Characterization of colorants and opacifiers in roman glass mosaic tesserae through spectroscopic and spectrometric techniques

Several glass mosaic tesserae were recovered during the archeological excavation of the thermal baths at the ‘Villa dei Quintili’ in Rome and dated to the second century ad . This work reports the results of an archeometrical investigation performed, through a multi‐technique approach, on 19 colored opaque tesserae. The aims of the study were (1) the characterization of coloring and opacifying agents used for the production of the glass tesserae and (2) the definition of the technological processes involved. Colorimetric measurements allowed us to classify the tesserae in color groups, while the glassy matrix and the dispersed crystallites were characterized in detail through micro‐Raman spectroscopy, field emission scanning electron microscopy with energy dispersive X‐ray spectroscopy, laser ablation‐inductively coupled plasma‐mass spectrometry, and X‐ray powder diffraction analyses. Most of the glass shows the typical soda‐lime‐silicate composition (except for the orange and red tesserae). Raman results and elemental analysis prove the use of Sn–Pb antimonates to create yellow glass and of Ca‐antimonates for the white tesserae. A mixture of Sn–Pb antimonates and copper ions was used to obtain the emerald green color, while Ca‐antimonates were employed in both copper‐colored and cobalt‐colored blue glass to obtain different shades (blue‐green, dark, and light blue). X‐ray powder diffraction analyses reveal the presence of metallic copper (Cu⁰) and Cu₂O particles (cuprite) in red and orange tesserae, respectively. These results confirm the high technological level reached by the glassmakers of the Imperial Age. Copyright © 2014 John Wiley & Sons, Ltd.     

Quantitative elemental analysis of individual particles with the use of micro‐beam X‐ray fluorescence method and Monte Carlo simulation

The aim of the work was to develop a Monte Carlo (MC) method and combine it with micro‐beam X‐ray fluorescence (XRF) technique for determination of chemical composition of individual particles. A collection of glass micro‐spheres, made of NIST (National Institute of Standards and Technoly) K3089 material of known chemical composition, with diameters in the range of 25–45 µm was investigated. The micro‐spheres were measured in a scanning micro‐beam XRF spectrometer utilising X‐ray tube as a source of primary radiation. Results obtained for low Z elements showed high dependence on particle size. It was found that the root mean square of concentration uncertainty, for the all elements present in the particle, increases with growing sample size. More accurate results were obtained for high Z elements such as Fe–Pb, as compared to others. The elemental percentage uncertainty did not exceed 14% for any particular sample and 6% for the whole group of the measured micro‐spheres as an average. Results obtained by the Monte Carlo method were compared with other analytical approaches. Copyright © 2009 John Wiley & Sons, Ltd.     

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.     

X‐ray fluorescence determination of the manganese valence state and speciation in manganese ores

This work concerns determination of the manganese valence state and speciation by wavelength‐dispersive X‐ray fluorescence analysis. The authors investigated the effect of the manganese valence state and speciation on the intensity of some К‐series lines of the X‐ray emission spectrum for the samples of manganese compounds. The intensities of MnKβ₅ line and MnKβ′ satellite are least influenced by speciation, and they may be used for evaluating the manganese valence state for the samples containing low iron. The intensities of MnKβ″ and MnKβ^x satellites may be employed for assessing the manganese speciation. The results of X‐ray fluorescence determination of the manganese valence state and speciation in the manganese ores of the South Ural deposits agree with the X‐ray diffraction data. The X‐ray fluorescence method is definitely advantageous, because it does not require a complicated process of sample preparation and allows to receive fast information on the manganese valence state and speciation with the purpose to assess the quality of manganese ores. Copyright © 2015 John Wiley & Sons, Ltd.     

The new PIXE‐alpha spectrometer for the analysis of Roman nummi surfaces

The particle‐induced X‐ray emission (PIXE)‐alpha portable spectrometer of the Laboratori Nazionali del Sud has been upgraded to improve X‐ray energy resolution and efficiency. A value of 124 eV at Mn Κα‐line and a factor of 3 were, respectively, achieved. These enhanced capabilities allowed the thin surface examination of 5 Roman nummi, in which previous near‐surface X‐ray fluorescence measurements revealed traces of mercury. In particular, the new version of the PIXE‐alpha spectrometer has allowed the distinction of the 2.19 keV Hg M‐line from the 2.30 keV S K‐line and the 2.34 keV Pb M‐line. Subsequent elemental association has demonstrated a correlation between surface mercury and silver. Copyright © 2012 John Wiley & Sons, Ltd.     

