Search Results (4,558)

In this work, a flexible and sustainable radar-absorbing material (RAM) based on porous carbon derived from raw Kraft black liquor was developed. The porous carbon filler was synthesized through a simple, eco-friendly one-pot polymerization route, thereby avoiding lignin extraction, purification, and chemical activation steps. Macroporosity was introduced by using poly(methyl methacrylate) microspheres as a hard template, yielding a lightweight carbon material with a foam-like morphology, low density, and high porosity. The carbon filler was incorporated into a silicone rubber matrix at different loadings (5–25 wt.%) to produce flexible composites. The structural, morphological, and textural properties of porous carbon were investigated by SEM, EDX, Raman spectroscopy, nitrogen adsorption, and mercury porosimetry. The electromagnetic properties of composites were measured in the X-band (8.2–12.4 GHz) using a vector network analyzer. The mechanical behavior was evaluated through Young’s modulus. The results show that increasing filler content enhances dielectric losses and attenuation capability. Among all composites, the sample containing 20 wt.% of porous carbon exhibited the best electromagnetic performance, achieving a reflection loss of −42.3 dB at 10.97 GHz with a thickness of 2.43 mm, corresponding to an absorption efficiency of 99.99%. This performance is attributed to a favorable combination of impedance matching and quarter-wavelength cancellation effects. The developed sustainable, lightweight, and flexible composites demonstrate potential as low-cost RAM for aerospace and electromagnetic interference mitigation applications. Full article

Hydrogen is increasingly adopted as a clean energy carrier for storing and transporting low-carbon energy. Achieving a practical volumetric energy density for real-world deployment typically requires compression to several hundred bar, which in turn demands dedicated high-pressure infrastructure. Because valves are indispensable for isolation and flow control within this infrastructure, durable sealing valve materials become a key reliability and safety requirement. This assembly-level screening study compares two valve configurations with different polymer assemblies: EPDM O-rings with PEEK seats/bushing and NBR O-rings with POM seats/bushing. Four new identical 500-bar ball valves were tested (two EPDM/PEEK and two NBR/POM). For each seal configuration, one valve was cycled 5000 times at 500 bar in helium (inert baseline), and a second identical valve was cycled 5000 times at 500 bar in hydrogen to isolate hydrogen effects from mechanical/metallic wear. Leakage was tracked during cycling, and seals were analyzed by SEM/EDX after testing. The EPDM/PEEK configuration remained leak-tight in both gases, with no cracking observed in the elastomer or thermoplastic components. The NBR/POM configuration exhibited POM bushing fracture during cycling and minor external leakage at the stem during the hydrogen phase, accompanied by micro-fissures on the NBR O-ring surface. EDX indicated composition changes after cycling, including oxygen and fluorine enrichment and occasional metallic transfer species, consistent with surface films and deposits. Under the present valve geometry and cycling protocol, EPDM/PEEK provided robust sealing, whereas NBR/POM showed failure modes relevant to high-pressure service. These findings are intended as configuration-level screening evidence to be used in valves rather than as a full qualification of the individual materials. Full article

Albumin is an important biomarker in biological fluids and plays a critical role, particularly in the diagnosis of renal dysfunction. Therefore, the sensitive detection of low concentrations of albumin in urine is of great importance. In this study, a composite nanohydrogel modified with carbon dots has been developed for the selective detection of albumin from human urine. The composite nanohydrogels were synthesised using a molecular imprinting technique specifically designed to recognise albumin. Characterisation studies were conducted using ZetaSizer, SEM, EDX, CLSM and ATR-FTIR methods. The albumin-binding capacities of the carbon dots (C-Dots) and synthesised composite nanohydrogels were evaluated using fluorescence spectroscopy. The effects of different concentration conditions on binding efficiency were systematically investigated. Selectivity studies have shown that albumin-imprinted nanohydrogels can detect target molecule albumin four times more selectively than competitive molecules, Hb and IgG. Imprinting efficiency was estimated by comparing the signals of albumin obtained from non-imprinted and albumin-imprinted composite nanohydrogels. Finally, artificial urine samples mimicking real biological environment conditions were examined to evaluate matrix effect on the albumin detection. The repeatability and long-term stability of albumin detection, performed with four consecutive and six-month measurements, was evaluated using the %RSD value, confirming that the albumin determination performance was maintained. Full article

