Effect Of Particle Geometry Research Articles

The effect of particle geometry on squirming in a heterogeneous medium

Biological microorganisms and artificial micro-swimmers often locomote in heterogeneous viscous environments consisting of networks of obstacles embedded into viscous fluid media. In this work, we use the squirmer model and present a numerical investigation of the effects of shape on swimming in a heterogeneous medium. Specifically, we analyse the microorganism's propulsion speed as well as its energetic cost and swimming efficiency. The analysis allows us to probe the general characteristics of swimming in a heterogeneous viscous environment in comparison with the case of a purely viscous fluid. We found that a spheroidal microorganism always propels faster, expends less energy and is more efficient than a spherical microorganism in either a homogeneous fluid or a heterogeneous medium. Moreover, we determined that above a critical eccentricity, a spheroidal microorganism in a heterogeneous medium can swim faster than a spherical microorganism in a homogeneous fluid. Based on an analysis of the forces acting on the squirmer, we offer an explanation for the decrease in the squirmer's speed observed in heterogeneous media compared with homogeneous fluids.

The effect of particle geometry (size & shape) on the recovery of gold and copper metallic particles from end-of-life random access memory cards by flotation

Since Random Access Memory (RAM), one of the main parts of computers contains a remarkable quantity of precious metals, applying flotation at the pre-concentration stage to recycle these metals can result in a more cost-effective, user-friendly, and environmentally friendly process compared to direct chemical methods. While the significance of physical characteristics like particle size and shape in the flotation process is well established, the impact of particle shape in the flotation process utilized in the recycling of end-of-life (EoL) RAMs hasn’t yet been thoroughly investigated. To fill this gap, a two-stage coarse flotation approach is used for the selective recovery of plastic and valuable metallic particles for sustainable development. The particle geometry of metallic particles recovered by flotation was characterized by axis measurement on the images by optical microscope that allows us to distinguish particles of different sizes and colors that make up the sample and evaluated in terms of particle size distribution (PSD), elongation (E) and roundness (R) parameters. The results showed that after the plastic fraction is effectively removed, it is possible to produce pre-concentrated products with high metal content (more than 50 % Cu content at the 1st stage and 1800 g/t Au content at the 2nd stage using 900 g/t KAX) in an economical and environmentally friendly way. Thus, it was concluded that the gold and copper metallic particles in the reduced-size EoL RAM cards could be easily floated by attaching them to the air bubble with the help of the collector, thanks to their flat shape.

Multiphase granular suspension flow of fresh concrete during pumping in complex geometries

AbstractDuring the pumping process of multiphase granular suspensions, such as concrete, through pipe systems, many parameters can influence the material's ability to flow. To understand the hydrodynamics and particle mechanics in granular, non‐Newtonian suspensions under nonlinear flow conditions, the authors have been working on a joint project within the Priority Program SPP 2005 “Opus Fluidum Futurum ‐ Rheology of Reactive, Multiscale, Multiphase Construction Materials” funded by the German Research Foundation (DFG). Based on the results obtained, it is possible to describe the relationships between concrete composition and the rheological properties of the fresh mixture for pumping applications. The effects of particle geometry and flow conditions on flow‐induced particle migration (FIPM), subsequently the formation of a lubricating layer (LL), and eventually on pumping pressure were also shown. While the behavior of concrete and other complex, multiscale suspensions in generic flows (Couette, Poiseuille) is still part of current research and only partially understood, the behavior in complex geometries is even less explored so far. Here, additional effects based on the curvature of streamlines and mass inertia of the particle phase come into play. In the framework of the project, these effects have been investigated experimentally and numerically. Various experimental approaches have been developed to observe the behavior of particles within their carrier fluid in an opaque, dense, and enclosed moving system, yielding insightful results. Currently, models are being developed and experimentally validated to describe particle migration quantitatively, allowing conclusions about the local rheological behavior to be drawn. This information is essential to predict the flow behavior necessary for modern processes such as 3D printing and energy‐optimized pumping.

