Irregular-shaped Particles Research Articles

Laboratory measurements of initial launch velocities of electrostatically lofted dust on airless planetary bodies

Electrostatic dust lofting may play an important role in surface evolution of airless bodies as indicated from a number of unexplained observations, including the lunar horizon glow and dust ponding on asteroids, for example. The initial launch velocity of a charged dust particle determines its range of motion, hence it is a critical quantity to assess the dynamics of electrostatic dust transport. Here we report on laboratory measurements of the launch velocity of electrostatically lofted dust and its relationship with the dust size. For irregularly-shaped dust, similar-sized particles show a large velocity dispersion, indicating a large variation in the inter-particle cohesive force. The maximum launch velocity is shown to decrease with the increase in the dust radius and it is on the order of ~0.7 m/s for 15 μm radius particles. Derived from the patched charge model (Wang et al., 2016a. Geophys. Res. Lett. 43, 6103–6110), the theoretical expectation of an inverse velocity-size relationship of lofted dust is shown to be consistent with the maximum launch velocity measurements. The dust shape is found to have a significant effect on the lofting process, showing that irregularly-shaped particles are lofted with much larger velocities than spherical particles. The initial launch angle relative to the surface shows a broad distribution.

Effect of particle shape on the liquefaction resistance of calcareous sands

The irregular particle shape is the significant feature of calcareous sands. It is known that calcareous sands generally show a higher liquefaction resistance than that of quartz sands, but the contribution of particle shape to the liquefaction resistance has not been well understood. In this paper, the particle shapes of calcareous sand, quartz sand and steel ball were quantitively assessed. Then, undrained monotonic and cyclic simple shear tests were conducted to investigate the influence of particle shape on the liquefaction resistance. The particle size and shape before and after simple shear were compared to assess the particle breakage. It is found that the degree of particle breakage is quite small, the surface grinding is the main mode, and the particle shape keeps almost unchanged during cyclic simple shear. Irregular sand particles show slow accumulation of excess pore pressure and need more cycles to trigger liquefaction in cyclic tests. It also shows the liquefaction resistance has a good linear correlation with the overall regularity of sand particles. Based on the fitting parameters, the liquefaction resistance of sand samples with different particle shapes can be directly obtained by the provided overall regularity of the sand particles.

Metal Powder Recyclability in Binder Jet Additive Manufacturing

The recyclability of 316L stainless steel powder in the binder jetting process has been determined. The powder characterization results demonstrated a 22% increase in the number of coarse particles (> 30 µm) and an 18.2% reduction in the number of small particles (< 10 µm) after recycling up to 16 times. A few elongated and irregular-shaped particles were found after recycling, possibly due to particle agglomeration during handling and sieving. A negligible increase in the oxygen content by 0.036% was detected in the recycled powder. The density of sintered parts produced using recycled powder was approximately 1.5% lower than when using fresh powder due to the changes in the particle size distribution and the flowability of the powder caused by the changes in morphology. Final parts built using fresh and recycled powder showed similar hardness (155 ± 3 HV and 165 ± 9 HV) and yield strength (206 ± 16 MPa and 192 ± 10 MPa), respectively.

A four-way coupled CFD-DEM modeling framework for charged particles under electrical field with applications to gas insulated switchgears

Particulate flows with charged particles under electric flow field exist in many practical applications, including metal particles in Gas Insulated Switchgear (GIS) or manipulation of powders in fluidized bed. The motions of these particles are affected by the electrical field, ambient flow and collisions. This work further develops the four-way coupled CFD-DEM framework under electric field, which not only computes the coupling of flow field, electric field with particle motion and particle charge, the particle-occupied solid fractions on CFD cell, particle-particle interactions and particle-wall interactions, but also considers the dielectrophoretic force, particle-particle Coulomb force, virtual mass force and Magnus force. Particle electrification on its contact with electrode is computed as well. Besides, the multi-sphere model is also introduced into the present framework in order to simulate particles of irregular shapes. The model is validated with theoretic solutions and experiments, and is applied to GIS and fluidized bed. Based on the framework, statistic information from the particulate flow in GIS, e.g., time-averaged solid fraction, time-averaged electric field or particles' velocity and charge distribution are analyzed. A dimensionless number is proposed to predict the particle motion in GIS with Alternating Current (AC), which is further conducive to reducing the parameter window in relevant simulations and studies.

