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Molecular dynamics investigation of plastic deformation in polycrystalline Ti–13Mn wt.% alloy
No full textTitanium alloys are widely used in the aerospace, biomedical, and energy engineering domains due to
their high specific strength, corrosion resistance, and biocompatibility. Among these, β-type titanium alloys
are particularly desirable for high-performance material design, leveraging microstructural control. In this
work, we investigate the atomic-scale deformation behavior of the Ti–13Mn wt.% alloy to gain fundamental
insights into its mechanical performance. Molecular dynamics (MD) simulations were performed at room temperature on polycrystalline structures
to assess the role of grain boundaries in plasticity. Tensile loading was applied at strain rates ranging from
10⁻⁹ to 10⁻⁷ s⁻¹ in order to evaluate strain-rate sensitivity. The analysis focused on strain response, Schmid
factor, slip system activation, and dislocation behavior. We track dislocation nucleation during mechanical testing by reporting dislocation density as a function
of strain, along with the visualization of the dislocation network at different strain values. The results show
that strain localization, dislocation nucleation, and grain boundary interactions are the primary mechanisms
governing plastic deformation in Ti–13Mn wt.%. Strain-rate effects were linked to the equilibrium between
dislocation motion and grain boundary accommodation. This study provides new insights into the relationship
between the mechanical performance of Ti–13Mn wt.% alloy and its microstructural properties, supporting
the design of improved β-type titanium alloys
Optimizacija tehničko-tehnoloških parametara proizvodnje vatrostalnih premaza na bazi pirofilitnog škriljca za primenu u livarstvu
No full textZeolite Fixed-bed System Enhanced with Recirculation for Improved Copper Ion Removal from Wastewater: Kinetic Models and Comparison with Batch System
No full textThis research investigates the feasibility of a novel approach involving a fixed-bed column system with recirculation for copper ion removal from wastewater. Adsorption kinetics of zeolites were examined using a well-established batch system and compared to a fixed-bed column recirculation system, a configuration for which only limited investigations exist. Zeolite was chosen as the adsorbent due to its efficiency, affordability, availability, and eco-friendliness. The recirculation system was designed for comparative analysis with the batch system, assessing adsorption kinetics, reaction rate constants, and orders under various initial copper concentrations (100, 300, and 500 mg dm-³). Zeolite particles (2–3 mm) were used in the recirculation system, while finer particles (63 µm) were employed in the batch system. Experimental conditions, such as adsorbent dosage and initial pH, were kept constant to ensure the comparability of the two systems. Copper concentrations in the filtrate were measured using an atomic absorption spectrophotometer (AAS). Three experimental kinetic models were developed to describe the adsorption processes. The results indicate that the adsorption processes correlate best with Ho's pseudo-second-order (PSO) kinetic model. Results revealed superior removal efficiency (9.77 mg g-1) with the recirculation system using coarser particles compared to the batch system (7.82 mg g-1) with finer particles, highlighting enhanced adsorption driving forces in the recirculation configuration. The fixed-bed column system with recirculation demonstrates superior efficiency over batch systems and reduced processing time compared to conventional fixed-bed configurations
Natural bentonite modified with cationic surfactants as adsorbent for the removal of non-steroidal anti-inflammatory drugs from aqueous solutions
No full textБентонит је познат по својој способности да адсорбује различите супстанце, али се његове карактеристике могу додатно побољшати модификацијом. У овом раду истражује се модификација бентонита употребом катјонских сурфактаната, са циљем побољшања његових својстава за адсорпцију лекова из водених средина. Процес модификације подразумева примену катјонских сурфактаната који мењају површинску структуру бентонита и тиме повећавају његов капацитет за адсорпцију.
