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Sample records for si phase frustrates

  1. Quantum phase transition with dissipative frustration

    Science.gov (United States)

    Maile, D.; Andergassen, S.; Belzig, W.; Rastelli, G.

    2018-04-01

    We study the quantum phase transition of the one-dimensional phase model in the presence of dissipative frustration, provided by an interaction of the system with the environment through two noncommuting operators. Such a model can be realized in Josephson junction chains with shunt resistances and resistances between the chain and the ground. Using a self-consistent harmonic approximation, we determine the phase diagram at zero temperature which exhibits a quantum phase transition between an ordered phase, corresponding to the superconducting state, and a disordered phase, corresponding to the insulating state with localized superconducting charge. Interestingly, we find that the critical line separating the two phases has a nonmonotonic behavior as a function of the dissipative coupling strength. This result is a consequence of the frustration between (i) one dissipative coupling that quenches the quantum phase fluctuations favoring the ordered phase and (ii) one that quenches the quantum momentum (charge) fluctuations leading to a vanishing phase coherence. Moreover, within the self-consistent harmonic approximation, we analyze the dissipation induced crossover between a first and second order phase transition, showing that quantum frustration increases the range in which the phase transition is second order. The nonmonotonic behavior is reflected also in the purity of the system that quantifies the degree of correlation between the system and the environment, and in the logarithmic negativity as an entanglement measure that encodes the internal quantum correlations in the chain.

  2. Magnetic phase diagram of a frustrated spin ladder

    Science.gov (United States)

    Sugimoto, Takanori; Mori, Michiyasu; Tohyama, Takami; Maekawa, Sadamichi

    2018-04-01

    Frustrated spin ladders show magnetization plateaux depending on the rung-exchange interaction and frustration defined by the ratio of first and second neighbor exchange interactions in each chain. This paper reports on its magnetic phase diagram. Using the variational matrix-product state method, we accurately determine phase boundaries. Several kinds of magnetization plateaux are induced by the frustration and the strong correlation among quasiparticles on a lattice. The appropriate description of quasiparticles and their relevant interactions are changed by a magnetic field. We find that the frustration differentiates the triplet quasiparticle from the singlet one in kinetic energy.

  3. Perfect synchronization in networks of phase-frustrated oscillators

    Science.gov (United States)

    Kundu, Prosenjit; Hens, Chittaranjan; Barzel, Baruch; Pal, Pinaki

    2017-11-01

    Synchronizing phase-frustrated Kuramoto oscillators, a challenge that has found applications from neuronal networks to the power grid, is an eluding problem, as even small phase lags cause the oscillators to avoid synchronization. Here we show, constructively, how to strategically select the optimal frequency set, capturing the natural frequencies of all oscillators, for a given network and phase lags, that will ensure perfect synchronization. We find that high levels of synchronization are sustained in the vicinity of the optimal set, allowing for some level of deviation in the frequencies without significant degradation of synchronization. Demonstrating our results on first- and second-order phase-frustrated Kuramoto dynamics, we implement them on both model and real power grid networks, showing how to achieve synchronization in a phase-frustrated environment.

  4. Phase-space networks of geometrically frustrated systems.

    Science.gov (United States)

    Han, Yilong

    2009-11-01

    We illustrate a network approach to the phase-space study by using two geometrical frustration models: antiferromagnet on triangular lattice and square ice. Their highly degenerated ground states are mapped as discrete networks such that the quantitative network analysis can be applied to phase-space studies. The resulting phase spaces share some comon features and establish a class of complex networks with unique Gaussian spectral densities. Although phase-space networks are heterogeneously connected, the systems are still ergodic due to the random Poisson processes. This network approach can be generalized to phase spaces of some other complex systems.

  5. Phase transition and frustration in nuclear physics and astrophysics

    International Nuclear Information System (INIS)

    Hasnaoui, K.

    2008-10-01

    The thermodynamics of nuclear matter which constitutes the crust of proto-neutron stars and neutron stars is studied in this thesis. Obtaining information on the star matter thermodynamics will enhance the understanding of physical phenomena involved in the cooling of proto-neutron stars, and in the formation of type II supernovae. One of the main goals is to extract the star-matter phase diagram in order to determine if instabilities and/or critical points are present. The work is divided into two parts: in the first one classical approaches are developed, while the second one presents a quantum approach. The classical approaches are based on the Ising model and on the renormalisation group. They give us qualitative information on the phenomenology of phase transitions for star matter, and allow a discussion on the properties of the phase diagram under the generic phenomenon of Coulomb frustration. The quantum approach is based on a fermionic molecular dynamics model that we have developed from the density functional formalism, and numerically implemented using Skyrme forces optimized on neutron rich nuclei and neutron matter. This thesis work shows some first applications to the study the thermodynamics of finite nuclear systems, as well as nuclear structure calculations for light nuclei. A new formalism based on the molecular dynamics model is sketched which will ultimately allow treating the numerical quantum problem for the infinite star matter. (author)

  6. Phase diagram of the Kondo-Heisenberg model on honeycomb lattice with geometrical frustration

    Science.gov (United States)

    Li, Huan; Song, Hai-Feng; Liu, Yu

    2016-11-01

    We calculated the phase diagram of the Kondo-Heisenberg model on a two-dimensional honeycomb lattice with both nearest-neighbor and next-nearest-neighbor antiferromagnetic spin exchanges, to investigate the interplay between RKKY and Kondo interactions in the presence of magnetic frustration. Within a mean-field decoupling technology in slave-fermion representation, we derived the zero-temperature phase diagram as a function of Kondo coupling J k and frustration strength Q. The geometrical frustration can destroy the magnetic order, driving the original antiferromagnetic (AF) phase to non-magnetic valence bond solids (VBS). In addition, we found two distinct VBS. As J k is increased, a phase transition from AF to Kondo paramagnetic (KP) phase occurs, without the intermediate phase coexisting AF order with Kondo screening found in square lattice systems. In the KP phase, the enhancement of frustration weakens the Kondo screening effect, resulting in a phase transition from KP to VBS. We also found a process to recover the AF order from VBS by increasing J k in a wide range of frustration strength. Our work may provide predictions for future experimental observation of new processes of quantum phase transitions in frustrated heavy-fermion compounds.

  7. Frustrated smectic liquid crystalline phases in lactic acid derivatives

    Czech Academy of Sciences Publication Activity Database

    Glogarová, Milada; Novotná, Vladimíra

    2016-01-01

    Roč. 89, č. 7-8 (2016), s. 829-839 ISSN 0141-1594 R&D Projects: GA ČR GA15-02843S Institutional support: RVO:68378271 Keywords : field * liquid crystals * TGB phases Subject RIV: JJ - Other Materials Impact factor: 1.060, year: 2016

  8. Quantum phases, supersolids and quantum phase transitions of interacting bosons in frustrated lattices

    International Nuclear Information System (INIS)

    Ye, Jinwu; Chen, Yan

    2013-01-01

    By using the dual vortex method (DVM), we develop systematically a simple and effective scheme to use the vortex degree of freedoms on dual lattices to characterize the symmetry breaking patterns of the boson insulating states in the direct lattices. Then we apply our scheme to study quantum phases and phase transitions in an extended boson Hubbard model slightly away from 1/3 (2/3) filling on frustrated lattices such as triangular and Kagome lattice. In a triangular lattice at 1/3, we find a X-CDW, a stripe CDW phase which was found previously by a density operator formalism (DOF). Most importantly, we also find a new CDW-VB phase which has both local CDW and local VB orders, in sharp contrast to a bubble CDW phase found previously by the DOF. In the Kagome lattice at 1/3, we find a VBS phase and a 6-fold CDW phase. Most importantly, we also identify a CDW-VB phase which has both local CDW and local VB orders which was found in previous QMC simulations. We also study several other phases which are not found by the DVM. By analyzing carefully the saddle point structures of the dual gauge fields in the translational symmetry breaking sides and pushing the effective actions slightly away from the commensurate filling f=1/3(2/3), we classified all the possible types of supersolids and analyze their stability conditions. In a triangular lattice, there are X-CDW supersolid, stripe CDW supersolid, but absence of any valence bond supersolid (VB-SS). There are also a new kind of supersolid: CDW-VB supersolid. In a Kagome lattice, there are 6-fold CDW supersolid, stripe CDW supersolid, but absence of any valence bond supersolid (VB-SS). There are also a new kind of supersolid: CDW-VB supersolid. We show that independent of the types of the SS, the quantum phase transitions from solids to supersolids driven by a chemical potential are in the same universality class as that from a Mott insulator to a superfluid, therefore have exact exponents z=2, ν=1/2, η=0 (with

  9. Enhancement of geometric phase by frustration of decoherence: A Parrondo-like effect

    Science.gov (United States)

    Banerjee, Subhashish; Chandrashekar, C. M.; Pati, Arun K.

    2013-04-01

    Geometric phase plays an important role in evolution of pure or mixed quantum states. However, when a system undergoes decoherence the development of geometric phase may be inhibited. Here we show that when a quantum system interacts with two competing environments there can be enhancement of geometric phase. This effect is akin to a Parrondo-like effect on the geometric phase which results from quantum frustration of decoherence. Our result suggests that the mechanism of two competing decoherence can be useful in fault-tolerant holonomic quantum computation.

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

    Energy Technology Data Exchange (ETDEWEB)

    Fredrickson, Daniel C [Univ. of Wisconsin, Madison, WI (United States)

    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.

  11. Quantum entanglement and quantum phase transitions in frustrated Majumdar-Ghosh model

    International Nuclear Information System (INIS)

    Liu Guanghua; Wang Chunhai; Deng Xiaoyan

    2011-01-01

    By using the density matrix renormalization group technique, the quantum phase transitions in the frustrated Majumdar-Ghosh model are investigated. The behaviors of the conventional order parameter and the quantum entanglement entropy are analyzed in detail. The order parameter is found to peak at J 2 ∼0.58, but not at the Majumdar-Ghosh point (J 2 =0.5). Although, the quantum entanglements calculated with different subsystems display dissimilarly, the extremes of their first derivatives approach to the same critical point. By finite size scaling, this quantum critical point J C 2 converges to around 0.301 in the thermodynamic limit, which is consistent with those predicted previously by some authors (Tonegawa and Harada, 1987 ; Kuboki and Fukuyama, 1987 ; Chitra et al., 1995 ). Across the J C 2 , the system undergoes a quantum phase transition from a gapless spin-fluid phase to a gapped dimerized phase.

  12. Quantum phase transitions and anomalous Hall effect in frustrated Kondo lattices

    Science.gov (United States)

    Paschen, Silke; Grefe, Sarah Elaine; Ding, Wenxin; Si, Qimiao

    Among the pyrochlore iridates, the metallic compound Pr2 Ir2O7 (Pr-227) has shown characteristics of a possible chiral spin liquid state and quantum criticality. An important question surrounding the significant anomalous Hall response observed in Pr-227 is the nature of the f-electron local moments, including their Kondo coupling with the conduction d-electrons. The heavy effective mass and related thermodynamic characteristics indicate the involvement of the Kondo effect in this system's electronic properties. In this work, we study the effects of Kondo coupling on candidate time-reversal-symmetry-breaking spin liquid states on frustrated lattices. Representing the f-moments as slave fermions Kondo-coupled to conduction electrons, we study the competition between Kondo-singlet formation and chiral spin correlations. We derive an effective chiral interaction between the local moments and the conduction electrons and calculate the anomalous Hall response across the quantum phase transition from the Kondo destroyed phase to the Kondo screened phase. We discuss our results' implications for Pr-227 and related frustrated Kondo-lattice systems.

  13. Dynamical phase transition in a fully frustrated Josephson array on a square lattice

    International Nuclear Information System (INIS)

    Fisher, K. D.; Stroud, D.; Janin, L.

    1999-01-01

    We study dynamical phase transitions at temperature T=0 in a fully frustrated square Josephson junction array subject to a driving current density, which has nonzero components i x , i y parallel to both axes of the lattice. Our numerical results show clear evidence for three dynamical phases: a pinned vortex lattice characterized by zero time-averaged voltages x > t and y > t , a ''plastic'' phase in which both x > t and y > t are nonzero, and a moving lattice phase in which only one of the time-average voltage components is nonzero. The last of these has a finite transverse critical current: if a current is applied in the x direction, a nonzero transverse current density i y is required before y > t becomes nonzero. The voltage traces in the moving lattice phase are periodic in time. By contrast, the voltages in the plastic phase have continuous power spectra that are weakly dependent on frequency. This phase diagram is found numerically to be qualitatively unchanged by the presence of weak disorder. We also describe two simple analytical models that recover some, but not all, the characteristics of the three dynamical phases, and of the phase diagram calculated numerically. (c) 1999 The American Physical Society

  14. Magnetic-field-induced Quantum Phase in S = 1/2 Frustrated Trellis Lattice

    Science.gov (United States)

    Yamaguchi, Hironori; Yoshizawa, Daichi; Kida, Takanori; Hagiwara, Masayuki; Matsuo, Akira; Kono, Yohei; Sakakibara, Toshiro; Tamekuni, Yusuke; Miyagai, Hirotsugu; Hosokoshi, Yuko

    2018-04-01

    We present a new model compound of an S = 1/2 frustrated system with ferromagnetic interaction composed of verdazyl radical β-2,3,5-Cl3-V. The ab initio molecular orbital calculation indicates the formation of an S = 1/2 trellis lattice in which zigzag chains and ladders with ferromagnetic rung interaction are two-dimensionally coupled. We observe a field-induced successive phase transition and an unconventional change in the magnetization curve near the saturation field, accompanied by T2 dependence on the magnetic specific heat. A two-dimensional spin-nematic state attributed to the ferromagnetic rung interactions is a possible candidate for the ground state in high-field regions.

  15. Frustration and quantum criticality

    Science.gov (United States)

    Vojta, Matthias

    2018-06-01

    This review article is devoted to the interplay between frustrated magnetism and quantum critical phenomena, covering both theoretical concepts and ideas as well as recent experimental developments in correlated-electron materials. The first part deals with local-moment magnetism in Mott insulators and the second part with frustration in metallic systems. In both cases, frustration can either induce exotic phases accompanied by exotic quantum critical points or lead to conventional ordering with unconventional crossover phenomena. In addition, the competition of multiple phases inherent to frustrated systems can lead to multi-criticality.

  16. Frustration and quantum criticality.

    Science.gov (United States)

    Vojta, Matthias

    2018-03-15

    This review article is devoted to the interplay between frustrated magnetism and quantum critical phenomena, covering both theoretical concepts and ideas as well as recent experimental developments in correlated-electron materials. The first part deals with local-moment magnetism in Mott insulators and the second part with frustration in metallic systems. In both cases, frustration can either induce exotic phases accompanied by exotic quantum critical points or lead to conventional ordering with unconventional crossover phenomena. In addition, the competition of multiple phases inherent to frustrated systems can lead to multi-criticality. © 2018 IOP Publishing Ltd.

  17. Phase transitions in two-dimensional uniformly frustrated XY models. II. General scheme

    International Nuclear Information System (INIS)

    Korshunov, S.E.

    1986-01-01

    For two-dimensional uniformly frustrated XY models the group of symmetry spontaneously broken in the ground state is a cross product of the group of two-dimensional rotations by some discrete group of finite order. Different possibilities of phase transitions in such systems are investigated. The transition to the Coulomb gas with noninteger charges is widely used when analyzing the properties of relevant topological excitations. The number of these excitations includes not only domain walls and traditional (integer) vortices, but also vortices with a fractional number of circulation quanta which are to be localized at bends and intersections of domain walls. The types of possible phase transitions prove to be dependent on their relative sequence: in the case the vanishing of domain wall free energy occurs earlier (at increasing temperature) than the dissociation of pairs of ordinary vortices, the second phase transition is to be associated with dissociation of pairs of fractional vortices. The general statements are illustrated with a number of examples

  18. Phase transition for a uniformly frustrated 19-vertex model by use of the density matrix renormalization group

    International Nuclear Information System (INIS)

    Honda, Yasushi; Horiguchi, Tsuyoshi

    2001-01-01

    We investigate a uniformly frustrated 19-vertex model with an anisotropy parameter η by use of the density matrix renormalization group for the transfer matrix for 0.6≤η≤1.3. The scaling dimension x is calculated from eigenvalues of the transfer matrix for several values η. The finite-size scaling analyses with a logarithmic correction are carried out in order to determine transition temperatures. It is found that there are two kinds of phase transitions, although there is a possibility of a single transition. This result is not compatible with the result for the uniformly frustrated XY model

  19. Frustration tuning and perfect phase synchronization in the Kuramoto-Sakaguchi model.

    Science.gov (United States)

    Brede, Markus; Kalloniatis, Alexander C

    2016-06-01

    We present an analysis of conditions under which the dynamics of a frustrated Kuramoto-or Kuramoto-Sakaguchi-model on sparse networks can be tuned to enhance synchronization. Using numerical optimization techniques, linear stability, and dimensional reduction analysis, a simple tuning scheme for setting node-specific frustration parameters as functions of native frequencies and degrees is developed. Finite-size scaling analysis reveals that even partial application of the tuning rule can significantly reduce the critical coupling for the onset of synchronization. In the second part of the paper, a codynamics is proposed, which allows a dynamic tuning of frustration parameters simultaneously with the ordinary Kuramoto dynamics. We find that such codynamics enhance synchronization when operating on slow time scales, and impede synchronization when operating on fast time scales relative to the Kuramoto dynamics.

  20. Transverse phase-locking in fully frustrated Josephson junction arrays: A new type of fractional giant steps

    International Nuclear Information System (INIS)

    Marconi, Veronica I.; Kolton, Alejandro B.; Dominguez, Daniel; Gronbech-Jensen, Niels

    2003-05-01

    We study, analytically and numerically, phase locking of driven vortex lattices in fully-frustrated Josephson junction arrays at zero temperature. We consider the case when an ac current is applied perpendicular to a dc current. We observe phase locking, steps in the current-voltage characteristics, with a dependence on external ac-drive amplitude and frequency qualitatively different from the Shapiro steps, observed when the ac and dc currents are applied in parallel. Further, the critical current increases with increasing transverse ac-drive amplitude, while it decreases for longitudinal ac-drive. The critical current and the phase-locked current step width, increase quadratically with (small) amplitudes of the ac-drive. For larger amplitudes of the transverse ac-signal, we find windows where the critical current is hysteretic, and windows where phase locking is suppressed due to dynamical instabilities. We characterize the dynamical states around the phase-locking interference condition in the IV curve with voltage noise, Lyapunov exponents and Poincare sections. We find that zero temperature phase-locking behavior in large fully frustrated arrays is well described by an effective four plaquette model. (author)

  1. Influence of strong single-ion anisotropy on phase states of 3D and 2D frustrated magnets

    International Nuclear Information System (INIS)

    Fridman, Yu.A.; Kosmachev, O.A.; Matunin, D.A.; Gorelikov, G.A.; Klevets, Ph.N.

    2010-01-01

    We investigated the influence of strong single-ion anisotropy, exceeding exchange interaction, and frustrated exchange interaction on spin-wave excitation spectra and phase states using the Hubbard operators' technique, allowing the exact account of single-ion anisotropy. The results show that both the homogeneous phases (ferromagnetic and quadrupolar) and the spatially inhomogeneous phase (spiral structure) are possible in the 3D magnetic crystal. The region of existence of the spiral structure is considerably smaller than that in the analogues system, but with weak single-ion anisotropy. The situation is more complex in the 2D system; another spatially inhomogeneous state (the domain structure) can be realized in addition to the spiral magnetic structure. The phase diagrams for both the 3D and 2D systems were plotted.

  2. Phase transitions in two-dimensional uniformly frustrated XY models. I. antiferromagnetic model on a triangular lattice

    International Nuclear Information System (INIS)

    Korshunov, S.E.; Uimin, G.V.

    1986-01-01

    A most popular model in the family of two-dimensional uniformly-frustrated XY models is the antiferromagnetic model on a triangular lattice (AF XY(t) model). Its ground state is both continuously and twofold discretely degenerated. Different phase transitions possible in such systems are investigated. Relevant topological excitations are analyzed and a new class of such (vortices with a fractional number of circulation quanta) is discovered. Their role in determining the properties of the system proves itself essential. The characteristics of phase transitions related to breaking of discrete and continuous symmetries change. The phase diagram of the ''generalized'' AF XY(t) model is constructed. The results obtained are rederived in the representation of the Coulomb gas with half-interger charges, equivalent to the AF XY(t) model with the Berezinskii-Villain interaction

  3. Fluorine incorporation during Si solid phase epitaxy

    International Nuclear Information System (INIS)

    Impellizzeri, G.; Mirabella, S.; Romano, L.; Napolitani, E.; Carnera, A.; Grimaldi, M.G.; Priolo, F.

    2006-01-01

    We have investigated the F incorporation and segregation in preamorphized Si during solid phase epitaxy (SPE) at different temperatures and for several implanted-F energies and fluences. The Si samples were amorphized to a depth of 550 nm by implanting Si at liquid nitrogen temperature and then enriched with F at different energies (65-150 keV) and fluences (0.07-5 x 10 14 F/cm 2 ). Subsequently, the samples were regrown by SPE at different temperatures: 580, 700 and 800 deg. C. We have found that the amount of F incorporated after SPE strongly depends on the SPE temperature and on the energy and fluence of the implanted-F, opening the possibility to tailor the F profile during SPE

  4. Topological phases in frustrated synthetic ladders with an odd number of legs

    Science.gov (United States)

    Barbarino, Simone; Dalmonte, Marcello; Fazio, Rosario; Santoro, Giuseppe E.

    2018-01-01

    The realization of the Hofstadter model in a strongly anisotropic ladder geometry has now become possible in one-dimensional optical lattices with a synthetic dimension. In this work, we show how the Hofstadter Hamiltonian in such ladder configurations hosts a topological phase of matter which is radically different from its two-dimensional counterpart. This topological phase stems directly from the hybrid nature of the ladder geometry and is protected by a properly defined inversion symmetry. We start our analysis by considering the paradigmatic case of a three-leg ladder which supports a topological phase exhibiting the typical features of topological states in one dimension: robust fermionic edge modes, a degenerate entanglement spectrum, and a nonzero Zak phase; then, we generalize our findings—addressable in the state-of-the-art cold-atom experiments—to ladders with a higher number of legs.

  5. Formation of AlFeSi phase in AlSi12 alloy with Ce addition

    Directory of Open Access Journals (Sweden)

    S. Kores

    2012-04-01

    Full Text Available The influence of cerium addition on the solidification sequence and microstructure constituents of the Al-Si alloys with 12,6 mass % Si was examined. The solidification was analyzed by a simple thermal analysis. The microstructures were examined with conventional light and scanning electron microscopy. Ternary AlSiCe phase was formed in the Al-Si alloys with added cerium during the solidification process. AlSiCe and β-AlFeSi phases solidified together in the region that solidified the last. Cerium addition influenced on the morphology of the α-AlFeSi phase solidification.

  6. Nonclassical disordered phase in the strong quantum limit of frustrated antiferromagnets

    International Nuclear Information System (INIS)

    Ceccatto, H.A.; Gazza, C.J.; Trumper, A.E.

    1992-07-01

    The Schwinger boson approach to quantum helimagnets is discussed. It is shown that in order to get quantitative agreement with exact results on finite lattices, parity-breaking pairing of bosons must be allowed. The so-called J 1 - J 2 - J 3 model is studied, particularly on the special line J 2 = 2J 3 . A quantum disordered phase is found between the Neel and spiral phases, though notably only in the strong quantum limit S = 1/2, and for the third-neighbor coupling J 3 ≥ 0.038 J 1 . For spins S≥1 the spiral phase goes continuously to an antiferromagnetic order. (author). 19 refs, 3 figs

  7. Experimental study of the magnetic phase transition in the MnSi itinerant helimagnet

    International Nuclear Information System (INIS)

    Stishov, S. M.; Petrova, A. E.; Khasanov, S.; Panova, G. Kh.; Shikov, A. A.; Lashley, J. C.; Wu, D.; Lograsso, T. A.

    2008-01-01

    Magnetic susceptibility, heat capacity, thermal expansion, and resistivity of a high-quality single crystal of MnSi were carefully studied at ambient pressure. The calculated change in magnetic entropy in the temperature range 0-30 K is less than 0.1R, a low value that emphasizes the itinerant nature of magnetism in MnSi. A linear temperature term dominates the behavior of the thermal expansion coefficient in the range 30-150 K, which correlates to a large enhancement of the linear electronic term in the heat capacity. A surprising similarity between variation of the heat capacity, the thermal expansion coefficient, and the temperature derivative of resistivity through the phase transition in MnSi is observed. Specific forms of the heat capacity, thermal expansion coefficient, and temperature derivative of resistivity at the phase transition to a helical magnetic state near 29 K are interpreted as a combination of sharp first-order features and broad peaks or shallow valleys of yet unknown origin. The appearance of these broad satellites probably hints at a frustrated magnetic state in MnSi slightly above the transition temperature. Present experimental findings bring the current views on the phase diagram of MnSi into question

  8. Possible quadrupolar nematic phase in the frustrated spin chain LiCuSbO4: An NMR investigation

    Science.gov (United States)

    Bosiočić, M.; Bert, F.; Dutton, S. E.; Cava, R. J.; Baker, P. J.; Požek, M.; Mendels, P.

    2017-12-01

    The frustrated one-dimensional quantum magnet LiCuSbO4 is a rare realization of the J1-J2 spin chain model with an easily accessible saturation field, formerly estimated at 12 T. Exotic multipolar nematic phases were theoretically predicted in such compounds just below the saturation field, but without unambiguous experimental observation so far. In this paper we present extensive experimental research on the compound in a wide temperature (30 mK to 300 K) and field (0-13.3 T) range by muon spin rotation (μ SR ), 7Li nuclear magnetic resonance (NMR), and magnetic susceptibility (SQUID). μ SR experiments in zero magnetic field demonstrate the absence of long-range 3D ordering down to 30 mK. Together with former heat capacity data [Dutton et al., Phys. Rev. Lett. 108, 187206 (2012), 10.1103/PhysRevLett.108.187206], magnetic susceptibility measurements suggest a short-range-correlated vector chiral phase in the field range 0-4 T. At the intermediate-field values (5-12 T), the system enters a 3D-ordered spin density wave phase with 0.75 μB per copper site at lowest temperatures (125 mK), estimated by NMR. At still higher field, the magnetization is found to be saturated above 13 T where the spin lattice T1-1 relaxation reveals a spin gap estimated at 3.2(2) K. We narrow down the possibility of observing a multipolar nematic phase to the range 12.5-13 T.

  9. Phases in U-Si alloys

    International Nuclear Information System (INIS)

    Domagala, R.F.

    1986-09-01

    The binary (two component) U-Si system contains a total of seven ''compounds.'' The most U-rich compounds are of interest to the RERTR community because they are now being employed as fuels in research and test reactors. The nomenclature used in describing these fuels and the metallurgical significance of the notations recorded may have different meanings to people from different technical backgrounds. This paper is a succinct exploration of the principles of phase equilibria and the realities of commerical fabrication as applied to U-Si alloys. It is an attempt to record in referenceable and retrievable form information of value to the continued development, application and understanding of silicide fuels

  10. Phase transitions and magnetization of the mixed-spin Ising–Heisenberg double sawtooth frustrated ladder

    Science.gov (United States)

    Arian Zad, Hamid; Ananikian, Nerses

    2018-04-01

    The mixed spin-(1,1/2) Ising–Heisenberg double sawtooth ladder containing a mixture of both spin-1 and spin-1/2 nodal atoms, and the spin-1/2 interstitial dimers are approximately solved by the transfer-matrix method. Here, we study in detail the ground-state phase diagrams, also influences of the bilinear exchange coupling on the rungs and cyclic four-spin exchange interaction in square plaquette of each block on the magnetization and magnetic susceptibility of the suggested ladder at low temperature. Such a double sawtooth ladder may be found in a Shastry-Sutherland lattice-type. In spite of the spin ordering of odd and even blocks being different from each other, due to the commutation relation between all different block Hamiltonians, phase diagrams, magnetization behavior and thermodynamic properties of the model are the same for odd and even blocks. We show that at low temperature, both exchange couplings can change the quality and quantity of the magnetization plateaus versus the magnetic field changes. Specially, we find a new magnetization plateau M/Ms= 5/6 for this model. Besides, we examine the magnetic susceptibility and specific heat of the model in detail. It is proven that behaviors of the magnetization and the magnetic susceptibility coincide at low temperature. The specific heat displays diverse temperature dependencies, which include a Schottky-type peak at a special temperature interval. We observe that with increase of the bilinear exchange coupling on the rungs, second peak temperature dependence grows.

  11. Rod-like β-FeSi2 phase grown on Si (111) substrate

    International Nuclear Information System (INIS)

    Han Ming; Tanaka, Miyoko; Takeguchi, Masaki; Furuya, Kazuo

    2004-01-01

    Pure Fe with coverage of 0.5-2.0 nm was deposited on Si (111) 7x7 surfaces by reactive deposition epitaxy (RDE) in an integrated ultrahigh vacuum (UHV) system. Transmission electron microscopy (TEM) confirmed that the as-deposited epitaxial phase exhibits rod-like and equilateral triangular morphology. The as-deposited phase was identified as c-FeSi 2 by electron diffraction and high-resolution transmission electron microscopy. It was found that there exists lattice distortion in epitaxial c-FeSi 2 phase. Upon annealing at 1073 K, the metastable c-FeSi 2 transforms into equilibrium β-FeSi 2 phase, the latter inherits completely the morphology of c-FeSi 2 phase. Based on RDE and subsequent annealing, a new fabrication technique to grow rod-like semiconducting β-FeSi 2 on a Si substrate has been proposed in the present work

  12. Superconducting frustration bit

    International Nuclear Information System (INIS)

    Tanaka, Y.

    2014-01-01

    Highlights: • A frustration bit element is proposed for a conventional superconducting circuit. • It is composed of π-junctions. • It mimics the multiband superconductor. - Abstract: A basic design is proposed for a classical bit element of a superconducting circuit that mimics a frustrated multiband superconductor and is composed of an array of π-Josephson junctions (π-junction). The phase shift of π provides the lowest energy for one π-junction, but neither a π nor a zero phase shift gives the lowest energy for an assembly of π-junctions. There are two chiral states that can be used to store one bit information. The energy scale for reading and writing to memory is of the same order as the junction energy, and is thus in the same order of the driving energy of the circuit. In addition, random access is also possible

  13. Si-Sb-Te materials for phase change memory applications

    International Nuclear Information System (INIS)

    Rao Feng; Song Zhitang; Ren Kun; Zhou Xilin; Cheng Yan; Wu Liangcai; Liu Bo

    2011-01-01

    Si-Sb-Te materials including Te-rich Si 2 Sb 2 Te 6 and Si x Sb 2 Te 3 with different Si contents have been systemically studied with the aim of finding the most suitable Si-Sb-Te composition for phase change random access memory (PCRAM) use. Si x Sb 2 Te 3 shows better thermal stability than Ge 2 Sb 2 Te 5 or Si 2 Sb 2 Te 6 in that Si x Sb 2 Te 3 does not have serious Te separation under high annealing temperature. As Si content increases, the data retention ability of Si x Sb 2 Te 3 improves. The 10 years retention temperature for Si 3 Sb 2 Te 3 film is ∼ 393 K, which meets the long-term data storage requirements of automotive electronics. In addition, Si richer Si x Sb 2 Te 3 films also show improvement on thickness change upon annealing and adhesion on SiO 2 substrate compared to those of Ge 2 Sb 2 Te 5 or Si 2 Sb 2 Te 6 films. However, the electrical performance of PCRAM cells based on Si x Sb 2 Te 3 films with x > 3.5 becomes worse in terms of stable and long-term operations. Si x Sb 2 Te 3 materials with 3 < x < 3.5 are proved to be suitable for PCRAM use to ensure good overall performance.

  14. Level crossing, spin structure factor and quantum phases of the frustrated spin-1/2 chain with first and second neighbor exchange.

    Science.gov (United States)

    Kumar, Manoranjan; Parvej, Aslam; Soos, Zoltán G

    2015-08-12

    The spin-1/2 chain with isotropic Heisenberg exchange J1, J2  >  0 between first and second neighbors is frustrated for either sign of J1. Its quantum phase diagram has critical points at fixed J1/J2 between gapless phases with nondegenerate ground state (GS) and quasi-long-range order (QLRO) and gapped phases with doubly degenerate GS and spin correlation functions of finite range. In finite chains, exact diagonalization (ED) estimates critical points as level crossing of excited states. GS spin correlations enter in the spin structure factor S(q) that diverges at wave vector qm in QLRO(q(m)) phases with periodicity 2π/q(m) but remains finite in gapped phases. S(q(m)) is evaluated using ED and density matrix renormalization group (DMRG) calculations. Level crossing and the magnitude of S(q(m)) are independent and complementary probes of quantum phases, based respectively on excited and ground states. Both indicate a gapless QLRO(π/2) phase between  -1.2  quantum critical points at small frustration J2 but disagree in the sector of weak exchange J1 between Heisenberg antiferromagnetic chains on sublattices of odd and even-numbered sites.

  15. Magnetic phase transitions in two-dimensional frustrated Cu3R(SeO3)2O2Cl. Spectroscopic study

    Science.gov (United States)

    Klimin, S. A.; Budkin, I. V.

    2017-01-01

    Using optical study of electronic spectra of rare-earth (RE) ions, magnetic phase transitions in the low-dimensional frustrated RE magnets Cu3R(SeO3)2O2Cl (R = Sm, Yb, Er, Nd, Pr, Eu) were investigated. Phase transitions were registered either by splittings of crystal-field (CF) doublets or by repulsion of CF levels of f-ions in a staggered magnetic field. Different scenarios of magnetic order in isostructural compounds of the francisite family are discussed.

  16. Ashkin-Teller criticality and weak first-order behavior of the phase transition to a fourfold degenerate state in two-dimensional frustrated Ising antiferromagnets

    Science.gov (United States)

    Liu, R. M.; Zhuo, W. Z.; Chen, J.; Qin, M. H.; Zeng, M.; Lu, X. B.; Gao, X. S.; Liu, J.-M.

    2017-07-01

    We study the thermal phase transition of the fourfold degenerate phases (the plaquette and single-stripe states) in the two-dimensional frustrated Ising model on the Shastry-Sutherland lattice using Monte Carlo simulations. The critical Ashkin-Teller-like behavior is identified both in the plaquette phase region and the single-stripe phase region. The four-state Potts critical end points differentiating the continuous transitions from the first-order ones are estimated based on finite-size-scaling analyses. Furthermore, a similar behavior of the transition to the fourfold single-stripe phase is also observed in the anisotropic triangular Ising model. Thus, this work clearly demonstrates that the transitions to the fourfold degenerate states of two-dimensional Ising antiferromagnets exhibit similar transition behavior.

  17. Frustrated spin systems

    CERN Document Server

    2013-01-01

    This book covers all principal aspects of currently investigated frustrated systems, from exactly solved frustrated models to real experimental frustrated systems, going through renormalization group treatment, Monte Carlo investigation of frustrated classical Ising and vector spin models, low-dimensional systems, spin ice and quantum spin glass. The reader can - within a single book - obtain a global view of the current research development in the field of frustrated systems.This new edition is updated with recent theoretical, numerical and experimental developments in the field of frustrated

  18. SiC-SiC and C-SiC Honeycomb for Advanced Flight Structures, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed project builds upon the work done in Phase I with the development of a C-SiC CMC honeycomb material that was successfully tested for mechanical...

  19. Frustration in biomolecules.

    Science.gov (United States)

    Ferreiro, Diego U; Komives, Elizabeth A; Wolynes, Peter G

    2014-11-01

    Biomolecules are the prime information processing elements of living matter. Most of these inanimate systems are polymers that compute their own structures and dynamics using as input seemingly random character strings of their sequence, following which they coalesce and perform integrated cellular functions. In large computational systems with finite interaction-codes, the appearance of conflicting goals is inevitable. Simple conflicting forces can lead to quite complex structures and behaviors, leading to the concept of frustration in condensed matter. We present here some basic ideas about frustration in biomolecules and how the frustration concept leads to a better appreciation of many aspects of the architecture of biomolecules, and especially how biomolecular structure connects to function by means of localized frustration. These ideas are simultaneously both seductively simple and perilously subtle to grasp completely. The energy landscape theory of protein folding provides a framework for quantifying frustration in large systems and has been implemented at many levels of description. We first review the notion of frustration from the areas of abstract logic and its uses in simple condensed matter systems. We discuss then how the frustration concept applies specifically to heteropolymers, testing folding landscape theory in computer simulations of protein models and in experimentally accessible systems. Studying the aspects of frustration averaged over many proteins provides ways to infer energy functions useful for reliable structure prediction. We discuss how frustration affects folding mechanisms. We review here how the biological functions of proteins are related to subtle local physical frustration effects and how frustration influences the appearance of metastable states, the nature of binding processes, catalysis and allosteric transitions. In this review, we also emphasize that frustration, far from being always a bad thing, is an essential feature

  20. Chiral Paramagnetic Skyrmion-like Phase in MnSi

    NARCIS (Netherlands)

    Pappas, C.; Lelièvre-Berna, E.; Falus, P.; Bentley, P.M.; Moskvin, E.; Grigoriev, S.; Fouquet, P.; Farago, B.

    2009-01-01

    We present a comprehensive study of chiral fluctuations in the reference helimagnet MnSi by polarized neutron scattering and neutron spin echo spectroscopy, which reveals the existence of a completely left-handed and dynamically disordered phase. This phase may be identified as a spontaneous

  1. Phase Equilibria of the Sn-Ni-Si Ternary System and Interfacial Reactions in Sn-(Cu)/Ni-Si Couples

    Science.gov (United States)

    Fang, Gu; Chen, Chih-chi

    2015-07-01

    Interfacial reactions in Sn/Ni-4.5 wt.%Si and Sn-Cu/Ni-4.5 wt.%Si couples at 250°C, and Sn-Ni-Si ternary phase equilibria at 250°C were investigated in this study. Ni-Si alloys, which are nonmagnetic, can be regarded as a diffusion barrier layer material in flip chip packaging. Solder/Ni-4.5 wt.%Si interfacial reactions are crucial to the reliability of soldered joints. Phase equilibria information is essential for development of solder/Ni-Si materials. No ternary compound is present in the Sn-Ni-Si ternary system at 250°C. Extended solubility of Si in the phases Ni3Sn2 and Ni3Sn is 3.8 and 6.1 at.%, respectively. As more Si dissolves in these phases their lattice constants decrease. No noticeable ternary solubility is observed for the other intermetallics. Interfacial reactions in solder/Ni-4.5 wt.%Si are similar to those for solder/Ni. Si does not alter the reaction phases. No Si solubility in the reaction phases was detected, although rates of growth of the reaction phases were reduced. Because the alloy Ni-4.5 wt.%Si reacts more slowly with solders than pure Ni, the Ni-4.5 wt.%Si alloy could be a potential new diffusion barrier layer material for flip chip packaging.

  2. Phase formation in Mg-Sn-Si and Mg-Sn-Si-Ca alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kozlov, A.; Groebner, J. [Institute of Metallurgy, Clausthal University of Technology, Robert-Koch-Str. 42, D-38678 Clausthal-Zellerfeld (Germany); Schmid-Fetzer, R., E-mail: schmid-fetzer@tu-clausthal.de [Institute of Metallurgy, Clausthal University of Technology, Robert-Koch-Str. 42, D-38678 Clausthal-Zellerfeld (Germany)

    2011-02-17

    Research highlights: > The solidification paths of ternary and quaternary alloys are analyzed in detail, using the tool of thermodynamic calculations. > The precipitation sequence of phases and their amounts compare well with the microstructure of alloys. > The most efficient comparison to the experimental thermal analysis data is done by calculation of the enthalpy variation with temperature. > The viability of a procedure for the selection of multicomponent key samples is demonstrated for the development of the Mg-Ca-Si-Sn phase diagram. - Abstract: Experimental work is done and combined with the Calphad method to generate a consistent thermodynamic description of the Mg-Ca-Si-Sn quaternary system, validated for Mg-rich alloys. The viability of a procedure for the selection of multicomponent key samples is demonstrated for this multicomponent system. Dedicated thermal analysis with DTA/DSC on sealed samples is performed and the microstructure of slowly solidified alloys is analyzed using SEM/EDX. The thermodynamic description and phase diagram of the ternary Mg-Si-Sn system, developed in detail also in this work, deviates significantly from a previous literature proposal. The phase formation in ternary and quaternary alloys is analyzed using the tool of thermodynamic equilibrium and Scheil calculations for the solidification paths and compared with present experimental data. The significant ternary/quaternary solid solubilities of pertinent intermetallic phases are quantitatively introduced in the quaternary Mg-Ca-Si-Sn phase diagram and validated by experimental data.

  3. Effects of SiC amount on phase compositions and properties of Ti3SiC2-based composites

    Institute of Scientific and Technical Information of China (English)

    蔡艳芝; 殷小玮; 尹洪峰

    2015-01-01

    The phase compositions and properties of Ti3SiC2-based composites with SiC addition of 5%−30% in mass fraction fabricated by in-situ reaction and hot pressing sintering were studied. SiC addition effectively prevented TiC synthesis but facilitated SiC synthesis. The Ti3SiC2/TiC−SiC composite had better oxidation resistance when SiC added quantity reached 20% but poorer oxidation resistance with SiC addition under 15%than Ti3SiC2/TiC composite at higher temperatures. There were more than half of the original SiC and a few Ti3SiC2 remaining in Ti3SiC2/TiC−SiC with 20% SiC addition, but all constituents in Ti3Si2/TiC composite were oxidized after 12 h in air at 1500 °C. The oxidation scale thickness of TS30, 1505.78μm, was near a half of that of T, 2715μm, at 1500 °C for 20 h. Ti3SiC2/TiC composite had a flexural strength of 474 MPa, which was surpassed by Ti3SiC2/TiC−SiC composites when SiC added amount reached 15%. The strength reached the peak of 518 MPa at 20%SiC added amount.

  4. Sr-Al-Si co-segregated regions in eutectic Si phase of Sr-modified Al-10Si alloy.

    Science.gov (United States)

    Timpel, M; Wanderka, N; Schlesiger, R; Yamamoto, T; Isheim, D; Schmitz, G; Matsumura, S; Banhart, J

    2013-09-01

    The addition of 200 ppm strontium to an Al-10 wt% Si casting alloy changes the morphology of the eutectic silicon phase from coarse plate-like to fine fibrous networks. In order to clarify this modification mechanism the location of Sr within the eutectic Si phase has been investigated by a combination of high-resolution methods. Whereas three-dimensional atom probe tomography allows us to visualise the distribution of Sr on the atomic scale and to analyse its local enrichment, transmission electron microscopy yields information about the crystallographic nature of segregated regions. Segregations with two kinds of morphologies were found at the intersections of Si twin lamellae: Sr-Al-Si co-segregations of rod-like morphology and Al-rich regions of spherical morphology. Both are responsible for the formation of a high density of multiple twins and promote the anisotropic growth of the eutectic Si phase in specific crystallographic directions during solidification. The experimental findings are related to the previously postulated mechanism of "impurity induced twinning". Copyright © 2012 Elsevier B.V. All rights reserved.

  5. Characterization of SiCf/SiC and CNT/SiC composite materials produced by liquid phase sintering

    International Nuclear Information System (INIS)

    Lee, J.K.; Lee, S.P.; Cho, K.S.; Byun, J.H.; Bae, D.S.

    2011-01-01

    This paper dealt with the microstructure and mechanical properties of SiC based composites reinforced with different reinforcing materials. The composites were fabricated using reinforcing materials of carbon nanotubes (CNT) and Tyranno Lox-M SiC chopped fibers. The volume fraction of carbon nanotubes was also varied in this composite system. An Al 2 O 3 -Y 2 O 3 powder mixture was used as a sintering additive in the consolidation of the SiC matrix. The characterization of the composites was investigated by means of SEM and three point bending tests. These composites showed a dense morphology of the matrix region, by the creation of a secondary phase. The composites reinforced with SiC chopped fibers possessed a flexural strength of about 400 MPa at room temperature. The flexural strength of the carbon nanotubes composites had a tendency to decrease with increased volume fraction of the reinforcing material.

  6. Transport properties and phase diagram of UNi2Si2

    International Nuclear Information System (INIS)

    Ning, Y.B.; Garrett, J.D.; Datars, W.R.; McMaster Univ., Hamilton, ON

    1992-01-01

    The resistivity and Hall coefficient of single-crystal UNi 2 Si 2 have been studied in detail for the temperature range 4.2-300 K. The resistivity of UNi 2 Si 2 is largely due to magnetic scattering and the phonon scattering contribution is estimated to be about 14% at room temperature. At low temperatures, the resistivity can be described by a gapped spin-wave model plus a T 2 term. The temperature dependence of the Hall coefficient is accounted for by a theoretical model invoking skew scattering of conduction electrons by localized magnetic moments. Among the three magnetic phase transition temperatures, the two lower ones are found to be magnetic field dependent and shift with the field applied along the tetragonal c axis. Using the resistivity measurement in an applied magnetic field, a field-temperature phase diagram of UNi 2 Si 2 is presented. (author)

  7. SiC/SiC composites through transient eutectic-phase route for fusion applications

    International Nuclear Information System (INIS)

    Katoh, Y.; Kohyama, A.; Nozawa, T.; Sato, M.

    2004-01-01

    Factors that may limit attractiveness of silicon-carbide-based ceramic composites to fusion applications include thermal conductivity, applicable design stress, chemical compatibility, hermeticity, radiation stability and fabrication cost. A novel SiC/SiC composite, which has recently been developed through nano-infiltration and transient eutectic-phase (NITE) processing route, surpasses conventional materials in many of these properties. In this paper, the latest development, property evaluation and prospect of the NITE SiC/SiC composites are briefly reviewed. The topics range from fundamental aspects of process development to industrial process development. Elevated temperature strength, fracture behavior, and thermo-physical properties in various environments are summarized. Future directions of materials and application technology development are also discussed

  8. Ternary systems Sr-{Ni,Cu}-Si: Phase equilibria and crystal structure of ternary phases

    International Nuclear Information System (INIS)

    Nasir, Navida; Melnychenko-Koblyuk, Nataliya; Grytsiv, Andriy; Rogl, Peter; Giester, Gerald; Wosik, Jaroslaw; Nauer, Gerhard E.

    2010-01-01

    Phase relations were established in the Sr-poor part of the ternary systems Sr-Ni-Si (900 deg. C) and Sr-Cu-Si (800 deg. C) by light optical microscopy, electron probe microanalysis and X-ray diffraction on as cast and annealed alloys. Two new ternary compounds SrNiSi 3 (BaNiSn 3 -type) and SrNi 9-x Si 4+x (own-type) were found in the Sr-Ni-Si system along with previously reported Sr(Ni x Si 1-x ) 2 (AlB 2 -type). The crystal structure of SrNi 9-x Si 4+x (own-type, x=2.7, a=0.78998(3), c=1.1337(2) nm; space group P4/nbm) was determined from X-ray single crystal counter to be a low symmetry derivative of the cubic, parent NaZn 13 -type. At higher Si-content X-ray Rietveld refinements reveal the formation of a vacant site (□) corresponding to a formula SrNi 5.5 Si 6.5 □ 1.0 . Phase equilibria in the Sr-Cu-Si system are characterized by the compounds SrCu 2-x Si 2+x (ThCr 2 Si 2 -type), Sr(Cu x Si 1-x ) 2 (AlB 2 -type), SrCu 9-x Si 4+x (0≤x≤1.0; CeNi 8.5 Si 4.5 -type) and SrCu 13-x Si x (4≤x≤1.8; NaZn 13 -type). The latter two structure types appear within a continuous solid solution. Neither a type-I nor a type-IX clathrate compound was encountered in the Sr-{Cu,Ni}-Si systems. Structural details are furthermore given for about 14 new ternary compounds from related alloy systems with Ba. - Graphical abstract: The crystal structure of SrNi 9-x Si 4+x (own-type, x=2.7, a=0.78998(3), c=1.1337(2) nm; space group P4/nbm) was determined from X-ray single crystal counter to be a low symmetry derivative of the cubic, parent NaZn 13 -type and is related to CeNi 8.5 Si 4.5 -type.

  9. Investigation of possible phase transition of the frustrated spin-1/2 J 1-J 2-J 3 model on the square lattice.

    Science.gov (United States)

    Hu, Ai-Yuan; Wang, Huai-Yu

    2017-09-05

    The frustrated spin-1/2 J 1 -J 2 -J 3 antiferromagnet with exchange anisotropy on the two-dimensional square lattice is investigated. The exchange anisotropy is presented by η with 0 ≤ η J 1 , J 2 , J 3 and anisotropy on the possible phase transition of the Néel state and collinear state are studied comprehensively. Our results indicate that for J 3  > 0 there are upper limits [Formula: see text] and η c values. When 0 J 3  ≤ [Formula: see text] and 0 ≤ η ≤ η c , the Néel and collinear states have the same order-disorder transition point at J 2  = J 1 /2. Nevertheless, when the J 3 and η values beyond the upper limits, it is a paramagnetic phase at J 2  = J 1 /2. For J 3  J 2  = J 1 /2. Therefore, for J 2  = J 1 /2, under such parameters, a first-order phase transition between the two states for these two cases below the critical temperatures may occur. When J 2  ≠ J 1 /2, the Néel and collinear states may also exist, while they have different critical temperatures. When J 2  > J 1 /2, a first-order phase transition between the two states may also occur. However, for J 2  J 1 /2, the Néel state is always more stable than the collinear state.

  10. Growth of β-FeSi2 layers on Si (111) by solid phase and reactive deposition epitaxies

    International Nuclear Information System (INIS)

    Miquita, D.R.; Paniago, R.; Rodrigues, W.N.; Moreira, M.V.B.; Pfannes, H.-D.; Oliveira, A.G. de

    2005-01-01

    Iron silicides were grown on Si (111) substrates by Solid Phase Epitaxy (SPE) and Reactive Deposition Epitaxy (RDE) to identify the optimum conditions to obtain the semiconducting β-FeSi 2 phase. The films were produced under different growth and annealing conditions and analyzed in situ and ex situ by X-ray Photoelectron Spectroscopy, and ex situ by Conversion Electron Moessbauer Spectroscopy. The use of these techniques allowed the investigation of different depth regions of the grown layer. Films of the ε-FeSi and β-FeSi 2 phases were obtained as well as the mixtures Fe 3 Si + ε-FeSi and ε-FeSi + β-FeSi 2 . The sequence Fe 3 Si→ε-FeSi→β-FeSi 2 was found upon annealing, where the phase transformation occurred due to the migration of silicon atoms from the substrate to the surface region of the grown layer. The best conditions for the phase transformation in SPE samples were met after annealing in the range 700 - 800 deg. C. For the RDE samples, the transition to the beta phase occurred between 600 and 700 deg. C, but pure β-FeSi 2 was obtained only after two hours of annealing at 700 deg. C

  11. Multipartite entanglement and frustration

    International Nuclear Information System (INIS)

    Facchi, P; Florio, G; Pascazio, S; Marzolino, U; Parisi, G

    2010-01-01

    Some features of the global entanglement of a composed quantum system can be quantified in terms of the purity of a balanced bipartition, made up of half of its subsystems. For the given bipartition, purity can always be minimized by taking a suitable (pure) state. When many bipartitions are considered, the requirement that purity be minimal for all bipartitions can engender conflicts and frustration will arise. This unearths an interesting link between frustration and multipartite entanglement, defined as the average purity over all (balanced) bipartitions.

  12. Multipartite entanglement and frustration

    Science.gov (United States)

    Facchi, P.; Florio, G.; Marzolino, U.; Parisi, G.; Pascazio, S.

    2010-02-01

    Some features of the global entanglement of a composed quantum system can be quantified in terms of the purity of a balanced bipartition, made up of half of its subsystems. For the given bipartition, purity can always be minimized by taking a suitable (pure) state. When many bipartitions are considered, the requirement that purity be minimal for all bipartitions can engender conflicts and frustration will arise. This unearths an interesting link between frustration and multipartite entanglement, defined as the average purity over all (balanced) bipartitions.

  13. Multipartite entanglement and frustration

    Energy Technology Data Exchange (ETDEWEB)

    Facchi, P [Dipartimento di Matematica, Universita di Bari, I-70125 Bari (Italy); Florio, G; Pascazio, S [Istituto Nazionale di Fisica Nucleare, Sezione di Bari, I-70126 Bari (Italy); Marzolino, U [Dipartimento di Fisica, Universita di Trieste, and Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34014 Trieste (Italy); Parisi, G [Dipartimento di Fisica, Universita di Roma ' La Sapienza' , Piazzale Aldo Moro 2, Centre for Statistical Mechanics and Complexity (SMC), CNR-INFM, and Istituto Nazionale di Fisica Nucleare, Sezione di Roma, 00185 Roma (Italy)], E-mail: paolo.facchi@ba.infn.it

    2010-02-15

    Some features of the global entanglement of a composed quantum system can be quantified in terms of the purity of a balanced bipartition, made up of half of its subsystems. For the given bipartition, purity can always be minimized by taking a suitable (pure) state. When many bipartitions are considered, the requirement that purity be minimal for all bipartitions can engender conflicts and frustration will arise. This unearths an interesting link between frustration and multipartite entanglement, defined as the average purity over all (balanced) bipartitions.

  14. Phase relations in the SiC-Al2O3-Pr2O3 system

    International Nuclear Information System (INIS)

    Pan, W.; Wu, L.; Jiang, Y.; Huang, Z.

    2016-01-01

    Phase relations in the Si-Al-Pr-O-C system, including the SiC-Al 2 O 3 -Pr 2 O 3 , the Al 2 O 3 -Pr 2 O 3 -SiO 2 and the SiC-Al 2 O 3 -Pr 2 O 3 -SiO 2 subsystems, were determined by means of XRD phase analysis of solid-state-reacted samples fabricated by using SiC, Al 2 O 3 , Pr 2 O 3 and SiO 2 powders as the starting materials. Subsolidus phase diagrams of the systems were presented. Two Pr-aluminates, namely PrAlO 3 (PrAP) and PrAl 11 O 18 (β(Pr) β-Al 2 O 3 type) were formed in the SiC-Al 2 O 3 -Pr 2 O 3 system. SiC was compatible with both of them. Pr-silicates of Pr 2 SiO 5 , Pr 2 Si 2 O 7 and Pr 9.33 Si 6 O 26 (H(Pr) apatite type) were formed owing to presence of SiO 2 impurity in the SiC powder. The presence of the SiO 2 extended the ternary system of SiC-Al 2 O 3 -Pr 2 O 3 into a quaternary system of SiC-Al 2 O 3 -SiO 2 -Pr 2 O 3 (Si-Al-Pr-O-C). SiC was compatible with Al 2 O 3 , Pr 2 O 3 and the Pr-silicates. The effect of SiO 2 on the phase relations and liquid phase sintering of SiC ceramics was discussed.

  15. Frustrated Lewis Pairs

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 19; Issue 11. Frustrated Lewis Pairs : Enabling via inability. Sanjoy Mukherjee ... Author Affiliations. Sanjoy Mukherjee Pakkirisamy Thilagar1. Department of Inorgainic and Physical Chemistry Indian Institute of Science Bangalore 560 012, India.

  16. Experimental investigation of phase equilibria in the Nb-Si-Ta ternary system

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jian; Wang, Cuiping; Yao, Jun; Yang, Shuiyuan; Zhan Shi; Liu, Xingjun [Xiamen Univ. (China). Dept. of Materials Science and Engineering; Xiamen Univ. (China). Fujian Provincial Key Laboratory of Materials Genome; Kang, Yongwang [Beijing Institute of Aeronautical Materials (China). Science and Technology on Advanced High Temperature Structural Materials Lab.

    2016-12-15

    The phase equilibria in the Nb-Si-Ta ternary system at 1 373 K, 1 473 K and 1 573 K were investigated by means of back-scattered electron imaging, electron probe microanalysis and X-ray diffraction. The isothermal sections at 1 373 K, 1 473 K and 1 573 K consist of two three-phase regions and seven two-phase regions, without any ternary compounds. The compounds of NbSi{sub 2} and TaSi{sub 2}, αNb{sub 5}Si{sub 3} and αTa{sub 5}Si{sub 3} form continuous solid solutions, respectively. The solubilities of Nb in Ta{sub 3}Si and Ta{sub 2}Si phases are extremely large, whereas the solubility of Si in the β(Nb, Ta) phase is relatively small.

  17. Phase selection and microstructure in directional solidification of glass forming Pd-Si-Cu alloys

    Science.gov (United States)

    Huo, Yang

    Phase selection and microstructure formation during the rapid solidification of alloy melts has been a topic of substantial interest over the last several decades, attributed mainly to the access to novel structures involving metastable crystalline and non-crystalline phases. In this work, Bridgeman type directional solidification was conducted in Pd-Si-Cu glass forming system to study such cooling rate dependent phase transition and microstructure formation. The equilibrium state for Pd-Si-Cu ternary system was investigated through three different works. First of all, phase stabilities for Pd-Si binary system was accessed with respects of first-principles and experiments, showing Pd5Si, Pd9Si2, Pd3Si and Pd 2Si phase are stable all way to zero Kevin while PdSi phase is a high temperature stable phase, and Pd2Si phase with Fe2P is a non-stoichiometry phase. A thermodynamic database was developed for Pd-Si system. Second, crystal structures for compounds with ternary compositions were studied by XRD, SEM and TEM, showing ordered and disordered B2/bcc phases are stable in Pd-rich part. At last, based on many phase equilibria and phase transitions data, a comprehensive thermodynamic discrption for Pd-Si-Cu ternary system was first time to be developed, from which different phase diagrams and driving force for kinetics can be calculated. Phase selection and microstructure formation in directional solidification of the best glass forming composition, Pd 77.5Si16.5Cu6, in this system with growth velocities from 0.005 to 7.5mm/s was systematically studied and the solidification pathways at different conditions were interpreted from thermodynamic simulation. The results show that for growth velocities are smaller than 0.1mm/s Pd 3Si phase is primary phase and Pd9Si2 phase is secondary phase, the difficulty for Pd9Si2 phase nucleation gives rise to the formation of two different eutectic structure. For growth velocities between 0.4 and 1mm/s, instead of Pd3Si phase, Pd9Si2

  18. Na-Si binary phase diagram and solution growth of silicon crystals

    International Nuclear Information System (INIS)

    Morito, H.; Yamada, T.; Ikeda, T.; Yamane, H.

    2009-01-01

    In the present study, a Na-Si binary phase diagram was first presented from the results of differential thermal analysis and X-ray diffraction. Based on the phase diagram, we performed low-temperature formation of single crystals, film and porous bulk of Si by vaporizing Na from a Na-Si melt at 800 or 900 deg. C.

  19. Synthesizing single-phase β-FeSi2 via ion beam irradiations of Fe/Si bilayers

    International Nuclear Information System (INIS)

    Milosavljevic, M.; Dhar, S.; Schaaf, P.; Bibic, N.; Lieb, K.P.

    2001-01-01

    This paper presents results on the direct synthesis of the β-FeSi 2 phase by ion beam mixing of Fe/Si bilayers with Xe ions. The influence of the substrate temperature, ion fluence and energy on the growth of this phase was investigated using Rutherford backscattering (RBS), X-ray diffraction (XRD) and conversion electron Moessbauer spectroscopy (CEMS). Complete growth of single-phase β-FeSi 2 was achieved by 205 keV Xe ion irradiation to a fluence of 2x10 16 ions/cm 2 at 600 deg. C. We propose a two-step reaction mechanism involving thermal and ion beam energy deposition

  20. Frustrated lattices of Ising chains

    International Nuclear Information System (INIS)

    Kudasov, Yurii B; Korshunov, Aleksei S; Pavlov, V N; Maslov, Dmitrii A

    2012-01-01

    The magnetic structure and magnetization dynamics of systems of plane frustrated Ising chain lattices are reviewed for three groups of compounds: Ca 3 Co 2 O 6 , CsCoCl 3 , and Sr 5 Rh 4 O 12 . The available experimental data are analyzed and compared in detail. It is shown that a high-temperature magnetic phase on a triangle lattice is normally and universally a partially disordered antiferromagnetic (PDA) structure. The diversity of low-temperature phases results from weak interactions that lift the degeneracy of a 2D antiferromagnetic Ising model on the triangle lattice. Mean-field models, Monte Carlo simulation results on the static magnetization curve, and results on slow magnetization dynamics obtained with Glauber's theory are discussed in detail. (reviews of topical problems)

  1. Quantum frustrated and correlated electron systems

    Directory of Open Access Journals (Sweden)

    P Thalmeier

    2008-06-01

    Full Text Available  Quantum phases and fluctuations in correlated electron systems with frustration and competing interactions are reviewed. In the localized moment case the S=1/2 J1 - J2 - model on a square lattice exhibits a rich phase diagram with magnetic as well as exotic hidden order phases due to the interplay of frustration and quantum fluctuations. Their signature in magnetocaloric quantities and the high field magnetization are surveyed. The possible quantum phase transitions are discussed and applied to layered vanadium oxides. In itinerant electron systems frustration is an emergent property caused by electron correlations. It leads to enhanced spin fluctuations in a very large region of momentum space and therefore may cause heavy fermion type low temperature anomalies as in the 3d spinel compound LiV2O4 . Competing on-site and inter-site electronic interactions in Kondo compounds are responsible for the quantum phase transition between nonmagnetic Kondo singlet phase and magnetic phase such as observed in many 4f compounds. They may be described by Kondo lattice and simplified Kondo necklace type models. Their quantum phase transitions are investigated by numerical exact diagonalization and analytical bond operator methods respectively.

  2. Effects of a Ta interlayer on the phase transition of TiSi2 on Si(111)

    Science.gov (United States)

    Jeon, Hyeongtag; Jung, Bokhee; Kim, Young Do; Yang, Woochul; Nemanich, R. J.

    2000-09-01

    This study examines the effects of a thin Ta interlayer on the formation of TiSi2 on Si(111) substrate. The Ta interlayer was introduced by depositing Ta and Ti films sequentially on an atomically clean Si(111) substrate in an ultrahigh vacuum (UHV) system. Samples of 100 Å Ti with 5 and 10 Å Ta interlayers were compared to similar structures without an interlayer. After deposition, the substrates were annealed for 10 min, in situ, at temperatures between 500 and 750 °C in 50 °C increments. The TiSi2 formation with and without the Ta interlayer was analyzed with an X-ray diffractometer, Auger electron spectroscopy (AES), Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and a four-point probe. The AES analysis data showed a 1:2 ratio of Ti:Si in the Ti-silicide layer and indicated that the Ta layer remained at the interface between TiSi2 and the Si(111) substrate. The C 49-C 54 TiSi2 phase transition temperature was lowered by ˜200 °C. The C 49-C 54 TiSi2 phase transition temperature was 550 °C for the samples with a Ta interlayer and was 750 °C for the samples with no Ta interlayer. The sheet resistance of the Ta interlayered Ti silicide showed lower values of resistivity at low temperatures which indicated the change in phase transition temperature. The C 54 TiSi2 displayed different crystal orientation when the Ta interlayer was employed. The SEM and TEM micrographs showed that the TiSi2 with a Ta interlayer significantly suppressed the tendency to islanding and surface agglomeration.

  3. Shrink, twist, ripple and melt: Studies of frustrated liquid crystals

    Science.gov (United States)

    Fernsler, Jonathan G.

    Complex structures can arise out of a simple system with more than one competing influence on its behavior. The protypical example of this is the two-dimensional triangular lattice Ising model. The ferromagnetic model has two simple degenerate ground states of all spins up or down, but the antiferromagnetic model is a frustrated system. Its geometry does not allow satisfaction of the antiferro condition everywhere, which produces complex ordered structures with dimerization of the spins [1]. Without frustration, the complex structures and phase behavior are lost. All of the topics discussed in this thesis concern smectic liquid crystals. Liquid crystals are perhaps uniquely adept at manifesting frustrated phases. Their combination of periodicity in one or more dimensions allows ordered structures, yet their fluid nature in remaining dimensions allows creation of defects and extraordinarily complex structures in ways that a normal crystal could not tolerate. Liquid crystals contain a huge menagerie of frustrated phases and effects including the polarization modulated [2], vortex lattice [3], twist grain boundary [4], and blue [5] phases, as well as frustrated structures such as cholesteric or SmC* helix unwinding [6], defect lattices in thin films [7], and bend melted grain boundary defects [8], arising from boundary conditions and field effects. In this thesis, we study four liquid crystal systems that show unusual phase behavior or complex structures, deriving from the effects of frustration. Frustration, despite some human prejudices against the word, leaves nature all the more interesting and beautiful.

  4. Structural, electronic, elastic, and thermodynamic properties of CaSi, Ca2Si, and CaSi2 phases from first-principles calculations

    Science.gov (United States)

    Li, X. D.; Li, K.; Wei, C. H.; Han, W. D.; Zhou, N. G.

    2018-06-01

    The structural, electronic, elastic, and thermodynamic properties of CaSi, Ca2Si, and CaSi2 are systematically investigated by using first-principles calculations method based on density functional theory (DFT). The calculated formation enthalpies and cohesive energies show that CaSi2 possesses the greatest structural stability and CaSi has the strongest alloying ability. The structural stability of the three phases is compared according to electronic structures. Further analysis on electronic structures indicates that the bonding of these phases exhibits the combinations of metallic, covalent, and ionic bonds. The elastic constants are calculated, and the bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and anisotropy factor of polycrystalline materials are deduced. Additionally, the thermodynamic properties were theoretically predicted and discussed.

  5. Mass Spectrometric Investigation of Silicon Extremely Enriched in (28)Si: From (28)SiF4 (Gas Phase IRMS) to (28)Si Crystals (MC-ICP-MS).

    Science.gov (United States)

    Pramann, Axel; Rienitz, Olaf

    2016-06-07

    A new generation of silicon crystals even further enriched in (28)Si (x((28)Si) > 0.999 98 mol/mol), recently produced by companies and institutes in Russia within the framework of a project initiated by PTB, were investigated with respect to their isotopic composition and molar mass M(Si). A modified isotope dilution mass spectrometric (IDMS) method treating the silicon as the matrix containing a so-called virtual element (VE) existing of the isotopes (29)Si and (30)Si solely and high resolution multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) were applied in combination. This method succeeds also when examining the new materials holding merely trace amounts of (29)Si (x((29)Si) ≈ 5 × 10(-6) mol/mol) and (30)Si (x((30)Si) ≈ 7 × 10(-7) mol/mol) extremely difficult to detect with lowest uncertainty. However, there is a need for validating the enrichment in (28)Si already in the precursor material of the final crystals, silicon tetrafluoride (SiF4) gas prior to crystal production. For that purpose, the isotopic composition of selected SiF4 samples was determined using a multicollector magnetic sector field gas-phase isotope ratio mass spectrometer. Contaminations of SiF4 by natural silicon due to storing and during the isotope ratio mass spectrometry (IRMS) measurements were observed and quantified. The respective MC-ICP-MS measurements of the corresponding crystal samples show-in contrast-several advantages compared to gas phase IRMS. M(Si) of the new crystals were determined to some extent with uncertainties urel(M) < 1 × 10(-9). This study presents a clear dependence of the uncertainty urel(M(Si)) on the degree of enrichment in (28)Si. This leads to a reduction of urel(M(Si)) during the past decade by almost 3 orders of magnitude and thus further reduces the uncertainty of the Avogadro constant NA which is one of the preconditions for the redefinition of the SI unit kilogram.

  6. Organometallic Routes into the Nanorealms of Binary Fe-Si Phases

    Directory of Open Access Journals (Sweden)

    Teddy M. Keller

    2010-02-01

    Full Text Available The Fe-Si binary system provides several iron silicides that have varied and exceptional material properties with applications in the electronic industry. The well known Fe-Si binary silicides are Fe3Si, Fe5Si3, FeSi, a-FeSi2 and b-FeSi2. While the iron-rich silicides Fe3Si and Fe5Si3 are known to be room temperature ferromagnets, the stoichiometric FeSi is the only known transition metal Kondo insulator. Furthermore, Fe5Si3 has also been demonstrated to exhibit giant magnetoresistance (GMR. The silicon-rich b-FeSi2 is a direct band gap material usable in light emitting diode (LED applications. Typically, these silicides are synthesized by traditional solid-state reactions or by ion beam-induced mixing (IBM of alternating metal and silicon layers. Alternatively, the utilization of organometallic compounds with reactive transition metal (Fe-carbon bonds has opened various routes for the preparation of these silicides and the silicon-stabilized bcc- and fcc-Fe phases contained in the Fe-Si binary phase diagram. The unique interfacial interactions of carbon with the Fe and Si components have resulted in the preferential formation of nanoscale versions of these materials. This review will discuss such reactions.

  7. Experimental investigation of phase equilibria in the Cu–Ni–Si ternary system

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xingjun; Xiang, Shulin; Yang, Shuiyuan; Shi, Rongpei; Wang, Cuiping, E-mail: wangcp@xmu.edu.cn

    2013-11-25

    Highlights: •Three isothermal sections of the Cu–Ni–Si system have been investigated. •The ternary compound τ{sub 1} and the liquid phase are confirmed at 1073 K. •The γ (Cu{sub 5}Si) and θ (Ni{sub 2}Si) phases can be stabilized at higher or lower temperatures. -- Abstract: The phase equilibria in the Cu–Ni–Si ternary system have been investigated experimentally by means of electron probe microanalysis (EPMA), X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analysis on equilibrated ternary alloys. Three isothermal sections at 1073, 1173 and 1273 K are determined in the whole composition range. The existence of liquid phase and the ternary compound τ{sub 1} is confirmed at 1073 K. The binary γ (Cu{sub 5}Si), γ (Ni{sub 31}Si{sub 12}), δ (Ni{sub 2}Si) and θ (Ni{sub 2}Si) phases exhibit a considerable solubility of a third element. In addition, the γ (Cu{sub 5}Si) and θ (Ni{sub 2}Si) phases can be stabilized by the addition of Ni and Cu, respectively.

  8. Effects of frustration on explosive synchronization

    Science.gov (United States)

    Huang, Xia; Gao, Jian; Sun, Yu-Ting; Zheng, Zhi-Gang; Xu, Can

    2016-12-01

    In this study, we consider the emergence of explosive synchronization in scale-free networks by considering the Kuramoto model of coupled phase oscillators. The natural frequencies of oscillators are assumed to be correlated with their degrees and frustration is included in the system. This assumption can enhance or delay the explosive transition to synchronization. Interestingly, a de-synchronization phenomenon occurs and the type of phase transition is also changed. Furthermore, we provide an analytical treatment based on a star graph, which resembles that obtained in scale-free networks. Finally, a self-consistent approach is implemented to study the de-synchronization regime. Our findings have important implications for controlling synchronization in complex networks because frustration is a controllable parameter in experiments and a discontinuous abrupt phase transition is always dangerous in engineering in the real world.

  9. Simulation of spheroidisation of elongated Si-particle in Al-Si alloys by the phase-field model

    International Nuclear Information System (INIS)

    Kovacevic, I.

    2008-01-01

    The application of the phase-field model for spheroidisation of undissolvable particles during high-temperature treatment of alloys is pointed out. Modelling of the spheroidisation of elongated Si-particles during annealing of Al-Si alloy is elaborated in this paper. The driving force for spheroidisation is the minimization of the total free-energy of the system or the minimization of the ratio between the interface areas and the particle volumes. The spheroidisation kinetics of elongated Si-particle for binary Al-Si system during homogenisation of aluminium alloys simulated by the phase-field model is demonstrated. The influences of the interface energy and the homogenisation temperature on the spheroidisation kinetics is presented. The lack of knowledge of the interface energy anisotropy between Si-particle and the aluminium phase is the only reason for using isotropic interface energy in simulations. The thermodynamic driving force for the phase transformation of the silicon into the aluminium phase is computed from the data obtained from the JMatPro software for aluminium alloys

  10. Experimental Investigation of Phase Equilibria in the Ho-Ti-Si Ternary System at 973 K (700 °C)

    Science.gov (United States)

    Han, Feng; Zhan, Yongzhong

    2018-02-01

    Phase equilibrium relations of the Ho-Ti-Si ternary system at 973 K (700 °C) were experimentally researched by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectrometer (EDS). The isothermal section of the system at 973 K (700 °C) consists of 14 three-phase regions, 27 two-phase regions, and 14 single-phase regions. The phases Ti5Si3, Ti5Si4, TiSi, TiSi2, Ho5Si3, Ho5Si4, HoSi, αHoSi2-b, and βHoSi2-a are proved to exist at 973 K (700 °C). Previously reported HoTiSi and Ho2Ti3Si4 ternary compounds were confirmed to exist at this temperature. The solubility of Ho in the intermediate phases (i.e., TiSi2, TiSi, Ti5Si4, and Ti5Si3) at the Ti-Si side is extremely small. The maximum solubilities of Ti in HoSi2-b, Ho5Si4, and Ho5Si3 are confirmed to be 8.0, 7.2, and 6.0 at. pct, respectively.

