Ratio Of Particles Research Articles

Effects of multiple factors on particle size selectivity under artificial extreme rainfall events on simulated Gobi surface

Understanding multiple-factor effects on particle size selectivity by extreme rainfall events in Ala-Shan Gobi desert is of great significance for better estimation of potential Asian dust emission sources. Artificial rainfall simulation experiments were used to investigate the particle size selectivity characteristics by extreme rainfall events under different rainfall intensities (20 mm h−1 and 40 mm h−1), slope gradients (3° and 15°) and gravel coverages (0, 30%, and 60%). Moreover, the relations of clay content (Clc), silt content (Sic), fine particle (< 50 μm) content (Fic) and enrichment ratio of fine particles (ER<50) with multiple factors were regressed and validated. Results show that rainfall intensity significantly (P < 0.05) affect runoff and sediment yield processes, but slope gradient was a dominant factor that changed particle size distribution (PSD). The selectivity of fine particles was higher at low rainfall intensity (20 mm h−1), gentle slope (3°) and moderate gravel coverage (30%), with ER<50 reaching 6.14, which dominate the potential Asian dust emission sources. The interaction were discussed and classified into ‘Synergy’ and ‘Trade-off’. Clc and Fic showed negative exponential relationship with rainfall intensity and slope gradient, but positive exponential relationship with gravel coverage. While Sic and ER<50 showed negative power function relationship with rainfall intensity, slope gradient and gravel coverage. These findings could help to understand the effects of multiple factors on potential sources of Asian dust emission under extreme rainfall events in Gobi region of northwestern China and provide basic science reference for the prediction of dust emission in this region.

The sedimentation behaviors of elliptical active particles in a rectangular box

The “squirmer” model, a micro-swimming model driven by an imposed tangential velocity at the boundaries, is used to simulate the sedimentation behaviors of one and two elliptical active particles in a two-dimensional rectangular box. Six typical locomotion modes (including the steady vertically moving (SVM), steady inclined sliding (SIS), unilateral attracted oscillating (UAO), bilateral attracted oscillating (BAO), chaotic attracted oscillating (CAO), and up-down alternate tumbling (UAT)) are identified. The effects of particle aspect ratio (AR = 0.2∼1.0), self-propelling strength (β = −5∼5), swimming Reynolds number (Res = 0.1∼5.0), and density ratio of particle to fluid (γ = 1.01∼2.1) on the sedimentation behaviors of particles (the locomotion modes and the terminal Reynolds number (Ret)), are discussed. It is concluded that the locomotion modes are closely relevant to AR, γ, and Res. The collision between particles only changes their orientations but is not sensitive to the final locomotion modes. At Res≥4.0, the modes of puller type particles change from UAO to SIS or SIS to UAT. Meanwhile, it is found that (ⅰ) particle's Ret increases with AR when it is in SIS; a larger AR leads to a greater decay of Ret when it is in UAO; the decay of Ret is smooth when it is in BAO. (ⅱ) A large |β| results in a large Ret for a particle in SIS, and it is more prominent for a puller type particle than a pusher type particle. (ⅲ) In the falling period, Res speeds up a pair of pusher type particles, while it is more prominent for the pusher type particle with a lower initial position; Res also speeds up both neutral type particles with a linear relationship of Ret∼1.35Res. γ and Ret are linear positive correlated for both a pair of pusher type particles and a pair of neutral type particles.

