Abstract Material corrosion represents a significant scientific and engineering challenge. Microorganisms on material surfaces accelerate corrosion. Due to the excellent properties of graphene, bifunctional anticorrosion and antibacterial coatings were developed by incorporating graphene into epoxy resin. To mitigate the detrimental effects of agglomeration on coating performance, graphene oxide (GO) was prepared, and a silane coupling agent was used to modify the surface of GO to enhance its stability and dispersibility within the coating matrix. The properties of graphene were analyzed before and after surface modification by Fourier transform infrared spectroscopy (FTIR) and Transmission electron microscope (TEM). Epoxy/modified-GO (0.1 wt%) coating revealed the highest corrosion resistance of 9.696 × 10 7 Ω cm 2 after 144 h immersion in 3.5% NaCl solution measured by the electrochemical impedance spectroscopy (EIS) technique. Higher protection against bacteria was observed for epoxy/modified-GO (0.1 wt%) as the most efficient antibacterial composite coating. These results indicated that the coatings with modified graphene exhibited superior corrosion resistance and effectively inhibited the growth of Staphylococcus aureus .
Abstract The aim of this study is to assess the applicability of UV-curable resin-based composite laminates containing solid lubricants as potential materials for sliding components. The tested laminates were produced from glass and carbon fiber fabrics impregnated with a photocurable resin modified with selected solid lubricants: molybdenum disulfide, polytetrafluoroethylene, and graphite. Tribological tests were carried out in a plate-roller configuration under technically dry friction conditions, using C45 steel as the counterelement. The analysis included the coefficient of kinetic friction, surface morphology after sliding, and maximum wear track depth. The results were compared with reference laminates without solid lubricant additives. The lowest coefficient of friction was obtained for the carbon-fiber-reinforced laminate containing molybdenum disulfide. For glass-fiber-reinforced laminates, graphite was the most effective additive in terms of friction reduction, decreasing the coefficient of friction by more than 17% compared with the reference sample. The results showed that the tribological effect of the same solid lubricant depends strongly on the reinforcement type. The investigated laminates therefore show potential for sliding applications; however, the selection of the lubricant additive should be adapted to the specific laminate system and operating conditions.
Abstract An eco-friendly biosynthetic route was developed for the synthesis of spinel-structured copper ferrite nanoparticles (CuFe 2 O 4 NPs) using Capsicum annuum (sweet green pepper) extract as a multifunctional reducing, capping, and stabilizing agent. This study systematically correlates the synthesis conditions with the structural, optical, magnetic, and biological properties of the synthesized material. X-ray diffraction analysis confirmed the formation of a cubic spinel structure with a nanocrystalline size of ≈26 nm, while Fourier transform infrared spectroscopy revealed the presence of metal–oxygen bonds and chemical reactions resulting from plant compounds. Optical analysis showed a low energy gap (≈1.5 eV), attributed to cation redistribution and the presence of defects in the crystal structure. Magnetic measurements also showed strong ferromagnetic behavior with a high coercivity value, attributed to the effects of single magnetic field. From a biological standpoint, the synthesized NPs showed improved antibacterial activity, along with low cytotoxicity against normal cells and excellent hematologic biocompatibility, with a hemolysis rate of <5%. These results demonstrate a clear correlation between the structural, physicochemical, and biological properties, highlighting the potential of green-synthesized CuFe 2 O 4 NPs in advanced biomedical applications.
Abstract Introduction Application of pit and fissure sealants is among the most effective methods of preventing dental caries. Despite their extensive use, the chemical composition of resin-based sealants is ambiguous and inconsistent. The presented integrative review analytically evaluates the composition of commercially available resin-based dental pit and fissure sealants. Data and sources Targeted searches were conducted between June 1 and November 15, 2025, using PubMed, ScienceDirect, Scopus, alongside general and academic search engines such as Google Scholar, Google. All relevant website entries were saved using the Internet Archive Wayback Machine platform. Study selection Sources providing information on key material components including resin matrix monomers and fillers; grey literature sources and scientific articles published in peer-reviewed journals regarding to the composition of resin-based commercial formulation of dental pit and fissure sealants. Structured data search resulted in identifying 52 formulations of 41 resin-based dental sealants. Among those, 116 unique ingredients were found, of which 41 were assigned a Chemical Abstracts Service number. Conclusions Components were classified according to their function into groups. Cluster analysis allowed for the proposal of a new classification of resin-based dental sealants based on their monomer composition. Three distinctive fluoride forms were identified in the analyzed formulations, with each one resulting in different release kinetics and therapeutic effect (fluoride salts, fluoride glass-ionomer fillers, and fluorinated monomers). Clinical significance The article highlights the significance and clinical importance of each group of identified compounds and aims to increase awareness of the correlation of composition with clinical properties.
