Nejdůležitější publikace 2. období (IRMA)

Nejdůležitější odborné publikace vydané během druhého období (do 31. září 2019). Seznam všech publikací výzkumného programu MATE vydaných v rámci projektu CAAS najdete na zvláštní stránce, seznam nejdůležitějších publikací za první období pak zde.

The effects of swift Xe ion bombardment on the amorphous structure of a VITROPERM type alloy
Š. Michalik, M. Cesnek, M. Pavlovič, M. Miglierini
Journal of Alloys and Compounds, Volume 795, 30 July 2019, Pages 69-78
Influence of swift Xe ion irradiation (ion energy of 11.1 MeV/u, ion fluences from 2.5 × 1012 to 1.0 × 1013 ions/cm2) on the local structural arrangement of a VITROPERM alloy is investigated using synchrotron-based X-ray diffraction, Fe and Nb K-edge X-ray absorption spectroscopy, and 57Fe Mössbauer spectroscopy techniques. The obtained data show an increase of structural disordering due to ion bombardment. However, no alterations in pairwise interatomic lengths are observed. The irradiation-induced structural modifications can be removed by an appropriate post-irradiation heat treatment. We suggest that the microscopic origin of changes induced by the swift heavy ions could be similar to the structural modifications caused by severe plastic deformation.

X-ray fluorescence mapping as a first-hand tool in disseminated ore assessment: sandstone-hosted U–Zr mineralization
Petr Mikysek, Tomáš Trojek, Noemi Mészárosová,Jiří Adamovič, Marek Slobodník
Minerals Engineering, Volume 141, September 2019, 105840
Analytical capabilities of X-ray fluorescence for 2-dimensional elemental analysis were tested on worldwide-unique sandstone-hosted U–Zr mineralization (Bohemian Cretaceous Basin, Czech Republic), and combined with measured spectral data. The applied approach was aimed at the detection of uranium and zirconium, visualization of their distribution across mineralized lithological units and description of their relationships with associated elements (As, Fe, Nb, Pb, Sr, Ti). The studied samples were low-grade uranium-bearing sediments. Experimental work employed laboratory 2D scanning X-ray fluorescence analyzer with the gold target Mini-X X-ray tube. Maps of U–Zr and other identified elements demonstrated their patchy distribution and a frequent association of the elements with mineral fillings (clay matrix, organic matter or Fe sulfides). A correlation-based analysis was used to verify geochemical coherence between the measured elements. This showed an extremely strong linear dependence (R ≥ 0.90) between U and Zr. In addition, a strong correlation (R ≥ 0.85) between U–Zr and some associated elements (As, Nb ± Fe, Pb, Sr) was confirmed. The efficiency and the limits of X-ray fluorescence mapping were tested by comparison with high-resolution techniques. Non-destructive mapping of large natural samples provided relevant data for further mineralogical study with respect to rapid pre-concentration of the ore material.

Parametrization of a tabletop micro‐XRF system
Žiga Šmit, Radek Prokeš, X-Ray Spectrometry, Volume 48, Issue 6, November/December 2019, Pages 682-690, First published: 20 August 2019
A table‐top micro X‐ray fluorescence apparatus composed of a conventional X‐ray tube with a polycapillary lens and a silicon drift X‐ray detector was parametrized according to an independent parameter approach. The tube bremsstrahlung spectrum was calculated from the Bethe‐Heitler equation, convoluted by the energy distribution of radiating electrons in the target. In this paper, we propose a simple analytical approximation for this energy distribution. An analytical approximation is also proposed for transmission of the lens composed of curved capillaries.

Nejdůležitější publikace 1. období (IRMA)

Tři nejdůležitější odborné publikace vydané během prvního období (do 31. března 2019). Seznam všech publikací výzkumného programu IRMA vydaných v rámci projektu CAAS najdete v předchozím příspěvku.

