High-density Particles Research Articles

Lagrangian and Eulerian modelling of river plumes in the Great Barrier Reef system, Australia

In this paper, we describe methods to verify the adequacy and accuracy of Lagrangian particles from a Lagrangian model to reproduce the concentrations of a passive tracer from an Eulerian-model in river plumes. The modelling simulates plumes from two major rivers discharging in the Great Barrier Reef (GBR), Australia, under real-world scenarios. The study has been a part of a major project to aid in the protection of the GBR system from the impacts of extreme events and climate change. We employ the Regional Ocean Modelling System (ROMS) activated with its built-in Lagrangian model, and forced with wind fields from global models and recorded river volume discharges. The ROMS-Lagrangian model tracks the Lagrangian particles using the spatially interpolated velocities computed on the Eulerian ROMS three-dimensional (3D) grid. The Lagrangian particles are released in the river in proportion to the measured river volume flux. We apply a novel technique that exploits Voronoi polygon areas to convert Lagrangian particle separation into a concentration field. This facilitates comparison with the passive tracer concentrations driven by the Eulerian velocities computed on the ROMS 3D grid. We evaluate the fate of Lagrangian particles activated on a 4-km grid resolution with those of equivalent Eulerian tracer concentrations. For validation, we compare the Lagrangian particles with the Eulerian passive tracer simulated using a higher model grid resolution of 500-m, and found that the computed Lagrangian particle concentrations showed similar overall patterns compared to the passive tracer concentrations from both the coarse 4-km, and high-resolution 500-m Eulerian models. The spatial extent of the particles was in better agreement with the coarse 4-km model than with the higher resolution 500-m model. The clustering of particles resulted in structures at finer scales than the Eulerian model, over the high particle density areas that compared well against observations. The Lagrangian particles are able to capture the general river plume patterns seen in the satellite MODIS images and the satellite derived Chlorophyll-a. We further compare the online ROMS model with an offline particle tracker, OceanPARCELS and determined the similarity of results from both online and offline methods. Overall, our study demonstrates the viability to use Lagrangian particles to reproduce the Eulerian tracer properties, which can be combined with particle properties include tracer age providing to enhance the guidance on the distribution and concentration of effluent from localised flooding river events.

Active droplet driven by collective chemotaxis.

Surfactant-laden fluid interfaces of soft colloids, such as bubbles and droplets, are ubiquitously seen in various natural phenomena and industrial settings. In canonical systems where microparticles are driven in hydrodynamic flows, convection of the surfactant changes local surface tension. Subsequently, the interplay of Marangoni and hydrodynamic stresses leads to rich interfacial dynamics that directly impact the particle motions. Here we introduce a new mechanism for self-propelled droplets, driven by a thin layer of chemically active microparticles situated at the interface of a suspended droplet, which is a direct extension of the planar collective surfing model by Masoud and Shelley (H. Masoud and M. J. Shelley, Phys. Rev. Lett., 2014, 112, 128304). These particles can generate chemicals locally, leading to spontaneous Marangoni flows that drive the self-aggregation of microparticles. This process, in turn, creates a polarized surfactant distribution, which induces collective chemotaxis and dipolar bulk flows, ultimately breaking the symmetry. By assuming the local surfactant production to be either proportional to particle density or saturated at a high particle density, we observe that the system can be chemotactically diverging or approach a steady state with constant migration velocity. The system is studied analytically in the linear region for the initial transient dynamics, yielding critical numbers and familiar patterns, as well as numerically for larger amplitudes and over a long time using spectral methods.

Single-Shot High-Density Volumetric Particle Imaging Enabled by Differentiable Holography

Single-Shot High-Density Volumetric Particle Imaging Enabled by Differentiable Holography

Maximizing Photoelectrochemical Performance in Metal-Oxide Hybrid Composites via Amorphous Exsolution-A New Exsolution Mechanism for Heterogeneous Catalysis.

