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Rare earth oxides: different synthesis pathways; structural, morphological, and electrochemical characterization
No full textRare earth elements (REEs) comprise 15 lanthanide elements plus Sm and Y. These elements are
characterized by unique 4f-electron structures, strong spin-orbit coupling, and large atomic magnetic
moments. Due to their unique chemical and physical properties, rare earth elements and their oxides,
known as rare earth oxides (REOs), have found numerous applications in electronics, electrocatalysis, and
materials science. In electrochemical sensing, the properties of REEs and REOs, such as excellent
electrical conductivity, high surface area, biocompatibility, and the possibility of functionalization with
different functional groups or biological species, significantly contribute to improving the sensitivity and
selectivity of the developed electrochemical (bio)sensors [1]. This research explores the various synthesis
methods of REOs (Eu2O3, La2O3, and Yb2O3) and their structural, morphological, and electrochemical
characterization. Pechini [2], co-precipitation [3], and hydrothermal [4] methods were used to synthesize
Eu2O3, La2O3, and Yb2O3. The obtained materials were structurally and morphologically characterized
using X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron
Microscopy (SEM). The XRD spectra patterns of the synthesized materials showed that the Pechini
method yielded the highest crystallinity of all the analyzed samples compared to the co-precipitation and
hydrothermal methods. The glassy carbon paste (GCP) was modified with Eu2O3, La2O3, and Yb2O3 for
the electrochemical characterization of the synthesized REOs (thus prepared GCP/Eu2O3, GCP/La2O3,
and GCP/Yb2O3 working electrodes). For the preparation of these working electrodes, REOs synthesized
by all three synthesis methods were used. The electrocatalytic and charge transfer resistance
performances of all working electrodes were examined using cyclic voltammetry (CV) and
electrochemical impedance spectroscopy (EIS) in 0.1 mol/L KCl containing 5 mmol/L [Fe(CN)6]
3−/4−
.
Comparing synthesized procedures, the CV results showed that GCP modified with REOs, synthesized by
the Pechini method, provided the highest intensity of the redox peaks of the [Fe(CN)6]
3−/4− compared to
the co-precipitation and hydrothermal methods. Furthermore, EIS measurements showed, comparing
REOs synthesized by the hydrothermal method, the GCP/La2O3 provided the lowest charge transfer
resistance. A similar electrochemical trend was observed for the GCP/La2O3, where La2O3 was
synthesized using Pechini and co-precipitation methods, compared to Eu2O3 and Yb2O3. For the further
application of synthesized REOs in electrochemical sensing, it is essential to investigate the
electrochemical behavior of working electrodes towards the appropriate analyte
Analysis of the behavior of the mullite samples surface exposed to the cavitation using a statistical analysis approach
No full textCavitation erosion which occurs under specific fluid flow conditions in industrial processes, demands suitable materials. This study investigates the cavitation resistance of mullite by observing surface changes during exposure. A novel method focuses on morphological descriptors of defects caused by cavitation. Using image analysis (IA), surface degradation was quantified by selecting specific defect parameters, with datasets analyzed through principal component analysis (PCA) to identify key damage descriptors. This approach simplified the estimation of lifespan for exposed parts. The PCA of datasets obtained from IA indicated that the most informative descriptors of surface damage vary remarkably throughout the cavitation and per different periods of the cavitation curve. Among eleven selected parameters, PCA identified critical parameters Radiusmax, Perimeter, and Sizelength consistent throughout testing for monitoring mullite’s cavitation resistance. By combining traditional, non-destructive methods and statistical analysis, this study offers a new framework for tracking surface damage progression. This enables a deeper understanding of cavitation-induced material erosion, improving predictions of material performance and optimizing industrial applications
Structural, morphological, mechanical and thermal properties of PMMA/SiC composites
