Large Particles Research Articles

An exact solution based on a three-energy equation model for gaseous transpiration cooling through a bi-disperse porous medium

Abstract A local thermal non-equilibrium analysis was made to assess potential use of bi-disperse porous walls for a transpiration cooling system. A three-energy equation model successfully used for the transient thermal analysis of bi-disperse packed bed thermocline storage systems was introduced to investigate various heat transfer aspects of transpiration cooling through a bi-disperse porous wall made of combination of large and small particles. Three independent energy balance equations, namely, the energy equation of the coolant gas phase, that of the solid phase of large particles and that of small particles are coupled with one another to obtain a set of exact expressions for all three individual temperature distributions across the porous wall for given thermal boundary conditions of the third kind. It has been revealed that the solid wall temperature of the bi-disperse porous wall stays lower than that of the mono-disperse porous wall in the high Peclet number range, resulting in a higher overall cooling efficiency for a given blowing flow rate. Furthermore, the analysis provides a suitable range of the Peclet number, under which the transpiration cooling should be operated to suppress excessive heat loss to the coolant reservoir at the same time to ensure a high overall cooling efficiency.

Numerical testing method and mechanical property evaluation of large particle size asphalt mixture

The large particle size asphalt mixture with nominal maximum aggregate size 53 mm(LSAM-50) has good technical and economic performance and will become an effective technical way to build a full-thick long-life asphalt pavement with Chinese characteristics. In order to reveal the mechanical properties and influencing factors of LSAM-50 in depth, a numerical test method for the mechanical properties of the large particle size LSAM-50 asphalt mixture was developed, and a reasonable specimen size for LSAM-50 performance test was proposed by combining the numerical test and the indoor test. The results show that: LSAM-50 numerical test conditions are the calculation time step 10−3 s/step, the loading rate is 2 mm/min (uniaxial compression numerical test) and 50 mm/min (splitting numerical test) when LSAM-50 numerical experiment calculation rate and numerical experiment accuracy are better; after the size of the specimen reaches 200×160mm, the influence of the size effect is eliminated. The reasonable specimen size of LSAM-50 is Φ200mm×h160mm; the LSAM-50 numerical test method and the indoor test have low error Less than 10%.

Nonclassical Optical Response of Particle Plasmons With Quantum‐Informed Local Optics

AbstractAs the dimensions of plasmonic structures or the field confinement length approach the mean free path of electrons, mesoscopic optical response effects, including nonlocality, electron spill‐in or spill‐out, and Landau damping, are expected to become observable. In this work, a quantum‐informed local analogue model (QILAM) that maps these nonclassical optical responses onto a local dielectric film is presented. The primary advantage of this model lies in its compatibility with the highly efficient boundary element method (BEM), which includes retardation effects with relatively large particle sizes. Furthermore, the approach offers a unified framework that connects two important semiclassical theories: the generalized nonlocal optical response (GNOR) theory and the Feibelman d‐parameters formalism. It is envisioned that QILAM can evolve into a multiscale electrodynamic tool for exploring nonclassical optical responses in diverse plasmonic structures in the future. This can be achieved by directly translating mesoscopic effects into observable phenomena, such as plasmon resonance energy shifts and linewidth broadening in the scattering spectrum.

Visualization Experiment on the Influence of the Lost Circulation Material Injection Method on Fracture Plugging

