Search Results (754)

HPMC, regulating slurry properties, is widely used in cement-based materials. Research on the application of HPMC in gangue slurry is still in its early stages. Moreover, the interactive effects of various factors on gangue slurry performance have not been thoroughly investigated. The work examined the effects of slurry concentration (X₁), maximum gangue particle size (X₂), and HPMC dosage (X₃) on slurry performance using response surface methodology (RSM). The microstructure of the slurry was characterized via scanning electron microscopy (SEM) and polarized light microscopy (PLM), while low-field nuclear magnetic resonance (LF-NMR) was employed to analyze water distribution. Additionally, industrial field tests were conducted. The results are presented below. (1) X₁ and X₃ exhibited a negative correlation with layering degree and slump flow, while X₂ showed a positive correlation. Slurry concentration had the greatest impact on slurry performance, followed by maximum particle size and HPMC dosage. HPMC significantly improved slurry stability, imposing the minimum negative influence on fluidity. Interaction terms X₁X₂ and X₁X₃ significantly affected layering degree and slump flow, while X₂X₃ significantly affected layering degree instead of slump flow. (2) Derived from the RSM, the statistical models for layering degree and slump flow define the optimal slurry mix proportions. The gangue gradation index ranged from 0.40 to 0.428, with different gradations requiring specific slurry concentration and HPMC dosages. (3) HPMC promoted the formation of a 3D floc network structure of fine particles through adsorption-bridging effects. The spatial supporting effect of the floc network inhibited the sedimentation of coarse particles, which enhanced the stability of the slurry. Meanwhile, HPMC only converted a small amount of free water into floc water, which had a minimal impact on fluidity. HPMC addition achieved the synergistic optimization of slurry stability and fluidity. (4) Field industrial trials confirmed that HPMC-optimized gangue slurry demonstrated significant improvements in both stability and flowability. The optimized slurry achieved blockage-free pipeline transportation, with a maximum spreading radius exceeding 60 m in the goaf and a maximum single-borehole backfilling volume of 2200 m³. Full article

Objectives: This research focuses on the development of fabrication approaches for microparticles intended for controlled drug delivery. The primary objective is to identify the most suitable polymer type, particle size, and morphology for encapsulating a water-soluble crystalline drug. Optimizing these parameters may enhance structural stability and prolong the release of this active substance. Methods: The microparticles were fabricated through the encapsulation of a drug substance within a polymer carrier and employing polymer casting on prepatterned surfaces, followed by the loading of drug precipitates and the application of a sealing layer. The crystalline powder 1-allyl-2,5-dimethylpiperidol-4 hydrochloride served as the core cargo material, while the walls of these particles were composed of polylactic acid (PLA) and a poly (α-caprolactone) (PCL) in a 70:30 composition ratio. Results: The size and volume of the microparticles were found to be dependent on the geometric parameters of the template and the concentration of the polymer solutions. The study demonstrates the formation, physical dimensions, and particle count at varied polymer compositions and concentrations. The formation of the PLA and PCL mixture occurred solely through physical interactions. Scanning electron microscopy (SEM) and optical microscopy were employed to observe the appearance and physical dimensions of the microparticles. The obtained data confirm that tailored polymer compositions can yield consistent particle morphology and a suitable drug elution rate. Conclusions: The results indicate that microparticles sealed with an optimal polymer composition exhibit enhanced release properties. This finding highlights the feasibility of microencapsulation at precise ratios and concentrations of polymers to achieve the long-lasting effects of water-soluble drugs. Full article

