Effect Of Particle Characteristics Research Articles

A computational study on the effect of particle characteristics on the deposition of small particles in turbulent wall-bounded flows

Particle deposition dynamics in a fully developed turbulent channel flow at a friction Reynolds number of Reτ=180 for two Stokes numbers (St=1 and 10) are investigated using the point particle-direct numerical simulation (PP-DNS) method, considering dilute system and thus, one-way coupling. In particular, the interplay between particle size, particle property (density) and deposition at the same Stokes number has been investigated. It turns out that the dimensionless particle relaxation time (the Stokes number) alone does not provide enough information to capture the deposition dynamics, and particle size (diameter) and density need to be considered to obtain a more comprehensive understanding of deposition process. Furthermore, we demonstrate that gravity significantly alter the deposition patterns of particles with different size and density differently, even if the Stokes number does not change, and therefore the results from zero gravity cannot be extrapolated to non-zero gravity settings, even for small particles. Finally, our results suggest that wall-normal particle velocity variance at the wall plays an integral role in the deposition process, as it approaches a finite value (significantly larger than particle mean velocity) at the wall.

Effect of particle characteristics, kinetics and transport phenomena on the prediction of particle mass loss and products yields during biomass fast pyrolysis

A low computational cost model for the pyrolysis of biomass anisotropic particles was used to study the effect of thermal conductivity of the particle, CRECK kinetic scheme implementation, intraparticle secondary reactions, heats of reaction, and advection on particle conversion prediction. The model considers a shrinking anisotropic cylindrical particle with biomass pseudo-components, the appearance of liquid intermediates, intra-particle mass and heat transport and secondary reactions of volatiles. The model was validated against oak and birchwood single particle experiments. More accurate predictions for mass loss evolution are found when considering the change of the particle thermal conductivity anisotropy with conversion and the temperature dependency of the thermal conductivities of the biomass and the gas phase, compared to ignoring these phenomena. The CRECK biomass pyrolysis reaction scheme provides insights into the effect of biomass composition on the evolution of the liquid intermediate phase allowing future studies about the presence of heavy compounds in the bio-oil and other phenomena such as aerosol ejection. Secondary intraparticle vapor phase reactions showed a negligible effect in volatiles conversion while heterogeneous reactions slightly overestimate its conversion. Heats of reaction and product advection are important for accurate prediction of particle mass loss.

Effect of particle characteristics and foaming parameters on resulting foam quality and stability

In this study, the effects of ten different food-grade particles on bubble quality and stabilization of particle-stabilized food foams in batch and continuous foaming with and without polyglycerol ester (PGE) as an emulsifier were investigated. Particle properties, such as contact angle and porosity, and varying process parameters, such as shear rate and gas fraction, were assessed with respect to their impact on bubble size x50,0, bubble size distribution width and drainage.The smallest bubble size x50,0 in foams without PGE could be achieved with banana powder (88 μm), calcium carbonate (89 μm) and microcrystalline cellulose (79 μm) particles. In comparison, the smallest size in the reference without particles were 105 μm. Combining the use of particles with PGE further reduced bubble size by up to 57% and drainage by up to 100%. Increasing the shear rate from 4922 s−1 (35 μm) to 9844 s−1 (14 μm) resulted in smaller mean bubble sizes and significantly narrower bubble size distributions whereas no distinct correlation between gas fraction and resulting bubble size was found.This study shows that using suitable particles in combination with an optimized foaming process promotes both bubble quality and the stability of foams.

Experimental study on the effects of particle characteristics and pressurization methods on powder compression

Both the particle characteristics and the pressurization methods have an important influence on powder compression behavior. Compression of powder with different average particle sizes, sphericity and adhesion were experimentally investigated by the FT4 rheometer and the pressurized visualization tank. The difference in compressibility caused by particle characteristics and pressurization methods were analyzed. The results show that the smaller the average particle size, the higher the sphericity and the greater the adhesion, the greater the compressibility of the powder. In the experimental range, the effect of gas pressurization is less than mechanical pressurization on powder compression. The relationship between normal stress and gas pressurization rate was proposed and the mechanism of different pressurization methods was also discussed with compression position and mode.

