Stirring Method Research Articles

Corrosion resistance and wear behavior of CoCrFeNiMn@Gr high entropy alloy-based composite coatings prepared by laser cladding

In this study, we utilize laser cladding to apply a CoCrFeNiMn HEA with 2 wt.% few-layer graphene (Gr) coating onto the surface of Q235B mild steel. Alcohol stirring method was used for HEA and Gr preparation of composite powder. Raman spectroscopy and energy dispersion spectroscope (EDS) indicate the successful mixing of HEA and Gr powders, with Gr adhering to the surface of the HEA powder in a lamellar structure. The X-ray diffraction (XRD), scanning electron microscope (SEM), EDS, and Electron backscatter diffraction (EBSD) analyses revealed that grain refinement and the formation of fine carbide-hard phases in the HEA/Gr coating improve microhardness and wear resistance. The average Schmidt factors of the coating decreased from 0.47 to 0.45 with the addition of Gr, indicating enhanced resistance to plastic deformation and anisotropy. Nanoindentation experiments demonstrated that the HEA/Gr coatings exhibit superior resistance to plastic deformation, effectively enhancing the coating’s durability against spalling under stress and wear conditions. The microhardness of the HEA/Gr coating increased by 99.25%, and the wear rate decreased by 86.31% compared to the HEA coating alone. The open circuit potential (OCP), linear polarization curve, Tafel curves, electrochemical impedance spectroscopy (EIS), and Mott-Schottky tests all indicated that the HEA/Gr coating possesses superior corrosion resistance. X-ray Photoelectron Spectroscopy (XPS) results suggest that the passivation film of the HEA/Gr coating, which contains more oxides and less hydroxide, is more protective and denser, thereby slowing the corrosion rate.

Atomized Reagent Addition with Synchronized Jet Pre-Mineralization to Enhance the Flotation Process: Study on Atomization Parameters and Mechanisms of Enhancement

The atomized reagent and synchronous jet pre-mineralization technology, as a novel method to enhance the flotation process, increases the solubility of fatty acid collectors in pulp through atomized reagent application and improves the mineralization effect and flotation rate via synchronous jet pre-mineralization technology, thereby laying a theoretical foundation for the flotation of minerals with fatty acid collectors. Systematic studies on the atomization method, atomization particle size, and flotation experiments revealed that, compared with conventional stirring methods, the atomized reagent method increases the solubility of sodium oleate in pulp from 82.5 mg/L to 142.9 mg/L at 288.15 K. The induction time for quartz particles treated with atomized reagents and bubbles is significantly lower than that of the conventional stirring method. Semi-industrial test results of the atomized reagent and synchronous jet pre-mineralization show that, compared to traditional roughing, the TFe grade increased by 0.87 percentage points, iron recovery increased by 3.95 percentage points, and reagent consumption decreased by 7.5 percentage points. Experimental and test results demonstrate that the atomized reagent and synchronous jet pre-mineralization technology can effectively enhance mineralization, accelerate the flotation rate, improve flotation indices, and reduce reagent consumption to a certain extent, providing significant guidance for the efficient recovery of fine-grained minerals.

Deep eutectic solvent (DES) pretreatment and lignin regeneration for the development of a bamboo leaf-based bioplastic.

The excessive utilization of petroleum-based plastic products has led to a pervasive environmental and human health threat. In response, the adoption of bioplastics derived from biomass has emerged as the foremost alternative to conventional plastics, owing to their inherent biodegradability and sustainability. The present study demonstrates the preparation of a biodegradable and cost-effective lignocellulosic bioplastic by utilizing dissolving bamboo leaf powder with deep eutectic solvents (DES) and regenerating lignin in situ. The DES was synthesized through a one-step heating and stirring method using choline chloride (ChCl) and anhydrous oxalic acid. The crystallinity of the bioplastics is enhanced by DES pretreatment, thereby improving the internal structural order of the material. Moreover, lignin regeneration reduces the pore size within the bioplastics and contributes to a more compact internal structure. The prepared lignocellulosic bioplastics exhibit remarkable mechanical strength, with a tensile strength of 113MPa. Additionally, they demonstrate good water stability, as evidenced by a contact angle of 55.52°. Moreover, these bioplastics possess an exceptional biodegradability with a degradation rate exceeding 98% after 60days. This study presents an innovative approach for the high-value utilization of bamboo leaf resources.