Abstract In this study, a quaternary Cu 2 FeSnS 4 (CFTS) nano-compound was prepared and characterized using the solvothermal method, with partial substitution between copper and silver ions to form the Cu 1.8 Ag 0.2 FeSnS 4 compound, in addition to a partial co-substitution between iron and manganese ions to form the Cu 1.8 Ag 0.2 Fe 0.5 Mn 0.5 SnS 4 compound. The aim of the study is to compare single doping and co-doping and their effect on structural, optical, and morphological properties. The X-ray diffraction and Raman spectroscopy results showed that all the prepared compounds have a kesterite crystal structure with the absence of secondary phases, while maintaining the crystalline phase during the substitution process, accompanied by a slight change in the crystal lattice constants. Field emission scanning electron microscopy analysis revealed a clear evaluation in nanoparticle morphology with doping and co-doping. Brunauer–Emmett–Teller analysis indicated a decrease in surface area upon doping. It was also observed that there is a gradual decrease in the energy gap accompanied by strong absorption in the visible region when the doping and co-doping process is carried out. According to these results, the authors confirm that co-doping with silver and manganese is an effective strategy for controlling optoelectronic properties. It also has a clear impact on surface properties, which must be considered to balance maintaining an effective surface area with minimizing the energy gap. Therefore, these co-doped compounds are promising candidates for photocatalysis and thin-film solar cell applications.
Abstract Amidst the global transition toward carbon-neutral infrastructure, circulating fluidized bed boilers co-fired with solid recovered fuel represent critical nodes for circular resource recovery. However, the resulting residues exhibit volumetric instability due to unreacted free calcium oxide and anhydrous calcium sulfate, which compromises durability in cementitious composites. This study conducts a multi-scale investigation into the competitive volume dynamics – the trade-off between expansion mitigation and the induction of drying shrinkage. Using integrated characterization (X-ray diffraction, thermogravimetry, and scanning electron microscopy with energy-dispersive spectroscopy), we elucidate the micro-macro correlation in dimensional stability. Experimental results demonstrate that raw ash exhibits a destructive 7-day linear expansion of 1.62% (±0.12%) under accelerated testing in a 70°C water bath. Controlled humidification stabilizes the atypical ash by converting reactive precursors into stable calcium hydroxide and ettringite (Aft). Crucially, a suitable balance is identified: while 100% humidification eliminates expansion, it triggers a significant 1.21% (±0.08%) drying shrinkage. This is attributed to excessive Aft formation that refines pore structures, thereby elevating capillary tension governed by the Kelvin–Laplace effect. A 30% humidification protocol for 1 day strikes an optimal balance, controlling expansion to 0.39% (±0.04%) while mitigating shrinkage risk and ensuring the environmental sequestration of heavy metals (leachable lead < 0.12 mg/L). This research provides insights into the safe integration of atypical residues in sustainable binders.
Abstract Na 0.5 Bi 0.5 Cu₃Ti₄O₁₂ (NBCTO) ceramics were synthesized by mechanochemical milling followed by spark plasma sintering (SPS) at 800–900°C. X-ray diffraction confirmed the cubic perovskite structure, with minor CuO traces at lower sintering temperatures and phase-pure NBCTO at 900°C. Scanning electron microscope and energy-dispersive X-ray spectroscopy revealed dense, fine-grained microstructures with average grain sizes below 400 nm, significantly smaller than those observed in conventionally sintered samples. All SPS-NBCTO ceramics exhibited colossal dielectric permittivity ( ε ′ > 10⁴) across wide frequency and temperature ranges, with values of 2.8–4.0 × 10⁴ at 1 kHz and room temperature. Impedance analysis revealed an internal barrier layer capacitance mechanism, with semiconducting grains and more resistive grain boundaries. Grain conductivity (∼3 × 10⁻² S/cm) and activation energies (0.089–0.096 eV) were consistent with CaCu₃Ti₄O₁₂-based systems, while grain boundary conductivity was unexpectedly high (2.5–3.5 × 10⁻³ S/cm) with relatively low activation energies (0.192–0.211 eV). These properties, linked to oxygen-vacancy-related conduction, led to unusually large dielectric losses. Relaxation analysis using the electric modulus confirmed thermally activated grain and grain boundary processes with activation energies matching conductivity values. The results demonstrate that SPS enables fine-grained, dense NBCTO ceramics with colossal dielectric constants, though excessive grain boundary conduction remains a challenge.
