Flat Particles Research Articles

Particle shape effect on the structural evolution and force propagation inside the three-dimensional sandpile.

This paper employs the discrete element method to examine the impact of particle shape on the pressure dip phenomenon and structural characterization of the three-dimensional sandpiles. Particular attention has been given to the underlying mechanism in the sandpile, which arises from the interplay of the initial created structure and the induced changes in the subsequent deposition process. Different aspect ratios produced different initial local geometry. The contact vector and strong contact force rotated away from the z-axis when the aspect ratio deviates from 1.0. The flat particles had a better memory of initial structures under the subsequent deposition process, which plays a vital role in force transmission and stress propagation. However, when the aspect ratio approaches 1.0, the stress state behaves as a joint result of maintained and gained contacts. For a certain range of aspect ratios, the newly generated interactions of elongated particles induced the major stress in the horizontal plane, which thus produces a significant pressure dip phenomenon. The results indicated that complex models accounting for contact creation are required to capture the pressure profile.

Role of morphology and chemical composition of PM for particle deposition in human respiratory system: A case study over megacity-Delhi

Morphology and chemical composition altogether determine the fate of atmospheric particulate matter(PM) deposition and inhalation. Site-wise(#20 sites) and cumulative variations in morphology and chemical composition of PM5 in Delhi showed dominance of non-spherical (sharp-edged, angular and flattened) particles followed by spherical ones, rich in elements like C, O, S, N, Al, Si, Cu, Ca, Na, Cl, Fe, Ni, Cr, Zn, Hg, Pb, Mo, etc. having potential health effects. #2650 individual particles analyzed for the morphological parameters like aspect ratio(AR), circularity factor(CIR), surface equivalent radius(SER) and area. Dominant AR and SER values found between ≥1–1.60 and > 0–0.50 μm, respectively showing dominance of non-spherical and fine-size particles in Delhi. The Multiple Path Particle Dosimetry (MPPD) Model used to study variations in deposition potential (regional deposition, lobar deposition, mass deposition and mass flux) of different PM sizes (PM0.4, PM1, PM2.5 and PM5) at different AR values which suggested that AR is an important input parameter of health models to get realistic and unbiased output health data. In addition, study revealed higher coarse particles deposition in the head region affecting upper respiratory tract with their non-spherical shapes whereas higher fine particles deposition in TB and pulmonary regions affecting inner parts of the lungs.

Study of the Tribological Properties of HVOF-Sprayed Ni-Based Coatings on Ti6Al4V Titanium Alloys

In aviation, the relative sliding between titanium alloy components causes varying degrees of wear. This work aimed at reducing abrasion between titanium alloy parts and improving their service life. Three different Ni-based coatings, WC-10Ni, Ni45, and NiCr coatings, are sprayed on the surface of Ti6Al4V alloy by HVOF. Test results of the mechanical and tribological properties of such coatings show that the hardness of the Ni45 and NiCr coatings are 673 HV0.1 and 438 HV0.1, respectively, which are lower than that of the WC-10Ni coating. When subjected to a high load, the Ni45 and NiCr coatings suffer a cracking of flat particle interfaces due to the low hardness, which lowers the fracture toughness more than that of the WC-10Ni coating. The specific wear rates of the coatings gradually decrease with the increase in the coating hardness and fracture toughness. However, the cutting of Ti6Al4V by the WC-10Ni coating and the adhesion of the NiCr coating to Ti6Al4V result in severe wear loss of the Ti6Al4V friction pair. The moderately hard Ni45 coating has a weaker cutting and adhesion effect on Ti6Al4V than the WC-10Ni and NiCr coatings, respectively, and the Ti6Al4V friction pair has the lowest wear loss. This study is a viable scheme for the design of wear-resistant coatings on titanium alloy surfaces and for improving the tribological properties between titanium alloy components.