Comparative experimental analysis of monocrystalline and polycrystalline photovoltaic panel through hybrid phase change material

Photovoltaics thermal management is utmost necessary as continuous heating of the module decreases the performance. This paper presents a comparative study in terms of performance of two photovoltaic modules namely monocrystalline and polycrystalline using hybrid phase change materials (PCMs). The hybrid PCMs of RT31 and RT 44HC were prepared by method of stirring. The final prepared hybrid PCMs were poured at the back of panel and panel was covered. The purpose of these experiments is to improve the efficiency of polycrystalline and monocrystalline photovoltaic modules and comparing which technology is more efficient having hybrid PCM. The experiments were performed under the room conditions in Taxila, Pakistan. The output parameters of the photovoltaic module appeared to be strongly dependent upon the solar irradiance. The power output and efficiency of monocrystalline and polycrystalline photovoltaic module were measured. The monocrystalline panel maximum temperature was 36.59 °C as compared to polycrystalline panel which was 40.23 °C. As the radiation intensity increased till noon, electrical power was improved, and it was 6.52 W in monocrystalline panel as compared to polycrystalline panel which was 6.32 W. Electrical conversion efficiency was also observed, and it was maximum up to 11.84 % in monocrystalline panel. The higher performance was observed in case of monocrystalline panel having hybrid in terms of performance as compared to polycrystalline panel.

Achieving enhanced strength-ductility synergy in Mg-6Zn-1Mn alloy by introducing deformable Ti particles

The Mg-based composites have been considered as an efficacious method to enhance the strength of Mg matrix. How to concurrently augment the strength and ductility of the Mg matrix composites remains a pivotal concern. In this work, Mg-6Zn-1Mn (ZM61) composites, reinforced with varying contents of deformable Ti particles, were successfully manufactured employing a method of semi-solid stirring coupled with ultrasonic treatment, subsequently followed by hot extrusion. The outcomes demonstrated marked enhancement in strength and ductility of composites. The interfacial reaction between Ti and Mg matrix minimized the precipitation of MgZn2 and α-Mn in the matrix. Ti particles boosted the dynamic recrystallization (DRX) behavior effectively. The TEM characterizations revealed that MgZn2 nucleated on the Ti particle and Mn diffusion layer was formed in the Ti particle. The 2Ti/ZM61 composite achieved superior comprehensive mechanical properties, marked by the YS of 288 MPa, the UTS of 383 MPa, and the elongation to 22.1%. The augmented strength was primarily owning to the grain boundary strengthening and the mismatch coefficient of thermal expansion (CTE) between Ti and Mg. The synergistic deformation of Ti particles was the main reason of improving the ductility.

Role of silicon in the growth of ZSM-5 synthesized with coal fly ash as raw materials

In this work, single-phase ZSM-5 zeolite was synthesized using solid waste coal fly ash (CFA) as raw material, providing a potential alternative for creating high-value-added products from this waste. X-ray diffraction (XRD), scanning electron microscopy, X-ray fluorescence, Fourier transform infrared spectroscopy, N2 physisorption, and other techniques were used to evaluate the crystallization and morphology of the ZSM-5 obtained. The results indicated that ZSM-5 can be synthesized by the simple method of mixing, stirring, and heating. A well-defined hexagonal shape of ZSM-5 with a specific surface area of 162 m2/g and mesoporous structure was obtained at the temperature of 160 °C during hydrothermal treatment for 72 h. Theoretically, the mechanism of crystal growth of ZSM-5, i.e. the liquid phase nucleation and step growth models, was clarified. These results open the possibility of exploring the crystallization of ZSM-5 and the utilization of CFA. Simultaneously, the critical roles of silicon in framework formation and crystallization control during the formation and growth of zeolites were elucidated.