Literature trends in x‐ray emission spectrometry in the period 1990–2000–a review

A quantitative overview is given of the role that x‐ray emission analysis methods, in their various forms, play in the literature for the period from January 1990 to the end of December 2000. The major sources of information were computerized searches through Chemical Abstracts and Web of Science and, specifically for 1998, a manual search through Analytical Abstracts. Areas that are covered in this review pertain to the recent trends in x‐ray emission spectrometry in general and in some specific techniques such as x‐ray fluorescence analysis, synchrotron radiation‐induced and particle‐induced x‐ray emission, total‐reflection and micro‐x‐ray fluorescence analysis. A brief outline of recent developments in the specific fields is given, with emphasis on the various excitation and detection modes, on different application areas and on relative contributions of different countries and languages to the x‐ray emission spectrometry literature. It appears that environmental monitoring and research continue to be particularly important publication fields for x‐ray spectrometry. Copyright © 2003 John Wiley & Sons, Ltd.     

Analysis of the Hoard of Beçin using X‐ray‐based techniques

Four hundred and sixteen silver coins stemming from the Ottoman Empire (16th and 17th centuries) were analyzed to confirm the fineness of the coinage as well as to study the provenance of the alloy used for the coins. As most of the coins showed the typical green patina on their surfaces due to corrosion processes that have led to the depletion of copper in the near surface domains of the silver coins in comparison to their core composition, small samples had to be taken, embedded in synthetic resin, and cross sectioned to investigate the true‐heart metal composition. μ‐synchrotron micro X‐ray fluorescence analysis and μ‐proton‐induced X‐ray emission were applied to determine the silver contents as well as the minor and trace elements. The type of the alloy was investigated as well as if coins minted in different locations demonstrated homogeneous traits concerning the predominant impurities (Au and Bi), which could suggest a common ore. Finally, energy‐dispersive microanalysis in a scanning electron microscope was applied to study the homogeneity/heterogeneity of the coins and the presence of surface enrichments and to explain differences between the μ‐synchrotron micro X‐ray fluorescence analysis and μ‐proton‐induced X‐ray emission measurements concerning the main component. In general, the silver content of the analyzed specimen varies between 90 and 95%. These outcomes have not supported the historical interpretations, which predict that during the period studied, a debasement of approximately 44% of the silver content of the coins should have occurred. Copyright © 2012 John Wiley & Sons, Ltd.     

Micro‐Raman spectroscopic study of cord‐marked pottery decorated with red coatings from Taiwan,ca 2600–1700 B.C.

Micro‐Raman spectroscopy is applied for the first time to identify mineralogical characteristics of ceramic bodies and red coatings on decorative cord‐marked pottery (ca 2600–1700 B.C.) from an archeological site in northern Taiwan. X‐ray diffraction and scanning electron microscopy‐energy dispersive X‐ray spectrometry were used as complementary techniques. The combined results of mineralogical and elemental composition suggest that the pottery items were produced from illitic clays and fired to a temperature less than 800 °C under oxidizing conditions. The slight discrepancy in composition between the red coatings and ceramic bodies possibly indicates a somewhat different source of raw materials and/or clay refining processes used by ancient potters. Additionally, feldspar, hornblende, and pyroxenes detected in the samples are closely related to the main compositions of nearby volcanic rocks, implying that the raw materials could have come from a local source. Copyright © 2010 John Wiley & Sons, Ltd.     

Application of field portable EDXRF spectrometry to analysis of pigments of Levantine rock art

The results of the analyses of elemental composition of red and black pigments of Levantine rock art from La Saltadora rock shelters (Valltorta gorge, Castellón, Spain) are presented in this paper. Nondestructive analyses were carried out using a portable energy dispersive X‐ray fluorescence (EDXRF) spectrometer developed for in situ analysis. The results revealed the strong presence of calcium in all the analyzed locations due to the contribution of the underlying calcareous bedrock and the overlying crust. Iron is the main element detected in red pigments and manganese in black pigments. Iron and calcium ratios have been found indicative of the degree of preservation of the pictorial layer. Trace elements detected in the pigment composition confirm the use of different raw materials. Therefore, this work illustrates the potential of the portable EDXRF spectrometers for in situ analysis of rock art paintings. Copyright © 2010 John Wiley & Sons, Ltd.     