Simulation of the oxidation of microencapsulated oil based on oxygen distribution – Impact of powder and matrix properties

Microencapsulation aims to separate oxidation sensitive compounds from environmental oxygen by a physical barrier. To further understand the effect of particle properties on the protection mechanism, a 2D simulation based on diffusion theory coupled with oxidation kinetics was applied to calculate an idealised hydroperoxide concentration after 100 days of storage. First, the effect of particle characteristics was studied including the particle size, oil droplet size and oil load followed by the impact of matrix properties such as oxygen solubility and diffusivity.Larger particles and larger oil droplets resulted in less hydroperoxides. Even though more oil led to more oxidation products, the hydroperoxides per oil volume decreased up to 26%v/v oil. Higher solubility and diffusion coefficients accelerated oxidation as long it was limited by diffusion transport. Apart from the amount of oxygen entering the system, the ratio of oil being reached by the diffusing O2 to the oil being protected determines the oxidation rate of the oil.

Effect of particle characteristics on particle collision behaviors and heat transfer performance in a down-flow circulating fluidized bed evaporator

The effects of particle characteristics on particle collision behaviors and heat transfer are investigated based on standard deviation and kurtosis analysis in a down-flow circulating fluidized bed evaporator. Results show particle addition can enhance heat transfer for all types of particles. The maximum enhancing factor reaches 33.0% within the experimental range by adding polytetrafluoroethylene particles at ε=1.5%, V=5.16 m3/h and q = 8 kW/m2. For different types of particles, with increased amount of added particles, enhancing factor initially increases and then decreases; standard deviation increases but kurtosis decreases. With increased circulation flow rate, standard deviation and enhancing factor tend to increase but kurtosis decrease. With increased heat flux, standard deviation tends to increase but kurtosis and enhancing factor decrease. Density, sedimentation velocity and surface wetting performance obviously influence particle collision and heat transfer performance. High standard deviation and low kurtosis are beneficial to heat transfer.

Effect of particle characteristics on the evolution of particle size, particle morphology, and fabric of sands loaded under uniaxial compression

This paper presents the results and analyses of uniaxial compression experiments performed on three silica sands. The sands have comparable particle-size distributions, but their particles differ in morphology and strength. Cylindrical samples of the three sands were compressed in a loading device placed inside an X-ray microscope (XRM) and scanned at multiple stress levels during uniaxial compression. 3D tomography data of the samples obtained from the XRM at different stress levels were then analyzed to obtain the distributions of particle size, particle morphology, and interparticle contact normals within the sample. Results indicate that: (1) the compressibility of the sands loaded under uniaxial compression is closely tied to particle morphology and strength and (2) the anisotropy in the orientations of interparticle contact normals generally increases with axial stress; however, this increase is limited by the occurrence of particle crushing in the sample.

Lattice Boltzmann simulation of fluid flow through random packing beds of Platonic particles: Effect of particle characteristics

The influence of particle characteristics, such as shape, size, and volume fraction, on the permeability of porous media was investigated by combining the randomly packed beds of Platonic particles with the lattice Boltzmann method. Quantitative solutions of the permeability as a function of these characteristic parameters in mono-sized particle packing structures were obtained. The D3Q19 model is presented here, which was tested by three simple benchmark tests. A series of packed beds of Platonic particles as well as spherical particles were generated in a random manner. Numerical studies on factors influencing the permeability of materials were carried out to comprehensively study their impacts. The results revealed that the permeability significantly increased with increasing equivalent diameter of the particles (or decreasing volume fraction). At a fixed size and volume fraction of particles, the permeability of the Platonic particle packing structures was also influenced by particle morphology: permeability significantly reduced as the particle sphericity decreased. The permeability of tetrahedral particle packing structures dropped by more than 40% compared with that of corresponding spherical particle systems.

