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Cavitation Resistance of Laser-Sintered MS1 Steel
No full textThis study focuses on the determination of cavitation rate for samples produced by Direct Metal Laser Sintering (DMLS) of MS1 maraging steel powder without any post-processing thermal or mechanical treatment (as-built). The test samples, fabricated using an EOSINT M280 machine in a nitrogen atmosphere, were evaluated for their cavitation resistance using the ultrasonic vibration method as proposed by the ASTM G32 standard. Surface characterization to determine the duration of the experiment, as well as during and after the experiment to analyze changes in surface characteristics, was conducted using Scanning Electron Microscopy (SEM). Additionally, chemical analysis was performed using the Energy Dispersive X-ray Spectroscopy (EDS) method before and after the experiment to identify any changes and locations of significant surface damage. The mass loss of the samples over time was measured to calculate the cavitation rate. The goal of this research was to explore the potential applications of laser-sintered MS1 steel powder for manufacturing machine components and parts that are subject to cavitation erosion, due to the numerous benefits of additive manufacturing over traditional conventional technologies.Ова студија је фокусирана на одређивање кавитационе брзине узорака
произведених директним металним ласерским синтеровањем (ДМЛС) МС1 челичног
праха, без икакве накнадне термичке или механичке обраде. Испитни узорци,
произведени коришћењем машине ЕОСИНГ M280 у азотној атмосфери, су
испитивањни на отпорност на кавитационо разарање коришћењем методе
ултразвучних вибрација, сагласно стандарду АСТМ Г32. Карактеризација површине за
одређивање трајања експеримента (изложености узорка кавитацији), као и током и
након експеримента ради анализе промене површине, спроведена је помоћу скенирајуће
електронске микроскопије (СЕМ). Поред тога, извршена је хемијска анализа
коришћењем методе енергетске дисперзивне рендгенске спектроскопије (ЕДС) пре и
после експеримента да би се идентификовале све промене и места значајних
површинских оштећења. Губитак масе узорака током времена је мерен да би се
израчунала кавитациона брзина. Циљ овог истраживања је био да се истражи
потенцијална примена ласерски синтерованог MС1 челичног праха за производњу
машинских елемената и делова који су изложени кавитационој ерозији, а због бројних
предности адитивне производње у односу на традиционалне конвенционалне
технологије
Novi biorafinerijski pristup za frakcionisanje žetvenih ostataka
No full textAgri-food waste comprises lignocellulosic biomass (LCB), which consists of cellulose, hemicellulose and lignin. This composition makes LCB suitable for producing energy, biofuels, and value-added products within the biorefinery framework. Different pretreatments were developed and widely used to convert lignocellulose into these products. However, many conventional pretreatments are being substituted due to a lack of sustainability, stressing the urge to shift to greener alternatives. This study employed cold plasma as a low-energy technique for corn stalk delignification. Four experimental set-ups were tested for pretreatment – water as a pH-neutral and chemical-free pretreatment, Fenton reagent as acidic, alkaline hydrogen peroxide as an alkaline pretreatment, and natural deep eutectic solvent (NADES) as an emerging green solvent for LCB pretreatment. Each pretreatment was optimised towards achieving the highest delignification rate. Delignified samples were subjected to enzymatic hydrolysis with a commercial mixture of cellulase, hemicellulase and β-glucosidase, Cellic CTec 2 (Novozymes, Denmark) to estimate the biomass digestibility. Selected samples were tested for biomethane production through anaerobic digestion. The highest delignification was achieved with cold plasma/alkaline pretreatment (79%), followed by cold plasma/NADES (75%), cold plasma/Fenton (56%), and finally cold plasma/water pretreatment (52%). Cold plasma/alkaline and cold plasma/NADES pretreatments also showed potential for increasing biomethane yield. After a 30-day-long anaerobic digestion, samples pretreated with