Publications

2006

• Polymorphism of Tricalcium Silicate, the Major Compound of Portland Cement Clinker: 2. Modelling alite for Rietveld analysis, an industrial challenge
  
  • de Noirfontaine Marie-Noëlle
  • Dunstetter Frederic
  • Courtial Mireille
  • Gasecki Gilles
  • Signes-Frehel Marcel
  Cement and Concrete Research, Elsevier, 2006, 36 (1), pp.54-64. A comprehensive quantification of the various phases of clinkers by X-ray diffraction with a Rietveld-like analysis is an important industrial challenge. Various available structural models are used for the most frequent M1 and M3 polymorphs of alite usually found in industrial clinkers, referred to as M1- or M3-based clinkers. In this paper, the effect of C3S structural model is investigated. Four models are tested and compared using either synthetic M1 and M3 alites or M1- and M3-based clinkers. The comparison validates the available models for M1 and M3 alites and an average model, given here, derived from our recently proposed M1 structure as a catch-all model when the nature of the clinker is unknown. The latter model is meant to be used for industrial on-line quantification. (10.1016/j.cemconres.2004.12.004)
  DOI : 10.1016/j.cemconres.2004.12.004
• Reflectionless Tunnelling of Light in Gradient Optics
  
  • Shvartsburg Alexander
  • Petite Guillaume
  Optics Letters, Optical Society of America - OSA Publishing, 2006, 31, pp.1127. We analyse the optical (or microwave) tunnelling properties of electromagnetic waves passing through thin films presenting a specific index profile providing a cut-off frequency, when they are used below this frequency. We show that contrary to the usual case of a square index profile, where tunnelling is accompanied with a strong attenuation of the wave due to reflection, such films present the possibility of a reflectionless tunnelling, where the incoming intensity is totally transmitted.
• XAS Investigation of biorelevant cobalt complexes in aqueous media
  
  • Bresson C.
  • Esnouf S.
  • Lamouroux C.
  • Solari P.-L.
  • den Auwer C.
  New Journal of Chemistry, Royal Society of Chemistry [1987-....], 2006, 30 (3), pp.416-424. Cobalt is an essential element of biological cycles involved in numerous metallobiomolecules, but it becomes a toxic element at high concentration or a radiotoxic element because of its use in the nuclear industry. “Molecular speciation” in biological media is an essential prerequisite to evaluate its chemical behaviour as well as its toxic or beneficial effects. In this scheme, we have focused on the coordination properties of the thiol-containing amino acid cysteine (Cys) and the pseudo-peptide N-(2-mercaptopropionyl)glycine (MPG) towards the Co²⁺ cation in aqueous media. XAS at the Co K edge and traditional spectroscopic techniques have been coupled in order to structurally characterize the cobalt coordination sphere. Oxidation states and geometries of the bis- and tris-cysteinato Co(III) complexes are in agreement with the literature data. In addition, bond lengths between the metallic centre and the donor atoms have been determined. The structure of a new dimeric N-(2-mercaptopropionyl)glycinato Co(II) complex in solution is also reported. The coordination of MPG to Co(II) through the thiolate and carboxylate functions is ascertained. This work provides fundamental structural information about biorelevant complexes of cobalt, which will contribute to our understanding of the chemical behaviour and the biological role of this radionuclide. (10.1039/B514454J)
  DOI : 10.1039/B514454J
• Bi-directional porous alumina wire templates for nanowire field-effect transistors
  
