Mechanical Stirring Research Articles

ZnO-MoS2 supported on boron nitride nano-sheets for the adsorptive removal and degradation of ciprofloxacin from aqueous solution

ABSTRACT MoS2/ZnO supported on boron nitride nanocomposite (BN/MoS2/ZnO) was synthesised via simple co-precipitation and mechanical stirring method. The removal of ciprofloxacin (CIP) from wastewater was examined by utilising synthesised BN/MoS2/ZnO nanomaterial. The synthesised nanomaterial was successfully characterised by sophisticated techniques such as FT-IR, XRD, HR-TEM, HR-SEM and EDX analysis. BN/MoS2/ZnO was further utilised to examine the impact of different optimising factors, including contact time and solution pH. The result shows that pH 4 was the optimum parameter for CIP removal within 90 min of contact time, on which 81% and 67.72% of CIP were removed. The adsorption follows the pseudo-second-order kinetics (R2 = 0.99) and isotherm modelling was best explained by the Langmuir model (qm = 83.333 mg g−1). Thermodynamic study shows the spontaneous and endothermic nature for the adsorption of CIP. For the catalytic degradation, the ultrasonication method gives the best result, where 98.25% of CIP was degraded within 60 min of ultrasonic wave exposure. Recycling of the nanocomposite was achieved by using a 0.1 M NaOH solution, and it can be used for up to five cycles.

The Effect of Particle Size of Recovered Carbon Black (rCB) on the Properties of Epoxy Conductive Material

This research investigates the effect of different particle sizes of recovered carbon black (rCB) on the electrical conductivity, flexural and fractured toughness properties and morphology of epoxy/rCB conductive composites. The rCB powder was a product from the pyrolysis process of waste rubber tires. This research aims for the application of tray production in semiconductor packaging. In this study, the composite was prepared by using a simple mechanical stirring method. The testing and characterizations carried out included electrical conductivity test, flexural test, fracture toughness test, Scanning Electron Microscopy (SEM) and viscosity. The epoxy/rCB conductive composite shows significant differences in electrical conductivity and mechanical properties when incorporated with different particle sizes of rCB. The conductivity percolation threshold was found at 1000 mesh with enhanced mechanical and electrical conductivity properties simultaneously.

Tensile Properties of Epoxy Composites Filled With Graphene Nanoplatelets and PUF Microcapsules

AbstractThis work evaluates the effect of poly(urea‐formaldehyde) (PUF) microcapsules filled with aminated polydimethylsiloxane (PDMS‐a), a self‐healing agent, on the tensile properties of epoxy composites reinforced with graphene nanoplatelets (GNP). The microcapsules are produced by interfacial polymerization and later are infiltrated with the healing agent (PDMS‐a). GNP are dispersed in epoxy resin using sonication, followed by the addition of hollow or filled PUF microcapsules to the system, using mechanical stirring, just before the addition of the curing agent (hardener). The mixture is then cast in soft molds to produce specimens for tensile tests. The results show that the presence of 1 wt% GNP changes the properties of the composites with an improvement in tensile strength and modulus, which achieves 37.4 MPa and 2.8 GPa, respectively, in comparison with neat epoxy and specimens containing just microcapsules. The addition of 2 wt% GNP, however, impairs these properties, with tensile strength and Young's modulus decreasing to 24.9 MPa and 2.3 GPa, due to the presence of GNP agglomerates. The presence of the microcapsules, however, decreases the immediate (no self‐healing) tensile performance of the composites.

A Review on Corrosion Behavior and Surface Modification Technology of Nickel Aluminum Bronze Alloys: Current Research and Prospects

Nickel aluminum bronze alloy, a complex alloy containing multiple phases, has become the most common material for naval propellers due to its good corrosion resistance. Traditional cast nickel aluminum bronze shows serious corrosion behavior in harsh service environments. This article reviews progress on the corrosion behaviors and corrosion mechanism of nickel aluminum bronze in highly corrosive and complex marine environments and systematically discusses the research status of the surface modification technologies such as laser surface strengthening, mechanical shot peening, friction stir and thermal spraying, and so on. To improve the comprehensive performance of nickel aluminum bronze, this work focuses on analyzing the effect of process parameters on the corrosion resistance of nickel aluminum bronze alloy while researching propeller blade surface modification technology. Finally, the future research and development direction of nickel aluminum bronze in the fields of laser and arc additive manufacturing is prospected.