Digital light processing (DLP)-based additive manufacturing systems offer high printing speeds; however, their resolution is inherently limited in low-cost configurations due to projector pixel size, optical divergence, and angular light incidence on the photopolymer surface. In this study, a compact optical module consisting of focusing and collimation lenses was integrated between a commercial DLP projector and the photopolymer vat to address these limitations. The proposed system concentrates the projected light onto a reduced exposure area and enforces near-normal light incidence, improving voxel definition and suppressing angular curing artifacts. Benchmark geometries were fabricated with and without the optical module using a single daylight-sensitive photopolymer resin. The results show that the effective pixel size was reduced from approximately 165-170 mu m to 43-46 mu m. In addition, the increased irradiance enabled a reduction in layer exposure time from 2,500 to 100 ms, resulting in an overall printing time reduction of about 30%. Although the optical configuration limits the build area, it provides a purely physical and effective alternative to software-based super-resolution approaches for low-cost DLP systems.
Ultra-high performance concrete (UHPC) faces cost and shrinkage challenges due to high binder contents. This study systematically investigates the influence of varying binder-to-sand (B/S) ratios (0.8, 0.9, 1.0, and 1.2) coupled with novel polyoxymethylene fibers (POMFs, 0 and 2% dosages) on UHPC properties. A fixed water-to-binder ratio (0.17) and 50% ground granulated blast-furnace slag replacement were used. Freshness, mechanical properties, durability, and microstructural properties were evaluated. Results indicate that the B/S ratio critically governs UHPC performance. Contrary to the assumption that higher binder content is always superior, an optimal balance emerged at a B/S ratio of 0.9. This ratio yielded the highest 28-day compressive and splitting tensile strengths, the lowest water absorption, and exceptional sulfate resistance, with no strength degradation after 180 days. A low B/S ratio (0.8) caused insufficient aggregate coating, increasing porosity, and reducing strength. Conversely, an excessive B/S ratio (1.2) induced severe autogenous shrinkage and microcracking, impairing durability and strength. While a 2% POMF addition provided limited gains in compressive strength, it significantly improved splitting tensile strength and shifted the failure mode from brittle to ductile. Scanning electron microscopy confirmed that POMF's hydrophilic nature ensures excellent interfacial bonding with the matrix. Ultimately, a B/S ratio of 0.9 provides the optimal eco-efficient mix design, balancing high performance with material economy for UHPC engineering applications.
Rapid urbanization and environmental regulations have led to a shortage of natural river sand, prompting the use of alternative aggregates. This study evaluates green waste glass and liquid crystal display (LCD) glass sand as partial substitutes for manufactured sand (MS) in concrete. Comprehensive tests assessed mechanical properties (compressive and flexural strength), durability (drying shrinkage, impermeability, sulfate resistance), and alkali-silica reaction (ASR) potential. Microstructural evolution was analyzed using mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and electrical resistivity. Results demonstrate that a 20% green glass substitution (GG20) achieved optimal performance, with 28-day compressive and flexural strengths of 51.8 MPa and 6.1 MPa, respectively. Both glass types significantly reduced drying shrinkage and enhanced sulfate resistance by refining pores. Despite increased ASR activity in the LCD group, pozzolanic reactions and the micro-filling effect densified the paste matrix. This research validates specialized waste glass as a sustainable performance enhancer for manufactured sand concrete, offering a robust theoretical foundation for eco-friendly construction.
