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Autor*in

  • Reinholz, Uwe (121)
  • Radtke, Martin (65)
  • Riesemeier, Heinrich (35)
  • Buzanich, Günter (16)
  • Emmerling, Franziska (12)
  • Guilherme Buzanich, Ana (12)
  • Reiche, I. (7)
  • Scharf, O. (7)
  • Streli, C. (7)
  • Constantinescu, B. (6)
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Erscheinungsjahr

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Dokumenttyp

  • Zeitschriftenartikel (71)
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  • Gold (12)
  • Synchrotron radiation (9)
  • XRF (8)
  • XANES (6)
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  • BAMline (5)
  • Color X-ray camera (5)
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Organisationseinheit der BAM

  • 6 Materialchemie (26)
  • 6.3 Strukturanalytik (26)
  • 1 Analytische Chemie; Referenzmaterialien (7)
  • 1.0 Abteilungsleitung und andere (7)
  • 4 Material und Umwelt (1)
  • 4.4 Thermochemische Reststoffbehandlung und Wertstoffrückgewinnung (1)
  • 5 Werkstofftechnik (1)
  • 5.0 Abteilungsleitung und andere (1)
  • 5.1 Materialographie, Fraktographie und Alterung technischer Werkstoffe (1)

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A study on gold and copper provenance for Romanian prehistoric objects using micro-SR XRF (2011)
Constantinescu, B. ; Vasilescu, A. ; Radtke, Martin ; Reinholz, Uwe
This study intends to clarify the metal provenance of gold archaeological items using the variation of the Au–Ag ratio and the presence of trace elements as Sn, Sb, Te, and Pb, concentrating on gold Dacian Koson coins, recovered recently. It also extends the area of our investigations to the copper provenance of Bronze Age artifacts—axes, sickles, and celts—found on Romanian territory. The experiments were performed by micro-SR XRF at BESSY Berlin, at the BAM-line facility. Two types of coins (Koson, with and without monogram) were analysed. The conclusions we reached were that most of the monogram coins are made from refined gold (3–5% Ag, less than 0.5% Cu), while the without monogram coins are made from native Transylvanian gold (9–20% Ag, 0.5–2% Cu), of alluvial origin, proved by the presence of Sn, Sb and Te embedded in the gold. The problem of provenance for prehistoric Romanian copper and bronze objects consists in linking their elemental compositional patterns to the ones of the Bronze Age regional mines from Bulgaria, Serbia or Transylvania, most likely used as ore sources for their manufacture. The studied samples present relevant traces of As, Ag, Sb, and Co, suggesting the most probable use of copper from Serbia or northern Bulgaria for their manufacture.
Iodine in alluvial platinum-palladium nuggets: evidence for biogenic precious-metal fixation (2011)
Cabral, A.R. ; Radtke, Martin ; Munnik, F. ; Lehmann, B. ; Reinholz, Uwe ; Riesemeier, Heinrich ; Tupinambá, M. ; Kwitko-Ribeiro, R.
Synchrotron radiation-induced X-ray fluorescence (SR-XRF) spectrometry was applied to determine iodine concentrations in alluvial Pt–Pd aggregates with delicate morphological features from Córrego Bom Sucesso, Minas Gerais, Brazil. The millimetre-sized botryoidal and rod-shaped grains of alluvial Pt–Pd–Hg intermetallic compounds have surprisingly high concentrations of iodine, in the range from 10 to ~ 120 μg/g. Because iodine is a strongly biophile element, known to be enriched in peatlands and plant remains in soils by microbial activity, its concentration in the Pt–Pd nuggets suggests biogenic precious-metal fixation in the aqueous alluvial milieu. Biogenic and inorganic processes, such as bioreduction and electrochemical metal accretion, could mutually have contributed to the growth of nanoparticles, formed on organic templates, to millimetric Pt–Pd nuggets.
SRXRF-measurements at non-planar objects: automatic determination of the angle of incidence of the exciting X-ray (2011)
Grunewald, Christian ; Radtke, Martin ; Reinholz, Uwe ; Buzanich, Günter ; Riesemeier, Heinrich
