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Sample records for feas cuo heavy-fermion

  1. Heavy fermion superconductivity

    Science.gov (United States)

    Brison, Jean-Pascal; Glémot, Loı̈c; Suderow, Hermann; Huxley, Andrew; Kambe, Shinsaku; Flouquet, Jacques

    2000-05-01

    The quest for a precise identification of the symmetry of the order parameter in heavy fermion systems has really started with the discovery of the complex superconducting phase diagram in UPt 3. About 10 years latter, despite numerous experiments and theoretical efforts, this is still not achieved, and we will quickly review the present status of knowledge and the main open question. Actually, the more forsaken issue of the nature of the pairing mechanism has been recently tackled by different groups with macroscopic or microscopic measurement, and significant progress have been obtained. We will discuss the results emerging from these recent studies which all support non-phonon-mediated mechanisms.

  2. Superfluid response in heavy fermion superconductors

    Science.gov (United States)

    Zhong, Yin; Zhang, Lan; Shao, Can; Luo, Hong-Gang

    2017-10-01

    Motivated by a recent London penetration depth measurement [H. Kim, et al., Phys. Rev. Lett. 114, 027003 (2015)] and novel composite pairing scenario [O. Erten, R. Flint, and P. Coleman, Phys. Rev. Lett. 114, 027002 (2015)] of the Yb-doped heavy fermion superconductor CeCoIn5, we revisit the issue of superfluid response in the microscopic heavy fermion lattice model. However, from the literature, an explicit expression for the superfluid response function in heavy fermion superconductors is rare. In this paper, we investigate the superfluid density response function in the celebrated Kondo-Heisenberg model. To be specific, we derive the corresponding formalism from an effective fermionic large- N mean-field pairing Hamiltonian whose pairing interaction is assumed to originate from the effective local antiferromagnetic exchange interaction. Interestingly, we find that the physically correct, temperature-dependent superfluid density formula can only be obtained if the external electromagnetic field is directly coupled to the heavy fermion quasi-particle rather than the bare conduction electron or local moment. Such a unique feature emphasizes the key role of the Kondo-screening-renormalized heavy quasi-particle for low-temperature/energy thermodynamics and transport behaviors. As an important application, the theoretical result is compared to an experimental measurement in heavy fermion superconductors CeCoIn5 and Yb-doped Ce1- x Yb x CoIn5 with fairly good agreement and the transition of the pairing symmetry in the latter material is explained as a simple doping effect. In addition, the requisite formalism for the commonly encountered nonmagnetic impurity and non-local electrodynamic effect are developed. Inspired by the success in explaining classic 115-series heavy fermion superconductors, we expect the present theory will be applied to understand other heavy fermion superconductors such as CeCu2Si2 and more generic multi-band superconductors.

  3. Heavy fermion material: Ce versus Yb case

    OpenAIRE

    Flouquet, J.; Harima, H.

    2009-01-01

    Heavy fermion compounds are complex systems but excellent materials to study quantum criticality with the switch of different ground states. Here a special attention is given on the interplay between magnetic and valence instabilities which can be crossed or approached by tuning the system by pressure or magnetic field. By contrast to conventional rare earth magnetism or classical s wave superconductivity, strong couplings may occur with drastic changes in spin or charge dynamics. Measurement...

  4. Strong coupling effective theory with heavy fermions

    CERN Document Server

    Fromm, Michael; Lottini, Stefano; Philipsen, Owe

    2011-01-01

    We extend the recently developed strong coupling, dimensionally reduced Polyakov-loop effective theory from finite-temperature pure Yang-Mills to include heavy fermions and nonzero chemical potential by means of a hopping parameter expansion. Numerical simulation is employed to investigate the weakening of the deconfinement transition as a function of the quark mass. The tractability of the sign problem in this model is exploited to locate the critical surface in the (M/T, mu/T, T) space over the whole range of chemical potentials from zero up to infinity.

  5. Magnetism and superconductivity in heavy fermion systems

    Energy Technology Data Exchange (ETDEWEB)

    Flouquet, J. (DRFMC, C.E.N.G., 38 - Grenoble (France)); Brison, J.P.; Hasselbach, K.; Taillefer, L. (C.N.R.S., 38 - Grenoble (France)); Behnia, K.; Jaccard, D. (DPMC, Geneva Univ. (Switzerland)); Visser, A. de (Natuurkundig Lab., Univ. van Amsterdam (Netherlands))

    1991-12-01

    The normal and superconducting properties of heavy fermion compounds are reviewed. The discussion is focus on the three uranium compounds: UBe{sub 13}, UPt{sub 3} and URu{sub 2}Si{sub 2}. Special attention is given: 1) to unusual (H.T) superconducting phase diagram as discovered in UPt{sub 3} where two successive superconducting phases seem to occur in zero magnetic field; 2) to the role of long range ordering as found in URu{sub 2}Si{sub 2} and UPt{sub 3}. (orig.).

  6. HEAVY FERMIONS. Strange metal without magnetic criticality.

    Science.gov (United States)

    Tomita, Takahiro; Kuga, Kentaro; Uwatoko, Yoshiya; Coleman, Piers; Nakatsuji, Satoru

    2015-07-31

    A fundamental challenge to our current understanding of metals is the observation of qualitative departures from Fermi liquid behavior. The standard view attributes such non-Fermi liquid phenomena to the scattering of electrons off quantum critical fluctuations of an underlying order parameter. Although the possibility of non-Fermi liquid behavior isolated from the border of magnetism has long been speculated, no experimental confirmation has been made. Here, we report on the observation of a strange metal region away from a magnetic instability in an ultrapure single crystal. In particular, we show that the heavy-fermion superconductor β-YbAlB4 forms a possible phase with strange metallic behavior across an extensive pressure regime, distinctly separated from a high-pressure magnetic quantum phase transition by a Fermi liquid phase.

  7. Superconducting gap anomaly in heavy fermion systems

    Indian Academy of Sciences (India)

    G C Rout; M S Ojha; S N Behera

    2008-04-01

    The heavy fermion system (HFS) is described by the periodic Anderson model (PAM), treating the Coulomb correlation between the -electrons in the mean-field Hartree-Fock approximation. Superconductivity is introduced by a BCS-type pairing term among the conduction electrons. Within this approximation the equation for the superconducting gap is derived, which depends on the effective position of the energy level of the -electrons relative to the Fermi level. The latter in turn depends on the occupation probability f of the -electrons. The gap equation is solved self-consistently with the equation for f; and their temperature dependences are studied for different positions of the bare -electron energy level, with respect to the Fermi level. The dependence of the superconducting gap on the hybridization leads to a re-entrant behaviour with increasing strength. The induced pairing between the -electrons and the pairing of mixed conduction and -electrons due to hybridization are also determined. The temperature dependence of the hybridization parameter, which characterizes the number of electrons with mixed character and represents the number of heavy electrons is studied. This number is shown to be small. The quasi-particle density of states (DOS) shows the existence of a pseudo-gap due to superconductivity and the signature of a hybridization gap at the Fermi level. For the choice of the model parameters, the DOS shows that the HFS is a metal and undergoes a transition to the gap-less superconducting state.

  8. Top Quark, Heavy Fermions and the Composite Higgs Boson

    Institute of Scientific and Technical Information of China (English)

    ZHANG Bin; ZHENG Han-Qing

    2001-01-01

    We study the properties of heavy fermions in the vector-like representation of the electroweak gauge group SU(2)w × U(1)y with Yukawa couplings to the standard model Higgs boson. Applying the renormalization group analysis,we discuss the effects of heavy fermions to the vacuum stability bound and the triviality bound on the mass of the Higgs boson. We also discuss the interesting possibility that the Higgs particle is composed of the top quark and heavy fermions.The bound on the composite Higgs mass is estimated using the method of Bardeen, Hill and Lindner (Phys. Rev. D41 (1990) 1647), 150 GeV≤ mH ≤450 GeV.

  9. Millikelvin cooling by heavy-fermion-based tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Prest, Martin; Min, Gao, E-mail: Min@cardiff.ac.uk [School of Engineering, Cardiff University, Cardiff CF24 3AA (United Kingdom); Whall, Terry [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom)

    2015-12-28

    This paper addresses a high-performance electron-tunneling cooler based on a novel heavy-fermion/insulator/superconductor junction for millikelvin cooling applications. We show that the cooling performance of an electronic tunneling refrigerator could be significantly improved using a heavy-fermion metal to replace the normal metal in a conventional normal metal/insulator/superconductor junction. The calculation, based on typical parameters, indicates that, for a bath temperature of 300 mK, the minimum cooling temperature of an electron tunneling refrigerator is reduced from around 170 mK to below 50 mK if a heavy-fermion metal is employed in place of the normal metal. The improved cooling is attributed to an enhancement in electron tunneling due to the existence of a resonant density of states at the Fermi level.

  10. Electron transmission in normal/heavy-fermion superconductor junctions

    OpenAIRE

    Araujo, M. A. N; Sacramento, P. D.

    2008-01-01

    The Andreev reflection between a normal metal (N) and a heavy-fermion superconductor (HFS) is studied and the boundary conditions for the electron's wave function in the two systems are established in the framework of a two band model for the HFS. Hence we show in a simple and explicit way that the mass enhancement factors in the heavy-fermion (HF) metal do not cause impedance at the N/HFS interface, in accordance with arguments previously presented. We also present an extension of the theory...

  11. High-pressure studies on heavy fermion systems

    Institute of Scientific and Technical Information of China (English)

    陈晔; 翁宗法; 路欣; 袁辉球

    2016-01-01

    In this review article, we give a brief overview of heavy fermions, which are prototype examples of strongly correlated electron systems. We introduce the application of physical pressure in heavy fermion systems to construct their pressure phase diagrams and to study the close relationship between superconductivity (SC) and other electronic instabilities, such as antiferromagnetism (AFM), ferromagnetism (FM), and valence transitions. Field-angle dependent heat capacity and point-contact spectroscopic measurements under pressure are taken as examples to illustrate their ability to investigate novel physical properties of the emergent electronic states.

  12. Electronic structure of heavy fermions: narrow temperature-independent bands

    Energy Technology Data Exchange (ETDEWEB)

    Arko, A.J.; Joyce, J.J.; Andrews, A.B.; Thompson, J.D.; Smith, J.L. [Los Alamos National Lab., NM (United States); Moshopoulou, E.; Fisk, Z. [NHMFL, Florida State Univ., Tallahassee, FL (United States); Menovsky, A.A. [Amsterdam Univ. (Netherlands). Natuurkundig Lab.; Canfield, P.C.; Olson, C.G. [Iowa State Univ., Ames, IA (United States). Ames Lab.

    1997-02-01

    The electronic structure of both Ce and U heavy fermions appears to consist of extremely narrow temperature independent bands. There is no evidence from ARPES data reported here for a collective phenomenon normally referred to as the Kondo resonance. In uranium compounds a small dispersion of the bands is easily measurable. (orig.).

  13. The electronic structure of heavy fermions: Narrow temperature independent bands

    Energy Technology Data Exchange (ETDEWEB)

    Arko, A.J.; Joyce, J.J.; Smith, J.L.; Andrews, A.B. [and others

    1996-08-01

    The electronic structure of both Ce and U heavy fermions appears to consist of extremely narrow temperature independent bands. There is no evidence from photoemission for a collective phenomenon normally referred to as the Kondo resonance. In uranium compounds a small dispersion of the bands is easily measurable.

  14. Photoelectron spectroscopy in heavy fermions: Inconsistencies with the Kondo model

    Energy Technology Data Exchange (ETDEWEB)

    Arko, A.J.; Joyce, J.J.; Blyth, R.R.; Canfield, P.C.; Thompson, J.D.; Bartlett, R.J.; Fisk, Z. [Los Alamos National Lab., NM (United States); Lawrence, J.; Tang, J. [California Univ., Irvine, CA (United States); Riseborough, P. [Polytechnic Univ., Brooklyn, NY (United States)

    1992-09-01

    We have investigated a number of Ce and Yb heavy fermion compounds via photoelectron spectroscopy and compared the results to the predictions of the Imurity Anderson Hamiltonian within the Gunnarson-Schonhammer approach. For the low T{sub K} materials investigated we find little or no correlation with T{sub K}, the only parameter that can be determined independent of photoemission.

  15. Superconductivity of heavy fermions in the Kondo lattice model

    Energy Technology Data Exchange (ETDEWEB)

    Sykora, Steffen [IFW Dresden (Germany); Becker, Klaus W. [Institut fuer Theoretische Physik, Technische Universitaet Dresden (Germany)

    2015-07-01

    Understanding of the origin of superconductivity in strongly correlated electron systems is one of the basic unresolved problems in physics. Examples for such systems are the cuprates and also the heavy-fermion metals, which are compounds with 4f and 5f electrons. In all these materials the superconducting pairing interaction is often believed to be predominantly mediated by spin fluctuations and not by phonons as in normal metals. For the Kondo-lattice model we present results, which are derived within the Projective Renormalization Method (PRM). Based on a recent study of the one-particle spectral function for the normal state we first derive an effective Hamiltonian which describes heavy fermion quasiparticle bands close to the Fermi surface. An extension to the superconducting phase leads to d-wave solutions for the superconducting order parameter in agreement with recent STM measurements.

  16. High-pressure studies on heavy fermion systems

    Science.gov (United States)

    Ye, Chen; Zongfa, Weng; Smidman, Michael; Xin, Lu; Huiqiu, Yuan

    2016-07-01

    In this review article, we give a brief overview of heavy fermions, which are prototype examples of strongly correlated electron systems. We introduce the application of physical pressure in heavy fermion systems to construct their pressure phase diagrams and to study the close relationship between superconductivity (SC) and other electronic instabilities, such as antiferromagnetism (AFM), ferromagnetism (FM), and valence transitions. Field-angle dependent heat capacity and point-contact spectroscopic measurements under pressure are taken as examples to illustrate their ability to investigate novel physical properties of the emergent electronic states. Project supported by the National Basic Research Program of China (Grant No. 2011CBA00103), the National Natural Science Foundation of China (Grant Nos. 11174245 and 11374257), the Science Challenge Program of China, and the Fundamental Research Funds for the Central Universities of China.

  17. New heavy-fermion antiferromagnet UPd2Cd20

    Science.gov (United States)

    Hirose, Yusuke; Doto, Hiroshi; Honda, Fuminori; Li, Dexin; Aoki, Dai; Haga, Yoshinori; Settai, Rikio

    2016-10-01

    We succeeded in growing a new high quality single crystal of a ternary uranium compound UPd2Cd20. From the electrical resistivity, magnetization, magnetic susceptibility, and specific heat experiments, UPd2Cd20 is found to be an antiferromagnetic heavy-fermion compound with the Néel temperature {{T}\\text{N}}   =  5 K and exhibits the large electronic specific heat coefficient γ exceeding 500 mJ (K2· mol)-1. This compound is the first one that exhibits the magnetic ordering with the magnetic moments of the U atom in a series of UT2X20 (T: transition metal, X  =  Al, Zn, Cd). UPd2Cd20 shows typical characteristic features in heavy-fermion systems such as a broad maximum in the magnetic susceptibility at {{T}{{χ\\text{max}}}} and a large coefficient A of T 2 term in the resistivity.

  18. Two-dimensional Confinement of Heavy Fermions in Artificial Superlattices

    Science.gov (United States)

    Shishido, Hiroaki

    2011-03-01

    Low dimensionality and strong electron-electron Coulomb interactions are both key parameters for novel quantum states of condensed matter. A metallic system with the strongest electron correlations is reported in rare-earth and actinide compounds with f electrons, known as heavy-fermion compounds, where the effective mass of the conduction electrons are strikingly enhanced by the electron correlations up to some hundreds times the free electron mass. To date the electronic structure of all heavy-fermion compounds is essentially three-dimensional. We realized experimentally a two-dimensional heavy fermion system, adjusting the dimensionality in a controllable fashion. We grew artificial superlattices of CeIn 3 (m)/ LaIn 3 (n), in which m -layers of heavy-fermion antiferromagnet CeIn 3 and n -layers of a non-magnetic isostructual compound LaIn 3 are stacked alternately, by a molecular beam epitaxy. By reducing the thickness of the CeIn 3 layers, the magnetic order was suppressed and the effective electron mass was further enhanced. The Néel temperature becomes zero at around m = 2 , concomitant with striking deviations from the standard Fermi liquid low-temperature electronic properties. Standard Fermi liquid behaviors are, however, recovered under high magnetic field. These behaviors imply new ``dimensional tuning'' towards a quantum critical point. We also succeeded to fabricate artificial superlattices of a heavy fermion superconductor CeCoIn 5 and non-magnetic divalent Yb-compound YbCoIn 5 . Superconductivity survives even in CeCoIn 5 (3)/ YbCoIn 5 (5) films, while the thickness of CeCoIn 5 layer, 2.3 nm, is comparable to the c -axis coherence length ξc ~ 2 nm. This work has been done in collaboration with Y. Mizukami, S. Yasumoto, M. Shimozawa, H. Kontani, T. Shibauchi, T. Terashima and Y. Matsuda.superconductivity is realized in the artificial superlattices. This work has been done in collaboration with Y. Mizukami, S. Yasumoto, M. Shimozawa, H. Kontani, T

  19. How Do Heavy Fermions Get Polarized And Die?

    Science.gov (United States)

    Julian, Stephen

    2009-03-01

    In paramagnetic heavy fermion systems the f-spins dissolve into Kondo singlets and reappear within the Fermi volume, producing a ``large" Fermi surface populated by heavy quasiparticles. According to theory, when a very large magnetic field is applied to such a system the Kondo singlets are broken and the fully polarized bare f-spins vanish from the Fermi volume, leaving behind a ``small" Fermi surface populated by light quasiparticles. How the system passes from the low-field to the high-field limit is not clear. This talk will discuss recent transport and de Haas van Alphen studies of the archetypal heavy fermion systems CeRu2Si2 [1] and YbRh2Si2 [2], which are interpreted as showing that the f-electron disappears from the Fermi volume via two successive Lifshitz transitions: in the first transition a majority spin band sinks below the Fermi level, while in the second a new minority spin band appears at the Fermi level. While this interpretation is in accord with recent theoretical work of Kusminskiy et al. [3], it could be criticized on the grounds that only the first of the two postulated Lifshitz transitions have so far been observed.[4pt] References:[0pt] [1] R. Daou, C. Bergemann and S.R. Julian, ``Continuous evolution of the Fermi surface of CeRu2Si2 across the metamagnetic transition,'' Physical Review Letters 96 (2006) 026401.[0pt] [2] P.M.C. Rourke, A. McCollam, G. Lapertot, G. Knebel, J. Flouquet and S.R. Julian, ``Magnetic field dependence of the YbRh2Si2 Fermi surface,'' arXiv:0807.3970; accepted, Physical Review Letters.[0pt] [3] S. Viola-Kusminskiy, K.S.D. Beach, A.H. Castro Neto and D.K. Campbell, ``Mean-field study of the heavy fermion metamagnetic transition,'' Physical Review B 77 (2008) 094419.

  20. Photoexcited electron dynamics in Kondo insulators and heavy fermions

    OpenAIRE

    Demsar, Jure; Thorsmolle, Verner K.; Sarrao, John L.; Taylor, Antoinette J.

    2005-01-01

    We have studied the photoexcited carrier relaxation dynamics in the Kondo insulator SmB6 and the heavy fermion metal YbAgCu4 as a function of temperature and excitation level. The dynamic response is found to be both strongly temperature dependent and nonlinear. The data are analyzed with a Rothwarf-Taylor bottleneck model, where the dynamics are governed by the presence of a narrow gap in the density of states near the Fermi level. The remarkable agreement with the model suggests that carrie...

  1. Exploring heavy fermions from macroscopic to microscopic length scales

    Science.gov (United States)

    Wirth, Steffen; Steglich, Frank

    2016-10-01

    Strongly correlated systems present fundamental challenges, especially in materials in which electronic correlations cause a strong increase of the effective mass of the charge carriers. Heavy fermion metals — intermetallic compounds of rare earth metals (such as Ce, Sm and Yb) and actinides (such as U, Np and Pu) — are prototype systems for complex and collective quantum states; they exhibit both a lattice Kondo effect and antiferromagnetic correlations. These materials show unexpected phenomena; for example, they display unconventional superconductivity (beyond Bardeen-Cooper-Schrieffer (BCS) theory) and unconventional quantum criticality (beyond the Landau framework). In this Review, we focus on systems in which Landau's Fermi-liquid theory does not apply. Heavy fermion metals and semiconductors are well suited for the study of strong electronic correlations, because the relevant energy scales (for charge carriers, magnetic excitations and lattice dynamics) are well separated from each other, allowing the exploration of concomitant physical phenomena almost independently. Thus, the study of these materials also provides valuable insight for the understanding — and tailoring — of other correlated systems.

  2. Peltier effect in normal metal-insulator-heavy fermion metal junctions

    Science.gov (United States)

    Goltsev, A. V.; Rowe, D. M.; Kuznetsov, V. L.; Kuznetsova, L. A.; Min, Gao

    2003-04-01

    A theoretical study has been undertaken of the Peltier effect in normal metal-insulator-heavy fermion metal junctions. The results indicate that, at temperatures below the Kondo temperature, such junctions can be used as electronic microrefrigerators to cool the normal metal electrode and are several times more efficient in cooling than the normal metal-heavy fermion metal junctions.

  3. Optical spectra of the heavy fermion uniaxial ferromagnet UGe2

    Science.gov (United States)

    Guritanu, V.; Armitage, N. P.; Tediosi, R.; Saxena, S. S.; Huxley, A.; van der Marel, D.

    2008-11-01

    We report a detailed study of UGe2 single crystals using infrared reflectivity and spectroscopic ellipsometry. The optical conductivity suggests the presence of a low-frequency interband transition and a narrow free-carrier response with strong frequency dependence of the scattering rate and effective mass. We observe sharp increase in the low-frequency mass and reduction in scattering rate below the upper ferromagnetic transition TC=53K indicating the emergence of a heavy fermion state triggered by the ferromagnetic order. The characteristic changes are exhibited most strongly at an energy scale below 12 meV. They recover their unrenormalized value above TC and for ω>40meV . In contrast no sign of an anomaly is seen at the lower transition temperature of unknown nature, Tx˜30K , observed in transport and thermodynamic experiments.

  4. Strong coupling theory of heavy fermion criticality II

    Science.gov (United States)

    Wölfle, Peter; Schmalian, Jörg; Abrahams, Elihu

    2017-04-01

    We present a theory of the scaling behavior of the thermodynamic, transport and dynamical properties of a three-dimensional metal governed by d-dimensional fluctuations at a quantum critical point, where the electron quasiparticle effective mass diverges. We determine how the critical bosonic order parameter fluctuations are affected by the effective mass divergence. The coupled system of fermions and bosons is found to be governed by two stable fixed points: the conventional weak-coupling fixed point and a new strong-coupling fixed point, provided the boson–boson interaction is irrelevant. The latter fixed point supports hyperscaling, characterized by fractional exponents. The theory is applied to the antiferromagnetic critical point in certain heavy fermion compounds, in which the strong-coupling regime is reached.

  5. Polar Kerr effect studies of time reversal symmetry breaking states in heavy fermion superconductors

    Science.gov (United States)

    Schemm, E. R.; Levenson-Falk, E. M.; Kapitulnik, A.

    2017-04-01

    The connection between chiral superconductivity and topological order has emerged as an active direction in research as more instances of both have been identified in condensed matter systems. With the notable exception of 3He-B, all of the known or suspected chiral - that is to say time-reversal symmetry-breaking (TRSB) - superfluids arise in heavy fermion superconductors, although the vast majority of heavy fermion superconductors preserve time-reversal symmetry. Here we review recent experimental efforts to identify TRSB states in heavy fermion systems via measurement of polar Kerr effect, which is a direct consequence of TRSB.

  6. Spin-Orbit Coupling and Novel Electronic States at the Interfaces of Heavy Fermion Materials

    Science.gov (United States)

    2016-02-22

    spin-orbit coupling (SOC) may induce new electronic phases that are difficult to realize in bulk materials . With the support of this STIR grant, we have...Report: Spin-Orbit Coupling and Novel Electronic States at the Interfaces of Heavy Fermion Materials Report Title This report summarizes the progress...regime in the correlated- electron “global” phase diagram of heavy fermion materials and, in addition, paving the way for interactions between the

  7. Scanning tunneling spectroscopy on heavy-fermion systems; Rastertunnelspektroskopie an Schwere-Fermionen-Systemen

    Energy Technology Data Exchange (ETDEWEB)

    Ernst, Stefan

    2011-06-24

    in the framework of this thesis different heavy-fermion systems were studied by means of scanning tunneling microscopy and spectroscopy. In the experiment two main topics existed. On the one hand the heavy-fermion superconductivity in the compounds CeCu{sub 2}Si{sub 2}, CeCoIn{sub 5}, and on the other hand the Kondo effect in the Kondo-lattice system YbRh{sub 2}Si{sub 2}.

  8. NQR Study of the Heavy-Fermion Pu-115 Superconductors

    Science.gov (United States)

    Koutroulakis, G.; Yasuoka, H.; Tobash, P. H.; Mitchell, J. N.; Bauer, E. D.; Thompson, J. D.

    2014-03-01

    We present 115In nuclear quadrupolar resonance (NQR) measurements on the heavy-fermion superconductors Pu MIn5 (M=Co, Rh; Tc=2.5K, 1.6K, respectively), in the temperature range 0 . 29 K <= T <= 100 K . From the identified spectral lines, we deduce the quadrupolar parameters for the two inequivalent In sites, which are found to be qualitatively similar to those for other Ce- and Pu-115s. The quadrupolar frequency νQ varies with temperature in the normal state as per the empirical formula for conventional metals. As superconductivity develops, however, νQ exhibits a sharp, albeit small shift, which is a key prediction of the theory of composite superconducting (SC) pairing. The temperature variation of the nuclear spin-lattice relaxation rate T1- 1 delineates distinctive regimes of dynamic behavior. An excess of strong in-plane antiferromagnetic spin fluctuations is observed in the vicinity of Tc, which are believed to be playing a central role in the formation of the SC condensate. Analysis of the T1- 1 data in the SC state suggests that these compounds are strong-coupling d-wave superconductors.

  9. Spin gap in heavy fermion compound UBe13

    Science.gov (United States)

    Storchak, V. G.; Brewer, J. H.; Eshchenko, D. G.; Mengyan, P. W.; Parfenov, O. E.; Tokmachev, A. M.; Dosanjh, P.; Fisk, Z.; Smith, J. L.

    2016-08-01

    Heavy fermion (HF) compounds are well known for their unique properties, such as narrow bandwidths, loss of coherence in a metal, non-Fermi-liquid behaviour, unconventional superconductivity, huge magnetoresistance etc. While these materials have been known since the 1970s, there is still considerable uncertainty regarding the fundamental mechanisms responsible for some of these features. Here we report transverse-field muon spin rotation (μ +SR) experiments on the canonical HF compound UBe13 in the temperature range from 0.025 to 300 K and in magnetic fields up to 7 T. The μ +SR spectra exhibit a sharp anomaly at 180 K. We present a simple explanation of the experimental findings identifying this anomaly with a gap in the spin excitation spectrum of f-electrons opening near 180 K. It is consistent with anomalies discovered in heat capacity, NMR and optical conductivity measurements of UBe13, as well as with the new resistivity data presented here. The proposed physical picture may explain several long-standing mysteries of UBe13 (as well as other HF systems).

  10. Photoemission and the electronic properties of heavy fermions -- limitations of the Kondo model

    Energy Technology Data Exchange (ETDEWEB)

    Joyce, J.J.; Arko, A.J.; Andrews, A.B. [and others

    1993-09-01

    The electronic properties of Yb-based heavy fermions have been investigated by means of high resolution synchrotron radiation photoemission and compared with predictions of the Kondo model. The Yb heavy fermion photoemission spectra show massive disagreement with the Kondo model predictions (as calculated within the Gunnarsson-Schonhammer computational method). Moreover, the Yb heavy fermion photoemission spectra give very strong indications of core-like characteristics and compare favorable to purely divalent Yb metal and core-like Lu 4f levels. The heavy fermions YbCu{sub 2}Si{sub 2}, YbAgCu{sub 4} and YbAl{sub 3} were measured and shown to have lineshapes much broader and deeper in binding energy than predicted by the Kondo model. The lineshape of the bulk component of the 4f emission for these three heavy fermion materials was compared with that from Yb metal and the Lu 4f levels in LuAl{sub 3}, the heavy fermion materials show no substantive spectroscopic differences from simple 4f levels observed in Yb metal and LuAl{sub 3}. Also, the variation with temperature of the 4f fineshape was measured for Yb metal and clearly demonstrates that phonon broadening plays a major role in 4f level lineshape analysis and must be accounted for before considerations of correlated electron resonance effects are presumed to be at work.

  11. Photoemission and the electronic properties of heavy fermions - limitations of the Kondo model

    Energy Technology Data Exchange (ETDEWEB)

    Joyce, J.J. [Los Alamos Nat. Lab., NM (United States); Arko, A.J. [Los Alamos Nat. Lab., NM (United States); Andrews, A.B. [Los Alamos Nat. Lab., NM (United States); Blyth, R.I.R. [Los Alamos Nat. Lab., NM (United States); Bartlett, R.J. [Los Alamos Nat. Lab., NM (United States); Thompson, J.D. [Los Alamos Nat. Lab., NM (United States); Fisk, Z. [Los Alamos Nat. Lab., NM (United States); Riseborough, P.S. [Polytechnic Institute of New York, Department of Physics, Brooklyn, NY 11201 (United States); Canfield, P.C. [Ames Laboratory USDOE, Ames, IA 50011 (United States); Olson, C.G. [Ames Laboratory USDOE, Ames, IA 50011 (United States); Benning, P.J. [Ames Laboratory USDOE, Ames, IA 50011 (United States)

    1995-03-01

    The electronic properties of Yb-based heavy fermions have been investigated by means of high resolution synchrotron radiation photoemission and compared with predictions of the Kondo model. The Yb heavy fermion photoemission spectra show significant disagreement with the Kondo model predictions (as calculated within the Gunnarsson-Schonhammer computational method). Moreover, the Yb heavy fermion photoemission spectra give strong indications of core-like characteristics and compare favorably to purely divalent Yb metal and core-like Lu 4f levels. The heavy fermions YbCu{sub 2}Si{sub 2}, YbAgCu{sub 4} and YbAl{sub 3} were measured and shown to have lineshapes much broader and deeper in binding energy than predicted by the Kondo model. The lineshape of the bulk component of the 4f emission for these three heavy fermion materials was compared with that from Yb metal and the Lu 4f levels in LuAl{sub 3}. The heavy fermion materials show no substantive spectroscopic differences from 4f levels observed in Yb metal and LuAl{sub 3}. Also, the variation with temperature of the 4f lineshape was measured for Yb metal and clearly demonstrates that phonon broadening plays a major role in 4f level lineshape analysis and must be accounted for before considerations of correlated electron resonance effects are presumed to be at work. ((orig.)).

  12. Anomalies of magnetoresistance in Ce-based heavy fermion compounds

    Science.gov (United States)

    Sluchanko, N. E.; Bogach, A. V.; Anisimov, M. A.; Glushkov, V. V.; Demishev, S. V.; Samarin, N. A.; Chistyakov, O. D.; Burkhanov, G. S.; Gabani, S.; Flachbart, K.

    2015-12-01

    Magnetoresistance Δρ(H,T) of several heavy-fermion compounds, CeAl2, CeAl3 and CeCu6, substitutional solid solutions with quantum critical behavior CeCu6-xAux (x = 0.1, 0.2) and alloys with magnetic ground state Ce(Al1-xMx)2 (M = Co, Ni, x ≤ 0.8) was studied in a wide range of temperatures (1.8-40 K) in magnetic fields up to 80 kOe. It was shown that a consistent interpretation of the field dependences of the resistance for both non-magnetic and magnetically ordered cerium-based intermetallic compounds with strong electron correlations can be achieved within the framework of an approach that accounts for scattering of charge carriers by localized magnetic moments in a metal matrix. Within this approach, three different components of the magnetoresistance of cerium intermetallic compounds were identified: the negative Brillouin contribution proportional to the local magnetization ( -Δρ/ρ˜Mloc2 ), the alternating linear contribution ( Δρ/ρ˜H ) and the magnetic component, saturating in magnetic fields below 15 kOe. In the framework of the Yosida model for the cerium alloys under study, estimates of the local magnetic susceptibility χloc(H, T0) were obtained from the magnetoresistance data. Numerical differentiation of the magnetoresistance with respect to the magnetic field and analysis of the obtained d (Δρ/ρ)/d H =f (H ,T ) dependences allowed us to reconstruct the H-T magnetic phase diagrams of the strongly correlated electron systems under study as well as to examine the effects of spin polarization and renormalization of the electronic states on charge transport both in the regime of quantum critical behavior and in the magnetically ordered state.

  13. Selective correlations and heavy-fermionic behaviour in iron-based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Medici, Luca d' [European Synchrotron Radiation Facility, 71 Av. des Martyrs, 38000 Grenoble (France); Ecole Superieure de Physique et Chimie industrielles de la Ville de Paris, 10 rue Vauquelin, 75005 Paris (France)

    2016-07-01

    The matching between recent experimental evidences from various probes and realistic theoretical calculations highlights the coexistence, in the normal phase of Fe-based superconductors, of strongly correlated and weakly correlated electrons. This peculiar situation can be backtracked to the influence of Hund's coupling exchange interaction between the conduction electrons in these materials, and can be controlled to some degree. In some of these compounds this differentiation can get quite extreme and gives rise to heavy-fermionic behaviour. We will speculate that these and similar d-electron materials could constitute a new ballpark for the exploration of heavy-fermionic physics, and of its applications. A new possible application of the strong thermomagnetic properties that can in principle be found in heavy-fermions is proposed: self-cooling of high-current cables.

  14. Emergence of anisotropic heavy fermions in antiferromagnetic Kondo lattice CeIn3 revealed by photoemission

    Science.gov (United States)

    Zhang, Yun; Lu, Haiyan; Zhu, Xiegang; Tan, Shiyong; Chen, Qiuyun; Feng, Wei; Xie, Donghua; Luo, Lizhu; Zhang, Wen; Lai, Xinchun; Donglai Feng Team; Huiqiu Yuan Team

    One basic concept in heavy fermions systems is the entanglement of localized spin state and itinerant electron state. It can be tuned by two competitive intrinsic mechanisms, Kondo effect and Ruderman-Kittel-Kasuya-Yosida interaction, with external disturbances. The key issue regarding heavy fermions properties is how the two mechanisms work in the same phase region. To investigate the relation of the two mechanisms, the cubic antiferromagnetic heavy fermions compound CeIn3 was investigated by soft x-ray angle resolved photoemission spectroscopy. The hybridization between f electrons and conduction bands in the paramagnetic state was observed directly, providing compelling evidence for Kondo screening scenario and coexistence of two mechanisms. The hybridization strength shows slight and regular anisotropy in K space, implying that the two mechanisms are competitive and anisotropic. This work illuminates the concomitant and competitive relation between the two mechanisms and supplies some evidences for the anisotropic superconductivity of CeIn3

  15. Foundations of heavy-fermion superconductivity: lattice Kondo effect and Mott physics

    Science.gov (United States)

    Steglich, Frank; Wirth, Steffen

    2016-08-01

    This article overviews the development of heavy-fermion superconductivity, notably in such rare-earth-based intermetallic compounds which behave as Kondo-lattice systems. Heavy-fermion superconductivity is of unconventional nature in the sense that it is not mediated by electron-phonon coupling. Rather, in most cases the attractive interaction between charge carriers is apparently magnetic in origin. Fluctuations associated with an antiferromagnetic (AF) quantum critical point (QCP) play a major role. The first heavy-fermion superconductor CeCu2Si2 turned out to be the prototype of a larger group of materials for which the underlying, often pressure-induced, AF QCP is likely to be of a three-dimensional (3D) spin-density-wave (SDW) variety. For UBe13, the second heavy-fermion superconductor, a magnetic-field-induced 3D SDW QCP inside the superconducting phase can be conjectured. Such a ‘conventional’, itinerant QCP can be well understood within Landau’s paradigm of order-parameter fluctuations. In contrast, the low-temperature normal-state properties of a few heavy-fermion superconductors are at odds with the Landau framework. They are characterized by an ‘unconventional’, local QCP which may be considered a zero-temperature 4 f-orbital selective Mott transition. Here, as concluded for YbRh2Si2, the breakdown of the Kondo effect concurring with the AF instability gives rise to an abrupt change of the Fermi surface. Very recently, superconductivity was discovered for this compound at ultra-low temperatures. Therefore, YbRh2Si2 along with CeRhIn5 under pressure provide a natural link between the large group of about fifty low-temperature heavy-fermion superconductors and other families of unconventional superconductors with substantially higher T c, e.g. the doped Mott insulators of the perovskite-type cuprates and the organic charge-transfer salts.

  16. Foundations of heavy-fermion superconductivity: lattice Kondo effect and Mott physics.

    Science.gov (United States)

    Steglich, Frank; Wirth, Steffen

    2016-08-01

    This article overviews the development of heavy-fermion superconductivity, notably in such rare-earth-based intermetallic compounds which behave as Kondo-lattice systems. Heavy-fermion superconductivity is of unconventional nature in the sense that it is not mediated by electron-phonon coupling. Rather, in most cases the attractive interaction between charge carriers is apparently magnetic in origin. Fluctuations associated with an antiferromagnetic (AF) quantum critical point (QCP) play a major role. The first heavy-fermion superconductor CeCu2Si2 turned out to be the prototype of a larger group of materials for which the underlying, often pressure-induced, AF QCP is likely to be of a three-dimensional (3D) spin-density-wave (SDW) variety. For UBe13, the second heavy-fermion superconductor, a magnetic-field-induced 3D SDW QCP inside the superconducting phase can be conjectured. Such a 'conventional', itinerant QCP can be well understood within Landau's paradigm of order-parameter fluctuations. In contrast, the low-temperature normal-state properties of a few heavy-fermion superconductors are at odds with the Landau framework. They are characterized by an 'unconventional', local QCP which may be considered a zero-temperature 4 f-orbital selective Mott transition. Here, as concluded for YbRh2Si2, the breakdown of the Kondo effect concurring with the AF instability gives rise to an abrupt change of the Fermi surface. Very recently, superconductivity was discovered for this compound at ultra-low temperatures. Therefore, YbRh2Si2 along with CeRhIn5 under pressure provide a natural link between the large group of about fifty low-temperature heavy-fermion superconductors and other families of unconventional superconductors with substantially higher T c, e.g. the doped Mott insulators of the perovskite-type cuprates and the organic charge-transfer salts.

  17. Inconsistencies with the single impurity Undersign model in photoelectron spectra of cerium heavy fermion compounds

    Energy Technology Data Exchange (ETDEWEB)

    Joyce, J.J.; Arko, A.J; Canfield, P.C.; Fisk, Z.; Barlett, R.J.; Smith, J.L.; Thompson, J.D. (Los Alamos National Lab., NM (United States)); Lawrence, J. (California Univ., Irvine, CA (United States))

    1991-01-01

    We have re-examined the temperature-dependence of the valence band 4f features in Ce-based heavy fermions. We measured the phonon broadening of the Si-2p core levels in CeSi{sub 2} by determining the increase of the full width at half-maximum (FWHM) as a function of temperature. We discovered that all the temperature dependence is exactly accounted for, and there is none left over to attribute to any Kondo effects. We concluded that the feature of E{sub F} in Ce-based heavy fermions cannot be a Kondo resonance. 16 refs., 3 figs.

  18. Final Technical Report, Grant DE-FG02-91ER45443: Heavy fermions and other highly correlated electron systems

    Energy Technology Data Exchange (ETDEWEB)

    Schlottmann, P.

    1998-10-12

    Properties of highly correlated electrons, such as heavy fermion compounds, metal-insulator transitions, one-dimensional conductors and systems of restricted dimensionality are studied theoretically. The main focus is on Kondo insulators and impurity bands due to Kondo holes, the low-temperature magnetoresistivity of heavy fermion alloys, the n-channel Kondo problem, mesoscopic systems and one-dimensional conductors.

  19. Neutron diffraction from the vortex lattice in the heavy-fermion superconductor UPt3

    DEFF Research Database (Denmark)

    Kleiman, R.N.; Broholm, C.; Aeppli, G.

    1992-01-01

    We have used neutron diffraction to observe the vortex lattice of UPt3. This is the first such measurement in a heavy-fermion system, a superconductor below 1 K, or in a system with such a long magnetic penetration depth (6000 +/- 75 angstrom). It also provides the first value for the pair...

  20. Magnetic excitations in the heavy-Fermion superconductor URu2Si2

    DEFF Research Database (Denmark)

    Broholm, C.; Lin, H.; Matthews, P.T.

    1991-01-01

    Antiferromagnetic order and fluctuations in the heavy-fermion superconductor URu2Si2 have been studied by magnetic neutron scattering. Below T(N) = 17.5 K, URu2Si2 is a type-I antiferromagnet with an anomalously small ordered moment of (0.04 +/- 0.01)mu-B polarized along the tetragonal c axis...

  1. In-NQR study of heavy fermion superconductor Ce2PdIn8 under pressure

    Science.gov (United States)

    Fukazawa, Hideto; Shimatani, Sho; Shigeta, Kazuhiko; Kohori, Yoh; Kaczorowski, Dariusz

    2015-03-01

    115In nuclear quadrupole resonance measurements were performed in the normal state of the heavy fermion superconductor Ce2PdIn8 under hydrostatic pressure up to about 2.3 GPa. The observed behavior of the spin-lattice relaxation rate revealed a systematic suppression of antiferromagnetic critical fluctuations with increasing pressure.

  2. Multiple quantum phase transitions and superconductivity in Ce-based heavy fermions.

    Science.gov (United States)

    Weng, Z F; Smidman, M; Jiao, L; Lu, Xin; Yuan, H Q

    2016-09-01

    Heavy fermions have served as prototype examples of strongly-correlated electron systems. The occurrence of unconventional superconductivity in close proximity to the electronic instabilities associated with various degrees of freedom points to an intricate relationship between superconductivity and other electronic states, which is unique but also shares some common features with high temperature superconductivity. The magnetic order in heavy fermion compounds can be continuously suppressed by tuning external parameters to a quantum critical point, and the role of quantum criticality in determining the properties of heavy fermion systems is an important unresolved issue. Here we review the recent progress of studies on Ce based heavy fermion superconductors, with an emphasis on the superconductivity emerging on the edge of magnetic and charge instabilities as well as the quantum phase transitions which occur by tuning different parameters, such as pressure, magnetic field and doping. We discuss systems where multiple quantum critical points occur and whether they can be classified in a unified manner, in particular in terms of the evolution of the Fermi surface topology.

  3. Multiple quantum phase transitions and superconductivity in Ce-based heavy fermions

    Science.gov (United States)

    Weng, Z. F.; Smidman, M.; Jiao, L.; Lu, Xin; Yuan, H. Q.

    2016-09-01

    Heavy fermions have served as prototype examples of strongly-correlated electron systems. The occurrence of unconventional superconductivity in close proximity to the electronic instabilities associated with various degrees of freedom points to an intricate relationship between superconductivity and other electronic states, which is unique but also shares some common features with high temperature superconductivity. The magnetic order in heavy fermion compounds can be continuously suppressed by tuning external parameters to a quantum critical point, and the role of quantum criticality in determining the properties of heavy fermion systems is an important unresolved issue. Here we review the recent progress of studies on Ce based heavy fermion superconductors, with an emphasis on the superconductivity emerging on the edge of magnetic and charge instabilities as well as the quantum phase transitions which occur by tuning different parameters, such as pressure, magnetic field and doping. We discuss systems where multiple quantum critical points occur and whether they can be classified in a unified manner, in particular in terms of the evolution of the Fermi surface topology.

  4. Many-body effects in heavy fermion compounds [sic]. Final technical report for period September 1984 - January 2001

    Energy Technology Data Exchange (ETDEWEB)

    Riseborough, Peter S.

    2002-05-01

    A theoretical investigation of many-body effects in Cerium and Uranium Heavy Fermion and Mixed Valent Compounds and their experimental manifestations in thermodynamic, transport, and spectroscopic properties is discussed in this report.

  5. Vortexlike excitations in the heavy-fermion superconductor CeIrIn5

    Science.gov (United States)

    Luo, Yongkang; Rosa, P. F. S.; Bauer, E. D.; Thompson, J. D.

    2016-05-01

    We report a systematic study of temperature- and field-dependent charge (ρ ) and entropy (S ) transport in the heavy-fermion superconductor CeIrIn5. Its large positive thermopower Sx x is typical of Ce-based Kondo lattice systems, and strong electronic correlations play an important role in enhancing the Nernst signal Sx y. By separating the off-diagonal Peltier coefficient αx y from Sx y, we find that αx y becomes positive and greatly enhanced at temperatures well above the bulk Tc. Compared with the nonmagnetic analog LaIrIn5, these results suggest vortexlike excitations in a precursor state to unconventional superconductivity in CeIrIn5. This study sheds light on the similarity of heavy-fermion and cuprate superconductors and on the possibility of states not characterized by the amplitude of an order parameter.

  6. First Observation of Heavy Fermion Behavior in Ce-Based Icosahedral Approximant

    Science.gov (United States)

    Imura, Keiichiro; Nobe, Kohei; Deguchi, Kazuhiko; Matsunami, Masaharu; Miyazaki, Hidetoshi; Yasui, Akira; Ikenaga, Eiji; Sato, Noriaki K.

    2017-09-01

    Since the discovery of unconventional quantum criticality in the Au-Al-Yb quasicrystal and pressure-induced quantum criticality in its approximant, quasicrystals and approximants with an icosahedral cluster of atoms have attracted much attention. Here we report magnetic, thermodynamic, transport, and hard x-ray photoemission spectroscopy experiments on the Ce-based approximant Ag-In-Ce. These results indicate the heavy fermion behavior of the 4f electrons and provide convincing evidence of a magnetic phase transition into a spin-glass-like short-range-ordered state at a low temperature. The Ag-In-Ce alloy is the first Ce-based heavy fermion approximant to a Tsai-type quasicrystal. Reflecting its unique crystal structure, the approximant shows an electrical resistivity distinct from that of traditional Kondo lattices.

  7. Two loop electroweak corrections from heavy fermions to b→s+γ

    Institute of Scientific and Technical Information of China (English)

    YANG Xiu-Yi; FENG Tai-Fu

    2010-01-01

    Applying an effective Lagrangian method and an on-shell scheme, we analyze the electroweak corrections to the rare decay b→, s+γ from some special two loop diagrams in which a closed heavy fermion loop is attached to the virtual charged gauge bosons or Higgs. At the decoupling limit where the virtual fermions in the inner loop are much heavier than the electroweak scale, we verify the final results satisfying the decoupling theorem explicitly when the interactions among Higgs and heavy fermions do not contain the nondecoupling couplings. Adopting the universal assumptions on the relevant couplings and mass spectrum of new physics, we find that the relative corrections from those two loop diagrams to the SM theoretical prediction on the branching ratio of B → Xsγ can reach 5% as the energy scale of new physics ANp=200 GeV.

  8. Energy Loss of a Heavy Fermion in an Anisotropic QED Plasma

    CERN Document Server

    Romatschke, P; Romatschke, Paul; Strickland, Michael

    2004-01-01

    We compute the leading-order collisional energy loss of a heavy fermion propagating in a QED plasma with an electron distribution function which is anisotropic in momentum space. We show that in the presence of such anisotropies there can be a significant directional dependence of the heavy fermion energy loss with the effect being quite large for highly-relativistic velocities. We also repeat the analysis of the isotropic case more carefully and show that the final result depends on the intermediate scale used to separate hard and soft contributions to the energy loss. We then show that the canonical isotropic result is obtained in the weak-coupling limit. For intermediate-coupling we use the residual scale dependence as a measure of our theoretical uncertainty. We also discuss complications which could arise due to the presence of unstable soft photonic modes and demonstrate that the calculation of the energy loss is safe.

  9. On the spin origin of heavy fermions in rare earth intermetallides

    Energy Technology Data Exchange (ETDEWEB)

    Kikoin, K.A. [RRC Kurchatov Inst., Moscow (Russian Federation); Kiselev, M.N. [RRC Kurchatov Inst., Moscow (Russian Federation); Mishchenko, A.S. [RRC Kurchatov Inst., Moscow (Russian Federation)

    1995-02-01

    Microscopic arguments are presented in favor of a spin nature of the heavy fermions in Kondo lattices with nearly integer valence of the f-elections. It is shown that the competition between the Kondo scattering and the indirect exchange interaction can result in stabilization of a spin-liquid state with a Fermi-type spectrum both for neutral spin and charged electron excitations. The origin of strong antiferromagnetic fluctuations is briefly discussed. ((orig.)).

  10. Theory of scanning tunneling spectroscopy: from Kondo impurities to heavy fermion materials

    Science.gov (United States)

    Morr, Dirk K.

    2017-01-01

    Kondo systems ranging from the single Kondo impurity to heavy fermion materials present us with a plethora of unconventional properties whose theoretical understanding is still one of the major open problems in condensed matter physics. Over the last few years, groundbreaking scanning tunneling spectroscopy (STS) experiments have provided unprecedented new insight into the electronic structure of Kondo systems. Interpreting the results of these experiments—the differential conductance and the quasi-particle interference spectrum—however, has been complicated by the fact that electrons tunneling from the STS tip into the system can tunnel either into the heavy magnetic moment or the light conduction band states. In this article, we briefly review the theoretical progress made in understanding how quantum interference between these two tunneling paths affects the experimental STS results. We show how this theoretical insight has allowed us to interpret the results of STS experiments on a series of heavy fermion materials providing detailed knowledge of their complex electronic structure. It is this knowledge that is a conditio sine qua non for developing a deeper understanding of the fascinating properties exhibited by heavy fermion materials, ranging from unconventional superconductivity to non-Fermi-liquid behavior in the vicinity of quantum critical points.

  11. Virtual hadronic and heavy-fermion O(α2) corrections to Bhabha scattering

    Science.gov (United States)

    Actis, Stefano; Czakon, Michał; Gluza, Janusz; Riemann, Tord

    2008-10-01

    Effects of vacuum polarization by hadronic and heavy-fermion insertions were the last unknown two-loop QED corrections to high-energy Bhabha scattering and have been announced in [S. Actis, M. Czakon, J. Gluza, and T. Riemann, Phys. Rev. Lett. 100, 131602 (2008).PRLTAO0031-900710.1103/PhysRevLett.100.131602]. Here we describe the corrections in detail and explore their numerical influence. The hadronic contributions to the virtual O(α2) QED corrections to the Bhabha-scattering cross section are evaluated using dispersion relations and computing the convolution of hadronic data with perturbatively calculated kernel functions. The technique of dispersion integrals is also employed to derive the virtual O(α2) corrections generated by muon-, tau-, and top-quark loops in the small electron-mass limit for arbitrary values of the internal-fermion masses. At a meson factory with 1 GeV center-of-mass energy the complete effect of hadronic and heavy-fermion corrections amounts to less than 0.5 per mille and reaches, at 10 GeV, up to about 2 per mille. At the Z resonance it amounts to 2.3 per mille at 3 degrees; overall, hadronic corrections are less than 4 per mille. For ILC energies (500 GeV or above), the combined effect of hadrons and heavy fermions becomes 6 per mille at 3 degrees; hadrons contribute less than 20 per mille in the whole angular region.

  12. Polar Kerr effect studies of time reversal symmetry breaking states in heavy fermion superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Schemm, E.R., E-mail: eschemm@alumni.stanford.edu [Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305 (United States); Levenson-Falk, E.M. [Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305 (United States); Department of Physics, Stanford University, Stanford, CA 94305 (United States); Kapitulnik, A. [Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305 (United States); Department of Physics, Stanford University, Stanford, CA 94305 (United States); Department of Applied Physics, Stanford University, Stanford, CA 94305 (United States); Stanford Institute of Energy and Materials Science, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States)

    2017-04-15

    Highlights: • Polar Kerr effect (PKE) probes broken time-reversal symmetry (TRS) in superconductors. • Absence of PKE below Tc in CeCoIn{sub 5} is consistent with dx2-y2 order parameter symmetry. • PKE in the B phase of the multiphase superconductor UPt3 agrees with an E2u model. • Data on URu2Si2 show broken TRS and additional structure in the superconducting state. - Abstract: The connection between chiral superconductivity and topological order has emerged as an active direction in research as more instances of both have been identified in condensed matter systems. With the notable exception of {sup 3}He-B, all of the known or suspected chiral – that is to say time-reversal symmetry-breaking (TRSB) – superfluids arise in heavy fermion superconductors, although the vast majority of heavy fermion superconductors preserve time-reversal symmetry. Here we review recent experimental efforts to identify TRSB states in heavy fermion systems via measurement of polar Kerr effect, which is a direct consequence of TRSB.

  13. Temperature-invariant photoelectron spectra in cerium heavy-fermion compounds: Inconsistencies with the Kondo model

    Energy Technology Data Exchange (ETDEWEB)

    Joyce, J.J.; Arko, A.J.; Lawrence, J.; Canfield, P.C.; Fisk, Z.; Bartlett, R.J.; Thompson, J.D. (Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States))

    1992-01-13

    4{ital f} levels in Ce heavy-fermion compounds are examined using resonant photoemission. We find the following inconsistencies with the predictions of the Kondo model: (a) All temperature dependence can be accounted for simply by phonon broadening and the Fermi function; (b) the spectral weights of the features near {ital E}{sub {ital F}} do not scale with {ital T}{sub {ital K}}; and (c) the line shape of the feature previously identified as the Kondo resonance is Lorentzian and about an order of magnitude broader than predictions. Instrument resolution is not a limiting factor.

  14. Temperature dependence of 4f PES features and hole occupancy in ytterbium heavy fermions

    Energy Technology Data Exchange (ETDEWEB)

    Andrews, A.B.; Blyth, R.I.R.; Arko, A.J. [and others

    1993-09-01

    We have measured the temperature dependence between 80 and 300K and spectral weight of the 4f features in clean single crystal Yb heavy fermions, cleaved in a vacuum of 5 {times} 10{sup {minus}11} Torr. A small ({approx}10%) decrease in spectral weight differs substantially from the reported {approx}50% decrease over this range. All divalent features are much larger than expected, yielding n{sub f} values far too small. The intensity of the divalent features in YbAuCu{sub 4} is about 2 orders of magnitude larger than expected.

  15. Temperature dependence of 4f PES features and hole occupancy in ytterbium heavy fermions

    Energy Technology Data Exchange (ETDEWEB)

    Andrews, A.B. (Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)); Blyth, R.I.R. (Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)); Arko, A.J. (Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)); Joyce, J.J. (Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)); Fisk, Z. (Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)); Thompson, J.D. (Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)); Bartlett, R.J. (Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)); Canfield, P.C. (Iowa State University, Ames, Iowa (United States)); Olson, C.G. (Iowa State University, Ames, Iowa (United States)); Benning, P. (Iowa State University, Ames, Iowa (United States)); Riseborough, P.S. (Polytechnic University, Brooklyn, New York (United States))

    1994-04-01

    We have measured the temperature dependence between 80 and 300 K and spectral weight of the 4f features in clean single crystal Yb heavy fermions, cleaved in a vacuum of 5x10[sup -11] Torr. A small ( similar 15%) decrease in spectral weight differs substantially from the reported similar 50% decrease over this range. All divalent features are much larger than expected, yielding n[sub f] values far too small. The intensity of the divalent features in YbAuCu[sub 4] is about two orders of magnitude larger than expected. ((orig.))

  16. de Haas van Alphen perspective on the origin of heavy fermions in UPt3

    Science.gov (United States)

    Rourke, Patrick; McCollam, Alix; McMullan, Greg; Norman, Mike; Julian, Stephen; Huxley, Andrew

    2006-03-01

    Precise de Haas van Alphen (dHvA) oscillation measurements on the heavy fermion superconductor UPt3 are available as a function of magnetic field angle. It was recently proposed that the heavy quasiparticles in this material arise from the localization of two of the three 5f electrons of the U ions [Zwicknagl et al., PRB 65, 081103R (2002)]. The predicted Fermi surface topology however differs from traditional bandstructure calculations. We will focus on the experimentally observed angle dependence of the hole-like δ-orbit, as this appears difficult to reconcile with the Fermi surface of Zwicknagl et al.

  17. Effect of electron-phonon interaction on resistivity of some heavy fermion (HF) systems

    Energy Technology Data Exchange (ETDEWEB)

    Sahoo, J., E-mail: jitendrasahoo2008@gmail.com [Assistant Director, Regional Office of Vocational Education, Sambalpur, Odisha-768004 (India); Shadangi, N. [Dept. of Physics, Silicon Institute of Technology, Sambalpur, Odisha-768200 (India); Nayak, P. [School of Physics, Sambalpur University, Sambalpur, Odisha-768019 (India)

    2014-04-24

    Here, we have analyzed the electron-phonon interaction in the Periodic Anderson Model (PAM) to describe the temperature dependence of resistivity in some heavy fermion (HF) systems for finite wave vector (q) and for finite temperature (T). Since the resistivity is related to the imaginary part of the electron self energy, the expression for the same is evaluated through double time temperature dependant Green function technique of the Zubarev type. The effect of different system parameters namely the position of 4f level, E{sub 0} and the electron - phonon coupling strengths on resistivity have been studied. The results obtained give satisfactory explanations to the experimental observations.

  18. Non-Fermi liquid picture and superconductivity in heavy fermion systems

    Energy Technology Data Exchange (ETDEWEB)

    Sykora, Steffen [IFW Dresden, D- 01171 Dresden (Germany); Becker, Klaus W. [Department of Physics, TU Dresden, D-01069 Dresden (Germany)

    2013-07-01

    We study the S = 1/2 Kondo lattice model which is widely used to describe heavy fermion behavior. In conventional treatments of the model a hybridization of conduction and localized f electrons is introduced by decoupling the Kondo interaction. However, such an approximation has the detrimental effect that a breaking of a local gauge symmetry is imposed which implicates that the local f occupation n{sub i}{sup f} is no longer conserved. To avoid such an artifact, we treat the model in an alternative approach based on the Projective Renormalization Method (PRM). Thereby, within the conduction electron spectral function we identify the lattice Kondo resonance as an almost flat incoherent excitation near the Fermi surface which is composed of conduction electron creation operators combined with localized spin fluctuations. This leads to a new concept of the Kondo resonance without having to resort to a symmetry breaking and Fermi liquid theory. Based on this new picture we develop a microscopic theory for superconductivity in heavy fermion systems. Thereby we study the momentum-dependence of the superconducting order parameter for singlet as well as triplet pairing. We show that in particular the triplet pairing components are strongly affected by the incoherent excitations found to be responsible for the Kondo resonance.

  19. Heavy-Fermion Superconductivity in the Quadrupole Ordered State of PrV2Al20

    Science.gov (United States)

    Tsujimoto, Masaki; Matsumoto, Yosuke; Tomita, Takahiro; Sakai, Akito; Nakatsuji, Satoru

    2014-12-01

    PrV2Al20 is a rare example of a heavy-fermion system based on strong hybridization between conduction electrons and nonmagnetic quadrupolar moments of the cubic Γ3 ground doublet. Here, we report that a high-quality single crystal of PrV2Al20 exhibits superconductivity at Tc=50 mK in the antiferroquadrupole-ordered state under ambient pressure. The heavy-fermion character of the superconductivity is evident from the specific heat jump of Δ C /T ˜0.3 J /mol K2 and the effective mass m*/m0˜140 estimated from the temperature dependence of the upper critical field. Furthermore, the high-quality single crystals exhibit double transitions at TQ=0.75 K and T*=0.65 K associated with quadrupole and octupole degrees of freedom of the Γ3 doublet. In the ordered state, the specific heat C /T shows a T3 dependence, indicating the gapless mode associated with the quadrupole order, the octupole order, or both. The strong sensitivity to impurity of the superconductivity suggests unconventional character due to significant quadrupolar fluctuations.

  20. Extended nuclear quadrupole resonance study of the heavy-fermion superconductor PuCoGa5

    Science.gov (United States)

    Koutroulakis, G.; Yasuoka, H.; Tobash, P. H.; Mitchell, J. N.; Bauer, E. D.; Thompson, J. D.

    2016-10-01

    PuCoGa5 has emerged as a prototypical heavy-fermion superconductor, with its transition temperature (Tc≃18.5 K) being the highest amongst such materials. Nonetheless, a clear description as to what drives the superconducting pairing is still lacking, rendered complicated by the notoriously intricate nature of plutonium's 5 f valence electrons. Here, we present a detailed Ga,7169 nuclear quadrupole resonance (NQR) study of PuCoGa5, concentrating on the system's normal state properties near to Tc and aiming to detect distinct signatures of possible pairing mechanisms. In particular, the quadrupole frequency and spin-lattice relaxation rate were measured for the two crystallographically inequivalent Ga sites and for both Ga isotopes, in the temperature range 1.6-300 K. No evidence of significant charge fluctuations is found from the NQR observables. On the contrary, the low-energy dynamics is dominated by anisotropic spin fluctuations with strong, nearly critical, in-plane character, which are effectively identical to the case of the sister compound PuCoIn5. These findings are discussed within the context of different theoretical proposals for the unconventional pairing mechanism in heavy-fermion superconductors.

  1. Virtual Hadronic and Heavy-Fermion O(alpha^2) Corrections to Bhabha Scattering

    CERN Document Server

    Actis, Stefano; Gluza, Janusz; Riemann, Tord

    2008-01-01

    Effects of vacuum polarization by hadronic and heavy-fermion insertions were the last unknown two-loop QED corrections to high-energy Bhabha scattering and have been first announced in \\cite{Actis:2007fs}. Here we describe the corrections in detail and explore their numerical influence. The hadronic contributions to the virtual O(alpha^2) QED corrections to the Bhabha-scattering cross-section are evaluated using dispersion relations and computing the convolution of hadronic data with perturbatively calculated kernel functions. The technique of dispersion integrals is also employed to derive the virtual O(alpha^2) corrections generated by muon-, tau- and top-quark loops in the small electron-mass limit for arbitrary values of the internal-fermion masses. At a meson factory with 1 GeV center-of-mass energy the complete effect of hadronic and heavy-fermion corrections amounts to less than 0.5 per mille and reaches, at 10 GeV, up to about 2 per mille. At the Z resonance it amounts to 2.3 per mille at 3 degrees; o...

  2. Simulating heavy fermion physics in optical lattice: Periodic Anderson model with harmonic trapping potential

    Science.gov (United States)

    Zhong, Yin; Liu, Yu; Luo, Hong-Gang

    2017-10-01

    The periodic Anderson model (PAM), where local electron orbitals interplay with itinerant electronic carriers, plays an essential role in our understanding of heavy fermion materials. Motivated by recent proposals for simulating the Kondo lattice model (KLM) in terms of alkaline-earth metal atoms, we take another step toward the simulation of PAM, which includes the crucial charge/valence fluctuation of local f-electrons beyond purely low-energy spin fluctuation in the KLM. To realize PAM, a transition induced by a suitable laser between the electronic excited and ground state of alkaline-earth metal atoms (1 S 0⇌3 P 0) is introduced. This leads to effective hybridization between local electrons and conduction electrons in PAM. Generally, the SU( N) version of PAM can be realized by our proposal, which gives a unique opportunity to detect large- N physics without complexity in realistic materials. In the present work, high-temperature physical features of standard [ SU(2)] PAM with harmonic trapping potential are analyzed by quantum Monte Carlo and dynamic mean-field theory, where the Mott/orbital-selective Mott state was found to coexist with metallic states. Indications for near-future experiments are provided. We expect our theoretical proposal and (hopefully) forthcoming experiments will deepen our understanding of heavy fermion systems. At the same time, we hope these will trigger further studies on related Mott physics, quantum criticality, and non-trivial topology in both the inhomogeneous and nonequilibrium realms.

  3. Crystal Field Excitations in Heavy Fermion Antiferromagnet CeRhIn5 and Heavy Fermion Superconductor CeIrIn_5

    Science.gov (United States)

    Christianson, A. D.; Bao, W.; Pagliuso, P. G.; Sarrao, J. L.; Lacerda, A. H.; Lawrence, J. M.; Kern, S.; Goremychkin, E. A.

    2002-03-01

    Bulk measurements by Takeuchi et al.^1 and Pagliuso et al.^2 indicate that crystal field effects may be important in understanding the exotic heavy fermion ground states exhibited by CeRhIn5 and CeIrIn_5. In an effort to understand the role of the crystal fields in these materials we have begun to study the crystal field excitations with inelastic neutron scattering. Inelastic neutron scattering probes the crystal field excitations directly. Our results indicate that a broad crystal field excitation is observed at 7 meV in CeRhIn_5. In CeIrIn_5, preliminary data suggest that the energy scale of the crystal field excitations is somewhat lower than in CeRhIn_5. We will discuss the temperature dependence of the crystal field excitations and possible crystal field level schemes as deduced from our data and compare our results with those obtained by bulk measurements. ^1T. Takeuchi et al., J. Phys. Soc. Japan 70, 877 (2001). ^2P.G. Pagliuso et al., private communication.

  4. Pairs of charged heavy fermions from an $SU(3)_{L}(-)U(1)_{N}$ model at $e^{+}e^{-}$ colliders

    CERN Document Server

    Cieza-Montalvo, J E; 10.1103/PhysRevD.67.075022

    2003-01-01

    We investigate the production, backgrounds, and signatures of pairs of charged heavy fermions using the SU(3)/sub L/(-)U(1)/sub N/ electroweak model in e/sup +/e/sup -/ colliders (Next Linear Collider and CERN Linear Collider). We also analyze the indirect evidence for a boson Z'. (23 refs).

  5. Grüneisen parameter studies on heavy fermion quantum criticality

    Science.gov (United States)

    Gegenwart, Philipp

    2016-11-01

    The Grüneisen parameter, experimentally determined from the ratio of thermal expansion to specific heat, quantifies the pressure dependence of characteristic energy scales of matter. It is highly enhanced for Kondo lattice systems, whose properties are strongly dependent on the pressure sensitive antiferromagnetic exchange interaction between f- and conduction electrons. In this review, we focus on the divergence of the Grüneisen parameter and its magnetic analogue, the adiabatic magnetocaloric effect, for heavy-fermion metals near quantum critical points. We compare experimental results with current theoretical models, including the effect of strong geometrical frustration. We also discuss the possibility of using materials with the divergent magnetic Grüneisen parameter for adiabatic demagnetization cooling to very low temperatures.

  6. Electronic structure of PuMGa5 (M = Co, Rh heavy Fermion compounds

    Directory of Open Access Journals (Sweden)

    A Tavana

    2009-08-01

    Full Text Available  Electronic properties of heavy Fermion superconductors PuCoGa5 and PuRhGa5 consisting of density of states, band structure and the Fermi surface have been calculated based on density functional theory in the local spin density approximation plus on site Coulomb correlation (LSDA+U. Calculated density of states is in overall consistency with a photo emission experiment. The bands with f character in the PuCoGa5 mostly form below the Fermi level while in PuRhGa5 some of these bands shift to above the Fermi energy. Comparison with other calculations implies that application of correlation correction, more separates the j=7/2 and j=5/2 band from each other. Fermi surfaces have been also extracted and discussed .

  7. On the interplay between heavy-fermion and soft crystal field excitations in Kondo lattices

    Energy Technology Data Exchange (ETDEWEB)

    Kagan, Yu.; Kikoin, K.A.; Mishchenko, A.S. [Rossijskij Nauchnyj Tsentr ``Kurchatovskij Inst.``, Moscow (Russian Federation)

    1997-06-13

    On the grounds of the microscopic theory of heavy-fermion spin-liquids a novel description of low-energy excitation spectra in CeNiSn and related compounds is offered. The anomalous properties of orthorhombic CeNiSn and related materials are explained by the interplay between the fermi-type spinon excitations with the energy scale T{sup *}{approx}T{sub K} and the one-site crystal field excitations with the energy {Delta}{sub CF}

  8. Inconsistencies with the single-impurity Anderson model in photoelectron spectra of cerium heavy fermion compounds

    Energy Technology Data Exchange (ETDEWEB)

    Joyce, J.J.; Arko, A.J.; Lawrence, J.; Canfield, P.C.; Fisk, Z.; Bartlett, R.J.; Thompson, J.D.; Smith, J.L. (Los Alamos National Lab., NM (United States))

    1992-04-03

    A series of cerium heavy fermion compounds have been studied in order to check for the systematics with T{sub K} and the temperature dependence of the Kondo resonance predicted by the Kondo model. Neither the systematics nor the temperature dependence is found, the latter primarily determined from a detailed study in CeSi{sub 2}. The qualitative shapes of the features at E{sub F} remain nearly constant irrespectively of T{sub K}, while all the temperature dependence can be explained as resulting from phonon broadening of core-like states as well as Fermi function broadening. In addition, if the d electron contribution to the spectra is subtracted, one obtains a symmetric, lorentzian line shape for the ''main'' 4f peak. (orig.).

  9. Fragile antiferromagnetism in the heavy-fermion compound YbBiPt

    Energy Technology Data Exchange (ETDEWEB)

    Ueland, Benjamin G. [Ames Laboratory; Kreyssig, Andreas [Ames Laboratory; Prokes, K. [Helmholtz-Zentrum Berlin fur Materialien und Energie; Lynn, J. W. [NIST Center for Neutron Research; Harriger, L. W. [NIST Center for Neutron Research; Pratt, D. K. [NIST Center for Neutron Research; Singh, D. K. [NIST Center for Neutron Research; Heitmann, T. W. [University of Missouri; Sauerbrei, Samantha [Ames Laboratory; Saunders, Scott M. [Ames Laboratory; Mun, E. D. [Ames Laboratory; Budko, Serguei L. [Ames Laboratory; McQueeney, Robert J. [Ames Laboratory; Canfield, Paul C. [Ames Laboratory; Goldman, Alan I. [Ames Laboratory

    2014-05-08

    We report results from neutron scattering experiments on single crystals of YbBiPt that demonstrate antiferromagnetic order characterized by a propagation vector, τAFM = (121212), and ordered moments that align along the [1 1 1] direction of the cubic unit cell. We describe the scattering in terms of a two-Gaussian peak fit, which consists of a narrower component that appears below TN≈0.4 K and corresponds to a magnetic correlation length of ξn≈ 80 Å, and a broad component that persists up to T*≈ 0.7 K and corresponds to antiferromagnetic correlations extending over ξb≈ 20 Å. Our results illustrate the fragile magnetic order present in YbBiPt and provide a path forward for microscopic investigations of the ground states and fluctuations associated with the purported quantum critical point in this heavy-fermion compound.

