Prijenosni uređaj za rentgensku fluorescentnu analizu (XRF) kao jedinstveni instrument za in situ elementnu karakterizaciju objekata kulturne baštine

U ovom su radu predstavljene prednosti korištenja prijenosnim uređajem za rentgensku fluorescentnu analizu – XRF (X-ray fluorescence analysis), kao prvog koraka za in situ elementnu analizu materijala na objektima kulturne baštine. XRF je metoda koja se bazira na pobuđivanju atoma ispitivanog uzorka rentgenskim zračenjem, što rezultira emisijom fluorescentnoga zračenja iz materijala, karakterističnog za elementni sastav. Te informacije daju nam i kvalitativnu i kvantitativnu sliku o elementnom sastavu uzorka. XRF je nedestruktivna, brza, univerzalna i relativno jednostavna analitička metoda za multielementnu analizu artefakata i kao takva u svijetu je tretirana kao jedna od najosnovnijih fizikalnih metoda za istraživanja u konzervatorsko-restauratorskom području. U svojoj prijenosnoj inačici, upotrebljavanoj u ovom radu, ova je tehnika također neinvazivna, a samo problemi koji nisu riješeni tom metodom na terenu analiziraju se dodatno primjenom specijaliziranije laboratorijske opreme. Dakle, XRF rezultati s terena služe i kao vrijedne smjernice za daljnje sustavno i ciljano uzimanja uzoraka, čime potrebu uzorkovanja svode na minimum. To je svojstvo od posebne važnosti kada je riječ o istraživanju vrijednih i jedinstvenih objekata, što je u ovom području gotovo i pravilo. Prednosti, dobrobiti i koristi od ove metode demonstrirane su na nekoliko primjera iz prakse na kojima je autor ovoga članka radio, a uključuju terensko istraživanje pigmenata drvene polikromije u crkvi sv. Marije Jeruzalemske u Trškom Vrhu i određivanje sastava legure skulpture Hrvatskog Apoksiomena

Protection of Stone Monuments Using a Brushing Treatment with Ammonium Oxalate

Stone monuments and buildings are susceptible to weathering. Carbonate-based stones are especially vulnerable in acidic environments, whereas magmatic acidic stones are more susceptible to chemical weathering in basic environments. To slow down surface corrosion of limestone and marble artworks/buildings, protective coatings which inhibit calcite dissolution have been proposed. In this work, samples from two stone types with different porosity were treated with ammonium oxalate (AmOx) to create a protective layer of calcium oxalate (CaOx) using the previously developed brushing method. Two different synchrotron microscopy experiments were performed to determine its protective capability. X-ray powder diffraction (SR-μ-XRPD) in transmission geometry allowed visualization of the distributions of calcium carbonate and oxalates along the sample depths. In a second step, X-ray fluorescence (SR-μ-XRF) was used to check the efficiency/integrity of the protective surface coating layer. This was done by measuring the sulfur distribution on the stone surface after exposing the protected stones to sulfuric acid. XRPD showed the formation of a protective oxalate layer with a thickness of 5–15 µm on the less porous stone, while a 20–30 µm thick layer formed on the more porous stone. The XRF study showed that the optimal treatment time depends on the stone porosity. Increasing the treatment time from 1 to 3 h resulted in a decreased efficiency of the protective layer for the low porosity stone. We assume that this is due to the formation of vertical channels (cracks) in the protective layer

Development, construction and application of a portable x-ray fluorescence device for analysis of art objects