For quantitative SRXRF measurements the angle of incidence of the incoming X-ray beam is an important factor. When the sample is focused by a long-range-microscope, the determination of the angle can be automatized using a simple algorithm. This was developed to improve the orientation of especially round or ornate samples. As a side effect the three dimensional surface can be reconstructed, too.
The charge of solid-liquid interfaces measured by X-ray standing waves and streaming current (2010)
Brücher, M. ; von Bohlen, A. ; Jacob, P. ; Franzke, J. ; Radtke, Martin ; Reinholz, Uwe ; Müller, Bernd R. ; Scharf, Oliver ; Hergenröder, R.
Measurements of ion distributions at a charged solid–liquid interface using X-ray standing waves (XSW) are presented. High energy synchrotron radiation (17.48 keV) is used to produce an XSW pattern inside a thin water film on a silicon wafer. The liquid phase is an aqueous solution containing Br and Rb ions. The surface charge is adjusted by titration. Measurements are performed over a pH range from 2.2–9, using the native Si oxide layer and functional (amine) groups as surface charge. The Debye length, indicating the extension of the diffuse layer, could be measured with values varying between 1–4 nm. For functionalized wafers, the pH dependent change from attraction to repulsion of an ion species could be detected, indicating the isoelectric point. In combination with the measurement of the streaming current, the surface charge of the sample could be quantified.
New insights of the nucleation and growth process of gold nanoparticles via in situ coupling of SAXS and XANES (2010)
Polte, Jörg ; Kraehnert, R. ; Radtke, Martin ; Reinholz, Uwe ; Riesemeier, Heinrich ; Thünemann, Andreas F. ; Emmerling, Franziska
Although metallic nanoparticles play an important role in the area of nanotechnology, a coherent mechanistic explanation for the evolution of the particles during their chemical synthesis has not yet been provided in many cases. To gain a profound understanding of the growth mechanism of colloidal nanoparticles, new approaches using Small Angle X-Ray Scattering (SAXS) combined with X-ray absorption near-edge structure (XANES) are presented. This combination allows for insights into two prominent syntheses routes of gold nanoparticles (GNP): The 'slow' reaction using sodium citrate (30-90 min) as a reducing agent and the 'fast' reaction employing NaBH4 (within few seconds). In the first case data derived with the coupled XANES and SAXS suggests a four-step particle formation mechanism. For the second system a time resolution in the order of 100-200 ms was achieved by coupling a common laboratory SAXS instrument with a microstructured mixer, which allows data acquisition in a continuous-flow mode. The results indicate a coalescence driven growth process. Based on the capabilities to deduce the size, number and polydispersity of the particles, the results of both methods enable the development of mechanistic schemes explaining the different phases of particle formation and growth, thus providing a basis for improved control over the synthesis processes.
Synchrotron radiation induced X-ray fluorescence for the characterization of ancient gold objects (2009)
Radtke, Martin ; Reinholz, Uwe ; Riesemeier, Heinrich
X-ray scattering in X-ray fluorescence spectra with X-ray monochromatic, polarised excitation - modelling, experiment, and Monte-Carlo simulation (2011)
Hodoroaba, Vasile-Dan ; Radtke, Martin ; Reinholz, Uwe ; Riesemeier, Heinrich ; Vincze, L. ; Reuter, Dirk
A systematic series of measurements has been carried out with monochromatic X-ray excitation with synchrotron radiation in order to check a physical model on X-ray scattering. The model has recently been successfully tested for the case of polychromatic, unpolarised excitation emitted by an X-ray tube. Our main purpose is the modelling of a physical background in X-ray fluorescence spectra, so that improved quantitative results can be achieved especially for strongly scattering specimens. The model includes single Rayleigh and Compton scattering in the specimen, the effect of bound electrons, the challenging Compton broadening and the polarisation degree. Representative specimens, measurement geometries and excitation energies have been selected with synchrotron monochromatic light at BAMline/BESSY II. Monte-Carlo simulations have been also carried out in order to evaluate the quality of the results achieved with the model.
