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Synthesis and characterisation of metal–glass composite materials fabricated by liquid phase sintering
No full textIn recent years, there has been a global increase in environmental awareness, which has
driven the application of natural materials or the synthesis of novel, environmentally
compatible materials. Composite materials hold a prominent position among modern
materials and are typically developed to achieve resistance to various damage mechanisms,
thereby extending the service life of structures. This study presents the synthesis and characterisation
of high-density metal–glass composite materials. The commercially available
316L stainless steel powder was used as the matrix material, while andesite basalt powder
was used as the reinforcement phase. Andesite basalt aggregate, ground into powder, is a
cost-effective, widely available, and environmentally friendly natural raw material. Powder
metallurgy was employed to produce the composite materials. Sintering was performed
at 1250 ◦C for 30 min in a vacuum. The density of the sintered composite samples was
analysed as a function of andesite basalt content, with sintering conducted in the presence
of a liquid phase. Composite materials were characterised using optical and scanning
electron microscopy, X-ray structural analysis, and hardness testing. This study confirmed
that the optimal combination of properties was achieved in the composite with 20 wt.%
andesite basalt, present as a glass phase within the 316L steel matrix
Polystyrene nanosized dots: structure and optical properties
No full textNowadays, modern civilization uses around 30% of objects that are made of the plastics. Disposed plastic can be found in water, in soil, in the air and even in living organisms. Plastic enters living organisms through water and food. Thus, plastics used can harm human health. In everyday life, polystyrene (PS) is one of the most used plastics that is hard to recycle. In this research, the structural and chemical properties of PS based micro and nanoplastics were studied. Namely, commercially available PS (Styrofoam) was dissolved in chloroform. The obtained colloid was irradiated by gamma rays at doses of 300, 400, 500 and 600 kGy, respectively. Thus, PS based micro and nanosized particles were synthesized and further characterized by different techniques. Nanomechanical and nano-electrical properties were investigated by using atomic force microscope (AFM) in order to determine Young’s modulus of elasticity and charge distribution of PS particles synthesized respectively. Particle size distribution, height and shape of PS particles were determined by AFM as well. To check chemical composition, different techniques were used: Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The optical properties of the samples were studied by using photoluminescence (PL) and ultraviolet–visible (UV–Vis) spectroscopy. The PS particles have a size from 183 to 112 nm. They are positively and negative charged depending on the applied irradiation dose. PS particles irradiated at 600 kGy have doughnut like shape and their Young’s modulus of elasticity is around 400 MPa. Chemical analysis conducted by FTIR shows that all samples are composed of C, O, and H atoms dominantly with C-H, C=O, C-C and C-O characteristic bonds. Partial carbonization of PS nanoparticles is established from the Raman spectra, which is also confirmed by AFM. In the UV-Vis spectra of all PL particles we noticed pick at 260 nm. PL spectra of PS particles irradiated at 600 kGy show that these spectra have emission-excitation dependence.Twenty-Third Young Researchers' Conference Materials Science and Engineering, December 3-5, 2025, Belgrade, Serbia
Influence of the graphene oxide content in the ZnO/GO composite on the selectivity and sensitivity of the electrode for detecting diclofenac in water
