T02_06

Is TiH₂ really necessary for Zn reduction? Discussion on graphitization at Circe Laboratory

Capone B¹,  Passariello I¹, Terrasi F¹, Porzio G¹, Di Palma A¹, Rubino M¹, Marzaioli F¹

¹Università Degli Studi Della Campania "Luigi Vanvitelli", Caserta, Italy

The sample preparation procedure in use at CIRCE laboratory involves 3 main steps: chemical pretreatment of the sample in order to extract the carbon fraction of interest, oxidation of carbon to CO₂ by combustion with CuO or H₃PO₄ digestion for carbonaceous materials, and graphitization. The graphitization reaction leads to the formation of solid graphite targets and takes place in the presence of TiH₂ and Zn reagents and Fe as catalyst. Over more than a decade of using the procedure with a sample measurament rate of c.a. 1000/year, we observed a sharp increase in graphitization yield variabilty.

In order to verify the quality of the procedure, test measurements were performed on the IAEA C3 (cellulose) standard for combustion and graphitization reactions only. A fixed amount of about 1 mg of C was combusted by varying the amount of CuO and then graphitized by varying the amount of reagents. At the end of each step, samples were measured by IRMS in order to estimate the C isotopic fractionation, which is used as an indicator of reaction efficiency (i.e., the lower fractionation, the higher the reaction efficiency). Preliminary results show that the presence of TiH₂ appears to reduce the graphitization efficiency suggesting that it is preferable to remove it from the reaction in agreement with the methods proposed for the ultra-small samples. AMS ¹⁴C measurements were also carried out in order to determine background induced, accuracy and precision of the procedure to be compared with data previously acquired in the same laboratory.