No full textIn this study, silicon carbide (SiC) microfibers were added as reinforcement to improve the thermomechanical properties of poly (methyl methacrylate) polymer, PMMA, since this type of composite has not been explored well enough so far. The aim of this study is to obtain PMMA/SiC composite materials with superior mechanical and thermal qualities out of the starting material, which are customizable for potential applications in flexible electronics as protective/buildable films. Thin PMMA composite films with 0.5 wt.% and 1.0 wt.% SiC microfibers regarding PMMA were made by casting. The Differential Scanning Calorimetry (DSC) analysis verified that the PMMA/SiC composites achieved greater thermal stability than the neat PMMA due to the presence of SiC microfibers. The glass transition temperatures of PMMA/0.5 wt.% SiC and PMMA/1.0 wt.% SiC films were around 2.4°C and 3.5°C higher, respectively, in comparison with the pure PMMA film. The results also showed that the PMMA films with 0.5 wt.% and 1.0 wt.% SiC reinforcement had 17.9% and 55.6% improvement in microhardness, respectively, compared to the neat PMMA film. The Atomic Force Microscopy (AFM) characterization of the PMMA composite films was also carried out. The addition of SiC microfibers to the PMMA polymer matrix also caused an increase in the roughness of the PMMA/SiC films. The average roughness values of the PMMA/SiC films were approximately 3.9 (with 0.5 wt.% SiC) and 13.7 (with 1.0 wt.% SiC) times larger than those obtained for the pure PMMA film. AFM in semi-contact operation mode was used to obtain 3D images of Vickers indents on the surface of PMMA and PMMA/SiC composite films. Both optical and atomic force microscopy approved the presence of pile-up effect after the indentation of PMMA films
Plasmonic Enhancement of Photocatalytic Microreactors by Gold Nanoparticle Dimers Embedded in Semiconductor Thin Films
No full textWe present an approach to use nanoparticle
dimers embedded in thin semiconductor layers to enhance
photocatalytic microreactors. We show that the plasmonic
resonant modes of the dimer and the refractive modes of the
multilayer structure couple, leading to an enhanced utilization
of the optical spectra with additional localization hotspots with
high field enhancement. This approach also demonstrates that
particle agglomeration can be beneficial when nanoparticles are
embedded in a semiconductor layer to enhance photocatalytic
processes. Furthermore, we show that depending on the
coupling, different modes intrinsically contribute differently to
different mechanisms of optical carrier generation in the
semiconductor, in addition to the constraints imposed by the
semiconductor band structure
Steroidal Thiazolidin-4-ones: in Silico Prediction of Toxicity
No full textCancer remains a leading cause of death worldwide, and as a result,
scientists are focused on discovering new drugs to combat this disease. To save
both time and money, it is desirable to predict the drug-likeness and toxicity of
new compounds. According to RDKit library, previosly synthesized, highly
cytotoxic and selective steroidal thazolidin-4-ones (TZDs) were drug-like. Based
on in vitro cytotoxicity results in HeLa cells for 12 TZDs, a reliable in silico toxicity
model was developed for other similar compounds. The polar surface area and
number of H-bond acceptors of the tested TZDs were identified as the parameters
with the best correlation to experimentally obtained cytotoxicity.SYMBIOTECH 3rd INTERNATIONAL SYMPOSIUM ON BIOTECHNOLOGY, 13–14 March 2025, Faculty of Agronomy in Čačak, University of Kragujevac, Serbi
Poster: "Modeling the extraction process of gallic acid from pomegranate peel in a packed bed with recirculation"
No full textThe extraction of gallic acid from the pomegranate peel was carried out in a column with a diameter of 40 mm, in which pomegranate peel grains with a diameter of 2 mm were placed in a packed bed. The extraction fluid is recirculated through the system using a centrifugal pump. The fluids used in the extraction are: water, ethanol:water=50:50 and ethanol:water=96:4 (vol%). The experimental equipment has a temperature control system. The temperatures at which the experiment was carried out are: 35, 50 and 65˚C. raction, as well as the models themselves. The models used in the analysis are: film theory, non-stationary diffusion. The equations used to describe the extraction are Peleg's equation and Ponomarjev's equation. The extraction parameters for gallic acid and the diffusion coefficient were determined. A model for the dependence of the mass transfer coefficient on temperature was established, as well as a criterion equation describing the extraction of gallic acid from the pomegranate peel. The yield of gallic acid in solution is good.Poster presented at the IX International Congress Engineering, Environment and Materials in Process Industry EEM 2025. Abstract: [https://cer.ihtm.bg.ac.rs/handle/123456789/8356
Metabarcoding as a Tool for Phytoplankton Identification in Saline Lakes