The drilling fluid loss or lost circulation via near-wellbore fractures is one of the most critical problems in the drilling of deep oil and gas resources, which causes other problems such as difficulty in achieving wellbore pressure control and reservoir damage. The conventional treatment is to introduce granular lost circulation material (LCM) into the drilling fluid to plug the fractures. As the migration mechanism of the LCM in irregular fractures has not been completely figured out as of yet, the low success rate of fracture plugging and repeated drilling fluid loss still obstruct the exploitation of deep oil and gas resources. In this paper, the spatial data of actual rock fracture surfaces were obtained through structured light scanning, and an irregular surface identical to the rock was machined on a transparent polymethyl methacrylate plate. On this basis, a visualization experimental apparatus for fracture plugging was established, and the fracture flow space of this device was consistent with that of the actual rock fracture. Employing cylindrical nylon particles as LCM, a visualization experiment study was carried out to investigate the process of LCM bridging and fracture plugging and the influence of LCM injection methods. The experimental results show that the process of fracture plugging includes the sporadic bridging, plugging zone extension and merging, thickening of the plugging zone and complete plugging of the fracture. It was observed in the visualization experiment that a large number of small particles flow deep into the fracture in the traditional fracture plugging method, where all types and sizes of LCM are injected at one time. After changing the injection sequence, which injects the large particles first and the small particles subsequently, it is found that the large particles will form single-particle bridging at a specific depth of the fracture, intercepting subsequently injected particles and thickening the plugging zone, which finally increases the area of the plugging zone by 19%. The visualization experiment results demonstrate that modifying the LCM injection method significantly enhances both the LCM utilization rate and the fracture plugging effect, thereby reducing reservoir damage. This is conducive to reducing the drilling cost of fractured formation. Additionally, the visualized experimental approach introduced in this study can also benefit other research areas, including proppant placement and solute transport in rock fractures.

Quantification of Particle-Associated Viruses in Secondary Treated Wastewater Effluent

Viruses can interact with a broad range of inorganic and organic particles in water and wastewater. These associations can protect viruses from inactivation by quenching chemical disinfectants or blocking ultraviolet light transmission, and a much higher dosage of disinfectants is required to inactivate particle-associated viruses than free viruses. There have been only few studies of the association of viruses with particles in wastewater, particularly in secondary treated effluent. As secondary effluent is the source water to the reclaimed water treatment system, this study quantified indigenous enteric viruses, and viral indicators associated with particles in secondary effluents collected from five full-scale water reclamation facilities in the United States. Particle-associated viruses were enumerated using a sequential filtration followed by microfluidic digital PCR. This study showed that enteric viruses and viral indicators (crAssphage and pepper mild mottle virus, PMMoV) were attached to particles of different sizes in secondary effluent. Significantly higher concentrations of RNA viruses including PMMoV, norovirus, and enterovirus were detected in filtrate of the sequential filtration, which contained particles < 0.45 µm. DNA viruses including adenovirus and crAssphage were found to be more associated with larger particles in secondary effluent. Overall, high correlations were observed between viral indicators and enteric viruses, supporting the use of crAssphage and PMMoV to evaluate virus removal efficiency in water and wastewater treatment processes. The association of viruses with particles in wastewater has significant implications on wastewater treatment and disinfection processes as well as virus enumeration in wastewater.Graphic

Ultrafast Synthesis of Nanoscale Metal Borides for Efficient Hydrogen Evolution

Nanoscale metal borides, with exceptional physicochemical properties, have been attracted widespread attention. However, traditional synthesis methods of metal borides often lead to surface coking and large particle sizes. Herein, we have employed a flash Joule heating (FJH) technique to enable the ultrafast synthesis of metal boride nanomaterials. The synthesized materials encompass a wide range of diverse categories, including alkaline‐earth metal borides (CaB6), transition metal borides (TiB2, VB2, CrB2, MoB, MoB2, MnB2, MnB4, FeB, CoB, NiB), noble‐metal borides (RuB2, RuB1.1), and rare‐earth metal borides (LaB6, CeB6). As an example, the RuB2 demonstrates highly desirable electrocatalytic performance for all‐pH hydrogen evolution reaction (HER). Especially, under the acidic condition, it exhibits an overpotential as low as 15 mV at a current density of 10 mA cm‐2, with a nearly 100% faradic efficiency. Additionally, in situ Raman spectra confirm that both Ru and B sites serve as active sites for the HER. Moreover, the stability of RuB2 can be further enhanced by optimizing the microenvironments of the anolyte composition (H+, K+). More importantly, the experimental and density functional theory (DFT) calculations reveal that the co‐existence of H+ and K+ localized around the RuB2 plays a crucial role in further enhancing the stability.

Ultrafast Synthesis of Nanoscale Metal Borides for Efficient Hydrogen Evolution.