Structural and physicochemical characterisation of binary glutamine-based deep eutectic solvents

Amino acid-based deep eutectic solvents (AADES) are a new subclass of natural deep eutectic solvents with prospective applications especially in the energy and pharmaceutical industries. In this study, binary DESs were formulated, for the first time, from glutamine and lactic acid by the heating and stirring method. Subsequently, the effect of varying molar ratios of the DES components on their physicochemical, structural and thermal properties was evaluated. In this regard, the refractive index, water content, conductivity, viscosity and pH of the formulated DESs were analysed. Furthermore, the thermal stabilities of the DESs were determined using differential scanning calorimetry and thermogravimetry analysis, while the hydrogen bond interactions within the solvents were elucidated using nuclear magnetic resonance (1H and 13C NMR) and Fourier transform infrared spectroscopy (FTIR). Results showed that the densities (1.25–1.29 g/cm3), refractive indices (1.45–1.48), conductivity (0.19–0.51 mS cm−1), water contents (3.88–7.87 %), viscosities (867.34–8712.50 mPa·s) and pHs (1.85–3.37) of the DESs were significantly influenced by lactic acid. The NMR and FTIR spectra profiles confirmed the interactions of the hydrogen bond forming groups within the DESs. In addition, the solvents showed stability at room temperature up to 100 °C, after which decomposition set in until 400 °C; however, they formed no crystals between −40 °C and 100 °C. The glass transition phase of the DESs was also observed at −20 °C which highlights the potential application of the solvents in cryopreservation. Thus, this study presents valuable insights into the proposed utilisation of these GL-based DESs as sustainable solvents in industrial applications.

Electrochemical evaluation of fenitrothion organophosphate pesticide in food samples: Novel tetra trifluoromethyl carboxamide zinc (II) macrocyclic complex composite with multiwalled carbon nanotubes

This study presents the development of a groundbreaking electrochemical sensor for detecting fenitrothion (FNT) using a multi-walled carbon nanotubes (MWCNTs) and a newly synthesized zinc (II) tetra trifluoromethyl carboxamide phthalocyanine (ZnTFMPCAPc). The ZnTFMPCAPc was synthesized concluding a two-step mechanical and magnetic stirring method, and the ensuing ZnTFMPCAPc@MWCNTs underwent comprehensive characterization employing X-ray diffraction (XRD), Ultraviolet visible spectroscopy (UV–Vis), mass spectrum, Fourier transform infrared spectroscopy (FT-IR), Thermo-gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), Mass, Raman spectra, Transmission Electron Microscopy (TEM) and scanning electron microscope (SEM). Cyclic voltammetry (CV) analysis demonstrated a remarkable seven-fold improvement in electrochemical signals with ZnTFMPCAPc@MWCNTs on modified glassy carbon electrode (GCE) compared to a bare and modified GCE. The correlation between peak current and FNT concentration (in the range of 10–310 μmol) was established. The estimated limits of detection (LOD) and quantification (LOQ) were determined to be 1.358 nmol and 4.075 nmol respectively. The ZnTFMPCAPc@MWCNTs/GCE sensor was successfully evaluated by quantifying FNT in tomatoes, grapes, paddy grains, and potato extracts, resulting in satisfactory results. Detecting fenitrothion is crucial due to its widespread use as a pesticide, which can result in environmental contamination and pose health risks. Regular monitoring is essential for protecting food and water supplies, preserving ecosystems, and ensuring compliance with regulations to prevent long-term environmental damage.

Superior electrochemical performances of Lithium vanadium oxide with coconut shell-based porous carbon as the anode of the aqueous Li ion battery