  10. Anisotropy in the thermal expansion of heavy-fermion UPt sub 3 at the superconducting transition

    Energy Technology Data Exchange (ETDEWEB)

    Visser, A. de; Menovsky, A.A.; Franse, J.J.M. (Natuurkundig Laboratorium, Valckenierstraat 65, 1018 XE Amsterdam, The Netherlands (NL)); Hasselbach, K.; Lacerda, A.; Taillefer, L.; Haen, P.; Flouquet, J. (Centre de Recherches sur les Tres Basses Temperatures, Centre National de la Recherche Scientifique, Boite Postale 166X, 38042 Grenoble CEDEX, France (FR))

    1990-04-01

    We have measured the coefficients of linear thermal expansion ({alpha}{sub {parallel}} and {alpha}{sub {perpendicular}}) of two single-crystalline samples of heavy-fermion UPt{sub 3} down to temperatures well below the superconducting transition ({ital T}{sub {ital c}}{approx equal}0.5 K). The thermal expansion is strongly anisotropic at {ital T}{sub {ital c}}, where only {alpha}{sub parrallel} has a discontinuity. This implies that {ital T}{sub {ital c}} is suppressed for a uniaxial stress along the hexagonal axis only. In the superconducting phase {alpha}{sub {parallel}} and {alpha}{sub {perpendicular}} vary approximately quadratically, with temperature, as does the specific heat. The Grueneisen parameter shows a large drop at {ital T}{sub {ital c}}; from 69 in the normal phase to {minus}10 in the superconducting phase.

  11. Magnetic and superconducting quantum critical points of heavy-fermion systems

    Energy Technology Data Exchange (ETDEWEB)

    Demuer, A.; Sheikin, I.; Braithwaite, D. E-mail: dbraithwaite@cea.fr; Faak, B.; Huxley, A.; Raymond, S.; Flouquet, J

    2001-05-01

    Two examples of heavy-fermion systems are presented : CePd{sub 2}Si{sub 2}, an antiferromagnet with a quantum critical point at P{sub C}=28 kbar and UGe{sub 2} an itinerant ferromagnet which transits in a paramagnetic phase above P{sub C}=16 kbar. In CePd{sub 2}Si{sub 2} the superconductivity domain is centered on P{sub C}. Special attention was given to the superconducting and magnetic anomalies at their superconducting and Neel temperatures. In UGe{sub 2} superconductivity appears in 9 kbar at a temperature T{sub S}, more than two orders of magnitude lower than the Curie temperature; furthermore, it occurs only on the magnetic border (P

  12. Magnetic and superconducting quantum critical points of heavy-fermion systems

    Science.gov (United States)

    Demuer, A.; Sheikin, I.; Braithwaite, D.; Fåk, B.; Huxley, A.; Raymond, S.; Flouquet, J.

    2001-05-01

    Two examples of heavy-fermion systems are presented : CePd 2Si 2, an antiferromagnet with a quantum critical point at PC=28 kbar and UGe 2 an itinerant ferromagnet which transits in a paramagnetic phase above PC=16 kbar. In CePd 2Si 2 the superconductivity domain is centered on PC. Special attention was given to the superconducting and magnetic anomalies at their superconducting and Néel temperatures. In UGe 2 superconductivity appears in 9 kbar at a temperature TS, more than two orders of magnitude lower than the Curie temperature; furthermore, it occurs only on the magnetic border ( P< PC). Another characteristic temperature TX is detected by resistivity; the zigzag uranium chain of the lattice may favor a supplementary nesting in the majority spin band.

  13. Antiferromagnetism in metals: from the cuprate superconductors to the heavy fermion materials.

    Science.gov (United States)

    Sachdev, Subir; Metlitski, Max A; Punk, Matthias

    2012-07-25

    The critical theory of the onset of antiferromagnetism in metals, with concomitant Fermi surface reconstruction, has recently been shown to be strongly coupled in two spatial dimensions. The onset of unconventional superconductivity near this critical point is reviewed: it involves a subtle interplay between the breakdown of fermionic quasiparticle excitations on the Fermi surface and the strong pairing glue provided by the antiferromagnetic fluctuations. The net result is a logarithm-squared enhancement of the pairing vertex for generic Fermi surfaces, with a universal dimensionless coefficient independent of the strength of interactions, which is expected to lead to superconductivity at the scale of the Fermi energy. We also discuss the possibility that the antiferromagnetic critical point can be replaced by an intermediate 'fractionalized Fermi liquid' phase, in which there is Fermi surface reconstruction but no long-range antiferromagnetic order. We discuss the relevance of this phase to the underdoped cuprates and the heavy fermion materials.

  14. 4f heavy fermion photoelectron spectra do not exhibit the Kondo scale

    Energy Technology Data Exchange (ETDEWEB)

    Arko, A.J.; Joyce, J.J.; Andrews, A.B.; Blyth, R.I.R.; Bartlett, R.J.; Fisk, Z. [Los Alamos National Lab., NM (United States); Canfield, P.C.; Olson, C.G.; Benning, P.J. [Iowa State Univ., Ames, IA (United States); Poirier, D.M.; Weaver, J.H. [Univ. of Minnesota, Minneapolis, MN (United States); Riseborough, P.S. [Polytechnic Univ., Brooklyn, NY (United States)

    1994-02-01

    It has been the authors contention for some time that the Single Impurity Anderson Model (SIAM), as extended by Gunnarsson and Schonhammer (GS), or the non-crossing approximation (NCA), does not correctly describe the 4f photoelectron spectra of heavy fermions. Recently, they have concentrated on Yb heavy fermions since in these materials the Kondo resonance (KR) is fully occupied and thus accessible via photoemission. In particular, they have repeatedly pointed out that the width, position, spectral weight, lineshape, and temperature dependence of the features assumed to be the KR and its sidebands, are nearly independent of the Kondo temperature, T{sub K}, while at the same time bearing a striking resemblance to the simple 4f core level spectra of pure Yb metal, or of Lu in isostructural Lu compounds. It is important to resolve these issues in view of the fundamental nature of the problem. Here, the authors chose to test the bulk vs. surface hypothesis by performing measurements on YbCu{sub 2}Si{sub 2} and YbAl{sub 3} single crystals at hv {approx} 120 eV (UPS) and hv {approx} 1,500 eV(XPS) to see if the n{sub f}, hole occupancy, values increase markedly at XPS energies as the electron escape depth increases by about a factor of 3--5. Measurements were performed at both 300K and 20K using single crystals cleaved in-situ, with photoelectrons collected in normal emission for maximum bulk sensitivity. UPS measurements were performed at NSLS and the University of Wisconsin SRC, while XPS measurements were done at the University of Minnesota. The UPS, ultraviolet photoelectron spectra, and the L{sub III} edge x-ray absorption and photoemission measurements are in fundamental disagreement.

  15. LiV{sub 2}O{sub 4}: A heavy fermion transition metal oxide

    Energy Technology Data Exchange (ETDEWEB)

    Kondo, Shinichiro

    1999-02-12

    The format of this dissertation is as follows. In the remainder of Chapter 1, brief introductions and reviews are given to the topics of frustration, heavy fermions and spinels including the precedent work of LiV{sub 2}O{sub 4}. In Chapter 2, as a general overview of this work the important publication in Physical Review Letters by the author of this dissertation and collaborators regarding the discovery of the heavy fermion behavior in LiV{sub 2}O{sub 4} is introduced [removed for separate processing]. The preparation methods employed by the author for nine LiV{sub 2}O{sub 4} and two Li{sub 1+x}Ti{sub 2{minus}x}O{sub 4} (x = 0 and 1/3) polycrystalline samples are introduced in Chapter 3. The subsequent structural characterization of the LiV{sub 2}O{sub 4} and Li{sub 1+x}Ti{sub 2{minus}x}O{sub 4} samples was done by the author using thermogravimetric analysis (TGA), x-ray diffraction measurements and their structural refinements by the Rietveld analysis. The results of the characterization are detailed in Chapter 3. In Chapter 4 magnetization measurements carried out by the author are detailed. In Chapter 5, after briefly discussing the resistivity measurement results including the single-crystal work by Rogers et al., for the purpose of clear characterization of LiV{sub 2}O{sub 4} it is of great importance to introduce in the following chapters the experiments and subsequent data analyses done by his collaborators. Heat capacity measurements (Chapter 6) were carried out and analyzed by Dr. C.A. Swenson, and modeled theoretically by Dr. D.C. Johnston. In Chapter 7 a thermal expansion study using neutron diffraction by Dr. O. Chmaissem et al. and capacitance dilatometry measurements by Dr. C.A. Swenson are introduced. The data analyses for the thermal expansion study were mainly done by Dr. O. Chmaissem (for neutron diffraction) and Dr. C.A. Swendon (for dilatometry), with assistances by Dr. J.D. Jorgensen, Dr. D.C. Johnston, and S. Kondo the author of this

  16. Effect of c-f hybridization on electric and magnetic properties of some Heavy Fermion (HF) systems

    Energy Technology Data Exchange (ETDEWEB)

    Sahoo, J., E-mail: jitendrasahoo2008@gmail.com [Regional Office of Vocational Education, Sambalpur, Odisha -768 004 (India); Nayak, P. [School of Physics, Sambalpur University, Sambalpur, Odisha - 768 019 (India)

    2017-02-01

    Representing the heavy fermion systems by the Periodic Anderson Model (PAM), we have used Zubarev technique to see the effect of c-f hybridization on the temperature dependence of resistivity and magnetic susceptibility. The calculated resistivity and magnetic susceptibility show the general features observed in these materials experimentally. Further, we have shown how the strength of hybridization as well as the position of the f-level affects both the properties and the Kondo temperature of these systems.

  17. Electric and Weak Electric Dipole Form Factors for Heavy Fermions in a General Two Higgs Doublet Model

    CERN Document Server

    Gómez-Dumm, D; Gomez-Dumm, Daniel

    1999-01-01

    The electric and weak electric dipole form factors for heavy fermions are calculated in the context of the most general two-Higgs-doublet model (2HDM). We find that the large top mass can produce a significant enhancement of the electric dipole form factor in the case of the b and c quarks. This effect can be used to distinguish between different 2HDM scenarios.

  18. Full-potential LMTO study on the electronic structure of heavy-fermion compound LiV2O4

    Institute of Scientific and Technical Information of China (English)

    TAN; Mingqiu(谭明秋); TAO; Xjangming(陶向明); HE; Junhui(何军辉)

    2002-01-01

    The electronic structure of heavy fermion compound LiV2O4 has been calculated using a self-consistent full-potential LMTO method. The results show that the conduction bands in this com pound are formed from V 3 d states with a bandwidth of 2.5 eV. The symmetric characteristics of con duction bands are of t2g in principle. The energy gap between conduction bands and fully occupied oxygen 2 p bands is 1.9 eV. The band dispersions near Fermi energy display complicated structures.Furthermore, the N(EF) and γcal are 11.1 (states/eV/f. u. ) and 26.7 mJ/mol@ K2 determined numer ically by LDA calculation, respectively. It is insufficient to clarify the origin of local moment in LiV2O4 from plain LDA calculations. In addition to the above LDA calculation, we also found a LSDA solution of LiV2O4 that is lower in total energy than that of LDA calculation. Similarly, LSDA + GGA calculation yields almost the identical result as that in LSDA. We conclude that the mechanism responsible for heavy fermion properties in LiV2O4 might be somewhat different from the plain Kondo mechanism in conventional 4 f and 5 f heavy fermion compounds and perhaps the quantum transition might play an adequate role in heavy-fermion behaviors in LiV2O4.

  19. Effect of c-f hybridization on electric and magnetic properties of some Heavy Fermion (HF) systems

    Science.gov (United States)

    Sahoo, J.; Nayak, P.

    2017-02-01

    Representing the heavy fermion systems by the Periodic Anderson Model (PAM), we have used Zubarev technique to see the effect of c-f hybridization on the temperature dependence of resistivity and magnetic susceptibility. The calculated resistivity and magnetic susceptibility show the general features observed in these materials experimentally. Further, we have shown how the strength of hybridization as well as the position of the f-level affects both the properties and the Kondo temperature of these systems.

  20. Chiral heavy fermions in a two Higgs doublet model: 750 GeV resonance or not

    CERN Document Server

    Bar-Shalom, Shaouly

    2016-01-01

    We revisit models where a heavy chiral 4th generation doublet of fermions is embedded in a class of two Higgs doublets models (2HDM) with a discrete $Z_2$ symmetry, which couples the "heavy" scalar doublet only to the 4th generation fermions and the "light" one to the Standard Model (SM) fermions - the so-called 4G2HDM introduced by us several years ago. We study the constraints imposed on the 4G2HDM from direct searches of heavy fermions, from precision electroweak data (PEWD) and from the measured production and decay signals of the 125 GeV scalar, which in the 4G2HDM corresponds to the lightest CP-even scalar h. We then show that the recently reported excess in the $\\gamma\\gamma$ spectrum around 750 GeV can be accommodated by the heavy CP-even scalar of the 4G2HDM, H, resulting in a unique choice of parameter space: negligible mixing (sin\\alpha ~ O(0.001)) between the two CP-even scalars h,H and heavy 4th generation quark and lepton masses m_t',m_b' 900 GeV, respectively. Whether or not the 750 GeV \\gamma...

  1. Search for heavy fermions with the ATLAS experiment at the LHC collider

    CERN Document Server

    AUTHOR|(INSPIRE)INSPIRE-00359999; Santiago, José; Onofre, António

    In the present thesis a search for new heavy fermions using LHC data collected in 2012 by the ATLAS experiment is presented. In particular, a search for pair and single production of vector-like quarks with electric charge 2/3 ($T$) and -1/3 ($B$) decaying to a $Z$ boson is discussed. For this search the analysis was divided in two channels, depending on the lepton multiplicity, and both channels were combined at the end for the final results. Since no evidence for signal was found, limits on the mass of the vector-like quarks were evaluated. The observed (expected) limit on the mass of an $SU(2)$ singlet $T$ quark is 655~GeV (625~GeV), while the observed (expected) limit on the mass of a $T$ quark in a $(T,B)$ doublet is 735~GeV (720~GeV). The observed (expected) limit on the mass of an $SU(2)$ singlet $B$ quark is 685~GeV (670~GeV), while the observed (expected) limit on the mass of a $B$ quark in a $(B,Y)$ doublet is 755~GeV (755~GeV). The impact of a heavy gluon in the searches for pair production of vect...

  2. Heavy fermions, quantum criticality, and unconventional superconductivity in filled skutterudites and related materials

    Energy Technology Data Exchange (ETDEWEB)

    Andraka, Bohdan [Univ. of Florida, Gainesville, FL (United States)

    2015-05-14

    The main goal of this program was to explore the possibility of novel states and behaviors in Pr-based system exhibiting quantum critical behavior, PrOs₄Sb₁₂. Upon small changes of external parameter, such as magnetic field, physical properties of PrOs₄Sb₁₂ are drastically altered from those corresponding to a superconductor, to heavy fermion, to field-induced ordered phase with primary quadrupolar order parameter. All these states are highly unconventional and not understood in terms of current theories thus offer an opportunity to expand our knowledge and understanding of condensed matter. At the same time, these novel states and behaviors are subjects to intense international controversies. In particular, two superconducting phases with different transition temperatures were observed in some samples and not observed in others leading to speculations that sample defects might be partially responsible for these exotic behaviors. This work clearly established that crystal disorder is important consideration, but contrary to current consensus this disorder suppresses exotic behavior. Superconducting properties imply unconventional inhomogeneous state that emerges from unconventional homogeneous normal state. Comprehensive structural investigations demonstrated that upper superconducting transition is intrinsic, bulk, and unconventional. The high quality of in-house synthesized single crystals was indirectly confirmed by de Haas-van Alphen quantum oscillation measurements. These measurements, for the first time ever reported, spanned several different phases, offering unprecedented possibility of studying quantum oscillations across phase boundaries.

  3. Heavy fermion and intermediate valence behaviour in Ce sub 24 Co sub 11

    Energy Technology Data Exchange (ETDEWEB)

    Kappler, J.P.; Schmerber, G. (IPCMS-GEMM, Inst. de Physique, 67 - Strasbourg (France)); Trovarelli, O.; Sereni, J.G. (Centro Atomico Bariloche (Argentina))

    1992-02-01

    Low temperature specific heat and magnetic susceptibility measurements on Ce{sub 24}Co{sub 11} are reported. The electronic specific heat can be decomposed into two contributions: a low temperature one (arising at T < 5 K), with a maximum of 2.2 J/K mol at 0.9 K, and another one becoming dominant at T > 5 K, characterized by a {gamma}{sub HT} = 1.8 J/K{sup 2} mol coefficient. The {chi}T product changes continuously with temperature, from 0.48 emu K/mol at 2 K to 7.85 emu K/mol at 200 K. Reminding that 1 mol = 1f.u. contains 24 Ce atoms distributed in ten unequivalent crystalline sites, we interpret the experimental results as due to: one atom which behaves as a heavy fermion, and the rest as intermediate valents, with a distribution of characteristic energies governed by nine different environments. The specific heat behaviour under applied field confirms this interpretation. (orig.).

  4. Quasi-particle interference of heavy fermions in resonant x-ray scattering

    Science.gov (United States)

    Gyenis, András; da Silva Neto, Eduardo H.; Sutarto, Ronny; Schierle, Enrico; He, Feizhou; Weschke, Eugen; Kavai, Mariam; Baumbach, Ryan E.; Thompson, Joe D.; Bauer, Eric D.; Fisk, Zachary; Damascelli, Andrea; Yazdani, Ali; Aynajian, Pegor

    2016-01-01

    Resonant x-ray scattering (RXS) has recently become an increasingly important tool for the study of ordering phenomena in correlated electron systems. Yet, the interpretation of RXS experiments remains theoretically challenging because of the complexity of the RXS cross section. Central to this debate is the recent proposal that impurity-induced Friedel oscillations, akin to quasi-particle interference signals observed with a scanning tunneling microscope (STM), can lead to scattering peaks in RXS experiments. The possibility that quasi-particle properties can be probed in RXS measurements opens up a new avenue to study the bulk band structure of materials with the orbital and element selectivity provided by RXS. We test these ideas by combining RXS and STM measurements of the heavy fermion compound CeMIn5 (M = Co, Rh). Temperature- and doping-dependent RXS measurements at the Ce-M4 edge show a broad scattering enhancement that correlates with the appearance of heavy f-electron bands in these compounds. The scattering enhancement is consistent with the measured quasi-particle interference signal in the STM measurements, indicating that the quasi-particle interference can be probed through the momentum distribution of RXS signals. Overall, our experiments demonstrate new opportunities for studies of correlated electronic systems using the RXS technique.

  5. Mean-field study of the heavy-fermion metamagnetic transition

    Science.gov (United States)

    Viola Kusminskiy, S.; Beach, K. S. D.; Castro Neto, A. H.; Campbell, D. K.

    2008-03-01

    We investigate the evolution of the heavy-fermion ground state under application of a strong external magnetic field. We present a richer version of the usual hybridization mean-field theory that allows for hybridization in both the singlet and triplet channels and incorporates a self-consistent Weiss field. We show that for a magnetic field strength B* , a filling-dependent fraction of the zero-field hybridization gap, the spin up quasiparticle band becomes fully polarized—an event marked by a sudden jump in the magnetic susceptibility. The system exhibits a kind of quantum rigidity in which the susceptibility (and several other physical observables) is insensitive to further increases in field strength. This behavior ends abruptly with the collapse of the hybridization order parameter in a first-order transition to the normal metallic state. We argue that the feature at B* corresponds to the “metamagnetic transition” in YbRh2Si2 . Our results are in good agreement with recent experimental measurements.

  6. Heavy fermion behaviour in the high pressure structure of CeSb{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Fedoseev, Vitaly; Feng, Zhuo; Zou, Yang; Grosche, F. Malte [Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE (United Kingdom); Giles, Terence; Niklowitz, Philipp [Department of Physics, Royal Holloway, University of London, Egham TW20 0EX (United Kingdom); Wilhelm, Heribert [Beamline I15, Diamond Light Source, Didcot OX11 0DE (United Kingdom); Lampronti, Giulio [Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ (United Kingdom)

    2015-07-01

    The Kondo lattice system CeSb{sub 2} crystallises in the orthorhombic SmSb{sub 2} structure and exhibits a series of magnetic phase transitions at low temperature. It has been reported to become ferromagnetic below 15 K, with the ordered moment oriented within the basal plane, and to undergo two further transitions at 9K and 12K. These transition are suppressed above a hydrostatic pressure p{sub c} ≅ 16 kbar. We present high pressure transport and x-ray diffraction results, which examine the high pressure state of CeSb{sub 2}. Our findings suggest that CeSb{sub 2} undergoes a drastic structural change at p{sub c} into a new and now fully resolved crystal structure. Whereas in the low pressure structure, CeSb{sub 2} is a local moment magnet, in the high pressure structure it exhibits transport properties characteristic of a heavy fermion material with a low Kondo temperature scale of the order of 10 K.

  7. Itinerant spin dynamics in iron-based superconductors and cerium-based heavy-fermion antiferromagnets

    Energy Technology Data Exchange (ETDEWEB)

    Friemel, Gerd

    2014-05-26

    This thesis contains a comprehensive study of the spin excitations by inelastic neutron scattering (INS) in two different correlated electron systems: the alkali-metal iron selenide superconductors (FeSe122) A{sub x}Fe{sub 2-y}Se{sub 2} (A=K, Rb, Cs) and the heavy-fermion antiferromagnet CeB6. Both systems exhibit intense modes in their spin-fluctuation spectrum below their respective transition temperatures that can be derived from the spin dynamics of the itinerant quasiparticles. However, the implications of these observations, presented here, are different for each particular compound. The A{sub x}Fe{sub 2-y}Se{sub 2} superconductors, with a uniform T{sub c} of 32 K, belong to a qualitative new family of superconductors. They possess a distinctly different Fermi surface compared to the iron-arsenide-based analogues XFe{sub 2}As{sub 2} (X=Ca, Sr, Ba). Instead of the central hole pockets at Γ and the electron pockets at X((1)/(2) 0), which are nested by the Q{sub AFM} = ((1)/(2) 0) vector, there exist only large electron pockets at the X point. Therefore, the magnetic instability along Q{sub AFM} that presumably provides the pairing glue for the superconductivity in the shape of spin fluctuations is absent in the FeSe122. The search for spin fluctuations by INS was motivated by a theoretical analysis that predicted their presence at an incommensurate wave vector near Q = (0.5 δ), δ = 0.3125 which results from a quasinesting by Q between the flat parts of the electron pockets. Two samples, namely Rb{sub 0.8}Fe{sub 1.6}Se{sub 2} and K{sub 0.77}Fe{sub 1.85}Se{sub 2}, were prepared and both showed a sizable anisotropic magnetic response at Q{sub sf} = ((1)/(2) (1)/(4)) in the normal state. Furthermore, upon entering the superconducting (SC) state a strong excitation appears at ℎω{sub res} = 14 meV in the spectrum at Q{sub sf}, which is referred to as magnetic resonant mode. This mode is interpreted as a bound spin-1 exciton below the SC charge gap. Its presence

  8. Ultrasonic investigation of a heavy fermion compound YbAgGe

    Energy Technology Data Exchange (ETDEWEB)

    Nakanishi, Y; Kashiwazaki, R; Deto, K; Shichinomiya, F; Nakamura, M; Yoshizawa, M [Graduate School of Engineering, Iwate University, Morioka 020-8551 (Japan); Kubo, H; Umeo, K; Onimaru, T; Takabatake, T, E-mail: yoshiki@iwate-u.ac.jp [Department of Quantum Matter, ADSM, Hiroshima University, Higashihiroshima 739-8530 (Japan)

    2011-01-01

    We have performed ultrasonic measurements on a heavy fermion compound with geometrical frustration YbAgGe which undergoes a complex series of phase transitions of TM{sub 1} = 0.8 K, and T{sub M2} = 0.65 K in zero field. A pronounced elastic softening toward the transition temperature T{sub M2} was observed in the temperature dependence of longitudinal elastic constants C{sub 11} and C{sub 33}, and transverse one C{sub 44}, while no softening was observed in transverse one C{sub 66}. Furthermore, a sharp drop was observed at T{sub M2} in all the elastic constants. The data is difficult to explain only by crystalline electric field effect proposed previously. Alternately, the deformation potential approximation can reproduce the experimental data reasonably. It is found that the bandwidth W of quasi-particles formed by hybridization between conduction electrons and 4f localized ones derived from Yb ion increases gradually with increasing the applied magnetic field, indicating an increase of Kondo temperature T{sub K}. A sudden change of the W appears in a field of 5 T, suggesting that the application of field suppresses in part the magnetic frustration, and enhances the Kondo temperature T{sub K}. We discuss our results with a model where the main contribution to the elastic softening arises from the deformation coupling between quasi-particles and elastic waves, and with an effect attributed to order-parameter fluctuations near T{sub M2}.

  9. Inhomogeneous disorder Dirac Fermions: from heavy fermion superconductors to graphene. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Vekhter, Ilya [Louisiana State University

    2013-08-11

    This is the final report on the award designed to foster a partnership between Louisiana State University and Los Alamos National Laboratory (LANL) in conducting fundamental research in support of energy needs. The general focus of the research effort was on developing a better understanding of materials with new functionalities. We investigated two distinct and very promising classes of new materials, which serve as a testing ground for many of the novel phenomena in condensed matter physics: the heavy fermion 115 series, where the interplay of strong interactions between the electrons leads to a rich variety of competing phases and anomalous properties, and newly discovered pnictide superconductors. The former focus was planned; the latter emerged during the collaborative effort with LANL. Our objective was to determine the origin, and to establish a functional effective theory description of the phases in these systems, and transitions between them. We report on the main accomplishments under the award that serves to clarify the nature of superconductivity in both families of materials. In particular, we collaborated with experimentalists to predict and analyze the magnetic field and temperature dependence of the bulk thermodynamic and transport properties and to determine the gap shape in CeCoIn₅ and in Ba(Fe1-xCox)₂As₂, investigated the Kondo temperature in the presence of spin-orbit coupling in the conduction band, and provided theoretical guidance for local probes such as scanning tunneling spectroscopy of vortex cores and impurity resonances, and magnetic force microscopy of the superconducting states.

  10. Superconductivity versus quantum criticality: what can we learn from heavy fermions?

    Science.gov (United States)

    Steglich, F; Arndt, J; Friedemann, S; Krellner, C; Tokiwa, Y; Westerkamp, T; Brando, M; Gegenwart, P; Geibel, C; Wirth, S; Stockert, O

    2010-04-28

    Two quantum critical point (QCP) scenarios are being discussed for different classes of antiferromagnetic (AF) heavy-fermion (HF) systems. In the itinerant one, where AF order is of the spin-density wave (SDW) type, the heavy 'composite' charge carriers keep their integrity at the QCP. The second one implies a breakdown of the Kondo effect and a disintegration of the composite fermions at the AF QCP. We discuss two isostructural compounds as exemplary materials for these two different scenarios: CeCu(2)Si(2) exhibits a three-dimensional (3D) SDW QCP and superconductivity, presumably mediated by SDW fluctuations, as strongly suggested by recent inelastic neutron scattering experiments. In Y bRh(2)Si(2), the AF QCP is found to coincide with a Kondo-destroying one. However, in the latter compound these two QCPs can be detached by varying the average unit-cell volume, e.g. through the application of chemical pressure, as realized by partial substitution of either Ir or Co for Rh. A comparison of CeCu(2)Si(2) and Y bRh(2)Si(2) indicates that the apparent differences in quantum critical behaviour go along with disparate behaviour concerning the (non-) existence of superconductivity (SC). No sign of SC could be detected in Y bRh(2)Si(2) down to mK temperatures. A potential correlation between the specific nature of the QCP and the occurrence of SC, however, requires detailed studies on further quantum critical HF superconductors, e.g. on β-Y bAlB(4), UBe(13), CeCoIn(5) and CeRhIn(5).

  11. A new ternary magnetically ordered heavy fermion compound Pr2Rh3Ge: magnetic, electronic and thermodynamic properties

    Science.gov (United States)

    Falkowski, M.; Strydom, A. M.

    2017-10-01

    The results of the magnetic, electron transport, heat capacity and heat conduction measurements on the new rhombohedral ternary compound Pr2Rh3Ge have been investigated. The synthesized polycrystalline compound was found to crystallize in the ternary ordered variant of the cubic Laves phase MgCu2 -type of structure with the space group R\\overline{3} m, as previously reported. Pr2Rh3Ge exhibits a ferromagnetic behaviour below TC = 8.5 K, which was found to be unstable in low applied magnetic fields, revealing characteristics usually attributed to the long-range order. In the entire paramagnetic region electrical resistivity shows monotonous metallic conductivity character. We estimated that the Sommerfeld coefficient γ  =  315 mJ/Pr-mol · K2 of Pr2 Rh3 Ge is very large with comparison to ordinary metals which indicate the existence of heavy fermion behaviour of itinerant charge carriers at low temperatures or enhanced density of the quasi-particle state at the Fermi level. The crucial role of the crystalline electric field effects on the ground state properties of Pr3+ (J  =  4) has been also observed. We think that the heavy fermion behaviour in Pr2 Rh3 Ge results from the dynamic low-lying crystal-field fluctuations, since there is no sign of Kondo effect in electrical resistivity and no enhancement of the slope S(T)/T in thermoelectric power data at low temperatures. It suggests that the conduction electrons at the Fermi level does not correlate with the 4f 2 states of Pr3+ atoms and hence there is no place for a typical spin Kondo effect, as it is commonly observed in Ce- and Yb-based heavy fermion systems.

  12. A new ternary magnetically ordered heavy fermion compound Pr2Rh3Ge: magnetic, electronic and thermodynamic properties.

    Science.gov (United States)

    Falkowski, M; Strydom, A M

    2017-10-04

    The results of the magnetic, electron transport, heat capacity and heat conduction measurements on the new rhombohedral ternary compound Pr2Rh3Ge have been investigated. The synthesized polycrystalline compound was found to crystallize in the ternary ordered variant of the cubic Laves phase [Formula: see text]-type of structure with the space group R[Formula: see text]m, as previously reported. Pr2Rh3Ge exhibits a ferromagnetic behaviour below [Formula: see text] K, which was found to be unstable in low applied magnetic fields, revealing characteristics usually attributed to the long-range order. In the entire paramagnetic region electrical resistivity shows monotonous metallic conductivity character. We estimated that the Sommerfeld coefficient γ  =  315 mJ/Pr-mol · [Formula: see text] of [Formula: see text] [Formula: see text]Ge is very large with comparison to ordinary metals which indicate the existence of heavy fermion behaviour of itinerant charge carriers at low temperatures or enhanced density of the quasi-particle state at the Fermi level. The crucial role of the crystalline electric field effects on the ground state properties of [Formula: see text] (J  =  4) has been also observed. We think that the heavy fermion behaviour in [Formula: see text] [Formula: see text]Ge results from the dynamic low-lying crystal-field fluctuations, since there is no sign of Kondo effect in electrical resistivity and no enhancement of the slope S(T)/T in thermoelectric power data at low temperatures. It suggests that the conduction electrons at the Fermi level does not correlate with the 4f (2) states of [Formula: see text] atoms and hence there is no place for a typical spin Kondo effect, as it is commonly observed in Ce- and Yb-based heavy fermion systems.

  13. Direct evidence for a magnetic f-electron-mediated pairing mechanism of heavy-fermion superconductivity in CeCoIn5.

    Science.gov (United States)

    Van Dyke, John S; Massee, Freek; Allan, Milan P; Davis, J C Séamus; Petrovic, Cedomir; Morr, Dirk K

    2014-08-12

    To identify the microscopic mechanism of heavy-fermion Cooper pairing is an unresolved challenge in quantum matter studies; it may also relate closely to finding the pairing mechanism of high-temperature superconductivity. Magnetically mediated Cooper pairing has long been the conjectured basis of heavy-fermion superconductivity but no direct verification of this hypothesis was achievable. Here, we use a novel approach based on precision measurements of the heavy-fermion band structure using quasiparticle interference imaging to reveal quantitatively the momentum space (k-space) structure of the f-electron magnetic interactions of CeCoIn5. Then, by solving the superconducting gap equations on the two heavy-fermion bands Ek(α,β) with these magnetic interactions as mediators of the Cooper pairing, we derive a series of quantitative predictions about the superconductive state. The agreement found between these diverse predictions and the measured characteristics of superconducting CeCoIn5 then provides direct evidence that the heavy-fermion Cooper pairing is indeed mediated by f-electron magnetism.

  14. Numerical simulation of heavy fermions in an SU(2){sub L}xSU(2){sub R} symmetric Yukawa model

    Energy Technology Data Exchange (ETDEWEB)

    Frick, C.; Trappenberg, T. [RWTH Aachen (Germany). Inst. fuer Theoretische Physik E; Lin, L.; Muenster, G.; Plagge, M. [Muenster Univ. (Germany). Inst. fuer Theoretische Physik 1; Montvay, I.; Wittig, H.

    1992-07-01

    An exploratory numerical study of the influence of heavy fermion doublets on the mass of the Higgs boson is performed in the decoupling limit of a chiral SU(2){sub L} x SU(2){sub R} symmetric Yukawa model with mirror fermions. The behaviour of fermion and boson masses is investigated at infinite bare quartic coupling on 4{sup 3} x 8, 6{sup 3} x 12 and 8{sup 3} x 16 lattices. A first estimate of the upper bound on the renormalized quartic coupling as a function of the renormalized Yukawa-coupling is given. (orig.).

  15. Numerical simulation of heavy fermions in an SU(2)_L x SU(2)_R symmetric Yukawa model

    CERN Document Server

    Frick, C; Montvay, István; Münster, G; Plagge, M; Trappenberg, T; Wittig, H

    1993-01-01

    An exploratory numerical study of the influence of heavy fermion doublets on the mass of the Higgs boson is performed in the decoupling limit of a chiral $\\rm SU(2)_L \\otimes SU(2)_R$ symmetric Yukawa model with mirror fermions. The behaviour of fermion and boson masses is investigated at infinite bare quartic coupling on $4^3 \\cdot 8$, $6^3 \\cdot 12$ and $8^3 \\cdot 16$ lattices. A first estimate of the upper bound on the renormalized quartic coupling as a function of the renormalized Yukawa-coupling is given.

  16. Phonon frequency shift and effect of correlation on the electron-phonon interaction in heavy fermion systems

    Indian Academy of Sciences (India)

    B Ojha; P Nayak; S N Behera

    2000-02-01

    The electron–phonon interaction in the periodic Anderson model (PAM) is considered. The PAM incorporates the effect of onsite Coulomb interaction () between -electrons. The influence of Coulomb correlation on the phonon response of the system is studied by evaluating the phonon spectral function for various parameters of the model. The numerical evaluation of the spectral function is carried out in the long wavelength limit at finite temperatures keeping only linear terms in . The observed behaviour is found to agree well with the general features obtained experimentally for some heavy fermion (HF) systems.

  17. Yb-based heavy fermion compounds and field tuned quantum chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Mun, Eundeok [Iowa State Univ., Ames, IA (United States)

    2010-01-01

    The motivation of this dissertation was to advance the study of Yb-based heavy fermion (HF) compounds especially ones related to quantum phase transitions. One of the topics of this work was the investigation of the interaction between the Kondo and crystalline electric field (CEF) energy scales in Yb-based HF systems by means of thermoelectric power (TEP) measurements. In these systems, the Kondo interaction and CEF excitations generally give rise to large anomalies such as maxima in ρ(T) and as minima in S(T). The TEP data were use to determine the evolution of Kondo and CEF energy scales upon varying transition metals for YbT2Zn20 (T = Fe, Ru, Os, Ir, Rh, and Co) compounds and applying magnetic fields for YbAgGe and YbPtBi. For YbT2Zn20 and YbPtBi, the Kondo and CEF energy scales could not be well separated in S(T), presumably because of small CEF level splittings. A similar effect was observed for the magnetic contribution to the resistivity. For YbAgGe, S(T) has been successfully applied to determine the Kondo and CEF energy scales due to the clear separation between the ground state and thermally excited CEF states. The Kondo temperature, TK, inferred from the local maximum in S(T), remains finite as magnetic field increases up to 140 kOe. In this dissertation we have examined the heavy quasi-particle behavior, found near the field tuned AFM quantum critical point (QCP), with YbAgGe and YbPtBi. Although the observed nFL behaviors in the vicinity of the QCP are different between YbAgGe and YbPtBi, the constructed H-T phase diagram including the two crossovers are similar. For both YbAgGe and YbPtBi, the details of the quantum criticality turn out to be complicated. We expect that YbPtBi will provide an additional example of field tuned quantum criticality, but clearly there are further experimental investigations left and more ideas needed to understand the basic physics of field-induced quantum

  18. Chiral heavy fermions in a two Higgs doublet model: 750 GeV resonance or not

    Science.gov (United States)

    Bar-Shalom, Shaouly; Soni, Amarjit

    2017-03-01

    We revisit models where a heavy chiral 4th generation doublet of fermions is embedded in a class of two Higgs doublets models (2HDM) with a discrete Z2 symmetry, which couples the ;heavy; scalar doublet only to the 4th generation fermions and the ;light; one to the Standard Model (SM) fermions - the so-called 4G2HDM introduced by us several years ago. We study the constraints imposed on the 4G2HDM from direct searches of heavy fermions, from precision electroweak data (PEWD) and from the measured production and decay signals of the 125 GeV scalar, which in the 4G2HDM corresponds to the lightest CP-even scalar h. We then show that the recently reported excess in the γγ spectrum around 750 GeV can be accommodated by the heavy CP-even scalar of the 4G2HDM, H, resulting in a unique choice of parameter space: negligible mixing (sin ⁡ α ≲ O (10-3)) between the two CP-even scalars h , H and heavy 4th generation quark and lepton masses mt‧ ,mb‧ ≲ 400 GeV and mν‧ ,mτ‧ ≳ 900 GeV, respectively. Whether or not the 750 GeV γγ resonance is confirmed, interesting phenomenology emerges in q‧ - Higgs systems (q‧ =t‧ ,b‧), that can be searched for at the LHC. For example, the heavy scalar states of the model, S = H , A ,H+, may have BR (S →qbar‧q‧) ∼ O (1), giving rise to observable qbar‧q‧ signals on resonance, followed by the flavor changing q‧ decays t‧ → uh (u = u , c) and/or b‧ → dh (d = d , s , b). This leads to rather distinct signatures, with or without charged leptons, of the form qbar‧q‧ →(nj + mb + ℓW) S (j and b being light and b-quark jets, respectively), with n + m + ℓ = 6- 8 and unique kinematic features. These high jet-multiplicity signals appear to be very challenging and may need new search strategies for detection of such heavy chiral quarks. It is also shown that the flavor structure of the 4G2HDM can easily accommodate the interesting recent indications of a percent-level branching ratio in the

  19. Magnetic Structure of the Heavy-fermion Compound CeAuSb2 in Zero-field

    Science.gov (United States)

    Marcus, Guy G.; Kim, Dae-Jeong; Lee, Hannoh; Fisk, Zachary; Rodriguez-Rivera, Jose A.; Broholm, Collin L.

    2015-03-01

    We have used neutron diffraction to determine the zero-field magnetic structure of the heavy-fermion compound CeAuSb2. Below TN ~ 6 . 2 K, we observe the development of antiferromagnetic Bragg diffraction consistent with previous transport and magnetization measurements. The intensities observed at 7 magnetic satellite locations indicate the staggered magnetization is predominantly along the c-axis. The maximum moment size is 1 . 15 +/- 0 . 08μB which is large compared with the 0 . 4μB moment in the iso-structural heavy fermion ferromagnet CeAgSb2. This suggests that the antiferromagnetic CeAuSb2 is deeper into a magnetic phase. The spin structure, due mainly to the Ce-4f sites, is described as a transverse polarized spin density wave with an incommensurate component of the wave vector in the basal plane. We will discuss these results and bulk measurements in terms of an ANNNI model and effective near neighbor exchange interactions. The work at IQM was supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Material Sciences and Engineering under Grant No. DE-FG02-08ER46544. GGM also acknowledges support from the NSF-GRFP Grant No. DGE-1232825.

  20. Unconventional superconductivity of the heavy fermion compound UNi{sub 2}Al{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Zakharov, Andrey

    2008-07-01

    The heavy fermion compound UNi{sub 2}Al{sub 3} exhibits the coexistence of superconductivity and magnetic order at low temperatures, stimulating speculations about possible exotic Cooper-pairing interaction in this superconductor. However, the preparation of good quality bulk single crystals of UNi{sub 2}Al{sub 3} has proven to be a non-trivial task due to metallurgical problems, which result in the formation of an UAl{sub 2} impurity phase and hence a strongly reduced sample purity. The present work concentrates on the preparation, characterization and electronic properties investigation of UNi{sub 2}Al{sub 3} single crystalline thin film samples. The preparation of thin films was accomplished in a molecular beam epitaxy (MBE) system. (100)-oriented epitaxial thin films of UNi{sub 2}Al{sub 3} were grown on single crystalline YAlO{sub 3} substrates cut in (010)- or (112)-direction. The high crystallographic quality of the samples was proved by several characterisation methods, such as X-ray analysis, RHEED and TEM. To study the magnetic structure of epitaxial thin films resonant magnetic X-ray scattering was employed. The magnetic order of thin the film samples, the formation of magnetic domains with different moment directions, and the magnetic correlation length were discussed. The electronic properties of the UNi{sub 2}Al{sub 3} thin films in the normal and superconducting states were investigated by means of transport measurements. A pronounced anisotropy of the temperature dependent resistivity {rho}(T) was observed. Moreover, it was found that the temperature of the resistive superconducting transition depends on the current direction, providing evidence for multiband superconductivity in UNi{sub 2}Al{sub 3}. The initial slope of the upper critical field H'{sub c2}(T) of the thin film samples suggests an unconventional spin-singlet superconducting state, as opposed to bulk single crystal data. To probe the superconducting gap of UNi{sub 2}Al{sub 3

  1. Numerical simulations of heavy fermion systems. From He-3 bilayers to topological Kondo insulators

    Energy Technology Data Exchange (ETDEWEB)

    Werner, Jan

    2015-03-27

    In this thesis the results of model calculations based on an extended Periodic Anderson Model are presented. The three particle ring exchange, which is the dominant magnetic exchange process in layered He-3, is included in the model. In addition, the model incorporates the constraint of no double occupancy by taking the limit of large local Coulomb repulsion. By means of Cellular DMFT, the model is investigated for a range of values of the chemical potential μ and inverse temperature β=1/T. The method is a cluster extension to the Dynamical Mean-Field Theory (DMFT), and allows to systematically include non-local correlations beyond the DMFT. The auxiliary cluster model is solved by a hybridization expansion CTQMC cluster solver, which provides unbiased, numerically exact results for the Green's function and other observables of interest. As a first step, the onset of Fermi liquid coherence is studied. At low enough temperature, the self-energy is found to exhibit a linear dependence on Matsubara frequency. Meanwhile, the spin susceptibility crossed over from a Curie-Weiss law to a Pauli law. The heavy fermion state appears at a characteristic coherence scale T{sub coh}. While the density is rather high for small filling, for larger filling T{sub coh} is increasingly suppressed. This involves a decreasing quasiparticle residue Z∝T{sub coh} and an enhanced mass renormalization m{sup *}/m∝T{sub coh}{sup -1}. Extrapolation leads to a critical filling, where the coherence scale is expected to vanish at a quantum critical point. At the same time, the effective mass diverges. This corresponds to a breakdown of the Kondo effect, which is responsible for the formation of quasiparticles, due to a vanishing of the effective hybridization between the layers. Cellular DMFT simulations are conducted for small clusters of size N{sub c}=2 and 3. Furthermore a simple two-band model for two-dimensional topological Kondo insulators is devised, which is based on a single

  2. Numerical simulation of heavy fermions in an SU(2)[sub L]xSU(2)[sub R] symmetric Yukawa model

    Energy Technology Data Exchange (ETDEWEB)

    Frick, C. (Technische Hochschule Aachen (Germany). Inst. fuer Theoretische Physik E HLRZ, Juelich (Germany)); Lin, L. (HLRZ, Juelich (Germany)); Montvay, I. (Muenster Univ. (Germany). Inst. fuer Theoretische Physik); Muenster, G. (HLRZ, Juelich (Germany)); Plagge, M. (HLRZ, Juelich (Germany)); Trappenberg, T. (Technische Hochschule Aachen (Germany). Inst. fuer Theoretische Physik E HLRZ, Juelich (Germany)); Wittig, H. (Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany))

    1993-05-24

    An exploratory numerical study of the influence of heavy fermion doublets on the mass of the Higgs boson is performed in the decoupling limit of a chiral SU(2)[sub L]xSU(2)[sub R] symmetric Yukawa model with mirror fermions. The behaviour of fermion and boson masses is investigated at infinite bare quartic coupling on 4[sup 3]x8, 6[sup 3]x12 and 8[sup 3]x16 lattices. A first estimate of the upper bound on the renormalized quartic coupling as a function of the renormalized Yukawa coupling is given. On the algorithmic side, several standard fermion matrix inversion methods were tried and tuned for better performance. (orig.)

  3. Ultrasonic study of the Yb-based heavy fermion compound YbRh{sub 2}Zn{sub 20}

    Energy Technology Data Exchange (ETDEWEB)

    Nakanishi, Y; Ito, K; Nakamura, M; Yoshizawa, M [Graduate School of Engineering, Iwate University, Morioka 020-8551 (Japan); Saiga, Y; Kosaka, M [Department of Physics, Saitama University, Saitama 338-8570 (Japan); Uwatoko, Y, E-mail: yoshiki@iwate-u.ac.j [Institute for Solid State Physics, University of Tokyo, Kashiwa 227-8581 (Japan)

    2009-03-01

    We report ultrasonic measurements on the high quality single crystal of the Yb-based heavy fermion compound YbRh{sub 2}Zn{sub 20} over a temperature range from 200 K to 0.5 K. A shallow, but clear minimum was observed in the temperature dependent elastic constants C{sub 11}, (C{sub 11} - C{sub 12})/2 and C{sub 44} around 15 K, probably attributed to the ground state and low-lying excited states of Yb{sup 3} in the cubic CEF. We discuss the low-temperature elastic properties and possible energy level scheme of localized 4f state of Yb{sup 3} ions in YbRh{sub 2}Zn{sub 20}. CEF ground state developed at the low temperatures and physical parameters relating to a quadrupolar moment in YbRh{sub 2}Zn{sub 20}

  4. The novel heavy-fermion system Nd{sub 2-x}Ce{sub x}CuO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Pyka, N. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France); Loewenhaupt, M. [Technische Univ., Dresden (Germany); Metz, A. [Forschungszentrum Juelich GmbH (Germany)

    1997-04-01

    Inelastic neutron scattering experiments are reported in the heavy fermion state of Nd{sub 2-x}Ce{sub x}CuO{sub 4}. A complex magnetic response has been observed in zero field that can be divided into contributions from correlated Nd spins (inelastic, q-dependent; reminiscent of the spin waves in Nd{sub 2}CuO{sub 4}) and from independent, slowly relaxing Nd spins (quasi-elastic, q-independent). An applied magnetic field of H > 3 Tesla gives rise to different correlations in Q - {omega} space than in zero field. Field dependent specific heat and {mu}SR experiments can be better understood in the light of these INS results. The experiments were performed on a single crystal at T {<=} 0.1 K with applied magnetic fields of H = 0 - 6 Tesla at the IN14 spectrometer. (author). 6 refs.

  5. Microscopic properties of the heavy-fermion superconductor PuCoIn5 explored by nuclear quadrupole resonance

    Science.gov (United States)

    Koutroulakis, G.; Yasuoka, H.; Chudo, H.; Tobash, P. H.; Mitchell, J. N.; Bauer, E. D.; Thompson, J. D.

    2014-05-01

    We report 115In nuclear quadrupolar resonance (NQR) measurements on the heavy-fermion superconductor PuCoIn5, in the temperature range 0.29K ≤ T ≤ 75K. The NQR parameters for the two crystallographically inequivalent In sites are determined, and their temperature dependence is investigated. A linear shift of the quadrupolar frequency with lowering temperature below the critical value Tc is revealed, in agreement with the prediction for composite pairing. The nuclear spin-lattice relaxation rate T1-1(T) clearly signals a superconducting (SC) phase transition at Tc ≃ 2.3 K, with strong spin fluctuations, mostly in-plane, dominating the relaxation process in the normal state near to Tc. Analysis of the T1-1 data in the SC state suggests that PuCoIn5 is a strong-coupling d-wave superconductor.

  6. Multiple superconducting phases in heavy fermion compounds PrOs4Sb12 and CeCoIn5

    Indian Academy of Sciences (India)

    Yuji Matsuda

    2006-01-01

    In recently discovered heavy fermion compounds, quasi-two-dimensional CeCoIn5 and skutterudite PrOs4Sb12, multiple superconducting phases with different symmetries manifest themselves below c. The angle-resolved magnetothermal transport measurements revealed that in PrOs4Sb12 a novel change in the symmetry of the superconducting gap function occurs deep inside the superconducting state. The ultrasound velocity measurements revealed that in CeCoIn5 the Fulde-Ferrel-Larkin-Ovchinikov (FFLO) phase, in which the order parameter is spatially modulated and has planar nodes aligned perpendicular to the vortices, appears at low temperature and high field. These results open up a new realm for the study of the superconductivity with multiple phases.

  7. Heavy fermion Ce{sub 3}Co{sub 4}Sn{sub 13} compound under pressure

    Energy Technology Data Exchange (ETDEWEB)

    Collave, J. R.; Borges, H. A. [Departamento de Física, Pontifícia Universidade Católica do Rio de Janeiro, 22453-900, Rio de Janeiro, RJ (Brazil); Ramos, S. M.; Hering, E. N. [Centro Brasileiro de Pesquisas Físicas, Rua Dr. Xavier Sigaud 150, 22290-180, Rio de Janeiro, RJ (Brazil); SPSMS, UMR-E CEA/UJF-Grenoble 1, INAC, 38054, Grenoble (France); Fontes, M. B.; Baggio-Saitovitch, E.; Bittar, E. M., E-mail: bittar@cbpf.br [Centro Brasileiro de Pesquisas Físicas, Rua Dr. Xavier Sigaud 150, 22290-180, Rio de Janeiro, RJ (Brazil); Mendonça-Ferreira, L. [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, 09210-170, Santo André, SP (Brazil); Pagliuso, P. G. [Instituto de Física “Gleb Wataghin,” UNICAMP, Campinas, SP 13083-859 (Brazil)

    2015-05-07

    The non-magnetic heavy fermion compound Ce{sub 3}Co{sub 4}Sn{sub 13} was studied under pressure. We report single crystalline measurements of electrical resistivity as a function of temperature ρ(T) under pressure. Some characteristic features related to a structural transition (T{sub S}), crystalline field effects (T{sub CEF}), and a low temperature maximum (T{sub max}), possibly connected simultaneously to the onset of Kondo lattice coherence and short range magnetic correlations, were identified in the ρ(T) data. A pressure-temperature phase diagram with T{sub S} and T{sub max} was constructed by mapping these features. Like for most Ce-based heavy fermion compounds, T{sub max} moves to higher temperatures with pressure, indicating that it is related to the Kondo energy scale, due to the increase of hybridization induced by pressure. On the other hand, T{sub S}, associated to a superlattice distortion and probably combined with a charge density wave transition, decreases as a function of pressure. However, differently from the Sr{sub 3−x}Ca{sub x}Ir{sub 4}Sn{sub 13} system, where a superlattice quantum phase transition is observed [L. E. Klintberg et al., Phys. Rev. Lett. 109, 237 008 (2012)], in Ce{sub 3}Co{sub 4}Sn{sub 13} T{sub S} ∼ 154 K, at ambient pressure (P = 0), seems to stabilize at around 143 K for P ≥ 19 kilobars. We also investigated ρ(T) in external magnetic fields, at P = 0. Negative magnetoresistance and increase of T{sub max} are observed, suggesting suppression of low temperature short range magnetic correlations.

  8. Tuning the electronic hybridization in the heavy fermion cage compound YbFe2Zn20 with Cd doping

    Science.gov (United States)

    Cabrera-Baez, M.; Ribeiro, R. A.; Avila, M. A.

    2016-09-01

    The tuning of the electronic properties of heavy fermion compounds by chemical substitution provides excellent opportunities for further understanding the physics of hybridized ions in crystal lattices. Here we present an investigation on the effects of Cd doping in flux-grown single crystals of the complex intermetallic cage compound YbFe2Zn20, which has been described as a heavy fermion with a Sommerfeld coefficient of 535 mJ mol-1 · K-2. The substitution of Cd for Zn disturbs the system by expanding the unit cell and, in this case, the size of the Zn cages that surround the Yb and Fe. With an increasing amount of Cd, the hybridization between the Yb 4f electrons and the conduction electrons is weakened, as shown by a decrease in the Sommerfeld coefficient, which should be accompanied by a valence shift of the Yb3+ due to the negative chemical pressure effect. This scenario is also supported by the low temperature DC magnetic susceptibility, which is gradually suppressed and shows an increment of the Kondo temperature, based on a shift to higher temperatures of the characteristic broad susceptibility peak. Furthermore, the DC resistivity decreases with the isoelectronic substitution of Cd for Zn, contrary to expectations in an increasingly disordered system, and implying that the valence shift is not related to charge carrier doping. The combined results demonstrate the excellent complementarity between positive physical pressure and negative chemical pressure, and point to a rich playground for exploring the physics and chemistry of strongly correlated electron systems in the general family of Zn20 compounds, despite their structural complexity.

  9. Protein: FEA4 [TP Atlas

    Lifescience Database Archive (English)

    Full Text Available FEA4 Proteins in gibberellin signaling GID2 F-box protein GID2 Gibberellin-insensitive dwarf protein 2, Prot...ein GIBBERELLIN INSENSITIVE DWARF2 39947 Oryza sativa subsp. japonica Q7XAK4 ...

  10. LiV2O4: A heavy fermion transition metal oxide

    Energy Technology Data Exchange (ETDEWEB)

    Kondo, Shinichiro [Iowa State Univ., Ames, IA (United States)

    1999-02-12

    The format of this dissertation is as follows. In the remainder of Chapter 1, brief introductions and reviews are given to the topics of frustration, heavy fermions and spinels including the precedent work of LiV2O4. In Chapter 2, as a general overview of this work the important publication in Physical Review Letters by the author of this dissertation and collaborators regarding the discovery of the heavy fermion behavior in LiV2O4 is introduced [removed for separate processing]. The preparation methods employed by the author for nine LiV2O4 and two Li1+xTi2-xO4 (x = 0 and 1/3) polycrystalline samples are introduced in Chapter 3. The subsequent structural characterization of the LiV2O4 and Li1+xT2-xO4 samples was done by the author using thermogravimetric analysis (TGA), x-ray diffraction measurements and their structural refinements by the Rietveld analysis. The results of the characterization are detailed in Chapter 3. In Chapter 4 magnetization measurements carried out by the author are detailed. In Chapter 5, after briefly discussing the resistivity measurement results including the single-crystal work by Rogers et al., for the purpose of clear characterization of LiV2O4 it is of great importance to introduce in the following chapters the experiments and subsequent data analyses done by his collaborators. Heat capacity measurements (Chapter 6) were carried out and analyzed by Dr. C.A. Swenson, and modeled theoretically by Dr. D.C. Johnston. In Chapter 7 a thermal expansion study using neutron diffraction by Dr. O. Chmaissem et al. and capacitance dilatometry measurements by Dr. C.A. Swenson are introduced. The data analyses for the thermal expansion study were mainly done by Dr. O. Chmaissem (for neutron diffraction) and Dr. C.A. Swendon (for dilatometry), with assistances by Dr. J

  11. The f-spin physics of rare-earth iron pnictides: influence of d-electron antiferromagnetic order on heavy fermion phase diagram

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Jian-xin [Los Alamos National Laboratory; Dai, Jianhui [ZHEJIANG UNIV; Si, Qimiao [RICE UNIV

    2009-01-01

    Some of the high {Tc} iron pnictides contain rare-earth elements, raising the question of how the existence and tunability of a d-electron antiferromagnetic order influences the heavy fermion behavior of the f-moments. With CeOFeP and CeOFeAs in mind as prototypes, we derive an extended Anderson lattice model appropriate for these quaternary systems. We show that the Kondo screening of the f-moments are efficiently suppressed by the d-electron ordering. We also argue that, inside the d-electron ordered state (as in CeOFeAs), the f-moments provide a rare realization of a quantum frustrated magnet with competing J{sub 1}-J{sub 2}-J{sub 3} interactions in an effective square lattice. Implications ofr the heavy fermion physics in broader contexts are also discussed.

  12. Main: FEA6 [TP Atlas

    Lifescience Database Archive (English)

    Full Text Available FEA6 Study on chemical biology of the deacetylase SIRT3 involved in the regulation of an energy...chondrial matrix regulates the activities of several enzymes involved in energy m...trix and found that SIRT3 regulates the activities of several enzymes involved in energy metabolism, suggest...reveal its physiology, especially biological functions of SIRT3 in the regulation of energy metabolism. FEA6.csml ... ...T3 in the regulation of energy metabolism is in progress using mouse models Acetylation and deacetylation of

  13. Geometrically frustrated magnetic structures of the heavy-fermion compound CePdAl studied by powder neutron diffraction

    Science.gov (United States)

    Dönni, A.; Ehlers, G.; Maletta, H.; Fischer, P.; Kitazawa, H.; Zolliker, M.

    1996-12-01

    The heavy-fermion compound CePdAl with ZrNiAl-type crystal structure (hexagonal space group 0953-8984/8/50/043/img8) 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 0953-8984/8/50/043/img9 with an incommensurate antiferromagnetic propagation vector 0953-8984/8/50/043/img10, 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.

  14. Electronic structure of the heavy fermion superconductor Ce{sub 2}PdIn{sub 8}: Experiment and calculations

    Energy Technology Data Exchange (ETDEWEB)

    Werwiński, M. [Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznań (Poland); Szajek, A. [Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznań (Poland); Centre for Advanced Materials and Smart Structures, Polish Academy of Sciences, Okólna 2, 50-950 Wrocław (Poland); Ślebarski, A. [Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland); Centre for Advanced Materials and Smart Structures, Polish Academy of Sciences, Okólna 2, 50-950 Wrocław (Poland); Kaczorowski, D., E-mail: D.Kaczorowski@int.pan.wroc.pl [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P. O. Box 1410, 50-950 Wrocław (Poland); Centre for Advanced Materials and Smart Structures, Polish Academy of Sciences, Okólna 2, 50-950 Wrocław (Poland)

    2015-10-25

    The electronic structure of a heavy-fermion superconductor Ce{sub 2}PdIn{sub 8} was investigated by means of X-ray photoelectron spectroscopy (XPS) and ab initio density functional band structure calculations. The Ce 3d core-level XPS spectra point to stable trivalent configuration of Ce atoms that is also reproduced in the band structure calculations within the generalized gradient approximation GGA+U approach. Analysis of the 3d{sup 9}f{sup 2} weight in the 3d XPS spectra within the Gunnarsson-Schönhammer model suggests that the onsite hybridization energy between Ce 4f and the conduction band states, Δ{sub fs}, is ∼120 meV, which is about 30 meV larger than Δ{sub fs} in isostructural Ce{sub 2}TIn{sub 8} compounds with T = Co, Rh, and Ir. Taking into account a Coulomb repulsion U on both the Ce 4f and Pd 4d states in electronic band structure calculations, a satisfactory agreement was found between the calculated density of states (DOS) and the measured valence band XPS spectra. - Highlights: • XPS data validated strong electronic correlations in superconducting Ce{sub 2}PdIn{sub 8}. • DFT calculations reproduced XPS spectra measured for Ce{sub 2}PdIn{sub 8}. • Crucial role of Pd d electrons in the HF behavior of Ce{sub 2}PdIn{sub 8} was established.

  15. Ferromagnetic quantum criticality in the new heavy-fermion system YbNi{sub 4}P{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Brando, Manuel; Steppke, Alexander; Lausberg, Stefan; Kuechler, Robert; Lengyel, Edit; Steinke, Lucia; Krellner, Cornelius; Borth, Robert; Nicklas, Michael; Geibel, Christoph; Steglich, Frank [Max-Planck-Institut fuer Chemische Physik Fester Stoffe Noethnitzer Str. 40, 01187 Dresden (Germany)

    2012-07-01

    We present measurements of the ac-susceptibility, specific heat (C) and thermal expansion ({alpha}) on single crystals of the new quasi-one-dimensional heavy-fermion system YbNi{sub 4}P{sub 2}. YbNi{sub 4}P{sub 2} is a Kondo-lattice system that orders ferromagnetically at a very low temperature T{sub c}=0.17 K. Ferromagnetism can be suppressed by arsenic substitution x on phosphorus site and a ferromagnetic (FM) quantum critical point (QCP) is approached at x=0.08. We provide evidence that such a FM-QCP exists in YbNi{sub 4}(P{sub 0.92}As{sub 0.08}){sub 2} by showing that (i) the magnetic transition remains ferromagnetic between x=0 and x=0.08, (ii) no phase transition nor Fermi-liquid ground state down to 0.02 K can be observed at x=0.08, and finally (iii) the Grueneisen ratio {Gamma}={alpha}/C strongly diverges with decreasing temperature as {Gamma}{proportional_to}T{sup -0.3}.

  16. Multipolar phases and magnetically hidden order: review of the heavy-fermion compound Ce1-x La x B6

    Science.gov (United States)

    Cameron, Alistair S.; Friemel, Gerd; Inosov, Dmytro S.

    2016-06-01

    Cerium hexaboride is a cubic f-electron heavy-fermion compound that displays a rich array of low-temperature magnetic ordering phenomena which have been the subject of investigation for more than 50 years. Its complex behaviour is the result of competing interactions, with both itinerant and local electrons playing important roles. Investigating this material has proven to be a substantial challenge, in particular because of the appearance of a ‘magnetically hidden order’ phase, which remained elusive to neutron-scattering investigations for many years. It was not until the development of modern x-ray scattering techniques that the long suspected multipolar origin of this phase was confirmed. Doping with non-magnetic lanthanum dilutes the magnetic cerium sublattice and reduces the f-electron count, bringing about substantial changes to the ground state with the emergence of new phases and quantum critical phenomena. To this day, Ce1-x La x B6 and its related compounds remain a subject of intense interest. Despite the substantial progress in understanding their behaviour, they continue to reveal new and unexplained physical phenomena. Here we present a review of the accumulated body of knowledge on this family of materials in order to provide a firm standpoint for future investigations.

  17. Heavy-Fermion Compound of the Ternary Phosphide Ce2Pt8P with a Non-Centrosymmetric Structure

    Science.gov (United States)

    Kase, Naoki; Furukawa, Shoh; Nakano, Tomohito; Takeda, Naoya

    2017-01-01

    The low-temperature properties of Ce2Pt8P are studied by magnetic susceptibility χ(T), electrical resistivity ρ(T), and specific heat C(T) measurements. The crystal structure is considered to be analogs of the CePt3Si-type structure. From the magnetic susceptibility χ(T), the effective paramagnetic moment μeff is estimated to be 2.30 μB/Ce, suggesting that the valence state of Ce ions is expected to be close to trivalent (Ce3+). The paramagnetic Curie-Weiss temperature θcw is determined to be 12 K. The electrical resistivity ρ(T) shows -ln T dependence with a small slope from 10 to 3 K, which indicates a weak Kondo anomaly. The specific heat exhibits a λ-type anomaly at around T* = 1.0 K, while the magnetic entropy at T* is reduced to 80% of R ln 2. The linear coefficient of specific heat is determined to be 145 mJ/(mol-Ce·K2). From several measurements, Ce2Pt8P can be classified as a moderate heavy-fermion compound. The ground state is far from the quantum-critical point (QCP) compared with CePt3Si. La2Pt8P shows normal metallic behavior and no superconductivity is observed above 0.28 K.

  18. Protein: FEA3 [TP Atlas

    Lifescience Database Archive (English)

    Full Text Available FEA3 AREB pathway: Signaling proteins ABI5 BZIP39, DPBF1, GIA1, NEM1 Protein ABSCIS...IC ACID-INSENSITIVE 5 Dc3 promoter-binding factor 1, Protein GROWTH-INSENSITIVITY TO ABA 1, bZIP transcription factor 39 3702 Arabidopsis thaliana 818199 Q9SJN0 ...

  19. Protein: FEA4 [TP Atlas

    Lifescience Database Archive (English)

    Full Text Available FEA4 Proteins in gibberellin signaling 20ox2 C20ox2, GA20, Sd-1 Gibberellin 20 oxid...ase 2 GA 20-oxidase 2, Gibberellin C-20 oxidase 2, Os20ox2, Protein semidwarf-1 39947 Oryza sativa subsp. japonica 4325003 Q0JH50 21646530 ...

  20. Protein: FEA3 [TP Atlas

    Lifescience Database Archive (English)

    Full Text Available FEA3 AREB pathway: Signaling proteins SRK2E OST1, SNRK2.6 Serine/threonine-protein kinase SRK2E Prot...ein OPEN STOMATA 1, SNF1-related kinase 2.6, Serine/threonine-protein kinase OST1 3702 Arabidopsis thaliana 829541 Q940H6 3UC4, 3ZUT, 3ZUU, 3UDB 19805022 ...

  1. Protein: FEA3 [TP Atlas

    Lifescience Database Archive (English)

    Full Text Available FEA3 AREB pathway: Signaling proteins AZF1 OZAKGYO, ZF1 At5g67450, Cys2/His2-type zinc finger prot...ein 1, Zinc finger protein OZAKGYO, Zinc-finger protein 1 3702 Arabidopsis thaliana 836881 Q9SSW1 21852415 ...

  2. Pairing symmetries of several iron-based superconductor families and some similarities with cuprates and heavy-fermions

    Directory of Open Access Journals (Sweden)

    Das Tanmoy

    2012-03-01

    Full Text Available We show that, by using the unit-cell transformation between 1 Fe per unit cell to 2 Fe per unit cell, one can qualitatively understand the pairing symmetry of several families of iron-based superconductors. In iron-pnictides and iron-chalcogenides, the nodeless s±-pairing and the resulting magnetic resonance mode transform nicely between the two unit cells, while retaining all physical properties unchanged. However, when the electron-pocket disappears from the Fermi surface with complete doping in KFe2As2, we find that the unit-cell invariant requirement prohibits the occurrence of s±-pairing symmetry (caused by inter-hole-pocket nesting. However, the intra-pocket nesting is compatible here, which leads to a nodal d-wave pairing. The corresponding Fermi surface topology and the pairing symmetry are similar to Ce-based heavy-fermion superconductors. Furthermore, when the Fermi surface hosts only electron-pockets in KyFe2-xSe2, the inter-electron-pocket nesting induces a nodeless and isotropic d-wave pairing. This situation is analogous to the electron-doped cuprates, where the strong antiferromagnetic order creates similar disconnected electron-pocket Fermi surface, and hence nodeless d-wave pairing appears. The unit-cell transformation in KyFe2-xSe2 exhibits that the d-wave pairing breaks the translational symmetry of the 2 Fe unit cell, and thus cannot be realized unless a vacancy ordering forms to compensate for it. These results are consistent with the coexistence picture of a competing order and nodeless d-wave superconductivity in both cuprates and KyFe1.6Se2.

  3. Protein: FEA6 [TP Atlas

    Lifescience Database Archive (English)

    Full Text Available FEA6 Histone Deacetylases BRD2 KIAA9001, RING3 BRD2 Bromodomain-containing protein 2 O27.1.1, Really interes...ting new gene 3 protein 9606 Homo sapiens P25440 6046 3ONI, 2YDW, 2YEK, 2G4A 2DVQ, 2DVV, 2DVS, 1X0J, 2E3K, 2DVR 3AQA 6046 21513886 ...

  4. Single crystal growth of the heavy fermion compounds YbRh{sub 2}Si{sub 2} and YbNi{sub 4}P{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Butzke, Constantin; Kliemt, Kristin; Krellner, Cornelius [Physikalisches Institut, Goethe Universitaet Frankfurt, 60438 Frankfurt am Main (Germany)

    2015-07-01

    Heavy fermion systems are model systems to unravel the exciting physics around quantum-phase transitions. Studying these emergent phenomena necessitates the preparation of large and high-quality single crystals. We report on the optimization of the single crystal growth for two Yb-based quantum critical materials, YbRh{sub 2}Si{sub 2} and YbNi{sub 4}P{sub 2}. The prototype heavy-fermion system YbRh{sub 2}Si{sub 2} is situated extremely close to an unconventional antiferromagnetic (AF) quantum critical point (QCP). The AF ordering (T{sub N} = 70 mK) can be further lowered by chemically induced negative pressure using Ir-substitution. The QCP is reached for an Ir-substitution of x ∼ 0.1 in Yb(Rh{sub 1-x}Ir{sub x}){sub 2}Si{sub 2}. Here, we report on the optimization of the crystal growth of the substitution series as well as of the unsubstituted compound. We also report on our attempts to determine the melting point of YbRh{sub 2}Si{sub 2} and present a phase analysis of the molten compound. In the heavy fermion metal, YbNi{sub 4}P{sub 2}, a ferromagnetic (FM) transition at T{sub C} = 0.17 K was observed recently and a FM QCP is reached at x ∼ 0.1 in YbNi{sub 4}(P{sub 1-x}As{sub x}){sub 2}. We report on the crystal growth of YbNi{sub 4}P{sub 2} by Czochralski method out of a Ni-P flux from a levitated melt. The obtained crystals were characterized by Laue X-ray scattering, X-ray powder diffraction, EDX microprobe analysis and resistivity measurements.

  5. Local Spin Density Approximation Solution for Spinel LiV2O4: Spin Fluctuation as a Possible Role for Heavy Fermion

    Institute of Scientific and Technical Information of China (English)

    谭明秋; 陶向明

    2001-01-01

    We report on a self-consistent full-potential linear muffin tin orbital band-structure calculation for the heavy fermion (HF) compound LiV2O4. It is found that a stable local spin density approximation solution for LiV2O4 is lower in total energy than the local density approximation calculation. We speculate that the mechanism responsible for HF properties in LiV2O4 might be of spin fluctuation type and is different from the Kondo mechanism in conventional 4f and 5f HF compounds.

  6. De Haas{endash}van Alphen effect, magnetic transitions, and specific heat in the heavy-fermion system UCd{sub 11}

    Energy Technology Data Exchange (ETDEWEB)

    Cornelius, A.L.; Arko, A.J.; Sarrao, J.L.; Harrison, N. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    1999-06-01

    We have used high pulsed magnetic fields to 50 T to observe de Haas{endash}van Alphen oscillations in the heavy fermion antiferromagnet UCd{sub 11}, which has a stongly enhanced value of the electronic specific-heat coefficient ({gamma}=803 mJ/molthinspK{sup 2}). The low-temperature magnetization shows the existence of two magnetic phase transitions. The presence of quantum oscillations above the first transition indicates that UCd{sub 11} has a coherent Fermi liquid, although there is little or no change in the Fermi-surface topology on passing through the second transition. {copyright} {ital 1999} {ital The American Physical Society}

  7. Connection between charge fluctuations and the coherent temperature in the heavy-fermion system SmOs4Sb12: a {121, 123}Sb NQR study.

    Science.gov (United States)

    Kotegawa, H; Hidaka, H; Kobayashi, T C; Kikuchi, D; Sugawara, H; Sato, H

    2007-10-12

    We report {121, 123}Sb nuclear quadrupole resonance measurements under pressure in a novel heavy fermion (HF) system SmOs4Sb12. The nuclear spin-spin relaxation rate 1/T{2} exhibits a distinct peak near the coherent temperature of the Kondo effect. The isotope effect of 121Sb and 123Sb indicates that the peak in 1/T{2} is electrical in origin. The connection between the peak in 1/T{2} and the development of coherency of the Kondo effect is robust even under pressure. It is conjectured that charge fluctuation plays an important role in forming the HF state in SmOs4Sb12.