У оквиру докторске дисертације разматрана је могућност модификације природног бентонита из лежишта Шипово у Босни и Херцеговини, ради побољшања његових адсорпционих својстава за уклањање нестероидних антиинфламаторних лекова из водених средина. Бентонит је модификован катјонским сурфактантима: октадецилдиметилбензиламонијум-хлоридом (ODMBA) и хексадецилтриметиламонијум-бромидом (HDTMA). Модификација је вршена методом јонске измене сурфактантима у количинама које су једнаке или мање од капацитета катјонске измене (ККИ) бентонита. Органобентонити су карактерисани различитим физичко-хемијским методама, укључујући рендгенску дифракциону анализу на праху, одређивање текстуралних својстава, инфрацрвену спектроскопију са Фуријеовом трансформацијом, скенирајућу електронску микроскопију, термијске анализе и одређивање зета потенцијала. Ове методе су показале утицај количине и врсте сурфактанта на модификацију бентонита и структуру.
Истраживање је обухватало анализу адсорпције лекова ибупрофена (IBU) и диклофенак натријума (DS) под различитим експерименталним условима, укључујући промену концентрација лекова, масеног односа адсорбата и адсорбента, времена контакта и температуре, као и анализу кинетичких, термодинамичких и адсорпционих параметара. Резултати указују на значајно побољшање адсорпционих карактеристика органобентонита у поређењу са природним бентонитом. У поређењу са другим минералима, каолином и зеолитима модификованим са ODMBA, органобентонит показује знатно боље резултате.
Добијени резултати омогућавају боље разумевање механизма адсорпције лекова и интеракцијa између молекула лекова и органобентонита, што је од значаја код практичних примена у заштити животне средине. Циљ рада је развој ефикасног и економичног адсорбента на бази локалног минералног материјала који може бити искоришћен за пречишћавање контаминираних вода. Ова студија не само да доприноси теоријском разумевању адсорпционих процеса, већ нуди и практична решења за проблеме загађења вода, побољшавајући квалитет животне средине. Резултати указују да је модификација бентонита катјонским сурфактантима успешна стратегија за побољшање његове ефикасности у адсорпцији лекова из водене средине, што може имати значајне примене у третману загађених вода и заштити животне средине.Bentonite is well-known for its ability to adsorb various substances, and its properties can be enhanced through modification. This study investigates the modification of bentonite using cationic surfactants to improve its ability to adsorb pharmaceuticals from aqueous environments. The modification process involves the application of cationic surfactants that change the surface structure of bentonite, thereby increasing its adsorption capacity.
This doctoral dissertation examines the possibility of modifying natural bentonite from the Šipovo deposit in Bosnia and Herzegovina in order to improve its adsorption properties for the removal of nonsteroidal anti-inflammatory drugs (NSAIDs) from aqueous environments. Bentonite was modified with cationic surfactants: octadecyltrimethylammonium chloride (ODMBA) and hexadecyltrimethylammonium bromide (HDTMA). The modification was carried out through an ion-exchange method using surfactant amounts equal to or less than the cation-exchange capacity (CEC) of bentonite. The organobentonites were characterized using various physicochemical methods, including powder X-ray diffraction analysis, determination of textural properties, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermal analysis, and determination of zeta potential. These methods revealed the effect of the type and amount of surfactant on the modification of bentonite and its structure.
The research includes the analysis of drug adsorption of ibuprofen (IBU) and diclofenac sodium (DS) under various experimental conditions, such as changes in drug concentration, mass ratio of adsorbate and adsorbent, contact time, and temperature, as well as the analysis of kinetic, thermodynamic, and adsorption parameters. The results indicate a significant improvement in the adsorption characteristics of the organobentonite compared to the natural bentonite. The obtained results were compared with the efficiency of other minerals, kaolin and zeolite modified with ODMBA, with organobentonite showing significantly better results.
