2)O(6) composition near the morphotropic phase boundary were examined for possible switching of the polarization vector. It is demonstrated that for the single crystal lead barium niobate of tetragonal symmetry, the polarization vector can be switched orthogonally to an orthorhombic phase simply by the application of an electric field.

  12. N-single-helix photonic-metamaterial based broadband optical range circular polarizer by induced phase lags between helices.

    PubMed

    Behera, Saraswati; Joseph, Joby

    2015-02-10

    In this work, we have designed a photonic-metamaterial based broadband circular polarizer using N=4 phase-lagged aluminum single helices arranged in a square array as a unit cell. The effect of phase differences between the helices in an array on the optical performance of the structure is studied, and a comparative study is done with that of multi-intertwined helices. It is observed that the proposed metamaterial structure shows circular polarization sensitivity over a broad optical wavelength range (≈450-900  nm), with improved optical performance in average extinction ratio and broad positive circular dichroism in comparison to multiple intertwined helices. The induced phase lag between the helices in a square-array based unit cell reduces the linear birefringence and leads to the recovery of circular space symmetry in the structure.

  13. Measurement of the earthshine polarization in the B, V, R, and I bands as function of phase

    NASA Astrophysics Data System (ADS)

    Bazzon, A.; Schmid, H. M.; Gisler, D.

    2013-08-01

    Context. Earth-like, extrasolar planets may soon become observable with upcoming high contrast polarimeters. Therefore, the characterization of the polarimetric properties of the planet Earth is important for interpreting expected observations and planning of future instruments. Aims: Benchmark values for the polarization signal of integrated light from the planet Earth in broad band filters are derived from new polarimetric observations of the earthshine backscattered from the Moon's dark side. Methods: The fractional polarization of the earthshine pes is measured in the B,V,R, and I filters for Earth-phase angles α between 30° and 110° with a new, specially designed wide field polarimeter. In the observations, the light from the bright lunar crescent is blocked with focal plane masks. Because the entire Moon is imaged, the earthshine observations can be corrected for the stray light from the bright lunar crescent and twilight. The phase dependence of pes is fitted by a function pes = qmaxsin2α. Depending on wavelength λ and the lunar surface albedo a, the polarization of the backscattered earthshine is significantly reduced. To determine the polarization of the planet Earth, we correct our earthshine measurements by a polarization efficiency function for the lunar surface ɛ(λ,a) derived from measurements of lunar samples from the literature. Results: The polarization of the earthshine decreases toward longer wavelengths and is about a factor 1.3 lower for the higher albedo highlands. For mare regions the measured maximum polarization is about qmax,B = 13% for α = 90° (half moon) in the B band. The resulting fractional polarizations for the planet Earth derived from our earthshine measurements and corrected by ɛ(λ,a) are 24.6% for the B band, 19.1% for the V band, 13.5% for the R band, and 8.3% for the I band. Together with the literature values for the spectral reflectivity, we obtain a contrast Cp between the polarized flux of the planet Earth and the

  14. Hexatic and blue phases in a chiral liquid crystal: optical polarizing microscopy, synchrotron radiation and dielectric study

    NASA Astrophysics Data System (ADS)

    Sinha, Debashis; Debnath, Asim; Mandal, Pradip Kumar

    2014-09-01

    Phase behavior, structure and molecular dynamics of a chiral liquid crystalline compound, which exhibits SmG*, SmJ*, SmF*, SmI*, SmC*, SmA*, N* and BP*, have been investigated. Observed optical textures, synchrotron radiation diffraction data and frequency dependent dielectric spectroscopic study clearly depict the temperature evolution of the different hexatic smectic phases along with cholesteric and blue phase in a single compound. In hexatic phases dielectric absorption spectra show one low frequency relaxation process, related to the phase fluctuation of the bond orientational order, and one high frequency process related to amplitude fluctuation of the bond orientational order coupled with the polarization and tilt of the molecules. Goldstone and soft mode relaxation processes are detected, respectively, in SmC* and SmA* phases.

  15. Phase-coherent orthogonally polarized optical single sideband modulation with arbitrarily tunable optical carrier-to-sideband ratio.

