Clusters Of Particles Research Articles

Microstructure Evolution and Creep Properties of AZ61 Magnesium Matrix Composites Reinforced with Bimodal-Sized SiC Particles

In the scope of this exploration, AZ61 magnesium matrix composites fortified with bimodal size SiC particles were synthesized using ultrasonic-assisted mixing in the semi-solid state, which exhibited optimal grain refinement and exceptional creep resistance. We examined the impact of bimodal SiC particles on the microscopic structure and creep deformation of the resulting composites. Our findings indicated that incorporating bimodal SiC particles resulted in the refinement of the matrix grains and alteration of the morphology of the Mg17Al12 phase. Furthermore, the micron-sized SiC particles exhibited a typical necklace-like particle distribution around the grain boundaries of the bimodal SiC particle/AZ61 composites, while the nano-sized SiC particles were mainly located around the micron-sized particles. As the volumetric percentage of micron SiC particles increased, the quantity of nano-sized particle clusters diminished noticeably. Creep analysis at 200 °C and 50 MPa revealed that the creep life of M−6+N−1 composite was increased by 111.9% compared to the AZ61 alloy. Additionally, the M−6+N−1 combination exhibited a significantly lower steady-state creep rate compared to the matrix alloy, with a reduction of approximately 11 times. These results indicate that the bimodal SiC particle/AZ61 composites have superior creep resistance, which is a consequence of the grain refinement and grain boundary pinning effects of SiC particles.

Motility-Induced Clustering of Active Particles under Soft Confinement.

We investigate the structural and dynamic properties of active Brownian particles (APs) confined within a soft annulus-shaped channel. Depending on the strength of the confinement and the Péclet number, we observe a novel reentrant behavior that is not present in unconfined systems. Our findings are substantiated by numerical simulations and analytical considerations, revealing that this behavior arises from the strong coupling between the Péclet number and the effective confining dimensionality of the APs. Our work highlights the peculiarities of soft boundaries for APs and how clogging can be avoided under such conditions.

Hexagonal vortices enable faster colloidal crystal grain coarsening.

We find that localized rotations of hexagonal clusters of particles occur during rapid dissolution of grain boundary loops in two-dimensional colloidal crystals. These particle vortices, or rotating "granules," are distinct from established models for grain boundary diffusion, which predict that a crystal grain enclosed within another crystal will dissolve at a constant rate. Our measurements of colloidal crystal experiments and Brownian dynamics simulations reveal grain boundary motion that is described by two distinct processes: slow dissolution due to the diffusion of individual particles, and rapid dissolution due to collective granule rotation. In the latter process, hexagonal clusters of particles rotate together in granules whose shape and position are determined by the underlying moiré pattern. Furthermore, these vortices guide cooperative strings of particles that move along the edges of the hexagonal granules. Including this vortex mechanism may improve models for grain coarsening in polycrystalline materials, ultimately offering improved predictions for the time evolution of material properties.

Discrete magnification lens model: A new hybrid multi-scale modelling method for fluid-particle systems

We present a novel hybrid multi-scale model, referred to as “discrete magnification lens” method, which utilizes a computational fluid dynamics coupled to discrete element method (CFD-DEM) approach within a specific region of interest in a two-fluid model (TFM) simulation. We applied the discrete magnification lens to the crossing jet problem, where the TFM fails due to lack of considering bi-modal velocity distribution in its formulation. It was observed that adopting the discrete magnification lens, can effectively alter the non-physical behavior of the TFM to obey the behavior seen from CFD-DEM simulations. Moreover, the ability of the discrete magnification lens in reproducing particle clusters and improving the TFM predictions in case of unbounded fluidization simulations was further shown. We found that the discrete magnification lens can effectively enhance the TFM predictions in a complex fluid-particle system while requiring less numerical costs compared to the full-scale CFD-DEM simulations.

Fabrication of a Stable and Highly Effective Anode Material for Li-Ion/Na-Ion Batteries Utilizing ZIF-12.