Extruded magnesium matrix composites reinforced with nano-sized tungsten disulfide were fabricated via powder metallurgy followed by hot extrusion, and their microstructural evolution, mechanical response, and tribological behavior were systematically investigated. Compared with monolithic magnesium, the incorporation of 0.5-2.0 wt% nano-reinforcement markedly altered dynamic recrystallization behavior during extrusion, resulting in pronounced grain refinement and texture modification. Electron backscatter diffraction analysis revealed that the average grain size decreased from approximately 8.5 & micro;m in pure magnesium to about 3.2 & micro;m at 2.0 wt% addition, accompanied by a reduction in basal texture intensity from 12.5 to 7.8 m.r.d. These microstructural changes translated into substantial strengthening, with Vickers hardness increasing from 58 to 92 HV0.1, yield strength from 135 MPa to 220 MPa, and ultimate tensile strength from 210 to 315 MPa, while maintaining elongation above 10%. Tribological tests under dry sliding against GCr15 steel demonstrated a pronounced reduction in friction and wear. The steady-state coefficient of friction decreased from similar to 0.45 for unreinforced magnesium to similar to 0.18 at 20 N for the composite containing 2.0 wt% reinforcement, and the corresponding wear rate was reduced by nearly one order of magnitude, from similar to 1.8 & times; 10(-)4 to similar to 1.5 & times; 10(-)5 mm3 Nm. Surface and debris analyses confirmed the formation of a continuous lubricious tribolayer that mitigated severe adhesive and abrasive wear. The results collectively demonstrate a clear composition-structure-property relationship, highlighting the effectiveness of nanoscale layered reinforcements combined with extrusion processing for achieving a balanced improvement in strength and wear resistance in lightweight metallic composites.
Na0.5Bi0.5Cu(3)Ti(4)O(1)(2) (NBCTO) ceramics were synthesized by mechanochemical milling followed by spark plasma sintering (SPS) at 800-900 degrees C. X-ray diffraction confirmed the cubic perovskite structure, with minor CuO traces at lower sintering temperatures and phase-pure NBCTO at 900 degrees C. Scanning electron microscope and energy-dispersive X-ray spectroscopy revealed dense, fine-grained microstructures with average grain sizes below 400 nm, significantly smaller than those observed in conventionally sintered samples. All SPS-NBCTO ceramics exhibited colossal dielectric permittivity (epsilon ' > 10(4)) across wide frequency and temperature ranges, with values of 2.8-4.0 & times; 10(4) at 1 kHz and room temperature. Impedance analysis revealed an internal barrier layer capacitance mechanism, with semiconducting grains and more resistive grain boundaries. Grain conductivity (similar to 3 & times; 10(-)& sup2; S/cm) and activation energies (0.089-0.096 eV) were consistent with CaCu3Ti4O12-based systems, while grain boundary conductivity was unexpectedly high (2.5-3.5 & times; 10(-)& sup3; S/cm) with relatively low activation energies (0.192-0.211 eV). These properties, linked to oxygen-vacancy-related conduction, led to unusually large dielectric losses. Relaxation analysis using the electric modulus confirmed thermally activated grain and grain boundary processes with activation energies matching conductivity values. The results demonstrate that SPS enables fine-grained, dense NBCTO ceramics with colossal dielectric constants, though excessive grain boundary conduction remains a challenge.
The objective of the current research is to study the effect of a central circular hole as a stress raiser and to obtain the corresponding stress concentration factors for polyvinyl chloride (PVC) reinforced with different types of short fibers. Five different types of fibers were used: glass wool (GW), rock wool (RW), cotton wool (CW), and glass fiber with two types (YGT101 and E6-CR). The fibers of 5, 10, 15, 20, 30, 40, and 50% were used for sample preparation. On the other hand, two different types of samples were used: unnotched samples and notched samples with central holes of 1, 3, and 5 mm in diameter. Tensile tests were carried out on dog bone samples according to ASTM D638 using a universal tensile testing machine. The experimental results showed that the tensile strength of the PVC/fiber composites decreases with the increase of wt% of the fibers, whereas the PVC/E6-CR fiber composites displayed different behaviors. On the other hand, the results obtained for stress concentration factors from finite element analysis models and analytical methods showed that there is no effect for the types of fibers, and additionally, the stress concentration factors obtained from the different models were approximately the same, with differences not more than 10% for the same hole diameter.