    PubMed

    Wang, Wen Ting; Liu, Jian Guo; Mei, Hai Kuo; Zhu, Ning Hua

    2016-01-11

    We propose and experimentally verify a novel approach to achieve phase-coherence orthogonally polarized optical single sideband (OSSB) modulation with a tunable optically carrier-to-sideband ratio (OCSR). In our scheme, the orthogonally polarized OSSB signal is achieved using a dual-polarization quadrature phase shift keying (DP-QPSK) modulator without an optical band-pass filter (OBPF). Therefore, the proposed method is wavelength independent. The DP-QPSK modulator includes two parallel QPSK modulators locating on its two arms. The upper QPSK modulator of the DP-QPSK modulator is driven by two quadrature sinusoidal microwave signals and works at the frequency shifting condition whose bias voltages are optimized to suppress the optical. The lower QPSK modulator of that works at the maximum transmission point and the optical carrier is not modulated. The OCSR is continuously tunable by simply adjusting the bias voltages of the lower modulator. The frequency shifting optical signal from the upper QPSK modulator and the optical carrier from the lower QPSK modulator are combined together at the output of the DP-QPSK modulator. The optical carrier and sideband are polarized orthogonally. The generated OSSB signals could be used to shift and code the phase of the microwave signal and generate ultra-wideband (UWB) microwave pulse. The proposed method is analyzed and experimental demonstrated.

  16. Polar Second-Harmonic Imaging to Resolve Pure and Mixed Crystal Phases along GaAs Nanowires.

    PubMed

    Timofeeva, Maria; Bouravleuv, Alexei; Cirlin, George; Shtrom, Igor; Soshnikov, Ilya; Reig Escalé, Marc; Sergeyev, Anton; Grange, Rachel

    2016-10-12

    In this work, we report an optical method for characterizing crystal phases along single-semiconductor III-V nanowires based on the measurement of polarization-dependent second-harmonic generation. This powerful imaging method is based on a per-pixel analysis of the second-harmonic-generated signal on the incoming excitation polarization. The dependence of the second-harmonic generation responses on the nonlinear second-order susceptibility tensor allows the distinguishing of areas of pure wurtzite, zinc blende, and mixed and rotational twins crystal structures in individual nanowires. With a far-field nonlinear optical microscope, we recorded the second-harmonic generation in GaAs nanowires and precisely determined their various crystal structures by analyzing the polar response for each pixel of the images. The predicted crystal phases in GaAs nanowire are confirmed with scanning transmission electron and high-resolution transmission electron measurements. The developed method of analyzing the nonlinear polar response of each pixel can be used for an investigation of nanowire crystal structure that is quick, sensitive to structural transitions, nondestructive, and on-the-spot. It can be applied for the crystal phase characterization of nanowires built into optoelectronic devices in which electron microscopy cannot be performed (for example, in lab-on-a-chip devices). Moreover, this method is not limited to GaAs nanowires but can be used for other nonlinear optical nanostructures.

  17. Structural and Electronic Investigations of Complex Intermetallic Compounds

    SciTech Connect

    Ko, Hyunjin

    2008-01-01

    structures of these and related materials. Such calculations allow us to examine various interactions at the atomic scale, interactions which include orbital overlap, two-electron interactions, and Madelung terms. Moreover, these electronic studies also provide links between the angstrom-scale atomic interactions and the macro-scale physical properties, such as magnetism. Over the past few decades, there have been many significant developments toward understanding structure-bonding-property relationships in extended solids in terms of variables including atomic size, valence electron concentration, and electronegativity. However, many simple approaches based on electron counting, e.g., the octet rule, the 18-electron rule, or Wade's rules for boranes, cannot be applied adequately or universally to many of the more complex intermetallic compounds. For intermetallic phases that include late transition metals and post transition main group elements as their constituents, one classification scheme has been developed and effectively applied by using their valence electron count per atom (vec). These compounds are known as Hume-Rothery electron phases, and they have a variety of structure types with vec < 2.0 as shown in Table 1.

  18. Online polar two phase countercurrent chromatography×high performance liquid chromatography for preparative isolation of polar polyphenols from tea extract in a single step.

    PubMed

    Chen, Wei-Bin; Li, Shu-Qi; Chen, Long-Jiang; Fang, Mei-Juan; Chen, Quan-Cheng; Wu, Zhen; Wu, Yun-Long; Qiu, Ying-Kun