Experimental Study on Preparation of Nano ZnO by Hydrodynamic Cavitation-Enhanced Carbonization Method and Response Surface Optimization

The carbonization method for preparing Nano ZnO is characterized by its simplicity, ease of reaction control, high product purity, environmental friendliness, and potential for CO2 recycling. However, traditional carbonization processes suffer from poor heat and mass transfer, leading to in situ growth and agglomeration, resulting in low carbonization efficiency, small specific surface area, and inferior product performance. To enhance micro-mixing and mass transfer efficiency, ZnO derived from zinc ash calcination was used as the raw material, and hydrodynamic cavitation technology was employed to intensify the carbonization reaction process. The reaction mechanism of hydrodynamic cavitation was analyzed, and a single-factor experimental study investigated the effects of reaction time, reaction temperature, solid–liquid ratio, calcination temperature, incident angle, cavitation number, and position height on the specific surface area and carbonization rate of Nano ZnO. The response surface method was utilized to explore the significance of the three most influential factors—solid–liquid ratio, cavitation number, and position height—on the carbonization rate and specific surface area. The products were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), laser particle size analysis, and specific surface area analysis. The results showed that the optimal process parameters were a reaction temperature of 80 °C, a reaction time of 120 min, a solid–liquid ratio of 5.011:100, a calcination temperature of 500 °C for 1 h, an incident angle of 60°, a cavitation number of 0.366, and a position height of 301.128 mm. The interaction between solid–liquid ratio and position height significantly influenced the process parameter variations. Under these conditions, the specific surface area and carbonization rate were 63.190 m2/g and 94.623%, respectively. The carbonized product was flaky Nano ZnO with good dispersion and small particle size. Compared to traditional mechanical stirring and bubbling methods, the specific surface area increased by 1.5 times, the carbonization rate improved by 10%, and the particle size decreased by half, significantly enhancing the product performance.

Evaluation of Different Blending Methods to Obtain Copper Composites with Graphene Oxide

This study evaluated mixing methods for producing graphene oxide-reinforced copper matrix composites aiming for a better dispersion of graphene oxide in the composite, using powder metallurgy techniques. The compacted specimens were prepared by four different mixing processes that employed either a mechanical stirrer, rotary evaporator, tip ultrasound, or ultrasound process followed by mechanical stirring. Characterizations were performed using optical microscopy, scanning electron microscopy, X-ray diffraction, Raman spectroscopy, transmission electron microscopy, compression tests, Vickers microhardness, and electrical conductivity measurements. The results indicate that the combined method yields a more homogeneous microstructure and superior mechanical properties, while electrical conductivity was maintained at a level higher than that achieved by the other methods.

A novel 3D uniformity measurement method in mechanical stirring systems

AbstractAccurate assessment of mixing uniformity is crucial in industrial mixing processes. This study proposes an evaluation method for three‐dimensional (3D) mixing processes that combines dual‐camera positioning and point pattern density fluctuation (PD) based on disordered hyperuniformity. This study employs a positioning method using dual‐camera to achieve precise capture and reconstruction of tracer particles in 3D space. The 3D reconstruction data is then evaluated for mixing performance using the PD method. A relationship model between |k| and time I values with mixing time was established for λ = 1. The results indicate that mixing time decreases with the increase of |k| and decreases with the decrease of I values. To ensure the accuracy of the PD method, feasibility analysis was conducted using conductometry. Additionally, the superiority of the PD method was validated by comparing it with the 3D‐Q method. The impact of bottom height of stirring paddle and motor speed on mixing effect were also investigated. This study establishes a fundamental groundwork and theoretical framework for optimizing parameters of stirring systems and assessing 3D mixing uniformity. It also offers important references and insights for engineering practices and theoretical research in related fields.