  8. Controlled creation of structural defects in the heavy fermion superconductor UPt{sub 3} and its influence on the superconducting properties

    Energy Technology Data Exchange (ETDEWEB)

    Suderow, H. [CEA, Grenoble (France). Dept. de Recherche Fondamentale sur la Mateiere Condensee]|[CNRS, Grenoble (France). Centre des Recherches sur les Tres Basses Temperatures]|[Univ. Autonoma de Madrid (Spain). Lab. de Bajas Temperaturas; Kambe, S.; Huxley, A.; Flouquet, J. [CEA, Grenoble (France). Dept. de Recherche Fondamentale sur la Mateiere Condensee; Brison, J.P. [CNRS, Grenoble (France). Centre des Recherches sur les Tres Basses Temperatures; Rullier-Albenque, F. [Ecole Polytechnique, Palaiseau (France). Lab. des Solides Irradies

    1999-09-01

    The superconducting properties of the heavy fermion UPt{sub 3} have been changed by irradiation with high energy electrons which creates point defects in a reproducible and controlled way. Measurements of the residual resistivity, critical temperature, upper critical field and thermal conductivity have been realized on these irradiated samples. The strong suppression of superconductivity with increasing defect concentration is in agreement with the theory of unconventional superconductivity. However, the thermal conductivity data contradicts the simple predictions derived from the most popular models (E{sub 1g} and E{sub 2u}) of the superconducting order parameter in UPt{sub 3}.

  9. Angular position of nodes in the superconducting gap of quasi-2D heavy-fermion superconductor CeCoIn5.

    Science.gov (United States)

    Izawa, K; Yamaguchi, H; Matsuda, Y; Shishido, H; Settai, R; Onuki, Y

    2001-07-30

    The thermal conductivity of the heavy-fermion superconductor CeCoIn5 has been studied in a magnetic field rotating within the 2D planes. A clear fourfold symmetry of the thermal conductivity which is characteristic of a superconducting gap with nodes along the ( +/- pi,+/- pi) directions is resolved. The thermal conductivity measurement also reveals a first-order transition at H(c2), indicating a Pauli limited superconducting state. These results indicate that the symmetry most likely belongs to d(x(2)-y(2)), implying that the anisotropic antiferromagnetic fluctuation is relevant to the superconductivity.

  10. Magnetic and superconducting properties of a heavy-fermion CeCoIn5 epitaxial film probed by nuclear quadrupole resonance

    Science.gov (United States)

    Yamanaka, Takayoshi; Shimozawa, Masaaki; Shishido, Hiroaki; Kitagawa, Shunsaku; Ikeda, Hiroaki; Shibauchi, Takasada; Terashima, Takahito; Matsuda, Yuji; Ishida, Kenji

    2017-08-01

    Since the progress in the fabrication techniques of thin films of exotic materials such as strongly correlated heavy-fermion compounds, microscopic studies of the magnetic and electronic properties inside the films have been needed. Herein, we report the observation of 115In nuclear quadrupole resonance (NQR) in an epitaxial film of the heavy-fermion superconductor CeCoIn5, for which the microscopic field gradient within the unit cell as well as magnetic and superconducting properties at zero field are evaluated. We find that the nuclear spin-lattice relaxation rate in the film is in excellent agreement with that of bulk crystals, whereas the NQR spectra show noticeable shifts and significant broadening indicating a change in the electric-field distribution inside the film. The analysis implies a displacement of In layers in the film, which, however, does not affect the magnetic fluctuations and superconducting pairing. This implies that inhomogeneity of the electronic field gradient in the film sample causes no pair-breaking effect.

  11. Pressure-induced magnetic transition exceeding 30 K in the Yb-based heavy-fermion β -YbAlB4

    Science.gov (United States)

    Tomita, Takahiro; Kuga, Kentaro; Uwatoko, Yoshiya; Nakatsuji, Satoru

    2016-12-01

    Measurements of the electric resistivity ρ (T ) under pressure up to 8 GPa were performed on high-quality single crystals of the Yb-based heavy-fermion system β -YbAlB4 in the temperature range 2 resistivity data, we observed pressure-induced magnetic ordering above the critical pressure Pc˜2 GPa. The clear difference in the phase diagram under pressure using two types of pressure media indicates that the transition temperature may be further enhanced under application of uniaxial pressure. With pressure, this phase-transition temperature TM is enhanced, reaching 32 K at 8 GPa, which is the highest transition temperature so far recorded for the Yb-based heavy-fermion compounds. The power-law exponent α in ρ =ρ0+A Tα below TM gradually changes from 3/2 to 5/2 with increasing pressure from 2 to 8 GPa. In contrast, the resistivity exhibits a T -linear behavior in the temperature range 2 ≤T ≤20 K and is insensitive to pressure below Pc. In this pressure regime, the magnetization is also nearly independent of pressure and shows no anomaly above 2 K. Our results indicate that a quantum critical point for β -YbAlB4 is also located near Pc in addition to the strange metal region near the ambient pressure.

  12. Robust upward dispersion of the neutron spin resonance in the heavy fermion superconductor Ce1-xYbxCoIn5

    Science.gov (United States)

    Song, Yu; van Dyke, John; Lum, I. K.; White, B. D.; Jang, Sooyoung; Yazici, Duygu; Shu, L.; Schneidewind, A.; Čermák, Petr; Qiu, Y.; Maple, M. B.; Morr, Dirk K.; Dai, Pengcheng

    2016-09-01

    The neutron spin resonance is a collective magnetic excitation that appears in the unconventional copper oxide, iron pnictide and heavy fermion superconductors. Although the resonance is commonly associated with a spin-exciton due to the d(s+/-)-wave symmetry of the superconducting order parameter, it has also been proposed to be a magnon-like excitation appearing in the superconducting state. Here we use inelastic neutron scattering to demonstrate that the resonance in the heavy fermion superconductor Ce1-xYbxCoIn5 with x=0, 0.05 and 0.3 has a ring-like upward dispersion that is robust against Yb-doping. By comparing our experimental data with a random phase approximation calculation using the electronic structure and the momentum dependence of the -wave superconducting gap determined from scanning tunnelling microscopy (STM) for CeCoIn5, we conclude that the robust upward-dispersing resonance mode in Ce1-xYbxCoIn5 is inconsistent with the downward dispersion predicted within the spin-exciton scenario.

  13. Electronic properties of a heavy-fermion U (Ru0.92Rh0.08 )2Si2 single crystal

    Science.gov (United States)

    Prokeš, K.; Huang, Y.-K.; Reehuis, M.; Klemke, B.; Hoffmann, J.-U.; Sokolowski, A.; de Visser, A.; Mydosh, J. A.

    2017-01-01

    We report the crystal structure and highly anisotropic magnetic, transport, and thermal properties of an exceptionally good single crystal of U (Ru0.92Rh0.08)2Si2 , prepared using a modified Czochralski method. Our study, that also includes neutron diffraction results, shows all the heavy-fermion signatures of pristine URu2Si2 ; however, the superconductivity, hidden order, and remnant weak antiferromagnetic orders are absent. Instead, the ground state of the doped system can be classified as a spin liquid that preserves the heavy-fermion character. U (Ru0.92Rh0.08)2Si2 exhibits a short-range magnetic order distinguished by reflections of a Lorentzian profile at qIII=(1/2 1/2 1/2 ) positions that disappear above ˜15 K. The short-range order seems to be a precursor of a long-range magnetic order that occurs with higher Rh concentration. We indicate that these short-range fluctuations involve, at least partially, inelastic scattering processes.

  14. Logarithmic temperature dependence of samarium ion valence in the heavy-fermion S mxL a1 -xO s4S b12

    Science.gov (United States)

    Fushiya, Kengo; Miyazaki, Ryoichi; Higashinaka, Ryuji; Yamada, Akira; Mizumaki, Masaichiro; Tsutsui, Satoshi; Nitta, Kiyofumi; Uruga, Tomoya; Suemitsu, Bunya; Sato, Hideyuki; Aoki, Yuji

    2015-08-01

    We have measured x-ray absorption spectra at the Sm L3 edge to investigate the Sm-ion valence of (S mxL a1 -x) O s4S b12 , in which field-insensitive heavy-fermion behavior appears at low temperatures for x =1 . It has been found that the Sm-ion valance shifts to 2 + with La ion substitution; from v =+2.78 (x =1 ) to v =+2.73 (x =0.2 ) at 10 K. For all x investigated, its temperature dependence shows a logT behavior, indicating that the valence change is caused by "an unconventional Kondo effect" associated with Sm 4 f -electron charge degrees of freedom. Almost x independence of "the associated Kondo temperature" (T˜K=56 ±10 K ) indicates that the Kondo effect has a local nature, attributable to the cage structure of the filled skutterudite.

  15. Coexistence of magnetic order, heavy fermion and intermediate valence behaviour in Ce{sub 7}X{sub 3} (X=Ni, Ru, Pd, Pt, Ir and Rh)

    Energy Technology Data Exchange (ETDEWEB)

    Trovarelli, O. [Comision Nacional de Energia Atomica, San Carlos de Bariloche (Argentina). Centro Atomico Bariloche; Sereni, J.G. [Comision Nacional de Energia Atomica, San Carlos de Bariloche (Argentina). Centro Atomico Bariloche; Schmerber, G. [IPCMS-GEMM, 23 rue du Loess, 67037 Strasbourg (France); Kappler, J.P. [IPCMS-GEMM, 23 rue du Loess, 67037 Strasbourg (France)

    1995-02-01

    Low temperature specific heat, AC magnetic susceptibility and magnetization measurements were performed on the Ce{sub 7}X{sub 3} compounds (X=Ni, Ru, Rh, Pd, Ir and Pt). They exhibit coexistence of magnetic order (MO), heavy fermion (HF) and intermediate valence (IV) behaviour and the results are interpreted in terms of the three Ce sublattices (1Ce{sub I}, 3Ce{sub II} and 3Ce{sub III}) present in the Th{sub 7}Fe{sub 3}-type structure. From entropic considerations it is found that sublattice Ce{sub III} presents an IV behaviour in all these compounds and Ce{sub II} show MO or have a HF behaviour depending on the Ce-ligand electronic structure. The Ce{sub I} atoms (more than 6A distant from each other) exhibit MO only when the Ce{sub II} sublattice provides a high density of electronic states. ((orig.)).

  16. Evidence for Coexistence of Bulk Superconductivity and Itinerant Antiferromagnetism in the Heavy Fermion System CeCo(In(1-x)Cdx)5.

    Science.gov (United States)

    Howald, Ludovic; Stilp, Evelyn; de Réotier, Pierre Dalmas; Yaouanc, Alain; Raymond, Stéphane; Piamonteze, Cinthia; Lapertot, Gérard; Baines, Christopher; Keller, Hugo

    2015-07-30

    In the generic phase diagram of heavy fermion systems, tuning an external parameter such as hydrostatic or chemical pressure modifies the superconducting transition temperature. The superconducting phase forms a dome in the temperature-tuning parameter phase diagram, which is associated with a maximum of the superconducting pairing interaction. Proximity to antiferromagnetism suggests a relation between the disappearance of antiferromagnetic order and superconductivity. We combine muon spin rotation, neutron scattering, and x-ray absorption spectroscopy techniques to gain access to the magnetic and electronic structure of CeCo(In(1-x)Cdx)5 at different time scales. Different magnetic structures are obtained that indicate a magnetic order of itinerant character, coexisting with bulk superconductivity. The suppression of the antiferromagnetic order appears to be driven by a modification of the bandwidth/carrier concentration, implying that the electronic structure and consequently the interplay of superconductivity and magnetism is strongly affected by hydrostatic and chemical pressure.

  17. Intermediate valence to heavy fermion through a quantum phase transition in Yb3(Rh 1 -xTx )4Ge13 (T =Co ,Ir ) single crystals

    Science.gov (United States)

    Rai, Binod K.; Oswald, Iain W. H.; Chan, Julia Y.; Morosan, E.

    2016-01-01

    Single crystals of Yb3(Rh 1 -xTx )4Ge13 (T =Co ,Ir ) have been grown using the self-flux method. Powder x-ray diffraction data on these compounds are consistent with the cubic structure with space group P m 3 ¯n . Intermediate-valence behavior is observed in Yb3(Rh 1 -xTx )4Ge13 upon T = Co doping, while T = Ir doping drives the system into a heavy-fermion state. Antiferromagnetic order is observed in the Ir-doped samples Yb3(Rh 1 -xTx )4Ge13 for 0.5 xc = 0.5, accompanied by non-Fermi-liquid behavior evidenced by logarithmic divergence of the specific heat and linear temperature dependence of the resistivity. The Fermi-liquid behavior is recovered with the application of large magnetic fields.

  18. Search for Type-III Seesaw Heavy Fermions with Multilepton Final States using 2.3/fb of 13 TeV proton-proton Collision Data

    CERN Document Server

    CMS Collaboration

    2016-01-01

    A search for type-III seesaw signal in events with three or more electrons or muons is presented. The data sample corresponds to $2.3\\,\\textrm{fb}^{-1}$ of integrated luminosity in $pp$ collisions at $\\sqrt{s} = 13\\,$TeV collected by the CMS experiment at the LHC. Since the signal populates channels with at least three leptons and diverse kinematic properties, the data is binned in exclusive channels. The primary selection is based on the number of leptons and the invariant mass of opposite-sign dilepton systems which helps discriminate the signal against the Standard Model background. The final optimization for the type-III seesaw signal is based on the sum of leptonic transerve momenta and missing transverse energy. Control samples in data are used to check the robustness of background evaluation techniques and to minimize the reliance on simulation. The observations are consistent with expectations from Standard Model processes. The results are used to exclude heavy fermions of the type-III seesaw model wi...

  19. Topological basis for understanding the behavior of the heavy-fermion metal β -YbAlB4 under application of magnetic field and pressure

    Science.gov (United States)

    Shaginyan, V. R.; Msezane, A. Z.; Popov, K. G.; Clark, J. W.; Khodel, V. A.; Zverev, M. V.

    2016-05-01

    Informative recent measurements on the heavy-fermion metal β -YbAlB4 performed with applied magnetic field and pressure as control parameters are analyzed with the goal of establishing a sound theoretical explanation for the inferred scaling laws and non-Fermi-liquid (NFL) behavior, which demonstrate some unexpected features. Most notably, the robustness of the NFL behavior of the thermodynamic properties and of the anomalous T3 /2 temperature dependence of the electrical resistivity under applied pressure P in zero magnetic field is at variance with the fragility of the NFL phase under application of a field B . We show that a consistent topological basis for this combination of observations, as well as the empirical scaling laws, may be found within fermion-condensation theory in the emergence and destruction of a flat band, and explains that the paramagnetic NFL phase takes place without magnetic criticality, not from quantum critical fluctuations. Schematic T -B and T -P phase diagrams are presented to illuminate this scenario.

  20. ACRT technique for the single crystal growth of the heavy fermion compound YbRh{sub 2}Si{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Witt, Sebastian; Kliemt, Kristin; Butzke, Constantin; Krellner, Cornelius [Goethe University Frankfurt, 60438 Frankfurt am Main (Germany)

    2016-07-01

    In the heavy fermion compound YbRh{sub 2}Si{sub 2} the antiferromagnetic ordering below 70 mK close to a quantum critical point is well-studied. Beneath the magnetic ordering a new phase transition was found recently at 2 mK. It is necessary to prepare large and high-quality single crystals for studying the nature of this new phase transition. Besides the optimization of the single crystal growth it is important to investigate single crystals with different isotopes at this phase transition. Here, we report the crystal growth of YbRh{sub 2}Si{sub 2} with the accelerated crucible rotation technique (ACRT). ACRT shows for other compounds, e.g. YAG (yttrium aluminum garnet, Y{sub 3}Al{sub 5}O{sub 12}), that this technique can reduce flux impurities and enhance the yield of larger crystals. We also report the attempt to receive metallic isotopes of ytterbium with metallothermic reduction. Crystals with different isotopes of silicon and ytterbium can be used for NMR measurements to investigate the underlying phenomena of quantum criticality in more detail.

  1. Coexistence of magnetic order and heavy fermion behavior in Ce sub 7 X sub 3. [Ce-Rh; Ce-Ni

    Energy Technology Data Exchange (ETDEWEB)

    Sereni, A.; Trovarelli, O. (Centro Atomico Bariloche (Argentina)); Schmerber, G.; Kappler, J.P. (IPCMS-GEMM, Inst. de Physique, 67 - Strasbourg (France))

    1992-02-01

    Low temperature specific heat and magnetic susceptibility measurements on Ce{sub 7}X{sub 3} (X = Rh, Ni) compounds are reported. Ce{sub 7}Rh{sub 3} shows an onset of spontaneous magnetization at 7.2 K. About 40% of the expected R In 2 entropy gain is found in the paramagnetic phase, related to a {gamma}{sub HT} = 1.1 J/K{sup 2} mol specific heat coefficient. In Ce{sub 7}Ni{sub 3} an antiferromagnetic transition is observed at 1.7 K, superimposed to a large C{sub P} / T electronic contribution, described by a {gamma}{sub HT} = 0.9 J/K{sup 2} mol coefficient for T > 10 K. These results are interpreted in terms of the three different crystal sublattices of Ce. The entropy gain related to each transition allows to identify the behaviour of each sublattice. In the case of Ce{sub 7}Ni{sub 3} one sublttice behaves as a heavy fermion system, with a value of C{sub P} / T = 3.3 J/K{sup 2} Ce at. Such a behaviour is confirmed under an applied magnetic field. (orig.).

  2. Anisotropic spin fluctuations in heavy-fermion superconductor CeCoIn sub 5. In-NQR and Co-NMR studies

    CERN Document Server

    Kawasaki, Y; Yashima, M

    2003-01-01

    We report In-NQR and Co-NMR experiments of CeCoIn sub 5 that undergoes a superconducting transition with a record high T sub c =2.3 K to date among heavy-fermion superconductors. At zero magnetic field, an anomalous temperature (T) dependence of nuclear spin-lattice relaxation rate 1/T sub 1 of sup 1 sup 1 sup 5 In is explained by the relation 1/T sub 1 propor to T centre dot chi sub Q (T) sup 3 sup / sup 4 based on the anisotropic spin-fluctuations model in case of the proximity to an antiferromagnetic (AFM) quantum critical point (QCP). The novel behavior of 1/T sub 1 - T sup 1 sup / sup 4 over a wide T range of T sub c < T < 40 K arises because the staggered susceptibility almost follows the Curie law chi sub Q (T) propor to 1/(T + theta) with theta=0.6 K and hence 1/T sub 1 propor to T/(T + 0.6) sup 3 sup / sup 4 - T sup 1 sup / sup 4 for theta < T. We highlight that the behavior 1/T sub 1 - T sup 1 sup / sup 4 is due to the proximity to the anisotropic AFM QCP relevant with its layered structure...

  3. Thermodynamic study of gap structure and pair-breaking effect by magnetic field in the heavy-fermion superconductor CeCu2Si2

    Science.gov (United States)

    Kittaka, Shunichiro; Aoki, Yuya; Shimura, Yasuyuki; Sakakibara, Toshiro; Seiro, Silvia; Geibel, Christoph; Steglich, Frank; Tsutsumi, Yasumasa; Ikeda, Hiroaki; Machida, Kazushige

    2016-08-01

    This paper presents the results of specific-heat and magnetization measurements, in particular their field-orientation dependence, on the first discovered heavy-fermion superconductor CeCu2Si2 (Tc˜0.6 K). We discuss the superconducting gap structure and the origin of the anomalous pair-breaking phenomena, leading, e.g., to the suppression of the upper critical field Hc 2, found in the high-field region. The data show that the anomalous pair breaking becomes prominent below about 0.15 K in any field direction, but occurs closer to Hc 2 for H ∥c . The presence of this anomaly is confirmed by the fact that the specific-heat and magnetization data satisfy standard thermodynamic relations. Concerning the gap structure, field-angle dependencies of the low-temperature specific heat within the a b and a c planes do not show any evidence for gap nodes. From microscopic calculations in the framework of a two-band full-gap model, the power-law-like temperature dependencies of C and 1 /T1 , reminiscent of nodal superconductivity, have been reproduced reasonably. These facts further support multiband full-gap superconductivity in CeCu2Si2 .

  4. Spin-fluctuation mediated superconductivity and magnetic order in the cuprate La1.88Sr0.12CuO4

    DEFF Research Database (Denmark)

    Rømer, Astrid Tranum

    High-temperature superconductivity in cuprates emerges as one out of many electronic phases when doping the antiferromagnetic Mott insulator La2CuO4 away from half _lling. The description of the superconducting phase is therefore complicated by intertwined electronic orders that compete...... with superconductivity. However, it is possible that the tendency towards additional ordering phenomena is a necessary condition for unconventional superconductivity to develop. Indeed most superconductors discovered throughout the last 29 years, including also the recently discovered class of iron-based superconductors......, show a very rich electronic phase diagram. A common feature that characterizes both cuprates, heavy fermions, and iron pnictides is the proximity to magnetic order. Therefore, the idea of spin-uctuation mediated pairing is a popular paradigm proposed for unconventional superconductivity. A _ngerprint...

  5. Finite Element Analysis (FEA) in Design and Production.

    Science.gov (United States)

    Waggoner, Todd C.; And Others

    1995-01-01

    Finite element analysis (FEA) enables industrial designers to analyze complex components by dividing them into smaller elements, then assessing stress and strain characteristics. Traditionally mainframe based, FEA is being increasingly used in microcomputers. (SK)

  6. Superconductivity and Non-Fermi-Liquid Behavior in the Heavy-Fermion Compound CeCo1-xNixIn5

    Science.gov (United States)

    Otaka, Ryo; Yokoyama, Makoto; Mashiko, Hiroaki; Hasegawa, Takeshi; Shimizu, Yusei; Ikeda, Yoichi; Tenya, Kenichi; Nakamura, Shota; Ueta, Daichi; Yoshizawa, Hideki; Sakakibara, Toshiro

    2016-09-01

    The effect of off-plane impurity on superconductivity and non-Fermi-liquid (NFL) behavior in the layered heavy-fermion compound CeCo1-xNixIn5 is investigated by specific heat, magnetization, and electrical resistivity measurements. These measurements reveal that the superconducting (SC) transition temperature Tc monotonically decreases from 2.3 K (x = 0) to 0.8 K (x = 0.20) with increasing x, and then the SC order disappears above x = 0.25. At the same time, the Ni substitution yields the NFL behavior at zero field for x = 0.25, characterized by the -ln T divergence in specific heat divided by temperature, Cp/T, and magnetic susceptibility, M/B. The NFL behavior in magnetic fields for x = 0.25 is quite similar to that seen at around the SC upper critical field in pure CeCoIn5, suggesting that both compounds are governed by the same antiferromagnetic quantum criticality. The resemblance of the doping effect on the SC order among Ni-, Sn-, and Pt-substituted CeCoIn5 supports the argument that the doped carriers are primarily responsible for the breakdown of the SC order. The present investigation further reveals the quantitative differences in the trends of the suppression of superconductivity between Ce(Co,Ni)In5 and the other alloys, such as the rates of decrease in Tc, dTc/dx, and specific heat jump at Tc, d(ΔCp/Tc)/dx. We suggest that the occupied positions of the doped ions play an important role in the origin of these differences.

  7. Investigation of the commensurate magnetic structure in the heavy-fermion compound CePt2In7 using magnetic resonant x-ray diffraction

    Science.gov (United States)

    Gauthier, Nicolas; Wermeille, Didier; Casati, Nicola; Sakai, Hironori; Baumbach, Ryan E.; Bauer, Eric D.; White, Jonathan S.

    2017-08-01

    We investigated the magnetic structure of the heavy-fermion compound CePt2In7 below TN=5.34 (2 ) K using magnetic resonant x-ray diffraction at ambient pressure. The magnetic order is characterized by a commensurate propagation vector k1 /2=(1/2 ,1/2 ,1/2 ) with spins lying in the basal plane. Our measurements did not reveal the presence of an incommensurate order propagating along the high-symmetry directions in reciprocal space but cannot exclude other incommensurate modulations or weak scattering intensities. The observed commensurate order can be described equivalently by either a single-k structure or by a multi-k structure. Furthermore we explain how a commensurate-only ordering may explain the broad distribution of internal fields observed in nuclear quadrupolar resonance experiments [Sakai et al., Phys. Rev. B 83, 140408 (2011), 10.1103/PhysRevB.83.140408] that was previously attributed to an incommensurate order. We also report powder x-ray diffraction showing that the crystallographic structure of CePt2In7 changes monotonically with pressure up to P =7.3 GPa at room temperature. The determined bulk modulus B0=81.1 (3 ) GPa is similar to those of the Ce-115 family. Broad diffraction peaks confirm the presence of pronounced strain in polycrystalline samples of CePt2In7 . We discuss how strain effects can lead to different electronic and magnetic properties between polycrystalline and single crystal samples.

  8. Competing orders in FeAs layers.

    Science.gov (United States)

    Lorenzana, J; Seibold, G; Ortix, C; Grilli, M

    2008-10-31

    Using the unrestricted Hartree-Fock approximation and Landau theory we identify possible phases competing with superconductivity in FeAs layers. We find that close to half-filling the transition from the paramagnet to the magnetically ordered phase is first order, making anharmonicities relevant and leading to a rich phase diagram. Between the already known one-dimensionally modulated magnetic stripe phase and the paramagnet we find a new phase which has the same structure factor as the former but in which magnetic moments at nearest-neighbor sites are at right angles making electrons acquire a nontrivial phase when circulating a plaquette at strong coupling. Another competing phase has magnetic and charge order and may be stabilized by charged impurities.

  9. First Principles Study on FeAs Single Layers

    Institute of Scientific and Technical Information of China (English)

    Jun Dai; Zhenyu Li; Jin-long Yang

    2009-01-01

    FeAs- single layer is tested as a simple model for LaFeAsO and BaFe2As2 based on firstprinciples calculations using generalized gradient approximation (GGA) and GGA+U. The calculated single-layer geometric and electronic structures are inconsistent with that of bulk materials. The bulk collinear antiferromagnetic ground state failed to be obtained in the FeAs- single layer. The monotonous behavior of the Fe-As distance in z direction upon electron or hole doping is also in contrast with bulk materials. The results indicate that,in LaFeAsO and BaFe2As2, interactions between FeAs layer and other layers beyond simple charge doping are important, and a single FeAs layer may not represent a good model for Fe based superconducting materials.

  10. Thermodynamic investigations of heavy-fermion superconductors UPt[sub 3] and URu[sub 2]Si[sub 2]. Thermodynamische Untersuchungen an den Schwer-Fermion-Supraleitern UPt[sub 3] und URu[sub 2]Si[sub 2

    Energy Technology Data Exchange (ETDEWEB)

    Hasselbach, K.W.

    1991-06-21

    This thesis presents the superconducting properties of the heavy fermion compounds UPt[sub 3] and URu[sub 2]Si[sub 2]. Measurements of the specific heat, thermal expansion coefficient and electrical resistivity have been performed in the temperature range between 0.1 and 1.5 kelvin. Results contribute to the understanding of superconductivity in heavy fermion compounds. The superconducting transition temperature of the hexagonal heavy fermion superconductor UPt[sub 3] lies at T[sub c] = 0.49 kelvin. Our specific heat measurements of UPt[sub 3] single crystals establish the existence of an additional phase transition in the superconducting state. This new phase transition lies sixty millikelvin below the transition from the normal to the superconducting state. Superconductivity in the heavy fermion superconductor URu[sub 2]Si[sub 2] occurs at 1.18 kelvin. The existence of a double peak, comparable to the one in UPt[sub 3], can be excluded. The phase diagrams (H, T) have been explored by means of specific heat and resistivity measurements in magnetic fields up to eight tesla. (orig./MM).

  11. Effect of Pressure on Valence and Structural Properties of YbFe2Ge2 Heavy Fermion Compound A Combined Inelastic X-ray Spectroscopy, X-ray Diffraction, and Theoretical Investigation

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Ravhi S.; Svane, Axel; Vaitheeswaran; #8741; , Ganapathy; Kanchana, Venkatakrishnan; Antonio, Daniel; Cornelius, Andrew L.; Bauer, Eric D.; Xiao, Yuming; Chow, Paul (Aarhus); (CIW); (Hyderabad - India); (IIT-India); (LANL); (UNLV)

    2016-06-03

    The crystal structure and the Yb valence of the YbFe2Ge2 heavy fermion compound was measured at room temperature and under high pressures using high-pressure powder X-ray diffraction and X-ray absorption spectroscopy via both partial fluorescence yield and resonant inelastic X-ray emission techniques. Furthermore, the measurements are complemented by first-principles density functional theoretical calculations using the self-interaction corrected local spin density approximation investigating in particular the magnetic structure and the Yb valence. While the ThCr2Si2-type tetragonal (I4/mmm) structure is stable up to 53 GPa, the X-ray emission results show an increase of the Yb valence from v = 2.72(2) at ambient pressure to v = 2.93(3) at ~9 GPa, where at low temperature a pressure-induced quantum critical state was reported.

  12. Comparison of FEA Calculations with Cryostat Dummy Weight Test Results

    CERN Document Server

    Guarino, V

    2004-01-01

    Extensive Finite Element analyses were performed to determine the loads and stresses acting on the EB and Barrel during assembly and in its final configuration. Up to now it has been difficult to verify the FEA results due to the unusual compression at the inner radius shims has resulted in larger than anticipated deflections. The cryostat dummy load test offers the first real chance for a direct comparison between the deflections of the Tilecal and the FEA model. By comparing the difference in position of the FM's before the cryostat load was applied and afterwards it is possible to eliminate all other variables and compare directly with the FEA model. This paper will present a comparison between the FEA model and the survey measurements for when the cryostat dummy weight load was applied at 32 modules and 46 modules in place.

  13. (75)As NQR studies on FeAs2.

    Science.gov (United States)

    Lehmann-Horn, J A; Yong, R; Miljak, D G; Bastow, T J

    2015-10-01

    (75)As NQR spectra and relaxation times of synthetic and natural FeAs2 samples have been studied at variable static magnetic field and temperature. FeAs2 is a well understood diamagnetic semiconductor and occurs as the natural mineral lollingite in selected ore deposits. We observed a spin-spin relaxation time enhancement of up to five in synthetic powders in the presence of a weak external static magnetic field. The effect is of interest with regard to signal-to-noise ratio improvement for materials characterization applications where broad NQR absorption lines are excited with wideband pulse sequences.

  14. Ambient pressure superconductivity emerging in the antiferromagnetic phases of the novel heavy fermion compounds Ce{sub 3}PdIn{sub 11} and Ce{sub 3}PtIn{sub 11}

    Energy Technology Data Exchange (ETDEWEB)

    Kratochvilova, Marie; Prokleska, Jan; Uhlirova, Klara; Sechovsky, Vladimir; Custers, Jeroen [Department of Condensed Matter Physics, Charles University, Prague, Ke Karlovu 5, 121 16 (Czech Republic)

    2015-07-01

    Ce{sub n}T{sub m}In{sub 3n+2m} (n=1,2; m=1; T=transition metal) heavy fermion compounds are known to be on the verge of a magnetic to non-magnetic quantum critical point (QCP). In close vicinity of the QCP they exhibit an unconventional superconducting state. However, this family of compounds is interesting for an other reason. The compounds crystallize in the tetragonal structures which provide the possibility to tune the structural dimensionality from more 2D to 3D (stoichiometries: 115-218-103). This makes them ideal candidates to investigate the influence of the parameter dimensionality with respect to quantum criticality. Ce{sub 3}TIn{sub 11} (T=Pd,Pt) single crystals were prepared for the first time. Ce{sub 3}PtIn{sub 11} (Ce{sub 3}PdIn{sub 11}) exhibits two successive transitions at T{sub 1}=2.2K (T{sub 1}=1.7K) and T{sub N}=2.0K (T{sub N} =1.5K) into incommensurate and commensurate local moment antiferromagnetic states, respectively. Applying magnetic field along the c-axis gradually suppresses both transitions; they merge at 4T and split again in higher fields. Superconductivity emerges at T{sub C}=0.32K (T{sub C}=0.39K) and it is enhanced by the application of hydrostatic pressure. The unusual magnetic phase diagram will be discussed in the context of superconductivity and magnetism in related compounds.

  15. High-Tc Superconductors Based on FeAs Compounds

    CERN Document Server

    Izyumov, Yuri

    2010-01-01

    Physical properties and models of electronic structure are analyzed for a new class of high-TC superconductors which belong to iron-based layered compounds. Despite their variable chemical composition and differences in the crystal structure, these compounds possess similar physical characteristics, due to electron carriers in the FeAs layers and the interaction of these carriers with fluctuations of the magnetic order. A tremendous interest towards these materials is explained by the prospects of their practical use. In this monograph, a full picture of the formation of physical properties of these materials, in the context of existing theory models and electron structure studies, is given. The book is aimed at a broad circle of readers: physicists who study electronic properties of the FeAs compounds, chemists who synthesize them and specialists in the field of electronic structure calculations in solids. It is helpful not only to researchers active in the fields of superconductivity and magnetism, but also...

  16. Temperature Evolution of Spin Fluctuations in FeAs

    Science.gov (United States)

    Podlesnyak, A.; Ehlers, G.; Tóth, S.; Gofryk, K.; Sefat, A. S.

    2015-03-01

    The discovery of superconductivity (SC) in iron pnictides has opened a new stage in SC research. The superconducting state appears in iron pnictides with doping in metallic parent compounds. This is an important difference to the cuprates, which exhibit SC near a correlated insulating state. Therefore, the nature of the magnetism in the simplest iron pnictide - binary FeAs - is of fundamental importance for understanding the interplay between localized and itinerant magnetism and superconductivity in these materials. We use inelastic neutron scattering to map spin wave excitations in the monoarsenide FeAs at temperatures above and below the antiferromagnetic transition TN ~ 70 K. We find magnetic excitation spectrum near the Néel temperature to be strongly different from the spectrum in the ground state. Near the transition temperature, magnetic fluctuations clearly indicate two-dimensional character in an intrinsically three-dimensional (3D) system. On the other hand, at low temperature, spin waves in FeAs are anisotropic 3D, suggesting a crossover from two-dimensional to three-dimensional character. Work at ORNL was sponsored by the US DOE Scientific User Facilities Division, Office of Basic Energy Sciences (AP, GE) and Materials Science and Engineering Division (KG, AS).

  17. Unusual magnetotransport properties in a FeAs single crystal

    Science.gov (United States)

    Khim, Seunghyun; Gillig, Matthias; Klingeler, Rüdiger; Wurmehl, Sabine; Büchner, Bernd; Hess, Christian

    2016-05-01

    We have investigated the magnetoresistance (MR) and Hall resistivity properties of a FeAs single crystal which exhibits magnetic order below TN = 69 K. We observe nonlinear Hall resistivity and linear MR in the presence of magnetic-order-connected Fermi surface reconstruction. The analysis of the magnetotransport data using a two-carrier model suggests the emergence of an additional minor hole Fermi surface which coexists with major electron carriers below TN. The origin of the linear MR, however, remains inconsistent with current explanations based on the electronic band structure, i.e., the quantum linear MR model from linearly dispersive Dirac cones and linear MR as a result from strong velocity changes of the cyclotron motion near nested Fermi surfaces. While a macroscopic inhomogeneity in a mobility distribution may cause the linear MR as widely observed in other semimetals with high mobilities, the spiral magnetic order of FeAs seems to ask for an alternative description which takes the specific magnetic order and details of the electronic structure of FeAs as well as a possible entanglement between them into account.

  18. Oxide Nanotube Analogues: CuO Nanobarrels

    Energy Technology Data Exchange (ETDEWEB)

    H. H. Farrell; R. D. Parra

    2011-11-01

    The principle 'form follows function' which dominated much of twentieth century architechture and industrial design has its parallel on the nanolevel in the concept of 'function follows form'. This has been realized in many technologically valuable ways on this level via nanoparticles such as nanotubes and quantum dots, for example. Now, a new material, copper oxide (CuO) nanobarrels, offers still another opportunity to exploit unusual form to obtain new functionality. Recently, CuO 'rings' on the order of 100 nm diameter have been observed experimentally by El-Azab and Liang (2003). In a separate effort, we have used first principles density functional calculations to investigate smaller, single walled CuO structures that appear to be nanotubes or nanobarrels with a square unit mesh rather than the hexagonal mesh of carbon nanotubes. These structures are unique and novel, and almost certainly will yield fascinating results when studied experimentally.

  19. Structural assessment of metal foam using combined NDE and FEA

    Science.gov (United States)

    Ghosn, Louis J.; Abdul-Aziz, Ali; Young, Philippe G.; Rauser, Richard W.

    2005-05-01

    Metal foams are expected to find use in structural applications where weight is of particular concern, such as space vehicles, rotorcraft blades, car bodies or portable electronic devices. The obvious structural application of metal foam is for light weight sandwich panels, made up of thin solid face sheets and a metallic foam core. The stiffness of the sandwich structure is increased by separating the two face sheets by a light weight foam core. The resulting high-stiffness structure is lighter than that constructed only out of the solid metal material. Since the face sheets carry the applied in-plane and bending loads, the sandwich architecture is a viable engineering concept. However, the metal foam core must resist transverse shear loads and compressive loads while remaining integral with the face sheets. Challenges relating to the fabrication and testing of these metal foam panels remain due to some mechanical properties falling short of their theoretical potential. Theoretical mechanical properties are based on an idealized foam microstructure and assumed cell geometry. But the actual testing is performed on as fabricated foam microstructure. Hence in this study, a high fidelity finite element analysis is conducted on as fabricated metal foam microstructures, to compare the calculated mechanical properties with the idealized theory. The high fidelity geometric models for the FEA are generated using series of 2D CT scans of the foam structure to reconstruct the 3D metal foam geometry. The metal foam material is an aerospace grade precipitation hardened 17-4 PH stainless steel with high strength and high toughness. Tensile, compressive, and shear mechanical properties are deduced from the FEA model and compared with the theoretical values. The combined NDE/FEA provided insight in the variability of the mechanical properties compared to idealized theory.

  20. Magnetic fluctuations in heavy-fermion metals

    DEFF Research Database (Denmark)

    Mason, T.E.; Petersen, T.; Aeppli, G.

    1995-01-01

    , the nature of the antiferromagnetic order and magnetic fluctuations is qualitatively quite different. UPd2Al3 resembles a rare earth magnetic system with coupling of the 4f electrons to the conduction electrons manifested in a broadening of otherwise conventional spin wave excitations. This is in marked...

  1. ANALYSIS OF COMPOSITE LEAF SPRING BY USING ANALYTICAL & FEA

    Directory of Open Access Journals (Sweden)

    Ranjeet Mithari

    2012-12-01

    Full Text Available Leaf spring are of the oldest suspension component they are still frequently used. The current leaf spring is multiple leaf spring types with a steel material. It has high weight, low natural frequency, high corrosion, more noise. Therefore current multiple leaf spring is replaced by mono composite (E- Glass epoxy leaf spring which has high natural frequency, low weight etc. The maximum stress produced at the cylindrically joint than fixed joint. Therefore stress analysis of composite material mono leaf spring is carried out. The result of finite element method is verified with analytical calculation. Also compare the natural frequency by FFT analyzer with FEA.

  2. Utilizing video animation to present FEA (Finite Element Analysis) results

    Energy Technology Data Exchange (ETDEWEB)

    Hayer, L.K.; Vossler, J.J. III.

    1990-01-01

    Finite element Analysis (FEA) technique are used to analyze forming, rolling, extrusion, and other continuous manufacturing processes to produce solutions at discrete points in time. These solutions are then displayed using a graphical post-processor. The post-processor displays one plot at a time making it difficult to follow events over the entire process. A means of linking these images that occur at discrete points in time and displaying them in a continuous fashion would aid in comprehending the significance of dynamic or time dependent events that evolve during the processes. Video recording of the graphics provides a means to link the graphical ouput at each discrete point in time and project the results in a continuous fashion upon playback. This presentation outlines the video hardware, the modifications to the pre- and post-processing software, and the process used to make video animation recording of FEA results. Several examples will be shown: Hydroforming of a Spherical Aluminum Shell'' and Three-Stage Forging.'' 5 refs., 7 figs.

  3. Superconductivity in Zigzag CuO Chains

    Energy Technology Data Exchange (ETDEWEB)

    Berg, E.

    2010-04-06

    Superconductivity has recently been discovered in Pr{sub 2}Ba{sub 4}Cu{sub 7}O{sub 15-{delta}} with a maximum T{sub c} of about 15K. Since the CuO planes in this material are believed to be insulating, it has been proposed that the superconductivity occurs in the double (or zigzag) CuO chain layer. On phenomenological grounds we propose a theoretical interpretation of the experimental results in terms of a new phase for the zigzag chain, labelled by C{sub 1}S{sub 3/2}. This phase has a gap in the relative charge mode and a partial gap in the relative spin mode. It has gapless uniform charge and spin excitations and can have a divergent superconducting susceptibility, even for repulsive interactions. A microscopic model for the zigzag CuO chain is proposed, and on the basis of density matrix renormalization group (DMRG) and bosonization studies, we adduce evidence that supports our proposal.

  4. Mesoscale organization of CuO nanoslices: Formation of sphere

    Indian Academy of Sciences (India)

    Jun Wang; Shunxiao Zhang; Zhanshuang Li; Jia You; Piaoping Yang; Xiaoyan Jing; Milin Zhang

    2008-04-01

    The nanocrystalline CuO powders were prepared by precipitation method using Cu(NO$_{3})_{2}$ as copper raw material, water and ethanol as dispersants, and NaOH and ammonia solution as precipitates. The structure, particle size and morphology of resulting CuO powders were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The mechanism of CuO formation was discussed.

  5. Synthesis of Thermally Spherical CuO Nanoparticles

    Directory of Open Access Journals (Sweden)

    Nittaya Tamaekong

    2014-01-01

    Full Text Available Copper oxide (CuO nanoparticles were successfully synthesized by a thermal method. The CuO nanoparticles were further characterized by thermogravimetric analysis (TGA, differential thermal analysis (DTA, X-ray diffraction (XRD, scanning electron microscopy (SEM, energy dispersive X-ray spectrometry (EDS, and high resolution transmission electron microscopy (HRTEM, respectively. The specific surface area (SSABET of CuO nanoparticles was determined by nitrogen adsorption. The SSABET was found to be 99.67 m2/g (dBET of 9.5 nm. The average diameter of the spherical CuO nanoparticles was approximately 6–9 nm.

  6. Iron biofortification and homeostasis in transgenic cassava roots expressing an algal iron assimilatory protein, FEA1

    Directory of Open Access Journals (Sweden)

    Uzoma eIhemere

    2012-09-01

    Full Text Available We have engineered the starchy root crop cassava (Manihot esculenta to express the Chlamydomonas reinhardtii iron assimilatory protein, FEA1, in roots to enhance its nutritional qualities. Iron levels in mature cassava storage roots were increased from 10 to 36 ppm in the highest iron accumulating transgenic lines. These iron levels are sufficient to meet the minimum daily requirement for iron in a 500 gm meal. Significantly, the expression of the FEA1 protein did not alter iron levels in leaves. Transgenic plants also had normal levels of zinc in leaves and roots consistent with the specific uptake of iron mediated by the FEA1 protein. Relative to wild-type plants, FEA1 expressing plants had reduced Fe(III chelate reductase activity and gene expression levels consistent with the more efficient uptake of iron in FEA1 transgenic plants. We also show that genes involved in iron homeostasis in cassava have altered tissue-specific patterns of expression in transgenic plants. Steady state transcript levels of the metal-chelate transporter MeYSL1, and the iron storage proteins, MeFER2 and MeFER6, were elevated in various tissues of FEA1 transgenic plants compared to wild-type plants. These results suggest that these gene products play a role in iron translocation and homeostasis in FEA1 transgenic cassava plants. These results are discussed in terms of enhanced strategies for the iron biofortification of plants.

  7. FEA for designing of floating raft shock-resistant system

    Institute of Scientific and Technical Information of China (English)

    ZHAO Ying-long; HE Lin; HUANG Ying-yun; WANG Yu

    2003-01-01

    Choosing the equipment with good shock-resistant performance and taking shock protection measures while designing the onboard settings, the safety of onboard settings can be assured when warships, especially submarine subjected to non-contact underwater explosion, that is, these means can be used to limit the rattlespace (i.e., the maximum displacement of the equipment relative to the base) and the peak acceleration experienced by the equipment. Using shock-resistant equipments is one of shock protection means. The shock-resistant performance of the shock-resistant equipments should be verified in the design phase of the equipments. The FEA (finite element analysis) software, for example, MSC.NASTRAN(R), can be used to verify the shock-resistant performance. MSC.PATRAN(R) and MSC.NASTRAN are used for modeling and analyzing the floating raft vibration isolating equipment. The model of the floating raft and the floating raft vibration isolating system are theoretically analyzed and calculated, and the analysis results are in agreement with the test results. The transient response analysis of the system model follows the modal analysis of the floating raft vibration isolating system. And it is used to verify the shock-resistant performance. The analysis and calculation method used in this paper can be used to analyze the shock-resistant performance of onboard shock-resistant equipments.

  8. Structure Analysis of a Turbocharger Compressor Wheel Using FEA

    Directory of Open Access Journals (Sweden)

    Shaik Mohammad Rafi

    2014-10-01

    Full Text Available When people talk about race cars or high-performance sports cars, the topic of turbochargers usually comes up. Turbochargers also appear on large diesel engines. A turbo can significantly boost an engine's horsepower without significantly increasing its weight, which is the huge benefit that makes turbos so popular. Turbochargers are a type of forced induction system. They compress the air flowing into the engine. The advantage of compressing the air is that it lets the engine squeeze more air into a cylinder, and more air means that more fuel can be added. Therefore, you get more power from each explosion in each cylinder. Here in this project we are designing the compressor wheel by using Pro-E and doing analysis by using FEA package. The main aim of the project is to increase the performance of the compressor wheel for this we are changing the material and also we are changing the existing design. By comparing the results we will get the best model from this data we suggests the design modifications to the company to improve the performance of the compressor wheel.

  9. Calculations of plastic collapse load of pressure vessel using FEA

    Institute of Scientific and Technical Information of China (English)

    Peng-fei LIU; Jin-yang ZHENG; Li MA; Cun-jian MIAO; Lin-lin WU

    2008-01-01

    This paper proposes a theoretical method using finite element analysis (FEA) to calculate the plastic collapse loads of pressure vessels under internal pressure, and compares the analytical methods according to three criteria stated in the ASME Boiler Pressure Vessel Code. First, a finite element technique using the arc-length algorithm and the restart analysis is developed to conduct the plastic collapse analysis of vessels, which includes the material and geometry non-linear properties of vessels. Second,as the mechanical properties of vessels are assumed to be elastic-perfectly plastic, the limit load analysis is performed by employing the Newton-Raphson algorithm, while the limit pressure of vessels is obtained by the twice-elastic-slope method and the tangent intersection method respectively to avoid excessive deformation. Finally, the elastic stress analysis under working pressure is conducted and the stress strength of vessels is checked by sorting the stress results. The results are compared with those obtained by experiments and other existing models. This work provides a reference for the selection of the failure criteria and the calculation of the plastic collapse load.

  10. Parametric study on patch repaired CFRP laminates using FEA

    Energy Technology Data Exchange (ETDEWEB)

    Kashfuddoja, M.; Ramji, M. [Indian Institute of Technology. Engineering Optics Lab. Dept. of Mechanical Engineering, Hyderabad (India)

    2012-07-01

    Carbon fibre reinforced plastic (CFRP) composite laminates have become popular for structural applications as they are lighter, stronger and tougher. Composite structures are also susceptible to damage while in service. For improved service life, the damage needs to be repaired so that repair structure integrity is enhanced. Various parameters like patch size and shape, it's layup sequence and adhesive thickness would influence the performance of the repaired structure. In present work, a parametric study is carried out using finite element analysis (FEA) to investigate the influence of various parameters involved in composite repair. The panel is made of carbon / epoxy composite laminate with stacking sequence of (0/{+-}45/900)s and is subjected to tensile load. Damaged CFRP laminates is repaired by symmetrical patch adhesively bonded over the damaged area. Circular patch of different stacking sequence and size is considered. Influence of adhesive material and it's thickness on repair efficiency is also investigated. The influence of various repair parameters on peel stress is also analysed. (Author)

  11. Iron biofortification and homeostasis in transgenic cassava roots expressing an algal iron assimilatory protein, FEA1

    OpenAIRE

    2012-01-01

    We have engineered the starchy root crop cassava (Manihot esculenta) to express the Chlamydomonas reinhardtii iron assimilatory protein, FEA1, in roots to enhance its nutritional qualities. Iron levels in mature cassava storage roots were increased from 10 to 36 ppm in the highest iron accumulating transgenic lines. These iron levels are sufficient to meet the minimum daily requirement for iron in a 500 gm meal. Significantly, the expression of the FEA1 protein did not alter iron levels in l...

  12. Composite Flywheels Assessed Analytically by NDE and FEA

    Science.gov (United States)

    Abdul-Aziz, Ali; Baaklini, George Y.

    2000-01-01

    As an alternative to expensive and short-lived lead-acid batteries, composite flywheels are being developed to provide an uninterruptible power supply for advanced aerospace and industrial applications. Flywheels can help prevent irregularities in voltage caused by power spikes, sags, surges, burnout, and blackouts. Other applications include load-leveling systems for wind and solar power facilities, where energy output fluctuates with weather. Advanced composite materials are being considered for these components because they are significantly lighter than typical metallic alloys and have high specific strength and stiffness. However, much more research is needed before these materials can be fully utilized, because there is insufficient data concerning their fatigue characteristics and nonlinear behavior, especially at elevated temperatures. Moreover, these advanced types of structural composites pose greater challenges for nondestructive evaluation (NDE) techniques than are encountered with typical monolithic engineering metals. This is particularly true for ceramic polymer and metal matrix composites, where structural properties are tailored during the processing stages. Current efforts involving the NDE group at the NASA Glenn Research Center at Lewis Field are focused on evaluating many important structural components, including the flywheel system. Glenn's in-house analytical and experimental capabilities are being applied to analyze data produced by computed tomography (CT) scans to help assess the damage and defects of high-temperature structural composite materials. Finite element analysis (FEA) has been used extensively to model the effects of static and dynamic loading on aerospace propulsion components. This technique allows the use of complicated loading schemes by breaking the complex part geometry into many smaller, geometrically simple elements.

  13. CoFea: A Novel Approach to Spam Review Identification Based on Entropy and Co-Training

    Directory of Open Access Journals (Sweden)

    Wen Zhang

    2016-11-01

    Full Text Available With the rapid development of electronic commerce, spam reviews are rapidly growing on the Internet to manipulate online customers’ opinions on goods being sold. This paper proposes a novel approach, called CoFea (Co-training by Features, to identify spam reviews, based on entropy and the co-training algorithm. After sorting all lexical terms of reviews by entropy, we produce two views on the reviews by dividing the lexical terms into two subsets. One subset contains odd-numbered terms and the other contains even-numbered terms. Using SVM (support vector machine as the base classifier, we further propose two strategies, CoFea-T and CoFea-S, embedded with the CoFea approach. The CoFea-T strategy uses all terms in the subsets for spam review identification by SVM. The CoFea-S strategy uses a predefined number of terms with small entropy for spam review identification by SVM. The experiment results show that the CoFea-T strategy produces better accuracy than the CoFea-S strategy, while the CoFea-S strategy saves more computing time than the CoFea-T strategy with acceptable accuracy in spam review identification.

  14. Effective Hamiltonian for FeAs based superconductors

    Science.gov (United States)

    Manousakis, Efstratios

    2009-03-01

    The Fe-pnictide superconductors exhibit unusual properties attributed to electrons and holes occupying the Fe d-orbitals and the outermost occupied s and p pnictide orbitals. Starting from the atomic limit, we carry out a strong coupling expansion for the FeAs layer, where the on-site Coulomb repulsion parameters are assumed to be significantly larger than the hopping between Fe d orbitals and the hybridization parameters between the Fe d and As 4s or 4p orbitals; we derive an effective Hamiltonian that describes the low energy electron/hole behavior. If this condition for strong coupling expansion is not satisfied, still, we believe that our qualitative results capture important aspects of the physics in these materials. The hopping and the hybridization parameters are obtained by fitting the results of our calculations based on the local density approximation to a tight-binding model. The effective Hamiltonian, in the strong coupling limit, consists of three parts which operate on three sub-spaces coupled through Hund's rule and spanned by the following Fe orbitals: (a) the dx^2-y^2; (b) the degenerate orbitals dxz and dyz; and (c) the dxy and dz^2. Each of these parts is an extended t-t^'-J-J^' model and is characterized by different coupling constants and filling factors. For the undoped material the second subspace alone prefers a ground state characterized by a spin-density-wave order similar to that observed in recent experimental studies, while the other two subspaces prefer (,) antiferromagnetic order. The observed spin-density-wave order is imposed by the dxz/dyz subspace as the ground state of the total Hamiltonian of the undoped parent compounds. However, due to the above mentioned frustration the magnetic moment is small in agreement with observation. Our calculation illustrates in a simple manner the reason for the difference in the magnetic ordering between the Fe-pnictides and the cuprates. It also suggests a different evolution of the magnetic

  15. Extraction of important electrical parameters of CuO

    Energy Technology Data Exchange (ETDEWEB)

    Serin, T. [Department of Engineering Physics, Faculty of Engineering, Ankara University, 06100 Ankara (Turkey); Yildiz, A., E-mail: yildizab@gmail.co [Department of Physics, Faculty of Science and Arts, Ahi Evran University, 40040 Kirsehir (Turkey); Horzum Sahin, S.; Serin, N. [Department of Engineering Physics, Faculty of Engineering, Ankara University, 06100 Ankara (Turkey)

    2011-02-01

    Conductivity, X-ray diffraction (XRD), optical absorption and atomic force microscopy (AFM) measurements of CuO thin film were presented. Three distinct electrical conduction contributions with discrete characteristic activation energies were observed. The applicability of various theoretical models was considered to explain results on electrical transport. We extracted important electrical parameters of CuO, which might be useful for its gas sensor applications. -- Research Highlights: {yields} The important electrical parameters of CuO were extracted. Three distinct activation contributions were observed. {yields} Above 200 K, conductivity was controlled by potential barrier. {yields} Below 200 K, conductivity was described in terms of hopping conduction.

  16. Magnetoelectric coupling in supercoducting Sr2 VO3 FeAs revealed by scanning tunneling microscopy

    Science.gov (United States)

    Choi, Seokhwan; Choi, Hyunwoo; Lee, Hyun-Jung; Jung, Jin-Oh; Son, Donghyun; Kim, Jun Sung; Ok, Jong Mok; Lee, Jhinhwan

    2015-03-01

    Sr2VO3FeAs is known to exhibit high Tc (~ 37K) superconductivity with no magnetic ordering in the FeAs layer but weak magnetic moment in the V sublattice. An angle resolved photo emission spectroscopy also shows the non-trivial Fermi surface due to the V 3d orbitals. We have studied on Sr2VO3FeAs single crystal using spectroscopic imaging scanning tunneling microscopy (SI-STM) with variable temperature from 4.6K to 100K, and magnetic field up to 7T. Our results show that Sr2VO3FeAs has charge density wave (CDW) modulation in the V sublattice with the same wave vector observed in the neutron scattering experiment. The modulation strength is reduced with applying magnetic field. An electronic Fermi surface with largest V 3d character shows suppressed superconductivity possibly due to strong V-site correlation. However the multi-orbital nature of FeAs allows overall unsuppressed superconductivity at high Tc.

  17. Syntheses of CuO nanostructures in ionic liquids

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A simple and efficient approach is developed to fabricate single-crystalline CuO nanostructures through an ionic liquid assisted one-step low-temperature solid-state route.Both nanoparticles(5 nm in size)and nanorods(5-10 nm in diameter and 50-100 nm in length)of monoclinic CuO were obtained. These synthesized CuO nanostructures were characterized by X-ray diffraction(XRD),transmission electron microscopy(TEM),selected area electron diffraction(SAED),X-ray photoelectron spectros- copy(XPS),energy dispersive spectroscopy(EDS)and nitrogen adsorption analysis.The morpholo- gies of the nanostructures can be controlled by tuning the amount of NaOH and ionic liquids.The growth mechanism of CuO nanostructures is investigated.

  18. Syntheses of CuO nanostructures in ionic liquids

    Institute of Scientific and Technical Information of China (English)

    WANG Li; ZHAO Bin; YUAN ZhongYong; ZHANG XueJun; Wu QingDuan; CHANG LiXian; ZHENG WenJun

    2007-01-01

    A simple and efficient approach is developed to fabricate single-crystalline CuO nanostructures through an ionic liquid assisted one-step low-temperature solid-state route. Both nanoparticles (5 nm in size) and nanorods (5-10 nm in diameter and 50-100 nm in length) of monoclinic CuO were obtained. These synthesized CuO nanostructures were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS) and nitrogen adsorption analysis. The morphologies of the nanostructures can be controlled by tuning the amount of NaOH and ionic liquids. The growth mechanism of CuO nanostructures is investigated.

  19. First-principles study on the ferrimagnetic half-metallic Mn2FeAs alloy

    Science.gov (United States)

    Qi, Santao; Zhang, Chuan-Hui; Chen, Bao; Shen, Jiang; Chen, Nanxian

    2015-05-01

    Mn-based full-Heusler alloys are kinds of promising candidates for new half-metallic materials. Basing on first principles, the electronic structures and magnetic properties of the Mn2FeAs full-Heusler alloy have been investigated in detail. The Hg2CuTi-type Mn2FeAs compound obeys the Slater-Pauling rule, while the anti-parallel alignment atomic magnetic moments of Mn locating at different sites indicate it a ferrimagnetic alloy. The calculated spin-down bands behave half-metallic character, exhibiting a direct gap of 0.46 eV with a 100% spin polarization at the Fermi level. More studies show the compound would maintain half-metallic nature in a large range of variational lattice constants. We expect that our calculated results may trigger Mn2FeAs applying in the future spintronics field.

  20. Preparation of solar selective absorbing CuO coating for medium temperature application

    Institute of Scientific and Technical Information of China (English)

    HUANG Qunwu; WANG Yiping; LI Jinhua

    2007-01-01

    A new method of preparing CuO solar selective absorbing coating for medium temperature is presented.After pretreatment,brass was overlaid with CuO by chemical plating.The effects of reactant concentration,reaction temperature and reaction time on the absorptivity of CuO coating were investigated.The optimized condition of preparing CuO coating was obtained.The CuO coating was analyzed with X-ray photoelectron spectroscopy(XPS) and scanning electron microscopy(SEM).In order to prolong the period of use,the CuO coating was protected by TiO2.The experiment shows that the TiO2/CuO coating is more heat-resistant,acid-resistant,and wear resistant than CuO coating,without Iosing absorptivity markedly.The TiO2 coating can reduce emissivity and protect the CuO coating.

  1. Iron Biofortification and Homeostasis in Transgenic Cassava Roots Expressing the Algal Iron Assimilatory Gene, FEA1

    OpenAIRE

    2012-01-01

    We have engineered the tropical root crop cassava (Manihot esculenta) to express the Chlamydomonas reinhardtii iron assimilatory gene, FEA1, in its storage roots with the objective of enhancing the root nutritional qualities. Iron levels in mature cassava storage roots were increased from 10 to 36 ppm in the highest iron accumulating transgenic lines. These iron levels are sufficient to meet the minimum daily requirement for iron in a 500 g meal. Significantly, the expression of the FEA1 gene...

  2. Modeling Electron Transport in Vertical-SOI NMOSFET by Directly Solving BTE with FEA

    Institute of Scientific and Technical Information of China (English)

    TONG Jian-nong; ZOU Xue-cheng; SHEN Xu-bang

    2004-01-01

    A numerical schemes applicable to the direct solution of Boltzmann transport equation (BTE) in vertical-SOI NMOSFET are investigated by means of the finite element analysis (FEA).The solution gives the electron distribution function,electrostatic potential,carriers concentration,drift velocity,average energy and drain current by directly solving the BTE and the Poisson equation self-consistency.The result shows that the direct numerical solution of the BTE with the aid of FEA and vertical SOI NMOSFET is a promising approach for ultra short channel transistors modeling.

  3. Finite element analysis (FEA): applying an engineering method to functional morphology in anthropology and human biology.

    Science.gov (United States)

    Panagiotopoulou, O

    2009-01-01

    A fundamental research question for morphologists is how morphological variation in the skeleton relates to function. Traditional approaches have advanced our understanding of form-function relationships considerably but have limitations. Strain gauges can only record strains on a surface, and the geometry of the structure can limit where they can be bonded. Theoretical approaches, such as geometric abstractions, work well on problems with simple geometries and material properties but biological structures typically have neither of these. Finite element analysis (FEA) is a method that overcomes these problems by reducing a complex geometry into a finite number of elements with simple geometries. In addition, FEA allows strain to be modelled across the entire surface of the structure and throughout the internal structure. With advances in the processing power of computers, FEA has become more accessible and as such is becoming an increasingly popular tool to address questions about form-function relationships in development and evolution, as well as human biology generally. This paper provides an introduction to FEA including a review of the sequence of steps needed for the generation of biologically accurate finite element models that can be used for the testing of biological and functional morphology hypotheses.

  4. Tailored 3D CuO Nanogrid Formation

    Directory of Open Access Journals (Sweden)

    Jusang Lee

    2011-01-01

    Full Text Available This paper reports on the controlled synthesis of 3D CuO nanogrids by the combined use of electrospinning and thermal oxidation of a composite metal mesh/polymer mat architecture. The obtained nanogrids result from three steps encompassing: (i Cu atom clusters diffusing into the nanofibers producing polymer-metal “core-shell”-type fibers (ii decomposition of the polymeric shell; (iii oxidation of the metallic core of the nanofibers to form self-supported, open nanogrids consisting of continuous nanofibers of CuO nanoparticles with an average diameter of 20 nm. The calculated band gap energy of the cupric oxide nanogrids was determined from the UV-Vis spectrum to be 1.32 eV. The unique 3D CuO nanogrids may be used as key components of 3D nanobatteries, photocatalysts, and p-type chemosensors.

  5. Correlated barrier hopping of CuO nanoparticles

    Science.gov (United States)

    Koshy, Jiji; Soosen, Samuel. M.; Chandran, Anoop; George, K. C.

    2015-12-01

    The ac conduction mechanism in copper oxide nanoparticles with 8 nm size, synthesized by a precipitation method was studied by analyzing ac conductivity in the frequency range of 50 Hz-1 MHz and in the temperature range of 373-573 K. X-ray diffraction and transmission electron microscopy (TEM) were employed for the structural and morphological characterization of CuO nanoparticles. The experimental and theoretical investigations suggested that the ac conduction mechanism in CuO nanoparticles can be successfully explained by a correlated barrier hopping model, which provided reasonable values for the maximum barrier height and characteristic relaxation time. It was also found that bipolaron hopping become prominent up to a particular temperature and beyond that single polaron hopping predominates. Physical parameters such as hopping distance and density of defect states were also calculated. Photoluminescence studies confirm the presence of a surface defect in CuO nanoparticles.

  6. Synthesis and Optical Properties of CuO Nanocrystals with Controllable Shapes and Size

    Directory of Open Access Journals (Sweden)

    Goraya Neelinder

    2016-01-01

    Full Text Available Highly dispersed copper oxide (CuO nanoparticles had been successfully prepared by a hydrothermal technique where different adding temperatures of NaOH were taken. The as-prepared CuO nanoparticles were characterized by X-ray diffraction (XRD, transmission electron microscopy (TEM and Raman spectroscopy. The results showed that the adding temperature of NaOH has an important influence on the shape and size of CuO nanocrystals The influence of reaction conditions on morphology of CuO nanocrystals was discussed. Furthermore, different shapes of obtained CuO nanocrystals exhibit different Raman properties.

  7. A compensation approach to the tool used in autoclave based on FEA

    Institute of Scientific and Technical Information of China (English)

    Zhang Ji; Li Yingguang; Li Nanya; and Liao Wenhe

    2012-01-01

    Optimization of the curing process can not control the deformation of composite part prepared in autoclave accurately. And traditional "trial-and-error" tool surface compensation approach is low efficiency, high cost and can not control part deformation quantificationally. In order to address these issues, tool compensation approach based on FEA is presented. Model of multi-field coupling relationship in autoclave is realized. And finite element analysis model of composite part's curing process is developed to analyze part deformation. According to displacement of the part surface nodes after deformation, tool surface which compensated by the displacement of composite part which analyzed by FEA is used to control part deformation. A cylindrical composite part is ana- lyzed to verify the approach, and the result proves the correctness and validity of the approach.

  8. Quantum oscillations in the anomalous spin density wave state of FeAs

    Science.gov (United States)

    Campbell, Daniel J.; Eckberg, Chris; Wang, Kefeng; Wang, Limin; Hodovanets, Halyna; Graf, Dave; Parker, David; Paglione, Johnpierre

    2017-08-01

    Quantum oscillations in the binary antiferromagnetic metal FeAs are presented and compared to theoretical predictions for the electronic band structure in the anomalous spin density wave state of this material. Demonstrating a method for growing single crystals out of Bi flux, we utilize the highest quality FeAs to perform torque magnetometry experiments up to 35 T, using rotations of field angle in two planes to provide evidence for one electron and one hole band in the magnetically ordered state. The resulting picture agrees with previous experimental evidence for multiple carriers at low temperatures, but the exact Fermi surface shape differs from predictions, suggesting that correlations play a role in deviation from ab initio theory and cause up to a fourfold enhancement in the effective carrier mass.

  9. Thermal conductivity enhancement in thermal grease containing different CuO structures.

    Science.gov (United States)

    Yu, Wei; Zhao, Junchang; Wang, Mingzhu; Hu, Yiheng; Chen, Lifei; Xie, Huaqing

    2015-01-01

    Different cupric oxide (CuO) structures have attracted intensive interest because of their promising applications in various fields. In this study, three kinds of CuO structures, namely, CuO microdisks, CuO nanoblocks, and CuO microspheres, are synthesized by solution-based synthetic methods. The morphologies and crystal structures of these CuO structures are characterized by field-emission scanning electron microscope and X-ray diffractometer, respectively. They are used as thermal conductive fillers to prepare silicone-based thermal greases, giving rise to great enhancement in thermal conductivity. Compared with pure silicone base, the thermal conductivities of thermal greases with CuO microdisks, CuO nanoblocks, and CuO microspheres are 0.283, 0256, and 0.239 W/mK, respectively, at filler loading of 9 vol.%, which increases 139%, 116%, and 99%, respectively. These thermal greases present a slight descendent tendency in thermal conductivity at elevated temperatures. These experimental data are compared with Nan's model prediction, indicating that the shape factor has a great influence on thermal conductivity improvement of thermal greases with different CuO structures. Meanwhile, due to large aspect ratio of CuO microdisks, they can form thermal networks more effectively than the other two structures, resulting in higher thermal conductivity enhancement.

  10. Structural and magnetic phase transitions in Ca0.73Le0.27FeAs2 with electron-overdoped FeAs layers

    Science.gov (United States)

    Jiang, Shan; Liu, Chang; Cao, Huibo; Birol, Turan; Allred, Jared M.; Tian, Wei; Liu, Lian; Cho, Kyuil; Krogstad, Matthew J.; Ma, Jie; Taddei, Keith M.; Tanatar, Makariy A.; Hoesch, Moritz; Prozorov, Ruslan; Rosenkranz, Stephan; Uemura, Yasutomo J.; Kotliar, Gabriel; Ni, Ni

    2016-02-01

    We report a study of the Ca0.73La0.27FeAs2 single crystals. We unravel a monoclinic to triclinic phase transition at 58 K, and a paramagnetic to stripe antiferromagnetic phase transition at 54 K, below which spins order 45∘ away from the stripe direction. Furthermore, we demonstrate this material is substantially structurally untwinned at ambient pressure with the formation of spin rotation walls (S walls). Finally, in addition to the central-hole and corner-electron Fermi pockets usually appearing in Fe pnictide superconductors, angle-resolved photoemission measurements resolve a fermiology where an extra electron pocket of mainly As chain character exists at the Brillouin zone edge.

  11. a Reexamination of the Red Band of CuO: Analysis of the [16.5] ^{2}Σ^{-} - X ^{2}Π_{i} Transition of ^{63}CuO and ^{65}CuO

    Science.gov (United States)

    Harms, Jack C.; Grames, Ethan M.; Yun, Sirkhoo; Ahmed, Bushra; O'Brien, Leah C.; O'Brien, James J.

    2017-06-01

    The red band of CuO has been observed at high resolution using Intracavity Laser Spectroscopy (ILS). The red band was rotationally analyzed in 1974 by Appelblad and Lagerqvist and a portion of the band structure was assigned as the spectrum of the [16.5] A ^{2}Σ^{+} - X ^{2}Π_{i} transition. Subsequent analyses of CuO showed that the character of the A state was ^{2}Σ^{-} in character, and thus the Λ-doubling parameter, p, was inverted, and the e/f parity assignments were reversed. In this study, the spectrum of CuO was recorded in the in the regions 16,150 \\wn - 16,270 \\wn and 16,405 \\wn - 16,545 \\wn. The CuO molecules were produced in the plasma discharge of a copper hollow cathode within the cavity of a tunable dye laser, using 0.6 torr of argon as the sputter gas and a trace amount of O_2 as the source of oxygen. The plasma spectra were recorded intermittently with spectra from an external I_2 cell, and line positions from the widely used Iodine Atlas were used for calibration. In uncongested regions of the spectrum, both ^{63}CuO and ^{65}CuO were observed with appreciable intensity. The resulting spectra were rotationally analyzed for both isotopologues, fitting the data as a ^{2}Σ^{-} - ^{2}Π_{i} transition using PGOPHER. Line positions from the millimeter wave and FTIR studies of ^{63}CuO performed in the late 1990s were included in the fit to overcome potential complications due to the ambiguous parity assignments prevalent in the CuO literature. Previously unreported molecular constants were obtained from the fit for ^{65}CuO, and the constants of ^{63}CuO are determined to at least an order of magnitude greater than the results of Appelblad and Lagerqvist. Results of this analysis will be presented.

  12. Onset of antiferromagnetism in heavy-fermion metals

    Science.gov (United States)

    Schroder; Aeppli; Coldea; Adams; Stockert; v. Lohneysen H; Bucher; Ramazashvili; Coleman

    2000-09-21

    There are two main theoretical descriptions of antiferromagnets. The first arises from atomic physics, which predicts that atoms with unpaired electrons develop magnetic moments. In a solid, the coupling between moments on nearby ions then yields antiferromagnetic order at low temperatures. The second description, based on the physics of electron fluids or 'Fermi liquids' states that Coulomb interactions can drive the fluid to adopt a more stable configuration by developing a spin density wave. It is at present unknown which view is appropriate at a 'quantum critical point' where the antiferromagnetic transition temperature vanishes. Here we report neutron scattering and bulk magnetometry measurements of the metal CeCu(6-x)Au(x), which allow us to discriminate between the two models. We find evidence for an atomically local contribution to the magnetic correlations which develops at the critical gold concentration (x(c) = 0.1), corresponding to a magnetic ordering temperature of zero. This contribution implies that a Fermi-liquid-destroying spin-localizing transition, unanticipated from the spin density wave description, coincides with the antiferromagnetic quantum critical point.