Exsolution generates metal nanoparticles anchored within crystalline oxide supports, ensuring efficient exposure, uniform dispersion, and strong nanoparticle-perovskite interactions. Increased doping level in the perovskite is essential for further enhancing performance in renewable energy applications; however, this is constrained by limited surface exsolution, structural instability, and sluggish charge transfer. Here, hybrid composites are fabricated by vacuum-annealing a solution containing SrTiO3 photoanode and Co cocatalyst precursors for photoelectrochemical water-splitting. In situ transmission electron microscopy identifies uniform, high-density Co particles exsolving from amorphous SrTiO3 films, followed by film-crystallization at elevated temperatures. This unique process extracts entire Co dopants with complete structural stability, even at Co doping levels exceeding 30%, and upon air exposure, the Co particles embedded in the film oxidize to CoO, forming a Schottky junction at the interface. These conditions maximize photoelectrochemical activity and stability, surpassing those achieved by Co post-deposition and Co exsolution from crystalline oxides. Theoretical calculations demonstrate in the amorphous state, dopant─O bonds become weaker while Ti─O bonds remain strong, promoting selective exsolution. As expected from the calculations, nearly all of the 30% Fe dopants exsolve from SrTiO3 in an H2 environment, despite the strong Fe─O bond's low exsolution tendency. These analyses unravel the mechanisms driving the amorphous exsolution.

Laser powder bed fusion of oxide dispersion strengthened FeCrAl alloy: Processing and microstructural evolution

Optimizing and regulating the process parameters to form a uniform distribution of nanosized dispersoids remains a major challenge in additive manufacturing oxide dispersion strengthened (ODS) alloys. This study introduces the influence of scanning speed and laser power on the microstructure evolution of laser powder bed fusion (LPBF) ODS FeCrAl alloy. Low laser power and high scanning speed reduce the size of oxide particles and increase their number density. The energy density threshold is 83 J/m3, below which the powder fails to achieve complete melting, leading to the formation of defects during solidification. High density and large number of oxide particles were obtained for the printed samples under the parameters of 140 W laser power and 600 mm/s scanning speed. The average size and number density of oxide particles were ∼ 21.61 nm and ∼ 1.8 × 1020/m3, respectively. High scanning speed have a rapid cooling rate which affects the dislocation density and the average width of the columnar grains. Low laser power significantly weakens the 〈100〉 fiber texture, which is related to the degree of recrystallization in the remelted region. The core-shell oxides consisting of Y-Al-O and Y-Ti-O were distributed in the samples deposited at low and high laser powers, respectively. The formation of core-shell oxide particles in LPBF ODS FeCrAl alloys involves solid-state amorphization and recrystallization. This study can be a guideline to achieve materials with specific microstructure for ODS alloys.

Dispersion stabilization of carbonyl iron particles and its applications in chemical mechanical planarization

A novel aqueous magnetorheological (MR) slurry is proposed for potential application in the planarization of dielectric substrates, eliminating the need for traditional polishing pads. The preparation of a stable MR slurry hinges on the dispersion properties of abrasives and magnetic responsive particles, particularly high-density carbonyl iron particles (CIP). This study focuses on investigating the dispersion stabilities of CIP and its modified form, SiO2-coated CIP (SiO2@CIP), with the addition of ammonium polyacrylic acid (PAA-NH4) as a dispersant. Experimental measurements, including adsorption isotherms and zeta potential, combined with numerical simulations using density-functional theory, explore the adsorption behavior of PAA-NH4 on CIP and SiO2@CIP. Rheological and sedimentation analyses confirm PAA-NH4’s effectiveness in dispersing both particles. We elucidate the dispersion stabilization mechanism through calculations based on the Derjaguin−Landau−Verwey−Overbeek theory. In MR polishing, SiO2 coating on CIP improves efficiency, reducing surface roughness from over 8 nm (using CIP) to less than 8 Å (using SiO2@CIP). The addition of PAA-NH4 augments dispersion properties, leading to further enhancements in polishing efficiency, resulting in a surface roughness reduction to 2 Å and a simultaneous increase in material removal rate. We thoroughly examine the underlying factors driving these improvements.

