Technical Faculty in Bor
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Influence of pre-deformation on mechanical properties and microstructure of EN-AW 7075 aluminium alloy
(Materials Research Society of Serbia, 2025) Kovačević, Avram; Stamenković, Uroš; Nedeljković, Milan
This study investigates the changes in mechanical properties and microstructure of the EN-AW 7075 aluminum alloy after thermomechanical treatment. The treatment included cold plastic deformation, induced by rolling prior to artificial aging at a temperature of 150 °C for 30 minutes. The variations in hardness and impact toughness were monitored depending on the applied thermomechanical treatment conditions. Hardness was determined using the Leeb method, while impact toughness was measured using the Charpy method. The lowest hardness values were recorded in the annealed condition (Temper O state), while the highest impact toughness was observed in the quenched condition (Temper W state). The applied cold plastic deformation induced before artificial aging significantly increased the hardness of the investigated alloy, accompanied by a progressive decrease in impact toughness. Optical microscopy was used to analyze the microstructural changes during the thermomechanical treatment. Precipitates of various sizes and morphologies were observed in the alloy structure. The annealed condition was characterized by poorly defined grain boundaries and coarse secondary phase particles uniformly distributed within the matrix. Cold plastic deformation before aging resulted in a structure oriented in the rolling direction and refined secondary phase particles.
Thermal Properties and Microstructure Evolution of the as‑cast and Annealed Al–Cu–Si Eutectic Alloy
(Springer Nature, 2025) Manasijević, Dragan; Marković, Ivana; Cimpoesu, Nicanor; Chelariu, Romeu; Stamenković, Uroš; Balanović, Ljubiša; Gorgievski, Milan
The Al–28%Cu–6%Si (mass%) eutectic alloy represents a possible high-temperature phase change material (PCM) for latent heat thermal energy storage (LHTES). In this paper, its microstructural characteristics and thermal properties were examined in the as-cast and annealed conditions using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), differential scanning calorimetry (DSC), and light flash method. The microstructure of the studied alloy consists of (Al) solid solution phase, θ-Al2Cu intermetallic phase, and (Si) phase. The annealing at 450°C for 50 h led to significant changes in the morphology of the θ-Al2Cu and (Si) eutectic phases. The temperature dependences of thermal diffusivity and thermal conductivity were investigated within the temperature range from 25 to 400 °C. It was found that the thermal diffusivity and thermal conductivity of the annealed alloy are considerably higher than that of the as-cast alloy at temperatures lower than 300 °C. With increasing temperature, due to changes in the microstructure of the as-cast alloy, these differences decrease and finally diminish at 400 °C. The measured eutectic temperature is 522.3 °C and latent heat of melting is 358.3 Jg-1. The findings suggest that the Al–Cu–Si eutectic alloy shows good potential for use in phase change energy storage technologies.
Enhancing Wastewater Treatment Through Python ANN-Guided Optimization of Photocatalysis with Boron-Doped ZnO Synthesized via Mechanochemical Route
(MDPI, 2025) Nedelkovski, Vladan; Radovanović, Milan B.; Medić, Dragana; Stanković, Sonja; Hulka, Iosif; Tanikić, Dejan; Antonijević, Milan
This study explores the enhanced photocatalytic performance of boron-doped zinc oxide (ZnO) nanoparticles synthesized via a scalable mechanochemical route. Utilizing X-ray diffraction (XRD) and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), the structural and morphological properties of these nanoparticles were assessed. Specifically, nanoparticles with 1 wt%, 2.5 wt%, and 5 wt% boron doping were analyzed after calcination at temperatures of 500 °C, 600 °C, and 700 °C. The obtained results indicate that 1 wt% B-ZnO nanoparticles calcined at 700 °C show superior photocatalytic efficiency of 99.94% methyl orange degradation under UVA light—a significant improvement over undoped ZnO. Furthermore, the study introduces a predictive model using the artificial neural network (ANN) technique, developed in Python, which effectively forecasts photocatalytic performance based on experimental conditions with R2 = 0.9810. This could further enhance wastewater treatment processes, such as heterogeneous photocatalysis, through ANN-guided optimization.
Application of Graphite Electrodes Prepared from Waste Zinc−Carbon Batteries for Electrochemical Detection of Xanthine
(MDPI, 2025) Radovanović, Milan B.; Simonović, Ana T.; Petrović Mihajlović, Marija B.; Tasić, Žaklina Z.; Antonijević, Milan M.
Waste from zinc−carbon batteries poses a serious environmental protection problem. One of the main problems is also the reliable and rapid determination of some compounds that may be present in food and beverages consumed worldwide. This study addresses these problems and presents a possible solution for the electrochemical detection of xanthine using carbon from spent batteries. Cyclic voltammetry and differential pulse voltammetry are electrochemical methods used for the detection of xanthine. The techniques used demonstrate the mechanism of xanthine oxidation in the tested environment. A linear correlation was found between the oxidation current peaks and the xanthine concentration in the range of 5·10−7 to 1·10−4 M, as well as the values for the limit of detection and the limit of quantification, 7.86·10−8 M and 2.62·10−7 M, respectively. The interference test shows that the electrode obtained from waste Zn-C batteries has good selectivity, which means that the electrode can be used for xanthine determination in the presence of various ions. The data obtained show that carbon sensors from used zinc−carbon batteries can be used to detect xanthine in real samples.
Electrochemical Detection of Cadmium Using a Bismuth Film Deposited on a Brass Electrode
(MDPI, 2025) Radovanović, Milan B.; Petrović Mihajlović, Marija B.; Simonović, Ana T.; Tasić, Žaklina; Antonijević, Milan M.
Cadmium is one of the most dangerous pollutants found in the environment, where it exists mainly due to human activities. High cadmium concentrations can cause serious problems, which is why the detection and determination of Cd is one of the most important tasks. Electroanalytical methods provide rapid and accurate results in the detection of cadmium in various solutions. In this study, the possibility of using a bismuth film electrode deposited on a brass surface and electroanalytical techniques for the detection of cadmium is investigated. The bismuth film was deposited on the surface of the brass electrode using a chronoamperometric technique. Cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the synthesized bismuth film electrode. The current peaks obtained by anodic square-wave stripping voltammetry under optimized conditions showed a linear relationship in the investigated concentration range of cadmium. The study of the interference of different cations (Cr3+, Mn2+, Zn2+, Ca2+, K+, Mg2+ and Na+) showed that the tested cations have no influence on the determination of Cd2+ ions in the investigated solution. This finding provides a good opportunity for the use of the synthesized electrode in real samples.