Nanotexturation de TiO2 sur nanotubes de carbone pour pseudosupercondensateurs dans des électrolytes organiques

International audienceTitanium oxides have been considered potential electrode materials for pseudocapacitors because of their exceptional properties, such as high thermal and chemical stabilities, ready availability and low cost. However, they are not ideal for practical applications due to their poor ionic and electrical conductivity. The electrochemical performance of TiO 2 can be greatly improved if the material is nanotextured by reducing the particle size in optimizing the synthesis pathway. Actually, for metallic oxides, the electrochemical performance significantly depends on the particle size/morphology. At relatively low current densities the higher capacity values are exhibited by noncrystalline TiO 2 having 2 nm particle size, with values reaching 704 C g −1 . However, only thin electrodes are able to operate at a high charge density, limiting the energy density of the final device. Here, we propose a solution to circumvent such a drawback by further nanotexturing TiO 2 over multiwalled carbon nanotubes (CNTs). For that purpose, CNTs were introduced during oxide preparation. The synthesis protocol has been optimized for obtaining a uniform coverage of small TiO 2 particles on the surface of the CNTs. At low current densities, high mass loading TiO 2 /CNT composites electrodes are able to deliver capacitances as high as 480 F g −1 and the presence of CNTs allows keeping 70% of the capacitance at high current densities while only 27% is retained when using a regular conductivity agent as carbon black. The results demonstrate that uniform nanotexturation of TiO 2 over CNTs allows good rate capabilities to be obtained for thick electrodes having sufficient active material loading to achieve high specific energy and power densities

Annealing of the defects observed by Raman spectroscopy in UO2 irradiated by 25 MeV He2+ ions

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Irradiation Defects in UO2 Leached in Oxidizing Water: An in-situ Raman Study

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Investigating the role of irradiation defects during UO2 oxidative dissolution

International audienceIn this study, the behavior of alpha irradiation-induced defects in UO2, when exposed to different interfaces, is investigated. Raman spectroscopy is used to measure the formation kinetics of irradiation defects in UO2 leached under oxidizing water environment and the data are then compared to a reference UO2/Ar system. The results reveal that the presence of either aerated water or inert argon gas modifies the formation kinetics of irradiation defects. The UO2 alteration in aerated water leads to the precipitation of secondary phases in the form of studtite and water chemical analysis reveals that the UO2 dissolution mechanism proceeds without the formation of an oxidized UO2 layer

In situ Raman monitoring of He2+ irradiation induced damage in a UO2 ceramic

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Characterization of Nuclear Materials in Extreme Conditions: Raman Spectroscopy Approach

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Effect of proton irradiation on 316L-stainless steel tribocorrosion behavior

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In situ Raman monitoring of materials under irradiation: study of uranium dioxide alteration by water radiolysis

International audienceIn situ Raman scattering studies allow following real‐time evolutions of volume or surface structures under extreme conditions. In nuclear materials sciences, ion irradiation‐induced atomic organization modification and water radiolysis are of a major interest. In order to better understand these phenomena, we have developed an in situ versatile portable Raman spectroscopy system coupled with a cyclotron accelerator, allowing monitoring of a solid/liquid interface under irradiation and thus giving access to effects of radiolysis. The different parts of the system and their improvements are described in details.The system efficiency is highlighted by a comparative study of the time dependence of UO2 surface modification induced, on one hand by contact with water under irradiation by 5 MeV He2+ particles, and on the other hand by pure chemical alteration, through contact with a hydrogen peroxide solution