  11. Grain Size and Phase Purity Characterization of U3Si2 Pellet Fuel

    Energy Technology Data Exchange (ETDEWEB)

    Hoggan, Rita E. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Tolman, Kevin R. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Cappia, Fabiola [Idaho National Lab. (INL), Idaho Falls, ID (United States); Wagner, Adrian R. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Harp, Jason M. [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2018-05-01

    Characterization of U3Si2 fresh fuel pellets is important for quality assurance and validation of the finished product. Grain size measurement methods, phase identification methods using scanning electron microscopes equipped with energy dispersive spectroscopy and x-ray diffraction, and phase quantification methods via image analysis have been developed and implemented on U3Si2 pellet samples. A wide variety of samples have been characterized including representative pellets from an initial irradiation experiment, and samples produced using optimized methods to enhance phase purity from an extended fabrication effort. The average grain size for initial pellets was between 16 and 18 µm. The typical average grain size for pellets from the extended fabrication was between 20 and 30 µm with some samples exhibiting irregular grain growth. Pellets from the latter half of extended fabrication had a bimodal grain size distribution consisting of coarsened grains (>80 µm) surrounded by the typical (20-30 µm) grain structure around the surface. Phases identified in initial uranium silicide pellets included: U3Si2 as the main phase composing about 80 vol. %, Si rich phases (USi and U5Si4) composing about 13 vol. %, and UO2 composing about 5 vol. %. Initial batches from the extended U3Si2 pellet fabrication had similar phases and phase quantities. The latter half of the extended fabrication pellet batches did not contain Si rich phases, and had between 1-5% UO2: achieving U3Si2 phase purity between 95 vol. % and 98 vol. % U3Si2. The amount of UO2 in sintered U3Si2 pellets is correlated to the length of time between U3Si2 powder fabrication and pellet formation. These measurements provide information necessary to optimize fabrication efforts and a baseline for future work on this fuel compound.

  12. User Frustrations as Opportunities

    Directory of Open Access Journals (Sweden)

    Michael Weiss

    2012-04-01

    Full Text Available User frustrations are an excellent source of new product ideas. Starting with this observation, this article describes an approach that entrepreneurs can use to discover business opportunities. Opportunity discovery starts with a problem that the user has, but may not be able to articulate. User-centered design techniques can help elicit those latent needs. The entrepreneur should then try to understand how users are solving their problem today, before proposing a solution that draws on the unique skills and technical capabilities available to the entrepreneur. Finally, an in-depth understanding of the user allows the entrepreneur to hone in on the points of difference and resonance that are the foundation of a strong customer value proposition.

  13. Secondary growth mechanism of SiGe islands deposited on a mixed-phase microcrystalline Si by ion beam co-sputtering.

    Science.gov (United States)

    Ke, S Y; Yang, J; Qiu, F; Wang, Z Q; Wang, C; Yang, Y

    2015-11-06

    We discuss the SiGe island co-sputtering deposition on a microcrystalline silicon (μc-Si) buffer layer and the secondary island growth based on this pre-SiGe island layer. The growth phenomenon of SiGe islands on crystalline silicon (c-Si) is also investigated for comparison. The pre-SiGe layer grown on μc-Si exhibits a mixed-phase structure, including SiGe islands and amorphous SiGe (a-SiGe) alloy, while the layer deposited on c-Si shows a single-phase island structure. The preferential growth and Ostwald ripening growth are shown to be the secondary growth mechanism of SiGe islands on μc-Si and c-Si, respectively. This difference may result from the effect of amorphous phase Si (AP-Si) in μc-Si on the island growth. In addition, the Si-Ge intermixing behavior of the secondary-grown islands on μc-Si is interpreted by constructing the model of lateral atomic migration, while this behavior on c-Si is ascribed to traditional uphill atomic diffusion. It is found that the aspect ratios of the preferential-grown super islands are higher than those of the Ostwald-ripening ones. The lower lateral growth rate of super islands due to the lower surface energy of AP-Si on the μc-Si buffer layer for the non-wetting of Ge at 700 °C and the stronger Si-Ge intermixing effect at 730 °C may be responsible for this aspect ratio difference.

  14. Teaching Students to Overcome Frustration.

    Science.gov (United States)

    Henley, Martin

    1997-01-01

    Offers concrete strategies for teaching students about frustration, reducing classroom stress, and integrating frustration-tolerance techniques into the regular curriculum. Discusses how to teach self-control within the curriculum with tips on relaxation, support, and acknowledging accomplishments. Claims that such steps will reduce related…

  15. MAX Phase Modified SiC Composites for Ceramic-Metal Hybrid Cladding Tubes

    International Nuclear Information System (INIS)

    Jung, Yang-Il; Kim, Sun-Han; Park, Dong-Jun; Park, Jeong-Hwan; Park, Jeong-Yong; Kim, Hyun-Gil; Koo, Yang-Hyun

    2015-01-01

    A metal-ceramic hybrid cladding consists of an inner zirconium tube, and an outer SiC fiber-matrix SiC ceramic composite with surface coating as shown in Fig. 1 (left-hand side). The inner zirconium allows the matrix to remain fully sealed even if the ceramic matrix cracks through. The outer SiC composite can increase the safety margin by taking the merits of the SiC itself. In addition, the outermost layer prevents the dissolution of SiC during normal operation. On the other hand, a ceramic-metal hybrid cladding consists of an outer zirconium tube, and an inner SiC ceramic composite as shown in Fig. 1 (right-hand side). The outer zirconium protects the fuel rod from a corrosion during reactor operation, as in the present fuel claddings. The inner SiC composite, additionally, is designed to resist the severe oxidation under a postulated accident condition of a high-temperature steam environment. Reaction-bonded SiC was fabricated by modifying the matrix as the MAX phase. The formation of Ti 3 SiC 2 was investigated depending on the compositions of the preform and melt. In most cases, TiSi 2 was the preferential phase because of its lowest melting point in the Ti-Si-C system. The evidence of Ti 3 SiC 2 was the connection with the pressurizing

  16. Noncollinear magnetic ordering in a frustrated magnet: Metallic regime and the role of frustration

    Science.gov (United States)

    Shahzad, Munir; Sengupta, Pinaki

    2017-12-01

    We explore the magnetic phases in a Kondo lattice model on the geometrically frustrated Shastry-Sutherland lattice at metallic electron densities, searching for noncollinear and noncoplanar spin textures. Motivated by experimental observations in many rare-earth-based frustrated metallic magnets, we treat the local moments as classical spins and set the coupling between the itinerant electrons and local moments as the largest energy scale in the problem. Our results show that a noncollinear flux state is stabilized over an extended range of Hamiltonian parameters. These spin states can be quenched efficiently by external fields like temperature and magnetic field as well as by varying the degree of frustration in the electronic itinerancy and exchange coupling between local moments. Interestingly, unlike insulating electron densities that we discussed in paper I of this sequence, a Dzyaloshinskii-Moriya interaction between the local moments is not essential for the emergence of their noncollinear ordering.

  17. Structures, phase stabilities, and electrical potentials of Li-Si battery anode materials

    KAUST Repository

    Tipton, William W.

    2013-05-28

    The Li-Si materials system holds promise for use as an anode in Li-ion battery applications. For this system, we determine the charge capacity, voltage profiles, and energy storage density solely by ab initio methods without any experimental input. We determine the energetics of the stable and metastable Li-Si phases likely to form during the charging and discharging of a battery. Ab initio molecular dynamics simulations are used to model the structure of amorphous Li-Si as a function of composition, and a genetic algorithm coupled to density-functional theory searches the Li-Si binary phase diagram for small-cell, metastable crystal structures. Calculations of the phonon densities of states using density-functional perturbation theory for selected structures determine the importance of vibrational, including zero-point, contributions to the free energies. The energetics and local structural motifs of these metastable Li-Si phases closely resemble those of the amorphous phases, making these small unit cell crystal phases good approximants of the amorphous phase for use in further studies. The charge capacity is estimated, and the electrical potential profiles and the energy density of Li-Si anodes are predicted. We find, in good agreement with experimental measurements, that the formation of amorphous Li-Si only slightly increases the anode potential. Additionally, the genetic algorithm identifies a previously unreported member of the Li-Si binary phase diagram with composition Li5Si2 which is stable at 0 K with respect to previously known phases. We discuss its relationship to the partially occupied Li7Si3 phase. © 2013 American Physical Society.

  18. Single-phase {beta}-FeSi{sub 2} thin films prepared on Si wafer by femtosecond laser ablation and its photoluminescence at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Lu Peixiang [State Key Laboratory of Laser Technology and Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China)]. E-mail: lupeixiang@mail.hust.edu.cn; Zhou Youhua [State Key Laboratory of Laser Technology and Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China) and Physics and Information School, Jianghan University, Wuhan 430056 (China)]. E-mail: yhzhou@jhun.edu.cn; Zheng Qiguang [State Key Laboratory of Laser Technology and Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China); Yang Guang [State Key Laboratory of Laser Technology and Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2006-02-06

    Single-phase {beta}-FeSi{sub 2} thin films were prepared on Si(100) and Si(111) wafers by using femtosecond laser deposition with a FeSi{sub 2} alloy target for the first time. X-ray diffraction (XRD), field scanning electron microscopy (FSEM), scanning probe microscopy (SPM), electron backscattered diffraction pattern (EBSD), and Fourier-transform Raman infrared spectroscopy (FTRIS) were used to characterize the structure, composition, and properties of the {beta}-FeSi{sub 2}/Si films. The orientation of {beta}-FeSi{sub 2} grains was found to depend on the orientation of the Si substrates, and photoluminescence at wavelength of 1.53 {mu}m was observed from the single-phase {beta}-FeSi{sub 2}/Si thin film at room temperature (20 {sup o}C)

  19. 450 {sup o}C isothermal section of the Fe-Zn-Si ternary phase diagram

    Energy Technology Data Exchange (ETDEWEB)

    Su, Xuping [Inst. of Materials Research, School of Mechanical Engineering, Xiangtan Univ., Xiangtan, Hunan (China); Univ. of Toronto, Dept. of Materials Science and Engineering, Toronto, Ontario (Canada); Tang, Nai-Yong [Cominco Ltd., Product Technology Centre, Mississauga, Ontario (Canada); Toguri, J.M. [Univ. of Toronto, Dept. of Materials Science and Engineering, Toronto, Ontario (Canada)

    2001-07-01

    The 450 {sup o}C isothermal section of the Fe-Zn-Si ternary phase diagram has been determined experimentally using optical microscopy, scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS) and X-ray diffractometry. The focus of the work has been concentrated on the Zn-rich corner which is relevant to general galvanizing. The present study has confirmed the existence of the equilibrium state between the liquid, the {zeta} phase and the FeSi phase. This three phase equilibrium state prevents the equilibrium between the liquid and the {delta} phase suggested by some researchers. Experimental results indicate that Si solubility in all four binary Zn-Fe compounds is limited. The Fe solubility in molten Zn was found to decrease with increasing Si content in the melt. The liquid phase boundary was determined using a model based phenomenological approach. (author)

  20. Frustration: A common user experience

    DEFF Research Database (Denmark)

    Hertzum, Morten

    2010-01-01

    % of their time redoing lost work. Thus, the frustrating experiences accounted for a total of 27% of the time, This main finding is exacerbated by several supplementary findings. For example, the users were unable to fix 26% of the experienced problems, and they rated that the problems recurred with a median....... In the present study, 21 users self-reported their frustrating experiences during an average of 1.72 hours of computer use. As in the previous studies the amount of time lost due to frustrating experiences was disturbing. The users spent 16% of their time trying to fix encountered problems and another 11...

  1. Evolution of 3C-SiC islands nucleated from a liquid phase on Si face α-SiC substrates

    International Nuclear Information System (INIS)

    Kim-Hak, Olivier; Ferro, Gabriel; Lorenzzi, Jean; Carole, Davy; Dazord, Jacques; Chaudouet, Patrick; Chaussende, Didier; Miele, Philippe

    2010-01-01

    The contact between α-SiC crystals and Si-Ge based melts provokes the nucleation of 3C-SiC islands on the crystal surface. Evolution of these islands as a function of various parameters was studied. On both 4H and 6H substrates, it was found that, after nucleation, 3C-SiC islands first enlarge and may form a complete 3C layer under certain conditions. The 3C deposit can then be dissolved by the liquid phase at high temperature or for prolonged contact at relatively moderate temperature. The graphite crucible is proposed to play a central role in these enlargement and dissolution mechanisms by providing extra carbon atoms on the seed surface (enlargement) or provoking thermal induced carbon transport toward the sidewall (dissolution). Several differences between the use of 4H and 6H substrates were also observed.

  2. Influence of Si and Ge on the magnetic phase transition and magnetocaloric properties of MnFe(P, Si, Ge)

    International Nuclear Information System (INIS)

    Cam Thanh, D.T.; Brueck, E.; Tegus, O.; Klaasse, J.C.P.; Buschow, K.H.J.

    2007-01-01

    Recently, we found a large magnetocaloric effect (MCE) and favourable magnetic properties in low cost and nontoxic MnFe(P, Si, Ge) compounds [D.T. Cam Thanh, E. Brueck, O. Tegus, J.C.P. Klaasse, T.J. Gortenmulder, K.H.J. Buschow, J. Appl. Phys. 99 (2006) 08Q107]. These compounds are promising for magnetic refrigeration applications. One of the interesting points in these compounds is a nonlinear dependence of the Curie temperature (T C ) on Si concentration. This dependence is associated with the change in the lattice parameters a and c, and their ratio c/a. Compounds with larger a parameter and smaller c/a ratio have higher T C . It is clear that Si and Ge atoms play an important role in the magnetic and magnetocaloric properties in the MnFe(P, Si, Ge) compounds. In this paper, we study the effect of Si and Ge on the magnetic phase transition in these materials. Our study shows that the temperature of the phase transition, from paramagnetic to ferromagnetic, can be tuned in the room temperature range without losing giant magnetocaloric properties

  3. Investigation of the {Fe}/{Si} interface and its phase transformations

    Science.gov (United States)

    Fanciulli, M.; Degroote, S.; Weyer, G.; Langouche, G.

    1997-04-01

    Thin 57Fe films (3-10 Å) have been grown by molecular beam epitaxy (MBE) on (7 × 7) reconstructed Si(111) and (2 × 1) reconstructed Si(001) surfaces and by e-gun evaporation on an H-terminated Si(111) surface. Conversion electron Mössbauer spectroscopy (CEMS) with high statistical accuracy and resolution allowed a detailed microscopic investigation of the silicide formation mechanism and of the structural phase transformations upon annealing.

  4. Identification of intermetallic phases in a eutectic Al-Si casting alloy using electron backscatter diffraction pattern analysis

    International Nuclear Information System (INIS)

    Kral, M.V.; McIntyre, H.R.; Smillie, M.J.

    2004-01-01

    Intermetallic phases in sand cast eutectic Al-Si alloys were characterized using a combination of SEM, EDS and EBSD pattern analysis. Chinese script α-phase particles were consistent with cubic Al 19 (Fe,Mn) 5 Si 2 . Plate-shaped β-phase particles were consistent with tetragonal Al 3 (Fe,Mn)Si 2

  5. Balance of optical, structural, and electrical properties of textured liquid phase crystallized Si solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Preidel, V., E-mail: veit.preidel@helmholtz-berlin.de; Amkreutz, D.; Haschke, J.; Wollgarten, M.; Rech, B.; Becker, C. [Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Division Renewable Energy, Kekuléstr. 5, 12489 Berlin (Germany)

    2015-06-14

    Liquid phase crystallized Si thin-film solar cells on nanoimprint textured glass substrates exhibiting two characteristic, but distinct different surface structures are presented. The impact of the substrate texture on light absorption, the structural Si material properties, and the resulting solar cell performance is analyzed. A pronounced periodic substrate texture with a vertical feature size of about 1 μm enables excellent light scattering and light trapping. However, it also gives rise to an enhanced Si crystal defect formation deteriorating the solar cell performance. In contrast, a random pattern with a low surface roughness of 45 nm allows for the growth of Si thin films being comparable to Si layers on planar reference substrates. Amorphous Si/crystalline Si heterojunction solar cells fabricated on the low-roughness texture exhibit a maximum open circuit voltage of 616 mV and internal quantum efficiency peak values exceeding 90%, resulting in an efficiency potential of 13.2%. This demonstrates that high quality crystalline Si thin films can be realized on nanoimprint patterned glass substrates by liquid phase crystallization inspiring the implementation of tailor-made nanophotonic light harvesting concepts into future liquid phase crystallized Si thin film solar cells on glass.

  6. Effect of Second Phase Particles on the Tensile Instability of a Nanostructured Al-1%Si Alloy

    DEFF Research Database (Denmark)

    Huang, Tian Lin; Wu, Gui Lin; Liu, Qing

    2014-01-01

    A nanostructured Al-1%Si alloy containing dispersed Si particles was produced by heavily cold-rolling to study the effect of second phase particles on the tensile instability of nanostructured metals. Tensile tests were conducted on the as-deformed sample and the samples after recovery annealing ...

  7. A Study of Phase Composition and Structure of Alloys of the Al - Mg - Si - Fe System

    Science.gov (United States)

    Mailybaeva, A. D.; Zolotorevskii, V. S.; Smagulov, D. U.; Islamkulov, K. M.

    2017-03-01

    The Thermo-Calc software is used to compute the phase transformations occurring during cooling of alloys. Polythermal and isothermal sections of the phase diagram of the Al - Mg - Si - Fe system are plotted. The phase composition and the structure of aluminum alloys in cast condition and after a heat treatment are studied experimentally.

  8. Modeling of Eutectic Formation in Al-Si Alloy Using A Phase-Field Method

    Directory of Open Access Journals (Sweden)

    Ebrahimi Z.

    2017-12-01

    Full Text Available We have utilized a phase-field model to investigate the evolution of eutectic silicon in Al-Si alloy. The interfacial fluctuations are included into a phase-field model of two-phase solidification, as stochastic noise terms and their dominant role in eutectic silicon formation is discussed. We have observed that silicon spherical particles nucleate on the foundation of primary aluminum phase and their nucleation continues on concentric rings, through the Al matrix. The nucleation of silicon particles is attributed to the inclusion of fluctuations into the phase-field equations. The simulation results have shown needle-like, fish-bone like and flakes of silicon phase by adjusting the noise coefficients to larger values. Moreover, the role of primary Al phase on nucleation of silicon particles in Al-Si alloy is elaborated. We have found that the addition of fluctuations plays the role of modifiers in our simulations and is essential for phase-field modeling of eutectic growth in Al-Si system. The simulated finger-like Al phases and spherical Si particles are very similar to those of experimental eutectic growth in modified Al-Si alloy.

  9. Structures, phase stabilities, and electrical potentials of Li-Si battery anode materials

    KAUST Repository

    Tipton, William W.; Bealing, Clive R.; Mathew, Kiran; Hennig, Richard G.

    2013-01-01

    of composition, and a genetic algorithm coupled to density-functional theory searches the Li-Si binary phase diagram for small-cell, metastable crystal structures. Calculations of the phonon densities of states using density-functional perturbation theory

  10. Metal organic vapor phase epitaxy growth of (Al)GaN heterostructures on SiC/Si(111) templates synthesized by topochemical method of atoms substitution

    DEFF Research Database (Denmark)

    Rozhavskaya, Mariia M.; Kukushkin, Sergey A.; Osipov, Andrey V.

    2017-01-01

    We report a novel approach for metal organic vapor phase epitaxy of (Al)GaN heterostructures on Si substrates. An approximately 90–100 nm thick SiC buffer layer is synthesized using the reaction between Si substrate and CO gas. Highresolution transmission electron microscopy reveals sharp...

  11. Nitrogen doping efficiency during vapor phase epitaxy of 4H-SiC

    Energy Technology Data Exchange (ETDEWEB)

    Rowland, L.B.; Brandt, C.D. [Northrop Grumman Science and Technology Center, Pittsburgh, PA (United States); Burk, A.A. Jr. [Northrop Grumman Advanced Technology Lab., Baltimore, MD (United States)

    1998-06-01

    This work examines the interrelationships among doping efficiency, mole fraction, and Si/C ratio for intentional doping of 4H-SiC during vapor phase epitaxy using N{sub 2}. For four Si/C ratios, the doping concentration increased linearly as a function of increasing N{sub 2} partial pressure with a slope of 1.0 {+-} 0.03. Variation of propane mole fraction while the SiH{sub 4} and N{sub 2} mole fractions were kept constant revealed two different modes of nitrogen incorporation, corresponding to carbon-rich and silicon-rich conditions. (orig.) 14 refs.

  12. The morphology of ceramic phases in B x C-SiC-Si infiltrated composites

    International Nuclear Information System (INIS)

    Hayun, S.; Frage, N.; Dariel, M.P.

    2006-01-01

    The present communication is concerned with the effect of the carbon source on the morphology of reaction bonded boron carbide (B 4 C). Molten silicon reacts strongly and rapidly with free carbon to form large, faceted, regular polygon-shaped SiC particles, usually embedded in residual silicon pools. In the absence of free carbon, the formation of SiC relies on carbon that originates from within the boron carbide particles. Examination of the reaction bonded boron carbide revealed a core-rim microstructure consisting of boron carbide particles surrounded by secondary boron carbide containing some dissolved silicon. This microstructure is generated as the outcome of a dissolution-precipitation process. In the course of the infiltration process molten Si dissolves some boron carbide until its saturation with B and C. Subsequently, precipitation of secondary boron carbide enriched with boron and silicon takes place. In parallel, elongated, strongly twinned, faceted SiC particles are generated by rapid growth along preferred crystallographic directions. This sequence of events is supported by X-ray diffraction and microcompositional analysis and well accounted for by the thermodynamic analysis of the ternary B-C-Si system. - Graphical abstract: Bright field TEM image of the rim area between two boron carbide grains

  13. (FeCo)3Si-SiOx core-shell nanoparticles fabricated in the gas phase

    International Nuclear Information System (INIS)

    Bai Jianmin; Xu Yunhao; Thomas, John; Wang Jianping

    2007-01-01

    A method of fabricating core-shell nanoparticles by using an integrated nanoparticle deposition technique in the gas phase is reported. The principle of the method is based on nanoparticle growth from the vapour phase, during which elements showing lower surface energies prefer to form the shells and elements showing higher surface energies prefer to stay in the cores. This method was applied successfully to the Fe-Co-Si ternary system to fabricate core-shell-type nanoparticles. The nanoparticles were exposed in air after collection to achieve oxidation. The analysis results based on transmission electron microscopy (TEM), Auger electron spectroscopy (AES), x-ray diffraction (XRD), and a superconducting quantum interference device (SQUID) showed that the core parts are magnetic materials of body-centred cubic (bcc) structured (FeCo) 3 Si of 15 nm in diameter, and the shell parts are amorphous SiO x of 2 nm in thickness. These core-shell-type nanoparticles show a magnetic anisotropy constant of about 7 x 10 5 erg cm -3 and a saturation magnetization of around 1160 emu cm -3 , which is much higher than that of iron oxide. After annealing at 300 deg. C in air (FeCo) 3 Si-SiO x core-shell-type nanoparticles showed a little bit of a drop in magnetic moment, while pure FeCo nanopariticles totally lost their magnetic moment. This means that the shells of SiO x are dense enough to prevent the magnetic cores from oxidation

  14. New investigation of phase equilibria in the system Al-Cu-Si.

    Science.gov (United States)

    Ponweiser, Norbert; Richter, Klaus W

    2012-01-25

    The phase equilibria and invariant reactions in the system Al-Cu-Si were investigated by a combination of optical microscopy, powder X-ray diffraction (XRD), differential thermal analysis (DTA) and electron probe micro analysis (EPMA). Isothermal phase equilibria were investigated within two isothermal sections. The isothermal section at 500 °C covers the whole ternary composition range and largely confirms the findings of previous phase diagram investigations. The isothermal section at 700 °C describes phase equilibria only in the complex Cu-rich part of the phase diagram. A new ternary compound τ was found in the region between (Al,Cu)-γ(1) and (Cu,Si)-γ and its solubility range was determined. The solubility of Al in κ-CuSi was found to be extremely high at 700 °C. In contrast, no ternary solubility in the β-phase of Cu-Al was found, although this phase is supposed to form a complete solid solution according to previous phase diagram assessments. Two isopleths, at 10 and 40 at.% Si, were investigated by means of DTA and a partial ternary reaction scheme (Scheil diagram) was constructed, based on the current work and the latest findings in the binary systems Al-Cu and Cu-Si. The current study shows that the high temperature equilibria in the Cu-rich corner are still poorly understood and additional studies in this area would be favorable.

  15. Topics on frustrated spin systems and high-temperature superconductors

    International Nuclear Information System (INIS)

    Lu Yong.

    1990-01-01

    The numerical study of frustrated spin systems using the Monte Carlo simulation method and the analytic study of fluctuation phenomenon of the thermoelectric power near the superconducting transition using Green's function techniques are presented. The first frustrated system considered is the B-site antiferromagnetic (AF) spinel. Based on an Ising model, various thermodynamic and magnetic properties were studied for both the fully frustrated structure and partially frustrated cases of a small tetragonal distortion. When fully frustrated, an interesting short-range order and some unusual scaling behavior were obtained. The other frustrated spin system studied is the magnetic phase of YBa 2 Cu 3 O 6+x via a classical spin model, with appropriate anisotropic exchange couplings and randomly located spins of distribution probability as a function of x. There is a first order boundary between Type 1 and Type 2 in the Ising case, while there is no real phase boundary in the cases of continuous spin. In the study on the thermopower fluctuation, the thermopower was determined by the linear response of the electric and heat currents to an electric field, and the linear responses were in turn calculated from correlation functions of the current

  16. Topics on frustrated spin systems and high-temperature superconductors

    International Nuclear Information System (INIS)

    Lu, Yong.

    1990-01-01

    The numerical study of frustrated spin systems using the Monte Carlo simulation method and the analytic study of fluctuation phenomenon of the thermoelectric power near the superconducting transition using Green's function techniques are presented. The first frustrated system considered was the B-site antiferromagnetic (AF) spinel. Based on an Ising model, various thermodynamic and magnetic properties for both the fully frustrated structure and partially frustrated cases of a small tetragonal distortion were studied. When fully frustrated, an interesting short range order and some unusual scaling behavior were obtained. In the two tetragonally distorted cases, contracting and expanding in the crystallographic c-direction, AF long range orders and some hysteresis behavior were found. A general phase diagram was constructed as a function of the degree of the distortion. The other frustrated spin system that was studied is the magnetic phase of YBa2Cu3O(6+x). A classical spin model, was constructed, and various properties in its Ising, Heisenberg, and x-y versions were studied. The susceptibility was calculated as a function of temperature for various values of x. In the study on the thermopower fluctuation, the thermopower was determined by the linear response of the electric and heat currents to an electric field, and the linear responses were in turn calculated from correlation functions of the current

  17. Phase composition of iron-rich R-Fe-Si (R=Dy, Ho, Er) alloys

    International Nuclear Information System (INIS)

    Ivanova, G.V.; Makarova, G.M.; Shcherbakova, E.V.; Belozerov, E.V.

    2005-01-01

    Phase composition is studied in iron-rich alloys of R-Fe-Si (R=Dy, Ho, Er). In the as-cast state R 2 (Fe, Si) 17 of type Th 2 Ni 17 and R(Fe, Si) 12 compounds are observed; in the alloys of rated composition of R(Fe 0.85 Si 0.15 ) 8.5 (R=Dy, Er) a compound R 2 (Fe, Si) 17 of Th 2 Zn 17 -type is revealed as well. The annealing at 1273 K results in formation of Dy 3 (Fe, Si) 29 and also the compounds with the presumed composition of Dy 4 (Fe, Si) 41 and Ho 4 (Fe, Si) 41 . As this takes place the alloys contain a transition structure as well that represents a set of small-sized areas with various type short-range order in mutual displacement of Fe-Fe(Si) dumpbell chains. The process of phase formation at 1273 K is faced with difficulties. Even the annealing for 1000 h does not result in the state of equilibrium [ru

  18. Phase relations and superconductivity in the binary Re-Si system

    International Nuclear Information System (INIS)

    Jorda, J.L.; Ishikawa, M.; Muller, J.

    1982-01-01

    The phase diagram of the Re-Si system was reinvestigated by means of high temperature methods of analysis. Several modifications were found to the existing diagram. An extended rhenium solid solution (up to 10 at.% Si) was established with a rapid quenching technique. Within this terminal solid solution, the superconducting transition temperature increased from 1.7 to 5.2 K. The phase corresponding to the Re 5 Si 3 compound was homogeneous at 33 at.% Si. The peritectically formed equiatomic compound decomposed eutectoidally at 1650 0 C and was superconducting at 1.5 K. The compound ReSi 2 was found to be off stoichiometric, occurring at the composition ReSisub(1.8). (Auth.)

  19. Effect of high temperature deposition on CoSi2 phase formation

    International Nuclear Information System (INIS)

    Comrie, C. M.; Ahmed, H.; Smeets, D.; Demeulemeester, J.; Vantomme, A.; Turner, S.; Van Tendeloo, G.; Detavernier, C.

    2013-01-01

    This paper discusses the nucleation behaviour of the CoSi to CoSi 2 transformation from cobalt silicide thin films grown by deposition at elevated substrate temperatures ranging from 375 °C to 600 °C. A combination of channelling, real-time Rutherford backscattering spectrometry, real-time x-ray diffraction, and transmission electron microscopy was used to investigate the effect of the deposition temperature on the subsequent formation temperature of CoSi 2 , its growth behaviour, and the epitaxial quality of the CoSi 2 thus formed. The temperature at which deposition took place was observed to exert a significant and systematic influence on both the formation temperature of CoSi 2 and its growth mechanism. CoSi films grown at the lowest temperatures were found to increase the CoSi 2 nucleation temperature above that of CoSi 2 grown by conventional solid phase reaction, whereas the higher deposition temperatures reduced the nucleation temperature significantly. In addition, a systematic change in growth mechanism of the subsequent CoSi 2 growth occurs as a function of deposition temperature. First, the CoSi 2 growth rate from films grown at the lower reactive deposition temperatures is substantially lower than that grown at higher reactive deposition temperatures, even though the onset of growth occurs at a higher temperature, Second, for deposition temperatures below 450 °C, the growth appears columnar, indicating nucleation controlled growth. Elevated deposition temperatures, on the other hand, render the CoSi 2 formation process layer-by-layer which indicates enhanced nucleation of the CoSi 2 and diffusion controlled growth. Our results further indicate that this observed trend is most likely related to stress and changes in microstructure introduced during reactive deposition of the CoSi film. The deposition temperature therefore provides a handle to tune the CoSi 2 growth mechanism.

  20. Phase stability in the Nb-rich region of the Nb-B-Si system

    Energy Technology Data Exchange (ETDEWEB)

    Nunes, C.A.; Coelho, G.C.; Pinto, D.M. Jr.; Camargo Gandolpho, K.C. de; Borges, L.A. Jr.; Rodrigues, G. [Polo Urbo-Ind., Gleba, Lorena (Brazil). Dept. de Engenharia de Materiais

    2000-07-01

    Alloys of the Me-B-Si systems (Me-refractory metal) have been evaluated due to their potential for use as high temperature structural materials (T>1400 C). In the present study, the phase stability in the Nb-rich region of the Nb-B-Si system has been evaluated in terms of the current information associated to the Nb-Si, Nb-B and Nb-B-Si systems as well as our own data. For the experiments several as-cast and heat-treated alloys of the Nb-B and Nb-B-Si systems were investigated by X-ray diffraction and scanning electron microscopy. Concerning the Nb-B system the results indicated the existence of the eutectic reaction L ({proportional_to} 16 at%B) <=> Nb{sub ss}+NbB. The Nb{sub 3}B{sub 2} phase was not observed in the microstructure of as-cast alloys with composition in the range of 0 to 50 at%B. The analysis of heat-treated ternary alloys at 1600 C and 1750 C confirmed the existence of the Nb{sub ss}+T{sub 2} two-phase field at those temperatures. This T{sub 2}-phase is isomorphous of the {alpha}Nb{sub 5}Si{sub 3} and is formed through the partial substitution of Si atomos for B atoms in the lattice of the {alpha}Nb{sub 5}Si{sub 3}-phase. All ternary alloys prepared in the present study presented either Nb{sub ss} or T{sub 2} primary phases in the as-cast microstructures. In addition, those alloys presented an eutectic-like microstructure formed by the Nb{sub ss} and T{sub 2} phases in the interdendritic region. (orig.)

  1. Galvanizing and Galvannealing Behavior of CMnSiCr Dual-Phase Steels

    Science.gov (United States)

    Lin, Ko-Chun; Chu, Peng-Wei; Lin, Chao-Sung; Chen, Hon-Bor

    2013-06-01

    Alloying elements, such as Mn, Mo, Si, and Cr, are commonly used to enhance the strength of advanced high-strength steels. Those elements also play an important role in the hot-dip galvanizing (GI) and galvannealing (GA) process. In this study, two kinds of CMnSiCr dual-phase steels were galvanized and galvannealed using a hot-dip simulator to investigate the effect of the alloying elements on the microstructure of the GI and GA coatings. The results showed that the dual-phase steels had good galvanizability because no bare spots were observed and the Fe-Zn phases were readily formed at the interface. However, the alloying reaction during the GA process was significantly hindered. XPS analysis showed that external oxidation occurred under an extremely low dew point [213 K to 203 K (-60 °C to -70 °C)] atmosphere during the annealing prior to hot dipping. However, most of the oxides were reduced during the GI process. After the GI process, the Al was present as solid solutes in the Fe-Zn phase, suggesting that the Fe-Zn phase was formed from the transformation of the Fe-Al inhibition alloy. Meanwhile, the solubility of Si in the ζ phase was extremely low. With continued GA reaction, the ζ phase transformed into the δ phase, which contained approximately 1.0 at.pct Si. The Si also diffused into the Zn layer during the GA reaction. Hence, the ζ phase did not homogeneously nucleate at the steel substrate/Zn coating interface, but was found at the area away from the interface. Therefore, the Fe-Zn phases on the CMnSiCr dual-phase steels were relatively non-uniform compared to those on interstitial-free steel.

  2. Advanced Si solid phase crystallization for vertical channel in vertical NANDs

    Directory of Open Access Journals (Sweden)

    Sangsoo Lee

    2014-07-01

    Full Text Available The advanced solid phase crystallization (SPC method using the SiGe/Si bi-layer structure is proposed to obtain high-mobility poly-Si thin-film transistors in next generation vertical NAND (VNAND devices. During the SPC process, the top SiGe thin film acts as a selective nucleation layer to induce surface nucleation and equiaxial microstructure. Subsequently, this SiGe thin film microstructure is propagated to the underlying Si thin film by epitaxy-like growth. The initial nucleation at the SiGe surface was clearly observed by in situ transmission electron microscopy (TEM when heating up to 600 °C. The equiaxial microstructures of both SiGe nucleation and Si channel layers were shown in the crystallized bi-layer plan-view TEM measurements. Based on these experimental results, the large-grained and less-defective Si microstructure is expected to form near the channel region of each VNAND cell transistor, which may improve the electrical characteristics.

  3. Two superconducting phases in CePt{sub 3}Si confirmed by NMR

    Energy Technology Data Exchange (ETDEWEB)

    Ueda, Koh-ichi; Motoyama, Gaku; Kohara, Takao, E-mail: ueda@sci.u-hyogo.ac.j [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan)

    2009-03-01

    Recent specific heat experiments in CePt{sub 3}Si of good quality gave an evidence of coexistence of two phases, which have distinct T{sub c} and T{sub n} for each phase. NMR spectrum of {sup 29}Si also showed a complicated line shape due to a co-existence of two phases below T{sub n}. One phase is an ordinary AF state and the other is a paramagnetic like phase, in which the internal field is somewhat small. The AF internal field deduced by NMR is expected to be parallel to the c-axis at Si site. With decreasing temperature below T{sub c}, 1/T{sub 1} measured at the satellite peak decreased rapidly followed by T{sup 3} with no enhancement just below T{sub c}.

  4. Excitations in the quantum paramagnetic phase of the quasi-one-dimensional Ising magnet CoNb2O6 in a transverse field: Geometric frustration and quantum renormalization effects

    Science.gov (United States)

    Cabrera, I.; Thompson, J. D.; Coldea, R.; Prabhakaran, D.; Bewley, R. I.; Guidi, T.; Rodriguez-Rivera, J. A.; Stock, C.

    2014-07-01

    The quasi-one-dimensional (1D) Ising ferromagnet CoNb2O6 has recently been driven via applied transverse magnetic fields through a continuous quantum phase transition from spontaneous magnetic order to a quantum paramagnet, and dramatic changes were observed in the spin dynamics, characteristic of weakly perturbed 1D Ising quantum criticality. We report here extensive single-crystal inelastic neutron scattering measurements of the magnetic excitations throughout the three-dimensional (3D) Brillouin zone in the quantum paramagnetic phase just above the critical field to characterize the effects of the finite interchain couplings. In this phase, we observe that excitations have a sharp, resolution-limited line shape at low energies and over most of the dispersion bandwidth, as expected for spin-flip quasiparticles. We map the full bandwidth along the strongly dispersive chain direction and resolve clear modulations of the dispersions in the plane normal to the chains, characteristic of frustrated interchain couplings in an antiferromagnetic isosceles triangular lattice. The dispersions can be well parametrized using a linear spin-wave model that includes interchain couplings and further neighbor exchanges. The observed dispersion bandwidth along the chain direction is smaller than that predicted by a linear spin-wave model using exchange values determined at zero field, and this effect is attributed to quantum renormalization of the dispersion beyond the spin-wave approximation in fields slightly above the critical field, where quantum fluctuations are still significant.

  5. Diffusion of Ag, Au and Cs implants in MAX phase Ti3SiC2

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Weilin; Henager, Charles H.; Varga, Tamas; Jung, Hee Joon; Overman, Nicole R.; Zhang, Chonghong; Gou, Jie

    2015-05-16

    MAX phases (M: early transition metal; A: elements in group 13 or 14; X: C or N), such as titanium silicon carbide (Ti3SiC2), have a unique combination of both metallic and ceramic properties, which make them attractive for potential nuclear applications. Ti3SiC2 has been considered as a possible fuel cladding material. This study reports on the diffusivities of fission product surrogates (Ag and Cs) and a noble metal Au (with diffusion behavior similar to Ag) in this ternary compound at elevated temperatures, as well as in dual-phase nanocomposite of Ti3SiC2/3C-SiC and polycrystalline CVD 3C-SiC for behavior comparisons. Samples were implanted with Ag, Au or Cs ions and characterized with various methods, including x-ray diffraction, electron backscatter diffraction, energy dispersive x-ray spectroscopy, Rutherford backscattering spectrometry, helium ion microscopy, and transmission electron microscopy. The results show that in contrast to immobile Ag in 3C-SiC, there is a significant outward diffusion of Ag in Ti3SiC2 within the dual-phase nanocomposite during Ag ion implantation at 873 K. Similar behavior of Au in polycrystalline Ti3SiC2 was also observed. Cs out-diffusion and release from Ti3SiC2 occurred during post-implantation thermal annealing at 973 K. This study suggests caution and further studies in consideration of Ti3SiC2 as a fuel cladding material for advanced nuclear reactors operating at very high temperatures.

  6. Cube-phase in excess Hg-type Al-Mg-Si alloy studied by EFTEM

    Czech Academy of Sciences Publication Activity Database

    Matsuda, K.; Ishida, Y.; Müllerová, Ilona; Frank, Luděk; Ikeno, S.

    2006-01-01

    Roč. 41, č. 9 (2006), s. 2605-2610 ISSN 0022-2461 Institutional research plan: CEZ:AV0Z20650511 Keywords : Al-Mg-Si alloy * beta-phase * cube-phase * EFTEM * EDS Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 0.999, year: 2006

  7. Liquid phase sintered SiC. Processing and transformation controlled microstructure tailoring

    Directory of Open Access Journals (Sweden)

    V.A. Izhevskyi

    2000-10-01

    Full Text Available Microstructure development and phase formation processes during sintering of silicon carbide based materials with AlN-Y2O3, AlN-Yb2O3, and AlN-La2O3 sintering additives were investigated. Densification of the materials occurred by liquid-phase sintering mechanism. Proportion of alpha- and beta-SiC powders in the initial mixtures was a variable parameter, while the molar ratio of AlN/RE2O3, and the total amount of additives (10 vol. % were kept constant. Shrinkage behavior during sintering in interrelation with the starting composition of the material and the sintering atmosphere was investigated by high temperature dilatometry. Kinetics of b-SiC to a-SiC phase transformation during post-sintering heat treatment at temperatures 1900-1950 °C was studied, the degree of phase transformation being determined by quantitative x-ray analysis using internal standard technique. Evolution of microstructure resulting from beta-SiC to alpha-SiC transformation was followed up by scanning electron microscopy on polished and chemically etched samples. Transformation-controlled grain growth mechanism similar to the one observed for silicon nitride based ceramics was established. Possibility of in-situ platelet reinforced dense SiC-based ceramics fabrication with improved mechanical properties by means of sintering was shown.

  8. Picosecond laser pulse-driven crystallization behavior of SiSb phase change memory thin films

    International Nuclear Information System (INIS)

    Huang Huan; Li Simian; Zhai Fengxiao; Wang Yang; Lai Tianshu; Wu Yiqun; Gan Fuxi

    2011-01-01

    Highlights: → We reported crystallization dynamics of a novel SiSb phase change material. → We measured optical constants of as-deposited and irradiated SiSb areas. → Optical properties of as-deposited and irradiated SiSb thin film were compared. → Crystallization of irradiated SiSb was confirmed by using AFM and micro-Raman spectra. → The heat conduction effect of lower metal layer of multi-layer films was studied. - Abstract: Transient phase change crystallization process of SiSb phase change thin films under the irradiation of picosecond (ps) laser pulse was studied using time-resolved reflectivity measurements. The ps laser pulse-crystallized domains were characterized by atomic force microscope, Raman spectra and ellipsometrical spectra measurements. A reflectivity contrast of about 15% can be achieved by ps laser pulse-induced crystallization. A minimum crystallization time of 11 ns was achieved by a low-fluence single ps laser pulse after pre-irradiation. SiSb was shown to be very promising for fast phase change memory applications.

  9. Evaluation of phase sensitive detection method and Si avalanche photodiode for radiation thermometry

    International Nuclear Information System (INIS)

    Hobbs, M J; Tan, C H; Willmott, J R

    2013-01-01

    We report the evaluation of Si avalanche photodiodes (APDs) for use in radiation thermometry as an alternative to Si photodiodes. We compared their performance when operated under phase sensitive detection (PSD), where the signal is modulated, and direct detection (DD) methods. A Si APD was compared with a Si photodiode with reference black body temperatures of 275 to 600°C, in terms of the mean output voltage and signal-to-noise ratio (SNR), measured at different APD gain values. We found that using both PSD and DD methods, the high internal gain of the Si APD achieved a lower minimum detection temperature in order to satisfy a specific minimum output voltage of the detector-preamplifier combination employed. The use of PSD over DD for the Si APD allowed for improved performance of the thermometer, with a lower minimum measurable temperature, as well as improvement in the SNR. For instance we found that at 350°C, the Si APD biased at 150 V using PSD can provide ∼ 88 times enhancement in the system SNR over that of a Si photodiode using DD. A corresponding temperature error of ±0.05°C was achieved using the APD with PSD compared to an error of ±2.75°C measured using the Si photodiode with DD.

  10. Phase equilibria in the Zr-Si-B ternary system (Zr-Si-ZrB{sub 2} region) at 1 173 K

    Energy Technology Data Exchange (ETDEWEB)

    Han, Feng; Luo, Hao [Guangxi Univ., Nanning (China). College of Materials Science and Engineering; Guangxi Univ., Nanning (China). Guangxi Key Lab. of Processing for Non-ferrous Metal and Featured Materials; Zhan, Yongzhong [Guangxi Univ., Nanning (China). College of Materials Science and Engineering; Guangxi Univ., Nanning (China). Guangxi Key Lab. of Processing for Non-ferrous Metal and Featured Materials; Guangxi Univ., Nanning (China). Center of Ecological Collaborative Innovation for Aluminum Industry

    2017-10-15

    The isothermal section of the Zr-Si-B ternary system (Zr-Si-ZrB{sub 2} region) at 1 173 K has been experimentally determined. All equilibrated alloys were characterized via X-ray powder diffraction and scanning electron microscopy equipped with energy-dispersive X-ray analysis. A ternary phase Zr{sub 5}(Si{sub 0.86}B{sub 0.14}){sub 3} was found at 1 173 K. The experimental results show that the isothermal section consists of 11 single-phase regions, 26 two-phase regions and 13 three-phase regions. The existence of eight compounds, i.e. ZrSi{sub 2}, ZrSi, Zr{sub 5}Si{sub 4}, Zr{sub 3}Si{sub 2}, Zr{sub 2}Si, ZrB, ZrB{sub 2} and Zr{sub 5}(Si{sub 0.86}B{sub 0.14}){sub 3} in this system has been confirmed in the Zr-Si-ZrB{sub 2} region at 1 173 K.

  11. Frustration in Condensed Matter and Protein Folding

    Science.gov (United States)

    Li, Z.; Tanner, S.; Conroy, B.; Owens, F.; Tran, M. M.; Boekema, C.

    2014-03-01

    By means of computer modeling, we are studying frustration in condensed matter and protein folding, including the influence of temperature and Thomson-figure formation. Frustration is due to competing interactions in a disordered state. The key issue is how the particles interact to reach the lowest frustration. The relaxation for frustration is mostly a power function (randomly assigned pattern) or an exponential function (regular patterns like Thomson figures). For the atomic Thomson model, frustration is predicted to decrease with the formation of Thomson figures at zero kelvin. We attempt to apply our frustration modeling to protein folding and dynamics. We investigate the homogeneous protein frustration that would cause the speed of the protein folding to increase. Increase of protein frustration (where frustration and hydrophobicity interplay with protein folding) may lead to a protein mutation. Research is supported by WiSE@SJSU and AFC San Jose.

  12. Phase Evolution in and Creep Properties of Nb-Rich Nb-Si-Cr Eutectics

    Science.gov (United States)

    Gang, Florian; Kauffmann, Alexander; Heilmaier, Martin

    2018-03-01

    In this work, the Nb-rich ternary eutectic in the Nb-Si-Cr system has been experimentally determined to be Nb-10.9Si-28.4Cr (in at. pct). The eutectic is composed of three main phases: Nb solid solution (Nbss), β-Cr2Nb, and Nb9(Si,Cr)5. The ternary eutectic microstructure remains stable for several hundred hours at a temperature up to 1473 K (1200 °C). At 1573 K (1300 °C) and above, the silicide phase Nb9(Si,Cr)5 decomposes into α-Nb5Si3, Nbss, and β-Cr2Nb. Under creep conditions at 1473 K (1200 °C), the alloy deforms by dislocation creep while the major creep resistance is provided by the silicide matrix. If the silicide phase is fragmented and, thus, its matrix character is destroyed by prior heat treatment [ e.g., at 1773 K (1500 °C) for 100 hours], creep is mainly controlled by the Laves phase β-Cr2Nb, resulting in increased minimum strain rates. Compared to state of the art Ni-based superalloys, the creep resistance of this three-phase eutectic alloy is significantly higher.

  13. A new quaternary phase observed in a laser treated Zn–Al–Mg–Si coating

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Z., E-mail: zchen@uowmail.edu.au [School of Mechanical, Materials and Mechatronic Engineering, Faculty of Engineering and Information Sciences, University of Wollongong, Wollongong, NSW 2522 (Australia); Peng, C.-T. [School of Mechanical, Materials and Mechatronic Engineering, Faculty of Engineering and Information Sciences, University of Wollongong, Wollongong, NSW 2522 (Australia); Liu, Q.; Smith, R.; Nolan, D. [Bluescope Steel Research, Bluescope Steel Limited, Locked Bag 8825, Wollongong DC, NSW 2500 (Australia)

    2014-03-15

    Highlights: • A new quaternary phase was discovered in laser treated Zn–55Al–2Mg–1Si coating. • The crystal structure of the new phase was determined by TEM. • The new phase was not a metastable phase induced by the rapid cooling of the laser treatment. • Laser treatment led to not only a much finer microstructure but also changes of phases in the interdendritic areas of the coating. -- Abstract: The microstructure of laser resurfaced Zn–55Al–2Mg–1.5Si coating produced on a hot-dip simulator was characterised by transmission electron microscopy. A new quaternary phase was observed and its crystal structure was determined by electron diffraction.

  14. A new quaternary phase observed in a laser treated Zn–Al–Mg–Si coating

    International Nuclear Information System (INIS)

    Chen, Z.; Peng, C.-T.; Liu, Q.; Smith, R.; Nolan, D.

    2014-01-01

    Highlights: • A new quaternary phase was discovered in laser treated Zn–55Al–2Mg–1Si coating. • The crystal structure of the new phase was determined by TEM. • The new phase was not a metastable phase induced by the rapid cooling of the laser treatment. • Laser treatment led to not only a much finer microstructure but also changes of phases in the interdendritic areas of the coating. -- Abstract: The microstructure of laser resurfaced Zn–55Al–2Mg–1.5Si coating produced on a hot-dip simulator was characterised by transmission electron microscopy. A new quaternary phase was observed and its crystal structure was determined by electron diffraction

  15. Unirradiated characteristics of U-Si alloys as dispersed-phase fuels

    International Nuclear Information System (INIS)

    Domagala, R.F.; Wiencek, T.C.

    1987-06-01

    To satisfy the power demands of many research reactors, a new LEU fuel with a high density and U content was needed. Any fuel must be compatible with Al and its alloys so that it may be fabricable as a dispersed-phase in Al alloy and Al matrix plate-type elements following, as nearly as possible, established commercial manufacturing techniques. U-Si and U-Si-Al alloys at or near the composition of U 3 Si were immediately attractive because of work documented by the Canadians. 8 refs., 2 figs

  16. The Prognosis of the Phase Equilibrium Diagram of the System Al-Cu-Si

    Directory of Open Access Journals (Sweden)

    Florentina Cziple

    2007-10-01

    Full Text Available The paper presents a model for establishing the mathematical functions of the liquidus and solidus curves, from the binary diagrams Al-Si, Si-Cu, Cu-Al and their use in the prognosis of the phase equilibrium diagram from the ternary system Al-Cu-Si. We have studied the model of the non-ideal liquid solution of the regular type. The calculus and graphic plotting of the equations for the binary systems has been performed on the computer

  17. Magnetic phase diagram of UNi2Si2 under magnetic field and high-pressure

    International Nuclear Information System (INIS)

    Honda, F.; Oomi, G.; Svoboda, P.; Syshchenko, A.; Sechovsky, V.; Khmelevski, S.; Divis, M.; Andreev, A.V.; Takeshita, N.; Mori, N.; Menovsky, A.A.

    2001-01-01

    Measurements of electrical resistance under high pressure and neutron diffraction in high-magnetic field of single crystalline UNi 2 Si 2 have been performed. We have found the analogy between the p-T and B-T magnetic phase diagrams. It is also found that the propagation vector q Z of incommensurate antiferromagnetic phase decreases with increasing magnetic field. A new pronounced pressure-induced incommensurate-commensurate magnetic phase transition has been detected

  18. Phase transformations behavior in a Cu-8.0Ni-1.8Si alloy

    Energy Technology Data Exchange (ETDEWEB)

    Lei, Q. [School of Materials Science and Engineering, Central South University, Changsha, 410083 (China); Li, Z., E-mail: lizhou6931@163.com [School of Materials Science and Engineering, Central South University, Changsha, 410083 (China) and Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Changsha, 410083 (China); Wang, M.P. [School of Materials Science and Engineering, Central South University, Changsha, 410083 (China); Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Changsha, 410083 (China); Zhang, L.; Gong, S. [School of Materials Science and Engineering, Central South University, Changsha, 410083 (China); Xiao, Z. [Department of Engineering, University of Liverpool, Liverpool, L693 GH (United Kingdom); Pan, Z.Y. [Hunan Nonferrous Metals Holding Group Co., Ltd., Changsha, 410015 (China)

    2011-02-24

    Research highlights: > High solute concentrations Cu-Ni-Si alloy with super high strength and high conductivity has a good prospect for replacing Cu-Be alloys. At least four different kinds of precipitation products (DO{sub 22} ordered structure, {beta}-Ni{sub 3}Si precipitate, {delta}-Ni{sub 2}Si precipitate and {gamma}-Ni{sub 5}Si{sub 2} precipitate) have been observed in previous investigation. Therefore, the overall phase transformation behavior of Cu-Ni-Si alloy appears to be very complex. And most previous studies on the phase transformation usually investigated the precipitation process at only one temperature or at most a few temperatures, which is far away to establish a time-temperature-transformation (TTT) diagram for Cu-Ni-Si alloy. > The phase transformation behavior of Cu-8.0Ni-1.8Si alloy has been studied systematically at wide temperature range in this paper. The results we have gained are that: after solution treatment, followed by different conditions of isothermal treatment, DO{sub 22} ordering, discontinuous precipitation and continuous precipitation were observed in the alloy; discontinuous precipitates of {beta}-Ni{sub 3}Si phase appeared when the alloy isothermal treated at 550 deg. C for short time, which had not been reported by the previous Cu-Ni-Si system alloy's researchers in their papers; two kinds of precipitates of {beta}-Ni{sub 3}Si and {delta}-Ni{sub 2}Si were determined by the TEM characterization; the orientation relationship between the two kinds of precipitates and Cu-matrix is that: (1 1 0){sub Cu}//(1 1 0){sub {beta}}//(211-bar){sub {delta}}, [112-bar]{sub Cu}//[11-bar 2]{sub {beta}}//[3 2 4]{sub {delta}}; during overaging treatment, Cu-matrix, {beta}-Ni{sub 3}Si, {delta}-Ni{sub 2}Si and {delta}'-Ni{sub 2}Si were distinguished in the samples and the orientation relationship between the precipitates and Cu-matrix can be expressed as that: (0 2 2){sub Cu}//(0 2 2){sub {beta}}//(1 0 0){sub {delta}}, (02-bar 2){sub Cu

  19. Synthesis of Zr-Si-O-N phases by carbonitriding reaction. Characterization of crystalline phases using the Rietveld method

    Directory of Open Access Journals (Sweden)

    Mazzoni A.D.

    2001-01-01

    Full Text Available Zirconium compounds are of great interest for ceramic application due to their excellent thermal and mechanical properties. Zirconium phases of the system Zr-O-C-N were obtained using carbonitriding reactions of zircon mineral (ZrO2.SiO2, under different reaction conditions. The reaction products were studied by X-ray diffraction (XRD using the Rietveld method. Silicon was employed as internal standard. Zirconium compounds formed were m-ZrO2 (monoclinic, beta"-zirconium oxynitride and a cubic Zr(C,N,O phase whose lattice parameter a o depends on the composition. The crystallite sizes of the three zirconium phases were determined also by XRD. The minority phases present are the ones of the Si-O-N-C system. The reaction conditions employed allows to obtain reaction products with low or without silicon content.

  20. Structural phase transition and precursor phenomena in V3Si

    International Nuclear Information System (INIS)

    Kobayashi, T.; Fukase, T.; Toyota, N.; Muto, Y.

    1982-01-01

    Thermal dilation experiments on the transforming single crystals V 3 Si indicated that the precursor of the structural transformation at Tsub(m) of about 21 K starts at anomalously high temperatures (proportional70 K) and grows drastically near Tsub(m). This anomaly is also accompanied by the critical increment of electrical resistivity showing a sharp peak at Tsub(m). The application of the uniaxial stress suppresses the resistivity anomaly and makes the superconducting transition width narrower. We propose a model for the precursor phenomena in terms of (1) the directional strain fields (non-cubic) pinned near the defects and (2) the memory effect of orientation of the tetragonal domains born by the defects such as dislocations. (orig.)

  1. Size- and phase-dependent mechanical properties of ultrathin Si films on polyimide substrates

    International Nuclear Information System (INIS)

    Schlich, Franziska F.; Spolenak, Ralph

    2016-01-01

    Ultrathin Si films in the nanometer range are extensively used for electronic and optoelectronic devices. Their mechanical properties have a high impact on the durability of the devices during lifetime. Here, fragmentation and buckling of 8–103 nm thin amorphous and polycrystalline (poly-) Si films on polyimide substrates have been studied by in situ light microscopy, Raman spectroscopy and resistance measurements. Generally, a smaller film thickness and a compressive residual stress delays the fracture of the film. The fracture strength of poly-Si films is larger compared to that of amorphous Si films while the adhesion to the substrate is better for amorphous Si compared to poly-Si. The onset delamination as a function of film thickness differs for the two phases and is described by two different models. Thin-film models for fracture toughness (amorphous Si: K 1C  = 1.49 ± 0.22, poly-Si: K 1C  = 3.36 ± 1.37) are applied, discussed, and found to be consistent with literature values.

  2. Reaction phases and diffusion paths in SiC/metal systems

    Energy Technology Data Exchange (ETDEWEB)

    Naka, M.; Fukai, T. [Osaka Univ., Osaka (Japan); Schuster, J.C. [Vienna Univ., Vienna (Austria)

    2004-07-01

    The interface structures between SiC and metal are reviewed at SiC/metal systems. Metal groups are divided to carbide forming metals and non-carbide forming metals. Carbide forming metals form metal carbide granular or zone at metal side, and metal silicide zone at SiC side. The further diffusion of Si and C from SiC causes the formation of T ternary phase depending metal. Non-carbide forming metals form silicide zone containing graphite or the layered structure of metal silicide and metal silicide containing graphite. The diffusion path between SiC and metal are formed along tie-lines connecting SiC and metal on the corresponding ternary Si-C-M system. The reactivity of metals is dominated by the forming ability of carbide or silicide. Te reactivity tendency of elements are discussed on the periodical table of elements, and Ti among elements shows the highest reactivity among carbide forming metals. For non-carbide forming metals the reactivity sequence of metals is Fe>Ni>Co. (orig.)

  3. Vanadium Influence on Iron Based Intermetallic Phases in AlSi6Cu4 Alloy

    Directory of Open Access Journals (Sweden)

    Bolibruchová D.

    2014-10-01

    Full Text Available Negative effect of iron in Al-Si alloys mostly refers with iron based intermetallic phases, especially Al5FeSi phases. These phases are present in platelet-like forms, which sharp edges are considered as main cracks initiators and also as contributors of porosity formation. In recent times, addition of some elements, for example Mn, Co, Cr, Ni, V, is used to reduce influence of iron. Influence of vanadium in aluminium AlSi6Cu4 alloy with intentionally increased iron content is presented in this article. Vanadium amount has been graduated and chemical composition of alloy has been analysed by spectral analysis. Vanadium influence on microstructural changes was evaluated by microstructural analysis and some of intermetallic particles were reviewed by EDX analysis.

  4. Identification of sigma and OMEGA phases in AA2009/SiC composites

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigo, P., E-mail: pilar.rodrigo@urjc.e [Departamento de Ciencia e Ingenieria de Materiales, Escuela Superior de Ciencias Experimentales y Tecnologia, Universidad Rey Juan Carlos, c/Tulipan s/n, 28933 Mostoles, Madrid (Spain); Poza, P.; Utrilla, M.V.; Urena, A. [Departamento de Ciencia e Ingenieria de Materiales, Escuela Superior de Ciencias Experimentales y Tecnologia, Universidad Rey Juan Carlos, c/Tulipan s/n, 28933 Mostoles, Madrid (Spain)

    2009-08-12

    The microstructure evolution during ageing treatment at 170 and 190 deg. C of AA2009/SiC composites, reinforced with 15 vol.% particulates and whiskers, was studied by transmission electron microscopy. Besides theta' and S' phases, the typical hardening precipitates on Al-Cu-Mg alloys, it was found the presence of OMEGA and sigma (Al{sub 5}Cu{sub 6}Mg{sub 2}) phases in the matrix. sigma phase was only found in the matrix of particulate composite, while OMEGA phase appeared in both. This phase has not been previously observed in Al matrix composites based on conventional Al-Cu-Mg alloys.

  5. Iron Intermetallic Phases in the Alloy Based on Al-Si-Mg by Applying Manganese

    Directory of Open Access Journals (Sweden)

    Podprocká R.

    2017-09-01

    Full Text Available Manganese is an effective element used for the modification of needle intermetallic phases in Al-Si alloy. These particles seriously degrade mechanical characteristics of the alloy and promote the formation of porosity. By adding manganese the particles are being excluded in more compact shape of “Chinese script” or skeletal form, which are less initiative to cracks as Al5FeSi phase. In the present article, AlSi7Mg0.3 aluminium foundry alloy with several manganese content were studied. The alloy was controlled pollution for achieve higher iron content (about 0.7 wt. % Fe. The manganese were added in amount of 0.2 wt. %, 0.6 wt. %, 1.0 wt. % and 1.4 wt. %. The influence of the alloying element on the process of crystallization of intermetallic phases were compared to microstructural observations. The results indicate that increasing manganese content (> 0.2 wt. % Mn lead to increase the temperature of solidification iron rich phase (TAl5FeSi and reduction this particles. The temperature of nucleation Al-Si eutectic increase with higher manganese content also. At adding 1.4 wt. % Mn grain refinement and skeleton particles were observed.

  6. Spin-Hall effect and emergent antiferromagnetic phase transition in n-Si

    Science.gov (United States)

    Lou, Paul C.; Kumar, Sandeep

    2018-04-01

    Spin current experiences minimal dephasing and scattering in Si due to small spin-orbit coupling and spin-lattice interactions is the primary source of spin relaxation. We hypothesize that if the specimen dimension is of the same order as the spin diffusion length then spin polarization will lead to non-equilibrium spin accumulation and emergent phase transition. In n-Si, spin diffusion length has been reported up to 6 μm. The spin accumulation in Si will modify the thermal transport behavior of Si, which can be detected with thermal characterization. In this study, we report observation of spin-Hall effect and emergent antiferromagnetic phase transition behavior using magneto-electro-thermal transport characterization. The freestanding Pd (1 nm)/Ni80Fe20 (75 nm)/MgO (1 nm)/n-Si (2 μm) thin film specimen exhibits a magnetic field dependent thermal transport and spin-Hall magnetoresistance behavior attributed to Rashba effect. An emergent phase transition is discovered using self-heating 3ω method, which shows a diverging behavior at 270 K as a function of temperature similar to a second order phase transition. We propose that spin-Hall effect leads to the spin accumulation and resulting emergent antiferromagnetic phase transition. We propose that the length scale for Rashba effect can be equal to the spin diffusion length and two-dimensional electron gas is not essential for it. The emergent antiferromagnetic phase transition is attributed to the site inversion asymmetry in diamond cubic Si lattice.

  7. Morphology of intermetallic phases in Al-Si cast alloys and their fracture behaviour

    Directory of Open Access Journals (Sweden)

    Lenka Hurtalová

    2015-03-01

    Full Text Available Applications of Al-Si cast alloys in recent years have increased especially in the automotive industry (dynamic exposed cast, en-gine parts, cylinder heads, pistons and so on. Controlling the microstructure of secondary aluminium cast alloys is very important, because these alloys contain more additional elements that form various intermetallic phases in the structure. Therefore, the contribution is dealing with the valuation type of intermetallic phases and their identification with using optical and scanning microscopy. Some of the intermetallic phases could be identified on the basis of morphology but some of them must be identified according EDX analysis. The properties of alu-minium alloy are affected by morphology of intermetallic phases and therefore it is necessary to study morphology and its fracture behav-iour. The present work shows morphology and typical fracture behaviour as the most common intermetallic phases forming in Al-Si alloys.

  8. Evolution of Fe based intermetallic phases in Al–Si hypoeutectic casting alloys: Influence of the Si and Fe concentrations, and solidification rate

    International Nuclear Information System (INIS)

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

    2013-01-01

    Highlights: •Anomalous evolution of Fe based intermetallic phases in Al–Si–Fe alloys. •XRF coupled with nano-diffraction to confirm the nano-size Fe intermetallic phases. •Crystallography of the θ-Al 13 Fe 4 , τ 5 -Al 8 Fe 2 Si and τ 6 -Al 9 Fe 2 Si 2 phases. •Peritectic reactions involving the Fe intermetallic phases in Al–Si–Fe alloys. -- Abstract: Al–Si–Fe hypoeutectic cast alloy system is very complex and reported to produce numerous Fe based intermetallic phases in conjunction with Al and Si. This publication will address the anomalies of phase evolution in the Al–Si–Fe hypoeutectic casting alloy system; the anomaly lies in the peculiarities in the evolution and nature of the intermetallic phases when compared to the thermodynamic phase diagram predictions and past publications of the same. The influence of the following parameters, in various combinations, on the evolution and nature of the intermetallic phases were analyzed and reported: concentration of Si between 2 and 12.6 wt%, Fe between 0.05 and 0.5 wt% and solidification rates of 0.1, 1, 5 and 50 K s −1 . Two intermetallic phases are observed to evolve in these alloys under these solidification conditions: the τ 5 -Al 8 SiFe 2 and τ 6 -Al 9 Fe 2 Si 2 . The τ 5 -Al 8 SiFe 2 phase evolves at all levels of the parameters during solidification and subsequently transforms into the τ 6 -Al 9 Fe 2 Si 2 through a peritectic reaction when promoted by certain combinations of solidification parameters such as higher Fe level, lower Si level and slower solidification rates. Further, it is also hypothesized from experimental evidences that the θ-Al 13 Fe 4 binary phase precludes the evolution of the τ 5 during solidification and subsequently transforms into the τ 6 phase during solidification. These observations are anomalous to the publications as prior art and simulation predictions of thermodynamic phase diagrams of these alloys, wherein, only one intermetallic phases in the

  9. The crystallographic phases and magnetic properties of Fe2MnSi1-xGex

    International Nuclear Information System (INIS)

    Zhang, L.; Brueck, E.; Tegus, O.; Buschow, K.H.J.; Boer, F.R. de

    2003-01-01

    Fe 2 MnSi 1-x Ge x (x=0, 0.2, 0.4, 0.5, 0.6, 0.8, 1) compounds were prepared by a mechanically activated solid-state diffusion method. Both X-ray diffraction and differential scanning calorimetry evidenced the presence of an amorphous phase after 10 h of milling. The X-ray data reveal that in the high-temperature annealing the single D0 3 -type phase can be retained up to 50% substitution of Ge for Si in Fe 2 MnSi. A metastable D0 3 phase is obtained after crystallization of the as-milled amorphous compounds with x>0.5. High-temperature annealing transforms the low-temperature D0 3 phase into a single D0 19 phase (x=1) or a mixture of D0 3 and D0 19 phase (x=0.6 and 0.8). Low-field thermomagnetic measurements show a moderately sharp ferromagnetic-paramagnetic transition, which becomes enormously broad in higher magnetic fields. The Curie temperature is significantly enhanced when going from the D0 3 phase to the D0 19 phase. Neither a magnetic-field-induced transition nor a reversible structural transition is observed throughout this compound series. The magnetocaloric effect associated with the magnetic transition is small

  10. Deliberate exotic magnetism via frustration and topology

    Science.gov (United States)

    Nisoli, Cristiano; Kapaklis, Vassilios; Schiffer, Peter

    2017-03-01

    Introduced originally to mimic the unusual, frustrated behaviour of spin ice pyrochlores, artificial spin ice can be realized in odd, dedicated geometries that open the door to new manifestations of a higher level of frustration.

  11. Magnetic structure and phase diagram of the frustrated spinel Cd{sub 1-x}Zn{sub x}Cr{sub 2}Se{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Loudghiri, E. [Laboratoire de Physique des Materiaux, Faculte des Sciences, Universite Mohammed V, B.P. 1014 Rabat (Morocco); Belayachi, A. [Laboratoire de Physique des Materiaux, Faculte des Sciences, Universite Mohammed V, B.P. 1014 Rabat (Morocco)], E-mail: belayach@fsr.ac.ma; Nogues, M. [Laboratoire de Magnetisme et d' Optique de l' Universite de Versailles (URA 1531), Batiment, Fermat, 45 Avenue des Etats Unis, 78035 Versailles Cedex (France); Taibi, M. [Laboratoire de Physico-Chimie des Materiaux associe a l' AUF (LAF 502), Ecole Normale, Superieure Takadoum, B.P. 5118 Rabat (Morocco); Cruz, M.M.; Godinho, M. [Dept. Fisica/CFMC-UL, Fac. Ciencias, Universidade de Lisboa, Campo Grande, Ed.C8, 1749-016 Lisbon (Portugal)

    2008-03-15

    In attempt to characterise the magnetic ordering in the whole composition range of the Cd{sub 1-x}Zn{sub x}Cr{sub 2}Se{sub 4} system, various magnetic measurements were performed on both crystalline and polycrystalline samples with 0{<=}x{<=}1. The magnetic properties of the system are typical of a ferromagnet below x=0.4 and of a complex antiferromagnet one above x=0.6. In this work the intermediate region was carefully studied. The variations of both M(T) and {chi}{sub ac} at low fields suggest that transitions from ferromagnetic to Gabay-Toulouse ferromagnetic-spin-glass mixed phase at low temperature occur in the range 0.41{<=}x{<=}0.58. The high-temperature susceptibility measurements show that for the whole concentration range the system obeys Curie-Weiss laws. The results can be explained by the coexistence of competing interactions (ferromagnetic between nearest neighbours and antiferromagnetic between higher order neighbours) and disorder due to the random substitution between zinc and cadmium ions in the tetrahedral sites of the spinel lattice. An experimental magnetic phase diagram of the system is established.

  12. Magnetic phase diagram of ErGe 1-xSi x (0

    Science.gov (United States)

    Thuéry, P.; El Maziani, F.; Clin, M.; Schobinger-Papamantellos, P.; Buschow, K. H. J.

    1993-10-01

    The composition-temperature magnetic phase diagram of ErGe 1- xSi x (0 0.40. For 0.17 ≥ x ≤ 0.55, a first-order transition occurs as function of the temperature between these two phases. For x ≥ 0.65, a lock-in transition takes place at TIC, leading from the wavevector ( k' x,0, k' z) to (1/2,0,1/2), as was already observed in ErSi. Finally, for x < 0.17 or 0.55 < x < 0.65, the wavevectors of the incommensurate phases characterized by (0,0, kz) or ( k' x,0, k' z) respectively remain unchanged in the whole temperature range below TN. For x≥0.65, a small amount of a magnetic phase characterized by the wavevector (0,0, 1/2) coexists with the main phases, below a Néel temperature T' N slightly lower than TN. In all cases, the erbium magnetic moments are colinear along the orthorhombic α-axis; the arrangement of the moments in the commensurate phases is the same as in ErSi and the incommensurate orderings correspond to sine-wave amplitude modulations. A brief account on the theoretical interpretation of this phase diagram is finally given.

  13. Effects of Si on microstructure and phase transformation at elevated temperatures in ferritic white cast irons

    Energy Technology Data Exchange (ETDEWEB)

    Wiengmoon, A., E-mail: ampornw@nu.ac.th [Department of Physics, Faculty of Science, Naresuan University, Phitsanulok 65000 (Thailand); Pearce, J.T.H. [Panyapiwat Institute of Management, Nonthaburi 11120 (Thailand); Nusen, S.; Chairuangsri, T. [Department of Industrial Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand)

    2016-10-15

    The effects of Si on microstructure and phase transformation at elevated temperature of ferritic 31wt.%Cr-1.1wt.%C white cast irons with up to 3wt.%Si have been studied. Applications of these irons include parts requiring heat resistance at elevated temperature. The irons were produced by sand casting. The microstructure in as-cast condition and after being subjected to high temperature (700 to 1000 °C) was investigated by light microscopy, X-ray diffraction, and electron microscopy. The results revealed that the as-cast microstructure consisted mainly of primary ferrite dendrites and eutectic (ferrite + M{sub 7}C{sub 3}). Si promotes M{sub 7}C{sub 3}-to-M{sub 23}C{sub 6} transformation in the irons subjected to transformation at elevated temperature, but no sigma phase was found. The extent of M{sub 7}C{sub 3}-to-M{sub 23}C{sub 6} transformation increases proportional to the increasing transformation temperature, holding time and Si content in the irons. For the iron with 1.0wt.%Si content after holding at elevated temperatures, martensite was also found, which could be attributed to carbon accretion effects in eutectic ferrite. Si was incorporated in M{sub 23}C{sub 6} such that M{sub 23}C{sub 6} containing Si can show darker contrast under SEM-BEI as compared to M{sub 7}C{sub 3}; this is the opposite to what has been observed for the cases of typical M{sub 23}C{sub 6} and M{sub 23}C{sub 6} containing Mo or W. The results obtained are important to understand the change in properties of ferritic, high chromium irons containing Si subjected to elevated temperature.

  14. Sequence of phase transitions in (NH4)3SiF7.

    Science.gov (United States)

    Mel'nikova, S V; Molokeev, M S; Laptash, N M; Pogoreltsev, E I; Misyul, S V; Flerov, I N

    2017-02-21

    Single crystals of silicon double salt (NH 4 ) 3 SiF 7 = (NH 4 ) 2 SiF 6 ·NH 4 F = (NH 4 ) 3 [SiF 6 ]F were grown and studied by the methods of polarization optics, X-ray diffraction and calorimetry. A sequence of symmetry transformations with the temperature change was established: P4/mbm (Z = 2) (G 1 ) ↔ Pbam (Z = 4) (G 2 ) ↔ P2 1 /c (Z = 4) (G 3 ) ↔ P1[combining macron] (Z = 4) (G 4 ) ↔ P2 1 /c (Z = 8) (G 5 ). Crystal structures of different phases were determined. The experimental data were also interpreted by a group-theoretical analysis of the complete condensate of order parameters taking into account critical and noncritical atomic displacements. Strengthening of the N-HF hydrogen bonds can be a driving force of the observed phase transitions.