Shape-dependent regions for inertialess spheroids in turbulent channel flow

The alignment between the inertialess spheroids and the directions of the fluid Lagrangian stretching or compression is sensitive to the particles shape near the wall but not near the center of the channel [Cui et al. “Alignment statistics of rods with the Lagrangian stretching direction in a channel flow,” J. Fluid Mech. 901, A16 (2020)]. This observation is further investigated in the current study to uncover the mechanism of particle alignment behavior in different regions of channel flows at Reτ≈180 and 1000. Meanwhile, by using the probability distributions of the sign of the discriminant of the linear term in the Jeffery equation, we find that the turbulent channel flow can be distinctly divided into strong and weak shape-dependent regions. In the weak shape-dependent region, the slender (flat) particles have extraordinarily similar alignments with the directions of fluid Lagrangian stretching (compression). However, in the strong shape-dependent region, the alignments of these inertialess particles are sensitive to the particles shape, especially with the particle positions approaching the wall. The ranges of these shape-dependent regions rely on the Reynolds number, but the probability distributions of the sign of the discriminant of the linear term in the Jeffery equation are a useful tool to distinguish these shape-dependent regions in the wall turbulence regardless of the Reynolds number.

Influence of particle shape on the interaction processes of coal particles and bubbles in saline solution

Understanding the role of coal particle shape in the flotation process is helpful in achieving a clean usage of coal slime flotation. In this investigation, the anthracite coal surface was modified using a chlorinated salt solution containing Na+, Ca2+, or Fe3+. Coal particles with four surface shapes were prepared: angular coal particles (ARPs), prismatic coal particles (PCPs), flat coal particles (FTPs), and spherical coal particles (SLPs). The ARPs were subdivided into five kinds of curvature: 3π/2, 21π/20, 7π/11, π/3, and π/10, and the PCPs were subdivided into five kinds of dihedral angles: 30°, 60°, 90°, 120°, and 150° according to the surface flatness of the ARPs and PCPs. Six ion concentrations, of 0, 5, 10, 20, 40, and 80 mmol/L, were examined. We tested the liquid film drainage time (LDT), maximum repulsive force (MRF), and maximum attractive force (MAF) between these coal particles and bubbles. The results show that at a constant solution concentration for a particular particle shape, the MRFs and LDTs increase in the order of Fe3+<Ca2+<Na+, and the MAFs decrease in the order of Fe3+>Ca2+>Na+. This indicates that Fe3+ enhances the adhesion probability and stability of anthracite particles and bubbles by the greatest extent, followed by Ca2+ and Na+. For a particular shape of coal particles, an increase in the ion concentration reduces the LDT and MRF and increases the MAF. When the curvature of the ARPs is 3π/2 and the dihedral angle of PCPs is 30°, the order of the LDTs of coal particles and bubbles is ARP < PCP < SLP < FTP. With a decrease in the curvature of ARPs and an increase in the dihedral angles of PCPs, their LDTs gradually approaches that of the FTP. The results for MRF and MAF are consistent with the LDT. Therefore, the ARPs with larger curvature and PCPs with smaller dihedral angles easily attach to air bubbles, and the decrease of the curvature and the increase of dihedral angles hindered the detachment. Adhesion and detachment experiments were conducted to confirm these results. The coal particles had a tendency to contact the bubbles with their available tips while sliding on the surfaces of bubbles to induce liquid film rupture. In addition, regardless of the coal particle shape, increasing ion concentration changes the detachment position of coal particles. These findings are consistent with the results of LDT, MRF, and MAF measurements. In this study, the role of coal particle shape in saline solution were systematically investigated, which provides a possible solution for the problems caused by the presence of ions in the flotation process using saline as the water source.

Effects of Coarse Aggregate Shape Parameters on Workability, Design, and Performance Characteristics of Stone Matrix Asphalt Mixes

The present study explores the effects of coarse aggregate shape characteristics on the performance of stone matrix asphalt (SMA) mixes. The aggregates were produced with two commonly using different crushing mechanisms, namely JH (jaw-horizontal shaft impactor) and JJV (jaw-jaw-vertical shaft impactor). The digital image based Aggregate Image Measurement System was used to capture aggregate shape parameters. The effects of aggregate shape on the SMA mix were captured via various indicators, such as workability, design (resilient and dynamic modulus), and performance parameters (i.e., shear, rutting, and fracture). The shape characterization showed that aggregate produced from JH had significantly higher angularity, texture, and flat and elongated particles compared to JJV. However, the JJV-produced aggregate had significantly higher sphericity/cubicity compared to JH. Moreover, the SMA mix derived from JJV offered better rutting and shear resistance, and modulus values, while both mixes (i.e., JH and JJV) showed a similar fracture resistance behavior. Conclusively, it was perceived that aggregates having high cubicity with moderate angularity and texture offered significantly improved performance. Therefore, it can be inferred that the type of crusher can significantly affect aggregate shape characteristics and the subsequent performance of SMA mixes.

