ritnms
Not a member yet
1551 research outputs found
Sort by
The innovative method for determining the approximate value of the Bond work index
No full textIn this study, we examine an innovative approach to determining the Bond work index, a key parameter in the mining and cement production industry that indicates material grindability. The method relies on the first-order kinetics law and allows for the estimation of approximate index values with any number of grinding cycles, depending on the desired data accuracy. An important aspect of this approach is the multiplication of parameters G and P80 for each cycle by specific coefficients, achieving values close to those of the last grinding cycle when equilibrium is reached in the standard test. In this paper, we compare the results obtained by the innovative method with the standard Bond procedure on various samples of mineral materials. Our analysis shows a significant reduction in the mean square error as the number of grinding cycles increases, indicating increased precision of the new approach
Hair trace elements analysis: a biomonitoring tool for the environmental exposures and helth risks
No full textHuman hair serves as a unique biomonitoring tool due to its ability to accumulate the trace elements over time, reflecting the environmental exposures and dietary intake. This study employed the Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to analyze the elemental composition of
human hair samples of different colors—red, black, blonde and gray. The results revealed varying levels of essential and toxic elements across different hair types, indicating the potential exposures to the environmental pollutants. Notably, red and blonde hair exhibited higher concentrations of Cu, Fe, and
Pb, which could be attributed to the environmental and dietary sources as well as the presence of metals in the hair coloring products. Gray hair also showed elevated Cu and Pb levels, possibly reflecting both environmental contamination and dietary intake. Non-washed hair generally displayed higher metal levels compared to washed samples, suggesting a prolonged exposure and accumulation. These findings highlight the utility of hair analysis as a non-invasive method for assessing the long-term metal
exposures and their implications for human health
Synthesis and characterization of glasses and glass-ceramics based on fly ash and waste glass
No full textPredmet ove doktorske disertacije je ispitivanje mogućnosti korišćenja otpadnih materijala za dobijanje staklastih i staklokeramičkih materijala. Leteći pepeo iz termolektrane „Nikola Tesla”, Obrenovac, stakleni krš ambalažnog stakla i saturacioni mulj fabrike šećera „Crvenka“, Crvenka korišćeni su kao polazne sirovine za dobijanje materijala. Ovi materijali obično se odlažu na deponije i nemaju upotrebnu vrednost. Njihovom primenom mogu se dobiti stakla i sinterovani staklasti i staklokeramički materijali velike gustine i dobrih mehaničkih svojstava. Upotrebom staklenog krša ambalažnog stakla i saturacionog mulja moguće je dobiti staklene pene visoke poroznoti koje imaju termoizolaciona svojstva.
Ispitivano je šest različitih sastava stakala na bazi letećeg pepela sa različitin dodacima: CaCO3 i Na2CO3, Na2CO3, CaCO3, saturacioni mulj, stakleni krš i CaCO3 i stakleni krš i saturacioni mulj. Struktura stakala ispitivana je FTIR metodom. Dekonvolucijom dela FTIR spekra na ~900 cm-1 određen je sadržaj vezujućeg i nevezujućeg kiseonika u tetraedrima koji izgrađuju staklenu mrežu. Termomikroskopskom analizom praćena je promena oblika silueta uzoraka stakla pri zagrevanju. Na osnovu temperatura fiksnih tačaka viskoznosti određene su viskoznosti stakala i energije aktivacije viskoznog toka. Primenom termomikroskopske i DTA analize definisane su temperature sinterovanja prahova stakala. XRD analizom identifikovane su kristalne faze nakon toplotne obrade uzoraka. Tvrdoća sinterovanih uzoraka određena je metodom po Vikersu. Primenom ultrazvučne vibracione metode određena je otpornost na dejstvo kavitacije sinterovanih uzoraka. SEM analizom identifikovana su oštećenja površine sinterovanih uzoraka nakon dejstva kavitacije. Hemijska postojanost sinterovanih uzoraka stakla ispitivana je TCLP metodom, kao i u destilovanoj vodi, 0,01 mol/dm3 rastvoru HCl i 0,01 mol/dm3 rastvoru NaOH. Potvrđeno da nije došlo do narušavanja strukture sinterovanih uzoraka nakon ispitivanja hemijske postojanosti.
