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Correlation between morphology of electrolytically produced copper thin films and their hardness has been considered. The Cu films were electrodeposited by galvanostatic (DC) and by the pulsating current (PC) regimes on cathodes of limiting values of hardness (Cu, brass, and Si(111)) from the basic sulfate electrolytes without and with addition of leveling/brightening additives, without and with various ways of electrolyte stirring (ultrasound and magnetic stirring), and characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. Hardness of Cu films was determined by microindentation and by application of composite hardness models (CHMs), such as Cheng–Gao (C–G) and Korsunsky (K), with the aim to eliminate a contribution of cathode hardness in the measured film hardness and to determine the absolute hardness of the Cu films. The fine-grained films obtained from the basic sulfate electrolyte were harder than the smooth film obtained from the electrolyte with additives and that obtained by the PC regime, indicating that the PC produced film represents transitional form between these two types of the films. The obtained values of the absolute film hardness in the 1.135–1.647 GPa range were in line with already published values for the electrolytically produced Cu thin films, clearly indicating on successful implementation of CHMs in determination of the absolute hardness of thin films. Correlation between morphology and hardness of Cu films was discussed by the basic laws of electrocrystallization and phenomena on boundary among grains during microindentation processes.

The microstructure–property relationship in poly(methyl methacrylate) PMMA composites is very important for understanding interface phenomena and the future prediction of properties that further help in designing improved materials. In this research, field emission scanning electron microscopy (FESEM) images of denture PMMA composites with SrTiO3, MnO2 and SrTiO3/MnO2 were used for fractal reconstructions of particle agglomerates in the polymer matrix. Fractal analysis represents a valuable mathematical tool for the characterization of the microstructure and finding correlation between microstructural features and mechanical properties. Utilizing the mathematical affine fractal regression model, the Fractal Real Finder software was employed to reconstruct agglomerate shapes and estimate the Hausdorff dimensions (HD). Controlled energy impact and tensile tests were used to evaluate the mechanical performance of PMMA-MnO2, PMMA-SrTiO3 and PMMA-SrTiO3/MnO2 composites. It was determined that PMMA-SrTiO3/MnO2 had the highest total absorbed energy value (Etot), corresponding to the lowest HD value of 1.03637 calculated for SrTiO3/MnO2 agglomerates. On the other hand, the highest HD value of 1.21521 was calculated for MnO2 agglomerates, while the PMMA-MnO2 showed the lowest Etot. The linear correlation between the total absorbed impact energy of composites and the HD of the corresponding agglomerates was determined, with an R2 value of 0.99486, showing the potential use of this approach in the optimization of composite materials’ microstructure–property relationship.

This study investigates hydration mechanism of a high volume fly ash (HVFA) binder, comprising 70 wt.% of fly ash (FA), chemically activated by using sodium oxalate (Na2C2O4) and calcium formate (Ca(HCOO)2). Prior to the binder synthesis, mechanical activation of FA was employed. Effects of the activators on the properties of the HVFA binders were determined by measuring setting times and compressive strength of the binders. Heat of hydration, pore solution composition, bound water and portlandite content, mineral composition, and microstructure of HVFA binder pastes were analyzed in order to compare the hydration mechanisms of the HVFA binders activated with the selected activators. The obtained results indicated that using of the two different activators led to the enhancement of the properties of the HVFA binders, but it was achieved in two distinct ways. It was found that the use of Ca(HCOO)2 mitigated adverse effects of the high alkalinity of the pore solution of chemically activated HVFA binder on hydration process and strength development in the later period. Therefore, it was concluded that Ca(HCOO)2 was more suitable for chemical activation of HVFA binders, compared to Na2C2O4.

