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Reaction Mechanisms in Talc under Ionizing Radiation: Evidence of a High Stability of H• Atoms
journal contribution
posted on 2016-02-04, 15:10 authored by Maxime Lainé, Thierry Allard, Etienne Balan, François Martin, H. Jurgen Von Bardeleben, Jean-Louis Robert, Sophie Le CaërThe
reactivity under ionizing radiation of synthetic and natural
talc was studied. The two samples were chosen as models of nonswelling
clays. H2 production measurements evidenced that the H2 yield in synthetic talc was of the same order of magnitude
as in water, implying a very efficient production, and then recombination,
of hydrogen atoms arising from the lysis of structural −OH
groups. This yield was 30 times smaller in natural talc. The discrepancy
between synthetic and natural talc is most likely related to transition
elements cationic impurities in the latter. Even if they are present
in very small amounts, they are able to efficiently scavenge the electrons
and/or the hydrogen atoms. The produced defects in irradiated synthetic
talc were investigated by means of electron paramagnetic resonance
(EPR) spectroscopy, which enabled proposing reaction mechanisms. Lastly,
the EPR spectra evidenced the presence, at 298 K, of hydrogen atoms,
which were detected few days after irradiation in both types of talc.
This surprisingly high stability was mainly attributed to the absence
of water molecules. It is proposed that the hydrogen atoms are stabilized
in octahedra between two tetraedra sheets.