This study presents the first quantitative comparison of catastrophic phase inversion behavior of water-in-oil emulsions stabilized by nanocrystalline cellulose (NCC) and molecular surfactants with different headgroup charge types: anionic (sodium dodecyl sulfate referred to as SDS), cationic (octadecyltrimethylammonium chloride referred to as OTAC), nonionic (C12–14 alcohol ethoxylate referred to as Alfonic), and zwitterionic (cetyl betaine referred to as Amphosol). By using conductivity measurements under controlled mixing and pendant drop tensiometry, this study shows that NCC markedly delays catastrophic phase inversion through interfacial jamming, whereas surfactant-stabilized systems exhibit concentration-dependent inversion driven by interfacial saturation. Specifically, NCC-stabilized emulsions exhibited a nonlinear increase in the critical aqueous phase volume fraction required for inversion, ranging from 0.253 (0 wt% NCC) to 0.545 (1.5 wt% NCC), consistent with enhanced resistance to inversion typically associated with the formation of rigid interfacial layers in Pickering emulsions. In contrast, surfactant-stabilized systems exhibited a concentration-dependent inversion trend with opposing effects. At low concentrations, limited interfacial coverage delayed inversion, while at higher concentrations, increased surfactant availability and interfacial saturation promoted earlier inversion and favored the formation of oil-in-water structures. Pendant drop tensiometry confirmed negligible surface activity for NCC, while all surfactants significantly lowered interfacial tension. Despite its weak surface activity, NCC imparted strong coalescence resistance above 0.2 wt%, attributed to steric stabilization. These findings establish distinct mechanisms for governing phase inversion in particle- versus surfactant-stabilized systems. To our knowledge, this is the first study to quantitively characterize the catastrophic phase inversion behavior of water-in-oil emulsions using NCC. This work supports the use of NCC as an effective stabilizer for emulsions with high internal phase volume. Full article

The pilot study is devoted to the assessment of both the accumulation and spatial distribution of microplastics in the snow cover of the Zhetysu region. The height of snow cover in the study area varied from 4.0 to 80.5 cm, with a volume of melt water ranging from 1.5 to 143 L. The analysis of 53 snow samples taken at different altitudes (from 350 to 1500 m above sea level) showed the presence of microplastics in 92.6% of samples in concentrations from 1 to 12 particles per square meter. In total, 170 microplastic particles were identified. The main polymers identified by Raman spectroscopy were polyethylene (PE), polypropylene (PP), and polystyrene (PS). These are typical components of plastic waste. The spatial distribution of microplastics showed elevated concentrations near settlements and roads. Notable contaminations were also recorded in remote mountainous areas, confirming the significant role of long-range atmospheric transport. Particles smaller than 0.5 mm dominated, having high aerodynamic mobility and capable of long-range atmospheric transport. Quantitative and qualitative characteristics of microplastics in snow cover have been realized for the first time both in Kazakhstan and in the Central Asian region, which contributes to the formation of primary ideas and future approaches about microplastic pollution in continental inland regions. The obtained results demonstrate the importance of atmospheric transport in the distribution of microplastics. They indicate the need for further monitoring and microplastic pollution analyses in Central Asia, taking into account its detection even in hard-to-reach and remote areas. Full article

Smectite clay minerals are known to readily form thixotropic physical gels in aqueous media, even at low volume fractions. Although the rheological properties of these gels are closely related to the microstructure of the network, the influence of the clay’s physicochemical characteristics remains insufficiently understood. In this study, we systematically investigated the relationships between particle size, cation exchange capacity, and zeta potential, and the rheological behavior of aqueous dispersions of four synthetic smectites. After thorough deionization, dispersions were prepared at controlled NaCl concentrations. We found that the zeta potential strongly correlates with the fineness of the network structure and governs macroscopic rheological responses such as viscosity, yield stress, and gelation behavior. Even under identical conditions, gel transparency and structural coarseness varied significantly among clay types. Furthermore, the storage modulus was influenced not only by network density but also by the intrinsic stiffness of the clay branches. These findings demonstrate that zeta potential serves as a unified indicator of structure and function in smectite dispersions and offer useful insights for gel design in colloidal and soft matter systems. Full article