Effect of in-situ submicron Al3Ti particles on grain refinement and strengthening of Al–Zn–Mg–Cu-based alloy

Extensive research has been conducted to improve the efficiency for grain refinement of aluminum cast alloys. Herein, we propose a novel strategy to significantly reduce the cast grain size using in-situ submicron Al3Ti particles. The ZnO nanoparticles with enhanced wettability via mechanical stirring process provide finely dispersed α-Al2O3 particles, which serve as heterogeneous nucleation sites for primary Al3Ti particles. A large number of primary Al3Ti nuclei are formed from the α-Al2O3 particles without coarsening even under a relatively slow cooling rate. As a consequence, the size of Al3Ti particles was reduced to approximately 600 nm, resulting in the fine cast grain size of approximately 20 μm. Furthermore, a sheet made of the refined cast alloy has reduced recrystallized grain size and simultaneously improved strength and ductility.

Cyanate Ester/TiO2 Composites for High‐Temperature and Miniaturized Microwave Substrate Applications

High‐temperature‐withstanding TiO2‐reinforced cyanate ester composites are developed by mechanical stirring, followed by curing at elevated temperatures. The uniform dispersion of the filler is confirmed using scanning electron microscopy and electron dispersive spectroscopy. All composites, up to a filler fraction of 30 vol%, exhibit a density of more than 90% while it reduces significantly after that. A high relative permittivity of 7.6 and a low loss tangent of 0.0112 are observed for the optimally filled 30 vol%. The addition of the filler further improves the temperature‐withstanding capability of the cyanate ester matrix. Moreover, a high thermal conductivity of 0.543 W mK−1, improved hardness of 24.88 HV, ultimate tensile strength of 11.68 MPa, and a low coefficient of thermal expansion of 36.44 ppm °C−1 are also shown by the optimally filled sample. A moisture absorption of 0.072 vol% observed for the optimal filled sample comes within the limit for microwave substrate applications. Thus, the developed composites are suitable candidates for high‐temperature microwave electronic applications.

G-C3N4/PP-CDs Heterostructure with Lewis acidity and alkalinity promoted photocatalytic CO2 reduction to CH3OH

It is expected that photocatalytic reduction of carbon dioxide to produce valuable chemicals play an important role in achieving carbon neutrality goals. Photogenerated electron-hole separation efficiency is one of the factors determining photocatalytic activity. Herein, carbon dots with oxygen-containing protoporphyrin (PP-CDs) were loaded on g-C3N4 nanosheets form a heterostructure by a facile mechanical stirring method. The g-C3N4/PP-CDs-3 has a conduction band potential of −1.31 eV and a bandgap of 2.51 eV, in the absence of any added photosensitizer and sacrificial agent under illumination, the methanol yield achieved 357.5 μmol·g−1·h−1, which is 2.2 times than that of g-C3N4 (162.1 μmol·g−1·h−1), after four cycles, the photocatalytic activity remained unchanged. Based on the experimental and characterizations results, it is indicated that the photocatalytic reduction performance of CO2 to methanol was improved mainly attributed to the visible light absorption and the high Lewis acidity and alkalinity. Furthermore, the steric hindrance was provided for photogenerated electron-hole recombination due to the recombination of carbon points his work offers a promising strategy for constructing efficient photocatalysts to achieve CO2 to CH3OH transformation.

Thorium Recovery with Crown Ether–Polymer Composite Membranes

Thorium is a weak radioactive element, but the control of its concentration in natural aqueous systems is of great interest for health, because it is a toxic heavy metal. The present paper presents the recovery of thorium from diluted synthetic aqueous systems by nanofiltration. The membranes used for the nanofiltration of systems containing thorium species are composites containing 4′-Aminobenzo-15-crown-5 ether (ABCE) and sulfonated poly–etherether–ketone (sPEEK). The composite membranes (ABCE–sPEEK) were characterized by scanning electron microscopy (SEM), energy-dispersive X–Ray spectroscopy (EDAX), thermal analysis (TG and DSC), and from the perspective of thorium removal performance. To determine the process performance, the variables were the following: the nature of the composite membrane, the concentration of thorium in the aqueous systems, the rotation speed of the stirrer, and the pressure and the pH of the thorium aqueous system. When using pure water, a permeate flux value of 12 L·m−2 h−1 was obtained for the sPEEK membrane, and a permeate flux value of up to 15 L·m−2 h−1 was obtained for the ABCE–sPEEK composite membrane. The use of mechanical stirring, with a propeller stirrer, lead to an increase in the permeate flux value of pure water by about 20% for each of the studied membranes. Depending on the concentration of thorium and the pH of the feed solution, retentions between 84.9% and 98.4% were obtained. An important observation was the retention jump at pH 2 for the ABCE–sPEEK composite membrane. In the paper, a thorium ion retention mechanism is proposed for the sPEEK membrane and the ABCE–sPEEK composite membrane.

