Nadežda Stanković (Serbia) was a young researcher at the Department for nanostructured materials, Jožef Stefan Institute (2011-2016), she completed her doctoral studies at Jožef Stefan International Postgraduate School, program Nanosciences and Nanotechnologies. She decided for doctoral studies in Slovenia based on the long lasting successful collaboration between the research groups at the Vinča Nuclear Institute and Department for Nanostructured Materials at JSI. The topic of her doctoral studies were solid-state diffusion controlled recrystallization processes, specifically oxidation of the Fe-Ti precursor mineral ilmenite with ferrous iron to rutile and hematite which contains ferric iron (WP-4: Rutile-corundum). The reaction is topotaxial meaning that it progresses gradually within the oxygen sublattice of the primary mineral and consequently, the precursor and products are in a close orientation relationship. It occurs regularly in nature and is an indicator of specific geochemical and geophysical conditions during the rock formation. Experimental work of the young researcher was dedicated to studies of natural samples (rutil/hematite intergrowths from Mwinilunga) and synthesis of intergrowths in the laboratory from ilmenite precursor. This unique combination of analyses has revealed that orientation relationship between the products of the topotaxial recrystallization depends mainly on kinetics of the process. Temperature and oxygen fugacity control the degree of oxidation of the ferrous iron on the surface and consequently trigger cation diffusion from the ilmenite lattice and exsolution of rutile lamellae. Our understanding of the processes leading to the formation of oriented rutile/hematite intergrowths is greatly improved and the results are also important for the production of rutile from ilmenite (as the main source of titanium metal). Young researcher has presented the results of her investigations in numerous domestic and international scientific conferences and she has published two extensive scientific papers. She is a coauthor of a paper in Contributions to Mineralogy and Petrology (ID-28374567), which is the first paper by Slovenian authors in this recognized journal and the first author of the paper published in Journal of Materials Science (ID-28879143). Publications of these related topics in journals from mineralogy and another from material science show that knowledge from natural minerals can be applied for controlled synthesis of materials. During her doctoral studies, the young researcher has gained expensive knowledge and experiences from the field of mineralogy, material science and electron microscopy which will be valuable for her further research work. She is independent in operating scanning and transmission electron microscopes (SEM and TEM), related spectroscopic techniques (EDS) and evaluation of the results. During her studies she attended additional training in electron microscopy techniques. After the successful defense of her PhD thesis, she returned to the Vinča Nuclear Institute, where she is involved in nanomaterials research. The knowledge related to electron microscopy techniques will be useful because the Institute is in the process of installation of a new transmission electron microscope, The successful scientific collaboration between the groups in Serbia and Slovenia will continue in the future, Nadezda Stanković and Nina Daneu have applied for a bilateral project on synthesis and characterization of phosphors.
D.09 Tutoring for postgraduate students
COBISS.SI-ID: 284144896Sandra Drev was a young researcher (PhD student) at Department for Nanostructured Materials, Jožef Stefan Institute and she completed her doctoral studies at the Jožef Stefan Postgraduate International School, program Nanosciences and Nanotechnologies. The topic of her research work was one of the fundamental problems from the field of mineralogy and crystallography - the reasons for the formation of growth-type twins in minerals. Growth-type twins are a special type of planar defects which are occasionally observed in crystal grains and the reasons for their formation are not understood completely. The candidate conducted her research work in the system spinel - chrysoberyl (MgAl2O4 - BeAl2O4), where twins on (111) planes are observed in spinel and twins on (110) and (130) in chrysoberyl crystals. The experimental work related to (111) twins in spinel (WP-2: Spinelloids) based on hypothesis that the formation of growth-twins in this systems is chemically induced and not a consequence of accidental attachment of crystal in twinned orientation in the initial stages of crystal growth (during nucleation) as generally accepted. With careful experimental work she showed for the first time that twining in spinel is triggered by the presence of a small amount of beryllium. She also demonstrated that at higher beryllium additions, the twin boundaries show a tendency to order into modulated polytypic taaffeite phases inside the spinel matrix. Using the most advanced techniques of transmission electron microscopy in collaboration with Prof. Dr. Goran Dražić from the National Institute of Chemistry she confirmed the presence of one atomic layer of beryllium at the twin boundary plane. The beryllium atoms replace magnesium atoms at their regular structural sites, triggering local hexagonal stacking inside the otherwise cubic spinel matrix, which results in the formation of a twin boundary. During her doctoral studies, the candidate performed three-month specialization at the Max Planck Institute in Stuttgart. The visit was dedicated to the analysis of the atomic structure and chemistry of the modulated taaffeite phases ((BexMgAl2(x+y)O4(x+y)), which contain subsequent layers of beryllium atoms in tetrahedral sites and change the stacking of the oxygen sublattice from cubic (as in spinel) to locally hexagonal (as in chrysoberyl). During the specialization, the candidate learned techniques for atomic-scale structural and chemical analysis using aberration corrected TEM (probe-corrected TEM; Jeol ARM CF 200), with spatial resolution below 0.2 nm, which corresponds to the thickness of tetrahedral layers in the spinel structure. At the Max Planck Institute she presented the results of her preliminary research work entitled: "Electron microscopy study of twinning and formation of modulated structures in Be-doped