  13. Effect of restoration technique on stress distribution in roots with flared canals: an FEA study.

    Science.gov (United States)

    Belli, Sema; Eraslan, Öznur; Eraslan, Oğuz; Eskitaşcıoğlu, Gürcan

    2014-04-01

    The aim of this finite element analysis (FEA) study was to test the effect of different restorative techniques on stress distribution in roots with flared canals. Five three-dimensional (3D) FEA models that simulated a maxillary incisor with excessive structure loss and flared root canals were created and restored with the following techniques/materials: 1) a prefabricated post: 2) one main and two accessory posts; 3) i-TFC post-core (Sun Medical); 4) the thickness of the root was increased by using composite resin and the root was then restored using a prefabricated post; 5) an anatomic post was created by using composite resin and a prefabricated glass-fiber post. Composite cores and ceramic crowns were created. A 300-N static load was applied at the center of the palatal surface of the tooth to calculate stress distributions. SolidWorks/Cosmosworks structural analysis programs were used for FEA analysis. The analysis of the von Mises and tensile stress values revealed that prefabricated post, accessory post, and i-TFC post systems showed similar stress distributions. They all showed high stress areas at the buccal side of the root (3.67 MPa) and in the cervical region of the root (> 3.67 MPa) as well as low stress accumulation within the post space (0 to 1 MPa). The anatomic post kept the stress within its body and directed less stress towards the remaining tooth structure. The creation of an anatomic post may save the remaining tooth structure in roots with flared canals by reducing the stress levels.

  14. Plant Mediated Green Synthesis of CuO Nanoparticles: Comparison of Toxicity of Engineered and Plant Mediated CuO Nanoparticles towards Daphnia magna

    Directory of Open Access Journals (Sweden)

    Sadia Saif

    2016-11-01

    Full Text Available Research on green production methods for metal oxide nanoparticles (NPs is growing, with the objective to overcome the potential hazards of these chemicals for a safer environment. In this study, facile, ecofriendly synthesis of copper oxide (CuO nanoparticles was successfully achieved using aqueous extract of Pterospermum acerifolium leaves. P. acerifolium-fabricated CuO nanoparticles were further characterized by UV-Visible spectroscopy, field emission scanning electron microscopy (FE-SEM, energy dispersive X-ray (EDX, Fourier transform infrared spectroscopy (FTIR, X-ray photoelectron spectroscopy (XPS and dynamic light scattering (DLS. Plant-mediated CuO nanoparticles were found to be oval shaped and well dispersed in suspension. XPS confirmed the elemental composition of P. acerifolium-mediated copper nanoparticles as comprised purely of copper and oxygen. DLS measurements and ion release profile showed that P. acerifolium-mediated copper nanoparticles were more stable than the engineered CuO NPs. Copper oxide nanoparticles are used in many applications; therefore, their potential toxicity cannot be ignored. A comparative study was performed to investigate the bio-toxic impacts of plant-synthesized and engineered CuO nanoparticles on water flea Daphnia. Experiments were conducted to investigate the 48-h acute toxicity of engineered CuO NPs and plant-synthesized nanoparticles. Lower EC50 value 0.102 ± 0.019 mg/L was observed for engineered CuO NPs, while 0.69 ± 0.226 mg/L was observed for plant-synthesized CuO NPs. Additionally, ion release from CuO nanoparticles and 48-h accumulation of these nano CuOs in daphnids were also calculated. Our findings thus suggest that the contribution of released ions from nanoparticles and particles/ions accumulation in Daphnia needs to be interpreted with care.

  15. Plant Mediated Green Synthesis of CuO Nanoparticles: Comparison of Toxicity of Engineered and Plant Mediated CuO Nanoparticles towards Daphnia magna.

    Science.gov (United States)

    Saif, Sadia; Tahir, Arifa; Asim, Tayyaba; Chen, Yongsheng

    2016-11-09

    Research on green production methods for metal oxide nanoparticles (NPs) is growing, with the objective to overcome the potential hazards of these chemicals for a safer environment. In this study, facile, ecofriendly synthesis of copper oxide (CuO) nanoparticles was successfully achieved using aqueous extract of Pterospermum acerifolium leaves. P. acerifolium-fabricated CuO nanoparticles were further characterized by UV-Visible spectroscopy, field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and dynamic light scattering (DLS). Plant-mediated CuO nanoparticles were found to be oval shaped and well dispersed in suspension. XPS confirmed the elemental composition of P. acerifolium-mediated copper nanoparticles as comprised purely of copper and oxygen. DLS measurements and ion release profile showed that P. acerifolium-mediated copper nanoparticles were more stable than the engineered CuO NPs. Copper oxide nanoparticles are used in many applications; therefore, their potential toxicity cannot be ignored. A comparative study was performed to investigate the bio-toxic impacts of plant-synthesized and engineered CuO nanoparticles on water flea Daphnia. Experiments were conducted to investigate the 48-h acute toxicity of engineered CuO NPs and plant-synthesized nanoparticles. Lower EC50 value 0.102 ± 0.019 mg/L was observed for engineered CuO NPs, while 0.69 ± 0.226 mg/L was observed for plant-synthesized CuO NPs. Additionally, ion release from CuO nanoparticles and 48-h accumulation of these nano CuOs in daphnids were also calculated. Our findings thus suggest that the contribution of released ions from nanoparticles and particles/ions accumulation in Daphnia needs to be interpreted with care.

  16. Characterization of Doped and Undoped CuO Nanoparticles

    Science.gov (United States)

    Gazioǧlu, Dilek Taşkin; Dumludaǧ, Fatih; Altindal, Ahmet

    2010-01-01

    Undoped and doped with Ti, Cd and Zn CuO nanoparticles were obtained by precipitation method. The crystal structures of the CuO nanoparticles were characterized by X-ray diffraction. Impedance spectroscopy (IS) and d.c conductivity (σd.c) measurements were performed on samples as a function of temperature and frequency (40-105 Hz.) to determine the electrical behavior of the nano powder. It was found that the Arrhenius graph of the samples consist of two linear regions and corresponding activation energies. The dependency of frequency exponent s on temperature and frequency suggests a conduction mechanism which is indication of hopping. The measured impedance spectra showed a furher semicircle at low frequencies for all temperatures. The low frequency semicirles in impedance spectra are attributted to the garin boundry effects.

  17. Investigation on CuO Dispersed PVA Polymer Films

    Directory of Open Access Journals (Sweden)

    R. Divya

    2015-05-01

    Full Text Available Addition of inorganic nanoparticles to polymers allows the modification of physical properties of polymers as well as the implementation of new features in polymer matrix. In the present work, we have made an attempt to disperse CuO nanoparticles in the polyvinyl alcohol (PVA and to understand the change in structural, optical and electrical properties of the polymer film. CuO nanoparticles were added in four different concentrations, viz. 2.5, 5.0, 7.5 and 10 wt%. A total of 5 films were prepared (including the pure PVA film, for comparison.The prepared films were subjected to XRD, FESEM, UV-Vis spectral, PL spectral and electrical analyses. The results obtained are reported.

  18. 3D FEA simulation of 4A11 piston skirt isothermal forging process

    Institute of Scientific and Technical Information of China (English)

    DONG Wan-peng; CHEN Jun

    2008-01-01

    To eliminate the defects during piston skirt isothermal forming process, simulations under different process parameters such as the deformation temperature and friction factor were analyzed with the rigid-plastic FEA. Deformation pattern, metal flow and influence of process parameters were concluded. The prediction load value with a relative error of 4.98% is more accurate to the testing one than that from the empirical formula whose relative error is up to 50.8%. Finally, based on the simulation results, an improved process at 300 ℃ and 0.005-0.05 s-1 was verified without any defects by the physical try-out.

  19. Dynamic characteristics of Semi-active Hydraulic Engine Mount Based on Fluid-Structure Interaction FEA

    OpenAIRE

    Tian Jiande; Jiang Xue; Liu Guozheng; Shi Wenku; Liu Baoquan; Ma Meiqin

    2015-01-01

    A kind of semi-active hydraulic engine mount is studied in this paper. After careful analysis of its structure and working principle, the FEA simulation of it was divided into two cases. One is the solenoid valve is open, so the air chamber connects to the atmosphere, and Fluid-Structure Interaction was used. Another is the solenoid valve is closed, and the air chamber has pressure, so Fluid-Structure-Gas Interaction was used. The test of this semi-active hydraulic engine mount was carried ou...

  20. A new optomechanical structural optimization approach: coupling FEA and raytracing sensitivity matrices

    Science.gov (United States)

    Riva, M.

    2012-09-01

    The design of astronomical instrument is growing in dimension and complexity following ELT class telescopes. The availability of new structural material like composite ones is asking for more robust and reliable designing numerical tools. This paper wants to show a new opto-mechanical optimization approach developed starting from a previously developed integrated design framework. The Idea is to reduce number of iteration in a multi- variable structural optimization taking advantage of the embedded sensitivity routines that are available both in FEA software and in raytracing ones. This approach provide reduced iteration number mainly in case of high number of structural variable parameters.

  1. Exchange bias effect in composites of cuo nanoparticles and nanosilica glass

    Energy Technology Data Exchange (ETDEWEB)

    Ranjan Saha, Dhriti [MLS Professor' s Unit, Indian Association for the Cultivation of Science, 2A and 2B Raja S.C. Mullick Road, Jadavpur, Kolkata 700032 (India); Kumar Nandi, Arun [Polymer Science Unit, Indian Association for the Cultivation of Science, 2A and 2B Raja S.C. Mullick Road, Jadavpur, Kolkata 700032 (India); Chakravorty, Dipankar, E-mail: mlsdc@iacs.res.in [MLS Professor' s Unit, Indian Association for the Cultivation of Science, 2A and 2B Raja S.C. Mullick Road, Jadavpur, Kolkata 700032 (India)

    2014-04-15

    Nanodimensional silica based glass containing iron ions was prepared within the compressed pellet of CuO nanoparicles. The nanocomposite material showed exchange bias effect. This effect arose due to ferromagnetic iron doped CuO phase and antiferromagnetic CuO interface formation within the nanocomposite during the synthesis process. Coercive field as a function of temperature was fitted with Arhenius–Neel equation and extracted blocking temperature was 511 K. The value of effective anisotropy constant for the nanocomposite was found to be 3.64x10{sup 5} erg/cc. - Highlights: • Nanoglass comprising SiO{sub 2} and Fe{sub 2}O{sub 3} was grown with pores of CuO nanoparticle compacts. • CuO (AFM)-core and Fe doped CuO (FM) shell were formed during synthesis. • The nanocomposite material showed exchange bias effect.

  2. Dynamics of Quasiparticles in CuO2 Planes

    Science.gov (United States)

    Mattis, Daniel C.

    At 5 electrons per cell, planar CuO2 is an antiferromagnetic insulator rather than a Fermi liquid. We consider the effects of adding a few electrons or holes into such an insulator and derive a relation between the insulating energy gap and effective mass m* of the added carriers. We find m{el}{*} to differ from m{hol}{*} , with both being temperature dependent.

  3. Multiphonon hopping of carriers in CuO thin films

    Science.gov (United States)

    Serin, T.; Yildiz, A.; Şahin, Ş. H.; Serin, N.

    2011-10-01

    We have performed a detailed study of the electrical conduction process in CuO thin films deposited by the sol-gel dip coating technique in a temperature range 280-420 K. The electrical conduction is analyzed within the framework of various hopping conduction models. Multiphonon hopping conduction mechanism is found to dominate the electrical transport in the entire temperature region. Our results are consistent with this model of hopping conduction mechanisms with weak carrier-lattice coupling.

  4. Transport measurements on individual CuO 2 double layers

    Science.gov (United States)

    Mößle, M.; Kleiner, R.; Gatt, R.; Onellion, M.; Müller, P.

    2000-11-01

    Oxygen loss at the surface of Bi 2Sr 2CaCu 2O 8+ x single crystals provides CuO 2 layers with different critical temperatures. Particularly for overdoped crystals this allows to achieve a T c maximum near the surface. We performed transport measurements of this oxygen depleted layer. Samples were prepared by evaporating four Pb or Ag electrodes on top of freshly cleaved Bi 2Sr 2CaCu 2O 8+ x single crystals. Using overdoped crystals with a bulk T c of 55 to 60 K, the outermost layer was found to be underdoped with T c down to 30 K while the adjacent one was near optimal doping with T c between 80 and 90 K. The T c of the third layer was close to the bulk value. For temperatures above the bulk T c often only one CuO 2 double layer was found to be superconducting. We discuss current transport measurements with current flow along the CuO 2 layers.

  5. Substrate effects on SILAR route synthesized CuO thin films

    Science.gov (United States)

    Dhanasekaran, V.; Mahalingam, T.; Ravi, G.; Rhee, Jin-Koo

    2012-06-01

    Cupric oxide (CuO) thin films are deposited using SILAR method onto various substrates. The X-ray diffraction patterns revealed that the deposited films are polycrystalline in nature with monoclinic structure. The microstructural parameters of chemical bath deposited CuO thin films are calculated using the structural studies. The optical band gap value is determined using transmission spectrum of CuO thin films and the results are discussed.

  6. Effect of CuO Addition on the Sintering Behavior and Electrical Conductivity of 3Y-TZP

    Institute of Scientific and Technical Information of China (English)

    Ahmed A.Hassan; Omar Abdelal A.; S.M. EL-Hout

    2007-01-01

    Yttria stabilized tetragonal zirconia polycrystals (3Y-TZP) doped with CuO was prepared, to get two compositions, 0.3 and 1 mole fraction CuO, respectively. The dilatometric study of the samples showed sintering to be improved for the samples doped with 0.3 mole fraction CuO, and to be deteriorated for the samples doped with 1 mole fraction CuO. The 1 mole fraction CuO doped 3Y-TZP showed higher tetragonal/monoclinic phase transformation which was accompanied by grain growth. The electrical conductivity decreased with the addition of CuO.

  7. Facile Synthesis of Colloidal CuO Nanocrystals for Light-Harvesting Applications

    Directory of Open Access Journals (Sweden)

    Yee-Fun Lim

    2012-01-01

    Full Text Available CuO is an earth-abundant, nontoxic, and low band-gap material; hence it is an attractive candidate for application in solar cells. In this paper, a synthesis of CuO nanocrystals by a facile alcohothermal route is reported. The nanocrystals are dispersible in a solvent mixture of methanol and chloroform, thus enabling the processing of CuO by solution. A bilayer solar cell comprising of CuO nanocrystals and phenyl-C61-butyric acid methyl ester (PCBM achieved a power conversion efficiency of 0.04%, indicating the potential of this material for light-harvesting applications.

  8. Facile Synthesis of Colloidal CuO Nanocrystals for Light-Harvesting Applications

    KAUST Repository

    Lim, Yee-Fun

    2012-01-01

    CuO is an earth-abundant, nontoxic, and low band-gap material; hence it is an attractive candidate for application in solar cells. In this paper, a synthesis of CuO nanocrystals by a facile alcohothermal route is reported. The nanocrystals are dispersible in a solvent mixture of methanol and chloroform, thus enabling the processing of CuO by solution. A bilayer solar cell comprising of CuO nanocrystals and phenyl-C61-butyric acid methyl ester (PCBM) achieved a power conversion efficiency of 0.04%, indicating the potential of this material for light-harvesting applications.

  9. CuO three-dimensional flowerlike nanostructures: Controlled synthesis and characterization

    Science.gov (United States)

    Zhang, Xia; Guo, Yong-Gang; Liu, Wei-Min; Hao, Jing-Cheng

    2008-06-01

    CuO three-dimensional (3D) flowerlike nanostructures were successfully synthesized on copper surface by a simple solution method. CuO nanostructure was systematically studied by scanning electron microscopy, transmission electron microscopy, x-ray powder diffraction, and x-ray photoelectron spectrum. The factors to control the morphology and size of the CuO nanostructures were explored, showing that the reaction time and the concentration of starting regents play important roles in the formation of the CuO 3D nanostructures.

  10. FEA Based Tool Life Quantity Estimation of Hot Forging Dies Under Cyclic Thermo-Mechanical Loads

    Science.gov (United States)

    Behrens, B.-A.; Bouguecha, A.; Schäfer, F.; Hadifi, T.

    2011-01-01

    Hot forging dies are exposed during service to a combination of cyclic thermo-mechanical, tribological and chemical loads. Besides abrasive and adhesive wear on the die surface, fatigue crack initiation with subsequent fracture is one of the most frequent causes of failure. In order to extend the tool life, the finite element analysis (FEA) may serve as a means for process design and process optimisation. So far the FEA based estimation of the production cycles until initial cracking is limited as tool material behaviour due to repeated loading is not captured with the required accuracy. Material models which are able to account for cyclic effects are not verified for the fatigue life predictions of forging dies. Furthermore fatigue properties from strain controlled fatigue tests of relevant hot work steels are to date not available to allow for a close-to-reality fatigue life prediction. Two industrial forging processes, where clear fatigue crack initiation has been observed are considered for a fatigue analysis. For this purpose the relevant tool components are modelled with elasto-plastic material behaviour. The predicted sites, where crack initiation occurs, agree with the ones observed on the real die component.

  11. Development of an integrated CAD-FEA system for patient-specific design of spinal cages.

    Science.gov (United States)

    Zhang, Mingzheng; Pu, Fang; Xu, Liqiang; Zhang, Linlin; Liang, Hang; Li, Deyu; Wang, Yu; Fan, Yubo

    2017-03-01

    Spinal cages are used to create a suitable mechanical environment for interbody fusion in cases of degenerative spinal instability. Due to individual variations in bone structures and pathological conditions, patient-specific cages can provide optimal biomechanical conditions for fusion, strengthening patient recovery. Finite element analysis (FEA) is a valuable tool in the biomechanical evaluation of patient-specific cage designs, but the time- and labor-intensive process of modeling limits its clinical application. In an effort to facilitate the design and analysis of patient-specific spinal cages, an integrated CAD-FEA system (CASCaDeS, comprehensive analytical spinal cage design system) was developed. This system produces a biomechanical-based patient-specific design of spinal cages and is capable of rapid implementation of finite element modeling. By comparison with commercial software, this system was validated and proven to be both accurate and efficient. CASCaDeS can be used to design patient-specific cages with a superior biomechanical performance to commercial spinal cages.

  12. Parametric CAD and Fea Model of a Saddle Tapping Tee

    DEFF Research Database (Denmark)

    A. Kristensen, Anders Schmidt; Lund Jepsen, Kristian

    2007-01-01

    is determined from paragraph K302.3.2 in ASME B31.3. A full parametric 3D CAD model of the Saddle Tapping Tee is developed where a number of user-defined parameters are controlled from an Excel spreadsheet allowing parameter studies and technical documentation to be generated effectively. The same Excel spread......-sheet control a full 3D parametric FEA model which is automatically updated from the user-defined parameters set for the CAD-model. As the gasket is subjected to a contact pressure arising from the clamping force acting on the pipe section, a FE contact analysis is carried out. This contact analysis is set up...... required and relevant user-defined parameter on the Saddle Tapping Tee from a single Excel spreadsheet in both the CAD model and the FE model. A full 3D CAD model is effectively generated for dimensions in the range from NPS ½ to NPS 24 and FEA can be performed to provide documentation of the behaviour...

  13. Correlation of FEA Prediction And Experiments On Dual-Phase Steel Automotive Rails

    Science.gov (United States)

    Du, C.; Chen, X. M.; Lim, T.; Chang, T.; Xiao, P.; Liu, S.-D.

    2007-05-01

    The North American Auto/Steel Partnership (A/SP) High-Strength Steel Forming Project Team has been studying the impact of advanced high-strength steels on stamping of structural components. Tooling was built to evaluate the effect of different grades of dual-phase steels on rail type stampings. The formed panels were laser scanned and the amount of springback was measured against the design intention. FEA simulation of the forming process was carried out to validate the numerical modeling techniques in the large and complex dual-phase steel stampings. The materials used in the study were Dual-Phase (DP) Steels DP600, DP780 and DP980. The FEA solver used was LS-Dyna version 971. The simulation results were correlated with the measurement data under various forming conditions including forming methods, trimming, binder and pad pressures. Reasonably good correlations were obtained across different grades of steels in terms of flange opening angles, wall opening angles, twist angles and dimensional deviations.

  14. Isolation of copper oxide (CuO) nanoparticles resistant Pseudomonas strains from soil and investigation on possible mechanism for resistance.

    Science.gov (United States)

    Soltani Nezhad, Shahla; Rabbani Khorasgani, Mohammad; Emtiazi, Giti; Yaghoobi, Mohammad Mehdi; Shakeri, Shahryar

    2014-03-01

    The present study deals with isolation and characterization of copper oxide nanoparticles resistant Pseudomonas strains that were isolated from the soil collected from mining and refining sites of Sarcheshmeh copper mine in the Kerman Province of Iran. The three isolates were selected based on high level of copper oxide nanoparticles (CuO NPs) resistance. The isolates were authentically identified as Pseudomonas fluorescens CuO-1, Pseudomonas fluorescens CuO-2 and Pseudomonas sp. CuO-3 by morphological, biochemical and 16S rDNA gene sequencing analysis. The growth pattern of these isolates with all the studied CuO NPs concentrations was similar to that of control (without CuO NPs) indicating that CuO NPs would not affect the growth of isolated strains. A reduction in the amount of exopolysaccharides was observed after CuO NPs-P. fluorescens CuO-1 culture supernatant interaction. The Fourier transform infrared spectroscopy (FT-IR) peaks for the exopolysaccharides extracted from the bacterial culture supernatant and the interacted CuO NPs were almost similar. The exopolysaccharide capping of the CuO NPs was confirmed by FT-IR and X-ray diffraction analysis. The study of bacterial exopolysaccharides capped CuO NPs with E. coli PTCC 1338 and S. aureus PTCC 1113 showed less toxicity compared to uncoated CuO NPs. Our study suggests that the capping of nanoparticles by bacterially produced exopolysaccharides serve as the probable mechanism of tolerance.

  15. First-principles study on the ferrimagnetic half-metallic Mn{sub 2}FeAs alloy

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Santao [Institute for Applied Physics, University of Science and Technology Beijing, Beijing 100083 (China); Zhang, Chuan-Hui, E-mail: zhangch@ustb.edu.cn [National Center for Materials Service Safety, University of Science and Technology Beijing, Beijing 100083 (China); Chen, Bao; Shen, Jiang [Institute for Applied Physics, University of Science and Technology Beijing, Beijing 100083 (China); Chen, Nanxian [Institute for Applied Physics, University of Science and Technology Beijing, Beijing 100083 (China); Department of Physics, Tsinghua University, Beijing 100084 (China)

    2015-05-15

    Mn-based full-Heusler alloys are kinds of promising candidates for new half-metallic materials. Basing on first principles, the electronic structures and magnetic properties of the Mn{sub 2}FeAs full-Heusler alloy have been investigated in detail. The Hg{sub 2}CuTi-type Mn{sub 2}FeAs compound obeys the Slater-Pauling rule, while the anti-parallel alignment atomic magnetic moments of Mn locating at different sites indicate it a ferrimagnetic alloy. The calculated spin-down bands behave half-metallic character, exhibiting a direct gap of 0.46 eV with a 100% spin polarization at the Fermi level. More studies show the compound would maintain half-metallic nature in a large range of variational lattice constants. We expect that our calculated results may trigger Mn{sub 2}FeAs applying in the future spintronics field. - Graphical abstract: The d orbitals of Mn and Fe atoms split into multi-degenerated levels which create new bonding and nonbonding states. These exchange splitting shift the Fermi level to origin band gap.▪ - Highlights: • The electronic structure and magnetic properties of Mn{sub 2}FeAs full-Heusler alloy were studied. • A total magnetic moment of 3μ{sub B} was obtained for Mn{sub 2}FeAs alloy, following the SP rule M{sub t}=Z{sub t}−24. • The origin of ferrimagnetism and half-metallic character in Mn{sub 2}FeAs were discussed.

  16. STRUCTURAL AND ELECTRONIC PROPERTIES OF CuO, CuO2 AND Cu2O NANOCLUSTERS – A DFT APPROACH

    Directory of Open Access Journals (Sweden)

    Chandiramouli RAMANATHAN

    2015-06-01

    Full Text Available The realistic structures of CuO, CuO2 and Cu2O were completely optimized using density functional theory approach. The different structures were optimized to study the structural stability, dipole moment, point symmetry, HOMO-LUMO gap, ionization potential, electron affinity and binding energy of CuO, CuO2 and Cu2O. The electronic properties of clusters were discussed in terms of HOMO-LUMO gap, density of states, ionization potential and electron affinity. This information will provide an insight for the synthesis of nanomaterials with proper geometry which finds its potential importance in engineering applications.DOI: http://dx.doi.org/10.5755/j01.ms.21.2.6459

  17. Study of the C-14-contamination potential of C-impurities in CuO and Fe

    NARCIS (Netherlands)

    Vandeputte, K; Moens, L; Dams, R; van der Plicht, Johannes

    1998-01-01

    The carbon concentration in CuO and iron was determined by isolating C. The values were in agreement with results reported in other studies. Contaminating carbon from CuO and Fe was transformed to AMS targets and measured for C-14. C-traces in CuO were shown to be the major contribution to the C-14

  18. Earthquake Disaster Simulation for an Urban Area, with GIS, CAD,FEA, and VR Integration

    Institute of Scientific and Technical Information of China (English)

    XU Feng; CHEN Xuping; REN Aizhu; LU Xinzheng

    2008-01-01

    For a disaster whose scale includes an urban area, it is difficult to be studied with physical ex-periments. Numerical simulation is found a very efficient tool for such problem. This paper aims at developing an integrated urban earthquake simulation system (UESS) that uses GIS as the model source, CAD as the model generating tools, FEA as damage prediction, and virtual reality (VR) as the post-process platform. Anautomatic procedure was developed to buildup the 3D structural model of buildings in an urban area, as well as to simulate their earthquake performances, from the digital map of GIS. And the simulation results were presented in an integrated interface with a GIS view-port for position finding, a CAD view-port for 3D struc-tural damage identification, and a VR view-port for 3D dynamic structural vibration display. An urban example with more than 7000 buildings was select to demonstrate the feasibility of proposed system.

  19. Parametric analysis of warm forming of aluminum blanks with FEA and DOE

    Institute of Scientific and Technical Information of China (English)

    CHEN Peng; LIN Zhong-qin; CHEN Guan-long; K. Muammer

    2006-01-01

    The effect of temperature distribution on warm forming performance was investigated for 5083-O (Al-Mg) sheet metal blanks. Combined isothermal/non-isothermal FEA with design of experiments tools were used to predict appropriate warm forming temperature conditions for deep drawing and two-dimensional stamping cases. In the investigated temperature range of 25-250 ℃,the formability of Al-5083 alloy is found to be greatly dependent on the temperature distribution of the die and punch. To achieve increased degrees of forming, different temperature levels should be assigned to the corner and body of the die and punch. And the optimal temperature distributions for warm deep drawing and warm two-dimensional stamping are not identical.

  20. APPLICATION OF FEA TO THE COLLOCATION OF ACTUATOR/SENSOR IN THE INTELLIGENT STRUCTURES

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The piezothermoelectric actuator/sensor collocation for advanced intelligent structure is studied. The quasi-static equations of piezothermoelasticity are used to analyze the coupling effects between the displacement, temperature and electric fields of piezothermoelasticity continua and the governing equations for piezothermoelectric continua are derived to discuss the effects of coupling factors on the control/sensing performance in intelligent structure. Based on those analyses,a finite element analysis model of distributed piezothermoelectric continua is developed later. The thermal stress and deformation of a beam are calculated by FEA method so as to determine the optimal actuator/sensor placement. Based on the results of the optimal analysis procedure of actuator/sensor placement, some conclusions of actuator/sensor placement are obtained. Thus, the optimal actuator/sensor placement for piezothermoelectric intelligent structure can be found from the actuator/sensor placements available so that intelligent system will have the best controllability and observability.

  1. Applications of DSP to Explicit Dynamic FEA Simulations of Elastically-Dominated Impact Problems

    Directory of Open Access Journals (Sweden)

    Ted Diehl

    2000-01-01

    Full Text Available Explicit Dynamic Finite Element techniques are increasingly used for simulating impact events of personal electronic devices such as portable phones and laptop computers. Unfortunately, the elastically-dominated impact behavior of these devices greatly increases the tendency of Explicit Dynamic methods to calculate noisy solutions containing high-frequency ringing, especially for acceleration and contact-force data. For numerous reasons, transient FEA results are often improperly recorded by the analyst, causing corruption by aliasing. If aliasing is avoided, other sources of distortion can still occur. For example, filtering or decimating Explicit Dynamic data typically requires extremely small normalized cutoff frequencies that can cause significant numerical problems for common DSP programs such as MATLAB. This paper presents techniques to combat the unique DSP-related challenges of Explicit Dynamic data and then demonstrates them on a very challenging transient problem of a steel ball impacting a plastic LCD display in a portable phone, correlating simulation and experimental results.

  2. Reliability design optimization of composite structures based on PSO together with FEA

    Institute of Scientific and Technical Information of China (English)

    Chen Jianqiao; Tang Yuanfu; Ge Rui; An Qunli; Guo Xiwei

    2013-01-01

    The present work aims to develop a method for reliability-based optimum design of composite structures.A procedure combining particle swarm optimization (PSO) and finite element analysis (FEA) has been proposed.Numerical examples for the reliability design optimization (RDO) of a laminate and a composite cylindrical shell are worked out to demonstrate the effectiveness of the method.Then a design for composite pressure vessels is studied.The advantages and necessity of RDO over the conventional equi-strength design are addressed.Examples show that the proposed method has good stability and is efficient in dealing with the probabilistic optimal design of composite structures.It may serve as an effective tool to optimize other complicated structures with uncertainties.

  3. Simulation of Thermal-Mechanical Strength for Marine Engine Piston Using FEA

    Directory of Open Access Journals (Sweden)

    Jiang Guo He

    2014-03-01

    Full Text Available Simulation of Thermal-Mechanical Strength for Marine Engine Piston Using FEA Abstract: This paper involves simulation of a 2-stroke 6S35ME marine diesel engine piston to determine its temperature field, thermal, mechanical and coupled thermal-mechanical stress. The distribution and magnitudes of the afore-mentioned strength parameters are useful in design, failure analysis and optimization of the engine piston. The piston model was developed in solid-works and imported into ANSYS for preprocessing, loading and post processing. Material model chosen was 10-node tetrahedral thermal solid 87. The simulation parameters used in this paper were piston material, combustion pressure, inertial effects and temperature. The highest calculated stress was the thermal-mechanical coupled stress and was below the yield stress of the piston material (580Mpa at elevated temperatures hence the piston would withstand the induced stresses during work cycles.

  4. Electronic structure of (Ca0.85La0.15)FeAs2

    Science.gov (United States)

    Liu, Z.-H.; Kim, T. K.; Sala, A.; Ogino, H.; Shimoyama, J.; Büchner, B.; Borisenko, S. V.

    2015-02-01

    We report a comprehensive study of orbital character and tridimensional nature of the electronic structure of (Ca0.85La0.15)FeAs2 from recently discovered "112" family of Iron-based superconductors (IBS), with angle-resolved photoemission spectroscopy. We observed that the band structure is similar to that of "122" family, namely, there are three hole-like bands at the Brillouin zone (BZ) center and two electron-like bands at the BZ corner. The bands near the Fermi level (EF) are mainly derived from the Fe t2g orbitals. On the basis of our present and earlier studies, we classify IBS into the three types according to their crystal structures. We show that although the bands near EF mainly originate from Fe 3d electrons, they are significantly modified by the interaction between the superconducting slabs and the intermediate atoms.

  5. FeAs2 formation and electronic nematic ordering: Analysis in terms of structural transformations

    Science.gov (United States)

    Pishtshev, A.; Rubin, P.

    2016-02-01

    By combining DFT-based computational analysis and symmetry constraints in terms of group-subgroup relations, we analyzed the formation of the native crystalline structure of loellingite FeAs2. We showed that the ground state of the material exhibits the ordered patterns of the electronic localization which are mainly associated with iron 3 dx2-y2 orbitals and can be characterized in terms of nematiclike ordering. The ordering is the result of the close interplay of the lattice and the electron degrees of freedom. In a structural aspect, the interplay pursues an energy quest to select the orthorhombic crystal lattice attributed to the P n n m space group. In a charge aspect, the ordering is connected with the valence charge density redistribution that not only provides a high electronic polarizability but also gives rise to an extra-large magnitude of the negative component of the dynamical p -d charge transfer.

  6. Incommensurate magnetism in FeAs strips: neutron scattering from CaFe(4)As(3).

    Science.gov (United States)

    Nambu, Yusuke; Zhao, Liang L; Morosan, Emilia; Kim, Kyoo; Kotliar, Gabriel; Zajdel, Pawel; Green, Mark A; Ratcliff, William; Rodriguez-Rivera, Jose A; Broholm, Collin

    2011-01-21

    Magnetism in the orthorhombic metal CaFe(4)As(3) was examined through neutron diffraction for powder and single crystalline samples. Incommensurate [q(m) ≈ (0.37-0.39) × b*] and predominantly longitudinally (|| b) modulated order develops through a 2nd order phase transition at TN = 89.63(6) K with a 3D Heisenberg-like critical exponent β = 0.365(6). A 1st order transition at T2 = 25.6(9)  K is associated with the development of a transverse component, locking q(m) to 0.375(2)b*, and increasing the moments from 2.1(1) to 2.2(3)  μ B for Fe2+ and from 1.3(3) to 2.4(4)  μB for Fe+. The ab initio Fermi surface is consistent with a nesting instability in cross-linked FeAs strips.

  7. Lattice Instability in High Temperature Superconducting Cuprates and FeAs Systems: Polarons Probed by EXAFS

    Directory of Open Access Journals (Sweden)

    H. Oyanagi

    2010-01-01

    Full Text Available Carrier-induced lattice distortion (signature of polaron in oxypnictide superconductors is found by an instantaneous local probe, extended X-ray absorption fine structure (EXAFS. Polaron formation is detected as two distinct nearest neighbor distances (Fe-As, implying an incoherent local mode that develops coherence at the critical temperature. Comparing the results with the unusual lattice response in cuprate superconductors, intimate correlation between evolution of local lattice mode and superconductivity is revealed. The results suggest that strong electron-lattice interaction is present as a common ingredient in the microscopic mechanism of superconducting transition. The effect of magnetic impurity atoms in cuprates further indicates that magnetic scattering becomes diluted as long as polaron formation is conserved. We argue that polaron coherence dominates electrical conduction and magnetic interaction in oxypnictide and cuprate superconductors.

  8. Dynamic characteristics of Semi-active Hydraulic Engine Mount Based on Fluid-Structure Interaction FEA

    Directory of Open Access Journals (Sweden)

    Tian Jiande

    2015-01-01

    Full Text Available A kind of semi-active hydraulic engine mount is studied in this paper. After careful analysis of its structure and working principle, the FEA simulation of it was divided into two cases. One is the solenoid valve is open, so the air chamber connects to the atmosphere, and Fluid-Structure Interaction was used. Another is the solenoid valve is closed, and the air chamber has pressure, so Fluid-Structure-Gas Interaction was used. The test of this semi-active hydraulic engine mount was carried out to compare with the simulation results, and verify the accuracy of the model. Then the dynamic characteristics-dynamic stiffness and damping angle were analysed by simulation and test. This paper provides theoretical support for the development and optimization of the semi-active hydraulic engine mount.

  9. Springback Control With Variable Binder Force — Experiments And FEA Simulation

    Science.gov (United States)

    Du, Changqing; Wu, Jin; Militisky, Marcio; Principe, James; Garnett, Mark; Zhang, Li

    2004-06-01

    Side-wall-curl is a springback phenomena in typical automotive structural components, such as channel like rails and cross members. Minimizing or eliminating the side-wall-curl is one of the major challenges in stamping production. This challenge is exasperated when the component is formed from advanced high strength steels (AHSS). In this study a standard three-piece draw die is used, in a series of experimental tests, to form a stamping with a hat-shaped section from dual phase 590 (DP590). During the forming stroke, the binder force is varied to evaluate its influence on side-wall-curl. FEA springback simulations for two types of experiments with varied binder forces are also performed. The binder force profiles for several sheet materials are discussed and the correlation between the simulation results and the actual part measurements are illustrated.

  10. Activities of liquid Fe-As and Fe-Sb alloys saturated with carbon

    Institute of Scientific and Technical Information of China (English)

    Leandro Voisin; Kimio Itagaki

    2006-01-01

    A solid iron base alloy of the so-called furnace residue is often formed as a by-product in reduction smelting of lead sinter and scraps with high contents of arsenic and antimony. The use of phase separation into a liquid iron-rich alloy and a liquid lead-rich alloy in lead-iron-arsenic and lead-iron-antimony systems saturated with carbon at relatively low temperatures of about 1200℃ was proposed in a new process for treating the furnace residue to recover valuable elements into the lead-rich alloy and fix toxic arsenic into the iron-rich alloy. As a fundamental study for the proposed process, the activity coefficients and interaction parameters of the Fe-As and Fe-Sb systems saturated with carbon at 1200℃ were derived in this study, based on the determined phase relations in the Fe-Pb-As and Fe-Pb-Sb systems saturated with carbon.

  11. Anomalous Raman spectra from La2CuO4

    Science.gov (United States)

    Burns, Gerald; Dacol, F. H.

    1990-03-01

    We show that some published Raman spectra from the superconductors (La2-xSrx)CuO4 and La2NiO4 are incorrect. We believe that these spectra were obtained when the samples were ``burnt'' by the focused laser beam and were actually due to La2O3. Similar anomalous results can be obtained when starting with Nd2CuO4 where the spectra come from Nd2O3. A spectrum distinctly different from those of La2O3 or Nd2O3 is obtained from Y2O3.

  12. Chronic effects of CuO Nanoparticles on Lymnaea stagnalis

    DEFF Research Database (Denmark)

    Falk, Nina; Zwicky, Julie; Rewentlow, Julie

    Due to their small size and high surface-to-volume ratio, the properties and reactivity of NPs are different from those of their bulk forms. However, these properties might cause different behaviour and effects in the environment and investigations of possible nano specific effects are thus highl...... relevant. Investigation of the long-term effects of CuO NPs on growth, mortality and precopulation of Hyalella azteca compared to CuCl2 and to further examine possible delayed effects and ability to recover from Cu exposure....

  13. Lifetime prediction for the subsurface crack propagation using three-dimensional dynamic FEA model

    Science.gov (United States)

    Yin, Yuan; Chen, Yun-Xia; Liu, Le

    2017-03-01

    The subsurface crack propagation is one of the major interests for gear system research. The subsurface crack propagation lifetime is the number of cycles remaining for a spall to appear, which can be obtained through either stress intensity factor or accumulated plastic strain analysis. In this paper, the heavy loads are applied to the gear system. When choosing stress intensity factor, the high compressive stress suppresses Mode I stress intensities and severely reduces Mode II stress intensities in the heavily loaded lubricated contacts. Such that, the accumulated plastic strain is selected to calculate the subsurface crack propagation lifetime from the three-dimensional FEA model through ANSYS Workbench transient analysis. The three-dimensional gear FEA dynamic model with the subsurface crack is built through dividing the gears into several small elements. The calculation of the total cycles of the elements is proposed based on the time-varying accumulated plastic strain, which then will be used to calculate the subsurface crack propagation lifetime. During this process, the demonstration from a subsurface crack to a spall can be uncovered. In addition, different sizes of the elements around the subsurface crack are compared in this paper. The influences of the frictional coefficient and external torque on the crack propagation lifetime are also discussed. The results show that the lifetime of crack propagation decreases significantly when the external load T increasing from 100 N m to 150 N m. Given from the distributions of the accumulated plastic strain, the lifetime shares no significant difference when the frictional coefficient f ranging in 0.04-0.06.

  14. A combined NDE/FEA approach to evaluate the structural response of a metal foam

    Science.gov (United States)

    Ghosn, Louis J.; Abdul-Aziz, Ali; Raj, Sai V.; Rauser, Richard W.

    2007-04-01

    Metal foams are expected to find use in structural applications where weight is of particular concern, such as space vehicles, rotorcraft blades, car bodies or portable electronic devices. The obvious structural application of metal foam is for light weight sandwich panels, made up of thin solid face sheets and a metallic foam core. The stiffness of the sandwich structure is increased by separating the two face sheets by a light weight metal foam core. The resulting high-stiffness structure is lighter than that constructed only out of the solid metal material. Since the face sheets carry the applied in-plane and bending loads, the sandwich architecture is a viable engineering concept. However, the metal foam core must resist transverse shear loads and compressive loads while remaining integral with the face sheets. Challenges relating to the fabrication and testing of these metal foam panels remain due to some mechanical properties falling short of their theoretical potential. Theoretical mechanical properties are based on an idealized foam microstructure and assumed cell geometry. But the actual testing is performed on as fabricated foam microstructure. Hence in this study, a detailed three dimensional foam structure is generated using series of 2D Computer Tomography (CT) scans. The series of the 2D images are assembled to construct a high precision solid model capturing all the fine details within the metal foam as detected by the CT scanning technique. Moreover, a finite element analysis is then performed on as fabricated metal foam microstructures, to calculate the foam mechanical properties with the idealized theory. The metal foam material is an aerospace grade precipitation hardened 17-4 PH stainless steel with high strength and high toughness. Tensile and compressive mechanical properties are deduced from the FEA model and compared with the theoretical values for three different foam densities. The combined NDE/FEA provided insight in the variability of

  15. Preparation of CuO Quantum Dots by Cost-Effective Ultrasonication Technique

    Science.gov (United States)

    Rathod, K. N.; Savaliya, Chirag; Babiya, K. R.; Vasvani, S. H.; Ramani, Rupeshkumar V.; Ramani, Bharat M.; Joshi, Ashvini D.; Pandya, Dhiren; Shah, N. A.; Markna, J. H.

    Due to exciting size-dependent chemical and physical properties, nanoscale materials have extensive range of applications compared with microstructural particles. CuO nanoparticles are very important among transition metal oxides because of their large number of applications. Quantum dots (QDs) of CuO (copper oxide) were prepared by the innovative ultrasonication method. Ultrasonic sound is used in this synthesis method to synthesize QDs of copper oxide. Structural and optical properties were studied in this research work. X-ray diffraction was used to study the formation of structural phase CuO QDs and found to be single phasic without any impurity. Transmission electron microscopic measurements were performed to study the morphology of QDs of CuO, which confirms spherical QDs with an average diameter of ˜4nm. In optical studies, absorption spectra of the CuO were analyzed by using UV-visible spectroscopy.

  16. Education in 2020: The Nature of Teaching and Learning in the 21st Century. F.E.A. Research and Policy Brief

    Science.gov (United States)

    Storm, Jeanne

    2009-01-01

    The Future Educators Association[R] (FEA), sponsored by Phi Delta Kappa International, convened a group of distinguished education leaders to discuss the nature of teaching and learning in the year 2020. The year 2020 was selected because today's middle school students involved in FEA programs will begin teaching 11 years from now. The group was…

  17. The behavior and effect of CuO in Ag/SnO{sub 2} materials

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jun, E-mail: Wangjun1983@stu.xjtu.edu.cn [MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Science, Xi’an Jiaotong University, Xi’an 710049 (China); Liu, Wei, E-mail: 810779396@qq.com [MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Science, Xi’an Jiaotong University, Xi’an 710049 (China); Li, Dongmei, E-mail: 946346365@qq.con [MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Science, Xi’an Jiaotong University, Xi’an 710049 (China); Wang, Yaping, E-mail: ypwang@mail.xjtu.edu.cn [MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Science, Xi’an Jiaotong University, Xi’an 710049 (China); State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049 (China)

    2014-03-05

    Highlights: • The crystallized monoclinic CuO in CuO-doped SnO{sub 2} nanoparticles had formed. • The crystallized monoclinic CuO distributed on the surface of SnO{sub 2} nanoparticles. • Ag/SnO{sub 2} materials adding CuO exhibited denser microstructure and better hardness. • Ag/SnO{sub 2} materials adding CuO exhibited better arc erosion resistance. • The addition of CuO can obviously inhibited the spattering loss of molten droplet. -- Abstract: In this paper, the behavior of CuO in CuO-doped SnO{sub 2} nanoparticles was investigated; the effect of the addition of CuO on physical properties and arc erosion behavior of Ag/SnO{sub 2} materials were examined. The CuO-doped SnO{sub 2} nanoparticles were structurally characterized by X-ray diffraction (XRD) and High-resolution Transmission Electron Microscope (HR-TEM). The surface morphology of arc eroded Ag/SnO{sub 2} materials was characterized by Scanning Electron Microscope (SEM). The results indicated that the crystallized monoclinic CuO in CuO-doped SnO{sub 2} nanoparticles has formed and distributed on the surface of SnO{sub 2} nanoparticles. It was found that Ag/SnO{sub 2} materials adding CuO exhibited denser microstructure and better hardness as well as better arc erosion resistance compared with Ag/SnO{sub 2} materials. The arc erosion results and theoretical analysis indicated that the addition of CuO in Ag/SnO{sub 2} materials can obviously inhibited the spattering loss of molten droplets.

  18. Charge transport in single CuO nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Junnan; Yin, Bo; Wu, Fei; Myung, Yoon; Banerjee, Parag, E-mail: parag.banerjee@wustl.edu [Department of Mechanical Engineering and Materials Science, One Brookings Drive, Washington University, St. Louis, Missouri 63130 (United States)

    2014-11-03

    Charge transport in single crystal, p-type cupric oxide (CuO) nanowire (NW) was studied through temperature based (120 K–400 K) current-voltage measurements. CuO NW with a diameter of 85 nm was attached to Au electrodes 2.25 μm apart, using dielectrophoresis. At low electrical field (<0.89 × 10{sup 3 }V/cm), an ohmic conduction is observed with an activation energy of 272 meV. The injected electrons fill traps with an average energy, E{sub T} = 26.6 meV and trap density, N{sub T} = 3.4 × 10{sup 15 }cm{sup −3}. After the traps are saturated, space charge limited current mechanism becomes dominant. For 120 K ≤ T ≤ 210 K phonon scattering limits mobility. For T ≥ 220 K, a thermally activated mobility is observed and is attributed to small polaron hopping with an activation energy of 44 meV. This mechanism yields a hole mobility of 0.0015 cm{sup 2}/V s and an effective hole concentration of 4 × 10{sup 18 }cm{sup −3} at 250 K.

  19. Charge transport in single CuO nanowires

    Science.gov (United States)

    Wu, Junnan; Yin, Bo; Wu, Fei; Myung, Yoon; Banerjee, Parag

    2014-11-01

    Charge transport in single crystal, p-type cupric oxide (CuO) nanowire (NW) was studied through temperature based (120 K-400 K) current-voltage measurements. CuO NW with a diameter of 85 nm was attached to Au electrodes 2.25 μm apart, using dielectrophoresis. At low electrical field (conduction is observed with an activation energy of 272 meV. The injected electrons fill traps with an average energy, ET = 26.6 meV and trap density, NT = 3.4 × 1015 cm-3. After the traps are saturated, space charge limited current mechanism becomes dominant. For 120 K ≤ T ≤ 210 K phonon scattering limits mobility. For T ≥ 220 K, a thermally activated mobility is observed and is attributed to small polaron hopping with an activation energy of 44 meV. This mechanism yields a hole mobility of 0.0015 cm2/V s and an effective hole concentration of 4 × 1018 cm-3 at 250 K.

  20. Ultrathin willow-like CuO nanoflakes as an efficient catalyst for electro-oxidation of hydrazine

    Science.gov (United States)

    Ma, Yuanyuan; Li, Hao; Wang, Rongfang; Wang, Hui; Lv, Weizhong; Ji, Shan

    2015-09-01

    In this paper, preparation of ultrathin willow-like CuO nanoflakes via a one-step process was reported. X-ray diffraction pattern showed the formation of monoclinic CuO crystal, which was also confirmed by result of high resolution transmission electron microscopy. Scanning electron microscopy showed that ultrathin willow-like CuO nanoflakes were formed. Catalytic testing indicated that the ultrathin willow-like CuO nanoflakes exhibited high electrocatalytic activity and durability toward the electro-oxidation of hydrazine in alkaline medium. The results suggested that the as-prepared CuO nanoflakes were potential electrode materials for hydrazine fuel cell.

  1. Synthesis and concentration dependent antibacterial activities of CuO nanoflakes

    Energy Technology Data Exchange (ETDEWEB)

    Pandiyarajan, T.; Udayabhaskar, R. [Department of Physics, National Institute of Technology, Tiruchirappalli 620 015 (India); Vignesh, S.; James, R. Arthur [Department of Marine Science, Bharathidasan University, Tiruchirappalli 620 024 (India); Karthikeyan, B., E-mail: balkarin@yahoo.com [Department of Physics, National Institute of Technology, Tiruchirappalli 620 015 (India)

    2013-05-01

    We report, synthesis and antibacterial activities of CuO nanoflakes. CuO nanoparticles are prepared at room temperature through sol–gel method. X-ray diffraction studies show the particles are monoclinic (crystalline) in nature. Scanning electron microscopy (SEM) images clearly show that the prepared particles are flake like in structure. Fourier transform infrared (FTIR) spectra exhibits three different bands that correspond to the A{sub u} and B{sub u} modes. Antibacterial studies were performed on Shigella flexneri, Staphylococcus aureus, Staphylococcus epidermidis, Salmonella typhimurium, Bacillus subtilis, Escherichia coli, Vibrio cholera, Pseudomonas aeruginosa and Aeromonas liquefaciens bacterial strains. Among these bacterial strains, S. flexneri and B. subtilis are most sensitive to copper oxide nanoparticles than the positive control (Penicillin G) and S. typhimurium strain shows the less sensitive. Results show that sensitivity is highly dependent on the concentrations of CuO nanoflakes. - Highlights: ► CuO nanoflakes are prepared through simple sol–gel method at room temperature. ► Bacterial strains are highly affected by CuO nanoflakes than the positive control. ► Zone of inhibition increases with an increase of CuO concentrations. ► Sensitivity is highly dependent on the concentrations of CuO nanoflakes.

  2. Effects of CuO nanoparticles on compressive strength of self-compacting concrete

    Indian Academy of Sciences (India)

    Ali Nazari; Shadi Riahi

    2011-06-01

    In the present study, the compressive strength, thermal properties and microstructure of self-compacting concrete with different amounts of CuO nanoparticles have been investigated. CuO nanoparticles with an average particle size of 15 nm were added to self-compacting concrete and various properties of the specimens were measured. The results indicate that CuO nanoparticles are able to improve the compressive strength of self-compacting concrete and reverse the negative effects of superplasticizer on compressive strength of the specimens. CuO nanoparticles as a partial replacement of cement up to 4 wt.% could accelerate C–S–H gel formation as a result of the increased crystalline Ca(OH)2 amount at the early ages of hydration. Increasing CuO nanoparticle content to more than 4 wt.%, causes reduced compressive strength because of unsuitable dispersion of nanoparticles in the concrete matrix. Accelerated peak appearance in conduction calorimetry tests, more weight loss in thermogravimetric analysis and more rapid appearance of peaks related to hydrated products in X-ray diffraction results, all indicate that CuO nanoparticles up to 4 wt.% could improve the mechanical and physical properties of the specimens. Finally, CuO nanoparticles improved the pore structure of concrete and caused shifting of the distributed pores from harmless to low harm.

  3. Preparation and photocatalytic activities of 3D flower-like CuO nanostructures

    Science.gov (United States)

    Qingfei, Fan; Qi, Lan; Meili, Zhang; Ximei, Fan; Zuowan, Zhou; Chaoliang, Zhang

    2016-08-01

    Hierarchical 3D flower-like CuO nanostructures on the Cu substrates were synthesized by a wet chemical method and subsequent heat treatment. The synthesis, structure and morphologies of obtained samples under different concentrations of Na2S2O3 were investigated in detail and the possible growth mechanisms of the 3D flower-like CuO nanostructures were discussed. Na2S2O3 plays a key role in the generation of the 3D flower-like CuO nanostructures. When the concentration of Na2S2O3 is more than 0.4 mol/L, the 3D flower-like CuO nanostructures can be prepared on the Cu foils. The photocatalytic performances were studied by analyzing the degradation of methyl orange (MO) in aqueous solution in the presence of hydroxide water (H2O2). The 3D flower-like CuO nanostructures exhibit higher photocatalytic activity (96.2% degradation rate) than commercial CuO particles (36.3% degradation rate). The origin of the higher photocatalytic activity of the 3D flower-like CuO nanostructures was also discussed. Project supported by the High-Tech Research and Development Program of China (No. 2009AA03Z427).

  4. Surfactant-free Synthesis of CuO with Controllable Morphologies and Enhanced Photocatalytic Property

    OpenAIRE

    Wang, Xing; Yang, Jiao; Shi, Liuxue; Gao, Meizhen

    2016-01-01

    A green synthesis for nanoleave, nanosheet, spindle-like, rugby-like, dandelion-like and flower-like CuO nanostructures (from 2D to 3D) is successfully achieved through simply hydrothermal synthetic method without the assistance of surfactant. The morphology of CuO nanostructures can be easily tailored by adjusting the amount of ammonia and the source of copper. By designing a time varying experiment, it is verified that the flower- and dandelion-like CuO structures are synthesized by the sel...

  5. The reactions of CuO at high pressure and high temperature

    CERN Document Server

    Ren, G Z; Wang, X C; Ma, H A; Guo, X B; Liu, J T; Zou Guang Tian

    2002-01-01

    The decomposition behaviour of CuO is studied at high temperature and high pressure. Experimental pressure and temperature determine the result. In the region of higher temperature and pressure (>=5.5 GPa, >=1400 deg. C), the product is just copper. In the region of lower temperature and pressure (< 5.0 GPa, < 1100 deg. C), CuO does not decompose. Between the two regions, the product is a mixture of Cu and Cu sub 2 O or a mixture of Cu sub 2 O and CuO.

  6. Theory of phonon properties in doped and undoped CuO nanoparticles

    Science.gov (United States)

    Bahoosh, S. G.; Apostolov, A. T.; Apostolova, I. N.; Wesselinowa, J. M.

    2012-07-01

    We have studied the phonon properties of CuO nanoparticles and have shown the importance of the anharmonic spin-phonon interaction. The Raman peaks of CuO nanoparticles shift to lower frequency and become broader as the particle size decreases in comparison with those of bulk CuO crystals owing to size effects. By doping with different ions, in dependence of their radius compared to the host ionic radius the phonon energies ω could be reduced or enhanced. The phonon damping is always enhanced through the ion doping effects.

  7. Exchange bias effect in composites of cuo nanoparticles and nanosilica glass

    Science.gov (United States)

    Ranjan Saha, Dhriti; Kumar Nandi, Arun; Chakravorty, Dipankar

    2014-04-01

    Nanodimensional silica based glass containing iron ions was prepared within the compressed pellet of CuO nanoparicles. The nanocomposite material showed exchange bias effect. This effect arose due to ferromagnetic iron doped CuO phase and antiferromagnetic CuO interface formation within the nanocomposite during the synthesis process. Coercive field as a function of temperature was fitted with Arhenius-Neel equation and extracted blocking temperature was 511 K. The value of effective anisotropy constant for the nanocomposite was found to be 3.64x105 erg/cc.

  8. Transforming from paramagnetism to room temperature ferromagnetism in CuO by ball milling

    Directory of Open Access Journals (Sweden)

    Daqiang Gao

    2011-12-01

    Full Text Available In this work, we experimentally demonstrate that it is possible to induce ferromagnetism in CuO by ball milling without any ferromagnetic dopant. The magnetic measurements indicate that paramagnetic CuO is driven to the ferromagnetic state at room temperature by ball milling gradually. The saturation magnetization of the milled powders is found to increase with expanding the milling time and then decrease by annealing under atmosphere. The fitted X-ray photoelectron spectroscopy results indicate that the observed induction and weaken of the ferromagnetism shows close relationship with the valence charged oxygen vacancies (Cu1+-VO in CuO.

  9. Lattice dynamics of La 2CuO 4 and YBa 2Cu 3O 7

    Science.gov (United States)

    Kimura, Shunji; Sota, Takayuki; Suzuki, Katsuo

    1990-08-01

    We report lattice dynamics calculations of La 2CuO 4 and YBa 2Cu 3O 7 where the mode assignment is fully performed. It is found that frequencies of the in-plane bond streching 0 vibration mode phonons are much higher than those of the bond bending 0 vibration mode phonons in La 2CuO 4 while they are close in YBa 2Cu 3O 7. The bond streching mode phonons and the bond bending mode phonons can couple to electrons near E F in YBa 2Cu 3O 7 but the latter can not in La 2CuO 4.

  10. Density of states in La2CuO4+y

    Science.gov (United States)

    Gold, A.; Ghazali, A.

    1991-06-01

    We describe the excess holes in the CuO2 sheets of La2CuO4+y as a two-dimensional hole gas in a quantum well in the presence of negatively charged impurities. We calculate the density of states with a multiple-scattering approach. We discuss the broadening of the impurity band with increasing y, which corresponds to an increasing hole concentration. The spectral density, which describes for vanishing hole concentration the Fourier transform of the squared wave function, is evaluated. We compare our results with recent measurements of La2CuO4+y with y<0.007.

  11. Absence of dipolar ordering in Co doped CuO

    Science.gov (United States)

    Chaudhary, N. Vijay Prakash; Murthy, J. Krishna; Venimadhav, A.

    2016-12-01

    Polycrystalline CuO samples with Co doping were prepared by solid state method with flowing oxygen condition and examined their structural and multiferroic properties. Structural studies have confirmed single phase monoclinic crystal structure of all samples, however, in Co doped samples a decrease in volume with an increase in monoclinic distortion is found. For pristine sample, temperature dependent magnetization has confirmed two antiferromagnetic (AFM) transitions at 213 K and 230 K and frequency independent dielectric peaks at these AFM transitions suggesting the ferroelectric nature. Magnetization of the Co doped samples has showed a marginal increase in ordering temperature of the high-temperature AFM transition and decrease in low temperature AFM ordering temperature. Further, doped samples have shown giant dielectric constant with no signature of ferroelectricity. The X-ray photoelectric spectroscopy study has revealed multiple valance states for both Co and Cu in the doped samples that simultaneously explain the giant dielectric constant and suppression of ferroelectric order.

  12. FEA analysis of diamond as IMCA{close_quote}s monochromator crystal

    Energy Technology Data Exchange (ETDEWEB)

    Chrzas, J.; Cimpoes, S.; Ivanov, I.N. [CSRRI, Illinois Institute of Technology, 3301 S. Dearborn Street, Chicago, IL 60616 (United States)

    1996-09-01

    A great deal of effort has been make in recent years in the field of undulator high heat load optics, and currently there are several tractable options [Rev. Sci. Instrum. {bold 69}, 2792 (1994); Nucl. Instrum. Methods A {bold 266}, 517 (1988); Nucl. Instrum. Methods A {bold 239}, 555 (1993)]. Diamond crystals offer some attractive options{endash}water as the coolant, the use of established monochromator mechanisms, simpler monochromator design as compared to the use of liquid nitrogen or gallium. The use of diamond crystals as the optical elements in a double-crystal monochromator for the IMCA-CAT and MR-CAT ID beamlines has been studied. A first crystal mounting scheme using an indium-gallium eutectic as the heat transfer medium developed in collaboration with DND-CAT and M. Hart will be presented. A FEA analysis of the IMCA-CAT ID beamline arrangement using the APS undulator A as the radiaiton source will be presented. {copyright} {ital 1996 American Institute of Physics.}

  13. DETERMINATION OF VEHICLE COMPONENTS FATIGUE LIFE BASED ON FEA METHOD AND EXPERIMENTAL ANALYSIS

    Directory of Open Access Journals (Sweden)

    Arif Senol SENER

    2012-01-01

    Full Text Available In this study, construction and standardization of a track for performing fatigue and reliability test of light commercial vehicles is described. For the design and process verification of the company’s vehicles one test track is defined. A questionnaire was used to determine the average usage of light commercial vehicles in Turkey. Fatigue characteristics of Turkish roads were determined by analyzing fifty different roads and this article focuses on defining the load spectrum and equivalent fatigue damage of the leaf spring resulting from the accelerated test route. Fatigue analysis and estimated lifespan of the part were calculated using Finite Element Analyses and verified by the Palmgren-Miner rule. When the customer profile is taken into consideration; Turkish customer automotive usage profile, the aim of usage of this kind of vehicle (LCV, fatigue characteristics of Turkish roads for this vehicle were determined and around Bursa one accelerated test tracks were formed for the reliability and fatigue test for the related company, linear analysis executed on the FEA of the spring was more convenient were obtained.

  14. Computer aided FEA simulation of EN45A parabolic leaf spring

    Directory of Open Access Journals (Sweden)

    Krishan Kumar

    2013-04-01

    Full Text Available This paper describes computer aided finite element analysis of parabolic leaf spring. The present work is an improvement in design of EN45A parabolic leaf spring used by a light commercial automotive vehicle. Development of a leaf spring is a long process which requires lots of test to validate the design and manufacturing variables. A three-layer parabolic leaf spring of EN45A has been taken for this work. The thickness of leaves varies from center to the outer side following a parabolic pattern. These leaf springs are designed to become lighter, but also provide a much improved ride to the vehicle through a reduction on interleaf friction. The CAD modeling of parabolic leaf spring has been done in CATIA V5 and for analysis the model is imported in ANSYS-11 workbench. The finite element analysis (FEA of the leaf spring has been carried out by initially discretizing the model into finite number of elements and nodes and then applying the necessary boundary conditions. Maximum displacement, directional displacement, equivalent stress and weight of the assembly are the output targets of this analysis for comparison & validation of the work.

  15. Design Modification & Failure Analysis of a Driven Plate/Friction Plate of a Clutch using FEA.

    Directory of Open Access Journals (Sweden)

    Marella. Veerendra

    2014-10-01

    Full Text Available Clutch is device which is used to transmit power one component to another. It is a device used to connect the driving shaft to a driven shaft, so that the driven shaft may be started or stopped at will, without stopping the driving shaft. A clutch thus provides an interruptible connection between two rotating shafts Clutches allow a high inertia load to be stated with a small power. The engine power transmitted to the system through the clutch. The failure of such a critical component during service can stall the whole application. The objective of present project is to do analysis on driven plate of a clutch which is often fails during the operation. In this present research work analysis is conducted on driven plate of a clutch used in TATA Vehicle. There are so many complaints are noted against the failure of clutch during heavy loads. The driven main plate failed normally during its operation due to cyclic loading. For this reason we designed the driven plate and modeled in Pro-E and analyzed using FEA package in the process of designing and analyzing the actual design is changed to lower down the failure values. And the design may suggest to the company.

  16. Pathological changes in Alzheimer"s brain evaluated with fluorescence emission analysis (FEA)

    Science.gov (United States)

    Christov, Alexander; Ottman, Todd; Grammas, Paula

    2004-07-01

    Development of AD is associated with cerebrovascular deposition of amyloid beta (Aβ) as well as a progressive increase in vasular collagen content. Both AΒ and collagen are naturally fluorescent compounds when exposed to UV light. We analyzed autofluorescence emitted from brain tissue samples and isolated brain resistance vessels harvested postmortem from patients with Alzheimer's disease (AD) and age-matched controls. Fluorescence emission, excited at 355 nm with an Nd:YAG laser, was measured using a fiber-optic based fluorescence spectroscopic system for tissue analysis. Significantly higher values of fluorescence emission intensity (Pcollagen, and reduced levels of type IV collagen in resistance vessels from AD patients, compared to control samples. In addition, using direct scanning of the cortical suface for fluoresxcence emission by the laser-induced fluorescence spectroscopy system we detected a significantly (P<0.05) higher level of apoptosis in AD brain tissue compared to age-matched controls. Fluorescence emission analysis (FEA) appears to be a sensitive technique for detecting structural changes in AD brain tissue.

  17. Dynamic Vibration Analysis of Heavy Vehicle Truck Transmission Gearbox Housing Using FEA

    Directory of Open Access Journals (Sweden)

    Ashwani Kumar

    2014-09-01

    Full Text Available The main objective of this original research article is to study the loose fixture mounting affect of heavy vehicle transmission gearbox housing. The studies were completed in three phases. In first phase the aim was to find the actual suitable boundary condition. After finding the boundary condition in second phase the fixture bolts were loosened to monitor the affect of looseness and in third phase the positional looseness based study were completed. The looseness of transmission housing causes heavy vibration and noise. In order to prevent this noise and vibration the transmission housing is tightly mounted on the chassis frame using bolts. In our design transmission housing is constraint on chassis frame using 37 bolts. Truck transmission system determines the level of noise together with the chassis, engine and bodywork. Vehicle transmissions under torsional vibration condition caused rattling and clattering noises. Reciprocity Principle was used to determine the failure frequencies for transmission housing. In reciprocity principle gear and shafts are suppressed and all the forces transmitted through the bearings are applied on the empty housing. FEA based ANSYS 14.5 has been used as analysis tool. The free vibration frequency for zero displacement condition varies from 1669 Hz to 2865 Hz and for loose transmission casing frequency varies from 1311 Hz to 3110 Hz. The analysis have theoretical and practical aspects and useful for transmission housing structure optimization.

  18. Fatigue of Fillet-welded Joint Assessment by the FEA Simulation of Damage Accumulation

    Directory of Open Access Journals (Sweden)

    Petinov S. V.

    2011-06-01

    Full Text Available Fatigue strength evaluation of non-continuous incomplete penetration fillet-welded joints transferring stress flow by the S-N criteria incorporating the «Hot-spot stress» or «Notch-stress» approaches is dubious since the characteristic stress at the crack initiation location is not established by the rules for fatigue design. Application of the linear fracture mechanics (LMF technique meets a problem of numerical modeling the crack three-dimensional shape and front extension, which becomes insoluble when the crack approaches the outer surface of weld bead and propagates along the seam. Apart from that, considering material plasticity beyond the initial phase of crack extensions from the cavity is off the frames of the principles of the LMF.An approach based on the FEA simulation of fatigue damage accumulation is suggested and applied to evaluate the crack initiation at the cavity and propagation in the non-continuous fillet-welded joint. The crack initiation at the cavity, its three-dimensional shape formation and evolution are simulated taking into account the elastic-plastic cyclic deformation of weld material until almost complete failure of the joint. The results of analysis are in good agreement with published experimental data.

  19. Parametric CAD and Fea Model of a Saddle Tapping Tee

    DEFF Research Database (Denmark)

    A. Kristensen, Anders Schmidt; Lund Jepsen, Kristian

    2007-01-01

    pressure 30[bar]. A parametric verification model is established based on considerations regarding the compaction of the gasket and the stress level in the brackets of the clamp. The required minimum compaction pressure in the gasket is 1.4[N/mm] according to the European Norm for pressure vessels DS EN...... is determined from paragraph K302.3.2 in ASME B31.3. A full parametric 3D CAD model of the Saddle Tapping Tee is developed where a number of user-defined parameters are controlled from an Excel spreadsheet allowing parameter studies and technical documentation to be generated effectively. The same Excel spread......-sheet control a full 3D parametric FEA model which is automatically updated from the user-defined parameters set for the CAD-model. As the gasket is subjected to a contact pressure arising from the clamping force acting on the pipe section, a FE contact analysis is carried out. This contact analysis is set up...

  20. Effects of reduction of diameter on microstructure and surface roughness of rotary swaged magnesium by FEA

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Combining the processing maps with FEA,the critical values of reduction of diameter(△R)for the appearance of as-cast microstructure,dynamic recrystallization grains and twins in the swaged magnesium were respectively studied,by which the rational range of AR was obtained.To ensure that the as-cast microstructure wouldn't be retained in the rotary-swaged magnesium.△R shouldbe larger than 0.25 mill.To avoid the appearance of twins in the microstructure of rotary-swaged magnesium.△R should be less than 1.0 mm.△R should be between 0.25 mm and 1.0 mm to ensue the appearance of recrystallized grains.The surface roughness of rotary-swaged magnesium increases with the increase of △R by quadratic function.The simulated results accord well with the experimental data.In the process control of rotary-swaging(RS),△R should be maximized between 0.25 mm and 1.0 mm on the precondition that the requests for surface roughness have been satisfied.

  1. Structural and magnetic phase transitions in triclinic Ca10(FeAs)10(Pt3As8).

    Science.gov (United States)

    Stürzer, T; Friederichs, G M; Luetkens, H; Amato, A; Klauss, H-H; Johrendt, Dirk

    2013-03-27

    We report the structural and magnetic phase transitions of triclinic Ca10(FeAs)10(Pt3As8), which is the parent compound of the 1038-type iron-arsenide superconductors. High-resolution x-ray diffraction reveals splitting of the in-plane (a,b) lattice parameters at T(s) ≈ 120 K. Platinum-doping weakens the distortion and shifts the transition temperature to 80 K in Ca10(Fe(1-x)Pt(x)As)10(Pt3As8) with x = 0.03. μSR experiments show the onset of magnetic order near T and a broad magnetic phase transition. The structural transition involves no reduction of the space group symmetry in contrast to the other parent compounds of iron-arsenide superconductors; nevertheless the local fourfold symmetry of the FeAs-layers in Ca10(FeAs)10(Pt3As8) is broken.

  2. SELDI-TOF MS-based discovery of a biomarker in Cucumis sativus seeds exposed to CuO nanoparticles.

    Science.gov (United States)

    Moon, Young-Sun; Park, Eun-Sil; Kim, Tae-Oh; Lee, Hoi-Seon; Lee, Sung-Eun

    2014-11-01

    Metal oxide nanoparticles (NPs) can inhibit plant seed germination and root elongation via the release of metal ions. In the present study, two acute phytotoxicity tests, seed germination and root elongation tests, were conducted on cucumber seeds (Cucumis sativus) treated with bulk copper oxide (CuO) and CuO NPs. Two concentrations of bulk CuO and CuO NPs, 200 and 600ppm, were used to test the inhibition rate of root germination; both concentrations of bulk CuO weakly inhibited seed germination, whereas CuO NPs significantly inhibited germination, showing a low germination rate of 23.3% at 600ppm. Root elongation tests demonstrated that CuO NPs were much stronger inhibitors than bulk CuO. SELDI-TOF MS analysis showed that 34 proteins were differentially expressed in cucumber seeds after exposure to CuO NPs, with the expression patterns of at least 9 proteins highly differing from those in seeds treated with bulk CuO and in control plants. Therefore, these 9 proteins were used to identify CuO NP-specific biomarkers in cucumber plants exposed to CuO NPs. A 5977-m/z protein was the most distinguishable biomarker for determining phytotoxicity by CuO NPs. Principal component analysis (PCA) of the SELDI-TOF MS results showed variability in the modes of inhibitory action on cucumber seeds and roots. To our knowledge, this is the first study to demonstrate that the phytotoxic effect of metal oxide NPs on plants is not caused by the same mode of action as other toxins.