Transition metal selenides (TMSs) are receiving considerable interest as improved anode materials for sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs) due to their considerable theoretical capacity and excellent redox reversibility. Herein, ZIF-12 (zeolitic imidazolate framework) structure is used for the synthesis of Cu2Se/Co3Se4@NPC anode material by pyrolysis of ZIF-12/Se mixture. When Cu2Se/Co3Se4@NPC composite is utilized as an anode electrode material in LIB and SIB half cells, the material demonstrates excellent electrochemical performance and remarkable cycle stability with retaining high capacities. In LIB and SIB half cells, the Cu2Se/Co3Se4@NPC anode material shows the ultralong lifespan at 2000 mAg-1, retaining a capacity of 543 mAhg-1 after 750 cycles, and retaining a capacity of 251 mAhg-1 after 200 cycles at 100 mAg-1, respectively. The porous structure of the Cu2Se/Co3Se4@NPC anode material can not only effectively tolerate the volume expansion of the electrode during discharging and charging, but also facilitate the penetration of electrolyte and efficiently prevents the clustering of active particles. In situ X-ray difraction (XRD) analysis results reveal the high potential of Cu2Se/Co3Se4@NPC composite in building efficient LIBs and SIBs due to reversible conversion reactions of Cu2Se/Co3Se4@NPC for lithium-ion and sodium-ion storage.

Machine Learning‐Based Clustering of Oceanic Lagrangian Particles: Identification of the Main Pathways of the Labrador Current

AbstractModeled geospatial Lagrangian trajectories are widely used in Earth Science, including in oceanography, atmospheric science and marine biology. The typically large size of these data sets makes them arduous to analyze, and their underlying pathways challenging to identify. Here, we show that we can use a machine learning unsupervised k‐means++ clustering method combined with expert aggregation of clusters to identify the pathways of the Labrador Current from a large set of modeled Lagrangian trajectories. The presented method requires simple pre‐processing of the data, including a Cartesian correction on longitudes and a principal component analysis reduction. The clustering is performed in a kernelized space and uses a larger number of clusters than the number of expected pathways. To identify the main pathways, similar clusters are grouped into pathway categories by experts in the circulation of the region of interest. We find that the Labrador Current mainly follows a westward‐flowing and an eastward retroflecting pathway (20% and 50% of the flow, respectively) that compensate each other through time in a see‐saw behavior. These pathways experience a strong variability (representing through time 4%–42% and 24%–73% of the flow, respectively). Two thirds of the retroflection occurs at the tip of the Grand Banks, and one quarter at Flemish Cap. The westward pathway is mostly fed by the on‐shelf branch of the Labrador Current, and the eastward pathway by the shelf‐break branch. Among the pathways of secondary importance, we identify a previously unreported one that feeds the subtropics across the Gulf Stream.

A method to prevent clogging and clustering in microfluidic systems using microbubble streaming.

This paper presents an innovative strategy to address the issues of clogging and cluster-related challenges in microchannels within microfluidic devices. Leveraging three-dimensional (3D) microbubble streaming as a dynamic solution, our approach involves the controlled activation of microbubbles near channel constrictions, inducing microstreaming with distinctive features. This microstreaming, characterized by a high non-uniform 3D gradient and significant shear stress, effectively inhibits arch formation at constrictions and disintegrates particle clusters, demonstrating real-time prevention of clogging incidents and blockages. This study includes experimental validation of the anti-clogging technique, a detailed examination of microstreaming phenomena, and their effects on clogging and clustering issues. It also incorporates statistical analyses performed in various scenarios to verify the method's effectiveness and adaptability. Moreover, a versatile control system has been designed that operates in event-triggered, continuous, or periodic modes, which suits different lab-on-a-chip applications and improves the overall functionality of microfluidic systems.