MgAl2O4" (ID-29335847). Second part of the research work by Sandra Drev was dedicated to twinning in chrysoberyl, where she identified another mechanism of twin formaiton. Based on the results of HRTEM/EDS analyses she determined local enrichment by iron and titanium in the form of solid solubility along the (130) twin boundaries. This indicated that the formation of twins in chrysoberyl is not chemically triggered as in spinel but is related to nucleation on structurally related Fe-Ti mineral or to topotaxial recrystallization of a precursor phase. The local atomic structure and chemistry of the twin boundary was determined with HRTEM. Based on the images, the candidate built structural models and the local atomic positions of the Be and Al atoms at the boundary were refined using density functional theory (DFT) calculations. TEM analyses revealed also the presence of nanosized rutile precipitates inside the chrysoberyl lattice. From the highly distorted crystal lattice of the rutiles it was possible to determine the formation temperature of the chrysoberyl crystals. The young researcher published the results of her research work a
D.09 Tutoring for postgraduate students
COBISS.SI-ID: 292016384MSc thesis by geology student Nina Grom (FNT, UL) is a thorough study of skarn-type ore deposit Kope on Pohorje, where interesting Bi-mineralization was discovered. Her research work was performed under the guidance of Prof. Dr. Tadej Dolenec and is related to the research work within the WP-1: Sulfosalts. In the thesis, the candidate gives an interpretation for the genesis of the ore deposit and describes relationships among the occurring minerals. Mineral paragenesis of the ore deposit formed during seven subsequent stages. The parent rock is limestone, which was later transformed into marble during regional metamorphosis. This stage was accompanied by the formation of biotite and muscovite. The following event was dacite intrusion, which caused high-temperature contact metamorphosis triggering the formation of anhydrous silicates like diopside, hedenbergite, garnets, scheelite, zircone and titanite. Aalanite crystallized after scheelite. Crystallization of calcite and quartz occur during all stages. Hydrous minerals like aalanite, biotite, actinolite, epidote and apatite followed in the next stage. Actinolite needles are occasionally overgrown by magnetite or, rarely, hematite crystals. Crystallization of ilmenite, hematite, elementary Bi and ferrosillite follows in the next stage, these minerals are later substituted and overgrowth by magnetite. Magnetite also forms interesting pseudomorphs after hematite. After crystallization of oxides, the conditions changed to reducing triggering crystallization of sulfides starting with molibdenite, pyrrhotite, sphalerite, galena, chalcopyrite and pyrite as the last sulfide phase. Calcite, quartz, actinolite and chlorite form during the third retrograde stage. Hematite overgrowths on structurally related magnetite are observed. During this stage, the high-temperature pyrite is replaced by pyrrhotite and chalcopyrite. The region was subjected to another tectonic event after the retrograde mineralization stage. Minerals like calcite, quartz, chlorite, magnetite, pyrite, chalcopyrite pyrrhotite and bornite crystallized during this stage along with Bi-phases and sulphosalts and elementary silver on the contact between pyrite and chlorite. During the following hydrothermal stage was the main crystallization stage of the Bi-minerals, which start to fill larger volumes within the rock. The majority of Bi-minerals are represented by Pb-Ni-S, bismuthinite and bismite, while tellurobismuthinite, tetradymite, Ag-Bi-Te-S, Ag-Pb-Bi-S, and Cu-Fe- Bi-S sulphosalts are present in minor amounts. The next crystallization stage was cementation by covellite. The last alteration stage of the ore deposit was oxidation, when malachite, cerussite, goethite and limonite form crusts on sulfides, oxides and Bi-phases.
D.11 Other
COBISS.SI-ID: 1149278The topics of investigations within the project were presented in the form of six invited lectures at internationals scientific conferences (ID-30810407, ID-28819751, ID-30812711, ID-30702119, ID-30653991, ID-28588839) and in eleven presentations at foreign universities and institutes (ID-29842215, ID-29772327, ID-29772327, ID-29773095, ID-29782567, ID-29773351, ID-29773607, ID-29335847, ID-29971495, ID-29772839, ID-27988007 and ID-30382631). These invitations reflect the high quality and significance of our research work focused to the atomic-scale investigations of initial stages of phase transformations in minerals. The work was performed in the frame of two basic research projects (the preceding project J1-4167 and this one J1-6742). Nanostructured phenomena in minerals are usually not investigated in much detail therefore our results offer many novel insights into atomic-scale processes during the (re)crystallization of rocks. We verify the results of our investigations on natural minerals by synthesis in laboratory and we apply the finding for the synthesis of novel functional materials. The main characterization technique are methods of transmission electron microscopy. For this reason our results are of great interest to a wide scientific community from mineralogists, petrologists, geologists, material scientists and microscopists and this is also shown in the broad spectrum of different thematic conferences where we present the results of our work.
B.04 Guest lecture
COBISS.SI-ID: 30812711Volcanic rocks from the Smrekovec Mountains are described in the present article. Their chemical composition, texture and structure are explained in a simplified manner to be understood by the target community – laics, mountaineers, hikers, pupils, and high-school and university students. The age, tectonic setting, magma source, sedimentary environments and the formation of a stratovolcano edifice in the Oligocene Smrekovec Basin are briefly explained. Some less common volcaniclastic rocks are explained as well such as peperites, hyaloclastite, hyaloclastite breccia and autobreccia. These autoclastic deposits are related to desintegration of lava flow owing to a rapid cooling in the sea-water or mixing and mingling of lava with water-saturated siliciclastic or volcaniclastic deposit.
F.27 Contribution to preserving/protecting natural and cultural heritage
COBISS.SI-ID: 2475861