Catalytic Hydrothermal Treatment for the Recycling of Composite Materials from the Aeronautics Industry

Epoxy resin composite matrices reinforced with carbon fibers are highly demanded by certain industries such as the aeronautics industry because of their exceptional mechanical properties. Unfortunately, the use of reinforcing carbon fibers makes these composite materials hard to recycle by conventional methods. Therefore, in this study, specific hydrothermal treatments have been employed to recover carbon fibers from the offcuts of composite parts from the aeronautics industry. The resin decomposition rates (DRs) achieved by different settings of the operating parameters, such as the use of alkaline catalysts (KOH, NaOH, or K2CO3), the application of mechanical stirring, the use of different reaction times, the solvent volume/composite mass ratio, the specific surface area (surface area/mass) of the composite pieces, and the operating temperature and pressure (subcritical or supercritical conditions), have been examined and assessed. Under the conditions that have been evaluated, resin decomposition rates nearly as high as 98% have been achieved, while the recycled fibers retained over 95% of their original tensile strength (TS).

Sustainable Valorisation of Coffee Waste as a Protein Source, Mycelium-Based Packaging Material and Renewable Energy Pellet.

This study investigates the valorization of spent coffee grounds (SCGs) through protein extraction and their application in mycelium-based packaging and renewable energy pellets. Three extraction methods-mechanical stirring, ultrasound-assisted, and CO2-assisted extraction-were applied to SCGs. CO2-assisted extraction yielded the highest protein content at 34.24%, followed by mechanical stirring (31.46%) and ultrasound-assisted extraction (28.51%). The total polyphenol content and antioxidant capacity were also highest in the CO2 extracts, suggesting that this method preserves bioactive compounds most effectively. After protein extraction, SCGs were tested as a component in mycelium-based packaging, with results showing an apparent density of 0.551 g/cm3 and compression resistance of 3.354 MPa, indicating its suitability for structural applications. The energy value of SCGs remained high, with a calorific value of 19,887 J/g DW, slightly decreasing after extraction but still sufficient for renewable energy production. These findings highlight the potential of SCGs as a multi-functional resource, contributing to sustainable solutions across various industries.

Pilot-scale study of turbid particle evolutional/removal characteristics during coagulation-sedimentation-filtration (CSF): Effects of coagulant dosage and secondary dosing after breakage

Considering the limitations of treated water turbidity, a thorough understanding of the changes in turbid particle size distribution during coagulation-sedimentation-filtration (CSF) is crucial for enhancing the removal efficiency of particulate and dissolved contaminants from raw water. In this study, a pilot-scale experimental system was utilized to track the evolution of turbid particles and assess how the characteristics of these turbid particles affected the quality of treated water in the CSF processes under varying cases of polyaluminum chloride (PAC) coagulant dosage and secondary coagulant dosage after breakage. It was found that differently from the role of PAC coagulant dosage (without high-shear breakage), different levels of secondary coagulant dosing after breakage had minimal influence on the aggregate structure produced by mechanical stirring flocculation. During the overall CSF processes, the changing trend in the total particle number for the filtered water appeared to be more consistent with the corresponding changing trend for the settled water, as the PAC coagulant dosage increased. In addition, the combined effects of shear-induced breakage and secondary dosing could not only improve the removal efficiency of organic matter after inclined-tube sedimentation following mechanical stirring flocculation, but also enhance the removal efficiencies of water turbidity and particulate matter through sand filtration. In order to reduce the frequency of backwashing and extend the service life of the filter media, greater emphasis should be placed on detecting and removing the number of smaller-sized particles existing in the sixth unit of the flocculation tank together with the effluent of the sedimentation tank.

