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Development of the experimental setup for investigations of the low frequency alternating electromagnetic field effects on plant growth and phytoremediation properties
No full textThe electromagnetic field application is emerging as an additional physical strategy to rise the yield of agricultural production. In addition, the application of physical methods, in comparison to conventional chemical treatments, offers reduced use of harmful fertilizers and thus decrease pollution. Our recent experimental study in which wheat seed samples were treated for 48 hours with alternating electromagnetic field (AEF), in the frequency range up to 1 MHz, indicated that low frequency AEF may not only enhance seed germination and its growth, but also revealed statistically significant differences between AEF treated and control samples in chlorophyll a, b and total chlorophyll content as well as in some vegetation indices used to monitor plant health. Moreover, our other recent study confirmed that use of AEF for seed treatment increased the rate of seed germination, but no difference in accumulation of PFAS compounds was found between wheat plants developed from AEF treated and untreated seeds. In order to emphasize effects of AEF on already developed plants (instead of 48 hours of only seed treatment) a 2.5 times longer AEF treatment was conducted. To conduct such experiments in the present research we worked on developing a six-well plant growing tray reactor, where every well was equipped with pair of stainless steel electrodes between which AEF was generated
Influence of Surface Pretreatments on Composition, Structure and Corrosion Performance of Zirconium Conversion Coating Applied to AA7075-T6
No full textThe effect of chemical pretreatment of aluminium alloy 7075-T6 on the composition, morphology, and structure of zirconium conversion coatings (ZrCC) was investigated. Chemical pretreatments included: (i) alkaline etching and desmutting using commercial reagents, (ii) alkaline etching using sodium hydroxide, (iii) acidic etching using nitric acid, (iv) desmutting using a commercial reagent and boiling in deionised water, and (v) alkaline etching and desmutting using nitric acid. ZrCCs were deposited at room temperature from a 200 ppm H2ZrF6 solution of pH 4.8. A commercial SurTec® coating containing zirconium and trivalent chromium was used as a benchmark. The electrochemical behaviour was evaluated using potentiodynamic polarisation measurements and electrochemical impedance spectroscopy conducted over a minimum of 5 days and up to 15 days in 0.1 M NaCl. Corrosion resistance was further assessed through immersion testing. Microstructural characterisation was performed using scanning electron microscopy with energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry. The SurTec® pretreatment of AA7075-T6 activated the self-sealing of the subsequently deposited ZrCC, about 40 nm thick, which exhibited the highest degree of compactness and uniformity. This study showed a significant impact of surface chemical pretreatment on the microstructural and protective properties of ZrCCs deposited on 7075 alloy
Sol–Gel-Derived Silica/Alumina Particles for Enhancing the Mechanical Properties of Acrylate Composite Materials
No full textSilica/alumina composite particles were synthesized via the sol–gel method to promote fine dispersion and homogenous mixing. Aluminum chloride hydroxide served as the alumina precursor, while amorphous silica, obtained from rice husk, was directly incorporated into the alumina sol. Following synthesis, the material was calcined at 1000 °C, yielding an α-cristobalite form of silica and corundum-phase alumina. These hybrid particles were introduced into polymer composites at reinforcement levels of 1 wt.%, 3 wt.%, and 5 wt.%. Mechanical behavior was evaluated through three-point bending tests, Shore D hardness measurements, and controlled-energy impact testing. Among the formulations, the 3 wt.% composite exhibited optimal performance, displaying the highest flexural modulus and strength, along with enhanced impact resistance. Hardness increased with rising particle content. Fractographic analysis revealed that the 3 wt.% loading produced a notably rougher fracture surface, correlating with improved energy absorption. In contrast, the 5 wt.% composite, although harder than the matrix and other composites, exhibited diminished toughness due to particle agglomeration
Explosively welded steel bi-layers interfacial integrity and cavitation erosion resistance
No full textThis study investigates the cavitation erosion resistance and structural integrity of explosively welded
steel plates. Structural steel and tool steel were selected to form bi-layer plates, as a combination of strength
and toughness desirable in advanced structural applications. Explosion welding was employed to join the two
dissimilar steels, with the objective to gain insight into how variations in explosive charge mass influence the
bonding integrity, microstructural properties of the joint, and resistance to cavitation-induced damage. The
plates were joined in a parallel configuration using "Demex" explosive, which is based on ammonium nitrate
and trinitrotoluene, with a small amount of inert additives. Cross-sectional microstructural analyses of the
welded joints were performed using stereo and optical microscopy to evaluate the interfacial morphology,
bonding characteristics, and potential defects. Cavitation erosion behavior was examined through ultrasonic
vibration testing in distilled water with a stationary specimen: cross-section of the joint bi-layer plate.
Progressive surface degradation was monitored through periodic mass loss measurements to generate mass
loss curves and optical microscopy of the eroded surfaces.