The effect of particle geometry on squirming through a shear-thinning fluid

Biological and artificial microswimmers often encounter fluid media with non-Newtonian rheological properties. In particular, many biological fluids such as blood and mucus are shear-thinning. Recent studies have demonstrated how shear-thinning rheology can impact substantially the propulsion performance in different manners. In this work, we examine the effect of geometrical shape upon locomotion in a shear-thinning fluid using a prolate spheroidal squirmer model. We use a combination of asymptotic analysis and numerical simulations to quantify how particle geometry impacts the speed and the energetic cost of swimming. The results demonstrate the advantages of spheroidal over spherical swimmers in terms of both swimming speed and energetic efficiency when squirming through a shear-thinning fluid. More generally, the findings suggest the possibility of tuning the swimmer geometry to better exploit non-Newtonian rheological behaviours for more effective locomotion in complex fluids.

Microscale magnetoelectricity: Effect of particles geometry, distribution, and volume fraction

Achieving efficient magnetoelectric coupling of core-shell and particulate multiferroic composites has been a challenging hurdle; however, research has shown unwavering interest to overcome this barrier in pursuit of their implementation into promising potential applications. Herein, a fully coupled computational model of core-shell and particulate composites is developed and verified to investigate the magnetoelectric interactions of the particle and matrix on the microscale. The effects of particle geometry, settling, and agglomeration were exhaustively studied by investigating seven different shapes and a wide range of vertical and lateral particle spacing. Overall, it was found that utilizing particle geometries and positioning that closely resemble a laminate configuration, such as a prolate ellipsoid and horizontal particle alignment, enhances the magnetoelectric coupling of the composite structure. The results coincided with the experimental results concerning settling and agglomeration.

Facile Synthesis and Size Control of 2D Cyclodextrin‐Based Metal–Organic Frameworks Nanosheet for Topical Drug Delivery

AbstractIn this work, a 2D nanosheet (NS) of γ‐cyclodextrin (CD)‐based metal–organic frameworks (MOFs) is synthesized through a facile green chemistry approach. NS‐MOF carrier is constructed using a water system in a simple one‐pot reaction involving CD and potassium carbonate. Particle size optimization is achieved by adjusting the reaction temperature and the introduction of crystal growth suppressor (appropriate proportion of acetone). The NS‐MOF stability in aqueous medium is improved by polymerization reaction of crosslinked CD‐MOF (CL‐CD‐MOF) without blocking its cavity for drug loading. The effects of particle geometry and size of nanoporous materials on their pharmacokinetics during drug delivery are compared between the sheet‐like DXM@CL‐NS‐MOF and 3D‐cubic‐shaped DXM@CL‐CD‐MOF loaded with the same quantity of dexamethasone (DXM). The bioefficiency of these carriers in tear fluids and aqueous humors to deliver DXM is investigated in vivo. The results demonstrate that the 2D‐nanosheet particles significantly improve precorneal residence time and intraocular bioavailability over the commercial Maxidex (0.1% dexamethasone) and its 3D‐cubes counterpart of similar chemical composition. It suggests that the geometry of a carrier play a significant role in the biodistribution, and the carrier of CL‐NS‐MOF is a good candidate for ocular drug delivery.

Jig separation of crushed plastics: the effects of particle geometry on separation efficiency

Secondary resources (i.e., wastes) contain a wide variety of materials (e.g., plastics, metals, and wood) of various sizes and shapes that complicate separation especially when using gravity-based separation techniques. In this study, the effects of particle geometry (i.e., size and shape) on jig separation of crushed plastics were investigated. Plastic boards with 2-mm and 3-mm thicknesses of acrylonitrile butadiene styrene (ABS, specific gravity (SG) = 1.03) and polystyrene (PS, SG = 1.06) were crushed to obtain a size fraction of + 2.0–8.0 mm. The shape distribution in each size fraction (+ 2.0–2.8, + 2.8–4.0, + 4.0–5.6, and + 5.6–8.0 mm) showed the strong effects of crushing on particle shape; that is, particles are more disk-like at coarser size fraction but becomes more sphere-like at finer size fraction. Settling velocity of sphere-like PS increased with increasing particle size while those of disk-like ABS had similar values regardless of the size, which were consistent with the results of jig separation of single-type plastics. The results of jig separation of mixed-type plastics showed that separation efficiency was higher for the mixture of light, disk-like particles (ABS) and heavy, sphere-like particles (PS).

