The mass median powder diameter, d50, is measured as a function of atomization conditions for a discrete jet type high pressure gas atomization system. Five different gas pressures are used between 3.0 and 5.0 MPa and, for each pressure, four different melt flow rates are studied by independently varying the forcing pressure under which the melt is ejected and the bore of the melt delivery nozzle. A poor fit to the conventional Lubanska model is found. However, it is shown that d50 correlates well with the ratio of melt flow rate to power embodied within the supersonic gas stream, as first suggested by Strauss & Miller [Adv. Powder Metall. Particulate Mater. 11, 2001, 2.17], provided their relationship is modified to include a minimum particle size at low melt flow rate. This we conjecture may be due to incomplete wetting of the melt nozzle at such low melt flow rates. We also note that the efficiency of atomizing systems in converting potential energy stored in the high pressure gas to kinetic energy embodied in the supersonic gas stream drops as the pressure increases, calling into question the current trend for increasing the atomizing pressure.
The effect of radial clearance on the vertical downward screw-feeding process of particles is investigated by combining experiments and discrete element method (DEM) simulations. The feeding behaviour is analysed in terms of mass flow rate, particle fraction, coordination number, maximum compressive force, axial velocity and particle flow pattern. Experimental results show that the mass flow rate increases with screw rotational speed, which is strongly affected by radial clearance. DEM simulations capture the main feeding trend when the particle motion is dominated by screw-driven conveying and wall confinement, while deviations appear when the clearance becomes large enough for real non-spherical particles to exhibit shape-dependent sliding and gravity-assisted leakage. Simulation results also show that radial clearance controls the balance between geometric confinement and particle rearrangement. A small clearance causes local trapping, repeated compression and disturbed contact networks, whereas a large clearance weakens confinement and promotes slipping or leakage-like downward motion. An intermediate clearance provides a more favourable matching condition between screw geometry and particle size, leading to denser packing and a more stable creeping-propulsion mode. Comparison with the theoretical screw-feeding equation indicates that the theory captures the main speed-dependent trend, but its accuracy is affected by clearance-dependent non-ideal particle motion.
This work presents a fully coupled Computational Fluid Dynamics and Discrete Element Method (CFD–DEM) simulation of powder transport in continuous coaxial Laser Metal Deposition (LMD) nozzles, implemented in Simcenter STAR-CCM+. The methodology integrates a Johnson–Kendall–Roberts (JKR) adhesive contact model via custom field functions to represent cohesive particle–wall interactions influencing residence times and temporal flow structure. A refined polyhedral mesh resolves internal channels and external jet regions while maintaining coupling stability, with physics including two-species gas mixing (argon/air), Gidaspow drag, Sommerfeld shear lift, and gravity. Validation at a representative operating point (3 L/min carrier gas, 15 L/min shielding flow, Rosin–Rammler size distribution, 4.5 g/min feed) yields spatial footprints, centerline peak acceleration of ∼50 m/s2, and a 19% exit mass-flow irregularity (2 ms moving average). The predicted mass-flow irregularity (19% vs. 16% experimental) and accelerations agree closely with measurements, confirming rebound-driven intermittency and azimuthal redistribution at distributor fins as the dominant unsteadiness sources. Conversely, the standoff underprediction (10.2 mm vs. 16 mm) is traced to unresolved exit gas expansion under the incompressible assumption and drag calibration for the particle-laden jet, defining concrete refinement priorities for predictive simulation.
With the challenges posed by the clean energy transformation, pulverized metal fuels have gained attention in recent years due to their potential as circular energy carriers. To ensure stable and safe combustion, currently operating experimental iron powder combustors often rely on gas assistance. Hence, for the design of such systems, it is important to understand the coupling of gas-phase and iron combustion under varying particle sizes, iron-to-methane ratios, and combined equivalence ratios. In addition, the development of reduced-order models is essential for enabling efficient numerical simulations and facilitating a rapid design process. In the present study, laminar, premixed iron–powder–methane flames are examined using a Lagrangian particle model in a channel. One objective is to elucidate the coupling between iron and methane combustion through detailed-chemistry simulations. Therefore, the iron and methane equivalence ratios, as well as the particle diameter, are varied. The investigation reveals coupling regimes characterized by the onset of oxygen consumption by either methane or iron. These regimes influence flame speed, particle temperatures, and conversion behavior. The second objective is the comprehensive validation of a tabulated flamelet manifold method based one one-dimensional flames that was developed in a previous work. The comparison of detailed and tabulated chemistry, across all investigated parameters, show good agreement with respect to coupling behavior, iron conversion, oxygen consumption, temperatures, and flame speed.