Material characterisation of anodising effects on small fatigue crack nucleation in AA7XXX alloys

The precursor cleaning steps in the anodising surface finish process for aluminium alloy aircraft parts are known to lead to etching of surface-breaking intermetallic particles and grain boundaries, which in turn leads to preferential sites for fatigue crack nucleation. Type 1C anodising per MIL-A-8625F, is a favoured aircraft aluminium part corrosion protection treatment meeting modern health and environmental requirements. Type 1C anodising uses electrolysis in a non-chromic acid bath (typically based on sulphuric, boric-sulphuric or phosphoric acid formulations) to develop a thick aluminium oxide surface layer. In previous studies the equivalent initial damage sizes of these nucleation sites was calculated from near surface fatigue crack growth measurements using quantitative fractography in both Type 1C anodised aluminium alloy 7050-T7451 and 7085-T7452. A notable difference was observed in the values for these two materials with AA7085-T7452 equivalent initial damage sizes being significantly smaller. Since these values are critical crack starting size assumptions in fatigue life analysis for aircraft fleets, the observed differences must be investigated and explained for notionally similar alloys under identical conditions.In this work, the material surrounding the population of crack nucleation sites in several Type 1C anodised fatigue tested specimens manufactured from AA7050-T7451 and AA7085-T7452 materials has been characterised using precise surface preparation methods and scanning electron microscopy techniques. It has been demonstrated that there is a statistically significant difference in the number, size, aspect ratio and distribution of surface breaking Al7Cu2Fe intermetallic particles beneath the anodising layer that, when etched out during the anodising process, are responsible for fatigue crack nucleation in 7050-T7451 over 7085-T7452 material. The increased size, angular shape and coverage of these intermetallics in AA7050 serves to increase their effectiveness as preferential locations for fatigue crack nucleation through two mechanisms, as a highly localised stress concentrating feature, as well as through their ability to sample more of the material's microstructural features ensuring a discontinuity is present in the most favourable orientation and location for fatigue crack nucleation.

Preparation and Characterization of Ultrafine Nitroguanidine with Different Aspect Ratios

Preparation and Characterization of Ultrafine Nitroguanidine with Different Aspect Ratios

Effects of Nickel Promotion on the Catalytic Performance of In Situ Synthesized Suspensions of Molybdenum Disulfide Nanoparticles

The study investigates the activity of in situ synthesized suspensions of nickel-promoted molybdenum disulfide particles in the hydroconversion of crude oil vacuum residues. The catalyst suspensions were prepared in situ from water-in-oil emulsions of aqueous solutions of precursors, specifically ammonium paramolybdate and nickel nitrate. The catalytic tests were carried out in a flow-type reactor at 430°C, WHSV 1 h–1, and 7 MPa hydrogen, with the Mo:Ni atomic ratio in the catalyst particles ranging from 1:0.022 to 1:1.43. The XRD of the toluene-insoluble solids (TIS) extracted from the hydrogenates identified sulfides such as MoS2, Ni3S4, and Ni3S2 in the dispersed catalyst. Increasing the nickel content in the catalyst favored its hydrogenation activity, which was indicated by an enhancement in the feed conversion, an increase in the content of paraffins and naphthenes, and a decrease in the sulfur content in the distillates and TIS derived from the hydrogenates. The conversion of high-molecular-weight feed components (resins, asphaltenes, and heavy aromatics) was enhanced as a result of the nickel promotion of the dispersed MoS2.

Influence of the abrasive shape-position characteristic on the grinding thermo-mechanical coupling

Grinding is a generally utilized method, removing excess materials through effective abrasives. The grinding abrasives with multiple shape-position characteristics play a dominant role in determining the thermo-mechanical coupling, which may influence the surface quality directly. To investigate this correlated influence mechanism, this paper focuses on the abrasive shape and position characteristic on the grinding thermo-mechanical process with the analytic single abrasive interaction force model by considering the abrasive shape and its distribution information. It can be found that the mapped dynamic grinding temperature is actually discretized on the workpiece surface, which is on account of the diversity of the abrasive shape and its distribution. Moreover, higher spherical and conical abrasive particles, as well as lower pyramid shaped abrasive particle ratios, can generate greater specific grinding energy with a discretized temperature distribution, when compared with a higher proportion of pyramid shaped abrasive. The study can be utilized to provide valuable theoretical foundation for engineering practice by preparing structural wheel and its grinding property.