Ispitivan je uticaj dodatka saturacionog mulja, otpada sa visokim udelom CaCO3, i temperature zagrevanja na svojstva staklene pene. Ispitivana su fizičko-mehanička svojstva dobijenih staklenih pena. XRD metodom identifikovane su kristalne faze nastale tokom toplotne obrade. Mikrostrukturne karakteristike, odnosno, veličina pora određena je analizom fotografija površina staklene pene visoke rezolucije. Ispitan je uticaj sastava staklene pene i temperature sinterovanja na toplotnu provodljivost staklene pene. Najnižu toplotnu provodljivost, 0,043 W/m·K, imao je uzorak najveće poroznosti, odnosno, uzorak sa 2,5 % CaCO3 sinterovan na 800 °C.
Upotrebom otpadnih sirovina sintetisani su materijali koji imaju upotrebnu vrednost. Mogućnost smanjenja količine otpada koji se odlaže na deponije, „besplatne“ sirovine i podsticanje otvorenog kruga reciklaže su samo neki od benefita primene otpadnih sirovina za dobijanje novih materijala.The subject of this doctoral dissertation is the study of the application of secondary raw materials for the production of glassy and glass-ceramic materials. Fly ash from the thermal power plant "Nikola Tesla", Obrenovac, glass cullet from container glass, and sugar beet factory lime from the sugar factory "Crvenka", Crvenka were used as starting raw materials for obtaining the materials. These materials usually end up in landfills and have no use value. By their application, glasses and sintered glass powders of high density and good mechanical properties can be obtained. By using glass powders of packaging glass and sugar beet factory lime, it is possible to obtain high-porosity foam glasses that have thermal insulation properties.
Six different compositions of fly ash-based glasses with different additives were studied: CaCO3 and Na2CO3, Na2CO3, CaCO3, sugar beet factory lime, glass powder and CaCO3, and glass powder and sugar beet factory lime. The structure of the glasses was examined by the FTIR method. Deconvolution of part of the FTIR spectrum at ~900 cm-1 determined the content of bridging and non-bridging oxygen in the tetrahedra that make up the glass network. The change in the shape of the glass samples during heating was monitored by thermomicroscopic analysis. Fixed points of viscosity have defined shapes of pressed glass powder when heated. Based on the temperatures at the fixed viscosity points, the viscosity of the glasses and the activation energy of the viscous flow were determined. Using thermomicroscopic and DTA analysis, the sintering temperatures of glass powders were defined. XRD analysis identified crystalline phases after heat treatment of the samples. The hardness of the sintered samples was determined by the Vickers method. The cavitation resistance of the sintered samples was determined using the ultrasonic vibration method. Damage to the surface of the sintered samples after cavitation was identified by SEM analysis. The chemical durability of sintered glass samples was tested by the TCLP method and in distilled water, 0.01 mol/dm3 HCl solution, and 0.01 mol/dm3 NaOH solution. The FTIR method confirmed that the structure of the sintered glass samples did not deteriorate after the chemical durability tests.
The influence of the addition of sugar beet factory lime, waste rich with CaCO3, and the heating temperature on the properties of the foam glass was investigated. The physical and mechanical properties of the obtained foam glasses were tested. The crystalline phases formed during the heat treatment were identified by the XRD method. The compressive strength of the foam glass samples was determined by a universal device for testing mechanical properties. Microstructural characteristics, i.e., pore size, were determined by analyzing high-resolution photographs of foam glass polished surfaces. The influence of foam glass composition and sintering temperature on the thermal conductivity of glass foam was examined. The sample with the highest porosity, i.e. the sample with 2.5% CaCO3 sintered at 800 °C, had the lowest thermal conductivity, 0.043 W/m·K.