cold plasma/alkaline and cold plasma/NADES pretreatment showed an increase in biomethane production compared to the raw biomass by 9% and 18%, respectively. Moreover, the time needed to achieve 80% of the final biomethane yield (t80) was significantly reduced from 13 days for raw biomass to 5 days for cold plasma/alkaline pretreated, and 7 days for cold plasma/NADES pretreated biomass. At the same time, the lignin fraction was successfully recovered for value-added products while preserving the carbohydrate fraction. Cold plasma proved to be a promising pathway for LCB valorisation following circular economy principles.Otpad iz poljoprivrede i prehrambene industrije predstavlja lignoceluloznu biomasu (LCB), koja se sastoji iz celuloze, hemiceluloze i lignina. Zahvaljujući svom sastavu, LCB je pogodna za proizvodnju energije, biogoriva i proizvoda sa dodatom vrednošću u okviru biorafinerijskih postupaka. Razvijeni su različiti pretretmani koji se koriste za prevođenje lignoceluloze u neki od ovih proizvoda. Međutim, usled nedostatka održivosti, sve više konvencionalnih pretretmana se zamenjuje novim alternativnim metodama, ukazujući na potrebu za prelazak na zelene tehnologije. U ovom radu korišćena je hladna plazma kao niskoenergetska tehnika za delignifikaciju kukuruzne stabljike. Ispitana je mogućnost primene četiri eksperimentalne postavke kao pretretmana – voda kao pH neutralni pretretman bez hemikalija, Fentonov reagens kao kiseli, alkalni rastvor vodonik peroksida kao alkalni pretretman i prirodne duboke eutektičke smeše (NADES, engl. Natural deep eutectic solvents), kao nova vrsta zelenih rastvarača koji se mogu koristiti za pretretman LCB. Pretretmani su optimizovani u cilju postizanja najvećeg stepena delignifikacije. Nakon uklanjanja lignina, uzorci su podvrgnuti enzimskoj hidrolizi primenom komercijalne smeše celulaza, hemicelulaza i β-glukozidaza, Cellic CTec 2 (Novozymes, Danska). Odabrani uzorci su podvrgnuti anaerobnoj digestiji kako bi se ispitala mogućnost proizvodnje biometana. Najveći stepen delignifikacije postignut je primenom kombinovanog plazma/alkalnog pretretmana (79%), zatim plazma/NADES pretretmana (75%), plazma/Fenton pretretmana (56%), i plazma pretretmana u vodi (52%). Nakon 30-dnevne anaerobne digestije, uzorci tretirani kombinovanim plazma/alkalnim i plazma/NADES pretretmanima pokazali su porast prinosa biometana za 9%, odnosno 18%, u odnosu na netretiranu biomasu. Takođe, vreme neophodno za proizvodnju 80% od ukupne količine nastalog biometana (t80) je skraćeno sa 13 dana u slučaju netretirane biomase, na 5 dana za plazma/alkalni, odnosno 7 dana za plazma/NADES pretretman. Istovremeno, ligninska frakcija je razdvojena od ugljenohidratne frakcije i izolovana za dalju upotrebu u biorafinerijskim procesima. Hladna plazma se pokazala kao dobar izbor za valorizaciju LCB u skladu sa principima cirkularne ekonomije
Tailoring multipurpose capabilities of jute (Corchorus) with a focus on the cleaner production and “zero waste” concept
No full textThis paper explores obtaining multipurpose jute fabrics via sodium periodate oxidation (0.2% or 0.4% NaIO4 for 60 or 120 min) and alginate coating, emphasizing the principles of cleaner production and the “zero waste” concept. Assessment of the suitability of raw and oxidized fabrics for carpet backings was conducted based on their abrasion resistance, volume electrical resistivity, and compression resilience. Fabric quality test revealed that both fabrics oxidized for 60 min (characterized by 4.3–6.9% mass loss after 1000 abrasion cycles, resistivity of 13.2–21.6 GΩcm at 50–40% relative air humidity, and compression resilience of 24.2–25.5%) are the most suitable for producing carpet backing. A separate segment of the manuscript focuses on developing geo-prebiotic supports with high water retention by alginate coating of studied fabrics. The highest water retention (146.8%) has alginate-coated fabric oxidized with 0.4% NaIO4 for 120 min, suggesting significant potential for supporting the growth of cyanobacteria, thereby facilitating the restoration of degraded terrains. Furthermore, the paper underscores the imperative of waste minimization, whereby waste of fabric identified as most suitable for carpet backing and geo-prebiotic supports was tested as an adsorbent for the antibiotic ciprofloxacin. To accomplish the “zero waste” concept, and to mitigate secondary pollution from ciprofloxacin-saturated adsorbents, conversion to activated carbon was pursued, enabling the exploration of new application such as charge storage devices—supercapacitors. Specific capacitance values of the resulting activated carbons ranged between 126 and 210 F/g for one electrode at a current density of 0.3 A/g