This study explores how variations in mechanical alloying time and sintering temperature influence the microstructure, mechanical properties, and corrosion resistance of MnAlCuFeTi high-entropy alloys (HEAs). The MnAlCuFeTi alloy was produced by means of mechanical alloying for 5, 10, 15, and 20 h. Afterward, the alloy samples were sintered at two different temperatures: 550 °C and 650 °C. Structural properties were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). Analysis of grain sizes, calculated using the Scherrer formula from SEM images, confirmed that grain size had decreased to the nanostructured regime and that microstructural homogeneity had improved. Corrosion behavior was evaluated using polarization curves, corrosion current density (I_corr), and corrosion rate measurements. The results show that increasing the mechanical alloying time reduces the alloy’s grain size, thereby improving its mechanical and corrosion resistance. At a sintering temperature of 550 °C, I_corr and corrosion rate decrease with increasing grinding time, whereas at 650 °C, although high temperatures accelerate diffusion processes and increase phase homogeneity, they weaken corrosion resistance. These findings emphasize the importance of balancing alloying time and sintering temperature to optimize performance in high-corrosion-resistant HEA applications. Full article

Boron coatings were deposited by RF magnetron sputtering in an Ar atmosphere at a constant power of 80 W, varying the working pressure in the 0.6–5 Pa range. Plasma diagnostics were performed by means of a Langmuir probe to determine the electron temperature and electron density under different operating conditions. Within the investigated pressure range, the deposition rate remained nearly constant, whereas a significant decrease in coating mass density was observed with increasing pressure. The coatings display a columnar structure at all investigated pressures, with no significant differences in bulk morphology. Pressure primarily affects the surface features, leading to an increase in the density, lateral dimensions, and height of surface agglomerates with increasing pressure. Compositional analysis by EDX revealed a substantial oxygen incorporation in the films, with the lowest oxygen content (~11 at.%) measured for the coating deposited at 0.6 Pa. XPS depth profiling confirmed the presence of oxygen and evidenced the formation of boron oxide species, while the boron concentration exceeded 80 at.% in all samples. These results highlight the strong sensitivity of boron film density and oxygen uptake to sputtering pressure. Full article

The invasive fall armyworm (Spodoptera frugiperda) threatens Philippine crops, highlighting the need for sustainable pest management. This study therefore optimizes the green synthesis of silver nanoparticles (AgNPs) from water hyacinth (Eichhornia crassipes), an abundant and problematic aquatic weed, as a potential pest control tool. Methanolic leaf extracts were prepared under varying methanol concentrations, temperatures, and extraction times, and total phenolic content was quantified using the Folin–Ciocalteu method. SEM–EDX confirmed the formation of silver nanoparticles synthesized from Eichhornia crassipes (Ec-AgNPs), with particles observed at ≤100 nm. Optimal extraction occurred at 47 °C, 90% methanol, and 76 min, maximizing phenolic yield. Overall, results suggest phenolic content and extract volume influence nanoparticle size and stability, with larger extract volumes increasing agglomeration risk. Pesticidal efficacy was not evaluated; further work is needed to assess pest control performance. Full article

Almond gum is a resource-rich natural polysaccharide; however, its high viscosity and low solubility severely limit industrial applications in separation, purification, and functional development. This study aimed to overcome these bottlenecks by optimizing an ethylenediaminetetraacetic acid (EDTA) preparation process and evaluating its protective efficacy against colitis. Using response surface methodology, optimal conditions were identified (1% EDTA, 3 h reaction, 10 h extraction), resulting in a modified polysaccharide (EAGP) with significantly reduced viscosity (from 640.8 to 238.7 mPa·s). SEM-EDX confirmed that EDTA efficiently removed cross-linking metal ions (K, Ca, Mg), creating a porous structure that facilitates purification. The purified fraction, EAGP-W1, was characterized as an arabinogalactan primarily composed of galactose (40.51%) and arabinose (38.38%). In vivo experiments demonstrated that EAGP-W1 significantly alleviated DSS-induced colitis, reducing colonic shortening and histopathological damage (p < 0.05). Mechanistically, EAGP-W1 reshaped the gut microbiota by downregulating pro-inflammatory genera and upregulating probiotics (p < 0.05). This shift promoted the production of short-chain fatty acids (SCFAs) (p < 0.05), thereby repairing the intestinal barrier and suppressing inflammation. Overall, this study establishes an efficient EDTA-based strategy for almond gum processing and elucidates its anti-inflammatory mechanism through the “microbiota–metabolite–barrier” axis, providing a theoretical basis for its development as a high-value functional food for gut health. Full article