By using waste raw materials, materials with useful value were synthesized. The possibility of reducing the amount of waste disposed of in landfills; ""free"" raw materials and promotion of open-loop recycling are just some of the benefits of using waste raw materials to obtain new materials
Micromechanical modeling of brittle transcrystalline fracture in medium-carbon microalloyed steels
No full textU radu su ispitivana dva komercijala srednjeugljenična čelika za kovanje mikrolegirana titanom i vanadijumom – TiV-čelik (0,099%V, 0,002%Ti i 0,256%С) i V-čelik (0,123%V,0,011%Ti i 0,309%С). Cilj rada je da modelovanjem dodatno produbi razumevanje i detaljnije opiše mikromehanizam krtog loma ovih srednjeugljeničnih mikrolegiranih čelika sa dominantnom strukturom acikularnog ferita (AF). Mikrostrukture oba čelika su dobijene termičkom obradom na 1250 °C u trajanju od 30 minuta u atmosferi argona, i kontinuiranim hlađenjem na mirnom vazduhu i ispitivane su primenom svetlosnog mikroskopa i skenirajućeg elektronskog mikroskopa. Mehanička ispitivanja savijanjem u četiri tačke i jednoosnim zatezanjem vršena su na temperaturi tečnog azota. Modelovanje je rađeno metodom konačnih elemenata softverom ABAQUS, a kvantitativna analiza mikrostrukture i merenje debljine cementita rađeno je softverom MIPAR. Izmereni udeo cementitnih pločica između iglica AF za V čelik iznosi 3,78% (maksimalne debljine 0,948 µm), dok za TiV-čelik 18,30% (maksimalne debljine 1,109 µm). Prema modelovanim raspodelama napona debljina izmerenih cementitnih pločica u AF nijedan od identifikovanih uključaka nisu utvrđeni kao izvor inicijacije loma. Prosečna vrednost efektivne površinske energije loma V-čelika iznosi 58,5 Jm-2dok za TiV-čelik iznosi 55,6 Jm-2. Mikromehanizam loma u oba ispitivana čelika može se svesti na dva koraka, u skladu sa Miler-Smitovim mehanizmom: I- Usled velike deformacije pri vrhu zareza dolazi do inicijacije loma stvaranjem inicijalnih mikroprslina lomom cementitnih lamela unutar perlita. II- Nastala mikroprslina lako se rasprostire kroz susedne perlitne kolonije i feritna zrna slične kristalografske orijentacije formirajući početnu mikroprsline kritične veličine.Two commercial medium carbon forging steels microalloyed with titanium and vanadium – Ti-V steel (0.099%V, 0.002%Ti and 0.256%S) and V-steel (0.123%V, 0.011%Ti and 0.309%S) were examined. The aim of the work is to deepen understanding and describe micromechanism of brittle fracture in the two medium carbon steels with a dominant structure of acicular ferrite AF). The microstructure of both steels was obtained by thermal treatment at 1250 °C for 30 minutes in an argon atmosphere, continuous cooling in still air and were examined using light microscopy and scanning electron microscopy. Four-point bending and uniaxial tension tests were performed at liquid nitrogen temperature. Modeling was performed with finite element method using ABAQUS software, and quantitative analysis of microstructure and cementite thickness was done using MIPAR image analysis software. The measured volume fraction of cement plates in AF for V-steel is 3.78% (maximum thickness 0.948 µm), while for TiV-steel 18.30% (maximum thickness 1.109 µm). According to the modeled stress distributions, the thickness of the measured cementite plates in AF, as well any of the identified inclusions, there were not detected to be the source of fracture initiation. The average value of the effective fracture surface energy of V-steel is 58.5 Jm-2 , while for TiV-steel it is 55.6 Jm-2. The micromechanism of fracture in both tested steels can be reduced to two steps, according to Miller-Smith's mechanism: I- Due to the large plastic deformation in front of the notch, fracture initiation occurs by creating microcracks by cracking the cementite lamellae inside pearlite. II- The resulting microcrack propagate easily through adjacent pearlite colonies and ferrite grains of similar crystallographic orientation, forming the initial facet of critical size