Characteristics of local flow structure with different particle properties in a gas-solid diameter-varying fluidized bed

The effects of particle property on gas-solid flow in the diameter-varying riser are experimentally examined using the optical fiber probe in this research. Local flow features are obtained by signal analysis method under the operating conditions of 3–7 m/s and 8–63 kg/m2s. The results show that solid holdup distribution of glass beads is wider than that of catalyst particle particles in the wall region but is narrow in the center region. Solid holdup fluctuations tend to decrease with the increase of particle density under low-concentration conditions but increase at high-concentration conditions. The results from power spectrum density (PSD) show that the increase in particle density strengthens the periodic flow features in the enlarged section. The motion intensity decreases at the particle level but increases at the cluster level for high-density particles. Additionally, as particle density rises, the solid concentration discrepancies between the straight section and the enlarged section widen. In contrast to the upper straight section, the effects of particle density on gas-solid flow are minimal in the enlarged section.

Enhancing strength and ductility of Al-matrix composite via a dual-heterostructure strategy

Aluminum matrix composites (AMCs) often have low ductility, which has been a long-lasting issue in the last few decades. This problem arises largely from the non-deformability of reinforcement particles, which leads to premature failure of the matrix-particle interfaces. Here we propose a new microstructural design strategy for AMCs: distribute the reinforcement particles non-uniformly to form dual-heterostructured AMCs. The zones with high-density particles are recognized as the hard zones, which carry less plastic strain than the particle-free zones to prevent premature interfacial failure. A dual-heterostructured Al-matrix nanocomposite is fabricated, in which AlN nanoparticles are distributed in a dual-level hierarchy: first level heterogeneous nanoparticle distribution and second level heterogeneous zones with different grain sizes. The dual heterostructure produced a unique dual level hetero-deformation induced (HDI) strengthening and hardening to produce high strength and ductility. The dual level HDI strengthening effect has been revealed by the inflection points on the loading-unloading-reloading stress-strain curves. Furthermore, the evolution of local strain fields during the in-situ tensile deformation directly proved the occurrence of strain partitioning, in which the ductile particle free zones have carried a larger strain than the hard particle rich zones. Dispersive shear strain bands are observed for the first time in AMCs. These findings are expected to help design other metal matrix composites with superior mechanical properties.

Measuring many-body distribution functions in fluids using test-particle insertion.

We derive a hierarchy of equations, which allow a general n-body distribution function to be measured by test-particle insertion of between 1 and n particles. We apply it to measure the pair and three-body distribution functions in a simple fluid using snapshots from Monte Carlo simulations in the grand canonical ensemble. The resulting distribution functions obtained from insertion methods are compared with the conventional distance-histogram method: the insertion approach is shown to overcome the drawbacks of the histogram method, offering enhanced structural resolution and a more straightforward normalization. At high particle densities, the insertion method starts breaking down, which can be delayed by utilizing the underlying hierarchical structure of the insertion method. Our method will be especially useful in characterizing the structure of inhomogeneous fluids and investigating closure approximations in liquid state theory.

Microwave plasma-produced Al/Al2O3 microparticles as precursors for high-temperature high-strength composites

Microwave plasma-produced Al/Al2O3 microparticles as precursors for high-temperature high-strength composites

Effect of Partial Replacement of Fine Aggregate with Copper Slag and CRT With Addition of Aramid Kevlar Fiber

Abstract: Concrete is the most widely used construction material and the second most consumed substance in the world. Different Copper Slag and CRT concretes were created in this study by using Aramid Kevlar fiber in place of fine Aggregates. Every construction makes use of a significant amount of concrete because of its importance. Cathode-Ray Tube (CRT) technology has lagged behind as a result of the constant replacement of new technologies, such as LED Display Panel and Liquid Crystal Displays (LCD), which is leading to an increase in the number of discarded CRTs that need to be disposed of each year globally. The heavy waste material known as CRT funnel glass can increase the weight per unit of concrete. In terms of the components of products made during the copper production process, copper slag qualifies as an industrial product. It is a crystalline granular substance that can be utilized as a finer aggregate in concrete because of its high density and sand-like particle size. Aramid Kevlar fiber are completely synthetic organic polymers, aromatic polyamides are sometimes known as kevlar fiber.