Potencijal odabranih biljnih pigmenata za korišćenje u solarnim ćelijama aktiviranim bojom: trenutni status
No full textDye-sensitized solar cells (DSSC) represent the third generation of solar cells which have revolutionized sustainable energy research owing to the fact that they act as a renewable energy source integrated with employment of environmentally benign light-harvesting pigments as sensitizers and cost-effective materials for manufacture. This review compiles the exploration of plant pigments with a potential for use as photosensitizers in solar cells, focusing on their isolation and the factors that affect their physicochemical properties to identify those pigments providing the optimum performance. Newly reported considerations of flavonoids, anthocyanins, carotenoids, betalains, and chlorophyll, as light-harvesting pigments are summarized. Further, outcomes of the solar cell efficiency obtained by various semiconductors and types of electrolytes are compared and discussed. The main goal of this review is to highlight the significance of naturally obtained light-harvesting pigments, which will be used as the promising class of sensitizers in DSSC.Treća generacija solarnih ćelija, u koje spadaju i solarne ćelije aktivirane bojom, privukla je veliku pažnju istraživača tokom poslednjih decenija, prevashodno zbog svoje netoksičnosti i ekonomičnosti. U ovom radu sumirano je dosadašnje istraživanje biljnih pigmenata sa mogućnošću primene kao fotosenzitizatora u solarnim ćelijama, pri čemu je fokus stavljen na njihovo izolovanje, prečišćavanje i faktore koji utiču na njihova fizičko-hemijska svojstva. Istraživanja o solarnim ćelijama uglavnom su usmerena ka flavonoidima, antocijaninima, karotenoidima, betalanima i hlorofilu, kao ekološki najprihvatljivijim prirodnim fotosenzitivnim jedinjenjima. Pored toga, podaci o solarnoj efikasnosti, do kojih se došlo primenom različitih tipova poluprovodnika i elektrolita, takođe su prikazani u ovom radu. Osnovni cilj ovog rada je da se istaknu mogućnosti upotrebe prirodnih fotosenzitivnih pigmenata u izradi solarnih ćelija i da se stavi akcenat na one kandidate čijom će se primenom u solarnim ćelijama postići najbolje performanse
Method for the preparation of low viscosity eco-friendly unsaturated polyester resin
No full textPredmet ovog pronalaska je metoda za dobijanje ekološki prihvatljivih nezasićenih poliestarskih smola niske viskoznosti korišćenjem postupka modifikacije terminalnih grupa predpolimera reaktivnim rastvaračem iz bio-obnovljivih izvora. Metoda se zasniva na upotrebi dimetil itakonata kao reaktivnog rastvarača, koji bi mogao istovremeno da se koristi i za modifikaciju terminalnih grupa predpolimera i za umrežavanje smole. Ovom metodom se postiže kontrolisano zaustavljanje rasta lanca predpolimera modifikacijom terminalnih hidroksilnih grupa dimetil itakonatom. Na ovaj način se eliminiše potreba za upotrebom toksičnih, ekološki neprihvatiljivih rastvarača, koji se koriste u postojećim tehnologijama. Primenom ove metode dobijaju se ekološki prihvatljive smole niske viskoznosti što može da olakša i njihovu preradu i omogući širok spektar primena, uz istovremeno smanjenje negativnog uticaja na životnu sredinu.Broj prijave: P-2025/045
Impact of trehalose-based cryoprotectant on immobilization and release of Lactobacillus plantarum obtained for wound dressing
No full textLactobacillus plantarum has been increasingly studied and applied in the context of wound healing and wound dressings, thanks to its antimicrobial, anti-inflammatory, and biofilm disruption properties. In some approaches, lyophilized (freeze-dried) L. plantarum is applied as a powder or mixed with a carrier to facilitate topical delivery.
