Integrated analytical methodologies for the study of corrosion processes in archaeological bronzes

The investigations on structure and micro-chemical composition of archaeological metal alloys are needed in archaeometry. The aim of this study is devoted both to acquire information about their provenance and production technology, and to improve our understanding about the corrosion processes. In this paper we present the study of the corrosion phenomena of bronze samples, laboratory-made according to binary, ternary and quaternary alloys typical of Roman archaeometallurgical production through an integrated methodology based on the use of non or micro invasive physical techniques. Among the analysed samples, two were artificially aged through burial in the archaeological site of Tharros, along the west coast of Sardinia (Italy). The corrosion products, typical of the bronzes in archaeological sites near the sea, have been characterized by non invasive and micro-destructive measurements. In particular, the corrosion patinas were examined through optical microscopy, scanning electron microscopy and microanalysis, X-ray fluorescence and laser ablation spectroscopy. The use of integrated technologies allowed us to determine both the elemental composition and surface morphology of the patina, highlighting the correlation between patina nature and chemical composition of the burial context. Moreover, data obtained by the laser-induced breakdown spectroscopy along the depth profile on the samples, have yielded information about the stratigraphic layers of corrosion products and their growth. Finally, the depth profiles allowed us to verify both the chemical elements constituting the patina, the metal ions constituting the alloy and the occurrence of migration phenomena from bulk to the surface.     

Mechanochemically synthesized pyrite and its electrochemical behavior as cathode for lithium batteries

Journal of Solid State Electrochemistry - This study presents a simple and scalable synthesis of pyrite (FeS2) starting from S and Fe powders, which involves high-energy ball milling of precursor...     

Voltammetric Behaviour of LMO at the Nanoscale: A Map of Reversibility and Diffusional Limitations

Understanding and optimizing single particle rate behaviour is normally challenging in composite commercial lithium-ion electrode materials. In this regard, recent experimental research has addressed the electrochemical Li-ion intercalation in individual nanosized particles. Here, we present a thorough theoretical analysis of the Li⁺ intercalation voltammetric behaviour in single nano/micro-scale LiMn₂O₄ (LMO) particles, incorporating realistic interactions between inserted ions. A transparent 2-dimensional zone diagram representation of kinetic-diffusional behaviour is provided that allows rapid diagnosis of the reversibility and diffusion length of the system depending on the particle geometry. We provide an Excel file where the boundary lines of the zone diagram can be rapidly recalculated by setting input values of the rate constant, and diffusion coefficient, . The model framework elucidates the heterogeneous behaviour of nanosized particles with similar sizes but different shapes. Hence, we present here an outlook for realistic multiscale modelling of real materials.     

The Newtonian limit in a family of metric affine theories of gravitation

A brief review of a first order theory with a quadratic LagrangianL=R+₀R² is presented. It is shown that a test particle follows a geodesic of the metric connection. The theory behaves in the Newtonian limit as the Newtonian theory with a correction which is proportional to the matter density at the field point. This behavior can be produced by a Yukawa potential with an atomic scale characteristic range and a coupling constant proportional to 1/ ². This type of potential is not excluded by the present experimental data.     

Degradation study of XVIII century graffiti on the walls of Chiaramonte Palace (Palermo, Italy)

A systematic investigation of the original materials and the degradation phenomena induced by soluble salts on the wall matrix and on the graffiti of the Inquisition jails of Chiaramonte Palace in Palermo (Italy) was carried out. Built in the XIV century, Chiaramonte Palace was used as Inquisition court during the XV–XVI centuries. The ancient graffiti, recently discovered, represent a unique historical witness of the prisoners that lived during that terrible period. In order to study the nature, the amount and the distribution of the salts in the masonry, stone materials sampled at different depth from the wall matrix and saline efflorescences were analysed. Different physical techniques were used, such as X-ray Photoelectron Spectroscopy, X-ray Fluorescence, Laser Induced Breakdown Spectroscopy, X-ray Diffraction and Ionic Chromatography. Results of the chemical and physical characterisation showed that the main cause of the degradation of graffiti and wall paintings was the presence of soluble salts, such as nitrates, chlorides and sulphates. Traces of oxalates, coming from a previous conservation treatment, were also found. The results obtained by the stratigraphical characterisation of soluble salts in the wall matrix can be used to recommend a procedure based on air humidification at high relative humidity values in order to avoid salt crystallisation and to prevent the crumbling process of the graffiti.     

Gilding and pigments of Renaissance marble of Abatellis Palace: non‐invasive investigation by XRF spectrometry

Most of the artworks constituting the collection of Renaissance statuary of Abatellis Palace in Palermo (Sicily) show evidence of colour layers and fragments of gold foil that probably once covered the whole marble surface. The restoration of some of these statues has allowed to carry out archaeometric studies about the painting technique and to highlight the original materials and inclusion present on the precious marbles by two famous Italian sculptors of the Renaissance, Francesco Laurana and Antonello Gagini. The measurements have been performed in situ through the integrated use of two non‐invasive techniques: visible fluorescence stimulated by ultraviolet light and X‐ray fluorescence. The ultraviolet‐induced fluorescence analysis has provided additional information on the conservation status of marble surfaces by differentiating the pictorial materials and highlighting the presence of gilding and pigment traces through their characteristic fluorescence response. The observation in ultraviolet light has been used as valuable guide for the identification of the significant points to be analysed by X‐ray fluorescence to characterise the original materials. X‐ray fluorescence measurements have cast light about their chemical composition and stratigraphical structure. Pictorial layers were identified: vermilion for red layers, blue pigment based on copper for blue layers and pure gold leaf for gilding layers. Principal component analysis of the data was capable of clustering the different painting materials, discriminating through their chemical content. The results represent an important scientific support both to the hypotheses about the original look of the artworks and to the resolution of restoration and conservation questions still open. Copyright © 2012 John Wiley & Sons, Ltd.     

Fast charging of alkali-ion batteries at the single-particle level: the impact of particle geometry on diffusional and kinetic bottlenecks in voltammetry

Journal of Solid State Electrochemistry - Shedding light onto the processes that limit the fast charging of alkali-ion battery cells constitutes a hotspot area. In the present work, we study two of...     

On how interactions influence kinetic limitations in alkali-ion batteries. Application to Li-ion intercalation into graphite through voltammetric experiments

Journal of Solid State Electrochemistry - Here, we report on a novel study for battery application regarding the impact of interactions in charge transfer and diffusional features in finite-size...     

Geodesic deviation and Minikowski space

We study the properties of the solution space of local surface-forming null sub-congruences in the neighbourhood of a given null geodesic in a pseudo-Riemannian space-time. This solution space is a three-dimensional manifold, naturally endowed with a conformai Minkowski metric.