Comparative analysis of particle density effects on initial fluidization in gas-solid fluidized beds

Gas-solids fluidization technology is commonly used in chemical engineering processes involving high-density particles, often encountering poor defluidization phenomena. However, there is limited research examining the applicability of flow characteristics and empirical correlations established for low-density, easily fluidizable particles in guiding the flow behavior of high-density particles. This knowledge gap poses significant challenges for designing and operating fluidized beds in relevant processes involving high-density particles. This study comprehensively evaluates the effect of particle density on hydrodynamics during the initial fluidization stage using experimental, empirical correlations and simulation methods. Results of preliminary experiments indicate that empirical correlations for predicting Umf may exhibit significant errors of high-density particles. However, the experiments face challenges in eliminating the influence of different particle size distribution. In contrast, the simulation results present a high consistency with the experiments after sensitivity analysis. Further simulation results illustrate that empirical correlations for Umf may only yield relatively accurate predictions within the narrow density range. As the particle density increases, the predicted errors tend to increase. During the initial fluidization stage, three distinct fluidization stages can be observed, as revealed by both experiments and simulations. These stages can be attributed to the practical particle size distribution. Furthermore, it is noted that as the particle density increases, the fluidization performance tends to deteriorate. This study endeavors to advance the understanding of the effect of particle density on hydrodynamics during the initial fluidization stage. Nonetheless, more studies are still needed to enhance and deepen the current knowledge of the fluidization of high-density particles.

Enhancement of recombinant adeno-associated virus activity by improved stoichiometry and homogeneity of capsid protein assembly

Studies of recombinant adeno-associated virus (rAAV) revealed the mixture of full particles with different densities in rAAV. There are no conclusive results because of the lack of quantitative stoichiometric viral proteins, encapsidated DNA, and particle level analyses. We report the first comprehensive characterization of low- and high-density rAAV serotype 2 particles. Capillary gel electrophoresis showed high-density particles possessing a designed DNA encapsidated in the capsid composed of (VP1+ VP2)/VP3= 0.27, whereas low-density particles have the same DNA but with a different capsid composition of (VP1+ VP2)/VP3= 0.31, supported by sedimentation velocity-analytical ultracentrifugation and charge detection-mass spectrometry. Invitro analysis demonstrated that the low-density particles had 8.9% higher transduction efficacy than that of the particles before fractionation. Further, based on our recent findings of VP3 clip, we created rAAV2 single amino acid variants of the transcription start methionine of VP3 (M203V) and VP3 clip (M211V). The rAAV2-M203V variant had homogeneous particles with higher (VP1+VP2)/VP3 values (0.35) and demonstrated 24.7% higher transduction efficacy compared with the wild type. This study successfully provided highly functional rAAV by the extensive fractionation from the mixture of rAAV2 full particles or by the single amino acid replacement.

CFD-DEM simulation of high density particles fluidization behaviors in 3D conical spouted beds

The spouted bed has been used in the coating process of high-density nuclear fuel particle. The particle fluidization behaviors in pseudo-2D and 3D spouted beds were simulated and validated. The effects of four independent variables (cone angle, particle density, inlet gas velocity, and particle loading) on particle fluidization behaviors in the 3D spouted bed were investigated systematically. The cone angle effect on fluidization mechanism was studied quantitatively first time. A new fluidization quality index was proposed based on the particle entrainment principle, and an extreme value was obtained when the cone angle was 60°, considered to be the optimum value for the 3D conical spouted bed. It was indicated the gas–solid contact efficiency can be kept up if the gas velocity was proportional to ρp0.65 and Np0.78 when the particle density or loading was increased. These results will be useful for geometry and operation parameters design of the 3D conical spouted bed and helpful for developing the fluidization mechanism of high-density particles.

