Search Results (139)

The paper presents a method for obtaining partially degradable capillary membranes from a polyethersulfone/polycaprolactone (PES/PCL) mixture. PES/PCL membranes were obtained by the phase inversion technique with dry/wet spinning and then subjected to controlled degradation in an alkaline environment (1 M NaOH) and simulated body fluid (SBF with pH 7.4) using the flow method. The aim of the work was to select and apply a degradable, non-toxic, simple polymer as a removable component of the membrane structure. The degradable component of the membranes was PCL, the gradual hydrolysis of which was aimed at increasing the porosity and improving the transport properties of the membranes during operation. The membrane properties, such as hydraulic permeability coefficient (UFC), retention coefficient, and structural morphology, were assessed using scanning electron microscopy (SEM) before and after degradation. Analysis of SEM images performed with MeMoExplorer^TM software showed an increase in the proportion of large pores (above 300 µm²) and total porosity of the membranes after degradation in NaOH and SBF. Low instability factor (<0.25) for all samples, both before and after degradation, confirms the good repeatability of the membrane structure. An increase in the UFC was observed, while the retention coefficients did not change significantly in the case of membranes after the etching process. The degradation of the PCL component in the membrane was assessed using the weight method. Measurements of the membrane mass loss before and after degradation confirmed the removal of over 50 wt.% of the PCL component in SBF and 70 wt.% in NaOH from the tested membranes, which resulted in an increase in permeability due to increased membrane porosity. The results indicate the possibility of using such structures as functional, partially self-regulating membranes, potentially useful in biomedical and environmental applications. Full article

The microstructure of polyacrylonitrile (PAN) precursor fibers has a profound influence on the performance of carbon fibers and depends on the spinning processes and processing conditions. This study compared the evolution of the microstructures and performance of PAN fibers between the wet-spinning and dry-jet wet-spinning processes, utilizing scanning electron microscopy, small/wide-angle X-ray scattering, dynamic mechanical analysis, and single-fiber tensile testing. Both spinning processes promoted the oriented alignment of microfibrils and fibrils, improved the crystal arrangement and molecular regularity, and facilitated the transition from a two-phase (crystalline/amorphous) structure to a single-phase structure, thereby gradually improving the fibers’ elastic character and mechanical properties. However, wet-spun fibers exhibited inherent defects (skin-core structure and large voids), which caused surface grooves, radial mechanical heterogeneity, and low breaking elongation during post-spinning. In contrast, dry-jet wet-spun fibers initially had a smooth surface and a homogeneous radial structure, which evolved into well-oriented, radially homogeneous structures during post-spinning. Furthermore, the dry-jet wet-spinning process produced greater increases in crystallinity (46%), crystal size (258%), and orientation index (146%) than the wet-spinning process did. The dry-jet wet-spinning process’s superiority in forming and optimizing the fiber microstructure gives it greater potential for producing high-quality PAN precursor fibers. Full article

In this study, a Ag/ZrO₂ hybrid coating prepared by the sol–gel method on a β-type Ti45Nb alloy was applied by the spin coating technique, and the microstructural, mechanical, electrochemical, and tribological properties of the surface were evaluated in a multi-dimensional manner. The hybrid solution was prepared using zirconium propoxide and silver nitrate and stabilized through a low-temperature two-stage annealing protocol. The crystal structure of the coating was determined by XRD, and the presence of dense tetragonal ZrO₂ phase and crystalline Ag phases was confirmed. SEM-EDS analyses revealed a compact coating structure of approximately 1.8 µm thickness with homogeneously distributed Ag nanoparticles on the surface. As a result of the electrochemical corrosion tests, it was determined that the open circuit potential shifted to more noble values, the corrosion current density decreased, and the corrosion rate decreased by more than 70% on the surfaces where the Ag/ZrO₂ coating was applied. In the tribological tests, a decrease in the coefficient of friction, narrowing of wear marks, and significant reduction in surface damage were observed in dry and physiological (HBSS) environments. The findings revealed that the Ag/ZrO₂ hybrid coating significantly improved the surface performance of the Ti45Nb alloy both mechanically and electrochemically and offers high potential for biomedical implant applications. Full article