  3. Surfactant-free Synthesis of CuO with Controllable Morphologies and Enhanced Photocatalytic Property

    Science.gov (United States)

    Wang, Xing; Yang, Jiao; Shi, Liuxue; Gao, Meizhen

    2016-03-01

    A green synthesis for nanoleave, nanosheet, spindle-like, rugby-like, dandelion-like and flower-like CuO nanostructures (from 2D to 3D) is successfully achieved through simply hydrothermal synthetic method without the assistance of surfactant. The morphology of CuO nanostructures can be easily tailored by adjusting the amount of ammonia and the source of copper. By designing a time varying experiment, it is verified that the flower- and dandelion-like CuO structures are synthesized by the self-assembly and Ostwald ripening mechanism. Structural and morphological evolutions are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-visible diffuse reflectance spectra. Additionally, the CuO nanostructures with different morphologies could serve as a potential photocatalyst on the photodecomposition of rhodamine B (RhB) aqueous solutions in the presence of H2O2 under visible light irradiation.

  4. Solution-processable carboxylate-capped CuO nanoparticles obtained by a simple solventless method

    Science.gov (United States)

    Estruga, Marc; Roig, Anna; Domingo, Concepción; Ayllón, José A.

    2012-08-01

    Carboxylate-capped CuO nanoparticles were obtained via a simple solventless route, based on the thermal decomposition at 120 °C of solid precursors. The reaction mixture consisted of copper acetate monohydrate, acting as the CuO precursor, and different organic carboxylic acids (lauric, phenylvaleric or 3,6,9-trioxadecanoic acid) used as the capping agent. The proposed method, in good agreement with environmentally friendly practices, produced dry nanoparticles, thereby totally eliminating the need of washing, filtration, or other downstream steps. Transmission electron micrographs show crystalline roughly spherical CuO nanoparticles with average diameters between 3.1 and 5.5 nm depending on the capping ligand. The laurate-capped CuO nanoparticles showed a paramagnetic behaviour at room temperature, while a weak ferromagnetic component was detected at low temperature (acid tail enabled the straightforward dispersibility of nanoparticles in common solvents and assisted in the deposition of the material as thin films.

  5. Ultrasonochemical-Assisted Synthesis of CuO Nanorods with High Hydrogen Storage Ability

    Directory of Open Access Journals (Sweden)

    Gang Xiao

    2011-01-01

    Full Text Available Uniform CuO nanorods with different size have been synthesized in a water-alcohol solution through a fast and facile ultrasound irradiation assistant route. Especially, the as-prepared CuO nanorods have shown a strong size-induced enhancement of electrochemical hydrogen storage performance and exhibit a notable hydrogen storage capacity and big BET surface area. These results further implied that the as-prepared CuO nanorods could be a promising candidate for electrochemical hydrogen storage applications. The observation of the comparison experiments with different concentrations of NaOH, ethanol, CTAB, and HTMA while keeping other synthetic parameters unchanged leads to the morphology and size change of CuO products.

  6. Flower-like CuO synthesized by CTAB-assisted hydrothermal method

    Indian Academy of Sciences (India)

    Yunling Zou; Yan Li; Nan Zhang; Xiulin Liu

    2011-07-01

    Flower-like CuO nanostructures have been synthesized by cetyltrimethylammonium bromide (CTAB)-assisted hydrothermal method. Here, CuCl2.2H2O was used as copper raw material, and sodium hydroxide was used as precipitate. The resulting CuO powders were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). X-ray diffraction (XRD) pattern exhibited the nanocrystalline nature with monoclinic structure for the as-synthesized nanostructures. FESEM images indicated that the flower-like CuO nanostructures are composed of many interconnected nanosheets in size of several micrometres in length and width and 60–80 nm in thickness. The possible formation mechanism of flower-like CuO nanostructures was discussed.

  7. Enhanced reactive oxygen species overexpression by CuO nanoparticles in poorly differentiated hepatocellular carcinoma cells

    Science.gov (United States)

    Kung, Mei-Lang; Hsieh, Shu-Ling; Wu, Chih-Chung; Chu, Tian-Huei; Lin, Yu-Chun; Yeh, Bi-Wen; Hsieh, Shuchen

    2015-01-01

    Copper oxide nanoparticles (CuO NPs) are known to exhibit toxic effects on a variety of cell types and organs. To determine the oxidative impact of CuO NPs on hepatocellular carcinoma (HCC) cells, well-differentiated (HepG2) and poorly differentiated (SK-Hep-1) cells were exposed to CuO NPs. Cell viability assay showed that the median inhibition concentration (IC50) for SK-Hep-1 and HepG2 cells was 25 μg ml-1 and 85 μg ml-1, respectively. Cellular fluorescence intensity using DCFH-DA staining analysis revealed significant intracellular reactive oxygen species (ROS) generation of up to 242% in SK-Hep-1 cells, compared with 86% in HepG2 cells. HPLC analysis demonstrated that a CuO NP treatment caused cellular GSH depletion of 58% and a GSH/GSSG ratio decrease to ~0.1 in SK-Hep-1 cells. The oxidative stress caused by enhanced superoxide anion production was observed in both HepG2 (146%) and SK-Hep-1 (192%) cells. The Griess assay verified that CuO NPs induced NO production (170%) in SK-Hep-1 cells. Comet assay and western blot further demonstrated that CuO NPs induced severe DNA strand breakage (70%) in SK-Hep-1 cells and caused DNA damage via increased γ-H2AX levels. These results suggest that well-differentiated HepG2 cells possess a robust antioxidant defense system against CuO NP-induced ROS stress and exhibit more tolerance to oxidative stress. Conversely, poorly differentiated SK-Hep-1 cells exhibited a deregulated antioxidant defense system that allowed accumulation of CuO NP-induced ROS and resulted in severe cytotoxicity.Copper oxide nanoparticles (CuO NPs) are known to exhibit toxic effects on a variety of cell types and organs. To determine the oxidative impact of CuO NPs on hepatocellular carcinoma (HCC) cells, well-differentiated (HepG2) and poorly differentiated (SK-Hep-1) cells were exposed to CuO NPs. Cell viability assay showed that the median inhibition concentration (IC50) for SK-Hep-1 and HepG2 cells was 25 μg ml-1 and 85 μg ml-1, respectively

  8. Azide-Alkyne Huisgen [3+2] Cycloaddition Using CuO Nanoparticles

    Directory of Open Access Journals (Sweden)

    Hyunjoon Song

    2012-11-01

    Full Text Available Recent developments in the synthesis of CuO nanoparticles (NPs and their application to the [3+2] cycloaddition of azides with terminal alkynes are reviewed. With respect to the importance of click chemistry, CuO hollow NPs, CuO hollow NPs on acetylene black, water-soluble double-hydrophilic block copolymer (DHBC nanoreactors and ZnO–CuO hybrid NPs were synthesized. Non-conventional energy sources such as microwaves and ultrasound were also applied to these click reactions, and good catalytic activity with high regioselectivity was observed. CuO hollow NPs on acetylene black can be recycled nine times without any loss of activity, and water-soluble DHBC nanoreactors have been developed for an environmentally friendly process.

  9. The interplay between magnetism, structure, and strong electron-phonon coupling in binary FeAs under pressure

    Energy Technology Data Exchange (ETDEWEB)

    Jeffries, J R; Butch, N P; Cynn, H; Saha, S R; Kirshenbaum, K; Weir, S T; Vohra, Y K; Paglione, J

    2010-11-10

    Unlike the ferropnictide superconductors, which crystallize in a tetragonal crystal structure, binary FeAs forms in an orthorhombic crystal structure, where the local atomic environment resembles a highly distorted variant of the FeAs{sub 4} tetrahedral building block of the ferropnictide superconductors. However, like the parent compounds of the ferropnictide superconductors, FeAs undergoes magnetic ordering at low temperatures, with no evidence favoring a superconducting ground state at ambient pressure. We employ pressure-dependent electrical transport and x-ray diffraction measurements using diamond anvil cells to characterize the magnetic state and the structure as a function of pressure. While the structure persists up to 25 GPa, compressing continuously with pressure, magnetotransport measurements suggests that the magnetic state is destroyed near 11 GPa. The magnetic transition temperature is found to be remarkably robust under pressure, and transport measurements suggest that a dynamical structural instability coupled to the Fermi surface via a strong electron-phonon interaction may play an important role in enabling magnetism in FeAs.

  10. The interplay between magnetism, structure, and strong electron-phonon coupling in binary FeAs under pressure

    Energy Technology Data Exchange (ETDEWEB)

    Jeffries, J R; Butch, N P; Cynn, H; Saha, S R; Kirshenbaum, K; Weir, S T; Vohra, Y K; Paglione, J

    2010-11-10

    Unlike the ferropnictide superconductors, which crystallize in a tetragonal crystal structure, binary FeAs forms in an orthorhombic crystal structure, where the local atomic environment resembles a highly distorted variant of the FeAs{sub 4} tetrahedral building block of the ferropnictide superconductors. However, like the parent compounds of the ferropnictide superconductors, FeAs undergoes magnetic ordering at low temperatures, with no evidence favoring a superconducting ground state at ambient pressure. We employ pressure-dependent electrical transport and x-ray diffraction measurements using diamond anvil cells to characterize the magnetic state and the structure as a function of pressure. While the structure persists up to 25 GPa, compressing continuously with pressure, magnetotransport measurements suggests that the magnetic state is destroyed near 11 GPa. The magnetic transition temperature is found to be remarkably robust under pressure, and transport measurements suggest that a dynamical structural instability coupled to the Fermi surface via a strong electron-phonon interaction may play an important role in enabling magnetism in FeAs.

  11. Chlorination of iodide-containing waters in the presence of CuO: Formation of periodate

    KAUST Repository

    Liu, Chao

    2014-11-18

    It has been shown previously that the disproportionation of halogen-containing oxidants (e.g., HOCl, HOBr, and ClO2) is enhanced by a CuO-catalyzed process. In this study, the transformation of iodine during chlorination in the presence of CuO was investigated. There is no significant enhancement of the disproportionation of hypoiodous acid (HOI) in the presence of CuO. The formation rate of iodate (IO3 -) in the CuO-HOCl-I- system significantly increased when compared to homogeneous solutions, which was ascribed to the activation of HOCl by CuO enhancing its reactivity toward HOI. In this reaction system, iodate formation rates increase with increasing CuO (0-0.5 g L-1) and bromide (0-2 μM) doses and with decreasing pH (9.6-6.6). Iodate does not adsorb to the CuO surfaces used in this study. Nevertheless, iodate concentrations decreased after a maximum was reached in the CuO-HOCl-I-(-Br-) systems. Similarly, the iodate concentrations decrease as a function of time in the CuO-HOCl-IO3 - or CuO-HOBr-IO3 - system, and the rates increase with decreasing pH (9.6-6.6) due to the enhanced reactivity of HOCl or HOBr in the presence of CuO. It could be demonstrated that iodate is oxidized to periodate by a CuO-activated hypohalous acid, which is adsorbed on the CuO surface. No periodate could be measured in filtered solutions because it was mainly adsorbed to CuO. The adsorbed periodate was identified by scanning electron microscopy plus energy dispersive spectroscopy and X-ray photoelectron spectroscopy.

  12. Electronic anisotropy in single-crystal La2CuO4

    Science.gov (United States)

    Cheong, S.-W.; Fisk, Z.; Kwok, R. S.; Remeika, J. P.; Thompson, J. D.; Gruner, G.

    1988-04-01

    We have measured resistivity ρ components both parallel and perpendicular to the Cu-O planes in single-crystalline La2CuO4. Substantial anisotropy, reaching values as large as 103, is observed in the resistivity. The temperature dependence of ρ, together with Hall effect and thermoelectric power measurements, suggests hopping conduction between localized states at low temperatures, with diffusive transport at higher temperatures. These results are in contradistinction to previous reports.

  13. Chlorination of iodide-containing waters in the presence of CuO: formation of periodate.

    Science.gov (United States)

    Liu, Chao; Salhi, Elisabeth; Croué, Jean-Philippe; von Gunten, Urs

    2014-11-18

    It has been shown previously that the disproportionation of halogen-containing oxidants (e.g., HOCl, HOBr, and ClO2) is enhanced by a CuO-catalyzed process. In this study, the transformation of iodine during chlorination in the presence of CuO was investigated. There is no significant enhancement of the disproportionation of hypoiodous acid (HOI) in the presence of CuO. The formation rate of iodate (IO3(-)) in the CuO-HOCl-I(-) system significantly increased when compared to homogeneous solutions, which was ascribed to the activation of HOCl by CuO enhancing its reactivity toward HOI. In this reaction system, iodate formation rates increase with increasing CuO (0-0.5 g L(-1)) and bromide (0-2 μM) doses and with decreasing pH (9.6-6.6). Iodate does not adsorb to the CuO surfaces used in this study. Nevertheless, iodate concentrations decreased after a maximum was reached in the CuO-HOCl-I(-)(-Br(-)) systems. Similarly, the iodate concentrations decrease as a function of time in the CuO-HOCl-IO3(-) or CuO-HOBr-IO3(-) system, and the rates increase with decreasing pH (9.6-6.6) due to the enhanced reactivity of HOCl or HOBr in the presence of CuO. It could be demonstrated that iodate is oxidized to periodate by a CuO-activated hypohalous acid, which is adsorbed on the CuO surface. No periodate could be measured in filtered solutions because it was mainly adsorbed to CuO. The adsorbed periodate was identified by scanning electron microscopy plus energy dispersive spectroscopy and X-ray photoelectron spectroscopy.

  14. Hydrogen gas detection of Nb2O5 nanoparticle-decorated CuO nanorod sensors

    Science.gov (United States)

    Kheel, Hyejoon; Sun, Gun-Joo; Lee, Jae Kyung; Mirzaei, Ali; Choi, Seungbok; Lee, Chongmu

    2017-01-01

    Pristine and Nb2O5 nanoparticles-decorated CuO nanorods were prepared successfully by a two step process: the thermal evaporation of a Cu foil and the spin coating of NbCl5 solution on CuO nanorods followed by thermal annealing. X-ray diffraction was performed to examine the structure and purity of the synthesized nanoatuctures. Scanning electron microscopy was used to examine the morphology and shape of the nanostuctures. The Nb2O5 nanoparticles-decorated CuO nanorod sensor showed responses of 217.05-862.54%, response times of 161-199 s and recovery times of 163-171 s toward H2 gas with concentrations in a range of 0.5 - 5% at the optimal working temperature of 300 °C. The Nb2O5 nanoparticle-decorated CuO nanorod sensor showed superior sensing performance to the pristine CuO nanorod sensor for the same H2 concentration range. The underlying mechanism for the enhanced hydrogen sensing performance of the CuO nanorods decorated with Nb2O5 nanoparticles is discussed.

  15. Combination of CuO nanoparticles and fluconazole: preparation, characterization, and antifungal activity against Candida albicans

    Energy Technology Data Exchange (ETDEWEB)

    Weitz, Iris S., E-mail: irisweitz@braude.ac.il; Maoz, Michal; Panitz, Daniel [ORT Braude College, Department of Biotechnology Engineering (Israel); Eichler, Sigal; Segal, Ester [Technion – Israel Institute of Technology, Department of Biotechnology and Food Engineering (Israel)

    2015-08-15

    Combination therapy becomes an important strategy in the management of invasive fungal infections and emergence of resistant fungi mutants. In this work, we examine the combination of copper oxide (CuO) nanoparticles (NPs) with fluconazole as potential treatment against the pathogenic fungi, Candidaalbicans. CuO NPs (∼7 nm in size) were synthesized with acetate ligands assembled on their surface, as shown by both thermal gravimetric analysis and FTIR spectroscopy. Unlike the commercial CuO (both bulk and 50 nm particles), that are poorly dispersed in water, the interaction with water allows the fine dispersion of the coated CuO NPs and their excellent colloidal stability. The addition of fluconazole to the aqueous CuO dispersion induced spontaneous self-assembly of the NPs into linear pearl-like chains network, shown by cryogenic transmission electron microscopy (cryo-TEM). The antifungal activity of the CuO NPs and their combination with fluconazole (fluconazole–CuO NPs) was studied against C. albicans. The best MIC values were obtained at concentrations as low as 0.2 and 0.3 mg/mL, respectively. The results suggest that fluconazole–CuO NPs can provide a potential alternative treatment for C. albicans infections.

  16. Synthesis of CuO nanoflower and its application as a H2O2 sensor

    Indian Academy of Sciences (India)

    Aixia Gu; Guangfeng Wang; Xiaojun Zhang; Bin Fang

    2010-02-01

    CuO three-dimensional (3D) flower-like nanostructures were successfully synthesized by a simple method at 100°C with Cu(NO3)2.3H2O and NH3.H2O for 6 h in the absence of any additives. We found that NH3.H2O amount was critical for CuO morphology evolution. The phase analysis was carried out using X-ray diffraction (XRD) and the result confirmed that the CuO nanoflowers were single-phase. The morphological investigations by field emission scanning electron microscope (FESEM) revealed that the CuO nanoflowers were mono-dispersed in a large quantity and consisted of nanosheets. And then, CuO nanoflowers were successfully used to modify a gold electrode to detect H2O2 with cyclic voltammetry (CV) and amperometric (AC). It was found that CuO nanoflowers may be of great potential for H2O2 electrochemical sensing.

  17. RF sputtered CuO thin films: Structural, optical and photo-catalytic behavior

    Science.gov (United States)

    Al-Ghamdi, Attieh A.; Khedr, M. H.; Shahnawaze Ansari, M.; Hasan, P. M. Z.; Abdel-wahab, M. Sh.; Farghali, A. A.

    2016-07-01

    Nanocrystalline CuO thin films were deposited for 600, 1200 and 1800 s on glass substrate using RF magnetron sputtering technique. The films deposited at room temperature were crystalline and showed Tenorite phase of CuO. The increase in average particle size from 6.67 nm to 9.09 nm and the thickness from 160 nm to 490 nm was observed with the increase in deposition time. The optical band gap was decreased from 2.2 eV to 1.73 eV as the film thickness was increased. The intensity of PL peak showed its maximum for the film deposited for 600 s and minimum for 1800 s. Some unusual emission peaks were observed due to the quantization effect and lattice/surface defects. The CuO films with different thicknesses could be used as photo-catalysts for the degradation of Methylene blue (MB) from the wastewater. Under the exposure of 200 W energy of tungsten lamp, CuO thin films showed excellent photo-catalytic activities. CuO thin film of minimum thickness of around 160 nm responded as a best catalyst for MB degradation. The films were very stable and have a speciality to be recycled without much loss of their photo-catalytic activity. These characteristics have proved the high possibility of commercial applications of CuO thin films in environmental remediation.

  18. Synthesis and characterization of CuO nano particles using precipitation method

    Energy Technology Data Exchange (ETDEWEB)

    Malviya, Nitin; Oswal, Nidhi [Department of Applied Physics, Shri G.S. Institute of Technology & Science, Indore – 452003 (India); Carpenter, Gopal; Gupta, Nitish, E-mail: nitish.nidhi75@gmail.com [Department of Applied Chemistry, Shri G.S. Institute of Technology & Science, Indore-452003 (India)

    2015-06-24

    A simple and efficient synthesis of CuO nanoparticles was carried out by precipitation method using copper metal chips as precursor and sodium hydroxide as a stabilizing agent at different calcinations temperatures (100°C, 150°C, and 175°C). The products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier Transform Infrared Spectroscopy (FTIR). XRD indicated monoclinic structure of CuO. SEM indicated the variation in nanostructures with the heating temperatures and FTIR inidcated Cu-O stretching frequencies. The CuO nanostructures with the average particle size of about 16.52 nm were prepared at 100°C for 3 hr. When the calcinations temperature was increased to 150°C and 175°C, CuO nanostructures with the particle size of about 17.41 nm, and 18.44 nm were obtained respectively. This aqueous precipitation method can give a large scale production of CuO nanoparticles easily.

  19. Combination of CuO nanoparticles and fluconazole: preparation, characterization, and antifungal activity against Candida albicans

    Science.gov (United States)

    Weitz, Iris S.; Maoz, Michal; Panitz, Daniel; Eichler, Sigal; Segal, Ester

    2015-08-01

    Combination therapy becomes an important strategy in the management of invasive fungal infections and emergence of resistant fungi mutants. In this work, we examine the combination of copper oxide (CuO) nanoparticles (NPs) with fluconazole as potential treatment against the pathogenic fungi, Candida albicans. CuO NPs ( 7 nm in size) were synthesized with acetate ligands assembled on their surface, as shown by both thermal gravimetric analysis and FTIR spectroscopy. Unlike the commercial CuO (both bulk and 50 nm particles), that are poorly dispersed in water, the interaction with water allows the fine dispersion of the coated CuO NPs and their excellent colloidal stability. The addition of fluconazole to the aqueous CuO dispersion induced spontaneous self-assembly of the NPs into linear pearl-like chains network, shown by cryogenic transmission electron microscopy (cryo-TEM). The antifungal activity of the CuO NPs and their combination with fluconazole (fluconazole-CuO NPs) was studied against C. albicans. The best MIC values were obtained at concentrations as low as 0.2 and 0.3 mg/mL, respectively. The results suggest that fluconazole-CuO NPs can provide a potential alternative treatment for C. albicans infections.

  20. Fabrication of CuO nanoplatelets for highly sensitive enzyme-free determination of glucose

    Energy Technology Data Exchange (ETDEWEB)

    Wang Juan [School of Chemistry and Chemical Engineering, South China University of Technology, 381 Wushan Road, Guangzhou 510640 (China); Zhang Weide, E-mail: zhangwd@scut.edu.cn [School of Chemistry and Chemical Engineering, South China University of Technology, 381 Wushan Road, Guangzhou 510640 (China)

    2011-09-01

    Highlights: > Adhered growth of CuO nanoplatelets on Cu foils. > Enzyme-free glucose sensor with very high sensitivity. > Excellent stability and good anti-interference ability. - Abstract: CuO nanoplatelets were grown on Cu foils by a one step, template free process. The structure and morphology of the CuO nanoplatelets were characterized by X-ray diffraction, scanning and transmission electron microscopy. The CuO nanoplatelets grown on Cu foil were integrated to be an electrode for glucose sensing. The electrocatalytic activity of the CuO nanoplatelets electrode for glucose in alkaline media was investigated by cyclic voltammetry and chronoamperometry. The electrode exhibits a sensitivity of 3490.7 {mu}A mM{sup -1} cm{sup -2} to glucose which is much higher than that of most reported enzyme-free glucose sensors and the linear range was obtained over a concentration up to 0.80 mM with a detection limit of 0.50 {mu}M (signal/noise = 3). Exhilaratingly, the electrode based on the CuO nanoplatelets is resistant against poisoning by chloride ion, and the interference from the oxidation of common interfering species, such as uric acid, ascorbic acid, dopamine and carbonhydrate compounds, can also be effectively avoided. Finally, the electrode was applied to analyze glucose concentration in human serum samples.

  1. CuO nanoparticles: Synthesis, characterization, optical properties and interaction with amino acids

    Energy Technology Data Exchange (ETDEWEB)

    El-Trass, A.; ElShamy, H.; El-Mehasseb, I. [Nanochemistry Laboratory, Chemistry Department, Faculty of Science, Kafrelsheikh, University, 33516 Kafr ElSheikh (Egypt); El-Kemary, M., E-mail: elkemary@yahoo.com [Nanochemistry Laboratory, Chemistry Department, Faculty of Science, Kafrelsheikh, University, 33516 Kafr ElSheikh (Egypt)

    2012-01-15

    Cupric oxide (CuO) nanoparticles with an average size of 6 nm have been successfully prepared by an alcothermal method. The prepared CuO nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared (FT-IR) and UV-visible absorption spectroscopy. A strong sharp emission under UV excitation is reported from the prepared CuO nanoparticles. The results show that the CuO nanoparticles have high dispersion and narrow size distribution. The fluorescence emission spectra display an intense sharp emission at 365 nm and weak broad intensity emission at 470 nm. Picosecond fluorescence measurements of the nanoparticles suggest bi-exponential function giving time constants of {tau}{sub 1} (330 ps, 94.21%) and {tau}{sub 2} (4.69 ns, 5.79%). In neutral and alkaline solutions, Zeta potential values of CuO nanoparticles are negative, due to the adsorption of COO{sup -} group via the coordination of bidentate. At low pH the zeta potential value is positive due to the increased potential of H{sup +} ions in solution. Comparative UV-visible absorption experiments with the model amino acid compounds of positive and negative charges as arginine and aspartic acid, respectively confirmed the negative surface of CuO nanoparticles. The results should be extremely useful for understanding the mode of the interaction with biological systems. This binding process also affects the particle's behavior inside the body.

  2. Short-term effects on antioxidant enzymes and long-term genotoxic and carcinogenic potential of CuO nanoparticles compared to bulk CuO and ionic copper in mussels Mytilus galloprovincialis.

    Science.gov (United States)

    Ruiz, Pamela; Katsumiti, Alberto; Nieto, Jose A; Bori, Jaume; Jimeno-Romero, Alba; Reip, Paul; Arostegui, Inmaculada; Orbea, Amaia; Cajaraville, Miren P

    2015-10-01

    The aim of this work was to study short-term effects on antioxidant enzyme activities and long-term genotoxic and carcinogenic potential of CuO nanoparticles (NPs) in comparison to bulk CuO and ionic copper in mussels Mytilus galloprovincialis after 21 days exposure to 10 μg Cu L(-1). Then, mussels were kept for up to 122 days in clean water. Cu accumulation depended on the form of the metal and on the exposure time. CuO NPs were localized in lysosomes of digestive cells, as confirmed by TEM and X ray microanalysis. CuO NPs, bulk CuO and ionic copper produced different effects on antioxidant enzyme activities in digestive glands, overall increasing antioxidant activities. CuO NPs significantly induced catalase and superoxide dismutase activities. Fewer effects were observed in gills. Micronuclei frequency increased significantly in mussels exposed to CuO NPs and one organism treated with CuO NPs showed disseminated neoplasia. However, transcription levels of cancer-related genes did not vary significantly. Thus, short-term exposure to CuO NPs provoked oxidative stress and genotoxicity, but further studies are needed to determine whether these early events can lead to cancer development in mussels.

  3. Synthesis and characterization of CuO nanoparticles using strong base electrolyte through electrochemical discharge process

    Indian Academy of Sciences (India)

    PURUSHOTTAM KUMAR SINGH; PANKAJ KUMAR; MANOWAR HUSSAIN; ALOK KUMAR DAS; GANESH CHANDRA NAYAK

    2016-04-01

    In the present study, cupric oxide (CuO) nanoparticles were synthesized by electrochemical discharge process using strong base electrolytes. The experiments were carried out separately using NaOH and KOH electrolytes.The mass output rate and the crystal size were obtained with variation of the rotation speed of magnetic stirrer for both types of electrolytes. The mass output rate of CuO nanoparticles increased with the increase in the speed of rotation, and, after an optimum speed, it started decreasing. However, the size of the particles reduced with the increase of the rotation speed. The crystal plane of the obtained CuO nanoparticles was similar for both the electrolytes whereas the yield of nanoparticles was higher in KOH as compared with NaOH under the sameexperiment conditions. In this set of experiments, the maximum output rates obtained were 21.66 mg h$^{−1}$ for NaOH and 24.66 mg h$^{−1}$ for KOH at 200 rpm for a single discharge arrangement. The average crystal size of CuO particles obtained was in the range of 13–18 nm for KOH electrolyte and 15–20 nm for NaOH electrolyte. Scanning electron microscopy images revealed that flower-like and caddice clew-shaped CuO nanocrystalline particles weresynthesized by the electrochemical discharge process. Fourier transform infrared spectrum showed that the CuO nanoparticles have a pure and monolithic phase. UV–vis–NIR spectroscopy was used to monitor oxidation course of Cu→CuO and the band gap energy was measured as 2 and 2.6 eV for CuO nanoparticle synthesized in NaOH and KOH solutions, respectively.

  4. Synthesis and electrochemical properties of SnO2-CuO nanocomposite powders

    Institute of Scientific and Technical Information of China (English)

    MA Ming-you; HE Ze-qiang; XIAO Zhuo-bing; HUANG Ke-long; XIONG Li-zhi; WU Xian-ming

    2006-01-01

    SnO2-CuO nanocomposite powders were prepared by chemical coprecipitation method using SnCl4·5H2O, NH3·H2O and Cu(NO3)2·3H2O as raw materials. The powders were characterized by thermogravimertric(TG) analysis and differential thermal analysis(DTA), X-ray diffraction(XRD), and scanning electron microscope(SEM). The electrochemical properties of SnO2-CuO and undoped SnO2 powders as anode materials of lithium ion batteries were investigated comparatively by galvanostatic charge-discharge experiments and AC impedance. The results show that SnO2-CuO nanocomposite powders with the average particle size of 87 nm can be obtained by this method. The structure of SnO2 does not change with the introduction of CuO, but the average particle size of nano-SnO2 decreases. SnO2-CuO nanocomposite powders show a reversible capacity of 752 mA·h/g and better cycleability compared with nano-SnO2. The capacity retention rates after 60 cycles of nano-SnO2-CuO and SnO2 are 93.6% and 92.0% at the chargedischarge rate of 0.1 C, respectively, which suggests that the introduction of CuO into SnO2 can improve the cycleability of nanoSnO2.

  5. On the low-lying states of CuO

    Science.gov (United States)

    Bagus, P. S.; Nelin, C. J.; Bauschlicher, C. W., Jr.

    1984-01-01

    Self consistent field and correlated wave functions have been computed for the ground and for several low-lying states of CuO. The ground state is X(2)PI and the lowest excited state, at approximately 8,000/cm above X(2)PI, is a previously unidentified 2-sigma(+) state. The separation of these states is compared to that for the similar states of KO and is analysed in terms of integrals between orbitals of the separated free ions. A classification of the states of the molecule based on states of Cu(+) and O(-) which leads to a division into manifolds of states arising from Cu(+) 3d(10) and Cu(+) 3d(9) 4s(1) is considered. It is predicted that the state of the 3d(9) 4s(1) manifold are 10,000 to 30,000/cm above the ground state and assign the observed A2-sigma(+) state at 16,500/cm to this manifold.

  6. Beware the black box: investigating the sensitivity of FEA simulations to modelling factors in comparative biomechanics.

    Science.gov (United States)

    Walmsley, Christopher W; McCurry, Matthew R; Clausen, Phillip D; McHenry, Colin R

    2013-01-01

    Finite element analysis (FEA) is a computational technique of growing popularity in the field of comparative biomechanics, and is an easily accessible platform for form-function analyses of biological structures. However, its rapid evolution in recent years from a novel approach to common practice demands some scrutiny in regards to the validity of results and the appropriateness of assumptions inherent in setting up simulations. Both validation and sensitivity analyses remain unexplored in many comparative analyses, and assumptions considered to be 'reasonable' are often assumed to have little influence on the results and their interpretation. HERE WE REPORT AN EXTENSIVE SENSITIVITY ANALYSIS WHERE HIGH RESOLUTION FINITE ELEMENT (FE) MODELS OF MANDIBLES FROM SEVEN SPECIES OF CROCODILE WERE ANALYSED UNDER LOADS TYPICAL FOR COMPARATIVE ANALYSIS: biting, shaking, and twisting. Simulations explored the effect on both the absolute response and the interspecies pattern of results to variations in commonly used input parameters. Our sensitivity analysis focuses on assumptions relating to the selection of material properties (heterogeneous or homogeneous), scaling (standardising volume, surface area, or length), tooth position (front, mid, or back tooth engagement), and linear load case (type of loading for each feeding type). Our findings show that in a comparative context, FE models are far less sensitive to the selection of material property values and scaling to either volume or surface area than they are to those assumptions relating to the functional aspects of the simulation, such as tooth position and linear load case. Results show a complex interaction between simulation assumptions, depending on the combination of assumptions and the overall shape of each specimen. Keeping assumptions consistent between models in an analysis does not ensure that results can be generalised beyond the specific set of assumptions used. Logically, different comparative datasets would

  7. Nanostructured CuO thin film electrodes prepared by spray pyrolysis: a simple method for enhancing the electrochemical performance of CuO in lithium cells

    Energy Technology Data Exchange (ETDEWEB)

    Morales, J.; Sanchez, L. [Cordoba Univ. (Spain). Departamento de Qumica Inorganica e Ingenieria Quimica; Martin, F.; Ramos-Barrado, J.R.; Sanchez, M. [Malaga Univ. (Spain). Lab. de Materiales y Superficie

    2004-10-15

    Nanostructured CuO thin films were prepared by using a spray pyrolysis method, copper acetate as precursor and stainless steel as substrate. The textural and structural properties of the films were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The SEM images revealed thorough coating of the substrate and thickness of 450-1250 nm; the average particle size as determined from the AFM images ranged from 30 to 160 nm. The XRD patterns revealed the formation of CuO alone and the XPS spectra confirmed the presence of Cu{sup 2+} as the main oxidation state on the surface. The films were tested as electrodes in lithium cells and their electrochemical properties evaluated from galvanostatic and step potential electrochemical spectroscopy (SPES) measurements. The discharge STEP curves exhibited various peaks consistent with the processes CuO {r_reversible} Cu{sub 2}O {r_reversible}Cu and with decomposition of the electrolyte, a reversible process in the light of the AFM images. The best electrode exhibited capacity values of 625 Ah kg{sup -1} over more than 100 cycles. This value, which involves a CuO {r_reversible} Cu reversible global reaction, is Ca. 50% higher than that reported for bulk CuO. The nanosize of the particles and the good adherence of the active material to the substrate are thought to be the key factors accounting for the enhanced electrochemical activity found. (author)

  8. Safe-by-Design CuO Nanoparticles via Fe-Doping, Cu-O Bond Length Variation, and Biological Assessment in Cells and Zebrafish Embryos.

    Science.gov (United States)

    Naatz, Hendrik; Lin, Sijie; Li, Ruibin; Jiang, Wen; Ji, Zhaoxia; Chang, Chong Hyun; Köser, Jan; Thöming, Jorg; Xia, Tian; Nel, Andre E; Mädler, Lutz; Pokhrel, Suman

    2017-01-24

    The safe implementation of nanotechnology requires nanomaterial hazard assessment in accordance with the material physicochemical properties that trigger the injury response at the nano/bio interface. Since CuO nanoparticles (NPs) are widely used industrially and their dissolution properties play a major role in hazard potential, we hypothesized that tighter bonding of Cu to Fe by particle doping could constitute a safer-by-design approach through decreased dissolution. Accordingly, we designed a combinatorial library in which CuO was doped with 1-10% Fe in a flame spray pyrolysis reactor. The morphology and structural properties were determined by XRD, BET, Raman spectroscopy, HRTEM, EFTEM, and EELS, which demonstrated a significant reduction in the apical Cu-O bond length while simultaneously increasing the planar bond length (Jahn-Teller distortion). Hazard screening was performed in tissue culture cell lines and zebrafish embryos to discern the change in the hazardous effects of doped vs nondoped particles. This demonstrated that with increased levels of doping there was a progressive decrease in cytotoxicity in BEAS-2B and THP-1 cells, as well as an incremental decrease in the rate of hatching interference in zebrafish embryos. The dissolution profiles were determined and the surface reactions taking place in Holtfreter's solution were validated using cyclic voltammetry measurements to demonstrate that the Cu(+)/Cu(2+) and Fe(2+)/Fe(3+) redox species play a major role in the dissolution process of pure and Fe-doped CuO. Altogether, a safe-by-design strategy was implemented for the toxic CuO particles via Fe doping and has been demonstrated for their safe use in the environment.

  9. CONTRASTANDO AS PRODUÇÕES DA REVISTA CONTABILIDADE & FINANÇAS (FEA-USP E REVISTA BASE (UNISINOS

    Directory of Open Access Journals (Sweden)

    FLÁVIO DONIZETE BATISTELLA

    2008-01-01

    Full Text Available La reestructuración del sistema de evaluación de publicaciones de la Funda-ción Coordinación de Perfeccionamiento de Personal de Nivel Superior (CAPES, el Sistema Qualis, produjo un fuerte incentivo a la publicación de artículos en periódicos. Aprehender la fase de la producción en dos periódicos nacionales es el foco de esta averiguación. Estos periódicos son: Revista Contabilidade & Finanças (FEA-USP e Revista Base (UNISINOS. El período de análisis engloba las publicaciones ocurridas en 2005 y en 2006. Los aspectos observados por la CAPES en su proceso de eva-luación de periódicos son eminentemente orientados en la edición y compaginación del periódico. En este sentido, el análisis adoptado en esta pesquisa posee enfoque en la forma de los periódicos, siendo que la metodología central es fundamentada en el modelo propuesto por Krzyzanowski y Ferreira (1998. Los resultados logrados sugieren que la Revista Contabilidad & Finanzas (FEA-USP presenta, con relación al apartado forma, un desempeño general clasificado como bueno, mientras que la Revista Base (Unisinos presenta un desempeño mediano. Se observó también una mayor concentración de autores en las publicaciones de la Revista Contabilidad & Finanzas (FEA-Usp (recurrencia con relación a la Revista Base (UNISINOS.

  10. Nanostructured CuO Thin Films Prepared through Sputtering for Solar Selective Absorbers

    Directory of Open Access Journals (Sweden)

    Senthuran Karthick Kumar

    2013-01-01

    Full Text Available Nanostructured cupric oxide (CuO thin films have been deposited on copper (Cu substrates at different substrate temperatures and oxygen to argon gas ratios through direct current (DC reactive magnetron sputtering. The deposited CuO thin films are characterized by using X-ray diffraction (XRD, scanning electron microscopy (SEM, energy dispersive spectroscopy (EDS, profilometry, and spectrophotometry techniques. The crystalline phases, morphology, optical properties, and photothermal conversion efficiency of the CuO thin films are found to be significantly influenced by the change in substrate temperature and oxygen to argon gas ratio. The variations in the substrate temperature and oxygen to argon gas ratio have induced changes in Cu+ and Cu2+ concentrations of the CuO thin films that result in corresponding changes in their optical properties. The CuO thin film prepared at a substrate temperature of 30°C and O2 to Ar gas ratio of 1 : 1 has exhibited high absorptance and low emittance; thus, it could be used as a solar selective absorber in solar thermal gadgets.

  11. Optical and structural properties of CuO nanofilm: Its diode application

    Energy Technology Data Exchange (ETDEWEB)

    Erdogan, Ibrahim Y. [Bingoel University, Faculty of Sciences and Arts, Department of Chemistry, 12000 Bingoel (Turkey); Guellue, O., E-mail: omergullu@gmail.co [Batman University, Faculty of Sciences and Arts, Department of Physics, 72060 Batman (Turkey)

    2010-03-04

    The high crystalline CuO nanofilms have been prepared by spin coating and annealing combined with a simple chemical method. The obtained films have been characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, ultraviolet-vis (UV-vis) spectroscopy and photoluminescence (PL) spectroscopy. Structural analysis results demonstrate that the single phase CuO on Si (1 0 0) substrate is of high a crystalline structure with a dominant in monoclinic (1 1 1) orientation. FT-IR results confirm the formation of pure CuO phase. UV-vis absorption measurements indicate that the band gap of the CuO films is 2.64 eV. The PL spectrum of the CuO films shows a broad emission band centered at 467 nm, which is consistent with absorption measurement. Also, Au/CuO/p-Si metal/interlayer/semiconductor (MIS) diodes have been fabricated. Electronic properties (current-voltage) of these structures were investigated. In addition, the interfacial state properties of the MIS diode were obtained. The interface-state density of the MIS diode was found to vary from 6.21 x 10{sup 12} to 1.62 x 10{sup 12} eV{sup -1} cm{sup -2}.

  12. Cutin-derived CuO reaction products from purified cuticles and tree leaves

    Science.gov (United States)

    Goñi, Miguel A.; Hedges, John I.

    1990-11-01

    Long chain (C 16-C 18) hydroxy fatty acids are obtained among the nonlignin-derived reaction products from the CuO oxidation of a variety of geochemical samples. In order to investigate the origin of these acids, the CuO reaction products of isolated cuticles and whole leaves were investigated. The reaction products from the CuO oxidation of purified apple ( Malus pumila) cuticle include 16-hydroxy-hexadecanoic acid, 10,16-dihydroxyhexadecanoic acid, 9,10,18-trihydroxyoctadec-12-enoic acid, and 9,10,18-trihydroxyoctadecanoic acid as major components. The distribution of these cutin-derived CuO reaction products is similar to the monomer compositions deduced from traditional methods of cutin analysis. Oxidation of whole English Holly ( Ilex aquifolium) leaves yields cutin-derived acidic reaction products (in addition to lignin-derived phenols) similar to those obtained from oxidation of the corresponding isolated cuticles, indicating that CuO oxidation of bulk plant tissue is a viable procedure of cutin analysis in geochemical applications.

  13. Preparation and characterization of CuO catalyst for the thermolysis treatment of distillery wastewater.

    Science.gov (United States)

    Sharma, Deepak; Prajapati, Abhinesh Kumar; Choudhary, Rumi; Kaushal, Rajesh Kumar; Pal, Dharm; Sawarkar, Ashish N

    2017-08-16

    CuO catalyst was prepared from copper sulfate by alkali precipitation method followed by drying and calcination. Characterization of CuO catalyst using X-ray diffraction, Brunauer-Emmett-Teller, and Barrett-Joyner-Halenda surface area analysis envisaged the effectiveness of CuO as a catalyst for the treatment of biodigester effluent (BDE) emanated from distilleries. The catalytic thermolysis is an efficient advance treatment method for distillery biodigester effluent (BDE). CT treatment of BDE was carried out in a 0.5 dm(3) thermolytic batch reactor using CuO as a catalyst at different pH (1-9), temperatures (80-110°C), and catalyst loadings (1-4 kg/m(3)). With CuO catalyst, a temperature of 110°C, catalyst loading of 4 kg/m(3), and pH of 2 was found to be optimal, providing a maximum reduction in chemical oxygen demand of 65%. The settling characteristics at different temperatures of CT-treated sludge were also presented.

  14. Structural, optical and room-temperature ferromagnetic properties of Fe-doped CuO nanostructures

    Science.gov (United States)

    Mohamed Basith, N.; Judith Vijaya, J.; John Kennedy, L.; Bououdina, M.

    2013-09-01

    Pure CuO and Fe-doped CuO nanostructures with different weight ratios (0.5, 1.0, 1.5, and 2.0 at wt% of Fe) were synthesized via the microwave combustion method. The synthesized samples were characterized by X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy and vibrating sample magnetometry (VSM). XRD patterns refined by the Rietveld method indicated the formation of single-phase monoclinic structure and also confirmed that Fe ions successfully incorporated into CuO crystal lattice by occupying Cu ionic sites. Interestingly, the morphology was found to change considerably from nanoflowers to nano-rod and disk-shaped then to nanoparticles with the variation of Fe content. The optical band gap calculated using DRS was found to be 2.8 eV for pure CuO and increases up to 3.4 eV with increasing ‘Fe’ content. Photoluminescence measurements also confirm these results. The magnetic measurements indicated that the obtained nanostructures are found to be room temperature ferromagnetism (RTF) with an optimum value of saturation magnetization at 2.0 wt% of Fe-doped CuO, i.e. 1.2960×10-3 emu/g.

  15. CuO nanostructures: optical properties and morphology control by pyridinium-based ionic liquids.

    Science.gov (United States)

    Sabbaghan, Maryam; Shahvelayati, Ashraf Sadat; Madankar, Kamelia

    2015-01-25

    Copper oxide nanostructures have been synthesized by a simple reflux method in aqueous medium of pyridinium based ionic liquids. The structural and optical properties of CuO nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence spectroscopy (PL) and UV-visible. The morphologies of the nanostructures can be controlled by changing the amount of NaOH and ionic liquids. The results show that the use identical pyridinium based ionic liquids in ratio of 4:1 NaOH/Cu(OAc)2⋅H2O yield minor differences in morphology of CuO nanostructures. Different morphologies of CuO nanostructures were obtained by changing the ratio NaOH/Cu(OAc)2⋅H2O to 2:1. Ionic liquids play an important role on optical properties of CuO nanostructures. The results of optical measurements of the CuO nanostructures illustrate that band gaps are estimated to be 1.67-1.85 eV. PL patterns studies show that the ionic liquids can be effect on PL patterns of the samples. The reasons of these phenomena are discussed.

  16. Toxicity of CuO Nanoparticles to Structure and Metabolic Activity of Allium cepa Root Tips.

    Science.gov (United States)

    Deng, Fei; Wang, Shuling; Xin, Hua

    2016-11-01

    Roots of Allium cepa were exposed to six CuO NPs suspensions (0, 5, 10, 20, 40, 80 mg L(-1)) in this study. Results revealed that with the increase of CuO NPs concentration, the Cu content in roots increased significantly. Compared to control, onion roots treated with CuO NPs (except 5 mg L(-1) suspension) grew slowly after 24 h. The surface of the root cap and meristematic zone were obviously damaged. The apical meristem of roots treated by 10 mg L(-1) and above concentrations stopped division. The nucleus of meristematic cells deformed, and nucleoli number increased. The plasmolysis occurred, and the cell membrane and nuclear membrane fractured. With the increase of CuO NPs concentration, the MDA content increased, and the root activity decreased. When dealt with 80 mg L(-1) CuO NPs for 72 h, onion roots appeared to be corroded.

  17. Chemical Quenching of Positronium in CUO/Al2O3 Catalysts

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hong-Jun; LIU Zhe-Wen; CHEN Zhi-Quan; WANG Shao-Jie

    2011-01-01

    CuO/Al2O3 catalysts were prepared by mixing CuO and γ-Al2O3 nanopowders. Microstructure and chemical environment of the catalysts are characterized by positron annihilation spectroscopy. The positron annihilation lifetime measurements reveal two long lifetime components τ3 and τ4, which correspond to ortho-positronium (o-Ps) annihilating in microvoids and large pores, respectively. With increasing CuO content from 0 to 40 wt%, both τ4 and its intensity I4 show significant decrease, which indicates quenching effect of o-Ps. The para-positronium (p-Ps) intensities derived from multi-Gaussian fitting of the coincidence Doppler broadening spectra also decreases gradually with increasing CuO content. This excludes the possibility of spin-conversion of positronium. Therefore, the chemical quenching by CuO is probably responsible for the decrease of o-Ps lifetime. Variation in the o-Ps annihilation rate λ4 (1/τ4) as a function of CuO content can be well fitted by a straight line, and the slope of the fitting Jine is (1.83 ± 0.05) × 107 s-1.

  18. Direct electrochemistry of hemoglobin immobilized in CuO nanowire bundles.

    Science.gov (United States)

    Li, Yueming; Zhang, Qian; Li, Jinghong

    2010-11-15

    It is one of main challenges to find the suitable materials to enhance the direct electron transfer between the electrode and redox protein for direct electrochemistry field. Nano-structured metal oxides have attracted considerable interest because of unique properties, well biocompatibility, and good stability. In this paper, the copper oxide nanowire bundles (CuO NWBs) were prepared via a template route, and the bioelectrochemical performances of hemoglobin (Hb) on the CuO NWBs modified glass carbon electrodes (denoted as Hb-CuO NWBs/GC) were studied. TEM and XRD were used to characterize the morphology and structure of the as synthesized CuO NWBs. Fourier transform-infrared spectroscopy (FT-IR) proved that Hb in the CuO NWBs matrix could retain its native secondary structure. A pair of well-defined and quasi-reversible redox peaks at approximately -0.325 V (vs. Ag/AgCl saturated KCl) were shown in the cyclic voltammogram curve for the Hb-CuO NWBs/GC electrode, which indicated the direct electrochemical behavior. The Hb-CuO NWBs/GC electrode also displayed a good electrocatalytic activity toward the reduction of hydrogen peroxide. These results indicate that the CuO NWBs are good substrates for immobilization of biomolecules and might be promising in the fields of (bio) electrochemical analysis. Copyright © 2010 Elsevier B.V. All rights reserved.

  19. Facile synthesis of Zn doped CuO hierarchical nanostructures: Structural, optical and antibacterial properties

    Energy Technology Data Exchange (ETDEWEB)

    Iqbal, Javed, E-mail: tariqjan84@gmail.com, E-mail: javed.suggau@iiu.edu.pk; Jan, Tariq, E-mail: tariqjan84@gmail.com, E-mail: javed.suggau@iiu.edu.pk; Ul-Hassan, Sibt; Umair Ali, M.; Abbas, Fazal [Laboratory of Nanoscience and Technology, Department of Physics, International Islamic University, H-10, Islamabad (Pakistan); Ahmed, Ishaq [Experimental Physics Labs, National Center for Physics, Islamabad (Pakistan); Mansoor, Qaisar; Ismail, Muhammad [Institute of Biomedical and Genetic Engineering (IBGE), Islamabad (Pakistan)

    2015-12-15

    Zn{sub x}Cu{sub 1−x}O (where x= 0, 0.01, 0.03, 0.05, 0.07 and 0.1 mol%) hierarchical nanostructures have been prepared via soft chemical route. X-ray diffraction (XRD) results of the synthesized samples reveal the monoclinic structure of CuO without any impurity related phases. The micro-structural parameters such as crystallite size and microstrain have been strongly influenced by Zn doping. Scanning electron microscope (SEM) analyses depict the formation of hierarchical nanostructures having average particle size in the range of 26-43 nm. The surface area of CuO nanostructures has been reduced systematically with the increase in Zn content which is linked with the variations in particle size. An obvious decrease in the optical band gap energy of the synthesized CuO hierarchical nanostructures has been observed with Zn doping which is assigned to the formation of shallow levels in the band gap of CuO and combined transition from oxygen 2p states to d sates of Cu and Zn ions. The bactericidal potency of the CuO hierarchical nanostructures have been found to be enhanced remarkably with Zn doping.

  20. X-ray transmission through nanostructured and microstructured CuO materials

    Energy Technology Data Exchange (ETDEWEB)

    Botelho, M.Z. [Area de Ciencias Tecnologicas, Centro Universitario Franciscano, Rua dos Andradas, 1614, CEP 97010-032 Santa Maria, RS (Brazil); Kuenzel, R., E-mail: roselikunzel@gmail.co [Universidade de Sao Paulo, Instituto de Fisica, Departamento de Fisica Nuclear, Cidade Universitaria, CEP 05508-090 Sao Paulo, SP (Brazil); Okuno, E. [Universidade de Sao Paulo, Instituto de Fisica, Departamento de Fisica Nuclear, Cidade Universitaria, CEP 05508-090 Sao Paulo, SP (Brazil); Levenhagen, R.S. [Universidade Federal de Sao Paulo, Departamento de Ciencias Exatas e da Terra, Rua Arthur Ridel, 275, Jardim Eldorado, CEP 09941-510 Diadema, SP (Brazil); Basegio, T.; Bergmann, C.P. [Universidade Federal do Rio Grande do Sul, Escola de Engenharia, Departamento de Materiais, Avenida Osvaldo Aranha, 99, CEP 90035-190 Porto Alegre, RS (Brazil)

    2011-02-15

    This study presents a comparison of the X-ray transmission through microsized and nanosized materials. For this purpose CuO nanoparticles, with 13.4 nm average grain size, and CuO microparticles, with a mean particle size of 56{mu}m, were incorporated separately to beeswax in a concentration of 5%. Results show that the transmission through the above material plates with microsized and nanosized CuO was almost the same for X-ray beams generated at 60 and 102 kV tube voltages. However, for the radiation beams generated at 26 and 30 kV tube voltages the X-rays are more attenuated by the nanostructured CuO plates by a factor of at least 14%. Results suggest that the difference in the low energy range may be due to the higher number of particles/gram in the plates designed with CuO nanoparticles and due to the grain size effect on the X-ray transmission.

  1. Fine CuO anisotropic nanoparticles supported on mesoporous SBA-15 for selective hydrogenation of nitroaromatics.

    Science.gov (United States)

    Sareen, Shweta; Mutreja, Vishal; Singh, Satnam; Pal, Bonamali

    2016-01-01

    SBA-15 modified with APTMS (3-aminopropyl trimethoxysilane) having pore diameter (∼8 nm) has been synthesized and impregnated with 1-10 wt.% Cu using Cu(NO3)2 as a metal source followed by calcination at 350 °C. As-prepared CuO/ap-SBA-15 powder showed changes in the color from white for bare SBA-15 to light green due to formation of anisotropic CuO nanoparticles that exhibited a characteristic plasmon absorption band at 359 and 747 nm. TEM studies showed a change in the morphology of CuO NPs as a function of increased Cu loading. Moreover, well dispersed CuO nanospheres (∼5-6 nm) and nanorods (aspect ratio ∼11-20 nm) having monoclinic crystal phase were observed within the mesoporous channels of SBA-15. Elemental mapping studies confirmed uniform distribution of CuO nanoparticles on the surface of SBA-15. An increase in surface area was also observed from 694 m(2) g(-1) for SBA-15 to 762 m(2) g(-1) for 10 wt.% Cu loading probably due to the deposition of excess of CuO nanoparticles on the outer siliceous surface. The catalytic activity also increased with Cu loading and 10 wt.% CuO/ap-SBA-15 catalyst displayed the highest catalytic activity for the reduction of m-chloronitrobenzene and m-nitrotoluene with 83% and 100% selectivity for m-chloroaniline and m-aminotoluene respectively.

  2. Highly efficient photocatalytic activity of CuO quantum dot decorated rGO nanocomposites

    Science.gov (United States)

    Dutta, Shibsankar; Das, Kajari; Chakrabarti, Kaushik; Jana, D.; De, S. K.; De, Sukanta

    2016-08-01

    CuO quantum dots (QD) of size 4.5 nm decorated on a rGO sheet to form nanocomposites with different weight percentages via a simple soft chemical route was reported here. Tuning of CuO QD absorption towards the visible region from the UV region in the presence of rGO was also observed. The luminescence of rGO was found to be quenched in rGO-CuO nanocomposites due to charge transfer from the lowest unoccupied molecular orbital of the rGO layer to the conduction band of CuO. Systematic and concise studies of photocatalytic performance towards degradation of methylene blue (MB) dye by CuO QD along with rGO-CuO nanocomposites were presented in this work. A nanocomposite with an equal weight percentage of rGO and CuO degrades almost 99% of MB under irradiation of visible light for 50 min, showing maximum degradation efficiency.

  3. Translocation and biotransformation of CuO nanoparticles in rice (Oryza sativa L.) plants.

    Science.gov (United States)

    Peng, Cheng; Duan, Dechao; Xu, Chen; Chen, Yongsheng; Sun, Lijuan; Zhang, Hai; Yuan, Xiaofeng; Zheng, Lirong; Yang, Yuanqiang; Yang, Jianjun; Zhen, Xiangjun; Chen, Yingxu; Shi, Jiyan

    2015-02-01

    Metal-based nanoparticles (MNPs) may be translocated and biochemically modified in vivo, which may influence the fate of MNPs in the environment. Here, synchrotron-based techniques were used to investigate the behavior of CuO NPs in rice plants exposed to 100 mg/L CuO NPs for 14 days. Micro X-ray fluorescence (μ-XRF) and micro X-ray absorption near edge structure (μ-XANES) analysis revealed that CuO NPs moved into the root epidermis, exodermis, and cortex, and they ultimately reached the endodermis but could not easily pass the Casparian strip; however, the formation of lateral roots provided a potential pathway for MNPs to enter the stele. Moreover, bulk-XANES data showed that CuO NPs were transported from the roots to the leaves, and that Cu (II) combined with cysteine, citrate, and phosphate ligands and was even reduced to Cu (I). CuO NPs and Cu-citrate were observed in the root cells using soft X-ray scanning transmission microscopy (STXM).

  4. Comparison of FEA with condition monitoring for real-time damage detection of bearing using infrared thermography techniques

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Yoon Jae; Ranjit, Shrestha; Kim, Won Tae [Dept. of Mechanical and Automotive Engineering, Kongju National University, Cheonan(Korea, Republic of)

    2015-06-15

    Since real-time monitoring systems, such as early fault detection, have been very important, an infrared thermography technique was proposed as a new diagnosis method. This study focused on damage detection and temperature characteristic analysis of ball bearings using the non-destructive, infrared thermography method. In this paper, for the reliability assessment, infrared experimental data were compared with finite element analysis (FEA) results from ANSYS. In this investigation, the temperature characteristics of ball bearing were analyzed under various loading conditions. Finally, it was confirmed that the infrared thermography technique was useful for the real-time detection of damage to bearings.

  5. Study of some electronics properties of new superconductor Sr2VO3FeAs in ground state

    Directory of Open Access Journals (Sweden)

    M Majidiyan

    2010-09-01

    Full Text Available In this paper, some electronics properties of new superconductor Sr2VO3FeAs, such as density of states, band structure, density of electron cloud and bound lengths in the ground state have been calculated. According to N(Ef in ground state CV/T value has been estimated. The calculations were performed in the framework of density functional theory (DFT, using the full potential linearized augmented plane wave (FP-LAPW method with the general gradient approximation (GGA.

  6. Assessment, Problems and Ways of Improvement of Technical Regulation of Foreign Economic Activity (FEA in the World

    Directory of Open Access Journals (Sweden)

    Steblyanko Maryna D.

    2013-12-01

    Full Text Available The article analyses the state of technical regulation of FEA in the world and Ukraine and identifies main problems and ways of increase of efficiency of certification. It considers the system of technical regulation of EU and provides examples of application of technical barriers by some countries for ensuring security of goods in the domestic market. The article offers to develop a strategy of development of the national system of information provision of technical regulation and suspend transition from the system of mandatory certification to the system of assessment of correspondence with requirements of technical orders of business.

  7. Arsenic-bridged magnetic interactions in an emerging two-dimensional FeAs nanostructure on MnAs

    Science.gov (United States)

    Helman, Christian; Ferrari, Valeria; Llois, Ana Maria

    2015-08-01

    The extreme case of an Fe monolayer deposited onto a manganese arsenide (MnAs) substrate is analyzed using density functional theory. We find that an FeAs quasi-two-dimensional antiferromagnetic surface nanostructure emerges. This nanostructure, which is magnetically nearly decoupled from the substrate, is due to bonding effects arising from the arsenic atoms bridging the Fe magnetic interactions. These interactions are studied and modeled using a Heisenberg-type Hamiltonian. They display an angular dependence which is characteristic of superexchange-like interactions, which are of the same order of magnitude as those appearing in Fe-based pnictides.

  8. Green synthesis of copper oxide (CuO) nanoparticles using banana peel extract and their photocatalytic activities

    Science.gov (United States)

    Aminuzzaman, Mohammod; Kei, Leong Mei; Liang, Wong Hong

    2017-04-01

    Copper oxide nanoparticles (CuO NPs) are interesting class of materials having multifunctional properties with promising applications in the areas of catalysts, gas sensors, batteries, magnetic storage media, solar energy, superconductors etc. Thus synthesis of CuO NPs has attracted tremendous interest to scientists and researchers Herein, we reported a green and simple method for biosynthesizing CuO NPs using banana peel extract as reducing and stabilizing agent. XRD, EDX, FE-SEM, FTIR have been used for characterization of biosynthesized CuO NPs. The results indicating that the CuO NPs synthesized by banana peel extract have high purity and the average particles size is 60 nm. The photocatalytic activity of the CuO NPs has been investigated by degradation of Congo red (CR) dye under solar irradiation. The extent of CR dye degradation by CuO NPs is monitored by using a UV-visible spectrophotometer. Due to the smaller size and high purity, the biosynthesized CuO NPs showed an excellent photocatlytic activity.

  9. Improved electrochemical performances of CuO nanotube array prepared via electrodeposition as anode for lithium ion battery

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Anguo, E-mail: hixiaoanguo@126.com; Zhou, Shibiao; Zuo, Chenggang; Zhuan, Yongbing; Ding, Xiang

    2015-10-15

    Graphical abstract: CuO nanotube array electrodes prepared by electrodeposition method exhibit an excellent lithium ion storage ability as anode of Li-ion battery. - Highlights: • CuO nanotube arrays are synthesized by an electrodeposition method. • CuO nanotube shows a high-rate performance. • CuO nanotube shows an excellent cycling performance. - Abstract: We report a facile strategy to prepared CuO nanotube arrays directly grown on Cu plate through the electrodeposition method. The as-prepared CuO nanotubes show a quasi-cylinder nanostructure with internal diameters of ca. ∼100 nm, external diameters of ca. ∼120 nm, and average length of ∼3 μm. As an anode for lithium ion batteries, the electrochemical properties of the CuO nanotube arrays are investigated by cyclic voltammetry (CV) and galvanostatic charge/discharge tests. Due to the unique nanotube nanostructure, the as-prepared CuO electrodes exhibit good rate performance (550 mAh g{sup −1} at 0.1 C and 464 mAh g{sup −1} at 1 C) and cycling performance (581 mAh g{sup −1} at 0.1 C and 538 mAh g{sup −1} at 0.5 C)

  10. Inhibition of anaerobic wastewater treatment after long-term exposure to low levels of CuO nanoparticles.

    Science.gov (United States)

    Otero-González, Lila; Field, Jim A; Sierra-Alvarez, Reyes

    2014-07-01

    CuO nanoparticles (NPs) are released into wastewater due to the widespread use and generation as by-product in various applications (e.g. semiconductor manufacturing). However, information on the behavior and impact of CuO NPs on wastewater treatment processes is very limited. The objective of this study was to evaluate the fate and long-term effect of CuO NPs (average size = 37 nm) on high-rate anaerobic bioreactors. A laboratory-scale upflow anaerobic sludge blanket reactor was operated with a synthetic wastewater containing low concentrations of CuO NPs (1.4 mg Cu L(-1)) and a mixture of volatile fatty acids for 107 days. CuO NPs were largely removed during anaerobic treatment and on the average only 20-32% of the NPs fed to the reactor escaped with the effluent. Scanning electron microscopy and chemical analysis confirmed that CuO NPs were partitioned into the anaerobic sludge. While short-term exposure to CuO NPs (1.4 mg Cu L(-1)) only caused minor inhibition to methanogenesis, extended exposure caused severe toxicity and reduced the acetoclastic methanogenic activity by more than 85%. Moreover, the reactor performance was completely disrupted and the methane production decreased by more than 50%. The study is the first to demonstrate a significant long-term effect of low levels of CuO NPs on methanogenesis.

  11. Effect of CuO on the Formation Mechanism of Calcium Sulphoaluminate

    Institute of Scientific and Technical Information of China (English)

    MA Suhua; SHEN Xiaohong; HUANG Yeping; ZHONG Baiqian

    2008-01-01

    Calcium sulphoaluminate was prepared with chemical reagents in this paper.The formation mechanism of calcium sulphoaluminate and effect of CuO on the formation mechanism of calcium sulphoaluminate were investigated by the chemical analysis,X-ray diffraction(XRD),and differential scanning calorimetry(DSC).The results show that there are three ways in the formation of calcium sulphoaluminate.CuO can promote the decomposition of calcium carbonate and decrease the formation temperature of calcium sulphoaluminate(C4A3S).When the burning temperature is below 1000℃,the addition of CuO can promote the formation of calcium sulphoaluminate,while CuO can not favor the formation of calcium sulphoaluminate above 1000℃.

  12. Magnetodielectric effect in composites of nanodimensional glass and CuO nanoparticles

    Science.gov (United States)

    Ranjan Saha, Dhriti; Mukherjee, Manabendra; Chakravorty, Dipankar

    2012-11-01

    Nanocomposites comprising CuO particles of average diameter 21 nm coated with 5 nm silica glass containing iron ions were synthesized by a chemical route. An ion exchange reaction at the nanoglass/CuO interface produced iron-doped CuO with copper ion vacancies within the nanoparticles. Room temperature ferromagnetic-like behavior was observed in the nanocomposites. This was ascribed to uncompensated spins contributed by Fe ions with associated copper ion vacancies. A rather high value of magnetodielectric parameter in the range 16-26% depending on the measuring frequency was exhibited by these nanocomposites at a magnetic field of 10 KOe. This was caused by a magnetoresistance of 33% in the iron doped CuO nanoparticles. The experimental results were fitted to the Maxwell-Wagner Capacitor model developed by Catalan. These materials will be suited for magnetic sensor applications.

  13. Synthesis and Structural Study of Sr2CuO3+δ Superconductor under High Pressure

    Institute of Scientific and Technical Information of China (English)

    LIU Qing-Qing; WANG Fu-Ren; LI Feng-Ying; CHEN Liang-Chen; YU Ri-Cheng; JIN Chang-Qing; LI Yan-Chun; LIU Jing

    2008-01-01

    A single-phase Sr2CuO3+δ superconductor is synthesized under high temperature and high pressure, in which oxygen atoms only partially occupy the apical sites next to the CuO2 planes and act as hole-dopants. The superconducting transition temperature with Tcmax = 75 K is achieved in the material. Structure analysis from x-ray powder diffraction data show that this material crystallizes into a K2NiF4 structure with tetragonal unit cell of α = 3.795(3) (A) and c = 12.507(1) (A). Energy-dispersive synchrotron x-ray-diffraction studies at ambient are performed on powder samples of St2CuO3+δ in a diamond-anvil cell at pressure up to 35 GPa. Anisotropic compressibility is found. Pressure-induced isostructural phase transition might exist as revealed by the discontinuous change of crystal cell volume V with pressure.

  14. Electronic structure of CuO2 planes: From insulator to superconductor

    Science.gov (United States)

    Larosa, S.; Vobornik, I.; Zwick, F.; Berger, H.; Grioni, M.; Margaritondo, G.; Kelley, R. J.; Onellion, M.; Chubukov, A.

    1997-07-01

    Using angle-resolved photoemission and linearly polarized synchrotron radiation, we measured the electronic band structure of electronic states of CuO2 plane materials ranging from insulators (Sr2CuO2Cl2) to overdoped superconductors (Bi2Sr2CaCu2O8+x). We report three results: (i) The CuO2 containing insulator possesses a spin-density-wave (SDW) ground state; (ii) there are precursors of the SDW state for underdoped Bi2Sr2CaCu2O8+x; (iii) an extended saddle-point-type van Hove singularity is neither a necessary nor a sufficient condition for a high superconducting transition temperature, Tc.

  15. High performance HTPB-based energetic nanomaterial with CuO nanoparticles.

    Science.gov (United States)

    de la Fuente, José Luis; Mosquera, Gonzalo; París, Rodrigo

    2009-12-01

    This work describes the first example to demonstrate the enhancement of performances of composite highly energetic materials by mean of employing standard CuO nano-powder as burning rate catalyst in comparison to micro-fillers. The solid composite propellants with CuO microparticles are less stable due to oversensitivity to pressure variations, but the nano-structured composite propellant yields high stable burning rates over a broad pressure range. In addition, the incorporation of CuO nanoparticles in the formulations of these energetic materials also improves their combustion and thermal properties, according to the characterization obtained by differential scanning calorimetry (DSC) and thermogravimetry analysis (TGA). These results indicate the excellent benefits found in using these nanoparticles as additive for solid rocket propulsion applications.

  16. Structure and magnetic properties of Mn-doped CuO solids

    Institute of Scientific and Technical Information of China (English)

    FAN Chong-fei; PAN Li-qing; ZHU Hao; QIU Hong-mei; WANG Feng-ping; WU Ping; QIU Hong; ZHANG Yue; J. Q. XIAO

    2005-01-01

    The CuO doped with 5%-20% Mn(molar fraction) solids were sintered from CuO and MnO2 powder at high temperature (1 273 K) for 8 h. X-ray diffraction was used to determine the solid crystallinity and to address the formation of secondary phases. It is found that it is difficult to achieve pure Cu1-xMnxO phase using standard solid phase reaction. However, sintering under a pressure of 27.7 MPa significantly reduces the undesirable second phase CuMn2O4, providing a route to achieve pure Cu1-xMnx O phase. SQUID magnetometry was employed to characterize the magnetic properties. Mn-doped CuO presents ferromagnetic characteristics below 70 K. Electrical transport properties were measured in a current-perpendicular-to-plane(CPP) geometry using the PPMS, which suggests variable-range hopping mechanism.

  17. Nonlinear optical properties of laser deposited CuO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Chen Aiping [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China); Yang Guang, E-mail: gyang@mail.hust.edu.c [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China); Long Hua; Li Fang; Li Yuhua [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China); Lu Peixiang, E-mail: lupeixiang@mail.hust.edu.c [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2009-06-01

    In this work we investigate the third-order optical nonlinearities in CuO films by Z-scan method using a femtosecond laser (800 nm, 50 fs, 200 Hz). Single-phase CuO thin films have been obtained using pulsed laser deposition technique. The structure properties, surface image, optical transmittance and reflectance of the films were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy and UV-vis spectroscopy. The Z-scan results show that laser-deposited CuO films exhibit large nonlinear refractive coefficient, n{sub 2} = - 3.96 x 10{sup -17} m{sup 2}/W, and nonlinear absorption coefficient, {beta} = - 1.69 x 10{sup -10} m/W, respectively.

  18. Growth and humidity sensing properties of plate-like CuO nanostructures

    Science.gov (United States)

    Bayansal, F.; Çetinkara, H. A.; Çankaya, G.

    2014-03-01

    This paper describes a simple, low-temperature and cost-effective liquid-phase method to synthesize homogenous plate-like CuO nanostructures and their sensitivity to humidity. Scanning electron microscopy illustrated that the synthesized CuO nanoplates have thicknesses of ~100 nm. X-ray diffraction measurements showed that the CuO nanostructures have high crystallinity with monoclinic crystal structure preferentially in ? and ? directions. From the temperature-dependant dark electrical resistivity measurements, the ionization energies of the impurity levels and thermal band gap energies of the films are found as 0.30, 0.32 and 1.37, 1.39 for as-synthesized and annealed films, respectively. Gas sensing characteristics of the films were investigated for different concentrations of humidity, isopropyl alcohol, methanol, ethanol, chloroform and acetone vapours. It was found that the sensor is sensitive to humidity but not to the other volatile organic compounds.

  19. Organometallic Synthesis of CuO Nanoparticles: Application in Low-Temperature CO Detection.

    Science.gov (United States)

    Jońca, Justyna; Ryzhikov, Andrey; Palussière, Ségolène; Esvan, Jérome; Fajerwerg, Katia; Menini, Philippe; Kahn, Myrtil L; Fau, Pierre

    2017-08-24

    A metal-organic approach has been employed for the preparation of anisotropic CuO nanoparticles. These nanostructures have been characterized by transmission and high resolution transmission electron microscopy, field-emission scanning electron microscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The CuO nanoparticles have been deposited as gas-sensitive layers on miniaturized silicon devices. At an operating temperature of 210 °C, the sensors present an optimum response toward carbon monoxide correlated with a fast response (Rn) and short recovery time. A high sensitivity to CO (Rn≈150 %, 100 ppm CO, RH 50 %) is achieved. These CuO nanoparticles serve as a very promising sensing layer for the fabrication of selective CO gas sensors working at a low temperature. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Morphology- and facet-controlled synthesis of CuO micro/nanomaterials and analysis of their lithium ion storage properties

    Science.gov (United States)

    Liu, Xiaodi; Liu, Guangyin; Wang, Lijuan; Li, Yinping; Ma, Yupei; Ma, Jianmin

    2016-04-01

    Hierarchical CuO architectures and monodisperse CuO nanoplates are synthesized via a hydrothermal method with the assistance of ionic liquid 1-butyl-3-methylimidazolium chloride ([Bmim]Cl). The products are characterized by XRD, SEM, TEM, HRTEM, BET, and XPS, and the results indicate that the CuO architectures are composed of nanosheets with exposed (001) facets and the CuO nanoplates are single crystals enclosed by (200) facets. More specially, it is found that [Bmim]Cl serves as an effective template for the synthesis of CuO nanoplates by adsorbing on the (200) planes of monoclinic CuO. When evaluated as anode materials for lithium-ion batteries, CuO architectures possess higher discharge capacity, better cycling stability, and better rate capability than CuO nanoplates. The initial discharge capacity of CuO architectures is 1096 mAh g-1 at a rate of 0.5 C, whereas CuO nanoplates exhibit a lower capacity of 878.4 mAh g-1. Moreover, after 50 cycles, CuO architectures and CuO nanoplates can deliver discharge capacities of 465.6 and 281.6 mAh g-1, respectively.

