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Bobina M.,Polytechnic University of Timisoara | Kellenberger A.,Polytechnic University of Timisoara | Millet J.-P.,CNRS Laboratory for Materials: Engineering and Science | Muntean C.,Polytechnic University of Timisoara | Vaszilcsin N.,Polytechnic University of Timisoara
Corrosion Science | Year: 2013

This paper presents the inhibitory properties of l-histidine on the corrosion of carbon steel in weak acid media containing acetic acid/sodium acetate. The inhibition efficiencies obtained by weight loss measurements are in good agreement with values given by Tafel method and electrochemical impedance spectroscopy. The adsorption of l-histidine obeys the Langmuir isotherm and the negative values of Gibbs energy indicate the nature of interactions between inhibitor molecules and metal surface. Further, the inhibition effect was studied using scanning electron microscopy and energy dispersive X-ray analysis. © 2013 Elsevier Ltd.

Maire E.,CNRS Laboratory for Materials: Engineering and Science | Withers P.J.,Manchester X ray Imaging Facility | Withers P.J.,Rutherford Appleton Laboratory
International Materials Reviews | Year: 2014

X-ray computer tomography (CT) is fast becoming an accepted tool within the materials science community for the acquisition of 3D images. Here the authors review the current state of the art as CT transforms from a qualitative diagnostic tool to a quantitative one. Our review considers first the image acquisition process, including the use of iterative reconstruction strategies suited to specific segmentation tasks and emerging methods that provide more insight (e.g. fast and high resolution imaging, crystallite (grain) imaging) than conventional attenuation based tomography. Methods and shortcomings of CT are examined for the quantification of 3D volumetric data to extract key topological parameters such as phase fractions, phase contiguity, and damage levels as well as density variations. As a non-destructive technique, CT is an ideal means of following structural development over time via time lapse sequences of 3D images (sometimes called 3D movies or 4D imaging). This includes information needed to optimise manufacturing processes, for example sintering or solidification, or to highlight the proclivity of specific degradation processes under service conditions, such as intergranular corrosion or fatigue crack growth. Besides the repeated application of static 3D image quantification to track such changes, digital volume correlation (DVC) and particle tracking (PT) methods are enabling the mapping of deformation in 3D over time. Finally the use of CT images is considered as the starting point for numerical modelling based on realistic microstructures, for example to predict flow through porous materials, the crystalline deformation of polycrystalline aggregates or the mechanical properties of composite materials. © 2014 Institute of Materials, Minerals and Mining and ASM International.

Tournus F.,University Claude Bernard Lyon 1 | Sato K.,Tohoku University | Epicier T.,CNRS Laboratory for Materials: Engineering and Science | Konno T.J.,Tohoku University | Dupuis V.,University Claude Bernard Lyon 1
Physical Review Letters | Year: 2013

The atomic structure of CoPt and FePt nanoparticles (with a diameter between 2 and 5 nm) has been studied by transmission electron microscopy. The particles have been produced by a laser vaporization cluster source and annealed under vacuum in order to promote chemical ordering. For both alloys, we observe a coexistence of crystalline and multiply twinned particles with decahedral or icosahedral shapes. In addition to particles corresponding to a single L1 0 ordered domain, we put into evidence that even small particles can display several L10 domains. In particular, the chemical order can be preserved across twin boundaries which can give rise to spectacular chemically ordered decahedral particles made of five L10 domains. The stability of such structures, which had been recently predicted from theoretical simulations, is thus unambiguously experimentally confirmed. © 2013 American Physical Society.

Palmero P.,Polytechnic University of Turin | Esnouf C.,CNRS Laboratory for Materials: Engineering and Science
Journal of the European Ceramic Society | Year: 2011

Well-dispersed nano-crystalline transition alumina suspensions were mixed with yttrium chloride aqueous solutions, with the aim of producing Al 2O 3-Y 3Al 5O 12 (YAG) composite powders. DTA analysis allowed to highlight the role of yttrium on the α-phase crystallization path. Systematic XRD and HRTEM analyses were carried out in parallel on powders calcined in a wide temperature range (600-1300°C) in order to follow phase and microstructural evolution. A thin, homogeneous yttrium-rich layer was yielded on the alumina particles surface; yttrium diffusion into the alumina matrix was negligible up to 1150°C whereas, starting from 1200°C, aggregates of partially sintered alumina particles appeared, stuck together by yttrium-rich thin films. Moreover, in the yttrium-richer zones, such as alumina grain boundaries and triple joints, yttrium-aluminates precipitated at alumina particles surface. Finally, at 1300°C, alumina-YAG composite powders were produced, in which YAG was homogenously distributed among the alumina grains. © 2010 Elsevier Ltd.

Blanc N.,CNRS Physics Laboratory of Condensed Matter and Nanostructure | Tournus F.,CNRS Physics Laboratory of Condensed Matter and Nanostructure | Dupuis V.,CNRS Physics Laboratory of Condensed Matter and Nanostructure | Epicier T.,CNRS Laboratory for Materials: Engineering and Science
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We discuss the possibility of L10 chemical order parameter quantification for an individual particle of CoPt, using transmission electron microscopy. While "usual" approaches are found to be unapplicable for small particles (less than 4 nm in diameter), we present a method based on the comparison between an experimental high-resolution image and simulated ones with various degrees of chemical order. © 2011 American Physical Society.

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