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Orléans, France

Amon A.,Rennes Institute of Physics | Nguyen V.B.,University Paris Diderot | Bruand A.,ISTO | Crassous J.,Rennes Institute of Physics | Clement E.,University Paris Diderot
Physical Review Letters | Year: 2012

We study experimentally the dynamical heterogeneities occurring at slow shear, in a model amorphous glassy material, i.e., a 3D granular packing. The deformation field is resolved spatially by using a diffusive wave spectroscopy technique. The heterogeneities show up as localized regions of strong deformations spanning a mesoscopic size of about 10 grains and called the "hot spots." The spatial clustering of hot spots is linked to the subsequent emergence of shear bands. Quantitatively, their appearance is associated with the macroscopic plastic deformation, and their rate of occurrence gives a physical meaning to the concept of "fluidity," recently used to describe the local and nonlocal rheology of soft glassy materials. © 2012 American Physical Society.

Bakkas B.,University Ibn Zohr | Douzi H.,University Ibn Zohr | Ibhi A.,University Ibn Zohr | Mammass D.,University Ibn Zohr | And 3 more authors.
International Conference on Multimedia Computing and Systems -Proceedings | Year: 2011

Percentages of metal are an important physical property in meteorite research and in studies of meteorite impact craters. Physical properties of meteorites have been used to rapidly classify meteorites into main classes and groups. In this paper, we use a max Entropy method [1] for 3D segmentation and visualization of 3D scanned images of meteorites collected in Morocco. This non-destructive analysis allows studying the mineral composition of these rocks. Results show that the percentage of metal is identical when estimated by 3D analysis compared to classical measurements (point counter). The main advantage of the 3D analysis is that the sample is not destroyed, more accurate, not expensive and faster. © 2011 IEEE.

Diaz M.,French National Institute for Agricultural Research | Robert J.-L.,ISTO | Schroeder P.A.,University of Georgia | Prost R.,French National Institute for Agricultural Research
Clays and Clay Minerals | Year: 2010

Far-infrared (FIR) analysis of synthetic Mg-, Ni-, Co-, and Fe-phlogopites coupled with structural data from X-ray diffraction revealed that the K interlayer environments are directly related to octahedral sheet composition and geometry. The general phlogopite formula, KM2+ 3 (Si3Al)O10(OH)2, was varied according to octahedral compositions, where M2+ = Mg2+, Fe2+, Co2+, and Ni2+. Octahedral substitutions have a direct effect on the b lattice parameter, which is related to the tetrahedral-octahedral sheet misfit and manifested by change in the tetrahedral rotation angle (a). The ditrigonal interlayer cavity geometry and the potential for retention of the compensating cations therefore varies according to the ionic size and the types and oxidation state of octahedral cations. These structural features appear as frequency shifts on FIR spectra. When Mg2+ is replaced by a smaller cation, Ni2+, the b parameter decreases and the tetrahedral rotation angle, a, increases, inducing the collapse of the ditrigonal ring. When this happens, the local anisotropy of the interlayer site increases, resulting in every other six out of 12 K-O bonds becoming shorter and the in-plane K-O vibration band shifts slightly to greater wavenumbers. Synthetic phlogopites with octahedral substitutions by cations of larger ionic radii (i.e. Co2+ and Fe2+) exhibit b parameter increases, where in the case of the annite end-member, a decreases to almost 0° As a decreases, compensating cation sites become more hexagonal like and the nearest K-O bond increases in length. The K-O vibration bands move toward much smaller wavenumbers. Far infrared offers the potential for a new approach to study the retention of interlayer cations in other phyllosilicates and the mechanisms by which they are altered, such as heating or by weathering reactions in the environment.

Ali F.,University of Savoy | Ali F.,Hazara University | Ali F.,Pakistan Institute of Engineering and Applied Sciences | Reinert L.,University of Savoy | And 5 more authors.
Ultrasonics Sonochemistry | Year: 2014

The effects of temperature, time, solvent and sonication conditions under air and Argon are described for the preparation of micron and sub-micron sized vermiculite particles in a double-jacketed Rosett-type or cylindrical reactor. The resulting materials were characterized via X-ray powder diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Fourier Transform Infrared (FTIR) Spectroscopy, BET surface area analysis, chemical analysis (elemental analysis), Thermogravimetry analysis (TGA) and Laser Granulometry. The sonicated vermiculites displayed modified particle morphologies and reduced sizes (observed by scanning electron microscopy and laser granulometry). Under the conditions used in this work, sub-micron sized particles were obtained after 5 h of sonication, whereas longer times promoted aggregation again. Laser granulometry data revealed also that the smallest particles were obtained at high temperature while it is generally accepted that the mechanical effects of ultrasound are optimum at low temperatures according to physical/chemical properties of the used solvent. X-ray diffraction results indicated a reduction of the crystallite size along the basal direction [0 0 1]; but structural changes were not observed. Sonication at different conditions also led to surface modifications of the vermiculite particles brought out by BET surface measurements and Infrared Spectroscopy. The results indicated clearly that the efficiency of ultrasound irradiation was significantly affected by different parameters such as temperature, solvent, type of gas and reactor type. © 2013 Elsevier B.V. All rights reserved.

Wille G.,Bureau de Recherches Geologiques et Minieres | Wille G.,University of Orleans | Bourrat X.,Bureau de Recherches Geologiques et Minieres | Bourrat X.,University of Orleans | And 6 more authors.
Spectroscopic Properties of Inorganic and Organometallic Compounds | Year: 2014

SEM-EDS and micro-Raman spectroscopy have been combined for material characterization in several recent studies. Switching from one to the other is frequently considered as a problem that cannot be solved using specific solutions. Although both techniques have followed a parallel but very different evolution since their introduction in the early 1930s, the concept of Raman-in-SEM first began in the 1980s and the first commercial systems were marketed in the early 2000s. The two main systems and techniques that have been developed and marketed by three manufacturers are presented and described in this chapter. An evaluation of their advantages and limitations is proposed. A metrological study is then proposed for one of these systems, based on the 'on-axis' technique using a curved mirror placed under the SEM pole piece. This study allows a discussion of the performance and limitations of Raman spectroscopy when performed in a SEM. A comprehensive review of published work is provided, although papers are rare in the open literature. The technique is essentially used for controls, expert assessments and high technology applications. Advanced techniques that allow the use of Raman-in-SEM spectroscopy are discussed in detail using application examples taken from different fields in geosciences, materials chemistry or from expert assessments. The conclusions of this study show that Raman-in-SEM spectroscopy is to date the first step in the combination of two well-known and mature techniques enabling the synergy between them to be maximised. Raman-in-SEM spectroscopy is relatively easy to set up and effectively complements the capabilities and efficiency of analytical SEM for material characterization. What are the most likely development perspectives that may be considered for this analytical coupling? Today, commercial systems are limited to only point-level micro-Raman analysis at the micrometre scale. In the near future, developments in both hardware and software will probably allow analysts to acquire Raman maps, or to employ multi-technique analyses based on a combination of data from SEM, EDS Raman, etc. New hardware developments may enhance the spatial resolution of both SEM and Raman spectroscopy. © The Royal Society of Chemistry 2014.

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