Marco Zoppi

Neutron diffractometer INES for quantitative phase analysis of archaeological objects.

With the Italian Neutron Experimental Station (INES) a new general purpose neutron powder diffractometer is available at ISIS, characterized by a high resolution at low d-spacings, and particularly suited for the quantitative phase analysis of a wide range of archaeological materials. Time-of-flight neutron diffraction is notable for being a non-destructive technique, allowing a reliable determination of the phase compositions of multiphase artefacts, with or without superficial corrosion layers. A selection of archaeometric studies carried out during the first year of the INES user programme is presented here to demonstrate the capabilities of the instrument.

Low temperature Raman spectra of hydrogen in simple and binary clathrate hydrates

The Raman spectrum of hydrogen clathrate hydrates has been measured, as a function of temperature, down to 20 K. Rotational bands of H(2) and HD, trapped into the small cages of simple (H(2)O-H(2)) and binary (H(2)O-THF-H(2)) hydrates, have been analyzed and the fivefold degeneracy of the molecular J=2 rotational level has been discussed in the light of the available theoretical calculations. The vibrational frequencies of H(2) molecules encapsulated in the large cages of simple hydrates turn out to be well separated from those pertaining to the small cages. Comparison with the equivalent D(2) spectra allowed us to assign the large cavity vibrational frequencies to three couples of Q(1)(1)-Q(1)(0) H(2) vibrational modes. Populations of ortho and para species have been measured as a function of time from rotational spectra and the rate of ortho-para conversion has been estimated for both simple and binary hydrates. We suggest, using the H(2) vibrational spectra, a model to analyze the cage population in simple hydrates.

Quantitative characterization of Japanese ancient swords through energy-resolved neutron imaging

Japanese blades are culturally interesting objects both from the stylistic point of view and because of their fantastic performance. In this work, we present new results, using a non-invasive approach, concerning these peculiar artefacts. Five Japanese swords pertaining to Koto (987–1596) and Shinto (1596–1781) periods have been analysed through white beam and energy resolved neutron-imaging techniques. The experiments have been performed at the ICON beam line, operating at the spallation neutron source SINQ, Paul Scherrer Institut in Switzerland. The reconstruction of projection data into neutron tomographic slices or volumes allowed us to identify some peculiar characteristics, related to the forging methods that were used by the different schools and traditions in Japan.

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.

A neutron imaging device for sample alignment in a pulsed neutron scattering instrument

A neutron-imaging device for alignment purposes has been tested on the INES beamline at ISIS, the pulsed neutron source of Rutherford Appleton Laboratory (U.K.). Its use, in conjunction with a set of movable jaws, turns out extremely useful for scattering application to complex samples where a precise and well-defined determination of the scattering volume is needed.

Non-invasive quantitative phase analysis and microstructural properties of an iron fragment retrieved in the copper-age Selvicciola Necropolis in southern Tuscia

This work presents the non-invasive analysis, through time of flight neutron diffraction, of a unique grey metal ferrous artefact in the shape of an awl. This object was found together with other copper samples in the Selvicciola Necropolis, which includes 34 eneolithic underground tombs, dated radiometrically between halfway through the fourth millennium and the end of the third millennium BC. The sample was originally covered with mineralization products. However, its main peculiarity resided in an almost total absence of rust. The uniqueness of such a sample imposed a non-invasive approach for its analytical study. In addition, being a singular object, in that environment, its study was considered mandatory to better understand the metallurgical skills of a copper-age community in central Italy. Thermal neutron scattering techniques have provided a wealth of information about the composition, the smelting process, and the mechanical and thermal treatments applied during the manufacture of the sample. The results obtained suggest that the sample had been treated according to the typical approach used for copper alloy smelting and smithing, i.e. cold working at room temperature and annealing at ∼700 to 800 °C.

An apparatus for simultaneous thermodynamic and optical measurements, with large temperature excursions

We report the design and realization of an integrated system for measuring, at the same time, the thermodynamic and spectroscopic features of nanoporous materials interesting for hydrogen storage purposes. The whole investigation cycle, from thermal activation to the actual investigation of uptake and release of hydrogen, is carried out in the same vacuum tight vessel, equipped with an optical window, whose temperature can range between 10 and 750 K, up to a maximum pressure of 50 bars. The system has been designed to investigate properties of carbon nanotubes but its use can be extended to any kind of nanoporous sample such as, for example, carbon nanofibers, zeolytes, metal organic frameworks, and similar materials.

Non-invasive characterization through X-ray fluorescence and neutron radiography of an ancient Japanese lacquer

Oriental lacquer artefacts represent very interesting objects of investigation, involving a huge variety of materials and manufacturing techniques. Lacquers are very attractive not only for their stylistic features but also for understanding the variety of production processes, time evolution, use and artistic applications involved in their manufacturing. Till recently, the research activity on these materials has been mainly based on standard, more or less invasive, analytical methods. With the aim to characterise a nineteenth century Japanese lacquer in a totally non-invasive and non-destructive way, in situ X-ray fluorescence (XRF) and neutron radiography (NR) have been employed. While XRF suggested an identification of the pigments embedded into superficial layers, NR allowed revealing, in a single measurement, the average bulk properties of the sample.

High pressure optical cell for synthesis and in situ Raman spectroscopy of hydrogen clathrate hydrates

We report the design, realization, and test of a high-pressure optical cell that we have used to measure the Raman spectra of hydrogen clathrate hydrates, synthesized in situ by the application of 200-300 MPa of gas pressure on solid water. The optical apparatus is mounted on a cryogenic system so to allow measurements and sample treatment at any temperature between 300 and 20 K. A capillary pipe is connected to the inside of the cell to allow the gas flow into and out of the cell, and to regulate the internal pressure at any value from 0 to 300 MPa. In the experimental test described in this paper, the cell has been partly filled, at room temperature, with a small amount of water, then frozen at 263 K before injecting hydrogen gas, at pressure of 150 MPa, into the cell. This procedure has permitted to study hydrogen clathrate formation, by measuring Raman spectra as a function of time.

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.