Colloid/nanoparticle formation and mobility in the context of deep geological nuclear waste disposal (Project KOLLORADO-2) ; final report (KIT Scientific Reports ; 7645)

To assess the relevance of colloidal influences on radionuclide transport for the long-term safety of a radioactive waste repository, the KOLLORADO-2 project integrates the results of geochemical and hydrogeological studies. The results may serve as a basis for an appraisal of the implications of colloid presence in the vicinity of radioactive waste repositories in different deep geological host-rock formations

ÉTUDE PAR MICROSCOPIE ÉLECTRONIQUE EN TRANSMISSION DE DÉFAUTS CRÉÉS PAR IMPLANTATION IONIQUE DANS DU SILICIUM < III >

Des échantillons de silicium ont subi soit une implantation phosphore (30 keV, 1016 at/cm2) soit des implantations arsenic (50 à 140 keV, dose de l'ordre de 1015 at/cm2). Dans le cas du phosphore, on observe en microscopie électronique une couche amorphe qui recristallise en épitaxie sur le substrat à 650 °C. Au cours de recuits à plus haute température, la formation et l'évolution de défauts tels que boucles de dislocations et dipôles ont été observées. Dans le cas de l'arsenic, la recristallisation de la couche amorphe s'accompagne d'une formation de micromacles et de défauts divers (boucles, défauts linéaires, ...).Silicon specimens have been implanted either with phosphorous ions (30 keV, 1016 at/cm2) or with arsenic ions (energies between 30 and 140 keV, doses in the order of 1015 at/cm2). In the case of phosphorous implantation, an amorphous layer has been observed using electron microscopy. The epitaxial recrystallization of this layer occurs at 650 °C. During annealing at higher temperatures, the formation and evolution of defects such as dislocation loops and dipoles have been observed. In the case of arsenic implantations, the formation of defects such as microtwins, loops, linear defects... takes place during the recrystallization of the amorphous layer

A two steps CVD process for the growth of silicon nano-crystals

International audienc

A new nondestructive X-ray method for the determination of the 3D mineralogy at the micrometer scale

The combination of synchrotron-based X-ray absorption and fluorescence computed tomographies (CT) is a new method allowing a noninvasive and nondestructive determination of the three-dimensional (3D) mineralogy with micrometer resolution of sub-millimeter silicate grains, possibly stored in a silica holder. These CT were performed with beams of a few tens of keV from a third-generation synchrotron source on one olivine grain of the NWA817 Martian meteorite presenting a reddish alteration phase. The reconstructed sections show a network of fractures and a few micrometer-thick layers formed on one grain. The 3D facet orientation and the X-ray attenuation coefficient indicate that this grain is an Fo(44+/-9) olivine crystal. The fluorescence section reveals rims enriched in Fe (a major element) or depleted in Ca (a minor element). This CT combination shows that the micrometer-thick layer is preferentially formed on the (010) olivine face and has a lower density (3.5 +/- 0.4 g/cm(3)) than the olivine, even though it is enriched in Fe. Its complex nano-petrography and the distributions of nanometer-sized voids and fractures in such a micrometer thick layer, first observed by scanning electron microscopy on focused ion-beam cuts, is not shown by CT. The precision presently achieved, although moderate, is sufficient to obtain a 3D semi-quantitative view of the mineralogy consistent with the one previously established by electron probe microanalyses (Sautter et al. 2002)