Investigating the Role of African Horse Sickness Virus VP7 Protein Crystalline Particles on Virus Replication and Release.

African horse sickness is a deadly and highly infectious disease of equids, caused by African horse sickness virus (AHSV). AHSV is one of the most economically important members of the Orbivirus genus. AHSV is transmitted by the biting midge, Culicoides, and therefore replicates in both insect and mammalian cell types. Structural protein VP7 is a highly conserved major core protein of orbiviruses. Unlike any other orbivirus VP7, AHSV VP7 is highly insoluble and forms flat hexagonal crystalline particles of unknown function in AHSV-infected cells and when expressed in mammalian or insect cells. To examine the role of AHSV VP7 in virus replication, a plasmid-based reverse genetics system was used to generate a recombinant AHSV that does not form crystalline particles. We characterised the role of VP7 crystalline particle formation in AHSV replication in vitro and found that soluble VP7 interacted with viral proteins VP2 and NS2 similarly to wild-type VP7 during infection. Interestingly, soluble VP7 was found to form uncharacteristic tubule-like structures in infected cells which were confirmed to be as a result of unique VP7-NS1 colocalisation. Furthermore, it was found that VP7 crystalline particles play a role in AHSV release and yield. This work provides insight into the role of VP7 aggregation in AHSV cellular pathogenesis and contributes toward the understanding of the possible effects of viral protein aggregation in other human virus-borne diseases.

Analysis of horizontal silo pressure distribution by filling method based on experimental data

The work presents an analysis of the results of the fill-in condition influence of particle inclination on horizontal silage pressure. Analyzed data were obtained from experiments on a rectangular silo model with rigid walls in a different fill-in condition. The filler was a composite mixture of sand and flat shell particles (2:1). The analysis of the results concluded that the volume weight of the composite mixture depends on the fill-in method, which affects the horizontal silage pressures. At filling of 0° and 45°, the pressure is slightly different from Jansen's theory (max 19%) which can be neglectable. Horizontal silage pressures are functionally dependent on the filling method (up to 44%), which should definitely be taken into account.

Spacing Dependent Mechanisms of Remagnetization in 1D System of Elongated Diamond Shaped Thin Magnetic Particles

Four different switching scenarios have been revealed for a linear chain of flat magnetic particles with long axes perpendicular to the axis of the chain. The diamond-like shape of the particles has been previously shown to be the best to ensure a uniform and stable magnetization within a single particle, that is, to behave as a macrospin. The occurrence of each scenario depends on the distance of the particles in the chain. Whereas long distances favor direct remagnetization of a ferromagnetic configuration “all up” to the one “all down”, a short enough distance allows the system to recover its ground state at a zero field, that is, an antiferromagnetic order. This allows any information stored by a magnetic field to be erased. Vortex-like metastable defects have been noticed for intermediate distances. A longitudinal magnetization component at extremely short distances has been noticed as well as specific systems of domain walls. The hysteresis loops and magnetization maps in the particles have been presented for each scenario. The potential applicability of the findings to the fabrication of memory storage devices has been discussed.

Al-Supermalloy and Al-Supermalloy@oxide magnetic powder. Structural, morphological, thermal, and magnetic characterization