This study developed and verified a novel, alkali-free cementless material for 3D printing, formulated entirely from industrial by-products: circulating fluidized bed co-fired fly ash (CFA), blast furnace slag, fly ash, and reactive ultra-fine fly ash (RUFA). The research aimed to eliminate cement and hazardous liquid alkali activators by using the self-activated properties of CFA to activate the slag. The experimental program evaluated rheological properties for printability, compared the compressive strength of cast and 3D-printed specimens to assess anisotropy, and analyzed thermal conductivity and interlayer bonding using optical microscopy. Results showed the optimized cementless mixtures achieved stable fluidity and good extrudability, though with longer setting times than traditional alkali-activated materials (AAMs). While AAMs had superior compressive strength (over 60 MPa), their rapid hardening created weak interlayer bonding. Conversely, the cementless composites maintained continuous fusion and achieved lower thermal conductivity (minimum, 0.233 W/m K) due to an interstitial pore structure from RUFA. The study concluded that while AAMs were better suited for high-strength applications, the developed alkali-free composite offered a sustainable and energy-efficient solution for non-structural elements, striking a balance between buildability and thermal insulation. Its innovation lay in creating a self-activating, all-waste binder system that avoided corrosive chemicals while enabling tunable thermal properties in additive manufacturing.
Abstract The manuscript provides a comprehensive overview of the W-temper forming (WT-F) process employed in the fabrication of sheet metal from 7xxx alloys. A diagram of the forming process is presented, taking into account the individual stages and the most important parameters of heat and plastic treatment. The literature review covers the characteristics of alloys tested during WT-F: EN AW-7075 and EN AW-7021. An analysis of previously published results was conducted in the following areas: strength and hardness tests, the effect of natural and artificial aging time on the mechanical properties of supersaturated aluminum alloys, determination of forming limit diagrams in the W-temper state and WT-F of U-profiles, car B-pillars, car floor panels, and door beams. A literature review showed that forming EN AW-7075 and EN AW-7021 in the W-temper state allows for the production of crack-free products, which is impossible to form with cold forming of sheets in the T6 state. Numerous studies have successfully formed components with complex geometries without defects or cracks, while achieving high true tensile strength values, reaching up to 600–620 MPa – significantly above the levels of typical 5000 and 6000 series alloys used in the automotive industry. While paint baking slightly reduces strength and ductility, it can also improve yield strength.
Aluminum oxide (Al 2 O 3 )/hafnium oxide (HfO 2 ) bi-layer resistive random access memory (RRAM) was fabricated by atomic layer deposition and sputtering method with a titanium (Ti)/titanium nitride (TiN) top electrode and a platinum (Pt) bottom electrode to achieve optimized performance. High-resolution transmission electron microscopy results clearly show the cross-sectional nanostructure of the Pt/Al 2 O 3 /HfO 2 /Ti/TiN RRAM devices. Examination of the X-ray photoelectron spectroscopy depth profile and X-ray diffraction peaks revealed the bonding state and presence of the proposed bi-layer structure. The device features a forming-free function with a stable resistance ratio (∼10) of ON/OFF states, low SET and RESET voltages, switching duration of up to 10 3 cycles, and longer data retention. The current–voltage characteristics of the proposed RRAM device implemented with the VTEAM simulation package and its performance with respect to the experimental results were studied. In addition, imply–inhibit logic gates were developed, and their performance was studied. The results show that the proposed imply–inhibit logic has significant advantages over typical CMOS logic in terms of performance, delay, and device count.
Geopolymer foam is a lightweight and environmentally friendly material that utilizes byproducts as raw materials. It consists of precursors, alkaline or acidic solutions, and foaming agents, with the option to incorporate stabilizing agents. The presence of dispersed pores significantly enhances its insulation properties, resulting in a reduced overall density, improved mechanical energy absorption, increased fire resistance, and greater durability. As an innovative alternative to conventional insulation products, geopolymer foam not only enhances overall building performance but also allows for the creation of complex shapes through additive manufacturing (AM), which is particularly beneficial in the architecture and aerospace sectors. To further advance this innovative material, this critical review summarizes recent experimental studies on geopolymer foam mortar in 3D printing, examining selected peer-reviewed literature to evaluate the type of material formulations and performance characteristics. By identifying key trends, strengths, and research gaps, this study provides a comprehensive understanding of current progress and future directions in the development of sustainable, high-performance geopolymer foam materials for AM. This technology effectively reduces energy consumption in construction and lowers carbon dioxide emissions by incorporating industrial waste, thereby supporting sustainable development goals.