In this study, an embedded stress measurement system was utilized to measure the static normal wall stress in silos. By varying the granular filling height, it was discovered that the stress distribution in deep silos deviates from the asymptotic saturation characteristic of the classical Janssen model, exhibiting the stress reduction phenomenon. Inversion results reveal that under high filling conditions, the enhanced friction of the granular system bears a portion of the vertical pressure, which consequently reduces the lateral compression of the particles against the silo wall, ultimately inducing this phenomenon. Finally, an empirical stress distribution model is proposed to quantify the stress reduction in deep silos. This research will provide a crucial data reference for the structural design and storage safety of silos in engineering applications.
A series of La0.8Sr0.2Mn1-xFexO3 (x = 0–0.03) ceramic materials were synthesized via the sol–gel method, and their structural, electrical, and magnetic properties were systematically investigated. Rietveld refinement of X-ray diffraction (XRD) patterns reveals that all LSMFO ceramics crystallize in a rhombohedral perovskite structure (space group: R3¯c). Scanning electron microscopy (SEM) analysis demonstrates that appropriate Fe doping (x = 0.01) can promote grain growth. With the increase of Fe doping content, both the temperature coefficient of resistance (TCR) and magnetoresistance (MR) of LSMFO samples exhibit a trend of first increasing and then decreasing. For the sample with x = 0.005, the TCR and MR reach their maximum (TCRpeak and MRpeak) values: 6.48%·K−1 (peak TCR temperature Tk = 301.48 K) and 27.06% (peak MR temperature Tm = 304.21 K), respectively, with both corresponding temperatures close to room temperature. The optimization of electrical and magnetic properties of LSMFO samples is attributed to the improvement of grain boundary density and grain size by Fe doping. In summary, these results demonstrate that LSMFO ceramics hold broad application prospects in fields such as uncooled infrared bolometers and magnetic sensors.
With the rapid advancement of power electronics toward high-frequency and miniaturization, there is an urgent demand for soft magnetic composites (SMCs) that possess both high permeability and low core loss. Herein, a novel Cr-O&(Ni,Zn)Fe2O4 synergistic hybrid insulation was synthesized on FeSiBCCr amorphous powders via sequential hydrothermal and chemical co-precipitation methods. The oxygen partial pressure during annealing was optimized using 0.8 wt.% carbon powder to enhance the crystallinity and magnetic properties of the ferrite insulating coating. The resulting SMCs exhibited a saturation magnetization (Ms) of 140.0 emu/g and an effective permeability (μe) of 35.03. Notably, the core loss P50mT/1MHz was reduced to 2143.10 mW/cm3, which is 50.72% lower than that of the core sample prepared by using raw powder without ferrite insulating coating. This synergistic hybrid insulation effectively suppresses inter-particle eddy currents and reduces domain wall pinning, offering a high-performance solution for high-frequency power electronics.
Iron sulfide (Fe3S4/FeS2) and cadmium-doped iron sulfide (Fe3S4/FeS2:Cd) nanoparticles with different Cd concentrations (2, 5, 8, and 15 wt%) were synthesized by a solvothermal approach, and the influence of Cd doping on their structural, morphological, optical, thermal, and biological properties was systematically examined. X-ray diffraction confirmed retention of the iron sulfide structure, with greigite (Fe3S4) and pyrite (FeS2) as the dominant phases together with a minor magnetite (Fe3O4) phase in all samples, while additional CdS peaks appeared at 8 and 15 wt% Cd. Scanning and transmission electron microscopy revealed irregular platelet-like particles that aggregated into flower-like clusters at higher doping. The optical band gap decreased from 2.76 eV for the pristine sample to 1.91 eV at 5 wt% Cd and then widened to 2.74 and 2.93 eV at 8 and 15 wt%, coinciding with the onset of the CdS phase. X-ray fluorescence confirmed Cd incorporation and revealed a sub-nominal, solubility-limited uptake, while Fourier-transform infrared spectroscopy verified Fe–S and Cd–S bonding. Thermogravimetric analysis showed that doping improved thermal stability, the total weight loss decreasing from about 22% for the pristine sample to 17% at 15 wt% Cd. Zeta-potential values were low and positive, indicating weakly stabilized, aggregation-prone particles. Cytotoxicity assays demonstrated negligible toxicity toward non-tumoral human dermal fibroblasts, whereas the pristine and 15 wt% samples reached IC50 against A549 lung cancer cells, with the 5 wt% sample at the 50% threshold; none of the samples reached IC50 for the MCF-7 breast cancer cell line. These findings highlight the potential of Fe3S4/FeS2:Cd nanocomposites as selective, Fenton-active anticancer nanomaterials.
