Reduction of acids at a platinum ultramicroelectrode: application to “in situ” acid number control of fluid lubricants (phosphate esters)

International audienceThe strength of acids, their charge and possibly their behaviour as polyacids can be deduced by comparing their limiting currents at a platinum ultramicroelectrode in the absence and presence of an excess of supporting electrolyte. Acid-base reactions in tributyl phosphate can be followed without deliberately added supporting electrolyte even if their dielectric constant is low. The acidity of phosphate esters resulting from their hydrolysis can be monitored by amperometry at a platinum ultramicroelectrode

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