  1. Low temperature synthesis of seed mediated CuO bundle of nanowires, their structural characterisation and cholesterol detection

    Energy Technology Data Exchange (ETDEWEB)

    Ibupoto, Z.H., E-mail: zafar.hussin.ibupoto@liu.se [Department of Science and Technology, Linköping University, Campus Norrköping, SE-60174 Norrköping (Sweden); Khun, K. [Department of Science and Technology, Linköping University, Campus Norrköping, SE-60174 Norrköping (Sweden); Liu, X. [Department of Physics, Chemistry, and Biology (IFM), Linköping University, 58183 Linköping Sweden (Sweden); Willander, M. [Department of Science and Technology, Linköping University, Campus Norrköping, SE-60174 Norrköping (Sweden)

    2013-10-15

    In this study, we have successfully synthesised CuO bundle of nanowires using simple, cheap and low temperature hydrothermal growth method. The growth parameters such as precursor concentration and time for duration of growth were optimised. The field emission scanning electron microscopy (FESEM) has demonstrated that the CuO bundles of nanowires are highly dense, uniform and perpendicularly oriented to the substrate. The high resolution transmission electron microscopy (HRTEM) has demonstrated that the CuO nanostructures consist of bundle of nanowires and their growth pattern is along the [010] direction. The X-ray diffraction (XRD) technique described that CuO bundle of nanowires possess the monoclinic crystal phase. The surface and chemical composition analyses were carried out with X-ray photoelectron spectroscopy (XPS) technique and the obtained results suggested the pure crystal state of CuO nanostructures. In addition, the CuO nanowires were used for the cholesterol sensing application by immobilising the cholesterol oxidase through electrostatic attraction. The infrared reflection absorption spectroscopy study has also revealed that CuO nanostructures are consisting of only Cu-O bonding and has also shown the possible interaction of cholesterol oxidase with the sharp edge surface of CuO bundle of nanowires. The proposed cholesterol sensor has demonstrated the wide range of detection of cholesterol with good sensitivity of 33.88 ± 0.96 mV/decade. Moreover, the CuO bundle of nanowires based sensor electrode has revealed good repeatability, reproducibility, stability, selectivity and a fast response time of less than 10 s. The cholesterol sensor based on the immobilised cholesterol oxidase has good potential applicability for the determination of cholesterol from the human serum and other biological samples. - Highlights: • This study describes the synthesis of bundle of CuO nanowires by hydrothermal method. • CuO nanostructures exhibit good alignment and

  2. Enhanced stability and dissolution of CuO nanoparticles by extracellular polymeric substances in aqueous environment

    Energy Technology Data Exchange (ETDEWEB)

    Miao, Lingzhan; Wang, Chao; Hou, Jun, E-mail: hhuhjyhj@126.com; Wang, Peifang; Ao, Yanhui; Li, Yi; Lv, Bowen; Yang, Yangyang; You, Guoxiang; Xu, Yi [Hohai University, Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes, Ministry of Education (China)

    2015-10-15

    Stability of engineered nanoparticles in aquatic environment is an essential parameter to evaluate their fate, bioavailability, and potential toxic effects toward living organisms. As CuO NPs enter the wastewater systems, they will encounter extracellular polymeric substances (EPS) from microbial community before directly interacting with bacterial cells. EPS may play an important role in affecting the stability and the toxicity of CuO NPs in aquatic environment. In this study, the influences of flocculent sludge-derived EPS, as well as model protein (BSA) and natural polysaccharides (alginate) on the dissolution kinetics and colloidal stability of CuO NPs were investigated. Results showed that the presence of NOMs strongly suppressed CuO NPs aggregation, confirmed by DLS, zeta potentials, and TEM analysis. The enhanced stability of CuO NPs in the presence of EPS and alginate were attributed to the electrostatic combined with steric repulsion, while the steric-hindrance effect may be the predominant mechanism retarding nano-CuO aggregation for BSA. Higher degrees of copper release were achieved with the increasing concentrations of NOMs. EPS are more effective than alginate and BSA in releasing copper, probably due to the abundant functional groups and the excellent metal-binding capacity. The ratio of free-Cu{sup 2+}/total dissolved Cu significantly decreased in the presence of EPS, indicating that EPS may affect the speciation and Cu bioavailability in aqueous environment. These results may be important for assessing the fate and transport behaviors of CuO NPs in the environment as well as for setting up usage regulation and treatment strategy.

  3. Local and CMOS-compatible synthesis of CuO nanowires on a suspended microheater on a silicon substrate.

    Science.gov (United States)

    Zhang, Kaili; Yang, Yang; Pun, E Y B; Shen, Ruiqi

    2010-06-11

    This paper presents the synthesis of CuO nanowires using a localized thermal heating method in ambient air. It employs local heat sources defined in micro-resistive heaters fabricated by a standard polysilicon-based surface micromachining process instead of a global furnace heating. Since the synthesis is performed globally at room temperature, the presented process is compatible with standard CMOS. The synthesized CuO nanowires are characterized by scanning electron microscopy, transmission electron microscopy and high resolution transmission electron microscopy. It is found that this approach provides a simple method to locally synthesize suspended CuO nanowires on polysilicon microbridges on silicon substrates, thus allowing for integration of CuO nanowires into silicon-based devices. It provides a significant step towards the process integration of CuO nanowires with MEMS to realize functional devices.

  4. Facile synthesis of Fe-incorporated CuO nanoarrays with enhanced electrochemical performance for lithium ion full batteries

    Energy Technology Data Exchange (ETDEWEB)

    Heng, Bojun [Institute of Nano-science and Technology, Central-China Normal University, Wuhan, 430079 (China); Department of Applied Physics, Wuhan University of Science and Technology, Wuhan, 430065 (China); Qing, Chen; Wang, Hai; Sun, Daming; Wang, Bixiao [Institute of Nano-science and Technology, Central-China Normal University, Wuhan, 430079 (China); Tang, Yiwen, E-mail: ywtang@phy.ccnu.edu.cn [Institute of Nano-science and Technology, Central-China Normal University, Wuhan, 430079 (China)

    2015-11-15

    CuO nanoarrays (CNAs) and Fe-incorporated CuO nanoarrays (FCNAs) were fabricated by hydrothermal method. Addition of Fe salt to the reaction mixture allowed the introduction of iron oxide onto the CNAs surface, which was characterized by XPS and HRTEM. Introducing Fe ion into reaction precursor significantly affected not only the morphologies of as-prepared products but also their electrochemical performance as anode for lithium ion full battery. The FCNAs electrodes showed higher specific capacity and better capacity retention at different current densities than that of CNAs. - Highlights: • Fe-incorporated CuO nanoarrays were fabricated by hydrothermal method. • Fe salt in reaction mixture leads to iron oxides forming on the surface of CuO. • Fe-incorporating improves the lithium ion battery performance of CuO anodes.

  5. Cumene Liquid Oxidation to Cumene Hydroperoxide over CuO Nanoparticle with Molecular Oxygen under Mild Condition

    Institute of Scientific and Technical Information of China (English)

    Meiying Zhang; Lefu Wang; Hongbing Ji; Bing Wu; Xiaoping Zeng

    2007-01-01

    CuO nanoparticle was synthesized via wet chemical method and was characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption, and scanning electron microscopy (SEM). Catalytic oxidation of cumene with molecular oxygen was studied over CuO nanoparticle. The catalysts showed markedly higher activities as compared to CuO prepared by conventional method, CUO/AI2O3, or homogeneous copper catalyst under comparable reaction conditions. The cumene conversion, cumene hydroperoxide (CHP) yield, and selectivity using 0.25 g CuO nanoparticle catalyst and 0.1 mol cumene at 358 K for 7 h were 44.2%, 41.2% and 93.2%, respectively. The catalyst can be recycled. After 6 recycled experiments, no loss of catalytic activity was observed.

  6. Multi-functional CuO nanowire/TiO2 nanotube arrays photoelectrode synthesis, characterization, photocatalysis and SERS applications.

    Science.gov (United States)

    Sheng, Pengtao; Li, Weili; Du, Pengwei; Cao, Kesheng; Cai, Qingyun

    2016-11-01

    Vertically aligned single crystalline CuO nanowire arrays (NWs) grown directly on TiO2 nanotube arrays (NTAs) supporting by Ti foil have been successfully fabricated using facile thermal oxidation of Cu nanocrystals in static air. CuO NWs growth behavior dependent on parent Cu nanocrystals sizes has been well investigated. Mass transport channel of Cu ions in horizontal and vertical for supporting CuO NWs diameter and length changes has been confirmed through a novel step-by-step surface diffusion process. CuO NWs, nano-mushrooms and nanosheets can be easily obtained by varying growth conditions. After photocatalytic synthesis of snow-like Ag nanocrystals upon CuO NWs/TiO2 NTAs, the hybrid photoelectrode exhibits superior catalytic property and detection sensitivity, which can clean themselves by photocatalytic degradation of RhB molecules adsorbed to the substrate under irradiation using surface enhanced Raman scattering (SERS) detection, a recycling can been achieved.

  7. Influence of specimens' design and manufacturing process on microtensile bond strength to enamel: laboratory and FEA comparison

    Directory of Open Access Journals (Sweden)

    Fernanda Tranchesi Sadek

    2010-06-01

    Full Text Available This study evaluated the effect of specimens' design and manufacturing process on microtensile bond strength, internal stress distributions (Finite Element Analysis - FEA and specimens' integrity by means of Scanning Electron Microscopy (SEM and Laser Scanning Confocal Microscopy (LCM. Excite was applied to flat enamel surface and a resin composite build-ups were made incrementally with 1-mm increments of Tetric Ceram. Teeth were cut using a diamond disc or a diamond wire, obtaining 0.8 mm² stick-shaped specimens, or were shaped with a Micro Specimen Former, obtaining dumbbell-shaped specimens (n = 10. Samples were randomly selected for SEM and LCM analysis. Remaining samples underwent microtensile test, and results were analyzed with ANOVA and Tukey test. FEA dumbbell-shaped model resulted in a more homogeneous stress distribution. Nonetheless, they failed under lower bond strengths (21.83 ± 5.44 MPac than stick-shaped specimens (sectioned with wire: 42.93 ± 4.77 MPaª; sectioned with disc: 36.62 ± 3.63 MPa b, due to geometric irregularities related to manufacturing process, as noted in microscopic analyzes. It could be concluded that stick-shaped, nontrimmed specimens, sectioned with diamond wire, are preferred for enamel specimens as they can be prepared in a less destructive, easier, and more precise way.

  8. Improving the correlation of structural FEA models by the application of automated high density robotized laser Doppler vibrometry

    Science.gov (United States)

    Chowanietz, Maximilian; Bhangaonkar, Avinash; Semken, Michael; Cockrill, Martin

    2016-06-01

    Sound has had an intricate relation with the wellbeing of humans since time immemorial. It has the ability to enhance the quality of life immensely when present as music; at the same time, it can degrade its quality when manifested as noise. Hence, understanding its sources and the processes by which it is produced gains acute significance. Although various theories exist with respect to evolution of bells, it is indisputable that they carry millennia of cultural significance, and at least a few centuries of perfection with respect to design, casting and tuning. Despite the science behind its design, the nuances pertaining to founding and tuning have largely been empirical, and conveyed from one generation to the next. Post-production assessment for bells remains largely person-centric and traditional. However, progressive bell manufacturers have started adopting methods such as finite element analysis (FEA) for informing and optimising their future model designs. To establish confidence in the FEA process it is necessary to correlate the virtual model against a physical example. This is achieved by performing an experimental modal analysis (EMA) and comparing the results with those from FEA. Typically to collect the data for an EMA, the vibratory response of the structure is measured with the application of accelerometers. This technique has limitations; principally these are the observer effect and limited geometric resolution. In this paper, 3-dimensional laser Doppler vibrometry (LDV) has been used to measure the vibratory response with no observer effect due to the non-contact nature of the technique; resulting in higher accuracy measurements as the input to the correlation process. The laser heads were mounted on an industrial robot that enables large objects to be measured and extensive data sets to be captured quickly through an automated process. This approach gives previously unobtainable geometric resolution resulting in a higher confidence EMA. This is

  9. CHARACTERISATION OF Cr DOPED CuO NANOPARTICLES AND ITS PERFORMANCE IN SOLAR CELL

    OpenAIRE

    2016-01-01

    Pure and Cr2+doped Copper oxide (CuO) nanoparticles were synthesized by simple precipitation method and subjected to photovoltaic activity by forming nanopowder –thin film as light absorbing  layer  on an  indigenously fabricated heterojunction by Doctor-Blade method.  Effect of concentration of the dopant (2, 4, and 6 mol%)  on the properties of CuO was analyzed from X-Ray Diffraction pattern (XRD), Scanning Electron Microscopy(SEM) Energy Dispersive Analysis (EDAX), UV-Vis studies and Photo...

  10. Archetypal sandwich-structured CuO for high performance non-enzymatic sensing of glucose.

    Science.gov (United States)

    Meher, Sumanta Kumar; Rao, G Ranga

    2013-03-07

    In the quest to enhance the selectivity and sensitivity of novel structured metal oxides for electrochemical non-enzymatic sensing of glucose, we report here a green synthesis of unique sandwich-structured CuO on a large scale under microwave mediated homogeneous precipitation conditions. The physicochemical studies carried out by XRD and BET methods show that the monoclinic CuO formed via thermal decomposition of Cu(2)(OH)(2)CO(3) possesses monomodal channel-type pores with largely improved surface area (~43 m(2) g(-1)) and pore volume (0.163 cm(3) g(-1)). The fascinating surface morphology and pore structure of CuO is formulated due to homogeneous crystallization and microwave induced self assembly during synthesis. The cyclic voltammetry and chronoamperometry studies show diffusion controlled glucose oxidation at ~0.6 V (vs. Ag/AgCl) with extremely high sensitivity of 5342.8 μA mM(-1) cm(-2) and respective detection limit and response time of ~1 μM and ~0.7 s, under a wide dynamic concentration range of glucose. The chronoamperometry measurements demonstrate that the sensitivity of CuO to glucose is unaffected by the absence of dissolved oxygen and presence of poisoning chloride ions in the reaction medium, which essentially implies high poison resistance activity of the sandwich-structured CuO. The sandwich-structured CuO also shows insignificant interference/significant selectivity to glucose, even in the presence of high concentrations of other sugars as well as reducing species. In addition, the sandwich-structured CuO shows excellent reproducibility (relative standard deviation of ~2.4% over ten identically fabricated electrodes) and outstanding long term stability (only ~1.3% loss in sensitivity over a period of one month) during non-enzymatic electrochemical sensing of glucose. The unique microstructure and suitable channel-type pore architecture provide structural stability and maximum accessible electroactive surface for unimpeded mobility of glucose

  11. Outcome of temperature variation on sol-gel prepared CuO nanostructure properties (optical and dielectric)

    Energy Technology Data Exchange (ETDEWEB)

    Bibi, Maryam [Nano Synthesis Laboratory, Department of Physics, National University of Sciences and Technology, Islamabad (Pakistan); Javed, Qurat-ul-Ain, E-mail: quratulain@sns.nust.edu.pk [Nano Synthesis Laboratory, Department of Physics, National University of Sciences and Technology, Islamabad (Pakistan); Abbas, Hussain [Institute of Avionics & Aeronautics (IAA), Air University, Islamabad (Pakistan); Baqi, Sabah [Nano Synthesis Laboratory, Department of Physics, National University of Sciences and Technology, Islamabad (Pakistan)

    2017-05-01

    The optical and dielectric properties of Copper Oxide (CuO) have made it a fascinating material to be used in solar energy harvesting, gas sensing, optoelectronics and catalytical applications. Focusing on the cost-effectiveness of Sol-gel method, it is employed for nanostructured CuO production. Effect of changing temperature is observed on the formation mechanism of CuO and its properties. The temperature range of 300 °C–500 °C was used in annealing of samples to produce defect free CuO nanomaterial. Prepared material was investigated using phase characterization (X-ray diffraction ‘XRD’) technique, scanning electron microscopy (SEM), UV–Visible absorption spectroscopy and LCR meter. A structural change in prepared CuO was observed from cluster formation to Nano-fibrils by increase in annealing temperature. 11.99 nm–29.17 nm crystallites of CuO were attained by using Debye Scherer formula. A large band gap of 3.15 eV was achieved by increasing the annealing temperature upto 400 °C. For better solar energy harvest, wide band gapped CuO structures are proved to be functional and practical materials. The fabricated CuO nanostructures were found suitable to be used in devices for stabilizing circuit designs for sensitive appliances as well as micro electromechanical systems (mems). - Highlights: • CuO was synthesized by using sol gel method post growth annealing process. • XRD and SEM characterizations confirm the successful synthesis of CuO. • Change in morphology was observed with varying annealing temperature. • Improved optical and dielectric properties were observed.

  12. Chamomile flower extract-directed CuO nanoparticle formation for its antioxidant and DNA cleavage properties

    Energy Technology Data Exchange (ETDEWEB)

    Duman, Fatih, E-mail: fduman@erciyes.edu.tr [Erciyes University, Science Faculty, Biology Department, Kayseri 38039, Kayseri (Turkey); Ocsoy, Ismail [Department of Analytical Chemistry, Faculty of Pharmacy, Erciyes University, 38039, Kayseri (Turkey); Erciyes University, Nanotechnology Research Center, 38039, Kayseri (Turkey); Kup, Fatma Ozturk [Erciyes University, Science Faculty, Biology Department, Kayseri 38039, Kayseri (Turkey)

    2016-03-01

    In this study, we report the synthesis of copper oxide nanoparticles (CuO NPs) using a medicinal plant (Matricaria chamomilla) flower extract as both reducing and capping agent and investigate their antioxidant activity and interaction with plasmid DNA (pBR322).The CuO NPs were characterized using Uv–Vis spectroscopy, FT-IR (Fourier transform infrared spectroscopy), DLS (dynamic light scattering), XRD (X-ray diffraction), EDX (energy-dispersive X-ray) spectroscopy and SEM (scanning electron microscopy). The CuO NPs exhibited nearly mono-distributed and spherical shapes with diameters of 140 nm size. UV–Vis absorption spectrum of CuO NPs gave a broad peak around 285 and 320 nm. The existence of functional groups on the surface of CuO NPs was characterized with FT-IR analysis. XRD pattern showed that the NPs are in the form of a face-centered cubic crystal. Zeta potential value was measured as − 20 mV due to the presence of negatively charged functional groups in plant extract. Additionally, we demonstrated concentration-dependent antioxidant activity of CuO NPs and their interaction with plasmid DNA. We assumed that the CuO NPs both cleave and break DNA double helix structure. - Highlights: • The synthesis of microwave assisted green synthesis of CuO nanoparticles • The synthesized nanoparticles were analyzed by FT-IR, DLS, XRD, EDX and SEM. • Concentration-dependent antioxidant activity of CuO NPs was determined. • CuO NPs cause both cleavage in the DNA double helix structure and breaks as well.

  13. Control of the superconducting properties of Sr{sub 2−x}Ca{sub x}VO{sub 3}FeAs through isovalent substitution

    Energy Technology Data Exchange (ETDEWEB)

    Corkett, Alex J.; Free, David G. [Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR (United Kingdom); Cassidy, Simon J. [Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR (United Kingdom); Diamond Light Source Limited, Harwell Science and Innovation Campus, Didcot, OX11 0DE (United Kingdom); Ramos, Silvia [Diamond Light Source Limited, Harwell Science and Innovation Campus, Didcot, OX11 0DE (United Kingdom); Clarke, Simon J., E-mail: simon.clarke@chem.ox.ac.uk [Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR (United Kingdom)

    2014-08-15

    The effect of the isovalent substitution of Sr{sup 2+} by Ca{sup 2+} on the structure and superconducting properties of Sr{sub 2−x}Ca{sub x}VO{sub 3}FeAs is described in the compositional range 0≤x≤0.5. SQUID magnetometry measurements reveal that after an initial increase in T{sub c}, which is maximised at 29.5 K in Sr{sub 1.95}Ca{sub 0.05}VO{sub 3}FeAs, a rapid suppression of superconductivity is observed with increasing x. XANES spectra of Sr{sub 2−x}Ca{sub x}VO{sub 3}FeAs collected on the Fe and V absorption K-edges show that the position of both edges are invariant with composition within the experimental uncertainty. A combination of synchrotron X-ray powder diffraction and neutron powder diffraction techniques is used to rationalise the observed changes in T{sub c} with x, in terms of changes to the structure of the FeAs layer upon partial Ca substitution. These findings demonstrate that superconductivity in the Fe-based superconductors is extremely sensitive to the crystal structure with T{sub c} maximised in samples with regular FeAs{sub 4}-tetrahedra. - Graphical abstract: Superconducting transition temperature is controlled by structural parameters in Sr{sub 2−x}Ca{sub x}VO{sub 3}FeAs. - Highlights: • Substitution of Sr by Ca in the superconductor Sr{sub 2}VO{sub 3}FeAs is isovalent. • Relationship between superconducting T{sub c} and structural parameters is demonstrated. • Linear dependence of T{sub c} on structural parameters rather than composition.

  14. FEA Analysis of AP-0 Target Hall Collection Lens (Current Design)

    Energy Technology Data Exchange (ETDEWEB)

    Hurh, P.G.; Tang, Z.

    2001-06-22

    The AP-0 Target Hall Collection Lens is a pulsed device which focuses anti-protons just downstream of the Target. Since the angles at which the anti-protons depart the Target can be quite large, a very high focusing strength is required to maximize anti-proton capture into the downstream Debuncher Ring. The current design of the Collection Lens was designed to operate with a focusing gradient of 1,000 T/m. However, multiple failures of early devices resulted in lowering the normal operating gradient to about 750 T/m. At this gradient, the Lens design fares much better, lasting several million pulses, but ultimately still fails. A Finite Element Analysis (FEA) has been performed on this Collection Lens design to help determine the cause and/or nature of the failures. The Collection Lens magnetic field is created by passing high current through a central conductor cylinder. A uniform current distribution through the cylinder will create a tangential or azimuthal magnetic field that varies linearly from zero at the center of the cylinder to a maximum at the outer surface of the cylinder. Anti-proton particles passing through this cylinder (along the longitudinal direction) will see an inward focusing kick back toward the center of the cylinder proportional to the magnetic field strength. For the current Lens design a gradient of 1,000 T/m requires a current of about 580,000 amps. Since the DC power and cooling requirements would be prohibitive, the Lens is operated in a pulsed mode. Each pulse is half sine wave in shape with a pulse duration of about 350 microseconds. Because of the skin effect, the most uniform current density actually occurs about two-thirds of the way through the pulse. This means that the maximum current of the pulse is actually higher than that required in the DC case (about 670,000 amps). Since the beam must pass through the central conductor cylinder it must be made of a conducting material that is also very 'transparent' to the beam

  15. Comparison of stripe modulations in La1.875Ba0.125CuO4 and La1.48Nd0.4Sr0.12CuO4

    Science.gov (United States)

    Wilkins, S. B.; Dean, M. P. M.; Fink, Jörg; Hücker, Markus; Geck, J.; Soltwisch, V.; Schierle, E.; Weschke, E.; Gu, G.; Uchida, S.; Ichikawa, N.; Tranquada, J. M.; Hill, J. P.

    2011-11-01

    We report combined soft and hard x-ray scattering studies of the electronic and lattice modulations associated with stripe order in La1.875Ba0.125CuO4 and La1.48Nd0.4Sr0.12CuO4. We find that the amplitude of both the electronic modulation of the hole density and the strain modulation of the lattice is significantly larger in La1.875Ba0.125CuO4 than in La1.48Nd0.4Sr0.12CuO4 and is also better correlated. The in-plane correlation lengths are isotropic in each case; for La1.875Ba0.125CuO4, ξhole=255±5 Å, whereas for La1.48Nd0.4Sr0.12CuO4, ξhole=111±7 Å. We find that the modulations are temperature independent in La1.875Ba0.125CuO4 in the low temperature tetragonal phase. In contrast, in La1.48Nd0.4Sr0.12CuO4, the amplitude grows smoothly from zero, beginning 13 K below the LTT phase transition. We speculate that the reduced average tilt angle in La1.875Ba0.125CuO4 results in reduced charge localization and incoherent pinning, leading to the longer correlation length and enhanced periodic modulation amplitude.

  16. Synthesis of High-Density Poinsettia-Like Microstructure of CuO by the Hydrothermal Method and Its Ethanol Sensing Properties

    Science.gov (United States)

    Hien, Vu Xuan; Minh, Vu Duy; Phuoc, Luong Huu; Vuong, Dang Duc; Heo, Young-Woo; Chien, Nguyen Duc

    2017-06-01

    Highly uniform and dense poinsettia-like microstructures of CuO were synthesized by a facile hydrothermal method. The effect of the treatment time on the growth of the CuO microstructures was investigated. The CuO microflowers with diameters in the range 3-5 μm were composed of many interconnected nanoleaves (1-2 μm in diameter and 20-30 nm in thickness). A plausible growth mechanism for the formation of the CuO microstructures has been proposed and discussed. In addition, the ethanol sensing properties of the CuO microflowers were characterized at 150-350°C. The poinsettia-like microstructures of CuO exhibited better response to ethanol when compared to the sensing properties of the CuO nanoleaves. The sensing mechanism based on the models of carrier transport and leaf-to-leaf contact has been proposed and discussed.

  17. In-plane optical response of $Bi_{2}Sr_{2}CuO_{6}$

    NARCIS (Netherlands)

    Tsvetkov, A. A.; Schützmann, J.; Marel, D. van der

    1997-01-01

    Published in: Phys. Rev. B 55 (1997) 14152 Citing articles (CrossRef) citations recorded in [Science Citation Index] Abstract: We report on infrared reflectivity measurements of the $ab$-plane response of superconducting Bi$_2$Sr$_2$CuO$_6$ single crystals. The frequency dependent conductivity has a

  18. Solution-processable carboxylate-capped CuO nanoparticles obtained by a simple solventless method

    Energy Technology Data Exchange (ETDEWEB)

    Estruga, Marc [Universitat Autonoma de Barcelona, Department of Chemistry (Spain); Roig, Anna; Domingo, Concepcion [CSIC, Institut de Ciencia de Materials de Barcelona (Spain); Ayllon, Jose A., E-mail: joseantonio.ayllon@uab.es [Universitat Autonoma de Barcelona, Department of Chemistry (Spain)

    2012-08-15

    Carboxylate-capped CuO nanoparticles were obtained via a simple solventless route, based on the thermal decomposition at 120 Degree-Sign C of solid precursors. The reaction mixture consisted of copper acetate monohydrate, acting as the CuO precursor, and different organic carboxylic acids (lauric, phenylvaleric or 3,6,9-trioxadecanoic acid) used as the capping agent. The proposed method, in good agreement with environmentally friendly practices, produced dry nanoparticles, thereby totally eliminating the need of washing, filtration, or other downstream steps. Transmission electron micrographs show crystalline roughly spherical CuO nanoparticles with average diameters between 3.1 and 5.5 nm depending on the capping ligand. The laurate-capped CuO nanoparticles showed a paramagnetic behaviour at room temperature, while a weak ferromagnetic component was detected at low temperature (<40 K). It was also proved that the chemical structure of the carboxylic acid tail enabled the straightforward dispersibility of nanoparticles in common solvents and assisted in the deposition of the material as thin films.

  19. Effect of triethanolamine:ethylenediamine ratios on CuO nanoparticles prepared by ultrasound irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Ayob, M. T. M.; Ahmad, A. F.; Mohd, H. M. K.; Rahman, I. Abdul; Radiman, S. [School of Applied Physics, Faculty of Science and Technology (FST), Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor Darul Ehsan (Malaysia)

    2014-09-03

    Coral-spherical-shaped of copper oxide nanoparticles have been successfully synthesized with different ratios of triethanolamine:ethylenediamine surfactant under ultrasonic condition. By controlling the amplitude of the ultrasonic radiation and concentration of metal salt precursors and surfactant, the formation of CuO nanospheres was obtained. Energy dispersive X-ray spectrum confirmed that Cu and O are the only elementary components present with a ratio of approximately 1:1. Furthermore, X-ray powder diffraction spectra for all the examined ratios of CuO showed well crystalline structures. UV-Vis spectroscopy was utilized to estimate the band gap energies of the CuO nanoparticles produced, which were found to be in the range of 2.74 eV to 2.95 eV. The field emission scanning electron micrographs of these nanospheres showed that their dimensions were in the range of 5-30 nm. These results indicate that the triethanolamine:ethylenediamine ratio plays an important role in the formation of different sized CuO nanoparticles, displaying a decrement in particle size with the increment in amount of triethanolamine ratios. This might be the key to synthesizing nanoparticles with specific sizes for various applications.

  20. Salts affect the interaction of ZnO or CuO nanoparticles with wheat.

    Science.gov (United States)

    Stewart, Jacob; Hansen, Trevor; McLean, Joan E; McManus, Paul; Das, Siddhartha; Britt, David W; Anderson, Anne J; Dimkpa, Christian O

    2015-09-01

    Exposure to nanoparticles (NPs) that release metals with potential phytotoxicity could pose problems in agriculture. The authors of the present study used growth in a model growth matrix, sand, to examine the influence of 5 mmol/kg of Na, K, or Ca (added as Cl salts) and root exudates on transformation and changes to the bioactivity of copper(II) oxide (CuO) and zinc oxide (ZnO) NPs on wheat. These salt levels are found in saline agricultural soils. After 14 d of seedling growth, particles with crystallinity typical of CuO or ZnO remained in the aqueous fraction from the sand; particles had negative surface charges that differed with NP type and salt, but salt did not alter particle agglomeration. Reduction in shoot and root elongation and lateral root induction by ZnO NPs were mitigated by all salts. However, whereas Na and K promoted Zn loading into shoots, Ca reduced loading, suggesting that competition with Zn ions for uptake occurred. With CuO NPs, plant growth and loading was modified equally by all salts, consistent with major interaction with the plant with CuO rather than Cu ions. Thus, for both NPs, loading into plant tissues was not solely dependent on ion solubility. These findings indicated that salts in agricultural soils could modify the phytotoxicity of NPs.

  1. Spin Dynamics of $La_{2}CuO_{4}$ and the Two-Dimensional Heisenberg Model

    CERN Document Server

    Sandvik, A W; Barbara, U C S; Barbara, UC Santa

    1994-01-01

    The spin-lattice relaxation rate $1/T_1$ and the spin echo decay rate $1/T_{2G}$ for the 2D Heisenberg model are calculated using quantum Monte Carlo and maximum entropy analytic continuation. The results are compared to recent experiments on La$_2$CuO$_4$, as well as predictions based on the non-linear $\\sigma$-model.

  2. Room temperature ferromagnetism in Fe-doped CuO nanoparticles.

    Science.gov (United States)

    Layek, Samar; Verma, H C

    2013-03-01

    The pure and Fe-doped CuO nanoparticles of the series Cu(1-x)Fe(x)O (x = 0.00, 0.02, 0.04, 0.06 and 0.08) were successfully prepared by a simple low temperature sol-gel method using metal nitrates and citric acid. Rietveld refinement of the X-ray diffraction data showed that all the samples were single phase crystallized in monoclinic structure of space group C2/c with average crystallite size of about 25 nm and unit cell volume decreases with increasing iron doping concentration. TEM micrograph showed nearly spherical shaped agglomerated particles of 4% Fe-doped CuO with average diameter 26 nm. Pure CuO showed weak ferromagnetic behavior at room temperature with coercive field of 67 Oe. The ferromagnetic properties were greatly enhanced with Fe-doping in the CuO matrix. All the doped samples showed ferromagnetism at room temperature with a noticeable coercive field. Saturation magnetization increases with increasing Fe-doping, becomes highest for 4% doping then decreases for further doping which confirms that the ferromagnetism in these nanoparticles are intrinsic and are not resulting from any impurity phases. The ZFC and FC branches of the temperature dependent magnetization (measured in the range of 10-350 K by SQUID magnetometer) look like typical ferromagnetic nanoparticles and indicates that the ferromagnetic Curie temperature is above 350 K.

  3. Magnetodielectric effect in composites of nanodimensional glass and CuO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Ranjan Saha, Dhriti [MLS Professor' s Unit, Indian Association for the Cultivation of Science, 2A and 2B Raja S.C. Mullick Road, Kolkata- 700032 (India); Mukherjee, Manabendra [Surface Physics Division, Saha Institute of Nuclear Physics, 1/AF BidhanNagar, Kolkata- 700064, India. (India); Chakravorty, Dipankar, E-mail: mlsdc@iacs.res.in [MLS Professor' s Unit, Indian Association for the Cultivation of Science, 2A and 2B Raja S.C. Mullick Road, Kolkata- 700032 (India)

    2012-11-15

    Nanocomposites comprising CuO particles of average diameter 21 nm coated with 5 nm silica glass containing iron ions were synthesized by a chemical route. An ion exchange reaction at the nanoglass/CuO interface produced iron-doped CuO with copper ion vacancies within the nanoparticles. Room temperature ferromagnetic-like behavior was observed in the nanocomposites. This was ascribed to uncompensated spins contributed by Fe ions with associated copper ion vacancies. A rather high value of magnetodielectric parameter in the range 16-26% depending on the measuring frequency was exhibited by these nanocomposites at a magnetic field of 10 KOe. This was caused by a magnetoresistance of 33% in the iron doped CuO nanoparticles. The experimental results were fitted to the Maxwell-Wagner Capacitor model developed by Catalan. These materials will be suited for magnetic sensor applications. - Highlights: Black-Right-Pointing-Pointer Synthesis of nanocomposites comprising CuO nanoparticles and interfacial nanodimensional silica glass. Black-Right-Pointing-Pointer These exhibited ferromagnetic-like behavior at room temperature. Black-Right-Pointing-Pointer High value of magnetodielectric parameter was obtained in the range 16-26% depending on the measuring frequency. Black-Right-Pointing-Pointer The Maxwell-Wagner Capacitor model of Catalan was used satisfactorily to explain the results.

  4. Theory of phonon properties in doped and undoped CuO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Bahoosh, S.G. [Institute of Physics, Martin-Luther-University, D-06099 Halle (Germany); Apostolov, A.T. [University of Architecture, Civil Engineering and Geodesy Faculty of Hydrotechnics, Department of Physics, 1, Hristo Smirnenski Blvd., 1046 Sofia (Bulgaria); Apostolova, I.N. [University of Forestry, Faculty of Forest Industry, 10, Kl. Ohridsky Blvd., 1756 Sofia (Bulgaria); Wesselinowa, J.M., E-mail: julia@phys.uni-sofia.bg [University of Sofia, Department of Physics, 5 J. Bouchier Blvd., 1164 Sofia (Bulgaria)

    2012-07-02

    We have studied the phonon properties of CuO nanoparticles and have shown the importance of the anharmonic spin–phonon interaction. The Raman peaks of CuO nanoparticles shift to lower frequency and become broader as the particle size decreases in comparison with those of bulk CuO crystals owing to size effects. By doping with different ions, in dependence of their radius compared to the host ionic radius the phonon energies ω could be reduced or enhanced. The phonon damping is always enhanced through the ion doping effects. -- Highlights: ► The phonon properties of CuO nanoparticles are studied using a miscroscopic model. ► The phonon energy decreases whereas the damping increases with decreasing of particle size. ► It is shown the importance of the anharmonic spin–phonon interaction. ► By doping with RE-ions the phonon energy is reduced, whereas with TM-ions it is enhanced. ► The phonon damping is always enhanced through the ion doping effects.

  5. Green synthesis of CuO nanoparticles using Cassia auriculata leaf ...

    African Journals Online (AJOL)

    Methods: CuO NPs were prepared by heating a mixture of 10 mL of 0.01 M CuSO4 ... Results: The gradual change in color of the reaction solution from brownish yellow to ... variety of applications, including in catalysts, gas .... that the surface charge and size distribution play .... in providing the funds and lab facilities for this.

  6. Growth of Horizontal Nanopillars of CuO on NiO/ITO Surfaces

    Directory of Open Access Journals (Sweden)

    Siddharth Joshi

    2014-01-01

    Full Text Available We have demonstrated hydrothermal synthesis of rectangular pillar-like CuO nanostructures at low temperature (~60°C by selective growth on top of NiO porous structures film deposited using chemical bath deposition method at room temperature using indium tin oxide (ITO coated glass plate as a substrate. The growth of CuO not only filled the NiO porous structures but also formed the big nanopillars/nanowalls on top of NiO surface. These nanopillars could have significant use in nanoelectronics devices or can also be used as p-type conducting wires. The present study is limited to the surface morphology studies of the thin nanostructured layers of NiO/CuO composite materials. Structural, morphological, and absorption measurement of the CuO/NiO heterojunction were studied using state-of-the-art techniques like X-ray diffraction (XRD, transmission electron microscopy (SEM, atomic force microscopy (AFM, and UV spectroscopy. The CuO nanopillars/nanowalls have the structure in order of (5 ± 1.0 μm × (2.0 ± 0.3 μm; this will help to provide efficient charge transport in between the different semiconducting layers. The energy band gap of NiO and CuO was also calculated based on UV measurements and discussed.

  7. CuO nanorods/graphene nanocomposites for high-performance lithium-ion battery anodes

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Qi; Zhao, Jun; Shan, Wanfei; Xia, Xinbei; Xing, Lili; Xue, Xinyu, E-mail: xuexinyu@mail.neu.edu.cn

    2014-03-25

    Highlights: • CuO/GNS nanocomposites are synthesized by a hydrothermal method. • CuO/GNSs as LIB anodes exhibit much higher cyclability and capacity than CuO nanostructures. • Such excellent performances can be attributed to the synergistic effect between CuO and GNSs. -- Abstract: CuO/graphene nanocomposites are synthesized by a hydrothermal method, and their application as anodes of lithium-ion batteries has been investigated. CuO nanorods are uniformly coating on the surface of graphene nanosheets. CuO/graphene nanocomposites exhibit high cyclability and capacity. After 50 cycles, the capacity can maintain at 692.5 mA h g{sup −1} at 0.1 C rate (10 h per half cycle). Such a high performance can be attributed to the synergistic effect between graphene nanosheets and CuO nanorods. The present results indicate that CuO/graphene nanocomposites have potential applications in the anodes of lithium-ion battery.

  8. Synthesis and evaluation of bactericidal properties of CuO nanoparticles against Aeromonas hydrophila

    Directory of Open Access Journals (Sweden)

    Sayedeh Fatemeh Shaffiey

    2014-04-01

    Full Text Available   Objective(s: CuO is one of the most important transition metal oxides due to its captivating properties. It is used in various technological applications such as high critical temperature superconductors, gas sensors, in photoconductive applications, and so on. Recently, it has been used as an antimicrobial agent against various bacterial species.   Materials and Methods: Here, we synthesized CuO nanoparticles (NPs and explored the antibacterial activity of CuO NPs preparation. Results: Single crystalline nanoparticles of copper oxide having almost uniform particle size of 5-6 nm has been synthesized by a facile and versatile route. XRD spectra confirmed the formation of single phase CuO NPs. Transmission electron microscopy results corroborate well with XRD results. The technique employed is free from toxic solvents, organics and amines, is based on a simple reaction of copper sulfate and de-ionized water (DI, and their bactericidal effects against of Aeromonas hydrophila ATCC 7966T bacteria were investigated. Minimum inhibitory concentration (MIC and minimum bactericidal concentration (MBC with liquid culture for all of the Aeromonas hydrophila culture Medias was done. Conclusion: Present study confirms that Copper oxide nanoparticles have great promise as antimicrobial agent against Aeromonas hydrophila

  9. In-plane optical response of $Bi_{2}Sr_{2}CuO_{6}$

    NARCIS (Netherlands)

    Tsvetkov, A. A.; Schützmann, J.; Marel, D. van der

    1997-01-01

    Published in: Phys. Rev. B 55 (1997) 14152 Citing articles (CrossRef) citations recorded in [Science Citation Index] Abstract: We report on infrared reflectivity measurements of the $ab$-plane response of superconducting Bi$_2$Sr$_2$CuO$_6$ single crystals. The frequency dependent conductivity has a

  10. Preparation and Characterization of CuO Nanoparticles by Novel Sol-Gel Technique

    Directory of Open Access Journals (Sweden)

    Y. Aparna

    2012-10-01

    Full Text Available Recent developments of nanosize materials of metal and metal oxide particles are intensively pursued because of their prominence in different fields of applications. Among all the transition metal oxides, CuO is a potential candidate for the application of magnetic storage devices, solar energy transfer, sensors, and super capacitors etc. Moreover CuO nanoparticles act as a good catalyst in some of the chemical reactions. CuO nanoparticles were prepared by novel sol-gel method. In this technique CuCl2.6H2O is added with acetic acid and heated to 100 °C with continuous stirring. To control the ph of the above solution, NaOH is added to the solution till ph reached desired value. The color of the solution changed from blue to black with precipitation. The black precipitation was washed 3 – 4 times with distilled water. Finally the solution was centrifuged and dried in air for one day. The CuO nanoparticles were characterized by studying their structure with X-ray diffraction and composition by energy dispersive X-ray analysis. The size of the nanoparticles is estimated by particle size analyzer and transmission electron microscopy. The optical studies were carried out with Uv-Vis spectrophotometer.

  11. Oxygen Isotope Effect and Structural Phase Transitions in La2CuO4-Based Superconductors.

    Science.gov (United States)

    Crawford, M K; Farneth, W E; McCarronn, E M; Harlow, R L; Moudden, A H

    1990-12-07

    The oxygen isotope effect on the superconducting transition temperature (alpha(o)) varies as a function of x in La2-xSrxCuO(4) and La2-xBaxCuO(4), with the maximum alpha(o) values (alpha(o) >/= 0.5) found for x near 0.12. This unusual x dependence implies that the isotope effect is influenced by proximity to the Abma --> P4(2)/ncm structural phase transition in these systems. Synchrotron x-ray difaction measurements reveal little change in lattice parameters or orthorhombicity due to isotope exchange in strontium-doped materials where alpha(o) > 0.5, eliminating static structural distortion as a cause of the large isotope effects. The anomalous behavior of alpha(o) in both strontium- and barium-doped materials, in combination with the previously discovered Abma --> P4(2)/ncm structural phase-transition in La(1.88)B(0.12)CuO(4), suggests that an electronic contribution to the lattice instability is present and maximizes at approximately 1/8 hole per copper atom. These observations indicate a dose connection between hole doping of the Cu-O sheets, tilting instabilities of the CuO(6) octahedra, and superconductivity in La(2)CuO(4)-based superconductors.

  12. Slave Boson Description of CuO2 Planes of the High-Temperature Superconductors

    Science.gov (United States)

    Mrkonjic, Ivana; Barisic, Slaven

    Slave-boson mean-field calculation is carried out analytically for doped CuO2 conduction planes, described by the extended Emery model which is parameterized by Cu-O charge transfer energy Δpd, Cu-O hopping t0, O-O hopping t' and Coulomb repulsion U localized on Cu site, taken as infinite. At zero doping δ, finite small t' expands the range of stability of the covalent, conducting state, characterized by renormalized band parameters Δpf and t, on the expense of insulating t=0 state, which, however, remains stable at larger Δpd. For sufficiently large Δpd, Δpf saturates at 4|t'|. Finite doping suppresses the insulating state nearly symmetrically with respect to its sign. The regime with Δpf close to 4|t'| fits remarkably well ARPES spectra of Y123, Bi2212 and LSCO, and, in the latter case, explains the observed strong doping-dependence of the effective Cu-O hopping.

  13. Magnetic fluctuations in La1.95Ba0.05CuO4

    DEFF Research Database (Denmark)

    Hayden, S.M.; Aeppli, G.; Mook, H.;

    1991-01-01

    Neutron-scattering and resistivity experiments on single crystals of La1.95Ba0.05CuO4 are described. On warming to as high as 250 K, the correlation length does not change, and the temperature dependence of the generalized susceptibility chi(Q, omega) is due solely to the temperature dependence o...

  14. Legionella pneumophila transcriptional response following exposure to CuO nanoparticles

    Science.gov (United States)

    Copper ions are an effective antimicrobial agent used to control Legionnaires’ disease and Pontiac fever arising from institutional drinking water systems. Here we present data on an alternative bactericidal agent, CuO nanoparticles (CuO-NPs), and test its efficacy at three conce...

  15. Separation of Arsenic from the Antimony-Bearing Dust through Selective Oxidation Using CuO

    Science.gov (United States)

    Zhong, Da-Peng; Li, Lei; Tan, Cheng

    2017-04-01

    A pyrometallurgical process of selective oxidation roasting of the antimony-bearing dust using CuO is put forward, in which the antimony component is oxidized to Sb2O4 staying in the roasted residue, and arsenic is volatilized in the form of As2O3. The addition of CuO has an active effect on the arsenic volatilization, because structures of some complicated As-Sb phases in the dust are destroyed after the "Sb" component in them is oxidized to Sb2O4, and this part of arsenic might be transformed to As2O3, which continues to volatilize. However, the arsenic volatilization rate decreases with the CuO amount in a certain range, which is attributed to the greater formation of Cu3 (AsO4)2 and Cu3As. Under the conditions of roasting temperature of 673 K (400 °C), roasting time of 100 minutes, CuO amount of 34.54 mass pct, and N2 flow rate of 30 mL/min, 91.50 pct arsenic and only 8.63 pct antimony go into the smoke.

  16. Separation of Arsenic from the Antimony-Bearing Dust through Selective Oxidation Using CuO

    Science.gov (United States)

    Zhong, Da-Peng; Li, Lei; Tan, Cheng

    2017-01-01

    A pyrometallurgical process of selective oxidation roasting of the antimony-bearing dust using CuO is put forward, in which the antimony component is oxidized to Sb2O4 staying in the roasted residue, and arsenic is volatilized in the form of As2O3. The addition of CuO has an active effect on the arsenic volatilization, because structures of some complicated As-Sb phases in the dust are destroyed after the "Sb" component in them is oxidized to Sb2O4, and this part of arsenic might be transformed to As2O3, which continues to volatilize. However, the arsenic volatilization rate decreases with the CuO amount in a certain range, which is attributed to the greater formation of Cu3 (AsO4)2 and Cu3As. Under the conditions of roasting temperature of 673 K (400 °C), roasting time of 100 minutes, CuO amount of 34.54 mass pct, and N2 flow rate of 30 mL/min, 91.50 pct arsenic and only 8.63 pct antimony go into the smoke.

  17. Polymer-Controlled Growth of CuO Nanodiscs in the Mild Aqueous Solution

    Institute of Scientific and Technical Information of China (English)

    PENG Yin; LIU Zhengyin; YANG Zihui

    2009-01-01

    CuO nanodiscs have been synthesized on a large scale by a facile solution-based method using polymers as crystal growth modifiers. X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and high resolu-tion transmission electron microscopy (HRTEM) were carded out to characterize the structures and morphologies of the obtained products. The effects of reaction temperature, concentrations of polyacrylamide (PAM) and reac-tants on the morphology and size of the product were studied. The results revealed that the CuO nanodisc had sin-gle-crystal monoclinic structures, and grew along (002) and (110) planes. Experimental conditions had all influence on the shape and size of the final products, but polymer PAM played the key role in formation of the CuO nanodisc.A possible growth mechanism of the CuO nanostructures based on typical polymer-crystal interactions in a mild aqueous solution was given. Polymer-directed crystal growth may provide promising routes to rational synthesis of various ordered inorganic and inorganic-organic hybrid materials with complex forms and structural specialization.

  18. Use of Vegetable Waste Extracts for Controlling Microstructure of CuO Nanoparticles: Green Synthesis, Characterization, and Photocatalytic Applications

    Directory of Open Access Journals (Sweden)

    Hameed Ullah

    2017-01-01

    Full Text Available Chemical syntheses involve either hazardous reactants or byproducts which adversely affect the environment. It is, therefore, desirable to develop synthesis processes which either do not involve hazardous reactants or consume all the reactants giving no byproducts. We have synthesized CuO nanoparticles (NPs adhering to some of the principles of green chemistry. The CuO NPs have been synthesized exploiting extracts of vegetable wastes, that is, Cauliflower waste and Potatoes and Peas peels. The extracts were aimed to work as capping agents to get control over the microstructure and morphology of the resulting CuO NPs. The green synthesized CuO NPs were characterized to explore the microstructure, morphology, optical bandgaps, and photocatalytic performances. XRD revealed that the CuO NPs of all the samples crystallized in a single crystal system, that is, monoclinic. However, the morphologies and the optical bandgaps energies varied as a function of the extract of vegetable waste. Similarly, the CuO NPs obtained through different extracts have shown different photocatalytic activities. The CuO NPs produced with extract of Cauliflower have shown high degradation of MB (96.28% compared to obtained with Potatoes peels (87.37% and Peas peels (79.11%.

  19. Characterization and adsorption performance of Pb(II) on CuO nanorods synthesized by the hydrothermal method

    Energy Technology Data Exchange (ETDEWEB)

    Arfaoui, Lobna; Kouass, Salah [Laboratoire des matériaux utiles, Institut National de Recherche et d' Analyse Physico-Chimique (INRAP) Sidi Thabet, 2020 Tunis (Tunisia); Dhaouadi, Hassouna, E-mail: dhaouadihassouna@yahoo.fr [Laboratoire Matériaux Traitement et Analyse, Institut National de Recherche et d' Analyse Physico-Chimique (INRAP) Sidi Thabet, 2020 Tunis (Tunisia); Jebali, Raouf [Laboratoire des matériaux utiles, Institut National de Recherche et d' Analyse Physico-Chimique (INRAP) Sidi Thabet, 2020 Tunis (Tunisia); Touati, Fathi [Laboratoire Matériaux Traitement et Analyse, Institut National de Recherche et d' Analyse Physico-Chimique (INRAP) Sidi Thabet, 2020 Tunis (Tunisia)

    2015-10-15

    Highlights: • The nanorods of CuO were synthesized by a hydrothermal route without any surfactant. • X-ray diffraction showed monoclinic structure with space group C{sub 2/c}. • The nanorods show relatively high adsorption capacity for the removal of Pb(II). • The adsorption kinetics could be fitted well by the pseudo-second-order model. • The equilibrium data can be fitted well using the Langmuir isotherm model - Abstract: Copper oxide (CuO) nanorods were synthesized by hydrothermal method. The detailed structural, compositional and optical characterization of this material was also evaluated with XRD, FT-IR, EDS, and UV–vis spectroscopy, which confirmed that the obtained nanorods are well-crystallized CuO and possess good optical properties. SEM and TEM studies revealed that the as-synthesized CuO nanorods are uniform with an average diameter of 17 nm. The adsorption activity of the CuO nanostructures was studied. The adsorption results showed that the CuO nanorods are an effective and efficient adsorbent for the removal of Pb(II) ions. The influence of various operational parameters such as the pH of the solution, the contact time and the initial concentrations were also studied and the results were discussed. The estimated maximum lead ion adsorption capacity of the CuO nanorods was found to be 188.67 mg g{sup −1} at an optimum pH of 6.

  20. Effects of CuO Nanoparticles on Microstructure, Physical, Mechanical and Thermal Properties of Self-Compacting Cementitious Composites

    Institute of Scientific and Technical Information of China (English)

    Ali Nazari; Shadi Riahi

    2011-01-01

    In the present study, split tensile strength of self-compacting concrete with different amount of CuO nanoparticles has been investigated. CuO nanoparticles with the average particle size of 15 nm were added partially to self compacting concrete and split tensile strength of the specimens has been measured. The results indicate that CuO nanoparticles are able to improve the split tensile strength of self compacting concrete and recover the negative effects of polycarboxylate superplasticizer on split tensile strength. CuO nanoparticle as a partial replacement of cement up to 4 wt% could accelerate C-S-H gel formation as a result of increased crystalline Ca(OH)2 amount at the early ages of hydration. The increase of the CuO nanoparticles more than 4 wt% causes the decrease of the split tensile strength because of unsuitable dispersion of nanoparticles in the concrete matrix. Accelerated peak appearance in conduction calorimetry tests, more weight loss in thermogravimetric analysis and more rapid appearance of related peaks to hydrated products in X-ray diffraction (XRD) results all also indicate that CuO nanoparticles up to 4 wt% could improve the mechanical and physical properties of the specimens. Finally, CuO nanoparticles could improve the pore structure of concrete and shift the distributed pores to harmless and few-harm pores.

  1. Preparation and characterization of nanocrystalline CuO powders with the different surfactants and complexing agent mediated precipitation method

    Energy Technology Data Exchange (ETDEWEB)

    Rajendran, V.; Gajendiran, J., E-mail: gaja.nanotech@gmail.com

    2014-08-15

    Highlights: • CuO nanostructures by surfactants mediated method. • Structural and optical properties of CuO nanostructures changes under the effect of surface modifier. • Citric acid assisted is the best, in terms of size, morphology and optical properties than that of CTAB, SDS and PEG-400. - Abstract: Nanostructures of copper oxide (CuO) was synthesized into crystallite sized ranging from 20 to 50 nm in the presence of different surfactants, and complex agent such as cityl tri methyl ammonium bromide (CTAB), sodium do decyl sulfate (SDS), poly ethylene glycol (PEG-400) and citric acid via a precipitation route. Variations in several parameters and their effects on the structural and optical properties of CuO nanostructures (crystallite size, morphology and band gap) were investigated by XRD, FTIR, SEM and UV analysis. The UV–visible absorption spectra of the different surfactants and complexing agent assisted CuO nanostructures indicates that the estimated optical band gap energy value (1.94–1.98 eV) is higher than that of the bulk CuO value (1.4 eV), which is attributed to the quantum confinement effect. The formation mechanism of different surfactants and complexing agent assisted CuO nanostructures is also proposed.

  2. Novel β-C3N4/CuO nanoflakes: facile synthesis and unique photocatalytic performance

    Science.gov (United States)

    Zou, Lan-Rong; Huang, Gui-Fang; Li, Dong-Feng; Tian, Qing-Nan; Yang, Ke; Si, Yuan; Chang, Shengli; Zhang, Xue-Ao; Huang, Wei-Qing

    2017-09-01

    For the first time, novel β-C3N4/CuO composites with superior photocatalytic activity are successfully fabricated via a facile reflux method followed by a thermal process. The morphologies, particle size and microstructure of the synthesized β-C3N4/CuO composites largely depended upon copper chloride and the volume ratio of V water:V ethanol in the mixed precursors. The fabricated β-C3N4/CuO nanoflakes exhibited obviously enhanced visible light photocatalytic activity for the degradation of methylene blue (MB) with an  ∼3.4 and 1.9 fold increase in efficiency over that of pure g-C3N4 and commercial P25, respectively. The β-C3N4/CuO composite photocatalyst also showed photocatalytic activity for the degradation of methyl orange (MO). Moreover, the β-C3N4/CuO nanoflakes showed almost no loss of photocatalytic activity after three recycles of the degradation of the MB. A multiple synergetic mechanism in β-C3N4/CuO nanoflakes, which is featured by the highly reactive {0 0 2} facets, exposed many active sites of nanoflakes and the efficient charge separation are proposed to account for the distinguished photocatalytic activity. This work provides a facile and cost-effective strategy for designing novel β-C3N4/CuO photocatalysts for application in environmental purification.

  3. Solution-dispersed CuO nanoparticles anode buffer layer: Effect of ultrasonic agitation duration on photovoltaic performance

    Science.gov (United States)

    Sabri, Nasehah Syamin; Yap, Chi Chin; Yahaya, Muhammad; Salleh, Muhamad Mat; Jumali, Mohammad Hafizuddin Haji

    2016-11-01

    The performance of inverted type hybrid organic solar cell based on poly(3-hexyltheopene):[6,6]-phenyl C61-butyric acid methyl ester (P3HT:PCBM) can be improved by adding an anode buffer layer of copper oxide (CuO). CuO that serves as an electron blocking layer which could effectively reduce the charge recombination at the photoactive layer (P3HT:PCBM)/silver (Ag) interfaces. At the same time, Cuo anode buffer layer could accelerate the holes collection from the photoactive layer to the top electrode. In this study we investigated the effects of ultrasonic agitation duration in preparation of solution-dispersed CuO anode buffer layer on the performance of the devices with a configuration of fluorine tin oxide (FTO)/zinc oxide (ZnO) nanorod arrays/P3HT:PCBM/ CuO/Ag. Different durations of ultrasonic agitation (0, 5, 15 and 25 min) were used for CuO nanoparticles solution dispersion to obtain the optimum particle size distribution of CuO. It was found that the smallest average particle size of CuO was obtained by applying the ultrasonic agitation for longest duration of 25 min. The highest power conversion efficiency of 1.22% was recorded from the device incorporating with CuO anode buffer layer with the smallest average particle size. It is believed that CuO anode buffer layer with the smallest average particle size had the least agglomerates, thus leading to better film formation and contact surface area.

  4. Electrochemical properties of CuO hollow nanopowders prepared from formless Cu–C composite via nanoscale Kirkendall diffusion process

    Energy Technology Data Exchange (ETDEWEB)

    Won, Jong Min [Department of Materials Science and Engineering, Korea University, Anam-Dong, Seongbuk-Gu, Seoul 136-713 (Korea, Republic of); Kim, Jong Hwa [Daegu Center, Korea Basic Science Institute, 80 Daehakro Bukgu, Daegu 702-701 (Korea, Republic of); Choi, Yun Ju [Suncheon Center, Korea Basic Science Institute, Suncheon 540-742 (Korea, Republic of); Cho, Jung Sang [Department of Materials Science and Engineering, Korea University, Anam-Dong, Seongbuk-Gu, Seoul 136-713 (Korea, Republic of); Kang, Yun Chan, E-mail: yckang@korea.ac.kr [Department of Materials Science and Engineering, Korea University, Anam-Dong, Seongbuk-Gu, Seoul 136-713 (Korea, Republic of)

    2016-06-25

    Hollow CuO nanopowders are prepared using a simple spray drying process that relied on nanoscale Kirkendall diffusion; these nanopowders have potential applications in lithium-ion batteries. Citric acid is used as both the carbon source material and chelating agent and plays a key role in the preparation of the hollow nanopowders. The formless Cu–C composite that formed as an intermediate product transforms into slightly aggregated CuO hollow nanopowders after post-treatment at 300 and 400 °C under an air atmosphere. The CuO hollow nanopowders exhibit higher initial discharge capacities and better cycling performances than those of the filled-structured CuO nanopowders, which are prepared at a post-treatment temperature of 500 °C under an air atmosphere. The discharge capacities of the CuO nanopowders post-treated at 300, 400, and 500 °C for the 150{sup th} cycle at a current density of 1 A g{sup −1} are 793, 632, and 464 mA h g{sup −1}, respectively, and their capacity retentions calculated from the maximum discharge capacities are 88, 80, and 73%, respectively. The CuO nanopowders with hollow structures exhibit better structural stability for repeated lithium insertion and desertion processes than those with filled structures. - Highlights: • Hollow CuO nanopowders are prepared using a simple spray drying process. • Cu–C composite transforms into CuO hollow nanopowders by Kirkendall diffusion. • Hollow CuO nanopowders show good electrochemical properties for lithium-ion storage.

  5. Temperature dependent structural modulation in {{Ca}}_{0.82}{{La}}_{0.18}FeAs2 pnictide superconductors

    Science.gov (United States)

    Joseph, Boby; Marini, Carlo; Demitri, Nicola; Capitani, Francesco; Bernasconi, Andrea; Zhou, Wei; Xing, Xiangzhuo; Shi, Zhixiang

    2015-09-01

    Temperature dependent synchrotron x-ray powder diffraction data on {{Ca}}0.82{{La}}0.18FeAs2 pnictide superconductor demonstrate anisotropic thermal expansion along the out-of-plane and in-plane lattice parameters. Thermal expansion along the c-axis shows a distinct change from 2.9 × 10-4 Å K-1 at ˜300 K to 1.0 × 10-4 Å K-1 at ˜110 K, whereas the in-plane axes, a and b, in the temperature range 300 to 100 K, show a constant thermal expansion that is an order of magnitude smaller (˜0.3×10-4 Å K-1). The temperature dependence of the out-of-plane lattice parameter is found to have a good correlation with the behavior of the resistivity indicating the importance of the interlayer interaction in governing the transport properties of 112 pnictide superconductors.

  6. A DIFFERENT APPROACH IN OPTIMUM DESIGN PROCESS AND FEA VALIDATION OF LOW-SPEED MULTI-PHASE IPMSMS

    Directory of Open Access Journals (Sweden)

    seyed asghar gholamian

    2017-05-01

    Full Text Available Magnets placement effects on permanent magnet motors performance, because of its different magnetic flux density distribution. Therefore, different types of magnet placement should be examined experimentally or by valid simulations. In this paper, first, an interior permanent magnet synchronous motor (IPMSM called spoke type with specifications related to the propulsion of ships is designed and then optimized by ant colony algorithm to increase the torque-to-volume ratio. The design procedure and its formulas presented as simple as possible. Then, to verify the optimization results of the optimized motor, a Two-dimensional finite element analysis (FEA is done. Also in this analyze the core and the slot saturation was studied.

  7. High-performance nanothermite composites based on aloe-vera-directed CuO nanorods.

    Science.gov (United States)

    Patel, Vinay Kumar; Bhattacharya, Shantanu

    2013-12-26

    In this work, we demonstrate the development of high-performance nanothermite composites derived from super-reactive CuO nanorods oxidizers fabricated by simple biogenic routes using Aloe vera plant extracts. Nanorods of various length scales have been realized via simple sonoemulsion and solid-state biosynthesis routes using Aloe vera gel as a green surfactant promoting the directional growth of CuO nanorods in both solid and emulsion phase. The biosynthesized CuO nanorods (oxidizers)/fuel (nanoaluminum) composites ignited vigorously with abundant gas generation, developing high heat of reaction of 1.66 kJ g(-1) and very high pressurization rate of around 1.09 MPa μs(-1) and peak pressure of 65.4 MPa when blasted inside a constant volume pressure cell with a charge density of 0.2 g cm(-3). The pressurization rates so obtained are four times higher with twice the peak pressure in comparison to such nanothermites formulated via other available state of the art wet-chemical techniques, which reflects the catalytic role of Aloe vera surface functional groups (A. vera-sfg) enhancing the reactivity of CuO oxidizers with excess gas release rate during exothermic reaction with nanoaluminum. Through this work, Aloe vera gel has for the first time been identified as a novel biotemplate for green synthesis of nanorod structures of metal oxides, and we have also studied the utility of A. vera-sfg in the creation of super-reactive CuO oxidizers producing excellent heat of reaction and dynamic pressure characteristics as demanded in propellants, explosives, and pyrotechnics.

  8. a Geometric Processing Workflow for Transforming Reality-Based 3d Models in Volumetric Meshes Suitable for Fea

    Science.gov (United States)

    Gonizzi Barsanti, S.; Guidi, G.

    2017-02-01

    Conservation of Cultural Heritage is a key issue and structural changes and damages can influence the mechanical behaviour of artefacts and buildings. The use of Finite Elements Methods (FEM) for mechanical analysis is largely used in modelling stress behaviour. The typical workflow involves the use of CAD 3D models made by Non-Uniform Rational B-splines (NURBS) surfaces, representing the ideal shape of the object to be simulated. Nowadays, 3D documentation of CH has been widely developed through reality-based approaches, but the models are not suitable for a direct use in FEA: the mesh has in fact to be converted to volumetric, and the density has to be reduced since the computational complexity of a FEA grows exponentially with the number of nodes. The focus of this paper is to present a new method aiming at generate the most accurate 3D representation of a real artefact from highly accurate 3D digital models derived from reality-based techniques, maintaining the accuracy of the high-resolution polygonal models in the solid ones. The approach proposed is based on a wise use of retopology procedures and a transformation of this model to a mathematical one made by NURBS surfaces suitable for being processed by volumetric meshers typically embedded in standard FEM packages. The strong simplification with little loss of consistency possible with the retopology step is used for maintaining as much coherence as possible between the original acquired mesh and the simplified model, creating in the meantime a topology that is more favourable for the automatic NURBS conversion.

  9. CONTRASTANDO AS PRODUÇÕES DA REVISTA CONTABILIDADE & FINANÇAS (FEA-USP E REVISTA BASE (Unisinos

    Directory of Open Access Journals (Sweden)

    FLÁViO DONIZETE BATiSTELLA

    2008-12-01

    Full Text Available A reestruturação do sistema de avaliação de publicações da Fundação Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Capes, o Sistema Qualis, produziu um forte incentivo à publicação de artigos em periódicos. Apreender o estágio da produção em dois periódicos nacionais é o foco desta investigação. Esses periódicos são: Revista Contabilidade & Finanças (FEAUSP e Revista Base (Unisinos. O período de análise engloba as publicações ocorridas em 2005 e em 2006. Os aspectos observados pela Capes em seu processo de avaliação de periódicos são eminentemente orientados na edição e formatação do periódico. Nesse sentido, a análise adotada nesta pesquisa possui foco na forma dos periódicos, sendo que a metodologia central é fundamentada no modelo proposto por Krzyzanowski e Ferreira (1998. Os resultados obtidos sugerem que a Revista Contabilidade & Finanças (FEA-USP apresenta, com relação ao quesito forma, um desempenho geral categorizado como bom, enquanto que a Revista Base (Unisinos apresenta um desempenho mediano. Observou-se também uma maior concentração de autores nas publicações da Revista Contabilidade & Finanças (FEA-USP (recorrência em relação à Revista Base (Unisinos

  10. Archetypal sandwich-structured CuO for high performance non-enzymatic sensing of glucose

    Science.gov (United States)

    Meher, Sumanta Kumar; Rao, G. Ranga

    2013-02-01

    In the quest to enhance the selectivity and sensitivity of novel structured metal oxides for electrochemical non-enzymatic sensing of glucose, we report here a green synthesis of unique sandwich-structured CuO on a large scale under microwave mediated homogeneous precipitation conditions. The physicochemical studies carried out by XRD and BET methods show that the monoclinic CuO formed via thermal decomposition of Cu2(OH)2CO3 possesses monomodal channel-type pores with largely improved surface area (~43 m2 g-1) and pore volume (0.163 cm3 g-1). The fascinating surface morphology and pore structure of CuO is formulated due to homogeneous crystallization and microwave induced self assembly during synthesis. The cyclic voltammetry and chronoamperometry studies show diffusion controlled glucose oxidation at ~0.6 V (vs. Ag/AgCl) with extremely high sensitivity of 5342.8 μA mM-1 cm-2 and respective detection limit and response time of ~1 μM and ~0.7 s, under a wide dynamic concentration range of glucose. The chronoamperometry measurements demonstrate that the sensitivity of CuO to glucose is unaffected by the absence of dissolved oxygen and presence of poisoning chloride ions in the reaction medium, which essentially implies high poison resistance activity of the sandwich-structured CuO. The sandwich-structured CuO also shows insignificant interference/significant selectivity to glucose, even in the presence of high concentrations of other sugars as well as reducing species. In addition, the sandwich-structured CuO shows excellent reproducibility (relative standard deviation of ~2.4% over ten identically fabricated electrodes) and outstanding long term stability (only ~1.3% loss in sensitivity over a period of one month) during non-enzymatic electrochemical sensing of glucose. The unique microstructure and suitable channel-type pore architecture provide structural stability and maximum accessible electroactive surface for unimpeded mobility of glucose as well as the

  11. FEA技术在CT新床体开发中的应用%FEA Technology Applied in the Design of CT Table

    Institute of Scientific and Technical Information of China (English)

    赵宏宇; 王君涛; 侯远成

    2013-01-01

    In this paper, we develop a method to build FEA model, boundary conditions and to analyse static strength and rigidity of the object based on the CT patient table. Especial y to introduce the examples of how to simplify the actual models to ideal models which can easily add some loads. In the end of the paper, we compare the results analysis of FEA with the results of experiment and we confirm the high accuracy of FEA, so we summarize that FEA technology is very important for the development of medical equipments.%  该文主要以CT扫描床体为例,详细的介绍了在CT床体的开发过程中如何应用FEA技术进行建模、建立边界条件以及进行静态强度和刚度分析,特别是对如何将具体的、实际的工作情形简化为模型中抽象的边界载荷条件进行了详细的介绍。最后将FEA分析结果与实际实验结果进行对比,对FEA分析结果的准确性进行了确认,得出FEA技术在医疗器械产品开发中的重大应用意义。

  12. 3D Two-way coupled TEHD analysis on the lubricating characteristics of thrust bearings in pump-turbine units by combining CFD and FEA

    Science.gov (United States)

    Zhai, Liming; Luo, Yongyao; Wang, Zhengwei; Liu, Xin

    2016-01-01

    The thermal elastic hydro dynamic (TEHD) lubrication analysis for the thrust bearing is usually conducted by combining Reynolds equation with finite element analysis (FEA). But it is still a problem to conduct the computation by combining computational fluid dynamics (CFD) and FEA which can simulate the TEHD more accurately. In this paper, by using both direct and separate coupled solutions together, steady TEHD lubrication considering the viscosity-temperature effect for a bidirectional thrust bearing in a pump-turbine unit is simulated combining a 3D CFD model for the oil film with a 3D FEA model for the pad and mirror plate. Cyclic symmetry condition is used in the oil film flow as more reasonable boundary conditions which avoids the oil temperature assumption at the leading and trailing edge. Deformations of the pad and mirror plate are predicted and discussed as well as the distributions of oil film thickness, pressure, temperature. The predicted temperature shows good agreement with measurements, while the pressure shows a reasonable distribution comparing with previous studies. Further analysis of the three-coupled-field reveals the reason of the high pressure and high temperature generated in the film. Finally, the influence of rotational speed of the mirror plate on the lubrication characteristics is illustrated which shows the thrust load should be balanced against the oil film temperature and pressure in optimized designs. This research proposes a thrust bearing computation method by combining CFD and FEA which can do the TEHD analysis more accurately.

  13. Charge redistribution and a shortening of the Fe--As bond at the quantum critical point of SmO1-xFxFeAs.

    Science.gov (United States)

    Cheng, Jie; Dong, Peng; Xu, Wei; Liu, Shengli; Chu, Wangsheng; Chen, Xianhui; Wu, Ziyu

    2015-07-01

    Many researchers have pointed out that there is a quantum critical point (QCP) in the F-doped SmOFeAs system. In this paper, the electronic structure and local structure of the superconductive FeAs layer in SmO(1-x)FxFeAs as a function of the F-doping concentration have been investigated using Fe and As K-edge X-ray absorption spectroscopy. Experiments performed on the X-ray absorption near-edge structure showed that in the vicinity of the QCP the intensity of the pre-edge feature at the Fe-edge decreases continuously, while there is a striking rise of the shoulder-peak at the As edge, suggesting the occurrence of charge redistribution near the QCP. Further analysis on the As K-edge extended X-ray absorption fine structure demonstrated that the charge redistribution originates mostly from a shortening of the Fe-As bond at the QCP. An evident relationship between the mysterious QCP and the fundamental Fe-As bond was established, providing new insights on the interplay between QCP, charge dynamics and the local structural Fe-As bond in Fe-based superconductors.

