Francesca Longo

Combined non-destructive XRF and SR-XAS study of archaeological artefacts

AbstractWe report on a non-destructive study of Sicilian ceramic fragments of cultural heritage interest, classified as “proto-majolica” pottery and dating back to the twelfth to thirteen centuries AD. The analytical approach used is based on the employment of two totally non-invasive spectroscopic techniques: X-ray fluorescence (XRF), using a portable energy-dispersive XRF analyser, and X-ray absorption spectroscopy, using synchrotron radiation as a probe (SR-XAS). XRF measurements allowed us to collect elemental and spatially resolved information on major and minor constituents of the decorated coating of archaeological pottery fragments, so providing preliminary results on the main components characterizing the surface. In particular, we assigned to Fe and Mn the role of key elements of the colouring agent. With the aim of obtaining more detailed information, we performed SR-XAS measurements at the Fe and Mn K-edges at the Italian BM08 beamline at the European Synchrotron Radiation Facility (Grenoble, France). The experimental data were analysed by applying principal component analysis and least-squares fitting to the near-edge part of the spectra (X-ray absorption near-edge structure) to determine the samples’ speciation. From the overall results, umber, a class of brownish pigments characterized by a mixture of hydrated iron and manganese oxides, has been ascribed as a pigmenting agent. FigureFe K-edge XANES spectra of selected proto-majolica samples and reference compounds (FeO, Fe3O4, Fe2O3, Fe+SiO2). D pigmented, L not pigmented.

A multi-technique approach for the determination of the porous structure of building stone

The complete knowledge of the porous structure of rocks is necessarily requested for the prediction of the damages induced by salt crystallization. Nevertheless, the geometric description of the porous structure is usually very difficult because of the variability of the size distribution of voids, ranging from nanometers to millimeters, which generally is not accessible by a single methodology. For this reason, a multi-technique approach was used here: the investigation at sub-micrometric dimensional scale (> 0.004 μm) was carried out by Hg intrusion porosimetry (MIP), whereas the study at the nanoscale required Small Angle Neutron Scattering (SANS) analysis. All the results were interpreted in the framework of a fractal model. The analyses were performed on limestones of different geological formations, cropping out in south-eastern Sicily and largely used as building stones in Baroque monuments of the Noto Valley (belonging to the UNESCO Heritage List).

Multi-technique characterization of ancient findings from Gela (Sicily, Italy)

In the present study we carried out an extensive non-destructive and micro-destructive surface investigation on ancient decorated Sicilian samples of cultural interest, using a combination of different spectroscopic methods. In particular, the elemental composition, obtained by a handheld XRF analyser, acted as a valuable guideline for subsequent targeted sampling actions, thus minimizing the sampling damage. Hence, some questions not answered by XRF measurements (identification of some pigments, preparation layers, etc.) were subsequently resolved using Scanning Electron Microscopy coupled with Energy-Dispersive Spectrometry (SEM-EDS) and Fourier Transform Infrared absorbance spectroscopy (FT-IR). This multi-technique approach allowed us to provide useful information to establish the pigments and the production technique used by the craftsmen.

Mobility of water in Linde type A synthetic zeolites: an inelastic neutron scattering study

In the present work the effects produced by cation substitution on the dynamics of water in Linde type A (LTA) synthetic zeolites were investigated by means of inelastic neutron spectroscopy (INS). In particular, we performed measurements on fully hydrated Na-A and Mg-exchanged-A zeolites. The collected INS spectra showed two broad bands due to the vibrational (water–cation and hydrogen bond stretch) and librational (rock, twist and wag) modes of water. To quantitatively assign these various modes, the spectra were decomposed into Gaussian components and compared with the INS spectra of ice and of water in other zeolites. The observed shifts of the band positions for different temperatures were discussed. In particular, a slight shift of the three librational modes towards higher frequencies with increasing temperature was revealed for both samples. The hydrogen bond stretching and librational modes of water in Na-A and Mg50-A zeolites shift to lower frequencies with respect to ice. Furthermore, in the case of Mg50-A zeolite, we observed a shift upwards in frequency of librational bands with respect to Na-A zeolite. The obtained results were discussed in relation to our previous elastic and quasi-elastic neutron scattering (ENS and QENS respectively) measurements on the same samples.

