Iron sulfides have attracted the attention of scientists in the past due to their interesting physical properties. In the last decade, many scientific groups investigate synthetic sulfides for the application in advanced technologies (batteries, solar cells, ecology). Although there are many studies on sulfides, some crucial questions mainly related to their nucleation, phase transformations and structural variations, remain unsolved. This doctoral dissertation is about the synthesis, structural defects and epitaxies in iron sulfides, the effect of copper doping on phase transformations in Fe-sulfides is also investigated. During his study, the candidate expanded the research from mono- and di-sulfides to the wide group of (Fe, Cu)-sulfides. This contributed to a wider knowledge about this complex system and offered some general answers about the initial stages of phase transformations in sulfides. The candidate used two synthesis routes: (i) high-temperature synthesis in vapor phase or the so-called chemical vapor transport (CVT) method and (ii) combined sonocemcial/sovothermal method. The standard CVT method was modified by the candidate for the use in a one-zone furnace, where the synthesis inside an evacuated tube is between 700° and 450°C. Besides Fe-disulfides (pyrite, marcasite) and Fe-monosulfides (pyrrhotite, troilite and others), the candidate synthesized yet unknown (Fe,Cu)S with the sphalerite-wurtzite structure. For the study of Fe-sulfides crystallization at low temperatures, the candidate used diethanolamine (DEA) as an organic precursor and managed to produce different types of sulfides, especially the (Fe,Cu)S with the sphalerite-wurtzite structure. The procedure for the synthesis of sulphides using the DEA is a simple and inexpensive method for the synthesis of clean Fe-sulfides. For the analysis and characterization of the products, the candidate used X-ray powder diffraction (XRD), scanning and transmission electron microscopy (SEM, TEM) wit energy dispersive X-day spectroscopy (EDS) and magnetic measurements. The scientific achievements, described in the dissertation, include also experiments on the relationship between the morphology of pyrite crystals with the crystallization temperature and the influence of copper addition on the stability of the initial FeS precipitates and the formation of the cubic (Fe,Cu)S that crystallizes in the sphalerite-wurtzite structure-type as (Zn,Fe)S analogue. Low-temperature synthesis revealed that already sonochemical treatment triggers the formation of metastable FeS phase that transforms into mackinawite and then to pyrite without greigite intermediate phase as reported in the literature. Greigite occurs only in the case of sulphurization of the cubic (Fe,Cu)S phase. At even higher Cu additions, chalcopyrite and bornite form instead of the sphalerite-type (Fe,Cu)S. The candidate measured magnetic properties of the samples with different Cu additions. These new and original results fit within the research fields of synthesis and structural characterization of different Fe-sulfides, especially their nucleation, crystallization conditions, phase transformations and structure of the inherent planar defects. The results can be applied for targeted synthesis of Fe-sulfides for novel technological applications and contribute to the understanding of basic principles of phase transformations in Fe-sulfides. In 2012, dr. Nina Daneu was habilitated for the Microscopy and microanalytical methods course at the Jožef Stefan International Postgraduate School. The increased amount of research in the last period resulted in numerous confirmations of our basic hypothesis on tropochemical twinning in different studied systems. This wouldn't be possible without the significant amount of work done by the group members. Altogether, five doctoral student were involved in research topics within this project in the period between 2011 and 2014: • Janez Zavašnik (phase transformaitons in Fe
D.09 Tutoring for postgraduate students
COBISS.SI-ID: 27575079In this series of lectures initial stages of phase transformations identified through the formation of chemically induced planar defects, such as twin, antiphase, or inversion boundaries were presented. Based on crystal chemistry principles, early researchers suggested that the atomic structure of twin boundary must be related to the existing polymorphic modification of the major phase. The confirmation of this hypothesis was not possible until the modern electron microscopy techniques, which enabled direct insight into the atomic structure of twin boundaries. Our studies of twins and other translational defects in many natural minerals have indicated that their formation is chemically induced by the presence of dopants that stabilize the particular polytypic structure. Inherent anisotropy imposed by the chemically induced transformation fault (e.g. growth twin) causes exaggerated growth of the crystal parallel to the fault plane as long as geochemical and thermodynamic conditions favor the formation of such a faulted stacking. These initial growth stages dictated by the growth of chemically induced fault are clearly reflected in a final morphology of the crystals and can be recognized by the twin-plane reentrant angles and the additional symmetry elements that can be observed on the crystals. Because of commonly complex geochemical conditions, natural minerals incorporate an assortment of foreign elements that are present during crystal growth, but only one of these elements, however, is responsible for the faulted stacking (e.g. twinning). In order to identify the elements that trigger twinning in minerals we developed new techniques enabling atomic-scale determination of the interfacial crystal chemistry. Our study of twinning in various minerals presented in this conference paper deal with one of the fundamental scientific challenges