Células de metalización programable: la carrera por la miniaturización
scienceinschool.org
El deseo de descargar, almacenar y llevarse música y vídeos de Internet ha llevado a unas necesid... more El deseo de descargar, almacenar y llevarse música y vídeos de Internet ha llevado a unas necesidades masivas, siempre crecientes, de almacenamiento móvil. Toda esa información se almacena en sólo los dos estados distintos de un bit: 0 ó 1. En la memoria flash que ...
Programmable metallisation cells: the race for miniaturisation
scienceinschool.org
Cutting-edge science www. scienceinschool. org 25 Science in School Issue 15: Summer 2010 trolyte... more Cutting-edge science www. scienceinschool. org 25 Science in School Issue 15: Summer 2010 trolyte film (an ion-containing medium, commonly silver germanium selenide (AgGeSe), disilver selenide (Ag2Se), copper germanium selenide (CuGeS) or dicopper ...
Crystal Structure of the Ordered Double Perovskite, Sr2NiTeO6
Zeitschrift für anorganische und allgemeine Chemie, 2005
ABSTRACT The crystal structure of the ordered double perovskite Sr2MnTeO6 has been refined at amb... more ABSTRACT The crystal structure of the ordered double perovskite Sr2MnTeO6 has been refined at ambient temperature from high resolution neutron and X-ray powder diffraction data in the monoclinic space group I 1 2/m 1 with a = 5.6166(1) Å, b = 5.5807(1) Å, c = 7.8797(1) Å and β = 90.048(2)°. The structure is the result of out-of-phase (–) rotations of virtually undistorted NiO6 and TeO6 octahedra in the (0 – –) sense about two of the axes of the ideal cubic perovskite. Electron diffraction measurements have been used to confirm the proposed space group and structure.
The crystal and oxygen defect structure of the n = 2 Ruddlesden-Popper phase Sr 3 Fe 2 O 6 + δ ha... more The crystal and oxygen defect structure of the n = 2 Ruddlesden-Popper phase Sr 3 Fe 2 O 6 + δ have been studied by in situ high temperature neutron powder diffraction in the temperature range 20 ≤ T ≤ 900°C in air. The analysis of the neutron diffraction data revealed the presence of structural oxygen vacancies on both the O(1) sites linking the octahedra along the c axis and the O(3) sites in the FeO 2 planes of the perovskite layers. The oxygen vacancies on the O(3) site increase with temperature up to ∼ 0.25 per formula unit at T = 900°C. This result supports previously proposed oxygen ion diffusion mechanism in Sr 3 Fe 2 O 6 + δ that involves the migration of vacancies from an O(3) site to an adjacent O(1) site. The total linear expansion along the c axis α c = 17.7(5) · 10 − 6 K − 1 mainly affects the perovskite block while the width of the rock salt layers remains stable with temperature. The total volumetric expansion α V / 3 = 20(1) · 10 − 6 K − 1 is around the average of the TEC values (14.8-27.1 K − 1 ) reported for the perovskite system La 1 − x Sr x Co 1 − y Fe y O 3 − δ .
Mechanism of magnetic recovery in the disorder-order transformation of Fe70Al30 mechanically deformed alloys
Physical Review B, 2005
The degree of order in Fe-Al intermetallic alloys has an important influence on their magnetic pr... more The degree of order in Fe-Al intermetallic alloys has an important influence on their magnetic properties. Moreover, the deformation of ordered alloys causes a dramatic increase of magnetization. If deformed alloys are heated, their magnetic properties decrease again. The reordering process was monitored by neutron diffraction, Moessbauer spectroscopy, and calorimetric measurements on the FeââAlââ crushed alloy. This indicates that the
Local structure in BaTi1−xZrxO3 relaxors from neutron pair distribution function analysis
Physical Review B, 2009
Page 1. Local structure in BaTi1−xZrxO3 relaxors from neutron pair distribution function analysis... more Page 1. Local structure in BaTi1−xZrxO3 relaxors from neutron pair distribution function analysis C. Laulhé,1 F. Hippert,1 R. Bellissent,2 A. Simon,3 and GJ Cuello4 1Laboratoire des Matériaux et du Génie Physique (CNRS-Grenoble ...
In this work we address the problem of multiple scattering and inelasticity corrections in neutro... more In this work we address the problem of multiple scattering and inelasticity corrections in neutron diffraction measurements for structural studies of molecular systems. A variety of pulsed neutron and reactor experiments was performed on hydrogenous samples under different experimental conditions. Monte Carlo simulations were carried out on the basis of a Synthetic Model to describe the neutron-molecule interaction, and they allowed a simultaneous evaluation of multiple, inelastic and beam attenuation processes into the samples. A very good agreement between measurements and simulations was obtained in all cases, for our demanding choice of samples and experimental conditions.
Powder x-ray diffraction patterns of the doped compounds Gd 5 Si 2 Ge 1.9 M 0.1 (M = Ga, Cu) show... more Powder x-ray diffraction patterns of the doped compounds Gd 5 Si 2 Ge 1.9 M 0.1 (M = Ga, Cu) show the same crystal structure, orthorhombic Gd 5 Si 4 -type, in the ferromagnetic and paramagnetic phases. This is different from Gd 5 Si 2 Ge 2 , whose paramagnetic phase is monoclinic. The magnetic structure at low temperature, solved from diffraction experiments with hot neutrons, is the same in all the three compounds, collinear ferromagnetic with moments along the crystal b-axis, or F y F By according to Bertaut's notation. These results, combined with those of heat capacity and magnetocaloric effect, indicate, similarly to Gd 5 Si 4 , a second-order, purely magnetic, transition in the doped compounds explaining the absence of hysteresis.