Nanoscale metal borides, with exceptional physicochemical properties, have been attracted widespread attention. However, traditional synthesis methods of metal borides often lead to surface coking and large particle sizes. Herein, we have employed a flash Joule heating (FJH) technique to enable the ultrafast synthesis of metal boride nanomaterials. The synthesized materials encompass a wide range of diverse categories, including alkaline-earth metal borides (CaB6), transition metal borides (TiB2, VB2, CrB2, MoB, MoB2, MnB2, MnB4, FeB, CoB, NiB), noble-metal borides (RuB2, RuB1.1), and rare-earth metal borides (LaB6, CeB6). As an example, the RuB2 demonstrates highly desirable electrocatalytic performance for all-pH hydrogen evolution reaction (HER). Especially, under the acidic condition, it exhibits an overpotential as low as 15 mV at a current density of 10 mA cm-2, with a nearly 100% faradic efficiency. Additionally, in situ Raman spectra confirm that both Ru and B sites serve as active sites for the HER. Moreover, the stability of RuB2 can be further enhanced by optimizing the microenvironments of the anolyte composition (H+, K+). More importantly, the experimental and density functional theory (DFT) calculations reveal that the co-existence of H+ and K+ localized around the RuB2 plays a crucial role in further enhancing the stability.

Enhancing Polylactic Acid (PLA) Performance: A Review of Additives in Fused Deposition Modelling (FDM) Filaments

This review explores the impact of various additives on the mechanical properties of polylactic acid (PLA) filaments used in Fused Deposition Modeling (FDM) 3D printing. While PLA is favored for its biodegradability and ease of use, its inherent limitations in strength and heat resistance necessitate enhancements through additives. The impact of natural and synthetic fibers, inorganic particles, and nanomaterials on the mechanical properties, printability, and overall functionality of PLA composites was examined, indicating that fiber reinforcements, such as carbon and glass fibers, significantly enhance tensile strength and stiffness, while natural fibers contribute to sustainability but may compromise mechanical stability. Additionally, the inclusion of inorganic particulate fillers like calcium carbonate improves dimensional stability and printability, although larger particles can lead to agglomeration issues. The study highlights the potential for improved performance in specific applications while acknowledging the need for further investigation into optimal formulations and processing conditions.

New particle formation dynamics in the central Andes: contrasting urban and mountaintop environments

Abstract. In this study, we investigate atmospheric new particle formation (NPF) across 65 d in the Bolivian central Andes at two locations: the mountaintop Chacaltaya station (CHC, 5.2 km above sea level) and an urban site in El Alto–La Paz (EAC), 19 km apart and at 1.1 km lower altitude. We classified the days into four categories based on the intensity of NPF, determined by the daily maximum concentration of 4–7 nm particles: (1) high at both sites, (2) medium at both, (3) high at EAC but low at CHC, and (4) low at both. These categories were then named after their emergent and most prominent characteristics: (1) Intense-NPF, (2) Polluted, (3) Volcanic, and (4) Cloudy. This classification was premised on the assumption that similar NPF intensities imply similar atmospheric processes. Our findings show significant differences across the categories in terms of particle size and volume, sulfuric acid concentration, aerosol compositions, pollution levels, meteorological conditions, and air mass origins. Specifically, intense NPF events (1) increased Aitken mode particle concentrations (14–100 nm) significantly on 28 % of the days when air masses passed over the Altiplano. At CHC, larger Aitken mode particle concentrations (40–100 nm) increased from 1.1 × 103 cm−3 (background) to 6.2 × 103 cm−3, and this is very likely linked to the ongoing NPF process. High pollution levels from urban emissions on 24 % of the days (2) were found to interrupt particle growth at CHC and diminish nucleation at EAC. Meanwhile, on 14 % of the days, high concentrations of sulfate and large particle volumes (3) were observed, correlating with significant influences from air masses originating from the actively degassing Sabancaya volcano and a depletion of positive 2–4 nm ions at CHC but not at EAC. During these days, reduced NPF intensity was observed at CHC but not at EAC. Lastly, on 34 % of the days, overcast conditions (4) were associated with low formation rates and air masses originating from the lowlands east of the stations. In all cases, event initiation (∼ 09:00 LT) generally occurred about half an hour earlier at CHC than at EAC and was likely modulated by the daily solar cycle. CHC at dawn is in an air mass representative of the regional residual layer with minimal local surface influence due to the barren landscape. As the day progresses, upslope winds bring in air masses affected by surface emissions from lower altitudes, which may include anthropogenic or biogenic sources. This influence likely develops gradually, eventually creating the right conditions for an NPF event to start. At EAC, the start of NPF was linked to the rapid growth of the boundary layer, which favored the entrainment of air masses from above. The study highlights the role of NPF in modifying atmospheric particles and underscores the varying impacts of urban versus mountain top environments on particle formation processes in the Andean region.