    2015-08-01

    Herein, we report an on-line two-dimensional system constructed by counter-current chromatography (CCC) coupling with preparative high-performance liquid chromatography (prep-HPLC) for the separation and purification of polar natural products. The CCC was used as the first dimensional isolation column, where an environmental friendly polar two-phase solvent system of isopropanol and 16% sodium chloride aqueous solution (1:1.2, v/v) was introduced for low toxicity and favorable resolution. In addition, by applying the stop-and-go flow technique, effluents pre-fractionated by CCC was further purified by a preparative column packed with octadecyl silane (ODS) as the second dimension. The interface between the two dimensions was comprised of a 6-port switching valve and an electronically controlled 2-position 10-port switching valve connected with two equivalent holding columns. To be highlighted here, this rationally designed interface for the purpose of smooth desalination, absorption and desorption, successfully solved the solvent compatibility problem between the two dimensional separation systems. The present integrated system was successfully applied in a one-step preparative separation and identification of 10 pure compounds from the water extracts of Tieguanyin tea (Chinese oolong tea). In short, all the results demonstrated that the on-line 2D CCC×LC method is an efficient and green approach for harvesting polar targets in a single step, which showed great promise in drug discovery.

  19. Microstrip Antennas with Polarization Diversity across a Wide Frequency Range and Phased Array Antennas for Radar and Satellite Communications

    NASA Astrophysics Data System (ADS)

    Ho, Kevin Ming-Jiang

    The thesis comprises of 3 projects; an L-band microstrip antenna with frequency agility and polarization diversity, X-band phased array antennas incorporating commercially packaged RFIC phased array chips, and studies for Ku/Ka-band shared aperture antenna array. The first project features the use of commercially packaged RF-MEMS SPDT switches, that boasts of high reliability, high linearity, low losses, hermetically packaged and fully compatible for SMTA processes for mass-assembly and production. Using the switches in a novel manner for the feed network, microstrip antennas with polarization diversity are presented. Frequency agility is achieved with the use of tuning diodes to provide capacitive loading to the antenna element. Additional inductance effects from surface-mounted capacitors, and its impact, is introduced. Theoretical cross-polarization of probe-fed antenna elements is presented for both linear and circular polarized microstrip antennas. Designs and measurements are presented, for microstrip antennas with polarization diversity, wide frequency tuning range, and both features. Replacement of the tuning diodes with commercially-packaged high Q RF MEMS tunable capacitors will allow for significant improvements to the radiation efficiency. In another project, multi-channel CMOS RFIC phased-array receiver chips are assembled in QFN packages and directly integrated on the same multi-layered PCB stack-up with the antenna arrays. Problems of isolation from the PCB-QFN interface, and potential performance degradation on antenna array from the use of commercial-grade laminates for assembly requirements, namely potential scan blindness and radiation efficiency, are presented. Causes for apparent drift of dielectric constant for microstrip circuits, and high conductor losses observed in measurements, are introduced. Finally, studies are performed for the design of a Ku/Ka-Band shared aperture array. Different approaches for developing dual-band shared apertures

  20. Quaternary borocarbides: New class of intermetallic superconductors

    NASA Technical Reports Server (NTRS)

    Nagarajan, R.; Gupta, L. C.; Dhar, S. K.; Mazumdar, Chandan; Hossain, Zakir; Godart, C.; Levy-Clement, C.; Padalia, B. D.; Vijayaraghavan, R.

    1995-01-01

    Our recent discovery of superconductivity (SC) in the four-element multiphase Y-Ni-B-C system at an elevated temperature (TC approximately 12 K) has opened up great possibilities of identifying new superconducting materials and generating new physics. Superconductivity with Tc (greater than 20 K) higher than that known so far in bulk intermetallics has been observed in multiphase Y-Pd-B-C and Th-Pd-B-C systems and a family of single phase materials RENi2B2C (RE= Y, rare earth) have been found. Our investigations show YNi2B2C to be a strong coupling hard type-II SC. HC2(T) exhibits an unconventional temperature dependence. Specific heat and magnetization studies reveal coexistence of SC and magnetism in RNi2B2C (R = Ho, Er, Tm) with magnetic ordering temperatures (Tc approximately 8 K, 10.5 K, 11 K and Tm approximately 5 K, approximately 7K, approximately 4 K respectively) that are remarkably higher than those in known magnetic superconductors . Mu-SR studies suggest the possibility of Ni atoms carrying a moment in TmNi2B2C. Resistivity results suggests a double re-entrant transition (SC-normal-SC) in HoNi2B2C. RENi2B2C (RE = Ce, Nd, Gd) do not show SC down to 4.2 K. The Nd- and Gd-compounds order magnetically at approximately 4.5 K and approximately 19.5 K, respectively. Two SC transitions are observed in Y-Pd-B-C (Tc approximately 22 K, approximately 10 K) and in Th-Pd-B-C (Tc approximately 20 K, approximately 14 K) systems, which indicate that there are at least two structures which support SC in these borocarbides. In our multiphase ThNi2B2C we observe SC at approximately 6 K. No SC was seen in multiphase UNi2B2C, UPd2B2C, UOs2Ge2C and UPd5B3C(0.35) down to 4.2 K. Tc in YNi2B2C is depressed by substitutions (Gd, Th and U at Y-sites and Fe, Co at Ni-sites).