Properties of flyash based wood geopolymer composite

Geopolymers are inorganic adhesive synthesized from industrial waste such as fly ash thus the development of wood geopolymer composite would be a low carbon footprint material. Geopolymers, being a non-formaldehyde adhesive can be used as an alternative binder for wood based composites where environmentally friendly and sustainability of product is important. In this study flyash as precursor is been used in the development of wood geopolymer composite product. Flyash is activated with a combination of sodium hydroxide and sodium silicate solutions at a weight ratio of 1:2.5 for geopolymer formation. The study investigated the properties of wood geopolymer composite made with ratios of wood particle to flyash percentage (23/77), (37/62), (44/55), (50/50) and (57/43). Geopolymer formation was observed by X-ray Diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Influence of wood particles in wood geopolymer composite were observed by Scanning electron microscope. The study shows that the water absorption and thickness selling properties of all the formulations of wood geopolymer composites are comparable with the medium density particle board and cement-bonded particleboard according to the IS:3087–2005 standard and IS: 12406: respectively. Highest mechanical properties and good bond strength was obtained by the composite containing 23% wood particle ratio with 77% percent flyash. However, still improvement in mechanical properties is needed to achieve the mechanical properties comparable to cement bonded particle board.

Improved Quality of Wood Plastic Composite (WPC) Through the Addition of Maleic Anhydride (MAH)

Due to the hydrophilic nature of wood particles compared to the hydrophobic nature of plastic, Wood Plastic Composite (WPC) has the weakness that it requires the use of a coupling agent to strengthen the bond between its constituent components. The aim of the study was to determine the effect of adding Maleic Anhydride (MAH) on the quality of WPC (P1 0%, P2 4% and P3 8%). The flat pressing process takes 20 minutes at a temperature of 180°C and a press machine pressure of 30 bar, using a plastic to wood particle ratio of 60:40. Data were processed using a completely randomized design (CRD). P3 treatment (8% MAH) gave the best test results (densityof 0.704 g/cm3, moisturecontentof 2.321%, waterabsorptionof 15.719%, thicknessswellingof 1.733%, modulusofelasticityof 869.029 N/mm2, modulusofruptureof 6.517 N/mm2, and internal bondingstrengthof 0.926 N/mm2). Almost all tests on the physical properties of WPC meet the SNI 8154-2015 standard, but none of the tests on the mechanical properties of WPC meet the standards. This WPC performs well for non-structural use although it is not yet suitable for structural use.

Eletrospun Polymer Composite to be Used in Cardiology

In order to restore the cardiac damaged tissues cardiac patches have been employed Electrospinning technique has been adopted to design cardiac patch and the same has been assessed with regard to its physicochemical characteristics. Polyurethane coated with cobalt nano particles has been used to prepare the patch and has been synthesized using green approach by means of green tea containing polyphenols. Nanoparticles with varied morphology have been obtained using different concentrations of cobalt salt concentrations mixed with green tea solution. Also, cobalt nanoparticles so synthesized CoNPs with specified concentration has been applied on the polyurethane adopting electrospinning technique. Studies using SEM have revealed that the developed patches having greater concentration of cobalt nano particles showed smaller diameter in comparison with polyurethane. The polyurethane cobalt nanoparticles patch rendered hydrophilic surface with lower ratio of cobalt nano particles. Whereas, greater ratio of cobalt nano particles have shown improved strength compared to the pristine polyurethae. Patches with the improved physicochemical properties and mechanical strength can be exploited for cardiac applications.