Effect of Particle Geometry and Nb2O5 Addition in the Sintering of Partially Stabilized Zirconia with Y2O3

Zirconia (ZrO 2 )has several applications in diverse industrial segments due to its excellent properties, especially regarding resistance to mechanical stress and high-temperature scenarios. However, due to phase transformations that this ceramic material exhibits at various temperatures, the appearance of cracks in the sintered compact during cooling is perceived. Studies have been performed in the way to stabilize zirconia during the sintering process by adding small quantities of other oxides, such as Y 2 O 3 , CeO, MgO and Nb 2 O 5 . Some studies show that the use of Nb 2 O 5 in the system ZrO 2 -Y 2 O 3 promotes an increase in its fracture toughness. Additionally, there are several controversies about the effect of the content and the polymorph of Nb 2 O 5 on zirconia stabilization. There are several commercial zirconia powders partially stabilized in the form of granules obtained by the spray dryer method which promotes better densification of the green and sintered compacts. This study aims at evaluating the effect of adding 0.8 % and 2.0 % (by weight) of monoclinic Nb 2 O 5 in 3Y-TZ-E (Tosoh) on the stabilization of this zirconia and the grinding effect of 3Y-TZ-E granules on the densification and on the sintered compact microstructure. Sintered compacts were characterized by X-ray diffraction, scanning electron microscopy, and Raman spectroscopy. The results indicate that the use of 2.0 % (in weight) of Nb 2 O 5 implies in the destabilization of tetragonal zirconia and in the formation of Zr 6 Nb 2 O 17 . No significant difference was observed in the densification and in the grain size of the unground TZ-3Y-E with the addition of 0.8 % (in weight) of monoclinic Nb 2 O 5 .

Thermal properties of some Egyptian kaolin pastes for pelotherapeutic applications: Influence of particle geometry on thermal dosage release

Abstract The present study aims to evaluate the potentiality of 7 selected structural highly ordered kaolinite-rich samples from Egyptian Carboniferous sedimentary deposits (located at Abu Zenima district, west central Sinai peninsula) to use them in medicinal semisolid formulations as peloids. The effect of particle geometry and kaolinite crystallite size are studied to check their influence on thermal dosage performance. The studied samples exhibit a variable mineralogy. Kaolinite is the main constituent (ranging from 81 to 94%), followed by quartz (up to 14%), lesser amounts of anatase and halite, and traces of hematite, magnetite, alunite and gypsum. The kaolinite order “Hinckley Index” varies from 1.28 to 1.50. 1:1 (w/w) kaolin mud pastes were prepared with purified water in Eppendorf tubes using a touch vibration vortex mixer for 2 min. The cooling kinetics of pastes were measured by using a differential scanning calorimetry equipment (Shimadzu DSC-50Q). Specific heats were calculated, following Cara et al. (2000). The granulometry and geometric surface area were measured by laser diffraction (Mastersizer 2000LF, Malvern Instruments) in the range 0.02 and 1500 μm. All analyzed samples showed a clear predominance of particles under 4 μm (ranging from 82 to 94%), with median size (D50) ranging from 0.93 to 1.35 μm. The heat retention time during cooling from 50 °C to 32 °C reached up to 30.82 min, oscillating around an average of 28.72 min, and the temperature corresponding to the minimal dosage time (T20) was not exceed below 34.7 °C. A good correlation (R2 = 0.875) was found between heat retention time and specific heats. There is no correlation between kaolinite content and thermal properties, but R2 values around 0.6 are found with granulometry (finer the particles, greater the heat retention time t32 and the specific heat). Even if sample H5 (Gabal Hazbar deposit) is not the richest in kaolinite, it exhibits the best thermal dosage performance, in accordance with the granulometry (D50 = 0.93 μm), and geometric surface area (3.73 m2/g).