Numerical Investigation of the Effect of Inhomogeneous Flow Behaviors inside a Particle Cluster in the OCM Reaction

Numerical Investigation of the Effect of Inhomogeneous Flow Behaviors inside a Particle Cluster in the OCM Reaction

Influence of Nanoparticles and PVA Fibers on Concrete and Mortar on Microstructural and Durability Properties

Nanoparticles are one of the effective methodologies implemented in concrete technology. The main objective of this research is to study the influence of nano alumina with different percentage variations ranging from 1% to 3% along with the incorporation of PVA fibers. From the mechanical properties test, the optimum dosage was determined to further study the durability behavior. This research work also investigates the hybridization of two nanoparticles such as nano silica (NS) and nano alumina (NA). The results show that the increasing quantity of NA reduces the compressive strength of the mortar due to agglomeration (cluster of particles), which results in a greater molecular attraction force. From the test results, it is concluded that the optimum dosage has been attained with an addition of 2% NA with 0.3% PVA. The compression strength test results at 14 days and 28 days reveal that the addition of NA tends the mineral admixture to react at early ages in the hydration process, which produces a new chemical compound to fill the pores. The rapid chloride penetration (RCPT) test results at 28 days significantly improved with the incorporation of nanoparticles due to their effective size and chemical reaction towards the other compounds. The test results from the hybridization of nanoparticles showed that the compressive strength was significantly enhanced compared to that of the control mortar and mortar with NA. They are effective up to certain limits beyond that addition, and the workability was reduced. Amongst all mixtures, the maximum compression strength has been attained for the mix with the addition of NA 0.5% and NS 2.5% comparatively. The microstructural properties of mortar were also studied through scanning electron microscope (SEM) analysis. The results showed that the incorporation of nanoparticles in the mortar matrix turns homogeneous with fewer pores and greater amount of hydration compounds; thereby, pore refinement has improved the hydration compounds remarkably.

Structural and chemical evolutions of a magnesium vanadium oxide cathode under electrochemical cycling in magnesium batteries

The design of cathode materials that remain chemically and structurally stable during repetitive ion insertion and extraction poses a significant challenge in developing multivalent batteries. The cycling stability of traditional metal oxide-based cathode is challenged by sluggish diffusion of multivalent cations and parasitic reactivity at interfacial regimes, including the cathode electrolyte interphase layer (CEI). Understanding the reactions at the cathode-electrolyte interface, particularly those induced by non-stoichiometric surface layers, is a crucial design parameter for both cathode materials and electrolytes. In this study, we employed multimodal analysis, including in situ and ex situ X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (TEM) and electrochemical impedance spectroscopy (EIS) to examine the surface reactions and subsequent structural and chemical evolutions of the CEI on high voltage magnesium vanadium oxide (MgV2O4) spinel cathode during the Mg2+ insertion/extraction processes. The results revealed that the presence of non-stoichiometric surface layers in the magnesium vanadium oxide cathode drive the decomposition of bis(trifluoromethanesulfonyl)imide (TFSI-) anion, leading to the formation of the CEI layer. The CEI layer could inhibit the Mg2+ ion transfer processes. Accompanying this reactivity-driven degradation, the magnesium vanadium oxide cathode undergoes pulverization, forming clusters of nanosized particles. This process likely improves cycling ability by creating new intercalation sites and shortening the diffusion pathway for the Mg2+ cations. This study demonstrates that controlling surface stoichiometry and engineering morphological properties are critical design parameters for high performance cathodes for multivalent batteries.

Synthesis and Characterization of Vanadium Nitride/Carbon Nanocomposites.

The present work focuses on the synthesis of a vanadium nitride (VN)/carbon nanocomposite material via the thermal decomposition of vanadyl phthalocyanine (VOPC). The morphology and chemical structure of the synthesized compounds were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), Fourier transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray photoemission spectroscopy (XPS). The successful syntheses of the VOPC and non-metalated phthalocyanine (H2PC) precursors were confirmed using FTIR and XRD. The VN particles present a needle-like morphology in the VN synthesized by the sol-gel method. The morphology of the VN/C composite material exhibited small clusters of VN particles. The XRD analysis of the thermally decomposed VOPC indicated a mixture of amorphous carbon and VN nanoparticles (VN(TD)) with a cubic structure in the space group FM-3M consistent with that of VN. The XPS results confirmed the presence of V(III)-N bonds in the resultant material, indicating the formation of a VN/C nanocomposite. The VN/C nanocomposite synthesized through thermal decomposition exhibited a high carbon content and a cluster-like distribution of VN particles. The VN/C nanocomposite was used as an anode material in LIBs, which delivered a specific capacity of 307 mAh g-1 after 100 cycles and an excellent Coulombic efficiency of 99.8 at the 100th cycle.

