Micro‐EDXRF investigation of Chalcolithic gold ornaments from Portuguese Estremadura

Chalcolithic gold artefacts assigned to the Bell Beaker Culture in Portuguese Estremadura were analysed by micro‐energy dispersive X‐ray fluorescence spectrometry. These high‐status jewels comprise beads of tubular, spiral and double‐conical type, a spiral ring and a wire fragment. The collection is mainly composed of gold with 8.7–16.3 wt% Ag and <0.04 wt% Cu. Additionally, there is a typologically uncommon double‐conical bead showing a lower Ag content (6.7 wt%). The relative intensity of the Ag‐Kα and Ag‐Lα X‐rays from artefacts established the existence of a surface layer depleted in silver, while the reasonable effective penetration depth of the Ag‐Kα (about 25–30 μm) provided suitable results for such high fineness gold alloys. A uniform Au–Ag composition at the joint indicates that the double‐conical bead was made by joining two sheets without solder. Overall, the collection shows a composition that is similar to known Chalcolithic gold in Portuguese Estremadura but different from coeval gold in Southwestern Iberian Peninsula. The distinct compositional pattern of Chalcolithic gold in Portuguese Estremadura seems to be inconsistent with the natural variability of silver content in alluvial deposits of gold in Iberian Peninsula, thus suggesting a continuous use of particular sources and limited exchange of nuggets and jewels with the neighbouring region. Copyright © 2017 John Wiley & Sons, Ltd.     

Complementary use of X‐ray methods to study ancient production remains and metals from Northern Portugal

Archaeological artefacts recovered at Castanheiro do Vento (Northern Portugal) were characterised by integrating macro and micro‐energy dispersive X‐ray fluorescence spectrometry (EDXRF) and scanning electron microscopy with X‐ray microanalysis. The collection includes metallurgical remains (ceramic crucibles, a metallic nodule and a vitrified fragment) and metals (tools and ornaments) whose chronology spans from the Chalcolithic to the Roman Age. The study of production remains was able to identify distinct copper‐based metallurgical operations including the smelting of copper ores, the melting of copper and tin and/or the melting of bronze scrap. Micro‐EDXRF identified copper and arsenical copper tools as well as bronze and leaded bronze ornaments. The composition of tools (Cu with varying As contents: 0.46–3.6%) reveals an incipient technology, typical of the Chalcolithic till the Middle Bronze Age. On the contrary, ornaments are composed by different alloys – low tin bronze (4.8% Sn), high tin bronze (14.9% Sn) and high tin‐leaded bronze (16.5% Sn and 2.4% Pb) ? evidencing technological and economic choices that clearly indicate a late period such as the Roman Age. In conclusion, this multiproxy approach was able to study those ancient artefacts with a minimum impact on their archaeological and museological significance while providing important answers to the interpretation of the archaeological settlement and to better understand the metallurgical evolution in the Portuguese territory. Copyright © 2014 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.     

Energy dispersive X‐ray fluorescence analysis of archeological metal artifacts from the Final Bronze Age

Energy dispersive X‐ray fluorescence (EDXRF) is widely used in the study of archeological metal artifacts, heritage and art history, where the fragile nature of the objects requires the use of noninvasive techniques such as the EDXRF, which in addition, is fast and very affordable. An EDXRF analysis of copper‐based artifacts from Late Bronze Age metal hoards from Central Portugal is presented. The EDXRF measurements were carried out by using an X‐ray tube with a Mo anode and a commercial Si‐PIN detector. The data acquisition was performed by keeping small distances between the X‐ray window, the sample and the detector. Both patinated and polished areas were analyzed: the relative composition of the artifacts was inferred from the fluorescence spectra obtained. Copyright © 2012 John Wiley & Sons, Ltd.     

A simple calibration procedure of polycapillary based portable micro‐XRF spectrometers for reliable quantitative analysis of cultural heritage materials

Portable micro‐X‐ray fluorescence (micro‐XRF) spectrometers mostly utilize a polycapillary X‐ray lens along the excitation channel to collect, propagate and focus down to few tens of micrometers the X‐ray tube radiation. However, the polycapillary X‐ray lens increases the complexity of the quantification of micro‐XRF data because its transmission efficiency is strongly dependent on the lens specifications and the propagated X‐ray energy. This feature results to a significant and not easily predicted modification of the energy distribution of the primary X‐ray tube spectrum. In the present work, we propose a simple calibration procedure of the X‐ray lens transmission efficiency based on the fundamental parameters approach in XRF analysis. This analytical methodology is best suited for compact commercial and portable micro‐XRF spectrometers. The developed calibration procedure is validated through the quantitative analysis of a broad range of samples with archeological relevance such as glasses, historical copper alloys, silver and gold alloys offering an overall accuracy of less than 10%–15%. Copyright © 2015 John Wiley & Sons, Ltd.     