The influence of microstructure on corrosion mechanism for brazed sheet of AA4045/AA3003mod/AA4045 laminated composites at different depths

The depth profiling of the element content and precipitation phase distribution of the AA4045/AA3003mod (Al-1.5Mn-0.35Cu alloy)/AA4045 brazed sheets were investigated by optical microscope observation, electron probe microanalysis (EPMA), focused ion beam-scanning transmission electron microscopy (FIB-STEM). The electrochemical test and sea water acetic acid test (SWAAT) were performed to obtain the evolution of electrochemical responses and corrosion forms of brazed sheet. EPMA results showed that a diffusion layer with the thickness of approximately 50 μm existed between the clad layer and core layer, where the Cu diffused from the core layer and Si diffused from the clad layer. It was found that brazing led to a significant low elements solid solution area at the end of the Si diffusion path, where the open circuit potential was lower by 25 mV comparing to the unaffected region. Thus the diffusion zone can provide effective cathodic protection to the unaffected region as sacrificial anode by the potential gradient. The SWAAT analysis revealed the corrosion mechanism of the residual cladding was pitting and intergranular corrosion. This area with high density of intermetallic compounds and Si particles increased sensitivity to localized attacks. These results demonstrated the successful application of the FIB-STEM system in illustrating the electrochemical responses and corrosion propagation by an accurate in-depth characterization of intermetallic particles and the matrix solid solution.

Axial gas mixing in conical spouted beds with high density particles

Conical spouted beds operating with high-density particles (ρp > 2500 kg/m3) have recently gained attention because of their potential use as nuclear fuel coaters for next-generation nuclear reactors. In the literature, the number of axial gas mixing studies in conical and conical-cylindrical spouted beds is very limited and all axial mixing studies were carried out with relatively light particles (ρp ≤ 2500 kg/m3). Therefore, the objective of this study was to generate experimental data that can be used to explain the gas axial mixing behavior in conical spouted beds operating with both low- and high-density particles. Experiments were conducted in two (γ = 30°, 60°) conical spouted beds with three different types of particles: zirconia (ρp = 6050 kg/m3), zirconia toughened alumina (ρp = 3700 kg/m3) and glass beads (ρp = 2460 kg/m3). In order to be able to compare experimental data obtained at different conditions, a 1-D convection-diffusion gas mixing model originally developed by San José et al. (1995) was implemented to determine the axial dispersion coefficients. The results show that the axial dispersion coefficients range between 1.75×10−2 m2/s and 9.35×10−2 m2/s, increase with superficial gas velocity and are higher than the corresponding dispersion coefficients of fixed beds, lower than the dispersion coefficients of fluidized beds and in the same range with the cylindrical spouted beds reported in the literature. The corresponding Peclet numbers were in the range of 0.6–7.8 for all operating conditions and slightly higher Peclet numbers were obtained with glass beads indicating the relative importance gas convective transport over gas dispersion for light particles compared to heavy particles.

Collaborative improvement of strength and ductility over Mo composites enabled by WC and La2O3

The low ductility of refractory Mo-based materials limits their further processing and wide applications. To address this challenge, a composite strengthening and toughening strategy was proposed by the simultaneous addition of WC and La2O3. And a collaborative improvement of strength and ductility is achieved over the as-sintered Mo-WC-La2O3, exhibiting a total elongation (TE) of 33.63% and an ultimate tensile strength (UTS) of 611.33 MPa, about 50.27% and 24.76% larger than those of pure Mo, respectively. Furthermore, the corresponding microstructural features and tensile fracture behavior were also discussed to explore the improvement mechanism. And it is found that the enhancement should be attributed to the high relative density, grain refinement, generated substructures and secondary phase particle refinement. Moreover, the additional toughening mechanisms of crack deflection, particles pull-out and crack halt can also prevent crack extension, which helps to give full play to the potential ductility of Mo composites. This work provides a new pathway for manufacturing advanced Mo-based products with excellent strength-ductility balance.