Carbon materials, as the skeleton structure of electrode materials, are composited with lithium-ion anode materials, which not only increase the electrical conductivity of the materials, but also enhance the electrochemical performance of the electrode materials. In this paper, LiV3O8@C composites were prepared by using coconut shell-based porous carbon to structurally modulate aqueous lithium-ion anode materials. And three composites with different structures and sizes were successfully synthesized by hydrothermal method, hydrothermal stirring method and improved solid-phase method. After XRD and SEM analyses, it was found that all three composites maintained the monoclinic crystal system structure of LiV3O8, and the materials prepared by the hydrothermal method showed a smooth layer structure, while the materials prepared by the hydrothermal stirring method and the solid-phase method showed nanorods with different sizes. The prepared anode materials and LiFePO4 cathode materials were assembled into an aqueous lithium-ion full battery, and were subjected to charge/discharge tests, cyclic voltammetry and electrochemical impedance spectroscopy. The results indicate that the electrochemical performances of the three composites are significantly improved compared with the pure LiV3O8. Specifically, the discharge capacities of the two groups of nanorod-like composites were 112.2 mAh/g and 85.5 mAh/g at a rate of 0.2 C, which were improved by as much as two times compared with the pure LiV3O8. However, the composite material with layered structure not only reaches an initial discharge specific capacity of 148.39 mAh/g, which is 2.7 times higher than that of the pure LiV3O8, but also effectively slows down the dissolution effect of LiV3O8 by compositing with the carbon material, and at the same time, it shows excellent rate performance.

Removal of Acid Orange 7 dye using Makgeolli lees with ultrasonic assistance

AbstractThis study investigated the efficient removal of Acid Orange 7 (AO7) dye in water by using Makgeolli lees, a popular by‐product obtained during the production of traditional Makgeolli beverages in Korea. By incorporating ultrasound, the effects of contact time, Makgeolli lees dosage, initial AO7 dye concentration, and initial pH of the dye solution were investigated and comprehensively compared with the same experiment using the stirring method. The results consistently showed ultrasound not only enhances the excellent adsorption ability of Makgeolli lees but also accelerates the process compared to the stirring method. The Langmuir isotherm model best described the adsorption process for both methods, suggesting monolayer adsorption on the surface of Makgeolli lees, with maximum capacities of 25.13 mg/g for ultrasound at 40 kHz and 20.41 mg/g for stirring methods. Furthermore, the study showed that optimal dye removal efficiency can be achieved with ultrasound conditions at 28 kHz frequency, 125 W/L power density, and 100% ultrasound intensity. This research promises that the integration of low‐cost biomass coupled with ultrasound could provide a potential solution for dye wastewater treatment.

The Impact Of Ultrasound-Assisted Mixing Method For Varnish And Components On The Varnish Layer’s Surface Hardness And Surface Scratch Resistance

The objective of this study was to determine effects of mechanical and ultrasound-assisted stirring methods for varnish + components mixing on the varnish layer’s surface hardness and surface scratch resistance. The study focused on polyurethane, acrylic, and polyester varnish systems, which were applied to three distinct wood types: Scots pine (Pinus sylvestris L.), Turkish beech (Fagus orientalis Lipsky), and African mahogany (Khaya ivorensis A. Chev.). The mixing processes included mechanical stirring for 3 and 5 minutes, as well as ultrasound-assisted stirring with varying power levels (80 watts and 120 watts) for 3 and 5 minutes. The results indicated that the highest surface hardness was achieved using the mechanical stirring method for Turkish beech with polyester varnish at 3 minutes of stirring (175.10), while the lowest surface hardness was observed for African mahogany with acrylic varnish and 120 watts ultrasound-assisted stirring for 5 minutes (66.80). The highest surface scratch resistance was observed in Scots pine treated with polyester varnish using mechanical stirring for 5 minutes (0.760 N), and in Turkish beech treated with acrylic varnish using 80 watts ultrasound-assisted stirring for 3 minutes (0.760 N). Overall, the findings suggested that the ultrasound-assisted mixing method generally fell short in terms of enhancing the varnish properties compared to the mechanical mixing technique.

On the Rapid Synthesis of Reduced Graphene Oxide via Ultrasound-Promoted Eco-Friendly Reduction Approach and Its Effects on Physicochemical Properties.