Modelling dynamic breakage in rock blocks with different elongation and flatness ratios upon impact

AbstractThe two crucial shape factors (elongation ratio and flatness ratio) of brittle particles may influence the dynamic breakage of brittle particles upon impact. Hence, three‐dimensional discrete element method simulations of brittle rock blocks with different shapes upon normal impact were performed. The simulated results indicate that the elongation ratio, that is, ratio of width to length and flatness ratio, that is, ratio of thickness to width can significantly affect the breakage of brittle rock blocks. Three fracture mechanisms, that is, fragmentation, horizontal tensile fracture and vertical tensile fracture, were revealed, which determine the dynamic breakage of rock blocks. The fragmentation results in numerous single‐sphered fragments with velocities even larger than 2 times of the initial velocities. Fragmentation can provide a buffering effect at high impact velocities of larger than 4 m/s. With an increasing elongation ratio or flatness ratio, the phenomenon of fragmentation gradually disappears. The reflection of a compression stress wave results in horizontal tensile fracture. The expansion in the plane perpendicular to the impact velocity results in vertical tensile fracture.

Influence of particle shape on creep and stress relaxation behaviors of granular materials based on DEM

The creep and stress relaxation behaviors stem from time-dependent changes in the microstructure of granular materials. As a non-negligible inherent granular material characteristic, particle shape plays a significant role on the formation and evolution of microstructure. However, the effects of particle shape on creep and stress relaxation behaviors of granular materials are still open questions. In this study, 3D DEM models based on the rate process theory and superellipsoids are incorporated to simulate the creep and stress relaxation of granular samples with different aspect ratios and blockiness. The results show that the aspect ratio and blockiness of particle have a great effect on creep and stress relaxation. However, the effects of aspect ratio and blockiness on creep and stress relaxation are coupled. Further analysis on contact forces shows the influences of aspect ratio and blockiness on creep mainly come from the contact force ratio. The influences of the aspect ratio and blockiness on stress relaxation mainly arise from the variation of the normal contact force anisotropy of the granular assemblies. The above results provide the tendency and mechanism on the effects of particle shape on creep and stress relaxation of granular assemblies.

Synergizing electrical, mechanical, and radiation shielding properties of dendritic copper filled epoxy polymer composites

The study examined the properties of epoxy composites with dendritic copper (Cu) particles through various tests, including FTIR, DSC, TGA, electrical conductivity, and mechanical tests. The addition of Cu particles to the composites improved their electrical conductivity and mechanical properties, particularly tensile strength and flexural modulus. The Tg temperature of the composites could be adjusted by varying the Cu particle ratio. Notably, in the study, we prepared composites with varying Cu particle concentrations, specifically at ratios of 1%, 2%, 3%, 4%, 5%, and 6%, and observed distinct effects on the properties of the epoxy-Cu composites. Although there was no chemical bonding between the epoxy and Cu particles, the Cu additive acted as a pinning agent, restricting the movement of the polymer chains. This suggests that incorporating small amounts of Cu into epoxy composites can enhance their properties, making them suitable for applications in the electrical and electronics industry. Additionally, we evaluated the shielding properties of selected epoxy-based composites incorporating copper powder against gamma radiation with energies of 59.5 keV, 661.6 keV, and 1332.5 keV, and also investigated the composites' ability to attenuate gamma rays, recommending specific composites (ECU6, ECU1, and ECU2) for different energy levels of gamma rays. SEM examinations showed that the addition of Cu particles significantly altered the microstructure and mechanical properties of the composites, resulting in an irregular and rough fracture surface and decreased structural integrity.

Micro-mechanical analysis of particle shape effect on suffusion of gap-graded soils

Suffusion refers to the process of fine particles carried away from a coarser soil matrix by seepage flow. Numerical simulations of coupled fluid–solid methods are wildly used in analyzing micro and macro behaviors of gap-graded soils during suffusion. However, the solid particles are usually simplified to spheres, resulting in inaccurate detachment, transmission and clogging mechanisms. In this study, the complex particle shape factor is taken into account in CFD–DEM. A series of numerical tests were conducted to explore the effects of aspect ratio both for fine and coarse particles. Macroscopic and microscopic information of suffusion process is obtained. Numerical results indicate that particle shape plays a significant role in suffusion.