Surface damage on both the base and welded zones was monitored and characterized by optical
microscopy to observe the mechanisms of erosion and their correlation with welding parameters. The
interfacial zone exhibited characteristic wavy patterns and localized plastic deformation, whose amplitude and
continuity increased with higher explosive charge mass, indicating improved metallurgical bonding. The
results showed that specimens fabricated using a higher mass of explosive during the welding procedure have
improved metallurgical bond quality, better cohesion at the interface, and greater resistance to cavitation
erosion. Overall, the findings suggest that optimizing the explosive charge parameters can affect the
interfacial microstructure and improve the functional durability of explosively welded joints, which is
important for the long-term reliability of multilayered metal plates operating in aggressive, cavitating
environments
Posterska sekcija "Korak u iskorak 2025"
No full textPosteri koje su istraživači IHTM-a objavljivali na skupovima u 2025. godini. Prikazani na skupu Korak u iskorak 2025, održanom 11. decembra 2025. u Madlenianumu, Zemun.zan
Energetics of steps in proton pumping mechanism of cytochrome C Oxidase
No full textCytochrome c oxidase (CcO) links the reduction of O2 to H2O with proton pumping across the mitochondrial membrane, generating an electrochemical proton gradient that conserves energy in aerobic cells [1]. The coupling of protonation and redox reactions is essential in this process. Recent timeresolved optical and electrometric experiments have anticipated a sequence of reaction steps for the proton translocation mechanism in CcO. DFT/ electrostatic calculations are employed to obtain energetics of the proton and electron transfer reaction steps during the O→E transition. The energy profile of the reaction mechanism is studied by examining how the redox state of the metal centers, dielectric solvation effects, and membrane potential gradient influence the energy levels and potential leakage of the protein pump through the Glu242 gating site. Particular emphasis is made on side reactions that may short-circuit the pump, resulting in a loss of proton pumping, and how this may be avoided in natural biological systems [2-5]
Kinetika faznih transformacija u sintezi barijum-titanata mehanohemijskom obradom
No full textThis article presents the research results on a dry mechanochemical synthesis of barium titanate at a low temperature in which the reaction model and kinetics were determined during the activation of a powder mixture of titanium dioxide and barium oxide. The solid-state reaction achieved high degree of conversion (0.99). Successive analyses were conducted throughout the reaction, revealing the presence of both the starting powders and newly formed intermediate compounds. Phase transformations were monitored via X-ray diffraction, allowing the dynamics of the synthesis to be characterized. It was established that, for the given system, 440 min of mechanical activation in a high-energy vibration mill was required to complete the neutralization reaction and produce barium titanate. The reaction mixture composition was tracked by sampling at five intervals, confirming the presence of intermediate compounds and mapping the reaction pathway from the initial barium and titanium oxides to the final BaTiO3 product.U radu su prikazani rezultati istraživanja sinteze barijum titanata (BaTiO3) na niskim temperaturama suvim mehanohemijskim postupkom. Bazni reaktant u eksperimentima je barijum oksid (BaO), dok je kao kiseli reaktant bio titanijum dioksid (TiO2). Optimalna količina polaznih uzoraka za aktivaciju je bila od 50 do 150 g. U cilju praćenja reakcije između polaznih uzoraka, reakciona smeša je uzorkovana nakon 30, 110, 200, 290 i 440 min aktivacije. Za reakcije neutralizacije između BaO i TiO2 korišćen je visokoenergetski vibracioni mlin sa torzionim oprugama i prstenastim radnim elementima. Produkti mehanohemijske reakcije su hemijski analizirani u cilju identifikacije neizreagovanih ostataka oksida zemnoalkalnih metala čija količina može da ukaže na stepen konverzije ili sinteze. Za identifikaciju kristalnih formi nastalih tokom reakcije i praćenje faznih transformacija korišćena je difrakciona rendgenska analiza praha (engl. X-ray powder diffraction, XRD). Dobijeni rezultati ovom analizom su omogućili definisanje dinamike sinteze. Sastav reakcione smeše, u tačno definisanim vremenskim intervalima tokom postupka sinteze, kvantitativno je analiziran atomskom apsorpcionom spektroskopijom. Cilj ovog istraživanja je bio da se tokom sinteze BaTiO3 odredi reakcioni model kao i kinetika reakcije. Rezultati dobijeni u prikazanom eksperimentu su pokazali da je tokom reakcije sinteze BaTiO3 u čvrstom stanju postignut izuzetno visok stepen konverzije (0,99). Uzorkovanjem reakcione smeše u pet različitih vremenskih intervala potvrđeno je prisustvo početnih prahova BaO i TiO2, zatim intermedijarnih jedinjenja i na kraju konačnog proizvoda, kristalnog BaTiO3. Analizom nastanka kristalnih struktura i njihove identifikacije ceo proces dobijanja BaTiO3 može se podeliti u tri etape: prva etapa u kojoj se urušava kristalna struktura reakcionog sistema BaO TiO2 (do 30 min); druga etapa je nastanak prelaznog stanja gde je teško utvrditi kristalnu i hemijsku strukturu, dovedena mehanička energija sistemu se akumulira u materijalu što ima za posledicu povećanje potencijalne energije i hemijske reaktivnosti (do 110 min); treća etapa u kojoj dolazi do značajnog formiranja kristalnog BaTiO3 (posle 200 min). Rezultati su pokazali da je za dati sistem potrebno 440 min mehaničke aktivacije da se izvrši potpuna reakcija neutralizacij
Influence of Aging and UV Radiation on Antibacterial Properties of Knitted Fabrics Dyed with Achillea millefolium L. Extract