Micro‐Raman innovative methodology to identify Ag–Cu mixed sulphides as tarnishing corrosion products

Mixed Cu–Ag alloys with different compositions have been produced and subjected to an accelerated sulphidation process which causes the development of a mixed sulphide‐rich corroded film on their surface. It was called tarnishing, that is, the formation of a blue‐brownish patina when Cu–Ag alloys are exposed in a sulfur‐containing atmosphere. The structures of the pristine alloys have been determined by the combined analytical techniques as scanning electron microscopy energy dispersive X‐ray microanalysis and X‐ray diffraction. The experimental conclusions confirmed the occurrence of micro phase separation with the formation of different dendritic domains of about 10 µm in width. The sulphidized samples were firstly investigated by optical microscopy and X‐ray diffraction in order to verify the homogeneity of the patina and to identify the different AgCuS phases appearing on the alloy surfaces. It was observed that, despite the inherent micro‐heterogeneity of the alloys, the sulphide layer was throughout uniform in composition at the micro‐scale. The complex scenario of the relative stability of all the various mixed sulphides involved was then explored by micro‐Raman spectroscopy (μ‐RS), pointing out that the Cu‐for‐Ag substitution in the crystal lattice of the mixed Ag–Cu sulphides caused a monotonous blue shift of the vibrational wavenumbers in Raman spectra. This study has unveiled microscopic details of the tarnishing process, furnishing an innovative, cheap and non‐destructive methodology based on μ‐Raman spectroscopy for the evaluation of the silver‐copper artefacts via the compositions of their corroded products. Copyright © 2016 John Wiley & Sons, Ltd.     

Use of the CEARXRF GUI‐Based Monte Carlo–Library Least‐Squares (MCLLS) Code for the Micro‐Focused EDXRF analyzer

The CEARXRF GUI‐Based Monte Carlo–Library Least‐Squares (MCLLS) Code is demonstrated with results from a micro‐focused EDXRF analyzer, which can be used to calculate elemental weight fractions in metal alloys or rock samples accurately by library least‐squares regression of the measured X‐ray spectrum with computer‐generated elemental library spectra. An elemental stratified sampling variance reduction technique has been implemented in the CEARXRF5 code, which equalizes the statistical precision of the elemental libraries within the measured sample independent of the relative elemental amounts that are present. Also, an improved Si(Li) detector response function (DRF) has been obtained for micro‐focused X‐ray fluorescence (XRF) analyzers, and the DRF parameters are obtained based on regression from pure elemental experimental spectra. It is demonstrated that the resulting MCLLS approach can greatly improve the accuracy of elemental XRF analysis results. Copyright © 2011 John Wiley & Sons, Ltd.     

Inclusions and metal composition of ancient copper‐based artefacts: a diachronic view by micro‐EDXRF and SEM‐EDS

A diachronic view of the metallurgy in the Portuguese territory during the first three millennia after its appearance in the Iberian Peninsula is presented based on the current state of the art. Results of micro‐energy dispersive X‐ray fluorescence (micro‐EDXRF) analyses made on metal artefacts to determine their composition and scanning electron microscopy with energy dispersive analysis (SEM‐EDS) analyses to study microstructural features as inclusions are shown to illustrate trends and specificities of each chronological period. Generally, in early periods, namely during the Copper Age and first stages of the Bronze Age, unalloyed copper and arsenical copper were at use, and only by the Late Bronze Age (LBA) did tin bronze substitute almost completely the previous role of copper. In the Early Iron Age, during the Orientalising period, a general decrease in the average tin content in bronzes seems to happen. Regarding the inclusions observed in the metal matrix, these seem to suffer a diversification with the appearance of tin bronzes. By the Copper Age, only Cu? O and Cu? As? O inclusions are observed, while by the LBA Cu? S inclusions become regular, besides others less frequent, as Sn? O, Cu? S? Fe and Pb globules. Overall, with the present analytical study, the complementary character of micro‐EDXRF and SEM‐EDS in the study of ancient metals is demonstrated, providing a first general overview of the ancient metallurgy at the Portuguese territory which is of key importance to specific investigations of the future. Copyright © 2011 John Wiley & Sons, Ltd.     