A new alloy, Supermalloy alloyed with aluminum, in powder form, has been obtained by mechanical alloying using elemental powders. An amount of 5 wt% of Al has been added to Supermalloy (Ni75Fe20Mo5) resulting a magnetic alloy (Al-Supermalloy) with the nominal chemical composition of Ni71·25Fe19Mo4·75Al5 wt.%. The powder obtained after 20 h of mechanical alloying has been subjected to superficial oxidation to obtain Al-Supermalloy@oxide powder. The alloy is single FCC phase after 15 h of mechanical alloying having a mean crystallite size of 15 nm. In the early period of alloying the particles are flattened and irregular shaped, but by increasing the alloying time the amount of flattened particles decreases. At about 550 °C the recrystallisation of the structure is finished and further increase of the temperature leads to the increase of the crystallite size. The particles size of the single-phase alloy ranges from a few to tens of microns. The Curie temperature of the newly alloy is around 440 °C. The magnetization of the material increases even after the full formation of the single phase and several phenomena compete to this increase. The oxidation of the particles was successful resulting oxidized particles of Al-Supermalloy@oxide. The presence of oxides was proved by FTIR and EDX investigations. The magnetization of the core-shell composite is lowered only by 1.5% as compared to the uncovered sample this indicate that the oxide is present as a thin layer. The thickness of the oxide layer was estimated by magnetization measurement at about 100–200 nm.

Kinematics of the discharge of flat particles from model silos

Kinematics of the discharge of flat particles from model silos

Chemical-mechanical treatment of potato starch for isolation of nanocrystal particles

Starch nanocrystals were isolated by a combination of acid hydrolysis and sonication of native potato starch. The obtained samples were examined by XRD, scanning electron microscopy and static light scattering. An increase in hydrolysis time increases the degree of crystallinity from 47 to 66%. By changing the processing conditions, it is possible to isolate particles of a given size. First, submicron flat particles with dimensions of 3000–5000 nm and a thickness of 80–100 nm are obtained. With longer processing, approximately isometric nanoscale particles remain. Based on the obtained data, a stepwise topochemical mechanism for the formation of starch nanoparticles was proposed.

Effect of particle shape on void fraction

Void fraction and bulk density are the fundamental characteristics of most practical analyses of particulate materials. Most industrial particles are not spherical and can have various shapes. In this study, the effect of particle shape on the free and tapped void fractions was tested. Based on the analysis of well-defined geometries, high circularities was considered equivalent to sphericity. All the experiments conducted with a high Archimedes number (Ar), where the Ar effect was negligible, demonstrated that three trend lines were obtained as a function of sphericity for long, flat, and high-sphericity particles. Two factors can be defined by dividing the void fractions of the non-spherical particles by that of spherical particles, namely, the shape and Ar factors. Accordingly, the void fractions are calculated and predicted to be within ±5% for free void fractions and ± 7% for tapped void fractions.

Sulfonation of the interlayer surface of kaolinite

The interlayer surface of kaolinite was functionalized with sulfonic acid groups through the grafting of propane sultone. The presence of the modifier was confirmed by the increase of the d001-value from 7.1 Å (starting kaolinite) to 12.3 Å. The formation of stable Al-O-C bond following the ring-opening reaction of the cyclic sultone was confirmed both by the 13C NMR and FTIR characterizations. After a full washing of the modified material with water, the clay mineral appears as functionalized flat particles with thicknesses not exceeding 0.02 μm. This was the consequence of the delamination, due to the ionization of the grafted sulfonic acid groups in water, followed by a substantial decrease of the interlayer cohesive force. The nanohybrid material with structural formula determined from the thermo gravimetric analysis, Al2Si2O5(OH)3.77(O(CH2)3SO3H)0.23, was tested as adsorbent for methylene blue, a cationic dye. The amount adsorbed was at least two times higher compared to pristine kaolinite (76.8 μmol g−1 instead of 32.9 μmol g−1). This performance was less important than expected because the dye was adsorbed as trimer (according to the UV–Vis analysis of the aqueous suspension of the modified clay in dye solution), a too bulky configuration to fit in the interlayer space of the modified kaolinite.

The influence of coal particle shapes on the interaction behavior of air bubbles and coal particles