No full textRad prikazuje metabarkoding analizu uzoraka fitoplanktona sakupljenih u jesen 2023. godine iz slanog jezera Pečena slatina (Južni Banat, Srbija). Cilj studije je identifikacija algi i cijanobakterija iz vodenog stuba koristeći jedan genski marker za obe grupe. Nakon filtriranja uzoraka vode obavljena je izolacija sredinske DNK, umnožavanje fragmenta gene za 23S rRNK i sekvencijanje pomoću MiSeq tehnologije. Bioinformatičkom obradom dobijenih sekvenci konstatovano je ukupno 54 avrijante sekvenci amplikona, od kojih je 45 povezano sa 25 taksona na nivou vrste pomoću Phytool v3 i NCBI baze sekvenci. Metabarkodingom je otkriveno da i po puta više taksona nego konvencionalnom metodom svetlosnog invertnog mikroskopa.This study presents a metabarcoding analysis of phytoplankton collected in autumn 2023 from saline lake Pečena slatina (Southern Banat, Serbia). The aim was to identify algae and cyanobacteria from the water column using a single genetic marker. After filtering the water, eDNA was isolated, fragment of the 23S rRNA gene was amplified, and sequencing was perfomed useing MiSeq technology. Bioinformatic analysis revealed a total of 54 amplicon sequence variants, 25 taxa were assigned to the species level using Phytool v.3 and NCBI database. The metabarcoding analysis revealed 2.5 gimes more taxa than the conventional method of light inverted microscopy.Mapa objavljena u radu: [https://cer.ihtm.bg.ac.rs/handle/123456789/8680
Experience Exchange on the Structuring and Functioning of the Project Management Office
No full textThe presentation outlines the establishment, growth, and strategic goals of the International Cooperation and Project Office (ICPO) of ICTM. It describes how ICPO supports research proposal development, post-award project administration, and international collaboration. Key initiatives include internal training, researcher surveys, networking efforts, digital tools for project monitoring, and the publication of institutional rulebooks.Presentation delivered on 17/01/2025 to Romanian institutes
The influence of TiO2 nanoparticles on thermal decomposition of polyurethane soft segments
No full textTesting the behavior of polymeric materials during heating, especially when it comes to materials
that have wide practical application and therefore large commercial importance, such as
polyurethanes, is essential. Results obtained by investigating thermal stability and thermal
decomposition of polymers, including kinetic modeling, can help to understand the mechanism of
thermal degradation reaction and also can be very helpful in an attempt to predict and roughly
evaluate lifetime of polymeric materials. In relation to that, the aim of this work was to examine
the effect of unmodified and surface modified TiO2 nanoparticles on thermal degradation and
thermal degradation kinetics of the soft segments of polyurethane network based on
polycaprolactone and aliphatic hyperbranched polyester. Surface modification of TiO2
nanoparticles was performed using gallic acid ester having C12 long alkyl chain (lauryl gallate).
Results obtained by thermogravimetric analysis performed at different heating rates in nitrogen
atmosphere for pure polyurethane and composites prepared by incorporation of 1.0 wt.% of
unmodified or surface modified TiO2 nanoparticles into polyurethane matrix were compared. It
was established that thermal decomposition of soft segments, i.e. polycaprolactone, is shifted to
higher temperatures for composites, and this shift is more pronounced for the sample prepared
with modified TiO2 nanoparticles. Furthermore, using values of the activation energy of thermal
degradation calculated by model-free Ozawa-Flyyn-Wall method, together with Coats-Redfern
model-fitting method and numerous kinetic models, the degradation mechanism of soft segments
was investigated. It has been shown that the best fitting kinetic model which can be applied to
describe thermal degradation mechanism of the soft polycaprolactone segments in the prepared
samples is the second (for pure polyurethane), i.e. the third (for composites) reaction order
kinetic model
Changes in the vibrational characteristics of clay samples during the drying process
No full textThis paper investigates the changes in the mechanical and acoustic properties of clay samples during drying. Variations in resonant behaviour over time were analysed using impulse excitation, with particular focus on the emergence and evolution of the fundamental vibration mode under free boundary conditions. During the drying process, there is a significant decrease in internal damping and an increase in the effective modulus of elasticity, which enables the appearance of clearly defined resonant frequencies only in the later stages of drying. Due to the relatively large thickness compared to the width of the sample, classical thin plate models are not fully applicable, so the results are interpreted while considering the limitations of the theory. Experimental data indicate that the first vibration mode becomes the dominant signal component only after the sample reaches a certain level of dryness. The results are relevant for the development of a methodology for non destructive monitoring of the mechanical properties of clay and similar materials during drying