The findings contribute to a better understanding of the drug adsorption mechanism and the interaction between drug molecules and organobentonite, with potential practical applications in environmental protection. The aim of this work was to develop an effective and cost-efficient adsorbent based on a local mineral material that can be used for the purification of contaminated waters. This study not only contributes to the theoretical understanding of adsorption processes but also offers practical solutions to water pollution issues, improving environmental quality. The results suggest that the modification of bentonite with cationic surfactants is a successful strategy for enhancing its efficiency in adsorbing pharmaceuticals from water, which may have significant applications in the treatment of polluted water and environmental protection
Phase Diagram Analysis of Ti-Mo-Sn System for β-Titanium Alloy Development
No full textTitanium (Ti), a metal with a hexagonal close-packed structure, exhibits outstanding mechanical and thermal
properties, making it ideal for applications in extreme environments. Structural integrity at elevated
temperatures has been extensively studied through experimental mechanical testing. In recent years,
computational modeling has provided critical insights into its plastic deformation mechanisms across different
temperatures as a complement to experimental data. In this work, we employ molecular dynamics simulations
to investigate the mechanical response of single-crystalline Ti under nanoindentation using a rigid spherical
diamond indenter (R = 12 nm) in the 10–900 K range. The empirical interatomic potential for simulating the
mechanical response of single-element materials was chosen by considering the generalized stacking fault
energy and slip dissociation pathways responsible for stacking fault formation and dislocation activity during
mechanical loading. Atomic strain mapping was used to visualize the evolution of plastic deformation beneath
the indenter at elevated temperatures. Nanoindentation simulations reveal the development of pile-ups and
changes in the surface morphology induced by dislocation motion at different temperatures. The obtained
results provide fundamental insights into temperature-driven changes in dislocation dynamics, slip
mechanisms, and local hardness, enhancing understanding of Ti’s thermomechanical stability. These findings
contribute to the design and optimization of Ti-based materials for high-temperature structural applications
Catalytic engineering of rare earth - transition metal oxides for high-performance oxygen evolution reaction
No full textGreen hydrogen is a key enabler of the sustainable energy transition, yet its large-scale production remains limited by the efficiency and cost of water electrolysis, particularly due to the sluggish kinetics of the oxygen evolution reaction (OER) at the anode. Iridium-based catalysts, while effective, suffer from high costs and limited global availability. Therefore, there is a critical need to design noble-metal efficient or noble metal-free OER catalysts with high activity, stability and scalability. This study focuses on the rational design of hybrid multivalent oxides based on rare earth elements (REEs)-including Ce. Y. Yb and Dy- combined with transition metals - Co and Mn. These materials were synthesized through a scalable one step ultrasonic spray pyrolysis (USP) method to generate spherical, nanoscale oxide particles with high compositional homogeneity. The REEs were selected due to their variable oxidation states and ability to introduce oxygen vacancies, while the transition metals were chosen for their known catalytic activity in alkaline OER conditions. Post-synthesis processing via microwave assisted hydrothermal treatment was employed to incorporate nanoscale IrO coatings in a controlled core-shell structure. Two different strategies were explored: (i) minimal Troz decoration of the REE-TM cores to enhance activity while reducing Ir usage and (i) multilayered core-shell architectures to evaluate performance stability and interfacial conductivity. The composite catalysts were characterized by XRD: SEM and EDS to assess crystal structure, morphology and oxidation states with particular attention paid to the formation of surface oxygen vacancies and lattice distortions induced by REE doping Electrochemical characterization was carried out in 1 M KOH and 0.5 M H2SO, electrolytes using cyclic voltammetry CV, linear sweep voltammetry (LS) and electrochemical impedance spectroscopy (EIS). The catalysts demonstrated superior OER activity compared to commercial IrO2, With overpotentials as ow as 270 mV at 10 mA cm2 and excellent long term operational stability over 20-hour chroncamperometric testing. Importantly, optimized Ir loadings below 30 wt% delivered comparable or improved performance, highlighting the critical role of REE-TM synergy in facilitating electron transfer and stabilizing l' active sites. This work showcases a cost-effective and environmentally conscious approach to electrocatalyst development by combining advanced synthetic techniques with smart compositional engineering
Combustion of contaminated Sorghum sp. for Zn extraction
No full textDue to its properties, forage sorghum can grow under unfavorable soil conditions and in places with very harsh
climatic conditions. Also, it is very tolerant of habitats that are contaminated with metals. Certain varieties of
sorghum are capable of absorbing Zn from polluted soil. In this study, the optimal burning time and
temperature of Sorghum spp. with the aim of obtaining ash with the highest possible concentration of Zn.
