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A transmission electron microscopy study of radiation damages to β-dicalcium (Ca2SiO4) and M3-tricalcium (Ca3SiO5) orthosilicates

In this paper, we present results of a first study of electron radiation damages to β-dicalcium silicate (Ca2SiO4:C2S) and M3-tricalcium silicate (Ca3SiO5:C3S) in a Transmission Electron Microscope. Electron irradiation is used here as a means to bring to light a difference of reactivity under the e...

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Published in:Journal of nuclear materials 2016-01, Vol.468, p.113-123
Main Authors: de Noirfontaine, Marie-Noëlle, Dunstetter, Frédéric, Courtial, Mireille, Signes-Frehel, Marcel, Wang, Guillaume, Gorse-Pomonti, Dominique
Format: Article
Language:English
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Summary:In this paper, we present results of a first study of electron radiation damages to β-dicalcium silicate (Ca2SiO4:C2S) and M3-tricalcium silicate (Ca3SiO5:C3S) in a Transmission Electron Microscope. Electron irradiation is used here as a means to bring to light a difference of reactivity under the electron beam between these two complex ceramic oxides, keeping in mind that C3S reacts faster with water than C2S and that this property remains unexplained, owing to the complex structural characteristics of these ceramics which have not yet been fully elucidated. The following results were obtained by coupling TEM imaging and EDS analysis: i) Rapid decomposition of both silicate particles into CaO nano-crystals separated by (presumably SiO2-rich) amorphous areas at low flux for both silicates; ii) once reached a threshold electron flux, formation of an amorphous crater in both silicates, fully calcium-depleted in C3S but never in C2S; iii) significant post-mortem structural evolution of the craters that at least partially recrystallize in C2S, to be compared to the quasi frozen damaged area in C3S; iv) hole drilling at high flux but only in C3S once reached a threshold flux, ϕth ∼ 7.9 × 1021 e− cm−2 s−1, of the same order of magnitude than previously estimated in a number of ceramic materials, whereas C2S still amorphizes under the electron beam for a flux as high as 2.2 × 1022 e− cm−2 s−1. The radiation damages and their post–mortem evolution differ largely between C2S and C3S. We attempted to relate the obtained results, and especially the evolution of the Ca content in the damaged areas under the electron beam to the available structural characteristics of these two orthosilicates. [Display omitted] •TEM study of electron damages in β-dicalcium (C2S), M3-tricalcium silicates (C3S).•Net difference of behavior between these two orthosilicates under irradiation.•Decomposition into CaO nano-crystals and SiO2 rich amorphous areas at low flux.•Above a threshold flux and dose, amorphization followed by hole drilling in C3S.•C2S appears much more electron-radiation resistant than C3S.
ISSN:0022-3115
1873-4820
DOI:10.1016/j.jnucmat.2015.10.060