EDXRF analysis of metal artefacts from the grave goods of the Royal Tomb 14 of Sipán,Peru

Several metallic sheets (about 1 mm thick) from the grave goods of the Royal Tomb 14 (Sipán, Peru) were characterised by energy dispersive X‐ray fluorescence analysis, using both a portable instrument and a capillary collimated spectrometer to investigate details, and micro‐Raman spectroscopy. The samples, belonging to the clothing of the warrior priest, resulted composed of thin copper sheets or tumbaga (natural alloy of copper, silver and gold). They were unearthed covered with typical green patina, formed during their long burial and characterised mainly by copper minerals, such as malachite, atacamite and magnetite identified with micro‐Raman spectroscopy. Due to deterioration of the original alloy, the artefacts analyzed in this work were rather fragile and could not resist hard polishing aimed at cleaning off corrosion products. So a non‐destructive qualitative EDXRF analysis was performed to identify the elemental composition of the metal alloy and a quantitative estimation was made applying the fundamental parameter method. The presence of superficial patina layer and the non‐homogeneous composition was also taken into account during calculation. The data obtained, compared to published results from several artefacts found in the nearby tombs, have been treated with a hierarchical statistic analysis. Copyright © 2011 John Wiley & Sons, Ltd.     

Assessment of chemical elements in cosmetics' eyeshadows by X‐ray fluorescence and International Nomenclature of Cosmetic Ingredients characterization

Energy dispersive X‐ray fluorescence (EDXRF) technique, as a qualitative and quantitative analysis, was used for inorganic chemical elements determination (K, S, Cl, Al, Si, Ca, Ti, Mn, Fe, Pb, Zn, Rb, and Bi) in eyeshadows for safe human use. International Nomenclature of Cosmetic Ingredients standardized nomenclature was used for labels investigation to obtain data on legal regularity. Data of 23 samples were clustered by similarity, measuring relative concentrations of detected chemical elements. Calculating the correlation among such values, a similarity matrix was used to generate a dendrogram. Pb was found in samples silver color S12E and copper color S22I above permissible limits (20 μg/g). Same composition was reported for the pink (S01A), black (S02A), and brown (S03A) samples, but the same chemical elements were not detected by EDXRF in them. The best correlation was found between samples S08D and S23 J (0.961). The least correlation was 0.0012 between S01A and S12E. The clustering analysis showed 7 groups of similar samples according to EDXRF data. Relations among 6 eyeshadows' colors and chemical compositions were discovered by using decision trees, where the most determinant elements were Mn, S, Cl, Ca, and Fe, in this order. Commercial regularization and International Nomenclature of Cosmetic Ingredients standardization of eyeshadows in Brazil are not fully complied by the manufacturers of the investigated brands.     

Measurement of the X‐ray mass attenuation coefficients of silver in the 5–20 keV range

The X‐ray mass attenuation coefficients of silver were measured in the energy range 5–20 keV with an accuracy of 0.01–0.2% on a relative scale down to 5.3 keV, and of 0.09–1.22% on an absolute scale to 5.0 keV. This analysis confirms that with careful choice of foil thickness and careful correction for systematics, especially including harmonic contents at lower energies, the X‐ray attenuation of high‐Z elements can be measured with high accuracy even at low X‐ray energies (<6 keV). This is the first high‐accuracy measurement of X‐ray mass attenuation coefficients of silver in the low energy range, indicating the possibility of obtaining high‐accuracy X‐ray absorption fine structure down to the L₁ edge (3.8 keV) of silver. Comparison of results reported here with an earlier data set optimized for higher energies confirms accuracy to within one standard error of each data set collected and analysed using the principles of the X‐ray extended‐range technique (XERT). Comparison with theory shows a slow divergence towards lower energies in this region away from absorption edges. The methodology developed can be used for the XAFS analysis of compounds and solutions to investigate structural features, bonding and coordination chemistry.     