Physical and mechanical properties of particleboard mixed with waste ACQ-treated wood

In this study, we recycle alkaline copper quaternary (ACQ) -treated wood used as a material for pyrolysis and gasification. The physical and mechanical properties of particleboards manufactured according to the mixing ratio and resin type (phenol–formaldehyde resin; PF, urea–melamine formaldehyde resin; UMF) were compared as materials for particleboard, which are used for wood recycling. According to the increase of ACQ particle input ratio, the PF particleboard did not differ in density; however, the thickness welling rate (TSR) and water absorption rate (WAR) decreased. The density of the UMF particleboard increased and the TSR and WAR also decreased. Although the bending strength (BS) of the PF particleboard increased, the internal bond strength (IB) did not show a difference. The UMF showed no difference in BS, but the IB improved. Through physical and mechanical properties, the mixing ratio of ACQ particle and untreated particles was 70:30 as the optimal mixing ratio. The surface was activated by the copper ions of the ACQ treated, which affected the improvement of adhesion and physical and mechanical properties. When ACQ-treated wood, which is classified as waste, was reused as a particleboard, its properties were superior to that of a board manufactured with untreated particles.

The influence of ball collision charging on carbon recovery of fly ash triboelectrostatic separation

ABSTRACT The recovery of unburned carbon particles from fly ash by triboelectrostatic separation can realize energy conservation and solid waste recycling. Collision charging by metal ball has been proposed to enhance the particle charging and improve the unburned carbon recovery efficiency. It can increase the particle contact area, shorten the contact time, and improve the charge–mass ratio of particles. The charging model of ball collision was established. The collision charging process between particles and ball was simulated by CFD-DEM coupling method. The influence of ball material and gas velocity on the charge–mass ratio was studied, and that of gas velocity and voltage on separation was evaluated by experiments. The results showed that the collision charge between particles and metal ball was greater than that between particles. With the gas velocity of 30 m/s, Cu ball collisions obtained a relative maximum charge–mass ratio of 0.393nC/g and 0.275nC/g for carbon and ash particles, respectively. The reasonable experimental conditions were gas velocity of 20 m/s and voltage of 15kV. The loss on ignition of 14.3% and carbon recovery of 90.36% were obtained. Compared with the no-ball system, the ball collision improved the carbon recovery rate by 55.20%.

Shape-dependent radial segregation in rotating drum: Insights from DEM simulations

This study evaluates how particle shape affects the segregation behavior of binary mixtures in a rotating drum. The Discrete Element Method (DEM) is used to investigate radial segregation and its dependence on particle shape by varying the particle’s aspect ratio. Two scenarios are examined: one when the shape of fine particles held constant and varying shape for coarse particles, and another when the shape of coarse particles held constant and varying shape for fine particles. These scenarios help quantify the relative mixing observed in the system for the considered shapes. The SI trend in terms of aspect ratio (AR) for coarse particles is as follows: AR (5.0) > AR (2.5) > AR (1). In contrast, for fine particles, the trend is AR (5.0) > AR (1) > AR (2.5). The results indicate that coarse particles with lower packing density exhibit higher segregation. Conversely, fine particles with pronounced elongation facilitate mixing.

Investigation on dynamic adhesion characteristics and evolution mechanism of charged particles

Understanding the dynamic characteristics and evolution mechanism of charged particles adhered to the wall is of great significance for strengthening production safety and reducing the risk of explosion caused by adhesion. In this study, experiments and simulations are combined to explore the adhesion characteristics of charged particles and reveal the adhesion mechanism. According to the charge-to-mass ratio and particle size distribution of the adhered particles in the experiment and simulation, the dynamic adhesion characteristics of the adhered particles are explored to verify the accuracy of the simulation model. The evolutionary pattern of adhered particles is obtained by exploring the charge characteristics and size distributions of particles. The forces acting on the adhered particles are analyzed to reveal the adhesion mechanism of the particles. Furthermore, the probability of adhered particles with different particle charge and size is studied and the criterion of particle adhesion is proposed.