  15. Investigation of environmental friendly Te-free SiSb material for applications of phase-change memory

    International Nuclear Information System (INIS)

    Zhang Ting; Song Zhitang; Liu Bo; Feng Songlin

    2008-01-01

    Te-free environmental friendly Si x Sb 100−x phase-change materials are investigated. The binary material, which is compatible with the complementary metal-oxide-semiconductor manufacturing process, is outstanding in various properties. Si x Sb 100−x shows a much better data retention as compared with Ge 2 Sb 2 Te 5 . The density change for Si 10 Sb 90 and Si 16 Sb 84 is only about 3% and 3.8%, respectively. The failure times for Si 10 Sb 90 and Si 16 Sb 84 are about 10 3 and 10 6 times longer than that of Ge 2 Sb 2 Te 5 at 110 °C. The crystallization temperature of Si x Sb 100−x increases with silicon content within the material. Si x Sb 100−x materials are good candidates for the phase-change memory applications

  16. Two-dimensional frustrated spin systems in high magnetic fields

    International Nuclear Information System (INIS)

    Schmidt, B; Shannon, N; Thalmeier, P

    2006-01-01

    We discuss our numerical results on the properties of the S = 1/2 frustrated J 1 -J 2 Heisenberg model on a square lattice as a function of temperature and frustration angle φ = tan -1 (J 2 /J 1 ) in an applied magnetic field. We cover the full phase diagram of the model in the range π ≤ φ ≤ π. The discussion includes the parameter dependence of the saturation field itself, and addresses the instabilities associated with it. We also discuss the magnetocaloric effect of the model and show how it can be used to uniquely determine the effective interaction constants of the compounds which were investigated experimentally

  17. Magnetic fluctuations and correlations in MnSi : Evidence for a chiral skyrmion spin liquid phase

    NARCIS (Netherlands)

    Pappas, C.; Lelièvre-Berna, E.; Bentley, P.; Falus, P.; Fouquet, P.; Farago, B.

    2011-01-01

    We present a comprehensive analysis of high-resolution neutron scattering data involving neutron spin echo spectroscopy and spherical polarimetry, which confirm the first-order nature of the helical transition in MnSi. The experiments reveal the existence of a totally chiral dynamic phase in a very

  18. Unusual vortex dynamics in the quantum-liquid phase of a-MoxSi1 ...

    Indian Academy of Sciences (India)

    liquid (QVL) phase has been well-determined in the field–temperature plane, δV (t) origi- ... [19], the field-driven SI transition corresponds to the VG transition from the VG to ... DC current I were measured using a four-terminal method. ..... tions is determined by T/Tc0, for these 'high-Tc' materials the quantum fluctuation.

  19. Formation, stability and crystal structure of the {sigma} phase in Mo-Re-Si alloys

    Energy Technology Data Exchange (ETDEWEB)

    Bei, H., E-mail: beih@ornl.gov [Oak Ridge National Laboratory, Materials Science and Technology Division, Oak Ridge, TN 37831 (United States); Yang, Y., E-mail: ying.yang@computherm.com [CompuTherm LLC, Madison, WI 53719 (United States); Viswanathan, G.B. [Air Force Research Laboratory, Wright-Patterson AFB, OH 45433 (United States); Rawn, C.J.; George, E.P. [Oak Ridge National Laboratory, Materials Science and Technology Division, Oak Ridge, TN 37831 (United States)] [University of Tennessee, Department of Materials Science and Engineering, Knoxville, TN 37996 (United States); Tiley, J. [Air Force Research Laboratory, Wright-Patterson AFB, OH 45433 (United States); Chang, Y.A. [CompuTherm LLC, Madison, WI 53719 (United States)] [University of Wisconsin-Madison, Madison, WI 53705 (United States)

    2010-10-15

    The formation, stability and crystal structure of the {sigma} phase in Mo-Re-Si alloys were investigated. Guided by thermodynamic calculations, six critically selected alloys were arc melted and annealed at 1600 deg. C for 150 h. Their as-cast and annealed microstructures, including phase fractions and distributions, the compositions of the constituent phases and the crystal structure of the {sigma} phase were analyzed by thermodynamic modeling coupled with experimental characterization by scanning electron microscopy, electron probe microanalysis, X-ray diffraction and transmission electron microscopy. Two key findings resulted from this work. One is the large homogeneity range of the {sigma} phase region, extending from binary Mo-Re to ternary Mo-Re-Si. The other is the formation of a {sigma} phase in Mo-rich alloys either through the peritectic reaction of liquid + Mo{sub ss} {yields} {sigma} or primary solidification. These findings are important in understanding the effects of Re on the microstructure and providing guidance on the design of Mo-Re-Si alloys.

  20. Addition of iron for the removal of the {beta}-AlFeSi intermetallic by refining of {alpha}-AlFeSi phase in an Al-7.5Si-3.6Cu alloy

    Energy Technology Data Exchange (ETDEWEB)

    Belmares-Perales, S. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon (Mexico); Zaldivar-Cadena, A.A., E-mail: azaldiva70@hotmail.com [Facultad de Ingenieria Civil, Departamento de Ecomateriales y Energia, Instituto de Ingenieria Civil, Av. Fidel Velasquez and Av. Universidad S/N, Cd. Universitaria, San Nicolas de los Garza, N.L. 66450 (Mexico)

    2010-10-25

    Addition of iron into the molten metal for the removal of the {beta}-AlFeSi intermetallic by refining of {alpha}-AlFeSi phase has been studied. Solidification conditions and composition determine the final microstructure and mechanical properties of a casting piece. It is known that increasing the iron content will produce an increasing of the {alpha}-AlFeSi and {beta}-AlFeSi phases. This phenomenon was confirmed with calculations made by Thermo-Calc{sup TM} software and validated with experimental results, however, the technique of iron addition in this study plays an important role on the solidification kinetics of these iron phases because the refining of {alpha}-AlFeSi and removal of {beta}-AlFeSi phases can be improved. Final results showed an improvement in mechanical properties by removal and refining of {beta}-AlFeSi and {alpha}-AlFeSi phases, respectively. This study shows a new method of removal of {beta}-AlFeSi that could be adopted in the aluminum smelting industry in aluminum alloys with a low cooling rate with a secondary dendritic spacing of about 37 {mu}m.

  1. Addition of iron for the removal of the β-AlFeSi intermetallic by refining of α-AlFeSi phase in an Al-7.5Si-3.6Cu alloy

    International Nuclear Information System (INIS)

    Belmares-Perales, S.; Zaldivar-Cadena, A.A.

    2010-01-01

    Addition of iron into the molten metal for the removal of the β-AlFeSi intermetallic by refining of α-AlFeSi phase has been studied. Solidification conditions and composition determine the final microstructure and mechanical properties of a casting piece. It is known that increasing the iron content will produce an increasing of the α-AlFeSi and β-AlFeSi phases. This phenomenon was confirmed with calculations made by Thermo-Calc TM software and validated with experimental results, however, the technique of iron addition in this study plays an important role on the solidification kinetics of these iron phases because the refining of α-AlFeSi and removal of β-AlFeSi phases can be improved. Final results showed an improvement in mechanical properties by removal and refining of β-AlFeSi and α-AlFeSi phases, respectively. This study shows a new method of removal of β-AlFeSi that could be adopted in the aluminum smelting industry in aluminum alloys with a low cooling rate with a secondary dendritic spacing of about 37 μm.

  2. Characteristic signatures of quantum criticality driven by geometrical frustration.

    Science.gov (United States)

    Tokiwa, Yoshifumi; Stingl, Christian; Kim, Moo-Sung; Takabatake, Toshiro; Gegenwart, Philipp

    2015-04-01

    Geometrical frustration describes situations where interactions are incompatible with the lattice geometry and stabilizes exotic phases such as spin liquids. Whether geometrical frustration of magnetic interactions in metals can induce unconventional quantum critical points is an active area of research. We focus on the hexagonal heavy fermion metal CeRhSn, where the Kondo ions are located on distorted kagome planes stacked along the c axis. Low-temperature specific heat, thermal expansion, and magnetic Grüneisen parameter measurements prove a zero-field quantum critical point. The linear thermal expansion, which measures the initial uniaxial pressure derivative of the entropy, displays a striking anisotropy. Critical and noncritical behaviors along and perpendicular to the kagome planes, respectively, prove that quantum criticality is driven be geometrical frustration. We also discovered a spin flop-type metamagnetic crossover. This excludes an itinerant scenario and suggests that quantum criticality is related to local moments in a spin liquid-like state.

  3. High-pressure phase relations and thermodynamic properties of CaAl 4Si 2O 11 CAS phase

    Science.gov (United States)

    Akaogi, M.; Haraguchi, M.; Yaguchi, M.; Kojitani, H.

    2009-03-01

    Phase relations in CaAl4Si2O11 were examined at 12-23 GPa and 1000-1800 °C by multianvil experiments. A three-phase mixture of grossular, kyanite and corundum is stable below about 13 GPa at 1000-1800 °C. At higher pressure and at temperature below about 1200 °C, a mixture of grossular, stishovite and corundum is stable, indicating the decomposition of kyanite. Above about 1200 °C, CaAl4Si2O11 CAS phase is stable at pressure higher than about 13 GPa. The triple point is placed at 14.7 GPa and 1280 °C. The equilibrium boundary of formation of CAS phase from the mixture of grossular, kyanite and corundum has a small negative slope, and that from the mixture of grossular, stishovite and corundum has a strongly negative slope, while the decomposition boundary of kyanite has a small positive slope. Enthalpies of the transitions were measured by high-temperature drop-solution calorimetry. The enthalpy of formation of CaAl4Si2O11 CAS phase from the mixture of grossular, kyanite and corundum was 139.5 ± 15.6 kJ/mol, and that from the mixture of grossular, stishovite and corundum was 94.2 ± 15.4 kJ/mol. The transition boundaries calculated using the measured enthalpy data were consistent with those determined by the high-pressure experiments. The boundaries in this study are placed about 3 GPa higher in pressure and about 200 °C lower in temperature than those by Zhai and Ito [Zhai, S., Ito, E., 2008. Phase relations of CaAl4Si2O11 at high-pressure and high-temperature with implications for subducted continental crust into the deep mantle. Phys. Earth Planet. Inter. 167, 161-167]. Combining the thermodynamic data measured in this study with those in the literature, dissociation boundary of CAS phase into a mixture of Ca-perovskite, corundum and stishovite and that of grossular into Ca-perovskite plus corundum were calculated to further constrain the stability field of CAS phase. The result suggests that the stability of CAS phase would be limited at the bottom of

  4. WxC-β-SiC Nanocomposite Catalysts Used in Aqueous Phase Hydrogenation of Furfural

    Directory of Open Access Journals (Sweden)

    Jacek Rogowski

    2017-11-01

    Full Text Available This study investigates the effects of the addition of tungsten on the structure, phase composition, textural properties and activities of β-SiC-based catalysts in the aqueous phase hydrogenation of furfural. Carbothermal reduction of SiO2 in the presence of WO3 at 1550 °C in argon resulted in the formation of WxC-β-SiC nanocomposite powders with significant variations in particle morphology and content of WxC-tipped β-SiC nano-whiskers, as revealed by TEM and SEM-EDS. The specific surface area (SSA of the nanocomposite strongly depended on the amount of tungsten and had a notable impact on its catalytic properties for the production of furfuryl alcohol (FA and tetrahydrofurfuryl alcohol (THFA. Nanocomposite WxC-β-SiC catalysts with 10 wt % W in the starting mixture had the highest SSA and the smallest WxC crystallites. Some 10 wt % W nanocomposite catalysts demonstrated up to 90% yield of THFA, in particular in the reduction of furfural derived from biomass, although the reproducible performance of such catalysts has yet to be achieved.

  5. WxC-β-SiC Nanocomposite Catalysts Used in Aqueous Phase Hydrogenation of Furfural.

    Science.gov (United States)

    Rogowski, Jacek; Andrzejczuk, Mariusz; Berlowska, Joanna; Binczarski, Michal; Kregiel, Dorota; Kubiak, Andrzej; Modelska, Magdalena; Szubiakiewicz, Elzbieta; Stanishevsky, Andrei; Tomaszewska, Jolanta; Witonska, Izabela Alina

    2017-11-22

    This study investigates the effects of the addition of tungsten on the structure, phase composition, textural properties and activities of β-SiC-based catalysts in the aqueous phase hydrogenation of furfural. Carbothermal reduction of SiO₂ in the presence of WO₃ at 1550 °C in argon resulted in the formation of W x C-β-SiC nanocomposite powders with significant variations in particle morphology and content of W x C-tipped β-SiC nano-whiskers, as revealed by TEM and SEM-EDS. The specific surface area (SSA) of the nanocomposite strongly depended on the amount of tungsten and had a notable impact on its catalytic properties for the production of furfuryl alcohol (FA) and tetrahydrofurfuryl alcohol (THFA). Nanocomposite W x C-β-SiC catalysts with 10 wt % W in the starting mixture had the highest SSA and the smallest W x C crystallites. Some 10 wt % W nanocomposite catalysts demonstrated up to 90% yield of THFA, in particular in the reduction of furfural derived from biomass, although the reproducible performance of such catalysts has yet to be achieved.

  6. Study on the Formation and Precipitation Mechanism of Mn5Si3 Phase in the MBA-2 Brass Alloy

    Science.gov (United States)

    Li, Hang; Jie, Jinchuan; Zhang, Pengchao; Jia, Chunxu; Wang, Tongmin; Li, Tingju

    2016-06-01

    Mn5Si3 is an attractive dispersion in the special brass, owing to its high hardness and high wear resistance. In the present study, synchrotron X-ray radiography and rapid cooling were applied to investigate the formation mechanism of Mn5Si3 phase in the MBA-2 brass alloy. The primary Mn5Si3 phase is proved to exist stably in the alloy melt and nucleate from the melt at temperatures above 1373 K (1100 °C). In addition, the precipitation mechanism of Mn5Si3 phase is addressed systematically by the isothermal heat treatment. The Mn5Si3 particles are observed to precipitate from the matrix at temperatures above 1023 K (750 °C), and a crystallographic orientation relationship is found between the precipitated Mn5Si3 particle and β phase: (110)_{β } //(1overline{1} 00)_{{{{Mn}}5 {{Si}}3 }} and [overline{1} 11]_{β } //[11overline{2} overline{2} ]_{{{{Mn}}5 {{Si}}3 }} . However, the precipitation of Mn5Si3 phase is thermodynamically inhibited at lower temperatures, which can be ascribed to the increase in the Gibbs free energy of formation of Mn5Si3 with decreasing the temperature.

  7. Prediction of novel hard phases of Si{sub 3}N{sub 4}: First-principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Lin; Hu, Meng; Wang, Qianqian; Xu, Bo; Yu, Dongli; Liu, Zhongyuan; He, Julong, E-mail: hjl@ysu.edu.cn

    2015-08-15

    Exploration of novel hard metastable phases of silicon nitride was performed using a recently developed particle-swarm optimization method within the CALYPSO software package. Three potential hard metastable phases of t-Si{sub 3}N{sub 4}, m-Si{sub 3}N{sub 4}, and o-Si{sub 3}N{sub 4} were predicted. These phases are mechanically and dynamically stable at ambient pressure based on their elastic constants and phonon dispersions. t-Si{sub 3}N{sub 4} and m-Si{sub 3}N{sub 4} exhibit lower energies than γ-Si{sub 3}N{sub 4} at pressures below 2.5 GPa and 2.9 GPa, respectively, which promise that the formers could be obtained by quenching from γ-Si{sub 3}N{sub 4}. o-Si{sub 3}N{sub 4} is a better high-pressure metastable phase than CaTi{sub 2}O{sub 4}-type Si{sub 3}N{sub 4} proposed by Tatsumi et al. and it can come from the transition of γ-Si{sub 3}N{sub 4} under 198 GPa. The theoretical band gaps of t-Si{sub 3}N{sub 4}, m-Si{sub 3}N{sub 4}, and o-Si{sub 3}N{sub 4} at ambient pressure were 3.15 eV, 3.90 eV, and 3.36 eV, respectively. At ambient pressure, the Vickers hardness values of t-Si{sub 3}N{sub 4} (32.6 GPa), m-Si{sub 3}N{sub 4} (31.5 GPa), and o-Si{sub 3}N{sub 4} (36.1 GPa) are comparable to β-Si{sub 3}N{sub 4} and γ-Si{sub 3}N{sub 4}. With the pressure increasing, t-Si{sub 3}N{sub 4}, m-Si{sub 3}N{sub 4}, and o-Si{sub 3}N{sub 4} will change from the brittle to ductile state at about 15.7 GPa, 7.3 GPa and 28.9 GPa, respectively. - Graphical abstract: This figure shows the crystal structures of three Si{sub 3}N{sub 4} predicted in this manuscript, and left to right: t-Si{sub 3}N{sub 4}, m-Si{sub 3}N{sub 4} and o-Si{sub 3}N{sub 4}. - Highlights: • We explored three metastable phases of Si{sub 3}N{sub 4} — t-Si{sub 3}N{sub 4}, m-Si{sub 3}N{sub 4}, and o-Si{sub 3}N{sub 4}. • The enthalpies of t and m- are much lower than that of γ at ambient pressure. • ois one further high pressure phase than γ. • o-Si{sub 3}N{sub 4} is the most hardest phase in Si

  8. The regulation of induced depression during a frustrating situation: benefits of expressive suppression in Chinese individuals.

    Science.gov (United States)

    Yuan, Jiajin; Liu, Yingying; Ding, Nanxiang; Yang, Jiemin

    2014-01-01

    Studies from European-American cultures consistently reported that expressive suppression was associated with worse emotional consequence (e.g. depression) in comparison with acceptance. However, this conclusion may not apply to Chinese, as suppressing emotional displays to maintain relational harmony is culturally valued in East Asian countries. Thus, the present study examined the effects of suppression and acceptance on the depressive mood induced by a frustrating task in a Chinese sample. Sixty-four subjects were randomly assigned to one of three instructions: suppression, acceptance or no-regulation during a frustrating arithmetic task. The experience of depressive emotion and skin conductance response (SCR) were recorded during pre-frustration baseline, frustration induction and post-frustration recovery phases, respectively. Compared with the control and acceptance instructions, suppression instruction was associated with decreased depressive experiences and smaller SCR activity during frustration. There were no significant differences between acceptance and control groups in both subjective depression and SCR activity during frustration. Moreover, the suppression group showed a better emotional recovery after the frustrating task, in comparison with the acceptance and control groups. Correlation analyses verified that SCR reactivity was a reliable index of experienced depression during the frustration. Expressive suppression is effective in reducing depressive experiences and depression-related physiological activity (SCR) when Chinese people are involved. By contrast, the acceptance of depressive emotion in Chinese people does not produce a similar regulation effect. These findings suggest that cultural context should be considered in understanding the emotional consequences of suppression and acceptance strategies.

  9. Ductile-phase toughening in V-V3Si in situ composites

    International Nuclear Information System (INIS)

    Henshall, G.; Strum, M.J.; Bewlay, B.P.; Sutliff, J.A.

    1997-01-01

    This article describes the room-temperature fracture behavior of ductile-phase-toughened V-V 3 Si in situ composites that were produced by arc melting (AM), cold-crucible induction melting (IM), and cold-crucible directional solidification (DS). Composites were produced containing a wide range of microstructures, interstitial impurity contents, and volume fractions of the ductile V-Si solid solution phase, denoted (V). The fracture toughness of these composites generally increases as the volume fraction of (V) increases, but is strongly influenced by the microstructure, the mechanical properties of the component phases, and the crystallographic orientation of the (V) phase with respect to the maximum principal stress direction. For eutectic composites that have a (V) volume fraction of about 50 pct, the fracture toughness increases with decreasing ''''effective'''' interstitial impurity concentration, [I] = [N] + 1.33 [O] + 9 [H]. As [I] decreases from 1,400 ppm (AM) to 400 ppm (IM), the fracture toughness of the eutectic composites increases from 10 to 20 MPa √m. Further, the fracture toughness of the DS eutectic composites is greater when the crack propagation direction is perpendicular, rather than parallel, to the composite growth direction. These results are discussed in light of conventional ductile-phase bridging theories, which alone cannot fully explain the fracture toughness of V-Si in situ composites

  10. Phase transformation in rapidly quenched Fe-Cr-Co-Mo-Ti-Si-B alloys

    Science.gov (United States)

    Zhukov, D. G.; Shubakov, V. S.; Zhukova, E. Kh; Gorshenkov, M. V.

    2018-03-01

    The research results of phase transformations in Fe-24Cr-16Co-3Mo-0.2Ti-1Si-B alloys (with a boron content of 1 to 3% by mass) obtained by rapid quenching are presented. The structure formation regularities during the melt spinning and during the subsequent crystallization annealing in rapidly quenched bands of the Fe-Cr-Co-Mo-Ti-Si-B system alloys were studied. The changes in the phase composition of the rapidly quenched Fe-Cr-Co-Mo-Ti- Si-B system alloys after quenching at various quench rates and at different boron concentrations in the alloys are studied. It is shown that during crystallization from an amorphous state, at temperatures above 570 °C, in addition to the α-phase, the σ-phase appears first, followed by the γ-phase. Heat treatment of rapidly quenched bands to high-coercive state was carried out. A qualitative assessment of magnetic properties in a high-coercivity state was carried out. An evaluation of the level of magnetic properties in a high-coercivity state allows us to conclude that the application of a magnetic field during crystallization from an amorphous state leads to anisotropy of the magnetic properties, that is, an anisotropic effect of thermo-magnetic treatment is detected.

  11. LEU fuel development at CERCA. Status as of October 1996: U5Si4: A new phase in the U/Si diagram

    International Nuclear Information System (INIS)

    Durand, J.P.; Olagnon, G.; Colomb, P.; Lavastre, Y.; Grasse, M.; Noel, H.; Queneau, V.

    1996-01-01

    A fundamental study has been carried out by CERCA and the French CNRS (National Scientific Research Center) as a partner in order to get a better understanding of the U 3 Si 2 casting process. On the occasion of this study, a new binary phase, U 5 Si 4 , has been discovered in the USi phase equilibrium diagram. Synthesis conditions of U 5 Si 4 have been determined and the impact of such a discovery is evaluated regarding the production process of U 3 Si 2 ingots. It can be concluded that keeping the CERCA's casting tools and within the allowed limits of production parameters, the U 3 Si 2 ingots are homogenous without any detectable trace of U 5 Si 4 even if a long term heat treatment at the hot rolling temperature is carried out. On the production point of view, perfect knowledge of both metallurgical phase synthesis and the casting process guarantee the quality of U 3 Si 2 ingots and powder produced by CERCA. (author)

  12. Chinese Script vs Plate-Like Precipitation of Beta-Al9Fe2Si2 Phase in an Al-6.5Si-1Fe Alloy

    Science.gov (United States)

    Ferdian, Deni; Josse, Claudie; Nguyen, Patrick; Gey, Nathalie; Ratel-Ramond, Nicolas; de Parseval, Philippe; Thebault, Yannick; Malard, Benoit; Lacaze, Jacques; Salvo, Luc

    2015-07-01

    The microstructure of a high-purity Al-6.5Si-1Fe (wt pct) alloy after solidification at various cooling rates was investigated. In most of the cases, the monoclinic beta-Al9Fe2Si2 phase was observed as long and thin lamellae. However, at a very slow cooling rate, Fe-bearing precipitates with Chinese script morphology appeared together with lamellae. Further analysis showed all these Chinese script precipitates correspond also to the monoclinic beta phase. This finding stresses that differentiating second phases according to their shape may be misleading.

  13. A study on the change in the phase transition temperature of TiSi sub 2 by adding the Zr element on different Si substrates

    CERN Document Server

    Yoon, S H

    1999-01-01

    The stabilization of C49 TiSi sub 2 at high temperature was investigated by adding Zr element to Ti-silicide both on single crystalline Si(100) and amorphous Si substrates. This stabilization of the C49 TiSi sub 2 phase, which exhibits lower surface and interface energies than those of the C54 TiSi sub 2 phase, was expected to suppress the problems of Ti-silicide, such as the phase transition and the agglomeration. Ti and Zr films of 40 nm were co-deposited on Si substrates in a dual e-beam evaporation system equipped with an ion pump and at a base pressure of approx 5x10 sup - sup 9 Torr. The amounts of Zr contents added to the Ti-silicide were 5, 10 and 20 atomic %, and the thicknesses were monitored by in-situ quartz-crystal thickness monitors. After the deposition, films were annealed by using an ex-situ vacuum furnace at temperatures between 600 .deg. C and 900 .deg. C in 100 .deg. C increments. The phase identification and the chemical compositions were investigated by X-ray diffraction (XRD) and Auger ...

  14. Introduction of nano-laminate Ti3SiC2 and SiC phases into Cf-C composite by liquid silicon infiltration method

    Directory of Open Access Journals (Sweden)

    Omid Yaghobizadeh

    2017-03-01

    Full Text Available The material Cf-C-SiC-Ti3SiC2 is promising for high temperature application. Due to the laminated structure and special properties, the Ti3SiC2 is one of the best reinforcements for Cf-C-SiC composites. In this paper, Cf-C-SiC-Ti3SiC2 composites were fabricated by liquid silicon infiltration (LSI method; the effect of the TiC amount on the various composites properties were studied. For samples with 0, 50 and 90 vol.% of TiC, the results show that bending strength are 168, 190, and 181 MPa; porosities are 3.2, 4.7, and 9%; the fracture toughness are 6.1, 8.9, and 7.8 MPa∙m1/2; interlaminar shear strength are 27, 36, and 30 MPa; the amount of the MAX phase are 0, 8.5, and 5.6 vol.%, respectively. These results show that amount of TiC is not the main effective parameter in synthesis of Ti3SiC2. The existence of carbon promotes the synthesis of Ti3SiC2 indicating that only sufficient carbon content can lead to the appearance of Ti3SiC2 in the LSI process.

  15. Deformation-induced phase transformation in 4H–SiC nanopillars

    International Nuclear Information System (INIS)

    Chen, Bin; Wang, Jun; Zhu, Yiwei; Liao, Xiaozhou; Lu, Chunsheng; Mai, Yiu-Wing; Ringer, Simon P.; Ke, Fujiu; Shen, Yaogen

    2014-01-01

    The deformation behaviour of single-crystal SiC nanopillars was studied by a combination of in situ deformation transmission electron microscopy and molecular dynamics simulations. An unexpected deformation-induced phase transformation from the 4H hexagonal structure to the 3C face-centred cubic structure was observed in these nanopillars at room temperature. Atomistic simulations revealed that the 4H to 3C phase transformation follows a stick–slip process with initiation and end stresses of 12.1–14.0 and 7.9–9.0 GPa, respectively. The experimentally measured stress of 9–10 GPa for the phase transformation falls within the range of these theoretical upper and lower stresses. The reasons for the phase transformation are discussed. The finding sheds light on the understanding of phase transformation in polytypic materials at low temperature

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

    Energy Technology Data Exchange (ETDEWEB)

    Manickaraj, Jeyakumar; Gorny, Anton; Shankar, Sumanth, E-mail: shankar@mcmaster.ca [Light Metal Casting Research Centre (LMCRC), Department of Mechanical Engineering, McMaster University, 1280 Main Street W, Hamilton, Ontario L8S 4L7 (Canada); Cai, Zhonghou [Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States)

    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.

  17. High-energy ion-beam-induced phase separation in SiOx films

    International Nuclear Information System (INIS)

    Arnoldbik, W.M.; Tomozeiu, N.; Hattum, E.D. van; Lof, R.W.; Vredenberg, A.M.; Habraken, F.H.P.M.

    2005-01-01

    The modification of the nanostructure of silicon suboxide (SiO x ) films as a result of high-energy heavy-ion irradiation has been studied for the entire range 0.1≤x x films have been obtained by radio-frequency magnetron sputter deposition. For 50 MeV 63 Cu 8+ ions and an angle of incidence of 20 deg. with the plane of the surface, and for x≥0.5, it takes a fluence of about 10 14 /cm 2 to reach a Si-O-Si infrared absorption spectrum, which is supposed to be characteristic for a Si-SiO 2 composite film structure. For smaller x values, it takes a much larger fluence. The interpretation of the IR spectra is corroborated for the surface region by results from x-ray photoelectron spectroscopy. The results present evidence for a mechanism, in which the phase separation takes place in the thermal spike, initiated by the energy deposited in many overlapping independent ion tracks. Such a process is possible since the suboxides fulfill the conditions for spinodal decomposition

  18. Tempering of Mn and Mn-Si-V dual-phase steels

    Science.gov (United States)

    Speich, G. R.; Schwoeble, A. J.; Huffman, G. P.

    1983-06-01

    Changes in the yield behavior, strength, and ductility of a Mn and a Mn-Si-V d11Al-phase (ferrite-martensite) steel were investigated after tempering one hour at 200 to 600 °C. The change in yield behavior was complex in both steels with the yield strength first increasing and then decreasing as the tempering temperature was increased. This complex behavior is attributed to a combination of factors including carbon segregation to dislocations, a return of discontinuous yielding, and the relief of resid11Al stresses. In contrast, the tensile strength decreased continuously as the tempering temperature was increased in a manner that could be predicted from the change in hardness of the martensite phase using a simple composite strengthening model. The initial tensile ductility (total elongation) of the Mn-Si-V steel was much greater than that of the Mn steel. However, upon tempering up to 400 °C, the ductility of the Mn-Si-V decreased whereas that of the Mn steel increased. As a result, both steels had similar ductilities after tempering at 400 °C or higher temperatures. These results are attributed to the larger amounts of retained austenite in the Mn-Si-V steel (9 pct) compared to the Mn steel (3 pct) and its contribution to tensile ductility by transforming to martensite during plastic straining. Upon tempering at 400 °C, the retained austenite decomposes to bainite and its contribution to tensile ductility is eliminated.

  19. Thermal excitations of frustrated XY spins in two dimensions

    International Nuclear Information System (INIS)

    Benakli, M.; Zheng, H.; Gabay, M.

    1996-11-01

    We present a new variational approach to the study of phase transitions in frustrated 2D XY models. In the spirit of Villain's approach for the ferromagnetic case we divide thermal excitations into a low temperature long wavelength part (LW) and a high temperature short wavelength part (SW). In the present work we mainly deal with LW excitations and we explicitly consider the cases of the fully frustrated triangular (FFTXY) and square (FFSQXY) XY models. The novel aspect of our method is that it preserves the coupling between phase (spin angles) and chiral degrees of freedom. LW fluctuations consist of coupled phase and chiral excitations. As a result, we find that for frustrated systems the effective interactions between phase variables is long range and oscillatory in contrast to the unfrustrated problem. Using Monte Carlo (MC) simulations we show that our analytical calculations produce accurate results at all temperature T; this is seen at low T in the spin wave stiffness constant and in the staggered chirality; this is also the case near T c : transitions are driven by the SW part associated with domain walls and vortices, but the coupling between phase and chiral variables is still relevant in the critical region. In that regime our analytical results yield the correct T dependence for bare couplings (given by the LW fluctuations) such as the Coulomb gas temperature T CG of the frustrated XY models. In particular, we find that T CG tracks chiral rather than phase fluctuations. Our results provide support for a single phase transition scenario in the FFTXY and FFSQXY models. (author). 35 refs, 8 figs

  20. First-principles study on the elastic properties of B′ and Q phase in Al-Mg-Si (-Cu) alloys

    International Nuclear Information System (INIS)

    Pan, Rong-Kai; Ma Li; Bian Nan; Wang Minghui; Li Pengbo; Tang Biyu; Peng Liming; Ding Wenjiang

    2013-01-01

    First-principles calculations within the density functional theory have been carried out to study the structural, elastic and electronic properties of B′ and Q phases in Al-Mg-Si (-Cu) alloys. The obtained lattice constant a is reduced while c is increased with the addition of Cu into B′ phase Al 3 Mg 9 Si 7 . The lower formation enthalpy of Q phase Al 3 Cu 2 Mg 9 Si 7 shows that the structural stability is improved after the addition of Cu into the B′ phase. The calculated elastic constants C ij with the exception of C 13 for Q phase are larger than for B′ phase. In addition, the derived bulk, shear, Young's modulus and Debye temperature except Poisson's ratio are also significantly increased with Cu addition, indicating that Q phase has a favorable improvement of hardness. The elastic anisotropies of the two phases are discussed in detail using several criteria, showing that the anisotropy degree of B′ phase is larger than of Q phase. The electronic structures show that the two phases possess a mixed bonding character of covalent and ionic, and Cu-Si bonding is beneficial in stabilizing the Q phase due to the hybridization of Cu 3d and Si 3p orbits.

  1. Magnetic phase diagram of MnSi near critical temperature studied by neutron small angle scattering

    International Nuclear Information System (INIS)

    Ishikawa, Yoshikazu; Arai, Masatoshi

    1984-01-01

    The magnetic phase diagram of MnSi near the critical temperature T sub(N)=29.5K has been studied by neutron small angle scattering at KENS. It has been found that the anomalous new phase predicted by various methods to exist around at 28 K and 2 kOe is the paramagnetic phase where the magnetic correlations exhibit the same characteristics as those found at 29.5 K and zero magnetic field. This phenomenon, together with the sharp decrease of the magnetic phase boundary at T sub(N) and the substantial increase of the satellite Q vector at this temperature, has been found not to be interpreted by the current theories. (author)

  2. Variation of the energy gap of the SbSI crystals at ferroelectric phase transition

    International Nuclear Information System (INIS)

    Audzijonis, A.; Zaltauskas, R.; Zigas, L.; Vinokurova, I.V.; Farberovich, O.V.; Pauliukas, A.; Kvedaravicius, A.

    2006-01-01

    Variation of the forbidden gap of SbSI crystals in the phase transition region is analyzed on the pseudopotential method for antiferroelectric and ferroelectric phase. The band gap at several special points of the Brillouin zone and some characteristic parameters of the band are considered. During the phase transition, the most significant changes are observed with the valence band top at points Q, C, R, H, E and with the conduction band bottom at points H, T and E of the Brillouin zone. At the ferroelectric phase transition, the valence and conduction bands change due to displacement of Sb and S atoms with respect to I and with respect to each other as a result of order-disorder and displacement-type transition. The obtained band gap values agree quite well with the experiment. This is apparently due to application of neutral rather than ionic atomic functions and inclusion of sufficiently many plane waves in the basis set for calculation

  3. Evolution of Fe based intermetallic phases in Al–Si hypoeutectic casting alloys: Influence of the Si and Fe concentrations, and solidification rate

    Energy Technology Data Exchange (ETDEWEB)

    Gorny, Anton; Manickaraj, Jeyakumar [Light Metal Casting Research Centre (LMCRC), Department of Mechanical Engineering, McMaster University, 1280 Main Street W, Hamilton, ON, Canada L8S 4L7 (Canada); Cai, Zhonghou [Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Shankar, Sumanth, E-mail: shankar@mcmaster.ca [Light Metal Casting Research Centre (LMCRC), Department of Mechanical Engineering, McMaster University, 1280 Main Street W, Hamilton, ON, Canada L8S 4L7 (Canada)

    2013-11-15

    Highlights: •Anomalous evolution of Fe based intermetallic phases in Al–Si–Fe alloys. •XRF coupled with nano-diffraction to confirm the nano-size Fe intermetallic phases. •Crystallography of the θ-Al{sub 13}Fe{sub 4}, τ{sub 5}-Al{sub 8}Fe{sub 2}Si and τ{sub 6}-Al{sub 9}Fe{sub 2}Si{sub 2} phases. •Peritectic reactions involving the Fe intermetallic phases in Al–Si–Fe alloys. -- Abstract: Al–Si–Fe hypoeutectic cast alloy system is very complex and reported to produce numerous Fe based intermetallic phases in conjunction with Al and Si. This publication will address the anomalies of phase evolution in the Al–Si–Fe hypoeutectic casting alloy system; the anomaly lies in the peculiarities in the evolution and nature of the intermetallic phases when compared to the thermodynamic phase diagram predictions and past publications of the same. The influence of the following parameters, in various combinations, on the evolution and nature of the intermetallic phases were analyzed and reported: concentration of Si between 2 and 12.6 wt%, Fe between 0.05 and 0.5 wt% and solidification rates of 0.1, 1, 5 and 50 K s{sup −1}. Two intermetallic phases are observed to evolve in these alloys under these solidification conditions: the τ{sub 5}-Al{sub 8}SiFe{sub 2} and τ{sub 6}-Al{sub 9}Fe{sub 2}Si{sub 2}. The τ{sub 5}-Al{sub 8}SiFe{sub 2} phase evolves at all levels of the parameters during solidification and subsequently transforms into the τ{sub 6}-Al{sub 9}Fe{sub 2}Si{sub 2} through a peritectic reaction when promoted by certain combinations of solidification parameters such as higher Fe level, lower Si level and slower solidification rates. Further, it is also hypothesized from experimental evidences that the θ-Al{sub 13}Fe{sub 4} binary phase precludes the evolution of the τ{sub 5} during solidification and subsequently transforms into the τ{sub 6} phase during solidification. These observations are anomalous to the publications as prior art and

  4. The topotactic transformation of Ti3SiC2 into a partially ordered cubic Ti(C0.67Si0.06) phase by the diffusion of Si into molten cryolite

    International Nuclear Information System (INIS)

    Barsoum, M.W.; El-Raghy, T.; Farber, L.; Amer, M.; Christini, R.; Adams

    1999-01-01

    Immersion of Ti 3 SiC 2 samples in molten cryolite at 960 C resulted in the preferential diffusion of Si atoms out of the basal planes to form a partially ordered, cubic phase with approximate chemistry Ti(C 0.67 , Si 0.06 ). The latter forms in domains, wherein the (111) planes are related by mirror planes; i.e., the loss of Si results in the de-twinning of the Ti 3 C 2 layers. Raman spectroscopy, X-ray diffraction, optical, scanning and transmission electron microscopy all indicate that the Si exists the structure topotactically, in such a way that the C atoms remain partially in their ordered position in the cubic phase

  5. Exploring the Phase Diagram SiO2-CO2 at High Pressures and Temperatures

    Science.gov (United States)

    Kavner, A.

    2015-12-01

    CO2 is an important volatile system relevant for planetary sciences and fundamental chemistry. Molecular CO2 has doubly bonded O=C=O units but high pressure-high temperature (HP-HT) studies have recently shown its transformation into a three-dimensional network of corner-linked [CO4] units analogous to the silica mineral polymorphs, through intermediate non-molecular phases. Here, we report P-V-T data on CO2-IV ice from time-of-flight neutron diffraction experiments, which allow determining the compressibility and thermal expansivity of this intermediate molecular-to-non-molecular phase.1 Aditionally, we have explored the SiO2-CO2 phase diagram and the potential formation of silicon carbonate compounds. New data obtained by laser-heating diamond-anvil experiments in CO2-filled microporous silica polymorphs will be shown. In particular, these HP-HT experiments explore the existence of potential CO2/SiO2 compounds with tetrahedrally-coordinated C/Si atoms by oxygens, which are predicted to be stable (or metastable) by state-of-the-art ab initio simulations.2,3 These theoretical predictions were supported by a recent study that reports the formation of a cristobalite-type Si0.4C0.6O2 solid solution at high-pressures and temperatures, which can be retained as a metastable solid down to ambient conditions.4 Entirely new families of structures could exist based on [CO4]4- units in various degrees of polymerisation, giving rise to a range of chain, sheet and framework solids like those found in silicate chemistry. References[1] S. Palaich et al., Am. Mineral. Submitted (2015) [2] A. Morales-Garcia et al., Theor. Chem. Acc. 132, 1308 (2013) [3] R. Zhou et al., Phys. Rev. X, 4, 011030 (2014) [4] M. Santoro et al. Nature Commun. 5, 3761 (2014)

  6. The Effect of SiC Polytypes on the Heat Distribution Efficiency of a Phase Change Memory.

    Science.gov (United States)

    Aziz, M. S.; Mohammed, Z.; Alip, R. I.

    2018-03-01

    The amorphous to crystalline transition of germanium-antimony-tellurium (GST) using three types of silicon carbide’s structure as a heating element was investigated. Simulation was done using COMSOL Multiphysic 5.0 software with separate heater structure. Silicon carbide (SiC) has three types of structure; 3C-SiC, 4H-SiC and 6H-SiC. These structures have a different thermal conductivity. The temperature of GST and phase transition of GST can be obtained from the simulation. The temperature of GST when using 3C-SiC, 4H-SiC and 6H-SiC are 467K, 466K and 460K, respectively. The phase transition of GST from amorphous to crystalline state for three type of SiC’s structure can be determined in this simulation. Based on the result, the thermal conductivity of SiC can affecting the temperature of GST and changed of phase change memory (PCM).

  7. Phase analysis and magnetocaloric properties of Zr substituted Gd-Si-Ge alloys

    International Nuclear Information System (INIS)

    Prabahar, K.; Raj Kumar, D.M.; Manivel Raja, M.; Chandrasekaran, V.

    2011-01-01

    The structure, microstructure, magneto-structural transition and magnetocaloric effect have been investigated in series of (Gd 5-x Zr x )Si 2 Ge 2 alloys with 0≤x≥0.20. X-ray powder diffraction analysis revealed the presence of orthorhombic structure for Zr containing alloys at room temperature in contrast to the monoclinic structure observed in the parent Gd 5 Si 2 Ge 2 alloy. The microstructural studies reveal that, low Zr addition (x≤0.1) resulted in low volume fraction of detrimental Gd 5 Si 3 -type secondary phase compared to that present in the parent alloy. All the Zr containing alloys have shown the presence of only second order magnetic transition unlike the parent alloy showing both first order structural and second order magnetic transition. A moderate (ΔS) M value of -5.5 J/kg K was obtained for the x=0.05 alloy at an enhanced operating temperature of 292 K compared to -7.8 J/kg K at 274 K of the parent alloy for an applied field of 2 T. The interesting feature of Zr (x=0.05) containing alloy is the wide operating temperature range of ∼25 K than that of ∼10-12 K for the parent, which resulted in enhanced net refrigerant capacity of 103 J/kg compared to that of 53 J/kg for the parent alloy. - Research highlights: → Zr addition in Gd 5 Si 2 Ge 2 alloy has been investigated for the first time to reduce the 5:3-type (Gd 5 Si 3 ) secondary phase formed when using commercial grade elements in Gd 5 Si 2 Ge 2 alloy. → It is interesting to observe that Zr addition decrease the volume fraction 5:3. → The refrigerator capacity and transition temperature of Zr added alloy is greater than the pure Gd 5 Si 2 Ge 2 which makes this alloy promising for room temperature application.

  8. Effect of Si additions on thermal stability and the phase transition sequence of sputtered amorphous alumina thin films

    Energy Technology Data Exchange (ETDEWEB)

    Bolvardi, H.; Baben, M. to; Nahif, F.; Music, D., E-mail: music@mch.rwth-aachen.de; Schnabel, V.; Shaha, K. P.; Mráz, S.; Schneider, J. M. [Materials Chemistry, RWTH Aachen University, Kopernikusstr. 10, D-52074 Aachen (Germany); Bednarcik, J.; Michalikova, J. [Deutsches Elektronen Synchrotron DESY, FS-PE group, Notkestrasse 85, D-22607 Hamburg (Germany)

    2015-01-14

    Si-alloyed amorphous alumina coatings having a silicon concentration of 0 to 2.7 at. % were deposited by combinatorial reactive pulsed DC magnetron sputtering of Al and Al-Si (90-10 at. %) split segments in Ar/O{sub 2} atmosphere. The effect of Si alloying on thermal stability of the as-deposited amorphous alumina thin films and the phase formation sequence was evaluated by using differential scanning calorimetry and X-ray diffraction. The thermal stability window of the amorphous phase containing 2.7 at. % of Si was increased by more than 100 °C compared to that of the unalloyed phase. A similar retarding effect of Si alloying was also observed for the α-Al{sub 2}O{sub 3} formation temperature, which increased by more than 120 °C. While for the latter retardation, the evidence for the presence of SiO{sub 2} at the grain boundaries was presented previously, this obviously cannot explain the stability enhancement reported here for the amorphous phase. Based on density functional theory molecular dynamics simulations and synchrotron X-ray diffraction experiments for amorphous Al{sub 2}O{sub 3} with and without Si incorporation, we suggest that the experimentally identified enhanced thermal stability of amorphous alumina with addition of Si is due to the formation of shorter and stronger Si–O bonds as compared to Al–O bonds.

  9. Effect of Si additions on thermal stability and the phase transition sequence of sputtered amorphous alumina thin films

    International Nuclear Information System (INIS)

    Bolvardi, H.; Baben, M. to; Nahif, F.; Music, D.; Schnabel, V.; Shaha, K. P.; Mráz, S.; Schneider, J. M.; Bednarcik, J.; Michalikova, J.

    2015-01-01

    Si-alloyed amorphous alumina coatings having a silicon concentration of 0 to 2.7 at. % were deposited by combinatorial reactive pulsed DC magnetron sputtering of Al and Al-Si (90-10 at. %) split segments in Ar/O 2 atmosphere. The effect of Si alloying on thermal stability of the as-deposited amorphous alumina thin films and the phase formation sequence was evaluated by using differential scanning calorimetry and X-ray diffraction. The thermal stability window of the amorphous phase containing 2.7 at. % of Si was increased by more than 100 °C compared to that of the unalloyed phase. A similar retarding effect of Si alloying was also observed for the α-Al 2 O 3 formation temperature, which increased by more than 120 °C. While for the latter retardation, the evidence for the presence of SiO 2 at the grain boundaries was presented previously, this obviously cannot explain the stability enhancement reported here for the amorphous phase. Based on density functional theory molecular dynamics simulations and synchrotron X-ray diffraction experiments for amorphous Al 2 O 3 with and without Si incorporation, we suggest that the experimentally identified enhanced thermal stability of amorphous alumina with addition of Si is due to the formation of shorter and stronger Si–O bonds as compared to Al–O bonds

  10. Phase Stability and Thermal Conductivity of Composite Environmental Barrier Coatings on SiC/SiC Ceramic Matrix Composites

    Science.gov (United States)

    Benkel, Samantha; Zhu, Dongming

    2011-01-01

    Advanced environmental barrier coatings are being developed to protect SiC/SiC ceramic matrix composites in harsh combustion environments. The current coating development emphasis has been placed on the significantly improved cyclic durability and combustion environment stability in high-heat-flux and high velocity gas turbine engine environments. Environmental barrier coating systems based on hafnia (HfO2) and ytterbium silicate, HfO2-Si nano-composite bond coat systems have been processed and their stability and thermal conductivity behavior have been evaluated in simulated turbine environments. The incorporation of Silicon Carbide Nanotubes (SiCNT) into high stability (HfO2) and/or HfO2-silicon composite bond coats, along with ZrO2, HfO2 and rare earth silicate composite top coat systems, showed promise as excellent environmental barriers to protect the SiC/SiC ceramic matrix composites.

  11. Neutron diffraction in a frustrated ferrite

    International Nuclear Information System (INIS)

    Mirebeau, I.; Iancu, G.; Gavoille, G.; Hubsch, J.

    1994-01-01

    The competition between a long range ordered ferrimagnetic lattice and small fluctuating clusters have been probed by neutron diffraction in a titanium magnesium frustrated ferrite. The description of the system is then compared to the predictions of several theoretical models for frustrated systems. 3 figs., 8 refs

  12. On the geometry of fracture and frustration

    NARCIS (Netherlands)

    Koning, Vinzenz

    2014-01-01

    Geometric frustration occurs when local order cannot propagate through space. A common example is the surface of a soccer ball, which cannot be tiled with hexaganons only. Geometric frustration can also be present in materials. In fact, geometry can act as an instrument to design the mechanical,

  13. Frustration Tolerance in Youth With ADHD.

    Science.gov (United States)

    Seymour, Karen E; Macatee, Richard; Chronis-Tuscano, Andrea

    2016-06-08

    The objective of this study was to compare children with ADHD with children without ADHD on frustration tolerance and to examine the role of oppositional defiant disorder (ODD) in frustration tolerance within the sample. Participants included 67 children ages 10 to 14 years-old with (n = 37) and without (n = 30) Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV) ADHD who completed the Mirror Tracing Persistence Task (MTPT), a validated computerized behavioral measure of frustration tolerance. Children with ADHD were more likely to quit this task than children without ADHD, demonstrating lower levels of frustration tolerance. There were no differences in frustration tolerance between children with ADHD + ODD and those with ADHD - ODD. Moreover, ODD did not moderate the relationship between ADHD and frustration tolerance. Our results suggest that low frustration tolerance is directly linked to ADHD and not better accounted for by ODD. This research highlights specific behavioral correlates of frustration in children with ADHD. © The Author(s) 2016.

  14. High Temperature All Silicon-Carbide (SiC) DC Motor Drives for Venus Exploration Vehicles, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This Small Business Innovation Research Phase I project seeks to prove the feasibility of creating high-temperature silicon-carbide (SiC) based motor drives for...

  15. Surface morphology and structure of Ge layer on Si(111) after solid phase epitaxy

    Science.gov (United States)

    Yoshida, Ryoma; Tosaka, Aki; Shigeta, Yukichi

    2018-05-01

    The surface morphology change of a Ge layer on a Si(111) surface formed by solid phase epitaxy has been investigated with a scanning tunneling microscope (STM). The Ge film was deposited at room temperature and annealed at 400 °C or 600 °C. The STM images of the sample surface after annealing at 400 °C show a flat wetting layer (WL) with small three-dimensional islands on the WL. After annealing at 600 °C, the STM images show a surface roughening with large islands. From the relation between the average height of the roughness and the deposited layer thickness, it is confirmed that the diffusion of Ge atoms becomes very active at 600 °C. The Si crystal at the interface is reconstructed and the intermixing occurs over 600 °C. However, the intermixing is fairly restricted in the solid phase epitaxy growth at 400 °C. The surface morphology changes with the crystallization at 400 °C are discussed by the shape of the islands formed on the WL surface. It is shown that the diffusion of the Ge atoms in the amorphous phase is active even at 400 °C.

  16. Electronic structure and quantum spin fluctuations at the magnetic phase transition in MnSi

    Science.gov (United States)

    Povzner, A. A.; Volkov, A. G.; Nogovitsyna, T. A.

    2018-05-01

    The effect of spin fluctuations on the heat capacity and homogeneous magnetic susceptibility of the chiral magnetic MnSi in the vicinity of magnetic transition has been investigated by using the free energy functional of the coupled electron and spin subsystems and taking into account the Dzyaloshinsky-Moriya interaction. For helical ferromagnetic ordering, we found that zero-point fluctuations of the spin density are large and comparable with fluctuations of the non-uniform magnetization. The amplitude of zero-point spin fluctuations shows a sharp decrease in the region of the magnetic phase transition. It is shown that sharp decrease of the amplitude of the quantum spin fluctuations results in the lambda-like maxima of the heat capacity and the homogeneous magnetic susceptibility. Above the temperature of the lambda anomaly, the spin correlation radius becomes less than the period of the helical structure and chiral fluctuations of the local magnetization appear. It is shown that formation of a "shoulder" on the temperature dependence of the heat capacity is due to disappearance of the local magnetization. Our finding allows to explain the experimentally observed features of the magnetic phase transition of MnSi as a result of the crossover of quantum and thermodynamic phase transitions.

  17. Chromospheric oscillations observed with OSO 8. III. Average phase spectra for Si II

    International Nuclear Information System (INIS)

    White, O.R.; Athay, R.G.

    1979-01-01

    Time series of intensity and Doppler-shift fluctuations in the Si II emission lines lambda816.93 and lambda817.45 are Fourier analyzed to determine the frequency variation of phase differences between intensity and velocity and between these two lines formed 300 km apart in the middle chromosphere. Average phase spectra show that oscillations between 2 and 9 mHz in the two lines have time delays from 35 to 40 s, which is consistent with the upward propagation of sound wave at 8.6-7.5 km s -1 . In this same frequency band near 3 mHz, maximum brightness leads maximum blueshift by 60 0 . At frequencies above 11 mHz where the power spectrum is flat, the phase differences are uncertain, but approximately 65% of the cases indicate upward propagation. At these higher frequencies, the phase lead between intensity and blue Doppler shift ranges from 0 0 to 180 0 with an average value of 90 0 . However, the phase estimates in this upper band are corrupted by both aliasing and randomness inherent to the measured signals. Phase differences in the two narrow spectral features seen at 10.5 and 27 mHz in the power spectra are shown to be consistent with properties expected for aliases of the wheel rotation rate of the spacecraft wheel section

  18. Liquid Solution Phase Epitaxial Growth of Al-doped f-SiC for LEDs

    DEFF Research Database (Denmark)

    Tang, Kai; Ma, Xiang; van der Eijk, Casper

    light quality and longer lifespan, compared to the current yellow phosphor based white LEDs. Liquid phase epitaxy technology is able to yield a high crystalline quality in terms of structural perfection owing to the fact that it is a near equilibrium process. In addition, the technological equipment...... are presented and discussed. Since operational temperature of LPE growth is much lower than that currently used in physical vapour transport (PVT) process, it is expected to save the energy consumption for SiC crystal growth....

  19. A model for metastable magnetism in the hidden-order phase of URu2Si2

    Science.gov (United States)

    Boyer, Lance; Yakovenko, Victor M.

    2018-01-01

    We propose an explanation for the experiment by Schemm et al. (2015) where the polar Kerr effect (PKE), indicating time-reversal symmetry (TRS) breaking, was observed in the hidden-order (HO) phase of URu2Si2. The PKE signal on warmup was seen only if a training magnetic field was present on cool-down. Using a Ginzburg-Landau model for a complex order parameter, we show that the system can have a metastable ferromagnetic state producing the PKE, even if the HO ground state respects TRS. We predict that a strong reversed magnetic field should reset the PKE to zero.

  20. Phase modulation spectroscopy of space-charge wave resonances in Bi12SiO20

    DEFF Research Database (Denmark)

    Vasnetsov, M.; Buchhave, Preben; Lyuksyutov, S.

    1997-01-01

    A new experimental method for the study of resonance effects and space-charge wave excitation in photorefractive Bi12SiO20 crystals by using a combination of frequency detuning and phase modulation technique has been developed. The accuracy of the method allows a detection of resonance peaks...... of diffraction efficiency within 0.5 Hz. Numerical simulations of the nonlinear differential equations describing the behaviour of the space-charge waves in photorefractive crystals have been performed and found to be in a good agreement with experiment. We have measured the photocurrent through the crystal...

  1. Influence of Al addition on phase transformation and thermal stability of nickel silicides on Si(0 0 1)

    International Nuclear Information System (INIS)

    Huang, Shih-Hsien; Twan, Sheng-Chen; Cheng, Shao-Liang; Lee, Tu; Hu, Jung-Chih; Chen, Lien-Tai; Lee, Sheng-Wei

    2014-01-01

    Highlights: ► The presence of Al slows down the Ni 2 Si–NiSi phase transformation but significantly promotes the NiSi 2−x Al x formation. ► The behavior of phase transformation strongly depends on the Al concentration of the initial Ni 1−x Al x alloys. ► The Ni 0.91 Al 0.09 /Si system exhibits remarkably improved thermal stability, even after high temperature annealing for 1000 s. ► The relationship between microstructures, electrical property, and thermal stability of Ni(Al) silicides is discussed. -- Abstract: The influence of Al addition on the phase transformation and thermal stability of Ni silicides on (0 0 1)Si has been systematically investigated. The presence of Al atoms is found to slow down the Ni 2 Si–NiSi phase transformation but significantly promote the NiSi 2−x Al x formation during annealing. The behavior of phase transformation strongly depends on the Al concentration of the initial Ni 1−x Al x alloys. Compared to the Ni 0.95 Pt 0.05 /Si and Ni 0.95 Al 0.05 /Si system, the Ni 0.91 Al 0.09 /Si sample exhibits remarkably enhanced thermal stability, even after high temperature annealing for 1000 s. The relationship between microstructures, electrical property, and thermal stability of Ni silicides is discussed to elucidate the role of Al during the Ni 1−x Al x alloy silicidation. This work demonstrated that thermally stable Ni 1−x Al x alloy silicides would be a promising candidate as source/drain (S/D) contacts in advanced complementary metal–oxide-semiconductor (CMOS) devices

  2. CHARACTERIZATION OF PHASES IN SECONDARY AlZn10Si8Mg CAST ALLOY

    Directory of Open Access Journals (Sweden)

    Eva Tillová

    2011-04-01

    Full Text Available Using recycled aluminium cast alloys is profitable in many aspects. Requiring only 5 % of the energy to produce secondary metal as compared to primary metal and generates only 5 % of the green house gas emissions, the recycling of aluminium is therefore beneficial of both environmental and economical point of view. Secondary AlZn10Si8Mg (UNIFONT® - 90 cast alloy are used for engine and vehicle constructions, hydraulic unit and mouldmaking without heat treatment. Properties include good castability, very good mechanical strength and elongation, light weight, good wear resistance, low thermal expansion and very good machining. Improved mechanical properties are strongly dependent upon the morphologies, type and distribution of the secondary phases, which are in turn a function of alloy composition and cooling rate. The presence of additional elements as Mg, Mn, Fe, or Cu allows many complex intermetallic phases to form, which make characterisation non-trivial. These include, for example, Mg2Si, Al2CuMg and AlFeMn phases, all of which may have some solubility for additional elements. Phase’s identification in aluminium alloys is often non-trivial due to the fact that some of the phases have either similar crystal structures or only subtle changes in their chemistries. A combination different analytical techniques (light microscopy upon black-white and colour etching, scanning electron microscopy (SEM upon deep etching, energy dispersive X-ray analysis (EDX and HV 0.01 microhardness measurement were therefore been used for the identification of the various phase.

  3. The influence of second-phase dispersion on environmental embrittlement of Ni3(Si,Ti) alloys

    International Nuclear Information System (INIS)

    Takasugi, T.; Hanada, S.

    1999-01-01

    Some quaternary Ni 3 (Si,Ti) alloyed with transition elements V, Nb, Zr and Hf was prepared beyond their maximum solubility limits to investigate the effect of second-phase dispersion on moisture-induced embrittlement. V-added Ni 3 (Si,Ti) alloy contained ductile fcc-type Ni solid solution as the second-phase, while Nb-, Zr- and Hf-added Ni 3 (Si,Ti) alloys contained hard dispersion compounds as the second-phase. V- and Nb-added Ni 3 (Si,Ti) alloys did not display reduced tensile elongation in air, indicating that their second phases have the effect of suppressing the moisture-induced embrittlement. Possible mechanisms for the beneficial effect by the second phase on the moisture-induced embrittlement of V- and Nb-added Ni 3 (Si,Ti) alloys are discussed in association with hydrogen behavior and deformation property in the constituent phases or at matrix/second-phase interface

  4. Possibilities of Fe-RICH phases elimination with using heat treatment in secondary Al-Si-Cu cast alloy

    Directory of Open Access Journals (Sweden)

    L. Hurtalová

    2015-01-01

    Full Text Available The mechanical properties of Al-Si-Cu cast alloy are strongly dependent upon the morphologies, type and distribution of the second phases. The skeleton like – Al15(FeMn 3Si2 and needles - Al5FeSi phases were observed in experimental material AlSi9Cu3. The Fe-rich phases morphology was affected with applying two types of heat treatment, T4 and T6, which caused positive changes of mechanical properties especially ultimate tensile strength, gives that for as cast state was Rm = 211 MPa, than at optimum T4 (515 °C/ 4 hours was Rm = 273 MPa and at optimum T6 (515 °C/ 4 hours with artificial aging 170 °C/ 16 hours was Rm = 311 MPa.

  5. Meperidine addiction or treatment frustration?

    Science.gov (United States)

    Hung, C I; Liu, C Y; Chen, C Y; Yang, C H; Yeh, E K

    2001-01-01

    There have been few studies of the psychiatric characteristics of analgesics addiction. The physician's perceptions that patients were addicted to analgesics might be partially attributable to frustration with poor response to treatment. In this retrospective study, we evaluated the medical records of 20 subjects (15 male and 5 female) who were perceived as having addiction to meperidine by general physicians. The most common medical diagnosis among these patients was chronic pancreatitis (7/20). Among them, five had a past history of suicide attempt and three had self-injury behavior during the index admission. The fact that subjects were perceived as being addicted might be attributable to a vicious cycle of the following factors: 1) chronic intractable pain; 2) poor staff-patient relationship; 3) lower pain threshold or tolerance due to anxiety or depression; 4) patients with a history or tendency of substance abuse; 5) placebo use and inadequate analgesics regimen. The findings of this study suggest that the importance of the following diagnostic and treatment procedures in these patients: 1) suicide risk should be evaluated; 2) comorbid psychiatric diseases should be treated; 3) factors that cause a vicious cycle in pain control should be identified; 4) misconceptions of opiate analgesics among medical staff should be discussed; 5) poor staff-patient relationship should be managed aggressively; and 6) "addiction" is a critical diagnosis that should be avoided if possible.

  6. Liquid-phase-deposited SiO2 on AlGaAs and its application

    International Nuclear Information System (INIS)

    Lee, Kuan-Wei; Huang, Jung-Sheng; Lu, Yu-Lin; Lee, Fang-Ming; Lin, Hsien-Cheng; Huang, Jian-Jun; Wang, Yeong-Her

    2011-01-01

    The silicon dioxide (SiO 2 ) on AlGaAs prepared by liquid phase deposition (LPD) at 40 °C has been explored. The LPD-SiO 2 film deposition rate is about 67 nm h −1 for the first hour. The leakage current density is about 1.21 × 10 −6 A cm −2 at 1 MV cm −1 . The interface trap density (D it ) and the flat-band voltage shift (ΔV FB ) are 1.28 × 10 12 cm −2 eV −1 and 0.5 V, respectively. After rapid thermal annealing in the N 2 ambient at 300 °C for 1 min, the leakage current density, D it , and ΔV FB can be improved to 4.24 × 10 −7 A cm −2 at 1 MV cm −1 , 1.7 × 10 11 cm −2 eV −1 , and 0.2 V, respectively. Finally, this study demonstrates the application of the LPD-SiO 2 film to the AlGaAs/InGaAs pseudomorphic high-electron-mobility transistor

  7. Effect of frustration on brain activation pattern in subjects with different temperament.

    Directory of Open Access Journals (Sweden)

    Maria eBierzynska

    2016-01-01

    Full Text Available In spite of the prevalence of frustration in everyday life, very few neuroimaging studies were focused on this emotional state. In the current study we aimed to examine effects of frustration on brain activity while performing a well-learned task in participants with low and high tolerance for arousal. Prior to the functional magnetic resonance imaging (fMRI session, the subjects underwent two weeks of Braille reading training. Frustration induction was obtained by using a novel highly difficult tactile task based on discrimination of Braille-like raised dots patterns and negative feedback. Effectiveness of this procedure has been confirmed in a pilot study using galvanic skin response (GSR and questionnaires. Brain activation pattern during tactile discrimination task before and after frustration were compared directly. Results revealed changes in brain activity in structures mostly reported in acute stress studies: striatum, cingulate cortex, insula, middle frontal gyrus and precuneus and in structures engaged in tactile Braille discrimination: SI and SII. Temperament type affected activation pattern. Subjects with low tolerance for arousal showed higher activation in the posterior cingulate gyrus, precuneus and inferior parietal lobule (IPL than high reactivity group. Even though performance in the discrimination trials following frustration was unaltered, we observed increased activity of primary and secondary somatosensory cortex processing the tactile information. We interpret this effect as an indicator of additional involvement required to counteract the effects of frustration.

  8. Effect of Frustration on Brain Activation Pattern in Subjects with Different Temperament.

    Science.gov (United States)

    Bierzynska, Maria; Bielecki, Maksymilian; Marchewka, Artur; Debowska, Weronika; Duszyk, Anna; Zajkowski, Wojciech; Falkiewicz, Marcel; Nowicka, Anna; Strelau, Jan; Kossut, Malgorzata

    2015-01-01

    In spite of the prevalence of frustration in everyday life, very few neuroimaging studies were focused on this emotional state. In the current study we aimed to examine effects of frustration on brain activity while performing a well-learned task in participants with low and high tolerance for arousal. Prior to the functional magnetic resonance imaging session, the subjects underwent 2 weeks of Braille reading training. Frustration induction was obtained by using a novel highly difficult tactile task based on discrimination of Braille-like raised dots patterns and negative feedback. Effectiveness of this procedure has been confirmed in a pilot study using galvanic skin response and questionnaires. Brain activation pattern during tactile discrimination task before and after frustration were compared directly. Results revealed changes in brain activity in structures mostly reported in acute stress studies: striatum, cingulate cortex, insula, middle frontal gyrus and precuneus and in structures engaged in tactile Braille discrimination: SI and SII. Temperament type affected activation pattern. Subjects with low tolerance for arousal showed higher activation in the posterior cingulate gyrus, precuneus, and inferior parietal lobule than high reactivity group. Even though performance in the discrimination trials following frustration was unaltered, we observed increased activity of primary and secondary somatosensory cortex processing the tactile information. We interpret this effect as an indicator of additional involvement required to counteract the effects of frustration.

  9. Phase control studies in Gd5Si2Ge2 giant magnetocaloric compound

    International Nuclear Information System (INIS)

    Belo, J.H.; Pereira, A.M.; Ventura, J.; Oliveira, G.N.P.; Araújo, J.P.; Tavares, P.B.; Fernandes, L.; Algarabel, P.A.; Magen, C.; Morellon, L.

    2012-01-01

    Highlights: ► Study of time dependence of O(I) to M phase. ► Determination of the optimal annealing time. ► New method for phase amount estimation (O(I) and M). ► Effect of annealing on the MCE. ► Analysis of the nature of the magnetic transition through the Arrot plot representation. - Abstract: A systematic set of annealings on arc-melted synthesized Gd 5 Si 2 Ge 2 sample was performed. Through powder X-ray diffraction (XRD) and magnetometry measurements we monitored the effect of varying the annealing time with constant temperature (T = 1473 K) on the formation of the monoclinic (M) crystallographic phase fraction, which is the one responsible for the giant magnetocaloric effect (GMCE) in this compound. The conversion of the orthorhombic O(I) crystallographic phase into M was achieved, resulting in a significant increase of the M mass fraction. Such conversion led to a change in the magnetic transition nature, evolving from a second to a first order transition for the as-cast and annealed samples, respectively. An optimal annealing time range for the M phase conversion was identified to be within 80–120 min at T = 1473 K followed by a rapid quenching to liquid N 2 . Furthermore, an increase up to ∼50% of the magnetocaloric effect was obtained for the sample annealed during 120 min.

  10. Thermal phase separation of ZrSiO4 thin films and frequency- dependent electrical characteristics of the Al/ZrSiO4/p-Si/Al MOS capacitors

    Science.gov (United States)

    Lok, R.; Kaya, S.; Yilmaz, E.

    2018-05-01

    In this work, the thermal phase separation and annealing optimization of ZrSiO4 thin films have been carried out. Following annealing optimization, the frequency-dependent electrical characteristics of the Al/ZrSiO4/p-Si/Al MOS capacitors were investigated in detail. The chemical evolution of the films under various annealing temperatures was determined by Fourier transform infrared spectroscopy (FTIR) measurements. The phase separation was determined by x-ray diffraction (XRD) measurements. The electrical parameters were determined via the capacitance–voltage (C–V), conductance–voltage (G/ω) and leakage-current–voltage (Ig–Vg ). The results demonstrate that zirconium silicate formations are present at 1000 °C annealing with the SiO2 interfacial layer. The film was in amorphous form after annealing at 250 °C. The tetragonal phases of ZrO2 were obtained after annealing at 500 °C. When the temperature approaches 750 °C, transitions from the tetragonal phase to the monoclinic phase were observed. The obtained XRD peaks after 1000 °C annealing matched the crystalline peaks of ZrSiO4. This means that the crystalline zirconium dioxide in the structure has been converted into a crystalline silicate phase. The interface states increased to 5.71 × 1010 and the number of border traps decreased to 7.18 × 1010 cm‑2 with the increasing temperature. These results indicate that an excellent ZrSiO4/Si interface has been fabricated. The order of the leakage current varied from 10‑9 Acm‑2 to 10‑6 Acm‑2. The MOS capacitor fabricated with the films annealed at 1000 °C shows better behavior in terms of its structural, chemical and electrical properties. Hence, detailed frequency-dependent electrical characteristics were performed for the ZrSiO4 thin film annealed at 1000 °C. Very slight capacitance variations were observed under the frequency variations. This shows that the density of frequency-dependent charges is very low at the ZrSiO4/Si interface. The

  11. The Study of Phase Transformations of AlSi9Cu3 Alloy by DSC Method

    Directory of Open Access Journals (Sweden)

    Piątkowski J.

    2016-12-01

    Full Text Available With the use of differential scanning calorimetry (DSC, the characteristic temperatures and enthalpy of phase transformations were defined for commercial AlSi9Cu3 cast alloy (EN AC-46000 that is being used for example for pressurized castings for automotive industry. During the heating with the speed of 10°C·min−1 two endothermic effects has been observed. The first appears at the temperature between 495 °C and 534 °C, and the other between 555 °C and 631 °C. With these reactions the phase transformation enthalpy comes up as +6 J g−1 and +327 J g−1. During the cooling with the same speed, three endothermic reactions were observed at the temperatures between 584 °C and 471 °C. The total enthalpy of the transitions is – 348 J g−1.

  12. CePdAl. A frustrated Kondo lattice at a quantum critical point

    Energy Technology Data Exchange (ETDEWEB)

    Fritsch, Veronika [EP 6, Electronic Correlations and Magnetism, University of Augsburg (Germany); Karlsruhe Institute of Technology (Germany); Sakai, Akito; Gegenwart, Philipp [EP 6, Electronic Correlations and Magnetism, University of Augsburg (Germany); Huesges, Zita; Lucas, Stefan; Stockert, Oliver [Max Planck Institute for Chemical Physics of Solids, Dresden (Germany); Kittler, Wolfram; Taubenheim, Christian; Grube, Kai; Loehneysen, Hilbert von [Karlsruhe Institute of Technology (Germany); Huang, Chien-Lung [Karlsruhe Institute of Technology (Germany); Max Planck Institute for Chemical Physics of Solids, Dresden (Germany)

    2016-07-01

    CePdAl is one of the rare frustrated Kondo lattice systems that can be tuned across a quantum critical point (QCP) by means of chemical pressure, i. e., the substitution of Pd by Ni. Magnetic frustration and Kondo effect are antithetic phenomena: The Kondo effect with the incipient delocalization of the magnetic moments, is not beneficial for the formation of a frustrated state. On the other hand, magnetic frustrated exchange interactions between the local moments can result in a breakdown of Kondo screening. Furthermore, the fate of frustration is unclear when approaching the QCP, since there is no simple observable to quantify the degree of frustration. We present thermodynamic and neutron scattering experiments on CePd{sub 1-x}Ni{sub x}Al close to the critical concentration x ∼0.14. Our experiments indicate that even at the QCP magnetic frustration is still present, opening the perspective to find new universality classes at such a quantum phase transition.

  13. Diffusion of Ag, Au and Cs implants in MAX phase Ti{sub 3}SiC{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Weilin, E-mail: weilin.jiang@pnnl.gov [Pacific Northwest National Laboratory, Richland, WA (United States); Henager, Charles H.; Varga, Tamas; Jung, Hee Joon; Overman, Nicole R. [Pacific Northwest National Laboratory, Richland, WA (United States); Zhang, Chonghong; Gou, Jie [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou (China)

    2015-07-15

    MAX phases (M: early transition metal; A: elements in group 13 or 14; X: C or N), such as titanium silicon carbide (Ti{sub 3}SiC{sub 2}), have a unique combination of both metallic and ceramic properties, which make them attractive for potential nuclear applications. Ti{sub 3}SiC{sub 2} has been considered as a possible fuel cladding material. This study reports on the diffusivities of fission product surrogates (Ag and Cs) and a noble metal Au (with diffusion behavior similar to Ag) in this ternary compound at elevated temperatures, as well as in dual-phase nanocomposite of Ti{sub 3}SiC{sub 2}/3C-SiC and polycrystalline CVD 3C-SiC for behavior comparisons. Samples were implanted with Ag, Au or Cs ions and characterized with various methods, including X-ray diffraction, electron backscatter diffraction, energy dispersive X-ray spectroscopy, Rutherford backscattering spectrometry, helium ion microscopy, and transmission electron microscopy. The results show that in contrast to immobile Ag in 3C-SiC, there is a significant outward diffusion of Ag in Ti{sub 3}SiC{sub 2} within the dual-phase nanocomposite during Ag ion implantation at 873 K. Similar behavior of Au in polycrystalline Ti{sub 3}SiC{sub 2} was also observed. Cs out-diffusion and release from Ti{sub 3}SiC{sub 2} occurred during post-implantation thermal annealing at 973 K. This study suggests caution and further studies in consideration of Ti{sub 3}SiC{sub 2} as a fuel cladding material for advanced nuclear reactors operating at very high temperatures.