In Situ Lung Dust Analysis by Automated Field Emission Scanning Electron Microscopy With Energy Dispersive X-ray Spectroscopy: A Method for Assessing Inorganic Particles in Lung Tissue From Coal Miners.

Overexposure to respirable coal mine dust can cause severe lung disease including progressive massive fibrosis (PMF). Field emission scanning electron microscopy with energy dispersive x-ray spectroscopy (FESEM-EDS) has been used for in situ lung dust particle analysis for evaluation of disease etiology. Automating such work can reduce time, costs, and user bias. To develop and test an automated FESEM-EDS method for in situ analysis of inorganic particles in coal miner lung tissue. We programmed an automated FESEM-EDS procedure to collect particle size and elemental data, using lung tissue from 10 underground coal miners with PMF and 4 control cases. A statistical clustering approach was used to establish classification criteria based on particle chemistry. Data were correlated to PMF/non-PMF areas of the tissue, using corresponding brightfield microscopy images. Results for each miner case were compared with a separate corresponding analysis of particles recovered following tissue digestion. In situ analysis of miner tissues showed higher particle number densities than controls and densities were generally higher in PMF than non-PMF areas. Particle counts were typically dominated by aluminum silicates with varying percentages of silica. Compared to digestion results for the miner tissues, in situ results indicated lower density of particles (number per tissue volume), larger size, and a lower ratio of silica to total silicates-probably due to frequent particle clustering in situ. Automated FESEM-EDS analysis of lung dust is feasible in situ and could be applied to a larger set of mineral dust-exposed lung tissues to investigate specific histologic features of PMF and other dust-related occupational diseases.

Dielectric resonance of composites containing randomly distributed ZrB2 particles with continuous dual-peak microwave absorption

Substantial efforts have been devoted to the elaborate component and microstructure design of absorbents (inclusions) in microwave absorbing (MA) composite materials. However, the mesoscopic architecture of composites also plays a significant role in prescribing their electromagnetic properties, which is rarely explored in studies of MA materials. Herein, a composite containing randomly distributed ZrB2 particles is fabricated to offer a mesoscopic cluster configuration, which produces dielectric resonance. The resonance disappears and reoccurs when ZrB2 is coated with insulating and semiconductive ZrO2 layers, respectively, suggesting that it is a plasmon resonance excited by electron transport between ZrB2 particles in clusters rather than any intrinsic resonance of the materials constituting the composite. The resonance strength can be regulated by controlling the quantity of electron transport between particles, which is accomplished by gradually increasing the insulating ZrO2-coated ZrB2 ratio, x, to disturb the electron transport in ternary disordered composites containing ZrB2 and insulating ZrO2-coated ZrB2. When x exceeds 0.7, the electron transport is cut off completely and the resonance thus disappears. The resonance induces double quarter-wavelength (1/4λ) interference cancellations or resonance absorption coupled with 1/4λ interference cancellation, giving rise to continuous dual-peak absorption. This work highlights the significance of mesoscopic architectures of composites in MA material design, which can be exploited to prescribe electromagnetic properties.

Study on the influence of TBM disc cutter on the penetration of extremely hard rock in Zijing Tunnel

The reasonable setting of TBM disc cutter penetration depth is crucial for its rock-breaking efficiency in extremely hard rock geology. In the construction section of the Dujiangyan to Mount Siguniang Zijing Tunnel project, which encountered extremely hard diorite rock (with uniaxial compressive strength exceeding 230 MPa), to reveal the influence of penetration depth on disc cutter cutting of extremely hard diorite rock, the following steps were taken: Firstly, using a self-developed small-scale disc cutter linear rock-breaking test platform, experiments were conducted for four penetration depths: 1.5, 2.0, 2.5, and 3.0 mm, under fixed cutter spacing and with/without confinement conditions. Secondly, employing a high-precision crystalline rock material modeling method based on three-dimensional particle clusters, a full-scale numerical model of disc cutter linear cutting of diorite rock was established. Seven penetration depths ranging from 1.0 to 10.0 mm were tested under a fixed cutter spacing of 80 mm. Results indicate that under lateral confinement, diorite failure shifts from slip and extrusion to crushing, while under no confinement, it primarily spalls laterally with increased rock debris and ejection distance as penetration increases. Disc cutter normal force rises with penetration, with a critical 4mm point after which load increases slowly but penetration significantly, marking an efficient rock breaking stage. Specific energy efficiency peaks at 3mm penetration in tests and 4mm in simulations, attributed to test bench limitations. Combined results suggest an optimal penetration of 4mm.