  • L. Wade Travis
  • Hoffer Xavier
  • Dayen Jean-François
  • Dughaim Mohammed Al
  • Humel Fahad
  • Wegrowe Jean-Eric
  Materials Research Society Symposia Proceedings, 2006, 901E, pp.Rb07-02.1. Using readily available materials and equipment we are able to sculpture aluminium wires into cylindrical, bi-directional templates for the synthesis and contacting of nanowires as field-effect transistors. The nanowire template is made by partial anodization of the wire perpendicular to its axis as an isolating layer for a gate electrode, vapour deposition of a metal on this layer as a gate, cutting the wire perpendicular to its axis, and finally anodizing the newly exposed area parallel to the wire axis as a template for nanowires. This results in a nanowire template surrounded by a gate electrode that is isolated from the template by the first anodisation layer. The utility of this structure is demonstrated by a ZnO nanowire field-effect transistor. The ZnO was made by electrodeposition of Zn nanowires in the interior nanoporous template during which an anodic pulse was applied to form a layer of ZnO in the middle of the zinc nanowires. The IV and transfer plots indicate that the ZnO is p-type in depletion mode. This 3-D transistor is unique in that it can be totally fabricated in a beaker without the need for costly clean room and lithography facilities. The ease and low cost of this new approach to nanodevices will have the effect of liberating nanoscience for scientists of moderate means. As a result this will open nanoscience to new ideas and more inputs.
• Synthesis of high aspect ratio of Ni0.5Zn0.5Fe2O4 platelets for electromagnetic devices
  
  • Hallynck Sylvain
  • Pourroy Geneviève
  • Vilminot Serge
  • Jacquart Pierre-Marie
  • Autissier Denis
  • Vukadinovic Nicolas
  • Pascard Hubert
  Solid State Sciences, Elsevier, 2006, 8 (1), pp.24-30. (10.1016/j.solidstatesciences.2005.10.007)
  DOI : 10.1016/j.solidstatesciences.2005.10.007
• Use of luminescent materials for the metrology of intense UVX bundles of ultrashort impulsions
  
  • Fedorov N.
  • Nagirnyi V.
  • Vasil'Ev A.
  • Belsky A.
  • Carré B.
  • Feldbach E.
  • Gaudin J.
  • Geoffroy G.
  • Guizard S.
  • de Grazia M.
  • Kirm M.
  • Martin P.
  • Merdji H.
  • Petite G.
  Journal de Physique IV Proceedings, EDP Sciences, 2006, 138, pp.251–257. Récemment nous avons débuté des séries d'expériences sur l'interaction d'impulsions intenses VUV avec les solides luminescents. Le but principal en est l'étude des mécanismes d'interaction et de transfert d'énergie entre les excitations électroniques dans les solides à large bande interdite. L'application directe de ces études sera le développement de matériaux et de méthodes de métrologie pour les faisceaux UVX intenses. Nous présentons les résultats obtenus pour CdWO4 qui montrent que ce cristal pourra servir comme un scintillateur pour le rayonnement VUV intense
• Anisotropic magnetothermopower: Contribution of interband relaxation
  
  • Wegrowe J.-E.
  • Nguyen Q.A.
  • Al-Barki M.
  • Dayen J.-F.
  • Wade T.L.
  • Drouhin H.-J.
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2006, 73 (13), pp.134422. Spin injection in metallic normal/ferromagnetic junctions is investigated taking into account interband relaxation and the consequences in terms of thermoelectric power. On the basis of a generalized two-channel model, it is shown that there is an interface resistance and thermoelectric power contribution due to anisotropic scattering, besides spin accumulation and giant magnetoresistance. The corresponding expression of the thermoelectric power is derived and compared with the expression accounting for the thermoelectric power produced by the giant magnetoresistance. Measurements of anisotropic magnetothermoelectric power are presented in electrodeposited Ni nanowires contacted with Ni, Au, and Cu. It is shown that a thermoelectric power is generated at the interfaces of the nanowire and that the experimental results strongly support the model. 2006 The American Physical Society. (10.1103/PhysRevB.73.134422)
  DOI : 10.1103/PhysRevB.73.134422
• X-ray magnetic circular dichroism at the Gd L2,3 absorption edges in GdN layers: The influence of lattice expansion
  