  14. Emergent reduced dimensionality by vertex frustration in artificial spin ice

    Science.gov (United States)

    Gilbert, Ian; Lao, Yuyang; Carrasquillo, Isaac; O'Brien, Liam; Watts, Justin D.; Manno, Michael; Leighton, Chris; Scholl, Andreas; Nisoli, Cristiano; Schiffer, Peter

    2016-02-01

    Reducing the dimensionality of a physical system can have a profound effect on its properties, as in the ordering of low-dimensional magnetic materials, phonon dispersion in mercury chain salts, sliding phases, and the electronic states of graphene. Here we explore the emergence of quasi-one-dimensional behaviour in two-dimensional artificial spin ice, a class of lithographically fabricated nanomagnet arrays used to study geometrical frustration. We extend the implementation of artificial spin ice by fabricating a new array geometry, the so-called tetris lattice. We demonstrate that the ground state of the tetris lattice consists of alternating ordered and disordered bands of nanomagnetic moments. The disordered bands can be mapped onto an emergent thermal one-dimensional Ising model. Furthermore, we show that the level of degeneracy associated with these bands dictates the susceptibility of island moments to thermally induced reversals, thus establishing that vertex frustration can reduce the relevant dimensionality of physical behaviour in a magnetic system.

  15. Quantum Monte Carlo Simulation of Frustrated Kondo Lattice Models

    Science.gov (United States)

    Sato, Toshihiro; Assaad, Fakher F.; Grover, Tarun

    2018-03-01

    The absence of the negative sign problem in quantum Monte Carlo simulations of spin and fermion systems has different origins. World-line based algorithms for spins require positivity of matrix elements whereas auxiliary field approaches for fermions depend on symmetries such as particle-hole symmetry. For negative-sign-free spin and fermionic systems, we show that one can formulate a negative-sign-free auxiliary field quantum Monte Carlo algorithm that allows Kondo coupling of fermions with the spins. Using this general approach, we study a half-filled Kondo lattice model on the honeycomb lattice with geometric frustration. In addition to the conventional Kondo insulator and antiferromagnetically ordered phases, we find a partial Kondo screened state where spins are selectively screened so as to alleviate frustration, and the lattice rotation symmetry is broken nematically.

  16. Mechanism of Properties of Noble ZnS-SiO2 Protection Layer for Phase Change Optical Disk Media

    Science.gov (United States)

    Tsu, David V.; Ohta, Takeo

    2006-08-01

    A ZnS-SiO2 composite dielectric is widely used in the optical stack designs of rewritable optical recording media as an index-matching medium and as a protection layer for the high-index chalcogenide (compound with sixth group element of S, Se, Te) phase change material used in these media. The addition of Si and O to ZnS is primarily intended to stabilize against crystalline grain growth of ZnS with high numbers of direct overwriting cycles. In this study, we carry out infrared (IR) spectroscopy to clarify the role of Si in this stabilization process. IR spectroscopy is performed on sputter as-deposited and annealed ZnS-SiO2 dielectric protection layers. We find that Si exists not in the SiO2 oxide phase but as [SiS4-nOn] tetrahedrons. Moreover, zinc and sulfur do not exist as ZnS, but in highly chemically disordered ZnS:O crystallites. The highly directional and rigid covalent bonds in the [SiS4-nOn] tetrahedrons are key to establishing thermal stability against the coalescence of ZnS. The importance of the Si-S bond also extends into a more thorough understanding of the low thermal conductivity of the ZnS-SiO2 material. The consideration of elastic implications allows us to predict an average phonon velocity less than 50% compared to that in SiO2. With this, we predict a thermal conductivity of 0.0067 W cm-1 K-1 for this material, which is in complete agreement with measured values.

  17. Cluster-assisted nucleation of silicon phase in hypoeutectic Al–Si alloy with further inoculation

    International Nuclear Information System (INIS)

    Zhang, Yong; Zheng, Hongliang; Liu, Yue; Shi, Lei; Xu, Rongfu; Tian, Xuelei

    2014-01-01

    The paper discusses the responses of eutectic silicon and eutectic cells in Al–10Si alloy upon inoculation with an Al–10Si–2Fe master alloy. The further inoculation hardly destroys the modification effect of Sr but significantly refines the eutectic cells in Sr-modified samples, while in unmodified samples, it stimulates the occurrences of polyhedral silicon particles and divorced eutectic. Thermal analysis, scanning electron microscopy, (high-resolution) transmission electron microscopy and scanning and transmission electron microscopy have been used to elucidate the underlying mechanism. A cluster-assisted nucleation mechanism responsible for the enhanced nucleation of silicon phase upon inoculation is proposed. Icosahedral (AlFeSi) clusters are speculated to evolve from the added Al–10Si–2Fe master alloy in Al–10Si melt, around which aggregations of silicon atoms form. Through a series of structural evolutions, these clusters transform into precursors of a silicon crystal. The subsequent formation of silicon particles is achieved by the agglomerations and attachments of these precursors and individual silicon atoms. This hypothesis is further consolidated by the increased characteristic temperatures of eutectic and the anomalous appearance of a high density of nanoscale particles, as well as the abnormal disappearance of Sr-induced twins in further inoculated silicon particles. The increased characteristic temperatures are strong indications of the enhanced nucleation of the silicon phase. The high density of nanoscale particles with an indeterminate crystal structure are the survivors of these precursors. In an Sr-modified and further inoculated sample, the formation of Sr-induced twins is consequently inhibited due to the participation of these precursors during the growth of silicon particles. Furthermore, based on the proposed nucleation mechanism, the dependence of eutectic cell size on Sr level is elucidated in detail

  18. Fabricating eco-friendly nanocomposites of SiC with morphologically-different nano-carbonaceous phases 

    DEFF Research Database (Denmark)

    Candelario, Victor M.; Moreno, Rodrigo; Guiberteau, Fernando

    2018-01-01

    A route based on aqueous colloidal processing followed by liquid-phase assisted spark-plasma-sintering (SPS) is described for fabricating eco-friendly nanocomposites of SiC with nano-carbonaceous phases (nanotubes, nanoplatelets, or nanoparticles). To this end, the conditions optimizing the aqueo...

  19. Neutron scattering studies on frustrated magnets

    International Nuclear Information System (INIS)

    Arima, Taka-hisa

    2013-01-01

    A lot of frustrated magnetic systems exhibit a nontrivial magnetic order, such as long-wavelength modulation, noncollinear, or noncoplanar order. The nontrivial order may pave the way for the novel magnetic function of matter. Neutron studies are necessary to determine the magnetic structures in the frustrated magnetic systems. In particular, spin-polarized neutron scattering is a useful technique for the investigation of the novel physical properties relevant to the nontrivial spin arrangement. Here some neutron studies on a multiferroic perovskite manganese oxide system are demonstrated as a typical case. The frustrated magnetic systems may also a playground of novel types of local magnetic excitations, which behave like particles in contrast to the magnetic waves. It is becoming a good challenge to study such particle-type magnetic excitations relevant to the magnetic frustration. (author)

  20. The Regulation of Induced Depression during a Frustrating Situation: Benefits of Expressive Suppression in Chinese Individuals

    Science.gov (United States)

    Ding, Nanxiang; Yang, Jiemin

    2014-01-01

    Background Studies from European-American cultures consistently reported that expressive suppression was associated with worse emotional consequence (e.g. depression) in comparison with acceptance. However, this conclusion may not apply to Chinese, as suppressing emotional displays to maintain relational harmony is culturally valued in East Asian countries. Thus, the present study examined the effects of suppression and acceptance on the depressive mood induced by a frustrating task in a Chinese sample. Method Sixty-four subjects were randomly assigned to one of three instructions: suppression, acceptance or no-regulation during a frustrating arithmetic task. The experience of depressive emotion and skin conductance response (SCR) were recorded during pre-frustration baseline, frustration induction and post-frustration recovery phases, respectively. Results Compared with the control and acceptance instructions, suppression instruction was associated with decreased depressive experiences and smaller SCR activity during frustration. There were no significant differences between acceptance and control groups in both subjective depression and SCR activity during frustration. Moreover, the suppression group showed a better emotional recovery after the frustrating task, in comparison with the acceptance and control groups. Correlation analyses verified that SCR reactivity was a reliable index of experienced depression during the frustration. Conclusions Expressive suppression is effective in reducing depressive experiences and depression-related physiological activity (SCR) when Chinese people are involved. By contrast, the acceptance of depressive emotion in Chinese people does not produce a similar regulation effect. These findings suggest that cultural context should be considered in understanding the emotional consequences of suppression and acceptance strategies. PMID:24827934

  1. The regulation of induced depression during a frustrating situation: benefits of expressive suppression in Chinese individuals.

    Directory of Open Access Journals (Sweden)

    Jiajin Yuan

    Full Text Available BACKGROUND: Studies from European-American cultures consistently reported that expressive suppression was associated with worse emotional consequence (e.g. depression in comparison with acceptance. However, this conclusion may not apply to Chinese, as suppressing emotional displays to maintain relational harmony is culturally valued in East Asian countries. Thus, the present study examined the effects of suppression and acceptance on the depressive mood induced by a frustrating task in a Chinese sample. METHOD: Sixty-four subjects were randomly assigned to one of three instructions: suppression, acceptance or no-regulation during a frustrating arithmetic task. The experience of depressive emotion and skin conductance response (SCR were recorded during pre-frustration baseline, frustration induction and post-frustration recovery phases, respectively. RESULTS: Compared with the control and acceptance instructions, suppression instruction was associated with decreased depressive experiences and smaller SCR activity during frustration. There were no significant differences between acceptance and control groups in both subjective depression and SCR activity during frustration. Moreover, the suppression group showed a better emotional recovery after the frustrating task, in comparison with the acceptance and control groups. Correlation analyses verified that SCR reactivity was a reliable index of experienced depression during the frustration. CONCLUSIONS: Expressive suppression is effective in reducing depressive experiences and depression-related physiological activity (SCR when Chinese people are involved. By contrast, the acceptance of depressive emotion in Chinese people does not produce a similar regulation effect. These findings suggest that cultural context should be considered in understanding the emotional consequences of suppression and acceptance strategies.

  2. Microstructural development in NiAl/Ni-Si-B/Ni transient liquid phase bonds

    International Nuclear Information System (INIS)

    Gale, W.F.; Orel, S.V.

    1996-01-01

    A transmission electron microscopy (TEM) based investigation of microstructural development during transient liquid phase bonding of near-stoichiometric NiAl to commercial purity nickel is presented in this article. The work described employed Ni-4.5 wt pct Si-3.2 wt pct B (BNi-3) melt-spun interlayers. The precipitation of both Ni-Al based phases and borides within the joint and adjacent substrate regions is discussed. The article considers martensite formation (within the NiAl substrate) and the precipitation of L1 2 type phases (both within the joint and at the interface with the NiAl substrate). The relative roles of the two substrate materials (NiAl and Ni) in the isothermal resolidification process are identified. The preferential formation of Ni 3 B boride phases in the Ni substrate near the original location of the Ni substrate-joint interface is discussed and contrasted with the absence of similar events in the NiAl substrate

  3. Reactively sputtered Ti-Si-N films for application as heating layers for low-current phase-change memory

    International Nuclear Information System (INIS)

    Yin, You; Noguchi, Tomoyuki; Ota, Kazuhiro; Higano, Naoya; Sone, Hayato; Hosaka, Sumio

    2009-01-01

    In this study, we investigate the properties of Ti-Si-N films for the application as the heating layers in phase-change memory (PCM). The experimental results show that the resistivity of Ti-Si-N films can be varied by over six orders of magnitude from 2.18 x 10 4 to 3.9x10 2 Ω-cm by increasing the flow rate ratio [N 2 /(N 2 +Ar)] from 0 to 10%. The controllability of resistivity might result from the concentration change from Ti-Si to mixture of TiN and Si 3 N 4 . Reversible switching was also successfully demonstrated by using a lateral PCM with these heating layers. The stability of the Ti-Si-N films at high temperatures implies that they can be used as the heating layers in the conventional vertical PCMs for current reduction.

  4. Elasticity of phase-Pi (Al3Si2O7(OH)3) - A hydrous aluminosilicate phase

    Science.gov (United States)

    Peng, Ye; Mookherjee, Mainak; Hermann, Andreas; Bajgain, Suraj; Liu, Songlin; Wunder, Bernd

    2017-08-01

    Phase-Pi (Al3Si2O7(OH)3) is an aluminosilicate hydrous mineral and is likely to be stable in hydrated sedimentary layers of subducting slabs. Phase-Pi is likely to be stable between the depths of 60 and 200 km and is likely to transport water into the Earth's interior. Here, we use first principles simulations based on density functional theory to explore the crystal structure at high-pressure, equation of state, and full elastic stiffness tensor as a function of pressure. We find that the pressure volume results could be described by a finite strain fit with V0 , K0 , and K0‧ being 310.3 Å3, 133 GPa, and 3.6 respectively. At zero pressure, the full elastic stiffness tensor shows significant anisotropy with the diagonal principal components C11 , C22 , and C33 being 235, 292, 266 GPa respectively, the diagonal shear C44 , C55 , and C66 being 86, 92, and 87 GPa respectively, and the off-diagonal stiffness C12 , C13 , C14 ,C15 , C16 , C23 , C24 , C25 , C26 , C34 , C35 , C36 , C45 , C46 , and C56 being 73, 78, 6, -30, 15, 61, 17, 2, 1, -13, -15, 6, 3, 1, and 3 GPa respectively. The zero pressure, shear modulus, G0 and its pressure derivative, G0 ‧ are 90 GPa and 1.9 respectively. Upon compression, hydrogen bonding in phase-Pi shows distinct behavior, with some hydrogen bonds weakening and others strengthening. The latter eventually undergo symmetrization, at pressure greater (>40 GPa) than the thermodynamic stability of phase-Pi. Full elastic constant tensors indicate that phase-Pi is very anisotropic with AVP ∼22.4% and AVS ∼23.7% at 0 GPa. Our results also indicate that the bulk sound velocity of phase-Pi is slower than that of the high-pressure hydrous aluminosilicate phase, topaz-OH.

  5. Solid solubility in 1:13 phase of doping element for La(Fe,Si13 alloys

    Directory of Open Access Journals (Sweden)

    S. T. Zong

    2016-05-01

    Full Text Available The influences of Ni, Cr and Nb as substitution elements for Fe were investigated. The change in microstructure and the magnetic properties have been discussed in detail. Substitution elements Ni, Cr and Nb not only have limited solubility in NaZn13-type (1:13 phase, but also hinder the peritectoid reaction. Ni element mainly enters into La-rich phase while Cr element mainly concentrates in α-Fe phase, which both have detriment effect on the peritectoid reaction, leading to a large residual of impurity phases after annealing and a decrease of magnetic entropy change. Besides, Ni and Cr participated in peritectoid reaction by entering parent phases but slightly entering 1:13 phase, which would cause the disappearance of first order magnetic phase transition. A new phase (Fe,Si2Nb was found when Nb element substitutes Fe in La(Fe,Si13, suggesting that Nb does not participate in peritectoid reaction and only exists in (Fe,Si2Nb phase after annealing. The alloy with Nb substitution maintains the first order magnetic phase transition character.

  6. The solidification and structure of Al-17wt.%Si alloy modified with intermetallic phases containing Ti and Fe

    Directory of Open Access Journals (Sweden)

    J. Piątkowski

    2011-10-01

    Full Text Available The article describes the process of casting and solidification of Al-17wt.%Si alloy that have been modified with composite powdercontaining the intermetallic phases of Ti and Fe. The chemical and phase composition of the applied modifier was described with thefollowingformula:FeAlx–TiAlx–Al2O3. Applying the method of thermal analysis ATD, the characteristic parameters of the solidificationprocess were determined, and exo-and endothermic effects of the modifying powder on the run of the silumin solidification curves wereobserved. By the methods of light, scanning, and X-ray microscopy, the structure of alloy and the chemical composition of the dispersionhardening precipitates were examined. A change in the morphology of Al-Si eutectic from the lamellar to fibrous type was reportedtogether with changes in the form of complex eutectics of an Al-Si-Ti and Al-Si-Fe type and size reduction of primary silicon crystals.

  7. Preparation of Nb-Si phases by cathode sputtering, in particulat the superconducting phase of epitactically grown A15-Nb3Si

    International Nuclear Information System (INIS)

    Siefken, U.

    1979-01-01

    The search for new superconducting materials with high transition temperatures is concentrated on alloys with a cubic A15 structure (Cr 3 Si structure). In this paper we present the preparation of metastable A15-Nb 3 Si which is expected to have a very high transition temperature Tsub(c). The properties of the A15 structure which are relevant for superconductivity are described, in particular the orthogonal chains as the most important structural characteristic, metastability, and the relation between lattice defects and transition temperature. For target compositions of 75% Nb / 25% Si and 80% Nb / 20% Si A15-Nb 3 Si transition temperatures of Tsub(c) = 5.3 K and Tsub(c) = 7.5 K have been measured respectively, with lattice constants asub(o) = 5.19 A and asub(o) = 5.18 A. (orig.) [de

  8. Phase relation of LaFe11· 6Si1· 4 compounds annealed at different ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 35; Issue 2. Phase relation of LaFe11.6Si1.4 compounds annealed at different high-temperature and the magnetic property of LaFe11.6−CoSi1.4 compounds. Xiang Chen Yungui Chen Yongbai Tang. Volume 35 Issue 2 April 2012 pp 175-182 ...

  9. Asymmetric, compressive, SiGe epilayers on Si grown by lateral liquid-phase epitaxy utilizing a distinction between dislocation nucleation and glide critical thicknesses

    Science.gov (United States)

    O'Reilly, Andrew J.; Quitoriano, Nathaniel

    2018-01-01

    Uniaxially strained Si1-xGex channels have been proposed as a solution for high mobility channels in next-generation MOSFETS to ensure continued device improvement as the benefits from further miniaturisation are diminishing. Previously proposed techniques to deposit uniaxially strained Si1-xGex epilayers on Si (0 0 1) substrates require multiple deposition steps and only yielded thin strips of uniaxially strained films. A lateral liquid-phase epitaxy (LLPE) technique was developed to deposit a blanket epilayer of asymmetrically strained Si97.4Ge2.6 on Si in a single step, where the epilayer was fully strained in the growth direction and 31% strain-relaxed in the orthogonal direction. The LLPE technique promoted the glide of misfit dislocations, which nucleated in a region with an orthogonal misfit dislocation network, into a region where the dislocation nucleation was inhibited. This created an array of parallel misfit dislocations which were the source of the asymmetric strain. By observing the thicknesses at which the dislocation network transitions from orthogonal to parallel and at which point dislocation glide is exhausted, the separate critical thicknesses for dislocation nucleation and dislocation glide can be determined.

  10. Interfacial microstructure of partial transient liquid phase bonded Si3N4-to-Inconel 718 joints

    International Nuclear Information System (INIS)

    Kim, Jae Joong; Park, Jin-Woo; Eagar, Thomas W.

    2003-01-01

    This work presents transmission electron microscopy (TEM) analysis of the interfacial microstructure in Si 3 N 4 -to-Inconel 718 joints with Ni interlayers produced by partial transient liquid phase bonding (PTLPB). Ti and Cu microfoils have been inserted between Si 3 N 4 and the Ni interlayer and joining has been performed at lower temperatures than previous PTLPBs of Si 3 N 4 with the same insert metals. The TEM work is focused on phase identification of the reaction layers between the Si 3 N 4 and the Ni interlayer. According to the TEM analysis, most of the Cu precipitates without reacting with Ti and Ni. Si diffused in the filler metal and thin reaction layer formed at the interface between Si 3 N 4 and the filler metal producing good bond-formation and hence, high interfacial strength. No interfacial fractures occurred after cooling from the bonding temperature of 900 deg. C, which supports the results observed in the TEM analysis. This work confirms that this joining process can produce a more heat resistant Si 3 N 4 -to-Inconel 718 joint than active brazing using Ag-Cu-Ti alloys

  11. Theoretical and experimental investigations of frustrated pyrochlore magnets

    International Nuclear Information System (INIS)

    Champion, John Dickon Mathison

    2001-01-01

    This thesis describes the investigation of frustrated magnetic systems based on the pyrochlore lattice of corner-sharing tetrahedra. Monte Carlo simulations and analytical calculations have been performed on a pyrochlore ferromagnet with local (111) easy-axis anisotropy related to the problem of 'spin ice'. The anisotropy-temperature-magnetic field phase diagram was determined. It contained a tricritical point as well as features related to some real ferroelectrics. A pyrochlore antiferromagnet with local (111) easy-plane anisotropy was studied by Monte Carlo simulation. A general expression for its degenerate ground states was discovered and normal- modes out of the ground states were calculated. Both systems are frustrated yet have a long-range ordered state at low temperature. The degeneracy lifting observed is discussed as well as the reasons for its presence. The rare-earth titanate series Ln 2 Ti 2 O 7 (Ln = rare earth), crystallizes in the Fd3-barm space group, with the magnetic ions situated on the 16c sites which constitute the pyrochlore lattice. Crystal-field effects are known to play a significant role in the frustration observed in these compounds. Powder neutron diffraction was performed on gadolinium and erbium titanate. Both systems are frustrated antiferromagnets yet show long-range magnetic order at ∼ 1 K and ∼ 1.2 K respectively. The magnetic structures of both these compounds have been determined by powder neutron diffraction techniques and related to other theoretical results as well as the theoretical results of the author. Further neutron scattering experiments on the 'spin ice' materials Ho 2 Ti 2 O 7 and Dy 2 Ti 2 O 7 are also described. (author)

  12. Microstructure formation and in situ phase identification from undercooled Co-61.8 at.% Si melts solidified on an electromagnetic levitator and an electrostatic levitator

    Energy Technology Data Exchange (ETDEWEB)

    Li Mingjun [National Institute of Advanced Industrial Science and Technology (AIST), Materials Research Institute for Sustainable Development, 2266-98 Shimo-Shidami, Moriyama, Nagoya, Aichi 463-8560 (Japan); Japan Aerospace Exploration Agency (JAXA), Institute of Space and Astronautical Science (ISAS), Tsukuba Space Centre, ISS Science Project Office, 2-1-1 Sengen, Tsukuba, Ibaraki 305-8505 (Japan)], E-mail: li.mingjun@aist.go.jp; Nagashio, Kosuke [Japan Aerospace Exploration Agency (JAXA), Institute of Space and Astronautical Science (ISAS), Sagamihara Campus, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510 (Japan); Ishikawa, Takehiko [Japan Aerospace Exploration Agency (JAXA), Institute of Space and Astronautical Science (ISAS), Tsukuba Space Centre, ISS Science Project Office, 2-1-1 Sengen, Tsukuba, Ibaraki 305-8505 (Japan); Mizuno, Akitoshi; Adachi, Masayoshi; Watanabe, Masahito [Department of Physics, Gakushuin University, 1-5-1 Mejiro, Toshima, Tokyo 171-8588 (Japan); Yoda, Shinichi [Japan Aerospace Exploration Agency (JAXA), Institute of Space and Astronautical Science (ISAS), Tsukuba Space Centre, ISS Science Project Office, 2-1-1 Sengen, Tsukuba, Ibaraki 305-8505 (Japan); Kuribayashi, Kazuhiko [Japan Aerospace Exploration Agency (JAXA), Institute of Space and Astronautical Science (ISAS), Sagamihara Campus, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510 (Japan); Katayama, Yoshinori [Japan Atomic Energy Agency (JAEA), 1-1-1 Kouto, Mikazuki, Sayo, Hyogo 679-5148 (Japan)

    2008-06-15

    Co-61.8 at.% Si (CoSi-CoSi{sub 2}) eutectic alloys were solidified on an electromagnetic levitator (EML) and an electrostatic levitator (ESL) at different undercooling levels. The results indicated that there is only a single recalescence event at low undercooling with the CoSi intermetallic compound as primary phase, which is independent of processing facilities, on either an EML or an ESL. The microstructure, however, is strongly dependent on the processing facility. The interior melt flow behavior in the sphere solidified at the EML differs substantially from that at the ESL, thus yielding different microstructures. On high undercooling, double recalescence takes place regardless of levitation condition. In situ X-ray diffraction of alloys solidified on the EML demonstrates that the CoSi{sub 2} compound becomes the primary phase upon the first recalescence, and the CoSi intermetallic phase crystallizes during the second recalescence. In addition to phase identification, real-time diffraction patterns can also provide additional evidence of the fragmentation of the primary phase and the ripening feature in the subsequent cooling process in the semisolid state. The phase competition between the CoSi and CoSi{sub 2} compounds is discussed when considering the nucleation barrier. The low interfacial energy of the CoSi{sub 2} phase favors a preferential nucleation event over the CoSi phase, which also plays a critical role in non-reciprocity nucleation and thus yields a double recalescence profile at high undercooling.

  13. Stacking faults and phase changes in Mg-doped InGaN grown on Si

    International Nuclear Information System (INIS)

    Liliental-Weber, Zuzanna; Yu, Kin M.; Reichertz, Lothar A.; Ager, Joel W.; Walukiewicz, Wladek; Schaff, William J.; Hawkridge, Michael E.

    2009-01-01

    We report evidence for the role of Mg in the formation of basal stacking faults and a phase transition in In x Ga 1-x N layers doped with Mg grown by molecular beam epitaxy on Si(111) substrates with AlN buffer layers. Several samples with varying In content between x∝0.1 and x∝0.3 are examined by transmission electron microscopy and other techniques. High densities of basal stacking faults are observed in the central region of the InGaN layer away from the substrate or layer surface, but at varying depths within this region. Selected area diffraction patterns show that while the InGaN layer is initially in the wurtzite phase (and of good quality) AlN buffer layer, there is a change to the zinc blende phase in the upper part of the InGaN layer. SIMS measurements show that the Mg concentration drops from a maximum to a steady concentration coinciding with the presence of the basal stacking faults. There is little change in In or Ga concentrations in the same area. High-resolution electron microscopy from the area of the stacking faults confirms that the change to the cubic phase is abrupt across one such fault. These results indicate that Mg plays a role in the formation of stacking faults and the phase change observed in In x Ga 1-x N alloys. We also consider the role of In in the formation of these defects. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Integrated Si-based nanoplasmonic sensor with phase-sensitive angular interrogation

    Energy Technology Data Exchange (ETDEWEB)

    Patskovsky, Sergiy; Meunier, Michel [Laser Processing and Plasmonics Laboratory, Ecole Polytechnique de Montreal, C. P. 6079, succ. Centre-Ville, Montreal, QC, H3C 3A7 (Canada)

    2013-06-15

    This work is related to the development of an integrated Surface Plasmon Resonance (SPR) sensor on silicon platform. The optical properties of metallic nanogratings fabricated on the semiconductor structure allow direct plasmonic detection in transmission mode. Specially designed angular interrogation method provides a periodic signal with phase dependent on the conditions of surface plasmon excitation. Proposed technique leads to sensitivity better than 10{sup -6} RIU for conventional SPR Kretschmann configuration and was tested on the integrated Si-based nanoplasmonic chip. Developed concept is promising for low-cost mono and multi -sensing applications by portable or stationary platforms. (copyright 2013 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Flux distribution in single phase, Si-Fe, wound transformer cores

    International Nuclear Information System (INIS)

    Loizos, George; Kefalas, Themistoklis; Kladas, Antonios; Souflaris, Thanassis; Paparigas, Dimitris

    2008-01-01

    This paper shows experimental results of longitudinal flux density and its harmonics at the limb, the yoke and the corner as well as normal flux in the step lap joint of a single phase, Si-Fe, wound transformer core. Results show that the flux density as well as the harmonics content is higher in the inner (window) side of the core and reduces gradually towards the outer side. Variations of flux density distribution between the limb and the corner or the yoke of the core were observed. A full record of normal flux around the step lap region of the model core was also obtained. Longitudinal and normal flux findings will enable the development of more accurate numerical models that describe the magnetic behavior of magnetic cores

  16. InAs film grown on Si(111) by metal organic vapor phase epitaxy

    International Nuclear Information System (INIS)

    Caroff, P; Jeppsson, M; Mandl, B; Wernersson, L-E; Wheeler, D; Seabaugh, A; Keplinger, M; Stangl, J; Bauer, G

    2008-01-01

    We report the successful growth of high quality InAs films directly on Si(111) by Metal Organic Vapor Phase Epitaxy. A nearly mirror-like and uniform InAs film is obtained at 580 0 C for a thickness of 2 μm. We measured a high value of the electron mobility of 5100 cm 2 /Vs at room temperature. The growth is performed using a standard two-step procedure. The influence of the nucleation layer, group V flow rate, and layer thickness on the electrical and morphological properties of the InAs film have been investigated. We present results of our studies by Atomic Force Microscopy, Scanning Electron Microscopy, electrical Hall/van der Pauw and structural X-Ray Diffraction characterization

  17. SR phase contrast imaging to address the evolution of defects during SiC growth

    International Nuclear Information System (INIS)

    Argunova, Tatiana S.; Gutkin, Mikhail Yu.; Je, Jung Ho; Mokhov, Evgeniy N.; Nagalyuk, Sergey S.; Hwu, Yeukuang

    2011-01-01

    Sliced SiC boule grown by physical vapor transport is investigated using synchrotron white beam phase contrast imaging combined with Bragg diffraction. The evolution of defects is revealed. In the early growth stage, foreign polytype inclusions not only induce massive generation of full-core dislocations and dislocated micropipes but also attract them, forming slit-type pores at the boundaries of inclusions. In the intermediate stage, when inclusions stop to grow and become overgrown by the matrix, the pore density significantly reduces, which is attributed to their transformation into new micropipes. In the later stage, the micropipe density decreases, providing evidence for their partial annihilation and healing. Mechanisms for the evolution from inclusions to pores and finally to micropipes during the crystal growth are further discussed. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. Effect of dispersed SiO2 on the phase behaviour of NH4HSO4

    Directory of Open Access Journals (Sweden)

    Vargas, R. A.

    2002-02-01

    Full Text Available Phase equilibria and electrical conductivity of (1-xNH4HSO4-xSiO2 composites were studied by thermal and impedance measurements. Silica with particle size of 14 nm was used. The phase transitions of NH4HSO4 (AHS at 154 K and 420 K (melting point were not affected by the silica doping. No large changes in the low-temperature (T Estudiamos el equilibrio de fases y la conductividad eléctrica de las compositas (1-xNH4HSO4-xSiO2 por medidas térmicas y de impedancia. Se utilizaron partículas de silica de diámetro 14 nm. Las transiciones de fase del NH4HSO4 (AHS en 154 K y 420 K (punto de fusión no fueron afectadas con el dopaje de silica. No se observaron grandes cambios a bajas temperaturas (T < 420 K en la conductividad dc y la relajación eléctrica de las compositas al ser dopadas con silica. La parte imaginaria de la conductividad corregida (después de haber substraído la contribución de la conductividad dc, ε″(ω,T, como función de la frecuencia (f = ω/ 2π y la temperatura muestra un pico de dispersión alrededor de 1 MHz para pequeñas concentraciones de silica, cuya posición (fmax esta también térmicamente activada. Los resultados dieléctricos se discuten en términos del efecto de la polarización de las celdas sobre el movimiento de los protones.

  19. Non-isothermal crystallization kinetics and phase transformation of Bi2O3-SiO2 glass-ceramics

    Directory of Open Access Journals (Sweden)

    Guo H.W.

    2011-01-01

    Full Text Available The Bi2O3-SiO2 (BS glass-ceramics were prepared by melt-quench technique, and the crystallization kinetics and phase transformation behavior were investigated in accordance with Kissinger and Johson-Mehl-Avrami equation, DSC, XRD and SEM. The results show that in the heat treatment process (or termed as re-crystallizing process Bi2SiO5 and Bi4Si3O12 crystals were found consequently. Respectively, the crystallization activation energies of the two crystals are Ep1=14.8kJ/mol and Ep2=34.1kJ/mol. And the average crystallization index of n1=1.73 and n2=1.38 suggested volume nucleation, one-dimensional growth and surface nucleation, one-dimensional growth from surface to the inside respectively. The meta-stable needle-like Bi2SiO5 crystals are easily to be transformed into stable prismatic Bi4Si3O12 crystals. By quenching the melt and hold in 850°C for 1h, the homogenous single Bi4Si3O12 crystals were found in the polycrystalline phase of the BS glassceramics system.

  20. Controlling the size of InAs quantum dots on Si1-xGex/Si(0 0 1) by metalorganic vapor-phase epitaxy

    International Nuclear Information System (INIS)

    Kawaguchi, Kenichi; Ebe, Hiroji; Ekawa, Mitsuru; Sugama, Akio; Arakawa, Yasuhiko

    2009-01-01

    The formation of III-V InAs quantum dots (QDs) on group-IV Si 1-x Ge x /Si(0 0 1) was investigated by metalorganic vapor-phase epitaxy. Two types of QDs, round-shaped QDs and giant QDs elongated in the [1 1 0] or [1,-1,0] direction, were observed in a growth condition of low V/III ratios. An increase in the V/III ratio and AsH 3 preflow during the cooling process was found to suppress the formation of giant QDs. It was considered that replacing the H-stabilized SiGe surface with the As-stabilized surface was necessary for increasing the QD nucleation. The size and density of InAs QDs on SiGe were controllable as well as that on III-V semiconductor buffer layers, and InAs QDs with a density as high as 5 x 10 10 cm -2 were obtained.

  1. Impact of concentration and Si doping on the properties and phase transformation behavior of nanocrystalline alumina prepared via solvothermal synthesis

    International Nuclear Information System (INIS)

    Mekasuwandumrong, Okorn; Tantichuwet, Panutin; Chaisuk, Choowong; Praserthdam, Piyasan

    2008-01-01

    Solvothermal reaction of 20 g aluminum isopropoxide (AIP) in mineral oil at 300 deg. C for 2 h gave χ-alumina showing high thermal stability while the reaction with higher amounts of starting AIP (30 and 40 g) contributed contamination of pseudoboehmite. The χ-alumina thus obtained directly transformed into α-alumina completely at approximately 1400 deg. C bypassing the other transition alumina phases whereas some part of the contaminated product transformed to γ-alumina through θ-alumina and finally α-alumina. When silicon was doped in the alumina matrix (5, 10, 20 and 50 at.%) using tetraethylorthosilicate as the silicon (Si) precursor, χ-alumina was still observed without any contaminations at low concentration doping (5-20 at.%). Amorphous structure was obtained by doping 50 at.% Si. The phase transformation temperature was shifted to the high temperature after loading the Si. The α-phase transformation did not go to completion even after calcinations at 1500 deg. C. This could be due to the incorporation of Si atom in alumina lattice forming SiO 2 -Al 2 O 3 solid solution

  2. The Computerised Calculus in the Prognosis of the Phase Equilibrium Diagram of the Ternary System Al-Cu-Si

    Directory of Open Access Journals (Sweden)

    Florentina A. Cziple

    2006-10-01

    Full Text Available The paper presents a model for establishing the mathematical functions of the liquidus and solidus curves, from the binary diagrams Al-Si, Si-Cu, Cu-Al and their use in the prognosis of the phase equilibrium diagram from the ternary system Al-Cu-Si. We have studied the model of the non-ideal liquid solution of the regular type. The calculus and graphic plotting of the equations for the binary systems has been performed on the computer with the software programmes MathCad 2000 Professional, Statistica 5, Curve Expert, and for the ternary system Al-Cu-Si, with the 3D StudioMax software

  3. Maximal frustration as an immunological principle.

    Science.gov (United States)

    de Abreu, F Vistulo; Mostardinha, P

    2009-03-06

    A fundamental problem in immunology is that of understanding how the immune system selects promptly which cells to kill without harming the body. This problem poses an apparent paradox. Strong reactivity against pathogens seems incompatible with perfect tolerance towards self. We propose a different view on cellular reactivity to overcome this paradox: effector functions should be seen as the outcome of cellular decisions which can be in conflict with other cells' decisions. We argue that if cellular systems are frustrated, then extensive cross-reactivity among the elements in the system can decrease the reactivity of the system as a whole and induce perfect tolerance. Using numerical and mathematical analyses, we discuss two simple models that perform optimal pathogenic detection with no autoimmunity if cells are maximally frustrated. This study strongly suggests that a principle of maximal frustration could be used to build artificial immune systems. It would be interesting to test this principle in the real adaptive immune system.

  4. Utilisation of mould temperature change in eliminating the Al5FeSi phases in secondary AlSi7Mg0.3 alloy

    Directory of Open Access Journals (Sweden)

    Bolibruchová D.

    2017-03-01

    Full Text Available This article describes the impact of the metal mould temperature change in eliminating the adverse effect of iron in the AlSi7Mg0.3 alloy. The kind of phases based on iron to be formed in aluminium alloys is determined by the alloy chemical composition, the melt overheating temperature prior to casting, and the cooling rate during crystallisation. In the experiment, we used three various mould temperatures, and their impact on the possible change in the adverse Al5FeSi phase, excreted in a needle form to a more compact form of Chinese writing or skeleton units. The experimental part did not use melt overheat that would result in impairment of the melt, for example due to increased gassing of the melt, as well as in a greater load on the smelting unit, thus resulting in increased energy expenditure. We can conclude from the obtained results that the mould temperature change does not have an adequate effect in eliminating the adverse effect of iron in Al-Si-Mg alloys.

  5. Quantitative hard x-ray phase contrast imaging of micropipes in SiC

    International Nuclear Information System (INIS)

    Kohn, V. G.; Argunova, T. S.; Je, J. H.

    2013-01-01

    Peculiarities of quantitative hard x-ray phase contrast imaging of micropipes in SiC are discussed. The micropipe is assumed as a hollow cylinder with an elliptical cross section. The major and minor diameters can be restored using the least square fitting procedure by comparing the experimental data, i.e. the profile across the micropipe axis, with those calculated based on phase contrast theory. It is shown that one projection image gives an information which does not allow a complete determination of the elliptical cross section, if an orientation of micropipe is not known. Another problem is a weak accuracy in estimating the diameters, partly because of using pink synchrotron radiation, which is necessary because a monochromatic beam intensity is not sufficient to reveal the weak contrast from a very small object. The general problems of accuracy in estimating the two diameters using the least square procedure are discussed. Two experimental examples are considered to demonstrate small as well as modest accuracies in estimating the diameters

  6. Polymorphism in the Laves-phase precipitates of a quinternary Nb-Mo-Cr-Al-Si alloy

    International Nuclear Information System (INIS)

    Hu Yanling; Vasiliev, Alexandre; Zhang Lichun; Song, Kai; Aindow, Mark

    2009-01-01

    Transmission electron microscopy has been used to study the precipitates that develop in the A2 phase of an Nb-Mo-Cr-Al-Si alloy upon heat treatment. The precipitates include a Laves-phase that adopts the cubic C15 structure initially and the hexagonal C14 structure in the later stages of precipitation. The morphologies, orientation relationships and defect microstructures indicate that the metastable C15 phase arises due to tensile coherency stresses and that a synchroshear polymorphic transformation to the equilibrium C14 phase occurs as these relax

  7. High efficiency three-phase power factor correction rectifier using SiC switches

    DEFF Research Database (Denmark)

    Kouchaki, Alireza; Nymand, Morten

    2017-01-01

    This paper presents designing procedure of a high efficiency 5 kW silicon-carbide (SiC) based threephase power factor correction (PFC). SiC switches present low capacitive switching loss compared to the alternative Si switches. Therefore, the switching frequency can be increased and hence the siz...

  8. Controller design and implementation of a three-phase Active Front End using SiC based MOSFETs

    DEFF Research Database (Denmark)

    Haase, Frerk; Kouchaki, Alireza; Nymand, Morten

    2015-01-01

    The design and implementation of a three phase Active Front End for power factor correction purposes using fast switching SiC based MOSFETs is presented. Possible applications are within the drives- and renewable energy sector. The controller is designed and implemented in the synchronous rotating...

  9. Phase transitions of titanite CaTiSiO5 from density functional perturbation theory

    Science.gov (United States)

    Malcherek, Thomas; Fischer, Michael

    2018-02-01

    Phonon dispersion of titanite CaTiSiO5 has been calculated using the variational density functional perturbation theory. The experimentally known out-of-center distortion of the Ti atom is confirmed. The distortion is associated with a Bu mode that is unstable for wave vectors normal to the octahedral chain direction of the C 2 /c aristotype structure. The layer of wave vectors with imaginary mode frequencies also comprises the Brillouin zone boundary point Y (0 ,1 ,0 ) , which is critical for the transition to the P 21/c ground-state structure. The phonon branch equivalent to the imaginary branch of the titanite aristotype is found to be stable in malayaite CaSnSiO5. The unstable phonon mode in titanite leads to the formation of transoriented short and long Ti-O1 bonds. The Ti as well as the connecting O1 atom exhibit strongly anomalous Born effective charges along the octahedral chain direction [001], indicative of the strong covalency in this direction. Accordingly and in contrast to malayaite, LO-TO splitting is very large in titanite. In the C 2 /c phase of titanite, the Ti-O1-Ti distortion chain is disordered with respect to neighboring distortion chains, as all chain configurations are equally unstable along the phonon branch. This result is in agreement with diffuse x-ray scattering in layers normal to the chain direction that is observed at temperatures close to the P 21/c to C 2 /c transition temperature and above. The resulting dynamic chains of correlated Ti displacements are expected to order in two dimensions to yield the P 21/c ground-state structure of titanite.

  10. [French validation of the Frustration Discomfort Scale].

    Science.gov (United States)

    Chamayou, J-L; Tsenova, V; Gonthier, C; Blatier, C; Yahyaoui, A

    2016-08-01

    Rational emotive behavior therapy originally considered the concept of frustration intolerance in relation to different beliefs or cognitive patterns. Psychological disorders or, to some extent, certain affects such as frustration could result from irrational beliefs. Initially regarded as a unidimensional construct, recent literature considers those irrational beliefs as a multidimensional construct; such is the case for the phenomenon of frustration. In order to measure frustration intolerance, Harrington (2005) developed and validated the Frustration Discomfort Scale. The scale includes four dimensions of beliefs: emotional intolerance includes beliefs according to which emotional distress is intolerable and must be controlled or avoided as soon as possible. The intolerance of discomfort or demand for comfort is the second dimension based on beliefs that life should be peaceful and comfortable and that any inconvenience, effort or hassle should be avoided. The third dimension is entitlement, which includes beliefs about personal goals, such as merit, fairness, respect and gratification, and that others must not frustrate those non-negotiable desires. The fourth dimension is achievement, which reflects demands for high expectations or standards. The aim of this study was to translate and validate in a French population the Frustration and Discomfort Scale developed by Harrington (2005), assess its psychometric properties, highlight the four factors structure of the scale, and examine the relationships between this concept and both emotion regulation and perceived stress. We translated the Frustration Discomfort Scale from English to French and back from French to English in order to ensure good quality of translation. We then submitted the scale to 289 students (239 females and 50 males) from the University of Savoy in addition to the Cognitive Emotional Regulation Questionnaire and the Perceived Stress Scale. The results showed satisfactory psychometric

  11. Sol-gel synthesis and characterization of single-phase Ni ferrite nanoparticles dispersed in SiO2 matrix

    International Nuclear Information System (INIS)

    Nadeem, K.; Traussnig, T.; Letofsky-Papst, I.; Krenn, H.; Brossmann, U.; Wuerschum, R.

    2010-01-01

    Nanoparticles of NiFe 2 O 4 dispersed in SiO 2 (25 wt%) matrix were synthesized by sol-gel method using tetraethyl orthosilicate (TEOS), as a precursor for SiO 2 . The sol-gel method for nanocomposites normally provides multi-phase nanoparticles. We investigated by a synopsis of different analysis methods, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and SQUID-magnetometry, how the various chemical phases are transformed to a single-phase spinel structure during the various stages of annealing from 300 to 900 o C. We have developed a full phase diagram of chemical phases as a function of annealing temperature. The average particle size lies in the range 16-27 nm. The chemical phases formed below 900 o C are NiFe, NiO, γ-Fe 2 O 3 , α-Fe 2 O 3 , and NiFe 2 O 4 , respectively. The role of the TEOS prepared SiO 2 matrix is to restrict the particle size in a small range in order to rule out particle size effects. In the mid-infrared, a shift of the vibrational Fe-O bond is observed from 568 to 586 cm -1 for annealing between 500 and 700 o C which indicates an increasing NiFe 2 O 4 phase formation. A systematic study of coercivity field (ranging from 32 to 200 Oe) and saturation magnetic moment (ranging from 12.2 to 32.1 emu/g) for differently annealed samples supports our findings about the evolution of single-phase NiFe 2 O 4 at 900 o C. The opposite trend of saturation magnetic moment and coercivity with respect to annealing temperature clearly separates the different phases of metallic, antiferromagnetic, and finally single-phase spinel NiFe 2 O 4 .

  12. Parameters of the preproduction series SiPMs for the CMS HCAL phase I upgrade

    Energy Technology Data Exchange (ETDEWEB)

    Heering, A., E-mail: Adriaan.Heering@cern.ch [University of Notre Dame, Notre Dame, IN 46556 (United States); Musienko, Yu., E-mail: Iouri.Musienko@cern.ch [University of Notre Dame, Notre Dame, IN 46556 (United States); Institute for Nuclear Research RAS, pr. 60-letiya Oktyabrya 7a, 117312 Moscow (Russian Federation); Ruchti, R.; Wayne, M. [University of Notre Dame, Notre Dame, IN 46556 (United States); Karneyeu, A.; Postoev, V. [Institute for Nuclear Research RAS, pr. 60-letiya Oktyabrya 7a, 117312 Moscow (Russian Federation)

    2016-07-11

    In 2012 the HCAL SiPM photo sensor upgrade was approved for the increased luminosity (5*10{sup 34}) of SLHC. The upgrade will replace the current hybrid photodiodes (HPDs) with multi-pixel Geiger-mode avalanche photodiodes, also known as silicon photomultipliers (SiPMs). A key aspect of the upgrade to SiPMs is to add longitudinal segmentation and improve signal to noise to compensate for scintillator radiation damage. After 5 years of R&D with multiple companies we developed custom large dynamic range SiPMs with large PDE and small ENC. To ensure good mechanical alignment and easy handling of the large number of production channels (>20,000) we have developed a custom ceramic package with a very thin 0.3 mm quartz window with Kyocera. Each package holds 8 channels of SiPMs. Here we report on the final SiPM parameters of the 2014 preproduction run from Hamamatsu (HPK) who has produced a series of 175 arrays with a total of 1400 SiPMs. An overview of our QA results and measurements of the photon detection efficiency, spectral response, crosstalk and cell recovery time will be discussed. - Highlights: • Uniformity of large scale SiPM production. • Small cell size SiPMs with high photo detection efficiency. • Fast recovery time SiPMs. • Custom packaging of SiPMs in High Energy Physics experiments.

  13. Sintering behaviour and phase relationships of Si[sub 3]N[sub 4] ceramics in the Si[sub 3]N[sub 4]-SiO[sub 2]-MgO-Y[sub 2]O[sub 3] system. Sinterverhalten und Phasenbeziehungen von Si[sub 3]N[sub 4]-Keramiken im System Si[sub 3]N[sub 4]-SiO[sub 2]-MgO-Y[sub 2]O[sub 3

    Energy Technology Data Exchange (ETDEWEB)

    Mahoney, F.M.

    1992-10-12

    The aim of this work is the investigation of the sintering or crystallisation behaviour of Si[sub 3]N[sub 4] ceramics depending on the additive composition in the Si[sub 3]N[sub 4]-SiO[sub 2]-MgO-Y[sub 2]O[sub 3] system. With regard to the complicated manufacturing process of sintered and heat-treated Si[sub 3]N[sub 4] ceramics, one should first determine which additive compositions make complete compression possible. The effect of the composition on the volume and the viscosity of the melting phase should be cleared up, where determining the Si[sub 3]N[sub 4] solubility relative to the additive composition is of special importance. The phase relationships between Si[sub 3]N[sub 4] and the possible crystalline secondary phases should be determined for the crystallisation behaviour. Due to the very fine distribution of only a 5-15% proportion of additive in conventional Si[sub 3]N[sub 4] samples, a characterisation of the secondary phases is difficult to carry out with X-ray or REM/EDX analysis. Therefore, experiments with oxy-nitridic model samples were carried out in this work, which have the same phase relationships as conventional Si[sub 3]N[sub 4] compositions, but with an appreciably higher proportion of additive. The possibility of transferring the results of the model samples were tested on examples of three Si[sub 3]N[sub 4] ceramics. (orig.)

  14. Frustration-Instigated Behavior and Learned Helplessness.

    Science.gov (United States)

    Winefield, Anthony H.

    1979-01-01

    Compares M. E. P. Seligman's recent work on learned helplessness with N. R. F. Maier's 30-year-old work on frustration behavior. Notes striking similarities between the two approaches. Concludes that the learned helplessness model might explain the "abnormal fixations" that Maier reported. (Author/RL)

  15. Children, Hyperactivity and Low Frustration Tolerance.

    Science.gov (United States)

    Shaughnessy, Michael F.; Scott, Patricia Carol

    This paper addresses issues regarding the hyperactive child, the impulsive child, and the low frustration tolerance child. It points out the subjectivity involved in identifying children as hyperactive, and outlines various forms of hyperactivity: the child who is in constant movement, the child who manages control in school but exhibits whirlwind…

  16. Frustrated Lewis pairs: Design and reactivity

    Indian Academy of Sciences (India)

    for FLP systems and their unique reactivity are discussed here. Keywords. Lewis .... we will concentrate on the design principles of such. FLPs and the ... Designs of frustrated Lewis pairs ..... 64 and neutral titanium (III) complex [Cp2TiOC6.

  17. Frustrated Lewis pairs-assisted tritium labeling

    Czech Academy of Sciences Publication Activity Database

    Marek, Aleš; Široká, Sabina; Elbert, Tomáš

    2016-01-01

    Roč. 14, č. 5 (2016), s. 219 ISSN 2336-7202. [Sjezd českých a slovenských chemických společností /68./. 04.09.2016-07.09.2016, Praha] Institutional support: RVO:61388963 Keywords : frustrated Lewis pairs * one-pot synthesis * tritium -labeling Subject RIV: CC - Organic Chemistry

  18. Solidifying incongruently melting intermetallic phases as bulk single phases using the example of Al{sub 2}Cu and Q-phase in the Al-Mg-Cu-Si system

    Energy Technology Data Exchange (ETDEWEB)

    Loeffler, Andrea [Institute of Materials Science and Technology, Friedrich-Schiller-University, Jena (Germany); Groebner, Joachim; Hampl, Milan [Institute of Metallurgy, Clausthal University of Technology, Clausthal-Zellerfeld (Germany); Engelhardt, Hannes [Institute of Materials Science and Technology, Friedrich-Schiller-University, Jena (Germany); Schmid-Fetzer, Rainer [Institute of Metallurgy, Clausthal University of Technology, Clausthal-Zellerfeld (Germany); Rettenmayr, Markus, E-mail: M.Rettenmayr@uni-jena.de [Institute of Materials Science and Technology, Friedrich-Schiller-University, Jena (Germany)

    2012-02-25

    Highlights: Black-Right-Pointing-Pointer Samples consisting of pure Al{sub 2}Cu and 95% Q-phase respectively were prepared. Black-Right-Pointing-Pointer The Q-phase composition is Al{sub 17}Cu{sub 9}Mg{sub 44}Si{sub 30}, its solubility range is negligible. Black-Right-Pointing-Pointer The Q-phase peritectic temperature was determined by DSC measurements as 703 Degree-Sign C. Black-Right-Pointing-Pointer A new thermodynamic dataset for the Q-phase has been assessed. - Abstract: Plane front directional solidification experiments were carried out for preparing incongruently melting intermetallic phases in the quaternary alloy system Al-Cu-Mg-Si, particularly the binary Al{sub 2}Cu phase and the quaternary phase ('Q-phase'). By this method, bulk samples that consist of only a single phase are generated. Sample sections consisting of 100% single phase Al{sub 2}Cu and of 95% Q-phase, respectively, were obtained. The composition of the Q-phase was measured by Energy Dispersive X-ray Spectroscopy (EDX). The measured concentrations are close to the Al{sub 3}Cu{sub 2}Mg{sub 9}Si{sub 7} composition that has recently been predicted as most stable by ab initio calculations. A peritectic temperature of 703 Degree-Sign C for the reaction Q {yields} L + Mg{sub 2}Si + (Si) was determined by differential scanning calorimetry (DSC). An optimization of the Calphad database was performed considering the measured composition and peritectic temperature. For validating the optimized database, Scheil calculations were performed and compared with the experimentally determined sequence of solidifying phases.

  19. A VUV photoionization measurement and ab-initio calculation of the ionization energy of gas phase SiO2

    Energy Technology Data Exchange (ETDEWEB)

    Kostko, Oleg; Ahmed, Musahid; Metz, Ricardo B.

    2008-12-05

    In this work we report on the detection and vacuum-ultraviolet (VUV) photoionization of gas phase SiO2 generated in situ via laser ablation of silicon in a CO2 molecular beam. The resulting species are investigated by single photon ionization with tunable VUV synchrotron radiation and mass analyzed using reflectron mass spectrometry. Photoionization efficiency (PIE) curves are recorded for SiO and SiO2 and ionization energy estimates are revealed from such measurements. A state-to-state ionizationenergy of 12.60 (+-0.05) eV is recorded by fitting two prominent peaks in the PIE curve for the following process: 1SUM O-Si-O --> 2PRODg [O-Si-O]+. Electronic structure calculations aid in the interpretation of the photoionization process and allow for identification of the symmetric stretch of 2PRODg [O-Si-O]+ which is observed in the PIE spectrum to be 0.11 eV (890 cm-1) above the ground state of the cation and agrees with the 892 cm-1 symmetric stretch frequency calculated at the CCSD(T)/aug-cc-pVTZ level.

  20. Electronic structures and superconductivity in LuTE2Si2 phases (TE = d-electron transition metal)

    Science.gov (United States)

    Samsel-Czekała, M.; Chajewski, G.; Wiśniewski, P.; Romanova, T.; Hackemer, A.; Gorzelniak, R.; Pikul, A. P.; Kaczorowski, D.

    2018-05-01

    In the course of our search for unconventional superconductors amidst the 1:2:2 phases, we have re-investigated the LuTE2Si2 compounds with TE = Fe, Co, Ni, Ru, Pd and Pt. In this paper, we present the results of our fully relativistic ab initio calculations of the band structures, performed using the full-potential local-orbital code. The theoretical data are supplemented by the results of low-temperature electrical transport and specific heat measurements performed down to 0.35 K. All the materials studied but LuPt2Si2 crystallize with the body-centered tetragonal ThCr2Si2-type structure (space group I4/mmm). Their Fermi surfaces exhibit a three-dimensional multi-band character. In turn, the Pt-bearing compound adopts the primitive tetragonal CaBe2Ge2-type structure (space group P4/nmm), and its Fermi surface consists of predominantly quasi-two-dimensional sheets. Bulk superconductivity was found only in LuPd2Si2 and LuPt2Si2 (independent of the structure type and dimensionality of the Fermi surface). The key superconducting characteristics indicate a fully-gapped BCS type character. Though the electronic structure of LuFe2Si2 closely resembles that of the unconventional superconductor YFe2Ge2, this Lu-based silicide exhibits neither superconductivity nor spin fluctuations at least down to 0.35 K.

  1. Influence of Si and N additions on structure and phase stability of Ge(2)Sb(2)Te(5) thin films.

    Science.gov (United States)

    Kölpin, Helmut; Music, Denis; Laptyeva, Galyna; Ghadimi, Reza; Merget, Florian; Richter, Silvia; Mykhaylonka, Ruslàn; Mayer, Joachim; Schneider, Jochen M

    2009-10-28

    The influence of Si and N in Ge(2)Sb(2)Te(5) (space group [Formula: see text]) on structure and phase stability thereof was studied experimentally by thin film growth and characterization as well as theoretically by ab initio calculations. It was found that Si and N most probably accumulate in the amorphous matrix embedding Ge(2)Sb(2)Te(5) grains. The incorporation of Si and N in these samples causes an increase of the crystallization temperature and the formation of finer grains. N is more efficient in increasing the crystallization temperature and in reducing the grain size than Si which can be understood based on the bonding analysis. The incorporation of both Si and N in Ge(2)Sb(2)Te(5) is energetically unfavourable, leading to finer grains and larger crystallization temperatures. While in the case of Si additions no significant changes in bonding are observed, N additions appear to enable the formation of strong Te-N bonds in the amorphous matrix, which are shown to be almost twice as strong as the strongest bonds in unalloyed Ge(2)Sb(2)Te(5).

  2. Influence of Si and N additions on structure and phase stability of Ge2Sb2Te5 thin films

    International Nuclear Information System (INIS)

    Koelpin, Helmut; Music, Denis; Mykhaylonka, Ruslan; Schneider, Jochen M; Laptyeva, Galyna; Ghadimi, Reza; Richter, Silvia; Mayer, Joachim; Merget, Florian

    2009-01-01

    The influence of Si and N in Ge 2 Sb 2 Te 5 (space group Fm3-barm) on structure and phase stability thereof was studied experimentally by thin film growth and characterization as well as theoretically by ab initio calculations. It was found that Si and N most probably accumulate in the amorphous matrix embedding Ge 2 Sb 2 Te 5 grains. The incorporation of Si and N in these samples causes an increase of the crystallization temperature and the formation of finer grains. N is more efficient in increasing the crystallization temperature and in reducing the grain size than Si which can be understood based on the bonding analysis. The incorporation of both Si and N in Ge 2 Sb 2 Te 5 is energetically unfavourable, leading to finer grains and larger crystallization temperatures. While in the case of Si additions no significant changes in bonding are observed, N additions appear to enable the formation of strong Te-N bonds in the amorphous matrix, which are shown to be almost twice as strong as the strongest bonds in unalloyed Ge 2 Sb 2 Te 5 .

  3. Amorphous-crystalline interface evolution during Solid Phase Epitaxy Regrowth of SiGe films amorphized by ion implantation

    International Nuclear Information System (INIS)

    D'Angelo, D.; Piro, A.M.; Mirabella, S.; Bongiorno, C.; Romano, L.; Terrasi, A.; Grimaldi, M.G.

    2007-01-01

    Transmission Electron Microscopy was combined with Time Resolved Reflectivity to study the amorphous-crystalline (a-c) interface evolution during Solid Phase Epitaxy Regrowth (SPER) of Si 0.83 Ge 0.17 films deposited on Si by Molecular Beam Epitaxy and amorphized with Ge + ion implantation. Starting from the Si/SiGe interface, a 20 nm thick layer regrows free of defects with the same SPER rate of pure Si. The remaining SiGe regrows with planar defects and dislocations, accompanied by a decrease of the SPER velocity. The sample was also studied after implantation with B or P. In these cases, the SPER rate raises following the doping concentration profile, but no difference in the defect-free layer thickness was observed compared to the un-implanted sample. On the other hand, B or P introduction reduces the a-c interface roughness, while B-P co-implantation produces roughness comparable to the un-implanted sample

  4. Intrinsic defect processes and elastic properties of Ti3AC2 (A = Al, Si, Ga, Ge, In, Sn) MAX phases

    Science.gov (United States)

    Christopoulos, S.-R. G.; Filippatos, P. P.; Hadi, M. A.; Kelaidis, N.; Fitzpatrick, M. E.; Chroneos, A.

    2018-01-01

    Mn+1AXn phases (M = early transition metal; A = group 13-16 element and X = C or N) have a combination of advantageous metallic and ceramic properties, and are being considered for structural applications particularly where high thermal conductivity and operating temperature are the primary drivers: for example in nuclear fuel cladding. Here, we employ density functional theory calculations to investigate the intrinsic defect processes and mechanical behaviour of a range of Ti3AC2 phases (A = Al, Si, Ga, Ge, In, Sn). Based on the intrinsic defect reaction, it is calculated that Ti3SnC2 is the more radiation-tolerant 312 MAX phase considered herein. In this material, the C Frenkel reaction is the lowest energy intrinsic defect mechanism with 5.50 eV. When considering the elastic properties of the aforementioned MAX phases, Ti3SiC2 is the hardest and Ti3SnC2 is the softest. All the MAX phases considered here are non-central force solids and brittle in nature. Ti3SiC2 is elastically more anisotropic and Ti3AlC2 is nearly isotropic.

  5. Intergranular phase of the Si3 N4 hot pressed with Mg O/Y2 O3

    International Nuclear Information System (INIS)

    Costa, Celio A.; Todd, Judith A.

    1997-01-01

    Monolithic and composite Si 3 N 4 hot-pressed with 3% Mgo or 6% Y 2 O 3 were analyzed with X-ray diffraction and transmission electron microscopy. The results showed materials to be composed of β-Si 3 N 4 grains and an intergranular phase which was partially crystalline and partially amorphous. For the materials sintered with Mg O, the identification of the intergranular phase was not conclusive. For the materials sintered with Y 2 O 3 . It was observed that the amount of intergranular crystalline phase decreased as whiskers were added to the material and the intergranular crystalline part had a crystallographic structure similar to yttrium-silicon-oxide-nitride family. (author)

  6. Effect of reinforced fiber on morphology of Si phases in Al2O3/AI-Si alloy composite

    Directory of Open Access Journals (Sweden)

    Zheng LIU

    2005-05-01

    Full Text Available Alumina/aluminum-silicon alloy composite is manufactured by squeeze casting. The effect of the reinforcement on the morphology of the silicon phase in aluminum-silicon alloy is studied. The results indicate that an alumina fiber can serve as propitious sites for the heterogeneous nucleation of the silicon phase, and the primary silicon in the composite can nucleate on the surface of the fiber. The fiber in the composite can trigger twin during the coupled growth of the aluminum-silicon eutectic and lead to modification of the eutectic silicon near the fiber.

  7. Porous asymmetric SiO2-g-PMMA nanoparticles produced by phase inversion

    KAUST Repository

    Munirasu, Selvaraj

    2014-07-22

    A new kind of asymmetric organic-inorganic porous structure has been proposed. Asymmetric lattices of polymer grafted silica nanoparticles were manufactured by casting and phase inversion in water. Silica nanoparticles were first functionalized with 3-(dimethylethoxysilyl)propyl-2-bromoisobutyrate, followed by grafting of poly(methylmethacrylate) (PMMA) segments, performed by atom-transfer radical polymerization. Mechanically stable self-standing films were prepared by casting a dispersion of functionalized nanoparticles in different solvents and immersion in water. The resulting asymmetrically porous morphology and nanoparticle assembly was characterized by scanning electron and atomic force microscopy. The PMMA functionalized SiO2 hybrid material in acetone or acetone/dioxane led to the best-assembled structures. Porous asymmetric membranes were prepared by adding free PMMA and PMMA terminated with hydrophilic hydroxyl group. Nitrogen flow of 2800 L m-2 h -1 was measured at 1.3 bar demonstrating the porosity and potential application for membrane technology. © 2014 Springer Science+Business Media New York.

  8. Studies of phase formation in CoSi2 buried layers fabricated using ion implantation

    International Nuclear Information System (INIS)

    Galaev, A.A.; Parkhomenko, Yu.N.; Podgornyi, D.A.; Shcherbachev, K.D.

    1998-01-01

    The processes of the formation of cobalt disilicide buried layers in silicon are studied under different conditions of implantation with Co. In particular, the effects of the implantation dose and the postimplantation annealing temperature on the state of the Co-implanted layer are considered. Two types of heteroepitaxial Si/CoSi 2 /Si structures are obtained with the conducting layers of thicknesses 70 and 90 nm buried at the depths 80 and 10 nm, respectively

  9. Ab initio study of the effect of Si on the phase stability and electronic structure of γ- and α-Al2O3

    International Nuclear Information System (INIS)

    Nahif, F; Music, D; Mráz, S; To Baben, M; Schneider, J M

    2013-01-01

    Using density functional theory, the effect of Si on the stability and electronic structure of γ- and α-Al 2 O 3 has been investigated. The concentration range from 0 to 5 at.% is probed and the additive is positioned at different substitutional sites in the γ-phase. The calculations for (Al,Si) 2 O 3 predict a trend towards spontaneous decomposition into α-/γ-Al 2 O 3 and SiO 2 . Therefore, the formation of the metastable γ-(Al,Si) 2 O 3 phase can only be expected during non-equilibrium processing where the decomposition is kinetically hindered. The Si-induced changes in stability of this metastable solid solution may be understood based on the electronic structure. As the Si concentration is increased, stiff silicon–oxygen bonds are formed giving rise to the observed stabilization of the γ-phase. (paper)

  10. Microstructural evolution during transient liquid phase bonding of Inconel 617 using Ni-Si-B filler metal

    International Nuclear Information System (INIS)

    Jalilian, F.; Jahazi, M.; Drew, R.A.L.

    2006-01-01

    The influence of process parameters on microstructural characteristics of transient liquid phase (TLP) bonded Inconel 617 alloy was investigated. Experiments were carried out at 1065 deg. C using nickel based filler metal (Ni-4.5% Si-3% B) with B as the melting point depressant (MPD) element. Two different thickness of interlayer and various holding times were employed. The influence of these processing parameters on the characteristics of the joint area particularly size, morphology and composition of precipitates was investigated. The presence of MoB, Mo 2 B, M 23 C 6 , TiC, M 23 (B, C) 6 and Ni 3 B precipitates in the diffusion layer and Ni 3 B, Ni 3 Si and Ni 5 Si 2 precipitates in the interlayer at the interface between the base metal and interlayer were demonstrated using electron back scattered diffraction (EBSD), energy dispersive spectrometry (EDS) and TEM

  11. Electroless Ni-P/Nano-SiO2 Composite Plating on Dual Phase Magnesium-Lithium Alloy

    Science.gov (United States)

    Zou, Y.; Zhang, Z. W.; Zhang, M. L.

    The application of Mg-Li alloys is restricted in practice due to mainly poor corrosion resistance and wear resistance. Electroless nickel plating is one of the common and effective ways to protect alloys from corrosion. In this study, nano-SiO2 particles with Ni-P matrix have been successfully co-deposited onto dual phase Mg-8Li base alloy through electroless plating, generating homogeneously Ni-P/nano-SiO2 composite coating. The morphology, elemental composition and structures of coatings were investigated. Coating performances were evaluated using hardness tests and electrochemical analysis. The results indicate that the Ni-P/nano-SiO2 composite coating can significantly improve the wear and corrosion resistance.

  12. Formation of Al15Mn3Si2 Phase During Solidification of a Novel Al-12%Si-4%Cu-1.2%Mn Heat-Resistant Alloy and Its Thermal Stability

    Science.gov (United States)

    Suo, Xiaojing; Liao, Hengcheng; Hu, Yiyun; Dixit, Uday S.; Petrov, Pavel

    2018-02-01

    The formation of Al15Mn3Si2 phase in Al-12Si-4Cu-1.2Mn (wt.%) alloy during solidification was investigated by adopting CALPHAD method and microstructural observation by optical microscopy, SEM-EDS, TEM-EDS/SAD and XRD analysis; SEM fixed-point observation method was applied to evaluate its thermal stability. As-cast microstructural observation consistently demonstrates the solidification sequence of the studied alloy predicted by phase diagram calculation. Based on the phase diagram calculation, SEM-EDS, TEM-EDS/SAD and XRD analysis, as well as evidences on Al-Si-Mn-Fe compounds from the literature, the primary and eutectic Mn-rich phases with different morphologies in the studied alloy are identified to be Al15Mn3Si2 that has a body-centered cubic (BCC) structure with a lattice constant of a = 1.352 nm. SEM fixed-point observation and XRD analysis indicate that Al15Mn3Si2 phase has more excellent thermal stability at high temperature than that of CuAl2 phase and can serve as the major strengthening phase in heat-resistant aluminum alloy that has to face a high-temperature working environment. Results of tension test show that addition of Mn can improve the strength of Al-Si-Cu alloy, especially at elevated temperature.

  13. Organizational Frustration: A Model and Review of the Literature.

    Science.gov (United States)

    Spector, Paul E.

    1978-01-01

    This discussion is divided into four parts: (1) the definition of frustration; (2) general behavioral reactions to frustration which have implications for organizations; (3) integration of the individual behavioral reactions into a model of organizational frustration; and (4) a review of the supporting evidence for the model. (Author)

  14. Effect of Carbon Doping on the Structure and Magnetic Phase Transition in (Mn,Fe2(P,Si))

    Science.gov (United States)

    Thang, N. V.; Yibole, H.; Miao, X. F.; Goubitz, K.; van Eijck, L.; van Dijk, N. H.; Brück, E.

    2017-08-01

    Given the potential applications of (Mn,Fe2(P,Si))-based materials for room-temperature magnetic refrigeration, several research groups have carried out fundamental studies aimed at understanding the role of the magneto-elastic coupling in the first-order magnetic transition and further optimizing this system. Inspired by the beneficial effect of the addition of boron on the magnetocaloric effect of (Mn,Fe2(P,Si))-based materials, we have investigated the effect of carbon (C) addition on the structural properties and the magnetic phase transition of Mn_{1.25}Fe_{0.70}P_{0.50}Si_{0.50}C_z and Mn_{1.25}Fe_{0.70}P_{0.55}Si_{0.45}C_z compounds by x-ray diffraction, neutron diffraction and magnetic measurements in order to find an additional control parameter to further optimize the performance of these materials. All samples crystallize in the hexagonal Fe_2P-type structure (space group P-62m), suggesting that C doping does not affect the phase formation. It is found that the Curie temperature increases, while the thermal hysteresis and the isothermal magnetic entropy change decrease by adding carbon. Room-temperature neutron diffraction experiments on Mn_{1.25}Fe_{0.70}P_{0.55}Si_{0.45}C_z compounds reveal that the added C substitutes P/Si on the 2 c site and/or occupies the 6 k interstitial site of the hexagonal Fe_2P-type structure.

  15. Synthesis and characterization of a novel stationary phase, Si-Zr/Ti(PMTDS), based upon ternary oxide support for high performance liquid chromatography

    Energy Technology Data Exchange (ETDEWEB)

    Amparo, Maura R.; Marques, Fabiana A.; Faria, Anizio M., E-mail: anizio@pontal.ufu.br [Universidade Federal de Uberlandia (FACIP/UFU), Ituiutaba, MG (Brazil). Faculdade de Ciencias Integradas do Pontal

    2013-09-15

    A new stationary phase based on the thermal immobilization of poly(methyltetradecylsiloxane) (PMTDS) on silica particles coated with a mixture of zirconia and titania was prepared and evaluated for the chromatographic separation of test mixtures. The spherical particles were characterized by elemental analysis, SEM, FTIR and {sup 29}Si NMR. The physicochemical properties of PMTDS phase supported on Si-Zr/Ti were intermediate between PMTDS phases supported on titanized silica and zirconized silica. The chromatographic performance of Si-Zr/Ti(PMTDS) phase was similar to PMTDS phases based on metal oxide coated silica having only one metal oxide and the preparation of a Si-Zr/Ti(PMTDS) phase allowed evaluation of the effect of each oxide, zirconia and titania, on the separation process and on the stability of the immobilized polymer phase. The hydrolytic stability of Si-Zr/Ti(PMTDS) stationary phase was similar to the Si-Ti(PMTDS) phase, improving the chemical stability of the silica-based PMTDS phase by about 100%. (author)

  16. Study on the Formation of Reaction Phase to Si Addition in Boron Steel Hot-Dipped in Al–7Ni Alloy

    Directory of Open Access Journals (Sweden)

    Jung-Gil Yun

    2017-11-01

    Full Text Available In order to reduce the intermetallic compounds formed during the application of an Al–7Ni wt % hot-dip multifunctional coating on boron steel, developed for Tailor Welded Blanks (TWB and hot stamping, 2–6 wt % Si was added to the coating to change the reaction layer. The coating was run at 690 °C for 120 s. Al9FeNi phases were formed on the steel interface, Fe2Al5 was formed on the steel, FeAl3 was generated between the existing layers, and flake-type Al2Fe3Si3 was formed in the Fe2Al5 phase, depending on the Si content. In addition, as Si was added to the coating, the thickness of the Fe2Al5 phase decreased and the thickness of the Al9FeNi phase and Al2Fe3Si3 increased. The decrease in the thickness of the Fe2Al5 phase was mainly due to the effect of the Si solid solution and the Al2Fe3Si3 formation in the Fe2Al5 phase. The reason for the growth of Al9FeNi is that the higher the Si content in the coating, the more the erosion of the interface of the steel material due to the coating solution. Therefore, the outflow of Fe into the coating liquid increased.

  17. Simple Heat Treatment for Production of Hot-Dip Galvanized Dual Phase Steel Using Si-Al Steels

    Science.gov (United States)

    Equihua-Guillén, F.; García-Lara, A. M.; Muñíz-Valdes, C. R.; Ortíz-Cuellar, J. C.; Camporredondo-Saucedo, J. E.