Determination of gold and silver in dross using EDXRF technique

Gold and silver in dross were determined by energy‐dispersive X‐ray fluorescence technique. Sample was prepared by pressed pellet method using microcrystalline cellulose powder as binder, and a method of standard additions was used for quantification. L_β X‐ray of gold (11.4 keV) and K_β X‐ray of silver (24.9 keV) were used for analysis. The measured concentrations of gold and silver were 132 ± 8 and 1181 ± 84 mg kg^?1, respectively. The results were validated by instrumental neutron activation analysis technique. The t‐test indicated that there was no significant difference between results obtained by the two techniques. Energy‐dispersive X‐ray fluorescence is a simple, precise and accurate technique for the determination of gold and silver in dross. Copyright © 2014 John Wiley & Sons, Ltd.     

A portable spectrometer for simultaneous PIXE and XRF analysis

A new portable system that performs simultaneous particle induced x‐ray emission and x‐ray fluorescence analysis is described. It is based on the use of a ²⁴⁴Cm radioactive source as α‐particle and x‐ray emitter, coupled to a Si drift detector. Particular care has been devoted to the choice of the materials surrounding the source. X‐ray fluorescence spectra are presented, showing high detection efficiency for elements from Na (K lines) to Pb (L and M lines). The system can be used as a qualitative tool for ‘fingerprint’ analysis and, in some cases, as a quantitative one. Examples are presented and discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

Non‐invasive approach in the study of polychrome terracotta sculptures: employment of the portable XRF to investigate complex stratigraphy

In the field of conservation science, in situ non‐invasive analytical techniques are widely used to investigate polychrome surfaces as frescoes, mural or easel paintings. Indeed, these techniques allow achieving information on materials composition and they often reduce the micro‐sampling. In this work, in situ non‐invasive techniques have been used to study a complex system, terracotta polychrome sculptures. The presence of the priming, the numerous painted layers and the ground layer spread on a porous material substrate are the main features of these sculptures; therefore, their study requires a scientific approach based on results obtained by different analytical techniques. In order to evaluate potentialities and limitations of the non‐invasive approach to this complex case, the results of energy‐dispersive X‐ray fluorescence (EDXRF), spectrophotometry and optical microscopy have been compared with the data achieved by laboratory analytical investigation as optical and scanning electron microscopy, energy‐dispersive X‐ray microanalysis and Raman spectroscopy. In particular, XRF data collected on several polychrome terracotta are here re‐examined on the basis of the results obtained by laboratory techniques. Even if, in some cases, portable XRF may induce to a wrong interpretation of the stratigraphy, it can be considered a suitable instrument for a preliminary diagnostic campaign of terracotta polychrome sculptures. Copyright © 2011 John Wiley & Sons, Ltd.     

Toward sub‐micro‐XRF working at nanometer range using capillary optics

Capillary optics are used for X‐ray fluorescence micro‐analysis using the Cu Kα line provided by a rotating anode. The excitation beam is focused using a polycapillary lens on a Co–Ti sample. Cylindrical glass capillaries of various diameters are fitted to the X‐ray detector (Energy Dispersive X‐Ray (EDX) analyzer) and displaced along the irradiated zone of the sample. The fluorescence is studied as a function of capillary position. Good agreement is found between experimental and calculated lateral widths of the fluorescence collection, taken into account the cylindrical capillary critical angles relevant in the experiment. The influence of the cylindrical capillary diameter on the signal level detected is studied to estimate the possibility of lateral resolution increase of X‐ray fluorescence technique both in‐lab and in synchrotron environment. Copyright © 2013 John Wiley & Sons, Ltd.     

Energy‐dispersive x‐ray fluorescence analysis of modern coloured glasses from Marinha Grande (Portugal)

The elemental composition (K, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Sr, Ba, Nd and Pb) of modern coloured glasses was obtained by energy‐dispersive x‐ray fluorescence (EDXRF) spectrometry. This non‐destructive technique is frequently used in the analysis of historical glass objects. Two reference glasses were also measured to assess the overall accuracy of the EDXRF method. Reference and unknown glasses were analysed without any preparation. The coloured glass samples studied belong to the Glass Museum of Marinha Grande and were chosen from two distinct collections, which were characterized by the different concentrations of some elements (K, Ti, Cr, Mn, Fe, Ba and Pb). The determined major elements allowed the identification of two raw materials used in glass manufacture, sand and lime. Multivariate statistical analysis, namely principal component extraction, simplified the identification of some of the colouring chemical elements, associating them with the different colours of the glass objects. Copyright © 2003 John Wiley & Sons, Ltd.     

Micro‐beam x‐ray fluorescence analysis of individual particles with correction for absorption effects

A method of correction for absorption effects in micro‐beam x‐ray fluorescence analysis is described. A fast, energy‐dispersive, silicon drift detector (SDD) was used to measure the primary x‐ray beam transmitted through the sample. The absorption factors were calculated using the data acquired with the SDD. The possibility of using the coherently, incoherently and multiple scattered primary radiation for determining the mass of individual particles was examined. The proposed methods were validated with the use of NIST K3089 glass micro‐spheres of known composition. Copyright © 2006 John Wiley & Sons, Ltd.     