ABSTRACT In order to study the influence of coal particle shape on the interaction behavior of air bubbles and coal particles, coal particles were divided into three types according to the contact region with air bubbles. They were angular coal particles (ARP) in point contact, prismatic coal particles (PCP) in line contact, and flat coal particles (FTP) in surface contact. Spherical coal particles (SLP) were used as a reference to compare the above three coal particles. We tested the acting time and force of coal particles with air bubbles using an instrument designed by us. For a systematic study, according to the angle of the contact location with the air bubble, the ARP and the PCP were subdivided into 5 types. By comparing the difference in the drainage time (DT) of the liquid film, the three-phase contact-line (TPCL) expansion time, the maximum repulsive force (MRF), and the maximum attractive force (MAF) during the acting process, the influence of the coal particle shape on the interaction process was systematically explored. The research results show that the order of DT, MRF, and MAF of the liquid film caused by the interaction of coal particles with bubbles is angular < prismatic < spherical < flat shape, while the order of TPCL expansion time is the opposite. As the angle of ARP and PCP increases, the DT, MRF, and MAF of the liquid film increase, the MAF of SLP and FTP are 54.50 μN and 104.99 μN, respectively, while the TPCL expansion time decreases with the increase of the angle. The MRF of SLP is similar to that of PCP of 120°, which are −43.42 μN and −41.84 μN, respectively. We further studied the adhesion and detachment processes. The results show that 95% of the coal particles will collide with the bubbles in thier sharp tip regions, and only 5% of the coal particles can collide with the bubbles in their plane regions when attachment is achieved. When the liquid film is induced to rupture, the irregularly shaped coal particles tend to contact the bubbles with their tips; when detachment occurs, the sharp tips of the coal particles will be dominant locations of detachment from the bubbles. Therefore, the shape of coal particles greatly affects the interacting process. This study provides a theoretical basis for effectively improving the flotation performance by changing the shape of coal particles in the process of coal flotation.

Three-Dimensional Nanoscale Morphological Surface Analysis of Polymeric Particles Containing Allium sativum Essential Oil.

Biodegradable particles were developed using poly-ε-caprolactone and gelatin carriers containing different concentrations of Allium sativum essential oil (EO) (360 µg/mL, 420 µg/mL, and 460 µg/mL). Atomic force microscopy was useful to evaluate the particles’ surface based on morphological parameters. The particles’ size varied from 150 nm to 300 nm. The diameter was related to the increase of the particles’ height as a function of the EO concentration, influencing the roughness of the surface core values (from 20 to 30 nm) and surface irregularity. The spatial parameters Str (texture aspect ratio) and Std (texture direction) revealed low spatial frequency components. The hybrid parameters Sdq (root mean square gradient) and Sdr (interfacial area ratio) also increased as a function of the EO concentration, revealing fewer flat particles. On the other hand, the functional parameters (inverse areal material ratio and peak extreme height) suggested differences in surface irregularities. Higher concentrations of EO resulted in greater microtexture asperity on the particles’ surface, as well as sharper peaks. The nanoscale morphological surface analysis allowed the determination of the most appropriate concentration of encapsulated EO, influencing statistical surface parameters.

Simultaneous Determination of Multi-Class Pesticide Residues and PAHs in Plant Material and Soil Samples Using the Optimized QuEChERS Method and Tandem Mass Spectrometry Analysis.

New analytical approaches to the simultaneous identification and quantification of 94 pesticides and 13 polycyclic aromatic hydrocarbons (PAHs) in five representative matrices (pepper, apple, lettuce, wheat, and soil) were developed. The analyses were based on gas chromatography coupled with triple quadrupole tandem mass spectrometry (GC-MS/MS). The procedure was optimized by changing the solvent used during the extraction, from acetonitrile to the acetone: n-hexane mixture at a volume ratio of 1:4 (v/v), as well as the use of a reduced amount of water during the extraction of compounds from cereals. An additional modification was the use of florisil instead of GCB in the sample cleanup step. A full method validation study was performed, at two concentration levels (LOQ and 1000 × LOQ), which showed satisfactory results for all analytes from the PAHs group, with recoveries ranging from 70.7–115.1%, and an average RSD of 3.9%. Linearity was tested in the range of 0.001–1.000 mg/kg and showed coefficients of determination (R2) ≥ 0.99 for all PAHs. Satisfactory recovery and precision parameters (LOQ and 100 × LOQ) were achieved for almost all analytes from the pesticide group in the range of 70.1–119.3% with the mean RSD equal to 5.9%. The observed linearity for all analytes in the concentration range of 0.005–1.44 mg/kg was R2 ≥ 0.99, with the exception of famoxadone, chizalofop-p-ethyl, prothioconazole, spirodiclofen, tefluthrin, and zoxamid. The extended uncertainties were estimated, using a top-down approach of 9.9% (average) and 15.3% (average) for PAHs and pesticides samples, respectively (the coverage factor k = 2, the 95% confidence level). Ultimately, the method was successfully applied to determine pesticide residues in commercial samples of fruit, vegetables and grain, and soil samples for PAHs, which were collected from selected places in the Podkarpacie region. A total of 38 real samples were tested, in which 10 pesticides and 13 PAHs were determined. Proposed changes allow us to shorten the sample preparation time (by 20%) and to reduce the consumption of organic solvents (by 17%). The use of florisil for sample cleanup, instead of GCB, improves the recovery of compounds with flat particles.