  1. Deformation-induced amorphization of Cu-Ti intermetallics

    SciTech Connect

    Askenazy, P.D.

    1992-12-31

    Two methods of inducing amorphization in Cu-Ti intermetallic Compounds by mechanical means have been investigated. Ingots of compositions Cu{sub 35}Ti{sub 65} and Cu{sub 33.3}Ti{sub 66.7} were rapidly quenched into ribbons. The microstructure consisted largely of microcrystals in an amorphous matrix, which were either quenched in or grown by annealing. The ribbons were cold-rolled, Which reduced their effective thickness by a factor of about 8. The status of the intermetallic compound CuTi{sub 2} was monitored by x-ray diffraction and transmission electron microscopy (TEM). The crystals were found to amorphize as rolling progressed. This behavior was not reproduced in polycrystalline samples that had no amorphous matrix present initially. The presence of the amorphous phase is thus necessary for amorphization of the crystal: it eliminates the need to nucleate the new glass, and it prevents the ribbon from disintegrating at high deformation stages. It may also change the deformation mechanism that occurs in the crystals, retarding the onset of amorphization. Diffuse scattering is close-packed directions is similar to that seen in electron irradiation experiments. It is postulated that the chemical disorder present in antiphase boundaries cause by deformation raises the free energy of the crystal higher than that of the amorphous phase. Ingots of the same compound were worn against each other in a custom-built wear apparatus. The design eliminates iron contamination of water sample and requires relatively small quantities of material. Alteration of the surface structure was monitored by plan-view and cross-sectional TEM. Larger subsurface crystals exhibit diffuse scattering, similar to that found in the rolled samples. A wide range of grain sizes was observed, due to the inhomogeneous nature of the wear process. An unusual phase was observed at the surface, consisting of a nanometer-scale mixture of aligned nanocrystalline regions and disordered areas.

  2. Bergman Clusters, Multiple Bonds, and Defect Planes: Synthetic Outcomes of Chemical Frustration in Ternary Intermetallic Systems

    NASA Astrophysics Data System (ADS)

    Hadler, Amelia Beth

    Intermetallics crystallize in a variety of complex structures, many of which show unusual bonding or intriguing properties. Understanding what factors drive this structural chemistry would be a valuable step towards designing new intermetallics with specific structures or properties. One pathway towards understanding and predicting the structures of complex intermetallics is chemical frustration, a design tool which harnesses competition between incompatible bonding or packing modes to induce complexity in ternary intermetallic systems. The research outlined in this thesis focuses on developing chemical frustration through exploratory synthesis in ternary systems designed to induce frustration between the tetrahedral close packing of many intermetallics and the simple cubic packing seen for ionic salts or elemental metals. Syntheses in three systems yielded six new ternary intermetallics, four of which crystallize in novel structure types. Three were discovered in the Ca-Cu-Cd system: Ca5Cu2Cd and Ca2Cu 2Cd9, which adopt ternary variants of binary structures, and Ca10Cu2Cd27, which crystallizes in a new structure built from Bergman clusters. All three structures can be traced to electronic packing frustration induced by the similar electronegativities but different metallic radii of Cu and Cd. The Gd-Fe-C system yielded the new carbometalate Gd13Fe 10C13 and an oxycarbide derivative. These phases crystallize in structures built from Gd tricapped trigonal prisms interpenetrated by an Fe-C network. Theoretical analyses reveal that Fe-Fe and Fe-C multiple bonding is found throughout this network. A theoretical investigation of similar carbides uncovers additional metal-metal, metal-carbon, and carbon-carbon multiple bonding. This unusual bonding stabilizes the carbides by satisfying preferred electron counts for their transition metal sites. One new phase, Mg4.5Pd5Ge1.5, was found in the Mg-Pd-Ge system. Its structure is closely related to the CsCl-type structure of

  3. Formation of a diffusion-based intermetallic interface layer in friction stir welded dissimilar Al-Cu lap joints

    NASA Astrophysics Data System (ADS)

    Marstatt, R.; Krutzlinger, M.; Luderschmid, J.; Zaeh, M. F.; Haider, F.