Applying the chemical analysis of the homogenized initial sample of sorghum, it was established that 1 kg of
sorghum contains 55.61 mg of Zn. Combustion experiments were performed at temperatures of 400, 450, 500
and 600 ºC for 120, 240 and 360 minutes. In all experiments, the mass loss was approximately 90%. It was
observed that the highest content of Zn has the ash that was formed after burning for 6 hours at a temperature
of 500 ºC. Differential thermogravimetric analysis showed that the greatest mass loss of the sample (ash) was
recorded at a temperature between 150 and 400 ºC. In order for the valorization of zinc from the ash to be
possible, it is necessary that the ash and leachate (after washing the ash) do not contain any substance that
would prevent the precipitation of zinc salts
Thermal analysisand kinetics of natural millerite oxidation process
No full textAs an important source for nickel extraction, millerite (NiS) has been investigated in the past, however there
is still a notable deficiency in literature data regarding its behaviour and phase transformations at elevated
temperatures. In order to better understand millerite oxidation process, the characterization of the initial sample
and its oxidation products was investigated. Thermal and kinetic analysis were performed in order to identify
phase transformations, propose a possible reaction mechanism and to determine the kinetic parameters of the
process when heating the sample in the temperature range from 25 oC to 1000 oC. Experimental results showed
that thermal decomposition end-products consist of nickel oxide and spinel phase trevorite as well as hematite
and maghemite at elevated temperatures. Kinetic analysis results indicate that oxidative roasting occurs in
kinetic field, with temperature-dependant reactions
Chemical cosmetic method for removal of mole according to doctor Dunkić
No full textU radu je prezentovana hemijska kozmetička metoda za uklanjanje mladeža i ostalih benignih lezija koju je razvio Dr Sci Gojko Dunkić. Metodu je osmislio 1946. godine u Šibeniku i tada je uspešno i bez traga sebi uklonio virusne bradavice i mladeže sa ruku i tela. Od tada, a intenzivno od 1970. godine, bavio se uklanjanjem benignih lezija, prvo porodici i bliskim prijateljima, a zatim i klijentima iz zemlje, okruženja i celoga sveta. Danas se metodom bave sin i kćerka dr Gojka Dunkića, koji su autori ovoga rada, u svojim ambulantama u Beogradu i Kragujevcu, i preko 10 godina u Hrvatskoj. Metoda je kao patentna prijava 2007. god. predata Zavodu za intelektualnu svojinu u Beogradu, P-2007/0438, RS52576B, publikovana je 07.08.2008., a dobijeni patent registrovan 30.04.2013. pod brojem 52576. Metoda je uspešno primenjena na više desetina hiljada ljudi, od toga preko 300 doktora medicinskih nauka i profesora Medicinskih fakulteta. Ovde ćemo predstaviti metodu i dati neke primere rezultata
Electronic Band Structure Modifications in Fe/TiO2 /VO4 and Fe/TiO2/VOOH Systems: A Theoretical Study for Photocatalytic Applications
No full textThis study theoretically investigates the electronic and photocatalytic properties of rutile-phase titanium dioxide (TiO2 ) modified with Fe-doped iron vanadate (Fe/TiO2 /VO4 ) and vanadium-substituted goethite (Fe/TiO2 /VOOH) using density functional theory (DFT) calculations. Our analysis of the density of states (DOS), band structure, and work function reveals that both dopant systems significantly modify the electronic structure of pure rutile TiO2 . The incorporation of Fe and V alters the valence and conduction bands, resulting in a reduced band gap and a modified work function. This suggests enhanced visible light absorption and improved charge carrier separation, key factors for increasing photocatalytic efficiency. Specifically, the DOS analysis highlights the contribution of Fe 3d and V 3d orbitals, which create new electronic states within the band gap, facilitating charge transfer. These theoretical insights provide a strong foundation for the rational design of novel, highly efficient TiO2-based photocatalysts for the degradation of organic pollutants