  • Leuenberger F.
  • Parge A.
  • Felsch W.
  • Baudelet F.
  • Giorgetti C.
  • Dartyge E.
  • Wilhelm F.
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2006, 73, pp.214430. We have measured core-level x-ray-absorption spectra and x-ray magnetic circular dichroism (XMCD) at the Gd-L2,3 edges to characterize the low-lying Gd-5d derived conduction-band states in thin films of the 4f ferromagnet GdN with a unit-cell volume 8.6% above that of bulklike layers. The nonequilibrium structure is obtained by N+ plasma-assisted reactive sputter deposition at room temperature. The Curie temperature TC, a key quantity for magnetism, amounts to only half the bulk value of ~60 K indicating a significant reduction of the effective exchange interaction between the 4f states. An intricate observation is that the ratio of the dichroic signal amplitudes in the lattice-expanded layers, |L3/L2|, is up to three times higher than the value expected from the degeneracy of the 2p3/2 and 2p1/2 core states, which is observed for the bulklike layers. This is mainly due to a reduced L2 XMCD amplitude. We suggest that the effect may be related to the different weight the crystal-field split Gd-5d final states (t2g and eg) have in the absorption process at the L2 and L3 edges, and to the special electronic band structure of this strongly correlated material and its modification upon lattice expansion. This hypothesis is supported by the observation that the L2 absorption edge is shifted to lower energies upon ferromagnetic ordering while the L3-edge position remains inert
• Exchange and correlation effects in electronic excitations of Cu2O
  
  • Bruneval Fabien
  • Vast Nathalie
  • Reining Lucia
  • Izquierdo M.
  • Sirotti F.
  • Barrett N.
  , 2006. The state-of-the-art theoretical methods to calculate electronic excitations are shown to fail in describing the highly complex optical absorption spectrum of Cu2O. In particular, the band gap and the optical onset are severely underestimated. We have implemented within a pseudopotential scheme a recently proposed self-consistent quasiparticle approach, based on the GW approximation, and we have extended it to the calculation of optical spectra, including excitonic e®ects. The calculated band structure compares favorably with photoemission data from the literature as well as our present angle-resolved photoemission (ARPES) measurements. Furthermore, the inclusion of the excitonic e®ects using this more precise band structure, together with the better description of the screening, has led to a calculated optical absorption spectrum which reproduces the measured structures. On the basis of these ¯ndings, we give a new interpretation of the origin of the main structures in the spectru
• Addition versus radiolytic production effects of hydrogen peroxide on aqueous corrosion of UO$_2$
  
  • Corbel Catherine
  • Sattonnay Gael
  • Guilbert Severine
  • Garrido Federico
  • Barthe Marie-France
  • Jegou Christophe
  Journal of Nuclear Materials, Elsevier, 2006, 348, pp.1-17. The effects of hydrogen peroxide, H2O2, on UO2 corrosion is investigated in aerated deionized water in two types of situations. The H2O2 species is either added to water or produced by radiolysis at UO2/H2O interfaces. The concentrations vary in the range 10−5–10−1 mol l−1. The radiolysis is induced by irradiating the UO2/H2O interfaces with a He2+-beam emerging from the UO2 discs into the solutions. Both the evolution of the aqueous solutions and the UO2 surfaces are characterised. In both types of experiments, the alteration of UO2 results in the formation of the same secondary phase, an hydrated uranium peroxide called studtite (UO2(O)2 · 4H2O). However, the uranium release at the interface differs strikingly. It is much higher when H2O2 is produced by irradiation than when it is simply added. Furthermore, it varies in opposite direction as a function of the H2O2 concentration. This gives evidence that the chemistry at the UO2 interface under irradiation differs significantly from the chemistry induced by simply adding H2O2 to the solution. Rutherford backscattering spectrometry is used to determine the growth rate of the corrosion layer. For H2O2 addition, the layer thickness increases with increasing leaching time, although as time increases, the U release tends towards zero. It is possible to establish the first empirical equation relating the corrosion rates to the added H2O2 concentrations. For H2O2 radiolytic production, the growth is continuous as irradiation time increases but the growth rate seems to decrease as the layer grows and to reach a limit. (10.1016/j.jnucmat.2005.05.009)
  DOI : 10.1016/j.jnucmat.2005.05.009
• Polymorphism of Tricalcium Silicate, the Major Compound of Portland Cement Clinker: 1. Structural data : review and unified analysis
  