The common synthesis approach of reduced graphene oxide (rGO) using toxic reducing agents poses a threat to environmental pollution. This study used banana peel extract as a green reducing agent for the synthesis of rGO. Ultrasonication was assimilated to expedite the synthesis process. For comparison, rGO was also produced by reducing GO with hydrazine treatment under conventional stirring. Both morphological (SEM) and physicochemical (FTIR and XRD) studies have revealed that banana peel extract can reduce GO to rGO, although its reducing effect is much weaker compared to hydrazine. Despite this, the rGO produced using banana peel extract with the assimilation of ultrasonication technique has a greater interlayer spacing than that formed under the conventional stirring method. In terms of electrical properties, the electrical conductance of hydrazine-produced rGO (5.69×10-6 S) is higher than the banana peel extract-produced rGO (3.55×10-6 S-4.56×10-6 S). Interestingly, it was found that most of the rGO produced by banana peel extract under ultrasound assistance has higher or comparable electrical conductance compared to the rGO produced by banana peel extract under stirring method. This implies the feasibility of using short-period ultrasound to replace conventional stirring in rGO synthesis.

Characterization of industrial pea canning by-product and its protein concentrate obtained by optimized ultrasound-assisted extraction

This work aimed to optimize protein extraction from an industrial pea canning by-product by developing an ultrasound-assisted alkaline solubilization and isoelectric precipitation method. Proximate composition and microbial contamination (total bacterial count, total lactic acid bacteria, Enterobacteriaceae, yeasts and moulds) were assessed in the wet by-product. The protein concentrate obtained, the dry by-product and a commercial pea flour were analysed for protein content, water activity, colour and techno-functional properties. The optimal extraction conditions from the wet by-product were liquid-solid ratio 20 mL/g, pH 11, ultrasound amplitude 80 μm, time 2 × 30 min. The extraction from the dry by-product was not feasible. Sonication reduced extraction time from 4 h (magnetic stirring method) to 1 h and increased three-fold the extraction recovery (from 21.5% to 66.6%). The concentrate had a 74.8 g/100 g DM protein content. The SDS-PAGE revealed protein degradation in some specimens, probably because of fermentation and enzymatic hydrolysis before sampling. However, the microbial counts in the concentrate, mainly related to lactic acid bacteria, were always below the guideline values. Our results demonstrate that the pea canning by-product is a valuable raw material for protein recovery and that the proposed method allows rapid and direct treatment, avoiding drying costs and microbial proliferation.

Facile synthesis of a novel CeCO3OH@(H/C–CdS) catalyst with synergistic effect of heterophase junction and heterojunction for enhanced visible-light photocatalytic degradation efficiency at room temperature

A new CeCO3OH@(hexagonal/cubic phases–CdS) (CeCO3OH@(H/C–CdS)) composite catalyst was facilely synthesized by a simple microinjection titration–stirring method, in which CdS nanoparticles were dispersed on the surface of CeCO3OH nanolines. The optimal conditions for the preparation of composite catalysts with high photocatalytic performance were determined by single-factor experiments and response surface experiments. Under these conditions, the degradation rate of 30 mL 2.000 g/L rhodamine B (Rh B) by CeCO3OH@(H/C-CdS) in a photocatalytic reaction for 1 h at 25 °C was up to 86.81 % and its degradation rate in a photocatalytic reaction for 150 min was up to 99.62 %. The degradation rate could be maintained above 80 % even after six times recycling. Especially, the photocatalytic degradation efficiency of 2.000 g/L Rh B on the composite catalyst under sunlight and at room temperature for 30 min reached 97.66 %. Meanwhile, the large size of CeCO3OH considerably alleviated the agglomeration of CdS, providing more adsorption and active sites for visible light-mediated degradation of Rh B. Importantly, the Z-scheme charge transfer realized by CdS and CeCO3OH enhanced the efficient separation of photogenerated electrons and holes, and successfully inhibited the recombination of photogenerated electrons with holes. At the same time, owing to the low energy band difference between the two phases of CdS, charge was transferred between the hexagonal and cubic phases, leaving more effective photogenerated charge to participate in the degradation of Rh B. The synergism of the heterophase junction and heterojunction and the presence of oxygen and sulfur vacancies considerably enhanced the degradation performance of the catalyst. Thus, this study provides a new strategy for the modification and enhanced visible-light catalysis performance of CdS-based catalysts.