No full textDiclofenac (DCF) is one of the most commonly used pharmaceuticals today. Due to its high consumption, DCF ends up in ecosystems and watercourses, where it becomes a pollutant, endangering the living world. Effective monitoring of contaminant concentrations in water is crucial for ensuring water quality, which can be achieved through electroanalytical methods. The performance of an electrochemical method is critically determined by the surface characteristics of the working electrode. Therefore, composites were designed to modify the surface of the working electrode to improve its properties. In this study, we propose zinc oxide/graphene oxide (ZnO/GO) composites with different weight percentages of GO relative to ZnO (0.005%, 0.01%, and 0.05%) to examine the influence of GO content on the characteristics of the electrode for the detection of DCF in water. The physicochemical characteristics of the materials were examined by X-ray diffraction analysis, Raman spectroscopy, and FESEM imaging. The materials were then combined with the carbon additive, distilled water, and ethanol into an ink to modify the glassy carbon electrode. After In Situ electrochemical reduction of GO, the obtained electrodes were tested for the oxidation of DCF in a neutral electrolyte (0.1 M phosphate buffer) by cyclic voltammetry (CV). CVs showed an irreversible anodic peak originating from the oxidation of DCF, as well as anodic and cathodic peaks originating from the oxidation/reduction of the decomposition product of the oxidized form of DCF. Parameters such as limit of detection (LOD), limit of quantification (LOQ), dynamic range, and sensitivity were evaluated. The measurements indicated that all electrodes are selective for DCF. The proposed materials are suitable for further investigation in the field of electrochemical detection of pharmaceuticals in aqueous electrolytes.Twenty-Third Young Researchers' Conference Materials Science and Engineering, December 3-5, 2025, Belgrade, Serbia
Uticaj promena izazvanih procesnim postupcima na performanse Ti-legure u biološkim sistemima
No full textThis work explores the impact of high-pressure torsion (HPT) and laser surface modification on the microstructure, surface features, mechanical properties, corrosion resistance, and biological response of the Ti-45Nb (mass%) alloy, considering its potential for biomedical application. HPT processing resulted in significant grain refinement, producing an ultrafine-grained alloy. Microstructural characterization revealed two phases, β-Ti and Ti₄Nb, present in both the coarse- and ultrafine-grained alloy microstructures, consistent with theoretical investigations. Subsequently, laser scanning of the Ti-45Nb alloy in both microstructural states produced uniform linear surface micropatterns accompanied by changes in surface chemistry (increased oxygen content and oxide layer formation) and surface topography (increased surface roughness). Mechanical testing showed that the elastic modulus, hardness, and plasticity increased in both microstructural variants after laser surface modification, with higher values observed in the ultrafine-grained alloy. Additionally, theoretical investigations confirmed these findings and highlighted the impact of both structural and surface modifications on the alloy’s mechanical behavior. Furthermore, corrosion testing demonstrated that all alloy samples exhibited high corrosion resistance, which was attributed to the formation of a dual-layer oxide film. The ultrafine-grained alloy developed a thicker inner barrier layer, whereas the coarse-grained alloy exhibited a thicker outer porous layer. Specifically, the best corrosion resistance was observed in the coarse-grained alloy prior to laser modification and in the ultrafine-grained alloy following laser modification. Finally, biological tests confirmed excellent cytocompatibility of the alloy in both microstructural states, before and after surface modification. In vitro tests further showed that laser surface modification enhances the attachment, adhesion, and proliferation of fibroblast cells on all alloy sample surfaces, indicating excellent biocompatibility, especially pronounced in the ultrafine-grained alloy. Overall, the combined influence of microstructural and surface modifications significantly enhanced the Ti-45Nb alloy’s performance, highlighting its strong potential for application in biological systems.Ovaj rad istražuje uticaj postupka uvijanjanja pod visokim pritiskom (HPT) i laserske površinske modifikacije na njenu mikrostrukturu, površinske karakteristike, mehanička svojstva, otpornost prema koroziji i biološki odgovor Ti-45Nb (mas.