    2017-03-01

    The joining of dissimilar metals is an important issue in modern lightweight design. Friction Stir Welding (FSW) is suitable for this task since the solidus temperature is usually not exceeded during the process. As a consequence, dissimilar joints can be produced with a minimum of deteriorating intermetallic phases. The latest studies showed the formation of intermetallic layers at the bonding interface with no significant negative influence on the seam quality. In this study, those intermetallic nanolayers at the interface of aluminium / copper lap joints were analysed. For the experiments, the commercially pure alloys EN AW-1050 and CW008A were chosen. The process temperature changed with respect to the parameter setup and was measured at different locations of the seam. The intermetallic layers at the interface were analysed by scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM). The experiments show that the thickness of the interlayer clearly correlates with the process temperature using an Arrhenius equation. It is supposed, that the rotating probe removes the oxide layers of the metal surfaces and a metallic bonding between the Al- and the Cu-phase is formed. Due to the elevated temperature after the probe has passed, the intermetallic layer has emerged by interdiffusion.

  4. Magnetic Anisotropy in Uranium Intermetallics

    NASA Astrophysics Data System (ADS)

    Nakotte, H.

    1997-03-01

    Neutron diffraction and High-Field Magnetisation have been used to study the magnetic anisotropy of antiferromagnetic metallic uranium compounds. In particular, noncollinear magnetic structures have now been determined unambiguously in a number of cases, most notably in the tetragonal U_2T_2X and orthorhombic UTX series, using powder, single-crystal and polarized-neutron diffraction techniques. These results will be compared with state-of-the-art total-energy calculations: both theory and experiment lead to the conjecture that substantial noncollinearity occurs in these compounds whenever it is allowed by symmetry. In addition, one can infer the magnitude of different anisotropy and exchange constants, and compare with the magnetization steps and transition fields of field-induced transitions: this has been done in the case of U_2Pd_2In which has such a transition at 26 T.

  5. Polarization-controlled evolution of light transverse modes and associated Pancharatnam geometric phase in orbital angular momentum

    SciTech Connect

    Karimi, Ebrahim; Marrucci, Lorenzo; Slussarenko, Sergei; Piccirillo, Bruno; Santamato, Enrico

    2010-05-15

    We present an easy, efficient, and fast method to generate arbitrary linear combinations of light orbital angular-momentum eigenstates l={+-}2 starting from a linearly polarized TEM{sub 00} laser beam. The method exploits the spin-to-orbital angular-momentum conversion capability of a liquid-crystal-based q plate and a Dove prism inserted into a Sagnac polarizing interferometer. The nominal generation efficiency is 100%, being limited only by reflection and scattering losses in the optical components. When closed paths are followed on the polarization Poincare sphere of the input beam, the associated Pancharatnam geometric phase is transferred unchanged to the orbital angular momentum state of the output beam.

  6. The effect of temperature on attenuation-correction schemes in rain using polarization propagation differential phase shift

    NASA Technical Reports Server (NTRS)

    Jameson, A. R.

    1992-01-01

    The study elucidates and quantifies differences in the response of the rate of change of polarization propagation differential phase shift Phi, the rate of attenuation for a horizontally/vertically polarized wave A(H,V), and the rate of polarization differential attenuation A(H-V) to temperature. It is shown that if the effects of temperature when estimating A(H) and A(H-V) from Phi are neglected, the average fractional standard error increases only slightly at 9 GHz but significantly at 5 and 3 GHz. Errors at 5 and 3 GHz are about two to three times those at 9 GHz. The performance of Phi-based schemes of attenuation correction at these lower frequencies is much more significantly degraded by temperature uncertainty than at 9 GHz. It is concluded that it is best to use Phi to correct for attenuation at the least-attenuating frequencies.

  7. A New Phase of Exploration and Understanding: Planning for The International Polar Year - 2007/2008

    NASA Astrophysics Data System (ADS)

    Rapley, C.; Bell, R.

