Déchloruration des objets archéologiques ferreux par le processus de stabilisation subcritique. Caractérisations physico-chimiques des systèmes transformés

Abstract : Iron archaeological artefacts from submarine and terrestrial origins have developed reactive and chlorinated corrosion systems. After excavation, their transformations in contact with air involve severe damages to the artefacts. In order to extract the chlorine and to maintain the artefacts’ integrity, stabilization processes are used. The subcritical treatment (NaOH, 180°C, 35 bars) accelerates the dechlorination process. Several artefacts are studied before and after treatment with subcritical techniques. The multi-scale description of heterogeneous and complex corrosion system shows that the phase precipitation in subcritical conditions depends on the precursor chemistry. The study of model systems (synthetic and archaeological iron oxyhydroxides) shows that particle sizes and shapes, specific surface area, chemical composition change their reactivity. The application of a heating ramp leads to the precipitation of goethite/hematite below 150°C and hematite above. The study of akaganeite at various stages of its treatment shows that the adsorbed chlorides and part of the structure ones are first removed. Then, a dehydroxylation under the effect of temperature leads to the phase dissolution. These results allowed to identify the nature of phase transformations and to propose mechanisms in order to improve stabilization protocols of archaeological artefacts by subcritical treatment.
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Marine Bayle. Déchloruration des objets archéologiques ferreux par le processus de stabilisation subcritique. Caractérisations physico-chimiques des systèmes transformés. Chimie-Physique [physics.chem-ph]. Université Pierre et Marie Curie - Paris VI, 2015. Français. ⟨NNT : 2015PA066656⟩. ⟨tel-01366638⟩

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