Pavle Tančić

The chemical compositions and formation temperatures of magnesian calcite and dolomite were estimated by using the combination of chemical analysis, crystallographic parameters, and a plethora of various diagrams and mathematical calculations. This study presents an example of the calculated crystallo-chemical formula (Ca_0.960Mg_0.039Fe_0.001)CO₃, obtained from chemical analysis on a representative marble sample from the Bukulja–Venčac area in central Serbia. Substituting CaCO₃ with MgCO₃ and FeCO₃ in dolomite adds approximately 3–5 mol. %, enhancing the classification and indicating that it is more accurately identified as magnesium-excess dolomite. The estimated formation temperature of magnesian calcite (1) is approximately 528 °C, whereas magnesian calcite (2) forms at about 341 °C. The ~187 °C difference corresponds to ~3.28 mol. % MgCO₃ (~7.18% dolomite), reflecting the distinction between magnesian calcite (1) and magnesian calcite (2). Considering the presence of the submicroscopic intergrowth and exsolution of dolomite within magnesian calcite (1), which are further subdivided in magnesian calcite (2), the estimated formation temperature of ~341 °C appears to be more realistic. The synthesis of the results suggests that this combined method could be helpful in the geothermometry of marble samples after the treatment with acetic acid. However, despite the promising results, additional experiments are necessary to validate the proposed modified geothermometry approach.

In this study, a novel zinc-doped phosphor-tungsten salt (Zn-PWA) was synthesized via the Zn2+ ion exchange of protons in H3PW12O40 × nH2O, followed by controlled thermal transformation into its corresponding zinc phosphate-tungsten bronze (Zn-PWB) by sintering process. Thermo-gravimetric and differential thermal analysis (TGA/DTA) revealed that the phase transition from Zn-PWA into Zn-PWB occurs at 580°C, signaling a critical structural reorganization from a Keggin-type heteropoly salt lattice into an open-framework bronze structure. Structural and morphological characterization via X-ray powder diffraction (XRPD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS) confirmed the preservation of the primary polyanionic structural units in Zn-PWA and the successful formation of the bronze phase after thermal treatment. The electrochemical properties by cyclic voltammetry (CV) of both materials were evaluated separately in aqueous LiNO3 solution. Comparative XRPD and electrochemical studies demonstrated that the thermally derived Zn-PWB exhibits highest crystallinity and significantly enhanced redox stability compared to its heteropoly salt precursor, as well as the highest capacity obtained compared to Fe-PWB and Co-PWB analogues.

An analysis of the extensive geoscientific legacy of the late Professors Milorad Dimitrijevic (“Kvaks”) and Stevan Karamata, a century after their birth, shows that both authors published numerous studies on the Neo-Tethys, primarily focused on the Mesozoic Vardar Ocean. The term “Vardar Ocean”, in its modern sense, was introduced by Prof. Dimitrijevic, whose work also addressed the geology of western Serbia and the Inner Dinaride Ophiolite Belt. Similarly, Prof. Stevan Karamata concentrated on the westernmost and central parts of the Vardar Zone (East Vardar Zone). Despite their detailed investiga­tions of the exposed ophiolite belts across the western Balkan Peninsula, both authors made only a few, though highly significant, observations regarding the largely overlooked western Paleotethys Ocean, interpreted as a precursor oceanic domain. Despite these contributions, the role of the Paleotethys Ocean in the evolution of the Neotethys Vardar Ocean remains poorly understood. Terms such as “Early Cimmerian” (a post-Variscan suturing event related to Paleotethys closure) and “Neocimmerian” (a suturing event related to the Neotethys and Innerdinaric oceans) have been omitted from many published studies. Importantly, both the Early Cimmerian and Neocimmerian events are characterized by weak accretion or “docking”. By examining the role of the Paleotethys Ocean, and whether its subduction and closure influenced the opening and development of the Neotethys Vardar Ocean, this study provides an initial insight into the overlapping early Alpine and Eocimmerian tectonic stages.

Heteropoly acids and their compounds are a fascinating class of multifunctional materials for use in various fields: medicine, magnetism, catalysis and nonlinear optics, as well as for electrochemistry and battery materials. This study used tungsten-phosphate heteropoly acid to synthesize and characterize its Co doped salt (Co-PWA) and tungsten-phosphate bronze (Co-PWB). Thermal analysis was used to determine Co-PWA salt phase transition into Co-PWB bronze occurring at 588 ?C. Both samples were further characterized using Fourier transform infrared spectroscopy, X-ray powder diffraction and scanning electron microscopy containing energy dispersive X-ray spectroscopy, and by use of electrochemical examina-tions. Cyclic voltammetry (as a rapid analytical method) showed that both materials yielded low capacities in an aqueous solution of LiNO3. However, a ?slow? analytical method, chronopotentiometry, in which more places of a crystal lattice are occupied with ions (as compared to cyclic voltammetry), yielded solid and stable discharge capacity, making Co-PWB attractive as a potential electrode material for aqueous Li-ion batteries. The results obtained fill the gap in the scientific literature dealing with similar materials.