Granular Columns of Binary‐Size Mixtures Collapse on a Horizontal Plane

ABSTRACTThe granular column collapse is a simple model to study natural disasters such as landslides, rock avalanches, and debris flows because of its potential to provide solid links of physical and mechanical properties to these catastrophic flows. Such flows are commonly composed of different grain‐size distributions, namely, polydispersity. Owing to the complexity of different particle‐size phases, explanations of the collapse dynamics, run out distance, and size‐segregation behavior of granular flows remain elusive. A binary‐size mixture of granular materials is well‐known as a simplified version of particle‐size distribution. This paper explores the effects of the large‐particle content on the collapse mobility, deposition morphology, and size segregation of binary‐size mixtures composed in each column geometry. Although the kinetic energy and deposition morphology are nearly insensitive to the content of large particles for each column geometry, the large and small particle‐size phases govern differently on total kinetic energy. Remarkably, the contribution of these two particle phases to the kinetic energy is similar when the large‐particle content reaches around 10% for all column geometries. By quantifying the difference of the apparent friction coefficient of small and large particle phases, the size‐segregation degree of binary‐size mixtures is evaluated. The results noted that the segregation degree increases exponentially with increasing the large‐particle content, but it is nearly independent of the column geometry. These findings complement insights into the flow properties of geological hazards, leading to offering valuable evidence for the management of natural disasters such as landslides and debris flows.

Direct measurement of brake wear particles from a light-duty vehicle under real-world driving conditions

Abstract As tailpipe emissions have decreased, there is a growing focus on the relative contribution of non-exhaust sources of vehicle emissions. Addressing these emissions is key to better evaluating and reducing vehicles’ impact on air quality and public health. Tailoring solutions for different non-exhaust sources, including brake emissions, is essential for achieving sustainable mobility. Studying emissions from vehicles in real-world scenarios provides a better understanding of their environmental impact compared to laboratory testing alone. This study presents findings on the direct measurement of brake particles and the characterization of this source of particulate matter in real-world conditions using a mobile laboratory. In situ measurements of particle concentration and size distribution showed good agreement with previous laboratory studies, indicating the suitability of the approach to investigate break particle emissions during real-world operation. The study demonstrates that particle size distributions can vary based on the temperature of the brake disk, which is influenced by the initial braking speed, with significant variations observed between speeds of 60, 80, 100, and 120 km/h. Particles with sizes between 6 and 523 nm were released into the air from the brake system, although it is likely that larger particles were also emitted but not captured due to the upper detection limit of the Engine Exhaust Particle Sizer. During harsh braking events, such as decelerations of 4.2 m/s2 from 120 km/h, a concentration of up 106 (#/cm3) was measured for particles under 8 nm. Moreover, scanning electron microscope analysis revealed that nanoparticles are present in the form of agglomerates, whose shape can change depending on the formation process. Elements present in the particles comprised mainly iron, copper, and aluminium, indicating wear of the brake pad materials and disk components.