Due to its unique wrinkled morphology and special electronic structure, the electrochemical specific surface area of Mo-NiCoS has been greatly increased, which can make it exhibit the low overpotential, thereby enhancing the catalytic activity. This is mainly because there is an excellent synergistic effect between metal atoms and sulfur, which jointly improves the catalytic activity with the NiCo precursor. Meanwhile, Mo-NiCoS has a large number of defects, which not only promotes the penetration of the electrolyte, but also enhances electron transfer as well as the adsorption of hydroxide ions (OH-) and water molecules (H2O). More importantly, X-ray photoelectron spectroscopy (XPS) indicates that there is a large amount of electron transfer inside Mo-NiCoS, which greatly reduces the overpotential of the NiCo precursor. Moreover, Mo-NiCoS only requires voltages of 1.485 V and 1.521 V to reach current densities of 70 mA·cm-2 and 100 mA·cm-2, respectively. This study mainly illustrates the role of the synergistic effect between metal atom doping and sulfidation in improving the catalytic activity of the NiCo precursor. Simultaneously, this methodology can be extended to introduce other metal dopants and non-metallic modifications for enhancing the performance, which paves a new avenue for designing the high-efficiency industrial water electrolysis catalysts.
Phosphogypsum (PG)–ground-granulated blast-furnace slag (GGBS) binders enable large-volume solid-waste valorisation, but their coupled thermo-mechanical activation remains insufficiently understood. Here, PG was calcined, blended with GGBS and co-milled to prepare a calcined PG–GGBS solid-waste cementitious material (CSCM). A Box–Behnken response-surface design quantified the effects of calcination temperature, milling speed and milling time on flowability, setting time, and 3- and 28-day compressive strength. The optimised process was validated by XRD, FTIR, SEM–EDS and XPS, combined with activity index and toxicity leaching assessments. Calcination at 600°C reduced soluble P2O5 in PG by 98.76%, while milling at 600 rpm for 20 min decreased D50 from 38.55 to 23.71 μm and produced the highest specific surface area of 2.66 m2 g−1. Multi-objective optimisation identified an optimum of 530°C, 600 rpm and 28 min. The optimised CSCM achieved a 28-day activity index of 118.4%, reduced the toxicity leaching index from 1.34 to 0.12, and lowered cradle-to-gate CO2 emissions by 68% relative to equivalent-strength Portland cement. These findings reveal an impurity immobilisation–mechanochemical activation–microaggregate densification mechanism for sustainable PG–GGBS binders.
Leaching Al from fly ash (FA) represents a critical pathway for its resource recovery. Some Al is imprinted in the stable mullite structure, making it difficult to leach out. Using the conventional strong acid or alkali methods to dissolve mullite has the disadvantages of environmental hazard and inefficient Al-Si separation. This study created a low-temperature NaHSO4 molten salt process that converts mullite into water-soluble NaAl(SO4)2 and insoluble SiO2, followed by the separation of Al and Si through water leaching. First, TG was used to define the temperature. Subsequently, the influence of calcination temperature, time, and the NaHSO4 dosage was explored. Finally, the leaching behavior of Al was investigated, and the leaching kinetics were analyzed. The conversion of mullite to NaAl(SO4)2 was confirmed to be best when calcined at 350 °C for 3 h, while the molar ratio of NaHSO4/Al2O3 was 10. Sequentially, leaching at 70 °C for 90 min with water can leach 85.28% and 0.60% of Al and Si. The leaching process conformed to the Avrami model and belonged to the interfacial reaction.