%) legure, uzimajući u obzir njen potencijal za primenu u biomedicini. Primena HPT procesa rezultirala je značajnom rafinacijom zrna, pri čemu je formirana sitnozrna legura. Mikrostrukturna karakterizacija otkrila je prisustvo dve faze, β-Ti i Ti₄Nb, u mikrostrukturama krupnozrne i sitnozrne legure, u skladu s teorijskim istraživanjima. Nakon toga, lasersko skeniranje Ti-45Nb legure u oba mikrostrukturna stanja proizvelo je uniformne linearne površinske mikroobrazce, uz promene u hemijskom sastavu površine (povećan sadržaj kiseonika i formiranje oksidnog sloja) i topografiji površine (povećana hrapavost). Mehanička ispitivanja pokazala su da su se vrednosti modula elastičnosti, tvrdoće i plastičnosti povećale kod obe mikrostrukturne varijante nakon laserske površinske modifikacije, pri čemu su veće vrednosti zabeležene kod sitnozrne legure. Takođe, teorijsko istraživanje potvrdilo je ove rezultate, ukazujući na uticaj i strukturnih i površinskih modifikacija na mehaničko ponašanje legure. Pored toga, ispitivanja korozije pokazala su da se svi uzorci legure odlikuju visokom otpornošću prema koroziji, što se pripisuje formiranju dvoslojnog oksidnog filma. Sitnozrna legura se odlikuje debljim unutrašnjim barijernim slojem, dok je krupnozrna legura pokazala deblji spoljašnji porozni sloj. Konkretno, najveća otpornost prema koroziji primećena je kod krupnozrne legure pre laserske modifikacije, odnosno kod sitnozrne legure nakon laserske modifikacije. Na kraju, biološki testovi potvrdili su odličnu citokompatibilnost legure u oba mikrostrukturna stanja i pre i nakon površinske modifikacije. In vitro ispitivanja su dodatno pokazala da laserska modifikacija površine poboljšava vezivanje, adheziju i proliferaciju fibroblastnih ćelija na površinama svih uzoraka legure, što ukazuje na izvanrednu biokompatibilnost, pri čemu je ovaj efekat najizraženiji kod sitnozrne legure. U celini, kombinovani uticaj mikrostrukturne i površinske modifikacije značajno je poboljšao ponašanje Ti-45Nb legure, ističući njen veliki potencijal za primenu u biološkim sistemima.26th YuCorr International Conference, November 3-5, 2025, Palić, Serbia
Short review on thermal conductivity of silicon nitride ceramics
No full textOne of the most promising substrate materials for the next-generation power devices with high thermal conductivity is silicon nitride (Si3N4). There are several ways to improve thermal conductivity of Si3N4. Substantially higher thermal conductivities for the Si3N4 ceramics could be attained by reduction of lattice oxygen content or by the increasing the β/α phase ratio during nitridation thus enhancing grain growth during post-sintering. The method of purification of the grains and decreasing the two-grain junction films by adding large β-Si3N4 grains to the raw Si3N4 powder, seeding by grain growth of Si3N4 crystals in polycrystalline ceramics also improves thermal conductivity. High thermal conductivity can be further achieved by development a textured microstructure in which elongated β-Si3N4 grains are oriented almost unidirectionally. This paper summarizes the extrinsic factors governing the thermal conductivity of Si3N4 ceramic regarding microstructural parameters such as lattice defects in single-crystal, sintering additives, change in microstructural parameters like α/β ratio, grain size, aspect ratio, grain orientation and the morphology, composition of grain-boundary, secondary phases, processing method
Development of low carbon and energy-efficient geopolymer-based paving blocks
Get PDFThe development of energy-efficient and low-carbon geopolymer-based paving blocks made from waste, as an environmental-friendly material, was evaluated. Ground concrete (GC) and solid brick (SB) powder, as the representatives of construction and demolition waste (C&DW), with the addition of fly ash (FA) and silica fume (SF), were used. Waste samples were characterized in terms of surface functional groups and radioactivity. The FT-IR spectra showed the required amorphous or semi-crystalline alumino-silicate structure. The gamma spectrometry confirmed waste samples' radiological safety. Hardened geopolymer samples were subjected to physical-mechanical investigation comprising of density, water content, compressive and flexural strengths determination. Based on strength characteristics, the three best prototype mixtures were selected and subjected to further compressive strength determination and durability assessment. Prototype sample SBFASFp1, with a compressive strength of 18.7 MPa, was shown the highest value of all samples, almost the same as the corresponding SBFASF1 sample. Freeze-thaw and the subsequent carbonation tests, as durability indicators, showed that the SBFASF1 sample had the slightest strength decrease, making it most durable in these conditions. These satisfactory test results showed the favorable effects of alternatives to cementitious materials, encouraging their utilization and contributing to the sustainability of the construction sector