External leakage from valve stem packings is a critical safety and reliability issue in high-pressure hydrogen systems. This work aims to quantify how packing geometry and polymer selection influence stem sealing in a PN650 needle valve (316L body and stem). Two geometries were compared: a conical V-ring (chevron style) stack and a flat three-disc stack. Two polymer material sets were assessed: Vespel^® polyimide (SP-1/SP-21) and a glass-filled PTFE sealing element combined with a virgin PEEK back-up ring. Four assemblies (one per geometry/material combination) were first screened by hydrostatic pressure hold testing up to 1500 bar and by helium mass spectrometer leak measurements under vacuum. All assemblies sustained the hydrostatic overpressure hold with negligible decay. Vacuum helium screening produced leak rates between 3.7 × 10⁻¹⁰ and 9.5 × 10⁻¹⁰ mbar·l·s⁻¹, with the conical V-ring geometry consistently outperforming the disc stack. A more demanding helium test at 700 bar with external vacuum yielded leak rates of 3.6–3.7 × 10⁻⁸ mbar·l·s⁻¹, for conical assemblies. Based on the screening results and practical industrial considerations, the PTFE/PEEK conical configuration was selected for endurance testing and completed 2500 open/close cycles in 650 bar hydrogen without gland readjustment. Post-cycling checks confirmed continued tightness, including a qualitative helium pressure hold result near 700 bar and 0 bubbles in 10 min in the seat tightness test. Microscopy/EDX revealed limited wear with minor metallic transfer. The proposed multi-stage workflow provides a pragmatic route for the early qualification of stem packings for high-pressure hydrogen valves. Full article

Calcium oxalate (CaOx) crystals in plants can form naturally within their idioblasts but may also be induced by other factors, such as environmental pollution. Here, we report qualitative and semiquantitative results obtained using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) from two experiments in which tomato seedlings were moderately irrigated with Sulfamethoxazole (SMX) and Amoxicillin (AMX) solutions (0.25 mM). Abundant prismatic CaOx co-crystals appeared on the leaf surface induced by these two antibiotics compared to the distilled water (DW) control. Applying a non-thermal plasma (NTP) treatment for 20 min (T20) to the SMX initial solution led to a dramatic suppression of these crystals, with a shift toward spherical structures. Furthermore, the investigation into the composition of both crystal types, indicated different percentual levels of O, C, Ca, K, Mg, S, and Mn as main constituent minerals involved in crystal formation. However, crystal morphology was affected by each applied experimental condition, while detecting their constituent elements depended on their mineral homogeneity at the micro- or macro-field scales. Although both antibiotics induced crystal formation and T20 phenotypically reduced the abundance of the acicular–prismatic crystals by removing the effects of SMX, their mode of action has not yet been clarified. Full article

This study reports the synthesis of a high-entropy AlFeCuTiNi alloy via high-energy ball milling. The study investigates the effects of mechanical alloying time and sintering temperature on the microstructure, mechanical properties, wear, and corrosion behavior of the high-entropy AlFeCuTiNi alloy. XRD, SEM, and EDX analyses revealed that the mechanical alloying time and sintering temperature significantly affected the alloy’s homogeneity, phase structure, and oxide film stability. As the mechanical alloying time increases, the corrosion resistance of alloys sintered at 550 °C initially increases and then stabilizes. In samples sintered at 650 °C, corrosion resistance is generally higher. The highest corrosion resistance was achieved after 15 h of mechanical alloying and sintering at 650 °C. The study reveals that the best corrosion, wear, hardness, and wear density performance was observed in samples obtained at medium conditions, achieved after 20 h of mechanical alloying and sintering at 650 °C. These findings may contribute to optimizing production processes for sustainable material design. Moreover, this research highlights that high-entropy alloys and powder-metallurgy-based production methods enable industrial applications for energy-efficient, sustainable material design and contribute to sustainable production and circular-economy principles. Full article

Wastewaters from the food industry and domestic sources contain large amounts of ammonium, a major contributor to eutrophication. Recovering this nutrient for fertilizer use offers both environmental and agricultural benefits. Poplar chop-derived biochars were prepared under different pyrolysis temperatures (300–500 °C) and chemical modifications (acidic and alkaline) to optimize ammonium (NH₄⁺) adsorption and fertilizer reuse. The biochars were characterized by zeta potential, SEM–EDX, FTIR, and specific surface area measurements. Batch adsorption tests revealed that the alkaline-modified biochar produced at 300 °C achieved the highest capacity (4.63 mg NH₄⁺/g biochar) and 62% removal efficiency. Adsorption kinetics followed a pseudo-second-order model (R² = 0.97) but showed only marginal differences among models without independent mechanistic evidence. The Temkin isotherm described the equilibrium data the best (R² > 0.99). Ammonium-enriched biochars enhanced seed germination by up to 54% compared to the control and increased plant biomass up to 12-fold in pot experiments. These results demonstrate that optimized biochars can effectively recover ammonium from wastewater; moreover, the observed plant growth improvement suggests potential slow-release behavior, promoting nutrient recycling and sustainable agriculture. Full article