    2014-01-01

    This work presents relevant metallurgical considerations to produce galvanized dual phase steels from low cost aluminum-silicon steels which are produced by continuous strip processing. Two steels with different contents of Si and Al were austenized in the two-phase field ferrite + austenite (α + γ) in a fast manner to obtain dual phase steels, suitable for hot-dip galvanizing process, under typical parameters of continuous annealing processing line. Tensile dual phase properties were obtained from specimens cooled from temperature below Ar3, held during 3 min, intermediate cooling at temperature above Ar1 and quenching in Zn bath at 465 °C. The results have shown typical microstructure and tensile properties of galvanized dual phase steels. Finally, the synergistic effect of aluminum, silicon, and residual chromium on martensite start temperature ( M s), critical cooling rate ( C R), volume fraction of martensite, and tensile properties has been studied.

  18. Spin-driven ferroelectricity and magneto-electric effects in frustrated magnetic systems

    International Nuclear Information System (INIS)

    Arima, Taka-hisa

    2011-01-01

    The interplay between magnetism and electricity in matter has become a central issue of condensed-matter physics. This review focuses on the ferroelectricity induced by magnetic order mostly in frustrated magnets, which is nowadays referred to as magneto-electric (ME) multiferroic, or often only as multiferroic. Some distinct types of microscopic origins relevant to the spin-driven ferroelectricity are discussed in detail. Then one sees that the frustration-based spin-driven ferroelectrics can exhibit nonlinear and giant ME responses of phase-transition type and of domain-control type, in contrast to the conventional magnetoelectrics hosting linear ME effects. (author)

  19. Nano-scale clusters formed in the early stage of phase decomposition of Al-Mg-Si alloys

    Energy Technology Data Exchange (ETDEWEB)

    Hirosawa, S.; Sato, T. [Dept. of Metallurgy and Ceramics Science, Tokyo Inst. of Tech. (Japan)

    2005-07-01

    The formation of nano-scale clusters (nanoclusters) prior to the precipitation of the strengthening {beta}'' phase significantly influences two-step aging behavior of Al-Mg-Si alloys. In this work, the existence of two kinds of nanoclusters has been verified in the early stage of phase decomposition by differential scanning calorimetry (DSC) and three-dimensional atom probe (3DAP). Pre-aging treatment at 373 K before natural aging was also found to form preferentially one of the two nanoclusters, resulting in the remarkable restoration of age-hardenability at paint-bake temperatures. Such microstructural control by means of optimized heat-treatments; i.e. nanocluster assist processing (NCAP), possesses great potential for enabling Al-Mg-Si alloys to be used more widely as a body-sheet material of automobiles. (orig.)

  20. Effects of Heat Treatment on the Microstructures and High Temperature Mechanical Properties of Hypereutectic Al-14Si-Cu-Mg Alloy Manufactured by Liquid Phase Sintering Process

    Science.gov (United States)

    Heo, Joon-Young; Gwon, Jin-Han; Park, Jong-Kwan; Lee, Kee-Ahn

    2018-05-01

    Hypereutectic Al-Si alloy is an aluminum alloy containing at least 12.6 wt.% Si. It is necessary to evenly control the primary Si particle size and distribution in hypereutectic Al-Si alloy. In order to achieve this, there have been attempts to manufacture hypereutectic Al-Si alloy through a liquid phase sintering. This study investigated the microstructures and high temperature mechanical properties of hypereutectic Al-14Si-Cu-Mg alloy manufactured by liquid phase sintering process and changes in them after T6 heat treatment. Microstructural observation identified large amounts of small primary Si particles evenly distributed in the matrix, and small amounts of various precipitation phases were found in grain interiors and grain boundaries. After T6 heat treatment, the primary Si particle size and shape did not change significantly, but the size and distribution of CuAl2 ( θ) and AlCuMgSi ( Q) changed. Hardness tests measured 97.36 HV after sintering and 142.5 HV after heat treatment. Compression tests were performed from room temperature to 300 °C. The results represented that yield strength was greater after heat treatment (RT 300 °C: 351 93 MPa) than after sintering (RT 300 °C: 210 89 MPa). Fracture surface analysis identified cracks developing mostly along the interface between the primary Si particles and the matrix with some differences among temperature conditions. In addition, brittle fracture mode was found after T6 heat treatment.

  1. Phase Diagram of Al-Ca-Mg-Si System and Its Application for the Design of Aluminum Alloys with High Magnesium Content

    Directory of Open Access Journals (Sweden)

    Nikolay A. Belov

    2017-10-01

    Full Text Available The phase transformations in the Al-Ca-Mg-Si system have been studied using thermodynamic calculations and experimental methods. We show that at 10% Magnesium (Mg, depending on the concentrations of calcium (Ca and silicon (Si, the following phases crystallize first (apart from the aluminum (Al solid solution: Al4Ca, Mg2Si, and Al2CaSi2. We have found that the major part of the calculated concentration range is covered by the region of the primary crystallization of the Al2CaSi2 phase. Regardless of the Ca and Si content, the solidification of the aluminum-magnesium alloys ends with the following nonvariant eutectic reaction: L → (Al + Al4Ca + Mg2Si + Al3Mg2. With respect to the temperature and composition of the liquid phase, this reaction is close to the eutectic reaction in the Al-Mg binary system. The addition of Ca and Si to the Al-10% Mg base alloy increases its hardness, reduces its density, and has no negative influence on its corrosion resistance. We have also established that the near-eutectic alloy containing about 3% Ca and 1% Si has the optimum structure.

  2. Heat capacity and phase equilibria of almandine, Fe3Al2Si3O12

    Science.gov (United States)

    Anovitz, Lawrence M.; Essene, E.J.; Metz, G.W.; Bohlen, S.R.; Westrum, E.F.; Hemingway, B.S.

    1993-01-01

    The heat capacity of a synthetic almandine, Fe3Al2Si3O12, was measured from 6 to 350 K using equilibrium, intermittent-heating quasi-adiabatic calorimetry and from 420 to 1000 K using differential scanning calorimetry. These measurements yield Cp298 = 342.80 ?? 1.4 J/mol ?? K and S298o = 342.60 J/mol ?? K. Mo??ssbauer characterizations show the almandine to contain less than 2 ?? 1% of the total iron as Fe3+. X-ray diffraction studies of this synthetic almandine yield a = 11.521 ?? 0.001 A?? and V298o = 115.11 +- 0.01 cm3/mol, somewhat smaller than previously reported. The low-temperature Cp data indicate a lambda transition at 8.7 K related to an antiferromagnetic-paramagnetic transition with TN = 7.5 K. Modeling of the lattice contribution to the total entropy suggests the presence of entropy in excess of that attributable to the effects of lattice vibrations and the magnetic transition. This probably arises from a low-temperature electronic transition (Schottky contribution). Combination of the Cp data with existing thermodynamic and phase equilibrium data on almandine yields ??Gf,298o = -4938.3 kJ/mol and ??Hf,298o= -5261.3 kJ/mol for almandine when calculated from the elements. The equilibrium almandine = hercynite + fayalite + quartz limits the upper T P for almandine and is metastably located at ca. 570??C at P = 1 bar, with a dP dT of +17 bars/??C. This agrees well with reversed experiments on almandine stability when they are corrected for magnetite and hercynite solid-solutions. In {norm of matrix}O2-T space, almandine oxidizes near QFM by the reactions almandine + O2 = magnetite + sillimanite + quartz and almandine + 02 = hercynite + magnetite + quartz. With suitable correction for reduced activities of solid phases, these equilibria provide useful oxygen barometers for medium- to high-grade metamorphic rocks. ?? 1993.

  3. Magnetic phase transition in MnFeP0.5As0.4Si0.1

    International Nuclear Information System (INIS)

    Wang, J L; Campbell, S J; Tegus, O; Brueck, E; Dou, S X

    2010-01-01

    We have carried out a detailed investigation of the magnetic phase transition in MnFeP 0.5 As 0.4 Si 0.1 . Temperature hysteresis has been observed in the variable temperature magnetization curves (B appl = 0.01 T) with T C W ∼ 302 K on warming and T C C ∼ 292 K on cooling. The first order nature of this transition in MnFeP 0.5 As 0.4 Si 0.1 is confirmed by the negative slope obtained from isotherms of M 2 versus B/M around the critical temperature. Linear thermal expansion measurements reveal a large volume change, ΔV/V∼8.7x10 -3 at the magnetic phase transition and that this magnetovolume effect is suppressed to ΔV/V ∼ 5.5x10 -3 in an applied field of B appl = 1.0 T. Analyses of 57 Fe Moessbauer spectra (4.5 - 300 K) using a random distribution model and taking nearest-neighbour environments into account, indicate that the paramagnetic and ferromagnetic phases coexist over a temperature range of ∼ 45 K around the Curie temperature. The Debye temperature for MnFeP 0.5 As 0.4 Si 0.1 has been evaluated as θ D = 350 ± 20 K from the temperature dependence of the average isomer shift.

  4. Phase formation in alloy-type anode materials in the quaternary system Li-Sn-Si-C

    Energy Technology Data Exchange (ETDEWEB)

    Druee, Martin; Seyring, Martin [Jena Univ. (Germany). Otto Schott Inst. of Materials Research; Liang, Song-Mao; Kozlov, Artem; Schmid-Fetzer, Rainer [Clausthal Univ. of Technology, Clausthal-Zellerfeld (Germany). Inst. of Metallurgy; Song, Xiaoyan [Beijing Univ. of Technology (China). Key Lab. of Advanced Functional Materials; Rettenmayr, Markus [Jena Univ. (Germany). Otto Schott Inst. of Materials Research; Jena Univ. (Germany). Center for Energy and Environmental

    2017-11-15

    Investigations on the thermodynamics of alloy-type anode materials have been carried out for the quaternary Li-C-Si-Sn system. Phase equilibria and phase stabilities were characterized in the binary subsystems Li-C, Li-Si, Li-Sn. The Calphad method was first used to optimize or completely re-establish all binary subsystems containing Li. For reasons of consistency, the binary subsystem Si-C had to be revisited and its Calphad description was modified. The ternary phase diagrams were then tentatively calculated by extrapolation from the binary subsystems and confirmed by key experiments. No ternary compounds were found. In order to verify the applicability of the anode materials in real batteries, some of the materials were nanostructured by ball milling and spark plasma sintering, the corresponding nanostructures were characterized. Theoretical predictions that nanograined Li{sub 2}C{sub 2} can also be used as cathode material were verified experimentally. The methodologies worked out in the present project (e.g. nanoscale structure transmission electron microscopy analysis, glow discharge optical emission spectroscopy) were also employed in other projects and led to publications concerning other materials such as Mg alloys, carbon nanofibers and an Mn-based antiperovskite.

  5. Growth and coalescence control of inclined c-axis polar and semipolar GaN multilayer structures grown on Si(111), Si(112), and Si(115) by metalorganic vapor phase epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Szymański, Tomasz, E-mail: tomasz.szymanski@pwr.edu.pl; Wośko, Mateusz; Paszkiewicz, Bartłomiej; Paszkiewicz, Bogdan; Paszkiewicz, Regina [The Faculty of Microsystem Electronics and Photonics, Wroclaw University of Technology, Janiszewskiego 11/17, 50-372 Wroclaw (Poland); Sankowska, Iwona [The Institute of Electron Technology, Al. Lotnikow 32/46, 02-668 Warszawa (Poland)

    2016-09-15

    Herein, silicon substrates in alternative orientations from the commonly used Si(111) were used to enable the growth of polar and semipolar GaN-based structures by the metalorganic vapor phase epitaxy method. Specifically, Si(112) and Si(115) substrates were used for the epitaxial growth of nitride multilayer structures, while the same layer schemes were also deposited on Si(111) for comparison purposes. Multiple approaches were studied to examine the influence of the seed layers and the growth process conditions upon the final properties of the GaN/Si(11x) templates. Scanning electron microscope images were acquired to examine the topography of the deposited samples. It was observed that the substrate orientation and the process conditions allow control to produce an isolated GaN block growth or a coalesced layer growth, resulting in inclined c-axis GaN structures under various forms. The angles of the GaN c-axis inclination were determined by x-ray diffraction measurements and compared with the results obtained from the analysis of the atomic force microscope (AFM) images. The AFM image analysis method to determine the structure tilt was found to be a viable method to estimate the c-axis inclination angles of the isolated blocks and the not-fully coalesced layers. The quality of the grown samples was characterized by the photoluminescence method conducted at a wide range of temperatures from 77 to 297 K, and was correlated with the sample degree of coalescence. Using the free-excitation peak positions plotted as a function of temperature, analytical Bose-Einstein model parameters were fitted to obtain further information about the grown structures.

  6. Impact of P and Sr on solidification sequence and morphology of hypoeutectic Al–Si alloys: Combined thermodynamic computation and phase-field simulation

    International Nuclear Information System (INIS)

    Eiken, Janin; Apel, Markus; Liang, Song-Mao; Schmid-Fetzer, Rainer

    2015-01-01

    Even small amounts of Phosphorus and Strontium strongly affect the microstructure of hypoeutectic Al–Si alloys. P is an unavoidable trace element in commercial Al-alloys which causes formation of AlP particles as potent nucleation sites for eutectic (Si). Sr, in contrast, is purposely added to modify the morphology of eutectic (Si) towards fine coral-like fibers. It is hypothesized that Sr does not only alter the growth kinetics of (Si), but additionally prevents detrimental (Si) nucleation due to neutralization of AlP particles by Al 2 Si 2 Sr formation. This presumes that both AlP and Al 2 Si 2 Sr precipitate prior to (Si). Using a newly assessed thermodynamic database for the Al–Si–Sr–P system, critical P and Sr thresholds for pre-silicon formation of AlP and Al 2 Si 2 Sr were evaluated and mapped under equilibrium and Scheil conditions. The competitive precipitation of AlP, Al 2 Si 2 Sr and (Si) and its impact on the evolution of the eutectic morphology was further studied by 3D phase-field simulations. Effective anisotropy functions for the (Si) interface mobility considered Sr-induced internal twinning. Depending on whether subcritical or supercritical P and Sr contents were selected, either a fine lamellar structure, a coarse flaky structure, or the targeted fine fibrous eutectic structure was reproduced

  7. Diffusion Bonded CVC SiC for Large UVOIR Telescope Mirrors and Structures, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Trex proposes to demonstrate a novel ceramic joining technology (solid state bonding) for CVC SiC® that allows "seamless" joining of smaller, easily manufactured,...

  8. Silicon Carbide (SiC) Power Processing Unit (PPU) for Hall Effect Thrusters, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — In this SBIR project, APEI, Inc. is proposing to develop a high efficiency, rad-hard 3.8 kW silicon carbide (SiC) Power Processing Unit (PPU) for Hall Effect...

  9. A High-Efficiency Compact SiC-based Power Converter System, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Wide-bandgap SiC semiconductors have been recently investigated for use in power devices, because of their potential capabilities of operating at high power...

  10. Uncooled Radiation Hard SiC Schottky VUV Detectors Capable of Single Photon Sensing, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This project seeks to design, fabricate, characterize and commercialize very large area, uncooled and radiative hard 4H-SiC VUV detectors capable of near single...

  11. Separation of primary solid phases from Al-Si alloy melts

    Directory of Open Access Journals (Sweden)

    Ki Young Kim

    2014-07-01

    Full Text Available The iron-rich solids formed during solidification of Al-Si alloys which are known to be detrimental to the mechanical, physical and chemical properties of the alloys should be removed. On the other hand, Al-Si hypereutectic alloys are used to extract the pure primary silicon which is suitable for photovoltaic cells in the solvent refining process. One of the important issues in iron removal and in solvent refining is the effective separation of the crystallized solids from the Al-Si alloy melts. This paper describes the separation methods of the primary solids from Al-Si alloy melts such as sedimentation, draining, filtration, electromagnetic separation and centrifugal separation, focused on the iron removal and on the separation of silicon in the solvent refining process.

  12. Porous asymmetric SiO2-g-PMMA nanoparticles produced by phase inversion

    KAUST Repository

    Munirasu, Selvaraj; Nunes, Suzana Pereira

    2014-01-01

    of functionalized nanoparticles in different solvents and immersion in water. The resulting asymmetrically porous morphology and nanoparticle assembly was characterized by scanning electron and atomic force microscopy. The PMMA functionalized SiO2 hybrid material

  13. A High-Efficiency Compact SiC-based Power Converter System, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Wide bandgap SiC power devices have the potential for reliable operations at higher junction temperatures, higher voltages, higher frequencies and thus higher power...

  14. Microdiffraction and CBED crystal structure determination of the Si-rich phase in laser-clad Ni alloy FP-5

    International Nuclear Information System (INIS)

    Liu, Y.; Mazumder, J.

    1995-01-01

    This paper demonstrates an example of using kinematical microdiffraction to solve an unknown Si-rich phase of micrometer size in a laser-clad Ni alloy FP-5 on Al alloy AA333. The composition of the Si-rich phase obtained by energy-dispersice X-ray spectroscopy (EDX) analysis in a transmission electron microscope is approximately 0.7wt%Al, 71wt%Si, 3.3wt%Cr, 0.8wt%Fe, 21wt%Ni and 2.8wt%Cu. The point group was identified by the standard convergent-beam symmetry analysis to be P6 3 /mmc (No. 194). Structure analysies by microdiffraction (MD) indicates that the Si-rich phase is a close-packed structure.The intensity distribution in the microdiffraction pattern of the [1120] zone axis taken with a very thin area showed a close match with kinematical calculation. A close-packed-structure model specified as ABCACB was deduced from the [1120] zone axis MD pattern. The randomly distributed atoms of all the elements in the unit cell are at 2/3, 1/3-1/12; 1/3, 1/12; 0, 0, 3/12, 1/3, 2/3, 5/12, 2/3, 1/3, 7/12; 0,0, 9/12. The model was checked by comparison with a simulated diffraction pattern map and with a simulated [0001] zone-axis CBED pattern, which showed complete agreement with the proposed model. (orig.)

  15. Ion irradiation effects on the matrix phase of SiCf/SiC composites prepared by the whisker growing assisted CVI process

    International Nuclear Information System (INIS)

    Park, Kyeong Hwan; Park, Ji Yeon; Kang, Suk Min; Kim, Weon Ju; Jung, Choong Hwan; Ryu, Woo Seog

    2005-01-01

    SiC f /SiC composites are one of promising candidates for structural material of the next generation energy system such as GFR and fusion reactors. A number of fabrication methods have been studied for obtaining an outstanding SiC f /SiC composite with a high density, high crystallinity and purity. SiC f /SiC composites consisted of whisker-reinforced matrix have a great potential at the viewpoint both of the fabrication process and the mechanical properties. SiC whiskers formed between SiC fibers improve the densification of SiC matrix during CVI process. In addition, the reinforced whiskers would be likely to enhance the mechanical properties of matrix and SiC f /SiC composite. While there has been significant developmental work on manufacturing the SiC f /SiC composite by the whisker growing assisted CVI process, detailed understanding of what effects the complex in the operating conditions combined with realistic materials property data is not adequately understood. Especially, its irradiation effects are even less clear and not well understood. A method of charged-particle irradiation is the most important R and D topics for simulating the core conditions of the advanced nuclear systems. Many studies on radiation effects of SiC and SiC f /SiC composites using a method of ion irradiation have in progress for R and D of the advanced nuclear systems. In this present work, changes of the mechanical property of SiC whisker-reinforced matrix in SiC f /SiC composite were evaluated by means of the depth sensing indentation method before and after chargedparticle irradiation

  16. Matrix solid-phase dispersion extraction of organophosphorus pesticide using SiO2-poly(N-vinylimidazole)

    International Nuclear Information System (INIS)

    Gutiérrez-Solís, M C; Muñoz-Rodríguez, D; Carrera-Figueiras, C; Ávila-Ortega, A; Medina-Peralta, S

    2013-01-01

    A sorbent material based on silica particles modified with poly(N-vinylimidazole) (SiO 2 -PVI) has been evaluated for the treatment of samples by matrix solid-phase dispersion (MSPD). The extraction of four organophosphorus pesticides was done from a spiked tomato and the extracts were analyzed by gas chromatography coupled to mass spectrometry. Six elution solvents were evaluated and acetone was selected due to better recovery of the four pesticides and low background signal in the chromatograms. A factorial design 2 4 was used for selection of extraction conditions. The factors were contact time, acetone volume, treatment (with or without freeze-drying) and adsorbent (SiO 2 or SiO 2 -PVI). The best recoveries were obtained using 15 minutes of contact, 2 mL of solvent and sorbent without freeze-drying. The recoveries were between 60 and 83% for SiO 2 -PVI in spiked tomato with 0.2 and 0.8μg/g.

  17. Phase transitions and magnetocaloric effects in intermetallic compounds MnFeX (X=P, As, Si, Ge)

    International Nuclear Information System (INIS)

    Tegus, O.; Bao Li-Hong; Song Lin

    2013-01-01

    Since the discovery of giant magnetocaloric effect in MnFeP 1−x As x compounds, much valuable work has been performed to develop and improve Fe 2 P-type transition-metal-based magnetic refrigerants. In this article, the recent progress of our studies on fundamental aspects of theoretical considerations and experimental techniques, effects of atomic substitution on the magnetism and magnetocalorics of Fe 2 P-type intermetallic compounds MnFeX (X=P, As, Ge, Si) is reviewed. Substituting Si (or Ge) for As leads to an As-free new magnetic material MnFeP 1−x Si(Ge) x . These new materials show large magnetocaloric effects resembling MnFe(P, As) near room temperature. Some new physical phenomena, such as huge thermal hysteresis and ‘virgin’ effect, were found in new materials. On the basis of Landau theory, a theoretical model was developed for studying the mechanism of phase transition in these materials. Our studies reveal that MnFe(P, Si) compound is a very promising material for room-temperature magnetic refrigeration and thermo-magnetic power generation. (topical review - magnetism, magnetic materials, and interdisciplinary research)

  18. A Medicago truncatula rdr6 allele impairs transgene silencing and endogenous phased siRNA production but not development.

    Science.gov (United States)

    Bustos-Sanmamed, Pilar; Hudik, Elodie; Laffont, Carole; Reynes, Christelle; Sallet, Erika; Wen, Jiangqi; Mysore, Kirankumar S; Camproux, Anne-Claude; Hartmann, Caroline; Gouzy, Jérome; Frugier, Florian; Crespi, Martin; Lelandais-Brière, Christine

    2014-12-01

    RNA-dependent RNA polymerase 6 (RDR6) and suppressor of gene silencing 3 (SGS3) act together in post-transcriptional transgene silencing mediated by small interfering RNAs (siRNAs) and in biogenesis of various endogenous siRNAs including the tasiARFs, known regulators of auxin responses and plant development. Legumes, the third major crop family worldwide, has been widely improved through transgenic approaches. Here, we isolated rdr6 and sgs3 mutants in the model legume Medicago truncatula. Two sgs3 and one rdr6 alleles led to strong developmental defects and impaired biogenesis of tasiARFs. In contrast, the rdr6.1 homozygous plants produced sufficient amounts of tasiARFs to ensure proper development. High throughput sequencing of small RNAs from this specific mutant identified 354 potential MtRDR6 substrates, for which siRNA production was significantly reduced in the mutant. Among them, we found a large variety of novel phased loci corresponding to protein-encoding genes or transposable elements. Interestingly, measurement of GFP expression revealed that post-transcriptional transgene silencing was reduced in rdr6.1 roots. Hence, this novel mis-sense mutation, affecting a highly conserved amino acid residue in plant RDR6s, may be an interesting tool both to analyse endogenous pha-siRNA functions and to improve transgene expression, at least in legume species. © 2014 Society for Experimental Biology, Association of Applied Biologists and John Wiley & Sons Ltd.

  19. Experimental study and thermodynamic modeling of the phase relation in the Fe-S-Si system with implications for the distribution of S and Si in a partially solidified core

    Science.gov (United States)

    Tao, R.; Fei, Y.

    2017-12-01

    Planetary cooling leads to solidification of any initially molten metallic core. Some terrestrial cores (e.g. Mercury) are formed and differentiated under relatively reduced conditions, and they are thought to be composed of Fe-S-Si. However, there are limited understanding of the phase relations in the Fe-S-Si system at high pressure and temperature. In this study, we conducted high-pressure experiments to investigate the phase relations in the Fe-S-Si system up to 25 GPa. Experimental results show that the liquidus and solidus in this study are slightly lower than those in the Fe-S binary system for the same S concentration in liquid at same pressure. The Fe3S, which is supposed to be the stable sub-solidus S-bearing phase in the Fe-S binary system above 17 GPa, is not observed in the Fe-S-Si system at 21 GPa. Almost all S prefers to partition into liquid, while the distribution of Si between solid and liquid depends on experimental P and T conditions. We obtained the partition coefficient log(KDSi) by fitting the experimental data as a function of P, T and S concentration in liquid. At a constant pressure, the log(KDSi) linearly decreases with 1/T(K). With increase of pressure, the slopes of linear correlation between log(KDSi) and 1/T(K) decreases, indicating that more Si partitions into solid at higher pressure. In order to interpolate and extrapolate the phase relations over a wide pressure and temperature range, we established a comprehensive thermodynamic model in the Fe-S-Si system. The results will be used to constrain the distribution of S and Si between solid inner core and liquid outer core for a range of planet sizes. A Si-rich solid inner core and a S-rich liquid outer core are suggested for an iron-rich core.

  20. Antiferromagnetism, structural instability and frustration in intermetallic AFe4X2 systems

    Science.gov (United States)

    Rosner, Helge; Bergmann, Christoph; Weber, Katharina; Kraft, Inga; Mufti, N.; Klauss, Hans-Henning; Dellmann, T.; Woike, T.; Geibel, Christoph

    2013-03-01

    Magnetic systems with reduced dimensionality or frustration attract strong interest because these features lead to an increase of quantum fluctuations and often result in unusual properties. Here, we present a detailed study of the magnetic, thermodynamic, and structural properties of the intermetallic AFe4X2 compounds (A=Sc,Y,Lu,Zr; X=Si,Ge) crystallizing in the ZrFe4Si2 structure type. Our results evidence that these compounds cover the whole regime from frustrated AFM order up to an AFM quantum critical point. Susceptibility χ(T), specific heat, resistivity, and T-dependent XRD measurements were performed on polycrystalline samples. In all compounds we observed a Curie-Weiss behavior in χ(T) at high T indicating a paramagnetic moment of about 3μB/Fe. Magnetic and structural transitions as previously reported for YFe4Ge2 occur in all compounds with trivalent A. However, transition temperatures, nature of the transition as well as the relation between structural and magnetic transitions change significantly with the A element. Low TN's and large θCW /TN ratios confirm the relevance of frustration. The results are analyzed and discussed with respect to electronic, structural and magnetic instabilities applying DFT calculations. Financial support from the DFG (GRK 1621) is acknowledged

  1. Frustration-free Hamiltonians supporting Majorana zero edge modes

    International Nuclear Information System (INIS)

    Jevtic, Sania; Barnett, Ryan

    2017-01-01

    A one-dimensional fermionic system, such as a superconducting wire, may host Majorana zero-energy edge modes (MZMs) at its edges when it is in the topological phase. MZMs provide a path to realising fault-tolerant quantum computation, and so are the focus of intense experimental and theoretical studies. However, given a Hamiltonian, determining whether MZMs exist is a daunting task as it relies on knowing the spectral properties of the Hamiltonian in the thermodynamic limit. The Kitaev chain is a paradigmatic non-interacting model that supports MZMs and the Hamiltonian can be fully diagonalised. However, for interacting models, the situation is far more complex. Here we consider a different classification of models, namely, ones with frustration-free Hamiltonians. Within this class of models, interacting and non-interacting systems are treated on an equal footing, and we identify exactly which Hamiltonians can realise MZMs. (paper)

  2. Frustration-free Hamiltonians supporting Majorana zero edge modes

    Science.gov (United States)

    Jevtic, Sania; Barnett, Ryan

    2017-10-01

    A one-dimensional fermionic system, such as a superconducting wire, may host Majorana zero-energy edge modes (MZMs) at its edges when it is in the topological phase. MZMs provide a path to realising fault-tolerant quantum computation, and so are the focus of intense experimental and theoretical studies. However, given a Hamiltonian, determining whether MZMs exist is a daunting task as it relies on knowing the spectral properties of the Hamiltonian in the thermodynamic limit. The Kitaev chain is a paradigmatic non-interacting model that supports MZMs and the Hamiltonian can be fully diagonalised. However, for interacting models, the situation is far more complex. Here we consider a different classification of models, namely, ones with frustration-free Hamiltonians. Within this class of models, interacting and non-interacting systems are treated on an equal footing, and we identify exactly which Hamiltonians can realise MZMs.

  3. CVI-R gas phase processing of porous, biomorphic SiC-ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Sieber, H.; Vogli, E.; Mueller, F.; Greil, P. [Erlangen-Nuernberg Univ., Erlangen (DE). Dept. of Materials Science (III) Glass and Ceramics; Popovska, N.; Gerhard, H. [Univ. of Erlangen-Nuremberg, Dept. of Industrial Chemistry I, Erlangen (Germany)

    2002-07-01

    Natural pine wood was converted into biomorphic SiC-ceramics by CVI-R processing (chemical vapour infiltration - reaction). The wood samples were first pyrolyzed in inert atmosphere at temperatures of 800 C to yield biocarbon-derived template structures. Subsequently, the biocarbon preforms were infiltrated with silicon by isothermal CVI processing with MTS (methyltrichlorosilane) in excess of hydrogen at temperatures between 800 and 850 C, then converted into SiC-ceramic by annealing in inert atmosphere at temperatures between 1200-1600 C. During processing, the inherent open porous structure of the pine wood is retained down to the submicrometer level, yielding a highly porous SiC-ceramic with a unique microcellular morphology. (orig.)

  4. Evolved Minimal Frustration in Multifunctional Biomolecules.

    Science.gov (United States)

    Röder, Konstantin; Wales, David J

    2018-05-25

    Protein folding is often viewed in terms of a funnelled potential or free energy landscape. A variety of experiments now indicate the existence of multifunnel landscapes, associated with multifunctional biomolecules. Here, we present evidence that these systems have evolved to exhibit the minimal number of funnels required to fulfil their cellular functions, suggesting an extension to the principle of minimum frustration. We find that minimal disruptive mutations result in additional funnels, and the associated structural ensembles become more diverse. The same trends are observed in an atomic cluster. These observations suggest guidelines for rational design of engineered multifunctional biomolecules.

  5. Complexity due to disorder and frustration

    International Nuclear Information System (INIS)

    Sherrington, D.

    1990-01-01

    In these lectures the author aims to demonstrate that quenched disorder and frustrated interactions combine to produce rich and complex behavior, static and dynamic, in a wealth of situations ranging from solid-state physics, through NP-hard optimization (e.g., in operational research), to neural models for memory. The techniques employed draw heavily on statistical mechanics and automaton theory, but the conventional versions of these subjects require non-trivial extension to deal with the new phenomena, leading to the development of new concepts. 16 refs., 12 figs

  6. Gifts and exchanges problems, frustrations, and triumphs

    CERN Document Server

    Katz, Linda S; Denning, Catherine

    2013-01-01

    This important book explores the many questions challenging librarians who work with gifts and exchanges (G&E) as part of their daily responsibilities. Too often, because of shrinking library budgets, library gifts are considered burdensome and unprofitable drains on both financial and personnel resources. However, Gifts and Exchanges: Problems, Frustrations, . . . and Triumphs gives you solutions that will allow you to embrace your library's gifts as rewards. In this book, you will discover the latest ways of disposing unwanted materials, planning and holding book sales and auctions, and oper

  7. Photoluminescence investigation of thick GaN films grown on Si substrates by hydride vapor phase epitaxy

    International Nuclear Information System (INIS)

    Yang, M.; Ahn, H. S.; Chang, J. H.; Yi, S. N.; Kim, K. H.; Kim, H.; Kim, S. W.

    2003-01-01

    The optical properties of thick GaN films grown by hydried vapor phase epitaxy (HVPE) using a low-temperature intermediate GaN buffer layer grown on a (111) Si substrate with a ZnO thin film were investigated by using photoluminescence (PL) measurement at 300 K and 77 K. The strong donor bound exciton (DBE) at 357 nm with a full width at half maximum (FWHM) of 15 meV was observed at 77 K. The value of 15 meV is extremely narrow for GaN grown on Si substrate by HVPE. An impurity-related peak was also observed at 367 nm. The origin of impurity was investigated using Auger spectroscopy.

  8. Effect of second phase particles topology on the onset temperature of abnormal grain growth in Fe - 3%Si steels

    Directory of Open Access Journals (Sweden)

    Stoyka, V.

    2008-01-01

    Full Text Available The relations between regimes of dynamic annealing, state of secondary particles system and the onset temperature of abnormal grain growth are investigated. Two distinguish types of Fe-3%Si grain-oriented steels, after one and two stage cold rolling, were studied. The second phase particles remain unaffected in first type of steel during the heat treatment. Vice versa, the increased density of second phases was observed after annealing in the second type of the investigated materials. It is shown that start/onset of abnormal grain growth strongly depends on both volume fraction of second phase particles and annealing temperature. Texture and magnetic properties of the investigated samples are investigated within the current study.

  9. Factors influencing shape memory effect and phase transformation behaviour of Fe-Mn-Si based shape memory alloys

    International Nuclear Information System (INIS)

    Li, H.; Dunne, D.; Kennon, N.

    1999-01-01

    The objective of this research work was to investigate the factors influencing the shape memory effect and phase transformation behaviour of three Fe-Mn-Si based shape memory alloys: Fe-28Mn-6Si, Fe-13Mn-5Si-10Cr-6Ni and Fe-20Mn-6Si-7Cr-1Cu. The research results show that the shape memory capacity of Fe-Mn-Si based shape memory alloys varies with annealing temperature, and this effect can be explained in terms of the effect of annealing on γ ε transformation. The nature and concentration of defects in austenite are strongly affected by annealing conditions. A high annealing temperature results in a low density of stacking faults, leading to a low nucleation rate during stress induced γ→ε transformation. The growth of ε martensite plates is favoured rather than the formation of new ε martensite plates. Coarse martensite plates produce high local transformation strains which can be accommodated by local slip deformation, leading to a reduction in the reversibility of the martensitic transformation and to a degradation of the shape memory effect. Annealing at low temperatures (≤673 K) for reasonable times does not eliminate complex defects (dislocation jogs, kinks and vacancy clusters) created by hot and cold working strains. These defects can retard the movement and rearrangement of Shockley partial dislocations, i.e. suppress γ→ε transformation, also leading to a degradation of shape memory effect. Annealing at about 873 K was found to be optimal to form the dislocation structures which are favourable for stress induced martensitic transformation, thus resulting in the best shape memory behaviour. (orig.)

  10. Subsolidus phase relationships of the {beta}-sialon solid solution in the oxygen-rich part of the Nd-Si-Al-O-N system

    Energy Technology Data Exchange (ETDEWEB)

    Kaiser, A.; Telle, R. [Rheinisch Westfaelische Technische Hochschule Aachen (Germany). Inst. fuer Gesteinshuettenkunde; Herrmann, M.; Richter, H.J.; Hermel, W. [Fraunhofer Inst. Keramische Technologien und Sinterwerkstoffe, Dresden (Germany)

    2001-10-01

    The subsolidus phase relationships in the Nd{sub 2}O{sub 3}-Al{sub 2}O{sub 3}-SiO{sub 2} system and in the Si{sub 6-z}Al{sub z}O{sub z}N{sub 8-z} (0 {<=} z {<=} 4)-''Al{sub 2}O{sub 3}:AlN''-Al{sub 2}O{sub 3}-Nd{sub 2}O{sub 3}-SiO{sub 2}-range of the Nd-Si-Al-O-N system have been determined. 50 three- and four-phase equilibria were established in this phase region. The phase equilibria define the regions of stable coexistence between {beta}-sialon Si{sub 6-z}Al{sub z}O{sub z}N{sub 8-z} (0 {<=} z {<=} 4) and oxide or oxynitride compounds, which are potential grain boundary phases for silicon nitride ceramics. {beta}-Si{sub 3}N{sub 4} coexists with N-melilite (Nd{sub 2}Si{sub 3-x}Al{sub x}N{sub 4-x} (0 {<=} x {<=} 1)), N-{alpha}-wollastonite NdSi{sub 2}ON, a nitrogen-rich (Al, N)-apatite solid solution and Nd{sub 2}Si{sub 2}O{sub 7}. Between 0 {<=} z {<=} 0.8 {beta}-sialon (Si{sub 6-z}Al{sub z}O{sub z}N{sub 8-z}) is compatible with N-melilite (Nd{sub 2}Si{sub 3-x}Al{sub x}N{sub 4-x} (x = 1)), an (Al,N)-apatite of intermediate composition and Nd{sub 2}Si{sub 2}O{sub 7}. The equilibrium phases between z = 0.8 to z = 4 are NdAlO{sub 3} and the U-phase (Nd{sub 3}Si{sub 3-x}Al{sub 3+x}O{sub 12+x}N{sub 2-x}) as well as NdAl{sub 11+x}O{sub 18}N{sub x} (x = 1) and corundum at the Al-rich terminal composition (z = 4). (orig.)

  11. Pressure dependence of morphology and phase composition of SiC films deposited by microwave plasma chemical vapor deposition on cemented carbide substrates

    Energy Technology Data Exchange (ETDEWEB)

    Yu Shengwang, E-mail: bkdysw@yahoo.cn; Fan Pengwei; Tang Weizhong; Li Xiaojing; Hu Haolin; Hei Hongjun; Zhang Sikai; Lu Fanxiu

    2011-11-01

    SiC films were deposited on cemented carbide substrates by employing microwave plasma chemical vapor deposition method using tetramethylsilane (Si(CH{sub 3}){sub 4}) diluted in H{sub 2} as the precursor. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and scratching technique were used to characterize morphology, composition, phases present and adhesion of the films. Experimental results show that the deposition pressure has great influence on morphologies and phase composition of the films. In sequence, SiC films with a cauliflower-like microstructure, granular films with terrace-featured SiC particles coexisting with Co{sub 2}Si compound and clusters of nanometer SiC nanoplatelets appear as a function of the deposition pressure. In terms of plasma density and substrate temperature, this sequential appearance of microstructures of SiC films was explained. Adhesion tests showed that among the three types of films studied, the films with the terrace-featured SiC particles have relatively higher adhesion. Such knowledge will be of importance when the SiC films are used as interlayer between diamond films and cemented carbide substrates.

  12. Pressure dependence of morphology and phase composition of SiC films deposited by microwave plasma chemical vapor deposition on cemented carbide substrates

    International Nuclear Information System (INIS)

    Yu Shengwang; Fan Pengwei; Tang Weizhong; Li Xiaojing; Hu Haolin; Hei Hongjun; Zhang Sikai; Lu Fanxiu

    2011-01-01

    SiC films were deposited on cemented carbide substrates by employing microwave plasma chemical vapor deposition method using tetramethylsilane (Si(CH 3 ) 4 ) diluted in H 2 as the precursor. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and scratching technique were used to characterize morphology, composition, phases present and adhesion of the films. Experimental results show that the deposition pressure has great influence on morphologies and phase composition of the films. In sequence, SiC films with a cauliflower-like microstructure, granular films with terrace-featured SiC particles coexisting with Co 2 Si compound and clusters of nanometer SiC nanoplatelets appear as a function of the deposition pressure. In terms of plasma density and substrate temperature, this sequential appearance of microstructures of SiC films was explained. Adhesion tests showed that among the three types of films studied, the films with the terrace-featured SiC particles have relatively higher adhesion. Such knowledge will be of importance when the SiC films are used as interlayer between diamond films and cemented carbide substrates.

  13. Probing quantum frustrated systems via factorization of the ground state.

    Science.gov (United States)

    Giampaolo, Salvatore M; Adesso, Gerardo; Illuminati, Fabrizio

    2010-05-21

    The existence of definite orders in frustrated quantum systems is related rigorously to the occurrence of fully factorized ground states below a threshold value of the frustration. Ground-state separability thus provides a natural measure of frustration: strongly frustrated systems are those that cannot accommodate for classical-like solutions. The exact form of the factorized ground states and the critical frustration are determined for various classes of nonexactly solvable spin models with different spatial ranges of the interactions. For weak frustration, the existence of disentangling transitions determines the range of applicability of mean-field descriptions in biological and physical problems such as stochastic gene expression and the stability of long-period modulated structures.

  14. The phenomenon of phase separated in Na2O-B2O3-SiO2, Na2O-SiO2-P2O5 glasses

    International Nuclear Information System (INIS)

    Procyk, B.; Bieniarz, P.; Plichta, E.; Pudelek, B.; Kucinski, G.; Staniewicz-Brudnik, B.

    1997-01-01

    During the thermal treatment, the phenomenon of phase separation has been observed in the some glasses. The glass has became opaque, due to the opalescence of phase separated. Investigations of the phenomenon of phase separation were conducted using the basic systems: Na 2 O-B 2 O 3 -SiO 2 , Na 2 O-SiO 2 -P 2 O 5 and theirs modifications. The occurrence of binodal and spinodal phase decomposition was observed by TEM. The phase separation inhomogeneities have drop-like character and with higher concentration shows a tendency for coalescence. The influence of the chemical composition, temperature and time on the phenomenon of phase separation in the investigated glasses has been defined. (author)

  15. Characterisation of phase composition, microstructure and microhardness of electroless nickel composite coating co-deposited with SiC on casting aluminium LM24 alloy substrate

    OpenAIRE

    Franco, M.; Sha, Wei; Malinov, Savko

    2013-01-01

    Electroless Ni-P (EN) and composite Ni-P-SiC (ENC) coatings were developed on cast aluminium alloy, LM24. The coating phase composition, microstructure and microhardness were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and microhardness tester, respectively, on as-plated and heat-treated specimens. The original microstructure of the Ni-P matrix is not affected by the inclusion of the hard particles SiC. No formation of Ni-Si phase was observed upto 500°C of ...

  16. Small-angle neutron-scattering studies of the magnetic phase diagram of MnSi

    DEFF Research Database (Denmark)

    Harris, P.; Lebech, B.; Hae Seop Shim

    1995-01-01

    The antiferromagnetic order of MnSi has been studied as function of temperature and applied magnetic field using small-angle neutron scattering. The results were analyzed using the three-dimensional resolution function and the scattering cross-section to model the diffraction data. Physical...

  17. Pressure-induced phase transformations in the Ba8Si46 clathrate

    DEFF Research Database (Denmark)

    Yang, Lirong; Ma, Y.M.; Iitaka, T.

    2006-01-01

    The nature of isostructural transformations of a type-I Ba8Si46 clathrate has been studied by in situ high-pressure angle-dispersive x-ray powder diffraction using liquid He as pressure transmitting medium. The good quality of the diffraction data permitted refinement of structural and thermal...

  18. Silicon Carbide (SiC) Power Processing Unit (PPU) for Hall Effect Thrusters, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — In this SBIR project, APEI, Inc. is proposing to develop a high efficiency, rad-hard 3.8 kW silicon carbide (SiC) power supply for the Power Processing Unit (PPU) of...

  19. Behavior of the antiferromagnetic phase transition near the fermion condensation quantum phase transition in YbRh{sub 2}Si{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Shaginyan, V.R., E-mail: vrshag@thd.pnpi.spb.r [Petersburg Nuclear Physics Institute, RAS, Gatchina 188300 (Russian Federation); Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Amusia, M.Ya. [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Popov, K.G. [Komi Science Center, Ural Division, RAS, Syktyvkar 167982 (Russian Federation)

    2010-01-11

    Low-temperature specific-heat measurements on YbRh{sub 2}Si{sub 2} at the second order antiferromagnetic (AF) phase transition reveal a sharp peak at T{sub N}=72 mK. The corresponding critical exponent alpha turns out to be alpha=0.38, which differs significantly from that obtained within the framework of the fluctuation theory of second order phase transitions based on the scale invariance, where alphaapprox =0.1. We show that under the application of magnetic field the curve of the second order AF phase transitions passes into a curve of the first order ones at the tricritical point leading to a violation of the critical universality of the fluctuation theory. This change of the phase transition is generated by the fermion condensation quantum phase transition. Near the tricritical point the Landau theory of second order phase transitions is applicable and gives alphaapprox =1/2. We demonstrate that this value of alpha is in good agreement with the specific-heat measurements.

  20. Packing frustration in dense confined fluids.

    Science.gov (United States)

    Nygård, Kim; Sarman, Sten; Kjellander, Roland

    2014-09-07

    Packing frustration for confined fluids, i.e., the incompatibility between the preferred packing of the fluid particles and the packing constraints imposed by the confining surfaces, is studied for a dense hard-sphere fluid confined between planar hard surfaces at short separations. The detailed mechanism for the frustration is investigated via an analysis of the anisotropic pair distributions of the confined fluid, as obtained from integral equation theory for inhomogeneous fluids at pair correlation level within the anisotropic Percus-Yevick approximation. By examining the mean forces that arise from interparticle collisions around the periphery of each particle in the slit, we calculate the principal components of the mean force for the density profile--each component being the sum of collisional forces on a particle's hemisphere facing either surface. The variations of these components with the slit width give rise to rather intricate changes in the layer structure between the surfaces, but, as shown in this paper, the basis of these variations can be easily understood qualitatively and often also semi-quantitatively. It is found that the ordering of the fluid is in essence governed locally by the packing constraints at each single solid-fluid interface. A simple superposition of forces due to the presence of each surface gives surprisingly good estimates of the density profiles, but there remain nontrivial confinement effects that cannot be explained by superposition, most notably the magnitude of the excess adsorption of particles in the slit relative to bulk.

  1. Approximate eigenvalue determination of geometrically frustrated magnetic molecules

    Directory of Open Access Journals (Sweden)

    A.M. Läuchli

    2009-01-01

    Full Text Available Geometrically frustrated magnetic molecules have attracted a lot of interest in the field of molecular magnetism as well as frustrated Heisenberg antiferromagnets. In this article we demonstrate how an approximate diagonalization scheme can be used in order to obtain thermodynamic and spectroscopic information about frustrated magnetic molecules. To this end we theoretically investigate an antiferromagnetically coupled spin system with cuboctahedral structure modeled by an isotropic Heisenberg Hamiltonian.

  2. Nematic quantum liquid crystals of bosons in frustrated lattices

    Science.gov (United States)

    Zhu, Guanyu; Koch, Jens; Martin, Ivar

    2016-04-01

    The problem of interacting bosons in frustrated lattices is an intricate one due to the absence of a unique minimum in the single-particle dispersion where macroscopic number of bosons can condense. Here, we consider a family of tight-binding models with macroscopically degenerate lowest energy bands, separated from other bands by a gap. We predict the formation of exotic states that spontaneously break rotational symmetry at relatively low filling. These states belong to three nematic phases: Wigner crystal, supersolid, and superfluid. The Wigner crystal phase is established exactly at low filling. Supersolid and superfluid phases, at larger filling, are obtained by making use of a projection onto the flat band, construction of an appropriate Wannier basis, and subsequent mean-field treatment. The nematic superfluid that we predict is uniform in real space but has an anisotropic momentum distribution, providing a novel scenario for Bose condensation with an additional nematic order. Our findings open up a promising direction of studying microscopic quantum liquid crystalline phases of bosons.

  3. Observation of a Griffiths-like Phase in the Magnetocaloric Compound Tb5Si2Ge2

    International Nuclear Information System (INIS)

    Magen, C.; Algarabel, P.A.; Morellon, L.; Ibarra, M.R.; Araujo, J.P.; Pereira, A.M.; Sousa, J.B.; Ritter, C.

    2006-01-01

    The onset of a Griffiths-like phase has been observed in Tb 5 Si 2 Ge 2 (T C =110 K) by means of magnetic susceptibility and small-angle neutron scattering experiments. We show the growth of a ferromagnetic cluster system characterized by an inverse susceptibility exponent lower than unity at T C G ≅200 K. We suggest that the Griffiths-like state is originated by local disorder within the crystallographic structure, stabilized and enhanced by competing intralayer and interlayer magnetic interactions. Both factors thus promote segregation of nanometric regions with ferromagnetic interactions

  4. Liquid Phase Epitaxial Growth of Al-doped f-SiC for White Light-Emitting Diodes

    DEFF Research Database (Denmark)

    Tang, Kai; Ma, Xiang; can der Eijk, Casper

    efficiency, better light quality and longer lifespan, compared to the current yellow phosphor based white LEDs.Liquid phase epitaxy technology can yield a high crystalline quality in terms of structural perfection owing to the fact that it is a near equilibrium crystalline growth process. In addition....... The experimental results are presented and discussed. Since operational temperature of LPE growth is much lower than that currently used in physical vapour transport (PVT) process, it is expected to save the energy consumption for SiC crystal growth....

  5. Effect of Si and Mn additions on ferrite and austenite phase fractions in 25Cr-7Ni-1.5Mo-3W base super duplex stainless steels

    International Nuclear Information System (INIS)

    Jeong, S.W.; Lee, Z.-H.; Lee, H.M.

    2000-01-01

    The effect of heat treatment and Si and Mn additions on the ferrite and austenite phase fractions of the super duplex stainless steel (SDSS), Fe-25Cr-7Ni-1.5Mo-3W-Si-Mn-0.25N (numbers are all in wt.% unless specified otherwise), was investigated. The thermodynamic calculations of phase equilibria and phase fractions were performed using the Thermo-Calc program. Based on the calculated results, specific compositions of Si and Mn were selected and alloys with these compositions were analysed by Feritscope, X-ray diffractometry and scanning electron microscopy. The calculated phase fractions and experimentally analysed ones were compared and there was a good agreement between calculations and measurements. The optimum heat treatment condition for Fe-25Cr-7Ni-1.5Mo-3W-0.5Si-0.5Mn-0.25N is to hold at 1050 to 1100 C for 2 h in considering the ferrite to austenite ratio of 50:50 and to avoid second phase precipitation such as the σ phase. It was suggested that an excessive addition of more than 0.8Si and 1.0Mn may induce the σ phase precipitation. (orig.)

  6. A simple transferable adaptive potential to study phase separation in large-scale xMgO-(1-x)SiO2 binary glasses.

    Science.gov (United States)

    Bidault, Xavier; Chaussedent, Stéphane; Blanc, Wilfried

    2015-10-21

    A simple transferable adaptive model is developed and it allows for the first time to simulate by molecular dynamics the separation of large phases in the MgO-SiO2 binary system, as experimentally observed and as predicted by the phase diagram, meaning that separated phases have various compositions. This is a real improvement over fixed-charge models, which are often limited to an interpretation involving the formation of pure clusters, or involving the modified random network model. Our adaptive model, efficient to reproduce known crystalline and glassy structures, allows us to track the formation of large amorphous Mg-rich Si-poor nanoparticles in an Mg-poor Si-rich matrix from a 0.1MgO-0.9SiO2 melt.

  7. Influence of Cu on modifying the beta phase and enhancing the mechanical properties of recycled Al-Si-Fe cast alloys.

    Science.gov (United States)

    Basak, C B; Babu, N Hari

    2017-07-18

    High iron impurity affects the castability and the tensile properties of the recycled Al-Si alloys due to the presence of the Fe containing intermetallic β-Al 9 Fe 2 Si 2 phase. To date only Mn addition is known to transform the β-Al 9 Fe 2 Si 2 phase in the Al-Si-Fe system. However, for the first time, as reported here, it is shown that β-phase transforms to the ω-Al 7 Cu 2 Fe phase in the presence of Cu, after solutionization at 793 K. The ω-phase decomposes below 673 K resulting into the formation of θ-Al 2 Cu phase. However, the present thermodynamic description of the Al-Si-Fe-Cu system needs finer tuning to accurately predict the stability of the ω-phase in these alloys. In the present study, an attempt was made to enhance the strength of Al-6wt%Si-2wt%Fe model recycled cast alloy with different amount of Cu addition. Microstructural and XRD analysis were carried out in detail to show the influence of Cu and the stability range of the ω-phase. Tensile properties and micro-hardness values are also reported for both as-cast and solutionized alloys with different amount of Cu without and with ageing treatment at 473 K. The increase in strength due to addition of Cu, in Fe-rich Al-Si alloys is promising from the alloy recyclability point of view.

  8. Discontinuous phase formation and selective attack of SiC materials exposed to low oxygen partial pressure environments

    Energy Technology Data Exchange (ETDEWEB)

    Butt, D.P. [Los Alamos National Lab., NM (United States); Tressler, R.E.; Spear, K.E. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Materials Science and Engineering

    1993-09-01

    Three SiC materials were exposed to gas mixtures containing N{sub 2}, H{sub 2}, and CO at 1000-1300C, 1-740 torr for a few to 1000 h. Kinetic and thermodynamic studies indicate that CO is the predominant oxidizing species. A variety of corrosion processes were observed, including surface and internal pit formation, needle growth, grain boundary attack, and attack of impurities and surrounding material. In the case of a siliconized SiC, impurities such as Ca, Al, and Fe diffused rapidly through the Si matrix forming complex calcium aluminosilicates on the surface, leaving behind internal voids. Evaluation of the mechanical properties, including fractography, revealed a variety of degradative phenomena. Efforts to identify causes of pit formation suggested that the overall process was complex. Pits formed during attack of grain boundaries and regions containing transition metal impurities. Studies of single crystals showed preferential attack near impurities and crystalline defects, indicating that damaged crystals or certain crystal orientations in the polycrystalline materials are susceptible to attack. In addition, under some conditions where pit formation was observed, the strength of certain materials increased apparently due to flaw healing. It is suggested that flaws can heal in the absence of mechanical stress due to their high surface energy. However, second phases observed within partially healed surface cracks suggest impurities also contribute to the flaw healing processes.

  9. Microstructural evolution during transient liquid phase bonding of Inconel 617 using Ni-Si-B filler metal

    Energy Technology Data Exchange (ETDEWEB)

    Jalilian, F. [McGill University, Department of Mining, Metals and Materials Engineering, 3610 University St., M.H. Wong Building, Montreal Que., H3A 2B2 (Canada); Jahazi, M. [Aerospace Manufacturing Technology Center, National Research Council of Canada (Canada); Drew, R.A.L. [McGill University, Department of Mining, Metals and Materials Engineering, 3610 University St., M.H. Wong Building, Montreal Que., H3A 2B2 (Canada)]. E-mail: robin.drew@mcgill.ca

    2006-05-15

    The influence of process parameters on microstructural characteristics of transient liquid phase (TLP) bonded Inconel 617 alloy was investigated. Experiments were carried out at 1065 deg. C using nickel based filler metal (Ni-4.5% Si-3% B) with B as the melting point depressant (MPD) element. Two different thickness of interlayer and various holding times were employed. The influence of these processing parameters on the characteristics of the joint area particularly size, morphology and composition of precipitates was investigated. The presence of MoB, Mo{sub 2}B, M{sub 23}C{sub 6}, TiC, M{sub 23}(B, C){sub 6} and Ni{sub 3}B precipitates in the diffusion layer and Ni{sub 3}B, Ni{sub 3}Si and Ni{sub 5}Si{sub 2} precipitates in the interlayer at the interface between the base metal and interlayer were demonstrated using electron back scattered diffraction (EBSD), energy dispersive spectrometry (EDS) and TEM.

  10. Thermal switching of the electrical conductivity of Si(111)(√3x√3)Ag due to a surface phase transition

    International Nuclear Information System (INIS)

    Wells, J W; Kallehauge, J F; Hofmann, Ph

    2007-01-01

    The temperature-dependent surface conductivity of the Si(111)(√3x√3)Ag surface was measured using a microscopic four-point probe. The conductivity was found to undergo a sharp increase of about three orders of magnitude when the system was heated above about 220 K. This strong conductivity change is reversible and attributed to the phase transition which is generally believed to occur on this surface. It is also shown that, in order to find the true surface conductivity, it is necessary to separate it from the contribution of the bulk and space charge layer. In this work, this is achieved by using a finite-element model. A percolating network of Ag islands on Si(111) was also studied and a much simpler behaviour (compared to that of Si(111))(√3x√3)Ag) was found. The temperature-dependent conductivity of this system was found to display typical metallic behaviour. The absolute value of the conductivity is comparable to the value expected by modelling the Ag film as exhibiting the bulk Ag transport properties

  11. The La(Fe,Mn,Si)13Hz magnetic phase transition under pressure

    DEFF Research Database (Denmark)

    Lovell, Edmund; Bez, Henrique N.; Boldrin, David C.

    2017-01-01

    We study the magnetocaloric metamagnetic transition in LaFe11.74Mn0.06Si1.20 and LaFe11.76Mn0.06Si1.18H1.65 under hydrostatic pressure up to 1.2 GPa. For both compounds, hydrostatic pressure depresses the zero field critical temperature. However, in detail, pressure influences the magnetic...... and extrinsic hysteresis loss brought about by the use of hydrostatic pressure. We explore the multicaloric field-pressure cycle, demonstrating that although the gain introduced by overcoming the magnetic hysteresis loss is closely countered by the loss introduced in the pressure cycle, there are significant...... properties in different ways in the two compounds. In the dehydrogenated case the transition broadens under pressure whereas in the hydrogenated case the transition sharpens. In both cases thermal hysteresis increases under pressure, although with different trends. These observations suggest both intrinsic...

  12. CHARACTERIZATION OF PHASES IN SECONDARY AlZn10Si8Mg CAST ALLOY

    OpenAIRE

    Eva Tillová; Emília Ďuriníková; Mária Chalupová

    2011-01-01

    Using recycled aluminium cast alloys is profitable in many aspects. Requiring only 5 % of the energy to produce secondary metal as compared to primary metal and generates only 5 % of the green house gas emissions, the recycling of aluminium is therefore beneficial of both environmental and economical point of view. Secondary AlZn10Si8Mg (UNIFONT® - 90) cast alloy are used for engine and vehicle constructions, hydraulic unit and mouldmaking without heat treatment. Properties include good casta...

  13. Oxidation induced crack healing of Cr2(Al,Si)C max phase ceramic

    NARCIS (Netherlands)

    Shen, L.; Li, S.B.; Van der Zwaag, S.; Sloof, W.G.

    2013-01-01

    The oxidation crack healing of Cr2AlC and Cr2(Al,Si)C was studied and compared with known healing of Ti2AlC. The oxidation induced crack healing of Ti2AlC is relatively fast and leads to full strength recovery, but the oxidation product contains besides ?-Al2O3 also undesired TiO2. However, when

  14. Thermodynamic modelling of phase equilibrium in system Ti-B-Si-C, synthesis and phases composition of borides and carbides layers on titanic alloyVT-1 at electron beam treatment in vacuum

    Science.gov (United States)

    Smirnyagina, N. N.; Khaltanova, V. M.; Lapina, A. E.; Dasheev, D. E.

    2017-01-01

    Composite layers on the basis of carbides and borides the titan and silicon on titanic alloy VT-1 are generated at diffused saturation in vacuum. Formation in a composite of MAX phase Ti3SiC2 is shown. Thermodynamic research of phase equilibrium in systems Ti-Si-C and Ti-B-C in the conditions of high vacuum is executed. The thermodynamics, formation mechanisms of superfirm layers borides and carbides of the titan and silicon are investigated.

  15. Formation of nanocrystalline and amorphous phase of Al-Pb-Si-Sn-Cu powder during mechanical alloying

    International Nuclear Information System (INIS)

    Ran Guang; Zhou Jingen; Xi Shengqi; Li Pengliang

    2006-01-01

    Al-15%Pb-4%Si-1%Sn-1.5%Cu alloys (mass fraction, %) were prepared by mechanical alloying (MA). Phase transformation and microstructure characteristics of the alloy powders were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that the nanocrystalline supersaturated solid solutions and amorphous phase in the powders are obtained during MA. The effect of ball milling is more evident to lead than to aluminum. During MA, the mixture powders are firstly fined, alloyed, nanocrystallized and then the nanocrystalline partly transforms to amorphous phase. A thermodynamic model is developed based on semi-experimental theory of Miedema to calculate the driving force for phase evolution. The thermodynamic analysis shows that there is no chemical driving force to form a crystalline solid solution from the elemental components. But for the amorphous phase, the Gibbs free energy is higher than 0 for the alloy with lead content in the ranges of 0-86.8 at.% and 98.4-100 at.% and lower than 0 in range of 86.8-98.4 at.%. For the Al-2.25 at.%Pb (Al-15%Pb, mass fraction, %), the driving force for formation of amorphization and nanocrystalline supersaturated solid solutions are provided not by the negative heat of mixing but by mechanical work

  16. Butterfly magnetoresistance, quasi-2D Dirac Fermi surface and topological phase transition in ZrSiS.

    Science.gov (United States)

    Ali, Mazhar N; Schoop, Leslie M; Garg, Chirag; Lippmann, Judith M; Lara, Erik; Lotsch, Bettina; Parkin, Stuart S P

    2016-12-01

    Magnetoresistance (MR), the change of a material's electrical resistance in response to an applied magnetic field, is a technologically important property that has been the topic of intense study for more than a quarter century. We report the observation of an unusual "butterfly"-shaped titanic angular magnetoresistance (AMR) in the nonmagnetic Dirac material, ZrSiS, which we find to be the most conducting sulfide known, with a 2-K resistivity as low as 48(4) nΩ⋅cm. The MR in ZrSiS is large and positive, reaching nearly 1.8 × 10 5 percent at 9 T and 2 K at a 45° angle between the applied current ( I || a ) and the applied field (90° is H || c ). Approaching 90°, a "dip" is seen in the AMR, which, by analyzing Shubnikov de Haas oscillations at different angles, we find to coincide with a very sharp topological phase transition unlike any seen in other known Dirac/Weyl materials. We find that ZrSiS has a combination of two-dimensional (2D) and 3D Dirac pockets comprising its Fermi surface and that the combination of high-mobility carriers and multiple pockets in ZrSiS allows for large property changes to occur as a function of angle between applied fields. This makes it a promising platform to study the physics stemming from the coexistence of 2D and 3D Dirac electrons as well as opens the door to creating devices focused on switching between different parts of the Fermi surface and different topological states.

  17. Butterfly magnetoresistance, quasi-2D Dirac Fermi surface and topological phase transition in ZrSiS

    Science.gov (United States)

    Ali, Mazhar N.; Schoop, Leslie M.; Garg, Chirag; Lippmann, Judith M.; Lara, Erik; Lotsch, Bettina; Parkin, Stuart S. P.

    2016-01-01

    Magnetoresistance (MR), the change of a material’s electrical resistance in response to an applied magnetic field, is a technologically important property that has been the topic of intense study for more than a quarter century. We report the observation of an unusual “butterfly”-shaped titanic angular magnetoresistance (AMR) in the nonmagnetic Dirac material, ZrSiS, which we find to be the most conducting sulfide known, with a 2-K resistivity as low as 48(4) nΩ⋅cm. The MR in ZrSiS is large and positive, reaching nearly 1.8 × 105 percent at 9 T and 2 K at a 45° angle between the applied current (I || a) and the applied field (90° is H || c). Approaching 90°, a “dip” is seen in the AMR, which, by analyzing Shubnikov de Haas oscillations at different angles, we find to coincide with a very sharp topological phase transition unlike any seen in other known Dirac/Weyl materials. We find that ZrSiS has a combination of two-dimensional (2D) and 3D Dirac pockets comprising its Fermi surface and that the combination of high-mobility carriers and multiple pockets in ZrSiS allows for large property changes to occur as a function of angle between applied fields. This makes it a promising platform to study the physics stemming from the coexistence of 2D and 3D Dirac electrons as well as opens the door to creating devices focused on switching between different parts of the Fermi surface and different topological states. PMID:28028541

  18. Giant Overlap between the Magnetic and Superconducting Phases of CeAu_{2}Si_{2} under Pressure

    Directory of Open Access Journals (Sweden)

    Z. Ren

    2014-09-01

    Full Text Available High pressure provides a powerful means for exploring unconventional superconductivity which appears mostly on the border of magnetism. Here, we report the discovery of pressure-induced heavy-fermion superconductivity up to 2.5 K in the antiferromanget CeAu_{2}Si_{2} (T_{N}≈10  K. Remarkably, the magnetic and superconducting phases are found to overlap across an unprecedentedly wide pressure interval from 11.8 to 22.3 GPa. Moreover, both the bulk T_{c} and T_{M} are strongly enhanced when increasing the pressure from 16.7 to 20.2 GPa. T_{c} reaches a maximum at a pressure slightly below p_{c}≈22.5  GPa, at which magnetic order disappears. Furthermore, the scaling behavior of the resistivity provides evidence for a continuous delocalization of the Ce 4f electrons associated with a critical end point lying just above p_{c}. We show that the maximum T_{c} of CeAu_{2}Si_{2} actually occurs at almost the same unit-cell volume as that of CeCu_{2}Si_{2} and CeCu_{2}Ge_{2}, and when the Kondo and crystal-field splitting energies become comparable. Dynamical mean-filed theory calculations suggest that the peculiar behavior in pressurized CeAu_{2}Si_{2} might be related to its Ce-4f orbital occupancy. Our results not only provide a unique example of the interplay between superconductivity and magnetism, but also underline the role of orbital physics in understanding Ce-based heavy-fermion systems.

  19. Fabrication of single-phase ε-GaSe films on Si(100) substrate by metal organic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Chia-Chen; Zeng, Jia-Xian; Lan, Shan-Ming [Department of Electronic Engineering, College of Electrical Engineering and Computer Science, Chung Yuan Christian University, Chung-Li 32023, Taiwan (China); Uen, Wu-Yih, E-mail: uenwuyih@ms37.hinet.net [Department of Electronic Engineering, College of Electrical Engineering and Computer Science, Chung Yuan Christian University, Chung-Li 32023, Taiwan (China); Liao, Sen-Mao [Department of Electronic Engineering, College of Electrical Engineering and Computer Science, Chung Yuan Christian University, Chung-Li 32023, Taiwan (China); Yang, Tsun-Neng; Ma, Wei-Yang [Institute of Nuclear Energy Research, P.O. Box 3-11, Lungtan 32500, Taiwan (China); Chang, Kuo-Jen [Chung-Shan Institute of Science and Technology, No.15, Shi Qi Zi, Gaoping Village, Longtan Township, Taoyuan County, Taiwan (China)

    2013-09-02

    Single-phase ε-gallium selenide (GaSe) films were fabricated on Si(100) substrate by metal organic chemical vapor deposition using dual-source precursors: triethylgallium (TEG) and hydrogen selenide (H{sub 2}Se) with the flow ratio of [H{sub 2}Se]/[TEG] being maintained at 1.2. In particular, an arsine (AsH{sub 3}) flow was introduced to the Si substrate before the film deposition to induce an arsenic (As)-passivation effect on the substrate. The crystalline structure of GaSe films prepared was analyzed using X-ray diffraction and the surface morphology of them was characterized by scanning electron microscopy. It was found that the film quality could be improved by the As-passivation effect. The optical properties of the films were studied by temperature dependent photoluminescence (PL) measurements. PL spectra obtained with different distributions and intensities favored for resolving the superior material quality of the films produced on the substrate with As-passivation compared to those produced on the substrate without As-passivation. The former was dominated by the excitonic emissions for the whole temperature range of 20–300 K examined, while the latter was initially dominated by the defect-related emission at 1.907 eV for a low-temperature range ≦ 80 K and then became dominated by the weak excitonic emission band instead. The ε modification of GaSe films prepared was further recognized by the Raman scattering measurements conducted at room temperature. - Highlights: • Gallium selenide (GaSe) layered structures are fabricated on Si(100) substrate. • Metal–organic chemical vapor deposition is used for film fabrication. • Arsenic-passivation effects of Si substrate on the GaSe film quality are analyzed. • Photoluminescence measurements of GaSe polycrystals are reported.

  20. The Faceted Discrete Growth and Phase Differentiation During the Directional Solidification of 20SiMnMo5 Steel

    Science.gov (United States)

    Ma, Xiaoping; Li, Dianzhong

    2018-03-01

    The microstructures, segregation and cooling curve were investigated in the directional solidification of 20SiMnMo5 steel. The typical characteristic of faceted growth is identified. The microstructures within the single cellular and within the single dendritic arm, together with the contradictive segregation distribution against the cooling curve, verify the discrete crystal growth in multi-scales. Not only the single cellular/dendritic arm but also the single martensite zone within the single cellular/dendritic arm is produced by the discrete growth. In the viewpoint of segregation, the basic domain following continuous growth has not been revealed. Along with the multi-scale faceted discrete growth, the phase differentiation happens for both the solid and liquid. The differentiated liquid phases appear and evolve with different sizes, positions, compositions and durations. The physical mechanism for the faceted discrete growth is qualitatively established based on the nucleation of new faceted steps induced by the composition gradient and temperature gradient.

  1. The Faceted Discrete Growth and Phase Differentiation During the Directional Solidification of 20SiMnMo5 Steel

    Science.gov (United States)

    Ma, Xiaoping; Li, Dianzhong

    2018-07-01

    The microstructures, segregation and cooling curve were investigated in the directional solidification of 20SiMnMo5 steel. The typical characteristic of faceted growth is identified. The microstructures within the single cellular and within the single dendritic arm, together with the contradictive segregation distribution against the cooling curve, verify the discrete crystal growth in multi-scales. Not only the single cellular/dendritic arm but also the single martensite zone within the single cellular/dendritic arm is produced by the discrete growth. In the viewpoint of segregation, the basic domain following continuous growth has not been revealed. Along with the multi-scale faceted discrete growth, the phase differentiation happens for both the solid and liquid. The differentiated liquid phases appear and evolve with different sizes, positions, compositions and durations. The physical mechanism for the faceted discrete growth is qualitatively established based on the nucleation of new faceted steps induced by the composition gradient and temperature gradient.

  2. Chiral Spin Texture in the Charge-Density-Wave Phase of the Correlated Metallic Pb /Si (111 ) Monolayer

    Science.gov (United States)

    Tresca, C.; Brun, C.; Bilgeri, T.; Menard, G.; Cherkez, V.; Federicci, R.; Longo, D.; Debontridder, F.; D'angelo, M.; Roditchev, D.; Profeta, G.; Calandra, M.; Cren, T.

    2018-05-01

    We investigate the 1 /3 monolayer α -Pb /Si (111 ) surface by scanning tunneling spectroscopy (STS) and fully relativistic first-principles calculations. We study both the high-temperature √{3 }×√{3 } and low-temperature 3 ×3 reconstructions and show that, in both phases, the spin-orbit interaction leads to an energy splitting as large as 25% of the valence-band bandwidth. Relativistic effects, electronic correlations, and Pb-substrate interaction cooperate to stabilize a correlated low-temperature paramagnetic phase with well-developed lower and upper Hubbard bands coexisting with 3 ×3 periodicity. By comparing the Fourier transform of STS conductance maps at the Fermi level with calculated quasiparticle interference from nonmagnetic impurities, we demonstrate the occurrence of two large hexagonal Fermi sheets with in-plane spin polarizations and opposite helicities.

  3. A new high-pressure phase of Fe2SiO4 and the relationship between spin and structural transitions

    Science.gov (United States)

    Yamanaka, T.; Kyono, A.; Nakamoto, Y.; Kharlamova, S. A.; Struzhkin, V. V.; Gramsch, S.; Mao, H.; Hemley, R. J.

    2013-12-01

    Structure transformation of Fe2SiO4 Angle-dispersive powder x-ray diffraction was carried out at beam line 16-BMD APS. Structure of a new high-pressure phase of I-Fe2SiO4 spinel was determined by Rietveld profile fitting of x-ray diffraction data up to 64GPa at ambient temperature. A structural transition from the cubic spinel to the new structure was observed at 34GPa. Diffraction patterns taken at 44.6GPa and 54.6GPa indicate a two-phase mixture of spinel and new high-pressure phase. Reversible transition from I-Fe2SiO4 to spinel was confirmed. Laser heating experiment at 1500K proved the decomposition of Fe2SiO4 spinel to two oxides of FeO and SiO2. Spin transition X-ray emission measurements of Fe2SiO4 were carried out up to 65GPa at ambient temperature at beam line 16-IDD APS. The spin transition exerts an influence to Fe2SiO4 spinel structure and triggers two distinct curves of the lattice constant in the spinel phase. Although the compression curve of the spinel is discontinuous at approximately 20 GPa, Fe Kβ emission measurements show that the transition from a high spin (HS) to an intermediate spin (IS) state begins at 17GPa in the spinel phase. The IS electronic state is gradually enhanced with pressure, which results in an isostructural phase transition. HS-to-LS transition of iron bearing spinels starts from 15.6GPa in Fe3O4 and 19.6GPa in Fe2TiO4. The transition is more capable due to Fe2+ in the octahedral site. The extremely shortened octahedral bonds result in a distortion of 6-fold cation site. New structure of Fe2SiO4 Monte Carlo method was applied to find candidates for the high-pressure phase using the diffraction intensities with fixed lattice constants determined by DICVOL. Rietveld profile fitting was then performed using the initial model. The new structure is a body centered orthorhombic phase (I-Fe2SiO4) with space group Imma and Z=4, with two crystallographically distinct FeO6 octahedra. Silicon exists in six-fold coordination in I-Fe2Si

  4. Domain wall motion in magnetically frustrated nanorings

    Science.gov (United States)

    Lubarda, M. V.; Escobar, M. A.; Li, S.; Chang, R.; Fullerton, E. E.; Lomakin, V.