Unraveling microforging principle during in situ shot-peening-assisted cold spray additive manufacturing aluminum alloy through a multi-physics framework

Cold spray (CS) is a highly potential solid-state additive manufacturing (AM) technique. In situ shot-peening-assisted CSAM was proposed to additively manufacture fully dense deposits using cost-effective and renewable nitrogen gas. The role of in situ shot-peening particles is critical but remains unclear. Here, the process was quantitatively modeled to visualize the dynamic deformation, energy conversion, as well as cell/sub-grain size and microhardness evolutions, compared to those during the conventional CSAM process, identifying the key role of in situ shot-peening particles in the AA6061 extreme deformation and microstructure characteristics during in situ shot-peening-assisted CSAM. High-fidelity modeling was verified fully by comparing the experimental and model-reproduced deformation profiles, cell/sub-grain size distributions, and increases in microhardness. The results show that the kinetic energy of in situ shot-peening particles was 470 times higher and dissipated mainly through AA6061 plastic deformation (86.36% of total energy), leading to significant enhancement of microhardness and tensile strength. Moreover, the mixing ratio of large-size SS410 particles required to create a fully dense deposit was evaluated from an energy perspective, in good agreement with the experiment. This study elucidates the microforging principle during in situ shot-peening-assisted CSAM, providing scientific guidelines for high-quality and low-cost CSAM of high-strength aluminum alloys.

Research on an epoxy resin magnetoelastic abrasive: Application in tool edge preparation

Magnetoelastic abrasive grains have low elastic modulus and magnetism, which can create magnetic brushes in magnetic fields. When magnetoelastic abrasive particles come into contact with a workpiece, they can cause deformation, which increases the effective contact surface area and improves machining quality and efficiency. A method for preparing epoxy resin magnetoelastic abrasives was proposed first. The magnetic particle micromorphology was detected through scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Secondly, based on the theory of particle-filled composite materials and mechanics, the representative volume element (RVE) model was developed using the finite element software ABAQUS. The size ratio of iron and silicon carbide filler particles, particle shape, and arrangement of stress and strain were found to further improve the magnetoelastic abrasive preparation process. To investigate the effect of time, abrasive size, tool speed, disc speed, and disc spacing on the flank face value, rake face value, and shape factor, double disc magnetic preparation was subjected to magnetoelastic abrasive. Compared to traditional drag finishing methods, the magnetoelastic abrasive demonstrated high efficiency and quality. Exploring the application of magnetoelastic abrasives, new technology and methods of edge preparation, and promoting progress in magnetic efficient processing and magnetic optical finishing technology is of great theoretical and practical value.

Thermosetting polymer composites: Manufacturing and properties study

Abstract In the proposed study, TiC is used in different sizes (i.e., 70–150 nm and 200–250 μm) and different ratios (e.g., 0, 10, 20, and 30 wt%) to reinforce the epoxy matrix. Micro- or nano-epoxy–TiC mixtures are poured into molds that have been prepared. The results obtained show a significant improvement in hardness, impact, creep, and tensile strength when the hard particles of nano- and micro-TiC are increased up to 20 wt%. This is due to the good dispersion of the TiC powder with minimal agglomeration and air bubbles. In addition, the results obtained show a decrease in hardness, impact, creep, and tensile strength when the ratio of the hard particles of nano- and micro-TiC is increased to 30 wt% due to agglomeration and air bubbles, which create a path for cracks to propagate. The results of the hardness, impact, creep, and tensile strength tests when 20 wt% nano-TiC composite specimens are used are 22.4, 67.55 J·m−2, 0.0132, and 34.7 MPa, respectively. These results show higher values than other composite specimens. A pin-on-disc wear testing process with various sliding lengths is used to analyze wear behavior. The maximum wear resistance of the 10 wt% of micro-epoxy–TiC composites is found at a load of 5 N and a 100 m sliding distance. Optical microscopy shows small scratches on the 10 wt% micro-epoxy–TiC composite specimens in comparison with the 10 wt% nano-epoxy–TiC composites at a load of 5 N and a 200 m sliding distance.