Activated carbon particles (ACPs) were obtained from biomass (hazelnut shells - HZs). Prepared HZs materials were carbonized in the furnace at 600° C for 1h, and activated in CO2 (850 °C, 2h). The microstructural properties of carbons were tested using the Field-Emission Scanning Electron Microscopy (FE-SEM) and Brunauer-Emmett-Teller (BET) equation methods. After shredding, and sifting processes, inert micro-sized particles were used as bio-reinforcement in electrochemically co-deposited copper coatings. The sulfate electrolytes without/with carbon particles (1.0 wt. %) were used for deposition/co-electrodeposition of 10 micrometers-thick Cu or Cu/C coatings on brass cathodes using the pulse current regime (PC). The structural, mechanical, and wettability properties of Cu and Cu/C metal matrix coatings with variations in amplitude current densities in the range of 30- 100 mA·cm-2 were investigated. An improvement in microhardness was observed for all Cu/C composites compared to pure Cu coatings. The wettability resistances of coatings were investigated using the sessile drop method, and the obtained results are correlated with the microstructures. The better results were obtained at a higher current density for the Cu/C coating.

While dental poly methyl methacrylate(PMMA) possesses distinctive qualities such as ease of fabrication, cost-effectiveness, and favorable physical and mechanical properties, these attributes alone are inadequate to impart the necessary impact strength and hardness. Consequently, pure PMMA is less suitable for dental applications. This research focused on the incorporation of Strontium titanate (SrTiO3-STO) and hybrid filler STO/Manganese oxide (MnO2) to improve impact resistance and hardness. The potential of STO in reinforcing PMMA is poorly investigated, while hybrid filler STO/MnO2 has not been presented yet. Differential scanning calorimetry is conducted in order to investigate the agglomeration influence on the PMMA glass transition temperature (Tg), as well as the leaching of residual monomer and volatile additives that could pose a threat to human health. It has been determined that agglomeration with 1 wt% loading had no influence on Tg, while the first scan revealed differences in evaporation of small molecules, in favor of composite PMMA-STO/MnO2, which showed the trapping potential of volatiles. Investigations of mechanical properties have revealed the significant influence of hybrid STO/MnO2 filler on microhardness and total absorbed impact energy, which were increased by 89.9% and 145.4%, respectively. Results presented in this study revealed the reinforcing potential of hybrid nanoparticles that could find application in other polymers as well.

This study presents comparison of our recently formulated two compartmental model with General fractional derivative (GFD) and Korsmeyer-Peppas, Makoid-Banakar and Kopcha diffusion models. We have used our GFD model to study the release of gentamicin in poly (vinylalcohol)/chitosan/gentamicin (PVA/CHI/Gent) hydrogel aimed for wound dressing in medical treatment of deep chronical wounds. The PVA/CHI/Gent hydrogel was prepared by physical cross linking of poly(vinyl alcohol)/chitosan dispersion using freezing-thawing method, and then was swollen for 48 h in gentamicin solution, at 37 °C. Different physico-chemical (FTIR, SEM), mechanical and biological (cytotoxicity, antibacterial activity) properties have been determined. The concentration of released gentamicin was determined using a high-performance liquid chromatography (HPLC) coupled with mass spectrometry (MS). The ratio between concentration of released gentamicin and initial concentration of gentamicin in the hydrogel was monitored for the prolonged time period in order to obtain gentamicin release profile. It was proven that our novel diffusion GFD model better fitted with experimental data, and enabled the determination of diffusion coefficient precisely for the entire time period.

Since acrylate-based materials are widely used in dentistry, their drawbacks such as low impact resistance and hardness, require continuous research in the field of materials science in order to avoid sudden fracture caused by chewing or fall. In this study, auto-polymerizing poly(methyl methacrylate) (PMMA), commonly used as denture base material, was reinforced with poly(4-styrenesulfonic acid-co-maleic anhydride) sodium salt (PSSMA) and strontium titanate (STO), with the aim of improving impact behavior and microhardness. Morphological analysis confirmed formation of phase-separated and co-continuous microscopic structures of PSSMA in PMMA, without visible agglomerates of STO nanoparticles, indicating that PSSMA-STO interaction contributed to a better distribution of nanoparticles. Fourier transformed infrared spectroscopy revealed that PSSMA and STO did not interfere in the polymerization of methyl methacrylate. This was further supported by thermal analysis, which also showed that the addition of PSSMA and STO had no significant influence on thermal degradation. On the other side, PSSMA and STO significantly enhanced mechanical performance of PMMA. The modulus of elasticity increased by up to 48.6%, total absorbed impact energy improved by up to 108.4%, and microhardness increased by up to 272.8% when PSSMA was combined with STO for reinforcing denture PMMA. These results demonstrate the significant potential of PSSMA, which could be combined with other ceramic nanoparticles for denture reinforcement in the future. Highlights: This research presents novel dental hybrid composite. Influence of strontium titanate (STO) and poly(4-styrenesulfonic acid-co-maleic anhydride) sodium salt (PSSMA) on poly(methyl methacrylate) (PMMA) was investigated. PSSMA/STO improved modulus of elasticity, microhardness and impact resistance. Sample with 5 wt% PSSMA and 1 wt% STO showed the highest improvement compared to PMMA. Presented hybrid composite could use as denture base mate