This study presents a multiscale characterization of flax fibers, from elementary fibers to technical bundles and yarns, to elucidate how fiber scale attributes influence yarn mechanics. Four yarn counts (111.11 tex, 100 tex, 90.9 tex, and 83.33 tex) were produced via dry spinning, and tensile testing performed at each structural level. The results revealed a progressive decline in a specific modulus from elementary fibers (1.09 ± 0.62 N/tex) to short bundles (14.41 ± 9.59 N/tex), primarily due to fiber misalignment. Post hoc analysis confirmed that finer yarns (83.33 tex) exhibited higher stiffness (7.32 ± 1.69 N/tex, p < 0.001), attributed to advanced processing (GN4 combing). These findings highlight the critical role of fiber length and alignment in optimizing flax yarns for high-performance textiles. Full article

In this work, the effect of the palladium precursor on the Oxygen Reduction Reaction (ORR) performance of lignin-based electrospun carbon fibers was studied. The fibers were spun from a lignin-ethanol solution free of any binder, where different Pd salts were added at two concentration levels. The system implemented to perform the spinning was a coaxial setup in which the internal flow contains the precursor dispersion with the metallic precursor, and ethanol was used as external flow to help fiber formation and prevent drying before generating the Taylor cone. The obtained cloths were thermostabilized in air at 200 °C and carbonized in nitrogen at 900 °C. The resulting carbon fibers were characterized by physicochemical and electrochemical techniques. The palladium precursor significantly affects nanoparticle distribution and size, fiber diameter, pore distribution, surface area and electrochemical behavior. The fibers prepared with palladium acetylacetonate at high Pd loading and carbonized at 900 °C under a CO₂ atmosphere showed high mechanical stability and the best ORR activity, showing near total selectivity towards the 4-electron path. These features are comparable to those of the commercial Pt/C catalyst but much lower metal loading (10.6 wt.% vs. 20 wt.%). The most promising fibers have been evaluated as cathodes in a zinc–air battery, delivering astonishing stability results that surpassed the performance of commercial Pt/C materials in both charging and discharging processes. Full article

The continuous provision of nitrogen (N) to the crop is critical for optimal cotton production; however, the constant and excessive application of synthetic fertilizers causes adverse impacts on soil, plants, animals, and human health. The current study focused on the short-term effects (one-year study) of adding different rates of clinoptilolite zeolite, as part of an integrated nutrient management plan, and different rates of inorganic N fertilizer to improve soil and crop performance of cotton in three locations (ATH, MES, and KAR) in Greece. Each experiment was set up according to a split-plot design with three replications, three main plots (zeolite application at rates of 0, 5, and 7.5 t ha⁻¹), and four sub-plots (N fertilization regimes at rates of 0, 100, 150, and 200 kg N ha⁻¹). The results of this study indicated that increasing rates of the examined factors increased cotton yields (seed cotton yield, lint yield, and lint percentage), with the greatest lint yield recorded under the highest rates of zeolite (7.5 t ha⁻¹: 1808, 1723, and 1847 kg ha⁻¹ in ATH, MES, and KAR, respectively) and N fertilization (200 kg N ha⁻¹: 1804, 1768, and 1911 kg ha⁻¹ in ATH, MES, and KAR, respectively). From the evaluated parameters, most soil parameters (soil organic matter, soil total nitrogen, and total porosity), root and shoot development (root length density, plant height, leaf area index, and dry weight), fiber maturity traits (micronaire, maturity, fiber strength, and elongation), fiber length traits (upper half mean length, uniformity index, and short fiber index), as well as color (reflectance and spinning consistency index) and trash traits (trash area and trash grade), were positively impacted by the increasing rates of the evaluated factors. In conclusion, the results of the present research suggest that increasing zeolite and N fertilization rates to 7.5 t ha⁻¹ and 200 kg N ha⁻¹, respectively, improved soil properties (except mean weight diameter), stimulated crop development, and enhanced cotton and lint yield, as well as improved the fiber maturity, length, and color parameters of cotton grown in clay-loam soils in the Mediterranean region. Full article

