1,720,976 research outputs found
Development of a 2D-XRF scanner for cultural heritage applications
No full textIn this work, the design conception and the construction of a 2D X-ray fluorescence scanner, from mechanical parts to software, are fully presented and discussed. The instrument is composed of one modular scanning head, with interchangeable parts and two different X-Y translation stages. It is controlled by one single program, using specifically tailored Application Programming Interfaces (APIs). The system design follows a plug-and-play approach, where the system can adapt to almost every need, being transported to galleries, and even overseas to remote excavation sites. A complete and open-source data analysis software for WindowsTM, XISMuS, was also developed and is available online with a distribution package. The software design and implementation are also fully described in this work, as well as its functionalities and a copy of the User Guide for version v2.4.3.
The fully constructed instrument and the data analysis software were tested against one commercial model and on a wide variety of materials, in combination with several different analytical techniques for a full characterization of tiles, painted leathers, metals, gildings, stones, sediments, and paintings. All the case studies are thoroughly presented. Among them, an innovative method, which combines micro-petrography and XRF scans of thin sections performed in-field at Koumasa, Crete
Monte Carlo simulations of ED-XRF spectra as an authentication tool for nuragic bronzes
Get PDFThe high artistic and cultural relevance of particular objects, in this case from the Nuragic civilization, have stimulated the growth of a forgery industry, replicating small bronze boats (navicelle), statues (bronzetti), and other objects. It is often the case where the forgeries are of such quality that it becomes difficult to distinguish them from authentic artifacts without a proper chemical analysis. In this research, a Monte Carlo simulation algorithm for X-ray interactions with matter is used to obtain the chemical composition from the bulk of each object from a set of five. The method employed has the advantage of being completely nondestructive and relatively fast. The objects’ chemical composition and morphology were compared with the data available from authentic artifacts so their authenticity could be inferred. Four of the five objects are likely to be authentic, where two of them could be associated with a Sardinian origin
Characterisation of corrosion products on copper-based artefacts: potential of MA-XRF measurementsties of MA-XRF measurement
No full textThe use of macro-X-ray fluorescence (MA-XRF) scanners is now widespread in cultural heritage applications. However, its use for the characterisation of metallic works of art is still limited. In this study, a novel portable MA-XRF scanner prototype was tested on artificially corroded copper samples to assess its analytical capabilities on corroded metals, yielding information on the spatial distribution of the corrosion products grown on the metal’s surface. A multi-analytical approach was used to thoroughly characterise the copper samples and compare the obtained results to verify the reliability of the MA-XRF data. The prototype was able to obtain distribution maps of different elements, such as sulphur and chlorine, which can be directly correlated to different corrosion products. With the use of imaging filtering techniques, it was possible to investigate the stratification of the corrosion product layers and observe gradients in the distribution of certain elements
Mechanical and thermal properties of high-density polyethylene/alumina/glass fiber hybrid composites
No full textIn this investigation, composite materials made from high-density polyethylene (HDPE) and alumina, as well as from HDPE, alumina, and glass fibers, were prepared, aiming to improve the thermal stability, stiffness, and mechanical strength. The combined effects of alumina and glass fibers and the individual effects of alumina were studied. Alumina concentrations ranged from 5 wt\% to 10 wt\% and glass fiber concentrations ranged from 10 wt\% to 30 wt\%. For the hybrid composite materials, alumina concentration was maintained constant as the glass fiber concentration increased. The composites were processed with a double-screw extruder. Their properties were evaluated through a multi-analytical approach. Results pointed to a significant increase of the elastic modulus for the hybrid composite (up to 501\% in comparison to the neat polymer), at the cost of a large decrease in toughness, alongside a decline in impact resistance. Elastic modulus improvement was observed in both hybrid and HDPE-alumina composites, being higher for the hybrid composites due to the addition of glass fibers. HDPE-alumina composites presented a decrease in mechanical strength, whereas the hybrid composites showed an increase of this parameter. Concerning thermal properties, the hybrid composites presented higher thermal stability than that of the HDPE-alumina composites and a similar degradation temperature as the neat polymer. Micrographs pointed to weak adhesion between alumina particles and the polymeric matrix as well as a slight degree of fiber detachment. Overall, the hybrid composites presented considerably higher stiffness and mechanical strength than the neat polymer and HDPE-alumina composite (19–26\% increase), with no significant change in thermal stability
Recent developments on portable XRF scanner
No full textA prototype X-ray fluorescence (XRF) scanner was developed with the aim of being reliable and portable, best suiting the needs of cultural heritage scientists who constantly face the difficulty of in-situ analysis. The instrument constructed is composed of an exchangeable scanning head (X-ray tube and detector), a motorized x-y stage with a controlling interface and a laptop. With the small stage, it can scan areas up to 20 x 20 cm 2 with a lateral resolution of 1 mm. The system can be transported inside a standard airplane cabin trolley and weights no more than 10 Kg. The controlling interface was programmed in LabView© and the data evaluation is performed on-the-go with a custom-made algorithm. The system has been put to test with a variety of materials and some results are discussed
Diagnostic studies on Nuragic bronzes from Sardinia using a Monte Carlo protocol
No full textIn this investigation, a protocol combining the use of Monte Carlo simulations together with energydispersive
X-ray fluorescence (EDXRF) analysis was used to determine the chemical composition of a set
of objects from a private collection, apprehended by Carabinieri and without archaeological context. The
artefacts are thought to belong to the Nuragic period from Sardinia, Italy (~1500 BCE to 500 CE). The