Postupak dobijanja hidroksiapatita određenih mikrostrukturnih i funkcionalnih karakteristika zelenim tehnologijama
No full textPrikazano tehničko rešenje predstavlja inovaciju u vidu novog jednostavnijeg i ekološki prihvatljivijeg tehnološkog postupka dobijanja hidroksiapatitkog materijala za upotrebu u kozmetici. Primenom novog tehnološkog postupka hemijskom precipitacijom je dobijen hidroksiapatitski materijal zahtevanih morfoloških karakteristika iz ekološki prihvatljivih prekursora. Literaturni podaci ukazuju da su do sada u kozmetici kao materijali sa filterskim osobinama pretežno korišćeni oksidi cinka i titanijuma međutim sve se više skreće pažnja na korišćenje alternativnih materijala sa jednako dobrim efektom. Prilikom apsorpcije sunčevog zračenja korišćenjem hidroksiapatita ne dolazi do elektronskog prelaza u struktuti kao što je slučaj sa oksidima metala. Izbegavanje slobodno radikalskih procesa korišćenjem hidroksiapatitskog materijala kao filterske komponente značajno doprinosi bezbednijoj upotrebi kozmetičkog preparata za kožu. Hidroksiapatit je neorgansko jedinjenje koje se dugo koristi u biomedicini sa poznatom bioaktivnošću, kao netoksičan i neinflamatorni materijal. Dobijeni rezultati analiza ukazuju na afiltersku aktivnost u UV-VIS delu spektra. Na ovaj način je dobijena komponenta tačno definisanih i zahtevanih strukturnih i morfoloških karakteristika koja se može koristiti u proizvodnji kozmetičkih proizvoda sa smanjenim sadržajem konzervanasa i sa pozitivnim efektom u zaštiti kože od sunca. Filterska aktivnost dokazana je apsorpcijom na talasnim dužinama od 266 do 300 nanometara. Tehnikom rendgenske difrakcije na polikristalnom uzorku (XRD) utvrđeno je da je dobijen čist monofazni uzorak hidroksiapatita definisanih mikrostrukturnih karakteristika. Tehnikom skenirajuće elektronske mikroskopije (SEM) potvrđeno je da je dobijen nanokristalični čist hidroksiapatitski materijal, dok je tehnikom energetski disperzivne rendgenske spektorskopije (EDS) potvrđen odnos Ca/P koji iznosi 1.63 i u skladu je sa teorijskom stehiometrijskom vrednošću za hidroksiapatit. Rezultati transmisione elektronske mikroskopije (TEM) pokazale su da su heksagonalni priznatični kristali veličine preko 100 nanometara u dužinu. Finalno je svim dobijenim analizama potvrđeno da primenjeni tehnološki postupak za pripremu hidroksiapatita ispunjava uslov u pogledu mikrostrukturnih i morfoloških karakteristika i može se dalje primeniti u kozmetičkoj industriji.M82 - Novo tehničko rešenje (metoda) primenjeno na nacionalnom nivo
Novi tehnološki postupak dobijanja funkcionalizovanog celuloznog hidrogela – bakterijske celuloze, upotrebom bakterija sirćetnog vrenja poreklom iz kombuhe
No full textPrikazano tehničko rešenje predstavlja inovaciju u vidu novog tehnološkog postupka – dobijanja hidroksiapatitom funkcionalizovane hidrogela bakterijske celuloze za upotrebu u kozmetici. Primenom novog tehnološkog postupka mikrobiološki je dobijen celulozni hidrogel u obliku bakterijske celuloze (BC), aktivnošću bakterija poreklom iz kombuhe. U nastavku je BC funkcionalizovana hidroksiapatitom (HAp) pri čemu je dobijen ekološki prihvatljiv kompozitni materijal sa antibakterijskim delovanjem koji se može koristiti kao dodatak kozmetičkom proizvodu, maski za lice. Literaturni podaci ukazuju da je do sada u kozmetici pretežno korišćena celuloza biljnog porekla, koja se najčešće dobija iz drveta. Korišćenjem celuloze dobijene mikrobiološkim putem smanjuje se potražnja za celulozom biljnog porekla, što doprinosi zaštiti šuma, čime se ublažava efekat staklene bašte. Hidroksiapatit je neorgansko jedinjenje koje se dugo koristi u biomedicini sa poznatom bioaktivnošću, kao netoksičan i neinflamatorni materijal.