that offers possibilities for true understanding of the basic building principles of solids and the fundamentals of phase transformations in minerals. Our research topics were presented to the international scientific public as a plenary lecture and three invited lectures at conferences and meetings and also at two universities: Plenary lecture at the Joint 5th Mineral Sciences in the Carpathians (MSCC) and 3rd Central-European Mineralogical Conference (CEMC) at the Miškolc University, Hungary. Our findings on twinning in natural minerals (sphalerite, spinel, rutile,…) were presented and a review paper was published in Acta mineralogica-petrographica: › Daneu N, Rečnik A. The atomic-scale aspects of twinning and polytypism in minerals. Joint MSCC+CEMC 2012, 5th Mineral Sciences in the Carpathians Conference, 3rd Central-European Mineralogical Conference, 19-21 April 2012, Miskolc, Hungary, (Acta mineralogica-petrographica, ISSN 1589-4835, Abstract series, vol. 7). Szeged: Dep. Mineral. Geochem. Petrol. Univ. Szeged, 2012, vol. 7, p. 32-37. [25754407] Invited presentation at the SloNano conference, in which I presented our technique of transmission electron microscopy (TEM), the Concentric Electron Probe (CEP) technique, for accurate and precise determination of the chemical composition of planar defects. Planar defects with different configurations where we successfully applied the CEP technique for the determination of their chemical composition were presented (ZnO, spinel, rutile,…): › Daneu N, Walther T, Rečnik A. Quantitative chemical analysis of interfaces on the sub-nanometer scale. SLONANO 2011, 26-28 October 2011, Ljubljana, Slovenia. Book of abstracts. Ljubljana, 2011, p. 67. [25492263] Dr. Aleksander Rečnik was indited to presented the topics of our research at the working meeting of the Hungarian group for nanomineralogy: › Rečnik A, Daneu N. Nanoscale determination of chemical triggers for twinning in minerals. 7th Joint Meeting of the Nanomineralogy Working Group of the Hungarian Academy of Sciences and the Mineralogy-Geochemistry Section of the Hungarian Geological Societ
B.04 Guest lecture
COBISS.SI-ID: 25761063PhD student Sandra Drev was selected as the Slovenian young-researcher speaker at the closing conference of the European 7FP project MACAN (Merging atomistic and continuum analysis of nanometer length-scale metal-oxide systems for energy and catalysis applications) in Israel. She received an opportunity to present her results on twinning in spinel to the leading scientists and professors from the scientific fields of thermodynamics and atomic structure of interfaces. After her 45 minutes presentation, she received 12 questions, which she defended successfully. In addition, she received several suggestions for cooperation and some useful advices for further scientific work: › Drev S, Rečnik A, Letofsky-Papst I, Gspan C, Hofer F, Daneu N. Electron microscopy study of twinning and formation od modulated structures in Be-doped MgAl2O4 spinel. MACAN CapStone Conference: April 20-26, 2013, Haifa, Israel. 2013, str. 47-48. [26721831] After this conference, the candidate prepared structural models of different types of twins in spinel in order to calculate energies for different boundary configurations using the density functional theory (DFT) in cooperation with dr. Matej Komelj (JSI). The calculations revealed that the beryllium-rich (dopant-rich) twin boundary has at least two orders of magnitude lower energy compared to the pure (dopant-less) boundary and even lower formation energy than the surrounding bulk spinel. This is the first theoretical confirmation showing that the tropochemcial growth-type boundaries indeed have a lower formation energy and this is the main reason for their distinct anisotropic growth observed in experiments. In 2013, the young researcher visited the group of Prof. Ferdinand Hofer at the Technical University Graz, Austria for several times (total visit duration 20 working days). These visits were in the frame of the European project ESTEEM2 and the main goal of this cooperation was the determination of Be at the twin boundaries in spinel at the aberration-corrected FEGTEM Titan G2 60300 with atomic-scale resolution. The main goal was not achieved due to the instabilities of the microscope, however, several high-quality HAADF-STEM photos of the twin boundaries, stacking faults and taaffeite-type modulated sequences were made that will be useful in studying the Be ordering within these spinel-related structures. With the installation of the new aberration-corrected Jeol ARM-200F at the National Institute of Chemistry in Ljubljana, the presence of Be at the (111) twin boundaries in spinel was successfully determined in cooperation with dr. Goran Dražić. She continued her work for 3 months (from March until July 2014) at the Max-Planck-Institute in Stuttgart with the financial support by Ad-Futura agency and ESTEEM2 project. At this facility, she specialized in the atomic-scale microscopy under supervision of dr. Vesna Šrot (MPI). The main topic of this research visit was the determination of Be ordering in polysomatic taaffeite homologous series, where substantial uncertainties in the structure of different modulations exist. Based on our findings on twinning in spinel, a new international cooperation with scientists from the Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences in Novosibirsk, Russia was initiated at the 3rd International Conference on Crystallogenesis and Mineralogy held in September 2013 in Novosibirsk. The result of this initiative is a Slovenian-Russian bilateral project with dr. Victor G. Thomas BI-RU/14-15-025 entitled Characterization of growth features and planar defects in crystal grown under hydrothermal conditions. This is important for the international recognition of the achievements by our research group and Slovenian science in general.