Synergistic enhancement of fluorescein-K3[Fe(CN)6] CL by MoO3-x NPs for sensitive and noninvasive detection of uric acid in saliva.

MoO3-x NPs was rapidly synthesized at room temperature by an easy stirring method. It was interestingto find that MoO3-x NPs induce OH- to generate active free radicals (ROS), which isa highly promising property in chemiluminescence (CL). Benefiting from the abundant oxygen vacancy, MoO3-x NPs adsorbsH2O2 and turn it into ·OH. The oxidase activity of fluorescein under visible light had already been reported, which catalyzesdissolved oxygen to become O2-· and continue to convert to H2O2. By creating the synergy effect with fluorescein, MoO3-x NPs strengthen the CL intensity of K3[Fe(CN)6]-fluorescein system significantly. Utilizing the quench effect of uric acid for the CL intensity, we developed a rapid, simple, and highly sensitive CL platform for uric acid detection. The linear range was 5-80µM and the detection limit (LOD) for uric acid was 3.11µM (S/N = 3). This work expanded the application of MoO3-x NPs in the CL field and developed a simple and highly sensitive CL sensing system to detect UA in human saliva.

Simultaneous Solar‐Driven Interfacial Evaporation and Photo‐Fenton Oxidation by Semiconducting Metal–Organic Framework From Waste Polyimide

The integrated technology of interfacial solar steam generation and photo‐Fenton oxidation has emerged as a promising way to simultaneously mitigate freshwater scarcity and degrade organic pollutants. However, fabricating low‐cost, multi‐functional evaporators with high water evaporation and catalytic ability still presents a significant challenge. Herein, we report the functional upcycling of waste polyimide into semiconducting Fe‐BTEC and subsequently construct Fe‐BTEC‐based composite evaporators for simultaneous freshwater production and photo‐Fenton degradation of pollutants. Firstly, through a two‐step solvothermal‐solution stirring method, Fe‐BTEC nanoparticles with the size of 20–100 nm are massively produced from waste polyimide, with a band gap energy of 2.2 eV. The composite evaporator based on Fe‐BTEC and graphene possesses wide solar‐spectrum absorption capacity, high photothermal conversion capacity, rapid delivery of water, and low enthalpy of evaporation. Benefiting from the merits above, the composite evaporator achieves a high evaporation rate of 2.72 kg m−2 h−1 from tetracycline solution, as well as the photothermal conversion efficiency of 97% when exposed to irradiation of 1 Sun, superior to many evaporators. What is more, the evaporator exhibits the tetracycline degradation rate of 99.6% with good recycling stability, ranking as one of the most powerful heterogeneous Fenton catalysts. COMSOL Multiphysics and density functional theory calculation results prove the synergistic effect of the concentrated heat produced by interfacial solar steam generation and catalytic active sites of Fe‐BTEC on promoting H2O2 activation to form reactive oxidation radicals. This work not only provides a green strategy for upcycling waste polyimide, but also proposes a new approach to fabricate multi‐functional evaporators.

Fabrication of electrospun PA66 nanofibers loaded with biosynthesized silver nanoparticles: investigation of dye degradation and antibacterial activity.

In the current study, silver nanoparticles (AgNPs) incorporated Polyamide 66 (PA66) nanofiber mat as a photocatalyst which was prepared using electrospinning technique for degradation of methyl orange (MO). Considering the lack of reported studies on the influence of the ultrasonication on the size and stability of AgNPs, the purpose of the study was to produce a small size of AgNPs and compare it with the continuous stirring method. It is reasonable to report that the advantage of ultrasonication is to generate relatively smaller AgNPs (u-AgNPs) compared to fabrication by continuous stirring method (s-AgNPs). Helichrysum arenarium (HA) extract was used as a reducing agent as well as a capping agent in green synthesis of AgNPs. AgNPs were characterized by UV-visible spectrophotometry, Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and transmission electron microscope (TEM). PA66/u-AgNs nanofibers were then successfully electrospun and characterized by using scanning electron microscope (SEM), FT-IR, thermal gravimetric analysis (TGA), and water contact angle measurement (WCA). Fabricated PA66-based nanofiber mat with smooth surface and uniform diameters (330-340nm) was used as a catalyst in MO degradation. PA66/u-AgNP nanofibers were also evaluated for antibacterial performance and showed significant inhibition against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa bacteria. According to these findings, it is expected that the fabricated novel PA66/u-AgNP nanofibers can be announced as a promising potent and applied to the wastewater applications.