Polyphenylene sulfide (PPS)-based separators have garnered significant attention as high-performance components for next-generation lithium-ion batteries (LIBs), driven by their exceptional thermal stability (>260 °C), chemical inertness, and mechanical durability. This review comprehensively examines advances in PPS separator design, focusing on two structurally distinct categories: porous separators engineered via wet-chemical methods (e.g., melt-blown spinning, electrospinning, thermally induced phase separation) and nonporous solid-state separators fabricated through solvent-free dry-film processes. Porous variants, typified by submicron pore architectures (<1 μm), enable electrolyte-mediated ion transport with ionic conductivities up to >1 mS·cm⁻¹ at >55% porosity, while their nonporous counterparts leverage crystalline sulfur-atom alignment and trace electrolyte infiltration to establish solid–liquid biphasic conduction pathways, achieving ion transference numbers >0.8 and homogenized lithium flux. Dry-processed solid-state PPS separators demonstrate unparalleled thermal dimensional stability (<2% shrinkage at 280 °C) and mitigate dendrite propagation through uniform electric field distribution, as evidenced by COMSOL simulations showing stable Li deposition under Cu particle contamination. Despite these advancements, challenges persist in reconciling thickness constraints (<25 μm) with mechanical robustness, scaling solvent-free manufacturing, and reducing costs. Innovations in ultra-thin formats (<20 μm) with self-healing polymer networks, coupled with compatibility extensions to sodium/zinc-ion systems, are identified as critical pathways for advancing PPS separators. By addressing these challenges, PPS-based architectures hold transformative potential for enabling high-energy-density (>500 Wh·kg⁻¹), intrinsically safe energy storage systems, particularly in applications demanding extreme operational reliability such as electric vehicles and grid-scale storage. Full article

Diaryldithiocarbamate complexes, [Fe(S₂CNAr₂)₃], have been prepared and their structure, reactivity, and thermal degradation to afford iron sulfide nanomaterials have been investigated. The addition of three equivalents of LiS₂CNAr₂ to FeCl₂·4H₂O in water-air affords dark red [Fe(S₂CNAr₂)₃] in high yields. All show magnetic measurements consistent with a predominantly high-spin electronic arrangement at room temperature. The molecular structure of [Fe{S₂C(N-p-MeOC₆H₄)₂}₃] reveals the expected distorted octahedral geometry, but Fe-S distances are more consistent with a low-spin electronic configuration, likely a result of the low temperature (120 K) of the data collection. The thermal stability of [Fe{S₂C(N-p-MeC₆H₄)₂}₃] has been investigated. TGA shows that it begins to decompose at a significantly lower temperature (ca. 160 °C) than previously observed for [Fe(S₂CNEt₂)₃], and this is further lowered (to ca. 100 °C) in oleylamine. The decomposition of [Fe{S₂C(N-p-MeC₆H₄)₂}₃] in oleylamine, via either a heat-up or hot injection process, affords nanoparticles of Fe₃S₄ (greigite), while in contrast, dry heating at 450 °C affords FeS (troilite) as large agglomerates. Full article

Sutures provide mechanical support for wound closure after various traumas and surgical operations. Absorbable sutures are increasingly favored as they eliminate the need for secondary procedures and minimize additional damage to the wound site. In this study, chitosan sutures were produced using the dry jet–wet spinning method, achieving number 7-0 sutures (approximately 76 μm diameter) with a homogeneous surface. FTIR analysis demonstrated molecular interactions between chitosan and TiO₂ or curcumin, confirming successful incorporation. The addition of 3% TiO₂ increased the tensile strength of chitosan sutures by 12.32%, reaching 189.41 MPa. Morphological analysis revealed smooth surfaces free of pores and bubbles, confirming the production of high-quality sutures. Radical scavenging activity analysis showed that curcumin-loaded sutures exhibited 43% scavenging ability after 125 h, which was significantly higher compared to pure chitosan sutures. In vitro antibacterial tests demonstrated that curcumin-loaded sutures provided 98.87% bacterial inactivation against S. aureus within 24 h. Additionally, curcumin release analysis showed a cumulative release of 77% over 25 h. The bioactivity of the sutures was verified by hydroxyapatite layer formation after incubation in simulated body fluid, supporting their potential for tissue regeneration. These findings demonstrate that TiO₂ reinforcement and curcumin loading significantly enhance the functional properties of chitosan sutures, making them strong candidates for biocompatible and absorbable surgical applications. Full article