The evolution of powder characteristics, phase formation, and microstructure in a rare-earth-modified AlGdNiCoMn high-entropy alloy (HEA) was systematically investigated during high-energy mechanical milling. Equiatomic Al, Gd, Ni, Co, and Mn powders were milled for 1–15 h, and their morphological, structural, mechanical, magnetic, and thermal responses were characterized. Progressive milling induced severe plastic deformation, pronounced particle refinement, and enhanced interdiffusion, leading to gradual solid-solution formation. XRD analysis revealed the transformation of elemental phases into a predominantly nanocrystalline BCC solid solution with minor FCC contributions at extended milling durations. The incorporation of Gd, owing to its large atomic radius, generated substantial lattice distortion, which facilitated nanocrystallization and promoted solid-solution strengthening. As a result, microhardness increased significantly, reaching ∼746 HV after 15 h of milling. Magnetic measurements demonstrated a reduction in saturation magnetization with increasing milling time, attributed to lattice strain, chemical disorder, and weakened 4f–3d exchange interactions. DSC analysis indicated defect annihilation and phase reorganization processes. These findings confirm that Gd microalloying, combined with mechanical milling, is an effective strategy for tailoring the microstructural and multifunctional properties of Al-based HEAs.
Expansive concrete is frequently used to counteract shrinkage; however, the incorporation of expansive agents (EAs) often compromises pore structure and strength development. To overcome these limits, this study proposes the novel incorporation of graphene nanoplatelets (GNPs) as a reinforcement for EA-cement composites. Five GNP dosages (0.02%, 0.05%, 0.1%, 0.2%, and 0.5% by binder mass) were examined to elucidate their effects on hydration kinetics, phase assemblage, morphology, and pore-structure evolution. The evaluation primarily focused on expansion, mechanical, and nanomechanical performance, with particular attention on the mechanisms linking macro- and micro-scale behavior. Results showed that GNPs can act as effective reinforcements in EA-cement composites, with an optimal dosage of 0.10 wt%, yielding a moderate increase in early-age expansion while enhancing 28-day compressive strength up to 8.5% and average indentation modulus up to 40%. GNPs accelerated early hydration by shortening the induction period and advancing the main silicate-hydration peak by 2–3 h. GNPs redistributed hydration products by reducing loosely packed and low-density C-S-H by up to 50% and 40%, respectively, and promoting high-density C-S-H formation up to 33%, while simultaneously enhancing portlandite crystallographic orientation. Adding 0.05–0.10 wt% GNPs reduced total porosity by up to 15% and refined gel pores, as localized Ca2⁺ enrichment on GNP surfaces promoted heterogeneous nucleation and a “more-but-smaller” hydrate morphology. This enhancement effect of GNP was attributed to template-directed nucleation and pore-filling. This study not only solves the strength-expansion conflict in EA systems but also establishes a fundamental framework for designing high-performance expansive cementitious composites.
In port operations for unloading granular materials, screw and pneumatic conveying are conventional methods whose performance is often evaluated solely by metrics such as the material recovery efficiency, which neglects energy consumption and overall operational efficiency, resulting in increased operational costs. This work presents a screw-gas conveying device (SGCD) that integrates the advantages of both screw and pneumatic conveying for granular material transport. A mathematical model describing the gas–solid separation process within the SGCD is developed, and its key operational parameters are analyzed. Subsequently, the SGCD is fabricated and tested to investigate in detail the effects of material type, screw speed, and airflow rate on the SGCD performance. Experimental results for separation efficiency show good agreement with the theoretical model (maximum relative error ≤ 9.6%), demonstrating the SGCD’s effectiveness. The optimal operational setting for the three granular materials tested is identified as a screw speed of approximately 350 rpm and an airflow rate of 4.625 L/s, at which the SGCD offers the best overall conveying performance among the tested conditions.
