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Li X.,Shanghai University | Ren Z.,Shanghai University | Shen Y.,Shanghai University | Fautrelle Y.,SIMAP
Philosophical Magazine Letters | Year: 2012

By eliminating the effect of the magnetic moment arising from the magnetic crystalline anisotropy, the effect of the thermoelectric magnetic force on the array of dendrites during directional solidification of Al-35wt%Cu and Al-40wt%Cu alloys in a high magnetic field has been investigated experimentally. The results indicate that the dendrite array is essentially destroyed, a result that could have general significance for understanding the processes involved in the solidification of alloys in a magnetic field. © 2012 Taylor & Francis.

Lucazeau G.,LEPMI | Le Bacq O.,SIMAP | Pasturel A.,SIMAP | Pasturel A.,French National Center for Scientific Research | And 2 more authors.
Journal of Raman Spectroscopy | Year: 2011

Polarized Raman spectra of a single crystal of gadolinium molybdate [Gd2(MoO4)3] were obtained between 1 atm and 7 GPa. Using a mixture of alcohols as the pressure-transmitting medium, YY, ZZ, XY components of scattering matrices were measured. The ZZ spectra were also obtained in argon. Five phase transitions and amorphization were identified. The first and second transitions are reversible, while amorphization is not. In alcohol, amorphization is observed above 6.5 GPa. With argon as the pressure-transmitting medium, amorphization is progressive and begins above 3 GPa. The spectral changes with pressure affect the high wavenumber bands attributed to symmetric and antisymmetric MoO4 stretching modes as well as the very low wavenumber modes such as librations of the tetrahedra. This means that both short-range and long-range organizations of the tetrahedra are involved in these phase transitions. The amorphization mechanism and its dependence on the pressure-transmitting medium are discussed, and the steric hindrance between polyhedra is believed to be the most relevant mechanism. The TO and LO low wavenumber modes of A1 symmetry, observed in the Y(ZZ)Y and Z(YY)Z geometries, respectively, below 50 cm-1, soften continuously through the first three phases when increasing pressure. The strong A2 mode observed in the Z(XY)Z spectra exhibits the same anomalous behavior by decreasing from 53 to 46 cm-1 at 2 GPa. The softening of these modes is related to the orientation change of tetrahedra observed by ab initio calculations when the volume of the cell is decreased. These orientation changes can explain the wavenumber decrease of the Mo-O stretching modes above 2 GPa, which indicates an increase of Mo coordination. © 2010 John Wiley & Sons, Ltd.

Buffiere J.-Y.,CNRS Laboratory for Materials: Engineering and Science | Maire E.,CNRS Laboratory for Materials: Engineering and Science | Adrien J.,CNRS Laboratory for Materials: Engineering and Science | Masse J.-P.,SIMaP | Boller E.,European Synchrotron Radiation Facility
Experimental Mechanics | Year: 2010

This paper aims at illustrating the potential of X-ray tomography for studying the mechanical behaviour of materials through in situ experiments. Typical experimental tomography set ups which use laboratory and synchrotron X ray sources are described; advantages and limitations of both types of sources are presented. Dedicated experimental devices which allow deformation and/or temperature changes to be applied to various types of materials are described. Examples of results of in situ mechanical experiments are presented and discussed; they include monotonic tensile testing of steel fiber entanglements, high temperature compression and room temperature fatigue of Al alloys. Examples of quantitative assessment of localisation of deformation in the interior of optically opaque samples under mechanical loading are also described. © Society for Experimental Mechanics 2010.

Liu Y.,Nanchang University | Blandin J.J.,SIMAP | Kapelski G.,SIMAP | Suery M.,SIMAP | Yang X.J.,Nanchang University
Intermetallics | Year: 2012

A BMG/Cu composite rod and a plate with a Cu 40Zr 44Ag 8Al 8 BMG core and a pure copper sleeve have been fabricated by the coextrusion process. The interfaces between the two materials have been analyzed through various techniques including optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). Good interface adhesion with metallurgical bonding has been formed, corresponding to two diffusion layers of about 100 nm near the Cu and BMG parts. An interface bonding model has been constructed based on these observations. The fracture mode of the BMG/Cu composite has been also characterized by compression tests, which involves debonding at the interface and plastic deformation of the Cu sleeve. © 2012 Elsevier Ltd.

Grenet T.,CNRS Neel Institute | Delahaye J.,CNRS Neel Institute | Cheynet M.C.,SIMAP
Journal of Physics: Conference Series | Year: 2012

We focus on the slow relaxations observed in the conductance of disordered insulators at low temperature (especially granular aluminum films). They manifest themselves as a temporal logarithmic decrease of the conductance after a quench from high temperatures and the concomitant appearance of a field effect anomaly centered on the gate voltage maintained. We are first interested in ageing effects, i.e. the age dependence of the dynamical properties of the system. We stress that the formation of a second field effect anomaly at a different gate voltage is not a "history free" logarithmic (lnt) process, but departs from lnt in a way which encodes the system's age. The apparent relaxation time distribution extracted from the observed relaxations is thus not "constant" but evolves with time. We discuss what defines the age of the system and what external perturbation out of equilibrium does or does not rejuvenate it. We further discuss the problem of relaxation times and comment on the commonly used "two dip" experimental protocol aimed at extracting "characteristic times" for the glassy systems (granular aluminum, doped indium oxide...). We show that it is inoperable for systems like granular Al and probably highly doped InO x where it provides a trivial value only determined by the experimental protocol. But in cases where different values are obtained like in lightly doped InO x or some ultra thin metal films, potentially interesting information can be obtained, possibly about the "short time" dynamics of the different systems. Present ideas about the effect of doping on the glassiness of disordered insulators may also have to be reconsidered.