Lambda motion and cluster states of [formula omitted] predicted via neural networks guided microscopic calculation

We investigate the Λ particle motion and cluster states of BeΛ9−11 using a novel multiple cooling approach guided by the Control Neural Networks method (Ctrl.NN). The numerical results are well reproduced, and the Ctrl.NN method shows rapid convergence concerning the set of the basis states in comparison to traditional generator coordinate method (GCM) calculations. Taking advantage of this merit, we calculate ground state energies and rotational bands of BeΛ9−11 which agree well with experimental observations. By analyzing the density distributions of the main basis, a slight short-range repulsive correlation between Λ particle and α clusters in directions perpendicular to the axis of the Be8 core is revealed. The Λ particle presents a significant broad distribution as a consequence of this correlation, which we call an “analog π-orbit” structure. Furthermore, we prove that this correlation originates from the competition between kinetic energy and Λ-N interaction, as indicated by the energy curves for different configurations of BeΛ9. In the ground states of BeΛ10 and BeΛ11, the Λ particle is confined in a cage-like structure of core nuclei formed by two α clusters and valence neutrons. These structures lead to the development of more compact Λ particle configurations, and the shrinkage of α-α relative distance is also well reproduced.

How does a structurally similar background language influence L3 grammars? A study on the syntax of L2/L3 Mandarin [SI 21/3]

ABSTRACT This article reports on an empirical study of L3 Mandarin, aiming to shed light on transfer effects and their interaction with other factors throughout the L3 acquisition trajectory. A fill-in-the-blank task was employed to examine L2 and L3 acquisition of three types of Mandarin sentence-final particle clusters. Participants in the study were Mandarin native speakers, L1 English-L2 Mandarin speakers, L1 English-L2 Cantonese-L3 Mandarin speakers, and L1 Cantonese-L2 English-L3 Mandarin speakers at low and high Mandarin proficiency levels. Our data support arguments in the L3 literature that transfer at the L3 initial stages is from a structurally more similar language. Facilitation takes place when the instantiation of the target property in the L3 is exactly the same as that in the transfer source language. Overall typological similarity might be helpful when transfer is from the L1, but it does not always facilitate the L3 acquisition of individual properties. For later L3 development, construction frequency and mapping paradigms have a great impact on the acquisition outcome. Moreover, a certain kind of non-facilitative transfer from an L1 is found to persist in L3 Mandarin grammars, which qualitatively supports the Cumulative Input Threshold Hypothesis.

Impact of ZnO nanoparticles on Mn0.5Fe2.5O4@C/ZnO-DOX nanocomposites as antibacterial agents and drug loading materials

A series of Mn0.5Fe2.5O4@C/ZnO-DOX nanocomposites were successfully synthesized using the hydrothermal method with different ZnO masses. The novelty of this study was the obtained Mn0.5Fe2.5O4@C/ZnO-DOX nanocomposite as a good candidate as an antibacterial agent and drug delivery material. The IR spectra showed that the samples were successfully formed. The vibrations of Fe–O and Mn–O were detected at 678.94–563.21cm−1, and that of Zn–O was located at 933.55–867.97cm−1. Meanwhile, the XRD pattern showed that the samples have two crystal phases, i.e. magnetite and ZnO. The nanostructure of the samples was studied by SAXS, showing that the Mn0.5Fe2.5O4@C/ZnO-DOX nanocomposite formed clustering particles that were structured by secondary and primary particles. The secondary particles in the samples contained about 3–4 primary particles. The magnetic properties were characterized using VSM, showing that the samples have superparamagnetic behavior. The increase in ZnO mass affected the saturation magnetization value. The highest saturation magnetization value was approximately 8.66 emu/g for the sample with the smallest ZnO mass. The samples contained Fe2+, Fe3+, and ZnO2+ ions, which created oxidative stress that damaged the DNA cells of bacteria, as seen from the results of the antibacterial activity test. In addition, it was found that the Mn0.5Fe2.5O4@C/ZnO-DOX nanocomposite has another potential as a drug loader material. As the ZnO mass increased, the drug loading efficiency also increased up to 75%. Thus, the prepared Mn0.5Fe2.5O4@C/ZnO-DOX nanocomposites have potential as antibacterial agents and drug loading materials.