Deconvolution of distinct lithology chemistry through oversampling with the Mars Science Laboratory Alpha Particle X‐Ray Spectrometer

The Alpha Particle X‐Ray Spectrometer (APXS) determines the chemical composition of Martian rocks and soils on‐board both active National Aeronautics and Space Administration (NASA) rovers using X‐ray emission spectroscopy through complementary particle‐induced X‐ray emission (PIXE) and X‐ray fluorescence (XRF) excitation methods. A single APXS spectrum represents the sum of the signals from within the instrument's field of view (FOV). In the past, features smaller than the FOV have been investigated through repeated measurements with stepwise lateral offsets. These lateral offsets allow for empirically extracting, through elemental correlations, distinct compositions of different features. Here, we present a novel analytical method for deconvolving the endmember chemistry of visually distinct components through oversampling and the integrated analysis of the elemental data and supporting images. We discuss specifically the method's application to three targets investigated by the Mars Science Laboratory rover Curiosity during its traverse, as well as the added information that can be gained from this method in the future. Copyright © 2016 John Wiley & Sons, Ltd.     

Depth profiling of dopants implanted in Si using the synchrotron radiation based high‐resolution grazing emission technique

We report on the surface‐sensitive grazing emission X‐ray fluorescence technique combined with synchrotron radiation excitation and high‐resolution detection to realize depth‐profile measurements of Al‐implanted Si wafers. The principles of grazing emission measurements as well as the benefits offered by synchrotron sources and wavelength‐dispersive detection setups are presented. It is shown that the depth distribution of implanted ions can be extracted from the dependence of the X‐ray fluorescence intensity on the grazing emission angle with nanometer‐scale precision provided that an analytical function describing the shape of the depth distribution is assumed beforehand. If no a priori assumption is made, except a bell shaped form for the dopant distribution, the profile derived from the measured angular distribution is found to reproduce quite satisfactorily the depth distribution of the implanted ions. Copyright © 2012 John Wiley & Sons, Ltd.     

A new approach to synchrotron energy‐dispersive X‐ray diffraction computed tomography

A new data collection strategy for performing synchrotron energy‐dispersive X‐ray diffraction computed tomography has been devised. This method is analogous to angle‐dispersive X‐ray diffraction whose diffraction signal originates from a line formed by intersection of the incident X‐ray beam and the sample. Energy resolution is preserved by using a collimator which defines a small sampling voxel. This voxel is translated in a series of parallel straight lines covering the whole sample and the operation is repeated at different rotation angles, thus generating one diffraction pattern per translation and rotation step. The method has been tested by imaging a specially designed phantom object, devised to be a demanding validator for X‐ray diffraction imaging. The relative strengths and weaknesses of the method have been analysed with respect to the classic angle‐dispersive technique. The reconstruction accuracy of the method is good, although an absorption correction is required for lower energy diffraction because of the large path lengths involved. The spatial resolution is only limited to the width of the scanning beam owing to the novel collection strategy. The current temporal resolution is poor, with a scan taking several hours. The method is best suited to studying large objects (e.g. for engineering and materials science applications) because it does not suffer from diffraction peak broadening effects irrespective of the sample size, in contrast to the angle‐dispersive case.     

Novel high‐temperature reactors for in situ studies of three‐way catalysts using turbo‐XAS

Two novel high‐temperature reactors for in situ X‐ray absorption spectroscopy (XAS) measurements in fluorescence are presented, each of them being optimized for a particular purpose. The powerful combination of these reactors with the turbo‐XAS technique used in a dispersive‐XAS beamline permits the study of commercial three‐way catalysts under realistic gas composition and temporal conditions.     

A furnace and environmental cell for the in situ investigation of molten salt electrolysis using high‐energy X‐ray diffraction

This paper describes the design, construction and implementation of a relatively large controlled‐atmosphere cell and furnace arrangement. The purpose of this equipment is to facilitate the in situ characterization of materials used in molten salt electrowinning cells, using high‐energy X‐ray scattering techniques such as synchrotron‐based energy‐dispersive X‐ray diffraction. The applicability of this equipment is demonstrated by quantitative measurements of the phase composition of a model inert anode material, which were taken during an in situ study of an operational Fray–Farthing–Chen Cambridge electrowinning cell, featuring molten CaCl₂ as the electrolyte. The feasibility of adapting the cell design to investigate materials in other high‐temperature environments is also discussed.