Simulation of Hip Joint Implants Using Finite Element Method with Time and Load Variations

This research aimed to analyze the results of a hip joint implant made from Mg alloy using experimental and simulation methods with Finite Element Analysis (FEA). The experimental method’s target was to observe the microstructure, crystallite size, and magnesium alloy chemical composition. The simulation method was designed to analyze the total deformation, maximum principal stress, and maximum shear stress with time and load variations. This research used SEM, XRD, and XRF instruments to obtain the above data whereas FEA simulation used the ANSYS software. The simulation was conducted through walking, jumping, and walking down the stairs activities for 0–4.5 seconds. The SEM results showed that Mg alloy powder had an irregular shape or non-uniform particles with cracks or porous. The XRD results indicated that the crystallite size was 0.516 x 10-4 nm. Then, the XRF results presented that Mg alloy powder had 11% Mg, 61.17% Ca, and 5.73% Zn. FEA results showed that the hip joint implant had a total deformation of 0.38 nm in walking activity, 0.82 nm in jumping activity, and 0.90 nm in walking down the stairs activity. The maximum shear strains were125.98 MPa in walking, 264 MPa in jumping, and 291 MPa in walking down the stairs. The maximum principal stress in walking activity was 192.76 MPa, in jumping was 397.48 MPa, and in walking down the stairs was 438.85 MPa.

Evolution of a major virion protein of the giant pandoraviruses from an inactivated bacterial glycoside hydrolase.

The diverse viruses in the phylum Nucleocytoviricota (also known as NLCDVs, Nucleo-cytoplasmic Large DNA Viruses) typically possess large icosahedral virions. However, in several families of Nucleocytoviricota, the icosahedral capsid was replaced by irregular particle shapes, most notably, the amphora-like virions of pandoraviruses and pithoviruses, the largest known virus particles in the entire virosphere. Pandoraviruses appear to be the most highly derived viruses in this phylum because their evolution involved not only the change in the virion shape, but also, the actual loss of the gene encoding double-jelly roll major capsid protein (DJR MCP), the main building block of icosahedral capsids in this virus assemblage. Instead, pandoravirus virions are built of unrelated abundant proteins. Here we show that the second most abundant virion protein of pandoraviruses, major virion protein 2 (MVP2), evolved from an inactivated derivative of a bacterial glycoside hydrolase of the GH16 family. The ancestral form of MVP2 was apparently acquired early in the evolution of the Nucleocytoviricota, to become a minor virion protein. After a duplication in the common ancestor of pandoraviruses and molliviruses, one of the paralogs displaces DJR MCP in pandoraviruses, conceivably, opening the way for a major increase in the size of the virion and the genome. Exaptation of a carbohydrate-binding protein for the function of the MVP is a general trend in virus evolution and might underlie the transformation of the virion shape in other groups of the Nucleocytoviricota as well.

VOX model: application of voxel-based packing algorithm on cementitious composites with 3D irregular-shape particles

The internal structure of composite materials is usually composed of a continuous matrix with dispersed particles. To simulate the spatial distribution of particles, the random sequential addition algorithm (RSA) is commonly used. The RSA using continuous geometric function is difficult to achieve a high packing density in allowable computer time and time-consuming in the case of irregularly shaped aggregates, such as in mortar and concrete systems. In this work, a geometrical model, named as VOX, is introduced to deal with 3D irregularly shaped particles. The model applies the voxel-based overlap determination in the RSA to improve the efficiency and packing density. Also, the model is applicable to the complex boundary conditions of any geometry and provides high-quality triangle meshes valuable for finite element analysis. The mortar and concrete cubes with real-shape particles are simulated, in which the packing density is increased to 65% and 51%, respectively. The VOX model successfully packs over 150,000 real-shape aggregates into the steel cage in a full-size reinforced concrete beam model on a desktop machine. Particle shape significantly affects the packing density in the RSA and the sphericity is recommended as an indicator. The particles with higher sphericity can achieve denser packing under the same effort of attempts. Real-shape gravel used in this study behaves similarly with regular octahedron because of the similar sphericity.