No full textIn recent years, there has been increasing public concern about ultraviolet radiation (UVR), and clothing is considered to provide the most effective protection against it. In this study, the influence of aging and UVR on the antibacterial properties and degree of coloration of knitted fabrics was investigated. Knitted fabrics of different raw materials compositions in single weaves made of three types of yarn: cotton (CO), bamboo (BAM), and polyester (PES), were used. Samples were treated with methanol extract of Achillea millefolium L. conc. 100 mg/mL, to which citric acid and tannic acid were added, using ultrasonic atomization. Using an ultrasonic atomizer increased the speed of dyeing, shortened the processing time and allowed the use of a smaller amount of extract compared to conventional dyeing. The antibacterial properties of knitted fabrics obtained against Staphylococcus aureus and Escherichia coli were evaluated. The tests of antibacterial properties and color strenght (K/S) of knitted fabrics were done after dyeing, after aging (30 months), and after exposure to UV light with a wavelength of 254 nm and 365 nm. The antibacterial effect of knitted fabrics dyed with A. millefolium L. extract on S. aureus after natural aging and treatment with UV wavelength of 254 nm results in a reduction of the zone of inhibition (Zi) from 23% (BAM) to 57% (CO), compared to Zi after dyeing. Treatment of the samples with UV light with a wavelength of 365 nm increased the Zi against S. aureus, in PES knitted fabric was even higher than after dyeing, while there were no significant changes in E. coli. In CO and BAM knitted fabrics, after aging and exposure to UV radiation, high protection factors (UPF) were found, the values of which ranged from 31.38 to 51.68. Aging and exposure to UV light affect the degree of dyeing and color fastness, which are more pronounced in knitted fabrics made of cotton and bamboo fibers compared to polyester. In addition to the research of the impact of UVA radiation (365 nm), it was important to emphasize that research on UVC radiation (254 nm) was conducted to determine how the disinfection process affects the antibacterial properties of knitted fabric treated with A. millefolium extract.The results obtained from research into the stability of antibacterial treatment to aging and UV radiation represent a significant contribution to the research in the field of medical textiles and textiles intended for the production of clothing for allergic dermatitis. These findings highlight the importance of studying the effects of UV radiation and aging processes on the color fastness and antimicrobial properties of textile materials treated with herbal extracts. The developed materials can be used to protect people from UV radiation. In addition, to create sustainable textiles, future research should include different ways of preparing extracts from plant waste, especially from juice or wine production. The obtained extracts from plant waste would be used to develop innovative processes for antimicrobial dyeing and printing of textiles. In this way, products with improved color fastness and antimicrobial properties against UV radiation and aging could be obtained. The antimicrobial effect of textiles would be tested on a larger number of microorganisms. Depending on the obtained antimicrobial effect, textiles treated with herbal extracts could be used for various purposes, for the production of children’s toys, decorative pillows, sportswear and work clothes in hospitals
A universal mathematical model for forward osmosis systems coupled with experimental validation
No full textA novel transport model for Forward Osmosis (FO) systems is introduced in this paper that integrates thermodynamic property models, thus enabling comprehensive computations of multicomponent interactions within the solution. This is because, traditional approaches that rely solely on the solution-diffusion theories have consistently shown limitations in accurately predicting feed mixture behaviors, especially in membrane separation systems that involve the presence of dissolved ions. This transport model offers a practical solution that is straightforward to apply and can seamlessly integrate with pre-existing thermodynamic property models. Through experimentation on a laboratory FO testing system, the efficacy of the model was tested with experimental data. The results demonstrate a high level of agreement between the model's predictions and the observed outcomes. As such, the presented model can be used as a reliable tool for modeling FO processes
Investigation of mirror bright metal coatings and electrolytically produced copper powders on turn of the century at Department of Electrochemistry, ICTM
No full textSome fundamental and applied aspects of formation of mirror bright metal coatings and copper powder production by electrolysis are presented. These investigations are performed in a period between 1995 and 2000, at University of Belgrade, Institute of Chemistry, Technology and Metallurgy, Department of Electrochemisty, partly under supervisor of Prof. Dr. Miomir G. Pavlović, long-standing president of Serbian Society of Corrosion and Materials Protection (UISKOZAM). The coatings of chrome, copper and zinc are explored and the working conditions (the current density, temperature, the types of electroplating bath and cathode, addition agents for levelling and brightness, ...) which enable their mirror bright appearance were defined. The electrolytic production of copper powders desired the apparent density, as well as their stabilisation to prevent corrosion were widely investigated, too. Some of these investigations were conducted for companies in the Republic of Serbia (mirror bright chrome coatings - Župa, Kruševac, and copper powder - RTB Bor, d.d. “Topionica i rafinacija”, Bor)