Examination of the biosorption capacity of various biological materials collected on the territory of Serbia for the removal of Cu2+ and Co2+ ions from aqueous solutions
No full textTeški metali predstavljaju značajne kontaminante otpadnih voda zbog svoje nebiorazgradive prirode i trajne sposobnosti da se akumuliraju u ekosistemima. Tehnologije bioadsorpcije, koje koriste biološke materijale kao što su mikroorganizmi, delovi biljaka i prirodni polimeri, predstavljaju efikasne metode za uklanjanje teških metala iz vodenih rastvora. Ova studija istražuje potencijal različitih prirodnih biomaterijala, poreklom iz Srbije, piljevinu, vunu i hrastovu galu za biosorpciju Cu²⁺ i Co²⁺ jona iz vodenih rastvora. Rezultati pokazuju da svi ispitani materijali imaju potencijal za remedijaciju Cu²⁺ i Co²⁺ jona, pri čemu hrastova gala demonstrira najveći kapacitet biosorpcije među analiziranim uzorcima.Heavy metals are persistent contaminants in wastewater due to their non biodegradable nature and their ability to accumulate in ecosystems. Biosorption technologies, which utilize biological materials such as microorganisms, plant parts, and natural polymers,
have emerged as effective methods for removing heavy metals from aqueous solutions. This study evaluates the biosorption potential of various natural biomaterials originating from Serbia—specifically sawdust, wool, and oak galls—for the removal of Cu²⁺ and Co²⁺ ions
from water. The examined biomaterials exhibit potential for the remediation of Cu²⁺ and Co²⁺ ions, with oak galls demonstrating the highest biosorption capacity among the tested
materials
The remediation potential of functionalised biochar based soil amendment
No full textIn this paper, thermochemical conversion was used to transform waste biomass into a stable,
carbon rich product – biochar. The starting material, waste plum stones (PS) were firstly
modified by magnesium salt in order to increase its binding potential toward phosphates, and
then converted by slow pyrolysis into the biochar, obtaining Mg-biochar composite (PS-M-B).
This material was further enriched by phosphates in a batch experiments resulting in PS-M-B-P,
characterised by its pH, electrical conductivity (EC) and SEM-EDX. Since the biochar is known
to reduce the soil acidity, phyto-toxicity and present metals mobility, synthetized material was
further applied as soil amendment at contaminated soil sampled on a former mine located in
France. Preliminary results confirmed that the application of enriched Mg-biochar composite
onto Pontgibaud technosol increased soil pH as well as soil EC, provided lead immobilisation
and supported the plant growth
Geochemical study of biomarkers in Eocene coal from the Bourgas Basin
No full textAn initial study of biomarker compositions of three coal samples from the Bourgas Basin is presented. Biomarkers were analyzed by gas chromatography-mass spectrometry (GC-MS) to assess organic matter source in the studied samples. The alkane distributions are dominated by long-chain n-alkanes (n-C27 to n-C31), usually found in higher terrestrial plants rich in cuticular waxes. The maximum relative intensity is determined at n-C31. Carbon preference index (CPI) values higher than 8.0 reflect a marked predominance of odd over even-numbered alkanes. The non-aromatic polycyclic hydrocarbons are dominated by hopanes, indicating microbial (bacterial) activity in the ancient swamp environment. The differences in the precursor vegetation are related to varying contributions of gymnosperms versus angiosperms during peat accumulation in the Bourgas Basin. The depositional environment was likely dynamic, with alternating oxidizing and reducing conditions
DETALJNA KARAKTERIZACIJA, I ODABIR UZORAKA PEĆNE PRAŠINE (EAF) ZA ISPITIVANJE MAGNETNE I GRAVITACIJSKE SEPARACIJE NA NJIMA ZA EU PROJEKAT RIS-DUSTREC-II NO 22009 IZ OBLASTI EIT RAW MATERIALS