    2012-06-01

    We describe a magnetically frustrated nanoring (MFNR) configuration which is formed by introducing antiferromagnetic coupling across an interface orthogonal to the ring's circumferential direction. Such structures have the unique characteristic that only one itinerant domain wall (DW) can exist in the ring, which does not need to be nucleated or injected into the structure and can never escape making it analogous to a magnetic Möbius strip. Numerical simulations show that the DW in a MFNR can be driven consecutively around the ring with a prescribed cyclicity, and that the frequency of revolutions can be controlled by the applied field. The energy landscapes can be controlled to be flat allowing for low fields of operation or to have a barrier for thermal stability. Potential logic and memory applications of MFNRs are considered and discussed.

  5. Magnetic properties of Gd5(Si1.5Ge2.5) near the temperature and magnetic field induced first order phase transition

    International Nuclear Information System (INIS)

    Levin, E.M.; Gschneidner, K.A.; Pecharsky, V.K.

    2001-01-01

    The temperature (from 5 to 300 K) and DC magnetic field (from 0 to 90 kOe) dependencies of the DC magnetization and magnetic susceptibility, and the temperature (from 5 to 350 K) dependency of the AC magnetic susceptibility of Gd 5 (Si 1.5 Ge 2.5 ) have been studied. The temperature and/or magnetic field induced magnetic phase transition in Gd 5 (Si 1.5 Ge 2.5 ) is a first order ferromagnet-paramagnet transition. The temperature of the magnetic transition in low AC magnetic field is 206 and 217 K for cooling and heating, respectively. The DC magnetic field increases the transition temperature by ∼0.36 K/kOe indicating that the paramagnetic phase can be reversibly transformed into the ferromagnetic phase. When the magnetic field is removed, the ferromagnetic phase transforms into the paramagnetic phase showing a large remanence-free hysteresis. The magnetic phase diagram based on the isothermal magnetic field dependence of the DC magnetization at various temperatures for Gd 5 (Si 1.5 Ge 2.5 ) is proposed. The magnetic field dependence of the magnetization in the vicinity of the first order phase transition shows evidence for the formation of a magnetically heterogeneous system in the volume of Gd 5 (Si 1.5 Ge 2.5 ) specimen where the magnetically ordered (ferromagnetic) and disordered (paramagnetic) phases co-exist

  6. Thermal stability of (AlSi)x(ZrVTi) intermetallic phases in the Al–Si–Cu–Mg cast alloy with additions of Ti, V, and Zr

    International Nuclear Information System (INIS)

    Shaha, S.K.; Czerwinski, F.; Kasprzak, W.; Friedman, J.; Chen, D.L.

    2014-01-01

    Highlights: • Al–Si–Cu–Mg alloy was modified by introducing Zr, V, and Ti. • The chemistry of the phases was identified using SEM/EDX. • The crystal lattice parameters of the phases were characterized using EBSD. • To investigate the phase stability, XRD was performed up to 600 °C. • Thermal analysis was done to find out the possible phase transformation reactions. - Abstract: The Al–Si–Cu–Mg cast alloy was modified with additions of Ti–V–Zr to improve the thermal stability of intermetallics at increased temperatures. A combination of electron microscopy, electron backscatter diffraction, and high temperature X-ray diffraction was explored to identify phases and temperatures of their thermal stability. The micro-additions of transition metals led to formation of several (AlSi) x (TiVZr) phases with D0 22 /D0 23 tetragonal crystal structure and different lattice parameters. While Cu and Mg rich phases along with the eutectic Si dissolved at temperatures from 300 to 500 °C, the (AlSi) x (TiVZr) phases were stable up to 696–705 °C which is the beneficial to enhance the high temperature properties. Findings of this study are useful for selecting temperatures during melting and heat treatment of Al–Si alloys with additions of transition metals

  7. Photoluminescence studies of cubic phase GaN grown by molecular beam epitaxy on (001) silicon covered with SiC layer

    International Nuclear Information System (INIS)

    Godlewski, M.; Ivanov, V.Yu.; Bergman, J.P.; Monemar, B.; Barski, A.; Langer, R.

    1997-01-01

    In this work we evaluate optical properties of cubic phase GaN epilayers grown on top of (001) silicon substrate prepared by new process. Prior to the growth Si substrate was annealed at 1300-1400 o C in propane. The so-prepared substrate is covered within a thin (∼ 4 nm) SiC wafer, which allowed a successful growth of good morphological quality cubic phase GaN epilayers. The present results confirm recent suggestion on smaller ionization energies of acceptors in cubic phase GaN epilayers. (author)

  8. The 480 deg. C and 405 deg. C isothermal sections of the phase diagram of Fe-Zn-Si ternary system

    Energy Technology Data Exchange (ETDEWEB)

    Wang Jianhua [Institute of Materials Research, School of Mechanical Engineering, Xiangtan University, Hunan 411105 (China)]. E-mail: super_wang111@hotmail.com; Su Xuping [Institute of Materials Research, School of Mechanical Engineering, Xiangtan University, Hunan 411105 (China); Yin Fucheng [Institute of Materials Research, School of Mechanical Engineering, Xiangtan University, Hunan 411105 (China); Li Zhi [Institute of Materials Research, School of Mechanical Engineering, Xiangtan University, Hunan 411105 (China); Zhao Manxiu [Institute of Materials Research, School of Mechanical Engineering, Xiangtan University, Hunan 411105 (China)

    2005-08-16

    The 480 deg. C and 405 deg. C isothermal sections of the Fe-Zn-Si ternary phase diagram have been determined experimentally using scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS) and X-ray diffractometry. The research of the work has concentrated on the Zn-rich corner, which is relevant to general galvanizing. The present studies have confirmed the existence of equilibrium state between the liquid, the {zeta} phase and the FeSi phase at the 480 deg. C isothermal section. There exist some changes in the phase relationships compared with the isothermal section at 450 deg. C. Experimental results indicate that Si solubility in all four Zn-Fe compounds is also limited at 480 deg. C and 405 deg. C.

  9. Study of alkylphenols, indol and pyridinic nucleus of HPAN compounds by SPE/SI and SPE/C{sub 18}/NEC: application of SPE/Si phase to oils from the Alagoas sub-basin

    Energy Technology Data Exchange (ETDEWEB)

    Reboucas, L.M.C.; Nogueira, F.A.R.; Sabino, A.R.; Araujo, O.R.P.; Sant' Ana, A.E.G. [Universidade Federal de Alagoas (LABIS/UFAL), Maceio, AL (Brazil). Inst. de Quimica e Biotecnologia. Lab. de Analise de Biomarcadores e Semioquimicos], E-mail: lmcr@qui.ufal.br

    2008-10-15

    Alkylphenols (AP) and hydrocarbon polycyclic aromatic nitrogen (HPAN) compounds are important to study secondary migrations of petroleum. The behavior of AP and HPAN standards was investigated by solid phase extraction (SPE) on silica gel (SPE/Si) and C{sub 18}/NEC (SPE/C{sub 18}) stationary phases. The AP standards were eluted with dichloromethane (DCM) in the F2 fraction, on both SPE/Si and SPE/C{sub 18} phases. The basic and neutral HPAN compounds were eluted together with DCM, in F2 fraction, when a SPE/C18 column was used. However in the SPE/Si column the HPAN compounds were separated by their basic and neutral character in two different fractions. The neutral HPAN compounds were eluted with DCM, F2 fraction, and the HPAN basic compounds were eluted with the mixture DCM:isopropanol 5%, F3 fraction. In general, the quantity of recovered AP and HPAN compounds was higher with SPE/Si than SPE/C{sub 18}. The nine oil samples were analyzed by SPE/Si and the saturated and aromatic hydrocarbon were separated from the polar AP and HPAN. (author)

  10. Characterizing and quantifying frustration in quantum many-body systems.

    Science.gov (United States)

    Giampaolo, S M; Gualdi, G; Monras, A; Illuminati, F

    2011-12-23

    We present a general scheme for the study of frustration in quantum systems. We introduce a universal measure of frustration for arbitrary quantum systems and we relate it to a class of entanglement monotones via an exact inequality. If all the (pure) ground states of a given Hamiltonian saturate the inequality, then the system is said to be inequality saturating. We introduce sufficient conditions for a quantum spin system to be inequality saturating and confirm them with extensive numerical tests. These conditions provide a generalization to the quantum domain of the Toulouse criteria for classical frustration-free systems. The models satisfying these conditions can be reasonably identified as geometrically unfrustrated and subject to frustration of purely quantum origin. Our results therefore establish a unified framework for studying the intertwining of geometric and quantum contributions to frustration.

  11. Equivalence of electronic and mechanical stresses in structural phase stabilization: A case study of indium wires on Si(111)

    Science.gov (United States)

    Kim, Sun-Woo; Kim, Hyun-Jung; Ming, Fangfei; Jia, Yu; Zeng, Changgan; Cho, Jun-Hyung; Zhang, Zhenyu

    2015-05-01

    It was recently proposed that the stress state of a material can also be altered via electron or hole doping, a concept termed electronic stress (ES), which is different from the traditional mechanical stress (MS) due to lattice contraction or expansion. Here we demonstrate the equivalence of ES and MS in structural stabilization, using In wires on Si(111) as a prototypical example. Our systematic density-functional theory calculations reveal that, first, for the same degrees of carrier doping into the In wires, the ES of the high-temperature metallic 4 ×1 structure is only slightly compressive, while that of the low-temperature insulating 8 ×2 structure is much larger and highly anisotropic. As a consequence, the intrinsic energy difference between the two phases is significantly reduced towards electronically phase-separated ground states. Our calculations further demonstrate quantitatively that such intriguing phase tunabilities can be achieved equivalently via lattice-contraction induced MS in the absence of charge doping. We also validate the equivalence through our detailed scanning tunneling microscopy experiments. The present findings have important implications for understanding the underlying driving forces involved in various phase transitions of simple and complex systems alike.

  12. Crystal structure and defects of Zr4Co4Si7( V-phase) investigated by high resolution transmission electron microscope

    International Nuclear Information System (INIS)

    Mao, J.F.; Ye, H.Q.; Ning, X.G.; He, L.L.; Yang, D.Z.

    1997-01-01

    The results of high resolution transmission electron microscope (HRTEM) observation and image simulation show that Zr 4 Co 4 Si 7 possesses the same structure type of Zr 4 Co 4 Ge 7 . Adding of Fe or Ni into the Zr 4 Co 4 Si 7 compound, except that the dimensions changed slightly, does not change the lattice type and coordination in the crystal structure, maintaining the V-phase structure. Also, twins with coherent boundaries and with partially coherent at interfaces are observed. The image conditions of Zr 4 Co 4 Si 7 and the structure differences between Zr 4 Co 4 Si 7 and tetrahedral close-packed phases are also discussed. copyright 1997 Materials Research Society

  13. Evaluation of liquid-phase sintering SiC using as additive the system Al2O3/DyO3

    International Nuclear Information System (INIS)

    Oliveira, M.R.; Atilio, I.; Garcia, G.C.R.; Ribeiro, S.

    2012-01-01

    The objective of this work was to study the liquid-phase sintering SiC with additives that has not been studied yet, Al 2 O 3 /Dy 2 O 3 , with 10% in volume. The powders were mixed, dried, and pressed in uniaxial and isostatic pressing. It was studied the melting temperature of the additives and bars were sintered at temperatures of 1900, 1950 e 2000 deg C, with averaged linear shrinkage of 17%, phase transformations of β-SiC into α-SiC and formation of Dy 3 Al 5 O 12 at all temperatures. The results showed that for further densification, the temperature of 1950 deg C is enough for a higher densification, with a low wetting angle, transformations of SiC and formation of Dy 3 Al 5 O 12 . (author)

  14. Field-induced cluster spin glass and inverse symmetry breaking enhanced by frustration

    Science.gov (United States)

    Schmidt, M.; Zimmer, F. M.; Magalhaes, S. G.

    2018-03-01

    We consider a cluster disordered model to study the interplay between short- and long-range interactions in geometrically frustrated spin systems under an external magnetic field (h). In our approach, the intercluster long-range disorder (J) is analytically treated to get an effective cluster model that is computed exactly. The clusters follow a checkerboard lattice with first-neighbor (J1) and second-neighbor (J2) interactions. We find a reentrant transition from the cluster spin-glass (CSG) state to a paramagnetic (PM) phase as the temperature decreases for a certain range of h. This inverse symmetry breaking (ISB) appears as a consequence of both quenched disorder with frustration and h, that introduce a CSG state with higher entropy than the polarized PM phase. The competitive scenario introduced by antiferromagnetic (AF) short-range interactions increases the CSG state entropy, leading to continuous ISB transitions and enhancing the ISB regions, mainly in the geometrically frustrated case (J1 =J2). Remarkably, when strong AF intracluster couplings are present, field-induced CSG phases can be found. These CSG regions are strongly related to the magnetization plateaus observed in this cluster disordered system. In fact, it is found that each field-induced magnetization jump brings a CSG region. We notice that geometrical frustration, as well as cluster size, play an important role in the magnetization plateaus and, therefore, are also relevant in the field-induced glassy states. Our findings suggest that competing interactions support ISB and field-induced CSG phases in disordered cluster systems under an external magnetic field.

  15. Constituent phase diagrams of the Al-Cu-Fe-Mg-Ni-Si system and their application to the analysis of aluminium piston alloys

    Energy Technology Data Exchange (ETDEWEB)

    Belov, N.A. [Moscow Institute of Steel and Alloys, Leninsky prosp. 4, Moscow 119049 (Russian Federation); Eskin, D.G. [Netherlands Institute for Metals Research, Rotterdamseweg 137, 2628AL Delft (Netherlands)]. E-mail: deskin@nimr.nl; Avxentieva, N.N. [Moscow Institute of Steel and Alloys, Leninsky prosp. 4, Moscow 119049 (Russian Federation)

    2005-10-15

    The evaluation of phase equilibria in quinary systems that constitute the commercially important Al-Cu-Fe-Mg-Ni-Si alloying system is performed in the compositional range of casting alloys by means of metallography, electron probe microanalysis, X-ray diffractometry, differential scanning calorimetry, and by the analysis of phase equilibria in the constituent systems of lesser dimensionality. Suggested phase equilibria are illustrated by bi-, mono- and invariant solidification reactions, polythermal diagrams of solidification, distributions of phase fields in the solid state, and isothermal and polythermal sections. Phase composition of as-cast alloys is analyzed in terms of non-equilibrium solidification. It is shown that the increase in copper concentration in piston Al-Si alloys results in the decrease in the equilibrium solidus from 540 to 505 deg C. Under non-equilibrium solidification conditions, piston alloys finish solidification at {approx}505 deg C. Iron is bound in the quaternary Al{sub 8}FeMg{sub 3}Si{sub 6} phase in low-iron alloys and in the ternary Al{sub 9}FeNi and Al{sub 5}FeSi phases in high-iron alloys.

  16. Magnetic phase diagram of UNi.sub.2./sub.Si.sub.2./sub. under pressure

    Czech Academy of Sciences Publication Activity Database

    Syshchenko, O.; Khmelevski, S.; Diviš, M.; Sechovský, V.; Honda, F.; Oomi, G.; Andreev, Alexander V.; Kamarád, Jiří; Šebek, Josef; Menovsky, A. A.

    2001-01-01

    Roč. 304, - (2001), s. 477-482 ISSN 0921-4526 R&D Projects: GA ČR GA106/99/0183 Institutional research plan: CEZ:AV0Z1010914 Keywords : U intermetallics * antiferromagnetism * magnetic phase diagram * electrical resistivity * pressure effects on magnetic phases * axial Ising model Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.663, year: 2001

  17. Effects of Sublattice Symmetry and Frustration on Ionic Transport in Garnet Solid Electrolytes

    Science.gov (United States)

    Kozinsky, Boris; Akhade, Sneha A.; Hirel, Pierre; Hashibon, Adham; Elsässer, Christian; Mehta, Prateek; Logeat, Alan; Eisele, Ulrich

    2016-02-01

    We use rigorous group-theoretic techniques and molecular dynamics to investigate the connection between structural symmetry and ionic conductivity in the garnet family of solid Li-ion electrolytes. We identify new ordered phases and order-disorder phase transitions that are relevant for conductivity optimization. Ionic transport in this materials family is controlled by the frustration of the Li sublattice caused by incommensurability with the host structure at noninteger Li concentrations, while ordered phases explain regions of sharply lower conductivity. Disorder is therefore predicted to be optimal for ionic transport in this and other conductor families with strong Li interaction.

  18. Stability of the high pressure phase Fe3S2 up to Earth's core pressures in the Fe-S-O and the Fe-S-Si systems

    Science.gov (United States)

    Zurkowski, C. C.; Chidester, B.; Davis, A.; Brauser, N.; Greenberg, E.; Prakapenka, V. B.; Campbell, A.

    2017-12-01

    Earth's core is comprised of an iron-nickel alloy that contains 5-15% of a light element component. The abundance and alloying capability of sulfur, silicon and oxygen in the bulk Earth make them important core alloy candidates; therefore, the high-pressure phase equilibria of the Fe-S-O and Fe-S-Si systems are relevant for understanding the possible chemistry of Earth's core. Previously, a Fe3S2 phase was recognized as a low-pressure intermediate phase in the Fe-FeS system that is stable from 14-21 GPa, but the structure of this phase has not been resolved. We report in-situ XRD and chemical analysis of recovered samples to further examine the stability and structure of Fe3S2 as it coexists with other phases in the Fe-S-O and Fe-S-Si systems. In situ high P-T synchrotron XRD experiments were conducted in the laser-heated diamond anvil cell to determine the equilibrium phases in Fe75S7O18 and Fe80S5Si15 compositions between 30 and 174 GPa and up to 3000 K. In the S,O-rich samples, an orthorhombic Fe3S2 phase coexists with hcp-Fe, Fe3S and FeO and undergoes two monoclinic distortions between 60 and 174 GPa. In the S,Si-rich samples, the orthorhombic Fe3S2 phase was observed up to 115 GPa. With increasing pressure, the Fe3S2 phase becomes stable to higher temperatures in both compositions, suggesting possible Fe3(S,O)2 or Fe3(S,Si)2 solid solutions. SEM analysis of a laser heated Fe75S7O18 sample recovered from 40 GPa and 1450 K confirms a Fe3(S,O)2 phase with O dissolved into the structure. Based on the current melting data in the Fe-S-O and Fe-S-Si systems, the Fe3(S,O)2 stability field intersects the solidus in the outer core and could be a possible liquidus phase in Fe,S,O-rich planetary cores, whereas Fe3S is the stable sulfide at outer core pressures in Fe,S,Si-rich systems.

  19. Changes of optical, dielectric, and structural properties of Si15Sb85 phase change memory thin films under different initializing laser power

    International Nuclear Information System (INIS)

    Huang Huan; Zhang Lei; Wang Yang; Han Xiaodong; Wu Yiqun; Zhang Ze; Gan Fuxi

    2011-01-01

    Research highlights: → We study the optical, dielectric, and structural characteristics of Si 15 Sb 85 phase change memory thin films under a moving continuous-wave laser initialization. → The optical and dielectric constants, absorption coefficient of Si 15 Sb 85 change regularly with the increasing laser power. → The optical band gaps of Si 15 Sb 85 irradiated upon different power lasers were calculated. → HRTEM images of the samples were observed and the changes of optical and dielectric constants are determined by crystalline structures changes of the films. - Abstract: The optical, dielectric, and structural characteristics of Si 15 Sb 85 phase change memory thin films under a moving continuous-wave laser initialization are studied by using spectroscopic ellipsometry and high-resolution transmission electron microscopy. The dependence of complex refractive index, dielectric functions, absorption coefficient, and optical band gap of the films on its crystallization extents formed by the different initialization laser power are analyzed in detail. The structural change from as-deposited amorphous phase to distorted rhombohedra-Sb-like crystalline structure with the increase of initialization laser power is clearly observed with sub-nanometer resolution. The optical and dielectric constants, the relationship between them, and the local atomic arrangements of this new phase change material can help explain the phase change mechanism and design the practical phase change memory devices.

  20. Kinetic study of the formation of the superconducting A15 phase in the Nb-Al-Si system

    International Nuclear Information System (INIS)

    Binh-Phung.

    1978-12-01

    So far, aluminum-containing superconductors showed excellent critical fields and temperatures. Powder Metallurgy shows the most promise in producing these particular kinds of superconductors in the near future. The scope of this research is to apply a kinetic study to observe the behavior of the Nb(Al,Si) system at elevated temperatures. From such observations, an optimized method of obtaining the A15 superconducting phase can be achieved. This study has resulted in a two step heat treatment to obtain the A15 phase. For the primary heat treatment of infiltrated rods, 600 0 C for 11 hours or 650 0 C for 1 hour was found suitable to form a barrier of intermetallic compound around the pores. For the secondary heat treatment, 1700 0 C for 15 seconds resulted in the formation of the A15 superconducting phase with a critical temperature of 18.25 0 K. A15 formation for wires is similar to infiltrated rods. The only difference is the diffusion path which is now much shorter. 600 0 C for 1 hour was found suitable for the primary heat treatment and 1700 0 C for 15 seconds was the most suitable for the secondary heat treatment. The highest critical temperature found thus far was 18.78 0 K

  1. Influence of Laser Welding Speed on the Morphology and Phases Occurring in Spray-Compacted Hypereutectic Al-Si-Alloys

    Directory of Open Access Journals (Sweden)

    Thomas Gietzelt

    2016-11-01

    Full Text Available Normally, the weldability of aluminum alloys is ruled by the temperature range of solidification of an alloy according to its composition by the formation of hot cracks due to thermal shrinkage. However, for materials at nonequilibrium conditions, advantage can be taken by multiple phase formation, leading to an annihilation of temperature stress at the microscopic scale, preventing hot cracks even for alloys with extreme melting range. In this paper, several spray-compacted hypereutectic aluminum alloys were laser welded. Besides different silicon contents, additional alloying elements like copper, iron and nickel were present in some alloys, affecting the microstructure. The microstructure was investigated at the delivery state of spray-compacted material as well as for a wide range of welding speeds ranging from 0.5 to 10 m/min, respectively. The impact of speed on phase composition and morphology was studied at different disequilibrium solidification conditions. At high welding velocity, a close-meshed network of eutectic Al-Si-composition was observed, whereas the matrix is filled with nearly pure aluminum, helping to diminish the thermal stress during accelerated solidification. Primary solidified silicon was found, however, containing considerable amounts of aluminum, which was not expected from phase diagrams obtained at the thermodynamic equilibrium.

  2. Phase-field modeling of Mn-Ni-Si precipitate behavior on the bcc-Fe matrix

    International Nuclear Information System (INIS)

    Chang, Kun Ok; Kwon, Jun Hyun

    2016-01-01

    The formation of Mn-Ni-Si precipitate (hereafter MNS precipitate) is widely accepted by one of the main reasons of late stage hardening and embrittlement of Reactor Pressure Vessel (RPV) during nuclear power plant (NPP) operation. Since MNS precipitate is not considered in current regulatory model, this late stage hardening can be a limiting factor for life extension of nuclear power plants up to 80 or more years. The stability of the MNS precipitate was investigated from the thermodynamic view point and they concluded that MNS precipitate is a stable phase even with very little Cu contents, and they assessed UW1 thermodynamic database which can predict the thermodynamic stability of MNS precipitate at operating temperature of NPP ( ∼ 290 .deg. C). Based on the non-classical nucleation theory, we performed the phase-field modeling of nucleation and growth of MNS precipitate. The microstructure evolution of Mn-Ni-Cu precipitate has been simulated using the phase-field method and their approaches are focused on a role of the Cu contents. Also, a role of the interstitial loop on the nucleation and growth kinetics of MNS precipitate was analyzed.

  3. The Mg{sub 2}Si phase evolution during thermomechanical processing of in-situ aluminum matrix macro-composite

    Energy Technology Data Exchange (ETDEWEB)

    Shafieizad, A.H. [The Complex Laboratory of Hot Deformation & Thermomechanical Processing of High Performance Engineering Materials, School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Zarei-Hanzaki, A., E-mail: Zareih@ut.ac.ir [The Complex Laboratory of Hot Deformation & Thermomechanical Processing of High Performance Engineering Materials, School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Abedi, H.R. [The Complex Laboratory of Hot Deformation & Thermomechanical Processing of High Performance Engineering Materials, School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Al-Fadhalah, K.J. [Department of Mechanical Engineering, College of Engineering & Petroleum, Kuwait University, P.O. Box 5969, Safat 13060 (Kuwait)

    2015-09-17

    The microstructure and flow stress behavior of thermomechanically processed Al–Cu/Mg{sub 2}Si in-situ composite was studied emphasizing the evolution of primary and secondary reinforcement phases. Toward this end, the hot compression tests were conducted over the wide range of temperature (300–500 °C) and strain rate (0.001–0.1 s{sup −1}). Both the temperature and strain rate are found to possess a significant effect on the microstructural characteristics where a considerable softening is identified specially at low temperature regime. Besides the occurrence of restoration processes (mainly particle stimulated nucleation) the dynamic evolution of the reinforcements is introduced as the main factors affecting the reported softening. In this regard, the mechanical fragmentation, thermal disintegration, micro-buckling, coalescence and spheroidization of the primary and secondary particles are quantitatively and qualitatively addressed through a comprehensive scanning electron microscopy studies.

  4. Silicon transport under rotating and combined magnetic fields in liquid phase diffusion growth of SiGe

    Energy Technology Data Exchange (ETDEWEB)

    Armour, N.; Dost, S. [Crystal Growth Laboratory, University of Victoria, Victoria, BC, V8W 3P6 (Canada)

    2010-04-15

    The effect of applied rotating and combined (rotating and static) magnetic fields on silicon transport during the liquid phase diffusion growth of SiGe was experimentally studied. 72-hour growth periods produced some single crystal sections. Single and polycrystalline sections of the processed samples were examined for silicon composition. Results show that the application of a rotating magnetic field enhances silicon transport in the melt. It also has a slight positive effect on flattening the initial growth interface. For comparison, growth experiments were also conducted under combined (rotating and static) magnetic fields. The processed samples revealed that the addition of static field altered the thermal characteristics of the system significantly and led to a complete melt back of the germanium seed. Silicon transport in the melt was also enhanced under combined fields compared with experiments with no magnetic field. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Effect of a static magnetic field on silicon transport in liquid phase diffusion growth of SiGe

    Energy Technology Data Exchange (ETDEWEB)

    Armour, N.; Dost, S. [Crystal Growth Laboratory, University of Victoria, Victoria, BC V8W 3P6 (Canada)

    2010-03-15

    Liquid phase diffusion experiments have been performed without and with the application of a 0.4 T static magnetic field using a three-zone DC furnace system. SiGe crystals were grown from the germanium side for a period of 72 h. Experiments have led to the growth of single crystal sections varying from 0 to 10 mm thicknesses. Examination of the processed samples (single and polycrystalline sections) has shown that the effect of the applied static magnetic field is significant. It alters the temperature distribution in the system, reduces mass transport in the melt, and leads to a much lower growth rate. The initial curved growth interface was slightly flattened under the effect of magnetic field. There were no growth striations in the single crystal sections of the samples. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Anomalous optical switching and thermal hysteresis during semiconductor-metal phase transition of VO2 films on Si substrate

    International Nuclear Information System (INIS)

    Leahu, G.; Li Voti, R.; Sibilia, C.; Bertolotti, M.

    2013-01-01

    We present a detailed infrared study of the semiconductor-to-metal transition (SMT) in a vanadium dioxide (VO 2 ) film deposited on silicon wafer. The VO 2 phase transition is studied in the mid-infrared region by analyzing the transmittance and the reflectance measurements, and the calculated emissivity. The reflectance has been measured in two configurations: from the side of the VO 2 film and from that of Si wafer. The results show a strong asymmetry between the emissivity in the two configurations, and the fact that the emissivity dynamic range from the silicon side is twice as large than that from the VO 2 side. The temperature behaviour of the emissivity during the SMT put into evidence the phenomenon of the anomalous absorption in VO 2 , which has been explained by applying the Maxwell Garnett effective medium approximation theory

  7. SiC MOSFET Based Single Phase Active Boost Rectifier with Power Factor Correction for Wireless Power Transfer Applications

    Energy Technology Data Exchange (ETDEWEB)

    Onar, Omer C [ORNL; Tang, Lixin [ORNL; Chinthavali, Madhu Sudhan [ORNL; Campbell, Steven L [ORNL; Miller (JNJ), John M. [JNJ-Miller PLC

    2014-01-01

    Wireless Power Transfer (WPT) technology is a novel research area in the charging technology that bridges the utility and the automotive industries. There are various solutions that are currently being evaluated by several research teams to find the most efficient way to manage the power flow from the grid to the vehicle energy storage system. There are different control parameters that can be utilized to compensate for the change in the impedance due to variable parameters such as battery state-of-charge, coupling factor, and coil misalignment. This paper presents the implementation of an active front-end rectifier on the grid side for power factor control and voltage boost capability for load power regulation. The proposed SiC MOSFET based single phase active front end rectifier with PFC resulted in >97% efficiency at 137mm air-gap and >95% efficiency at 160mm air-gap.

  8. The system Ta-V-Si: Crystal structure and phase equilibria

    Czech Academy of Sciences Publication Activity Database

    Khan, A.U.; Brož, P.; Niu, H.Y.; Buršík, Jiří; Grytsiv, A.; Chen, X.-Q.; Giester, G.; Rogl, P.

    2012-01-01

    Roč. 187, - (2012), s. 114-123 ISSN 0022-4596 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0068 Institutional research plan: CEZ:AV0Z20410507 Keywords : ternary alloy system * microstructure * phase diagram Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.040, year: 2012

  9. Synthesis of PANi-SiO2 Nanocomposite with In-Situ Polymerization Method: Nanoparticle Silica (NPS) Amorphous and Crystalline Phase

    Science.gov (United States)

    Munasir; Luvita, N. R. D.; Kusumawati, D. H.; Putri, N. P.; Triwikantoro; Supardi, Z. A. I.

    2018-03-01

    Silica which is synthesized from natural materials such as Bancar Tuban’s sand composited with Polyaniline (PANi), where the silica used are silica has an amorphous phase and cristobalite phase. In this research, the composite method used is in- situ polymerization, which is silica entered during the fabrication of PANi, then automatically silica will be substitute into the chain bonding of PANi. The aim of this research is to find out the results of a composite process using in-situ methods as well as differences in the morphology of PANi/a- SiO2 and PANi/c-SiO2. For the characterization of samples tested in the form of FTIR to determine the functional groups of the composite and SEM to determine the morphology of the sample. From the test results of FTIR are known composite possibility has occurred because there are several functional groups belonging to silica also functional groups belonging polyaniline, functional group that’s happened in wave numbers were almost identical between PANi/a-SiO2 and PANi/c-SiO2, but there are little differences were seen in the form of a graph generated from the peak and intensity that occurred charts for PANi/c-SiO2 has peak more pointed or sharp compared to PANi/a-SiO2 because that bond of crystal is strong, stiff and has a larger particle size than the amorphous composite. Then from the data of SEM seen clearly their morphological differences between PANi/a-SiO2 and PANi/c-SiO2 where polyaniline is composited with amorphous silica will have a fault that is not uniform or irregular different from PANi/c -SiO2 has a regular fault and this is corresponding with the nature of the typical structure of amorphous and crystalline.

  10. Edge currents in frustrated Josephson junction ladders

    Science.gov (United States)

    Marques, A. M.; Santos, F. D. R.; Dias, R. G.

    2016-09-01

    We present a numerical study of quasi-1D frustrated Josephson junction ladders with diagonal couplings and open boundary conditions, in the large capacitance limit. We derive a correspondence between the energy of this Josephson junction ladder and the expectation value of the Hamiltonian of an analogous tight-binding model, and show how the overall superconducting state of the chain is equivalent to the minimum energy state of the tight-binding model in the subspace of one-particle states with uniform density. To satisfy the constraint of uniform density, the superconducting state of the ladder is written as a linear combination of the allowed k-states of the tight-binding model with open boundaries. Above a critical value of the parameter t (ratio between the intra-rung and inter-rung Josephson couplings) the ladder spontaneously develops currents at the edges, which spread to the bulk as t is increased until complete coverage is reached. Above a certain value of t, which varies with ladder size (t = 1 for an infinite-sized ladder), the edge currents are destroyed. The value t = 1 corresponds, in the tight-binding model, to the opening of a gap between two bands. We argue that the disappearance of the edge currents with this gap opening is not coincidental, and that this points to a topological origin for these edge current states.

  11. Silicon Carbide (SiC) Device and Module Reliability, Performance of a Loop Heat Pipe Subjected to a Phase-Coupled Heat Input to an Acceleration Field

    Science.gov (United States)

    2016-05-01

    AFRL-RQ-WP-TR-2016-0108 SILICON CARBIDE (SiC) DEVICE AND MODULE RELIABILITY Performance of a Loop Heat Pipe Subjected to a Phase-Coupled...CARBIDE (SiC) DEVICE AND MODULE RELIABILITY Performance of a Loop Heat Pipe Subjected to a Phase-Coupled Heat Input to an Acceleration Field 5a...Shukla, K., “Thermo-fluid dynamics of Loop Heat Pipe Operation,” International Communications in Heat and Mass Transfer , Vol. 35, No. 8, 2008, pp

  12. Disintegration of the net-shaped grain-boundary phase by multi-directional forging and its influence on the microstructure and properties of Cu-Ni-Si alloy

    Science.gov (United States)

    Zhang, Jinlong; Lu, Zhenlin; Zhao, Yuntao; Jia, Lei; Xie, Hui; Tao, Shiping

    2017-09-01

    Cu-Ni-Si alloys with 90% Cu content and Ni to Si ratios of 5:1 were fabricated by fusion casting, and severe plastic deformation of the Cu-Ni-Si alloy was carried out by multi-direction forging (MDF). The results showed that the as-cast and homogenized Cu-Ni-Si alloys consisted of three phases, namely the matrix phase α-Cu (Ni, Si), the reticular grain boundary phase Ni31Si12 and the precipitated phase Ni2Si. MDF significantly destroyed the net-shaped grain boundary phase, the Ni31Si12 phase and refined the grain size of the Cu matrix, and also resulted in the dissolving of Ni2Si precipitates into the Cu matrix. The effect of MDF on the conductivity of the solid solution Cu-Ni-Si alloy was very significant, with an average increase of 165.16%, and the hardness of the Cu-Ni-Si alloy also increased obviously.

  13. Quantitative analysis of crystalline and remaining glass phases in CaO-B2O3-SiO2 ternary system glass ceramics

    International Nuclear Information System (INIS)

    He Ming; Wu Mengqiang; Zhang Shuren; Zhou Xiaohua; Zhang Ting; Chen Song

    2010-01-01

    Research highlights: → As for CBS ternary system glass ceramics, due to the complex phase compositions, many methods could be difficult to determine quantitatively the absolute amounts of crystalline and remaining oxides. In this study, an available method based on the Rietveld method was used to quantitatively analyze the relative weight fraction and densities of crystalline phases. These above data are used to obtain a table of both relative weight fraction of crystalline phases and densities of all phases including CBS LTCC. Using volume additivity rule, it is possible to analysis quantitatively the absolute weight fraction of crystalline phases and also the oxides molar content in the remaining glass. - Abstract: Based on Rietveld method of X-ray techniques and volume additivity rule, a new method was developed to quantitatively analyze the phase composition of CaO-B 2 O 3 -SiO 2 ternary system glass ceramics. Lattice parameters, densities and relative weight fractions of crystalline phases in CaO-B 2 O 3 -SiO 2 ternary system were obtained by X-ray diffraction (XRD) refinement. According to the relative weight fraction of crystalline phases and densities of various components, the volume additivity rule was revealed by calculating the absolute weight fraction of crystalline phases of CaO-B 2 O 3 -SiO 2 glass ceramics. In addition, molar contents of the oxides in the remaining glass can also be determined by this method. Comparing this method with internal standard method, it is found that the maximum deviations of the crystallinity and the absolute weight fraction of crystalline phases are less than 2.6% and 2.9%, respectively. As a result, quantitative evaluation of CaO-B 2 O 3 -SiO 2 ternary system glass ceramics can be achieved using this method.

  14. Study of the time evolution of correlation functions of the transverse Ising chain with ring frustration by perturbative theory

    Science.gov (United States)

    Zheng, Zhen-Yu; Li, Peng

    2018-04-01

    We consider the time evolution of two-point correlation function in the transverse-field Ising chain (TFIC) with ring frustration. The time-evolution procedure we investigated is equivalent to a quench process in which the system is initially prepared in a classical kink state and evolves according to the time-dependent Schrödinger equation. Within a framework of perturbative theory (PT) in the strong kink phase, the evolution of the correlation function is disclosed to demonstrate a qualitatively new behavior in contrast to the traditional case without ring frustration.

  15. d-wave superconductivity in the frustrated two-dimensional periodic Anderson model

    Directory of Open Access Journals (Sweden)

    Wei Wu

    2015-02-01

    Full Text Available Superconductivity in heavy-fermion materials can sometimes appear in the incoherent regime and in proximity to an antiferromagnetic quantum critical point. Here, we study these phenomena using large-scale determinant quantum Monte Carlo simulations and the dynamical cluster approximation with various impurity solvers for the periodic Anderson model with frustrated hybridization. We obtain solid evidence for a d_{x^{2}−y^{2}} superconducting phase arising from an incoherent normal state in the vicinity of an antiferromagnetic quantum critical point. There is a coexistence region, and the width of the superconducting dome increases with frustration. Through a study of the pairing dynamics, we find that the retarded spin fluctuations give the main contribution to the pairing glue. These results are relevant for unconventional superconductivity in the Ce-115 family of heavy fermions.

  16. On the Fluctuations that Order and Frustrate Liquid Water

    Science.gov (United States)

    Limmer, David Tyler

    At ambient conditions, water sits close to phase coexistence with its crystal. More so than in many other materials, this fact is manifested in the fluctuations that maintain a large degree of local order in the liquid. These fluctuations and how they result in long-ranged order, or its absence, are emergent features of many interacting molecules. Their study therefore requires using the tools of statistical mechanics for their their systematic understanding. In this dissertation we develop such an understanding. In particular, we focus on collective behavior that emerges in liquid and solid water. At room temperatures, the thermophysical properties of water are quantified and rationalized with simple molecular models. A key feature of these models is the correct characterization of the competition between entropic forces of packing and the energetic preference for tetrahedral order. At cold temperatures, the properties of ice surfaces are studied with statistical field theory. The theory we develop for the long wavelength features of ice interfaces allows us to explain the existence of a premelting layer on the surface of ice and the stability of ice in confinement. In between these extremes, the dynamics of supercooled water are considered. A detailed theory for the early stages of coarsening is developed and used to explain the peculiar observation of a transient second liquid state of water. When coarsening dynamics are arrested, the result is the formation of a glassy states of water. We show that out-of-equilibrium the phase diagram for supercooled water exhibits a rich amount of structure, including a triple point between two glass phases of water and the liquid. At the end, we explore possible technological implications for the interplay between ordering and frustration in studies of water at metal interfaces.

  17. Liquid phase epitaxy of binary III–V nanocrystals in thin Si layers triggered by ion implantation and flash lamp annealing

    Energy Technology Data Exchange (ETDEWEB)

    Wutzler, Rene, E-mail: r.wutzler@hzdr.de; Rebohle, Lars; Prucnal, Slawomir; Bregolin, Felipe L.; Hübner, Rene; Voelskow, Matthias; Helm, Manfred; Skorupa, Wolfgang [Helmholtz-Zentrum Dresden - Rossendorf, Institute of Ion Beam Physics and Materials Research, Bautzner Landstraße 400, 01328 Dresden (Germany)

    2015-05-07

    The integration of III–V compound semiconductors in Si is a crucial step towards faster and smaller devices in future technologies. In this work, we investigate the formation process of III–V compound semiconductor nanocrystals, namely, GaAs, GaSb, and InP, by ion implantation and sub-second flash lamp annealing in a SiO{sub 2}/Si/SiO{sub 2} layer stack on Si grown by plasma-enhanced chemical vapor deposition. Raman spectroscopy, Rutherford Backscattering spectrometry, and transmission electron microscopy were performed to identify the structural and optical properties of these structures. Raman spectra of the nanocomposites show typical phonon modes of the compound semiconductors. The formation process of the III–V compounds is found to be based on liquid phase epitaxy, and the model is extended to the case of an amorphous matrix without an epitaxial template from a Si substrate. It is shown that the particular segregation and diffusion coefficients of the implanted group-III and group-V ions in molten Si significantly determine the final appearance of the nanostructure and thus their suitability for potential applications.

  18. Distribution of Al atoms in the clathrate-I phase Ba8AlxSi46-x at x = 6.9.

    Science.gov (United States)

    Bobnar, Matej; Böhme, Bodo; Wedel, Michael; Burkhardt, Ulrich; Ormeci, Alim; Prots, Yurii; Drathen, Christina; Liang, Ying; Nguyen, Hong Duong; Baitinger, Michael; Grin, Yuri

    2015-07-28

    The clathrate-I phase Ba8AlxSi46-x has been structurally characterized at the composition x = 6.9 (space group Pm3[combining macron]n, no. 223, a = 10.4645(2) Å). A crystal structure model comprising the distribution of aluminium and silicon atoms in the clathrate framework was established: 5.7 Al atoms and 0.3 Si atoms occupy the crystallographic site 6c, while 1.2 Al atoms and 22.8 Si atoms occupy site 24k. The atomic distribution was established based on a combination of (27)Al and (29)Si NMR experiments, X-ray single-crystal diffraction and wavelength-dispersive X-ray spectroscopy.

  19. Complexation of Nitrous Oxide by Frustrated Lewis Pairs

    NARCIS (Netherlands)

    Otten, Edwin; Neu, Rebecca C.; Stephan, Douglas W.

    2009-01-01

    Frustrated Lewis pairs comprised of a basic yet sterically encumbered phosphine with boron Lewis acids bind nitrous oxide to give intact PNNOB linkages. The synthesis, structure, and bonding of these species are described.

  20. Frustrated Total Internal Reflection: A Simple Application and Demonstration.

    Science.gov (United States)

    Zanella, F. P.; Magalhaes, D. V.; Oliveira, M. M.; Bianchi, R. F.; Misoguti, L.; Mendonca, C. R.

    2003-01-01

    Describes the total internal reflection process that occurs when the internal angle of incidence is equal to or greater than the critical angle. Presents a demonstration of the effect of frustrated total internal reflection (FTIR). (YDS)

  1. Low Tolerance for Frustration: Target Group for Reading Disabilities

    Science.gov (United States)

    Orlow, Maria

    1974-01-01

    Presents findings which can aid in the prevention and remediation of reading disabilities in children who have a low tolerance for frustration, many of whom often become acute reading disability cases. (TO)

  2. Solid-state compound phase formation of TiSi2 thin films under stress

    Directory of Open Access Journals (Sweden)

    C. Theron

    2010-02-01

    Full Text Available Different stress situations were created on an Si(100 wafer by depositing either Si3N4 or SiO2 thin films on the back side. Si3N4 has a different thermal expansion coefficient from that of SiO2. A thin Ti film was then deposited on the front side of the Si wafer. The structures were then annealed at various high temperatures for different periods of time. Real-time Rutherford backscattering spectrometry, as well as sample curvature measurements, were used to characterise the samples. Different reaction rates were found between Si3N4-deposited samples and SiO2-deposited samples.

  3. Phase relationships in the quasi-ternary LaO1.5–SiO2–MgO system at 1773 K

    Directory of Open Access Journals (Sweden)

    Kiyoshi Kobayashi and Yoshio Sakka

    2012-01-01

    Full Text Available Phase relationships in the LaO1.5–SiO2–MgO quasi-ternary system at 1773 K were investigated by powder x-ray diffraction (XRD analysis applying single- and multiple-phase Rietveld methods. Most of the formed phases satisfied the Gibbs' phase rule, except for the samples containing LaO1.5 and a liquid phase at 1773 K. The detection of segregated MgO phases was difficult in the XRD profiles of the compositional samples around the oxyapatite single phase because the MgO peaks were weak and heavily overlapped by peaks from the oxyapatite and La(OH3 phases. The solid solubility limit of MgO in oxyapatite was determined not only from the chemical composition of the oxyapatite phase, which was confirmed by XRD, but also from several phase boundary compositions among the two-phase and three-phase regions based on the Gibbs' phase rule. Formation of a liquid phase at 1773 K was observed in a wide range of compositions and considered when constructing the phase diagram.

  4. Si{sub 2}Sb{sub 2}Te{sub 5} phase change material studied by an atomic force microscope nano-tip

    Energy Technology Data Exchange (ETDEWEB)

    Liu Yanbo; Min Guoquan; Zhang Jing; Zhou Weimin; Wan Yongzhong; Zhang Jianping; Li Xiaoli [Laboratory of Nano-Technology, Shanghai Nanotechnology Promotion Center, Shanghai 200237 (China); Zhang Ting; Niu Xiaoming; Song Zhitang; Feng Songlin, E-mail: liuyanbo@snpc.org.c, E-mail: tzhang@mail.sim.ac.c [State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China)

    2009-06-01

    The Si{sub 2}Sb{sub 2}Te{sub 5} phase change material has been studied by applying a nano-tip (30 nm in diameter) on an atomic force microscopy system. Memory switching from a high resistance state to a low resistance state has been achieved, with a resistance change of about 1000 times. In a typical I-V curve, the current increases significantly after the voltage exceeds approx4.3 V. The phase transformation of a Si{sub 2}Sb{sub 2}Te{sub 5} film was studied in situ by means of in situ X-ray diffraction and temperature dependent resistance measurements. The thermal stability of Si{sub 2}Sb{sub 2}Te{sub 5} and Ge{sub 2}Sb{sub 2}Te{sub 5} was characterized and compared as well.

  5. Solid-phase reduction of silico-12-molybdic acid H4SiMo12O40 by some organic oxygen containing compounds

    International Nuclear Information System (INIS)

    Chuvaev, V.F.; Pinchuk, I.N.; Spitsyn, V.I.

    1982-01-01

    A study is made on reduction reactions of anhydrous silico-12-molybdic acid by vapors of organic oxygen-containing compounds at 170 deg C: alcohols, simple carbonyl compounds. Methods of thermal analysis, electron paramagnetic resonance, paramagnetic resonance were used to established that depending on the nature of organic reagent and temperature, H 6 SiMo 2 5 Mo 10 6 O 40 two-electron or H 8 SiMo 4 5 Mo 8 6 O 40 four-electron flues form. It is shown that the increase of heterogeneous reduction temperature can lead to formation of anhydrous phases of SiMo 12 O 38 -(n/2), able to attach water reversibly with formation of corresponding blue. Characteristics of blues, prepared during solid-phase reduction of silico-12-molybdic acid and mixed valent forms with corresponding reduction degree, separated from water solutions, were compared

  6. Constructing first-principles phase diagrams of amorphous LixSi using machine-learning-assisted sampling with an evolutionary algorithm

    Science.gov (United States)

    Artrith, Nongnuch; Urban, Alexander; Ceder, Gerbrand

    2018-06-01

    The atomistic modeling of amorphous materials requires structure sizes and sampling statistics that are challenging to achieve with first-principles methods. Here, we propose a methodology to speed up the sampling of amorphous and disordered materials using a combination of a genetic algorithm and a specialized machine-learning potential based on artificial neural networks (ANNs). We show for the example of the amorphous LiSi alloy that around 1000 first-principles calculations are sufficient for the ANN-potential assisted sampling of low-energy atomic configurations in the entire amorphous LixSi phase space. The obtained phase diagram is validated by comparison with the results from an extensive sampling of LixSi configurations using molecular dynamics simulations and a general ANN potential trained to ˜45 000 first-principles calculations. This demonstrates the utility of the approach for the first-principles modeling of amorphous materials.

  7. Magnetic domains and frustration in metallic CePdAl

    Energy Technology Data Exchange (ETDEWEB)

    Lucas, Stefan; Huesges, Zita; Huang, Chien-Lung; Stockert, Oliver [Max Planck Institute CPfS, Dresden (Germany); Fritsch, Veronika; Sakai, Akito [EP 6, Electronic Correlations and Magnetism, University of Augsburg (Germany); Grube, Kai; Taubenheim, Christian; Loehneysen, Hilbert von [Karlsruhe Institute of Technology (Germany)

    2016-07-01

    Magnetic frustration is an exciting topic in condensed matter physics, since it can lead to new ground states of materials, e.g. a spin liquid or spin glass state. Effects of magnetic frustration have been investigated intensively for insulating materials. However, the existence of magnetic frustration in metallic systems is still under debate. CePdAl is a metallic Kondo system, where geometric magnetic frustration arises from the formation of Ce ions on a distorted Kagome lattice. Neutron scattering experiments revealed, that only two thirds of the magnetic Ce moments order antiferromagnetically below T{sub N}=2.7 K, whereas the other third remains mainly disordered. Thermodynamic as well as neutron scattering measurements are presented to verify the existence of partial magnetic frustration in CePdAl. Recently neutron diffraction experiments under magnetic fields applied along two orthogonal directions in the magnetically hard basal plane were performed. They show opposite effects on the magnetic intensity of a selected magnetic domain depending on the field direction with respect to the propagation vector. If this is only an effect of different domain population or also due to a change in magnetic frustration shall be discussed.

  8. The Establishment, Plotting and Statistic– Mathematical Interpretation of the Liquidus Surface from the Phase Equilibrium Diagram of the Ternary System Al-Cu-Si

    Directory of Open Access Journals (Sweden)

    Florentina A. Cziple

    2006-10-01

    Full Text Available The paper forwards the conclusions of a survey performed on a mathematical model of the phase equilibrium from the ternary system Al-Cu-Si. The author presents the calculus of the statistic equation of the liquidus surface model from this diagram, the plotting and statistical-mathematical interpretation of the results obtained.

  9. Investigation of phases obtained from the Ce.sub.20./sub.Ru.sub.60./sub.Si.sub.20./sub. composition

    Czech Academy of Sciences Publication Activity Database

    Vejpravová, J.; Sechovský, V.; Prokleška, J.; Daniš, S.; Jurek, Karel

    2008-01-01

    Roč. 466, 1-2 (2008), s. 17-25 ISSN 0925-8388 Institutional research plan: CEZ:AV0Z10100521 Keywords : rare earth compounds * laves phase * superconductivity * ternary Ce-Ru-Si system Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.510, year: 2008

  10. Effective Chemical Route to 2D Nanostructured Silicon Electrode Material: Phase Transition from Exfoliated Clay Nanosheet to Porous Si Nanoplate

    International Nuclear Information System (INIS)

    Adpakpang, Kanyaporn; Patil, Sharad B.; Oh, Seung Mi; Kang, Joo-Hee; Lacroix, Marc; Hwang, Seong-Ju

    2016-01-01

    Graphical abstract: Effective morphological control of porous silicon 2D nanoplate can be achieved by the magnesiothermically-induced phase transition of exfoliated silicate clay nanosheets. The promising lithium storage performance of the obtained silicon materials with huge capacity and excellent rate characteristics underscores the prime importance of porously 2D nanostructured morphology of silicon. - Highlights: • 2D nanostructured silicon electrode materials are successfully synthesized via the magnesiothermically-induced phase transition of exfoliated clay 2D nanosheets. • High discharge capacity and rate capability are achieved from the 2D nanoplates of silicon. • Silicon 2D nanoplates can enhance both Li"+ diffusion and charge-transfer kinetics. • 2D nanostructured silicon is beneficial for the cycling stability by minimizing the volume change during lithiation-delithiation. - Abstract: An efficient and economical route for the synthesis of porous two-dimensional (2D) nanoplates of silicon is developed via the magnesiothermically-induced phase transition of exfoliated clay 2D nanosheets. The magnesiothermic reaction of precursor clay nanosheets prepared by the exfoliation and restacking with Mg"2"+ cations yields porous 2D nanoplates of elemental silicon. The variation in the Mg:SiO_2 ratio has a significant effect on the porosity and connectivity of silicon nanoplates. The porous silicon nanoplates show a high discharge capacity of 2000 mAh g"−"1 after 50 cycles. Of prime importance is that this electrode material still retains a large discharge capacity at higher C-rates, which is unusual for the elemental silicon electrode. This is mainly attributed to the improved diffusion of lithium ions, charge-transfer kinetics, and the preservation of the electrical connection of the porous 2D plate-shaped morphology. This study highlights the usefulness of clay mineral as an economical and scalable precursor of high-performance silicon electrodes with

  11. The combined use of EBSD and EDX analyses for the identification of complex intermetallic phases in multicomponent Al-Si piston alloys

    International Nuclear Information System (INIS)

    Chen, C.-L.; Thomson, R.C.

    2010-01-01

    Multicomponent Al-Si based casting alloys are used for a variety of engineering applications, including for example, piston alloys. Properties include good castability, high strength, light weight, good wear resistance and low thermal expansion. In order for such alloys to continue operation to increasingly higher temperatures, alloy element modifications are continually being made to further enhance the properties. Improved mechanical and physical properties are strongly dependent upon the morphologies, type and distribution of the second phases, which are in turn a function of alloy composition and cooling rate. The presence of additional elements in the Al-Si alloy system allows many complex intermetallic phases to form, which make characterisation non-trivial. These include, for example, CuAl 2 , Al 3 Ni 2 , Al 7 Cu 4 Ni, Al 9 FeNi and Al 5 Cu 2 Mg 8 Si 6 phases, all of which may have some solubility for additional elements. Identification is often non-trivial due to the fact that some of the phases have either similar crystal structures or only subtle changes in their chemistries. A combination of electron backscatter diffraction (EBSD) and energy dispersive X-ray analysis (EDX) has therefore been used for the identification of the various phases. This paper will present comparisons of phase identification methodologies using EBSD alone, and in combination with chemical information, either directly or through post processing.

  12. Defects annihilation behavior of neutron-irradiated SiC ceramics densified by liquid-phase-assisted method after post-irradiation annealing

    Directory of Open Access Journals (Sweden)

    Mohd Idzat Idris

    2016-12-01

    Full Text Available Numerous studies on the recovery behavior of neutron-irradiated high-purity SiC have shown that most of the defects present in it are annihilated by post-irradiation annealing, if the neutron fluence is less than 1×1026 n/m2 (>0.1MeV and the irradiation is performed at temperatures lower than 973K. However, the recovery behavior of SiC fabricated by the nanoinfiltrated and transient eutectic phase (NITE process is not well understood. In this study, the effects of secondary phases on the irradiation-related swelling and recovery behavior of monolithic NITE-SiC after post-irradiation annealing were studied. The NITE-SiC specimens were irradiated in the BR2 reactor at fluences of up to 2.0–2.5×1024 n/m2 (E>0.1MeV at 333–363K. This resulted in the specimens swelling up ∼1.3%, which is 0.1% higher than the increase seen in concurrently irradiated high-purity SiC. The recovery behaviors of the specimens after post-irradiation thermal annealing were examined using a precision dilatometer; the specimens were heated at temperatures of up to 1673K using a step-heating method. The recovery curves were analyzed using a first-order model, and the rate constants for each annealing step were obtained to determine the activation energy for volume recovery. The NITE-A specimen (containing 12 wt% sintering additives recovered completely after annealing at ∼1573K; however, it shrank because of the volatilization of the oxide phases at 1673K. The NITE-B specimen (containing 18wt% sintering additives did not recover fully, since the secondary phase (YAG was crystallized during the annealing process. The recovery mechanism of NITE-A SiC was based on the recombination of the C and Si Frenkel pairs, which were very closely sited or only slightly separated at temperatures lower than 1223K, as well as the recombination of the slightly separated C Frenkel pairs and the migration of C and Si interstitials at temperatures of 1223–1573K. That is to say, the

  13. Phase dynamics of single long Josephson junction in MgB2 superconductor

    Science.gov (United States)

    Chimouriya, Shanker Pd.; Ghimire, Bal Ram; Kim, Ju H.

    2018-05-01

    A system of perturbed sine Gordon equations is derived to a superconductor-insulator-superconductor (SIS) long Joseph-son junction as an extension of the Ambegaokar-Baratoff relation, following the long route of path integral formalism. A computer simulation is performed by discretizing the equations using finite difference approximation and applied to the MgB2 superconductor with SiO2 as the junction material. The solution of unperturbed sG equation is taken as the initial profile for the simulation and observed how the perturbation terms play the role to modify it. It is found initial profile deformed as time goes on. The variation of total Josephson current has also been observed. It is found that, the perturbation terms play the role for phase frustration. The phase frustration achieves quicker for high tunneling current.

  14. Comparative analysis of oxide phase formation and its effects on electrical properties of SiO{sub 2}/InSb metal-oxide-semiconductor structures

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jaeyel [Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); Park, Sehun [Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); WCU Hybrid Materials Program, Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); Kim, Jungsub; Yang, Changjae; Kim, Sujin; Seok, Chulkyun [Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); Park, Jinsub [Department of Electronic Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Yoon, Euijoon, E-mail: eyoon@snu.ac.kr [Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); WCU Hybrid Materials Program, Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); Department of Nano Science and Technology, Graduate School of Convergence Science and Technology, Seoul National University, Suwon 443-270 (Korea, Republic of); Energy Semiconductor Research Center, Advanced Institutes of Convergence Technology, Seoul National University, Suwon 443-270 (Korea, Republic of)

    2012-06-01

    We report on the changes in the interfacial phases between SiO{sub 2} and InSb caused by various deposition temperatures and heat treatments. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy were used to evaluate the relative amount of each phase present at the interface. The effect of interfacial phases on the electrical properties of SiO{sub 2}/InSb metal-oxide-semiconductor (MOS) structures was investigated by capacitance-voltage (C-V) measurements. The amount of both In and Sb oxides increased with the deposition temperature. The amount of interfacial In oxide was larger for all samples, regardless of the deposition and annealing temperatures and times. In particular, the annealed samples contained less than half the amount of Sb oxide compared with the as-deposited samples, indicating a strong interfacial reaction between Sb oxide and the InSb substrate during annealing. The interface trap density sharply increased for deposition temperatures above 240 Degree-Sign C. The C-V measurements and Raman spectroscopy indicated that elemental Sb accumulation due to the interfacial reaction of Sb oxide with InSb substrate was responsible for the increased interfacial trap densities in these SiO{sub 2}/InSb MOS structures. - Highlights: Black-Right-Pointing-Pointer We report the quantitative analysis of interfacial oxides at the SiO{sub 2}/InSb interface. Black-Right-Pointing-Pointer Interfacial oxides were measured quantitatively by X-ray Photoelectron Spectroscopy. Black-Right-Pointing-Pointer As-grown and annealed samples showed different compositions of oxide phases. Black-Right-Pointing-Pointer Considerable reduction of antimony oxide phases was observed during annealing. Black-Right-Pointing-Pointer Interface trap densities at the SiO{sub 2}/InSb interface were calculated.

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

    Science.gov (United States)

    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.

  16. Nanoselective area growth of GaN by metalorganic vapor phase epitaxy on 4H-SiC using epitaxial graphene as a mask

    International Nuclear Information System (INIS)

    Puybaret, Renaud; Jordan, Matthew B.; Voss, Paul L.; Ougazzaden, Abdallah; Patriarche, Gilles; Sundaram, Suresh; El Gmili, Youssef; Salvestrini, Jean-Paul; Heer, Walt A. de; Berger, Claire

    2016-01-01

    We report the growth of high-quality triangular GaN nanomesas, 30-nm thick, on the C-face of 4H-SiC using nanoselective area growth (NSAG) with patterned epitaxial graphene grown on SiC as an embedded mask. NSAG alleviates the problems of defects in heteroepitaxy, and the high mobility graphene film could readily provide the back low-dissipative electrode in GaN-based optoelectronic devices. A 5–8 graphene-layer film is first grown on the C-face of 4H-SiC by confinement-controlled sublimation of silicon carbide. Graphene is then patterned and arrays of 75-nm-wide openings are etched in graphene revealing the SiC substrate. A 30-nm-thick GaN is subsequently grown by metal organic vapor phase epitaxy. GaN nanomesas grow epitaxially with perfect selectivity on SiC, in the openings patterned through graphene. The up-or-down orientation of the mesas on SiC, their triangular faceting, and cross-sectional scanning transmission electron microscopy show that they are biphasic. The core is a zinc blende monocrystal surrounded with single-crystal wurtzite. The GaN crystalline nanomesas have no threading dislocations or V-pits. This NSAG process potentially leads to integration of high-quality III-nitrides on the wafer scalable epitaxial graphene/silicon carbide platform.

  17. Nanoselective area growth of GaN by metalorganic vapor phase epitaxy on 4H-SiC using epitaxial graphene as a mask

    Energy Technology Data Exchange (ETDEWEB)

    Puybaret, Renaud; Jordan, Matthew B.; Voss, Paul L.; Ougazzaden, Abdallah, E-mail: aougazza@georgiatech-metz.fr [School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); CNRS UMI 2958, Georgia Institute of Technology, 2 Rue Marconi, 57070 Metz (France); Patriarche, Gilles [CNRS, Laboratoire de Photonique et de Nanostructures, Route de Nozay, 91460 Marcoussis (France); Sundaram, Suresh; El Gmili, Youssef [CNRS UMI 2958, Georgia Institute of Technology, 2 Rue Marconi, 57070 Metz (France); Salvestrini, Jean-Paul [Université de Lorraine, CentraleSupélec, LMOPS, EA4423, 57070 Metz (France); Heer, Walt A. de [School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Berger, Claire [School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); CNRS, Institut Néel, BP166, 38042 Grenoble Cedex 9 (France)

    2016-03-07

    We report the growth of high-quality triangular GaN nanomesas, 30-nm thick, on the C-face of 4H-SiC using nanoselective area growth (NSAG) with patterned epitaxial graphene grown on SiC as an embedded mask. NSAG alleviates the problems of defects in heteroepitaxy, and the high mobility graphene film could readily provide the back low-dissipative electrode in GaN-based optoelectronic devices. A 5–8 graphene-layer film is first grown on the C-face of 4H-SiC by confinement-controlled sublimation of silicon carbide. Graphene is then patterned and arrays of 75-nm-wide openings are etched in graphene revealing the SiC substrate. A 30-nm-thick GaN is subsequently grown by metal organic vapor phase epitaxy. GaN nanomesas grow epitaxially with perfect selectivity on SiC, in the openings patterned through graphene. The up-or-down orientation of the mesas on SiC, their triangular faceting, and cross-sectional scanning transmission electron microscopy show that they are biphasic. The core is a zinc blende monocrystal surrounded with single-crystal wurtzite. The GaN crystalline nanomesas have no threading dislocations or V-pits. This NSAG process potentially leads to integration of high-quality III-nitrides on the wafer scalable epitaxial graphene/silicon carbide platform.

  18. Influence of Si and N additions on structure and phase stability of Ge{sub 2}Sb{sub 2}Te{sub 5} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Koelpin, Helmut; Music, Denis; Mykhaylonka, Ruslan; Schneider, Jochen M [Materials Chemistry, RWTH Aachen University, D-52056 Aachen (Germany); Laptyeva, Galyna; Ghadimi, Reza; Richter, Silvia; Mayer, Joachim [Central Facility for Electron Microscopy, RWTH Aachen University, Ahornstrasse 55, D-52074 Aachen (Germany); Merget, Florian [Institute of Semiconductor Electronics, RWTH Aachen University, Sommerfeldstrasse 24, D-52074 Aachen (Germany)

    2009-10-28

    The influence of Si and N in Ge{sub 2}Sb{sub 2}Te{sub 5} (space group Fm3-barm) on structure and phase stability thereof was studied experimentally by thin film growth and characterization as well as theoretically by ab initio calculations. It was found that Si and N most probably accumulate in the amorphous matrix embedding Ge{sub 2}Sb{sub 2}Te{sub 5} grains. The incorporation of Si and N in these samples causes an increase of the crystallization temperature and the formation of finer grains. N is more efficient in increasing the crystallization temperature and in reducing the grain size than Si which can be understood based on the bonding analysis. The incorporation of both Si and N in Ge{sub 2}Sb{sub 2}Te{sub 5} is energetically unfavourable, leading to finer grains and larger crystallization temperatures. While in the case of Si additions no significant changes in bonding are observed, N additions appear to enable the formation of strong Te-N bonds in the amorphous matrix, which are shown to be almost twice as strong as the strongest bonds in unalloyed Ge{sub 2}Sb{sub 2}Te{sub 5}.

  19. The effects of phase transformation on the structure and mechanical properties of TiSiCN nanocomposite coatings deposited by PECVD method

    Science.gov (United States)

    Abedi, Mohammad; Abdollah-zadeh, Amir; Bestetti, Massimiliano; Vicenzo, Antonello; Serafini, Andrea; Movassagh-Alanagh, Farid

    2018-06-01

    In the present study, the effects of phase transformations on the structure and mechanical properties of TiSiCN coatings were investigated. TiSiCN nanocomposite coatings were deposited on AISI H13 hot-work tool steel by a pulsed direct current plasma-enhanced chemical vapor deposition process at 350 or 500 °C, using TiCl4 and SiCl4 as the precursors of Ti and Si, respectively, in a CH4/N2/H2/Ar plasma as the source of carbon and nitrogen and reducing environment. Some samples deposited at 350 °C were subsequently annealed at 500 °C under Ar atmosphere. Super hard self-lubricant TiSiCN coatings, having nanocomposite structure consisting of TiCN nanocrystals and amorphous carbon particles embedded in an amorphous SiCNx matrix, formed through spinodal decomposition in the specimens deposited or annealed at 500 °C. In addition, it was revealed that either uncomplete or relatively coarse phase segregation of titanium compounds was achieved during deposition at 350 °C and 500 °C, respectively. On the contrary, by deposition at 350 °C followed by annealing at 500 °C, a finer structure was obtained with a sensible improvement of the mechanical properties of coatings. Accordingly, the main finding of this work is that significant enhancement in key properties of TiSiCN coatings, such as hardness, adhesion and friction coefficient, can be obtained by deposition at low temperature and subsequent annealing at higher temperature, thanks to the formation of a fine grained nanocomposite structure.

  20. Phase diagram study for the PbO-ZnO-CaO-SiO{sub 2} -“Fe{sub 2}O{sub 3} ” system in air with CaO/SiO{sub 2} in 1.1 and PbO/(CaO+SiO{sub 2}) in 2.4 weight ratios

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Rodriguez, Josue; Romero-Serrano, Antonio; Hernandez-Ramirez, Aurelio; Cruz-Ramirez, Alejandro, E-mail: romeroipn@hotmail.com [Instituto Politecnico Nacional-ESIQIE, Zacatenco, Mexico City (Mexico); Almaguer-Guzman, Isaias; Benavides-Perez, Ricardo; Flores-Favela, Manuel [Servicios Administrativos Penoles S.A de C.V., Torreon, Coahuila (Mexico)

    2017-07-15

    An experimental study on the phase equilibrium and the liquidus isotherms for the PbO-ZnO-CaO-SiO{sub 2} -“Fe{sub 2}O{sub 3} ” system with CaO/SiO{sub 2} in 1.1 and PbO/(CaO+SiO{sub 2}) in 2.4 weight ratios, respectively, was carried out in the temperature range 1100-1300 deg C (1373-1573 K). High temperature phases were determined by the equilibrium-quenching method. Results are presented in the form of pseudo-ternary sections “Fe{sub 2}O{sub 3} ”-ZnO-(PbO+CaO+SiO{sub 2}). X-Ray diffraction (XRD) and SEM-EDS results showed that the phase equilibria in this system are dominated by the high melting temperature spinel and zincite phases. It was observed that if the system is at a temperature below 1300 deg C and the total (Fe{sub 2}O{sub 3} + ZnO) is greater than 20 wt%, spinel and/or zincite will be present in the slag system. As an application of the phase diagram, the liquid phase compositions below the liquidus surface were estimated, then their viscosities were calculated using FACTSage software. (author)

  1. Phase diagram study for the PbO-ZnO-CaO-SiO_2 -“Fe_2O_3 ” system in air with CaO/SiO_2 in 1.1 and PbO/(CaO+SiO_2) in 2.4 weight ratios

    International Nuclear Information System (INIS)

    Lopez-Rodriguez, Josue; Romero-Serrano, Antonio; Hernandez-Ramirez, Aurelio; Cruz-Ramirez, Alejandro; Almaguer-Guzman, Isaias; Benavides-Perez, Ricardo; Flores-Favela, Manuel

    2017-01-01

    An experimental study on the phase equilibrium and the liquidus isotherms for the PbO-ZnO-CaO-SiO_2 -“Fe_2O_3 ” system with CaO/SiO_2 in 1.1 and PbO/(CaO+SiO_2) in 2.4 weight ratios, respectively, was carried out in the temperature range 1100-1300 deg C (1373-1573 K). High temperature phases were determined by the equilibrium-quenching method. Results are presented in the form of pseudo-ternary sections “Fe_2O_3 ”-ZnO-(PbO+CaO+SiO_2). X-Ray diffraction (XRD) and SEM-EDS results showed that the phase equilibria in this system are dominated by the high melting temperature spinel and zincite phases. It was observed that if the system is at a temperature below 1300 deg C and the total (Fe_2O_3 + ZnO) is greater than 20 wt%, spinel and/or zincite will be present in the slag system. As an application of the phase diagram, the liquid phase compositions below the liquidus surface were estimated, then their viscosities were calculated using FACTSage software. (author)

  2. Construction of the Al-Ni-Si phase diagram over the whole composition and temperature ranges: thermodynamic modeling supported by key experiments and first-principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Xiong Wei; Du Yong; Wang Jiong; Zhang Wei-Wei [State Key Lab. of Powder Metallurgy, Central South Univ., Changsha (China); Hu Rong-Xiang; Nash, P. [Thermal Processing Technology Center, Illinois Inst. of Tech., Chicago (United States); Lu Xiao-Gang [Thermo-Calc AB, Stockholm Technology Park, Stockholm (Sweden)

    2008-06-15

    An extensive thermodynamic investigation of the Al-Ni-Si system is carried out via an integrated approach of calculation of phase diagrams, first-principles calculations, and key experiments. Eighteen decisive alloys are prepared in order to verify the existence of the previously reported ternary compounds and to provide new phase equilibrium data. Phase compositions, microstructure, and phase transition temperatures are determined using the combined techniques of X-ray diffraction, scanning electron microscopy, energy dispersion X-ray analysis, and differential thermal analysis. The order/disorder transition between disordered bccA2 and ordered bccB2 phases as well as that between disordered fccA1 and ordered L1{sub 2} phase are described using a two-sublattice model. A self-consistent parameter set is finally obtained by considering the huge amount of experimental data including 13 vertical sections and 5 isothermal sections from both the literature and the present experiments. Almost all of the reliable phase diagram data can be well described by the present modeling. The reliability of the calculated thermodynamic properties for ternary phases is verified through enthalpy measurement employing drop calorimetry and first-principles calculations. The thermodynamic parameters obtained can also successfully predict most of the thermodynamic properties and describe the solidification path for the selected as-cast alloy Al{sub 6}Ni{sub 55}Si{sub 39}. (orig.)

  3. The impact of Ti and temperature on the stability of Nb5Si3 phases: a first-principles study.

    Science.gov (United States)

    Papadimitriou, Ioannis; Utton, Claire; Tsakiropoulos, Panos

    2017-01-01

    Nb-silicide based alloys could be used at T > 1423 K in future aero-engines. Titanium is an important additive to these new alloys where it improves oxidation, fracture toughness and reduces density. The microstructures of the new alloys consist of an Nb solid solution, and silicides and other intermetallics can be present. Three Nb 5 Si 3 polymorphs are known, namely αNb 5 Si 3 ( tI 32 Cr 5 B 3 -type, D8 l ), βNb 5 Si 3 ( tI 32 W 5 Si 3 -type, D8 m ) and γNb 5 Si 3 ( hP 16 Mn 5 Si 3 -type, D8 8 ). In these 5-3 silicides Nb atoms can be substituted by Ti atoms. The type of stable Nb 5 Si 3 depends on temperature and concentration of Ti addition and is important for the stability and properties of the alloys. The effect of increasing concentration of Ti on the transition temperature between the polymorphs has not been studied. In this work first-principles calculations were used to predict the stability and physical properties of the various Nb 5 Si 3 silicides alloyed with Ti. Temperature-dependent enthalpies of formation were computed, and the transition temperature between the low (α) and high (β) temperature polymorphs of Nb 5 Si 3 was found to decrease significantly with increasing Ti content. The γNb 5 Si 3 was found to be stable only at high Ti concentrations, above approximately 50 at. % Ti. Calculation of physical properties and the Cauchy pressures, Pugh's index of ductility and Poisson ratio showed that as the Ti content increased, the bulk moduli of all silicides decreased, while the shear and elastic moduli and the Debye temperature increased for the αNb 5 Si 3 and γNb 5 Si 3 and decreased for βNb 5 Si 3 . With the addition of Ti the αNb 5 Si 3 and γNb 5 Si 3 became less ductile, whereas the βNb 5 Si 3 became more ductile. When Ti was added in the αNb 5 Si 3 and βNb 5 Si 3 the linear thermal expansion coefficients of the silicides decreased, but the anisotropy of coefficient of thermal expansion did not change significantly.