Effects of particle characteristics and consolidation pressure on the compaction of non-spherical particles

The mechanical strength of compacts depends on particle shape, materials properties as well as compaction conditions. This work presented a numerical study on the effects of interparticle friction, yield pressure of particles and consolidation pressure on the mechanical response of compacts formed of non-spherical particles. Non-convexity of the particle shape and interparticle bonding were explicitly considered in a model based on the Discrete Element Method (DEM). In unconfined uniaxial compression, the results showed that compressive strength of compacts increases with interparticle friction, consolidation pressure but decreases with yield pressure of particles. Larger inter-particle friction and consolidation pressure also lead to a more dispersed and uprising failure zones due to the inhomogeneous structure of compacts formed by die compaction. The non-convexity of particle and consolidation pressure enhanced the role of inter-particle friction in the compressive strength. However, failure mechanism during the unconfined compression showed no dependence on the particle characteristics and operational conditions as most of the bonds were broken by shearing. A large compressive strength was linked to an increased average bond size while a more dispersed bond failure corresponds to an increased proportion of horizontally aligned shear-induced bond failure.

Physical and mechanical properties of Gravel-Tire Chips Mixture (GTCM)

In this study, a series of experimental programs were conducted to investigate the physical properties and mechanical behavior of a gravel-tire chips mixture (GTCM). The effects of particle characteristics, tire chips-gravel particle size ratio, relative density, gravel fraction by volume in GTCM, effective confining pressure and drainage condition on shear strength and the deformation characteristics of gravel and GTCM have been investigated. Additionally, the influence of the tire chips-gravel particle ratio and gravel fraction on the maximum and minimum void ratio of GTCM were also examined. Three behavioral zones, gravel-like, gravel-tire chips-like and tire chips-like, were clearly observed and reported by varying the tire chips proportion in the mixture. Outcomes revealed that the gravel fraction along with the particle size ratio of the tire chips to gravel are the main parameters controlling the skeleton, as well as the compaction behavior of GTCM. Results of consolidated compression triaxial tests revealed that the gravel fraction, particle size ratio of tire chips to gravel and confining pressure have significant influence on the stress-strain and dilatancy behaviors of soil and the effects are more pronounced at lower tire chips content ratio in the mixture.

Micro-tomographic analyses of specific interfacial area inside unconsolidated porous media with differing particle characteristics from microscopic to macroscopic scale

HypothesisIn capillary trapping in an unconsolidated porous medium, the interphase area is influenced by the distribution of the trapped phase clusters. These attributes, in turn, are affected by particle characteristics, indicating that the interphase area is affected by the particle characteristics. ExperimentsA micro-tomography technique was used to observe capillary trapping of a nitrogen-water system. The effect of particle characteristics on micro- to macroscopic properties was measured, respectively: pore size distribution (PSD) and porosity, bubble size distribution (BSD) and saturation, and bubble surface area and specific interfacial area. Capillary trapping experiments were carried out for media consisting of different particle shapes, range of sizes, and degrees of uniformity. FindingsParticle characteristics govern not only the PSD but also the pore shape. Then, the PSD and pore shape govern the BSD and bubble surface area, thus, affecting the specific interfacial area. The specific interfacial area of highly angular particles differs from that of highly spherical particles and natural sands. On the basis of these findings, a statistical model of PSD and a bubble morphology model are developed. Comparisons of specific interfacial area with uniform bubble distribution and thermodynamic filling assumption models show that those assumptions predict interfacial area less accurately.

Effects of particle characteristics on the microstructure and mechanical properties of 17-4 PH stainless steel fabricated by laser-powder bed fusion

The effects of powder characteristics (powder shape, size and type) and processing conditions (laser power and scanning speed) on the mechanical properties and microstructures of laser powder bed fusion (L-PBF) 17-4 PH stainless steel were studied using four types of powders. The % theoretical density, ultimate tensile strength, hardness of L-PBF parts are sensitive to energy density and starting powder shape, size and type. The density and mechanical properties of both water and gas-atomized powders increased with increased energy density. The gas-atomized (D50 = 13 μm) powders which are spherical in shape and water-atomized (D50 = 17 μm) powders of high tap density produced low-porosity and high-density (~97% density) L-PBF parts at low energy densities of 64 and 80 J/mm3. The increase in energy density to 104 J/mm3 resulted in high dense (97 ± 0.5%) water- and gas-atomized powders L-PBF parts. However, even at a high % theoretical density (97 ± 1%), the properties of L-PBF parts varied over a relatively large range (UTS: 500–1100 MPa; hardness: 25–39 HRC; elongation: 10–25%). This large variation in mechanical properties could be attributed the martensite and austenite phase as well as grain size in the L-PBF parts. Furthermore, the martensite and austenite phase content and of the L-PBF parts were also sensitive to the energy density and starting powder type.