    2004-05-01

    Planning is underway for an International Polar Year in 2007-2008. (IPY 2007/8) which will be a significant research opportunity to further our understanding of polar regions and polar processes. The International Polar Year has the potential to capture the public's imagination and convey the crucial role that the polar regions play in global systems. IPY 2007/8 will be an international programme of coordinated, interdisciplinary, scientific research in the Earth's polar regions to explore new frontiers, to increase our ability to detect changes at the Earth's poles and to deepen our understanding of polar processes and their global linkages. A crucial component of the IPY 2007/8 will be to attract and develop the next generation of polar scientists, engineers and leaders and to capture the interest of the public and decision-makers. The vision is for many nations to work together to gain holistic insights into planetary processes, targeted at exploring and increasing our understanding of the poles and their role in the global system. The concept of an International Polar Year 2007/8 has been endorsed and advanced by a broad range of global and polar research groups both internationally and nationally. To date 18 nations have formed national committees who are coordinating IPY activities nationally. The International Council for Science (ICSU) formed an International Polar Year Planning Group (IPY-PG) to stimulate, encourage and organize a debate on the International Polar Year 2007/8, formulate a set of objectives and develop a high level Science Plan. The Planning Group has sought input from the international science community and to date has received 138 ideas from over 22 nations. This input from the international community covers both poles, global processes and a diverse spectrum of disciplines. To date the input from the science community has identified key questions and proposed projects within the three major themes proposed by the ICSU IPY Planning Group

  8. Forging of FeAl intermetallic compounds

    SciTech Connect

    Flores, O.; Juarez, J.; Campillo, B.; Martinez, L.; Schneibel, J.H.

    1994-09-01

    Much activity has been concentrated on the development of intermetallic compounds with the aim of improving tensile ductility, fracture toughness and high notch sensitivity in order to develop an attractive combination of properties for high and low temperature applications. This paper reports experience in processing and forging of FeAl intermetallic of B2 type. During the experiments two different temperatures were employed, and the specimens were forged after annealing in air, 10{sup {minus}2} torr vacuum and argon. From the results it was learned that annealing FeAl in argon atmosphere prior to forging resulted in better deformation behavior than for the other two environments. For the higher forging temperature used in the experiments (700C), the as-cast microstructure becomes partially recrystallized.

  9. Dependence of Polarization of the near-Earth Asteroids (1036) Ganymed and (5143) Heracles on Wavelength and Phase Angle

    NASA Astrophysics Data System (ADS)

    Maleszewski, C.; McMillan, R.; Smith, P.

    2012-12-01

    We are measuring the polarization of asteroids with the SPOL polarimeter of Steward Observatory. With monthly access to the instrument, we can obtain many observations throughout phase angle. This is in contrast to other recent work that had to rely on aggregate properties of targets of similar taxonomic type. Comparing individual objects to these aggregate results may reveal differences of regolith properties from object to object. Both the phase angle and spectral dependence of polarization are being measured. SPOL provides simultaneous coverage from 0.40-0.75 microns, equivalent to BVR filters. Three phase curves thus reveal differences of phase angle dependences with respect to wavelength. The spectral dependence of the linear polarization is determined according to a linear trend previously used to describe the dependence for Main Belt Asteroids (MBAs) in various taxonomic classes (Belskaya et al. 2009). The slopes of these linear trends vs. phase angle are also investigated as was also done in the Belskaya analysis for MBAs in the C-, M-, and S-types. Two initial objects of interest are the NEAs (1036) Ganymed and (5143) Heracles. The taxonomic types of Ganymed and Heracles are S-type and Q-type respectively (DeMeo et al. 2009). For Ganymed, twelve observations were made between 2011 September and 2012 March. These include observations below ten degrees phase angle, which are currently lacking in the polarimetric databases. The positive branch of Ganymed's polarization phase curve behaved similarly across SPOL's wavelength range. But for wavelengths associated with a typical B-filter, the negative branch is more shallow and narrow. The negative phase branch of Ganymed is smaller compared to the aggregate phase curve of S-types determined by Gil-Hutton and Cañada-Assandri (2011). The linear polarization decreases with increasing wavelength at all observed phase angles. As the phase angle increases, the slope of the wavelength dependence of polarization

  10. Use of vancomycin silica stationary phase in packed capillary electrochromatography: III. enantiomeric separation of basic compounds with the polar organic mobile phase.

    PubMed

    Fanali, Salvatore; Catarcini, Paolo; Quaglia, Maria Giovanna

    2002-02-01

    The separation of basic compounds into their enantiomers was achieved using capillary electrochromatography in 50 or 75 microm inner diameter (ID) fused-silica capillaries packed with silica a stationary phase derivatized with vancomycin and mobile phases composed of mixtures of polar organic solvents containing 13 mM ammonium acetate. Enantiomer resolution, electroosmotic flow, and the number of theoretical plates were strongly influenced by the type and concentration of the organic solvent. Mobile phases composed of 13 mM ammonium acetate dissolved in mixtures of acetonitrile/methanol, ethanol, n-propanol, or isopropanol were tested and the highest enantioresolutions were achieved using the first mobile phase, allowing the separation of almost all investigated enantiomers (9 from 11 basic compounds). The use of capillaries with different ID (50 and 75 microm ID) packed with the same chiral stationary phase revealed that a higher number of theoretical plates and higher enantioresolution was achieved with the tube with lowest ID.