Hilbert space fragmentation and slow dynamics in particle-conserving quantum East models

Quantum kinetically constrained models have recently attracted significant attention due to their anomalous dynamics and thermalization. In this work, we introduce a hitherto unexplored family of kinetically constrained models featuring conserved particle number and strong inversion-symmetry breaking due to facilitated hopping. We demonstrate that these models provide a generic example of so-called quantum Hilbert space fragmentation, that is manifested in disconnected sectors in the Hilbert space that are not apparent in the computational basis. Quantum Hilbert space fragmentation leads to an exponential in system size number of eigenstates with exactly zero entanglement entropy across several bipartite cuts. These eigenstates can be probed dynamically using quenches from simple initial product states. In addition, we study the particle spreading under unitary dynamics launched from the domain wall state, and find faster than diffusive dynamics at high particle densities, that crosses over into logarithmically slow relaxation at smaller densities. Using a classically simulable cellular automaton, we reproduce the logarithmic dynamics observed in the quantum case. Our work suggests that particle conserving constrained models with inversion symmetry breaking realize so far unexplored dynamical behavior and invite their further theoretical and experimental studies.

Fabrication of tungstate metal foams as efficient catalysts for dimethyl sulfoxide oxidation in a microreactor

To overcome the problems of traditional catalyst in the microreaction technology, a microreactor system with tungstate metal foam catalyst was constructed and the catalytic efficiency were investigated by dimethyl sulfoxide (DMSO) oxidation reaction as a probe reaction. Three tungstate metal (CuWO4, NiWO4, FeWO4) foams were fabricated, and inherited the porous structure from the metal foam and had a high loading density of tungstate metal crystal particles. In the lab-built flat-plate microreactor, the effects of reaction temperature, residence time, molar ratio and pH on the yield of dimethyl sulfone (MSM) were investigated, and the tungstate metal foams showed prefect catalytic activity. Compared with NiWO4 foam and FeWO4 foam, the larger specific surface area and higher porosity endow CuWO4 with a better catalytic performance. When the reaction temperature was 80 °C, the residence time was 40 min, the molar ratio was 1:1 and the pH value of the reaction system was 3, the yield of MSM reached 82.1%. Furthermore, the NiWO4 foam catalyst system showed a better performance compared with other two catalyst system. This work indicates the potential opportunity of the construction of various metal foam catalysts in the versatile continuous microreaction technology.

Synthesis and characterization of magnetite particles from Syiah Kuala iron sand prepared by co-precipitation method

Iron sand is abundant in Aceh but it has not been supported by maximum efforts to improve the quality and usability of this material, it is only used as a raw material in the industry. This research aims to synthesize and characterize Syiah Kuala iron sand to become magnetite by the co-precipitation method. Prior to synthesis, iron sand was separated from impurities with a bar magnet and sieved with a size of 200 mesh. 37% HCl was added to the iron sand while stirring and heated at 70°C as the first step in the synthesis. After being filtered, the iron sand precipitate was added with 6.5 M NH4OH then stirred and heated. At this stage, a precipitate is formed and then washed until the pH is normal and dried. XRF data shows the total composition of Fe elements and Fe2O3 compounds from Syiah Kuala iron sands is 87.1 mass % and 84.2 mass %, respectively. XRD data shows that iron sand before and after synthesis has the same phase, namely the magnetite phase with a lattice structure of FCC. The high density of magnetite particles showed by SEM but the particle uniformity is still low. The effect of oxidation by outside air during synthesis causes the particles to agglomerate with a size range of 500 nm – 3000 nm. The Fe-O functional group was found from the FTIR analysis. Therefore, the Syiah Kuala iron sand has crystal purity quality and the opportunity to develop in various science and technology applications.