  4. Emergent criticality and Friedan scaling in a two-dimensional frustrated Heisenberg antiferromagnet

    Science.gov (United States)

    Orth, Peter P.; Chandra, Premala; Coleman, Piers; Schmalian, Jörg

    2014-03-01

    We study a two-dimensional frustrated Heisenberg antiferromagnet on the windmill lattice consisting of triangular and dual honeycomb lattice sites. In the classical ground state, the spins on different sublattices are decoupled, but quantum and thermal fluctuations drive the system into a coplanar state via an "order from disorder" mechanism. We obtain the finite temperature phase diagram using renormalization group approaches. In the coplanar regime, the relative U(1) phase between the spins on the two sublattices decouples from the remaining degrees of freedom, and is described by a six-state clock model with an emergent critical phase. At lower temperatures, the system enters a Z6 broken phase with long-range phase correlations. We derive these results by two distinct renormalization group approaches to two-dimensional magnetism: Wilson-Polyakov scaling and Friedan's geometric approach to nonlinear sigma models where the scaling of the spin stiffnesses is governed by the Ricci flow of a 4D metric tensor.

  5. The magnetic structures and the magnetic phase diagram of the TbMn{sub 2}(Ge,Si){sub 2} system

    Energy Technology Data Exchange (ETDEWEB)

    Granovsky, S.A. [Department of Physics, M.V. Lomonosov Moscow State University, GSP-2, 119992 Moscow (Russian Federation) and TU Dresden, Institut fuer Festkoerperphysik, D-01062, Dresden (Germany)]. E-mail: ser@plms.phys.msu.ru; Gaidukova, I.Yu. [Department of Physics, M.V. Lomonosov Moscow State University, GSP-2, 119992 Moscow (Russian Federation); Doerr, M. [TU Dresden, Institut fuer Festkoerperphysik, D-01062, Dresden (Germany); Loewenhaupt, M. [TU Dresden, Institut fuer Festkoerperphysik, D-01062, Dresden (Germany); Markosyan, A.S. [Department of Physics, M.V. Lomonosov Moscow State University, GSP-2, 119992 Moscow (Russian Federation); State Center for Condensed Matter Physics, Rogova str.5., 123060 Moscow (Russian Federation); Ritter, C. [Institut Laue-Langevin, 38042 Grenoble Cedex 9 (France)

    2007-03-15

    Magnetic structures and magnetic phase transitions in natural-layered TbMn{sub 2}(Ge {sub x} Si{sub 1-} {sub x} ){sub 2} compounds have been studied by magnetisation, low-field AC-susceptibility, electrical resistivity and neutron-diffraction experiments. Non-collinear magnetic structures were observed in the concentration range 0 phase was observed (detected by a significant change in the electrical resistivity). The magnetic x-T phase diagram of the TbMn{sub 2}(Ge {sub x} Si{sub 1-} {sub x} ){sub 2} system is constructed and the role of magnetic couplings of different type for the stabilisation of the various magnetic structures is discussed.

  6. Geometric Magnetic Frustration in Li3Mg2OsO6 Studied with Muon Spin Relaxation

    Science.gov (United States)

    Carlo, J. P.; Derakhshan, S.; Greedan, J. E.

    Geometric frustration manifests when the spatial arrangement of ions inhibits magnetic order. Typically associated with antiferromagnetically (AF)-correlated moments on triangular or tetrahedral lattices, frustration occurs in a variety of structures and systems, resulting in rich phase diagrams and exotic ground states. As a window to exotic physics revealed by the cancellation of normally dominant interactions, the research community has taken great interest in frustrated systems. One family of recent interest are the rock-salt ordered oxides A5BO6, in which the B sites are occupied by magnetic ions comprising a network of interlocked tetrahedra, and nonmagnetic ions on the A sites control the B oxidation state through charge neutrality. Here we will discuss studies of Li3Mg2OsO6 using muon spin relaxation (μSR), a highly sensitive local probe of magnetism. Previous studies of this family included Li5OsO6, which exhibits AF order below 50K with minimal evidence for frustration, and Li4MgReO6, which exhibits glassy magnetism. Li3Mg2RuO6, meanwhile, exhibits long-range AF, with the ordering temperature suppressed by frustration. But its isoelectronic twin, Li3Mg2OsO6 (5d3 vs. 4d3) exhibits very different behavior, revealed by μSR to be a glassy ground state below 12K. Understanding why such similar systems exhibit diverse ground-state behavior is key to understanding the nature of geometric magnetic frustration. Financial support from the Research Corporation for Science Advancement.

  7. EM study of crystallography and phase relationships in the Be/sub 3/N/sub 2/--BeSiN/sub 2/ system

    Energy Technology Data Exchange (ETDEWEB)

    Shaw, T.M.

    1977-12-01

    Transmission electron microscopy and diffraction have been used to examine structural aspects of phases along the BeSiN/sub 2/-Be/sub 3/N/sub 2/ tie line of the Be-Si-O-N system. Electron diffraction experiments are found to substantiate previous x-ray evidence for the derived structures of BeSiN/sub 2/, ..beta.. Be/sub 3/N/sub 2/, ..cap alpha.. Be/sub 3/N/sub 2/ and the presence of a number of long period superstructures at intermediate compositions. Real space observations using direct fringe and structure imaging techniques have been made and are in agreement with the 15R polytype structure derived from x-ray diffraction data. In addition, these observations indicate that beryllium atoms are preferentially sited in cubic stacked layers, allowing the polytype structures to be described as a coherent intergrowth of layers of the BeSiN/sub 2/ and ..beta.. Be/sub 3/N/sub 2/ structure. Further observations made on a non stoichiometric BeSiN/sub 2/ sample suggests that alternatively the polytypes may be described in terms of a regularly faulted BeSiN/sub 2/ structure. Each fault changes the coordination of tetrahedral sites from base sharing to edge sharing in the fault, allowing excess beryllium atoms to be accommodated in the close packed nitrogen lattice. For larger deviations from the BeSiN/sub 2/ stoichiometric composition a higher density of faults occur which interact to form ordered arrangements and the observed polytype structures. The present observations establish that polytypism in the Be-Si-N system is related to the general phenomenon of crystallographic shear as observed in other complex oxide and ceramic systems. It is suggested that similar faulting may account for the polytype structures in other Sialon systems.

  8. PEG/SiO2–Al2O3 hybrid form-stable phase change materials with enhanced thermal conductivity

    International Nuclear Information System (INIS)

    Tang, Bingtao; Wu, Cheng; Qiu, Meige; Zhang, Xiwen; Zhang, Shufen

    2014-01-01

    The thermal conductivity of form-stable PEG/SiO 2 phase change material (PCM) was enhanced by in situ doping of Al 2 O 3 using an ultrasound-assisted sol–gel method. Fourier transform infrared spectroscopy (FT-IR) was used to characterize the structure, and the crystal performance was characterized by the X-ray diffraction (XRD). Differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA) were used to determine the thermal properties. The phase change enthalpy of PEG/SiO 2 –Al 2 O 3 reached 124 J g −1 , and thermal conductivity improved by 12.8% for 3.3 wt% Al 2 O 3 in the PCM compared with PEG/SiO 2 . The hybrid PCM has excellent thermal stability and form-stable effects. - Highlights: • The PEG/SiO 2 –Al 2 O 3 hybrid form-stable phase change material (PCM) was obtained through the sol–gel method. • The inexpensive aluminum nitrate and tetraethyl orthosilicate were used as sol precursors. • This organic–inorganic hybrid process can effectively enhance the thermal conductivity of PCMs. • The PCM exhibited high thermal stability and excellent form-stable effects

  9. PEG/SiO{sub 2}–Al{sub 2}O{sub 3} hybrid form-stable phase change materials with enhanced thermal conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Bingtao, E-mail: tangbt@dlut.edu.cn; Wu, Cheng; Qiu, Meige; Zhang, Xiwen; Zhang, Shufen

    2014-03-01

    The thermal conductivity of form-stable PEG/SiO{sub 2} phase change material (PCM) was enhanced by in situ doping of Al{sub 2}O{sub 3} using an ultrasound-assisted sol–gel method. Fourier transform infrared spectroscopy (FT-IR) was used to characterize the structure, and the crystal performance was characterized by the X-ray diffraction (XRD). Differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA) were used to determine the thermal properties. The phase change enthalpy of PEG/SiO{sub 2}–Al{sub 2}O{sub 3} reached 124 J g{sup −1}, and thermal conductivity improved by 12.8% for 3.3 wt% Al{sub 2}O{sub 3} in the PCM compared with PEG/SiO{sub 2}. The hybrid PCM has excellent thermal stability and form-stable effects. - Highlights: • The PEG/SiO{sub 2}–Al{sub 2}O{sub 3} hybrid form-stable phase change material (PCM) was obtained through the sol–gel method. • The inexpensive aluminum nitrate and tetraethyl orthosilicate were used as sol precursors. • This organic–inorganic hybrid process can effectively enhance the thermal conductivity of PCMs. • The PCM exhibited high thermal stability and excellent form-stable effects.

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

    OpenAIRE

    Steinbach, Sonja; Ratke, Lorenz; Zimmermann, Gerhard; Budenkova, Olga

    2016-01-01

    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-Al 5 SiFe in the dendritic microstructure was investigated, to study the influence ...

  11. Strain relaxation during solid-phase epitaxial crystallisation of Ge{sub x}Si{sub 1-x} alloy layers with depth dependent G{sub e} compositions

    Energy Technology Data Exchange (ETDEWEB)

    Wong, Wahchung; Elliman, R G; Kringhoj, P [Australian National Univ., Canberra, ACT (Australia). Research School of Physical Sciences

    1994-12-31

    The solid-phase epitaxial crystallisation of depth dependent Ge{sub x}Si{sub lx} alloy layers produced by implanting Ge into Si substrates was studied. In-situ monitoring was done using time-resolved reflectivity (TRR) whilst post-anneal defect structures were characterised by Rutherford backscattering and channeling spectrometry (RBS-C) and transmission electron microscopy (TEM). Particular attention was directed at Ge concentrations above the critical concentration for the growth of fully strained layers. Strain relief is shown to be correlated with a sudden reduction in crystallisation velocity caused by roughening of the crystalline/amorphous interface. 11 refs., 1 tab., 2 figs.

  12. The Effect of Dispersion Phases of SiC and Al2O3 on the Properties of Galvanic Nickel Coatings

    OpenAIRE

    Kozik A.; Nowak M.; Gawlik M.; Bigaj M.; Karaś M.

    2016-01-01

    In this study, Ni, Ni-SiC and Ni-Al2O3 coatings were electroplated on the 2xxx series aluminium alloy. The following parameters of the electroplating process were applied: current density - 4A/dm2, time - 60 minutes, and temperature - 60°C. Hard particles of submicrometric size were used. The results of the research showing the effect of the addition of hard particles (introduced into the nickel bath as a dispersed phase) on the properties of coatings, including the effect of the type (SiC or...

  13. Strain relaxation during solid-phase epitaxial crystallisation of Ge{sub x}Si{sub 1-x} alloy layers with depth dependent G{sub e} compositions

    Energy Technology Data Exchange (ETDEWEB)

    Wong, Wahchung; Elliman, R.G.; Kringhoj, P. [Australian National Univ., Canberra, ACT (Australia). Research School of Physical Sciences

    1993-12-31

    The solid-phase epitaxial crystallisation of depth dependent Ge{sub x}Si{sub lx} alloy layers produced by implanting Ge into Si substrates was studied. In-situ monitoring was done using time-resolved reflectivity (TRR) whilst post-anneal defect structures were characterised by Rutherford backscattering and channeling spectrometry (RBS-C) and transmission electron microscopy (TEM). Particular attention was directed at Ge concentrations above the critical concentration for the growth of fully strained layers. Strain relief is shown to be correlated with a sudden reduction in crystallisation velocity caused by roughening of the crystalline/amorphous interface. 11 refs., 1 tab., 2 figs.

  14. Frustrated S = 1/2 Two-Leg Ladder with Different Leg Interactions

    Science.gov (United States)

    Tonegawa, Takashi; Okamoto, Kiyomi; Hikihara, Toshiya; Sakai, Tôru

    2017-04-01

    We explore the ground-state phase diagram of the S = 1/2 two-leg ladder. The isotropic leg interactions J1,a and J1,b between nearest neighbor spins in the legs a and b, respectively, are different from each other. The xy and z components of the uniform rung interactions are denoted by Jr and ΔJr, respectively, where Δ is the XXZ anisotropy parameter. This system has a frustration when J1,aJ1,b employ the physical consideration, the level spectroscopy analysis of the results obtained by the exact diagonalization method and also the density-matrix renormalization-group method. It is found that the non-collinear ferrimagnetic (NCFR) state appears as the ground state in the frustrated region of the parameters. Furthermore, the direct-product triplet-dimer (TD) state in which all rungs form the TD pair is the exact ground state, when J1,a + J1,b = 0 and 0≤ Δ ≲ 0.83. The obtained phase diagrams consist of the TD, XY and Haldane phases as well as the NCFR phase.

  15. Solid Phase Equilibrium Relations in the CaO-SiO2-Nb2O5-La2O3 System at 1273 K

    Science.gov (United States)

    Qiu, Jiyu; Liu, Chengjun

    2018-02-01

    Silicate slag system with additions Nb and RE formed in the utilization of REE-Nb-Fe ore deposit resources in China has industrial uses as a metallurgical slag system. The lack of a phase diagram, theoretical, and thermodynamic information for the multi-component system restrict the comprehensive utilization process. In the current work, solid phase equilibrium relations in the CaO-SiO2-Nb2O5-La2O3 quaternary system at 1273 K (1000 °C) were investigated experimentally by the high-temperature equilibrium experiment followed by X-ray diffraction, scanning electron microscope, and energy dispersive spectrometer. Six spatial independent tetrahedron fields in the CaO-SiO2-Nb2O5-La2O3 system phase diagram were determined by the Gibbs Phase Rule. The current work combines the mass fraction of equilibrium phase and corresponding geometric relation. A determinant method was deduced to calculate the mass fraction of equilibrium phase in quaternary system according to the Mass Conservation Law, the Gibbs Phase Rule, the Lever's Rule, and the Cramer Law.

  16. Modified spin-wave theory with ordering vector optimization: frustrated bosons on the spatially anisotropic triangular lattice

    Energy Technology Data Exchange (ETDEWEB)

    Hauke, Philipp [ICFO-Institut de Ciencies Fotoniques, Meditarranean Technology Park, E-08860 Castelldefels, Barcelona (Spain); Roscilde, Tommaso [Laboratoire de Physique, Ecole Normale Superieure de Lyon, 46 Allee d' Italie, F-69007 Lyon (France); Murg, Valentin; Ignacio Cirac, J; Schmied, Roman, E-mail: Philipp.Hauke@icfo.e [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748 Garching (Germany)

    2010-05-15

    We investigate a system of frustrated hardcore bosons, modeled by an XY antiferromagnet on the spatially anisotropic triangular lattice, using Takahashi's modified spin-wave (MSW) theory. In particular, we implement ordering vector optimization on the ordered reference state of MSW theory, which leads to significant improvement of the theory and accounts for quantum corrections to the classically ordered state. The MSW results at zero temperature compare favorably to exact diagonalization (ED) and projected entangled-pair state (PEPS) calculations. The resulting zero-temperature phase diagram includes a one-dimensional (1D) quasi-ordered phase, a 2D Neel ordered phase and a 2D spiraling ordered phase. Strong indications coming from the ED and PEPS calculations, as well as from the breakdown of MSW theory, suggest that the various ordered or quasi-ordered phases are separated by spin-liquid phases with short-range correlations, in analogy to what has been predicted for the Heisenberg model on the same lattice. Within MSW theory, we also explore the finite-temperature phase diagram. In agreement with the Berezinskii-Kosterlitz-Thouless (BKT) theory, we find that zero-temperature long-range-ordered phases turn into quasi-ordered phases (up to a BKT transition temperature), while zero-temperature quasi-ordered phases become short-range correlated at finite temperature. These results show that, despite its simplicity, MSW theory is very well suited to describing ordered and quasi-ordered phases of frustrated XY spins (or, equivalently, of frustrated lattice bosons) both at zero and finite temperatures. While MSW theory, just as other theoretical methods, cannot describe spin-liquid phases, its breakdown provides a fast and reliable method for singling out Hamiltonians that may feature these intriguing quantum phases. We thus suggest a tool for guiding our search for interesting systems whose properties are necessarily studied with a physical quantum simulator

  17. The experimental exploration of nano-Si{sub 3}N{sub 4}/paraffin on thermal behavior of phase change materials

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Yanyang [Advanced Materials Institute and Clearer Production Key Laboratory, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Key Laboratory of Advanced Materials, School of Materials Science and Engineering, Tsinghua University, Haidian District, Beijing 100084 (China); Luo, Jie; Song, Guolin; Liu, Yuan [Advanced Materials Institute and Clearer Production Key Laboratory, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Tang, Guoyi, E-mail: tanggy@tsinghua.edu.cn [Advanced Materials Institute and Clearer Production Key Laboratory, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Key Laboratory of Advanced Materials, School of Materials Science and Engineering, Tsinghua University, Haidian District, Beijing 100084 (China)

    2014-12-10

    Highlights: • A new high thermal conductivity phase change materials. • Experimental study of strengthening thermal conductivity of phase change materials. • Theoretical analyses of thermal conductivity and crystallization. • Increased latent heat of phase change materials. - Abstract: In this study, nano-Si3N4 was employed to enhance thermal performance of phase change materials (PCMs), and a new formula was proposed to explain the relationship between the thermal conductivity and the latent heat. Ultrasonically stirred, the composite PCMs were prepared at 80 °C with different additional rate (1, 2, 3, 4, 5, 10wt%). The experimental results showed that the thermal conductivity of composite PCMs increased with the increasing Si3N4 loading contents, and the thermal conductivity increased by 35% while the thermal diffusivity increased by 47% at 10wt% Si{sub 3}N{sub 4} additional fraction. Additionally, there was an interesting phenomenon. The latent heat of the composite PCMs at 1wt% addition rate was 3.4% higher than that of paraffin, that has been rarely reported in articles. An explanation was provided from crystallography and thermodynamic. A calculation method was also performed with relative errors in the range of 5.68%.

  18. Phase Evolution and Mechanical Properties of AlCoCrFeNiSi x High-Entropy Alloys Synthesized by Mechanical Alloying and Spark Plasma Sintering

    Science.gov (United States)

    Kumar, Anil; Swarnakar, Akhilesh Kumar; Chopkar, Manoj

    2018-05-01

    In the current investigation, AlCoCrFeNiSi x (x = 0, 0.3, 0.6 and 0.9 in atomic ratio) high-entropy alloy systems are prepared by mechanical alloying and subsequently consolidated by spark plasma sintering. The microstructural and mechanical properties were analyzed to understand the effect of Si addition in AlCoCrFeNi alloy. The x-ray diffraction analysis reveals the supersaturated solid solution of the body-centered cubic structure after 20 h of ball milling. However, the consolidation promotes the transformation of body-centered phases partially into the face-centered cubic structure and sigma phases. A recently proposed geometric model based on the atomic stress theory has been extended for the first time to classify single phase and multi-phases on the high-entropy alloys prepared by mechanical alloying and spark plasma sintering process. Improved microhardness and better wear resistance were achieved as the Si content increased from 0 to 0.9 in the present high-entropy alloy.

  19. Dynamics of the phase transitions in the system of nonequilibrium charge carriers in quantum-dimensional Si{sub 1−x}Ge{sub x}/Si structures

    Energy Technology Data Exchange (ETDEWEB)

    Bagaev, V. S.; Krivobok, V. S., E-mail: krivobok@lebedev.ru; Nikolaev, S. N.; Onishchenko, E. E.; Pruchkina, A. A.; Aminev, D. F.; Skorikov, M. L. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Lobanov, D. N.; Novikov, A. V. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)

    2013-11-15

    The dynamics of the phase transition from an electron-hole plasma to an exciton gas is studied during pulsed excitation of heterostructures with Si{sub 1−x}Ge{sub x}/Si quantum wells. The scenario of the phase transition is shown to depend radically on the germanium content in the Si{sub 1−x}Ge{sub x} layer. The electron-hole system decomposes into a rarefied exciton and a dense plasma phases for quantum wells with a germanium content x = 3.5% in the time range 100–500 ns after an excitation pulse. In this case, the electron-hole plasma existing in quantum wells has all signs of an electron-hole liquid. A qualitatively different picture of the phase transition is observed for quantum wells with x = 9.5%, where no separation into phases with different electronic spectra is detected. The carrier recombination in the electron-hole plasma leads a gradual weakening of screening and the appearance of exciton states. For a germanium content of 5–7%, the scenario of the phase transition is complex: 20–250 ns after an excitation pulse, the properties of the electron-hole system are described in terms of a homogeneous electron-hole plasma, whereas its separation into an electron-hole liquid and an exciton gas is detected after 350 ns. It is shown that, for the electron-hole liquid to exist in quantum wells with x = 5–7% Ge, the exciton gas should have a substantially higher density than in quantum wells with x = 3.5% Ge. This finding agrees with a decrease in the depth of the local minimum of the electron-hole plasma energy with increasing germanium concentration in the SiGe layer. An increase in the density of the exciton gas coexisting with the electron-hole liquid is shown to enhance the role of multiparticle states, which are likely to be represented by trions T{sup +} and biexcitons, in the exciton gas.

  20. Dynamics of the α-β phase transitions in quartz and cristobalite as observed by in-situ high temperature 29Si and 17O NMR

    Science.gov (United States)

    Spearing, Dane R.; Farnan, Ian; Stebbins, Jonathan F.

    1992-12-01

    Relaxation times (T1) and lineshapes were examined as a function of temperature through the α-β transition for 29Si in a single crystal of amethyst, and for 29Si and 17O in cristobalite powders. For single crystal quartz, the three 29Si peaks observed at room temperature, representing each of the three differently oriented SiO4 tetrahedra in the unit cell, coalesce with increasing temperature such that at the α-β transition only one peak is observed. 29Si T1's decrease with increasing temperature up to the transition, above which they remain constant. Although these results are not uniquely interpretable, hopping between the Dauphiné twin related configurations, α1 and α2, may be the fluctuations responsible for both effects. This exchange becomes observable up to 150° C below the transition, and persists above the transition, resulting in β-quartz being a time and space average of α1 and α2. 29Si T1's for isotopically enriched powdered cristobalite show much the same behavior as observed for quartz. In addition, 17O T1's decrease slowly up to the α-β transition at which point there is an abrupt 1.5 order of magnitude drop. Fitting of static powder 17O spectra for cristobalite gives an asymmetry parameter (η) of 0.125 at room T, which decreases to <0.040 at the transition temperature. The electric field gradient (EFG) and chemical shift anisotropy (CSA), however, remain the same, suggesting that the decrease in η is caused by a dynamical rotation of the tetrahedra below the transition. Thus, the mechanisms of the α-β phase transitions in quartz and cristobalite are similar: there appears to be some fluctuation of the tetrahedra between twin-related orientations below the transition temperature, and the β-phase is characterized by a dynamical average of the twin domains on a unit cell scale.

  1. Decaying shock studies of phase transitions in MgO-SiO2 systems: implications for the Super-Earths' interiors

    Science.gov (United States)

    Bolis, R.; Morard, G.; Vinci, T.; Ravasio, A.; Bambrink, E.; Guarguaglini, M.; Koenig, M.; Musella, R.; Françoise, R.; Bouchet, J.; Ozaki, N.; Miyanishi, K.; Sekine, T.; Sakawa, Y.; Sano, T.; Kodama, R.; Guyot, F. J.; Benuzzi, A.

    2016-12-01

    Mantles of telluric exoplanets, so-called Earth-like and Super-Earths, are expected to be mainly composed of different type of oxides, such as periclase (MgO), enstatite (MgSiO3) and forsterite (Mg2SiO4). Determining the phase diagrams, melting curves and liquid properties of these compounds under extreme pressure (0.2-1 TPa) is crucial to model the internal dynamic of these exoplanets, as the melting of mantle components controls planetary temperature profiles [6]. Experimentally, these planetary thermodynamic states can be achieved with laser-shock compression. Here we present laser-driven decaying shock experiments on MgO, MgSiO3 and Mg2SiO4 samples performed at LULI and GEKKO laser facilities, where we focused 1.2-2.5 ns laser pulses with an intensity between 3-8 1013 W/cm2 exploring pressures between 0.2 and 1 TPa and temperature between 5000 and 30000 K. We determined the thermodynamic states using rear side optical diagnostics. We observed a single transition for MgO associated to melting (at 0.47 TPa ± 0.04 and 9863 ± 812 K) and no evidence of a liquid-liquid transition, dissociation or melting for all the other compounds in the range 150-500 Gpa and 200-800 Gpa respectively for MgSiO3 and Mg2SiO4. Some implications are presented comparing our data experimental and theoretical data found in literature [1, 2, 3, 4, 5]. In particular these results represent a key input to solve the controversy on a possible MgSiO3 liquid-liquid phase transition. Moreover we propose a revision of the phase diagram of MgO, with a lower melting line which results in a lower temperature profile for super-Earths. Finally our data evidence the presence of a poor electrically conducting liquid in the phase diagram of all the studied material, with implications for the modelling of magnetic field generation via dynamo mechanism.[1] McWilliams et al., Science 338 (2012): 1330-1333. [2] Spaulding et al., Physical Review Letters108 (2012): 065701. [3] Root et al., Physical Review

  2. Acid-base chemistry of frustrated water at protein interfaces.

    Science.gov (United States)

    Fernández, Ariel

    2016-01-01

    Water molecules at a protein interface are often frustrated in hydrogen-bonding opportunities due to subnanoscale confinement. As shown, this condition makes them behave as a general base that may titrate side-chain ammonium and guanidinium cations. Frustration-based chemistry is captured by a quantum mechanical treatment of proton transference and shown to remove same-charge uncompensated anticontacts at the interface found in the crystallographic record and in other spectroscopic information on the aqueous interface. Such observations are untenable within classical arguments, as hydronium is a stronger acid than ammonium or guanidinium. Frustration enables a directed Grotthuss mechanism for proton transference stabilizing same-charge anticontacts. © 2015 Federation of European Biochemical Societies.

  3. Ordering due to disorder in frustrated quantum magnetic system

    International Nuclear Information System (INIS)

    Yildirim, T.

    1999-01-01

    The phenomenon of order by disorder in frustrated magnetic systems is reviewed. Disorder (thermal or quantum fluctuations) may sometimes give rise to long range ordering in systems with frustration, where one must often consider the selection among classically degenerate ground states which are not equivalent by any symmetry. The lowest order effects of quantum fluctuations in such frustrated systems usually resolves the continues degeneracy of the ground state manifold into discrete Ising-type degeneracy. A unique ground state selection out of this Ising degenerate manifold then occurs due to higher order effects of quantum fluctuations. For systems such as face-centered cubic and body-centered tetragonal antiferromagnets where the number of Ising parameters to describe the ground state manifold is not macroscopic, we show that quantum fluctuations choose a unique ground state at the first order in 1/S

  4. Phase Stability and Electronic Structure of Prospective Sb-Based Mixed Sulfide and Iodide 3D Perovskite (CH3NH3)SbSI2.

    Science.gov (United States)

    Li, Tianyang; Wang, Xiaoming; Yan, Yanfa; Mitzi, David B

    2018-06-29

    Lead-free antimony-based mixed sulfide and iodide perovskite phases have recently been reported to be synthesized experimentally and to exhibit reasonable photovoltaic performance. Through a combination of experimental validation and computational analysis, we show no evidence of the formation of the mixed sulfide and iodide perovskite phase, MASbSI 2 (MA = CH 3 NH 3 + ), and instead that the main products are a mixture of the binary and ternary compounds (Sb 2 S 3 and MA 3 Sb 2 I 9 ). Density functional theory calculations also indicate that such a mixed sulfide and iodide perovskite phase should be thermodynamically less stable compared with binary/ternary anion-segregated secondary phases and less likely to be synthesized under equilibrium conditions. Additionally, band structure calculations show that this mixed sulfide and iodide phase, if possible to synthesize (e.g., under nonequilibrium conditions), should have a suitable direct band gap for photovoltaic application.

  5. Crystallization of pyroxene phases and physico-chemical properties of glass-ceramics based on Li{sub 2}O–Cr{sub 2}O{sub 3}–SiO{sub 2} eutectic glass system

    Energy Technology Data Exchange (ETDEWEB)

    Salman, S.M.; Salama, S.N.; Abo-Mosallam, H.A., E-mail: abomosallam@yahoo.com.au

    2015-01-15

    The crystallization characteristics, crystalline phase assemblages and solid solution phases developed due to thermally crystallized glasses based on the Li{sub 2}SiO{sub 3}–Li{sub 2}Si{sub 2}O{sub 5}–LiCrSi{sub 2}O{sub 6} (1028 ± 3 °C) eutectic glass system by replacing some trivalent oxides instead of Cr{sub 2}O{sub 3} were investigated. The microhardness and chemical durability of the glass-ceramics were also determined. Lithium meta and disilicate (Li{sub 2}SiO{sub 3} and Li{sub 2}Si{sub 2}O{sub 5}), lithium gallium silicate (LiGaSiO{sub 4}), and varieties of pyroxene phases, including Cr-pyroxene phase, i.e. lithium-kosmochlor (LiCrSi{sub 2}O{sub 6}), lithium aluminum silicate (LiAlSi{sub 2}O{sub 6}), lithium indium silicate (LiInSi{sub 2}O{sub 6}) and pyroxene solid solution of Li-aegerine type [Li (Fe{sub 0.5}, Cr{sub 0.5}) Si{sub 2}O{sub 6}] were the main crystalline phases formed in the crystallized glasses. There is no evidence for the formation of solid solution or liquid immiscibility gaps between LiAlSi{sub 2}O{sub 6} or LiInSi{sub 2}O{sub 6} phases and LiCrSi{sub 2}O{sub 6} phase. However, LiCrSi{sub 2}O{sub 6} and LiFeSi{sub 2}O{sub 6} components were accommodated in the pyroxene structure under favorable conditions of crystallization to form monomineralic pyroxene solid solution phase of the probably formula [Li (Fe{sub 0.5}, Cr{sub 0.5}) Si{sub 2}O{sub 6}]. The type and compatibility of the crystallized phases are discussed in relation to the compositional variation of the glasses and heat-treatment applied. The microhardness values of the crystalline materials ranged between 5282 and 6419 MPa while, the results showed that the chemical stability of the glass-ceramics was better in alkaline than in acidic media. - Highlights: • Glass ceramics based on Li{sub 2}O–Cr{sub 2}O{sub 3}–SiO{sub 2} eutectic (1028 ± 3 °C) glass were prepared. • LiCrSi{sub 2}O{sub 6} and LiFeSi{sub 2}O{sub 6} phases form monomineralic pyroxene solid

  6. Cooper pair induced frustration and nematicity of two-dimensional magnetic adatom lattices

    Science.gov (United States)

    Schecter, Michael; Syljuâsen, Olav F.; Paaske, Jens

    2018-05-01

    We propose utilizing the Cooper pair to induce magnetic frustration in systems of two-dimensional (2D) magnetic adatom lattices on s -wave superconducting surfaces. The competition between singlet electron correlations and the RKKY coupling is shown to lead to a variety of hidden-order states that break the point-group symmetry of the 2D adatom lattice at finite temperature. The phase diagram is constructed using a newly developed effective bond theory [M. Schecter et al., Phys. Rev. Lett. 119, 157202 (2017), 10.1103/PhysRevLett.119.157202], and exhibits broad regions of long-range vestigial nematic order.

  7. Simultaneous multi-wavelength ultraviolet excited single-phase white light emitting phosphor Ba1-x(Zr,Ti)Si3O9:xEu

    Science.gov (United States)

    Zhou, Zhenzhen; Liu, Guanghui; Ni, Jia; Liu, Wanlu; Liu, Qian

    2018-05-01

    A kind of novel compound Ba1-x(Zr,Ti)Si3O9:xEu simultaneously activated by different-valence Eu2+ and Eu3+ ions has been successfully synthesized. The existence of Ti4+-O2- charge transfer (CT) transitions in Ba1-xZrSi3O9:xEu is proved by the photoluminescence spectra and first principle calculations, and the Ti4+ ions come from the impurities in commercial ZrO2 raw materials. Under the excitation of multi-wavelength ultraviolet radiation (λEX = 392, 260, 180 nm), Ba1-xZrSi3O9:xEu (x = 0.15) can directly emit nearly white light. The coexistence of multiple luminescent centers and the energy transfer among Zr4+-O2- CT state, Ti4+-O2- CT state, Eu2+ and Eu3+ ions play important roles in the white light emission. Ba1-xZrSi3O9:xEu (x = 0.15) has good thermal stability, in particular, the intensity of emission spectrum (λEX = 392 nm) at 150 °C is ∼96% of that at room temperature. In general, the multi-wavelength ultraviolet-excited single-phase white light emitting phosphor Ba1-x(Zr,Ti)Si3O9:xEu possesses a promise for applications in white light emitting diodes (WLEDs), agriculture, medicine and other photonic fields.

  8. NATpipe: an integrative pipeline for systematical discovery of natural antisense transcripts (NATs) and phase-distributed nat-siRNAs from de novo assembled transcriptomes

    Science.gov (United States)

    Yu, Dongliang; Meng, Yijun; Zuo, Ziwei; Xue, Jie; Wang, Huizhong

    2016-01-01

    Nat-siRNAs (small interfering RNAs originated from natural antisense transcripts) are a class of functional small RNA (sRNA) species discovered in both plants and animals. These siRNAs are highly enriched within the annealed regions of the NAT (natural antisense transcript) pairs. To date, great research efforts have been taken for systematical identification of the NATs in various organisms. However, developing a freely available and easy-to-use program for NAT prediction is strongly demanded by researchers. Here, we proposed an integrative pipeline named NATpipe for systematical discovery of NATs from de novo assembled transcriptomes. By utilizing sRNA sequencing data, the pipeline also allowed users to search for phase-distributed nat-siRNAs within the perfectly annealed regions of the NAT pairs. Additionally, more reliable nat-siRNA loci could be identified based on degradome sequencing data. A case study on the non-model plant Dendrobium officinale was performed to illustrate the utility of NATpipe. Finally, we hope that NATpipe would be a useful tool for NAT prediction, nat-siRNA discovery, and related functional studies. NATpipe is available at www.bioinfolab.cn/NATpipe/NATpipe.zip. PMID:26858106

  9. Frustrations among graduates of athletic training education programs.

    Science.gov (United States)

    Bowman, Thomas G; Dodge, Thomas M

    2013-01-01

    Although previous researchers have begun to identify sources of athletic training student stress, the specific reasons for student frustrations are not yet fully understood. It is important for athletic training administrators to understand sources of student frustration to provide a supportive learning environment. To determine the factors that lead to feelings of frustration while completing a professional athletic training education program (ATEP). Qualitative study. National Athletic Trainers' Association (NATA) accredited postprofessional education program. Fourteen successful graduates (12 women, 2 men) of accredited professional undergraduate ATEPs enrolled in an NATA-accredited postprofessional education program. We conducted semistructured interviews and analyzed data with a grounded theory approach using open, axial, and selective coding procedures. We negotiated over the coding scheme and performed peer debriefings and member checks to ensure trustworthiness of the results. Four themes emerged from the data: (1) Athletic training student frustrations appear to stem from the amount of stress involved in completing an ATEP, leading to anxiety and feelings of being overwhelmed. (2) The interactions students have with classmates, faculty, and preceptors can also be a source of frustration for athletic training students. (3) Monotonous clinical experiences often left students feeling disengaged. (4) Students questioned entering the athletic training profession because of the fear of work-life balance problems and low compensation. In order to reduce frustration, athletic training education programs should validate students' decisions to pursue athletic training and validate their contributions to the ATEP; provide clinical education experiences with graded autonomy; encourage positive personal interactions between students, faculty, and preceptors; and successfully model the benefits of a career in athletic training.

  10. Rapid ultrasound-induced transient-liquid-phase bonding of Al-50Si alloys with Zn interlayer in air for electrical packaging application.

    Science.gov (United States)

    Wang, Qian; Chen, Xiaoguang; Zhu, Lin; Yan, Jiuchun; Lai, Zhiwei; Zhao, Pizhi; Bao, Juncheng; Lv, Guicai; You, Chen; Zhou, Xiaoyu; Zhang, Jian; Li, Yuntao

    2017-01-01

    Al-50Si alloys were joined by rapid ultrasound-induced transient-liquid-phase bonding method using Zn foil as interlayer at 390°C in air, below the melt point of interlayer. The fracture of oxide films along the edge of Si particles led to contact and inter-diffusion between aluminum substrate and Zn interlayer, and liquefied Zn-Al alloys were developed. The width of Zn-Al alloys gradually decreased with increasing the ultrasonic vibration time due to liquid squeezing out and accelerated diffusion. A stage of isothermal solidification existed, and the completion time was significantly shortened. In the liquid metal, the acoustic streaming and ultrasonic cavitations were induced. As the process developed, much more Si particles, which were particulate-reinforced phases of Al-50Si, gradually migrated to the center of soldering seam. The highest average shear strength of joints reached to 94.2MPa, and the fracture mainly occurred at the base metal. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Ultrathin highly uniform Ni(Al) germanosilicide layer with modulated B8 type Ni5(SiGe)3 phase formed on strained Si1−xGex layers

    International Nuclear Information System (INIS)

    Liu, Linjie; Xu, Dawei; Jin, Lei; Knoll, Lars; Wirths, Stephan; Nichau, Alexander; Buca, Dan; Mussler, Gregor; Holländer, Bernhard; Zhao, Qing-Tai; Mantl, Siegfried; Feng Di, Zeng; Zhang, Miao

    2013-01-01

    We present a method to form ultrathin highly uniform Ni(Al) germanosilicide layers on compressively strained Si 1−x Ge x substrates and their structural characteristics. The uniform Ni(Al) germanosilicide film is formed with Ni/Al alloy at an optimized temperature of 400 °C with an optimized Al atomic content of 20 at. %. We find only two kinds of grains in the layer. Both grains show orthogonal relationship with modified B8 type phase. The growth plane is identified to be (10-10)-type plane. After germanosilicidation the strain in the rest Si 1−x Ge x layer is conserved, which provides a great advantage for device application

  12. Psychometric properties of Frustration Discomfort Scale in a Turkish sample.

    Science.gov (United States)

    Ozer, Bilge Uzun; Demir, Ayhan; Harrington, Neil

    2012-08-01

    The present study assessed the psychometric properties of the Frustration Discomfort Scale for Turkish college students. The Frustration Discomfort Scale (FDS), Procrastination Assessment Scale-Student, and Rosenberg Self-Esteem Scale were administered to a sample of 171 (98 women, 73 men) Turkish college students. The results of the confirmatory factor analysis yielded fit index values demonstrating viability of the four-dimensional solution as in the original. Findings also revealed that, as predicted, the Discomfort Intolerance subscale of Turkish FDS was most strongly correlated with procrastination. Overall results provided evidence for the factor validity and reliability of the Turkish version of the scale for use in a Turkish population.

  13. Liquid structure as a guide for phase stability in the solid state: Discovery of a stable compound in the Au-Si alloy system

    International Nuclear Information System (INIS)

    Tasci, Emre S.; Sluiter, Marcel H.F.; Pasturel, Alain; Villars, Pierre

    2010-01-01

    A new crystalline ground state was discovered in the Au-Si system through first-principles electronic structure calculations. The new structure was found using the experimentally and theoretically determined local atomic structure in the liquid as a guide for the solid state. Local atomic structure in the liquid was matched with that for all known crystal structures as compiled in the Pauling File structural database. The best matching crystalline structures were then explicitly calculated using first-principles methods. Most candidate crystal structures were found to be close, but above the enthalpy of a composition weighted average of the face-centered cubic Au and diamond structure Si terminal phases, but one crystal structure was more stable than the terminal phases by about 10 meV atom -1 at T = 0 K. As first-principles simulations of local structure are feasible for most liquid alloys, the present methodology is applicable to other alloys lying near a eutectic composition.

  14. Spin-orbit interaction driven dimerization in one dimensional frustrated magnets

    Science.gov (United States)

    Zhang, Shang-Shun; Batista, Cristian D.

    Spin nematic ordering has been proposed to emerge near the saturation of field of a class of frustrated magnets. The experimental observation of this novel phase is challenging for the traditional experimental probes. Nematic spin ordering is expected to induce a local quadrupolar electric moment via the spin-orbit coupling. However, a finite spin-orbit interaction explicitly breaks the U(1) symmetry of global spin rotations down to Z2, which renders the traditional nematic order no longer well-defined. In this work we investigate the relevant effect of spin-orbit interaction on the 1D frustrated J1 -J2 model. The real and the imaginary parts of the nematic order parameter belong to different representations of the discrete symmetry group of the new Hamiltonian. We demonstrate that spin-orbit coupling stabilizes the real component and simultaneously induces bond dimerization in most of the phase diagram. Such a bond dimerization can be observed with X-rays or nuclear magnetic resonance. In addition, an incommensurate bond-density wave (ICBDW) appears for smaller values of J2 / |J1 | . The experimental fingerprint of the ICBDW is a double-horn shape of the the NMR line. These conclusions can shed light on the experimental search of this novel phase.

  15. Effect of Low-Melting Metals (Pb, Bi, Cd, In) on the Structure, Phase Composition, and Properties of Casting Al-5% Si-4% Cu Alloy

    Science.gov (United States)

    Yakovleva, A. O.; Belov, N. A.; Bazlova, T. A.; Shkalei, I. V.

    2018-01-01

    The effect of low-melting metals (Pb, Bi, Cd, In) on the structure, phase composition, and properties of the Al-5% Si-4% Cu alloy was studied using calculations. Polythermal sections have been reported, which show that the considered systems are characterized by the presence of liquid regions and monotectic reactions. The effect of low-melting metals on the microstructure and hardening of base alloy in the cast and heat-treated states has been studied.

  16. Phase transitions of Cu.sub.3+x./sub.Si observed by temperature-dependent x-ray powder diffraction

    Czech Academy of Sciences Publication Activity Database

    Correa, Cinthia Antunes; Poupon, Morgane; Kopeček, Jaromír; Král, Robert; Zemenová, Petra; Lecourt, J.; Barrier, N.; Brázda, Petr; Klementová, Mariana; Palatinus, Lukáš

    2017-01-01

    Roč. 91, Dec (2017), s. 129-139 ISSN 0966-9795 R&D Projects: GA ČR GC15-08842J Institutional support: RVO:68378271 Keywords : X-ray powder diffraction * differential scanning calorimetry * phase transitions * Cu3+xSi Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 3.140, year: 2016

  17. Development of SiC Nanoparticles and Second Phases Synergistically Reinforced Mg-Based Composites Processed by Multi-Pass Forging with Varying Temperatures

    Directory of Open Access Journals (Sweden)

    Kaibo Nie

    2018-01-01

    Full Text Available In this study, SiC nanoparticles were added into matrix alloy through a combination of semisolid stirring and ultrasonic vibration while dynamic precipitation of second phases was obtained through multi-pass forging with varying temperatures. During single-pass forging of the present composite, as the deformation temperature increased, the extent of recrystallization increased, and grains were refined due to the inhibition effect of the increasing amount of dispersed SiC nanoparticles. A small amount of twins within the SiC nanoparticle dense zone could be found while the precipitated phases of Mg17Al12 in long strips and deformation bands with high density dislocations were formed in the particle sparse zone after single-pass forging at 350 °C. This indicated that the particle sparse zone was mainly deformed by dislocation slip while the nanoparticle dense zone may have been deformed by twinning. The yield strength and ultimate tensile strength of the composites were gradually enhanced through increasing the single-pass forging temperature from 300 °C to 400 °C, which demonstrated that initial high forging temperature contributed to the improvement of the mechanical properties. During multi-pass forging with varying temperatures, the grain size of the composite was gradually decreased while the grain size distribution tended to be uniform with reducing the deformation temperature and extending the forging passes. In addition, the amount of precipitated second phases was significantly increased compared with that after multi-pass forging under a constant temperature. The improvement in the yield strength of the developed composite was related to grain refinement strengthening and Orowan strengthening resulting from synergistical effect of the externally applied SiC nanoparticles and internally precipitated second phases.

  18. Probing the electronic structure of Ni–Mn–In–Si based Heusler alloys thin films using magneto-optical spectra in martensitic and austenitic phases

    Energy Technology Data Exchange (ETDEWEB)

    Novikov, A. [Department of Physics, Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Sokolov, A., E-mail: asokol@unlserve.unl.edu [Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE 68588 (United States); Gan’shina, E.A. [Department of Physics, Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Quetz, Abdiel; Dubenko, I.S. [Department of Physics, Southern Illinois University, Carbondale, IL 62901 (United States); Stadler, S. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States); Ali, N. [Department of Physics, Southern Illinois University, Carbondale, IL 62901 (United States); Titov, I.S.; Rodionov, I.D. [Department of Physics, Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Lähderanta, E. [Lappeenranta University of Technology, 53851 (Finland); Zhukov, A. [Dpto. de Física de Materiales, Fac. Químicas, UPV/EHU, 20018 San Sebastian (Spain); IKERBASQUE, Basque Foundation for Science, 48011 Bilbao (Spain); Granovsky, A.B. [Department of Physics, Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Sabirianov, R. [Department of Physics, University of Nebraska at Omaha, Omaha, NE 68182 (United States)

    2017-06-15

    Highlights: • Magneto-optical properties of NiMnIn thin films with a magnetostructural transition. • Comparative analysis of magnetic properties in martensitic and austenite phases. • DFT calculations of the MO Kerr effect and site-resolved DOS agree with experiment. • The electronic structure does not change significantly with Martensitic transition. - Abstract: Thin films of Ni{sub 52}Mn{sub 35−x}In{sub 11+x}Si{sub 2} were fabricated by magnetron sputtering on MgO (0 0 1) single crystal substrates. Magnetization as function of temperature for Ni{sub 52}Mn{sub 35}In{sub 11}Si{sub 2} exhibits features consistent with a magnetostructural transition (MST) from an austenitic phase to a martensitic phase, similar to the bulk material. We observed that the martensitic transformation is externally sensitive to small changes in chemical composition and stoichiometry. It has been found that thin films of Ni{sub 52}Mn{sub 34−x}In{sub 11+x}Si{sub 2} with x = 0 and 1 undergo a temperature-induced MST or remain in a stable austenitic phase, respectively. Comparison of magneto-optical transverse Kerr effect spectra obtained at 0.5–4.0 eV in the 35–300 K temperature interval reveal insignificant differences between the martensitic and austenite phases. We found that the field and temperature dependencies of the transverse Kerr effect are quite different from the magnetization behavior, which is attributed to magnetic inhomogeneity across the films. To elucidate the effects of magnetostructural phase transitions on the electronic properties, we performed density functional calculations of the magneto-optical Kerr effect.

  19. How Is Frustration Related to Online Gamer Loyalty? A Synthesis of Multiple Theories.

    Science.gov (United States)

    Huang, Han-Chung; Liao, Gen-Yih; Chiu, Kay-Ling; Teng, Ching-I

    2017-11-01

    Online games can frustrate their gamers, but little was known about how such frustration impacts gamer loyalty. Because novice and experienced gamers may respond differently to frustration, this study investigates how gamers' frustration influences their loyalty and how this influence may differ between novice and experienced gamers. Because of the complexity of this issue, multiple theories were synthesized to develop the theoretical model. This study collected responses from 558 online gamers. Findings indicate that frustration is positively related to novice gamers' participation in task teams, and subsequently their loyalty. However, frustration is negatively related to the self-efficacy of experienced gamers and to their loyalty.

  20. Phase formation kinetics, hardness and magnetocaloric effect of sub-rapidly solidified LaFe11.6Si1.4 plates during isothermal annealing

    Science.gov (United States)

    Dai, Yuting; Xu, Zhishuai; Luo, Zhiping; Han, Ke; Zhai, Qijie; Zheng, Hongxing

    2018-05-01

    High-temperature phase transition behavior and intrinsic brittleness of NaZn13-type τ1 phase in La-Fe-Si magnetocaloric materials are two key problems from the viewpoint of materials production and practical applications. In the present work, the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation was introduced to quantitatively characterize the formation kinetics of τ1 phase in sub-rapidly solidified LaFe11.6Si1.4 plates during the isothermal annealing process. Avrami index was estimated to be 0.43 (∼0.5), which suggests that the formation of τ1 phase is in a diffusion-controlled one-dimensional growth mode. Meanwhile, it is found that the Vickers hardness as a function of annealing time for sub-rapidly solidified plates also agrees well with the JMAK equation. The Vickers hardness of τ1 phase was estimated to be about 754. Under a magnetic field change of 30 kOe, the maximum magnetic entropy change was about 22.31 J/(kg·K) for plates annealed at 1323 K for 48 h, and the effective magnetic refrigeration capacity reached 191 J/kg.

  1. Phase stability, swelling, microstructure and strength of Ti{sub 3}SiC{sub 2}-TiC ceramics after low dose neutron irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Ang, Caen, E-mail: angck@ornl.gov [Oak Ridge National Laboratory, Oak Ridge, TN 37830 (United States); Zinkle, Steven [Oak Ridge National Laboratory, Oak Ridge, TN 37830 (United States); University of Tennessee, Knoxville, TN 37996 (United States); Shih, Chunghao; Silva, Chinthaka; Cetiner, Nesrin; Katoh, Yutai [Oak Ridge National Laboratory, Oak Ridge, TN 37830 (United States)

    2017-01-15

    M{sub n+1}AX{sub n} (MAX) phase Ti{sub 3}SiC{sub 2} materials were neutron irradiated at ∼400, ∼630, and 700 °C to a fluence of ∼2 × 10{sup 25} n/m{sup 2} (E > 0.1 MeV). After irradiation at ∼400 °C, anisotropic c-axis dilation of ∼1.5% was observed. Room temperature strength was reduced from 445 ± 29 MPa to 315 ± 33 MPa and the fracture surfaces showed flat facets and transgranular cracks instead of typical kink-band deformation and bridging ligaments. XRD phase analysis indicated an increase of 10–15 wt% TiC. After irradiation at ∼700 °C there were no lattice parameter changes, ∼5 wt% decomposition to TiC occurred, and strength was 391 ± 71 MPa and 378 ± 31 MPa. The fracture surfaces indicated kink-band based deformation but with lesser extent of delamination than as-received samples. Ti{sub 3}SiC{sub 2} appears to be radiation tolerant at ∼400 °C, and increasingly radiation resistant at ∼630–700 °C, but a higher temperature may be necessary for full recovery. - Highlights: • Ti{sub 3}SiC{sub 2} candidate nuclear material for intrinsic toughness. • Neutron irradiation to 2 dpa complete (∼equivalent to a few months in LWR core). • First reported fracture strengths of Ti{sub 3}SiC{sub 2} after irradiation. • All toughening mechanisms in Ti{sub 3}SiC{sub 2} observed to be operational during irradiation at 700 °C. • Swelling recovery dominated by threshold migration in TiC (or TiC{sub 6}).

  2. Electron-beam-induced structure transformation of the quasicrystalline phases of the Al 62Cu 20Co 15Si 3 alloy

    Science.gov (United States)

    Reyes-Gasga, J.; R. Garcia, G.; Jose-Yacaman, M.

    1995-02-01

    Some details on the phase transformation experienced by the quasicrystalline phases of the Al 62Cu 20Co 15Si 3 alloy under a 400 kV electron beam are given. The transition is observed in situ with a high resolution electron microscope and recorded on video tape. The results show that the electron beam radiation produces a sequence of changes similar to the ones observed in an ion-beam-induced amorphization process. Considering electron radiation damage analysis, the results agree well with the "flip-flop" model [Coddens, Bellisent, Calvayrac and Ambroise (1991) Europhys. Lett.16, 271] where the transition from a quasicrystalline phase to a crystalline phase is produced by atomic displacements but not in a cascade way.

  3. Phase diagrams of aluminium alloys of Al-Cu-Mg, Al-Mg-Si-Cu, and Al-Mg-Li system

    International Nuclear Information System (INIS)

    Ber, L.B.; Kaputkin, E.Ya.

    2001-01-01

    Isothermal diagrams of phase transformations (DPT) and temperature-time charts (TTC) of variation of electric conductivity and of mechanical features at tension were plotted following thermal treatment according to the pattern of direct hardening and ageing and according to the pattern of normal aging for D16 commercial alloy, Al-Cu-Mg model alloy of the same system, AD37 commercial alloys of Al-Mg-Si-Cu and 1424 one of Al-Li-Mg system. Phase transformations were studied by means of fluorescence electron microscopy, micro-X-ray spectral analysis, X-ray phase analysis of single crystals and polycrystals and differential scanning calorimetry. For every alloy comparison of TTC and DPT enables to clarity the mechanism of phase composition effect on features and to optimize conditions of hardening cooling and ageing [ru

  4. Influence of job frustration, narcissism and demographic variables ...

    African Journals Online (AJOL)

    The study examines the hypothesised relationship among job frustration, narcissism, demographic variables and professional ethical behaviour among Nigerian Police officers. One hundred policemen drawn from four police divisions of Benin Area Command of Edo State participated in the study. There were 18 females ...

  5. More Opportunities than Wealth. A Network of Power and Frustration

    Energy Technology Data Exchange (ETDEWEB)

    Mahault, Benoit Alexandre [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Saxena, Avadh Behari [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Nisoli, Cristiano [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-08-17

    We introduce a minimal agent-based model to qualitatively conceptualize the allocation of limited wealth among more abundant opportunities. We study the interplay of power, satisfaction and frustration in the problem of wealth distribution, concentration, and inequality. This framework allows us to compare subjective measures of frustration and satisfaction to collective measures of fairness in wealth distribution, such as the Lorenz curve and the Gini index. We find that a completely libertarian, law-of-the-jungle setting, where every agent can acquire wealth from, or lose wealth to, anybody else invariably leads to a complete polarization of the distribution of wealth vs. opportunity, only minimally ameliorated by disorder in a non-optimized society. The picture is however dramatically modified when hard constraints are imposed over agents, and they are forced to share wealth with neighbors on a network. We discuss the case of random networks and scale free networks. We then propose an out of equilibrium dynamics of the networks, based on a competition of power and frustration in the decision-making of agents that leads to network evolution. We show that the ratio of power and frustration controls different dynamical regimes separated by kinetic transition and characterized by drastically different values of the indices of equality.

  6. 41 CFR 101-26.311 - Frustrated shipments.

    Science.gov (United States)

    2010-07-01

    ... 41 Public Contracts and Property Management 2 2010-07-01 2010-07-01 true Frustrated shipments. 101-26.311 Section 101-26.311 Public Contracts and Property Management Federal Property Management Regulations System FEDERAL PROPERTY MANAGEMENT REGULATIONS SUPPLY AND PROCUREMENT 26-PROCUREMENT SOURCES AND...

  7. Frustrated Lewis pairs-assisted reduction of carbonyl compounds

    Czech Academy of Sciences Publication Activity Database

    Marek, Aleš; Pedersen, M. H. F.

    2015-01-01

    Roč. 71, č. 6 (2015), s. 917-921 ISSN 0040-4020 Institutional support: RVO:61388963 Keywords : frustrated Lewis pairs * hydrogen activation * benzyl alcohol * tritium labeling * labeled compounds Subject RIV: CC - Organic Chemistry Impact factor: 2.645, year: 2015

  8. Academic Culture in Malaysia: Sources of Satisfaction and Frustration

    Science.gov (United States)

    Da Wan, Chang; Chapman, David W.; Zain, Ahmad Nurulazam Md; Hutcheson, Sigrid; Lee, Molly; Austin, Ann E.

    2015-01-01

    This paper examines the sources of satisfaction and frustration among Malaysian academics across three types of higher education institutions (HEIs)--public research university, public comprehensive university and private non-profit university. Based on interview with 67 academics across six HEIs, there is a clear pattern and relationship between…

  9. Getting Frustrated: Modelling Emotion Contagion in Stranded Passengers

    NARCIS (Netherlands)

    van der Wal, C. Natalie; Couwenberg, Maik; Bosse, T.

    2017-01-01

    Train passengers can get stranded due to a variety of events, such as a delay, technical malfunctioning or a natural disaster. Stranded passengers can get frustrated, which could escalate in misbehaviours. Examples are verbal and physical violence or dangerous behaviours such as opening emergency

  10. Frustrated Lewis pairs-assisted reduction of carbonyl compounds

    DEFF Research Database (Denmark)

    Marek, Ales; Pedersen, Martin Holst Friborg

    2015-01-01

    An alternative and robust method for the reduction of carbonyl groups by frustrated Lewis pairs (FLPs) is reported in this paper. With its very mild reaction conditions, good to excellent yields, absolute regioselectivity and the non-metallic character of the reagent, it provides an excellent too...

  11. Effect of Alloying Additions on the Phase Equilibria and Oxidation in the Mo-Si-B System

    National Research Council Canada - National Science Library

    Mendiratta, M

    2001-01-01

    .... For high-pressure turbine blade application, the ternary Mo-Si-B compositions exhibit adequate oxidation resistance in the temperature range of 1000 to 1300 deg C, but below 1000 deg C, the oxidation...

  12. THE INFLUENCE OF HEAT TREATMENT WITH THE LIQUID PHASE ON FORMATION OF A MICROSTRUCTURE OF EUTECTIC Al-Si-ALLOY

    Directory of Open Access Journals (Sweden)

    A. Anikin

    2015-01-01

    Full Text Available The effect of heat treatment on the structure of the eutectic Al-Si-alloy, a theoretical substantiation process based on thermal analyzer and cooked microstructures was presented in this paper.

  13. High Quality, Low-Scatter SiC Optics Suitable for Space-based UV & EUV Applications, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — SSG Precision Optronics proposes the development and demonstration of a new optical fabrication process for the production of EUV quality Silicon Carbide (SiC)...

  14. Uncooled Radiation Hard Large Area SiC X-ray and EUV Detectors and 2D Arrays, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — This project seeks to design, fabricate, characterize and commercialize large area, uncooled and radiative hard 4H-SiC EUV ? soft X-ray detectors capable of ultra...

  15. SUPERPOLISHED SI COATED SIC OPTICS FOR RAPID MANUFACTURE OF LARGE APERTURE UV AND EUV TELESCOPES, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — SSG/Tinsley proposes an innovative optical manufacturing process that will allow the advancement of state-of-the-art Silicon Carbide (SiC) mirrors for large aperture...

  16. Magnetic phase transitions and magnetocaloric effect of MnCoGe{sub 1−x}Si{sub x}

    Energy Technology Data Exchange (ETDEWEB)

    Lai, J.W.; Zheng, Z.G.; Montemayor, R.; Zhong, X.C.; Liu, Z.W.; Zeng, D.C., E-mail: medczeng@scut.edu.cn

    2014-12-15

    Here a cheaper alternative magnetic refrigeration material using MnCoGe{sub 1−x}Si{sub x} (x=0, 0.1, 0.3, and 0.5) alloys were investigated. The polycrystalline MnCoGe{sub 1−x}Si{sub x} alloys were prepared by arc-melting followed by annealing at 1123 K for 72 h. At a 0.5 at% Si substitution, the Curie temperatures increased by 10% to 374 K, the magnetic entropy change (|ΔS{sub M}|) values decreased by 32% to 2.1 J kg{sup −1} K{sup −1} in an applied field from 0 to 2 T and by 24% to 4.4 J kg{sup −1} K{sup −1} in an applied field from 0 to 5 T. However, the refrigeration capacity (RC{sub FWHM}) of this MnCoGe{sub 0.5}Si{sub 0.5} alloy improved by 27% to 282 J kg{sup −1} and the operation temperature range (δT{sub FWHM}) improved by 92% to 96 K in an applied field at 5 T. The MnCoGe{sub 0.5}Si{sub 0.5} alloy can compete with some of the MCE properties of the MnCo{sub 0.95}Ni{sub 0.05}Ge, LaFe{sub 11}Al{sub 2}C{sub 0.5}, (Fe{sub 85}Co{sub 5}Cr{sub 10}){sub 91}Zr{sub 7}B{sub 2}, and even the Gd{sub 5}Si{sub 2}Ge{sub 2} alloys. The broad operation temperature range (96 K) at a higher Curie temperature (374 K) suggests that the MnCoGe{sub 0.5}Si{sub 0.5} alloy can become a cheaper alternative MCE material (costing 70% less than a MnCoGe alloy). - Highlights: • The economic Si substitutes the noble metal Ge and broadens temperature span(96 K). • The T{sub C} arises when increasing Si in higher room temperature range, 340–374 K. • High thermal stability make them attractive for service temperature of above 300 K. • When Si increases, ΔS{sub M} decreases slightly due to the spontaneous magnetization M{sub S}. • The superior refrigerant capacity indicates that Si substitution benefits the MCE.

  17. A new approach to establish both stable and metastable phase equilibria for fcc ordered/disordered phase transition: application to the Al–Ni and Ni–Si systems

    International Nuclear Information System (INIS)

    Yuan Xiaoming; Zhang Lijun; Du Yong; Xiong Wei; Tang Ying; Wang Aijun; Liu Shuhong

    2012-01-01

    Both two-sublattice (2SL) and four-sublattice (4SL) models in the framework of the compound energy formalism can be used to describe the fcc ordered/disordered transitions. When transferring the parameters of 2SL disregarding the metastable ordered states into those of 4SL, inconsistence in either stable or metastable phase diagrams could appear, as detected in both Al–Ni and Ni–Si systems. To avoid such a kind of drawback, this behavior was analyzed and investigated in the Ni–Si and Al–Ni systems with the aid of first–principle calculations. Furthermore, a new approach considering both the stable and metastable fcc ordered phase equilibria deduced from the first–principles calculations was proposed to perform a reliable thermodynamic modeling for the fcc ordered/disordered transition. The Ni–Si system was then thermodynamically assessed using the presently proposed approach. The good agreement between the calculation and experiments demonstrates the reliability of the proposed approach. It is expected that the approach is valid for other systems showing complex ordered/disordered transitions. - Highlights: ► We discuss the drawbacks of order/disorder modeling in the Ni–Si and Al–Ni systems. ► We perform ab initio calculation of thermodynamic properties in the Ni–Si system. ► A CALPHAD–type approach is proposed to model the fcc ordered/disordered transition. ► The Ni–Si system was thermodynamically assessed using the new approach.

  18. Low-temperature nuclear magnetic resonance investigation of systems frustrated by competing exchange interactions

    Science.gov (United States)

    Roy, Beas

    This doctoral thesis emphasizes on the study of frustrated systems which form a very interesting class of compounds in physics. The technique used for the investigation of the magnetic properties of the frustrated materials is Nuclear Magnetic Resonance (NMR). NMR is a very novel tool for the microscopic study of the spin systems. NMR enables us to investigate the local magnetic properties of any system exclusively. The NMR experiments on the different systems yield us knowledge of the static as well as the dynamic behavior of the electronic spins. Frustrated systems bear great possibilities of revelation of new physics through the new ground states they exhibit. The vandates AA'VO(PO4)2 [AA' ≡ Zn2 and BaCd] are great prototypes of the J1-J2 model which consists of magnetic ions sitting on the corners of a square lattice. Frustration is caused by the competing nearest-neighbor (NN) and next-nearest neighbor (NNN) exchange interactions. The NMR investigation concludes a columnar antiferromagnetic (AFM) state for both the compounds from the sharp peak of the nuclear spin-lattice relaxation rate (1/T1) and a sudden broadening of the 31P-NMR spectrum. The important conclusion from our study is the establishment of the first H-P-T phase diagram of BaCdVO(PO4)2. Application of high pressure reduces the saturation field (HS) in BaCdVO(PO4)2 and decreases the ratio J2/J1, pushing the system more towards a questionable boundary (a disordered ground state) between the columnar AFM and a ferromagnetic ground state. A pressure up to 2.4 GPa will completely suppress HS. The Fe ions in the `122' iron-arsenide superconductors also sit on a square lattice thus closely resembling the J1-J2 model. The 75As-NMR and Nuclear Quadrupole Resonance (NQR) experiments are conducted in the compound CaFe2As2 prepared by two different heat treatment methods (`as-grown' and `annealed'). Interestingly the two samples show two different ground states. While the ground state of the `as

  19. The role of the bimodal distribution of ultra-fine silicon phase and nano-scale V-phase (AlSi2Sc2) on spark plasma sintered hypereutectic Al–Si–Sc alloys

    International Nuclear Information System (INIS)

    Raghukiran, Nadimpalli; Kumar, Ravi

    2016-01-01

    Hypereutectic Al–Si and Al–Si–Sc alloys were spark plasma sintered from corresponding gas-atomized powders. The microstructures of the Al–Si and Al–Si–Sc alloys possessed remarkably refined silicon particles in the size range of 0.38–3.5 µm and 0.35–1.16 µm respectively in contrast to the silicon particles of size greater than 100 µm typically found in conventionally cast alloys. All the sintered alloys exhibited significant ductility of as high as 85% compressive strain without failure even with the presence of relatively higher weight fraction of the brittle silicon phase. Moreover, the Al–Si–Sc alloys have shown appreciable improvement in the compressive strength over their binary counterparts due to the presence of intermetallic compound AlSi 2 Sc 2 of size 10–20 nm distributed uniformly in the matrix of those alloys. The dry sliding pin-on-disc wear tests showed improvement in the wear performance of the sintered alloys with increase in silicon content in the alloys. Further, the Al–Si–Sc ternary alloys with relatively lesser silicon content exhibited appreciable improvement in the wear resistance over their binary counterparts. The Al–Si–Sc alloys with bimodal distribution of the strengthening phases consisting of ultra-fine (sub-micron size) silicon particles and the nano-scale AlSi 2 Sc 2 improved the strength and wear properties of the alloys while retaining significant amount of ductility.

  20. Frustrated antiferromagnets at high fields: Bose-Einstein condensation in degenerate spectra

    International Nuclear Information System (INIS)

    Jackeli, G.; Zhitomirsky, M.E.

    2004-01-01

    Quantum phase transition at the saturation field is studied for a class of frustrated quantum antiferromagnets. The considered models include (i) the J 1 -J 2 frustrated square-lattice antiferromagnet with J 2 =(1/2)J 1 and (ii) the nearest-neighbor Heisenberg antiferromagnet on a face centered cubic lattice. In the fully saturated phase the magnon spectra for the two models have lines of degenerate minima. Transition into a partially magnetized state is treated via a mapping to a dilute gas of hard-core bosons and by complementary spin-wave calculations. Momentum dependence of the exact four-point boson vertex removes the degeneracy of the single-particle excitation spectra and selects the ordering wave vectors at (π,π) and (π,0,0) for the two models. We predict a unique form for the magnetization curve ΔM=S-M≅μ (d-1)/2 (logμ) (d-1) , where μ is a distance from the quantum critical point

  1. Phase Equilibria Study in the TeO2-Na2O-SiO2 System in Air Between 723 K (500 °C) and 1473 K (1200 °C)

    Science.gov (United States)

    Santoso, Imam; Taskinen, Pekka

    2016-08-01

    Knowledge of phase equilibria in the TeO2-Na2O-SiO2 system at elevated temperatures is important for ceramic and glass industries and for improving the operation of the smelting process of tellurium-containing materials. A review of previous investigations has indicated, however, that there are omissions in the available datasets on the liquidus temperatures of the molten TeO2-Na2O-SiO2 mixtures. The employed experimental method included equilibration of mixtures made from high purity oxides, rapid quenching of the equilibrated samples in water and followed by compositional analysis of the phases using an electron probe X-ray microanalyzer. The liquidus and phase equilibria in the TeO2-SiO2, TeO2-Na2O, and SiO2-TeO2-Na2O systems have been studied for a wide range of compositions between 723 K (500 °C) and 1473 K (1200 °C) at TeO2, SiO2, and Na2SiO3 saturations. New data have been generated in the SiO2-TeO2-Na2O system at SiO2 saturation. The liquidus compositions in the TeO2-Na2O system at TeO2 saturation have been compared with the previous data and an assessed phase diagram.

  2. Kinetic Analysis of Recovery, Recrystallization, and Phase Precipitation in an Al-Fe-Si Alloy Using JMAEK and Sesták-Berggren Models

    Science.gov (United States)

    Luiggi Agreda, Ney José

    2015-02-01

    When studying the phase changes process in a rolled AA8011 alloy using DSC, we find that the peaks associated with phase precipitation under this microstructural condition are different from those obtained in homogenized microstructures. The differences observed are attributable, first, to the recovery process occurring at temperatures below 423 K (150 °C), which interacts with the precipitation of Si-rich precipitates or with Guinier-Preston zones both coexistent in that temperature range; and second, to the recrystallization above 473 K (200 °C), which coexists with precipitation of the α-AlFeSi phase. In this work, the precipitation and recovery-recrystallization kinetics are experimentally obtained and deconvoluted in peaks characteristic for each of the mechanisms involved; i.e., precipitation of GP zones, recovery, precipitation of α phase, and recrystallization. The deconvolution is achieved using functions of Gauss, Weibull, and Fraser-Suzuki; and the characterization of each reaction deconvoluted is realized through both Jhonson-Melh-Avrami-Erofeev-Kolmorokov kinetic models and Sesták-Berggren combined kinetic model. The kinetic study evinces that in addition to the expected reactions, other reactions, necessary for good experimental adjustment, appear. An isoconversional study is undertaken to numerically evaluate the kinetic triplet of every process.

  3. Revising the Subsystem Nurse’s A-Phase-Silicocarnotite within the System Ca3(PO42–Ca2SiO4

    Directory of Open Access Journals (Sweden)

    Patricia Ros-Tárraga

    2016-04-01

    Full Text Available The subsystem Nurse’s A-phase-silicocarnotite within the system Ca3(PO42–Ca2SiO4 was conducted as a preliminary step toward obtaining new biomaterials with controlled microstructures. Phase composition of the resulting ceramics was studied by X-ray diffraction, differential thermal analysis, and scanning electron microscopy with attached wavelength dispersive spectroscopy. The results showed that the sub-system presents an invariant eutectoid point at 1366 ± 4 °C with a composition of 59.5 wt % Ca3(PO42 and 40.5 wt % Ca2SiO4, and typical eutectoid microstructure of lamellae morphology. These results are in disagreement with the previous reported data, which locate the invariant eutectoid point at 1250 ± 20 °C with a composition of 55 wt % Ca3(PO42 and 45 wt % Ca2SiO4. In addition, cell attachment testing showed that the new eutectoid material supported the mesenchymal stem cell adhesion and spreading, and the cells established close contact with the ceramic after 28 days of culture. These findings indicate that the new ceramic material with eutectoid microstructure of lamellae morphology possesses good bioactivity and biocompatibility and might be a promising bone implant material.

  4. fNIRS Evidence of Prefrontal Regulation of Frustration in Early Childhood

    OpenAIRE

    Perlman, Susan B.; Luna, Beatriz; Hein, Tyler C.; Huppert, Theodore J.

    2013-01-01

    The experience of frustration is common in early childhood, yet some children seem to possess a lower tolerance for frustration than others. Characterizing the biological mechanisms underlying a wide range of frustration tolerance observed in early childhood may inform maladaptive behavior and psychopathology that is associated with this construct. The goal of this study was to measure prefrontal correlates of frustration in 3–5 year-old children, who are not readily adaptable for typical neu...

  5. Assessment of off-stoichiometric Zr33-xFe52+xSi15 C14 Laves phase compounds as permanent magnet materials

    Science.gov (United States)

    Gabay, A. M.; Hadjipanayis, G. C.

    2018-05-01

    Recently, Fe-based rare-earth-free compounds with non-cubic crystal structures were proposed as a base for permanent magnets which would not rely on critical elements. In this work, two series of alloys, Zr27Fe73-wSiw (0 ≤ w ≤ 15) and Zr33-xFe52+xSi15 (0 ≤ x ≤ 11), were prepared and characterized after annealing at 1538 K in order to determine the fundamental magnetic properties of the C36 and C14 hexagonal Laves phase compounds. A mixture of the cubic C15 and Zr6Fe23 structures was observed instead of the expected C36 structure. The hexagonal C14 was found in all Zr33-xFe52+xSi15 alloys with its lattice parameters linearly decreasing as the Fe(Si) atoms occupy the Zr sites in the Laves phase crystal structure. The solubility limit of Fe in the C14 structure at 1538 K corresponds to x = 9.5. The Curie temperature of the C14 compounds increases with deviation from the Laves phase stoichiometry from 290 K to 530 K. The room-temperature spontaneous magnetization also increases reaching, after correcting for the non-magnetic impurities, a value of 6.7 kG. The magnetocrystalline anisotropy of the off-stoichiometric C14 Laves phase was found to be uniaxial with the easy magnetization direction parallel to the hexagonal axis. Unfortunately, the anisotropy field, which does not exceed 10 kOe, is not sufficiently high to make the compounds interesting as permanent magnet materials.

  6. Synthesis, characterization and magnetic properties of a manganese (II) silicate containing frustrated S=5/2 zig–zag ladders

    International Nuclear Information System (INIS)

    Brandão, P.; Santos, A.M. dos; Paixão, L.S.; Reis, M.S.