The determination of the structural and dynamical properties of non-crystalline materials is usua... more The determination of the structural and dynamical properties of non-crystalline materials is usually a difficult task because any scientific insight must be achieved without the mathematical amenities useful in the crystalline state. Special experimental techniques need to be employed and among them, neutron scattering is one of the most powerful. The Institut Laue Langevin (ILL) operates a nuclear reactor, which is the finest steady-state source of neutrons in the world. In this work we introduce a large suite of instruments available at the ILL for structural and dynamical studies on non-crystalline solids or, more generally, amorphous systems, including liquids.
Systematic study of the reordering process in FeAl alloys by neutron diffraction
Journal of Non-Crystalline Solids, 2003
In this work, the authors performed in situ neutron diffraction experiments in order to study the... more In this work, the authors performed in situ neutron diffraction experiments in order to study the reordering process of deformed Fe70Al30 alloy at a continuous heating rate from room temperature up to 875 K. The results indicate that the reordering process takes place in two steps. First at around 450 K, a precipitation of the B2 phase occurs, and again at around 610 K. The changes in structure observed at around 450 K explain the decrease of the magnetism observed in the reordering of this alloy.
The temperature variation of the structure and microstructure of molten eutectic Al 1Àx Si x allo... more The temperature variation of the structure and microstructure of molten eutectic Al 1Àx Si x alloys (x = 0.122 and 0.20) have been studied by neutron diffraction and small-angle neutron scattering (SANS), as well as measurements performed on pure liquid Al. All measurements have been performed at five temperatures in a heating-cooling loop. The SANS results unambiguously show that for the eutectic alloy (x = 0.122) the microstructure changes with increasing temperature in a partly reversible way while for the hypereutectic (x = 0.20) alloy the change is almost completely irreversible. This change in microstructure also manifests itself in the shape of the static structure factor S(Q).
The degree of order in Fe-Al intermetallics has an important influence on their magnetic properti... more The degree of order in Fe-Al intermetallics has an important influence on their magnetic properties. Moreover, the disorder-order transition provokes a dramatical change on the magnetism of these alloys. In order to clarify this phenomenon, neutron diffraction and M .
Spinels. -The title compounds are synthesized from stoichiometric mixtures of either Li2CO3, MnCO... more Spinels. -The title compounds are synthesized from stoichiometric mixtures of either Li2CO3, MnCO3·0.5H2O, and TiO2 at 1173 K for M: Ti or LiNO3, Cr(NO3)3·9H2O, and MnO2 at 1223 K for M: Cr. Neutron diffraction results reveal that both compounds crystallize in the space group Fd3m. Both compounds show semiconducting behavior. Magnetic data indicate that no long-range magnetic ordering is present, suggesting a spin-glass transition for M: Cr at low temperature, while for M: Ti the presence of non-magnetic ions in the octahedral sublattice provokes an inherent magnetic frustration. -(ARILLO*, M. A.; CUELLO, G.; LOPEZ, M. L.; MARTIN, P.; PICO, C.; VEIGA, M. L.; Solid State Sci. 7 (2005) 1, 25-32;
Structural evolution and magnetic properties in Fe70Cr10B20 ribbons
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M ssbauer Spectroscopy, Dilatometry and Neutron Diffraction Detection of the?-Phase Fraction in Fe? Mn Shape Memory Alloys
Prions, Radionuclides and Clays: Impact of clay interlayer
ABSTRACT
Arsenic removal by gypsum and calcite: the continuum between sorption and solid-solution phenomenon
ABSTRACT The sorption of As onto mineral surface, via the precipitation of Ca3(AsO4)2, controls t... more ABSTRACT The sorption of As onto mineral surface, via the precipitation of Ca3(AsO4)2, controls the As solubility in industrial and mining sites. In spite of the progress in environmental chemistry, there is little data on As sorption reactions in calcite and gypsum and on the precipitation/dissolution of Ca3(AsO4)2. Recent studies have reported that As (III) can be adsorbed by the calcite and As(V) by the gypsum. In order to determine the kinetic reactions developed during the As (III, V) uptake by calcite and gypsum from aqueous solutions, we have performed adsorption isotherm and neutron diffraction experiments. The influence of pH and CO2(g) concentration was also tested. Our results show a continuum between adsorption and the formation of solid solutions Ca(SO4,HAsO4) and Ca(CO3, HAsO3 ). Higher As adsorption was registered for both, calcite and gypsum at increasing CO2(g) levels in aqueous solutions and pH conditions between 7 and 10. The study of the interaction of different arsenic compounds with geological materials is of regional relevance concerning both environmental and health aspects. Immobilisation of arsenic in presence of gypsum (CaSO4 .2H2O) and calcite (CaCO3) should be undertaken to remove arsenic in calcium rich sites if their long-term stability is assessed. Understanding the behavior of the different compounds of As is necessary to estimate and predict possible consequences to forecasted or accidental events and to propose remediation actions at the concerned sites.
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Papers by G. Cuello