The urgent need to mitigate carbon dioxide (CO₂) emissions from fossil-fuel-based electricity generation has driven research into advanced materials for post-combustion carbon capture. This paper presents a modified solvothermal technique to synthesize zinc (Zn) and magnesium (Mg) based MOF-74 suitable for CO₂ capture from coal-fired power plants. The materials were synthesized through a solvothermal method using N,N-dimethylformamide (DMF) as the primary solvent, and subsequently characterized using Brunauer–Emmett–Teller (BET) surface area analysis, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), and thermogravimetric analysis (TGA). Both MOFs contained oxygen-containing functional groups and were thermally stable up to 430 °C and 600 °C respectively, making them ideal for carbon capture. The low-pressure N₂-BET surface areas were 55 m²/g and 24.73 m²/g. In conclusion, the Zn material had a mesoporous structure, making it more favorable for carbon capture. It was found that prolonged synthesis time weakened the MOF structure. Future work should experimentally evaluate CO₂ capture from coal-derived flue gas using Zn/Mg-MOF-74 materials, investigating adsorption behavior and kinetics through isotherm and kinetic models, while also assessing the effect of varying Zn: Mg ratios under optimized synthesis conditions. Full article

This study investigates the hydrophobic properties of hexamethyldisiloxane (HMDSO)-based coatings deposited by atmospheric pressure plasma-enhanced chemical vapor deposition (AP-PECVD). The objective of this procedure is to enable the extraction of molded components from the mold cavity. The test specimen geometry employed in the present investigation were made of tool steel 1.2311, a material that is frequently utilized in industrial applications. A series of experiments was conducted to assess the coating performance. Initially, surface energy measurements based on contact angle analysis were performed to determine the polar and dispersive surface components. Finally, energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscope (SEM) images are used to perform an exact measurement of the elemental composition and an optical comparison of the surface. The results of the work indicate that the material composition on the surface of silicon and oxygen is of particular importance. In addition, the results indicate that the use of argon as a carrier gas has a positive effect on reducing surface energy and increasing the contact angle to water drops. Full article

Corrosion resistance of steel wires can be achieved through several approaches, one of the most established being hot-dip galvanizing. The effectiveness of anticorrosive protection of a galvanized wire is considered to depend not only on the galvanizing process itself, namely bath composition, temperature, and immersion duration—but also on the post-galvanizing wiping method, which ultimately determines the final thickness and uniformity of the zinc coating. This study describes and quantifies the resulting parameters of the Zn layer, systematically comparing two technical variants. Four parameters were analyzed to characterize the coating: the effective thickness of the constituent layers, their morphology (examined by SEM), their compositional profile (EDX mapping), and their microhardness. To comprehensively assess the influence of the wiping method on the anticorrosion performance of the galvanized wire, the final corrosion tests, fifth in the sequence, will be conducted in a salt fog environment using an Erichsen chamber, in accordance with standardized procedures. Full article

The study investigates the catalytic activity of vanadium-containing catalysts in the selective oxidation of 4-methylpyridine (4-MP) in the gas phase. V-Cr, V-Ti, and V-Ti-Cr catalysts were synthesised and studied. The phase composition and structural features of the catalysts were determined by X-ray diffraction (XRD) and Raman spectroscopy, and their thermal stability was investigated using thermogravimetric analysis (TGA/DTA). Textural characteristics were evaluated by low-temperature nitrogen adsorption–desorption (BET, BJH), surface morphology was studied using scanning electron microscopy (SEM), and the distribution of elements was investigated using energy-dispersive X-ray spectroscopy (EDX). The chemical composition of the catalysts was determined using inductively coupled plasma atomic emission spectrometry (ICP-OES) and catalytic activity was evaluated in the selective gas-phase oxidation reaction of 4-methylpyridine in the temperature range 280–380 °C. It was found that an increase in temperature is accompanied by an increase in the conversion of 4-methylpyridine, but at the same time, deep oxidation reactions intensify. The best result is achieved on the V-Ti-Cr catalyst, for which the conversion of 4-MP reaches 86.88% and the selectivity is 73.06% at 320 °C. However, V-Ti provides moderate stable performance, while V-Cr demonstrates relatively low efficiency. Thus, it can be concluded that the nature of the temperature dependence of 4-methylpyridine conversion reflects the different nature of the active centres and their stability. Full article