Failure of the boiler, gas turbine, incinerator, and other power-producing machines is mainly caused by the metals’ oxidation and alloys at high temperature service environment. It is a common practice to apply thermal barrier coating to increase the resistance to oxidation of metal alloys when subjected to high temperatures. In the current research, an effort has been made to apply a coating of Cr 3 C 2 –NiCr using the detonation gun (D-gun) technique on stainless steel (SS) 304L and SS 316L. The characteristics of coatings have been studied at 750 and 850°C. A cyclic oxidation process was carried out in a muffle furnace for 50 cycles. For each cycle, 304L and 316L SS, both bare and coated, are heated for 1 h in a muffle furnace and cooled for 20 min in ambient air. Under the investigated conditions, the Cr 3 C 2 –NiCr coating sprayed with a D-gun exhibited outstanding adhesion to the substrate alloy. A weight change/area versus the number of cycles plot has been drawn to understand the kinetics of oxidation. SS 304L coating has shown approximately 26.54 and 21.93% improvement in oxidation resistance at 850 and 750°C, respectively. For SS, 316L coating has shown approximately 27.67 and 25.92% improvement in the oxidation resistance, respectively, at 850 and 750°C. The oxide-scale-generated Cr 2 O 3 phase demonstrated notable resistance to oxidation throughout the 50 cycles of cyclic oxidation at 750 and 850°C. The weight change/area shows that 316L has much better oxidation resistance than 304L at both temperatures of 750 and 850°C. The application of such coatings at high temperatures may reduce the formation of oxide scale which attacks and corrodes exhaust valves, turbocharger nozzles, and blade.
In this research work, Mg 30 -Al 25 -Ti 25 -Li 15 -Si 5 lightweight high-entropy alloys (LWHEAs) were synthesized via mechanical alloying (MA) with different milling times of 0, 5, 10, and 20 h. The X-ray diffraction (XRD) results of MAed powders exhibited the formation of intermetallic phases (Mg 2 Si and Al 12 Mg 17 ) and nanocrystalline structures with prolonged milling times, enhancing diffusion, lattice strain, and grain refinement. Scanning electron microscopy powder surface morphology, EDAX analyses, and elemental mapping were examined to confirm the structural refinement and uniform elemental distribution, though lithium detection remained challenging. Further, based on XRD results, peak broadening models (Scherrer, Williamson–Hall, and size–strain plot) were employed to estimate the crystallite size and lattice strain, with the Williamson–Hall model showing the highest accuracy. Compaction studies at room and high temperatures (275 and 550°C) with pressures up to 200 MPa demonstrated improved densification and mechanical integrity, attributed to the phase formation and structural refinement during milling. A relative density of 94.42% was achieved at 200 MPa and 550°C in the 20 h MAed sample due to improved atomic diffusion-driven densification, grain-boundary diffusion, and decreased work-hardening effect. The nanocrystalline nature, refined grain morphology, and enhanced densification emphasize the potential of Mg 30 -Al 25 -Ti 25 -Li 15 -Si 5 LWHEAs for lightweight structural applications in aerospace, automotive, and advanced manufacturing industries.
Abstract The article presents an overview of the warm forming process used to form 7xxx alloy sheets. The literature review covers the characteristics of alloys tested during forming at elevated temperatures: AA7075, AA7020, and a non-commercial alloy with a lower chromium content, higher zirconium content, and higher zinc-to-magnesium ratio than commercial alloys. A diagram of the forming process is presented, taking into account the individual stages and the most important parameters of heat treatment and deformation. An analysis was carried out of the results published to date in the field of basic research, such as tensile tests of alloys in the temperature range of 20–300°C, limiting dome high and limiting drawing ratio tests in the temperature range of 20–260°C, and tests of forming blanks such as a bracket, U-profile, lower part of a B-pillar, and B-pillar. Based on an extensive literature review, it can be concluded that warm stamping with accelerated heating allows for achieving at least 90% of the original strength of the AA7075 alloy. The use of a paint baking process (heat treatment at 180°C for 30 min) after stamping can contribute to a final product strength of up to 85–90% of the strength of the alloy in the T6 state.