To address the technical problems of broad droplet size spectrum, insufficient atomization uniformity, and spray drift in plant protection unmanned aerial vehicle (UAV) applications, this study developed a novel two-stage aerial electrostatic spraying device based on the coupled mechanisms of hydraulic atomization and electrostatic induction, and, through the integration of three-dimensional numerical simulation and additive manufacturing technology, a new two-stage inductive charging device was designed on the basis of the traditional hydrodynamic nozzle structure, and a synergistic optimization study of the charging effect and atomization characteristics was carried out systematically. With the help of a charge ratio detection system and Malvern laser particle sizer, spray pressure (0.25–0.35 MPa), charging voltage (0–16 kV), and spray height (100–1000 mm) were selected as the key parameters, and the interaction mechanism of each parameter on the droplet charge ratio (C/m) and the particle size distribution (Dv50) was analyzed through the Box–Behnken response surface experimental design. The experimental data showed that when the charge voltage was increased to 12 kV, the droplet charge-to-mass ratio reached a peak value of 1.62 mC/kg (p < 0.01), which was 83.6% higher than that of the base condition; the concentration of the particle size distribution of the charged droplets was significantly improved; charged droplets exhibited a 23.6% reduction in Dv50 (p < 0.05) within the 0–200 mm core atomization zone below the nozzle, with the coefficient of variation of volume median diameter decreasing from 28.4% to 16.7%. This study confirms that the two-stage induction structure can effectively break through the charge saturation threshold of traditional electrostatic spraying, which provides a theoretical basis and technical support for the optimal design of electrostatic spraying systems for plant protection UAVs. This technology holds broad application prospects in agricultural settings such as orchards and farmlands. It can significantly enhance the targeted deposition efficiency of pesticides, reducing drift losses and chemical usage, thereby enabling agricultural enterprises to achieve practical economic benefits, including reduced operational costs, improved pest control efficacy, and minimized environmental pollution, while generating environmental benefits. Full article

Natural polymer-based nanoparticles have emerged as promising stabilizers for Pickering emulsions, offering biocompatibility, environmental sustainability, and improved protection of active compounds. This study developed chitosan/gum arabic (CH/GA) nanoparticles as solid stabilizers for quercetin-loaded Pickering emulsions to enhance the stability and antioxidant bioactivity of quercetin (QE), a plant-derived flavonoid known for its potent radical-scavenging activity but limited by oxidative degradation. A systematic formulation strategy was employed to evaluate the effects of CH/GA concentration (0.5–2.0% w/v), oil type (olive, soybean, sunflower, and coconut), and oil volume fraction (ϕ = 0.5–0.7) on emulsion stability. The formulation containing 1.5% CH/GA and olive oil at ϕ = 0.6 exhibited optimal physical and interfacial stability. Quercetin (0.1% w/w) was incorporated into the optimized emulsions and characterized for long-term stability, particle size, droplet morphology, rheology, antioxidant activity (DPPH), cytocompatibility, and intracellular reactive oxygen species (ROS) protection using HaCaT keratinocytes. The olive oil-based formulation (D1-QE) exhibited greater viscosity retention and antioxidant stability than its soybean-based counterpart (E2-QE) under both room temperature (RT) and accelerated heating–cooling (H/C) storage conditions. Confocal microscopy confirmed the accumulation of CH/GA nanoparticles at the oil–water interface, forming a dense interfacial barrier and enhancing emulsion stability. HPLC analysis showed that D1-QE retained 92.8 ± 0.5% of QE at RT and 82.8 ± 1.5% under H/C conditions after 30 days. Antioxidant activity was largely preserved, with only 4.7 ± 1.7% and 14.9 ± 4.8% loss of DPPH radical scavenging activity at RT and H/C, respectively. Cytotoxicity testing in HaCaT keratinocytes confirmed that the emulsions were non-toxic at 1 mg/mL QE and effectively reduced H₂O₂-induced oxidative stress, decreasing intracellular ROS levels by 75.16%. These results highlight the potential of CH/GA-stabilized Pickering emulsions as a polymer-based delivery system for maintaining the stability and functional antioxidant activity of QE in bioactive formulations. Full article

