Search Results (524)

Macrosegregation in continuous casting slabs remains a critical defect that adversely affects the homogeneity and mechanical properties of the final rolled products. Industrial experiments were conducted on E355 steel continuous casting slabs to investigate the effects of electromagnetic stirring (EMS) and soft reduction (SR) on the evolution of slab macrosegregation. Furthermore, the inheritance of segregation from the slab to the rolled plate was analyzed. The results indicate that the equiaxed crystal ratio increases and the centerline segregation decreases with increasing stirring intensity. The application of both secondary EMS and SR minimized the centerline segregation in the slab. When the current intensity was increased from 0 A to 320 A in continuous stirring mode, the equiaxed crystal fraction increased from 22.52% to 32.52%, and the centerline segregation index decreased from 1.23 to 1.17. Compared with the continuous stirring mode, the alternating stirring mode promoted a more pronounced increase in the equiaxed crystal ratio and a further reduction in the centerline segregation. The centerline segregation in the slab correlates with the banded structure observed in the rolled plate. A higher degree of slab centerline segregation corresponds to a more severe banded structure and greater fluctuations in the mechanical properties of the plate. Through parameter optimization, the recommended settings are an alternating stirring mode with a current of 320 A at 5 Hz and an SR amount of 3 mm. Under these optimized conditions, the equiaxed crystal ratio of the slab increased to 35.22%, the centerline segregation index dropped to 1.15, and the banded structure in the rolled plate was reduced to grade 2.0. Consequently, the standard deviations of the tensile strength and elongation were 8.03 MPa and 1.1%, respectively. Full article

This study investigates the development and characterization of bioactive films incorporating silver nanoparticles (AgNPs) into biocompatible polymers, namely alginate and chitosan, fabricated using two methods, spin-coating and drop-casting, and aiming to enhance their antimicrobial properties. Dynamic light scattering (DLS) and electrophoretic mobility (EM) of the film precursor solutions revealed significant changes in the nanoparticles’ size and Zeta potential (ZP), reflecting the influence of polymer coatings. Alginate contributed to high electrostatic stability due to its negative charge, while chitosan facilitated specific interactions with negatively charged surfaces. Raman spectroscopy revealed that spin-coating conditions did not successfully result in film formation, highlighting the need for further optimization. Therefore, subsequent characterization studies were conducted only for the films formed by drop-casting. Topographical and nanomechanical assessments of these drop-cast films, using atomic force microscopy (AFM) and force spectroscopy, demonstrated that AgNPs reduced adhesion and elasticity in alginate films, while increasing rigidity and adhesion in chitosan-based films. Antimicrobial tests confirmed the efficacy of AgNPs in both precursor solutions and polymer films, with chitosan-based films that retained structural integrity, which makes them suitable for prolonged applications, while alginate films displayed rapid gelation upon hydration, potentially advantageous in short-term applications. The findings underscore the potential of these biopolymer-AgNP composites in creating antimicrobial materials for food packaging, wound dressings, and other biomedical applications. However, challenges related to film deposition methods, such as spin-coating, require further optimization to improve film formation and reproducibility. Full article

Kraft paper, commonly known as brown paper, has been widely used in the preservation of various food products and is increasingly explored in the development of active packaging materials with antimicrobial functionality by incorporating metal nanoparticles. This study aimed to comparatively investigate the surface modification of Kraft paper with silver nanoparticles (AgNPs) using dip-coating and drop-casting techniques. AgNPs were produced via green synthesis and incorporated onto the surface of Kraft paper samples. The modified samples were characterized using physicochemical techniques, including atomic force microscopy (AFM), Raman spectroscopy and light microscopy, as well as nanomechanical characterization via force spectroscopy. The antimicrobial activity of the modified papers was assessed using the disk diffusion method. The results demonstrated that the modification techniques resulted in distinct surface characteristics. Samples treated with the drop-casting method exhibited the highest AgNP surface loading; however, this was accompanied by pronounced surface heterogeneity and a tendency toward reduced load-bearing capacity. Overall, the findings indicate that the choice of deposition technique plays a key role in controlling nanoparticle distribution and surface properties. Within the limitations of the techniques evaluated, the incorporation of nanomaterials with potential antimicrobial activity into Kraft paper may offer opportunities for the development of active food packaging, although further optimization is required. Full article