Technological Analysis of Sicilian Prehistoric Pottery Production through Small Angle Neutron Scattering Technique

The Middle Bronze Age in Sicily (15th-13th century BC) represents a crucial moment in the evolution of Prehistoric pottery production. However, the scarcity of specific petrographic and chemical studies has represented until now a serious interpretative handicap for archaeologists. The recent study of an important Middle Bronze Age pottery complex from the site of Grotte di Marineo (Licodia Eubea, Catania), offers the possibility to add new significant data in this field. The analyses, carried out on a group of diagnostic samples represent 13% of the whole complex. This allowed us to obtain a precise characterization that surpassed the misleading identification based on the simple autoptic exam. In this context, this paper highlights the potentiality of the small angle neutron scattering (SANS) technique as a non-invasive analytical tool for the study of technological aspects, in conjunction with other, more usual, methodologies such as scanning electron microscopy (SEM), in order to better investigate production technology of Middle Bronze Age Sicilian pottery.

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.

Neutron radiography for the characterization of porous structure in degraded building stones

As it is well known, the porous structure of stones can change due to different degradation processes that modify the characteristics of freshly quarried blocks. Their knowledge is fundamental for predicting the behavior of stones and the efficacy of conservative treatments. In this context, neutron radiography is a useful tool not only to visualize the structure of porous materials, but also to evaluate the degree of degradation and surface modifications resulting from weathering processes. Furthermore, since thermal neutrons suffer a strong attenuation by hydrogen, this technique is effective in order to investigate the amount of absorbed water in building materials. In the present work, we report a neutron radiography investigation of limestones cropping out in the South-Eastern Sicily and widely used as building stones in Baroque monuments of the Noto Valley. The analyzed samples have been submitted to cyclic salt crystallization that simulate degradation processes acting in exposed stones of buildings. The obtained results demonstrate the interest of neutron radiography to better understand deterioration processes in limestones and to acquire information useful for restoration projects.

Handheld and non-destructive methodologies for the compositional investigation of meteorite fragments

In the present study, an innovative methodological approach has been proposed in order to characterize meteoritic samples without removing or causing damage to any part of them. In particular, Raman and X-ray fluorescence (XRF) measurements have been preliminarily performed, using portable instruments, in order to obtain qualitative and semi-quantitative compositional information, respectively. These analyses have been followed and supported by time of flight neutron diffraction (TOF-ND) experiments, which allowed us to perform quantitative mineralogical phase analysis. Such a methodological approach was tested on four meteoritic samples, of different types and sizes, coming from several different regions of the Solar System (e.g., the Moon, Mars and asteroids). The validity and strength of the results obtained using these techniques are discussed and compared with results available in the literature.

Hydrogen bonding in the Raman O–H stretching band of propylene glycol in nanometre-confined space: surface interactions and finite-size effects

The O–H stretching vibration of propylene glycol (PG) has been investigated by Raman spectroscopy in the −15 to +60°C temperature range, in the bulk state and confined to the ∼26 Å pores of a controlled porous glass. By modifying the nature of the substrate (from hydrophilic to hydrophobic), we separated the surface-like and the finite-size contributions to the high-frequency vibrational dynamics of this glass-forming system. The spectra have been fitted by four Gaussian peaks associated with PG molecules exhibiting different H-binding states (i.e. non H-bonded, chain-end and doubly bonded). The T-dependencies of the peak wavenumbers and relative areas of the resolved components furnished a quantitative description of the role played by polymer–surface interactions and topological effects on the connectivity distribution of confined PG molecules.