L. Bartoli

From Koto age to modern times: Quantitative characterization of Japanese swords with Time of Flight Neutron Diffraction

Japanese blades have always been considered very interesting objects, both from the stylistic point of view and their peculiar performances. It is amazing how the test and try process with a semi-empirical approach which lead to the optimization of Japanese blades, an almost ideal tool, is yet to be fully understood. In this work, we present results from a new non invasive approach to the study of these peculiar artefacts. Time of Flight Thermal Neutron Diffraction (TOF-ND) measurements were taken on two instrument INES and ENGIN-X, at the ISIS facility, RAL, UK. Two Japanese blades and eight blade fragments have been successfully characterized in terms of composition of the steel, smelting and smithing processes, and forging techniques. The differences among the production periods and forging traditions have been clearly determined. Further work is needed on standards to fully understand the production technique of a sample by comparison of the object under study with objects of known production methods.

Non Destructive Characterization of Phase Distribution and Residual Strain/Stress Map of Two Ancient (Koto) Age Japanese Swords

Two Japanese long swords (katanas) belonging to the Koto Age (X-XVI century A.D.) were measured through time of flight neutron diffraction to analyze the phases, and the stress and strain distribution, in selected parts of the blades. The swords are representative of two different forging schools (Aoe and Kanesada) and one of the main aims of the measurements was to evidence possible similarities and differences. Two independent experiments were carried out at the ISIS pulsed neutron source using the INES and ENGIN-X diffractometers. The former was employed to map the average phase distribution on two selected cross sections, of each blade, distinguishing among the ridge, the core, and the edge of the blades. In this way, we were able to quantify the coarse distribution of the carbon content and, moreover, we could evidence the presence of martensite. These data were then complemented measuring detailed stress and strain distribution maps on ENGIN-X. As far as the ridge and the core are concerned, the tang data were taken as a reference. These measurements significantly improve the knowledge and understanding of the technology used to produce Japanese swords belonging to the Koto Age.

Comparison between TOF-ND and XRD quantitative phase analysis of ancient potteries

A non-invasive time-of-flight neutron diffraction (TOF-ND) analysis has been performed on archaeological pottery fragments from the excavation sites in the “Strait of Messina” area (Sicily, Southern Italy). The revealed quantitative information on the mineralogical composition have been compared, in the case of two samples representative of coarse and fine grained pottery, with the weight fractions of the crystalline phases as obtained from X-ray diffraction on powders (XRPD), for different amounts of extracted powder. From the results, the consistency of these micro-destructive and non-invasive approaches has been checked. This research may contribute to better define the most efficient sampling and analytical method for the determination of mineralogical composition on ceramics different in structure and composition.

Integrated X-ray and neutron-based analysis of bronze artefacts from the Ligurian settlement of Guardamonte-Monte Vallassa

Archaeological finds from the pre-Roman Ligurian settlement of Guardamonte-Monte Vallassa (Pavia, Italy) were made available for a series of material analysis measurements based on X-ray and neutron radiation. With the objects not yet cleaned and restored, the XRF analysis obtained from a standard low-power spectrometer was limited to the surface of the objects, covered by corrosion and concretion layers. Time of flight neutron diffraction (TOF-ND), however, is widely recognised as a promising technique for non-destructive bulk analysis of cultural heritage objects allowing to access depths of a few centimetres in metallic objects. Moreover, the INES beamline at the ISIS neutron source offered the unique possibility of performing TOF-ND together with neutron resonance transmission (NRT) measurements. We present XRF and neutron-based results on selected objects, showing how the use of integrated techniques can get information on the physical nature of both the corrosion layers and bulk properties of the objects, and in some cases giving indications on the method of production, for instance, casting or hammering.

Time-of-flight neutron diffraction: a new analytical technique for conservation?

Historical metallurgy is an important aspect of archaeometry, and the study of the process of steel making is of great interest in this field. In order to achieve a high level of material characterization by traditional analytical methods, a destructive approach is usually necessary. This article reports the first systematic use of a neutron-based, non-destructive method that enables resolution of the complex microstructure of a metallic object while retaining full authenticity and artefact integrity. Historical Japanese swords represent some of the best examples of historical metalwork and are, therefore, one of the most rewarding classes of artefacts to study in order to elucidate the evolution of metallurgy. With the aim of characterizing the materials and forging methods used, we analysed two Japanese long swords from the Pitt Rivers Museum, using time-of-flight neutron diffraction (ToF-ND). The results showed that ToF-ND is a very promising method of analysis and investigation for ancient metals.