No full textVelike količine prašine iz EAF peći se stvaraju u Evropi (1,3Mt), kao i u svetu (8,764Mt). Zbog visokog sadržaja Fe i Zn (zbirni sadržaj često između 50 i 60% maseno) u EAF prašini, ona je oduvek bila interesantna za reciklažu. Do sada, najčešće primenjivana metoda prerade EAF prašine je pirometalurški process ekstrakcije Zn u Waelz pećima (85% tržišnog učešća). Cilj EU Projekta iz oblasti EIT Raw Materials: Zero waste reprocessing of EAF and CF dust with competence build-up: RIS-DustRec-II 22009, je razvoj inovativnih tehnologija za odvajanje, ponovnu obradu i korisnu upotrebu svih komponenti EAF i CF prašine iz peći, kako bi se smanjila količina toksičnog otpada i postigla njegova nulta vrednost –što je cilj za otpad u EU. Za ova ispitivanja uzeto je 8 uzoraka EAF prašine iz postrojenja sa područja jugoistočne Evrope i na njima je obavljena detaljna fizičko-hemijska I mineraloška karakterizacija. Hemijska anliza je obavljena na XRF i ICP-OS-u, mineraloška analiza: XRD i Ritveldovom metodom, kao i na optičkom i SEM mikroskopu. Na osnovu dobijenih rezultata, odlučeno je da se na dva uzorka EAF prašine ZGH Boleslaw-Poland i SIJ Metal Ravne-Slovenija obave opiti magnetne I gravitacijske separcije, radi sveobuhvatnog izdvajanja svih korisnih komponenti iz njih. Urađene su i predstavlјene hemijske, XRD i SEM analize na dva odabrana uzorka prašine EAF i CF obavljena u Italiji
Key material characteristics to consider when pelletizing limestone
No full textWhile pelletizing limestone has become a standard practice due to the numerous advantages it offers, the process demands careful engineering to guarantee a consistently reliable and continuous operation, maximizing on-size yield. Several material characteristics play a crucial role in this endeavor. These include factors such as particle size distribution, moisture content, bulk density, and chemical composition. Each of these characteristics must be meticulously managed to produce a high-quality final product and optimize the efficiency of the pelletizing process. Understanding and addressing these variables is essential for achieving the desired outcomes and maintaining operational effectiveness
Cavitation resistance of refractory coatings
No full textIn this study, the resistance to the cavitation effect of three types of refractory samples based on
talc with the addition of 10%, 15% and 20% cordierite was investigated. Talc has a fine structure,
low hygroscopicity, insensitivity to temperature changes, low coefficient of thermal conductivity,
low coefficient of linear thermal expansion, great ability to stick and coat surfaces, good
grindability, low hardness. Cordierite has high refractoriness, high hardness, high density, low
value of dielectric constant, low coefficient of thermal conductivity, low coefficient of linear
thermal expansion, high resistance to thermal shock, relatively high melting temperature with the
possibility of application up to 1380 C, high inertness towards liquid metal. Cordierite was added
in order to improve properties, primarily to increase resistance to the effect of cavitation. The
prepared mixtures of refractory powders were pressed under a pressure of 1 MPa and sintered at
1200 C.To evaluate the cavitation resistance properties of the investigated refractory samples, the
ultrasonic vibration method with a stationary sample was applied. The change in the mass of the
samples as a function of the cavitation time was monitored and the cavitation speed was
determined. The formation and development of damage to the surface of the samples was
monitored using a scanning electron microscope. The mechanism of degradation and resistance to
the effect of cavitation of the tested samples was monitored by measuring the mass loss and
morphological analysis of the pits formed on the surface of the tested samples. Research has
shown that the addition of cordierite in the composition of the tested samples based on talc
significantly improves the properties of resistance to the effect of cavitation