Determination of the provenance of medieval silver coins: potential and limitations of x‐ray analysis using photons,electrons or protons

One hundred and fifty seven ‘Tiroler Kreuzer’, a medieval currency from the county of Tyrol/Austria, were analysed in order to determine their place of mintage. The silver coins were produced during the 15th century in the mints of Merano (South Tyrol) and Hall (North Tyrol) but they have no marks or punches which would allow a clear distinction. Energy‐dispersive x‐ray fluorescence analysis (EDXRF) was applied without sampling in order to determine the silver contents and also minor (Cu, Pb, Bi) and trace elements (Fe, Au, Hg, Ni). Owing to corrosion processes, which changed the chemical composition of the surfaces of the coins, investigations of cross‐sections were necessary using energy‐dispersive x‐ray microanalysis in a scanning electron microscope (SEM/EDX) to determine the stage of corrosion and the Ag concentration of the core of the coins. The results showed differences of up to 50% between the composition of the core and the surface. Finally, proton‐induced x‐ray emission (PIXE) at an external proton beam was applied, in order to detect also Ni, an element which could not be measured by either EDXRF or SEM/EDX in the ppm range. The data show a clear difference in the Ni content between the coins from Merano (～0.1% Ni) and Hall (～0.01% Ni). Copyright © 2003 John Wiley & Sons, Ltd.     

EDXRF with an audio digitizer

We utilized an audio digitizer in energy‐dispersive X‐ray fluorescence (EDXRF) with a silicon drift detector and achieved a full width at half maximum (FWHM) of 178 eV at Mn Kα (92‐µs peaking time). To confirm the ability of EDXRF with an audio digitizer, we also examined energy versus channel number linearity and output count rate. We applied it to EDXRF analysis of (ZnCd)S : Ag and showed a proper energy versus channel number linearity from 5.9 keV (Mn Kα) to 26.1 keV (Cd Kβ). And, the maximum output count rate of more than 10 kcps was obtained with 23‐µs peaking time (296‐eV FWHM). Copyright © 2011 John Wiley & Sons, Ltd.     

Analysis of the spectacular gold and silver from the Moche tomb ‘Señora de Cao’

On the north coast of present‐day Peru, between the Andes and the Pacific Ocean, approximately between 100 and 600 ad , the Moche civilization prospered. The Moche were very sophisticated artisans and metal smiths, so that they are considered the finest producers of jewels and artifacts of the region. Their metalworking ability was impressively demonstrated by the excavations of the tomb of the ‘Lady of Cao’ (dated around third–fourth century ad ) discovered by Regulo Franco in 2005. Impressive is the beauty of the artifacts, and also the variety of metallurgical solutions, demonstrated by not only the presence of objects composed of gold and silver alloys but also of gilded copper, gilded silver, and tumbaga, a poor gold Cu‐Au alloy subject to depletion gilding. About 100 metal artifacts from the tomb of the Lady of Cao, never before analyzed, were studied by using various portable equipments based on following non‐destructive and non‐invasive methods:

• energy‐dispersive X‐ray fluorescence with completely portable equipments;
• transmission of monenergetic X‐rays;
• radiographic techniques; and
• optical microscopy.

Gold objects and gold areas of nose decorations are characterized by approximately the same composition, that is, Au = (79.5 ± 2.5) %, Ag = (16 ± 3) %, and Cu = (4.5 ± 1.5) %, while silver objects and silver areas of the same nose decorations show completely erratic results, and a systematic high gold concentration. Many gilded copper and tumbaga artifacts were identified and analyzed. Further, soldering gold–silver was specifically studied by radiographs. Additional measurements are needed, particularly because of the suspect that depletion gilding was systematically employed also in the case of some nose decorations. Copyright © 2016 John Wiley & Sons, Ltd.     

HOPG as powerful x‐ray optics

A new method of producing strongly bent highly oriented pyrolytic graphite (HOPG) is presented. The method allows one to make a crystal of almost arbitrary shape, but has some thickness limits. A review of the results obtained on this type of crystal by different laboratories during the last 10 years is given. An x‐ray intensity gain from a synchrotron radiation source and Mo Kα tube beams of one order of magnitude could be achieved when using a crystal of optimized shape. The application of the crystals for secondary monochromatization in EDXRF improves by one order of magnitude the detection limits for the elements of interest. Copyright © 2003 John Wiley & Sons, Ltd.     