  11. Plasma spray forming metals, intermetallics, and composites

    NASA Astrophysics Data System (ADS)

    Sampath, Sanjay; Herman, Herbert

    1993-07-01

    Plasma spray processing is a droplet deposition method that combines the steps of melting, rapid solidification, and consolidation into a single step. The versatility of the technology enables the processing of freestanding bulk, near-net shapes of a wide range of alloys, intermetallics, ceramics, and composites, while still retaining the benefits of rapid solidification processing. In particular, it is possible to produce dense forms through vacuum plasma spraying.

  12. Oxygen stabilized zirconium vanadium intermetallic compound

    DOEpatents

    Mendelsohn, Marshall H.; Gruen, Dieter M.

    1982-01-01

    An oxygen stabilized intermetallic compound having the formula Zr.sub.x OV.sub.y where x=0.7 to 2.0 and y=0.18 to 0.33. The compound is capable of reversibly sorbing hydrogen at temperatures from -196.degree. C. to 450.degree. C. at pressures down to 10.sup.-6 Torr. The compound is also capable of selectively sorbing hydrogen from gaseous mixtures in the presence of CO and CO.sub.2.

  13. Polarization sensitivity analysis of an earth remote sensing instrument - The MODIS-N phase B study

    NASA Technical Reports Server (NTRS)

    Waluschka, E.; Silverglate, P.; Ftaclas, C.; Turner, A.

    1992-01-01

    Polarization analysis software that employs Jones matrix formalism to calculate the polarization sensitivity of an instrument design was developed at Hughes Danbury Optical Systems. The code is capable of analyzing the full ray bundle at its angles of incidence for each optical surface. Input is based on the system ray trace and the thin film coating design at each surface. The MODIS-N (Moderate Resolution Imaging Spectrometer) system is used to demonstrate that it is possible to meet stringent requirements on polarization insensitivity associated with planned remote sensing instruments. Analysis indicates that a polarization sensitivity less than or equal to 2 percent was achieved in all desired spectral bands at all pointing angles, per specification. Polarization sensitivities were as high as 10 percent in similar remote sensing instruments.

  14. Measurement of the surface profile of an axicon lens with a polarization phase-shifting shearing interferometer.

    PubMed

    Chatterjee, Sanjib; Kumar, Y Pavan

    2011-11-10

    We present a Twyman-Green interferometer (TGI)-based polarization phase-shifting shearing interferometric technique for testing the conical surface of an axicon (AX) lens. In this technique, the annular beam generated due to the passing of an expanded collimated laser beam traveling along the axis of revolution of the transparent glass AX element is split up into its reflected and transmitted components, having the plane of polarization in the orthogonal planes, by the polarization beam splitter (PBS) cube of the TGI-based optical setup. The split-up components are made to travel unequal paths along the two arms of the TGI and are recombined by the PBS. Because of the difference in path lengths traveled by the annular conical beams, a linear shear is introduced along the radial direction between the interfering components. Thus, the resulting interference pattern gives a map of the optical path difference (OPD) between two successive close points along a radial direction on the conical surface of the AX lens. The OPD map along radial directions, and hence the slopes/profiles of the conical surface, are obtained by applying polarization phase-shifting interferometry. Results obtained for an AX lens are presented.

  15. Frequency-dependence of the linear-polarization-angle phase-shift in the microwave radiation-induced magnetoresistance oscillations

    NASA Astrophysics Data System (ADS)

    Liu, Han-Chun; Samaraweera, Rasanga; Wegscheider, Werner; Mani, Ramesh

    High-mobility GaAs/AlGaAs heterojunctions subjected to microwave photoexcitation in the perpendicular magnetic field configuration exhibit ¼-cycle phase-shifted oscillatory magnetoresistance and zero-resistance states at low magnetic fields or high filling factors. Recent studies showed that the amplitude of oscillatory magnetoresistance is polarization-angle sensitive and can be described by a fitting formula, Rxx(θ) = A+/-Ccos2(θ- θ0) with diagonal resistance, Rxx, polarization angle θ, and the extracted phase shift, θ0. Previous works have demonstrated that θ0 is frequency-dependent by investigating some specific frequencies. Here, we examine the continuous variation of θ0 with frequency over the bands, 36-40 GHz and 45-49 GHz. Surprisingly, the results indicate dissimilar θ0 variation within the two frequency bands. A comparison of θ0(f) with the microwave polarization reported by an in-situ polarization sensor suggests that the frequency variation of θ0 might be caused by two different mechanisms in the two examined bands.

