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In the keV-energy regime, the scattering of krypton ions off a copper sample has been studied. In addition to the broad energy spectrum arising from multiple-collision scattering, the energy distributions of the backscattered ions exhibit prominent peaks at energies where single-collision (SC) scattering peaks are expected. Such SC peaks were shown to be absent in Sn – Mo/Ru scattering, systems of similar mass ratio and thus similar kinetics. The present Kr on Cu results allow for a comparison to a simulation package as SRIM. An important difference found between the present experiment and the predictions of SRIM is that the SC contribution is observed to decrease with scattering angle, whereas SRIM predicts this contribution to be constant. The intensity of the experimental SC peaks, though much weaker than in the SRIM simulations, may be used as markers to improve SRIM in its description of low-energy heavy particle scattering off surfaces.

International audience; In case of a severe accident occurring in a nuclear reactor, surfaces of the reactor coolant system (RCS), made of stainless steel (304L) rich in Cr (>10%) and Ni (8–12%), are oxidised. Fission products (FPs) are released from melt fuel and flow through the RCS. A part of them is deposited onto surfaces either by vapour condensation or by aerosol deposition mechanisms. To be able to understand the nature of interactions between these FPs and the RCS surfaces, a preliminary step is to characterize the RSC surface states in steam and air atmosphere at high temperatures. Pieces of 304L stainless steel have been treated in a flow reactor at two different temperatures (750 °C and 950 °C) for two different exposition times (24 h and 72 h). After surfaces analysing by a unique combination of surface analysis techniques (XPS, ToF-SIMS and LEIS), for 304L, the results show a deep oxide scale with multi layers and the outer layer is composed of chromium and manganese oxides. Oxide profiles differ in air or steam atmosphere. Fe2O3 oxide is observed but in minor proportion and in all cases no nickel is detected near the surface. Results obtained are discussed and compared with the literature data.

Made available in DSpace on 2020-12-12T02:49:27Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-12-01 Biobased polyurethane coatings derived from vegetable oils, with 2 different compositions, were prepared and applied on the AA1200 aluminum alloy to confer corrosion protection. The influence of the ratio between the polyester (flexible segment) and the prepolymer (rigid segment) was investigated. Infrared spectroscopy studies evidenced the difference between the areas of the bands (–NH) and optical and scanning electron microscopy evidenced the morphological features of the coating surface before and after immersion in aggressive medium. The barrier properties and anti-corrosion performance of the coatings were evaluated by electrochemical impedance spectroscopy and the results revealed an increase of impedance over the immersion time. Localized corrosion studies confirmed the self-healing effect in coatings formulated with the highest content of polyester. Universidade Estadual Paulista-UNESP Instituto de Química Centro de Química Estrutural CQE Departamento de Engenharia Química DEQ Instituto Superior Técnico Universidade de Lisboa, Av. Rovisco Pais Universidade Estadual Paulista-UNESP Instituto de Química

We explore under which conditions low-energy ion scattering experiments are capable of obtaining reliable quantitative results in surface composition analysis. Additionally, we elaborate on the effective information depth of this technique considering the effect of different dominant charge exchange mechanisms. Based on concrete examples, we also point out possible problems and pitfalls in the evaluation of experimental data.

The use of sintered yttria stabilized zirconia dental implants is a recent development. After initial successes with these new implants a pattern of erratic results emerged. Reliable osseointegration would not always occur. High-sensitivity low energy ion scattering (HS-LEIS) is used to investigate both virgin and rejected implants. The surfaces of the implant are found to be covered with both an organic and inorganic contamination layer. Sterilization does not remove this contamination. Using LEIS as analytic tool a new cleaning process has been developed. Since this cleaning process is in use, the failure rate has dropped to a very low value.

Low energy ion scattering (LEIS) is a unique tool in surface analysis, since it provides the atomic composition of the outer atomic layer, and time of flight ion scattering (TOF) is a non-destructive method of analysis that is sensitive to all elements. The outer surface atoms dominate many processes such as adhesion, electron emission, growth, wetting and overall catalysis. In catalysis, LEIS applications include understanding and improvement of catalytic phenomena, site of poisoning, size of nanoclusters and quantification of promoters. In this work, we study the neutralization of low energy He+ ions on graphite (highly oriented pyrolytic graphite, HOPG) verifying that the ion fraction is close to null, i.e., a large neutralization probability. Resonant neutralization to the ground state (RN) has been the main mechanism expected for He+ scattered by HOPG, but we found that only by including the resonant neutralization to the first excited state (1s, 2s), the small ion fractions measured can be explained. © 2007 Elsevier B.V. All rights reserved. Fil: Bajales Luna, Noelia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Bonetto, Fernando Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Vidal, Ricardo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Goldberg, Edith Catalina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Ferron, Julio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina

The W-Ti thin films are deposited by the dc Ar+ sputtering of W(70%)-Ti(30%) a.t. target on silicon substrates. The surface composition and structure of the thin film, previously exposed to air, was carded out. The surface structure was undertaken using grazing incidence X-ray diffraction (GIXRD), and compared to that of the thin film interior. The surface morphology was determined by the Scanning Tunneling Microscopy (STM). The surface composition and chemical bonding of elements on the Ti-W film were analyzed by X-ray photoelectron spectroscopy (XPS) and Low Energy Ion Scattering (LEIS). The measurements show that the overlayer of metallic oxides TiO2, and WO3 is formed. The first atomic layer is occupied by TiO2 only, and its thickness is estimated to about 3.2 +/- 0.4 nm. The strong surface segregation of Ti is triggered by the surface oxidation, which is confirmed by the thermodynamical considerations. (c) 2007 Elsevier B.V All rights reserved.

Nichrome coatings have been deposited using the d.c. sputtering of the target (80% Ni-20% Cr wt.) by Ar+ ions at a working pressure of 10(-1) Pa and at room temperature. After the air exposure of samples at room temperature, their phase composition and structure was studied by X-ray diffraction, while the surface elemental composition was determined by low energy ion scattering (LEIS) and Auger electron spectroscopy (AES). AES has been also used for the bulk composition analysis. There is a significant difference between the compositions of the surface and of the bulk. Surface segregation of chromium was observed using both LEIS and AES, and it was found that the chromium concentration increases with that of oxygen adsorbed at the surface during the air exposure. The nichrome surface composition is qualitatively the same as in the case of its exposure to O-2 at room temperature, but significantly different from that of the thermally annealed nichrome to 400 degrees C in air. (c) 2006 Elsevier B.V. All rights reserved. 22nd International Conference on Atomic Collisions in Solids, Jul 21-26, 2006, Tech Univ Berlin, Berlin, Germany

The effect of preparation method (sol-gel, wet mixing or coprecipitation) on the surface structure of zinc aluminate is reported. Coprecipitated and sol-gel prepared ZnAl2O4 were found to be present spinel structure. If calcium was added during synthesis, it was found to be deposited on top of the spinel surface while, if tin was added, the surface of ZnAl2O4 was reconstructed. These aluminates were impregnated with platinum and tested in the isobutane dehydrogenation. The characterization techniques used were LEIS and X-ray diffraction.