Lactobacillus plantarum was diluted in 10 % trehalose and a mixture of 5 % trehalose and skim milk. The mixtures were aseptically added on top of AC pads, frozen at −80 °C, and freeze-dried for 5 h. Immobilized probiotics on AC pads were incubated in normal saline at 37 °C for 24 h. Immobilization efficiency after lyophilization and the release of probiotics from the pad after 10 and 180 minutes, as well as after 24 hours were determined.
The combination of trehalose and skim milk showed significantly better results, maintaining almost 80 % viability after 24 h, Trehalose alone preserved almost half as many probiotics compared to trehalose with milk. Since the controlled release of probiotics is essential for their antimicrobial effectiveness in wound dressings, it can be concluded that the AC pad containing probiotics protected with both trehalose and skim milk is a more effective option than the probiotics protected with trehalose alone
Poly(vinyl alcohol)/Gentamicin and Poly(vinyl alcohol)/Chitosan/Gentamicin: Promising Materials for Rapid Burn Wound Healing
No full textScar formation and delayed wound healing pose significant challenges in treating skin injuries, especially in severe cases like burns and diabetic wounds. This study investigates the effectiveness of novel Poly(vinyl alcohol) (PVA)/Gentamicin (Gent) and PVA/Chitosan (CHI)/Gent hydrogels in promoting healing of second-degree burn wounds in a rat model. Following in vitro testing, these hydrogels were deemed non-toxic and suitable for in vivo analysis. Clinical evaluations were conducted on the 3rd, 7th, 14th, and 21st post-injury days, assessing parameters such as blistering, edema, redness, crust, bleeding, secretion, scar tissue formation, and wound contraction percentage. Histological analyses focused on re-epithelization and dermal evaluation at specific time points. Results showed that both hydrogels significantly reduced inflammation, particularly redness, by the 14th day and improved re-epithelization, with the PVA/CHI/Gent group outperforming on the 14th day and the PVA/Gent group excelling on the 21st day. Histological findings indicated increased fibroblast proliferation and collagen deposition in treated groups, suggesting enhanced dermal healing. The PVA/CHI/Gent hydrogel demonstrated notable antibacterial properties, likely due to the synergistic effects of CHI and Gent, leading to reduced inflammation and edema. Overall, both hydrogels show promise as effective wound dressings, facilitating faster healing and improved tissue recovery in burn injuries. This study supports the use of biomimetic scaffolds for enhanced wound management in clinical practices
Development of Grain Microstructure and Formation of Abnormal Grain Bands in AA5182 Al–Mg Alloy: Role of Thermo-mechanical Processing, Texture, and Dispersoids
No full textThis study investigates the impact of thermo-mechanical processing (TMP) parameters, microstructure, and texture on abnormal grain growth (AGG) in AA5182 Al–Mg alloy. The TMP included cold rolling with reductions ranging from 40 to 85 pct and annealing between 200 °C and 520 °C. The microstructure developed during annealing was characterized by optical, scanning, and transmission electron microscopy, including energy-dispersive X-ray spectroscopy. The texture was studied by electron backscatter diffraction. Hardness and electrical resistance measurements were employed to assess recrystallization processes and dispersoid reactions during treatment. Abnormal grain bands formed parallel to the cold-rolled sheet surface and propagated toward the sheet center. It was found that AGG morphological features, such as subsurface as a preferential initiation site for AGG and growth anisotropy, resembled the growth of Goss grains in transformer steel. The initial recrystallization texture was weak, with the retained deformation texture fiber being the strongest component. During AGG, a strong texture developed with the {114} 〈110〉 and {113}〈110〉 as the prominent orientations. The initiation of AGG appeared to be conditioned by the strength of the retained deformation texture fiber, while the distribution and reactions of dispersoids controlled the growth mode of the abnormal grains
Амино–скробни деривати за адсорпцију специфичних фармацеутика и пестцида из загађених вода: испитивање вештачки онечишћених и реалних узорака вода