Shear Modulus and Damping Ratio of Sand–Gravel Mixtures Over a Wide Strain Range

ABSTRACTA total of 153 cyclic triaxial tests were performed on 19 sand–gravel mixtures over the strain range of 10–5–10–2, which shows that the particle characteristics have significant influence on the small-strain shear-modulus G0, shear modulus reduction G/G0, and damping ratio λ. An improved Hardin’s equation for the G0 was proposed to consider the effects of particle characteristics and consolidation state. Furthermore, the KZM model correlation was improved to characterize the G/G0 curve. A four-parameter equation of λ with parent rock type, particle gradation, and consolidation condition was also introduced to characterize the λ curve.

Effect of PEGylation on assembly morphology and cellular uptake of poly ethyleneimine-cholesterol conjugates for delivery of sorafenib tosylate in hepatocellular carcinoma.

Introduction: Sorafenib (SFB) is an FDA-approved chemotherapeutic agent with a high partition coefficient (log P = 4.34) for monotherapy of hepatocellular carcinoma (HCC). The oral bioavailability is low and variable, so it was aimed to study the application of the polymeric nanoassembly of cholesterol conjugates of branched polyethyleneimine (PEI) for micellar solubilization of SFB and to investigate the impact of the polymer PEGylation on the physicochemical and cellular characteristics of the lipopolymeric dispersions. Methods: Successful synthesis of cholesterol-PEI lipopolymers, either native or PEGylated, was confirmed by FTIR, 1H-NMR, pyrene assay methods. The nanoassemblies were also characterized in terms of morphology, particle size distribution and zeta-potential by TEM and dynamic light scattering (DLS). The SFB loading was optimized using general factorial design. Finally, the effect of particle characteristics on cellular uptake and specific cytotoxicity was investigated by flow cytometry and MTT assay in HepG2 cells. Results: Transmission electron microscopy (TEM) showed that PEGylation of the lipopolymers reduces the size and changes the morphology of the nanoassembly from rod-like to spherical shape. However, PEGylation of the lipopolymer increased critical micelle concentration (CMC) and reduced the drug loading. Moreover, the particle shape changes from large rods to small spheres promoted the cellular uptake and SFB-related cytotoxicity. Conclusion: The combinatory effects of enhanced cellular uptake and reduced general cytotoxicity can present PEGylated PEI-cholesterol conjugates as a potential carrier for delivery of poorly soluble chemotherapeutic agents such as SFB in HCC that certainly requires further investigations in vitro and in vivo.

Estimation of flotation rate constant and collision efficiency using regression and artificial neural networks

ABSTRACTThe effects of particle characteristics and hydrodynamic conditions on the flotation rate constant (k) and bubble–particle collision efficiency (Ec) of pyrite and chalcopyrite particles were investigated. Experimental results showed that k increases with increase of bubble surface area flux (Sb) and Ec. Artificial neural network (ANN) and multivariable linear regression procedures were used to predict both k and Ec based on the particle characteristics and hydrodynamic conditions. Multivariable linear regression resulted in R2 of 0.6 and 0.93 for k and Ec, respectively. Using an ANN model, R2 as high as 0.98 was achieved in modeling the Ec with regard to the available parameters. The proposed ANN model can be reliably used to determine both k and Ec parameters in froth flotation.

Synthesis and characterization of amino acid-functionalized calcium phosphate nanoparticles for siRNA delivery