The incorporation of solid particles as a filler to a hydrogel is a strategy to modulate its properties for specific applications, or even to introduce new functionalities to the hydrogel itself. The efficacy of such a modification depends on the filler content and its interaction with the hydrogel matrix. In drug delivery applications, solid particles can be added to hydrogels to improve drug loading capacity, enable the inclusion of poorly soluble drugs, and modulate release kinetics. This work focuses on the case of alginate (ALG)-based hydrogels, obtained following an internal gelation procedure using CaCO₃ as the Ca²⁺ source and containing a high solid volume fraction (up to 50%) of metronidazole (MTZ), a drug with low water solubility, as a potential extrusion-based drug delivery system. The impact of the hydrogel precursor composition (ALG and MTZ content) on the rheological behavior of the filled hydrogel and precursor suspension were investigated, as well as the hydrogel stability and MTZ dissolution. In the absence of solid MTZ, the precursor solutions showed a slightly shear thinning behavior, more accentuated with the increase in ALG concentration. The addition of drugs exceeding the saturation concentration in the precursor suspension resulted in a substantial increase (about one order of magnitude) in the low-shear viscosity and, for the highest MTZ loadings, a yield stress. Despite the significant changes, precursor formulations retained their extrudability, as confirmed by both numerical estimates and experimental validation. MTZ particles did not affect the crosslinking of the precursors to form the hydrogel, but they did control its viscoelastic behavior. In unfilled hydrogels, the ALG concentration controls stability (from 70 h for the lowest concentration to 650 h for the highest) upon immersion in acetate buffer at pH 4.5, determining the MTZ release/hydrogel dissolution behavior. The correlations between composition and material properties offer a basis for building predictive models for fine-tuning their composition of highly filled hydrogel systems. Full article

In order to improve oil recovery efficiency in low-permeability reservoirs, this study developed amphiphilic Janus-SiO₂ nanoparticles to prepare polymer gel microspheres for enhanced oil recovery (EOR). Firstly, Janus-SiO₂ nanoparticles were synthesized via surface modification using (3-aminopropyl)triethoxysilane and α-bromoisobutyryl bromide. Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) characterization confirmed the successful grafting of amino and styrene chains, with the particle size increasing from 23.8 nm to 32.9 nm while maintaining good dispersion stability. The Janus nanoparticles exhibited high interfacial activity, reducing the oil–water interfacial tension to 0.095 mN/m and converting the rock surface wettability from oil-wet (15.4°) to strongly water-wet (120.6°), thereby significantly enhancing the oil stripping efficiency. Then, polymer gel microspheres were prepared by reversed-phase emulsion polymerization using Janus-SiO₂ nanoparticles as emulsifiers. When the concentration range of nanoparticles was 0.1–0.5 wt%, the particle size range of polymer gel microspheres was 316.4–562.7 nm. Polymer gel microspheres prepared with a high concentration of Janus-SiO₂ nanoparticles can ensure the moderate swelling capacity of the particles under high-temperature and high-salinity conditions. At the same time, it can also improve the mechanical strength and shear resistance of the microspheres. Core displacement experiments confirmed the dual synergistic effect of this system. Polymer gel microspheres can effectively plug high-permeability zones and improve sweep volume, while Janus-SiO₂ nanoparticles enhance oil displacement efficiency. Ultimately, this system achieved an incremental oil recovery of 19.72%, exceeding that of conventional polymer microsphere systems by more than 5.96%. The proposed method provides a promising strategy for improving oil recovery in low-permeability heterogeneous reservoir development. Full article