    2014-01-01

    The hydrothermal synthesis, structural characterization and magnetic properties of a manganese silicate with ideal formula of NaMn 2 Si 3 O 8 (OH) is reported. This compound is a synthetic analog to the naturally occurring mineral Serandite. The crystal structure comprises MnO 6 octahedra and SiO 4 tetrahedra. The MnO 6 share four edges with neighboring octahedra forming double chains. These chains are connected by silicate chains Si 3 O 8 (OH) resulting in an open framework structure with six-member ring channels where sodium ions are located. From the magnetic point of view, the intra-chain exchange between neighboring S=5/2 manganese ions is weak, partly due to the distortion observed in the octahedra, but also due to the frustrated topology of the chain. A successful fitting of the magnetic susceptibility was obtained by considering a double chain numerical model with Monte Carlo derived empirical parameters. -- Graphical abstract: A manganese silicate prepared hydrothermally with formula NaMn 2 Si 3 O 8 (OH) possessing the structure of the mineral Serandite contains doubled chains of edge-sharing MnO 6 octahedra. The magnetic susceptibility was measured and shows an antiferromagnetic behavior. Highlights: • Characterization of a synthetic analog to the mineral Serandite: NaMn 2 Si 3 O 8 (OH). • Fitting of the magnetic susceptibility considering a classical regular chain. • Weak metal–oxygen–metal super-exchange interactions; antiferromagnetic in nature. • Elevated degree of frustration along the chain, without sign of interchain ordering

  7. Improvement of electrical property of Si-doped GaN grown on r-plane sapphire by metalorganic vapor-phase epitaxy

    International Nuclear Information System (INIS)

    Kusakabe, K.; Furuzuki, T.; Ohkawa, K.

    2006-01-01

    Electrical property of Si-doped GaN layers grown on r-plane sapphire substrates by atmospheric metalorganic vapor-phase epitaxy was investigated. The electron mobility was drastically improved when GaN was grown by means of optimized combinations of growth temperature and low-temperature GaN buffer thickness. The highest room-temperature mobility of 220cm 2 /Vs was recorded at the carrier density of 1.1x10 18 cm -3 . Temperature dependence of electrical property revealed that the peak mobility of 234cm 2 /Vs was obtained at 249K. From the slope of carrier density as a function of inverse temperature, the activation energy of Si-donors was evaluated to be 11meV

  8. The Effect of Dispersion Phases of SiC and Al2O3 on the Properties of Galvanic Nickel Coatings

    Directory of Open Access Journals (Sweden)

    Kozik A.

    2016-03-01

    Full Text Available In this study, Ni, Ni-SiC and Ni-Al2O3 coatings were electroplated on the 2xxx series aluminium alloy. The following parameters of the electroplating process were applied: current density - 4A/dm2, time - 60 minutes, and temperature - 60°C. Hard particles of submicrometric size were used. The results of the research showing the effect of the addition of hard particles (introduced into the nickel bath as a dispersed phase on the properties of coatings, including the effect of the type (SiC or Al2O3 and content (0, 25, 50 g / l of these particles, were discussed. Based on extensive investigations, it was found that the type of ceramic particles significantly affects the structure of produced coatings. The dispersed particles incorporated into the nickel coatings improve their abrasion resistance. Improving of the corrosion properties were observed only in the case of coatings containing silicon carbide particles.

  9. Real-space and reciprocal-space Berry phases in the Hall effect of Mn(1-x)Fe(x)Si.

    Science.gov (United States)

    Franz, C; Freimuth, F; Bauer, A; Ritz, R; Schnarr, C; Duvinage, C; Adams, T; Blügel, S; Rosch, A; Mokrousov, Y; Pfleiderer, C

    2014-05-09

    We report an experimental and computational study of the Hall effect in Mn(1-x)Fe(x)Si, as complemented by measurements in Mn(1-x)Co(x)Si, when helimagnetic order is suppressed under substitutional doping. For small x the anomalous Hall effect (AHE) and the topological Hall effect (THE) change sign. Under larger doping the AHE remains small and consistent with the magnetization, while the THE grows by over a factor of 10. Both the sign and the magnitude of the AHE and the THE are in excellent agreement with calculations based on density functional theory. Our study provides the long-sought material-specific microscopic justification that, while the AHE is due to the reciprocal-space Berry curvature, the THE originates in real-space Berry phases.

  10. Structure-composition sensitivity in 'Metallic' Zintl phases: A study of Eu(Ga1-xTtx)2 (Tt=Si, Ge, 0≤x≤1)

    International Nuclear Information System (INIS)

    You, Tae-Soo; Zhao Jingtai; Poettgen, Rainer; Schnelle, Walter; Burkhardt, Ulrich; Grin, Yuri; Miller, Gordon J.

    2009-01-01

    Two isoelectronic series, Eu(Ga 1-x Tt x ) 2 (Tt=Si, Ge, 0≤x≤1), have been synthesized and characterized by powder and single-crystal X-ray diffraction, physical property measurements, and electronic structure calculations. In Eu(Ga 1-x Si x ) 2 , crystal structures vary from the KHg 2 -type to the AlB 2 -type, and, finally, the ThSi 2 -type structure as x increases. The hexagonal AlB 2 -type structure is identified for compositions 0.18(2)≤x 3 nets. As smaller Si atoms replace Ga atoms while the number of valence electrons increases, the lattice parameters, unit cell volumes, and Ga-Si distances in this phase region decrease significantly. Although aspects of X-ray diffraction results suggest puckering of the 6 3 nets for the Si-richest example of the AlB 2 -type Eu(Ga 1-x Si x ) 2 , the complete experimental evidence remains inconclusive. On the other hand, in Eu(Ga 1-x Ge x ) 2 , six different structural types were observed as x varies. In addition to EuGa 2 (KHg 2 -type; space group Imma) and EuGe 2 (own structure type, space group P3-barm1), the ternary phases studied show four different structures: the AlB 2 -type for Ga-rich compositions; the YPtAs-type structure for EuGaGe; and two new structures, which are intergrowths of the YPtAs-type EuGaGe and EuGe 2 , for Ge-rich compositions. These two Ge-rich phases include: (1) Eu(Ga 0.45(2) Ge 0.55(2) ) 2 containing two YPtAs-type motifs of EuGaGe plus one EuGe 2 motif; and (2) Eu(Ga 0.40(2) Ge 0.60(2) ) 2 containing one YPtAs-type motif alternating with a split site at x=2/3 ,y=1/3 and z=0.4798(2) with ca. 50% site occupancy by Ga and Ge along the c-axis. Magnetic susceptibilities of three Eu(Ga 1-x Ge x ) 2 compounds display Curie-Weiss behavior above ca. 100 K, and show effective magnetic moments indicative of divalent Eu with a 4f 7 electronic configuration, consistent with. X-ray absorption spectra (XAS). Density of states (DOS) and crystal orbital Hamilton population (COHP) analyses, based on first

  11. Crystallization of cristobalite from glass phase in mullite ceramics with excess SiO{sub 2} compositions; Sirika kajo muraito seramikkusu chu no garasuso no kesshoka kyodo

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Takashi; Sugai, Mikio; Nakagawa, Zenbee [Akita University, Akita (Japan). Faculty of Engineering and Resource Science; Sawabe, Yoshinari [Sumitomo Chemical Corp., Ibaraki (Japan). Tsukuba Research Laboratory; Oya, Yutaka [Gifu University, Gifu (Japan). Faculty of Engineering

    1999-09-01

    Crystallization of glass phase to cristobalite was investigated in mullite-glass ceramics with excess SiO{sub 2} compositions (5.3-16.4 mass %), namely, higher than stoichiometric mullite. Starting powders were prepared by alkoxide hydrolysis method. Compact specimens were sintered at 1600 degree C above the eutectic temperature (1587 degree C) for 2 h. Crystallization treatment was carried out at 1500 degree C, below the eutectic temperature, for times from 4 h to 96 h. Crystallization of glass phase proceeded from the surface of the specimen toward its inner part, in linear dependence on the annealing time. At the polished surface of the specimen, crystallization started in large glass pockets and the crystallized area extended spherically toward the inner part. This phenomenon suggests that nucleation occurs at the minimum parts in the elastic energy generated by the volume change involved in the crystallization of glass phase to cristobalite. (author)

  12. The effect on phase separation of the oxidation state of molybdenum in a Na2O-B2O3-SiO2 glass

    International Nuclear Information System (INIS)

    Kawamoto, Y.; Clemens, K.; Tomozawa, M.; Warden, J.T.

    1981-01-01

    The effect of oxidation state on phase separation was studied for 13Na 2 O, 49B 2 O 3 , 38SiO 2 (mol%) glasses containing 1 mol% Mo oxide. The glasses were melted under various conditions to vary the oxidation states of Mo ions. The oxidation states of Mo ions were determined by chemical analysis and ESR. The crystallisation tendency, the immiscibility temperature, and the phase separation morphology of the glasses were examined by DTA, x-ray diffraction, opalescence method, and replica electron microscopy. Glasses containing Mo 4+ ions have a great tendency to precipitate MoO 2 crystals. The immiscibility temperature of glass goes through a minimum when the oxidation states of Mo ions are changed. It was suggested that there is an optimum oxidation state to prevent crystallisation and to suppress the phase separation tendency of this system. (author)

  13. Heat capacity and thermal expansion of the itinerant helimagnet MnSi.

    Science.gov (United States)

    Stishov, S M; Petrova, A E; Khasanov, S; Kh Panova, G; Shikov, A A; Lashley, J C; Wu, D; Lograsso, T A

    2008-06-11

    The heat capacity and thermal expansion of a high quality single crystal of MnSi were measured at ambient pressure at zero and high magnetic fields. The calculated magnetic entropy change in the temperature range 0-30 K is less than 0.1R, a low value that emphasizes the itinerant nature of magnetism in MnSi. A linear temperature term dominates the thermal expansion coefficient in the range 30-150 K, which correlates with an enhancement of the linear electronic term in the heat capacity. A surprising similarity among the variations of the heat capacity, thermal expansion coefficient and temperature derivative of the resistivity is observed through the phase transition in MnSi. Specific forms of the heat capacity, thermal expansion coefficient and temperature derivative of resistivity at the phase transition to a helical magnetic state near 29 K are interpreted as the combination of sharp first-order features and broad peaks or shallow valleys of as yet unknown origin. The appearance of these broad satellites probably hints at a frustrated magnetic state slightly above the transition temperature in MnSi.

  14. Heat capacity and thermal expansion of the itinerant helimagnet MnSi

    International Nuclear Information System (INIS)

    Stishov, S M; Petrova, A E; Khasanov, S; Panova, G Kh; Shikov, A A; Lashley, J C; Wu, D; Lograsso, T A

    2008-01-01

    The heat capacity and thermal expansion of a high quality single crystal of MnSi were measured at ambient pressure at zero and high magnetic fields. The calculated magnetic entropy change in the temperature range 0-30 K is less than 0.1R, a low value that emphasizes the itinerant nature of magnetism in MnSi. A linear temperature term dominates the thermal expansion coefficient in the range 30-150 K, which correlates with an enhancement of the linear electronic term in the heat capacity. A surprising similarity among the variations of the heat capacity, thermal expansion coefficient and temperature derivative of the resistivity is observed through the phase transition in MnSi. Specific forms of the heat capacity, thermal expansion coefficient and temperature derivative of resistivity at the phase transition to a helical magnetic state near 29 K are interpreted as the combination of sharp first-order features and broad peaks or shallow valleys of as yet unknown origin. The appearance of these broad satellites probably hints at a frustrated magnetic state slightly above the transition temperature in MnSi

  15. Social comparison mediates chimpanzees' responses to loss, not frustration

    DEFF Research Database (Denmark)

    Hopper, Lydia M; Lambeth, Susan P; Schapiro, Steve

    2014-01-01

    Why do chimpanzees react when their partner gets a better deal than them? Do they note the inequity or do their responses reflect frustration in response to unattainable rewards? To tease apart inequity and contrast, we tested chimpanzees in a series of conditions that created loss through...... individual contrast, through inequity, or by both. Chimpanzees were tested in four social and two individual conditions in which they received food rewards in return for exchanging tokens with an experimenter. In conditions designed to create individual contrast, after completing an exchange, the chimpanzees...... were given a relatively less-preferred reward than the one they were previously shown. The chimpanzees' willingness to accept the less-preferred rewards was independent of previously offered foods in both the social and individual conditions. In conditions that created frustration through inequity...

  16. VHA Chaplains: challenges, roles, rewards, and frustrations of the work.

    Science.gov (United States)

    Beder, Joan; Yan, Grace W

    2013-01-01

    Chaplains working in the Veterans Health Administration have numerous roles and challenges. They work closely with other behavioral health professionals, especially social workers, to address the multiplicity of needs of the Veteran population. They are essentially an understudied subset of the military Chaplaincy service (most studies focus on those engaged in combat areas). In this exploratory qualitative study, VHA Chaplains responded to a survey to determine how they defined their role and professional challenges, what they felt were the rewards and frustrations of their work and their unique function within the VHA system. Findings showed that role differences between Chaplains and social workers and other behavioral health providers are clearly defined; rewards and challenges were diverse and frustrations were common to those working in a bureaucratic structure.

  17. An investigation on the role of texture evolution and ordered phase transition in soft magnetic properties of Fe–6.5 wt%Si electrical steel

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Guojun; Li, Changsheng, E-mail: lics@ral.neu.edu.cn; Cai, Ban; Wang, Qiwen

    2017-05-15

    Fe–6.5 wt%Si electrical steel characterized with excellent soft magnetic properties such as almost zero magnetostriction, low eddy current and hysteresis losses characteristics has been widely applied in high frequency fields. In this work, the role of texture evolution and ordered phase transition in soft magnetic properties of annealed sheets was explored using EBSD, XRD and TEM. The results demonstrate that accompanied with the increase of annealing temperatures, an increase on the B8 is attributable to a contribution combining the sizes of recrystallization grains with APBs of ordered phases as pinning the migration of magnetic domain wall. Whereas B50 declines to a minimum value (1.479 T) and then increases to a certain value (1.695 T) due to different types and intensities of textures affecting on the magnetocrystalline anisotropy energy. Meanwhile, the dislocation density gradually decreases and corresponding to a gradual decline in the internal stress, which makes the coercive force (H{sub c}) decrease monotonically. - Highlights: • Role of texture and ordered phase in Fe–6.5 wt%Si were studied. • With increasing annealing temperatures, H{sub c} decreases monotonically. • Combining grain sizes with APBs in B8 measurements. • Increasing annealing temperatures, B50 declines and then increases due to texture.

  18. Field-controlled spin current in frustrated spin chains

    Directory of Open Access Journals (Sweden)

    A.K. Kolezhuk

    2009-01-01

    Full Text Available We study states with spontaneous spin current, emerging in frustrated antiferromagnetic spin-S chains subject to a strong external magnetic field. As a numerical tool, we use a non-Abelian symmetry realization of the density matrix renormalization group. The field dependence of the order parameter and the critical exponents are presented for zigzag chains with S=1/2, 1, 3/2, and 2.

  19. Nuclear and magnetic correlations in a topologically frustrated elemental magnet

    International Nuclear Information System (INIS)

    Stewart, J.R.; Andersen, K.H.; Cywinski, R.

    1999-01-01

    β-Mn is an exchange enhanced paramagnetic metal on the verge of antiferromagnetic order. However, strong spin-fluctuations and topological frustration prevent the formation of static long-range order. We investigate the magnetic properties of the β-MnAl series of alloys in which short-range magnetic order is achieved at low temperature. We extract the short-range nuclear and magnetic correlations using a novel reverse Monte-Carlo procedure. (authors)

  20. Devil's staircase in a fully frustrated superconducting array

    International Nuclear Information System (INIS)

    Kim, S.; Choi, M.Y.

    1993-01-01

    A two-dimensional fully frustrated superconducting array with a combined direct and alternating applied current is studied both analytically and numerically. At zero temperature equations of motion can be reduced through the use of the translational symmetry present in the system. Remarkably, we find a series of subharmonic steps in addition to standard integer and half-integer giant Shapiro steps, leading to devil's staircase structure. We also present results of detailed numerical simulations, which indeed reveal such subharmonic fine structure. (orig.)

  1. Level of Ethics, Ethical Frustration and Accountant Discretionary Practices

    OpenAIRE

    Tamminen, Rauno; Leskinen, Markku

    1996-01-01

    In this paper it is shown with the help of a small sample that accounting is ethically loaded; that there exists ethical frustration caused by situational factors related to accounting; and that most probably the situational pressures may also change the level of ethics in the Kohlbergian sense; and that in studying accounting-related ethical problems empirically, the paper-and pencil tests and interviewing may give biased results. The accountant's model of the world is supplemented with ...

  2. Disulfide Bridges: Bringing Together Frustrated Structure in a Bioactive Peptide.

    Science.gov (United States)

    Zhang, Yi; Schulten, Klaus; Gruebele, Martin; Bansal, Paramjit S; Wilson, David; Daly, Norelle L

    2016-04-26

    Disulfide bridges are commonly found covalent bonds that are usually believed to maintain structural stability of proteins. Here, we investigate the influence of disulfide bridges on protein dynamics through molecular dynamics simulations on the cysteine-rich trypsin inhibitor MCoTI-II with three disulfide bridges. Correlation analysis of the reduced cyclic peptide shows that two of the three disulfide distances (Cys(11)-Cys(23) and Cys(17)-Cys(29)) are anticorrelated within ∼1 μs of bridge formation or dissolution: when the peptide is in nativelike structures and one of the distances shortens to allow bond formation, the other tends to lengthen. Simulations over longer timescales, when the denatured state is less structured, do not show the anticorrelation. We propose that the native state contains structural elements that frustrate one another's folding, and that the two bridges are critical for snapping the frustrated native structure into place. In contrast, the Cys(4)-Cys(21) bridge is predicted to form together with either of the other two bridges. Indeed, experimental chromatography and nuclear magnetic resonance data show that an engineered peptide with the Cys(4)-Cys(21) bridge deleted can still fold into its near-native structure even in its noncyclic form, confirming the lesser role of the Cys(4)-Cys(21) bridge. The results highlight the importance of disulfide bridges in a small bioactive peptide to bring together frustrated structure in addition to maintaining protein structural stability. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  3. Adiabatic cooling processes in frustrated magnetic systems with pyrochlore structure

    Science.gov (United States)

    Jurčišinová, E.; Jurčišin, M.

    2017-11-01

    We investigate in detail the process of adiabatic cooling in the framework of the exactly solvable antiferromagnetic spin-1/2 Ising model in the presence of the external magnetic field on an approximate lattice with pyrochlore structure. The behavior of the entropy of the model is studied and exact values of the residual entropies of all ground states are found. The temperature variation of the system under adiabatic (de)magnetization is investigated and the central role of the macroscopically degenerated ground states in cooling processes is explicitly demonstrated. It is shown that the model parameter space of the studied geometrically frustrated system is divided into five disjunct regions with qualitatively different processes of the adiabatic cooling. The effectiveness of the adiabatic (de)magnetization cooling in the studied model is compared to the corresponding processes in paramagnetic salts. It is shown that the processes of the adiabatic cooling in the antiferromagnetic frustrated systems are much more effective especially in nonzero external magnetic fields. It means that the frustrated magnetic materials with pyrochlore structure can be considered as very promising refrigerants mainly in the situations with nonzero final values of the magnetic field.

  4. A Scoping Analysis Of The Impact Of SiC Cladding On Late-Phase Accident Progression Involving Core–Concrete Interaction

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, M. T. [Argonne National Lab. (ANL), Argonne, IL (United States)

    2015-11-01

    The overall objective of the current work is to carry out a scoping analysis to determine the impact of ATF on late phase accident progression; in particular, the molten core-concrete interaction portion of the sequence that occurs after the core debris fails the reactor vessel and relocates into containment. This additional study augments previous work by including kinetic effects that govern chemical reaction rates during core-concrete interaction. The specific ATF considered as part of this study is SiC-clad UO2.

  5. Competing Spin Liquids and Hidden Spin-Nematic Order in Spin Ice with Frustrated Transverse Exchange

    Directory of Open Access Journals (Sweden)

    Mathieu Taillefumier

    2017-12-01

    Full Text Available Frustration in magnetic interactions can give rise to disordered ground states with subtle and beautiful properties. The spin ices Ho_{2}Ti_{2}O_{7} and Dy_{2}Ti_{2}O_{7} exemplify this phenomenon, displaying a classical spin-liquid state, with fractionalized magnetic-monopole excitations. Recently, there has been great interest in closely related “quantum spin-ice” materials, following the realization that anisotropic exchange interactions could convert spin ice into a massively entangled, quantum spin liquid, where magnetic monopoles become the charges of an emergent quantum electrodynamics. Here we show that even the simplest model of a quantum spin ice, the XXZ model on the pyrochlore lattice, can realize a still-richer scenario. Using a combination of classical Monte Carlo simulation, semiclassical molecular-dynamics simulation, and analytic field theory, we explore the properties of this model for frustrated transverse exchange. We find not one, but three competing forms of spin liquid, as well as a phase with hidden, spin-nematic order. We explore the experimental signatures of each of these different states, making explicit predictions for inelastic neutron scattering. These results show an intriguing similarity to experiments on a range of pyrochlore oxides.

  6. USER FRUSTRATION IN HIT INTERFACES: EXPLORING PAST HCI RESEARCH FOR A BETTER UNDERSTANDING OF CLINICIANS' EXPERIENCES.

    Science.gov (United States)

    Opoku-Boateng, Gloria A

    2015-01-01

    User frustration research has been one way of looking into clinicians' experience with health information technology use and interaction. In order to understand how clinician frustration with Health Information Technology (HIT) use occurs, there is the need to explore Human-Computer Interaction (HCI) literature that addresses both frustration and HIT use. In the past three decades, HCI frustration research has increased and expanded. Researchers have done a lot of work to understand emotions, end-user frustration and affect. This paper uses a historical literature review approach to review the origins of emotion and frustration research and explore the research question; Does HCI research on frustration provide insights on clinicians' frustration with HIT interfaces? From the literature review HCI research on emotion and frustration provides additional insights that can indeed help explain user frustration in HIT. Different approaches and HCI perspectives also help frame HIT user frustration research as well as inform HIT system design. The paper concludes with a suggested directions on how future design and research may take.

  7. fNIRS evidence of prefrontal regulation of frustration in early childhood.

    Science.gov (United States)

    Perlman, Susan B; Luna, Beatriz; Hein, Tyler C; Huppert, Theodore J

    2014-01-15

    The experience of frustration is common in early childhood, yet some children seem to possess a lower tolerance for frustration than others. Characterizing the biological mechanisms underlying a wide range of frustration tolerance observed in early childhood may inform maladaptive behavior and psychopathology that is associated with this construct. The goal of this study was to measure prefrontal correlates of frustration in 3-5-year-old children, who are not readily adaptable for typical neuroimaging approaches, using functional near infrared spectroscopy (fNIRS). fNIRS of frontal regions were measured as frustration was induced in children through a computer game where a desired and expected prize was "stolen" by an animated dog. A fNIRS general linear model (GLM) was used to quantify the correlation of brain regions with the task and identify areas that were statistically different between the winning and frustrating test conditions. A second-level voxel-based ANOVA analysis was then used to correlate the amplitude of each individual's brain activation with measure of parent-reported frustration. Experimental results indicated increased activity in the middle prefrontal cortex during winning of a desired prize, while lateral prefrontal cortex activity increased during frustration. Further, activity increase in lateral prefrontal cortex during frustration correlated positively with parent-reported frustration tolerance. These findings point to the role of the lateral prefrontal cortex as a potential region supporting the regulation of emotion during frustration. Copyright © 2013 Elsevier Inc. All rights reserved.

  8. Understanding the Impact of User Frustration Intensities on Task Performance Using the OCC Theory of Emotions

    Science.gov (United States)

    Washington, Gloria

    2012-01-01

    Have you heard the saying "frustration is written all over your falce"? Well this saying is true, but that is not the only place. Frustration is written all over your face and your body. The human body has various means to communicate an emotion without the utterance of a single word. The Media Equation says that people interact with computers as if they are human: this includes experiencing frustration. This research measures frustration by monitoring human body-based measures such as heart rate, posture, skin temperature. and respiration. The OCC Theory of Emotions is used to separate frustration into different levels or intensities. The results of this study showed that individual intensities of frustration exist, so that task performance is not degraded. Results from this study can be used by usability testers to model how much frustration is needed before task performance measures start to decrease.

  9. HBr Formation from the Reaction between Gas-phase Bromine Atom and Vibrationally Excited Chemisorbed Hydrogen Atoms on a Si(001)-(2 x 1) Surface

    International Nuclear Information System (INIS)

    Ree, J.; Yoon, S. H.; Park, K. G.; Kim, Y. H.

    2004-01-01

    We have calculated the probability of HBr formation and energy disposal of the reaction exothermicity in HBr produced from the reaction of gas-phase bromine with highly covered chemisorbed hydrogen atoms on a Si (001)-(2 x 1) surface. The reaction probability is about 0.20 at gas temperature 1500 K and surface temperature 300 K. Raising the initial vibrational state of the adsorbate(H)-surface(Si) bond from the ground to v = 1, 2 and 3 states causes the vibrational, translational and rotational energies of the product HBr to increase equally. However, the vibrational and translational motions of product HBr share most of the reaction energy. Vibrational population of the HBr molecules produced from the ground state adsorbate-surface bond (vHSi = 0) follows the Boltzmann distribution, but it deviates seriously from the Boltzmann distribution when the initial vibrational energy of the adsorbate-surface bond increases. When the vibration of the adsorbate-surface bond is in the ground state, the amount of energy dissipated into the surface is negative, while it becomes positive as vHSi increases. The energy distributions among the various modes weakly depends on surface temperature in the range of 0-600 K, regardless of the initial vibrational state of H(ad)-Si(s) bond

  10. Microstructure and phase constitution near the interface of Cu/3003 torch brazing using Al Si La Sr filler

    International Nuclear Information System (INIS)

    Yan, Fei; Wang, Chun Ming; Wang, Ya Jun; Xu, Dao Rong; Wu, S.C.; Sun, Qin De

    2012-01-01

    It has been mainly studied in this paper on brazing of Cu to Al using Al.Si filler metal. The optimized scanning rate of 2.5 mm/s is first obtained through simulating the temperature field of Cu Al brazing process based on ANSYS software. Then the brazing of Cu C11000 to Al 3003 using Al.Si.La.Sr filler is carried out by torch brazing technology. It is found that the brazing seam region is mainly consisted of α Al solid solution and CuAl2 IMC. Further experimental results also show that the rare earth element La in filler metal can not only refine the grain, but also promote the dispersion of intermetallic compounds into the brazing seam, which significantly improves the brazing seam microstructure and mechanical properties of the joints

  11. Phase and thickness dependence of thermal diffusivity in a-SiCxNy and a-BCxNy

    International Nuclear Information System (INIS)

    Chattopadhyay, S.; Chen, L.C.; Chien, S.C.; Lin, S.T.; Wu, C.T.; Chen, K.H.

    2002-01-01

    Thermal diffusivity (α) and bonding configuration of amorphous silicon carbon nitride (a-SiC x N y ) and boron carbon nitride (a-BC x N y ) films on silicon substrates were studied. Measurement of α by the traveling wave technique and bonding characterisation through X-ray photoelectron spectroscopy in a-SiC x N y and a-BC x N y films having different carbon concentrations revealed that lower coordinated bonds were detrimental to the thermal diffusivity of these films. Furthermore, α was found to depend on the thickness of these films deposited on silicon. This was attributed to the interface thermal resistance between two thermally different materials, the film and the substrate, although other factors such as film microstructure could also play a role. An empirical relation for the variation of thermal diffusivity with thickness is proposed

  12. High-pressure phase relations in the composition of albite NaAlSi3O8 constrained by an ab initio and quasi-harmonic Debye model, and their implications

    Science.gov (United States)

    Deng, L.; Liu, X.; Liu, H.; Dong, J.

    2010-12-01

    The high pressure physical-chemical behaviors of feldspar in subducted slab are very important to the geodynamic process in the deep interior of the Earth. Albite (NaAlSi3O8;Ab) is one of the few end members in the feldspar family, and its high-P behavior is obviously a prerequisite to the full understanding of the physical-chemical properties of feldspar at high pressures. So far it has been well accepted that Ab breaks down to the phase assemblage of Jadeite+Stishovite(NaAlSi2O6; Jd, SiO2; St,JS hereafter) at ~9-10 GPa. The JS phase assemblage might be stable up to ~23 GPa, and eventually directly change into the phase assemblage of calcium-ferrite type NaAlSiO4 (Cf) +2St (CS hereafter). However, some independent researches suggest there is an intermediate phase Na-hollandite (Na-Hall; a phase with the composition of NaAlSi3O8 and the structure of hollandite) between JS phase assemblage transition into CS phase assemblage (Liu 1978; Tutti 2007; Sekine and Ahrens, 1992; Beck et al., 2004). Whether Na-Hall is a thermodynamic stable phase under high P-T conditions remains unknown. In this work, phase relations in the composition of albite NaAlSi3O8 at pressures up to 40 GPa were constrained by a theoretical method that combines the ab initio calculation and quasi-harmonic Debyemodel. First, the P-T dependence of the thermodynamic potentials of the individual phase, St, Cf, Jd and the hypothetical Na-Holl were derived. Our results are generally in consistent agreement with available experimental data and previous theoretical predictions. Second, the Gibbs free energy of the hypothetical Na-Holl phase was compared with that of the phase assemblages JS and CS. Our results show that the Na-Holl phase is not a thermodynamically stable phase over the studied P-T conditions of 0-40 GPa and 100-600 K, which rules it out as a possible intermediate phase along the transition path from the JS phase assemblage to CS phase assemblage. Our calculations have predicted that the JS

  13. EXAFS study of Mn1.28Fe0.67P0.46Si0.54 compound with first-order phase transition

    International Nuclear Information System (INIS)

    L, Yingjie; Huliyageqi, B; Haschaolu, W; Song, Zhiqiang; Tegus, O; Nakai, Ikuo

    2014-01-01

    Highlights: • We have investigated the Fe and Mn K edge XAFS spectra of the Mn 1.28 Fe 0.67 P 0.46 Si 0.54 compound at 25 K and 295 K. • The site occupation of the Fe and Mn atoms and local structure of Mn 1.28 Fe 0.67 P 0.46 Si 0.54 are determined. • The atomic distances between Fe–Fe in c-plane for the ferromagnetic state are larger than those in the paramagnetic state. - Abstract: The Fe 2 P-type MnFe(P,Si) compounds are investigated by means of magnetic measurements and X-ray absorption fine structure spectroscopy. Magnetic measurements show that the Mn 1.28 Fe 0.67 P 0.46 Si 0.54 compound undergoes a first-order phase transition at the Curie temperature of 254 K. The Fe K-edge and Mn K-edge X-ray absorption fine structure spectra show that Mn atom mainly located at the 3g sites, while the 3f sites are occupied by Fe atoms and Mn atom randomly. The distances between the Fe atom and its nearest neighbor atoms in a triangle Fe–Mn–Fe change from 2.80 Å at 25 K to 2.74 Å at 300 K. On the other hand, the distances between Fe atom and its second neighbor atoms change from 4.06 Å at 25 K to 4.02 Å at 300 K

  14. Partial redetermination of the phase diagram of the system Al2O3 - ZrO2 - SiO2

    International Nuclear Information System (INIS)

    Greca, M.C.; Emiliano, J.V.; Segadaes, A.M.

    1990-01-01

    Current research on the mechanical behaviour of ceramic matrices reinforced by zirconia particles, and on the processing of mullite-zirconia via reaction-sintering, has brought about the need to update the phase diagram of the system Al 2 O 3 -ZrO 2 -SiO 2 , whose available version dates back to 1956. In the present work, selected compositions in this system were prepared from reagent-grade oxides, uniaxially pressed into 6 mm cylindrical pellets, fired at temperatures between 1550 and 1750 0 C for 6 to 24 h, water-quenched, and observed by X-ray diffraction and SEM, the composition of some of the phases identified being evaluated by EPMA. The data so obtained led to the relocation of the boundary curves neighbouring the ternary eutectic involving alumina, zirconia and mullite. This eutectic was found to occur at ∼ 1750 0 C, a temperature significantly lower than previously reported. (author) [pt

  15. Analysis of the first-order phase transition of (Mn,Fe)2(P,Si,Ge) using entropy change scaling

    International Nuclear Information System (INIS)

    Wang, G F; Zhao, Z R; Zhang, X F; Song, L; Tegus, O

    2013-01-01

    For materials with small size of the discontinuities of the free energy derivatives at transition, it is not so easy to determine the order of the transition using the criterion of the Arrott plot. In our previous paper, we found that the Mn 2−x Fe x P 0.6 Si 0.25 Ge 0.15 compounds with x = 0.7 and 0.8 undergo first-order phase transitions but apparently shows some characteristics of a second-order phase transition. In this paper, we have employed the Arrott plot and entropy change scaling to analyse the nature of the transitions for those compounds. The results reveal that the use of entropy change scaling is more effective than the Arrott plot for determining the nature of the transition in such materials. (paper)

  16. Effect of H2O on Upper Mantle Phase Transitions in MgSiO3: is the Seismic X-discontinuity an Indicator of Mantle Water Content

    Energy Technology Data Exchange (ETDEWEB)

    S Jacobsen; Z Liu; T Boffa Ballaran; E Littlefield; L Ehm; R Hemley

    2011-12-31

    The mantle X-discontinuity, usually assigned to positive seismic velocity reflectors in the 260-330 km depth range, has proved difficult to explain in terms of a single mineralogical phase transformation in part because of its depth variability. The coesite to stishovite transition of SiO{sub 2} matches deeper X-discontinuity depths but requires 5-10% free silica in the mantle to match observed impedance contrast. The orthoenstatite (OEn) to high-pressure clinoenstatite (HPCen) transformation of MgSiO{sub 3} also broadly coincides with depths of the X but requires chemically depleted and orthoenstatite-rich lithology at 300 km depth in order to match observed seismic impedance contrast. On the basis of high-pressure infrared spectroscopy, X-ray diffraction, and Raman spectroscopy, we show that 1300 ppm variation of H{sub 2}O content in MgSiO{sub 3} can displace the transition of low-pressure clinoenstatite (LPCen) to HPCen by up to 2 GPa, similar to previous quench experiments on the OEn to HPCen phase transition, where about 30-45 km (1.0-1.5 GPa) of deflection could occur per 0.1 wt% H{sub 2}O. If the mantle X-discontinuity results from pyroxene transitions in a depleted harzburgite layer, because of the strong influence of minor amounts of water on the transformation boundary, the depth of the mantle X-discontinuity could serve as a potentially sensitive indicator of water content in the uppermantle.

  17. Selective Dispersive Solid Phase Extraction of Ser-traline Using Surface Molecularly Imprinted Polymer Grafted on SiO2/Graphene Oxide

    Directory of Open Access Journals (Sweden)

    Faezeh Khalilian

    2017-01-01

    Full Text Available A surface molecularly imprinted dispersive solid phase extraction coupled with liquid chromatography–ultraviolet detection is proposed as a selective and fast clean-up technique for the determination of sertraline in biological sample. Surface sertraline-molecular imprinted polymer was grafted and synthesized on the SiO2/graphene oxide surface. Firstly SiO2 was coated on synthesized graphene oxide sheet using sol-gel technique. Prior to polymerization, the vinyl group was incorporated on to the surface of SiO2/graphene oxide to direct selective polymerization on the surface. Methacrylic acid, ethylene glycol dimethacrylate and ethanol were used as monomer, cross-linker and progen, respectively. Non-imprinted polymer was also prepared for comparing purposes. The properties of the molecular imprinted polymer were characterized using field emission-scanning electron microscopy and Fourier transform infrared spectroscopy methods. The surface molecular imprinted polymer was utilized as an adsorbent of dispersive solid phase extraction for separation and preconcentration of sertraline. The effects of the different parameters influencing the extraction efficiency, such as sample pH were investigated and optimized. The specificity of the molecular imprinted polymer over the non-imprinted polymer was examined in absence and presence of competitive drugs. Sertraline calibration curve showed linearity in the ranges 1–500 µg L-1. The limits of detection and quantification under optimized conditions were obtained 0.2 and 0.5 µg L-1. The within-day and between-day relative standard deviations (n=3 were 4.3 and 7.1%, respectively. Furthermore, the relative recoveries for spiked biological samples were above 92%.

  18. Ca8Mg(SiO4)4Cl2:Ce3+, Tb3+: A potential single-phased phosphor for white-light-emitting diodes

    International Nuclear Information System (INIS)

    Zhu Ge; Wang Yuhua; Ci Zhipeng; Liu Bitao; Shi Yurong; Xin Shuangyu

    2012-01-01

    A single-phased white-light-emitting phosphor Ca 8 Mg(SiO 4 ) 4 Cl 2 :Ce 3+ , Tb 3+ (CMSC:Ce 3+ , Tb 3+ ) is synthesized by a high temperature solid-state reaction method, and its photoluminescence properties are investigated. The obtained phosphor exhibits a strong excitation band between 250 and 410 nm, matching well with the dominant emission band of a UV light-emitting-diode (LED) chip. Energy transfer from Ce 3+ to Tb 3+ ions has been investigated and demonstrated to be a resonant type via a dipole–dipole mechanism. The energy transfer efficiency as well as the critical distance is also estimated. Furthermore, the phosphors can generate light from yellow-green through white and eventually to blue by properly tuning the relative ratio of Ce 3+ to Tb 3+ ions grounded on the principle of energy transfer. The results show that this phosphor has potential applications as a single-phased phosphor for UV white-light LEDs. - Highlights: ► The luminescence properties of Ca 8 Mg(SiO 4 ) 4 Cl 2 :Ce 3+ , Tb 3+ were investigated for the first time. ► The strong absorption of phosphors matches well with the emission band of UV LED chips. ► The energy transfer from Ce 3+ to Tb 3+ in Ca 8 Mg(SiO 4 ) 4 Cl 2 was investigated in detail. ► The white light (CIE=(0.29, 0.34)) is generated by tuning the relative ratio of Ce 3+ to Tb 3+ .

  19. Paraffin/expanded graphite phase change composites with enhanced thermal conductivity prepared by implanted β-SiC nanowires with chemical vapor deposition method

    Science.gov (United States)

    Yin, Zhaoyu; Zhang, Xiaoguang; Huang, Zhaohui; Liu, Silin; Zhang, Weiyi; Liu, Yan'gai; Wu, Xiaowen; Fang, Minghao; Min, Xin

    2018-02-01

    Expanded graphite/β-SiC nanowires composites (ESNC) were prepared through chemical vapor deposition, and paraffin/expanded graphite/β-SiC nanowires composites (PESNC) were made through vacuum impregnation to overcome liquid leakage during phase transition and enhance the thermal conductivity of paraffin. Fourier transform infrared spectroscopy showed no chemical interactions between the paraffin and ESNC. Differential scanning calorimetry estimated the temperature and latent heat of PESNC during melting to 45.73 °C and 124.31 J g-1, respectively. The respective values of these quantities during freezing were recorded as 48.93 °C and 124.14 J g-1. The thermal conductivity of PESNC was estimated to 0.75 W mK-1, which was 3.26-folds that of pure paraffin (0.23 W mK-1). PESNC perfectly maintained its phase transition after 200 melting-freezing cycles. The resulting ideal thermal conductivity, good chemical stability, thermal properties and thermal reliability of PESNC are promising for use in energy efficient buildings and solar energy systems.

  20. Single-phased CaAl2Si2O8:Tm3+, Dy3+ white-light phosphors under ultraviolet excitation

    International Nuclear Information System (INIS)

    Yang, Penghui; Yu, Xue; Xu, Xuhui; Jiang, Tingming; Yu, Hongling; Zhou, Dacheng; Yang, Zhengwen; Song, Zhiguo; Qiu, Jianbei

    2013-01-01

    A novel white-light-emitting phosphor CaAl 2 Si 2 O 8 :Tm, Dy was synthesized in ambient atmosphere by solid-state reaction. The energy transfer from Tm 3+ to Dy 3+ ions via a dipole–quadrupole reaction was observed and investigated. Upon UV excitation, white light emission was achieved by integrating a blue emission band located at 455 nm and an orange one located at 574 nm attributed to Tm 3+ and Dy 3+ ions, respectively. In addition, the energy-transfer efficiency and critical distance were calculated. Results suggested that the phosphor might be promising as a single-phased white-light-emitting phosphor for UV white-light LED. - Graphical abstract: The results indicate the existence of energy transfer from Tm 3+ to Dy 3+ . By tuning the concentration of Dy 3+ , single-phased white light can be realized. - Highlights: ► Energy transfer from Tm 3+ to Dy 3+ was investigated. ► Color tunable from blue to white can be achieved. ► White light can be realized in CaAl 2 Si 2 O 8 :Tm 3+ , Dy 3+ phosphor

  1. Thermal stability of (AlSi){sub x}(ZrVTi) intermetallic phases in the Al–Si–Cu–Mg cast alloy with additions of Ti, V, and Zr

    Energy Technology Data Exchange (ETDEWEB)

    Shaha, S.K. [Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, Ontario M5B 2K3 (Canada); Czerwinski, F., E-mail: Frank.Czerwinski@nrcan.gc.ca [CanmetMATERIALS, Natural Resources Canada, 183 Longwood Road South, Hamilton, Ontario L8P 0A5 (Canada); Kasprzak, W. [CanmetMATERIALS, Natural Resources Canada, 183 Longwood Road South, Hamilton, Ontario L8P 0A5 (Canada); Friedman, J.; Chen, D.L. [Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, Ontario M5B 2K3 (Canada)

    2014-11-10

    Highlights: • Al–Si–Cu–Mg alloy was modified by introducing Zr, V, and Ti. • The chemistry of the phases was identified using SEM/EDX. • The crystal lattice parameters of the phases were characterized using EBSD. • To investigate the phase stability, XRD was performed up to 600 °C. • Thermal analysis was done to find out the possible phase transformation reactions. - Abstract: The Al–Si–Cu–Mg cast alloy was modified with additions of Ti–V–Zr to improve the thermal stability of intermetallics at increased temperatures. A combination of electron microscopy, electron backscatter diffraction, and high temperature X-ray diffraction was explored to identify phases and temperatures of their thermal stability. The micro-additions of transition metals led to formation of several (AlSi){sub x}(TiVZr) phases with D0{sub 22}/D0{sub 23} tetragonal crystal structure and different lattice parameters. While Cu and Mg rich phases along with the eutectic Si dissolved at temperatures from 300 to 500 °C, the (AlSi){sub x}(TiVZr) phases were stable up to 696–705 °C which is the beneficial to enhance the high temperature properties. Findings of this study are useful for selecting temperatures during melting and heat treatment of Al–Si alloys with additions of transition metals.

  2. Influence of the substitution of Ni for Fe on the microstructure evolution and magnetic phase transition in La(Fe1−xNix)11.5Si1.5 compounds

    International Nuclear Information System (INIS)

    Sun, Song; Ye, Rongchang; Long, Yi

    2013-01-01

    Graphical abstract: M–T curves show that all the compounds undergo a ferromagnetic–paramagnetic magnetic phase transition process. Besides, the Curie temperature T c of La(Fe 1−x Ni x ) 11.5 Si 1.5 (x = 0, 0.01, 0.02, 0.03) compounds increase monotonously from 195 K to 219 K when Ni content x varies from 0 to 0.03. Highlights: ► We substituted Fe by new element Ni in La(Fe 1−x Ni x ) 11.5 Si 1.5 compounds. ► The microstructure evolution, magnetic phase transition and Curie temperature of La(Fe 1−x Ni x ) 11.5 Si 1.5 compounds were investigated. ► The small substitution of Ni for Fe in La(Fe 1−x Ni x ) 11.5 Si 1.5 compounds enhances the formation of 1:13 phase and helps the elimination of impurity phase significantly. ► The Curie temperature T C of La(Fe 1−x Ni x ) 11.5 Si 1.5 compounds increase monotonously from 195 K to 219 K when x varies from 0 to 0.03. - Abstract: The influence of Ni substitution on the microstructure evolution and magnetic phase transition has been investigated in La(Fe 1−x Ni x ) 11.5 Si 1.5 (x = 0, 0.01, 0.02, 0.03) compounds. Results show that partial substitution of Ni for Fe in La(Fe 1−x Ni x ) 11.5 Si 1.5 (x = 0, 0.01, 0.02, 0.03) alloys promotes fining of the as-cast microstructure. Besides, the formation of 1:13 phase and the elimination of impurity phases is facilitated significantly when annealed at 1373 K for 5 days. Large amounts of inhomogeneities are present in the annealed LaFe 11.5 Si 1.5 alloy. While almost single 1:13 phase is obtained in La(Fe 1−x Ni x ) 11.5 Si 1.5 (x = 0.02, 0.03) alloys. Moreover, the Curie temperature T C of La(Fe 1−x Ni x ) 11.5 Si 1.5 (x = 0, 0.01, 0.02, 0.03) compounds increase monotonously from 195 K to 219 K when Ni content x varies from 0 to 0.03.

  3. Geometrically frustrated magnetic structures of the heavy-fermion compound CePdAl studied by powder neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Doenni, A.; Fischer, P.; Zolliker, M. [Laboratory for Neutron Scattering, ETH Zuerich and Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Ehlers, G.; Maletta, H. [Hahn Meitner Institute Berlin, Glienicker Strasse 100, D-14092 Berlin (Germany); Kitazawa, H. [National Research Institute for Metals, Tsukuba, Ibaraki 305 (Japan)

    1996-12-09

    The heavy-fermion compound CePdAl with ZrNiAl-type crystal structure (hexagonal space group P6-bar2m) was investigated by powder neutron diffraction. The triangular coordination symmetry of magnetic Ce atoms on site 3f gives rise to geometrical frustration. CePdAl orders below T{sub N} = 2.7 K with an incommensurate antiferromagnetic propagation vector k=[1/2, 0, {tau}], {tau} approx. 0.35, and a longitudinal sine-wave (LSW) modulated spin arrangement. Magnetically ordered moments at Ce(1) and Ce(3) coexist with frustrated disordered moments at Ce(2). The experimentally determined magnetic structure is in agreement with group theoretical symmetry analysis considerations, calculated by the program MODY, which confirm that for Ce(2) an ordered magnetic moment parallel to the magnetically easy c-axis is forbidden by symmetry. Further low-temperature experiments give evidence for a second magnetic phase transition in CePdAl between 0.6 and 1.3 K. Magnetic structures of CePdAl are compared with those of the isostructural compound TbNiAl, where a non-zero ordered magnetic moment for the geometrically frustrated Tb(2) atoms is allowed by symmetry. (author)

  4. The heat capacity of a natural monticellite and phase equilibria in the system CaO-MgO-SiO2-CO2

    Science.gov (United States)

    Sharp, Z.D.; Essene, E.J.; Anovitz, Lawrence M.; Metz, G.W.; Westrum, E.F.; Hemingway, B.S.; Valley, J.W.

    1986-01-01

    The heat capacity of a natural monticellite (Ca1.00Mg.09Fe.91Mn.01Si0.99O3.99) measured between 9.6 and 343 K using intermittent-heating, adiabatic calorimetry yields Cp0(298) and S2980 of 123.64 ?? 0.18 and 109.44 ?? 0.16 J ?? mol-1 K-1 respectively. Extrapolation of this entropy value to end-member monticellite results in an S0298 = 108.1 ?? 0.2 J ?? mol-1 K-1. High-temperature heat-capacity data were measured between 340-1000 K with a differential scanning calorimeter. The high-temperature data were combined with the 290-350 K adiabatic values, extrapolated to 1700 K, and integrated to yield the following entropy equation for end-member monticellite (298-1700 K): ST0(J ?? mol-1 K-1) = S2980 + 164.79 In T + 15.337 ?? 10-3 T + 22.791 ?? 105 T-2 - 968.94. Phase equilibria in the CaO-MgO-SiO2 system were calculated from 973 to 1673 K and 0 to 12 kbar with these new data combined with existing data for akermanite (Ak), diopside (Di), forsterite (Fo), merwinite (Me) and wollastonite (Wo). The location of the calculated reactions involving the phases Mo and Fo is affected by their mutual solid solution. A best fit of the thermodynamically generated curves to all experiments is made when the S0298 of Me is 250.2 J ?? mol-1 K-1 less than the measured value of 253.2 J ?? mol-1 K-1. A best fit to the reversals for the solid-solid and decarbonation reactions in the CaO-MgO-SiO2-CO2 system was obtained with the ??G0298 (kJ ?? mole-1) for the phases Ak(-3667), Di(-3025), Fo(-2051), Me(-4317) and Mo(-2133). The two invariant points - Wo and -Fo for the solid-solid reactions are located at 1008 ?? 5 K and 6.3 ?? 0.1 kbar, and 1361 ?? 10 K and 10.2 ?? 0.2 kbar respectively. The location of the thermodynamically generated curves is in excellent agreement with most experimental data on decarbonation equilibria involving these phases. ?? 1986.

  5. PREFACE: The International Conference on Highly Frustrated Magnetism HFM2008

    Science.gov (United States)

    Eremin, Ilya; Brenig, Wolfram; Kremer, Reinhard; Litterst, Jochen

    2009-01-01

    The International Conference on Highly Frustrated Magnetism 2008 (HFM2008) took place on 7-12 September 2008 at the Technische Universität Carolo-Wilhelmina zu Braunschweig, Germany. This conference was the fourth event in a series of meetings, which started in Waterloo, Canada (HFM 2000), followed by the second one in Grenoble, France (HFM 2003), and the third meeting in Osaka, Japan (HFM 2006). HFM2008 attracted more than 220 participants from all over the world. The number of participants of the HFM conference series has been increasing steadily, from about 80 participants at HFM 2000, to 120 participants at HFM 2003, and 190 participants at HFM 2006, demonstrating that highly frustrated magnetism remains a rapidly growing area of research in condensed matter physics. At the end of HFM2008 it was decided that the next International Conference on Highly Frustrated Magnetism will be held in Baltimore, USA in 2010. HFM2008 saw four plenary talks by R Moessner, S Nakatsuji, S-W Cheong, and S Sachdev, 18 invited presentations, 30 contributed talks and about 160 poster presentations from all areas of frustrated magnetism. The subjects covered by the conference included: Kagome systems Itinerant frustrated systems Spinels and pyrochlore materials Triangular systems Unconventional order and spin liquids Chain systems Chain systems Novel frustrated systems This volume of Journal of Physics: Conference Series contains the proceedings of HFM2008 with 83 papers that provide a scientific record of the scientific topics covered by the conference. All articles have been refereed by experts in the field. It is our hope that the reader will enjoy and profit from the HFM2008 Proceedings. Ilya Eremin Proceedings Editor Wolfram Brenig, Reinhard Kremer, and Jochen Litterst Co-Editors International Advisory Board L Balents (USA) F Becca (Italy) S Bramwell (UK) P Fulde (Germany) B D Gaulin (Canada) J E Greedan (Canada) A Harrison (France) Z Hiroi (Japan) H Kawamura (Japan) A Keren

  6. Magnetization plateaux and jumps in frustrated four-leg spin tubes in magnetic fields

    International Nuclear Information System (INIS)

    Rosales, H D; Arlego, M; Albarracín, F A Gómez

    2014-01-01

    We study the ground state phase diagram of a frustrated spin-1/2 four-leg tube in an external magnetic field. We explore the parameter space of this model in the regime of all-antiferromagnetic exchange couplings by means of three different approaches: density matrix renormalization group (DMRG), a low-energy effective Hamiltonian (LEH) and a Hartree variational approach (HVA). We find that in the limit of weakly interacting plaquettes, singlet and triplet states play an important role in the formation of magnetization plateaux. We study the transition regions numerically and analytically, and find that they are described, at first order in a strong- coupling expansion, by an XXZ spin-1/2 chain in a magnetic field. These results are consistent with the DMRG and HVA calculations

  7. Calcite Phase Conversion Prediction Model for CaO-Al2O3-SiO2 Slag: An Aqueous Carbonation Process at Ambient Pressure

    Science.gov (United States)

    Zhang, Huining; Dong, Jianhong; Li, Hui; Xiong, Huihui; Xu, Anjun

    2018-06-01

    To evaluate the effect of the mineralogical phase on carbonation efficiency for CaO-Al2O3-SiO2 slag, a calcite phase conversion prediction model is proposed. This model combines carbon dioxide solubility with carbonation reaction kinetic analysis to improve the prediction capability. The effect of temperature and carbonation time on the carbonation degree is studied in detail. Results show that the reaction rate constant ranges from 0.0135 h-1 to 0.0458 h-1 and that the mineralogical phase contribution sequence for the carbonation degree is C2S, CaO, C3A and CS. The model accurately predicts the effect of temperature and carbonation time on the simulated calcite conversion, and the results agree with the experimental data. The optimal carbonation temperature and reaction time are 333 K and 90 min, respectively. The maximum carbonation efficiency is about 184.3 g/kg slag, and the simulation result of the calcite phase content in carbonated slag is about 20%.

  8. Effect of Magnesium Content and Processing Conditions on Phase Formation and Stability in Mg2+ δ Si0.3Sn0.7

    Science.gov (United States)

    Goyal, Gagan K.; Dasgupta, T.

    2018-03-01

    Mg2+ δ Si0.3Sn0.7 compositions with nominal Mg content of δ = 0, 0.2 are synthesized using a single-step quartz tube reaction method with different heating rates and holding times. The resulting powders are sintered using a uniaxial induction hot press under similar conditions to produce near-dense compacts. The effect of Mg content and processing conditions on the phase formation and its stability are studied using x-ray diffraction measurements, scanning electron microscopy (SEM) with elemental mapping and compositional analysis using energy dispersive spectroscopy (EDS). Results indicate that with sufficient Mg content and shorter synthesis time, the powder remains single phasic; however, prolonged heat treatment during synthesis results in Mg loss and causes the system to become biphasic. Compaction results in single-phase formation in all the specimens. This is attributed to the removal of the low-melting secondary Sn-rich phases present in the system. The decomposition of the specimens depends on the Mg content after the compaction step with a δ around - 0.15 necessary to preserve the single phase. The decomposition also results in Mg enrichment of the matrix (due to formation of elemental Sn), thereby acting as a self-healing mechanism. Annealing the dense products at 773 K for 24 h in static vacuum is carried out. Progressive Mg loss is observed resulting in degradation of the specimen.

  9. High temperature creep deformation of glass-phase containing MoSi sub 2 sintered compacts. Glass so wo fukumu MoSi sub 2 shoketsutai no koon henkei

    Energy Technology Data Exchange (ETDEWEB)

    Shobu, K.; Watanabe, T.; Tani, E. (Government Industrial Research Inst., Kyushu, Saga (Japan))

    1991-07-25

    As such deformation mechanisms as diffusion, grain boundary sliding and motion of dislocation are known for high temperature deformation of polycrystallines, these atomic theoretical mechanism and quantitative side are not resolved perfectly. In this report, high temperature plasticity of sintered MoSi {sub 2} containing glass phase was examined and obtained some results shown as follows: its transient feature was same as usually observed one; and according to observe its structure, the deformation mechanism was mainly based on grain boundary sliding, and viscous flow of glass phase and diffusion therethrough; stress feature in deformation was shown a transient phenomenon at about 10MPa, and stress index approached to 3 under low stress and to 1 under high stress, in other words stress feature was controlled by viscous flow under high stress and by grain boundary sliding under low stress; and the stress index of grain boundary sliding was supposed to be 3 at low inclined angle and responsive grain boundary and 2 at high inclined angle. 4 refs., 5 figs.

  10. Proposed frustrated-total-reflection acoustic sensing method

    International Nuclear Information System (INIS)

    Hull, J.R.

    1981-01-01

    Modulation of electromagnetic energy transmission through a frustrated-total-reflection device by pressure-induced changes in the index of refraction is proposed for use as an acoustic detector. Maximum sensitivity occurs for angles of incidence near the critical angle. The minimum detectable pressure in air is limited by Brownian noise. Acoustic propagation losses and diffraction of the optical beam by the acoustic signal limit the minimum acoustic wavelength to lengths of the order of the spatial extent of the optical beam. The response time of the method is fast enough to follow individual acoustic waves

  11. The La(Fe,Mn,Si){sub 13}H{sub z} magnetic phase transition under pressure

    Energy Technology Data Exchange (ETDEWEB)

    Lovell, Edmund; Boldrin, David C.; Cohen, Lesley F. [Department of Physics, Blackett Laboratory, Imperial College London (United Kingdom); Bez, Henrique N. [The Ames Laboratory of the US DOE, Iowa State University, Ames, IA (United States); Nielsen, Kaspar K.; Smith, Anders; Bahl, Christian R.H. [Department of Energy Conversion and Storage, Technical University of Denmark, Roskilde (Denmark)

    2017-08-15

    We study the magnetocaloric metamagnetic transition in LaFe{sub 11.74}Mn{sub 0.06}Si{sub 1.20} and LaFe{sub 11.76}Mn{sub 0.06}Si{sub 1.18}H{sub 1.65} under hydrostatic pressure up to 1.2 GPa. For both compounds, hydrostatic pressure depresses the zero field critical temperature. However, in detail, pressure influences the magnetic properties in different ways in the two compounds. In the dehydrogenated case the transition broadens under pressure whereas in the hydrogenated case the transition sharpens. In both cases thermal hysteresis increases under pressure, although with different trends. These observations suggest both intrinsic and extrinsic hysteresis loss brought about by the use of hydrostatic pressure. We explore the multicaloric field-pressure cycle, demonstrating that although the gain introduced by overcoming the magnetic hysteresis loss is closely countered by the loss introduced in the pressure cycle, there are significant advantages in that the temperature range of operation can be finely tuned and extended, and the magnetocaloric transition can operate in lower absolute applied fields (<0.5 T), potentially overcoming one of the most significant bottlenecks to the commercialization of this technology. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. Crystal structure, equation of state, and elasticity of hydrous aluminosilicate phase, topaz-OH (Al2SiO4(OH)2) at high pressures

    Science.gov (United States)

    Mookherjee, Mainak; Tsuchiya, Jun; Hariharan, Anant

    2016-02-01

    We examined the equation of state and high-pressure elasticity of the hydrous aluminosilicate mineral topaz-OH (Al2SiO4(OH)2) using first principles simulation. Topaz-OH is a hydrous phase in the Al2O3-SiO2-H2O (ASH) ternary system, which is relevant for the mineral phase relations in the hydrated sedimentary layer of subducting slabs. Based on recent neutron diffraction experiments, it is known that the protons in the topaz-OH exhibit positional disorder with half occupancy over two distinct crystallographic sites. In order to adequately depict the proton environment in the topaz-OH, we examined five crystal structure models with distinct configuration for the protons in topaz-OH. Upon full geometry optimization we find two distinct space group, an orthorhombic Pbnm and a monoclinic P21/c for topaz-OH. The topaz-OH with the monoclinic P21/c space group has a lower energy compared to the orthorhombic Pbmn space group symmetry. The pressure-volume results for the monoclinic topaz-OH is well represented by a third order Birch-Murnaghan formulation, with V0mon = 348.63 (±0.04) Å3, K0mon = 164.7 (±0.04) GPa, and K0mon = 4.24 (±0.05). The pressure-volume results for the orthorhombic topaz-OH is well represented by a third order Birch-Murnaghan formulation, with V0orth = 352.47 (±0.04) Å3, K0orth = 166.4 (±0.06) GPa, and K0orth = 4.03 (±0.04). While the bulk moduli are very similar for both the monoclinic and orthorhombic topaz-OH, the shear elastic constants and the shear moduli are very sensitive to the position of the proton, orientation of the O-H dipole, and the space group symmetry. The S-wave anisotropy for the orthorhombic and monoclinic topaz-OH are also quite distinct. In the hydrated sedimentary layer of subducting slabs, transformation of a mineral assemblage consisting of coesite (SiO2) and diaspore (AlOOH) to topaz-OH (Al2SiO4(OH)2) is likely to be accompanied by an increase in density, compressional velocity, and shear wave velocity. However

  13. Phase formation in as-solidified and heat-treated Al-Si-Cu-Mg-Ni alloys: Thermodynamic assessment and experimental investigation for alloy design

    Energy Technology Data Exchange (ETDEWEB)

    Farkoosh, A.R., E-mail: amir.rezaeifarkoosh@mail.mcgill.ca [Department of Mining and Materials Engineering, McGill University, 3610 University, Aluminum Research Center - REGAL, Montreal, Quebec, Canada H3A 2B2 (Canada); Javidani, M. [Laval University, Department of Mining, Metallurgy and Materials Engineering, Aluminum Research Center - REGAL, 1065 Ave de la Medecine, Quebec, Canada G1V 0A6 (Canada); Hoseini, M. [Department of Mining and Materials Engineering, McGill University, 3610 University, Aluminum Research Center - REGAL, Montreal, Quebec, Canada H3A 2B2 (Canada); Larouche, D. [Laval University, Department of Mining, Metallurgy and Materials Engineering, Aluminum Research Center - REGAL, 1065 Ave de la Medecine, Quebec, Canada G1V 0A6 (Canada); Pekguleryuz, M. [Department of Mining and Materials Engineering, McGill University, 3610 University, Aluminum Research Center - REGAL, Montreal, Quebec, Canada H3A 2B2 (Canada)

    2013-02-25

    Highlights: Black-Right-Pointing-Pointer Phase formation in Al-Si-Ni-Cu-Mg-Fe system have been investigated. Black-Right-Pointing-Pointer T-Al{sub 9}FeNi, {gamma}-Al{sub 7}Cu{sub 4}Ni, {delta}-Al{sub 3}CuNi and {epsilon}-Al{sub 3}Ni are formed at different Ni levels. Black-Right-Pointing-Pointer Thermally stable Ni-bearing precipitates improved the overaged hardness. Black-Right-Pointing-Pointer It was found that Ni:Cu and Ni:Fe ratios control the precipitation. Black-Right-Pointing-Pointer {delta}-Al{sub 3}CuNi phase has more contribution to strength compare to other precipitates. - Abstract: Thermodynamic simulations based on the CALPHAD method have been carried out to assess the phase formation in Al-7Si-(0-1)Ni-0.5Cu-0.35Mg alloys (in wt.%) under equilibrium and non-equilibrium (Scheil cooling) conditions. Calculations showed that the T-Al{sub 9}FeNi, {gamma}-Al{sub 7}Cu{sub 4}Ni, {delta}-Al{sub 3}CuNi and {epsilon}-Al{sub 3}Ni phases are formed at different Ni levels. By analyzing the calculated isothermal sections of the phase diagrams it was revealed that the Ni:Cu and Ni:Fe ratios control precipitation in this alloy system. In order to verify the simulation results, microstructural investigations in as-cast, solution treated and aged conditions were carried out using electron probe microanalysis (EPMA), scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Furthermore, cooling curve analysis (CCA) was also performed to determine the freezing range of the new alloys and porosity formation during solidification. Hardness measurements of the overaged samples showed that in this alloy system the {delta}-Al{sub 3}CuNi phase has a greater influence on the overall strength of the alloys compared to the other Ni-bearing precipitates.

  14. The system study of 1:13 phase formation, the magnetic transition adjustment, and magnetocaloric property in La(Fe,Co){sub 13−x}Si{sub x} alloys

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xiang, E-mail: gxucx@163.com [School of Materials Science and Engineering, Sichuan University, Chengdu 610065 (China); Department of Physics and Electronic Informational Engineering, Neijiang Teachers College, Neijiang 641002 (China); Chen, Yungui, E-mail: ygchen60@yahoo.com.cn [School of Materials Science and Engineering, Sichuan University, Chengdu 610065 (China); Tang, Yongbo; Xiao, Dingquan [School of Materials Science and Engineering, Sichuan University, Chengdu 610065 (China)

    2014-11-15

    The effects of Co on the formation of NaZn{sub 13}-type phase in as-cast and annealed LaFe{sub 16−x}Co{sub x}Si{sub 1.4} and LaFe{sub 11.6}Si{sub 1.4−x}Co{sub x} alloys have been investigated systematically by XRD, SEM, and EDS, respectively. In LaFe{sub 11.6}Si{sub 1.4−x}Co{sub x} alloys, the introduction of Co will hamper the formation of 1:13 and LaFeSi phases, and help the formation of αof (Co, Si) solid solution, so there is almost only α-Fe(Co, Si) solid solution when x reaches 0.7 in as-cast and annealed LaFe{sub 11.6}Si{sub 1.4−x}Co{sub x} alloys. Although the amounts of 1:13 phase increases when x reaches 0.7 in as-cast LaFe{sub 16−x}Co{sub x}Si{sub 1.4} alloys, there is a small amount of α-Fe in LaFe{sub 11.6−x}Co{sub x}Si{sub 1.4} alloys annealed at 1523 K (5 h), which indicates that the annealing time for obtaining a 1:13 single-phase cannot be shortened in our high-temperature and short-time annealing. The studies on the magnetic properties show that the Curie temperature T{sub C} goes up from 207 K to 285 K with increase of Co content from x=0.1 to 0.8. The introduction of Co element weakens the first order magnetic phase transition, which results in the change of magnetic transition type from first to second order at about x=0.3–0.5. At the same time, it has effects on the phase transition temperature interval and magnetic filed interval, and the changing rate of magnetic entropy change dependence on the Co content in LaFe{sub 16−x}Co{sub x}Si{sub 1.4} alloys. The maximum entropy values of LaFe{sub 11.6−x}Co{sub x}Si{sub 1.4} alloys decrease with the increase of Co content, but the relative cooling power does not decrease, the reason of which is that the phase transition temperature interval increases and the first order phase transition character decreases, and the effective refrigeration temperature range becomes big, which is useful to the application of magnetic refrigeration material. - Highlights: • The introduction of Co

  15. Mossbauer and XRD characterization of the phase transformations in a Fe-Mn-Al-C-Mo-Si-Cu as cast alloy during tribology test

    Science.gov (United States)

    Ramos, J.; Piamba, J. F.; Sánchez, H.; Alcazar, G. A. Pérez

    2015-06-01

    In present study Fe-29.0Mn-6Al-0.9C-1.8Mo-1.6Si-0.4Cu (%w) alloy was obtained after melted in an induction furnace, and then molded as an ingot. From the as cast ingot it were cut samples for the different characterization measurements. The microstructure of the as-cast sample is of dendritic type and its XRD pattern was refined with the lines of the austenite, with a big volumetric fraction, and the lines of the martensite, with small volumetric fraction. The Mössbauer spectrum of the sample was fitted with a broad singlet which corresponds to disordered austenite. After the tribology test, its XRD pattern was refined with the lines of two austenite phases, one similar to the previous one and other with bigger lattice parameter. The total volumetric fraction of the austenite is smaller than that obtained for sample without wear. It was added the lines of the martensite phase with bigger volumetric fraction than that of the previous sample. The Mössbauer spectrum of the weared sample was fitted with two paramagnetic sites which correspond to the two Fe austenite phases and a hyperfine magnetic field distribution which is associated to the disordered original martensite and the new one which appears in the surface as a consequence of the wear process. These results show that during wear process the original austenite phase is transformed in martensite and in a new austenite phase. The increases of the martensitic phase improves mechanical properties and wear behavior.

  16. Mossbauer and XRD characterization of the phase transformations in a Fe-Mn-Al-C-Mo-Si-Cu as cast alloy during tribology test

    Energy Technology Data Exchange (ETDEWEB)

    Ramos, J. [Universidad Autónoma de Occidente (Colombia); Piamba, J. F. [Universidad del Valle, Departamento Física (Colombia); Sánchez, H. [Universidad del Valle, Escuela de Materiales (Colombia); Alcazar, G. A. Pérez, E-mail: gpgeperez@gmail.com [Universidad del Valle, Departamento Física (Colombia)

    2015-06-15

    In present study Fe-29.0Mn-6Al–0.9C-1.8Mo-1.6Si-0.4Cu (%w) alloy was obtained after melted in an induction furnace, and then molded as an ingot. From the as cast ingot it were cut samples for the different characterization measurements. The microstructure of the as-cast sample is of dendritic type and its XRD pattern was refined with the lines of the austenite, with a big volumetric fraction, and the lines of the martensite, with small volumetric fraction. The Mössbauer spectrum of the sample was fitted with a broad singlet which corresponds to disordered austenite. After the tribology test, its XRD pattern was refined with the lines of two austenite phases, one similar to the previous one and other with bigger lattice parameter. The total volumetric fraction of the austenite is smaller than that obtained for sample without wear. It was added the lines of the martensite phase with bigger volumetric fraction than that of the previous sample. The Mössbauer spectrum of the weared sample was fitted with two paramagnetic sites which correspond to the two Fe austenite phases and a hyperfine magnetic field distribution which is associated to the disordered original martensite and the new one which appears in the surface as a consequence of the wear process. These results show that during wear process the original austenite phase is transformed in martensite and in a new austenite phase. The increases of the martensitic phase improves mechanical properties and wear behavior.

  17. Titanium as an intermetallic phase stabilizer and its effect on the mechanical and thermal properties of Al-Si-Mg-Cu-Ti alloy

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Se-Weon [Korea Institute of Industrial Technology, 6 Cheomdan-gwagiro 208 beon-gil, Buk-gu, Gwangju 500-480 (Korea, Republic of); Cho, Hoon-Sung [School of Materials Science and Engineering, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwangju 500-757 (Korea, Republic of); Kumai, Shinji [Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, S8-10, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8552 (Japan)

    2016-12-15

    The effect of precipitation of intermetallics on the mechanical and thermal properties of Al-6.5Si-0.44Mg-0.9Cu-(Ti) alloys (in wt%) during various artificial aging treatments was studied using a universal testing machine and a laser flash apparatus. The solution treatment of the alloy samples was conducted at 535 °C for 6 h, followed by quenching in warm water. The solution-treated samples were artificially aged for 5 h at different temperatures ranging from 170 °C to 220 °C. After the artificial aging treatment, the Al-6.5Si-0.44Mg-0.9Cu alloy (the Ti-free alloy) had a lower ultimate tensile strength (UTS) than the Al-6.5Si-0.44Mg-0.9Cu-0.2Ti alloy. The UTS response of the alloys was enhanced by the addition of Ti, with the maximum UTS showing an increase from 348 MPa for the Ti-free alloy to 363 MPa for that containing 0.2 wt% Ti, aged at 180 °C. The Ti-free alloy had a higher thermal diffusivity than the Ti-containing alloy over all temperature ranges. Upon increasing the temperature from 180 °C to 220 °C, the room temperature thermal diffusivities increased because the solute concentration in the α-Al matrix rapidly decreased. In particular, the thermal diffusivity increased significantly between 200 °C and 400 °C. This temperature range matched the range of intermetallic phase precipitation as confirmed by differential scanning calorimetry and measurement of the coefficient of thermal expansion. During the artificial aging treatment, the intermetallic phases precipitated and grew rapidly. These reactions induced a reduction of the solute atoms in the solid solution, thus producing a more significant reduction in the thermal diffusivity. As the temperature was increased to above 400 °C, the formation of intermetallic phases ceased, and the thermal diffusivity showed a steady value, regardless of the aging temperature.

  18. Frustration in the pattern formation of polysyllabic words

    Science.gov (United States)

    Hayata, Kazuya

    2016-12-01

    A novel frustrated system is given for the analysis of (m + 1)-syllabled vocal sounds for languages with the m-vowel system, where the varieties of vowels are assumed to be m (m > 2). The necessary and sufficient condition for observing the sound frustration is that the configuration of m vowels in an m-syllabled word has a preference for the ‘repulsive’ type, in which there is no duplication of an identical vowel. For languages that meet this requirement, no (m + 1)-syllabled word can in principle select the present type because at most m different vowels are available and consequently the duplicated use of an identical vowel is inevitable. For languages showing a preference for the ‘attractive’ type, where an identical vowel aggregates in a word, there arises no such conflict. In this paper, we first elucidate for Arabic with m = 3 how to deal with the conflicting situation, where a statistical approach based on the chi-square testing is employed. In addition to the conventional three-vowel system, analyses are made also for Russian, where a polysyllabic word contains both a stressed and an indeterminate vowel. Through the statistical analyses the selection scheme for quadrisyllabic configurations is found to be strongly dependent on the parts of speech as well as the gender of nouns. In order to emphasize the relevance to the sound model of binary oppositions, analyzed results of Greek verbs are also given.

  19. An exact method for computing the frustration index in signed networks using binary programming

    OpenAIRE

    Aref, Samin; Mason, Andrew J.; Wilson, Mark C.

    2016-01-01

    Computing the frustration index of a signed graph is a key step toward solving problems in many fields including social networks, physics, material science, and biology. The frustration index determines the distance of a network from a state of total structural balance. Although the definition of the frustration index goes back to 1960, its exact algorithmic computation, which is closely related to classic NP-hard graph problems, has only become a focus in recent years. We develop three new b...

  20. Frustration of contract e impossibility of performance en el common law inglés

    OpenAIRE

    José Félix Chamie

    2009-01-01

    Sumario: i. Premisa. Formación de la doctrina de la frustration of contract. ii. Implied term theory. iii. Just and reasonable solution theory. iv. Foundation of contract theory. v. Radical change in the obligation: The “Construction theory”. vi. Efectos de la aplicación de la doctrine of frustration. vii. Límites de la jurisprudencia a la aplicación de la doctrine of frustration of contract