Investigation of electrochemical supercapacitor performance of WO3-CdS nanocomposites in 1 M H2SO4 electrolyte prepared by microwave-assisted method

In this work, we have prepared WO3-CdS nanocomposites for supercapacitor electrode by Microwave-Assisted Method. The orthorhombic and monoclinic mixed structure of WO3 and hexagonal structure of CdS was observed by XRD pattern. The FESEM micrograph showed the irregular particle shape and HRTEM images demonstrated the small rod shape morphology with irregularity. The EDAX analysis confirmed the presence of W and Cd elements. From the electrochemical analysis, we have calculated the maximum capacitance as 650 F/g for WO3-CdS (6 wt%) electrode. The long cycle test showed 133% of capacitance retention with 100% Coulombic efficiency.

Synthesis of the porous spinel Co-Al2O4 powder produced by ball milling and annealing

Ball milling (BM) of elemental Co and Al was conducted for 30 h (h). This process has altered the original morphologies of both elemental Co and Al powders. Spherical Al powder particles has changed into a smooth pancake-shape while the original irregular-shaped Co agglomerates became disintegrated ultrafine particles. BM of the Co20 wt.% Al powder mixture after 30 h yielded thin irregular-shaped particles. XRD analysis revealed a partial structural transformation after BM and further structural change upon annealing the powder at 600 °C, as confirmed by the SEM images. The formation of the cubic spinel superstructure with lattice parameter a = 8.066 Å (ZnAl2O4 prototype) and Fd-3 m # 227 space group was realized. By means of LEO 1525 field-emission scanning electron microscope (FE-SEM), a fibrous mesoporous structure was revealed on the milled powder after annealing the Co-Al mixture at 600 °C. The EDS analysis confirmed a minor N impurity on the annealed powder.

A dimensional analysis based model to predict completion of solvent debinding step for Metal Injection Moulded parts

ABSTRACT The objective of this study is to develop a mathematical model to predict, for instance, the time for complete debinding of a metal injection moulded (MIM) part, the extent of solvent debinding (%) at any point of time and the debinding rate (g/min). To this end, two feedstocks, one containing carbonyl iron powder and the other made from irregular-shaped metallic particles from the shopfloor grinding sludge (both mixed with an organic binder system) were used to make by MIM, parts of nine different geometries. Each geometry has its own modulus. The effects of powder material, solid loading (influencing the binder content) and debinding temperature on the debinding characteristics were studied for the moduli of the nine parts. Parts with smaller moduli (thin parts) were found to debind faster than those with higher moduli. Parts, made of carbonyl iron feedstock (CI90), debind faster than that made of irregular-shaped particulates. A generalised solvent debinding model based on dimensional analysis has been proposed and verified experimentally. The root mean square error was found to be approximately 4% between experimentally determined and predicted debinding characteristics. These predictions are used to effectively design and curtail the solvent debinding cycles in MIM process.

Foam-Mat Freeze-Drying of Blueberry Juice by Using Trehalose-β-Lactoglobulin and Trehalose-Bovine Serum Albumin as Matrices

This study aimed to evaluate the effect of pure protein compounds and trehalose incorporated into blueberry juice for foam-mat freeze-drying on the foam and powder properties. Foam-mat freeze-drying (FMFD) of blueberry juice was tested at − 55 °C for 24 h. Matrices used were trehalose + β-lactoglobulin (T3BL1) and trehalose + bovine serum albumin (T3A1) and compared with maltodextrin + whey protein isolate (M3W1). Physicochemical properties of foam and powder, e.g., foam stability, foam density, moisture, rehydration time, color, particle morphology, total phenolic, and anthocyanins (total and individuals), were investigated. T3BL1 and T3A1 had more stable foam than M3W1. However, overrun of T3BL1 and T3A1 foamed were inferior to the M3W1 sample. The M3W1 sample recovered 79% powder (dry weight) and was superior to others. Rehydration time of powdered T3BL1 and T3A1, with bulk densities of 0.55–0.60 g cm−3, was the fastest (34–36 s). The blueberry powders of M3W1 showed more irregular particle size and shape, while the samples with trehalose and pure proteins generated particles of more uniform size with obvious pores. T3BL1 and T3A1 showed less redness (a*) values than the M3W1 product. All samples were considered pure red due to hue values < 90. M3W1 was superior in total phenolic content (TPC) and total monomeric anthocyanins (TMA) compared with both samples made with trehalose + β-lactoglobulin and trehalose+bovine serum albumin. Delphinidin-3-glucoside (Del3Gl) concentration was found to be higher in M3W1. Also, M3W1 had higher cyanidin-3-glucoside (Cyn3Gl) and malvidin-3-glucoside (Mal3Gl) concentration. M3W1 also prevented the degradation of these bioactive compounds better than the other FMFD samples. The use of pure proteins and trehalose as matrices in the FMFD process had little advantage compared with maltodextrin/whey protein isolate. Thus, maltodextrin/whey protein isolate seems an ideal matrix for the manufacture of FMFD blueberry.