The wall deposition of fine particles restricts the separation performance and long-term stable operation of cyclone separators. In this study, the deposition behavior of fine silica powder (d50 = 2.03 μm) was investigated. Through designed stepwise visualization experiments conducted in a cyclone (D = 100 mm), the contributions of airflow shear and particle-induced erosion to the overall removal process were separately quantified under various inlet conditions (Uin = 10–30 m/s, Cin = 1–100g/m3). The results indicate that with increasing gas velocity, the net particle deposition rate exhibits a non-monotonic evolution pattern (increasing initially and then decreasing). Regarding removal characteristics, a critical velocity threshold (Ucr ≈ 20 m/s) exists for the airflow shear mechanism. Furthermore, the intense erosion effect induced by the high-concentration ash band is identified as the primary cause of the Spiral Adhesion Pattern (SAP), with the erosion process following first-order removal kinetics. Moreover, comparison of the particle deposition rate with removal rates demonstrates that their relative magnitudes govern the evolution of different deposition patterns. This work reveals the growth and detachment mechanisms of the deposit layer in cyclone separators, providing a theoretical basis for anti-fouling strategies in industrial cyclones.
The shear-dependent evolution of electrically active networks in carbon black (CB) electrode slurries remains insufficiently resolved under processing-relevant flow conditions, limiting rational slurry design for scalable battery manufacturing. Here, we apply continuous-flow broadband electrochemical impedance spectroscopy (EIS, 7 MHz-10 mHz) using a custom laminar flow cell to investigate acetylene black slurries (0.3–5.0 wt% CB in PVDF/NMP) under static and flowing conditions up to 50 mL min−1. Under no-flow conditions, the impedance spectra evolve systematically with CB loading and exhibit a connectivity transition near 3.2 wt% CB, above which an additional high-frequency response becomes spectrally resolvable. The spectra were analyzed using hierarchical R||CPE models, and CPE-derived effective capacitance-like parameters were used to describe the frequency-resolved redistribution of electrically active processes. These analyses show that the composition near the connectivity transition is the most sensitive to flow: at 3.2 wt% CB, lower flow conditions within the laminar regime shift the response from fast to intermediate relaxation contributions, whereas higher flow conditions within the laminar regime suppresses the distinct high-frequency contribution entirely. In contrast, the 5.0 wt% slurry shows comparatively limited spectral redistribution, consistent with a more robust and redundant conductive network. Together, these results establish laminar-flow broadband EIS as a process-relevant approach for diagnosing flow-induced reorganization of electrically active slurry networks under pressure-driven, coating-relevant hydrodynamic conditions.
Heterogeneous nucleation and hygroscopic mechanisms at inorganic salt micro-interfaces remain pivotal for atmospheric water harvesting and aerosol phase transition technologies. Employing molecular dynamics (MD) simulations, this study systematically elucidates the hygroscopic growth behaviors and lattice dissociation mechanisms of LiCl, NaCl, and CaCl2 nanoparticles under supersaturated environments. Benefiting from the small ionic radius and high charge density of Li+, LiCl exhibits an accelerated nucleation kinetics profile and superior hygroscopic kinetics. Its strong electrostatic interactions suppress the water self-diffusion coefficient to (1.48 ± 0.16) × 10−6 m2/s, sustaining a low water activity that drives continuous moisture uptake. Furthermore, environmental parameters exert significant nonlinear regulatory effects on mass transfer pathways. Elevated supersaturation (NH2O = 315) and mass loading (Nsalt = 72) notably enhance interfacial hygroscopic dynamics, whereas a moderately high temperature of 320 K effectively suppresses homogeneous nucleation competition, maximizing the heterogeneous condensation potential of LiCl. By delineating the physical evolution from surface adsorption to deliquescent phase transition at the atomic level, this study provides a theoretical foundation for the molecular design of high-efficiency liquid desiccants.
Coal wettability strongly affects water imbibition and capillary-driven penetration in coal porous media. Nanoparticle-surfactant composite solutions have shown strong potential for wettability alteration. However, the interfacial regulation mechanisms governing their interaction with coal particles of different ranks remain insufficiently understood. In this study, a silica nanoparticle-cetyltrimethylammonium bromide (CTAB) composite system was employed to investigate wettability regulation mechanisms across coals with different ranks. Wettability evolution was evaluated at both macro- and micro-scales. It is indicated that the composite system alters the wettability of all coal samples, as evidenced by reduced contact angles, increased hydration film thickness, and a higher content of hydrophilic functional groups. However, the magnitude and persistence of the wettability enhancement are strongly coal-rank dependent, with the most pronounced improvement observed in high-rank coal. This effect is attributed to the uniform and continuous nano-particle coating on the surface of high-rank coal.