  16. Measurement of the surface profile of an axicon lens with a polarization phase-shifting shearing interferometer

    SciTech Connect

    Chatterjee, Sanjib; Kumar, Y. Pavan

    2011-11-10

    We present a Twyman-Green interferometer (TGI)-based polarization phase-shifting shearing interferometric technique for testing the conical surface of an axicon (AX) lens. In this technique, the annular beam generated due to the passing of an expanded collimated laser beam traveling along the axis of revolution of the transparent glass AX element is split up into its reflected and transmitted components, having the plane of polarization in the orthogonal planes, by the polarization beam splitter (PBS) cube of the TGI-based optical setup. The split-up components are made to travel unequal paths along the two arms of the TGI and are recombined by the PBS. Because of the difference in path lengths traveled by the annular conical beams, a linear shear is introduced along the radial direction between the interfering components. Thus, the resulting interference pattern gives a map of the optical path difference (OPD) between two successive close points along a radial direction on the conical surface of the AX lens. The OPD map along radial directions, and hence the slopes/profiles of the conical surface, are obtained by applying polarization phase-shifting interferometry. Results obtained for an AX lens are presented.

  17. Intermetallic compounds in heterogeneous catalysis-a quickly developing field.

    PubMed

    Armbrüster, Marc; Schlögl, Robert; Grin, Yuri

    2014-06-01

    The application of intermetallic compounds for understanding in heterogeneous catalysis developed in an excellent way during the last decade. This review provides an overview of concepts and developments revealing the potential of intermetallic compounds in fundamental as well as applied catalysis research. Intermetallic compounds may be considered as platform materials to address current and future catalytic challenges, e.g. in respect to the energy transition.

  18. Intermetallic compounds in heterogeneous catalysis—a quickly developing field

    PubMed Central

    Armbrüster, Marc; Schlögl, Robert; Grin, Yuri

    2014-01-01

    The application of intermetallic compounds for understanding in heterogeneous catalysis developed in an excellent way during the last decade. This review provides an overview of concepts and developments revealing the potential of intermetallic compounds in fundamental as well as applied catalysis research. Intermetallic compounds may be considered as platform materials to address current and future catalytic challenges, e.g. in respect to the energy transition. PMID:27877674

  19. Overview of the development of FeAl intermetallic alloys

    SciTech Connect

    Maziasz, P.J.; Liu, C.T.; Goodwin, G.M.

    1995-09-01

    B2-phase FeAl ordered intermetallic alloys based on an Fe-36 at.% Al composition are being developed to optimize a combination of properties that includes high-temperature strength, room-temperature ductility, and weldability. Microalloying with boron and proper processing are very important for FeAl properties optimization. These alloys also have the good to outstanding resistance to oxidation, sulfidation, and corrosion in molten salts or chlorides at elevated temperatures, characteristic of FeAl with 30--40 at.% Al. Ingot- and powder-metallurgy (IM and PM, respectively) processing both produce good properties, including strength above 400 MPa up to about 750 C. Technology development to produce FeAl components for industry testing is in progress. In parallel, weld-overlay cladding and powder coating technologies are also being developed to take immediate advantage of the high-temperature corrosion/oxidation and erosion/wear resistance of FeAl.

  20. Plastic deformation of ordered intermetallic alloys: Fundamental aspects

    SciTech Connect

    Yoo, M.H.

    1994-10-01

    Fundamental aspects of plastic deformation in ordered intermetallic alloys are reviewed by directly comparing the temperature-dependent yield stresses of Ni{sub 3}Al and Ni{sub 3}Si (the L1{sub 2} structure), NiAl and FeAl (the B2 structure), and TiAl and Ti{sub 3}Al (non-cubic L1{sub 0} and D0{sub 19} structures, respectively). While the yield strength anomaly observed in Ni{sub 3}Al is consistent with the prevailing dislocation models, that found in stoichiometric Ni{sub 3}Si is not. The strong plastic anisotropy observed in NiAl stems from the high antiphase boundary energy, and that found in two-phase {gamma}-TiAl/{alpha}{sub 2}-Ti{sub 3}Al is due to the exceptionally high compressive yield strength along the c-axis of Ti{sub 3}Al.