Röntgenfluoreszenzanalyze (RFA) gehört zu den am besten geeigneten Methoden für die Untersuchung von archäologischen, historischen und Kunstobjekten. Die Entwicklung von tragbaren RFA-Geräten, die einen Einsatz direkt vor Ort erlauben, ermöglicht eine noch breitere Anwendung dieser Methode an Objekten unabhängig von ihrer Größe, Form und dem Ort, an welchem sie aufbewahrt bzw. ausgestellt sind. Diese Arbeit beschreibt die Entwicklung und den Bau eines portablen RFA-Geräts, das entwickelt wurde, um in situ Untersuchungen zu ermöglichen. Das Ziel war ein tragbares und handliches Gerät zu bauen, das aber gleichzeitig die Leistung und Genauigkeit eines Laborgeräts aufbringen kann. Bei der Komponentenauswahl wurde daher beachtet, dass sie gute Auflösung und schnelle Datenerfassungsvermögen besitzen, und gleichzeitig klein, leicht und robust sind. Der Messkopf des Systems besteht aus einer 50 Watt Röntgenröhre (50 kV, 1,0 mA, Modell 5011 der Fa. Oxford/USA), einem Silicon-Driftkammer-Detektor (SDD - Modell XFlash 1000 der Fa. Röntec/Deutschland) und zwei Laser-Pointer als Positionierungssystem. Unter Verwendung des mittels Peltier-Element thermoelektrisch gekühlten SDDs ist ein unhandliches und sperriges Detektorkühlsystem mit flüssigem Stickstoff nicht mehr notwendig. Bei typischen Arbeitsbedingungen wird eine Energieauflösung von Damit sind auch Untersuchungen und Analysen an Konstobjekten z.B. von Wandmalereien direkt vor Ort möglich. Die Verwendung einer 50 Watt Röntgenröhre gewährleistet genügend hohe Strahlungsintensitäten auch für die Anregung kleineren Probenmengen, womit die mit dem portablen RFA-Gerät erhaltenen Ergebnisse mit den Laborwerten durchaus vergleichbar sind. Einige konkrete Anwendungen des portablen RFA-Geräts sind als Fallbeispiele genauer beschrieben. Im Besonderen handelt es sich hier um Pigmentcharakterisierung der Wandmalerei an Wandfragmenten aus dem Wiener Stephansdom, der romanischen Wandmalerei in der St. Nikolaus Kirche in Winkl bei Wien, Charakterisierung von chinesischen Lacktafeln im Wiener Schloss Schönbrunn, sowie von belgischen Glasemailfragmenten aus dem 17. und 20. Jahrhundert.X-ray fluorescence analysis (XRF) is regarded as one of the most appropriate analytical techniques for examination of artistic, historic and archaeological objects. Development of XRF instrumentation suitable for portable employment expands the range of use of this technique to an even wider area, by allowing in situ measurements on objects disregarding of their shape, size or place where they are stored and/or displayed.This thesis describes design, construction and assembly of a field portable XRF (PXRF) analyzer, which was developed in order to enable in situ examinations in the field of archaeometry. The goal to design a portable instrument with lab-like precision performance was achieved by careful selection of individual components based on several important factors - high precision, high-speed data acquisition, and at the same time undemanding and simple portability. The system is based on energy dispersive XRF using a 50 kV and 1.0 mA x-ray tube from Oxford Instruments, USA, type XTF5011, a silicon drift chamber detector (SDD) from Roentec, Germany, type XFlash 1000, and two lasers as pointing devices. The air cooled 50 W x-ray tube and the Peltier-cooled SDD provide a strong excitation source and a very efficient detection system resulting in fast measurements (short acquisition time) with very good precision - two highly important features in the field of archaeometric examinations. SDD circumvents the need of a bulky liquid N2 detector cooling system. In combination with the overall miniaturization of all components and versatile positioning of the measuring head, it allows also high quality in situ measurements. For communication between the particular system components, for data acquisition and qualitative spectrum evaluation a software package based on LabVIEW© from National Instruments was developed and adapted to specific needs and requirements encountered in the field of archaeometry. The collected data are subsequently quantitatively analyzed using WinAxil© Software from Canberra Eurisys, Belgium. To fully evaluate the assembled instrument, the system's analytical capabilities are tested, compared with the results obtained by a laboratory XRF, and a comparative evaluation of the systems is established. After the completion of construction, the instrument was used for studies of art objects in museums and galleries, ceiling frescoes in churches and cathedrals, archaeological findings at the excavation sites etc. Several case studies, where the PXRF has been utilized, have been presented in more details, in particular characterization of mural paintings on the wall fragments from the St. Stephan's Cathedral in Vienna, Romanesque mural paintings from the St. Nicholas church in Winkl, Chinese wood panel lacquer decoration (lacquerware) in Schoenbrunn Castle in Vienna, and Belgian enameled stained glass fragments from the 17th and the 20th century

High-performance zig-zag and meander inductors embedded in ferrite material

This paper describes the design, modeling, simulation and fabrication of zig-zag and meander inductors embedded in low- or high-permeability soft ferrite material. These microinductors have been developed with ceramic coprocessing technology. We compare the electrical properties of zig-zag and meander inductors structures installed as surfacemount devices. The equivalent model of the new structures is presented, suitable for design, circuit simulations and for prediction of the performance of proposed inductors. The relatively high impedance values allow these microinductors to be used in high-frequency suppressors. The components were tested in the frequency range of 1 MHz–3GHz using an Agilent 4287A RF LCR meter. The measurements confirm the validity of the analytical model. r 2005 Elsevier B.V. All rights reserved