Hidrogel poli(vinil alkohol)/hitozan/gentamicin (PVA/CHI/Gent) pripremljen je fizičkim umrežavanjem disperzije poli(vinil alkohola)/hitozana i namenjen je za upotrebu kao materijal za medicinske obloge dubokih nekrotičnih rana kao što su dekubitusi. Ispitivane su fizičko-hemijske (FTIR, SEM), mehaničke i biološke (citotoksičnost, antibakterijska aktivnost) osobine. Mehanizam difuzije gentamicina iz hidrogela PVA/CHI/Gent proučavan je upoređivanjem novog dvo-kompartmentskog modela sa opštim frakcionim izvodima (GFD) i Korsmajer-Pepas, Makoid-Banakar i Kopča difuzionih modela. GFD model bolje se poklapao sa eksperimentalnim podacima od drugih modela i takođe je omogućio određivanje koeficijenta difuzije gentamicina tokom celog proučavanog vremenskog perioda.

The objective of this study was to processand evaluatea suitablescaffold matrix system for drug delivery and tissue regeneration. Abioinspired approachwas applied.Thescaffold based onnatural polymer gelatin,blended with polyvinylpyrrolidone,and crosslinked by genipin,was 3D printed by semi-solid extrusion(SSE).This 3D printing techniquedoes not require high temperature or UV curing, so it allows the use ofthermo-and UV-sensitive drugs, cells, or other biological components.The influence of genipin, a natural crosslinking agent, and itscontent on the mechanical properties and the cytotoxicity of obtained scaffolds were investigated.

In this study, polycaprolactone (PCL), as a biocompatible polymer was functionalized by addition of medicinal plant extract- Achillea millefolium L. (yarrow). Nanofiber mats were fabricated from PCL solutions containing dry yarrow extract in four concentrations (5%, 10%, 15%, and 20% relative to the weight of the polymer) by using blend electrospinning method. The nanofibers were characterized for their biological, mechanical and drug release behavior. In vitro release of yarrow polyphenols from the electrospun PCL nanofibers over a period of 5 days showed the release of up to 98% of the total loaded polyphenols. The released polyphenols retained its antioxidant activity, which was determined by DPPH assay. Electrospun PCL/yarrow nanofiber mats exhibited the antibacterial effect against Staphylococcus aureus, but had no effect on the growth of Pseudomonas aeruginosa. All PCL/yarrow nanofiber mats had improved mechanical properties compared to the neat PCL nanofibers, as evident by an increase in Young's modulus of elasticity (up to 5.7 times), the tensile strength (up to 5.5 times), and the strain at break (up to 1.45 times). Based on our results, yarrow-loaded PCL nanofiber mats appeared to be multi-functional biomaterials suitable for the production of catheter-coating materials, patches, or gauzes with antibacterial and antioxidant properties.

