Uncertainty of Quantitative X-ray Fluorescence Micro-Analysis of Metallic Artifacts Caused by Their Curved Shapes

This paper summarizes the effects of irregular shape on the results of a quantitative X-ray fluorescence (XRF) micro-analysis. These effects become relevant when an XRF analysis is performed directly on an investigated material. A typical example is XRF analyses of valuable and historical objects whose measurements should be performed non-destructively and non-invasively, without taking samples. Several measurements and computer simulations were performed for selected metallic materials and shapes to evaluate the accuracy and precision of XRF. The described experiments and the corresponding Monte Carlo simulations were related to the XRF device designed and utilized at the Czech Technical University. It was found that the relative uncertainty was typically about 5–10% or even higher in quantitative analyses of minor elements due to irregular shapes of surfaces. This must be considered in cases of the interpretation of XRF results, especially in the cultural heritage sciences. The conclusions also contain several recommendations on how to measure objects under hard-to-define geometric conditions with respect to reduction in the surface effect in quantitative or semi-quantitative XRF analyses

X-ray Fluorescence Analysis of Pigments in Gothic Frescoes, Coats of Arms, and Polychromy on Sculptures on the Triforium in St. Vitus Cathedral on the Territory of the Czech Kingdom in the 14th Century

Pigments in the paints used for the coats of arms, polychromy on sculptures, and pigments in frescoes characterize not only the epoch but also individual creators or groups of artists involved in their creation. X-ray fluorescence analysis is a non-destructive method suitable for determining the chemical composition of these artifacts. This article covers the results of measurements of selected objects, and compares them with similar objects from the territory of the Czech Kingdom in the 14th century

Alteration halos around radioactive minerals in plutonic and metamorphic rocks of the northern Moldanubian area, Bohemian massif

International audienceEffects of strongly radioactive primary minerals (mainly monazite) on the surroundings are compared in various rocks of similar chemical and mineral composition (mainly granites and paragneisses) of the Moldanubian area in the Bohemian massif. All these rocks cooled to ,150 C at similar time (300-250 Ma B.P.). Aureoles of secondary phases formed which extend up to 20 mm from the monazite surface (the thickness probably corresponds to the zone of most intense damage by a-particles). They mainly consist of low temperature clay minerals usually mixed with Fe-hydroxides; in some samples pyrite is common too. Pyrrhotite and pyrite also penetrate into the monazite and locally partly replace it. In a granite affected by strongly oxidizing alteration, monazite was finally replaced by a complicated hydrated phosphate. The halos of secondary phases most commonly occur around monazite in cordierite, but also in plagioclase and in quartz. It is unimportant if the monazite is included in one mineral grain or is located at grain boundaries. Compared to previous studies in similar rocks with similar cooling ages (e.g., in Erzgebirge and Massif Central, as documented in literature), quartz was destroyed relatively easily. In most cases the alteration of primary minerals close to radioactive grains cannot be explained in a conservative way that the radiation damage only helps to precipitation of secondary phases during a ''ubiquitous'' fluid alteration. It seems that the radioactivity promotes reactions of the primary minerals with fluid (fluid inclusions and H 2 O in channels of the cordierite structure) even at ''static'' conditions. The volume changes (caused by hydration or amorphization) make easier a later import of external fluid. The reason why these phenomena are observed in some regions and not in very similar rocks in other regions is not understood yet, but it is likely that the rocks of the Moldanubian area are mostly above-averagely rich in aqueous fluids. The frequent association of monazite with hydrated secondary phases may contribute significantly to resetting monazite ages during metamorphism and partial melting. In addition, the neglecting of the chemical transformation of the nuclear energy for the calculations of radioactive heat production and heat budgets of rocks is questioned