Dobijeni rezultati analiza ukazuju na antibakterijsku aktivnost funkiconalnog kompozitnog BC/HAp hidrogela inhibicijom bakterije Staphylococcus aureus, izazivača infekcije kože. Na ovaj način je dobijen proizvod koji se može koristiti u proizvodnji kozmetičkih proizvoda sa smanjenim sadržajem konzervanasa i sa pozitivnim efektom u tretmanu kože lica. Atibakterijska aktivnost se objašnjava kroz dokazano visoko pozitivno naelektrisanje HAp, utvrđivanjem pHpzc vrednosti. HAp je delovao sa negativno naelektrisanim ćelijskim zidom mikoorganizma izazivajući oštećenje ćelije. Tehnikom skenirajuće elektronske mikroskopije (SEM) potvrđeno je da je HAp materijal inkorporiran u BC, dok je tehnikom energetski disperzivne rendgenske spektorskopije (EDS) potvrđeno prisustvo C, O, Ca i P elemenata koji potiču od HAp i BC. Odnos Ca/P bio je u skladu sa teorijskom stehiometrijskom vrednošću za HAp. Dodatno je očigledna razlika u FT-IR spektru za uzorak HAp celuloze u odnosu na HAp potvrdila da je metoda sinteze i funkcionalizacije BC uspešno sprovedena. Finalno je analizom mikrobiološke ispravnosti uzoraka utvđeno da primenjeni tehnološki postupak za pripremu funkcionalnog BC/HAp hidrogela ispunjava uslov u pogledu mikrobiološke bezbednosti proizvoda i može se dalje primeniti u kozmetičkoj industriji.M82 - Novo tehničko rešenje (metoda) primenjeno na nacionalnom nivo
Machine learning-based predictions of the 4fn-4fn-15d1 UV absorption for Pr3+ and Ce3+ ions in fluoride and oxide compounds
No full textThe development of UV-C (100–280 nm) emitting phosphors utilizing the upconverted 4fn-15 d1→4fn interconfigurational broad band emission transition of lanthanide ions requires the fundamental understanding of the host-impurity interaction, which determines the positions of energy levels of the 4fn-15 d1 electronic configuration. In this work, we developed an ML Random Forest–based prediction algorithm utilizing a set of 22 dataset descriptors, such as structural characteristics of the host materials, electronic band gaps, ionic radii, and other material properties. The model was successfully tested across 46 impurity centers in various fluoride (chloride) and oxide compounds doped with the Pr3+ or Ce3+ ions. As an outcome of the developed model, predictions of the 4f-5d absorption wavelengths of Pr3+ and Ce3+ ions in the investigated hosts, were generated, demonstrating good correlation with the available literature data used initially for training. The obtained results indicate that host materials characterized by (i) a higher polyhedral volume (defined as the volume of the polyhedron formed by the impurity ion and its nearest neighbors), (ii) a higher coordination number (8 or 9), and (iii) high anion electronegativity—particularly fluorides doped with Pr3+ and Ce3+—may be of interest for applications in the UV-C domain. The resulting prediction model is characterized by the mean absolute errors between the predicted and literature data on the absorption wavelength of less than 3 nm only, which confirms the model's robust and effective performance. The approach developed in this work can be readily extended to other families of materials and/or dopant ions. © 2025 Elsevier B.V
Design principles for (efficient) excited-state absorption-based blue-to-UV upconversion phosphors with Pr3+
No full textUV light generation is generally not very efficient, expensive, or may even require toxic elements such as mercury. In contrast, blue light (λ = 450 nm) is cheaply available from semiconductor LEDs and its use in phosphor-converted LEDs is technologically mature and could be envisioned as an intense, sustainable light source in an upconversion scheme. The electronic energy level landscape of the 4f2 ion Pr3+ does allow such a blue-to-UV upconversion (UC) by resonantly exciting the 3PJ (J = 0, 1, 2) levels with blue light, followed by absorption of a second blue photon, thus populating the 4f15d1 configuration states located in the UV range. While the second absorption step is expected to be efficient based on selection rules, no clear guidelines on how to optimize the expected upconversion efficiency for Pr3+ by appropriate choice of a surrounding host are known up to now. Within this work, selected halidoelpasolites, oxyfluorides, garnets, silicates and borates are activated with Pr3+ to understand the relation between ESA-based UC efficiency, the energy and configurational offset of the 4f15d1 states as well as the excited-state dynamics. For that purpose, quantum yield measurements, as well as steady-state, time-resolved and temperature-dependent luminescence spectroscopy with different excitation sources and powers are combined. It turns out that several parameters must be carefully mutually matched within a host compound for efficient ESA-based blue-to-UV UC with Pr3+. Not only does the decay time of the intermediate 3P0 level have to be particularly long in an excited-state absorption upconversion scheme, but also the non-radiative crossover from the excited 4f15d1 states needs to be limited. All these conditions are particularly well fulfilled in the Pr3+-activated chloridoelpasolite Cs2NaYCl6:Pr3+, which shows the highest upconversion quantum yield (ΦUC = 0.11%, P = 0.59 W cm−2) among all investigated compounds within this work and even surpasses the efficiency of well-known upconverters in this field such as Lu3Al5O12:Pr3+ (LuAG:Pr3+) or β-Y2Si2O7:Pr3+ (YPS:Pr3+). The relatively high efficiency of this compound compared to the other standards is a consequence of its low cut-off phonon energy and rigid, densely packed structure with large mutual distances between the rare-earth ions. © 2025 The Royal Society of Chemistry