Alpha localized radiolysis and corrosion mechanisms at the iron/water interface: Role of molecular species

This paper is devoted to the iron corrosion phenomena induced by the α (4He2+) water radiolysis species studied in conjunction with the production/consumption of H2 at the solid/solution interface. On one hand, the solid surface is characterized during the 4He2+ ions irradiation by in situ Raman spectroscopy; on another hand, the H2 gas produced by the water radiolysis is monitored by ex situ gas measurements. The 4He2+ ions irradiation experiments are provided either by the CEMHTI (E = 5.0 MeV) either by the ARRONAX (E = 64.7 MeV) cyclotron facilities. The iron corrosion occurs only under irradiation and can be slowed down by H2 reductive atmosphere. Pure iron and carbon steel solids are studied in order to show two distinct behaviors of these surfaces vs. the 4He2+ ions water irradiation: the corrosion products identified are the magnetite phase (Fe(II)Fe(III)2O4) correlated to an H2 consumption for pure iron and the lepidocrocite phase (γ-Fe(III)OOH) correlated to an H2 production for carbon steel sample. This paper underlined the correlation between the iron corrosion products formation onto the solid surface and the H2 production/consumption mechanisms. H2O2 species is considered as the single water radiolytic species involved into the corrosion reaction at the solid surface with an essential role in the oxidation reaction of the iron surface. We propose to bring some light to these mechanisms, in particular the H2 and H2O2 roles, by the in situ Raman spectroscopy during and after the 4He2+ ions beam irradiation. This in situ experiment avoids the evolution of the solid surface, in particular phases which are reactive to the oxidation processing

Spectrophotometric study of the behaviour of pertechnetate in trifluoromethanesulfonic acid: effect of alpha irradiation on the stability of Tc(VII)

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LET effects on the hydrogen production induced by the radiolysis of pure water

Radiation chemical primary yields g(H2) have been determined for irradiations performed with 60Co γ-rays source of LCP (Orsay, France) and with helium ion beams (Eα=5.0 MeV-64.7 MeV) using protective agent bromide anions in solution. The α (4He2+) irradiation experiments were performed either at CEMHTI or at the new ARRONAX cyclotron facility (2010). Both sources (γ and cyclotrons) allow working with a large LET value range between 0.23 and 151.5 keV/μm. On one hand, the obtained results have been compared with those available in the literature and plotted as a function of the LET parameter in order to discuss the effects of track structure on the production of molecular hydrogen. On the other hand, the primary radiation chemistry yield g(H2) values are compared with global radiation chemical yields G(H2) obtained during irradiations of pure water irradiated under air or argon without scavenging. For each system, it appears that radiation chemical yields increase with the LET value. Our results suggest that using bromide anions, at low concentration, as a protective agent becomes ineffective when the LET value used is higher than 120±20 keV/μm

Two new acidic diphosphates Rb2M(H2P2O7)2·2H2O (M = Zn and Mg): Crystal structures and vibrational study

Two new complex diphosphates Rb2M(H2P2O7)2·2H2O [M = Zn (I), Mg (II)], have been synthesized using wet chemistry. Their crystals have been isolated and characterized by X-ray diffraction, FTIR and micro-Raman techniques. Both compounds crystallize in the triclinic system, S.G. P-1, Z = 1 and following parameters (Å,°), [6.9573(1), 7.3615(1), 7.7938(1), 81.851(1), 70.622(1), 86.263(1), R1 / w R2 = 0.0315 / 0.1083 for (I) and 6.9546(1), 7.3752(1), 7.8117(1), 81.986(1), 70.275(1), 85.988(1), R1 / w R2 = 0.0275 / 0.0865 for (II)]. The crystal packing in (I) and (II) consists in a three-dimensional network made by layers, parallel to ac-plane. H2P2O72- shows bent eclipsed conformation and the M2+ ion lies on inversion centre. IR and Raman spectra confirm the bent geometry of the POP bridge angle

Monte Carlo simulation to reveal the copper dissolution kinetics of an ion selective electrode based on copper sulfide

The present work aims at studying copper dissolution of a Cu2+ ion-selective electrode based on a CuS thin film. The electrode is prepared using electrochemical deposition of CuS on a silicon substrate. The obtained film exhibits an apparent cohesive granular structure with an average grain size of about 33 μm, a small porosity content (<4%) and a thickness of about 7.48 μm. The Cu2+ electrochemical response shows a nearly Nernstian behavior in the range of pCu 6-1. The copper dissolution is experimentally studied in a wide pH range. In order to quantitatively predict copper mass dissolution, an original numerical model is developed based on Monte Carlo simulation. Our main hypothesis is based on dissolution probability that triggers the whole dissolution process through solution/electrode surface exchanges. Several probability forms are suggested accounting for the real observed electrochemical kinetics. The experimental results show that, under a low pH, the dissolution process severely leads to the consumption of large material. Moreover, our predictions suggest a dissolution profile as a two-stage process irrespective of pH. Our numerical model is able to fit correctly the observed kinetics considering an exponential probability form under all pH conditions

H-2 Production by water radiolysis in presence of M/TiO2 (M= Pt; Au) nanocomposite films

International Conference in Energy and Sustainability in Small Developing Economies (ES2DE), PORTUGAL, JUL 10-12, 2017International audienceIn the present work we report on the synthesis of M/TiO2 (M=Pt, Au) nanocomposite films processed on Si-substrate. X-Ray diffraction and Raman experiments allowed the identification of formed phases. The hydrogen production has been carried out by gamma-irradiation of water in the presence of the nanocomposite films. The existence of Au- and Pt-TiO2 thin films resulted in a significant enhancement of H-2 production which is promising for clean energy applications