Small interfering RNAs (siRNA) are short nucleic acid fragments of about 20–27 nucleotides, which can inhibit the expression of specific genes. siRNA based RNAi technology has emerged as a promising method for the treatment of a variety of diseases. However, a major limitation in the therapeutic use of siRNA is its rapid degradation in plasma and cellular cytoplasm, resulting in short half-life. In addition, as siRNA molecules cannot penetrate into the cell efficiently, it is required to use a carrier system for its delivery. In this work, chemically and morphologically different calcium phosphate (CaP) nanoparticles, including spherical-like hydroxyapatite (HA-s), needle-like hydroxyapatite (HA-n) and calcium deficient hydroxyapatite (CDHA) nanoparticles were synthesized by the sol-gel technique and the effects of particle characteristics on the binding capacity of siRNA were investigated. In order to enhance the gene loading efficiency, the nanoparticles were functionalized with arginine and the morphological and their structural characteristics were analyzed. The addition of arginine did not significantly change the particle sizes; however, it provided a significantly increased binding of siRNA for all types of CaP nanoparticles, as revealed by spectrophotometric measurements analysis. Arginine functionalized HA-n nanoparticles showed the best binding behavior with siRNA among the other nanoparticles due to its high, positive zeta potential (+18.8mV) and high surface area of Ca++ rich “c” plane. MTT cytotoxicity assays demonstrated that all the nanoparticles tested herein were biocompatible. Our results suggest that high siRNA entrapment in each of the three modified non-toxic CaP nanoparticles make them promising candidates as a non-viral vector for delivering therapeutic siRNA molecules to treat cancer.

Experimental investigation on the mechanical properties of methane hydrate-bearing sand formed with rounded particles

A series of triaxial compression tests were performed on the methane hydrate-bearing sands formed with rounded glass beads and natural sands to examine their mechanical properties. The effect of particle characteristics on the mechanical response of methane hydrate-bearing sands with regard to the exertion of bonding force and de-bond mechanism between grains is explained from the grain-scale viewpoint. In comparison with the natural sand, methane hydrate-bearing glass beads owns a similar initial stiffness and rapidly attains the peak shear strength at a smaller axial strain. The obvious post-peak strain-softening behaviour of methane hydrate-bearing glass beads which differs from the tender post-peak strain-softening tendency of methane hydrate-bearing natural sand is observed. It is attributed to almost simultaneous exfoliation of hydrate mass from the glass beads with smooth surface within the straightly sheared layers. The substantial resource of shear strength enhancement for methane hydrate-bearing glass beads is the cohesion but the shear strength of methane hydrate-bearing natural sand was jointly governed by the cohesion and angle of internal friction. In contrast to the increasing tendency of difference of shear strength with the level of effective confining pressure for methane hydrate-bearing natural sand, the methane hydrate-bearing glass beads exerts a stronger effect of bonding force on the difference of shear strength at relatively lower pressures but this effect decreases at higher pressures.

Effect of Particle Characteristics on Coating Formation of Cold Sprayed Titanium Oxide Ceramic

Effect of Particle Characteristics on Coating Formation of Cold Sprayed Titanium Oxide Ceramic

Effect of Particle Characteristics and Temperature on Shear Yield Stress of Magnetorheological Fluid

Aiming to improve the shear yield stress of magnetorheological fluid, magnetorheological fluids with different particle characteristics are prepared, and the influence rules of particle mass fraction, particle size, nanoparticles content and application temperature on shear yield stress are investigated. Experimental results indicate that shear yield stress increases approximate linearly with the enhancement of particle mass fraction. Particle size and the nanoparticles within 10% mass fraction can improve the shear yield stress effectively. When the application temperature is higher than 100℃, the shear yield stress decreases rapidly because of thermal expansion and thermal magnetization effect.

Effect of particle characteristics on the two-body abrasive wear behaviour of a pearlitic steel

The specific wear rate and friction coefficient of a pearlitic microstructure subjected to different abrasive environments (i.e. SiC and alumina) were examined. A CSM high temperature pin-on-disc tribometer was used to simulate the two-body abrasive condition (i.e. the metallic surface abrading against the abrasive particles). The characteristics of the abrasive particles (i.e. particle size and density) revealed a significant impact on the amount of material loss. The specific wear rate of the pearlitic microstructure decreased with a reduction in the abrasive particle size, irrespective of the particle type. In addition, distinct particle deterioration mechanisms were observed during the abrasion process, which was largely determined by the abrasive particle size. Attrition, shelling and fracture were some of the dominant particle deterioration mechanisms occurring in both of the abrasive environments. SEM and EDX analysis on the wear debris displayed a unique metallic chip formation with respect to the particle type. Furthermore, the abrading efficiency (i.e. threshold level) of the abrasive particles was identified by means of interrupted abrasive wear tests. The dense packing nature of the alumina abrasive particles resulted in a significantly higher material removal rate than the SiC abrasive environment.