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Claverie M.,French National Center for Scientific Research | Martin F.,French National Center for Scientific Research | Tardy J.P.,Argeco Developpement | Cyr M.,INSA Toulouse | And 3 more authors.
Applied Clay Science | Year: 2015

To understand the morphological changes of three commercial kaolins during flash calcination and to compare them with those obtained during traditional heat treatments in the laboratory (an electric furnace at 700 °C for 5 h), this paper presents the physical and chemical characteristics of metakaolins obtained from an industrial flash calciner. In the metakaolin products, kaolinite was not completed dehydroxylated during calcination, and the proportion of untransformed kaolinite was greater in flashed metakaolins than in traditional rotary-calcined metakaolins. Several particle morphologies were discernible in the metakaolins, including spherical particles that were formed in flash calcinations. These spherical particles were cut with a focused ion beam (FIB) and were revealed to contain a vitrified aluminum silicate phase with traces of mullite and various gases. These spherical particles were produced from the direct calcination of several submicron kaolinites near the flame of the calciner. © 2015 Elsevier B.V.

Monsalve K.,French National Center for Scientific Research | Mazurenko I.,French National Center for Scientific Research | Lalaoui N.,CNRS Molecular Chemistry Department | Le Goff A.,CNRS Molecular Chemistry Department | And 7 more authors.
Electrochemistry Communications | Year: 2015

We report the first example of an H2/O2 enzymatic fuel cell able to power a wireless transmission system. Oxygen-tolerant hydrogenase from Aquifex aeolicus and bilirubin oxidase from Myrothecium verrucaria were incorporated from diluted solutions in carbon felt-based material, allowing mediatorless catalytic currents more than 1 mA to be reached. The enzymatic fuel cell open circuit voltage was 1.12 V, and short circuit current was 767 μA. It delivered a maximum power of 410 μW, sufficient to power the electronic device that measured in real time the anodic/cathodic compartments and room temperatures, the voltage of the capacitor and voltage output of the enzymatic fuel cell itself. Notably, data were sent every 25 s during 7 hours of continuous operation which constitute the highest performances ever reported for a realistic environmental application fully powered with an enzymatic fuel cell. © 2015 Elsevier B.V.

Perriot R.,University of South Florida | Lin Y.,University of South Florida | Zhakhovsky V.V.,University of South Florida | Pineau N.,CEA DAM Ile-de-France | And 5 more authors.
AIP Conference Proceedings | Year: 2012

Two recently developed interatomic potentials for carbon, the screened environment dependent - reactive empirical bond order (SED-REBO) and the long-range carbon bond-order (LCBOPII), were used in molecular dynamics (MD) simulations of shocked diamond. Static uniaxial compressions showed that both potentials offer an improved accuracy compared to the commonly used REBO potential. MD simulations were run in the [110] direction, and a split elastic-elastic shock wave regime was observed with one of the potentials. Isothermal compression allowed us to explain the origin of this regime, characterized by a solidsolid phase transition, leading to a non-monotonic stress-strain response below the Hugoniot elastic limit of the material. © 2012 American Institute of Physics.

Pizzagalli L.,University of Poitiers | David M.-L.,University of Poitiers | Charaf-Eddin A.,CINaM
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2015

First-principles calculations of the aggregation of helium interstitials in silicon have been performed to determine whether the first steps of helium-filled bubbles formation could occur by a self-trapping mechanism. These simulations show that the interaction between helium interstitials is repulsive, of low magnitude, and that this effect will saturate for a large number of interstitials. Considering the relaxation of the computational cell only leads to a small reduction of the binding energy. These results imply that the aggregation of interstitial helium atoms is highly unlikely in silicon, which allowed us to conclude that a self-trapping mechanism can not occur, and that an initial amount of vacancies is required for helium-filled bubbles formation. © 2014 Elsevier B.V. All rights reserved.

Monsalve K.,French National Center for Scientific Research | Roger M.,French National Center for Scientific Research | Gutierrez-Sanchez C.,French National Center for Scientific Research | Ilbert M.,French National Center for Scientific Research | And 4 more authors.
Bioelectrochemistry | Year: 2015

For the first time, gold nanoparticle-based electrodes have been used as platforms for efficient immobilization of the [NiFe] hydrogenase from the hyperthermophilic bacterium Aquifex aeolicus. AuNPs were characterized by electronic microscopy, dynamic light scattering and UV-Vis spectroscopy. Two sizes around 20.0±5.3nm and 37.2±4.3nmnm were synthesized. After thiol-based functionalization, the AuNPs were proved to allow direct H2 oxidation over a large range of temperatures. A high current density up to 1.85±0.15mA·cm-2 was reached at the smallest AuNPs, which is 170 times higher than the one recorded at the bare gold electrode. The catalytic current was especially studied as a function of the AuNP size and amount, and procedure for deposition. A synergetic effect between the AuNP porous deposit and the increase surface area was shown. Compared to previously used nanomaterials such as carbon nanofibers, the covalent grafting of the enzyme on the thiol-modified gold nanoparticles was shown to enhance the stability of the hydrogenase. This bioanode was finally coupled to a biocathode where BOD from Myrothecium verrucaria was immobilized on AuNP-based film. The performance of the so-mounted H2/O2 biofuel cell was evaluated, and a power density of 0.25mW·cm-2 was recorded. © 2015 Elsevier B.V.

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