A unified description of ion exchange and complete adsorption isotherms, including cluster growth and cavity filling

In the context of micro- and mesoporous materials, the interpretation of ion exchange and gas adsorption isotherms rarely covers the full information content of the experimental data. Based on our earlier work regarding the role of entropy in multiple equilibria, we have revisited cation exchange data of zeolite A in more detail and addressed the analysis of Ar and N2 adsorption isotherms of nonporous, microporous and mesoporous silicates. The previously reported analysis is thereby extended and improved. The theory is presented in a unified and compact manner through rigorous application of the concept of fractional amount, including particle distribution, cluster growth, and cavity filling. A result is that the structure of mesoporous silica MCM-41 can be described as consisting of the main channel and two types of cavities, which can be interpreted as surface roughness. In a further step, the information delivered by the inflection points in type I, II and IV gas adsorption isotherms is considered. The adsorption of simple gases begins with the formation of a monolayer on the pristine surface. The inflection point thereby represents the start of a new process, indicating that the adsorption isotherms must be understood as the signature of several sequential chemical equilibrium steps. Information can be extracted by inspecting this signature more closely. The results demonstrate the ability of the reported procedure to elicit additional insight including structural features from experimental equilibrium isotherm data.

Ring-shaped colloidal patterns on saline water films

HypothesisElectrostatically stabilised colloidal particles destabilise when brought into contact with cations causing the particles to aggregate in clusters. When a drop with stabilised colloidal partices is deposited on a liquid film containing cations the delicate balance between the fluid-mechanical and physicochemical properties of the system governs the spreading dynamics and formation of colloidal particle clusters. ExperimentsHigh-speed imaging and digital holographic microscopy were used to characterise the spreading process. FindingsWe reveal that a spreading colloidal drop evolves into a ring-shaped pattern after it is deposited on a thin saline water film. Clustered colloidal particles aggregate into larger trapezoidally-shaped ‘supraclusters’. Using a simple model we show that the trapezoidal shape of the supraclusters is determined by the transition from inertial spreading dynamics to Marangoni flow. These results may be of interest to applications such as wet-on-wet inkjet printing, where particle destabilisation and hydrodynamic flow coexist.

Research on the generalization issue of the heterogeneous QC-EMMS drag model for gas-solid fluidization

In the circulating fluidized bed (CFB), the non-uniform mesoscale structure formed by the particle clustering effect causes a substantial decrease in the gas-solid drag. Since the degree of particle clustering varies with operating conditions, an accurate drag model needs to be universal in different heterogeneous flow conditions. In this study, the relationships between the Ψ factor in clusters' solid holdup model that characterizes the flow non-uniformity and the operating parameters of CFB (including slip velocity Reynolds number, Re*, bed-averaged solid volume fraction, εs,bed, and solid mass circulation rate, Gs) are established. It improves the adaptability of the QC-EMMS drag model under different working conditions. In previous research, we established two types of models that related Ψ factor to Re* and εs,bed respectively. However, there exists a problem of high dispersion of points, indicating that the selected parameters cannot fully describe the flow non-uniformity. Therefore, Gs is reintroduced to modify the two types of models. The results show that the prediction accuracy of the modified models is improved and the relative error is <10%, indicating that the non-uniform factor Ψ has a strong correlation with Gs. In addition, the quantitative relation between Re*, εs,bed, and Gs is derived from modified models, and the trend of relation is highly consistent with the fluidization diagram proposed by Yerushalmi J., which verifies the accuracy of modified models. Finally, numerical simulation of typical CFB cases proves the adaptability of the modified models in wide operating conditions of fluidization.