Antimony leaching from antimony-bearing ferric oxyhydroxides by filamentous fungi and biotransformation of ferric substrate
Author Martin Urík, Filip Polák, Marek Bujdoš, Marcel B. Miglierini, Barbora Milová-Žiaková, Bence Farkas, Zuzana Goneková, Hana Vojtková, Peter Matúš
Science of The Total Environment, Volume 664, 10 May 2019, Pages 683-689
Ferric oxyhydroxides are natural scavengers of antimony, thus, they contribute significantly to antimony immobilization in soils and sediments. Recent studies, however, usually omit microbial influence on geochemically stable antimony-ferric oxyhydroxide association. Therefore, we have evaluated fungal contribution to antimony mobility during static cultivation of common soil fungus Aspergillus niger in presence of ferric oxyhydroxides. Our results indicate distinguished effect of fungus on antimony distribution at two different antimony concentrations that were used for antimony pre-adsorbtion onto ferric oxyhydroxides prior to the inoculation. Approximately 36% of antimony was bioextracted by fungus from antimony bearing ferric oxyhydroxide after 14-day cultivation when the 8.9 mg·L−1 antimony concentration was used for pre-adsorption. However, no statistically significant change of antimony content in ferric oxyhydroxides was observed after cultivation when initial 48 mg·L−1 antimony concentration was used for pre-adsorption. As Mössbauer spectroscopy and XRD analysis indicated, nanosized akageneite, goethite, and lepidocrocite enhanced their crystallinity during cultivation, while hematite was identified only after the cultivation. Nevertheless, presence of ferric oxyhydroxides at both initial concentrations enabled transformation of antimony into volatile derivatives, and almost 9.5% of antimony was biovolatilized after cultivation. These results contribute significantly to environmental geochemistry of antimony-ferric oxyhydroxides association and highlight the importance of microbial activity in relation to ferric component of natural geochemical barriers.

Neutron activation analysis of Tibetan traditional medicinal pills at the VR-1 training reactor
Milan Stefanik, Lubomir Sklenka, Martin Cesnek, Marcel Miglierini, Jan Rataj
Radiation Physics and Chemistry, Available online 18 March 2019
The nuclear analytical methods provide the research techniques usually used in hard sciences such as physics, chemistry, engineering and technology, or natural sciences and technology, but it is very rare to use them in social sciences and humanities. The Czech Technical University (CTU) in Prague operates the VR-1 training reactor primarily focused on training students, nuclear engineering, reactor physics, and research; however, the utilization of this nuclear reactor has also been extended to humanities in recent years. In this direction, the research activities carried out at the reactor include the investigation of historical artefacts and testing of pharmaceutical and food industry samples. This contribution deals with the detailed study of traditional Tibetan medicinal pills by means of instrumental neutron activation analysis (NAA) at the VR-1 nuclear reactor. Three various kinds of Tibetan pills were irradiated by thermal neutrons in the experimental vertical channel at maximum reactor power (80 W), and irradiated samples were analysed using the semiconductor HPGe detector; saturated activities were obtained by means of the nuclear gamma-ray spectrometry, and subsequently the composition of the pills was determined (qualitative and quantitative analysis). The presence of Au, K, Fe, Na, As, Sr, Sb, and Hg was revealed in studied samples. The results presented in this paper show clearly that the low-power research reactor VR-1 is excellent tool for the neutron activation analysis experiments.

The effects of swift Xe ion bombardment on the amorphous structure of a VITROPERM type alloy
S. Michalik, M. Cesnek, M. Pavlovič, M. Miglierini
Journal of Alloys and Compounds, Available online 1 May 2019
The single crystalline Lu3Al5O12: Ce3+0.6%,Ca2+0.6% garnet films co-doped with Si4+ions were prepared by liquid phase epitaxy technique and their optical, luminescence, and scintillation properties were studied. The Ca co-doping into the Lu3Al5O12:Ce films resulted in a drastic acceleration of decay kinetics and decreased light yield due to the oxidization of Ce3+ into Ce4+ ions. The Si4+ co-doping regenerated the Ce3+ ions by virtue of charge compensation between Ca2+ and Si4+ions. The Ce valence changes were evidenced from the optical, photoluminescence and scintillation studies. Significant differences between the photoluminescence and scintillation properties were observed in Si + Ca co-doped samples. The influence of Si co-doping and the effect of Ce3+-to-Ce4+ ratio on the scintillation properties of Lu3Al5O12:Ce epitaxial garnet films is discussed.

Instrumentální radiační analytické metody (IRMA)

Koordinátor programu: prof. Ing. Ladislav Musílek, CSc.

Program integruje aktivity a staví na zkušenostech čtyř kateder FJFI ČVUT – dozimetrie a aplikace ionizujícího záření, inženýrství pevných látek, fyzikální elektroniky a jaderných reaktorů – v oblasti moderních instrumentálních metod zkoumání materiálové kompozice a
struktury.

Mezi unikátní pomůcky používané týmem patří například jaderný reaktor VR-1 řízený FJFI (http://reaktorvr1.eu/index.php). ČVUT spravuje také Van der Graafův urychlovač a využívá řadu analytických metod – například Mössbauerovu spektroskopii, PIXE a RBS analýzy, rentgenovou fluorescenční analýzu aj.

Práce v rámci výzkumného programu IRMA budou tematicky rozděleny do tří oblastí (podprogramů):

A) Detektory záření
B) Instrumentální analytické metody
C) Analýza materiálů užívající difrakci záření