Hydrogel particles, renowned for their high water content and biocompatibility in drug delivery and tissue engineering, typically rely on complex, costly microfluidic systems to reach sub 5 µm dimensions. We present a vortex-based inverse-emulsion polymerization strategy in which UV crosslinking of polyethylene glycol diacrylate (PEGDA) dispersed in n-hexadecane and squalene yields tunable micro- and nanogels while delineating the parameters that govern particle size and uniformity. Systematic variation in surfactant concentration, vessel volume, continuous phase viscosity, vortex speed and duration, oil-to-polymer ratio, polymer molecular weight, and pulsed vortexing revealed that increases in surfactant level, vortex intensity/duration, vessel volume, and oil-to-polymer ratio each reduced mean diameter and PDI, whereas higher polymer molecular weight and continuous phase viscosity broadened the size distribution. We further investigated how these same parameters can be tuned to shift particle populations between nano- and microscale regimes. Under optimized conditions, microhydrogels achieved a coefficient of variation of 0.26 and a PDI of 0.07, with excellent reproducibility, and nanogels measured 161 nm (PDI = 0.05). This rapid, cost-effective method enables precise and scalable control over hydrogel dimensions using only standard laboratory equipment, without specialized training. Full article

The sol–gel synthesis of titanium dioxide (TiO₂) nanostructures is investigated in the present work in order to optimize synthesis parameters and enhance the optical properties and cost-effectiveness of the obtained materials. TiO₂ is widely used in photocatalysis, photovoltaics, and environmental applications due to its high stability, tunable band gap, and strong light absorption. The sol–gel method offers a scalable, cost-effective route for producing nanostructured TiO₂, although the precise control over particle morphology remains challenging. For this reason, in the present work, a statistical design of experiments (DOE) approach is employed to systematically refine reaction conditions through the manipulation of precursor concentrations, solvent ratios, and reaction volume. The experimental results obtained indicate that acetic acid is a key catalyst and stabilizing agent, significantly improving nucleation control and particle formation. Moreover, it is also shown that solvent dilution, particularly with acetic acid, leads to the formation of TiO₂ nanorods with enhanced optical properties. Additionally, scanning electron micrographs revealed that controlled synthesis conditions can reduce the particle size distribution and improve structural uniformity. Moreover, X-ray diffraction analyses confirmed the formation of a pure anatase crystalline phase, while ultraviolet–visible spectroscopy analyses indicated the existence of an optimal band gap for photocatalytic applications. Finally, the cost analysis showed that acetic acid-assisted synthesis can reduce production costs and simultaneously maintain high optical properties. Therefore, the present study highlights that proper manipulation and control of reaction conditions during sol–gel syntheses can allow the manufacture of high-performance TiO₂ nanomaterials for advanced technological applications, also providing a foundation for the development of cost-effective materials. Full article

Nanofluids—engineered suspensions of nanometer-sized particles—have attracted significant attention due to their reportedly enhanced thermal properties, making them promising candidates for advanced heat transfer applications. However, despite extensive studies, uncertainties remain regarding the magnitude and origin of these effects, limiting their practical implementation. To address this, we present a comprehensive study on nanofluid formulations based on the commercial refrigerant HFE-7500, incorporating surfactant-stabilized dispersions of several metal oxide and nitride nanoparticles. We measured key physicochemical properties, including zeta potential, particle size, viscosity, and thermal conductivity. Our results show that while the nanofluids exhibited high stability, their particle sizes in suspension were significantly larger than the primary nanoparticle sizes measured by TEM. Notably, alumina-based suspensions demonstrated the greatest enhancement, exhibiting approximately 10–15% increases in thermal conductivity as a function of volume percentage. These surpassed the 5–10% improvements observed with other metal oxides, an effect that may be linked to their comparatively larger particle sizes. However, the observed enhancements were lower than some previously reported values that claimed anomalously high thermal conductivity increases. Furthermore, steady shear viscosity increased with particle concentration, showing enhancements of 10–20%, which suggests a potential trade-off for practical implementation. Our findings refine the understanding of nanofluid behavior in refrigerants and establish a foundation for optimizing their performance in thermal management applications. However, viscosity increases must be carefully considered when designing next-generation nanofluids for real-world use. Full article