B.04 Guest lecture
COBISS.SI-ID: 26721831Dr. Polona Kralj (GeoZS) was actively involved into the setting of an exhibition entitled Vulkanija (Volcania) in 2013. Higher-quality dissemination of geological science to laic communities and all-level education processes including university programmes has been accomplished in the year 2013 with the opening of Vulkanija in the place of Grad, Goričko, NE Slovenia. The basic idea for this education centre is enclosed in the above cited Scenario and several scientific publications related to the development and eruptive history of the Pliocene volcanism at Grad, from the initial formation of the structure of maar, tuff cone and tuff ring, and hydrothermal processes reflected in the crystallisation of zeolites phillipsite, chabasite and analcime. › Kralj P. Eruptive and sedimentary evolution of the Pliocene Grad Volcanic Field, North-east Slovenia. J. Volcanol. Geotherm. Res. 1-4 (2011) 272. [1790293] › Kralj O. Submarine pyroclastic deposits in Tertiary basins, NE Slovenia = Podmorski piroklastični sedimenti terciarnih bazenov severovzhodne Slovenije. Geologija 56 (2013) 187. [2227285] The visitors get a deeper insight into geological history of Goričko in the time of Tertiary including the formation of petroleum, mineral and thermal waters, sandstone, gravel and clay, the basic resources for development of technology and tourism in the whole Pomurje region. In a pleasant and non-formal manner, Vulkanija addresses in particular young generations to encourage them to observe and understand natural processes on our planet and be aware of the future of the Earth in the sense of the development of humankind and society as well as integration of our planet into the galaxy an the entire space. Hazards related to volcanic activity are presented, too, such as hot pyroclastic flows, lahars and airborn volcanic dust in the atmosphere and troposphere or volcanism-induced climate changes that may last several years after particular volcanic activity. Clear object lessons of volcanic landforms and volcanic eruptions are given and can be computer-modelledindividually by visitors to produce a specific morphology of the volcano edifice, explosivity index, volcanic products and primary and secondary processes. Supervolcanoes are explained, their eruption frequency, probability of eruption in the near future and possible impact on the extinction or further development of the biosphere on the Earth including humankind and modern society. Particular emphasis of Vulkanija is on mineral heritage of local volcanic rocks, which is exceptional in Slovenia. The visitors learn about the formation and occurrence of olivine which occurs in peridotite xenoliths, the unmolten remains of the rock of Asthenosphere in alkali basaltic lavas. The occurrence of pillipsite is also unique on the territory of Slovenia. Its formation is related to alteration and degradation of alkali basaltic glass under the action of hydrothermal fluids. Phillipsite is associated with chabasite,and both zeolites fill interstitial space in volcaniclastic rocks and imparted them hardness that makes them useful in civil engineering and architecture. Phillipsite and chabasite hav very good ionic exchange properties and can be used in environment-protection industry and agriculture as natural molecular sieves. In alkali basalts from Grad some exceptional automethasomatic replacement reactions of quartzite pebble by hydrothermal apophyllite or pyroxenes have been recognized. Volcanic rocks with magmatic and autigenic minerals are placed in the geological environment of the Mura-Zala basin and the neighboring Styrian basin where several genetically and temporally related alkali basaltic rocks occur, such as basanites, trachybasalts and nephelinites. The basins are also characterized by energy resources – coal, petroleum, natural gas and geothermal energy, mineral waters, raw materials for civil engineering such as gravels, sands and clays, and ornamental stone essential for pres
F.27 Contribution to preserving/protecting natural and cultural heritage
COBISS.SI-ID: 1279477