Synthesis of nano-diamond modified Ti3C2Tx MXene heterostructure for enhanced electromagnetic wave absorption

The highly efficient electromagnetic wave (EMW) absorption materials are considered a promising approach to combatting electromagnetic radiation pollution. We synthesized a novel heterostructure 2D Ti3C2Tx MXene composite film modified by 0D nano-diamond (ND) particles using simple mechanical stirring and a vacuum filtration method. Subsequently, we investigated its microstructure and EMW absorption properties. The ND modification not only regulated the impedance matching of the composite films but also enhanced the diversity of EMW losses, demonstrating excellent microwave absorption performance. With a 40 wt% ND content, the minimum reflection loss (RLmin) of the films reached −43.0 dB, corresponding to a film thickness of 2.5 mm. This study explored a novel and promising microwave absorption film, expanding the application of diamond in microwave absorption, and addressing the theoretical gap in diamond-enhanced MXene microwave absorption performance.

TEMPO oxidized cellulose nanofiber-reinforced sodium alginate encapsulated poly(acrylamide) microcapsules and its releasing behaviours for enhancing oil recovery

Poly(acrylamide) (PAM) has excellent thickening ability as a conventional flooding agent. However, PAM confronts the problems of high injection pressure and high shear loss in the process of oil extraction, which have limited its application in this field. In this work, 2, 2, 6, 6-Tetramethylpiperidinooxy oxidized cellulose nanofibers (TOCNFs) enhanced sodium alginate (SA) shell was used to encapsulate PAM to form microcapsule. The composition, morphology, structure and the releasing behaviours of TOCNFs enhanced microcapsules was tested. Mechanical stirring was used to simulate the state of polymer subjected to shear during stratigraphic transport. The release performance of the microcapsules was characterized by measuring the change of viscosity with time. The ratio of the shell material with the best performance was explored, and the enhancement mechanism of the SA shell by TOCNFs was discussed. The experiments showed that the release time of PAM from the microcapsules was significantly prolonged with the addition of TOCNFs. The longest release time was observed when the ratio of SA and TOCNFs was 5: 1, with the release time of the microcapsules from the original 8 h to 16 h. The enhanced shear resistance of the microcapsules was attributed to the semi-interpenetrating network structure of SA and TOCNFs via Ca2+ cross-linking as well as hydrogen bonding. The prepared microcapsules have promising applications in enhancing oil recovery.

Adjustable Humidity Response: Ultrahigh Green EMI Shielding Gel with Double‐Side Constant Temperature Capability

AbstractWith the increasingly serious secondary pollution of electromagnetic waves (EMWs), efficient green shielding materials have become an urgent need. MXene is widely used in electromagnetic interference (EMI) shielding due to its large surface area and high conductivity. Here, this work constructs MXene islands with better shielding performance through viscosity control and continuous mechanical stirring. Benefiting from the MXene islands, Janus‐structural gel with humidity response is successfully prepared, showing controllable ultrahigh green shielding property (up to 100.5 dB, thickness of 2 mm). Interestingly, this gel can spontaneously adjust its water content according to the humidity, resulting in a reversible transformation in three states to meet the needs of different environments. By Janus‐structural design and reasonable material combination, this gel demonstrates excellent electrothermal (rise to 111.6 °C, 5 s, 2 V)/thermal insulation (thermal conductivity is low to 0.029 W m−1 K−1) properties to meet the needs of shielding in underwater/fire operations.

Calendula Flowers (Calendulae officinalis flos): Methods to Obtain Fractions of Biologically Active Substances

