T03_P12

First attempt of carbon extration for radiocarbon dating of ancient iron

PERRON M¹, Farcage D², Delqué-Kolic E¹, Semerok A², Leroy S³

¹Laboratoire des Sciences du Climat et de l’Environnement (LSCE - LMC14), Gif Sur Yvette, France, ²Service d’Études Analytiques et de Réactivité des Surfaces (SEARS), Gif Sur Yvette, France, ³Laboratoire Archéomatériaux et Prévision de l’Altération (LAPA), Gif Sur Yvette, France

The dating of steels by carbon 14 is a complex process involving the preliminary analysis of the material in order to identify the most carburized areas. Indeed, in archaeological steels, the low level of carbon and its heterogeneous distribution in the ferrous matrix lead to targeted sampling in areas rich in cementite (iron carbide). Currently, the sampling is carried out using a drill equipped with high-speed steel forests coated with titanium nitride of 2 to 3 mm in diameter. Finding that the precision of the samples was not optimal, we tested the extraction of carbon using a laser beam (Ytterbium 1064 nm fiber laser). In our device, the sample is placed in an enclosure in the presence of oxygen and then scanned by the laser beam that follows the sampling area defined by the metallographic observation. Another advantage of laser beam extraction is the direct formation of CO₂ in the cell, thus combining sampling and combustion in one step.

After some reminders on the dating of steels by carbon 14, we will present the installation developed for the extraction of carbon by laser beam and the conditions of handling. We will explain the first dating result obtained.