Attachment Probability of Particle on Bubble Surface and the Stability of Its Aggregate

Three processes are involved in the bubble-particle interaction during a flotation process. These processes can be analyzed in terms of collision, attachment, and aggregate stability. Each process plays an important role in determining flotation efficiency. Particle size and geometry also affect the particle-bubble interaction. Information about the irregular shape of particles is important for achieving a full understanding of the flotation process. This research focuses on understanding the effect of particle geometry on the particle-bubble interaction during a flotation process. The experimental setup was made up of a 9 × 9 × 26 cm glass flotation column, a bubble generator system, a particle feeding system, and a high speed video camera. The bubble generator system was made of a 0.3 mm diameter nozzle attached to a programmable syringe pump. The particle feeding system was made of pipettes. This research used real particles collected from an open pit in the Grasberg mine in Timika, Papua. The particle size variation ranges from 38 to 300 µm. Collector type reagent was added to the flotation column. Bubble-particle interaction is recorded using a high-speed video camera. The data recorded by the high-speed video camera were analyzed using image processing software. The results of the experiment show that particle geometry is dominated by sub-angular geometry. Attachment, aggregate stability, and interaction time are found to depend on particle size. Small particles ranging from 38 and 106 μm have a long interaction time and are able to adhere to bubbles easily. Big particles ranging from 150 to 300 μm have a short interaction time and are unable to adhere to bubbles easily. All particles from 38 to 300 μm size generated the same value of aggregate stability. The aggregate stability of all particles is 1 or stable.

Bioaerosols in the lungs of subjects with different ages-part 1: deposition modeling.

In this contribution the inhalation and deposition of bioaerosols including particles with various shapes and sizes were investigated for probands with different ages (1, 5, 15 and 20 y). The study should help to increase our knowledge with regard to the behavior of variably shaped and sized particles in lungs being subject to different developmental stages. Simulation of particle transport and deposition in single structures of the respiratory tract was conducted by using a stochastic model of the tracheobronchial tree and well-validated analytical and empirical deposition formulae. Possible effects of particle geometry on deposition were taken into consideration by application of the aerodynamic diameter concept. Age-dependent lung morphometry and breathing parameters were computed by using appropriate scaling factors. Theoretical simulations came to the result that bioparticle deposition in infants and children clearly differs from that in adolescents and adults insofar as the amount of deposited mass exhibits a positive correlation with age. Nose breathing results in higher extrathoracic deposition rates than mouth breathing and, as a consequence of that, lower particle amounts are enabled to enter the lung structures after passing the nasal airways. Under sitting breathing conditions highest alveolar deposition rates were calculated for particles adopting aerodynamic diameters of 10 nm and 4 µm, respectively. The study comes to the conclusion that bioparticles have a lower chance to reach the alveoli in infants' and children's lungs, but show a higher alveolar deposition probability in the lungs of adolescents and adults. Despite of this circumstance also young subjects may increasingly suffer from biogenic particle burden, when they are subject to a long-term exposure to certain bioaerosols.

Estimation of elastic moduli of particulate-reinforced composites using finite element and modified Halpin–Tsai models

In this paper, the effect of particle geometry on Young’s modulus for particulate-reinforced composites was estimated using finite elements analysis (FEA) and modified Halpin–Tsai (HT) equations, including not only the effect of the aspect ratio but also the particle shape. This modified HT model includes a new parameter (a) which depends on the angle of the particle corners. FEA was used as a starting point to find the composites behavior depending on the reinforcement features, results that were compared to experimental values. Young’s moduli and stresses distribution were estimated using an AlA356/SiC(p) composite as starting material . Selected particle geometries for modeling were cylinders, truncated cylinders, double cones, and double-truncated cones; while aspect ratios were modified from 0.6 to 1.8. There was an excellent agreement between experimental results, FEA, and modified Halpin–Tsai estimations, showing that the predicting ability of the Halpin–Tsai model could be improved by introducing different shape parameters.