Biodegradable mulch films from cellulose (CELL), cellulose/polycaprolactone (CELL/PCL), cellulose/polycaprolactone/keratin (CELL/PCL/KER) and cellulose/polycaprolactone/keratin/ground calcium carbonate (CELL/PCL/KER/GCC) were prepared using Ionic liquid as a green solvent. Pure cellulose biopolymer is characterised by better mechanical properties (tensile strength - force per unit cross-sectional area at breakage - of 75.3 MPa and modulus of elasticity of 944.4 MPa) than the other studied samples which is attributed to the formation of partially miscible polymer blends. Among samples containing PCL, CELL/PCL/KER/GCC has the highest tensile strength and modulus of elasticity. The addition of KER or KER/GCC to CELL/PCL films resulted in an increment in melting temperature and an improvement of sample crystallinity. The light transmittance of all films was >60 %. The incorporation of KER enhanced the biodegradability of the biocomposites, while KER/GCC addition slightly inhibited degradation due to an increased hydrophobicity and crystallisation growth of semi-crystalline biopolymers. The reported method for mulch film preparation is green and recyclable, and, when including a readily available source of KER, such as by extraction from waste chicken feathers, enables conversion to organic biofertiliser. The findings of this study contributed to sustainable agriculture by providing nutrients that enhance the growth speed of the plant, and hence food production, and reduce environmental pressure. Inclusion of GCC additionally provides not only Ca2+ for plant consumption but also soil pH control.

Copper from sulfate baths without and with added inorganic pigment particles based on strontium aluminate doped with europium and dysprosium (SrAl2O4: Eu2+, Dy3+) was electrodeposited on a brass cathode by a galvanostatic regime. Morphological, structural, and roughness analysis of the pigment particles, the pure (pigment-free) Cu coating, and the Cu coatings with incorporated pigment particles were performed using SEM, XRD, and AFM techniques, respectively. Hardness and creep resistance were considered for the examination of the mechanical properties of the Cu coatings, applying Chicot–Lesage (for hardness) and Sargent–Ashby (for creep resistance) mathematical models. The wettability of the Cu coatings was examined by the static sessile drop method by a measurement of the water contact angle. The incorporation of pigment particles in the Cu deposits did not significantly affect the morphology or texture of the coatings, while the roughness of the deposits rose with the rise in pigment particle concentrations. The hardness of the Cu coatings also increased with the increasing concentration of pigments and was greater than that obtained for the pigment-free Cu coating. The presence of the pigments caused a change in the wettability of the Cu coatings from hydrophilic (for the pigment-free Cu coating) to hydrophobic (for Cu coatings with incorporated particles) surface areas.

Wood–plastic composites (WPCs) are some of the most common modern composite materials for interior and exterior design that combine natural waste wood properties and the molding possibility of a thermoplastic polymer binder. The addition of reinforcing elements, binding agents, pigments, and coatings, as well as changes to the microstructure and composition, can all affect the quality of WPCs for particular purposes. To improve the properties, hybrid composite panels of WPCs with 30 wt. % and 40 wt. % of wood content and reinforced with one or three metal grid layers were prepared sequentially by extrusion and hot pressure molding. The results show an average 20% higher moisture absorption for composites with higher wood content. A high impact test (HIT) revealed that the absorbed energy of deformation increased with the number of metal grid layers, regardless of the wood content, around two times for all samples before water immersion and around ten times after water absorption. Also, absorbed energy increases with raised wood content, which is most pronounced in three-metal-grid samples, from 21 J to 26 J (before swelling) and from 15 J to 24 J (after swelling). Flexural tests follow the trends observed by HIT, indicating around 65% higher strength for samples with three metal grid layers vs. samples without a metal grid before water immersion and around 80% higher strength for samples with three metal grid layers vs. samples without a grid after water absorption. The synthesis route, double reinforcing (wood and metal), applied methods of characterization, and optimization according to the obtained results provide a WPC with improved mechanical properties ready for an outdoor purpose.

