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Collinet-Fressancourt M.,CNRS Materials and Transformations Unit of UMET | Nuns N.,Institute Des Molecules Et Of La Matiere Condensee Of Lille | Bellayer S.,University of Lille Nord de France | Traisnel M.,CNRS Materials and Transformations Unit of UMET
Applied Surface Science | Year: 2013

The present study assesses the formation of an interfacial oxide layer on aluminum alloys concomitant to the electrodeposition of an anaphoretic coating. The morphology, size, chemical composition and corrosion resistance properties are investigated for 2024-T3 clad aluminum substrate. The morphology and thickness of the oxide layer was examined using TEM. On the other hand, a ToF-SIMS method combining depth profiling and high resolution imaging has been developed as a new approach to determine simultaneously the chemical composition, the thickness and the homogeneity of the oxide layer. The results obtained with this method are validated through comparison with those from the TEM standard approach. Finally the two complementary methods have been used to investigate the growing mechanism of the oxide layer. © 2013 Elsevier B.V. All rights reserved. Source

Sobanska S.,CNRS Laboratory of Infrared and Raman Spectrochemistry | Barbillat J.,CNRS Laboratory of Infrared and Raman Spectrochemistry | Moreau M.,CNRS Laboratory of Infrared and Raman Spectrochemistry | Nuns N.,Institute Des Molecules Et Of La Matiere Condensee Of Lille | And 4 more authors.
Physical Chemistry Chemical Physics | Year: 2015

In the atmosphere, sea salt aerosols, containing mainly NaCl, can accumulate fatty acids and undergo heterogeneous chemistry with atmospheric nitrogen oxides. The effect of stearic acid (SA) coating on the reactivity of the NaCl(100) surface with NO2 under humidity was studied by atomic force microscopy (AFM), Raman mapping and time-of-flight secondary ion mass spectrometry (ToF-SIMS) to highlight processes occurring on NaCl surfaces. The vapor-deposition of SA on the NaCl surface generates heterogeneous coating with discontinuous monolayer islands. The SA molecules with all-trans conformation stick to the NaCl surface through -CO2H groups and are organized in parallel between them and nearly perpendicularly to the surface. The SA coating does not prevent the NaNO3 particle formation when the sample is exposed to NO2 under low humidity conditions. The initial abilities of the NaCl surface coated with SA to pick up NO2 from the gas phase are correlated with the fraction of bare NaCl area evidencing the spatially heterogeneous reactivity of the surface. The role of H2O in the NO2 uptake and the catalytic conversion of NaCl to NaNO3 is shown. Under humidity (RH = 50%), the H2O uptake by NaNO3 particles on the coated-NaCl surface is significantly more important than that adsorbed under analogous conditions without the presence of NaNO3 particles. This unusual water absorption initiates transitions (i) from solid NaNO3 particles to NaNO3 aqueous solution and (ii) from the SA monolayer with well-ordered all trans alkyl chains to the SA gel with completely disordered conformation. This mixed SA/NaNO3 layer on the particle surface may have significant consequences on the hygroscopic properties and reactivity of the sea salt aerosols in the atmosphere. © the Owner Societies 2015. Source

Nuns N.,University of Lille Nord de France | Nuns N.,Institute Des Molecules Et Of La Matiere Condensee Of Lille | Lamonier J.-F.,University of Lille Nord de France | Lamonier J.-F.,CNRS Laboratory of Catalysis and Solid State Chemistry | And 5 more authors.
Surface and Interface Analysis | Year: 2013

New pre-reduced titanium-zirconium (x/1-x) oxide(s) supported palladium samples 0.5w% Pd/TixZr1-x (x = 0; 0.2; 0.3; 0.5; 0.7; 0.8; 1) have been shown to be efficient catalysts for the total oxidation of trichloroethylene (solvent widely used in dry cleaning and degreasing processes) in humid air (1mol%). A challenging task which must be addressed regarding that type of reaction is the chlorine location on the used catalyst surface in order to better understand the catalyst functioning. In spite of a few studies, time-of-flight secondary ion mass spectroscopy (ToF-SIMS) has been elsewhere proved to be a highly relevant tool to resolve such a problem. Hence, in this study, Tof-SIMS measurements have been performed on as-prepared and selected used Pd/TixZr1-x catalysts (x = 0; 0.2; 0.5; 1). On fresh catalysts, the Pd-based ions detected in both polarities are Pd+, PdO- and PdO2-. In addition, detection of Ti2ZrO5+ and TiZr2O5 + cluster ions provides for the first time a direct proof of titanium-zirconium mixed oxides (x≠ 0; 1). The negative ion-mass spectrum of the related used samples exhibit relevant signals attributed to PdCl 2-, ZrO2Cl- and TiO 2Cl- cluster ions. The chlorinated PdCl2 - ion provides direct spectroscopic clue that some Cl atoms are still bound to Pd. By opposition, the quasi non-observance of MCl- (M = Zr; Ti) indicates that chlorine deposit on the support does not directly affect the titanium and zirconium atoms. Copyright © 2012 John Wiley & Sons, Ltd. Copyright © 2012 John Wiley & Sons, Ltd. Source

Jimenez M.,University of Lille Nord de France | Delaplace G.,French National Institute for Agricultural Research | Nuns N.,Institute Des Molecules Et Of La Matiere Condensee Of Lille | Bellayer S.,University of Lille Nord de France | And 5 more authors.
Journal of Colloid and Interface Science | Year: 2013

The microstructures of two dairy fouling deposits obtained at a stainless steel surface after different processing times in a pilot plate heat exchanger were investigated at different scales. Electron-Probe Micro Analysis, Time-of-Flight Secondary Ion Mass Spectrometry, Atomic Force Microscopy, and X-Ray Photo-electron Spectroscopy techniques were used for this purpose. The two model fouling solutions were made by rehydrating whey protein in water containing calcium or not. Results on samples collected after 2. h processing show that the microstructure of the fouling layers is completely different depending on calcium content: the layer is thin, smooth, and homogeneous in absence of calcium and on the contrary very thick and rough in presence of calcium. Analyses on substrates submitted to 1. min fouling reveal that fouling mechanisms are initiated by the deposit of unfolded proteins on the substrate and start immediately till the first seconds of exposure with no lag time. In presence of calcium, amorphous calcium carbonate nuclei are detected in addition to unfolded proteins at the interface, and it is shown that the protein precedes the deposit of calcium on the substrate. Moreover, it is evidenced that amorphous calcium carbonate particles are stabilized by the unfolded protein. They are thus more easily trapped in the steel roughnesses and contribute to accelerate the deposit buildup, offering due to their larger characteristic dimension more roughness and favorable conditions for the subsequent unfolded protein to depose. © 2013 Elsevier Inc. Source

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