Compact pnCCD-based X-ray camera with high spatial and energy resolution: a color X-ray camera (2011)
Scharf, Oliver ; Ihle, S. ; Ordavo, I. ; Arkadiev, V. ; Bjeoumikhov, A. ; Bjeoumikhova, S. ; Buzanich, Günter ; Gubzhokov, R. ; Günther, A. ; Hartmann, R. ; Kühbacher, M. ; Lang, M. ; Langhoff, N. ; Liebel, A. ; Radtke, Martin ; Reinholz, Uwe ; Riesemeier, Heinrich ; Soltau, H. ; Strüder, L. ; Thünemann, Andreas F. ; Wedell, R.
For many applications there is a requirement for nondestructive analytical investigation of the elemental distribution in a sample. With the improvement of X-ray optics and spectroscopic X-ray imagers, full field X-ray fluorescence (FF-XRF) methods are feasible. A new device for high-resolution X-ray imaging, an energy and spatial resolving X-ray camera, is presented. The basic idea behind this so-called 'color X-ray camera' (CXC) is to combine an energy dispersive array detector for X-rays, in this case a pnCCD, with polycapillary optics. Imaging is achieved using multiframe recording of the energy and the point of impact of single photons. The camera was tested using a laboratory 30 µm microfocus X-ray tube and synchrotron radiation from BESSY II at the BAMline facility. These experiments demonstrate the suitability of the camera for X-ray fluorescence analytics. The camera simultaneously records 69696 spectra with an energy resolution of 152 eV for manganese Kα with a spatial resolution of 50 µm over an imaging area of 12.7 × 12.7 mm². It is sensitive to photons in the energy region between 3 and 40 keV, limited by a 50 µm beryllium window, and the sensitive thickness of 450 µm of the chip. Online preview of the sample is possible as the software updates the sums of the counts for certain energy channel ranges during the measurement and displays 2-D false-color maps as well as spectra of selected regions. The complete data cube of 264 × 264 spectra is saved for further qualitative and quantitative processing.
Further metallurgical analyses on silver coins of Trajan (AD 98-117) (2011)
Rodrigues, M. ; Cappa, F. ; Schreiner, M. ; Ferloni, P. ; Radtke, Martin ; Reinholz, Uwe ; Woytek, B. ; Alram, M.
Within an interdisciplinary project, preliminary results of which were published in 2007, a group of 65 silver coins (denarii) of Trajan, evenly distributed over the entire span of his reign (2nd to 6th consulate), as well as 3 coins from the reign of his predecessor, the emperor Nerva (AD 96–98), had been acquired on the coin market. These pieces could be cross-sectioned in order to carry out analyses. Measurements were performed with µ-XRF and µ-SRXRF to check the fineness of the denarius alloy as well as to investigate if the coins of the different consulates showed distinct traits concerning the main impurities which could suggest a change of ore sources. Furthermore, it was examined whether the influx of precious metals into the Roman treasury after Trajan's Dacian campaigns (AD 101/102 and 105/106) could have had any repercussions on the composition of the denarius alloy; comparative data was provided by the analysis of nine imitations of Roman Republican denarii presumably struck in Dacia. Documentation of the cross-sections was performed with SEM/EDX in order to clarify details concerning the specific microstructure of the coins. An enrichment of Ag of approx. 100 to 200 µm in the near surface regions of most of the coins could be observed, which is due to corrosion effects. Previous metallographic analyses done by several scholars had been inadequate to clarify the central numismatic and economic questions. With the presented analyses, it was possible to correct the results of the earlier research and to provide, for the first time, a secure basis of data for the investigation of the development of the silver alloy used for denarii in Trajan's reign.
Water content of hydrated soda lime silica surface layers with IR spectroscopy and Nuclear Reaction Analysis (NRA) (2001)
Geißler, Heinz ; Reinholz, Uwe ; Geotti-Bianchini, F. ; Preo, M.
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