Two types of T800 grade carbon fibers, produced using distinct spinning processes, were utilized to fabricate thermoplastic prepregs via the hot melt method. These prepregs were subsequently employed to produce thermoplastic composites. A universal testing machine was used to assess the tensile, bending, and interlaminar shear properties of the composites, evaluating the impact of the two different spinning processes on their mechanical characteristics. The experimental results indicate that the dry spray wet spinning carbon fiber (T800-DJWS) exhibits a smoother surface, more regular cross-section, and more uniform distribution compared to the wet spinning carbon fiber (T800-WS), enhancing the prepreg preparation via the hot melt method. The T800-DJWS/PAEK composite demonstrates a tensile strength that is 706 MPa higher than the T800-WS/PAEK composite, while the latter exhibits a bending modulus 31 GPa higher than the former. Full article

The problem of estimation the friction torque in operating miniature ball bearings lubricated with oil or grease is a complex one. Generally, in an angular contact ball bearing (ACBB), various types of losses can appear including losses caused by kinematics in ball-race contacts (rolling, sliding and pivoting), losses between the cage and the balls and between the cage and the guiding race and losses generated by lubricant, especially at high speeds. In the miniature ACBB, the applied loads have generally low values, and some losses can be ignored. In these circumstances, the most important contribution to the increase in the losses in miniature ACBB is the presence of the lubricant. In normal rolling bearings, the lubricant has an important contribution to decrease the losses and increase the reliability in miniature ball bearing; the lubricant (oil or grease) leads to the increase in the losses compared to the dry or limit lubrication conditions. The catalogues of various rolling bearing companies have not provided more details referring to the friction losses in miniature ball bearings. In order to evaluate the total friction torque in the rolling bearings, some empirical complex relations are presented via the SKF methodology, which can be applied only to moderate and high loads applied to the rolling bearings. Other empirical relations are presented by the Schaeffler catalogue. Based on previous experiments, the authors determined the friction torque in a 7000C ACBB with the spin-down method. The experimental results were correlated with the results obtained via the theoretical model developed by Houpert for IVR lubrication conditions. The theoretical results evidenced that the hydrodynamic rolling resistance generated by the lubricant is the most important component of the friction torque for 7000C ACBB. The experimental and theoretical results were compared to the results obtained according to the SKF and Schaeffler relations. The experimental results and the results obtained with the Houpert model generally had higher values compared to the results obtained with the SKF and Schaeffler relations. Full article

Nuclear magnetic resonance relaxation of the proton spins of liquid molecules and their evolution during processes such as drying, fluid flow, and phase change of a sample can be monitored in a nondestructive way. A unilateral ¹H NMR sensor made with a permanent magnet array, inspired by the NMR MOUSE, with an RF coil tuned to 11.71 MHz was developed. This creates a sensitive homogeneous measuring volume parallel to the sensor surface and located 14 mm from its surface, allowing contactless measurements from the sample’s interior. As this sensitive volume is moved across the sample using a semi-automatic linear displacement mechanism with millimetric precision, spatial T₂ lifetime and signal intensity 1D profiles can be obtained. To characterize the sensor’s sensitive volume, eraser samples were used. To evaluate the sensor’s ability to characterize different materials, cement paste samples containing ordinary and white Portland cement were prepared and measured at seven days of age. In addition, measurements were made on organic samples such as a Hass avocado and beef steak. Based on the results, a 1 mm spatial resolution of the sensor was achieved. The sensor was able to detect differences in T₂ lifetimes in eraser specimens composed of layers of three different erasers. Also, a clear difference in T₂ lifetimes and signal intensities was observed in cement pastes composed of white and ordinary Portland cement. On the other hand, it was possible to obtain signals from the peel and pulp of the avocado fruit, as well as from the fat and meat in a beef steak in a nondestructive way. The T₂ lifetimes of the different materials agreed with those obtained using a commercial NMR spectrometer. Full article