U okviru predmetnog pronalaska izvedeno je istaživanje uticaja stukture poliedarnih oligo silsekvioksana (POSS) na adheziju kompozitnih filmova na metalnoj podlozi. Kompozitni filmovi se sastoje od UV polimerizovane Bisfenol A-glicidil dimetakrilata i trietilen glikol dimetakrilat (Bis-GMA/TEGDMA) matrice i reaktivne POSS strukture za poboljšanje adhezije. Kompozitni filmovi napravljeni su sa 1, 3, 5 i 10 mas. % POSS reagenasa. Adhezija je procenjena pomoću ispitivanja mikrotvrdoće metodom po Vikersu. Ugao kvašenja kompozitnih filmova metalne podloge od mesinga meren je i poređen sa parametrom adhezije koji je dobijen iz merenja mikrotvrdoće. Optička mikroskopija pokazala je fazno razdvajanje POSS reagensa koji ukazuju na meru kompatibilnosti između matrice i svake čestice. Analiziran je oblik i veličina otiska i bio je u korelaciji sa kvalitetom adhezije. Metode korišćene u ovom radu za procenu jačine i kvaliteta adhezije jasno su pokazale da je poboljšanje adhezije Bis- GMA/TEGDMA matrice i POSS reagensa koji sadrži funkcionalnu hidoksilnu i metakrilnu grupu., Within the scope of the present invention,the effect of the structure ofpolyhedral oligomeric silsesquioxane (POSS) on the adhesion of composite filmson metal supstrate has been researched. Composite filmscosistof UV polymerisedBisphenol A-glycidylmethacrylateandtriethylene glycol dimethacrylate (Bis-GMA/TEGDMA) matrixand reactive POSS structure to improve adhesion. Composite films are made with 1, 3, 5 and 10 wt. % of POSS reagents. Adhesion was assessedby Vickers micro-hardness test method. The wetting angle ofcomposite filmsof the brass metal substrate was measured and compared with the adhesion parameter obtained from the microhardness measurement.Optical microscopy showed phase separation of POSS reagentwhich indicating a measure of compatibility between the matrix and each particle. The shape and size of the print were analysed and correlated with the quality of adhesion. The methods used in this studyto evaluatethe strength and quality of adhesion clearly showed that the improvement of adhesion ofBis-GMA/TEGDMA matrxand POSS reagentcontaining a functional hydroxyl and methacrylic group.

MXenes are a relatively new class of 2D nanomaterials with promising properties. The functional groups on the surface of the nanosheets play a vital role in interacting with other materials, especially in nanocomposites. Biocompatibility, admirable mechanical properties, and thermal stability are the most significant properties of poly(dimethylsiloxane)-based polyurethanes (PU). They are highly convenient for applications in electronic devices and implants. In this study, the MXene content was 1 wt. % for two series and 0.5 wt. % for the other two series, while the soft segment content was 50 wt. % for all the series. The nanocomposites were obtained using an in-situ polymerization method. The timing of adding the MXene nanoparticles to the reaction mixture was also varied to examine the changes in the physico-mechanical properties of the nanocomposites. Differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and tensile tests were conducted to analyze the properties of the resulting materials. The glass transition temperature is highest for the series in which MXenes are added in the first phase of polyaddition after the solvation of MDI, while the series with 0.5 wt.% MXene added later into the reaction exhibit two transitions. SEM images revealed uneven distribution and agglomeration of MXene nanoflakes when added into the siloxane prepolymer. The tensile test indicated that the series with 0.5 wt. % nanoflakes have significantly lower Young's modulus and tensile strength. The distribution of nanoparticles and surface morphology are strongly influenced by the timing of adding the MXene dispersion into the reaction mixture, as well as the nanoparticle content.

MXenes are a relatively new class of 2D nanomaterials with promising properties. The functional groups on the surface of the nanosheets play a vital role in interacting with other materials, especially in nanocomposites. Biocompatibility, admirable mechanical properties, and thermal stability are the most significant properties of poly(dimethylsiloxane)-based polyurethanes (PU). They are highly convenient for applications in electronic devices and implants. In this study, the MXene content was 1 wt. % for two series and 0.5 wt. % for the other two series, while the soft segment content was 50 wt. % for all the series. The nanocomposites were obtained using an in-situ polymerization method. The timing of adding the MXene nanoparticles to the reaction mixture was also varied to examine the changes in the physico-mechanical properties of the nanocomposites. Differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and tensile tests were conducted to analyze the properties of the resulting materials. The glass transition temperature is highest for the series in which MXenes are added in the first phase of polyaddition after the solvation of MDI, while the series with 0.5 wt.% MXene added later into the reaction exhibit two transitions. SEM images revealed uneven distribution and agglomeration of MXene nanoflakes when added into the siloxane prepolymer. The tensile test indicated that the series with 0.5 wt. % nanoflakes have significantly lower Young's modulus and tensile strength. The distribution of nanoparticles and surface morphology are strongly influenced by the timing of adding the MXene dispersion into the reaction mixture, as well as the nanoparticle content.