  14. In-vivo assessment of femoral bone strength using Finite Element Analysis (FEA based on routine MDCT imaging: a preliminary study on patients with vertebral fractures.

    Directory of Open Access Journals (Sweden)

    Hans Liebl

    Full Text Available To experimentally validate a non-linear finite element analysis (FEA modeling approach assessing in-vitro fracture risk at the proximal femur and to transfer the method to standard in-vivo multi-detector computed tomography (MDCT data of the hip aiming to predict additional hip fracture risk in subjects with and without osteoporosis associated vertebral fractures using bone mineral density (BMD measurements as gold standard.One fresh-frozen human femur specimen was mechanically tested and fractured simulating stance and clinically relevant fall loading configurations to the hip. After experimental in-vitro validation, the FEA simulation protocol was transferred to standard contrast-enhanced in-vivo MDCT images to calculate individual hip fracture risk each for 4 subjects with and without a history of osteoporotic vertebral fractures matched by age and gender. In addition, FEA based risk factor calculations were compared to manual femoral BMD measurements of all subjects.In-vitro simulations showed good correlation with the experimentally measured strains both in stance (R2 = 0.963 and fall configuration (R2 = 0.976. The simulated maximum stress overestimated the experimental failure load (4743 N by 14.7% (5440 N while the simulated maximum strain overestimated by 4.7% (4968 N. The simulated failed elements coincided precisely with the experimentally determined fracture locations. BMD measurements in subjects with a history of osteoporotic vertebral fractures did not differ significantly from subjects without fragility fractures (femoral head: p = 0.989; femoral neck: p = 0.366, but showed higher FEA based risk factors for additional incident hip fractures (p = 0.028.FEA simulations were successfully validated by elastic and destructive in-vitro experiments. In the subsequent in-vivo analyses, MDCT based FEA based risk factor differences for additional hip fractures were not mirrored by according BMD measurements. Our data suggests, that MDCT

  15. Study of Object Oriented FEA and Its Realization%面向对象有限元分析技术及其实现方法研究

    Institute of Scientific and Technical Information of China (English)

    周晴; 杜平安; 刘孝保

    2012-01-01

    面向对象有限元分析技术将面向对象技术应用于有限元分析过程,将整个过程抽象为一个模型,形成仿真基类。然后根据不同结构的有限元分析特点和规律,对分析过程进行参数化描述,形成各种仿真子类,各仿真子类构成仿真类库。介绍了面向对象有限元分析技术的基本原理和仿真类库的设计方法,提出了面向对象多任务协同仿真概念。通过探针零件有限元分析程序的开发,说明了面向对象有限元分析程序的实现过程。%Object-oriented finite element analysis(FEA) applies object-oriented technology to the process of FEA.It abstracts the FEA process into a model and forms the simulation basic class,then,according to the characteristics of FEA process of different structure,describes parametrically the process and creates the simulation sub-classes,witch form the simulation class library.The principal of the object-oriented FEA and the design of simulation class library are introduced,the concept of multi-task co-simulation is presented,and the development of the object-oriented FEA program is illustrated through a probe part.

  16. Toxicity of CuO nanoparticles and Cu ions to tight epithelial cells from Xenopus laevis (A6)

    DEFF Research Database (Denmark)

    Thit, Amalie; Selck, Henriette; Bjerregaard, Henning F.

    2013-01-01

    ) was used to investigate toxicity of copper (Cu) in 3 different forms; Cu ions (Cu2+), CuO NPs (6 nm) and poly-dispersed CuO NPs (100 nm, poly-CuO). Continuous exposures at concentrations of 143–200 μM demonstrated that cytotoxicity differed among the 3 Cu forms tested and that the effects depend on cell...... state (dividing or differentiated). Dividing cells treated with poly-CuO, CuO NPs (6 nm) or Cu2+ showed cell cycle arrest and caused significant increase in cell death via apoptosis after 48 h, 6 and 7 days of treatment, respectively. Treatment with either CuO NPs (6 nm) or Cu2+ caused significant...... decrease in cell proliferation. Treatments of differentiated cells, revealed the same patterns of toxicity for Cu forms tested, but after shorter exposure periods....

  17. CuFe2 O4 -CuO Nanocomposites as Promising Materials for Solar Hydrogen Generation

    Science.gov (United States)

    Razavi, Mehdi; Amrollahi, Pouya; Yazdimamaghani, Mostafa; Tayebi, Lobat; Vashaee, Daryoosh

    2014-03-01

    Currently, hydrogen is produced, almost exclusively, by waterelectrolysis. This method can take advantage of economies of scale and most established techniques of producing hydrogen. We developed a nanocomposite material system composed of CuFe2O4 and CuO semiconductor particles to produce hydrogen by electrolysis of water. The nanocomposite powder was prepared using the sol-gel method. Techniques of X-ray diffraction, scanning electron microscopy with energy dispersive spectroscopy, transmission electron microscopy and UV diffuse reflectance analysis were employed to characterize the synthesized products.The results confirmed the formation of CuFe2O4-CuO nanocomposite powder. The hydrogen evolution was successfully observed over the new hetero-system of CuFe2O4-CuO. The electrolysis activity depended on the concentration of CuO in the system. In order to enhance the hydrogen production, we further optimized the composite material versus the concentration of the compounds.

  18. Characterization and DC Conductivity of Novel CuO doped Polyvinyl Alcohol (PVA Nano-composite Films

    Directory of Open Access Journals (Sweden)

    Chivukula Srikanth

    2014-10-01

    Full Text Available DC conductivity of PVA-CuO nano-composite films have been studied in the present work. The composites were prepared by solution-casting technique. The prepared PVA-CuO composites have been characterized by X-ray diffraction (XRD analysis, Fourier Transform Infrared Spectroscopy (FT-IR, Scanning Electron Microscopy (SEM and Energy Dispersive X-ray Spectroscopy (EDXS; which confirmed the presence of CuO in polyvinyl alcohol and the formation of the composite. DC conductivity studies show thermally activated behavior of all the composites. The conductivity was found to increase with the increase in temperature indicating the semiconducting behavior of all the compositions. The activation energy increases as the content of CuO nanoparticles increases from 1 to 4 in wt% in the PVA- CuO nano-composites. Maximum conductivity was observed in 4 wt% of CuO in polyvinyl alcohol.

  19. Formation of Hierarchical CuO Nanostructures on Copper Foil by Chemical Bath Deposition for Applications in Superhydrophobic Surfaces

    Directory of Open Access Journals (Sweden)

    Felizco Jenichi Clairvaux

    2016-01-01

    Full Text Available Hierarchical CuO nanostructures (urchin-like and grassy island structure were successfully synthesized by a simple chemical bath deposition method at low temperature of 70°C in a short reaction time of 1h. XRD analysis revealed the presence of pure crystalline monoclinic CuO. Morphological analysis revealed the formation of spherical structures composed of numerous hair-like structures. The pH of the solution was also investigated to have a great effect on the morphology of the CuO nanostructures. At lower pH, the structures tend to form urchin-like structures; while at higher pH, the structures tend to form grass-like islands. A growth mechanism was also proposed in this paper. Lastly, wettability test proved the stable superhydrophobic property of the CuO nanostructured thin film surface.

  20. Speciation of ZnO and CuO nanoparticles exposed to culture medium and lymphocyte cells

    Data.gov (United States)

    U.S. Environmental Protection Agency — Spectral fits and linear combination data for ZnO and CuO nanoparticles exposure during toxicity testing. This dataset is associated with the following publication:...

  1. Magnetoresistive study of the antiferromagnetic-weak ferromagnetic transition in single-crystal La2CuO4+δ

    Science.gov (United States)

    Belevtsev, B. I.; Dalakova, N. V.; Savitsky, V. N.; Panfilov, A. S.; Braude, I. S.; Bondarenko, A. V.

    2004-05-01

    Resistive measurements were made to study the magnetic field-induced antiferromagnetic (AF)—weak ferromagnetic (WF) transition in the La2CuO4 single crystal. The magnetic field (dc or pulsed) was applied normally to the CuO2 layers. The transition manifested itself in a drastic decrease of the resistance in critical fields of 5-7 T. The study is the first to display the effect of the AF-WF transition on the conductivity of the La2CuO4 single crystal in the direction parallel to the CuO2 layers. The results provide support for the three-dimensional nature of the hopping conduction of this layered oxide.

  2. Synthesis of chrysalis-like CuO nanocrystals and their catalytic activity in the thermal decomposition of ammonium perchlorate

    Indian Academy of Sciences (India)

    Jun Wang; Shanshan He; Zhanshuang Li; Xiaoyan Jing; Milin Zhang; Zhaohua Jiang

    2009-11-01

    Chrysalis-like morphologies of CuO have been synthesized in large-quantity via a simple chemical deposition method without the use of any complex instruments and reagents. CuO nanocrystals showed a different morphology at three different temperatures, 25, 60 and 100°C. The particle size, morphology and crystal structure of the samples were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectra. The catalytic effect of CuO nanoparticles on the decomposition of ammonium perchlorate (AP) was investigated by STA 409 PC thermal analyzer at a heating rate of 10°C min-1 from 35 to 500°C. Compared with the thermal decomposition of pure AP, the addition of CuO nanoparticles decreased the decomposition temperature of AP by about 85°C.

  3. Preparation and sonocatalytic activity of monodisperse porous bread-like CuO via thermal decomposition of copper oxalate precursors

    Science.gov (United States)

    Zhang, Lihui; Liu, Rong; Yang, Heqing

    2012-04-01

    Porous bread-like CuO have been obtained via the thermal decomposition of copper oxalate precursor synthesized by the room temperature reaction of Cu(NO3)2 with Na2C2O4 in water. These bread-like CuO with the monoclinic structure are well dispersed with good monodispersity, their diameters are about 1.5 μm. The sonocatalytic activity of porous CuO for the degradation of acid scarlet dye was studied. It was found that the as-prepared porous CuO nanostructures exhibit efficient sonocatalytic ability for the degradation of acid scarlet dye in the presence of H2O2, which are expected to be useful in the treatment of non- or low-transparent wastewaters.

  4. Unravelling the quantum-entanglement effect of noble gas coordination on the spin ground state of CUO

    CERN Document Server

    Tecmer, Pawel; Legeza, Ors; Reiher, Markus

    2013-01-01

    The accurate description of the complexation of the CUO molecule by Ne and Ar noble gas matrices represents a challenging task for present-day quantum chemistry. Especially, the accurate prediction of the spin ground state of different CUO--noble-gas complexes remains elusive. In this work, the interaction of the CUO unit with the surrounding noble gas matrices is investigated in terms of complexation energies and dissected into its molecular orbital quantum entanglement patterns. Our analysis elucidates the anticipated singlet--triplet ground-state reversal of the CUO molecule diluted in different noble gas matrices and demonstrates that the strongest uranium-noble gas interaction is found for CUOAr4 in its triplet configuration.

  5. Cupric Oxide (CuO) Oxidation Detects Pyrogenic Carbon in Burnt Organic Matter and Soils.

    Science.gov (United States)

    Hatten, Jeff; Goñi, Miguel

    2016-01-01

    Wildfire greatly impacts the composition and quantity of organic carbon stocks within watersheds. Most methods used to measure the contributions of fire altered organic carbon-i.e. pyrogenic organic carbon (Py-OC) in natural samples are designed to quantify specific fractions such as black carbon or polyaromatic hydrocarbons. In contrast, the CuO oxidation procedure yields a variety of products derived from a variety of precursors, including both unaltered and thermally altered sources. Here, we test whether or not the benzene carboxylic acid and hydroxy benzoic acid (BCA) products obtained by CuO oxidation provide a robust indicator of Py-OC and compare them to non-Py-OC biomarkers of lignin. O and A horizons from microcosms were burned in the laboratory at varying levels of fire severity and subsequently incubated for 6 months. All soils were analyzed for total OC and N and were analyzed by CuO oxidation. All BCAs appeared to be preserved or created to some degree during burning while lignin phenols appeared to be altered or destroyed to varying extents dependent on fire severity. We found two specific CuO oxidation products, o-hydroxybenzoic acid (oBd) and 1,2,4-benzenetricarboxylic acid (BTC2) that responded strongly to burn severity and withstood degradation during post-burning microbial incubations. Interestingly, we found that benzene di- and tricarboxylic acids (BDC and BTC, respectively) were much more reactive than vanillyl phenols during the incubation as a possible result of physical protection of vanillyl phenols in the interior of char particles or CuO oxidation derived BCAs originating from biologically available classes of Py-OC. We found that the ability of these compounds to predict relative Py-OC content in burned samples improved when normalized by their respective BCA class (i.e. benzene monocarboxylic acids (BA) and BTC, respectively) and when BTC was normalized to total lignin yields (BTC:Lig). The major trends in BCAs imparted by burning

  6. CdS quantum dots modified CuO inverse opal electrodes for ultrasensitive electrochemical and photoelectrochemical biosensor

    OpenAIRE

    2015-01-01

    The CuO inverse opal photonic crystals (IOPCs) were synthesized by the sol-gel method and modified with CdS quantum dots by successive ionic layer adsorption and reaction (SILAR). CdS QDs modified CuO IOPCs FTO electrodes of different SILAR cycles were fabricated and their electrochemical properties were studied by cyclic voltammetry (CV) and chronoamperometry (I–t). Structure and morphology of the samples were characterized by transmission electron microscopy (TEM), scanning electron microsc...

  7. The effect of CuO NPs on reactive oxygen species and cell cycle gene expression in roots of rice.

    Science.gov (United States)

    Wang, Shuling; Liu, Hanzhu; Zhang, Yuxi; Xin, Hua

    2015-03-01

    To evaluate the effect of CuO nanoparticles (NPs) on root growth, root reactive oxygen species (ROS) production, and the expression of 2 genes (OsCDC2 and OsCYCD) associated with root growth of Oryza sativa (rice), rice roots were treated with 5 mg/L CuO NP suspension, 5 mg/L CuO bulk particle suspension, and 0.27 mg/L CuSO4  · 5H2 O solution, with distilled water as control. The results indicated that CuO NPs and Cu(2+) severely inhibited the elongation and biomass of rice roots after 72-h exposure. Dyeing with 7'-dichlorodihydrofluorescein-diacetate (DCFH-DA) showed that in all 3 treatment groups, the fluorescence was primarily located in the meristem zone, demonstrating that the meristem zone was where ROS were primarily generated. In addition, a significant increase in ROS was detected in the meristem zone of roots treated with the CuO NP suspension and the CuSO4  · 5H2 O solution, both of which greatly influenced the expression level of OsCDC2 and OsCYCD. The impact of Cu(2+) on these 2 genes was smaller than that of CuO NPs. The Cu content in roots of rice after treatment with CuO NPs was much higher than that found after the other treatments, which indicated that CuO NPs may have been absorbed into root tissue. Collectively, these data suggest that growth inhibition, higher ROS production, and gene expression inhibition may be caused not only by the ions themselves, but also the NPs. © 2014 SETAC.

  8. Magnetic properties of doped and undoped CuO nanoparticles taking into account spin-phonon interactions

    Science.gov (United States)

    Wesselinowa, J. M.

    2011-03-01

    We have studied the influence of doping effects on magnetization M and Neel temperature T of CuO nanoparticles based on the Heisenberg model including spin-phonon interactions. The experimentally obtained room temperature magnetization M is due to surface or/and doping effects in CuO nanoparticles. We have shown the importance of the effect of the spin-phonon interaction on different properties.

  9. Shape-controlled synthesis of Sn-doped CuO nanoparticles for catalytic degradation of Rhodamine B.

    Science.gov (United States)

    Vomáčka, Petr; Štengl, Václav; Henych, Jiří; Kormunda, Martin

    2016-11-01

    The uniform Sn-doped CuO nanoparticles were synthesized by a simple solution method at a low temperature. The prepared samples were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electron microscopy techniques (HRSEM, HRTEM, SAED, STEM and EDS elemental mapping), atomic force microscopy (AFM), UV/Vis spectroscopy, nitrogen physisorption (BET) and by evaluation of the catalytic activity on the degradation of Rhodamine B. The tin doping had a considerable influence on the morphology of CuO. The gradual narrowing of the particles morphology in the crystallographic [010] direction was observed with increasing the dopant concentration. The plate-like, rectangularsquare and rod-like CuO nanoparticles were obtained. The mechanism of a crystal growth of CuO associated with doping is proposed. The tin doping also affected the structural and optical properties of CuO. Increasing the amount of a dopant led to a red-shift of a band gap from 1.33 to 1.18eV. The incorporation of tin into the structure of copper oxide was confirmed by XRD and distribution of tin mapped by EDS analysis. The good catalytic properties of the as-prepared doped material were demonstrated by the enhanced catalytic removal of Rhodamine B in the presence of H2O2. The undoped CuO nanosheets reached only 24% efficiency in the removal of Rhodamine B within two hours. The best result exhibited CuO_050Sn sample containing 4at.% of tin and the degradation of Rhodamine B reached 99% within the same time. We have demonstrated a simple, scalable process for the preparation of catalytically very active Sn-doped CuO nanoparticles with varying properties.

  10. Magnetic properties of doped and undoped CuO nanoparticles taking into account spin-phonon interactions

    Energy Technology Data Exchange (ETDEWEB)

    Wesselinowa, J.M., E-mail: julia@phys.uni-sofia.b [University of Sofia, Department of Physics, 5 J. Bouchier Blvd., 1164 Sofia (Bulgaria)

    2011-03-14

    We have studied the influence of doping effects on magnetization M and Neel temperature T{sub N} of CuO nanoparticles based on the Heisenberg model including spin-phonon interactions. The experimentally obtained room temperature magnetization M is due to surface or/and doping effects in CuO nanoparticles. We have shown the importance of the effect of the spin-phonon interaction on different properties.

  11. One-dimensional variable range hopping conduction in a single crystal of La 2CuO 4+y

    Science.gov (United States)

    Corraze, B.; Ribault, M.

    1993-02-01

    We have measured the resistivity perpendicular to the CuO 2 planes, in the magnetically ordered phases of a single crystal of La 2CuO 4+y as a function of temperature. Within a limited temperature range a one-dimensional variable range hopping conduction mechanism is identified, in zero magnetic field. The analysis of both the temperature range and the magnetic field variation shows that this mechanism is strongly dependent on the intraplane and on the interplane couplings.

  12. One dimensional CuO nanocrystals synthesis by electrical explosion: A study on structural, optical and electronic properties

    Energy Technology Data Exchange (ETDEWEB)

    Krishnan, Shutesh, E-mail: shutesh.k@onsemi.com [Department of Mechanical Engineering University of Malaya, 50603 Kuala Lumpur (Malaysia); ON Semiconductor Package Innovation and Development Center, 70450 Seremban (Malaysia); Haseeb, A.S.M.A.; Johan, Mohd Rafie [Department of Mechanical Engineering University of Malaya, 50603 Kuala Lumpur (Malaysia)

    2014-02-15

    Highlights: • One-dimensional CuO nanoflakes were synthesized by novel wire explosion technique. • A physical synthesis method capable of producing high aspect ratio (1:16) nanocrystals. • Most energy efficient and eco-friendly synthesis of low-dimensional transition metal oxide nanocrystals. -- Abstract: One-dimensional (1D) copper oxide (CuO) nanocrystals were synthesized using a novel wire explosion in de-ionized (DI) water without any chemical additives. Highly crystalline 1D CuO nanocrystals with 1:16 aspect ratio were successfully synthesized using this technique. The chemical nature and physical structure of the nanocrystals were controlled by simply modulating the exploding medium temperature. The results showed that nanocrystals produced at explosion temperatures 65 °C and 95 °C are pure CuO with optical band-gap energy of 2.38 eV. High Resolution Transmission Electron Microscope analysis (HRTEM) indicates that the CuO nanocrystals are with growth in [1{sup ¯}11] and [1 1 1] directions. The epitaxial crystal growth kinetics of the 1D nanostructure by aggregation was discussed. The incorporation of microstructural features like edge dislocations and porosity in the growth mechanism was examined. X-ray photoelectron spectroscopy (XPS) characterization indicates the formation of high purity CuO nanocrystals with valence state +2. This study provides an energy efficient and eco-friendly synthesis method of 1D transition metal oxide nanocrystals for electronic applications.

  13. Novel CuCr2O4 embedded CuO nanocomposites for efficient photodegradation of organic dyes

    Science.gov (United States)

    Mageshwari, K.; Sathyamoorthy, R.; Lee, Jeong Yong; Park, Jinsub

    2015-10-01

    Novel photocatalyst based on CuO-CuCr2O4 nanocomposites was synthesized for different Cr3+ concentration by reflux condensation method, and their photocatalytic activity was evaluated by monitoring the photodegradation of methyl orange (MO) and methylene blue dyes (MB) under UV light irradiation. Phase evolution by X-ray diffraction showed monoclinic CuO and tetragonal CuCr2O4 as the components of the prepared nanocomposites. Morphological analysis by scanning electron microscope and transmission electron microscope revealed that the incorporation of Cr3+ in CuO lattice alters the morphology of CuO from microsphere to cluster shape. Photoluminescence spectra of CuO-CuCr2O4 nanocomposites exhibited reduced PL emissions compared to pure CuO, indicating the low recombination rate of photogenerated electrons and holes. As expected, the CuCr2O4 loaded CuO showed enhanced photocatalytic activity for MO and MB dyes, and the kinetic studies suggest that the degradation follows pseudo-first-order kinetics. The enhanced photocatalytic activity of CuO-CuCr2O4 nanocomposites can be attributed to the presence of CuCr2O4 as an electron acceptor, which improves the effective charge separation in CuO.

  14. Bioaccumulation and toxicity of CuO nanoparticles by a freshwater invertebrate after waterborne and dietborne exposures

    Science.gov (United States)

    Croteau, Marie-Noele; Misra, Superb K.; Luoma, Samuel N.; Valsami-Jones, Eugenia

    2014-01-01

    The incidental ingestion of engineered nanoparticles (NPs) can be an important route of uptake for aquatic organisms. Yet, knowledge of dietary bioavailability and toxicity of NPs is scarce. Here we used isotopically modified copper oxide (65CuO) NPs to characterize the processes governing their bioaccumulation in a freshwater snail after waterborne and dietborne exposures. Lymnaea stagnalis efficiently accumulated 65Cu after aqueous and dietary exposures to 65CuO NPs. Cu assimilation efficiency and feeding rates averaged 83% and 0.61 g g–1 d–1 at low exposure concentrations (–1), and declined by nearly 50% above this concentration. We estimated that 80–90% of the bioaccumulated 65Cu concentration in L. stagnalis originated from the 65CuO NPs, suggesting that dissolution had a negligible influence on Cu uptake from the NPs under our experimental conditions. The physiological loss of 65Cu incorporated into tissues after exposures to 65CuO NPs was rapid over the first days of depuration and not detectable thereafter. As a result, large Cu body concentrations are expected in L. stagnalis after exposure to CuO NPs. To the degree that there is a link between bioaccumulation and toxicity, dietborne exposures to CuO NPs are likely to elicit adverse effects more readily than waterborne exposures.

  15. A chemical reaction controlled mechanochemical route to construction of CuO nanoribbons for high performance lithium-ion batteries.

    Science.gov (United States)

    Chen, Kunfeng; Xue, Dongfeng

    2013-12-07

    We reported a chemical reaction controlled mechanochemical route to synthesize mass CuO nanosheets by manual grinding in a mortar and pestle, which does not require any solvent, complex apparatus and techniques. The activation of chemical reactions by milling reactants was thus proved, and the energy from mechanical grinding promotes the fast formation of CuO nanoribbons. The resultant materials have preferential nanoscale ribbon-like morphology that can show large capacity and high cycle performance as lithium-ion battery anodes. After 50 cycles, the discharge capacity of CuO nanoribbon electrodes is 614.0 mA h g(-1), with 93% retention of the reversible capacity. The thermodynamic reactions of the CuO battery showed size-dependent characterization. The microstructures of CuO nanosheets and reaction routes can be controlled by the ratio of NaOH/CuAc2 according to the chemical reactions involved. The intact nanoribbon structure, thin-layer, and hierarchical structures endow present CuO materials with high reversible capacity and excellent cycling performances. The simple, economical, and environmentally friendly mechanochemical route is of great interest in modern synthetic chemistry.

  16. Effect of Cobalt Doping on Nanostructured CuO Thin Films

    Science.gov (United States)

    Bayansal, Fatih; Taşköprü, Turan; Şahin, Bünyamin; Çetinkara, Hacı Ali

    2014-07-01

    The growth of cobalt-doped nanostructured CuO thin films using the successive ionic layer adsorption and reaction (SILAR) method is presented. It is found that Co doping considerably influences the structural (X-ray diffraction (XRD)), morphological (finite-element-scanning electron microscopy (FESEM)), and optical (ultraviolet/visible (UV/vis.) and Raman) properties of the films. XRD experiments evidence that the crystallite size of the films decreased with increasing Co doping. FESEM images reveal that the grain size of the nanostructures decreased with increasing doping concentration. By UV/vis. analysis, it is found that Co doping has a decreasing effect on band gap energy. The broadening and downshift of the Raman peaks are mainly attributed to the quantum confinement effect of CuO nanostructures.

  17. Realistic electronic structure calculations for magnetic insulators like La2CuO4

    Science.gov (United States)

    Grant, J. B.; McMahan, A. K.

    1991-01-01

    We suggest that Hartree-Fock theory is a good starting point for the solution of ab initio-derived extended Hubbard Hamiltonians for magnetic insulators like La2CuO4, as indicated by surprisingly accurate results for the superchange frequencies and insulating gaps for this material and isostructural La2NiO4, K2CuF4, and K2NiF4. Limited configuration interaction beyond Hartree-Fock theory is then used to demonstrate that admixtures of a1- (d23z-r2 -) symmetry states at energies somewhat away from the gap edge are essential to the dispersion of the first quasiparticle branch in La2CuO4 for doped-in holes.

  18. Study of Optical Band Gap of CuO Using Fermi's Golden Rule

    Science.gov (United States)

    Nemade, K. R.; Waghuley, S. A.

    2012-05-01

    Quantum size effect where the electronic and optical properties of solids are altered due to changes in the band structures, enhanced the surface/volume ratio in nano dimensions forces more than 33% of the atoms to be on the surface (for 10nm dot 35), which drastically altering the physical properties such as having lower melting temperature and lower sintering temperature, and higher diffusion force at elevated temperatures. Consequently, its Fermi's golden rule analysis becomes crucial. Cupric oxide (CuO) is an important transition metal oxide with the basis of several high temperature superconductors and giant magnetoresistance materials. In present investigation, optical Band Gap from UV data using Fermi's golden rule for single step chemically synthesized CuO was computed.

  19. Preparation and characterization of nanostructured CuO thin films for photoelectrochemical splitting of water

    Indian Academy of Sciences (India)

    Diwakar Chauhan; V R Satsangi; Sahab Dass; Rohit Shrivastav

    2006-12-01

    Nanostructured copper oxide thin films (CuO) were prepared on conducting glass support (SnO2: F overlayer) via sol–gel starting from colloidal solution of copper (II) acetate in ethanol. Films were obtained by dip coating under room conditions (temperature, 25–32°C) and were subsequently sintered in air at different temperatures (400–650°C). The evolution of oxide coatings under thermal treatment was studied by glancing incidence X-ray diffraction and scanning electron microscopy. Average particle size, resistivity and band gap energy were also determined. Photoelectrochemical properties of thin films and their suitability for splitting of water were investigated. Study suggests that thin films of CuO sintered at lower temperatures (≈ 400°C) are better for photoconversion than thick films or the films sintered at much higher temperatures. Plausible explanations have been provided.

  20. Controlled synthesis of CuO nanostructures on Cu foil, rod and grid

    Energy Technology Data Exchange (ETDEWEB)

    Vanithakumari, S.C.; Shinde, S.L. [Materials Research Centre, Indian Institute of Science, C.V. Raman Avenue, Malleswaram, Bangalore 560012, Karnataka (India); Nanda, K.K., E-mail: nanda@mrc.iisc.ernet.in [Materials Research Centre, Indian Institute of Science, C.V. Raman Avenue, Malleswaram, Bangalore 560012, Karnataka (India)

    2011-05-15

    CuO nanowires are synthesized by heating Cu foil, rod and grid in ambient without employing a catalyst or gas flow at temperatures ranging from 400 to 800 deg. C for a duration of 1-12 h. Scanning electron microscopy (SEM) investigation reveals the formation of nanowires. The structure, morphology and phase of the as-synthesized nanowires are analyzed by various techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). It is found that these nanowires are composed of CuO phase and the underlying film is of Cu{sub 2}O. A systematic study is carried out to find the possibilities for the transformation of one phase to another completely. A possible growth mechanism for the nanowires is also discussed.

  1. Growth and characterisation of bulk Sr2CuO2Cl2 single crystals

    NARCIS (Netherlands)

    Hien, NT; Franse, JJM; Pothuizen, JJM; Li, TW; Menovsky, AA

    1997-01-01

    Large bulk single crystals of the Sr2CuO2Cl2 compound with dimensions of 15 x 6 x 4 mm(3) have been grown directly from the melt by the floating-zone method using a light-image furnace. The optimal growth conditions are found in a mixed atmosphere of 0.2 bar oxygen and 1.2 bar argon. Results of the

  2. Spontaneous ferromagnetic spin ordering at the surface of La$_2$CuO$_4$

    OpenAIRE

    2007-01-01

    Magnetic properties of high purity stoichiometric La$_2$CuO$_4$ nanoparticles are systematically investigated as a function of particle size. Ferromagnetic single-domain spin clusters are shown to spontaneously form at the surface of fine grains as well as paramagnetic defects. Hysteresis loops and thermomagnetic irreversibility are observed in a wide temperature range $5 - 350$ K with the remnant moment and coercivity gradually decreasing with increasing temperature. Possible origins of the ...

  3. Solid-State Thermal Decoposition Method for the Preparation of CuO Nanoparticles

    Directory of Open Access Journals (Sweden)

    A. Dehno Khalaji

    2012-12-01

    Full Text Available In this paper, CuO nanoparticles  have been synthesized via solid- state thermal decomposition using copper(II Schiff base complexes as new precursors at 600ºC under air atmosphere for 3 h. Surface morphology of the products were characterized by Fourier transform infrared spectroscopy (FT-IR, X-ray diffraction (XRD and scanning electron microscopy (SEM.

  4. The structure and energies of peroxy bipolarons in La sub 2 CuO sub 4

    CERN Document Server

    Catlow, C R A; Zhang, X

    1998-01-01

    We present calculations of the binding energies of peroxy (O sub 2 sup 2 sup -) bipolarons in La sub 2 CuO sub 4. Our results strongly suggest that these species are weakly bound with respect to isolated hole species. Estimates of the effective mass of the bipolaronic species based on our calculated relaxed geometries are consistent with experimental observation for the superconducting state of the material. (author). Letter-to-the-editor

  5. Fluctuating in the hopping rate of CuO thin films with respect to substrate temperature

    Science.gov (United States)

    Serin, N.; Yildiz, A.; Çam, E.; Uzun, Ş.; Serin, T.

    2012-10-01

    Electrical transport properties in CuO thin films processed using d.c. magnetron sputtering technique is investigated to understand the correlation between the processing conditions and electrical properties. It is identified that the temperature dependent conductivity of the investigated films is controlled by the multi-phonon hopping conduction mechanism. A detailed analysis in terms of carrier hopping parameters is used to correlate electrical transport properties with the d.c. magnetron sputtering conditions.

  6. Proximity-induced superconductivity in monolayer CuO2 on cuprate substrates

    Science.gov (United States)

    Zhu, Guo-Yi; Zhang, Fu-Chun; Zhang, Guang-Ming

    2016-11-01

    To understand the recently observed high temperature superconductivity in the monolayer CuO2 grown on the Bi2Sr2CaCu2O8 + δ substrates, we propose a two-band model of the hybridized oxygen px and py orbitals with the proximity effect of the substrate. We demonstrate that both the nodal and nodeless superconducting states can be induced by the proximity effect, depending on the strengths of the pairing parameters.

  7. Microwave absorption and resistively shunted Josephson junctions in high temperature CuO superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Ramachandran, J.S.; Huang, M.X.; Bhagat, S.M. (Dept. of Physics, Univ. of Maryland, College Park, MD (United States)); Kish, K.; Tyagi, S. (Dept. of Physics and Atmospheric Science, Drexel Univ., Philadelphia, PA (United States))

    1992-11-01

    We report that the field dependence of the magnetoabsorption (virgin curve) in all pristine granular CuO type (HTSC) superconductors follows a one-parameter expression. This ''universal'' result is combined with previous measurements on field and temperature dependences of microwave absorption in HTSC to demonstrate that a simple model based on resistively shunted Josehpson junctions is adequate to qualitatively account for almost all the observations on powders, pellets, thin films and single crystals. (orig.).

  8. Building Selectivity for NO Sensing in a NOx Mixture with Sonochemically Prepared CuO Structures

    Directory of Open Access Journals (Sweden)

    Max R. Mullen

    2015-12-01

    Full Text Available Several technologies are available for decreasing nitrogen oxide (NOx emissions from combustion sources, including selective catalytic reduction methods. In this process, ammonia reacts with nitric oxide (NO and nitrogen dioxide (NO2. As the stoichiometry of the two reactions is different, electrochemical sensor systems that can distinguish between NO and NO2 in a mixture of these two gases are of interest. Since NO and NO2 can be brought to equilibrium, depending on the temperature and the surfaces that they are in contact with, the detection of NO and NO2 independently is a difficult problem and has not been solved to date. In this study, we explore a high surface area sonochemically prepared CuO as the resistive sensing medium. CuO is a poor catalyst for NOx equilibration, and requires temperatures of 500 C to bring about equilibration. Thus, at 300 C, NO and NO2 retain their levels after interaction with CuO surface. In addition, NO adsorbs more strongly on the CuO over NO2. Using these two concepts, we can detect NO with minimal interference from NO2, if the latter gas concentration does not exceed 20% in a NOx mixture over a range of 100–800 ppm. Since this range constitutes most of the range of total NOx concentrations in diesel and other lean burn engines, this sensor should find application in selective detection of NO in this combustion application. A limitation of this sensor is the interference with CO, but with combustion in excess air, this problem should be alleviated.

  9. Photoelectrochemical Properties of CuO Grown by Using a Modified Chemical Bath Deposition Method

    Energy Technology Data Exchange (ETDEWEB)

    Ha, Jin-wook; Ryu, Hyukhyun [Inje University, Gimhae (Korea, Republic of); Lee, Won-Jae [Dong-Eui University, Busan (Korea, Republic of)

    2016-06-15

    In this study, cupric oxide (CuO) nanorods were grown on the fluorine-doped tin oxide (FTO) glass substrate using a modified-chemical bath deposition (M-CBD) method. We investigated the morphology, structural, optical and photoelectrochemical properties of the cupric oxide nanorods with various growth durations by using field-emission scanning-electron microscopy (FE-SEM), X-ray diffraction (XRD), UV-visible spectroscopy (UV-vis) and three-electrode potentiostat, respectively. In this work, we found that the morphologies, thickness, growth rate, crystallinities, grain sizes and optical bandgap were controllable on the growth duration, which affected photocurrent density and photo-stability. The highest growth rate of CuO nanorods was 126 nm/min. From the XRD measurement, we also confirmed that (020) directional growth affected the growth of the CuO nanorods. A maximum photocurrent density of-1.88 mA/cm² at -0.55 V (vs. SCE) and high photo-stability value about 40% was obtained with 10 minutes growth duration.

  10. Spectral studies on CuO in sodium–calcium borophosphate glasses

    Indian Academy of Sciences (India)

    S SHAILAJHA; K GEETHA; P VASANTHARANI

    2016-08-01

    Transparent borophosphate glasses doped with CuO were prepared by melt quenching technique. X-ray diffraction (XRD), optical and luminescence properties of sodium–calcium borophosphate glasses doped with CuO have been studied. The XRD results showed the amorphous nature of the sample. The introduction of CuO was favourable for the colour changes from light blue to dark bluish green colour. Direct optical energy bandgaps before and after doping with different percents of copper oxide obtained in the range 4.81–2.99 eV indicated the role of copper in the glassy matrix by ultraviolet (UV) spectra. The glasses have more than 80% transparency for emission wavelength range, and strong absorption bands due to the charge transition of the Cu$^+$ and Cu$^{2+}$ ions were observed. The emission bands observed in the UV and blue regions are attributed to 3d$^9$4s–3d$^{10}$ triplet transition in Cu$^+$ ion.

  11. Synthesis and characterization of tenorite (CuO nanoparticles from smelting furnace dust(SFD

    Directory of Open Access Journals (Sweden)

    Darezereshki E.

    2013-01-01

    Full Text Available Tenorite (CuO nanoparticles were prepared from a dilute CuSO4 solution. The solution was obtained by leaching (pH=1.5 of smelting furnace dust of Sarcheshmeh Copper Complex, Iran. The recovery of copper from the acidic sulphate solution was carried out by solvent extraction using Lix 984-N. Tenorite nanoparticles were synthesized by direct thermal decomposition of Langite [Cu4(OH6SO4(H2O2] as a precursor which was calcinated in air for 2 h at 750°C. The Samples were characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. The average diameter of the spherical pure CuO nanoparticles and their crystallite size were estimated to be 92 nm and 40nm, respectively. The simplicity of the present method suggests its potential application at industrial scale as a cheap and convenient way to produce pure CuO nanoparticles from dilute CuSO4 solutions obtained from leaching of smelting furnace dust.

  12. Heterojunction characteristics of ZnO and CuO substrates formed by direct bonding

    Energy Technology Data Exchange (ETDEWEB)

    Abe, Hiroshi; Fujishima, Masahide; Komiyama, Takao; Chonan, Yasunori; Yamaguchi, Hiroyuki; Aoyama, Takashi [Department of Electronics and Information Systems, Akita Prefectural University, Yuri-honjo, Akita 015-0055 (Japan)

    2012-06-15

    The n-ZnO/p-CuO heterojunction characteristics have been investigated by direct bonding of ZnO and CuO substrates at room temperatures, and by post-annealing at 800 C. The ZnO substrate was fabricated by mixing of ZnO and Al{sub 2}O{sub 3} (2%) powders, pressing at 50 MPa, and sintering at 1400 C while the CuO substrate was fabricated by mixing of CuO and Li{sub 2}CO{sub 3} (1%) powders, pressing at 300 MPa, and sintering at 700 C. Rectifying behaviour with an ideality factor of 126 was observed after bonding of these substrates. Post-annealing of the heterojunction, however, significantly increased both the forward and the reverse currents, and the rectifying behaviour was lost. Symmetrical I-V curves with threshold voltages of about {+-} 1 V were observed and this degradation could be explained by impurity (Al and Li) segregation at the junction interface. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. CuO and Co3O4 Nanoparticles: Synthesis, Characterizations, and Raman Spectroscopy

    Directory of Open Access Journals (Sweden)

    M. Rashad

    2013-01-01

    Full Text Available Copper oxide and cobalt oxide (CuO, Co3O4 nanocrystals (NCs have been successfully prepared in a short time using microwave irradiation without any postannealing treatment. Both kinds of nanocrystals (NCs have been prepared using copper nitrate and cobalt nitrate as the starting materials and distilled water as the solvent. The resulted powders of nanocrystals (NCs were characterized by X-ray diffraction (XRD, transmission electron microscopy (TEM, scanning electron microscopy (SEM, and atomic force microscopy (AFM measurements. The obtained results confirm the presence of the both of oxides nanopowders produced during chemical precipitation using microwave irradiation. A strong emission under UV excitation is obtained from the prepared CuO and Co3O4 nanoparticles. The results show that the nanoparticles have high dispersion and narrow size distribution. The line scans of atomic force microscopy (AFM images of the nanocrystals (NCs sprayed on GaAs substrates confirm the results of both X-ray diffraction and transmission electron microscopy. Furthermore, vibrational studies have been carried out using Raman spectroscopic technique. Specific Raman peaks have been observed in the CuO and Co3O4 nanostructures, and the full width at half maximum (FWHM of the peaks indicates a small particle size of the nanocrystals.

  14. Effect of Extracellular Polymeric Substances on CuO Nanoparticle Dissolution and Colloidal Stability

    Science.gov (United States)

    Adeleye, A. S.; Keller, A. A.

    2013-12-01

    Extracellular polymeric substances (EPS) are high molecular weight polymers produced by microorganisms growing in natural as well as artificial environments. EPS may interact with engineered nanomaterials (ENMs) in aquatic systems via electrostatic and/or hydrophobic associations, therefore, influencing the fate and transport of ENMs. In this study the effect of soluble EPS isolated from Isochrysis galbana, a marine phytoplankton, on the dissolution kinetics and colloidal stability of CuO nanoparticles was investigated. EPS was characterized by measuring hydrodynamic diameter, total organic carbon, carbohydrate, and protein concentrations. CuO nanoparticles were more stable in the presence of EPS in aqueous media as indicated by hydrodynamic size and average count rate measurements. The effect of pH and ionic strength on dissolution was also studied. [Cu2+] and [Cu]total detected after a week were 5.70 mg L-1 and 7.08 mg L-1 respectively when 10 mg L-1 CuO nanoparticles was kept in 10 mM NaCl at pH 4. In the presence of 5 mg-C EPS L-1, [Cu2+] and [Cu]total were slightly lower at 5.0 mg L-1 and 5.53 mg L-1 respectively. Although observed [Cu2+] and [Cu]total were significantly lower at neutral and alkaline pH conditions, a similar pattern was observed.

  15. Size-dependent antimicrobial properties of CuO nanoparticles against Gram-positive and -negative bacterial strains

    Directory of Open Access Journals (Sweden)

    Azam A

    2012-07-01

    Full Text Available Ameer Azam,1,2 Arham S Ahmed,2 M Oves,3 MS Khan,3 Adnan Memic11Center of Nanotechnology, King Abdulaziz University, Jeddah, Saudi Arabia; 2Center of Excellence in Materials Science (Nanomaterials, Department of Applied Physics, 3Department of Agricultural Microbiology, Aligarh Muslim University, Aligarh, IndiaBackground: CuO is one of the most important transition metal oxides due to its captivating properties. It is used in various technological applications such as high critical temperature superconductors, gas sensors, in photoconductive applications, and so on. Recently, it has been used as an antimicrobial agent against various bacterial species. Here we synthesized different sized CuO nanoparticles and explored the size-dependent antibacterial activity of each CuO nanoparticles preparation.Methods: CuO nanoparticles were synthesized using a gel combustion method. In this approach, cupric nitrate trihydrate and citric acid were dissolved in distilled water with a molar ratio of 1:1. The resulting solution was stirred at 100°C, until gel was formed. The gel was allowed to burn at 200°C to obtain amorphous powder, which was further annealed at different temperatures to obtain different size CuO nanoparticles. We then tested the antibacterial properties using well diffusion, minimum inhibitory concentration, and minimum bactericidal concentration methods.Results: XRD spectra confirmed the formation of single phase CuO nanoparticles. Crystallite size was found to increase with an increase in annealing temperature due to atomic diffusion. A minimum crystallite size of 20 nm was observed in the case of CuO nanoparticles annealed at 400°C. Transmission electron microscopy results corroborate well with XRD results. All CuO nanoparticles exhibited inhibitory effects against both Gram-positive and -negative bacteria. The size of the particles was correlated with its antibacterial activity.Conclusion: The antibacterial activity of CuO nanoparticles

  16. FEA of the clinching process of short fiber reinforced thermoplastic with an aluminum sheet using LS-DYNA

    Science.gov (United States)

    Behrens, B.-A.; Bouguecha, A.; Vucetic, M.; Grbic, N.

    2016-10-01

    A structural concept in multi-material design is used in the automotive industry with the aim of achieving significant weight reductions of conventional car bodies. In this respect, the use of aluminum and short fiber reinforced plastics represents an interesting material combination. A wide acceptance of such a material combination requires a suitable joining technique. Among different joining techniques, clinching represents one of the most appealing alternative for automotive applications. This contribution deals with the FE simulation of the clinching process of two representative materials PA6GF30 and EN AW 5754 using the FE software LS-DYNA. With regard to the material modelling of the aluminum sheet, an isotropic material model based on the von Mises plasticity implemented in LS-DYNA was chosen. Analogous to aluminum, the same material model is used for modelling the short fiber reinforced thermoplastic. Additionally, a semi-analytical model for polymers (SAMP-1) also available in LS-DYNA was taken. Finally, the FEA of clinching process is carried out and the comparison of the simulation results is presented above.

  17. Magnetic lattice dynamics of the oxygen-free FeAs pnictides: how sensitive are phonons to magnetic ordering?

    Science.gov (United States)

    Zbiri, Mohamed; Mittal, Ranjan; Rols, Stéphane; Su, Yixi; Xiao, Yinguo; Schober, Helmut; Chaplot, Samrath L; Johnson, Mark R; Chatterji, Tapan; Inoue, Yasunori; Matsuishi, Satoru; Hosono, Hideo; Brueckel, Thomas

    2010-08-11

    To shed light on the role of magnetism on the superconducting mechanism of the oxygen-free FeAs pnictides, we investigate the effect of magnetic ordering on phonon dynamics in the low-temperature orthorhombic parent compounds, which present a spin density wave. The study covers both the 122 (AFe(2)As(2); A = Ca, Sr, Ba) and 1111 (AFeAsF; A = Ca, Sr) phases. We extend our recent work on the Ca (122 and 1111) and Ba (122) cases by treating, computationally and experimentally, the 122 and 1111 Sr compounds. The effect of magnetic ordering is investigated through detailed non-magnetic and magnetic lattice dynamical calculations. The comparison of the experimental and calculated phonon spectra shows that the magnetic interactions/ordering have to be included in order to reproduce well the measured density of states. This highlights a spin-correlated phonon behavior which is more pronounced than the apparently weak electron-phonon coupling estimated in these materials. Furthermore, there is no noticeable difference between phonon spectra of the 122 Ba and Sr, whereas there are substantial differences when comparing these to CaFe(2)As(2) originating from different aspects of structure and bonding.

  18. Strength Enhancement of Car Front Bumper for Slow Speed Impact by FEA Method as per IIHS Regulation

    Science.gov (United States)

    Sonawane, Chandrakant Rameshchandra; Shelar, Ajit Lavaji

    2017-05-01

    Low speed collisions happen significantly due to on road slow moving heavy traffic as well as during parking of vehicles. The bumpers are provided in front and back side of a vehicle has two main purposes: first is to absorb the energy generated during these kinds of slow speed impacts and secondly to protect the expensive parts like main engine parts, radiators and connected engine cooling mechanism, headlights, taillights, etc, by slowing down the vehicles. The problem often in various cars bumper is that they doesn't line-up vertically during low speed impact and leads to damage of various parts which are costly to repair. Many a times bumper design does not have sufficient capacity to absorb the energy generated during these impact. Guideline by International Institute Highway Safety (IIHS) regulation provides useful insight for such low speed impact study. In this paper, slow speed impact test were conducted as per IIHS regulation in three positions namely central impact, left hand corner impact and right hand corner impact. Parameters including bumper material, shape, thickness and impact condition are analyzed using fine element analysis (FEA) to enhance crashworthiness design in low speed impact. Then the vehicle front structure has been modified suitably. It has been observed that lining up the front metal bumper with suitable stiffness provides the best result which ultimately reduces the damage to the vehicle parts.

  19. Evaluation of common tests for fracture characterisation of advanced high-strength sheet steels with the help of the FEA

    Science.gov (United States)

    Peshekhodov, I.; Dykiert, M.; Vucetic, M.; Behrens, B.-A.

    2016-11-01

    The paper presents results of evaluation of common tests for fracture characterization of advanced high-strength sheet steels with the help of the FEA. The tests include three in-plane shear tests, two uniaxial tension tests, two plane strain tension tests and two equibiaxial tension tests. Three high-strength steels with different yield loci, strain hardening rates and strengths in three different thicknesses each were used. The evaluation was performed based on the spatial distribution of the equivalent plastic strain and damage variable in the specimen at the moment of crack initiation as well as on the time variation of the stress state at the crack initiation location. For in-plane shear, uniaxial tension and plane strain tension, no test can be unconditionally recommended as disadvantages of all studied tests in these groups cannot be neglected. However, in each of these groups, a test can be chosen, which represents an acceptable compromise between its advantages and disadvantages: the shear test on an IFUM butterfly specimen for in-plane shear, the tensile test on a holed specimen for uniaxial tension and the tensile test on a waisted specimen for plane strain tension. On the contrary, the bulge test on a circular specimen with a punch of Ø 100 mm can be unconditionally recommended for equibiaxial tension. In the future, optimisation of the studied tests for in-plane shear, uniaxial tension and plane strain tension appears to be necessary.

  20. Probing the Elastic-Plastic, Time-Dependant Response of Test Fasteners using Finite Element Analysis (FEA)

    Energy Technology Data Exchange (ETDEWEB)

    ML Renauld; H Lien

    2004-12-13

    The evolution of global and local stress/strain conditions in test fasteners under test conditions is investigated using elastic-plastic, time-dependent finite element analyses (FEA). For elastic-plastic response, tensile data from multiple specimens, material heats and test temperatures are integrated into a single, normalized flow curve from which temperature dependency is extracted. A primary creep model is calibrated with specimen- and fastener-based thermal relaxation data generated under a range of times, temperatures, stress levels and environments. These material inputs are used in analytical simulations of experimental test conditions for several types of fasteners. These fastener models are constructed with automated routines and contact conditions prescribed at all potentially mating surfaces. Thermal or mechanical room temperature pre-loading, as appropriate for a given fastener, is followed by a temperature ramp and a dwell time at constant temperature. While the amount of thermal stress relaxation is limited for the conditions modeled, local stress states are highly dependent upon geometry (thread root radius, for example), pre-loading history and thermal expansion differences between the test fastener and test fixture. Benefits of this FE approach over an elastic methodology for stress calculation will be illustrated with correlations of Stress Corrosion Cracking (SCC) initiation time and crack orientations in stress concentrations.

  1. 丝网印刷三极CNT-FEA的研制%Fabrication of Triode CNT-FEA Using Screen Print Process

    Institute of Scientific and Technical Information of China (English)

    刘卫华; 朱长纯

    2008-01-01

    制作三极型场发射阵列(FEA),传统上都依赖薄膜工艺及光刻技术.这在很大程度上限制了印刷型碳纳米管阴极的优势.通过改进全丝网印刷工艺,包括一项改进的栅极烧结工艺和一项洁网技术,成功地制作出,32×32的三极型以碳纳米管为阴极的场发射阵列(CNT-FEA).该三极型CNT-FEA具有显著的栅控特性.栅压在150~300 V可以对阳极电流实现良好的控制.栅控电流放大系数超过180.

  2. 数字档案馆顶层架构参考模型设计%The FEA Reference Model Design of Digital Archives

    Institute of Scientific and Technical Information of China (English)

    郭伟; 方昀

    2015-01-01

    本文分析了数字档案馆功能需求,阐述了顶层架构方法FEA,构建了数字档案馆总体架构参考模型DAFEA,比较了FEA、NARA联邦机构档案管理框架RMP和DAFEA的对应关系,为数字档案馆开展顶层设计提供新方法.

  3. Synthesis methods and character of iron-based mixed-anion superconductor with suppression of the amorphous FeAs impurity phase

    Science.gov (United States)

    Fujioka, Masaya; Ozaki, Toshinori; Okazaki, Hiroyuki; Saleem, Denholme; Deguchi, Keita; Demura, Satoshi; Hara, Hiroshi; Watanabe, Tohru; Takeya, Hiroyuki; Yamaguchi, Takahide; Kumakura, Hiroaki; Takano, Yoshihiko

    2013-03-01

    To obtain the high superconducting properties of polycrystalline SmFeAsO1-xFx, we investigated the following three synthesis methods: a high pressure synthesis, a low temperature synthesis with gradual cooling and a metal added synthesis. Generally, polycrystalline SmFeAsO1-xFx is composed of superconducting grains and a little amorphous FeAs compounds. These areas randomly co-exist and amorphous areas are located between the superconducting grains. Therefore, we suggest that the superconducting current is prevented by the amorphous areas. In fact, although the single crystal of this material shows a large critical current density of 106 A/cm2, polycrystalline SmFeAsO1-xFx shows a significant depression of critical current density due to this grain boundary blocking effect. To obtain a high global critical current density, it is important to investigate how to remove the amorphous FeAs. It is found that the impurity phase of amorphous FeAs is decreased by using the above three synthesis methods.

  4. Optical study of the antiferromagnetic ordered state in electron-overdoped Ca0.77Nd0.23FeAs2

    Science.gov (United States)

    Yang, Run; Xu, Bing; Dai, Yaomin; Zhang, Wei; Liu, Jinyun; Qiu, Ziyang; Qiu, Xianggang

    2016-06-01

    In Ca1 -xRxFeAs2 (R =rare earth), an antiferromagnetic (AFM) phase as well as a structural transition have been reported, even in the electron-overdoped regime. Here, we investigated the temperature-dependent in-plane optical spectroscopy of overdoped Ca0.77Nd0.23FeAs2 . Upon entering the AFM state, we found an abrupt reduction of low-frequency (500-2000 cm-1) spectral weight in the optical conductivity. In sharp contrast to the parent compounds of the 122 system, where spin-density-wave gaps have been clearly observed in the AFM state, a gap signature is absent in Ca0.77Nd0.23FeAs2 . This may be a consequence of the poor nesting condition between the hole and electron pockets. However, a spectral weight analysis shows that the reduced spectral weight at low frequency is transferred to the high-frequency range (≳4000 cm-1), pointing to a localization effect. These observations suggest that the AFM order in Ca0.77Nd0.23FeAs2 is most likely to originate from a localized nature rather than Fermi-surface nesting.

  5. Magnetism and electronic structures of novel layered CaFeAs2 and Ca0.75(Pr/La)0.25FeAs2

    Science.gov (United States)

    Huang, Yi-Na; Yu, Xiang-Long; Liu, Da-Yong; Zou, Liang-Jian

    2015-05-01

    The magnetic and electronic properties of the parent material CaFeAs2 of new superconductors are investigated using first-principles calculations. We predict that the ground state of CaFeAs2 is a spin-density-wave (SDW)-type striped antiferromagnet driven by Fermi surface nesting. The magnetic moment around each Fe atom is about 2.1 μB. We also present electronic and magnetic structures of electron-doped phase Ca0.75(Pr/La)0.25FeAs2, the SDW order was suppressed by La/Pr substitution. The As in arsenic layers is negative monovalent and acts as blocking layers enhancing two-dimensional character by increasing the spacing distance between the FeAs layers. This favors strong antiferromagnetic fluctuations mediated pairing, implying higher Tc in Ca0.75(Pr/La)0.25FeAs2 than Ca0.75(Pr/La)0.25Fe2As2.

  6. Struture stability and compressibility of iron-based superconductor Nd(O0.88F0.12)FeAs under high pressure.

    Science.gov (United States)

    Zhao, Jinggeng; Wang, Luhong; Dong, Dawei; Liu, Zhiguo; Liu, Haozhe; Chen, Genfu; Wu, Dan; Luo, Jianlin; Wang, Nanlin; Yu, Yong; Jin, Changqing; Guo, Quanzhong

    2008-10-22

    The high-pressure angle-dispersive X-ray diffraction experiments on the iron-based superconductor Nd(O0.88F0.12)FeAs were performed up to 32.7 GPa at room temperature. An isostructural phase transition starts at approximately 10 GPa. When pressure is higher than 13.5 GPa, Nd(O0.88F0.12)FeAs completely transforms to a high-pressure phase, which remains the same tetragonal structure with a larger a-axis and smaller c-axis than those of the low-pressure phase. The ambient conditions isothermal bulk moduli B0 are derived as 102(2) and 245(9) GPa for the low-pressure phase and high-pressure phase, respectively. The structure analysis based on the Rietveld refinement methods shows the difference of pressure dependence of the Fe-As and Nd-(O, F) bonding distances, as well as As-Fe-As and Nd-(O, F)-Nd angles between the low-pressure phase and high-pressure phase.

  7. Comparison of the local structures of Ca0.82La0.18FeAs2 and Ba0.64K0.36Fe2As2 pnictide superconductors using atomic pair distribution function analysis

    Science.gov (United States)

    Joseph, Boby; Iadecola, Antonella; Bernasconi, Andrea; Rispoli, Pasquale; Demitri, Nicola; Xing, Xiangzhuo; Zhou, Wei; Shi, Zhixiang

    2015-09-01

    A comparative local structure study of pnictide superconductors Ca0.82La0.18FeAs2 (112-type, Tc∼ 40 K) and Ba0.64K0.36Fe2As2 (122-type, Tc∼ 37 K), using room temperature x-ray total scattering measurements is reported. The Fe-As superconducting active layer is found to be globally similar in both the systems consisting of edge-sharing FeAs4/4 tetrahedra as in all the iron-pnictide superconductors discovered so far. Although optimally superconducting, the active layer in these compounds is found to sustain a large local inhomogeneity. These results thus imply that a nanoscopic manipulation of the Fe-As active layer, rather than its isotropic structural tuning, is the key parameter to control the superconducting properties of the iron-based systems.

  8. Flexible 3D porous CuO nanowire arrays for enzymeless glucose sensing: in situ engineered versus ex situ piled

    Science.gov (United States)

    Huang, Jianfei; Zhu, Yihua; Yang, Xiaoling; Chen, Wei; Zhou, Ying; Li, Chunzhong

    2014-12-01

    Convenient determination of glucose in a sensitive, reliable and cost-effective way has aroused sustained research passion, bringing along assiduous investigation of high-performance electroactive nanomaterials to build enzymeless sensors. In addition to the intrinsic electrocatalytic capability of the sensing materials, electrode architecture at the microscale is also crucial for fully enhancing the performance. In this work, free-standing porous CuO nanowire (NW) was taken as a model sensing material to illustrate this point, where an in situ formed 3D CuO nanowire array (NWA) and CuO nanowires pile (NWP) immobilized with polymer binder by conventional drop-casting technique were both studied for enzymeless glucose sensing. The NWA electrode exhibited greatly promoted electrochemistry characterized by decreased overpotential for electro-oxidation of glucose and over 5-fold higher sensitivity compared to the NWP counterpart, benefiting from the binder-free nanoarray structure. Besides, its sensing performance was also satisfying in terms of rapidness, selectivity and durability. Further, the CuO NWA was utilized to fabricate a flexible sensor which showed excellent performance stability against mechanical bending. Thanks to its favorable electrode architecture, the CuO NWA is believed to offer opportunities for building high-efficiency flexible electrochemical devices.Convenient determination of glucose in a sensitive, reliable and cost-effective way has aroused sustained research passion, bringing along assiduous investigation of high-performance electroactive nanomaterials to build enzymeless sensors. In addition to the intrinsic electrocatalytic capability of the sensing materials, electrode architecture at the microscale is also crucial for fully enhancing the performance. In this work, free-standing porous CuO nanowire (NW) was taken as a model sensing material to illustrate this point, where an in situ formed 3D CuO nanowire array (NWA) and CuO nanowires

  9. Improved photocatalytic activity of ZnO coupled CuO nanocomposites synthesized by reflux condensation method

    Energy Technology Data Exchange (ETDEWEB)

    Mageshwari, K. [Department of Electronic Engineering, Hanyang University, Seoul (Korea, Republic of); PG and Research Department of Physics, Kongunadu Arts and Science College, Coimbatore 641 029, Tamil Nadu (India); Nataraj, D. [Department of Physics, Bharathiar University, Coimbatore 641 046 (India); Pal, Tarasankar [Department of Chemistry, Indian Institute of Technology, Kharagpur 721 302 (India); Sathyamoorthy, R., E-mail: rsathya59@gmail.com [PG and Research Department of Physics, Kongunadu Arts and Science College, Coimbatore 641 029, Tamil Nadu (India); Park, Jinsub, E-mail: jinsubpark@hanyang.ac.kr [Department of Electronic Engineering, Hanyang University, Seoul (Korea, Republic of)

    2015-03-15

    Highlights: • CuO–ZnO nanocomposites were synthesized by reflux condensation method. • Photodegradation of methyl orange and methylene blue dyes was investigated. • Morphological studies show 3D flower-like CuO microspheres adorned with ZnO nanorods. • Optical analysis showed characteristic absorption bands of CuO and ZnO. • CuO–ZnO nanocomposites exhibited superior photocatalytic activity than CuO. - Abstract: Nanostructured CuO–ZnO nanocomposites were successfully synthesized for different Zn{sup 2+} concentrations by reflux condensation method without using any surfactant, and their photocatalytic activity was evaluated using methyl orange and methylene blue dyes under UV light irradiation. XRD revealed the formation of CuO–ZnO nanocomposites, composing of monoclinic CuO and hexagonal ZnO. XPS analysis revealed that CuO–ZnO nanocomposites are made up of Cu(II), Zn(II) and O. FESEM and TEM images showed that pure CuO exhibit 3D flower-like microstructure, while the CuO–ZnO nanocomposites prepared for different Zn{sup 2+} concentrations have 3D flower-like CuO, microstructure adorned with rod-like ZnO particles. UV–Vis DRS showed absorption bands corresponding to CuO and ZnO around 960 nm and 395 nm, respectively. PL spectra of CuO–ZnO nanocomposites exhibited reduced PL emissions compared to pure CuO, indicating the low recombination rate of photogenerated electrons and holes. Photodegradation assay revealed that catalytic activity of CuO–ZnO nanocomposites increased with Zn{sup 2+} concentration, and also effectively degrade methyl orange and methylene blue dyes when compared to pure CuO. The enhanced photocatalytic activity of CuO–ZnO nanocomposites were mainly ascribed to the reduced recombination and efficient separation of photogenerated charge carriers. The possible mechanism for the improved photocatalytic activity of CuO–ZnO nanocomposites was proposed.

  10. Solid state green synthesis and catalytic activity of CuO nanorods in thermal decomposition of potassium periodate

    Science.gov (United States)

    Patel, Vinay Kumar; Bhattacharya, Shantanu

    2017-09-01

    The present study reports a facile solid state green synthesis process using the leaf extracts of Hibiscus rosa-sinensis to synthesize CuO nanorods with average diameters of 15–20 nm and lengths up to 100 nm. The as-synthesized CuO nanorods were characterized by x-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and selected area electron diffraction. The formation mechanism of CuO nanorods has been explained by involving the individual role of amide I (amino groups) and carboxylate groups under excess hydroxyl ions released from NaOH. The catalytic activity of CuO nanorods in thermal decomposition of potassium periodate microparticles (µ-KIO4) microparticles was studied by thermo gravimetric analysis measurement. The original size (~100 µm) of commercially procured potassium periodate was reduced to microscale length scale to about one-tenth by PEG200 assisted emulsion process. The CuO nanorods prepared by solid state green route were found to catalyze the thermal decomposition of µ-KIO4 with a reduction of 18 °C in the final thermal decomposition temperature of potassium periodate.

  11. Effect of CuO addition on structure and electrical properties of low temperature sintered quaternary piezoelectric ceramics

    Indian Academy of Sciences (India)

    Jianhua Li

    2013-10-01

    The ceramics were prepared successfully by CuO additions to Pb[(Mn1/3Sb2/3)0.06(Ni1/2W1/2)0.02-(Zr0.49Ti0.51)0.92]O3. Effect of the addition on sintering temperature, structure and electrical properties of ceramics was investigated. The piezoelectric ceramics was prepared by solid-state reaction. Sintering experiments were accomplished at temperature between 950 and 1100 °C added 0.3–1.0 wt% CuO. The sintering temperature was reduced from 1250 °C (without CuO additions) to 970 °C when CuO-doped. The ceramics sintered at 970 °C for 2 h with 0.7 wt% CuO exhibited r = 1845, tan = 0.15%, 33 = 395 pC/N, p = 0.58 and m = 1830, which were the highest values. With increasing CuO doping, c becomes lower. Jahn–Teller effect was used to explain the contraction of -axis and simultaneous extension of -axis in the lattice.

  12. Structural studies of Nd$_{1.85}$Ce$_{0.15}$CuO$_{4}$ $+$ Ag superconducting system

    Indian Academy of Sciences (India)

    N RADHIKESH RAVEENDRAN; A K SINHA; R RAJARAMAN; M PREMILA; E P AMALADASS; K VINOD; J JANAKI; S KALAVATHI; AWADHESH MANI

    2016-06-01

    We have studied for the first time the effect of Ag addition (0–15 wt%) to the superconducting system, Nd$_{1.85}$Ce$_{0.15}$CuO$_{4}$, on its crystal structure and local structural features, using synchrotron X-ray diffraction(SXRD) and Raman spectroscopy, respectively. SXRD and subsequent Rietveld refinement studies on powders of Nd$_{1.85}$Ce$_{0.15}$CuO$_4$ $+$ Ag system indicate a small but significant change in lattice parameter upon Ag addition, showing evidence for possible incorporation of Ag to the extent of $\\sim$1 wt%. Raman spectroscopic studies indicate that the parent structure of Nd$_{1.85}$Ce$_{0.15}CuO$_{4}$ remains unaffected with no major local structural changes on doping with silver. However, all Raman modes show minor phonon hardening upon Ag addition, which is consistent with the unit cell volume reduction as is observed in XRD. A systematic bleaching out of the apical oxygen defect mode was also observed with increased Ag addition. Polarized Raman measurements helped to identify the asymmetric nature of the B1g Raman mode. X-ray diffraction studies on pellets of Nd$_{1.85}$Ce$_{0.15}CuO$_4$ $+$ Ag system further indicate a randomization of preferred orientation upon Ag addition. The superconductivity of the Nd$_{1.85}$Ce$_{0.15}$CuO$_4$ $+$ Ag system has been well characterized for all the compositions studied.

  13. Onion-like carbon coated CuO nanocapsules: A highly reversible anode material for lithium ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xianguo, E-mail: liuxianguohugh@gmail.com [Anhui Key Laboratory of Metal Materials and Processing, School of Materials Science and Engineering, Anhui University of Technology, Maanshan 243002 (China); Bi, Nannan; Feng, Chao [Anhui Key Laboratory of Metal Materials and Processing, School of Materials Science and Engineering, Anhui University of Technology, Maanshan 243002 (China); Or, Siu Wing [Department of Electrical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon (Hong Kong); Sun, Yuping [Center for Engineering practice and Innovation Education, Anhui University of Technology, Maanshan 243002 (China); Jin, Chuangui; Li, Weihuo; Xiao, Feng [Anhui Key Laboratory of Metal Materials and Processing, School of Materials Science and Engineering, Anhui University of Technology, Maanshan 243002 (China)

    2014-02-25

    Highlights: • Onion-like carbon–coated CuO nanocapsules have been synthesized. • Onion-like carbon leads to the improved stability and electric conductivity. • CuO/C nanocapsules maintain a reversible capacity of 628.7 mA h g{sup −1} after 50 cycles. -- Abstract: The synthesis and characterization of CuO/C nanocapsules for application as anode material in lithium ion batteries are reported. Introduction of onion-like carbon shell on the CuO nanoparticles leads to the improved stability, electric conductivity and electrochemical performance. When evaluated as potential anode materials for lithium-ion batteries, the novel CuO/C nanocapsules deliver an initial discharge capacity of 1043.9 mA h g{sup −1} at 100 mA g{sup −1} and maintain a high reversible capacity of 628.7 mA h g{sup −1} after 50 charge–discharge cycles, much higher than those of the CuO nanoparticles. A postmortem analysis of the CuO and CuO/C anodes subjected to prolonged cycling reveals the existence of a lower degree of surface cracking and particle breakage in the CuO/C anode than the CuO anode.

  14. Morphology-controllable synthesis of CuO nanostructures and their catalytic activity for the reduction of 4-nitrophenol

    Science.gov (United States)

    Che, Wei; Ni, Yonghong; Zhang, Yuxing; Ma, Yue

    2015-02-01

    The investigation on the correlation between properties and shapes of nanomaterials always draws increased interest. However, the correlation between properties and shapes of CuO nanostructures was rarely reported in the previous works. The shape-controlled preparation of CuO nanostructures was successfully realized in the present work via a simple oil-bath route in air at 170 °;C for 30 min, employing CuCl2•2H2O and NaOH as the reactants. It was found that CuO nanocrystals with leaf-like, dumbbell-like and flowerlike structures were obtained through introducing various additives. At the same time, the correlation between properties and shapes was investigated. It was found that the catalytic performances of the as-prepared CuO nanostructures for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in NaBH4 aqueous solution were dependent on its morphologies. Experiments showed that the first-order rate constants for CuO nanostructures with various shapes were in turn 35.5‧ 10-3 s-1 (leaf-like nanosheets), 4.77‧ 10-3 s-1 (dumbbell-like architectures), 10.6‧ 10-3 s-1 (flowerlike nanostructures). The present research provides a new catalyst selection for the reduction of 4-NP to 4-AP in excess NaBH4 aqueous solution, which has potential application in industrial production.

  15. Free-standing CuO nanoflake arrays coated Cu foam for advanced lithium ion battery anodes

    Science.gov (United States)

    Yang, Wanfeng; Wang, Jiawei; Ma, Wensheng; Dong, Chaoqun; Cheng, Guanhua; Zhang, Zhonghua

    2016-11-01

    For lithium ion batteries (LIBs), low electronic conductivity of CuO leads to rapid capacity decay and poor structural stability. Herein, we successfully fabricate three-dimensional CuO nanoflake arrays coated Cu foam by facile and efficient electrochemical oxidation. When being applied as anode material for LIBs, the CuO electrodes deliver stable reversible capacities of 523.9 mA h g-1 at 0.5 A g-1, 376.1 mA h g-1 at 1.0 A g-1 and 322.7 mA h g-1 at 2.0 A g-1 with high coulombic efficiency (>99%) after 100 cycles. A long cycle life of up to 400 cycles at 2.0 A g-1 is also achieved with the retention capacity of 193.5 mA h g-1. Moreover, the electrode exhibits excellent rate capability and can regain its original capacities as reversing to the low current densities. Noticeably, on-line differential electrochemical mass spectrometry and in situ Raman measurements confirm the formation of solid electrolyte interface film and the conversion mechanism for the CuO electrodes, respectively. The superior lithium storage performance can be attributed to the favorable nanoflake structures with high surface area and the perfect electrical contact between CuO and Cu substrate.

  16. Magnetic-Field-Induced Soft-Mode Quantum Phase Transition in the High-Temperature Superconductor La1.855Sr0.145CuO4

    DEFF Research Database (Denmark)

    Chang, J.; Christensen, Niels Bech; Niedermayer, C.

    2009-01-01

    Inelastic neutron-scattering experiments on the high-temperature superconductor La1.855Sr0.145CuO4 reveal a magnetic excitation gap Delta that decreases continuously upon application of a magnetic field perpendicular to the CuO2 planes. The gap vanishes at the critical field required to induce long...