Characterization of Modified Polyurethane Foam Adsorbents for Mercury Adsorption Applications

The use of modified polyurethane foam adsorbents for mercury adsorption applications can reduce the impact of mercury pollution. This study aims to study the characteristics of adsorbents made from castor oil, MDI (Methylene diphenyl diisocyanate), glycerol, distilled water and modified by the addition of zeolite and bentonite. Polyurethane foam which has optimum performance is further characterized to determine physical and chemical properties, including: functional groups (FTIR), morphology (SEM) and area (BET). The results of FTIR Characterization showed that in polyurethane foams without modification there was a C = O group which is a typical group in the polyurethane group shown in wavenumber (1654-1516 cm−1, 1680-1514 cm−1, and 1593-1516 cm−1) Whereas in zeolite modified polyurethane foam there is a C = CH group with a wavenumber of 3008 cm−1 which is a typical group for zeolite whereas in bentonite there is a C = CH group with a wavenumber of 3007 cm−1 which is a typical group for bentonite. The results of SEM characterization show that zeolite modified polyurethane foam has a smooth and flat structure with small pores and polyurethane foam with bentonite has irregular or irregular particle shape. The average BET area obtained in the PUF modification is 1.3778 m2 g−1. Whereas for the smallest BET area obtained at synthetic PUF 19.1 gr + Zeolite 40% for 0.773 m2 g−1, the area is influenced by the comparison of composition from polyurethane foam synthesis.

CaSiO3:Eu2+, Er3+, BaSiO3:Eu2+, Er3+ and SrSiO3:Eu2+, Er3+ phosphors: molten salt synthesis, optical and thermal studies

In this study, thermal and optical behaviors of CaSiO3:Eu2+, Er3+, BaSiO3:Eu2+, Er3+ and SrSiO3:Eu2+, Er3+ phosphors synthesized by molten salt synthesis technique are investigated. The doped phosphors activated with Eu2+ and Er3+ ions with varying doping concentrations of 0 mol% to 1 mol% were subjected to structural, optical, and thermal analyses. The powder X-ray diffraction analysis confirms the triclinic structure of CaSiO3: Eu2+, Er3+, orthorhombic structure of BaSiO3: Eu2+, Er3+, and monoclinic structure of SrSiO3: Eu2+, Er3+ phosphors with good homogeneity and phase purity. The morphological and topographical traits are studied via field emission scanning electron microscopy and transmission electron microscopy analyses. These analyses indicate the irregular shape and size of particles along with agglomeration that occurred as a result of prolonged heat treatment processes. The thermal behavior studied by thermogravimetric (TG) analysis confirms the thermal stability of these phosphors with less weight loss occurring while heating the phosphors from room temperature to 700 °C. The study of thermoluminescent spectra of ultraviolet (UV) and gamma-irradiated phosphors confirms deep trapping that occurred in the synthesized phosphors along with second-order kinetics. The trap depth analysis indicates the trapping of electrons in deep trap centers and hence high activation energy (~ 3 eV) is required to vacate the trapped electrons. Doping of conjugate rare earth pair Eu2+ and Er3+ in the host lattice leads to formation of more defects and hence enhances the trapping mechanism. The gamma-irradiated phosphors exhibit increased TL intensity, efficient trapping in much deeper trap centers, and improved fading characteristics in comparison to the UV-irradiated phosphors.