To meet the mechanical property requirements of gray cast iron for the shells of coal mine explosion-proof equipment and investigate the effect of austenitizing temperature on the microstructure and mechanical properties of gray cast iron, isothermal quenching was conducted at four austenitizing temperatures (890 °C, 910 °C, 930 °C, and 950 °C), with cast samples as the control group. The microstructure was using a scanning electron microscope, and the mechanical properties were tested using a universal tensile testing machine, a drop-weight impact testing machine and a hardness tester. The results show that the matrix microstructure of gray cast iron transforms from ferrite + pearlite to ausferrite after isothermal quenching, and the proportion of ausferrite increases gradually with the rise of austenitizing temperature. At an austenitizing temperature of 930 °C, the hardness of the sample reaches a maximum value of 247.6 HBW, which is 31.9% higher than that of the cast sample. At 910 °C, the impact energy and tensile strength achieve the optimal values of 9.59 J and 219 MPa, respectively, with an increase of 6.43 J and 51 MPa compared with the cast sample. Comprehensive analysis indicates that the austenitizing temperature of 910 °C can improve the strength while maintaining good toughness, which makes it more suitable for application scenarios requiring both strength and toughness such as coal mine explosion-proof equipment. Full article

Heat sinks for high-power devices are frequently manufactured via integral casting to ensure long-term stability and superior thermal performance. This study investigates the effects of the location, number, and arrangement of casting gates on heat transfer performance and temperature uniformity. The results indicate that positioning gates on the inlet side enhances heat transfer, whereas an outlet-side arrangement improves temperature uniformity. The 3-O configuration (casting gate diameter of 3 mm positioned at the front) was observed to exhibit the optimal hydrothermal performance factor (HTPF), achieving a maximum improvement of 32% compared to the benchmark 0-OMT (finned heat sink without gates). Meanwhile, the best temperature uniformity was demonstrated by the 5-M configuration (gate diameter of 5 mm positioned in the middle), with a maximum improvement of 64.8% over the benchmark. Furthermore, a power-law predictive model correlating the variables with the objective functions was established, and multi-objective optimization was conducted in conjunction with a Genetic Algorithm (GA). The results indicated that a significant enhancement in comprehensive performance was achieved by the optimized model; compared with the initial model, the temperature rise (ΔT) and pressure loss (ΔP) were reduced by 59.06% and 39.94%. Full article

Herein, a cobalt–molybdenum bimetallic oxide precursor was synthesized via a hydrothermal route, followed by a phosphidation strategy in a tube furnace to produce a CoMoP cocatalyst. Subsequently, a CoMoP/BiVO₄ composite photoanode was successfully constructed by loading the CoMoP cocatalyst onto the surface of an electrodeposited BiVO₄ film using a drop-casting method. A suite of analytical tools such as TEM, XRD, and XPS was utilized to comprehensively examine the material morphology and crystalline features, verifying that CoMoP was effectively anchored on the BiVO₄ surface with intimate interfacial contact. Photoelectrochemical (PEC) performance testing indicated that the composite photoanode achieved optimal performance with a 200 µL loading of the CoMoP dispersion (2 mg/mL). Under front-side illumination, the photocurrent density of the CoMoP/BiVO₄ composite photoelectrode reached a photocurrent density of 2.8 mA/cm² at 1.23 V (vs. RHE), which is approximately 3.1 times higher than that of unmodified BiVO₄ (0.9 mA/cm²). Under back-side illumination, the composite photoanode generated 3.5 mA/cm², representing a 2.3-fold improvement over the 1.5 mA/cm² recorded for bare BiVO₄. The bandgap energy of BiVO₄ was determined to be approximately 2.44 eV based on UV–vis absorption spectra and the corresponding Tauc plot. Owing to its metallic nature, CoMoP exhibits strong broadband absorption in the visible-light region and does not display an intrinsic semiconductor bandgap behavior. Combined with photoluminescence (PL) spectroscopy and PEC results, it was demonstrated that the CoMoP loading effectively promoted interfacial charge separation and transport while accelerating water oxidation kinetics. These results demonstrate that the CoMoP/BiVO₄ system serves as an advanced semiconductor material with excellent performance for photoelectrocatalytic water splitting. Full article

