Salvatore Siano 1 , Marcello Miccio 2 , Laura Bartoli 1 , Mark Daymond 3 , Winfried Kockelmann 3

1. 15 cm Neutron beam Neutron beam Repair patch 0.7 mm ACHAEOMETALLURGICAL STUDIES BY NEUTRON DIFFRACTION Bank 3 Slit S ( planes) Salvatore Siano1 , Marcello Miccio2, Laura Bartoli1, Mark Daymond3, Winfried Kockelmann3 1) Istituto di Fisica Applicata “Nello Carrara”, Consiglio Nazionale delle Ricerche, Firenze, Italy, 2) Soprintendenza per i Beni Arheologici della Toscana. 3)Rutherford Appleton Laboratory, ISIS Neutron Facility, Chilton, England 2.7 cm The discovery of an ancient object typically originates a variety of problems, which can be broadly grouped into the following categories: 1) the correct determination of the historical and cultural frame where it was realised, 2) the restoration, 3) the selection of protection treatments and microclimatic conditions providing its preservation. In this concern, a fundamental role is played by material characterisation analyses. These can address the selection of the most suitable preservation strategy, as well as to investigate ancient manufacturing techniques and to reconstruct commercial and human exchanges among contemporaneous civilisations. The whole of chemical, physical, and microstructural techniques presently employed in the practice of the archaeometallurgical characterisation is rather wide. Along with the metallographic approaches, various elemental and structural analysis techniques are usually applied, such as for examples Absorption Spectrophotometry, SEM-EDX (WDX), X-Ray diffraction, and other. All these techniques are subjected to some limitations because of the very localised chemical and structural information and destructivity. Actually, the most significant analyses are those based on invasive sampling such as coring or cutting. Thus, in case of high value artefacts, a thorough scientific investigation is often impracticable.This problem stimulated many researches aiming at the development of novel diagnostic techniques not requiring material sampling or, at least, strongly reducing the amount of material to be removed. The non-destructive ones based on X-Ray Fluorescence (XRF), Proton Induced X-Ray Emission (PIXE), Synchrotron Radiation (SR), and Neutron Diffraction (ND), underwent significant technological and methodological developments along the last years. Among these, ND is the only one which can provide fundamental information on bulk composition and structure of a metal object, through the whole thickness of its walls and on meaningful volumes.In the present work, we investigated and demonstrated for the first time, a number of peculiar diagnostic potentials of the ND in the study of ancient bronzes. This was achieved through a systematic analysis carried out on standardised bronze specimens an d a number of original Etruscan and Roman artefacts. 12.5 cm RATIONALE ETRUSCAN AND ROMAN ARTEFACTS Binary bronze for a(%Sn) calibration, eutectoid and peak shape investigations Aim Experimental evaluation of the Time of Flight Neutron Diffraction (TOF-ND) potentials to characterise archaeological bronzes  Alloy and mineralisation phase analyses  Residual stress measurements  Texture analysis Systematic approach  Production and investigation of standardised bronze specimens simulating possible working processes  Suitable selection and investigation of archaeological artefacts with different expected features  Study of archaeometrical problems Fibula (VIII BC) Mirror (II BC) Vessel base (IV BC) 13.5 cm 12 cm Razor (IX BC) 14 cm Mechanically and thermally treated specimens to investigate identifying features Jug (IV-III BC) Roma (III AC) Olpe (V-IV BC) STANDARDISED SPECIMENS Ternary bronzes to check quantitative phase analysis 9.6 cm Courtesy of the National Archaeological Museum of Chiusi (Dr. M. Iozzo) ROTAX HOMOGENISED BINARY BRONZES AS-CAST SPECIMENS QUANTITATIVE PHASE ANALYSIS  Evidence of “dendritic peak broadening”  Strong texture  Linear d-shift up to 6% tin content  Detection of the eutectoid peaks at 8% tin content Medium resolution powder diffractometer at the pulsed spallation source ISIS, Rutherford Appleton Laboratory, UK.  Strong texture (preferred orientations)  Linear d-shift up to 14% tin content  Detection of the eutectoid peaks at 16% tin content Rietveld refinement by GSAS code Check on DIII(81:6:13): Cu 79.9 %, Sn 6%, Pb 14.1 [Å] - Large cylindrical sample tank: diameter 40 cm, height 60 cm - Three detector banks providing a d-spacing coverage between 0.3-20 Å - A collimator cuts out reflections occurring outside a 90 mm radius around the centre Vessel base a=23/2rCu+23/2(rSn-rCu)CSn Setups Olpe: pattern splitting at the repair patch Experimental linear dependence of the lattice parameter on Sn content, as derived by Le Bail full pattern refinements Lateral wall (o.l.w.) Bottom wall (o.b.w.) Handle (o.h.) Repair patch Jug Bank 2 Bank 3 Bank 1 Neutron beam Sample tank IDENTIFICATION OF THE WORKING PROCESSES Effect of thermal and mechanical treatments on peak shape MEASUREMENT OF RESIDUAL STRESSES BY ENGIN-X TEXTURE (PREFERRED ORIENTATIONS) ANALYSIS   Neutron beam f f Incomplete experimental pole figures ODF calculation algorithm Reconstructed pole figures by MAUD code • One dimensional spatial resolution up to 0.5 mm (typical gauge volume 0.50.55 mm3) N (// planes) MIRROR:absence of preferred orientation (multiple treatments) Following homogenisation, peak broadening is essentially due to residual stresses Vessel base (200) JUG (111) COIN: weak fiber texture demonstrating it was produced by striking N 27 mm    Lattice parameter associated with planes // to the coin surface          TOF-ND diagnostic techniques were designed and successfully applied to investigate archaeological bronze artefacts through the comparison with suitable reference specimens. The demonstration of non-destructive analyses, such as phase quantification through relatively thick or multiple bronze walls, determination ofcomposition and homogeneity of the alloy, residual stresses evaluations by reflection peak broadening (ROTAX) or shift (ENGIN-X), and eventually texture analysis provide a peculiar and powerful characterisation set. This proves a real application perspective for this novel characterisation approach, which is ready for a large-scale employ in archaeometallurgical studies.      Goss {011}<001> Some references on the topic W. Kockelmann, E. Pantos, A. Kirfel, in: Radiation in Art and Archaeometry, Ed. D.C. Creagh, D. Bradley (Elsevier, Amsterdam, 2000) pp. 347-377. W. Kockelmann, A. Kirfel, E. Haehnel, J. Arch. Sci. 28, (2001) 213. S. Siano, W. Kockelmann, U. Bafile, M. Celli, M. Iozzo, M. Miccio, O. Moze, R. Pini, R. Salimbeni, M. Zoppi, Appl. Phys. A 74 (2002) S1139. S. Siano, L. Bartoli, M. Zoppi, W. Kockelmann, M. Daymond, J.A. Dann, M G. Garagnani, M. Miccio, in: Archaeometallurgy in Europe, Associazione Italiana di Metallurgia, Milano (2003) 319-329. S. Siano, L. Bartoli, W. Kockelmann, M. Zoppi, and M. Miccio, in press in Physica B (2004). Acknowledgements This work was carried out within the activity frame of the CNR Agenzia 2000 Project “Development of neutron diffraction techniques for non-destructive analysis of metal archaeological findings”. The authors wish also to thank Dr. Renzo Salimbeni and Dr. Marco Zoppi for having encouraged and supported this research.