Synchrotron‐induced EDXRF determination of uranium and thorium in mixed uranium–thorium oxide pellets

Uranium and thorium in their mixed oxides were determined by synchrotron‐induced energy dispersive X‐ray fluorescence (EDXRF) spectrometry. Mixed oxide calibration mixtures containing uranium and thorium in different relative amounts and approximately fixed amount of yttrium were prepared in the form of pellets. The EDXRF spectra of the pellets were measured at the microfocus XRF (BL‐16) beam line of Indus‐2 synchrotron radiation facility (Raja Ramanna Centre of Advanced Technology, Indore, India). Characteristic X‐ray lines U Lα, Th Lα, and Y Kα were used as analyte lines. Calibration plot for the determination of uranium was prepared by plotting amount ratios of U and Y against the intensity ratios of U Lα and Y Kα. Similarly, a calibration plot for thorium analysis was also made. The amounts of uranium and thorium in the sample mixtures prepared in similar way as the calibration mixtures were determined using the aforementioned calibration plots. The precision values obtained for uranium and thorium determinations were found to be 0.3 and 0.2% (relative standard deviation, 1σ), respectively. The EDXRF results deviated from the expected values by 1% for uranium and 0.9% for thorium determinations. These analytical features are much superior compared with laboratory‐based analysis results. Copyright © 2012 John Wiley & Sons, Ltd.     

Determination of cobalt marker in cow ruminal fluid by EDXRF and SRTXRF

This article describes a comparison of conventional energy‐dispersive X‐ray fluorescence (EDXRF) and synchrotron radiation total‐reflection X‐ray fluorescence (SRTXRF) for Co determination in ruminal fluid from Holstein cow. This element is used as marker for animal nutrition studies. For EDXRF, 200 µl of the sample were dried on 6.35 µm Mylar film at 60 °C. The excitation was carried out using an X‐ray tube with Mo target and Zr filter operated at 30 kV/20 mA. For SRTXRF, 10 µl of the sample were pipetted on a Lucite carrier and dried at 60 °C. In both the techniques, Ga was used as internal standard and the acquisition time was 200 s. The trueness of both techniques was evaluated through the standard addition method, the recoveries obtained by SRTXRF and EDXRF were 76 and 99%, and the limits of detection, 13 and 240 µg l^?1, respectively. Copyright © 2011 John Wiley & Sons, Ltd.     

A Roman bronze statuette with gilded silver mask from Sardinia: an EDXRF study

A Roman bronze statuette from the 2nd Century BC was recovered from a nuragic sanctuary close to Florinas, in the north of Sardinia. The facial portion of the statuette is covered by a silver mask, partially gilded and attached to the bronze by tin-lead welding. The silver mask was carefully analyzed by portable energy-dispersive X-ray fluorescence (EDXRF), a non-destructive and non-invasive method. The aim of the analysis was to reconstruct the layered structure of the silver gilt mask, and to determine homogeneity and thickness of the gold, silver and lead–tin sheets. This is possible by using the internal ratio of the X-ray lines, i.e. starting from the surface, Au (Lα/Lβ), Ag (Kα/Kβ), Au-Lα/Ag-Kα and Pb (Lα/Lβ).The results were compared with those obtained with simulated X-ray spectra, obtained both experimentally and by using the Monte Carlo simulation technique.     

银纳米颗粒/多孔硅复合材料的制备与气敏性能研究

采用双槽电化学腐蚀法以电阻率为10-15 Ω·cm的p型<100>晶向的单晶硅片制备了孔径约为1.5 μm, 孔深约为15-20 μm的p型多孔硅, 并以此多孔硅作为基底采用无电沉积法通过调控沉积时间在其表面沉积了不同厚度的银纳米颗粒薄膜. 采用扫描电子显微镜和X 射线衍射仪表征了银纳米颗粒/多孔硅复合材料的形貌和微观结构, 结果表明银纳米颗粒较均匀的分布于多孔硅的表面上且沉积时间对产物的形貌有重要影响. 采用静态配气法在室温下研究了银纳米颗粒/多孔硅复合材料对NH₃的气敏性能. 气敏测试结果表明沉积时间对产物的气敏性能影响较大. 当沉积时间较短时, 适量银纳米颗粒掺杂的多孔硅复合材料由于其较高的比表面积以及特殊的形貌和结构, 对NH₃气体表现出较高的灵敏度、优良的响应/恢复性能. 室温下, 其对50 ppm 的NH₃气体的气敏灵敏度可以达到5.8左右.