INTRODUCTION. The pharmaceutical industry aims at developing sustainable resource-saving technologies for manufacturing medicines. Approaches to the effective use of herbal drugs include applying technologies yielding compounds with various pharmacological effects in one production cycle. To date, no standardised herbal drug processing technology has been designed to produce calendula flower-based medicinal products with various pharmacological effects. The Member States of the Eurasian Economic Union (EAEU) process calendula flowers by extraction methods yielding one fraction of biologically active substances per cycle (either only flavonoids or only carotenoids).AIM. This article aimed to investigate the possibility of stepwise processing of calendula flowers to obtain biologically active substances with different polarities (carotenoids, flavonoids, and polysaccharides) per cycle.MATERIALS AND METHODS. The authors extracted carotenoids using hexane. The study included additional thermal pretreatment of the herbal drug. Carotenoids and flavonoids were quantified by spectrophotometry, and polysaccharides were quantified by gravimetric analysis. After hexane removal, the dry oily residue was dissolved in oil with mechanical stirring to obtain the oil extract. The study included a three-step processing method that comprised hexane extraction (extraction of carotenoids with a low-polarity organic solvent), extraction with a water–organic solvent system (extraction of flavonoids), and aqueous extraction (precipitation of polysaccharides).RESULTS. The lipophilic extracts obtained by single hexane extraction or by single hexane extraction and heat treatment had the maximum carotenoid content (~4%), which was 10 times the carotenoid content in the extracts obtained using a water– organic solvent system. Oil extracts were prepared from the dry residue left after removing hexane by distillation at its boiling point. The content of biologically active substances in the oil extracts was comparable to that in the intact herbal drug. Water–organic solvent extraction yielded 68.5% more flavonoids from the herbal drug extracted with hexane than from the intact herbal drug. In contrast, aqueous extraction applied to the intact herbal drug yielded 1.7 times the amount of flavonoids obtained by aqueous extraction preceded by hexane extraction. The water-soluble polysaccharide fraction extracted from the intact herbal drug had 10 times the flavonoid content observed in the fraction extracted from the processed herbal drug. Each subsequent processing step decreased the total polysaccharide content and the content of individual polysaccharide fractions and increased their purity. The ratio of polysaccharide fractions remained unchanged across all processing methods tested.CONCLUSIONS. Stepwise processing of calendula flowers ensured that one processing cycle provided three fractions containing increased amounts of carotenoids, flavonoids, and polysaccharides. Relative to the intact herbal drug, there was a 3.3-fold increase in the yield of carotenoids, and the yields of flavonoids and polysaccharides increased by 44.8 and 41.3%, respectively. The resulting product had a higher degree of purity than the products obtained by pretreatment and double hexane extraction or by using the intact herbal drug. The stepwise processing method is advisable for the production of medicines that are enriched with a specific group of biologically active substances or contain smaller amounts of impurities.

Calcium chloride dihydrate as a promising system for seasonal heat storage in a suspension reactor

The shift to renewable energy sources increases the demand for energy storage to balance supply and demand. The call for heat storage solutions is particularly high with heat dominating residential energy needs. Simultaneously, significant industrial waste heat potential could be seasonally stored in reversible chemical reactions using thermochemical energy storage technologies. This study investigates the reversible dehydration of calcium chloride dihydrate which has been recognised as a suitable thermochemical material in prior studies. A new method is introduced by investigating the reaction in a lab-scale batch-type suspension reactor. In the reactor, a mechanical stirrer suspends the solid thermochemical material in an inert liquid, to prevent agglomeration of the particles. The investigation involves a parameter variation that includes different suspension media, different mass fractions of the solid reactant, as well as different system pressures during charging. The experimental investigation renders 40 wt% solid or lower as the most promising mass fraction to avoid agglomeration. Vegetable oils show promising results as suspension media. However, they lack thermal stability in the temperature range of up to 210 °C. Mineral oil can ensure thermal and cycle stability. Furthermore, a notable reduction in the dehydration reaction temperatures (176 to 109 °C) is observed when the system pressure is decreased down to 50 mbar. The study concludes that calcium chloride dihydrate has the potential to be used for 22 stable charging and discharging cycles in a mineral oil suspension and that lowering the system pressure can reduce the required charging temperature of the system. To further enhance the suspension method, it is essential to focus on mass transfer and foam mitigation during the dehydration reaction.

High-turbulence fine particle flotation cell optimization and verification

Microfine mineral particles have a small size, light weight, and low inertia, making it difficult for them to deviate from streamlines and collide with bubbles. Conventional flotation operations consume a large amount of reagents and exhibit poor flotation indicators. This study employs computational fluid dynamics (CFD) simulation and hydrodynamic testing to investigate the flow field within a high-turbulence microfine particle flotation machine equipped with a multilayer impeller–stator configuration, and validates the practical application performance of the microfine particle flotation machine through single-batch flotation experiments. Result shows that the impeller region of the traditional mechanical stirring flotation machine has a turbulent energy dissipation rate of 20 m²/s³, whereas that for the microfine particle flotation machine averages over 120 m²/s³. In the flotation verification, the cumulative recovery rate of the fine particle flotation machine is increased by 28% compared with that of the traditional KYF flotation machine. The flotation rate is also 1.3 times that of the KYF, demonstrating stronger selectivity for fine particle concentrates. It has certain guiding significance for the resource utilization of fine particle minerals.