Multi-physics coupled numerical simulation study to optimize process parameters for electromagnetic stirring of semi-solid A356 aluminum alloy under the influence of skin effect

The electromagnetic stirring (EMS) method stands as a widely used technique in creating semi-solid aluminum alloy slurry due to its convenience and precision in parameter control compared to other methods. In this study, a comprehensive model that combines electromagnetics, flow, heat transfer and solidification was formed. By analyzing the influence of input current and frequency on the electromagnetic force, the behavior of various process parameters in velocity field and temperature field under influence of the skin effect is investigated. The aim is to find the optimal process parameters for production of slurry using the low-frequency EMS. The results show that within the investigated range, by adjusting the input current and frequency to 150 A and 15 Hz, higher fluid velocities and appropriate distribution of vortex zones can be observed, while achieving a uniform temperature field, the highest cooling rate and the minimum radial temperature difference. In addition, the sample prepared under the optimal process parameters shows that the melt edge is least affected by the skin effect, which leads to a higher stirring strength and a smaller overall grain size, which is consistent with the theoretical skin effect research found within the simulation section.

Unraveling the mystery of sandwich structure: Emerging photocatalytic hydrogen production by g-C3N5 coupled Nb2C MXene forming Schottky heterojunction

The development of new photocatalysts and photocatalytic systems is the essence of the development of photocatalytic hydrogen production engineering. Nitrogen-rich graphite carbon nitride (g-C3N5) has gradually replaced conventional graphite phase carbon nitride (g-C3N4) with a smaller bandgap and high-efficiency visible light utilization. In this study, g-C3N5 and Nb2C MXene coupled composition with sandwich structure were manufactured by a simple ultrasonic magnetic stirring method and used for photocatalytic hydrogen production. By adjusting the ratios of single components in the system, the hydrogen production rate of the optimal sample 4:1g-C3N5/Nb2C under visible light irradiation is 2529.5 μmol·g−1·h−1, which is 21 times higher than that of g-C3N5. The high apparent quantum yield (AQY) value of 17.3 % also proves a high light utilization rate. The atomic force microscopy (AFM) technique reveals variations in the thickness of the samples, while strongly demonstrating the formation of sandwich structure. In addition, X-ray photoelectron spectroscopy (XPS) analysis further reveals the electron transfer paths within the system, preliminarily verifying the formation of Schottky heterojunctions. Kelvin probe force microscopy (KPFM) tests not only re-validate the correctness of the electron transfer path but also demonstrate the accuracy of the energy bands. The density-functional theory (DFT) calculations corroborate that Nb2C MXene plays the role of a photoco-catalyst to form Schottky heterojunctions with g-C3N5 for efficient carrier separation and migration. This work highlights the key role of sandwich structure photocatalytic systems on photocatalytic performance.

Influence of temperature and stirring on the synthesis of magnetite nanoparticles

This study investigates the impact of temperature variations and stirring methods on the synthesis of magnetite nanoparticles. Conducted experiments employed a controlled precipitation method, with temperature ranges from 22 °C to 60 °C and four stirring methods, including magnetic stirring, sonication, vertical stirring, and vertical stirring combined with an ultrasonic bath. The synthesized nanoparticles were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and UV–Vis spectrophotometry. Results revealed significant influences of temperature and stirring on magnetite nanoparticles’ size, crystallinity, and optical properties. Elevated temperatures induced strain in the crystal lattice, resulting in a noisy signal, while the choice of stirring method influenced particle size stability. These findings offer valuable insights for optimizing synthesis conditions tailored to specific applications of magnetite nanoparticles, providing users with a better understanding of the factors influencing nanoparticle synthesis.