Self-assembly of hydrophobic–amphiphilic diblock copolymers in solution

Thermoresponsive polymers are usually characterized by a locally amphiphilic chain structure and their self-assembly in solution is controlled, in particular, by the surface activity of the monomer units or side chains. We theoretically study the condensed state of a single diblock copolymer molecule consisting of a hydrophobic block and amphiphilic block with hydrophobic groups in the backbone and pendant polar groups. The equilibrium parameters of the polymer globules of different shapes are determined using the mean-field approach to determine the most favorable structure. Morphological diagrams of condensed macromolecules are presented depending on the chain length, amphiphilic block fraction, interaction parameters, and pendant volume and length. The diagrams are compared with those of a copolymer molecule with the same fraction of amphiphilic monomer units which are regularly distributed along the chain. The diblock copolymer molecule is found to form a single spherical or flattened particle, with the core from the hydrophobic block, or a granular micelle consisting of spherical or nearly spherical particles, in agreement with the experimental data in the literature. The optimal chain parameters for self-assembly into a stable single core–shell particle are predicted.

Hydrothermal oxidation improves corrosion and wear properties of multi-arc ion plated titanium nitride coating for biological application

Surface oxidation is found to improve the osseointegration of titanium nitride (TiN) coatings on implantable titanium devices; nevertheless, systematic studies on effects of oxidation are still needed. In this study, multi-arc ion plated (MAIP) titanium nitride (TiN) coating was hydrothermally oxidized in pure water and then the structural, corrosion and wear properties of the coating were studied. A dense oxide layer of 20–50 nm in thickness is formed on TiN after hydrothermal oxidation above 200 °C. The layer is composed of flat anatase particles with a length of 50–150 nm and smaller anatase nanocrystallines located on their surface. The passivation behavior of TiN becomes much stronger in simulated saliva after oxidation treatment, showing a wider passivation range, a lower corrosion current and greatly improved impedance. In addition, the open circuit potential (OCP) of oxidized TiN remains much higher than that of untreated after 50 days of immersion. Sliding friction experiments against zirconia (ZrO2) ceramic balls show that the wear type for the untreated TiN coating involves severe plowing and deformation. In contrast, only slight plowing is found on the surface of TiN covered with a compact anatase layer; the friction coefficient decreases sharply and the wear loss decreases obviously.

Experimental Study on Microstructure of Unsaturated Expansive Soil Improved by MICP Method

The soil water characteristic curve and microstructure evolution of unsaturated expansive soil improved by microorganisms in Nanning, Guangxi were studied by means of filter paper method and scanning electron microscope imaging (SEM). Based on Fredlung &amp; Xing model, the influence law of different cement content on the soil water characteristic curve of improved expansive soil is proved. According to the analysis of SEM test results, the influence mechanism of MICP method on the engineering characteristics of improved expansive soil is revealed. The results show that with the increase of cement content, the saturated water content and residual water content of the improved expansive soil gradually increased. At the same time, the water stability gradually increased while the air inlet value gradually decreased. The improved expansive soil changes from the superposition of flat particles and flake particles to the contact between spherical particles and flake particles, which indicates that the aggregate increases significantly. With the increase of the content of cement solution, the contact between particles tends to be smooth and the soil pores gradually tend to be evenly distributed. The particle size and microstructure of soil particles was changed and the connection between particles was enhanced in the improved expansive soil. Eventually the strength and water stability of expansive soil were improved. The conclusions above not only provide a theoretical basis for the in-depth study of engineering characteristics of unsaturated expansive soil improved by MICP method, but also offer theoretical evidence for perfecting engineering technology of expansive soil improved by MICP method.