No full textIn this study, the possibility of using modified potato starch, with nitrogen-containing chemical agents (melamine, cysteine and histidine) as green adsorbents for removing pharmaceuticals and pesticides from water has been investigated. The influence of additional modification of amino-starch with clay and diatomaceous earth was examined. The effect of the applied modification on the structural, surface and morphological properties was deter-mined by FTIR, XRD and SEM analysis, while the adsorption properties were determined through the effectiveness of prepared materials to remove selected pollutants from spiked and real water samples. The efficiency of investigated amino–starches for the adsorption of pharmaceuticals and pesticides decreases in order: starch–histidine > starch–cysteine > starch–melamine, with a slightly better efficiency for pharmaceuticals adsorption. Additional modification of amino–starches with clay/diatomaceous earth did not contribute to the increase in adsorption efficiency. It was found that the influence of the matrix of real water samples on the adsorption efficiency is up to 10%, which represents a promising potential for applying amino–starch as a cheap and effective adsorbent for wastewater treatment. Also, starch–histidine and starch–cysteine showed the possibility of reusing up to three cycles of adsorption.У овој студији испитана је могућност употребе модификованог кромпировог скроба,
са хемијским агенсима који садрже азот (меламин, цистеин и хистидин) као зеленог
адсорбента за уклањање лекова и пестицида из воде. Испитан је и утицај додатне модификације амино–скроба глином и дијатомејском земљом. Ефекат примењене модификације на структурна, површинска и морфолошка својства одређен је FTIR, XRD и SEM
анализом, док су адсорпциона својства припремљених адсорбената одређена кроз ефикасност уклањања изабраних загађујућим материја из спајкованих и реалних узорака воде.
Ефикасност припремљених амино–скробова за адсорпцију лекова и пестицида смањује се
по следећем редоследу: скроб–хистидин > скроб–цистеин > скоб–меламин, уз нешто бољу
ефикасност свих материјала за адсорпцију лекова. Додатна модификација амино–скробова глином/дијатомејском земљом није допринела повећању ефикасности адсорпције.
Утврђено је да матрица реалних узорака воде утиче на ефикасност адсорпције до 10 %,
што указује на обећавајући потенцијал за примену амино–скроба као јефтиног и ефикасног адсорбента за третман отпадних вода. Такође, адсорбенти скроб–хистидин и скроб–
цистеин су показали могућност поновне употребе кроз три циклуса адсорпције
Activated Carbons from Apricot Kernel Shells for Wastewater Treatment: Adsorption of Pb2+ and Rhodamine B with Equilibrium, Kinetics, Thermodynamics, and DFT Analysis
No full textApricot kernel shells were evaluated as a sustainable activated carbon precursor for wastewater treatment using experimental and theoretical methods. Two adsorbents were synthesized: physically activated with CO2 (AKS-CO2) and chemically activated with H3PO4 (AKS-H3PO4). Comprehensive materials characterization and adsorption tests using Pb2+ ions and Rhodamine B dye (RhB) as model pollutants revealed that AKS-H3PO4 significantly outperformed its physically activated counterpart. With an exceptionally high specific surface area (1159.4 m2/g) enriched with phosphorus-containing functional groups, the chemically activated carbon demonstrated outstanding removal efficiencies of 85.1% for Pb2+ and 80.3% for RhB. Kinetic studies showed Pb2+ adsorption followed pseudo-second-order kinetics, indicating chemisorption, while RhB adsorption fitted pseudo-first-order kinetics, suggesting intra-particle diffusion control. The thermodynamic analysis confirmed the spontaneity of both processes: Pb2+ adsorption was exothermic under standard conditions with positive isosteric heat at higher concentrations, reinforcing its chemisorption nature, whereas RhB adsorption was endothermic, consistent with physisorption. Density Functional Theory (DFT) calculations further elucidated the mechanisms, revealing that Pb2+ preferentially binds to oxygen-containing functional groups, while RhB interacts through hydrogen bonding and π–π stacking. These findings establish chemically activated apricot kernel shell carbon as a high-performance adsorbent, exhibiting exceptional removal capacity for both ionic and molecular contaminants through distinct adsorption mechanisms