  17. Morphology and gas sensing characteristics of density-controlled CuO nanostructures obtained by varying the oxygen partial pressure during growth

    Science.gov (United States)

    Lee, Dongjin; Jin, Changhyun; Noh, Youngwook; Park, Seokhyun; Choi, Sun-Woo

    2016-07-01

    By exerting different O2 partial pressures (0, 20, 40, and 60 sccm) onto copper substrates, we discovered that the growth parameter, namely, the O2 flow rate, affects the degree of nucleation, diameter, length, and crystalline quality of CuO nanowires (NWs). Scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM) were used to analyze the evolution of the morphological and the microstructural changes in the CuO nanostructures. The formation of a Cu2O interlayer between the Cu and the CuO layers could be adjusted by controlling more precisely the O2 flow rate. In addition, the reducing (H2S) and the oxidizing (O2, NO2, and SO2) gas sensing performances of these O2-assisted CuO NWs were compared with those of CuO NWs grown in static air. The response to the reducing H2S of the sensors based on CuO NWs grown using O2 at 40 sccm showed a higher electrical change and faster response and recovery times than the sensors based on CuO NWs grown using lower O2 flow rates, including the ones grown in static air and/or used for sensing oxidizing gases (O2, NO2, and SO2) did. On the basis of their growth and their gas-sensing applications, the possible mechanisms characteristic of the density-controlled CuO NWs grown using various O2 partial pressures are discussed.

  18. Long-term effects of cupric oxide nanoparticles (CuO NPs) on the performance, microbial community and enzymatic activity of activated sludge in a sequencing batch reactor.

    Science.gov (United States)

    Wang, Sen; Li, Zhiwei; Gao, Mengchun; She, Zonglian; Ma, Bingrui; Guo, Liang; Zheng, Dong; Zhao, Yangguo; Jin, Chunji; Wang, Xuejiao; Gao, Feng

    2017-02-01

    The long-term effects of cupric oxide nanoparticles (CuO NPs) on the performance, microbial activity and microbial community of activated sludge were investigated in a sequencing batch reactor (SBR). The SBR performance had no evident change at 0-10 mg/L CuO NPs, whereas the CuO NPs concentration at 30-60 mg/L affected the COD, NH4(+)-N and soluble orthophosphate (SOP) removal, nitrogen and phosphorus removal rate and microbial enzymatic activity of activated sludge. Some CuO NPs might be absorbed on the surface of activated sludge or penetrate the microbial cytomembrane into the microbial cell interior of activated sludge. Compared to 0 mg/L CuO NPs, the reactive oxygen species (ROS) production and lactate dehydrogenase (LDH) release increased by 43.6% and 56.4% at 60 mg/L CuO NPs, respectively. The variations of ROS production and LDH release demonstrated that CuO NPs could induce the toxicity towards the microorganisms and destroy the integrity of microbial cytomembrane in the activated sludge. High throughput sequencing of 16S rDNA indicated that CuO NPs could evidently impact on the microbial richness, diversity and composition of activated sludge in the SBR.

  19. Field-induced interplanar magnetic correlations in the high-temperature superconductor La1.88Sr0.12CuO4

    DEFF Research Database (Denmark)

    Rømer, A. T.; Jensen, P.; Jacobsen, H.

    2015-01-01

    We present neutron-scattering studies of the interplanar magnetic correlations in the high-temperature superconductor La1.88Sr0.12CuO4 (Tc=27 K). The correlations are studied both in a magnetic field applied perpendicular to the CuO2 planes, and in zero field under different cooling conditions. We...

  20. Evolution of CuO poly-crystalline layers to coherent single-crystalline dots on ZnO nanorods upon annealing

    Science.gov (United States)

    Wang, Ruey-Chi; Hou, Yuan-Ru; Chen, Yi-Wen

    2017-02-01

    ZnO/CuO p-n heterojunctions have attracted much attention for device applications, but coherent junctions, which are crucial for controlling electrical properties, still remain a challenge due to different crystal structure. In this work, CuO single-crystalline dots are coherently synthesized on ZnO nanorods by using a proposed two-step process. Transmission electron microscopy images confirm the formation of CuO coherent dots on single-crystalline ZnO nanorods upon annealing the nanorods covered with a poly-crystalline CuxO layer. The coherent dots exhibit two types of epitaxial orientations: CuO [002] ǀǀ ZnO [ 10 1 bar 1 ], CuO [111] ǀǀ ZnO [0002], and CuO [002] ǀǀ ZnO [ 10 1 bar 1 bar ], CuO [111] ǀǀ ZnO [ 000 2 bar]. As the thickness of the as-deposited CuxO layer increases from 10 to 30 nm, the aspect ratio of the resulting CuO dots decreases from 0.43 to 0.21, approaching a film-like morphology. This work provides a route to prepare CuO coherent single-crystalline structures on ZnO, which is one step further toward fabricating excellent CuO/ZnO nanodevices.

  1. Microwave-assisted template-free synthesis of butterfly-like CuO through Cu2Cl(OH)3 precursor and the electrochemical sensing property

    Science.gov (United States)

    Xie, Hanjie; Zhu, Lianjie; Zheng, Wenjun; Zhang, Jing; Gao, Fubo; Wang, Yan

    2016-11-01

    An energy-efficient and environmentally friendly microwave-assisted method was adopted for synthesis of butterfly-like CuO assembled by nanosheets through a Cu2Cl(OH)3 precursor, using no template. Formation mechanism of the butterfly-like CuO was explored and discussed systematically for the first time on the basis of both experimental results and crystal structure transformations in atomic level. The electrochemical sensing properties of the butterfly-like CuO modified electrode to ascorbic acid (AA) were studied for the first time. The results reveal that Cu(OH)2 nanowires were formed once the Cu2+ ions, located in between two CuO4 parallelogram chains of a Cu2Cl(OH)3 precursor, dissolve into the solution as Cu(OH)42- complex ions after ion exchange reactions and simultaneous assemble along a axis. Upon microwave irradiation, the adjacent CuO4 parallelogram chains of the Cu(OH)2 nanowires dehydrate and assemble along c axis, forming CuO nanosheets with (002) as the main exposed facet, which were further assembled to butterfly-like CuO under the action of microwave field, suggesting that microwave field functions like a 'directing agent'. The butterfly-like CuO modified electrode shows good electrochemical sensing properties to AA with a low detecting limit, short response time and wide linear response range.

  2. Experimental study of enhanced heat transfer by addition of CuO nanoparticle

    Science.gov (United States)

    Jesumathy, Stella; Udayakumar, M.; Suresh, S.

    2012-06-01

    An energy storage system has been designed to study the thermal characteristics of paraffin wax with an embedded nano size copper oxide (CuO) particle. This paper presents studies conducted on phase transition times, heat fraction as well as heat transfer characteristics of paraffin wax as phase change material (PCM) embedded with CuO nanoparticles. 40 nm mean size CuO particles of 2, 5 and 10% by weight were dispersed in PCM for this study. Experiments were performed on a heat exchanger with 1.5-10 l/min of heat transfer fluid (HTF) flow. Time-based variations of the temperature distributions are revealed from the results of observations of melting and solidification curves. The results strongly suggested that the thermal conductivity enhances 6, 6.7 and 7.8% in liquid state and in dynamic viscosity it enhances by 5, 14 and 30% with increasing mass fraction of the CNEPs. The thermal conductivity ratio of the composites can be augmented by a factor up to 1.3. The heat transfer coefficient during solidification increased about 78% for the maximum flow rate. The analysis of experimental results reveals that the addition of copper oxide nanoparticles to the paraffin wax enhances both the conduction and natural convection very effectively in composites and in paraffin wax. The paraffin wax-based composites have great potential for energy storage applications like industrial waste heat recovery, solar thermal applications and solar based dynamic space power generation with optimal fraction of copper oxide nanoparticles.

  3. Optical and other spectroscopic studies of lead, zinc bismuth borate glasses doped with CuO

    Science.gov (United States)

    Rajyasree, Ch.; Vinaya Teja, P. Michael; Murthy, K. V. R.; Krishna Rao, D.

    2011-12-01

    10MO·20Bi2O3·(70-x)B2O3·xCuO [M=Pb, Zn] with x=0, 0.4 and 0.8 (wt%) glasses were synthesized by the melt-quenching technique and were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Physical parameters, like density, and spectroscopic studies (optical absorption, EPR, FTIR and photoluminescence) were used to understand the role of modifier oxide and CuO in the glass matrix. A red shift of the absorption band corresponds to 2B1g→2B2g transition of Cu2+ ions from P2 to Z4 samples and the increase of hyperfine splitting factor (A‖) from P2 to Z2 shows that with the integration of PbO by ZnO the electron density around copper ion is increased. It is also supported by the gradual increase in theoretical optical basicity values of ZnO mixed glasses, as compared to that of PbO mixed glass matrix. Reduced bismuth radicals are found in undoped and 0.4% CuO doped glasses of both the series. Analysis of the absorption and emission studies indicates that the concentration of luminescence centers of bismuth ions (Bi3+ ions in UV region) is decreased by the integration of ZnO as well as by increasing the dopant concentration. In lead series PbO4 and BiO3 units are increased from P2 to P4 and in zinc series BiO3 units are decreased from Z0 to Z4. The conductivity of the glass matrices is increased in both the series with the dopant of CuO.

  4. Tailoring oxides of copper-Cu{sub 2}O and CuO nanoparticles and evaluation of organic dyes degradation

    Energy Technology Data Exchange (ETDEWEB)

    Raghav, Ragini; Aggarwal, Priyanka; Srivastava, Sudha, E-mail: sudha.srivastava@jiit.ac.in [Department of Biotechnology, Jaypee Institute of Information Technology, A-10, Sector-62, Noida-201307,Uttar Pradesh (India)

    2016-04-13

    We report a simple one-pot colloidal synthesis strategy tailoring cuprous or cupric nano-oxides in pure state. NaOH provided alkaline conditions (pH 12.5 -13) for nano-oxides formation, while its concentration regulated the oxidation state of the nano-oxides. The morphological, structural and optical properties of synthesized Cu{sub 2}O and CuO nanoparticles were studied by transmission electron microscopy (TEM), X-Ray diffraction (XRD) and UV-vis spectroscopy. Dye degradation capability of CuO and Cu2O nanoparticles was evaluated using four organic dyes - Malachite green, Methylene blue, Methyl orange and Methyl red. The results demonstrate effective degradation of all four dyes employing with almost comparable activity both Cu{sub 2}O and CuO nanoparticles.

  5. Tailoring oxides of copper-Cu2O and CuO nanoparticles and evaluation of organic dyes degradation

    Science.gov (United States)

    Raghav, Ragini; Aggarwal, Priyanka; Srivastava, Sudha

    2016-04-01

    We report a simple one-pot colloidal synthesis strategy tailoring cuprous or cupric nano-oxides in pure state. NaOH provided alkaline conditions (pH 12.5 -13) for nano-oxides formation, while its concentration regulated the oxidation state of the nano-oxides. The morphological, structural and optical properties of synthesized Cu2O and CuO nanoparticles were studied by transmission electron microscopy (TEM), X-Ray diffraction (XRD) and UV-vis spectroscopy. Dye degradation capability of CuO and Cu2O nanoparticles was evaluated using four organic dyes - Malachite green, Methylene blue, Methyl orange and Methyl red. The results demonstrate effective degradation of all four dyes employing with almost comparable activity both Cu2O and CuO nanoparticles.

  6. Synthesis and microwave modification of CuO nanoparticles: crystallinity and morphological variations, catalysis, and gas sensing.

    Science.gov (United States)

    Yang, Chao; Xiao, Feng; Wang, Jide; Su, Xintai

    2014-12-01

    CuO nanoparticles with different morphologies were synthesized by chemical precipitation and subsequently modified by microwave hydrothermal processing. The nanoparticles were precipitated by the introduction of a strong base to an aqueous solution of copper cations in the presence/absence of the polyethylene glycol and urea additives. The modification of the nanoparticles was subsequently carried out by a microwave hydrothermal treatment of suspensions of the precipitates, precipitated with and without the additives. X-ray powder diffraction analysis indicated that the crystallinity and crystallite size of the CuO nanoparticles increased after the microwave hydrothermal modification. Microscopy observations revealed the morphology changes induced by microwave hydrothermal processing. The thermal decomposition of ammonium perchlorate and the detection of volatile gases were performed to evaluate the catalytic and gas sensing properties of the synthesized CuO nanoparticles.

  7. Building energetic material from novel salix leaf-like CuO and nano-Al through electrophoretic deposition

    Energy Technology Data Exchange (ETDEWEB)

    Yin, Yan Jun; Li, Xueming [College of Chemistry and Chemical Engineering, Chongqing University, Chongqing (China)

    2016-11-15

    In this study, an energetic material was prepared by depositing nano-Al on CuO arrays via electrophoretic deposition (EPD), which offers a feasible route for nano-Al integration. The morphology and structure of the CuO arrays and Al/CuO composites were characterized by scanning electron microscopy and X-ray diffraction. The CuO arrays were homogenously salix leaf-like structure with a width of ⁓150 to 200 nm. The energy density of Al/CuO composites was approximate to 1454.5 J/g by integrating the differential scanning calorimetry (DSC) plot and the combustion performance was recorded by a high-speed camera. Moreover, the combustion flames were violent and the whole reaction process only lasted 72.2 ms, indicating that the energy of the Al/CuO nanothermite can be released effectively.

  8. Temperature dependence of the electronic structure of La2CuO4 in the multielectron LDA+GTB approach

    Science.gov (United States)

    Makarov, I. A.; Ovchinnikov, S. G.

    2015-09-01

    The band structure of La2CuO4 in antiferromagnetic and paramagnetic phases is calculated at finite temperatures by the multielectron LDA+GTB method. The temperature dependence of the band spectrum and the spectral weight of Hubbard fermions is caused by a change in the occupation numbers of local multielectron spin-split terms in the antiferromagnetic phase. A decrease in the magnetization of the sublattice with temperature gives rise to new bands near the bottom of the conduction band and the top of the valence band. It is shown that the band gap decreases with increasing temperature, but La2CuO4 remains an insulator in the paramagnetic phase as well. These results are consistent with measurements of the red shift of the absorption edge in La2CuO4 with increasing temperature.

  9. Effect of nano CuO on the ionic conductivity of PVC-PEG blend polymer electrolytes

    Science.gov (United States)

    Ravindran, Dhandapani; Vickraman, Palanichamy

    2013-06-01

    Nano CuO was prepared by co-precipitation method and it was incorporated as filler in PVC-PEG blend based solid polymer electrolytes with lithium perchlorate (LiClO4) as salt. The PVC: CuO ratio was systematically varied in order to study its effect on the ionic conductivity behavior of electrolyte membranes. The membranes were subjected to XRD and impedance analysis. The analysis shows that the conductivity profile was strongly influenced by the PVC: CuO ratio. The membrane with PVC/CuO: PEG: PC: LiClO4=23/2:15:50:10 exhibits higher conductivity of 4.0×10-6 S/cm at room temperature.

  10. Characterization of CuO Species and Thermal Solid-Solid Interaction in CuO/CeO2-Al2O3 Catalyst by In-Situ XRD, Raman Spectroscopy and TPR

    Institute of Scientific and Technical Information of China (English)

    He Mai; Luo Mengfei; Fang Ping

    2006-01-01

    Transference of CuO species and thermal solid-solid interaction in CuO/CeO2-Al2O3 catalyst prepared by an impregnation method were characterized by in-situ XRD, Raman spectroscopy and H2-TPR techniques.For the catalyst calcined at 300 ℃, two kinds of CuO species coexist on the surface, that is, highly dispersed and bulk CuO crystalline phase.Four kinds of CuO species are present for the catalyst calcined at 600 ℃: (1) highly dispersed CuO, (2) bulk CuO on the surface, (3) bulk CuO in the internal layer of CeO2, and (4) CuAl2O4 formed from CuO-Al2O3 interaction.For the catalyst calcined at 800 ℃, besides very little highly dispersed and bulk CuO on the surface, most of the CuO has transferred into the internal layer of CeO2 and the mass of CuAl2O4 are increased.At 900 ℃, all of CuO has diffused into the internal layer of CeO2 and formed CuAl2O4.The results show that the distribution of CuO species in the catalysts depends on the calcination temperature;the different CuO species can be effectively confirmed by in-situ XRD, Raman spectroscopy and H2-TPR techniques.

  11. Electrochemical oxygen intercalation in La 2CuO 4 prepared by nitrates method: Microstructural effects

    Science.gov (United States)

    Michel, C. R.; Casan˜-Pastor, N.

    2000-11-01

    In order to determine microstructural effects in the electrochemical oxygen intercalation for La 2CuO 4, and the relative abundance of the two superconducting phases (T c = 33 and 44K), this oxide was prepared using the nitrates method, which involves the dissolution of La and Cu oxides in nitric acid. The product was pressed as pellets. A narrow grain size distribution and a density higher than 95% ϱ T was obtained. After electrochemical oxygen intercalation, at room temperature, this material gave a main superconducting phase with T c = 33K, whereas porous pellets obtaiined from the same oxide, with intermediate grinding, gave a T c = 44K.

  12. Spontaneous ferromagnetic spin ordering at the surface of La2CuO4

    Science.gov (United States)

    Yusupov, R. V.; Kabanov, V. V.; Mihailovic, D.; Conder, K.; Müller, K. A.; Keller, H.

    2007-07-01

    Magnetic properties of high purity stoichiometric La2CuO4 nanoparticles are systematically investigated as a function of particle size. Ferromagnetic single-domain spin clusters are shown to spontaneously form at the surface of fine grains as well as paramagnetic defects. Hysteresis loops and thermomagnetic irreversibility are observed in a wide temperature range 5-350K with the remnant moment and coercivity gradually decreasing with increasing temperature. Possible origins of the spontaneous surface ferromagnetic clusters and the relation of our data to the appearance of unusual magnetic phenomena and phase separation of doped cuprates are discussed.

  13. Dielectric constant of multiferroic pure and doped CuO nanoparticles

    Science.gov (United States)

    Apostolov, A. T.; Apostolova, I. N.; Wesselinowa, J. M.

    2014-08-01

    Within a microscopic model and a Green's function technique we have calculated the temperature and magnetic field dependence of the dielectric function ɛ(T,H) in CuO nanoparticles (NPs) taking into account frustration, single-ion anisotropy, s-d coupling, spin-phonon interaction and linear magnetoelectric coupling. ɛ(T) shows weak and broad anomalies at the two magnetic phase transition temperatures TN 2 and TN 1 due to the magnetoelectric coupling. ɛ(H) decreases with increasing of H and the kinks disappear. The changes of ɛ with ion doping are discussed. Comparisons to experimental data are made.

  14. Hall effect studies of Bi 2Sr 2CuO x crystals

    Science.gov (United States)

    Hou, X. H.; Li, J. W.; Zhang, J. L.; Guo, S. Q.; Yin, B.; Xiong, J. W.; Dong, C.; Zhao, Z. X.

    1994-12-01

    We have investigated the temperature dependencies of the in-plane resistivity and the Hall coefficient in Bi 2Sr 2CuO x crystals across the metal-insulator (MI) transition. In the insulator crystal at low temperature (32Kconduction is governed by a two-dimensional variable-range-hopping mechanism. In the superconducting crystal the Hall coefficient Rh exhibit a characteristic maximum at about 90 K, and after MI transition the maximum disappeared. We believe that the maximum in Rh-T curve represents the common feature of all the high Tc superconductors.

  15. Hopping conduction in In-doped CuO thin films

    Science.gov (United States)

    Yildiz, A.; Horzum, Ş.; Serin, N.; Serin, T.

    2014-11-01

    Electrical transport properties of undoped and In-doped CuO thin films (1, 5 and 10 at. %) are investigated by mean of resistivity in the temperature range of 115-300 K. Electrical transport mechanism of films is explained on the basis of the variable-range hopping (VRH) conduction. Upon doping, appreciable changes are found in resistivity. Temperature dependent resistivity shows a complex correlation with increasing In concentration. This situation is well explained by fluctuations in the hopping distance and the density of states at the Fermi level.

  16. Synthesis of Cu3N from CuO and NaNH2

    Directory of Open Access Journals (Sweden)

    Akira Miura

    2014-12-01

    Full Text Available We report on the low-temperature synthesis of submicron-sized Cu3N powder produced from CuO and NaNH2 powder mixture by heating at 150–190 °C in a Teflon-sealed autoclave. The structure was the anti-RuO3 type with a lattice parameter of 0.3814(1 nm, and strong optical absorption was observed below ∼1.9 eV. This synthesis method has the potential of facile control of the reaction with less use of ammonia sources.

  17. A Class of Effective of Decarboxylative Perfluoroalkylating Reagents: [(phen)2Cu](O2CRF)

    KAUST Repository

    Huang, Yangjie

    2016-04-13

    This article describes the invention of a class of effective reagents [(phen)2Cu](O2CRF) (1) for the decarboxylative perfluoroalkylation of aryl and heteroaryl halides. Treatment of the copper tert-butyloxide with phenanthroline ligands, with subsequent addition of perfluorocarboxylic acids afforded the air-stable copper(I) perfluorocarboxylato complexes 1. These complexes reacted with a variety of aryl and heteroaryl halides to form perfluoroalkyl(hetero)arenes in moderate to high yields. Computational studies suggested that the coordination of the second phen ligand may reduce the energy barrier for the decarboxylation of perfluorocarboxylate to facilitate the perfluoroalkylation.

  18. Effect of CuO Doping on the Electrical Behavior of ZrO2

    Institute of Scientific and Technical Information of China (English)

    SABA,Beg; SARITA; POOJA,Varshney

    2007-01-01

    Electrical conductivity has been measured at different temperatures for ZrO2 doped with various molar ratios of CuO. The conductivity increases due to migration of vacancies, created by doping. The conductivity was found to increase with increase in temperature till 220 ℃ and thereafter decrease due to collapse of the fluorite framework.A second rise in conductivity around 500 ℃ was observed due to phase transition of ZrO2. X-ray powder diffraction, DTA and IR studies were carried out for confirming doping effect and phase transition in ZrO2.

  19. Thermoforming simulation with FEA

    Energy Technology Data Exchange (ETDEWEB)

    Luca, P. de [Engineering Systems International SA, Rungis (France); Pickett, A.K. [T. Queckboerner Engineering Systems International GmbH, Eschborn (Germany); Johnson, A.F. [DLR, Stuttgart (Germany)

    1996-09-01

    This article describes how the ability to produce high-quality, lightweight structural parts quickly with complex shapes promises to make thermoforming competitive with conventional metal-stamping methods. Thermoforming--the press-forming of continuous fiber-reinforced-thermoplastic (FRTP) sheets--is a promising option for fabricating lightweight structural composite components. Thermoplastic polymers offer improved mechanical and physical properties compared with thermoset polymers, and perhaps most important for industry, they make rapid part production possible using the press-forming process. Despite its promise, thermoforming has not been used to its full potential because tool designers generally rely on trial and error to obtain a detailed understanding of how well this process lends itself to producing a particular part. Because trial-and-error methods are costly and inefficient, tool designers typically cannot gain the sophisticated understanding of the process needed to optimize it for the particular part at hand. Recent advances in the finite-element method may make it easier for tool designers to obtain the insights that have typically come from trial and error. An explicit finite-element code has been developed to simulate the thermoforming process, thereby enabling tool designers to experiment on a computer. The codes use detailed temperature-dependent rheological models to account for intraply shearing, squeeze flow, fiber reorientation, and fiber buckling. They also rely on advanced friction laws--both temperature- and pressure-dependent--to account for the interply sliding mechanism between plies.

  20. Complete transformation of ZnO and CuO nanoparticles in culture medium and lymphocyte cells during toxicity testing.

    Science.gov (United States)

    Ivask, Angela; Scheckel, Kirk G; Kapruwan, Pankaj; Stone, Vicki; Yin, Hong; Voelcker, Nicolas H; Lombi, Enzo

    2017-03-01

    Here, we present evidence on complete transformation of ZnO and CuO nanoparticles, which are among the most heavily studied metal oxide particles, during 24 h in vitro toxicological testing with human T-lymphocytes. Synchrotron radiation-based X-ray absorption near edge structure (XANES) spectroscopy results revealed that Zn speciation profiles of 30 nm and 80 nm ZnO nanoparticles, and ZnSO4- exposed cells were almost identical with the prevailing species being Zn-cysteine. This suggests that ZnO nanoparticles are rapidly transformed during a standard in vitro toxicological assay, and are sequestered intracellularly, analogously to soluble Zn. Complete transformation of ZnO in the test conditions was further supported by almost identical Zn spectra in medium to which ZnO nanoparticles or ZnSO4 was added. Likewise, Cu XANES spectra for CuO and CuSO4-exposed cells and cell culture media were similar. These results together with our observation on similar toxicological profiles of ZnO and soluble Zn, and CuO and soluble Cu, underline the importance of dissolution and subsequent transformation of ZnO and CuO nanoparticles during toxicological testing and provide evidence that the nano-specific effect of ZnO and CuO nanoparticles is negligible in this system. We strongly suggest to account for this aspect when interpreting the toxicological results of ZnO and CuO nanoparticles.

  1. Electrochemical synthesis of multi-armed CuO nanoparticles and their remarkable bactericidal potential against waterborne bacteria

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, Pratibha, E-mail: rkpratibha@yahoo.com; Merwyn, S.; Agarwal, G. S.; Tripathi, B. K.; Pant, S. C. [Defence Research and Development Establishment (India)

    2012-01-15

    Copper (II) oxide multi-armed nanoparticles composed of 500-1000 nm long radiating nanospicules with 100-200 nm width near the base and 50-100 nm width at the tapered ends and {approx}25 nm thickness were synthesized by electrochemical deposition in the presence of an oxidant followed by calcination at 150 Degree-Sign C. The nanoparticles were characterized using SEM/EDX for morphology and composition, Raman spectroscopy for compound identification, and broth culture method for antibacterial efficacy. The CuO nanoparticles have shown remarkable bactericidal efficacy against Gram-positive and -negative waterborne disease causing bacteria like Escherichia coli, Salmonella typhi, staphylococcus aureus and Bacillus subtilis. E. coli has been chosen as representative species for waterborne disease causing bacteria. In antibacterial tests 500 {mu}g/mL nano CuO killed 3 Multiplication-Sign 10{sup 8} CFU/mL E. coli bacteria within 4 h of exposure. Moreover, 8.3 Multiplication-Sign 10{sup 6} CFU/mL E. coli were killed by 100 and 10 {mu}g/mL nano CuO within 15 min and 4 h of exposure, respectively. Antibacterial activity of nano CuO has been found many-fold compared with commercial bulk CuO. The fate of nanoparticles after antibacterial test has also been studied. The synthesized CuO nanoparticles are expected to have potential antibacterial applications in water purification and in paints and coatings used on frequently touched surfaces and fabrics in hospital settings.

  2. Embalagem a vácuo: efeito no escurecimento e endurecimento do feijão durante o armazenamento

    Directory of Open Access Journals (Sweden)

    Rafaella Araújo Zambaldi Lima

    2014-09-01

    Full Text Available A influência do uso de embalagem a vácuo no controle do escurecimento e endurecimento do tegumento foi avaliada em feijões da cv. 'Pérola'. Os feijões após secos foram submetidos a diferentes embalagens: polietileno seladas a vácuo (espessura de 80µm, polietileno seladas sem vácuo (espessura de 80µm e embalagem comercial (espessura de 20µm, armazenados por oito meses em condições ambiente. Foram realizadas análises de umidade, tempo de cozimento, cor, atividade enzimática e compostos fenólicos, logo após a secagem e em intervalos de dois meses até o oitavo mês. O tempo de cozimento foi maior para os grãos acondicionados em embalagem comercial do que nas outras embalagens, ao final do armazenamento. Os grãos embalados em sacos de polietileno selados a vácuo apresentaram menor queda nos valores de L*. As amostras da embalagem selada a vácuo apresentaram atividade da Peroxidase e Polifenoloxidase inferior aos grãos da embalagem comercial. O teor de fenólicos totais não apresentou diferença significativa. O uso da embalagem selada a vácuo foi eficiente em retardar o aumento no tempo de cozimento, o escurecimento do tegumento, a atividade das enzimas Polifenoloxidase e Peroxidase da cultivar 'Pérola', durante o armazenamento por oito meses em condição ambiente.

  3. Synthesis, Characterization, and Sunlight Mediated Photocatalytic Activity of CuO Coated ZnO for the Removal of Nitrophenols.

    Science.gov (United States)

    Qamar, M Tariq; Aslam, M; Ismail, Iqbal M I; Salah, Numan; Hameed, A

    2015-04-29

    CuO@ZnO core-shell catalysts, coated by varying the CuO layer density ranging from 0.5% to 10%, were synthesized with the aim to enhance the photocatalytic activity of ZnO in sunlight and control its photocorrosion. Initially, the Cu(2+) ions were impregnated on presynthesized ZnO by wet impregnation and finally converted to CuO layers by calcination. The optical and structural characterization of the synthesized powders was performed by DRS, PL, Raman spectroscopy, and XRD analysis, respectively. The homogeneity of the coated layers was explored by FESEM. The photocatalytic activity of CuO coated ZnO was investigated for the degradation of mononitrophenols (2-, 3-, and 4-nitrophenol) and dinitrophenols (2,4-, 2,5-, and 2,6-dinitrophenol) in the exposure of the complete spectrum and visible region (420-800 nm) of sunlight. The effect of the increasing density coated layers of CuO on photocatalytic activity was evaluated for the degradation of 4-NP. Compared to pristine ZnO, a substantial increase in the degradation/mineralization ability was observable for the catalysts coated with 0.5% and 1% CuO, whereas a detrimental effect was noticed for higher coating density. Prior to photocatalytic studies, as evaluated by cyclic voltammetry (CV), compared to pure ZnO, a significant suppression of photocorrosion was noticed, under illumination, for catalysts coated with lower CuO coating. The progress of the photocatalytic degradation process was monitored by HPLC while the mineralization ability of the synthesized catalysts was estimated by TOC. The estimation of the released ions and their further interaction with the excited states and the reactive oxygen was monitored by ion chromatography (IC).

  4. Chemical bond properties and Mossbauer spectroscopy in (La1-xMx)2CuO4 (M=Ba, Sr)

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    By using the average band-gap model, the chemical bond properties of (La1-x Mx)2CuO4(M=Ba, Sr) were calculated . The calculated covalencies for Cu(O and La(O bond in the compounds are 0.3 and 0.03 respectively. M?ssbauer isomer shifts of 57Fe doped in La2CuO4 and 119Sn doped in La2CuO4 were calculated by using the chemical surrounding factor defined by covalency and electronic polarizability. Four valence state tin and three valence iron sites were identified in 57Fe and 119Sn doped La2CuO4.

  5. Monitoring a CuO gas sensor at work: an advanced in situ X-ray absorption spectroscopy study.

    Science.gov (United States)

    Volanti, D P; Felix, A A; Suman, P H; Longo, E; Varela, J A; Orlandi, M O

    2015-07-28

    X-ray absorption near edge structure (XANES) and electrical measurements were used to elucidate the local structure and electronic changes of copper(II) oxide (CuO) nanostructures under working conditions. For this purpose, a sample holder layout was developed enabling the simultaneous analysis of the spectroscopic and electrical properties of the sensor material under identical operating conditions. The influence of different carrier gases (e.g., air and N2) on the CuO nanostructures behavior under reducing conditions (H2 gas) was studied to analyze how a particular gas atmosphere can modify the oxidation state of the sensor material in real time.

  6. Jahn-Teller assisted polaronic hole hopping as a charge transport mechanism in CuO nanograins

    Science.gov (United States)

    Younas, M.; Nadeem, M.; Idrees, M.; Akhtar, M. J.

    2012-04-01

    Impedance spectroscopy has been employed to investigate the dielectric and electric transport phenomena in sol-gel synthesized CuO nanograins. Semiconducting features of the grains and grain boundaries have been endorsed to the thermal activation of the localized charge carriers. On cooling below 303 K, a transition from Jahn-Teller polaron hopping mechanism to the Mott's variable range hopping mechanism has been observed owing to random potential fluctuations among localized sites. Activation energies for conduction and relaxation processes at grain boundaries provide strong signatures for the involvement of Jahn-Teller adiabatic small polarons as a charge transport mechanism in CuO nanograins.

  7. Double-exchange driven ferromagnetic metal-paramagnetic insulator transition in Mn-doped CuO

    Science.gov (United States)

    Filippetti, Alessio; Fiorentini, Vincenzo

    2006-12-01

    Employing ab initio self-interaction-corrected local-spin-density calculations, we explain the nature of the ferromagnetic, metallic phase of Mn-doped CuO (an antiferromagnetic insulator when undoped), and of its concurrent transitions to a paramagnetic, insulating phase. Mn-induced donor levels enable conduction through ferromagnetically aligned Mn centers and ferromagnetic CuO planes via double exchange. In the paramagnetic insulating phase, a polaron hopping mechanism consistent with the experiments is envisaged. Our results suggest the intriguing possibility of designing double-exchange driven ferromagnetic cuprates.

  8. Catalysis of the rare earth containing mixed oxides Ln2CuO4 in phenol hydroxylation

    Institute of Scientific and Technical Information of China (English)

    刘持标; 赵震; 叶兴凯; 吴越

    1997-01-01

    Mixed oxides Ln2CuO4±λ(Ln=La,Pr,Nd,Sm,Gd) with K2NiF4 structure were prepared Their crystal structures were studied with XRD and IR spectra.Meanwhile,the average valence of Cu ions and non stoichiometric oxygen (λ) were determined through chemical analyses.Catalysis of the above-mentioned mixed oxides in the phenol hydroxylation was investigated.Results show that the catalysis of these mixed oxides has close relation with their structures and composition.Substitution of A site atom in Ln2CuO4λ has a great influence on then eatalysis in the phenol hydroxylation.

  9. Facile synthesis of novel tunable highly porous CuO nanorods for high rate lithium battery anodes with realized long cycle life and high reversible capacity.

    Science.gov (United States)

    Wang, Linlin; Gong, Huaxu; Wang, Caihua; Wang, Dake; Tang, Kaibin; Qian, Yitai

    2012-11-07

    Various CuO nanostructures have been well studied as anode materials for lithium ion batteries (LIBs); however, there are few reports on the synthesis of porous CuO nanostructures used for anode materials, especially one-dimensional (1D) porous CuO. In this work, novel 1D highly porous CuO nanorods with tunable porous size were synthesized in large-quantities by a new, friendly, but very simple approach. We found that the pore size could be controlled by adjusting the sintering temperature in the calcination process. With the rising of calcination temperature, the pore size of CuO has been tuned in the range of ∼0.4 nm to 22 nm. The porous CuO materials have been applied as anode materials in LIBs and the effects of porous size on the electrochemical properties were observed. The highly porous CuO nanorods with porous size in the range of ∼6 nm to 22 nm yielded excellent high specific capacity, good cycling stability, and high rate performance, superior to that of most reported CuO nanocomposites. The CuO material delivers a high reversible capacity of 654 mA h g(-1) and 93% capacity retention over 200 cycles at a rate of 0.5 C. It also exhibits excellent high rate capacity of 410 mA h g(-1) even at 6 C. These results suggest that the facile synthetic method of producing a tunable highly porous CuO nanostructure can realize a long cycle life with high reversible capacity, which is suitable for next-generation high-performance LIBs.

  10. Structural Anomalies Detected in Ceramic Matrix Composites Using Combined Nondestructive Evaluation and Finite Element Analysis (NDE and FEA)

    Science.gov (United States)

    Abdul-Aziz, Ali; Baaklini, George Y.; Bhatt, Ramakrishna T.

    2003-01-01

    Most reverse engineering approaches involve imaging or digitizing an object and then creating a computerized reconstruction that can be integrated, in three dimensions, into a particular design environment. The rapid prototyping technique builds high-quality physical prototypes directly from computer-aided design files. This fundamental technique for interpreting and interacting with large data sets is being used here via Velocity2 (an integrated image-processing software, ref. 1) using computed tomography (CT) data to produce a prototype three-dimensional test specimen model for analyses. A study at the NASA Glenn Research Center proposes to use these capabilities to conduct a combined nondestructive evaluation (NDE) and finite element analysis (FEA) to screen pretest and posttest structural anomalies in structural components. A tensile specimen made of silicon nitrite (Si3N4) ceramic matrix composite was considered to evaluate structural durability and deformity. Ceramic matrix composites are being sought as candidate materials to replace nickel-base superalloys for turbine engine applications. They have the unique characteristics of being able to withstand higher operating temperatures and harsh combustion environments. In addition, their low densities relative to metals help reduce component mass (ref. 2). Detailed three-dimensional volume rendering of the tensile test specimen was successfully carried out with Velocity2 (ref. 1) using two-dimensional images that were generated via computed tomography. Subsequent, three-dimensional finite element analyses were performed, and the results obtained were compared with those predicted by NDE-based calculations and experimental tests. It was shown that Velocity2 software can be used to render a three-dimensional object from a series of CT scan images with a minimum level of complexity. The analytical results (ref. 3) show that the high-stress regions correlated well with the damage sites identified by the CT scans

  11. Optical Spectroscopy of Strongly Correlated (MOTT-HUBBARD, Heavy-Fermion, Unconventional Superconductor) Materials Tuned Pressure

    Energy Technology Data Exchange (ETDEWEB)

    Goncharov, A; Struzhkin, V V

    2003-11-12

    During the past years, the Co-PI's have been responsible for the development and operation of optical techniques (Raman, IR, fluorescence, absorption and reflectance spectroscopy at ultrahigh pressures and high and low temperatures) which have proven to be extremely powerful for studying low-Z, molecular solids including hydrogen, ice, etc. (see results below). Meanwhile, it has become increasingly clear that optical spectroscopy has an equally extraordinary potential for studying metals and superconductors at ultrahigh pressures, thus the result will have a major impact on material research. However, because of the extreme difference in optical properties of opaque metals and transparent insulating molecular solids, successful accomplishment of the present project will require substantial effort in improving the present equipment and developing new techniques, and funds for this are requested here. Below we provide a short description of the work done and techniques developed during the last years. We also propose to explore new frontiers in compressed materials close to the insulator-metal boundaries, spin-crossover, and other quantum critical points.

  12. Critical quasiparticle theory applied to heavy fermion metals near an antiferromagnetic quantum phase transition.

    Science.gov (United States)

    Abrahams, Elihu; Wölfle, Peter

    2012-02-28

    We use the recently developed critical quasiparticle theory to derive the scaling behavior associated with a quantum critical point in a correlated metal. This is applied to the magnetic-field induced quantum critical point observed in YbRh(2)Si(2), for which we also derive the critical behavior of the specific heat, resistivity, thermopower, magnetization and susceptibility, the Grüneisen coefficient, and the thermal expansion coefficient. The theory accounts very well for the available experimental results.

  13. Unusual signatures of the ferromagnetic transition in the heavy Fermion compound UMn$_2$Al$_{20}$

    OpenAIRE

    Wang, C H; Lawrence, J. M.; Bauer, E.D.; Kothapalli, K.; Gardner, J S; Ronning, F.; Gofryk, K.; Thompson, J.D.; Nakotte, H.; Trouw, F.

    2010-01-01

    Magnetic susceptibility results for single crystals of the new cubic compounds UT$_2$Al$_{20}$ (T=Mn, V, and Mo) are reported. Magnetization, specific heat, resistivity, and neutron diffraction results for a single crystal and neutron diffraction and inelastic spectra for a powder sample are reported for UMn$_2$Al$_{20}$. For T = V and Mo, temperature independent Pauli paramagnetism is observed. For UMn$_2$Al$_{20}$, a ferromagnetic transition is observed in the magnetic susceptibility at $T_...

  14. Separation of charge-order and magnetic QCPs in heavy fermions and high Tc cuprates

    Science.gov (United States)

    Harrison, Neil

    2010-03-01

    The Fermi surface topology of high temperature superconductors inferred from magnetic quantum oscillation measurements provides clues for the origin of unconventional pairing thus previously not accessed by other spectroscopy techniques. While the overdoped regime of the high Tc phase diagram has a large Fermi surface consistent with bandstructure calculations, the underdoped regime of YBa2Cu2O6+x is found to be composed of small pockets. There is considerable debate as to whether the small observed ``pocket'' is hole-like or electron-like- whether the Fermi surface is best described by a t-J model or a conventional band folding picture- whether or not a Fermi liquid description applies- or- whether bilayer coupling splits the degeneracy of the observed pockets. We (myself and collaborators) have now collected an extensive body of experimental data that brings this debate to rest, but raises new questions about the nature of itinerant magnetism in underdoped high Tc cuprates. Quantum oscillation measurements are performed on multiple samples in magnetic fields extending to 85 T, temperatures between 30 mK (dilution fridge in dc fields to 45 T) and 18 K, over a range of hole dopings and with samples rotated in-situ about multiple axes with respect to the magnetic field. We perform a topographical map of the Fermi surface, enabling the in-plane shape of one of the pockets to be determined- imposing stringent constraints on the origin of the Fermi surface. While quantum oscillations measurements are consistent with a topological Fermi surface change associated with magnetism near optimal doping, they also point to a secondary instability deep within the underdoped regime beneath a high Tc superconducting sub-dome. An steep upturn in the quasiparticle effective mass is observed on underdoping, suggestive of a quantum critical point near x= 0.46 separating the metallic regime (composed of small pockets) from a more underdoped insulating charge-ordered regime (earlier reported in neutron scattering measurements). Our findings suggest the importance of two critical instabilities affecting the Fermi surface beneath the high Tc superconducting dome(s). While one of these has been proposed to provide the likely origin of unconventional pairing in the cuprates, the other can be an important factor in boosting transition temperatures. [4pt] This work is supported by the DoE BES grant ``Science in 100 T''. The author would like to thank collaborators S. E. Sebastian, C. H. Mielke, P. A. Goddard, M. M. Altarawneh, R. Liang, D. A. Bonn, W. N. Hardy and G. G. Lonzarich, and supporting staff at the National High Magnetic Field Laboratory (NHMFL). Quantum oscillation experiments are performed at the NHMFL, which is funded by the NSF with support from the DoE and State of Florida.

  15. Effect of pressure on magnetic structure in heavy-fermion CeRhIn5

    Science.gov (United States)

    Bao, W.; Trevino, S. F.; Lynn, J. W.; Pagliuso, P. G.; Sarrao, J. L.; Thompson, J. D.; Fisk, Z.

    The effect of hydrostatic pressure on the incommensurate antiferromagnetic structure of CeRhIn5 is investigated with neutron diffraction using a He pressure cell. At 3.8 kbar, the staggered magnetic moment is 0.37(4) μB per Ce ion at 1.6 K, which is the same as the ambient-pressure value. The Néel temperature TN=3.8(1) K is also the same as the ambient-pressure one, although the curve of the order parameter has changed with pressure. The incommensurability δ of the magnetic wave vector qM=(1/2,1/2,δ) has reduced from δ=0.297 at ambient pressure to δ=0.294(1) at 3.8 kbar.

  16. Thermal expansion of the heavy-fermion superconductor UNi[sub 2]Al[sub 3

    Energy Technology Data Exchange (ETDEWEB)

    Modler, R. (Kernforschungszentrum Karlsruhe GmbH, INFP, Postfach 3640, D-76021 Karlsruhe (Germany)); Lang, M. (Institut fuer Festkoerperphysik, TH Darmstadt, Hochschulstr. 8, D-64289 Darmstadt (Germany)); Geibel, C. (Institut fuer Festkoerperphysik, TH Darmstadt, Hochschulstr. 8, D-64289 Darmstadt (Germany)); Schank, C. (Institut fuer Festkoerperphysik, TH Darmstadt, Hochschulstr. 8, D-64289 Darmstadt (Germany)); Steglich, F. (Institut fuer Festkoerperphysik, TH Darmstadt, Hochschulstr. 8, D-64289 Darmstadt (Germany))

    1994-04-01

    We have investigated the superconducting and the antiferromagnetic transition of polycrystalline UNi[sub 2]Al[sub 3] by means of high-resolution dilatometry. At T[sub c]=0.95 K and T[sub N]=4.6 K the thermal-expansion coefficient [alpha] shows second-order phase-transition anomalies of negative sign. Investigations of the antiferromagnetic transition under magnetic fields indicate a complex magnetic phase diagram reminiscent of that of the Pd homolog. ((orig.))

  17. Hybridization and Magnetic Ground States in Heavy Fermion Compound CeRhIn5

    Institute of Scientific and Technical Information of China (English)

    XU Ying; WANG Jiang-Long; ZENG Zhi

    2005-01-01

    @@ The magnetic properties of CeRhIn5 are studied by first-principles calculation. Spin-orbit coupling is considered as well as different corrections including local density approximation plus on-site Coulomb interaction U (U = 1,1.5, 3 eV) and orbital polarization. The results show the existence of only moderate correlation in CeRhIn5 and Ce-4f electrons are on the border of localization and itinerancy. The effect of pressure by changing the volume of the unit cell is also studied.

  18. Enhancement of antiferromagnetic spin wave in the heavy-fermion superconductors

    Science.gov (United States)

    Koh, Shun-ichiro

    2000-06-01

    Recently, the inelastic neutron scattering experiments of UPd 2Al 3 showed that a sharp peak indicating a magnetic excitation appears below the superconducting phase transition temperature (M. Metoki et al., J. Phys. Soc. Japan 66 (1997) 2560, N. Bernhoeft et al., Phys. Rev. Lett. 81 (1998) 4244). Assuming this excitation to be an antiferromagnetic (AFM) spin wave, this paper deals with its enhancement by the superconductivity.

  19. Spectroscopic evidence for 5f bands at room temperature in uranium-based heavy fermions

    Energy Technology Data Exchange (ETDEWEB)

    Arko, A.J.; Koelling, D.D.; Dunlap, B.D.; Capasso, C.; del Giudice, M.

    1988-01-01

    We present data on the alloy system UPd/sub 3-x/Pt/sub x/ and show that in the double hexagonal phase (x < 2.4) where the electrons are known to be localized, one obtains two Gaussian 5f features in the photoemission spectrum. A satellite (at approx.-1eV) is found in the itinerant phase (x > 2.4) as well, except that the low-binding energy feature is locked in at E/sub F/ and shows evidence of energy dispersion at room temperature/endash/consistent with well-defined bands. Conversely, we show that even in well-behaved narrow band systems (USn/sub 3/ there is evidence for satellite formation. 44 refs., 8 figs.

  20. Heavy Fermion Character in Ce2Sb and Ce2Bi

    Science.gov (United States)

    Oyamada, Akira; Isobe, Atsushi; Kitazawa, Hideaki; Ochiai, Akira; Suzuki, Takashi; Kasuya, Tadao

    1993-05-01

    Magnetic susceptibilities, electrical resistivities and specific heats of Ce2Sb, Ce2Bi and CeLaBi were measured to clarify these physical properties. The most characteristic points of these compounds are the following. Ce site are two dimensional and the distance between Ce atoms are very small. The similarity between these compounds and CeRh3B2, in which Ce sites are one dimensional and the distance between Ce atoms are very small, are discussed.

  1. Surface superconductivity in the heavy-fermion superconductor UPt{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Keller, N. [Van der Waals-Zeeman Laboratory, University of Amsterdam, Valckenierstraat 65, 1018 XE Amsterdam (The Netherlands); Tholence, J.L. [Centre de Recherche sur les Tres Basses Temperatures-Centre National de Recherche Scientifique, BP 166, 38042 Grenoble Cedex 9 (France); Huxley, A.; Flouquet, J. [DRFMC-Centre des Etudes Nucleaires de Grenoble, BP 85X, 38041 Grenoble Cedex (France)

    1996-11-01

    We present a study of the surface critical field {ital H}{sub {ital c}3}({Phi},{Theta},{ital T}) measured for two needlelike whiskers of UPt{sub 3}. Dominant surface effects were observed in the angular dependence of the critical field by means of ac-resistivity measurements. These surface superconductivity effects show a surprisingly nonlinear thermal variation of {ital H}{sub {ital c}3} contrary to behavior expected from conventional theory, where {ital H}{sub {ital c}3}/{ital H}{sub {ital c}2}=1.69 is predicted. The ratio {ital H}{sub {ital c}3}/{ital H}{sub {ital c}2} is strongly depressed from its initial value 1.7 when going from the {ital A} to the {ital C} phase as the temperature is decreased. It seems to remain constant in the {ital C} phase for even lower {ital T}. Nevertheless, for temperatures close to {ital T}{sub {ital c}+} it is possible to describe the angular behavior of {ital H}{sub {ital c}3}({Theta},{Phi}) with a standard model by introducing an effective-mass anisotropy of the heavy quasiparticles. These results are compared to recent {ital H}{sub {ital c}3} calculations for different representations of the order parameter and seem to provide a direct evidence for the suppression of one component of the order parameter at the surface. The restrictions imposed by these measurements on the choice of the representations of the unconventional order parameter will be discussed by also taking into account the limitations imposed due to the temperature dependence of the basal plane {ital H}{sub {ital c}2} modulation. {copyright} {ital 1996 The American Physical Society.}

  2. Hall resistivity in the heavy Fermion normal state of ? up to 26 T

    Science.gov (United States)

    Kambe, S.; Huxley, A.; Flouquet, J.; Jansen, A. G. M.; Wyder, P.

    1999-01-01

    The Hall resistivity 0953-8984/11/1/018/img10 has been measured in single crystal 0953-8984/11/1/018/img11 at low temperatures (0.1-4.2 K) for magnetic field 0953-8984/11/1/018/img12-axis up to 26 T. For temperatures 0953-8984/11/1/018/img13, the Hall coefficient goes asymptotically to zero, indicating a compensated-metal ground state. Since the Hall resistivity does not show an anomaly at the metamagnetic crossover of 20 T in the Fermi-liquid state below 0.8 K, a drastic change of the Fermi surface is unlikely at the crossover. A change of the skew scattering contribution to the Hall effect has been observed around 6 and 2 K, i.e. near respectively the magnetic ordering temperature and the temperature below which the Fermi-liquid state appears.

  3. Phase transition of a heavy-fermion superconductor in a high magnetic field: Entanglement analysis

    Science.gov (United States)

    Afzali, R.; Ebrahimian, N.

    2013-08-01

    When the magnetic field is only acting on the spin of electrons, a transition from a normal to a modulated superconducting state or Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superconducting state may occur at low temperatures. A FFLO superconducting state, which accompanies an order parameter that oscillates spatially, may be stabilized by a high applied magnetic field or a molecular field. Quantum multipartite entanglement is a new procedure for investigating quantum phase transitions. In this article, we deal with the phase transition of the FFLO state of CeCoIn5 to a normal state by obtaining quantum multipartite entanglement of the system. For this purpose, using normal and anomalous Green functions and the density matrix, we obtain concurrence, as a measure of bipartite entanglement. Then, the order parameter and the magnetic -field dependence of multipartite entanglement in momentum space is calculated. The phase transition is determined, and the behavior of the system based on order parameter is discussed. Furthermore, the phase transitions of both the Bardeen-Cooper-Schrieffer (BCS) and FFLO states to the normal state are compared.

  4. Dynamical Electroweak Symmetry Breaking with a Heavy Fermion in Light of Recent LHC Results

    Directory of Open Access Journals (Sweden)

    Pham Q. Hung

    2013-01-01

    Full Text Available The recent announcement of a discovery of a possible Higgs-like particle—its spin and parity are yet to be determined—at the LHC with a mass of 126 GeV necessitates a fresh look at the nature of the electroweak symmetry breaking, in particular if this newly-discovered particle will turn out to have the quantum numbers of a Standard Model Higgs boson. Even if it were a 0+ scalar with the properties expected for a SM Higgs boson, there is still the quintessential hierarchy problem that one has to deal with and which, by itself, suggests a new physics energy scale around 1 TeV. This paper presents a minireview of one possible scenario: the formation of a fermion-antifermion condensate coming from a very heavy fourth generation, carrying the quantum number of the SM Higgs field, and thus breaking the electroweak symmetry.

  5. Magnetic structure of the heavy-fermion compound U2Zn17

    DEFF Research Database (Denmark)

    Cox, D. E; Shirane, G.; Shapiro, S. M.

    1986-01-01

    The phase transition of U2Zn17 at 9.7K has been investigated by neutron powder diffraction. The transition corresponds to the onset of antiferromagnetic order where the U moments are oriented antiparallel to their neighbors within the basal planes and the near neighbor along the c^ axis...

  6. Size effects on the magnetic and optical properties of CuO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Rehman, Shama, E-mail: shama_r4@yahoo.com; Mumtaz, A.; Hasanain, S. K. [Quaid-I-Azam University, Department of Physics (Pakistan)

    2011-06-15

    Optical and magnetic studies on CuO nanoparticles prepared by a chemical route are reported and the effect of size variation on these properties is discussed. SEM images show that the nanoparticles are interlinked into microspheres with the cages containing visible nanoscale holes. Diffuse reflectance spectroscopy indicates a consistent red shift in the fundamental band gap (indirect band gap) from 1.23 to 1 eV as the size decreases from 29 to 11 nm. This observed red shift is attributed to the presence of defect states within the band gap. A clear blue shift is observed in the direct band gap of these nanoparticles presumably due to the quantum confinement effects. Air-annealed samples show a paramagnetic response whereas particles annealed in a reducing atmosphere show additionally a weak ferromagnetic component at room temperature. For both types of particles, the paramagnetic and ferromagnetic moments, respectively, increase with decreasing size. The role of oxygen vacancies is understood to relate to the generation of free carriers mediating ferromagnetism between Cu spins. AC susceptibility measurements show both the antiferromagnetic transitions of CuO including the one at 231 K which is associated with the onset of the spiral antiferromagnetic phase transition.

  7. Structural and dielectric properties of Mn doped copper oxide (CuO) nanostructure

    Science.gov (United States)

    Khan, Imran; Khan, Shakeel; Ahmed, Hilal; Nongjai, Razia

    2013-06-01

    Undoped and Mn doped CuO nanocrystalline powder samples were prepared through standard solid state reaction method. The crystal structures of the CuO nanoparticles were characterized by X-ray diffraction. Dielectric measurements were performed on samples as a function of frequency at room temperate to determine the dielectric behavior of the samples. XRD data exhibited the presence of monoclinic crystal structure similar to the parent compound in all samples, suggesting that doped Mn ions sit at the regular lattice sites. The average crystallite size, calculated using Scherrer formula from XRD data, is found within the range of 23-27 nm. The dielectric constant (ɛ'), imaginary part of dielectric constant (ɛ") and loss tangent (tanδ) were studied as a function of frequency and composition at room temperature. The dependence of dielectric constant (ɛ') on frequency suggests a conduction mechanism in terms of hopping. This behavior can be explained on the basis of space charge polarization according to Maxwell and Wagner's two-layer model.

  8. GMI effect in CuO coated Co-based amorphous ribbons

    Energy Technology Data Exchange (ETDEWEB)

    Taysioglu, Asli Ayten [Department of Physics, Sciences and Arts Faculty, Uludag University, 16059 Gorukle, Bursa (Turkey); Peksoz, Ahmet, E-mail: peksoz@uludag.edu.t [Department of Physics, Sciences and Arts Faculty, Uludag University, 16059 Gorukle, Bursa (Turkey); Kaya, Yunus [Department of Chemistry, Sciences and Arts Faculty, Uludag University, 16059 Gorukle, Bursa (Turkey); Derebasi, Naim [Department of Physics, Sciences and Arts Faculty, Uludag University, 16059 Gorukle, Bursa (Turkey); Irez, Gazi [Department of Chemistry, Sciences and Arts Faculty, Uludag University, 16059 Gorukle, Bursa (Turkey); Kaynak, Gokay [Department of Physics, Sciences and Arts Faculty, Uludag University, 16059 Gorukle, Bursa (Turkey)

    2009-11-13

    A Copper oxide (CuO) film has been grown on a surface of Co-based amorphous ribbon using chemical successive ionic layer adsorption and reaction technique, at room temperature and atmosphere pressure. The influence of coating and width of ribbon on giant magneto impedance have been investigated over a frequency range from 0.1 to 3 MHz and under a static magnetic field between -8 and +8 kA/m. The results showed that Co-based amorphous ribbons, which are coated CuO film, have a significant effect on the magnitude and operation frequency for the giant magneto impedance effect as compared to the samples without coating. The highest giant magneto impedance effect was found to be 14.90 on 5 mm width coated ribbon, which is 60% higher than the sample without coating. A surface observation of these samples has been carried out by an atomic force microscope. The AFM images reveal the difference between surfaces of coated and as-cast sample.

  9. How assembly matters to catalysis and thermal conductivity mediated by CuO nanoparticles

    Science.gov (United States)

    Mohsen Ismail, Ahmed; Emara, Mahmoud Mohamed; Salah El din Kassem, Taher; Moussa, Mahmoud Ahmed

    2017-02-01

    CuO nanostructures (NSs) of different morphologies were prepared, applied as catalysts for the pyrolysis of sugarcane bagasse (PSCB), and applied for thermally-conductive nanofluids. Both size and shape of the prepared NSs ranged from 5 to 1000 nm, and from nanodots (NDs) to spindle nano-aggregates (NAs), respectively. The catalytic activity of these NSs towards the PSCB was followed up by thermogravimetric analysis (TGA), where they increased the percentage of total weight loss, and lowered the decomposition temperatures of PSCB. The Coats-Redfern kinetic model showed a decline in activation energy by 57 and 9-43 kJ mol-1 for NDs and NAs, respectively. Colloidal dispersions of CuO NDs and NAs in monoethylene glycol (MEG) were prepared with volume fractions ({\\varphi }v) of 0.01-0.04%, where thermal conductivity improved with increasing {\\varphi }v. At all values of {\\varphi }v, the best enhancements were exerted by NDs. The nature of assembly impacted the catalyzed PSCB and the thermal conductivity of MEG. This behavior depends to a large extent on the NAs that expose a different fraction of crystal facets of different reactivities and surface areas, not on the constituent nanorods (NRs).

  10. The chronic toxicity of CuO nanoparticles and copper salt to Daphnia magna.

    Science.gov (United States)

    Adam, Nathalie; Vakurov, Alexander; Knapen, Dries; Blust, Ronny

    2015-01-01

    In this study, the effects of CuO nanoparticles and CuCl2·2H2O were tested on Daphnia magna under chronic exposure scenarios. During a 21-day exposure to the nanoparticles and salt, the reproduction was followed by a daily count of the number of offspring. After the exposure, the adult Daphnia length and uptake of copper was measured. The dissolved, nanoparticle and aggregated fractions were distinguished in the exposure medium. The results showed that only a small fraction of the nanoparticles dissolved, while the majority of the particles formed large aggregates (>450 nm). The dissolved fraction of the nanoparticles corresponded with the dissolved fraction of the copper salt. The effects of the nanoparticles (reproduction EC10: 0.546 mg Cu/l, EC20: 0.693 mg Cu/l, EC50: 1.041 mg Cu/l) on reproduction and length were much lower than the effects of the copper salts (reproduction EC10: 0.017 mg Cu/l, EC20: 0.019 mg Cu/l, EC50: 0.022 mg Cu/l). Based upon total body analysis, the Daphnia copper concentration appeared much higher when exposed to the nanoparticles than when exposed to the salt. These combined results indicate that the toxicity of CuO nanoparticles to D. magna is caused by copper ions formed during dissolution of the nanoparticles in the exposure medium. Copyright © 2014 Elsevier B.V. All rights reserved.

  11. Positron annihilation spectroscopy study on annealing effect of CuO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Jianjian; Wang, Jiaheng; Yang, Wei; Zhu, Zhejie; Wu, Yichu, E-mail: ycwu@whu.edu.cn [School of Physics and Technology, Hubei Key Laboratory of Nuclear Solid State Physics, Wuhan University (WHU), Wuhan (China)

    2016-03-15

    The microstructure and defects of CuO nanoparticles under isochronal annealing were investigated by positron annihilation spectroscopy (PAS), X-ray diffraction (XRD) and scanning electron microscope (SEM). XRD and SEM results indicated that the average grain sizes of CuO nanoparticles grew slowly below 800 °C, and then increased rapidly with the annealing temperature from 800 to 1000 °C. Positron lifetime analysis exhibited that positrons were mainly annihilated in mono-vacancies (V{sub Cu}, V{sub O}) and vacancy clusters when annealing from 200 to 800 °C. Furthermore, W-S plot of Doppler broadening spectra at different annealing temperatures found that the (W, S) points distributed on two different defect species, which suggested that V{sup −}{sub Cu} - V{sup +}{sub O} complexes were produced when the grains grew to bigger size after annealing above 800 °C, and positrons might annihilate at these complexes. (author)

  12. Photocatalytic generation of hydrogen under visible light on La2CuO4

    Indian Academy of Sciences (India)

    H Lahmar; M Trari

    2015-08-01

    The semiconducting properties of La2CuO4 prepared by a chemical route are investigated for the first time by the photo-electrochemical technique. The optical gap is found to be 1.27 eV and the transition is directly allowed. p-Type conductivity is demonstrated from the Mott–Schottky plot in alkaline KOH solution (0.1 M), extrapolation of the linear region to the potential axis gives a flat band potential of −0.41 VSCE, a holes density of 1.75 × 1019 cm−3 and a space-charge region of 18 nm. The electrochemical impedance spectroscopy, measured over the frequency range (1 mHz–105 Hz), reveals the predominance of the bulk contribution with a constant phase element. The energy diagram shows the feasibility of La2CuO4 for the H2 evolution under visible light. The best performance occurs at pH 12.5 in the presence of S2O$^{2-}_{3}$ as holes scavenger. A liberation rate of 20.6 mol mn−1 (g catalyst)−1 is obtained under full light (29 mW cm−2).

  13. Controllable fabrication of nanowire-like CuO film by anodization and its properties

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yongqian, E-mail: cugwyq@126.com [Faculty of Material Science and Chemistry, China University of Geoscience, Wuhan 430074 (China); Jiang, Tingting; Meng, Dawei; Jin, Hongyun [Faculty of Material Science and Chemistry, China University of Geoscience, Wuhan 430074 (China); Yu, Meihua [Guangxi Experiment Centre of Science and Technology, Nanning 530004 (China)

    2015-09-15

    Graphical abstract: - Highlights: • The average diameter of single nanowire is only 25 nm and the length can be tuned. • The method has the advantages of pure CuO phase and fast reaction rate. • H{sub 2}O–EtOH mix solvent can significantly improve optical and photocatalytic activities. • Clarify the growth process in detail. - Abstract: We report a simple electrochemical etching and a subsequent heat treatment to synthesize nanowire-like CuO thin films with pure phase at room temperature. The reaction media has great effect on microstructure of products to significantly improve optical and photocatalytic activities of materials. Detailed characterizations of the synthesized nanomaterials are performed utilizing X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) to study their crystalline phase and morphology. The photoluminescence (PL) spectrum shows a main emission peak and a blue emission band whose centers are located at 352 nm and 463 nm, respectively. Photocatalytic study demonstrated the degradation of methylene blue (MB) can reach 95.6% after 210 min irradiation, showing its potential application in waste water treatment. A plausible growth mechanism for the transformation is also proposed.

  14. Ecotoxicity of nanoparticles of CuO and ZnO in natural water

    Energy Technology Data Exchange (ETDEWEB)

    Blinova, I., E-mail: irina.blinova@kbfi.e [Laboratory of Molecular Genetics, National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, Tallinn 12618 (Estonia); Ivask, A. [Laboratory of Molecular Genetics, National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, Tallinn 12618 (Estonia); Heinlaan, M. [Laboratory of Molecular Genetics, National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, Tallinn 12618 (Estonia); Estonian University of Life Sciences, Kreutzwaldi 5, Tartu 51014 (Estonia); Mortimer, M. [Laboratory of Molecular Genetics, National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, Tallinn 12618 (Estonia); Tallinn University of Technology, Akadeemia tee 15, Tallinn 12618 (Estonia); Kahru, A. [Laboratory of Molecular Genetics, National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, Tallinn 12618 (Estonia)

    2010-01-15

    The acute toxicity of CuO and ZnO nanoparticles in artificial freshwater (AFW) and in natural waters to crustaceans Daphnia magna and Thamnocephalus platyurus and protozoan Tetrahymena thermophila was compared. The L(E)C{sub 50} values of nanoCuO for both crustaceans in natural water ranged from 90 to 224 mg Cu/l and were about 10-fold lower than L(E)C{sub 50} values of bulk CuO. In all test media, the L(E)C{sub 50} values for both bulk and nanoZnO (1.1-16 mg Zn/l) were considerably lower than those of nanoCuO. The natural waters remarkably (up to 140-fold) decreased the toxicity of nanoCuO (but not that of nanoZnO) to crustaceans depending mainly on the concentration of dissolved organic carbon (DOC). The toxicity of both nanoCuO and nanoZnO was mostly due to the solubilised ions as determined by specific metal-sensing bacteria. - Natural waters remarkably reduced the toxicity of nanoCuO but not nanoZnO.

  15. Flow drag and heat transfer characteristics of drag-reducing nanofluids with CuO nanoparticles

    Science.gov (United States)

    Wang, Ping-Yang; Wang, Xue-Jiao; Liu, Zhen-Hua

    2017-02-01

    A new kind of aqueous CuO nanofluid with drag-reducing performance was developed. The new working fluid was an aqueous CTAC (cetyltrimethyl ammonium chloride) solution with CuO nanoparticles added and has both special effects of drag-reducing and heat transfer enhancement. An experiment was carried out to investigate the forced convective flow and heat transfer characteristics of conventional drag reducing fluid (aqueous CTAC solution) and the new drag-reducing nanofluid in a test tube with an inner diameter of 25.6 mm. Results indicated that there were no obvious differences of the drag-reducing characteristics between conventional drag reducing fluid and new drag-reducing nanofluid. However, their heat transfer characteristics were obvious different. The heat transfer characteristics of the new drag-reducing nanofluid significantly depend on the liquid temperature, the nanoparticle concentration and the CTAC concentration. The heat transfer enhancement technology of nanofluid could be applied to solve the problem of heat transfer deterioration for conventional drag-reducing fluids.

  16. Flow drag and heat transfer characteristics of drag-reducing nanofluids with CuO nanoparticles

    Science.gov (United States)

    Wang, Ping-Yang; Wang, Xue-Jiao; Liu, Zhen-Hua

    2016-05-01

    A new kind of aqueous CuO nanofluid with drag-reducing performance was developed. The new working fluid was an aqueous CTAC (cetyltrimethyl ammonium chloride) solution with CuO nanoparticles added and has both special effects of drag-reducing and heat transfer enhancement. An experiment was carried out to investigate the forced convective flow and heat transfer characteristics of conventional drag reducing fluid (aqueous CTAC solution) and the new drag-reducing nanofluid in a test tube with an inner diameter of 25.6 mm. Results indicated that there were no obvious differences of the drag-reducing characteristics between conventional drag reducing fluid and new drag-reducing nanofluid. However, their heat transfer characteristics were obvious different. The heat transfer characteristics of the new drag-reducing nanofluid significantly depend on the liquid temperature, the nanoparticle concentration and the CTAC concentration. The heat transfer enhancement technology of nanofluid could be applied to solve the problem of heat transfer deterioration for conventional drag-reducing fluids.

  17. 3D graphene foams decorated by CuO nanoflowers for ultrasensitive ascorbic acid detection.

    Science.gov (United States)

    Ma, Ye; Zhao, Minggang; Cai, Bin; Wang, Wei; Ye, Zhizhen; Huang, Jingyun

    2014-09-15

    When the in vitro research works of biosensing begin to mimic in vivo conditions, some certain three-dimensional (3D) structures of biosensors are needed to accommodate biomolecules, bacteria or even cells to resemble the in vivo 3D environment. To meet this end, a novel method of synthesizing CuO nanoflowers on the 3D graphene foam (GF) was first demonstrated. The 3DGF/CuO nanoflowers composite was used as a monolithic free-standing 3D biosensor for electrochemical detection of ascorbic acid (AA). The 3D conductive structure of the GF is favorable for current collection, mass transport and loading bioactive chemicals. And CuO nanoflowers further increase the active surface area and catalyze the redox of AA. Thus, all these features endows 3DGF/CuO composite with outstanding biosensing properties such as an ultrahigh sensitivity of 2.06 mA mM(-1) cm(-2) to AA at 3 s response time.

  18. The specific heat of the electron-doped La-1038 compound (Ca0.85La0.15)10(FeAs)10(Pt3As8).

    Science.gov (United States)

    Kim, J S; Stürzer, T; Johrendt, D; Stewart, G R

    2013-04-01

    The specific heat of polycrystalline (Ca0.85La0.15)10(FeAs)10(Pt3As8), an electron-doped iron-based superconductor (T(c)(onset) = 34.6 K) with Ca/La ions and Pt3As8 separating the FeAs layers, was measured between 0.4 and 48 K.This compound has been recently reported to represent an electron-doped variant of the non-superconducting 10-3-8 phase, featuring a superconducting transition in the range of that of the 10-4-8 phase. This family of compounds is unique among the iron pnictide superconductors discovered to date due to the second metal pnictide layer, Pt3As8, present in the structure competing with the familiar FeAs layer for the electron from the Ca/La. This superconductor is further unusual in that it has a rather low crystalline symmetry (triclinic) for such a high superconducting transition temperature. The specific heat γ is found to be approximately 26 mJ/(Ca/La mol)K(2), comparable to 122 iron-based superconductors electron-doped on the Fe sites and a factor of two smaller than 122 compounds hole-doped on the cation site, e.g., Ba(1-x)K(x)Fe2As2. The present work also investigates the discontinuity in the specific heat at T(c), ΔC, to compare with the global trend, established by Bud'ko, Ni and Canfield (BNC), of ΔC/T(c) versus T(c) found for essentially all iron-based superconductors. The result is a value lower than the BNC trend by a factor of ten, consistent with a severely broadened superconducting transition.

  19. Critical state and low-field electrodynamics in LaO{sub 0.85}F{sub 0.15}FeAs superconductor polycrystals

    Energy Technology Data Exchange (ETDEWEB)

    Gerashchenko, O. V., E-mail: gerashch@pnpi.spb.ru [National Research Centre “Kurchatov Institute,”, Petersburg Institute of Nuclear Physics (Russian Federation); Kholmetskii, A. L. [Belarus State University (Belarus); Mashlan, M. [Palacky University (Czech Republic); Yarman, T. [Okan University (Turkey); Aldushchenkov, A. V.; Okunev, I. S. [National Research Centre “Kurchatov Institute,”, Petersburg Institute of Nuclear Physics (Russian Federation); Lomonosov, V. A.; Makhnach, L. V. [Belarus State University (Belarus)

    2015-06-15

    The penetration of a weak magnetic field into LaO{sub 0.85}F{sub 0.15}FeAs polycrystalline superconductors is investigated using two mutually complementing techniques: measurement of the higher harmonics of nonlinear magnetization and the current-voltage characteristics. The dependences of the critical current density and resistivity on the temperature and magnetic field strength are determined. The results confirm the theory of the critical state in the low-field electrodynamics of a Josephson medium. The universality of this theoretical concept is demonstrated for a new class of ceramic superconductors.

  20. Joint EPA/UMTA/FEA strategy for urban transportation and air quality. Volume 3. The potential of dual mode. Literature review, 1964--1974

    Energy Technology Data Exchange (ETDEWEB)

    Krzyczkowski, R.; Henneman, S.S.

    1974-12-01

    Interdependence of goals of the three agencies, EPA, UMTA, and FEA generates this four-volume study. The common issue around which all three agencies' policies revolve is the use of the private auto involving both incentives and penalties to catalyze a change in existing urban travel characteristics. This third volume expresses INTERPLAN's judgment about the applicability, timing, and impact of dual mode urban transportation technologies. A three-system, three-phase, gradual evolution of demand for dual mode is suggested. The dual mode essay is prefaced by a short overview and comparison of the propulsion and energy use characteristics of conventional and future urban transportation modes.