With the implementation of the ISO 8217-2024 marine fuel standard, the use of high-concentration biofuels in ships has become viable. However, relatively few studies have been conducted on the effects of biofuels on cylinder lubrication performance in low-speed, two-stroke marine diesel engines. In this study, catering waste oil was blended with 180 cSt low-sulfur fuel oil (LSFO) to prepare biofuels with volume fractions of 24% (B24) and 50% (B50). These biofuels were evaluated in a MAN marine diesel engine under load conditions of 25%, 50%, 75%, and 90%. The experimental results showed that, at the same engine load, the use of B50 biofuel led to lower kinematic viscosity and oxidation degree of the cylinder residual oil, but higher total base number (TBN), nitration level, PQ index, and concentrations of wear elements (Fe, Cu, Cr, Mo). These results indicate that the wear of the cylinder liner–piston ring interface was more severe when using B50 biofuel than when using B24 biofuel. For the same type of fuel, as the engine load increased, the kinematic viscosity and TBN of the residual oil decreased, while the PQ index and the concentrations of Fe, Cu, Cr, and Mo increased, reflecting the aggravated wear severity. Ferrographic analysis further revealed that ferromagnetic wear particles in the oil mainly consisted of normal wear debris. When using B50 biodiesel, a small amount of fatigue wear particles were detected. These findings offer crucial insights for optimizing biofuel utilization and improving cylinder lubrication systems in marine engines. Full article

The atomization performance of methanol fuel plays a crucial role in enhancing methanol engine efficiency, contributing to the decarbonization of the shipping industry. The droplet microscopic characteristics of methanol spray were experimentally investigated using a single-hole direct injection injector in a constant volume chamber. The particle image analysis (PIA) system equipped with a slicer was employed for droplet detecting at a series of measurement positions in both the dense spray region and dilute spray region, then the spatial distributions of droplet size and velocity were examined. Key findings reveal distinct atomization behaviors between dense and dilute spray regions. Along the centerline, the methanol spray exhibited poor atomization, characterized by a high concentration of aggregated droplets, interconnected liquid structures, and large liquid masses. In contrast, the spray periphery demonstrated effective atomization, with only well-dispersed individual droplets observed. Droplet size distribution analysis showed a sharp decrease from the dense region to the dilute region near the nozzle. In the spray midbody, droplet diameter initially decreased significantly within the dense spray zone, stabilized in the transition zone, and then exhibited a slight increase in the dilute region—though remaining smaller than values observed at the central axis. Velocity measurements indicated a consistent decline in the axial velocity component due to air drag. In contrast, the radial velocity component displayed irregular variations, attributed to vortex-induced flow interactions. These experimentally observed droplet behaviors provide critical insights for refining spray models and enhancing computational simulations of methanol injection processes. Full article

This study numerically investigates the solid–liquid mixing characteristics in solid–liquid stirred tanks with solid volume fraction as high as 35%, focusing on the effect of impeller and baffle configurations on solid and liquid flow behaviors. Three stirred tanks with different capacities and impellers were analyzed to evaluate liquid flow field, solid suspension, and free surface profiles. It has demonstrated superior shear rate uniformity in the multi-impeller systems compared to the single-impeller, attributed to the enhanced fluid circulation. Multi-impeller systems can achieve near-complete off-bottom suspension, while the single-impeller configuration exhibited band-shaped particle accumulation above the impeller. Free surface vortices, significantly deeper in the 6 m³ multi-impeller tank due to high blade tip velocities, were mitigated through the integration of four circumferentially arranged triangular baffles. The existence of baffles can suppress surface turbulence, promote axial flow patterns, and eliminate particle accumulation at the tank bottom, improving shear rate and solid concentration homogeneity. These findings provide a beneficial guideline for the optimization of solid–liquid mixing efficiency the similar flow system or processes. Full article