Thermally evaporated Ag nanoparticle films for plasmonic enhancement in organic solar cells: effects of particle geometry

We report on the simple fabrication of Ag NP films via thermal evaporation and subsequent annealing. The NPs are formed on indium tin oxide electrodes, coated with PEDOT:PSS and implemented into PCPDTBT:PC70BM solar cells. Scanning electron microscopy and atomic force microscopy are used to determine the size distributions and surface coverage of the NP film. We apply finite‐difference time‐domain techniques to model the optical properties of different nanoparticle films and compare this with the absorption properties of the organic active layer. The simulations demonstrate that the absorption and scattering efficiency of the particles are very sensitive to particle geometry. Solar cells prepared with window electrodes containing NP layers with less surface coverage, show a 14.8% improvement in efficiency. We discuss variations in the external quantum efficiency of the devices in terms of forward scattering and parasitic absorption losses induced by the NP layer. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)

Numerical Study of Interaction and Aggregation of Non-Spherical Particles in Forming Li-Ion Battery Cathodes

Aggregation between additive particles and active particles in battery electrode material strongly affects their interfacial phenomena and eventually battery performance. This paper proposes a three dimensional model to simulate the aggregation process of spherical carbon black (CB) and ellipsoidal LiMn2O4 active material (AM) particles within a liquid medium (PVDF polymer dissolved in NMP solvent) in the electrode materials of Li-ion batteries. Monte Carlo method is employed and the resulting aggregates are characterized by the number of CB particles connected to the percolated cluster of AM, which affects the effective conductivity. The effects of particle geometry and constituent mass ratio are investigated. It is found that a larger AM particle aspect ratio contributes positively to the percentage of CB attachment. For a given AM particle aspect ratio of 2 or 3, the average percentage of CB attachment is found to decrease as the CB:AM mass ratio increases from 2%:94% to 4%:92%.

Effect of wood particle geometry and pre-treatments on the strength and sorption properties of cement-bonded particle boards

The effect of particle geometry and pretreatments on the strength and sorption properties of wood particle cement composite boards was investigated. Wood particles (flakes and sawdust) of Gmelina arborea were mixed with cement and water in the production of composite boards. The wood particles were pretreated with hot water, calcium chloride and a combination of both treatments to enhance bonding with cement. The slurry was poured into rectangular moulds for board formation. After demoulding, the boards formed were tested for modulus of rupture (MOR), modulus of elasticity (MOE), water absorption (WA) and thickness swelling (TS). The results revealed that the mean MOR for flakes boards was 3.23N mm-2 while the mean MOR for sawdust boards was 3.01N mm-2. Hot water and calcium chloride treatment produced the best effect in flake composite boards with MOR and MOE values of 6.90 N/mm2 and 1897.36 N mm-2 while sawdust composite boards had mean MOR and MOE values of 5.69N mm-2 and 1664.31N mm-2 respectively. The WA rate after 24 hours of flakes and sawdust boards treated with hot water and calcium chloride was 3.63% and 4.28% while the TS rate was 0.69% and 1.44% respectively. Particle geometry and pretreatments significantly improved strength and sorption properties of wood particle cement composite boards (p<0.05).

Effect of Carbonisate Particles on the Properties of Active Carbons

In this article, the effect of particle geometry on the properties of active carbons, which are obtained by treating steam with hard coal-tar carbonisate, is reported. Different shapes of carbonisates were activated by superheated steam at 1123 K in a monolayer reactor with burn-off rates between 45.3% and 72.0%. Steam activation leads to a faster development of ring-shaped particles, and the kinetics of the process influence surface area Brunauer-Emmet-Teller, surface mesoporosity and the micropore volume. The micropore and mesopore structures of active carbons are evaluated using nitrogen adsorption/desorption isotherms and the corresponding parameters of the Dubinin-Radushkevich equation are presented. Micropore-size distribution is calculated using the Horvath-Kawazoe method. The results of these textural investigations showed that a more uniform micropore structure and better mechanical properties are present in ring-shaped active carbon particles than that were reported earlier.

Effect of Particle Geometry and Microstructure on Fast Pyrolysis of Beech Wood

The influence of particle geometry and microstructure in fast pyrolysis of beech wood has been investigated. Milled wood particles (<0.08–2.4 mm) and natural wood cylinders (2–14 mm) with different lengths (10–50 mm) and artificial wood cylinders (Dp = 0.5–14 mm) made of steel walls, filled with small milled wood particles (<0.08–0.140 mm), have been pyrolyzed in a fluidized bed at 500 °C. From the results of the experiments, the influence of particle geometry and microstructure on char, gas, and pyrolysis oil yield and pyrolysis oil composition has been derived. The product yields of large cylinders with diameters of 6–14 mm are primarily determined by the outer diameter and resulting heating rate. The microstructure of these cylinders, being either natural channels or randomly packed small milled wood particles, has turned out to be much less important. For the smaller milled wood particles, the microstructure does have a profound effect on the product yields. The smallest particles (<0.140 mm), which consist only out of cell wall material and have lost their typical wood channel structure, show a clearly higher oil yield and lower char yield. It is postulated that the high pyrolysis oil yield can be explained by larger mass transfer rates of pyrolysis products from these smallest particles, as compared to mass transfer from particles containing channels