Measurement report: Rocket-borne measurements of large ions in the mesosphere and lower thermosphere – detection of meteor smoke particles

Abstract. We present mass spectroscopic in situ data from rocket flights of two improved ion mass spectrometers in the mesosphere and lower thermosphere region. The instruments were optimized to detect large ions with a mass-to-charge ratio (m/z, mass) of up to m/z 2000 and 20 000 respectively, for analysis of meteor smoke particles. The flights were performed in the framework of the polar mesospheric winter echo (PMWE) campaigns, initiated and coordinated by the Leibniz Institute of Atmospheric Physics (IAP), to investigate polar mesospheric winter radar echoes in Andøya (Norway) in 2018 and 2021. Both flights were successful and allowed the mass number and chemical composition of charged meteor smoke particles to be investigated. We found a complex and diverse composition of positively and negatively charged molecules and particles within our mass range in a region that is notoriously difficult to get mass spectroscopic data from. While at altitudes below 85 km we observed negatively charged particles of up to several thousands of atomic mass units, above this altitude we found possible building blocks of these large particles that form right after their ablation from the parent meteorite material. In the first flight we detected no positively charged particles above m/z 100 and a difficult-to-interpret signal for negatively charged particles beyond our mass range of m/z 2000. In the second flight, however, we detected positively charged particles between around m/z 180 and 350 and a number of different negatively charged particles up to m/z 5500. Due to the very large mass range of m/z 20 000 used in the second flight and the subsequent lower mass resolution, unambiguous mass identification is not possible. A particular interesting pattern was found at 80.8 km of a compound that seems to double its mass around m/z 225, 450, 900 and 1800. Comparing our findings to proposed meteor smoke particle compounds by other authors, our observations would be consistent with magnetite, fayalite and forsterite. However, other possible compounds cannot be excluded.

Using Commercial Bio-Functional Fungal Polysaccharides to Construct Emulsion Systems by Associating with SPI

Fungi polysaccharides are nutraceutical-rich compounds with bioactive properties, offering promising applications in food formulation. This study examined the non-covalent complexation of commercial polysaccharides derived from the fruiting bodies of Auricularia auricula-judae (AA) and Ganoderma lucidum (GL) and soy protein isolate to enhance emulsifying properties. Complexes were examined across protein-to-polysaccharide ratios (0:1 to 1:0), pH levels (3 to 7), and heat treatment conditions. Results indicated a maximum insoluble association at pH 4 for both SPI-AAP and SPI-GLP complexes, with SPI-AAP complexes remaining soluble at pH 3, while SPI-GLP complexes exhibited insolubility. Heat treatment had a limited effect on electrostatically driven complexation but resulted in larger particles through a protein-denaturation-induced increase of hydrophobic interactions. In terms of emulsifying properties, individual GLPs demonstrated superior performance compared to individual AAPs. The GLPs engaged in competitive adsorption at the oil–water interface alongside SPI, resulting in larger emulsion droplet sizes compared to either component alone. The association of either AAPs or GLPs with SPI enhanced the emulsion stability against coalescence and Ostwald ripening. Commercial fungal polysaccharides demonstrate substantial potential for incorporation into manufactured food products, particularly in colloidal formulations.

Optimisation of gradation based on fractal dimension for large-size graded crushed stone

To improve the mechanical properties of large particle size graded crushed stone mixture and obtain the optimal grading. By using different design methods to obtain the grading of large particle size graded crushed stone, the maximum dry density test, CBR penetration test, static pressure test, and cyclic repeated compaction test were conducted on the large particle size graded crushed stone samples. Finally, fractal theory was introduced to quantitatively calculate the grading of large particle size graded crushed stone, and the fractal dimension of large particle size graded crushed stone was obtained. The relationship between the fractal dimension of large particle size graded crushed stone and density, CBR value, compressive strength, and deformation resistance was analyzed through grey correlation analysis. The experimental results show that large particle size graded crushed stone has better skeleton performance than conventional graded crushed stone; The density, CBR value, compressive strength, and deformation resistance of large-sized graded crushed stone are related to the grading. The skeleton dense grading ratio has stronger mechanical properties compared to the suspended dense grading and skeleton interlocking grading. And the optimal fractal dimension for the optimal configuration should be between 2.59−2.61.