The influence of annealing temperature on the chemical, structural, and electrophysical properties of porous OSG low-k films containing terminal methyl groups was investigated. The films were deposited via spin coating, followed by drying at 200 °C and annealing at temperatures ranging from 350 °C to 900 °C. In the temperature range of 350–450 °C, thermal degradation of surfactants occurs along with the formation of a silicon-oxygen framework, which is accompanied by an increase in pore radius from 1.2 nm to 1.5 nm. At 600–700 °C, complete destruction of methyl groups occurs, leading to the development of micropores. FTIR spectroscopy reveals that after annealing at 700 °C, the concentration of silanol groups and water reaches its maximum. By 900 °C, open porosity is no longer observed, and the film resembles dense SiO₂. JV measurements show that the film annealed at 450 °C exhibits minimal leakage currents, approximately 5 × 10⁻¹¹ A/cm² at 700 kV/cm. This can be attributed to the near-complete removal of surfactant residues and non-condensed silanols, along with non-critical thermal degradation of methyl groups. Leakage current models obtained at various annealing temperatures suggest that the predominant charge carrier transfer mechanism is Poole–Frenkel emission. Full article

Both annual (cotton, flax, hemp, etc.) and perennial (trees and grasses) plants can serve as a source of cellulose for fiber production. In recent years, the perennial herbaceous plant miscanthus has attracted particular interest as a popular industrial plant with enormous potential. This industrial crop, which contains up to 57% cellulose, serves as a raw material in the chemical and biotechnology sectors. This study proposes for the first time the utilization of miscanthus, namely Miscanthus Giganteus “KAMIS”, to generate spinning solutions in N-methylmorpholine-N-oxide. Miscanthus cellulose’s properties were identified using standard methods for determining the constituent composition, including also IR and atomic emission spectroscopy. The dry-jet wet method was used to make fibers from cellulose solutions with an appropriate viscosity/elasticity ratio. The structural characteristics of the fibers were studied using IR and scanning electron microscopy, as well as via X-ray structural analysis. The mechanical and thermal properties of the novel type of hydrated cellulose fibers demonstrated the possibility of producing high-quality fibers from miscanthus. Full article

Giant unilamellar vesicles (GUVs) are frequently used as membrane models in studies of membrane properties. They are most often produced using the electroformation method. However, there are a number of parameters that can influence the success of the procedure. Some of the most common conditions that have been shown to have a negative effect on GUV electroformation are the presence of high cholesterol (Chol) concentrations, the use of mixtures containing charged lipids, and the solutions with an elevated ionic strength. High Chol concentrations are problematic for the traditional electroformation protocol as it involves the formation of a dry lipid film by complete evaporation of the organic solvent from the lipid mixture. During drying, anhydrous Chol crystals form. They are not involved in the formation of the lipid bilayer, resulting in a lower Chol concentration in the vesicle bilayer compared to the original lipid mixture. Motivated primarily by the issue of artifactual Chol demixing, we have modified the electroformation protocol by incorporating the techniques of rapid solvent exchange (RSE), ultrasonication, plasma cleaning, and spin-coating for reproducible production of GUVs from damp lipid films. Aside from decreasing Chol demixing, we have shown that the method can also be used to produce GUVs from lipid mixtures with charged lipids and in ionic solutions used as internal solutions. A high yield of GUVs was obtained for Chol/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) samples with mixing ratios ranging from 0 to 2.5. We also succeeded in preparing GUVs from mixtures containing up to 60 mol% of the charged lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-L-serine (POPS) and in NaCl solutions with low ionic strength (<25 mM). Full article