Mechanical properties and durability of rubberized and SBR latex modified rubberized concrete

This paper analyses how rubber waste, used as replacement of fine aggregate in concrete mixes, affects mechanical properties and durability of concrete: freeze-thaw resistance, water absorption by immersion, and sulphate resistance. Concrete was modified by carboxylated styrene butadiene rubber (SBR) latex to get better bonding properties between rubber and hardened cement paste. Control specimens were made of concrete mix without crumb rubber. Scrap tyre rubber powder (crumb rubber – CR) of fraction 0/1mm and 1/2mm was used as fine aggregate. CR was used to replace a portion of fine aggregate at 5% of the total aggregate content. CR of fraction 0/1mm was found to improve freeze-thaw resistance: freeze-thaw resistance test results were similar to those of concrete with traditional air entrainment systems. On the contrary, coarser rubber particles of fraction 1/2mm had a negative effect on freeze-thaw resistance of concrete. These findings can be explained by the smoother texture and a more regular shape of coarse rubber particles up to 2 mm in size and the rougher texture and irregular shape of fine particles up to 1 mm in size. A complex profile of rubber particle surface results in higher volume of air voids, higher closed porosity and higher freeze-thaw resistance of concrete modified with crumb rubber. The test results confirmed that concrete modified with crumb rubber of smaller fraction had higher closed porosity and higher freeze-thaw durability factor Kf. The results also confirmed that Kf values calculated from concrete porosity parameters can be conveniently used to predict freeze-thaw resistance and durability of concrete. The tests have shown that the modification of concrete with rubber waste has no positive effect on sulphate resistance, compressive strength and modulus of elasticity.

Preparation and Study of the Properties of Aluminum Powders, Suitable for the Manufacture of Powder Electrodes

The results of the study of the shape, morphology and elemental composition of aluminum powder particles obtained in distilled water with the following electrical parameters of the electroerosive dispersion unit are presented: the capacity of discharge capacitors is 65 μF, voltage 100 V, pulse frequency 50 Hz. It is established that the powder consists of particles of regular spherical shape (or elliptical), irregular shape (conglomerates) and fragmentation, and the main elements of the powder are aluminum and oxygen. The obtained powder materials can be used for the manufacture of powder electrodes used in welding and surfacing of a wide range of parts.

Polystyrene microplastics do not affect juvenile brown trout (Salmo trutta f. fario) or modulate effects of the pesticide methiocarb

BackgroundThere has been a rising interest within the scientific community and the public about the environmental risk related to the abundance of microplastics in aquatic environments. Up to now, however, scientific knowledge in this context has been scarce and insufficient for a reliable risk assessment. To remedy this scarcity of data, we investigated possible adverse effects of polystyrene particles (104 particles/L) and the pesticide methiocarb (1 mg/L) in juvenile brown trout (Salmo trutta f. fario) both by themselves as well as in combination after a 96 h laboratory exposure. PS beads (density 1.05 g/mL) were cryogenically milled and fractionated resulting in irregular-shaped particles (< 50 µm). Besides body weight of the animals, biomarkers for proteotoxicity (stress protein family Hsp70), oxidative stress (superoxide dismutase, lipid peroxidation), and neurotoxicity (acetylcholinesterase, carboxylesterases) were analyzed. As an indicator of overall health, histopathological effects were studied in liver and gills of exposed fish.ResultsPolystyrene particles by themselves did not influence any of the investigated biomarkers. In contrast, the exposure to methiocarb led to a significant reduction of the activity of acetylcholinesterase and the two carboxylesterases. Moreover, the tissue integrity of liver and gills was impaired by the pesticide. Body weight, the oxidative stress and the stress protein levels were not influenced by methiocarb. Effects caused by co-exposure of polystyrene microplastics and methiocarb were the same as those caused by methiocarb alone.ConclusionsOverall, methiocarb led to negative effects in juvenile brown trout. In contrast, polystyrene microplastics in the tested concentration did not affect the health of juvenile brown trout and did not modulate the toxicity of methiocarb in this fish species.