Real-time visualisation of fast nanoscale processes during liquid reagent mixing by liquid cell transmission electron microscopy

Liquid cell transmission electron microscopy (LCTEM) is a powerful technique for investigating crystallisation dynamics with nanometre spatial resolution. However, probing phenomena occurring in liquids while mixing two precursor solutions has proven extremely challenging, requiring sophisticated liquid cell designs. Here, we demonstrate that introducing and withdrawing solvents in sequence makes it possible to maintain optimal imaging conditions while mixing liquids in a commercial liquid cell. We succeeded in visualising a fast nanoscale crystallisation mechanism when an organic molecule of R-BINOL-CN dissolved in chloroform interacts with methanol. The scanning transmission electron microscopy images recorded in real-time during the interaction of the two volatile solvents reveal the formation of chain-like structures of R-BINOL-CN particles, whereas they coalesce to form single large particles when methanol is absent. Our approach of mixing liquids establishes a platform for novel LCTEM studies of a wide range of electron-beam-sensitive materials, including drug molecules, polymers and molecular amphiphiles.

Unveiling the impact of biodegradable polylactic acid microplastics on meadow soil health.

Soil microplastics (MPs) pollution has garnered considerable attention in recent years. The use of biodegradable plastics for mulching has led to significant quantities of plastic entering agro-ecosystems. However, the effects of biodegradable polylactic acid (PLA) plastics on meadow soils remain underexplored. This study investigates the impacts of PLA-MPs of varying particle sizes and concentrations on soil physicochemical properties, enzyme activities, and microbial communities through a 60-day incubation experiment. PLA-MPs increased the pH, soil organic matter, total nitrogen (TN) and available potassium (AK) content, as well as enhanced the activities of superoxide dismutase (S-SOD), peroxidase (S-POD), soil catalase (S-CAT), β-glucosidase (S-β-GC) and urease (S-UE) activities. Conversely, a decrease in alkaline phosphatase (S-ALP) activity was observed. The influence of PLA-MPs on soil physicochemical properties was more pronounced with larger particle sizes, whereas smaller particles had a greater effect on enzyme activities. Additionally, PLA-MPs led to an increase in the abundance of Acidobacteriota, Chloroflexi, and Gemmatimonadota, while the abundance of Proteobacteria, Actinobacteriota, and Patescibacteria declined. Mantel test analysis showed that changes in microbial community composition affected soil properties such as pH, AK, S-UE and S-β-GC. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt2) analysis demonstrated that PLA-MPs modify bacterial metabolic pathways. Our results suggest that particle size and concentration of PLA-MPs differentially affect soil nutrients and microbial community structure and function, with more significant effects observed at larger particle sizes and higher concentrations.

Operando Gravimetric and Energy Loss Analysis of Na3V2(PO4)2F3 Composite Films by Electrochemical Quartz Microbalance with Dissipation Monitoring.

The rising demand for energy storage calls for technological advancements to address the growing needs. In this context, sodium-ion (Na-ion) batteries have emerged as a potential complementary technology to lithium-ion batteries (Li-ion). Among other materials, Na3V2(PO4)2F3 (NVPF) is a promising cathode for Na-ion batteries due to its high operating voltage and good energy density. In order to further characterize the (dis)charge behavior of NVPF, the electrochemical quartz crystal microbalance with dissipation monitoring (EQCM-D) was employed to track both the frequency and dissipation loss changes at the electrode/electrolyte interface. The electrode composite preparation proved to be crucial for extending the potential window to both Na3V2(PO4)2F3/Na2V2(PO4)2F3 and Na2V2(PO4)2F3/Na1V2(PO4)2F3 domains. Composites prepared with rawNVPF powder (1-20 μm particles) and polyvinylidene fluoride (PVDF) binder (raw-NVPF:PVDF) exhibited large dissipation changes during (dis)charging, attributed to the soft viscoelastic nature of the binder and substantial hydrodynamic interaction caused by the large particles. On the other hand, composites prepared by sieved NVPF particles (<1 μm particles) with sodium carboxymethyl cellulose (NaCMC) binder (sieved-NVPF:NaCMC) showed rigid properties, enabling an extended and more accurate gravimetric analysis. This allowed for the determination of a linear charge-to-mass relationship for the full potential window of NVPF, reflecting the potential independent insertion/deinsertion of bare Na ions (23 g·mol-1). Additionally, reversible dissipative changes were observed for the Na3V2(PO4)2F3/Na2V2(PO4)2F3 transition, with no further dissipative changes observed during the Na2V2(PO4)2F3/Na1V2(PO4)2F3 process.