Ionic liquid 1-butyl-3-methylimidazolium chloride [BMIM][Cl] was used to prepare cellulose (CELL), cellulose/polycaprolactone (CELL/PCL), cellulose/polycaprolactone/keratin (CELL/PCL/KER), and cellulose/polycaprolactone/keratin/ground calcium carbonate (CELL/PCL/KER/GCC) biodegradable mulch films. Attenuated Total Reflectance Fourier-Transform Infrared (ATR-FTIR) spectroscopy, optical microscopy, and Field-Emission Scanning Electron Microscopy (FE-SEM) were used to verify the films’ surface chemistry and morphology. Mulch film made of only cellulose regenerated from ionic liquid solution exhibited the highest tensile strength (75.3 ± 2.1 MPa) and modulus of elasticity of 944.4 ± 2.0 MPa. Among samples containing PCL, CELL/PCL/KER/GCC is characterized by the highest tensile strength (15.8 ± 0.4 MPa) and modulus of elasticity (687.5 ± 16.6 MPa). The film’s breaking strain decreased for all samples containing PCL upon the addition of KER and KER/GCC. The melting temperature of pure PCL is 62.3 °C, whereas that of CELL/PCL film has a slight tendency for melting point depression (61.0 °C), which is a characteristic of partially miscible polymer blends. Furthermore, Differential Scanning Calorimetry (DSC) analysis revealed that the addition of KER or KER/GCC to CELL/PCL films resulted in an increment in melting temperature from 61.0 to 62.6 and 68.9 °C and an improvement in sample crystallinity by 2.2 and 3.0 times, respectively. The light transmittance of all studied samples was greater than 60%. The reported method for mulch film preparation is green and recyclable ([BMIM][Cl] can be recovered), and the inclusion of KER derived by extraction from waste chicken feathers enables conversion to organic biofertilizer. The findings of this study contribute to sustainable agriculture by providing nutrients that enhance the growth rate of plants, and hence food production, while reducing environmental pressure. The addition of GCC furthermore provides a source of Ca2+ for plant

The present study reports on the preparation of nanocomposites consisting of polyurethane (PU) as the matrix and Ti 3 C 2 T x MXene as the nanofiller, utilizing an in-situ polymerization method. The synthesis parameters of polyurethane remained constant, while the method of adding and preparing MXene was varied. The MXene content was maintained at 1 wt.% for all prepared nanocomposites, and the soft segment content was held constant as well. For the characterization of our materials, FTIR, SEM, TGA and tensile tests were employed. Also, the properties of the prepared nanocomposites were compared to pure PU. FTIR spectra confirmed the formation of urethane bonds. SEM images demonstrated the dispersion state of MXene in the polymer matrix. TGA revealed higher thermal stability of the prepared nanocomposites compared to pure PU. Moreover, the Young’s modulus and tensile strength increased for all prepared nanocomposites.

High performance polymers with bio-based modifiers are promising materials in terms of applications and environmental impact. In this work, raw acacia honey was used as a bio-modifier for epoxy resin, as a rich source of functional groups. The addition of honey resulted in the formation of highly stable structures that were observed in scanning electron microscopy images as separate phases at the fracture surface, which were involved in the toughening of the resin. Structural changes were investigated, revealing the formation of a new aldehyde carbonyl group. Thermal analysis confirmed the formation of products that were stable up to 600 °C, with a glass transition temperature of 228 °C. An energy-controlled impact test was performed to compare the absorbed impact energy of bio-modified epoxy containing different amounts of honey with unmodified epoxy resin. The results showed that bio-modified epoxy resin with 3 wt% of acacia honey could withstand several impacts with full recovery, while unmodified epoxy resin broke at first impact. The absorbed energy at first impact was 2.5 times higher for bio-modified epoxy resin than it was for unmodified epoxy resin. In this manner, by using simple preparation and a raw material that is abundant in nature, a novel epoxy with high thermal and impact resistance was obtained, opening a path for further research in this field.