  • Dunstetter Frederic
  • de Noirfontaine Marie-Noëlle
  • Courtial Mireille
  Cement and Concrete Research, Elsevier, 2006, 36 (1), pp.39-53. This paper reviews the literature devoted to structural investigations, with a special concern to the various notations used by different authors. A unified analysis of the known T1, M1, M3 and R polymorphs is proposed. The superstructure relations between the various unit cells are discussed, together with the evidence of common 1D and 2D structural elements in all these polymorphs. These structural elements are related to the observed properties. (10.1016/j.cemconres.2004.12.003)
  DOI : 10.1016/j.cemconres.2004.12.003
• Thermal recovery of colour centres induced in cubic yttria-stabilized zirconia by charged particle irradiations
  
  • Beuneu Francois
  • Costantini Jean-Marc
  Journal of Physics: Condensed Matter, IOP Publishing [1989-....], 2006, 18, pp.3671. We have used electron paramagnetic resonance to study the thermal annealing of colour centres induced in cubic yttria-stabilized zirconia by swift electron and heavy ion-irradiations. Single crystals were irradiated with 1 or 2-MeV electrons, and 200-MeV 127I, or 200-MeV 197Au ions. Electron and ion beams produce the same colour centres: namely i) an F+-like centre, ii) the so-called T-centre (Zr3+ in a trigonal oxygen local environment), and iii) a hole center. Isochronal annealing was performed up to 973 K. Isothermal annealing was performed at various temperatures on samples irradiated with 2-MeV electrons. The stability of paramagnetic centres increases with fluence and with a TCR treatment at 1373 K under vacuum prior to the irradiations. Two distinct recovery processes are observed depending on fluence and/or thermal treatment. The single-stage type I process occurs for F+-like centres at low fluences in as-received samples, and is probably linked to electron-hole recombination. T-centres are also annealed according to a single-stage process regardless of fluence. The annealing curves allow one to obtain activation energies for recovery. The two-stage type II process is observed only for the F+-like centres in as-received samples, at higher fluences, or in reduced samples. These centres are first annealed in a first stage below 550 K, like in type I, then transform into new paramagnetic centres in a second stage above 550 K. A simple kinetics model is proposed for this process. Complete colour centre bleaching is achieved at about 1000 K. (10.1088/0953-8984/18/15/013)
  DOI : 10.1088/0953-8984/18/15/013
• Beyond time-dependent exact-exchange : the need for long-range correlation.
  
  • Bruneval F.
  • Sottile F.
  • Olevano Valério
  • Reining L.
  The Journal of Chemical Physics, American Institute of Physics, 2006, 124, pp.144113. In the description of the interaction between electrons beyond the classical Hartree picture, bare exchange often yields a leading contribution. Here we discuss its effect on optical spectra of solids, comparing three different frameworks: time-dependent Hartree-Fock, a recently introduced combined density-functional and Green's function approaches applied to the bare exchange self-energy, and time-dependent exact exchange within time-dependent density-functional theory (TD-EXX). We show that these three approximations give rise to identical excitonic effects in solids; these effects are drastically overestimated for semiconductors. They are partially compensated by the usual overestimation of the quasiparticle band gap within Hartree-Fock. The physics that lacks in these approaches can be formulated as screening.We show that the introduction of screening in TD-EXX indeed leads to a formulation that is equivalent to previously proposed functionals derived from many-body perturbation theory. It can be simulated by reducing the long-range part of the Coulomb interaction: this produces absorption spectra of semiconductors in good agreement with experiment.
• New sulfonated pyrrole and pyrrole 3-carboxylic acid copolymer membranes via track-etched templates
  
  • Clochard M.-C
  • Baudin C
  • Betz N
  • Le Moël A
  • Bittencourt C
  • Houssiau L
  • Pireaux J.-J
  • Caldemaison Daniel
  Reactive and Functional Polymers, Elsevier, 2006, pp.1296. New copolymers of polypyrrole and poly(3-carboxylic acid pyrrole) have been synthesized via a diaphragmatic method using a track-etched polycarbonate matrix. The presence of carboxylic acid substituents enables the introduction of new functionalities such as sulfonate groups. The resulting copolymer membranes with tubules microstructure have been characterized through scanning electron microscopy, X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry and FT-IR. By SEM, it was observed that ion-track trajectories can cross. XPS, ToF-SIMS and FT-IR spec-troscopy showed that it was possible to attach other molecules to the membrane. The polypyrrole copolymer membranes have exceptional thermal stabilities, with decomposition observed at 900 °C. (10.1016/j.reactfunctpolym.2006.03.012)
  DOI : 10.1016/j.reactfunctpolym.2006.03.012
• Deformation bands in metallic glasses induced by swift heavy ions
  