A conservative momentum‐exchange algorithm for interaction problem between fluid and deformable particles

AbstractA new method for studying interaction between elastic object and a fluid is developed. The fluid phase including solid interface is solved by our immersed boundary method of body‐force type (Kajishima et al., JSME Int. J. Ser. B 2001; 44(4):526–535, Kajishima and Takiguchi, Int. J. Heat Fluid Flow 2002; 23(5):639–646). The method has enabled the simulation of interaction problem between a fluid and rigid spherical particles of a total number of O(103) by an efficient momentum‐exchange technique through volume‐averaged velocity field of multiple phases. In the present study, the fluid–solid interaction force is incorporated into FEM. This process is done by a superposition of the hydrodynamic force field with the solid internal force field. The uniqueness of the present approach lies in the implementation of the inter‐phase momentum exchange through the distributed force field shared by both Eulerian and moving Lagrangian references. The applicability of the present method is demonstrated in two 2‐D flow fields including a large number of elastic particles. The effects of particle geometry and elasticity are investigated. The results suggest that particles' neutral geometry and deformability exhibit strong correlation to rotating motions and clustering behaviours of the particles in the fluid flow. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Effect of particle geometry on the properties of binderless particleboard manufactured from oil palm trunk

Experimental binderless composite panels were manufactured using fine particles and strands of oil palm ( Elaeis guineensis) trunks. Modulus of rupture (MOR), internal bond strength (IB), dimensional stability, and surface roughness of the panels made with a target density of 0.80 g/cm 3 were evaluated. Strand type samples had MOR and IB values of 24.95 and 0.95 MPa, respectively. Corresponding values for the fine particle type samples were 4.04 and 0.49 MPa. Panels made from strands met MOR requirement stated in Japanese Industrial Standard (JIS). Enhanced bonding between strands observed by micrographs taken using scanning electron microscopy (SEM) also supported the findings. However, the samples having fine particles had lower MOR values than minimum requirement listed in JIS. Strand type panels had 41.6% thickness swelling which is only 4.6% lower than that of the panels made from fine particles. It appears that dimensional stability of both types of panels exhibited insufficient results according to JIS. Surface roughness quality of the samples made from fine particles had average surface roughness values comparable to those of panels made in past studies. Based on initial results of this work, raw material from oil palm trunks can have some potential to be used to manufacture binderless panels without using any adhesives. This study revealed that mechanical and physical properties of such experimental panels were influenced by the particle geometry. It would be important to consider possible addition of chemical or wax in the particles to improve their dimensional stability in further studies.

Geometrical study of electrorheological activity with shape-controlled titania-coated silica nanomaterials

The titania-coated silica nanomaterials with three different shapes (nanosphere, nanorod, nanotube) are fabricated to examine the influence of particle geometry on ER fluid in nanometer-size region. The effect of particle geometry on ER activity is studied by varying the geometric aspect ratio of dispersing materials. The ER activities of titania-coated silica nanomaterials exhibit a dependence on their aspect ratio. Interestingly, the shear stress of titania-coated silica nanomaterials based ER fluids increases with increasing the aspect ratio. Geometrical study is performed to give deep insights into the primary factors that determine the ER activity. It is believed that the geometrical effect originated from high aspect ratio played a dominant role in enhancing the performance of ER fluid. Furthermore, the dielectric property analysis based on dielectric loss model clarifies that an increase in aspect ratio has been coupled with the larger achievable polarizability and short relaxation time of interfacial polarization. Consequently, the increment in aspect ratio has strong influence on ER activity, provides outstanding enhancement in shear stress value of titania-coated silica nanotube based ER fluid.