Fourier series-based discrete element method for computational mechanics of irregular-shaped particles

Many natural and engineered granular materials consist mainly of irregular-shaped non-spherical particles. In this work, a novel Fourier series-based Discrete Element Method (FS-DEM) is developed for the computational mechanics of irregular-shaped particles. In FS-DEM, Fourier series-based particle geometric description and coordinate representation are introduced, where particle shapes are implicitly determined by FS coefficients, which remain constant and are independent of particle positions or kinematics. Using the FS-based particle representation, contact detection and resolution algorithms are then developed to identify contacts and resolve contact geometric features. The FS-DEM method is completed with recourse to conventional contact behavior, laws of motion, and movement integration. The accuracy and computational efficiency of the FS-DEM framework are evaluated via three numerical examples and compared with the Overlapping Discrete Element Cluster-based DEM method. Results demonstrate the robust and superior performance of the FS-DEM method and its potential for efficient computational modeling of irregular-shaped particle systems.

DEM study of the shear behavior and formation of shear band in biaxial test

This paper aims to study the shear behavior of granular matter by DEM simulations. Granular samples are prepared by automatic clump generation algorithm to create particles of irregular shapes. Simulations of the biaxial test with membrane boundary condition are used to test the shear behavior of samples. A new method for computing sample volume in membrane boundary condition is proposed. Deviatoric stress and volumetric strain curves are plotted to describe contracting-dilatancy of granular materials during the shearing stage. Formation of the shear band is studied from particle rotation and particle displacement fields. The influence of confining pressure, initial porosity, and friction coefficient on the development of shear band are studied. Lower confining pressure, higher initial porosity can be resulted in later formation of shear bands.

Photocatalytic activity of ZnO + CuO thin films deposited by dip coating: coupling effect between oxides

ZnO + CuO thin films were obtained by the dip-coating method on glass substrates. The precursor solution was obtained from the mixture of ZnO and CuO independent precursor solutions prepared at room temperature (RT). The atomic percentage of Cu in solution (X at.%), in steps of 10 at.%, was varied in the full range. The number of coatings was fixed to obtain thicknesses of ~250 nm for all films, which were sintered in an open atmosphere at 450 °C for 1 h. A detriment of crystalline quality was observed for ZnO as the X value was increased up to 50, decreasing its crystallite size (CS) from 20 to 12 nm. For CuO, CS remained almost constant (~10 nm). No presence of other compounds was observed in X-ray diffraction measurements. EDS measurements showed that Cu and Zn contents in the films (Y) are in accordance with the nominal concentration set in solution, being both uniformly distributed in the films. SEM images showed dependence of the texture on the X value: (i) a homogeneous distribution of spherical particles of higher size for X = 0 (ZnO) and X = 50 (CuO + ZnO), and (ii) particles of irregular shape–size for other X values. The direct band gap for ZnO (3.28 eV) and, indirect band gap for CuO (1.2 eV) were calculated from transmission spectra. A shift of edge absorption to higher wavelengths was observed as the Cu content increased. The photocatalytic activity was quantified by the photobleaching of methylene blue. ZnO films showed the highest photocatalytic activity, but also another maximum was obtained for the ZnO + CuO films with X = 50 at.%. This result has been attributed to the coupling effect among both oxides and a higher packing density of the crystallites.

Morphological and structural properties of barium strontium titanate nanopowders synthesized via a sol-gel method

Barium strontium titanate (Ba1–xSrxTiO3, BSTO) powders were prepared using a sol-gel method. All of the samples were calcined at 800 °C. Effect of Sr concentration (x = 0, 0.3, 0.5, and 0.7) on morphological and structural properties of BSTO powders were investigated and discussed. Morphology of the BSTO powders revealed agglomerates of uniform irregular-shaped particles with sizes less than 100 nm. From X-ray analysis, all BSTO powders exhibited a cubic structure without any impurity or intermediate crystalline phases. The contraction of lattice constant and unit-cell volume of BSTO crystals was observed as the Sr concentration increased, confirming the incorporation of Sr into the Ba site. More detailed structural information of the BSTO powders was evaluated further through X-ray line profile analysis using the Williamson–Hall (W-H) plot. It was found that both the crystallite size and lattice strain of BSTO powders remained mostly unchanged with changing Sr concentration.