  • Rizza G.
  • Dunlop A.
  • Kopcewicz M.
  Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Elsevier, 2006, 245, pp.130-132. We present a direct experimental evidence that shear bands in metallic glasses can be induced by swift heavy ion irradiation. Transmission electron microscopy micrographs show that shear bands nucleate in the vicinity of the ion paths. Finally, we state that swift heavy-ion irradiation can be used as a nanometer-size probe to test the structural stability of metallic glasses under high local stresses (10.1016/j.nimb.2005.11.089)
  DOI : 10.1016/j.nimb.2005.11.089
• Murnaghan's equation of state for the electronic ground state energy
  
  • Tyuterev V.G.
  • Vast N.
  Computational Materials Science, Elsevier, 2006, 38, pp.350–353. In this work, we study the formulae of Murnaghan's equation of state, reported in the literature and used to fit the theoretical electronic ground state energy and obtain thermodynamical quantities like the bulk modulus. We find that the expression of the energyversus- volume dependence, obtained by a straightforward integration of the pressure-versus-volume equation of state, does not satisfy the requirement of independent parameters imposed by the least-square fitting process. Instead, a change in the definition of the integration constant leads to a well-behaved fitting function, which is recommended in order to obtain reliable thermodynamical quantities
• Thermal annealing study of swift heavy-ion irradiated zirconia
  
  • Costantini Jean-Marc
  • Kahn-Harari Andrée
  • Beuneu Francois
  • Couvreur François
  Journal of Applied Physics, American Institute of Physics, 2006, 99, pp.123501. Sintered samples of monoclinic zirconia (alpha-ZrO2) have been irradiated at room temperature with 6.0-GeV Pb ions in the electronic slowing down regime. X-ray diffraction (XRD) and micro-Raman spectroscopy measurements showed unambiguously that a transition to the 'metastable' tetragonal phase (beta-ZrO2) occurred at a fluence of 6.5x10^12 cm-2 for a large electronic stopping power value (approx 32.5 MeV $\mu$m-1). At a lower fluence of 1.0x10^12 cm-2, no such phase transformation was detected. The back-transformation from beta- to alpha-ZrO2 induced by isothermal or isochronal thermal annealing was followed by XRD analysis. The back-transformation started at an onset temperature around 500 K and was completed by 973 K. Plots of the residual tetragonal phase fraction deduced from XRD measurements versus annealing temperature or time are analyzed with first- or second-order kinetic models. An activation energy close to 1 eV for the back-transformation process is derived either from isothermal annealing curves, using the so-called "cross-cut" method, or from the isochronal annealing curve, using a second-order kinetic law. Correlation with the thermal recovery of ion-induced paramagnetic centers monitored by EPR spectroscopy is discussed. Effects of crystallite size evolution and oxygen migration upon annealing are also addressed. (10.1063/1.2198927)
  DOI : 10.1063/1.2198927
• Lithium colloids and color center creation in electron-irradiated Li2NH observed by electron-spin resonance
  
  • Beuneu Francois
  • Vajda Peter
  • Nakamori Y.
  • Orimo S.
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2006, 74, pp.174122. We have irradiated Li2NH powder with MeV electrons at room temperature and investigated the introduced defects with electron spin resonance. CESR indicates the presence of nanosize metallic Li colloids seen as a Lorentzian line with a g = 2.0023 and a line width DeltaH = 50 microT. A second, broader, signal (DeltaH = 3 to 4 mT) appears superimposed upon the Li line at low T (Curie-type behavior) which exhibits complex T-dependence with a break near 180 K for its g-value and DeltaH. We are suggesting for the latter a vacancy-type defect in the NH-sublattice, with freezing of its H-component below 180 K. When heated both the Li colloids and the color centers anneal around 100 C probably due to hydrogen evolution and subsequent chemical degradation. (10.1103/PhysRevB.74.174122)
  DOI : 10.1103/PhysRevB.74.174122