protocol employed is a powerful and non-destructive method useful for cultural heritage applications where
usually no sampling is allowed. The protocol digitally recreates the objects surface and generates random
photons to interact with the volume. It was herein applied with the main objective of attesting the authenticity
of the objects. The samples were simulated as multi-layered structures composed of bulk material and
outer corrosion layer so the patina thickness and composition could be estimated as well by the X-ray Monte
Carlo (XRMC) package. The method proved useful and powerful, capable of efficiently determining the
composition and structure of most of the objects in a total non-destructive approach, attesting the existence
of at least one fake in the set. Nevertheless, for a more throughout evaluation and a better estimation of
the patina composition, the use of complementary non-destructive analytical techniques and further
enhancements in the code package have shown to be required
Differential X-Ray Attenuation in MA-XRF Analysis for a Non-invasive Determination of Gilding Thickness
No full textWhen investigating gilded artifacts or works of art, the determination of the gilding thickness plays a significant role in establishing restoration protocols or conservation strategies. Unfortunately, this is done by cross-sectioning the object, a destructive approach not always feasible. A non-destructive alternative, based on the differential attenuation of fluorescence radiation from the sample, has been developed in the past years, but due to the intrinsic random nature of X-rays, the study of single or few spots of an objects surface may yield biased information. Furthermore, considering the effects of both porosity and sample inhomogeneities is a practice commonly overlooked, which may introduce systematic errors. In order to overcome these matters, here we propose the extrapolation of the differential-attenuation method from single-spot X-ray fluorescence (XRF) measurements to macro-XRF (MA-XRF) scanning. In this work, an innovative algorithm was developed for evaluating the large amount of data coming from MA-XRF datasets and evaluate the thickness of a given overlapping layer over an area. This approach was adopted to study a gilded copper-based buckle from the sixteenth to seventeenth century found in Rome. The gilded object under investigation was also studied by other analytical techniques including scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). Previous results obtained from SEM-EDS were used to confront the data obtained with the proposed methodology and validate it. MA-XRF elemental distribution maps were fundamental in identifying and choosing sampling areas to calculate the thickness of the gilding layer, avoiding lead islands present in the sample that could negatively influence the results. Albeit the large relative standard deviation, the mean thickness values fell within those found in literature and those obtained from previous studies with SEM-EDS. Surface fissure has been found to deeply affect the results obtained, an aspect that is often disregarded
Multispectral analysis of miniature nuragic bronze flasks
Get PDFMiniaturized bronze flasks represent a small portion of a wide metallurgical production that flourished in Sardinia (Italy) between the Final Bronze Age (FBA) and the Early Iron Age (EIA). They replicate a well-known and symbolic type of object, the pilgrims’ flask, common in all Europe and Mediterranean basin, and have but few archaeological parallels. For these reasons, their characterization can be considered important from an archaeological perspective. Three flasks, preserved at the Antiquarium Arborense museum (Oristano), were analyzed by X-Ray Fluorescence Spectroscopy (XRF) and Raman spectroscopy, integrated by multispectral images. The samples, coming from illegal excavations, posed two problems: establishing their authenticity and investigating the alloy composition of such particular objects. All specimens presented a widespread degradation in the outer surface: XRF and Raman spectroscopy indicated the presence of copper oxides, calcium and copper carbonates deposits. The abscence of Zn, a clear marker of forgeries, was not detected by XRF. In two of the flasks, an unusual Sn content above 20%, was detected. For FBA and EIA, especially regarding southern Europe, Sn was extremely rare, and was possibly used with caution. Further results are presented herein
La Fornarina MA-XRF animation
No full text3D animation of the "La Fornarina" macro X-Ray fluorescence scanning campaign carried by La Sapienza University, Ars Mensurae, National Institute of Nuclear Physics (INFN - Roma TRE) and Gallerie Nazionali Barberini Corsini.This video was made possible thanks to a collaboration between La Sapienza University of Rome, Ars Mensurae, INFN Roma TRE and Gallerie Nazionali Barberini Corsini
Testing the accuracy of the calculation of gold leaf thickness by MC simulations and MA-XRF scanning
Get PDFThe use of X-ray fluorescence (XRF) scanning systems has become a common practice in many application sectors. In multistratified and heterogeneous samples, the simple analysis of an XRF spectrum as a response of the entire sample is not reliable, so different spectral analysis techniques have been proposed to detect the presence of surface stratification. One commonly studied case is that of gilding, i.e., the presence of a superimposing gold-leaf layer. The observation of changes in the net peak ratios of a single element or of several elements in an XRF spectrum is a well-developed practice, but is still not used in the case of XRF scanning (macro-X-Ray fluorescence scanning, MA-XRF), a technique that can be described as the extrapolation of XRF spot analysis to a second dimension, scanning a sample surface instead. This practice can yield information on the overlaying layer thickness, if some properties of the sample are known—or estimated—beforehand, e.g., the overlapping layer’s chemical composition and the matrix effect contribution from the bulk material (thick ratio). This work proposes the use of an algorithm to calculate the thickness distribution of a superimposing gold layer accurately and automatically through the differential attenuation method by using MA-XRF datasets in a total noninvasive manner. This approach has the clear advantage over the traditional spot sampling of allowing the generation of a surface heightmap to better visualize and interpret the data, as well as a considerably larger sample space. Monte Carlo simulations were used to verify the influence of the medium used to adhere the gold leaves to the substrate and to generate known spectra to assess the algorithm’s accuracy
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