This study aims to develop an electrochemical sensor based on a glassy carbon electrode (GCE) modified with Fe₃O₄ and graphene for the detection of myristicin as a characteristic compound in nutmeg plants. Electrode modification materials were prepared from a combination of graphene and magnetite, synthesized via a hydrothermal method, and further characterized using X-ray diffraction (XRD), scanning electron microscope–energy dispersive spectroscopy (SEM-EDS), and transmission electron microscopy (TEM). The two modifying materials were then optimized, and the optimum conditions were obtained at a w/w ratio of 1:2, which was applied to the GCE surface using the drop-casting technique. The electrochemical performance of the Fe₃O₄/graphene-modified electrode was evaluated under optimum experimental conditions using a Britton–Robinson buffer solution at pH 5. The scan-rate analysis of the electrode to evaluate its electrochemical performance showed an increase in surface area from 0.101 cm² for the bare GCE to 0.534 cm² for the GCE/Fe₃O₄–graphene. Electroanalytical performance was evaluated using differential pulse voltammetry (DPV), which showed a linear response over the concentration range of 1–100 µM, with a limit of detection of 0.19 µM and a limit of quantitation of 0.58 µM. The developed electrode was applied successfully to detect myristicin in nutmeg seed extract samples, and its calculated concentrations were not significantly different from those obtained with the GC-MS method. These results suggest that the developed sensor may have further potential as an alternative detection tool for characterizing electroactive compounds in nutmeg plants. Full article

In this study, we have investigated heterostructural TiO₂/BiVO₄ anodes to determine the effect of the amount and form of BiVO₄ nanoparticles on TiO₂ on the response of photoanodes under UV and visible illumination. BiVO₄ nanopowders were prepared and annealed at temperatures ranging from 200 to 500 °C. Structural and optical characterization indicates that as the annealing temperature is increased, a phase transition from a weakly ordered to a dominant monoclinic BiVO₄ phase is observed, which is accompanied by an increase in visible light absorption. Subsequently, the most crystalline powder was utilized to deposit BiVO₄ on nanostructured TiO₂ either as a compact overlayer (drop-casting) or as a progressively grown nanoparticle (TiO₂@S series) in the successive ionic layer adsorption and reaction process (SILAR). Photoelectrochemical measurements were performed, revealing a morphology-dependent photocurrent response under UV and visible illumination. A further increase in the number of cycles systematically increases the photocurrent in the visible light range while limiting the response to UV radiation. The TiO₂@d photoanode demonstrates the highest relative activity within the visible range; however, it also generates the lowest absolute photocurrent, indicating the presence of significant transport and recombination losses within the thick BiVO₄ layer. The results demonstrate that the presence of BiVO₄ nanoparticles on TiO₂ exerts a substantial influence on the separation of charge between semiconductors and the synergistic utilization of photons from the UV and visible ranges. This research yielded a proposed scheme of mutual band arrangement and charge carrier transfer mechanism in TiO₂@BiVO₄ heterostructures. Full article

This study introduces a synergistic drop-casting, sonication, and thermal treatment (DSTT) method for fabricating multi-walled carbon nanotube (MWCNT)-coated conductive cotton fabrics. The process produced uniform MWCNT networks with a minimum sheet resistance of 0.072 ± 0.004 kΩ/sq. at ~30 wt.% loading. Scanning electron microscopy confirmed an improved MWCNT network. Reproducibility was demonstrated for different fabric sizes, with resistance values remaining consistent within experimental errors. Stability tests showed only minor changes in sheet resistance after 16 weeks of ambient storage and periodic manual bending. Compared to conventional methods such as room-temperature drying, vacuum drying, and sonication alone, DSTT consistently performed better, yielding fabrics with lower resistance and more reliable conductivity. These results highlight DSTT as a reproducible and scalable method for producing conductive cotton fabrics suitable for smart textiles and wearable electronics. Full article