Galand R.,STMicroelectronics | Clement L.,STMicroelectronics | Waltz P.,STMicroelectronics | Wouters Y.,SIMaP
AIP Conference Proceedings | Year: 2010

In this article, we propose to use Electron Backscattered Diffraction (EBSD) to characterize microstructure of copper interconnects of thin metal level in top view and cross view. These two views give very complementary information about microstructure of copper and thus about recrystallization of copper during annealing. Moreover, for minimum width, as interconnect is two times thicker than wide; It will be easier to analyze smaller interconnect of 45 nm node technology in cross-section. We look for evolution of texture and microstructure of copper with line width in top view and in cross view. We highlight the presence of two recrystallization mechanisms and also the fact that transition from one to the other is progressive with competition of both mechanisms. © 2010 American Institute of Physics.

Galand R.,STMicroelectronics | Clement L.,STMicroelectronics | Waltz P.,STMicroelectronics | Wouters Y.,SIMaP
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

In this article, we focus on the characterization of copper interconnect by Electron Backscattered Diffraction (EBSD) in the final aim of reliability issue investigation. In a first time we demonstrate that we achieve to characterize copper lines of 70 nm width after some improvements in sample preparation. Then, after showing that EBSD is well adapted to characterize our structure even for very small dimensions (line width smaller than 100 nm), we propose to associate Transmission Electron Microscope in scanning mode (STEM) to complete information given by EBSD and localize defects due to electromigration. We begin by highlighting the very good correspondence between EBSD map and STEM images on line with small microstructure and finally we apply both techniques on a tested copper line after electromigration. In this case we show the relevance of using STEM to localize the defect due to electromigration which can not be seen on EBSD map. © 2010 Copyright SPIE - The International Society for Optical Engineering.

Altenberend J.,SIMAP | Chichignoud G.,SIMAP | Delannoy Y.,SIMAP
Spectrochimica Acta - Part B Atomic Spectroscopy | Year: 2013

Atomic emission spectrometry was used to measure the distribution of concentration ratios and temperature in thermal plasmas produced by high power torches for process engineering. The spectroscopic method is based on absolute line intensity measurement and Abel inversion. Assuming local thermal equilibrium, the temperature is deduced from the absolute emission of an argon line and the concentration ratio is deduced from the emission ratio of two lines. Using the two dimensions of the camera for spatial and spectral resolution, fast measurements with high resolution can be done. The method has been tested on a 60 kW inductively coupled plasma torch at atmospheric pressure. The results show that the concentration ratios n(O)/n(Ar) and n(H)/n(Ar) can be measured with an accuracy of 25% and that errors due to deviations from LTE are small. Demixing occurs in the induction zone. The application of the method showed that hydrogen diffuses much more than oxygen. The main disadvantage of this method is that, using emission, it does not permit to measure the concentration in the "cold" zones in the center and at the edge of the plasma. © 2013 Elsevier B.V.

De Geuser F.,SIMaP | Bley F.,SIMaP | Denquin A.,ONERA | Deschamps A.,SIMaP
Journal of Physics: Conference Series | Year: 2010

The friction-stir welding (FSW) process induces both heat and deformation which lead to inhomogeneous precipitation microstructures in structural hardening alloys. A map of this microstructure can be obtained by 2D scanning SAXS in alloys where (a) a single phase is precipitating and (b) the precipitates are roughly isotropic. In Al-Li-Cu alloys, these conditions are not fullfilled. Very anisotropic precipitates are forming (T1 and θ′) with aspect ratios in the range 10 to 100. The inhomogeneity in the texture of the material (due to the deformation and recrystallisation) is a strong obstacle to the interpretation of the SAXS signal. This paper is an attempt to apply systematic simple interpretation models to characterise the precipitation microstructure across the weld area. It shows that in certain condition, it is possible to apply simple Guinier-type plot to extract the morphologies (length and thickness) of the particles. © 2010 IOP Publishing Ltd.

Wargnier H.,University of Bordeaux 1 | Kromm F.X.,University of Bordeaux 1 | Danis M.,University of Bordeaux 1 | Brechet Y.,SIMAP
Materials and Design | Year: 2014

This paper describes a proposal for a multi-material design procedure. First, the context of the study and the requirements of the multi-material must be clearly defined in order to specify the parameters that the designer must select or optimise in order to produce the design: the components and their volume fraction, the architecture and morphology at different scales, etc. The general design procedure proposed here starts with the reasons why the designer has turned to multi-materials, from which a multi-material concept with fixed parameters can be defined. In this first stage the design problem can be made less complex by reducing the number of unknown parameters and guiding the designer towards the appropriate selection or optimisation tools: (i) subdivision of requirements, guided by applying statistical analysis tools to the materials database to search for appropriate multi-material components, (ii) tools to filter the materials database and search for multi-material components and their volume fraction, (iii) optimisation tools to search for the appropriate architecture when components are known or to search for architecture and components simultaneously. The paper demonstrates how these tools can be applied to different design concepts. © 2013 Elsevier Ltd.

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