Research on Controllable Synthesis and Growth Mechanism of Sodium Vanadium Fluorophosphate Nanosheets.

Sodium vanadium fluorophosphate is a sodium ion superconductor material with high sodium ion mobility and excellent cyclic stability, making it a promising cathode material for sodium-ion batteries. However, most of the literature and patents report preparation through traditional methods, which involve complex processes, large particle sizes, and low electronic conductivity, thereby limiting development progress. Aiming at the limitation of high cost and poor performance of vanadium sodium fluorophosphate cathode material, the low temperature and high-efficiency nano preparation technology was developed. This study uses a homogenizer with high dispersion and shear force to directionally control the collision of sodium vanadium fluorophosphate nanoparticles with higher specific surface energy during the initial nucleation stage, forming nanosheet structures. The growth mechanism of these nanosheets was analyzed using SEM, XRD, AFM, and DFT simulation. Results indicate that the crystal surfaces with higher surface energy undergo directional collisions in the early nucleation stage, gradually reducing the surface energy and stabilizing the system, resulting in sodium vanadium fluorophosphate nanosheets. Due to the larger specific surface area and pore structure, these nanosheets exhibit excellent rate performance and cycle stability, making them suitable for application and promotion in the field of fast-charging energy storage.

Complementary Reducing Agents are Responsible for Temporally Distinct Nucleation and Growth Phases During the Polyol Synthesis of Ag Nanocubes

AbstractEthylene glycol or one of its oxidation products are believed to serve as reducing agents in the shape‐controlled synthesis of Ag nanocubes (NCs) by the polyol process. The identity of end‐groups of polyvinylpyrrolidone (PVP) impacts shape control with alcohol and aldehyde moieties serving as a primary Ag reducing agent. We explored the role of PVP end‐groups in the polyol process by measuring the dependence of particle number density of Ag NCs produced on the initial concentration(s) of Ag and PVP using small angle x‐ray scattering and statistically large particle size distributions analyzed by scanning electron microscopy. The number density of Ag NCs is strongly dependent on the starting concentration of PVP chains demonstrating PVP end‐groups play an important role in the nucleation of NCs. The concentration of Ag+ is 2 orders of magnitude higher than the end‐groups suggesting ethylene glycol must participate in the reduction of Ag+ during growth. Perturbation experiments and analysis of resultant particle size distribution reveal nucleation is fast relative to growth of NCs, reinforcing the synergy between PVP end‐groups and ethylene glycol. The evidence demonstrates PVP end‐groups and ethylene glycol are tandem reducing agents operative in temporally distinct phases of the polyol synthesis of Ag NCs.

Settling velocity of weakly inertial particles in vertical flow

We investigate the settling velocity change of weakly inertial particles, whose density ratio to fluid ranges from 1.35 to 1.38, in vertical water flow. To assess the effect of turbulence, we experimentally examine the dependence of modifications of velocity on physical scales, including time, velocity, and length, between particles and turbulence. It is observed that the settling velocity is either enhanced or hindered by the turbulence compared to stagnant conditions. The change in settling velocity is observed to be responsive to both the inertia of particles and the turbulence intensity. In cases of weak turbulence or with larger particles, the settling velocity exhibits small changes and even decreases. Conversely, the change in settling velocity is more pronounced for smaller particles and in more intense turbulence, reaching a maximum increase at St≈O(10−3). We compare our experimental results with existing studies conducted in solid–liquid two-phase flow, finding a consistent tendency. In both prior research and the present study, the length scale parameter, StSv, has consistently been important in discerning inertial conditions that determine the change in settling velocity under turbulent conditions.