Magnetotactic bacteria (MTB) have attracted interest in recent years, mainly due to their natural ability to form intracellular magnetic nanocrystals with potential for biomedical and environmental applications. In this study, we focused on the morphological analysis of the Paramagnetospirillum magnetotacticum MS-1 strain, trying to keep the bacteria as close to their natural state as possible. An important element of this work is the use of untreated bacterial cells, without conductive coating or chemical fixation, using a simple and low-cost support. This choice was made intentionally to avoid changes induced by metallization and to allow direct observation of characteristics that may be relevant in applications where the interaction of the bacteria with the environment plays an important role, such as biosensors. In addition, the analysis was performed on a bacterial suspension stored for approximately 10 months at 4 °C to assess whether the morphology specific to the MS-1 strain is maintained over time. The obtained results show that the general cell morphology and magnetosome organization can be clearly and reproducibly observed even after long-term storage. Without attempting to replace studies based on conventional sample preparation methods, this work provides a complementary perspective and suggests that magnetotactic bacteria may represent a natural and effective alternative to synthetic magnetic nanoparticles, with potential applications in the biomedical and environmental fields. Full article

Active packages have become a significant center of attention, and especially those based on biodegradable materials, due to their ability to enhance food preservation and extend shelf life. A suitable base for obtaining such types of packages has turned out to be polymers with natural origin, such as hydroxylpropyl methylcellulose (HPMC) and zein. Therefore, the present study is focused on developing films using the casting method based on pure HPMC and blends between HPMC and zein. Three types of polymer matrices were developed: pure HPMC film, HPMC 3:1 zein, and HPMC 1:1 zein. Further, all of them were loaded with curcumin to improve their biological activity, and mainly their antioxidant activity. In order to investigate the potential of these films, some of their most vital properties in terms of potential application as packaging material are established, such as mechanical properties (strain at break, Young’s modulus), barrier properties (water vapor transmission rate), and morphology. A significant change in the Young’s modulus was present after the addition of zein; it went from 276.98 ± 28.48 MPa for pure HPMC to 52.17 ± 10.19 MPa in a 1:1 ratio between the polymers. Meanwhile, strain at break showed a slight drop from 86.74 ± 8.64% to 72.44 ± 9.62%. Barrier properties were also influenced by the formation of composite film and the addition of polyphenol, lowering the water vapor transmission rate from 913.07 ± 74.01 g/m².24 h for pure HPMC to 873.05 ± 9.07 g/m².24 h for 1:1 ratio film and further to 826.35 ± 33.67 g/m².24 h after the addition of rutin to the latter. Additional characterization of radical scavenging ability towards DPPH free radicals showed a similar A-shaped trend to the values of Young’s modulus, due to the presence of hydrogen bonds, which affect both properties of the film structures. Thermal behavior and phase state investigation of the films obtained by differential scanning calorimetry prior to and after polyphenol addition was carried out, indicating full phase transition of rutin from crystalline to amorphous state. Full article

rGO/ZnO composites have been widely studied for use as toxic gas sensors due to the synergistic effect between the materials and the reduction in sensor operating temperature promoted by rGO. However, few studies have employed rGO/ZnO sensors for ozone detection, as graphene materials are oxidized and/or degraded when exposed to ozone. This paper reports on a study of ZnO/rGO/ZnO-based sensors with different ZnO NP morphologies for ozone sensing. ZnO nanoparticles with needle-like and donut-like morphologies were synthesized by the precipitation method, and bare ZnO and ZnO/rGO/ZnO composite sensors were fabricated by layer-deposition of ZnO and/or rGO via drop-casting, forming a “sandwiched” structure that protects the rGO sheets. Bare ZnO and ZnO/rGO/ZnO composites were analyzed by varying the temperature from 200 to 300 °C. The ZnO/rGO/ZnO sensor provided a high 13.3 response (R_gas/R_air) and recovery times of 442 s and 253 s, respectively, for 50 ppb of O₃, as well as high selectivity to ozone gas compared to CO, NH₃, and NO₂ gases. No oxidation or degradation of the sensor was observed during ozone detection measurements, indicating that the adopted manufacturing methodology was successful. Full article

