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Structural modifications in ceramics : from basic mechanisms to nuclear materials applications

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Involved people : Abdenacer Benyagoub, Serge Bouffard, Emmanuel Gardes, Clara Grygiel, Henning Lebius, Florent Moisy, Isabelle Monnet, Marcel Toulemonde

Contracts : LABEX EMC3 : PICOLIBS (2013-2017) and Naninox (2013-2014) , EMIR, NEEDS, GENESIS (2012-2019)

Recently, we worked on the studies of the fundamental phenomena occuring in ceramics under irradiation.

To characterize these modifications the MADIR team has at hand significant experimental facilities (XRD, HRTEM, SEM, Raman, optical absorption, AFM, furnaces, some of them in-situ on GANIL beam lines and recently completed thanks to the equipex GENESIS with HRXRD, dualbeam FIB/SEM, EFTEM )). To complete TEM observations on the morphology of the individual tracks and the simulation by the inelastic themal spike models, a new XRD instrument, allowing real in-situ measurement, permits to describe with accuracy the phase transition kinetics up to high fluences. The studies are conducted on model oxide considered as potential inert matrix for storage or transmutation of nuclear waste.

Full studies of the model materials have been undertaken in the past years by combination of the different experimental techniques : ABO3 perovskites (A=Ba or Sr, B=Ti), ABO4 spinels (A=Zn or Mg, B=Al), Al2O3 corindon, AO2 fluorite(A=Zr or Hf), A2B2O7 pyrochlores.
Among the radiation responses, phase transition C (crystalline) to A (amorphous), C to C’, C to C’+A, etc, point defect formation, dislocation loops, grain subdivivion, have been observed, indicating the complexity of the behavior of iono-covalent materials, strongly dependant of the intensity of the excitation and of the material itself (influence of ionic radius ratio, or iono-covalent bond character are evidenced).

Amorphization of Al2O3 polycristalline material under swift heavy ion irradiation, in-situ grazing x-ray diffraction recorded at 0.5°.

The MADIR group has also a research axis concerning materials for the nuclear industry, either for structural materials or in the nuclear waste management. In this research, there are numerous collaborations with CEA/DEN groups (Marcoule concerning nuclear glasses, Saclay for the ODS, MAX phases, spinel and SiC, Cadarache concerning UO2 or MAX phases), but also with other French groups (CSNSM-orsay for the pyrochlores, GPM-Rouen for nanostructured steel) as well as groups worldwide (USA, India, Germany, …).

HRTEM images of the track structure indicating the regions where FFT analyses were completed for Gd2Ti2O7, Gd2(Zr,Ti)2O7 and Nd2Zr2O7 irradiated with 120-MeV U ions at 2e11 ions/cm2.
G. Sattonnay, C. Grygiel, I. Monnet, C. Legros, M. Herbst-Ghysel, L. Thomé, Acta Materialia, Volume 60, Issue 1, 22-34 (2012)