The integration of molecular imprinting technology with electrochemical methods has become fundamental in the development of next-generation sensors. This study explores two different strategies for developing a dopamine-based molecularly imprinted polymer (MIP) for the electrochemical sensing of levofloxacin. In the first case, the MIP is developed by electropolymerization on a screen-printed carbon electrode (SPCE) surface using cyclic voltammetry, while in the second, the MIP is obtained by an oxidation process, and the resulting dispersion is drop-cast on the SPCE surface. The same approach is used for a non-imprinted polymer. The physicochemical properties of the synthesized materials and the surface morphology of the modified electrodes are investigated by several techniques. Differential pulse voltammetry is used to evaluate the performance of the modified electrodes, assessing their linear concentration range, limit of detection, and limit of quantification, together with repeatability and selectivity. MIP-based SPCEs obtained with these two fabrication strategies exhibited comparable imprinting factor values and linear concentration ranges, along with comparable limits of detection and quantification. The MIP-based SPCE obtained by electropolymerization showed greater repeatability, whereas the MIP-based SPCE produced by drop-casting provided higher sensitivity in levofloxacin detection. Full article

Alpha-case formation, originating from interfacial reactions between molten titanium and oxide molds, remains a critical issue limiting the surface integrity and mechanical performance of titanium castings. In this study, the effect of aluminum content (0–52 at%) on alpha-case formation was systematically investigated using plasma arc melting and drop casting with alumina-based molds. The reaction kinetics between titanium melts and alumina molds were evaluated through cooling rate measurements and thermodynamic modeling. Microstructural and compositional analyses using optical microscopy, hardness testing, and electron probe microanalysis revealed that increasing aluminum content effectively suppressed alpha-case development. No distinct reaction layer was observed when the aluminum concentration exceeded 30 at%. The alpha-case consisted primarily of Ti₃Al, TiO₂, and Ti₅Si₃ phases, indicating that the molten titanium reacted with both alumina and silica constituents of the mold. Oxygen was identified as the dominant element controlling the reaction depth, consistent with its diffusion behavior across titanium phases. Calculated alpha-case thicknesses showed excellent agreement with experimental measurements, confirming that the reduction in alpha-case depth with increasing aluminum content results from decreased oxygen diffusivity, shorter reaction time, and lower interfacial temperature. These findings establish aluminum addition as a key strategy for minimizing interfacial reactions during titanium investment casting, thereby improving dimensional accuracy and surface quality in high-temperature components. Full article

ITIC’s superior electron-accepting capacity and efficient oxygen reduction motivated the design of a sensor to enhance sensitivity, selectivity, and stability over conventional oxygen-dependent or fullerene-based systems. As oxygen acts as the terminal reagent in enzymatic glucose oxidation, we developed an ITIC-mediated glucose oxidase (GOx) biosensor on glassy carbon (GCE) and screen-printed carbon electrodes (SPCE). ITIC, a non-fullerene organic semiconductor, was drop-cast onto the electrode to catalyze oxygen reduction, followed by GOx immobilization in a chitosan matrix. Scanning electron microscopy (SEM) confirmed uniform, ultrathin coatings without significant morphological changes upon ITIC and GOx deposition. Electrochemical studies (cyclic (CV) and differential pulse voltammetry (DPV)) revealed a distinct ITIC reduction peak at –0.7 V (vs. Ag/AgCl) and a glucose-dependent current decrease, consistent with mediated electron transfer during enzymatic oxidation. Under optimized conditions, the GCE-based biosensor showed a sensitivity of 10.7 μA L mmol⁻¹, a linear dynamic range (LDR) of 0.10–1.00 mmol L⁻¹, and detection (LOD)/quantification (LOQ) limits of 0.02 and 0.06 mmol L⁻¹, respectively. The SPCE device displayed sensitivity (3.8 μA L mmol⁻¹) and maintained excellent linearity (R² > 0.99) with LOD and LOQ of 0.05 and 0.16 mmol L⁻¹. Both platforms showed good precision (RSD < 5%) and reliable recovery in deproteinized plasma and artificial tears (90–104%). The superior performance of the GCE is attributed to higher ITIC loading, faster electron transfer, and reduced background current, while the SPCE offers a low-cost, disposable format with sufficient analytical performance for point-of-care glucose monitoring. Full article