Small Fraction Of Particles Research Articles

Yield stress behavior of colloidal gels with embedded active particles

The yield stress behavior of colloidal gels with embedded active particles is studied with three experiments: start-up of steady shear, oscillatory strain amplitude sweep, and creep testing. Activity is generated by Janus particles with a platinum hemisphere; these particles undergo self-diffusiophoretic and self-electrophoretic motion in hydrogen peroxide solutions. The free particle active motion of the Janus colloids is consistent with an active energy of 25 times thermal energy at the highest hydrogen peroxide concentration studied. Consistent with prior work, the gels with embedded active particles display enhanced microdynamics and a reduction in linear viscoelastic moduli. Furthermore, at the activity levels studied, the yield stress decreases by as much as threefold for gels with an active-to-passive particle ratio of only 1:1200. We additionally find the yield strain is independent of activity. The significant reduction in yield stress at a very low active-to-passive particle ratio is modeled by combining the theory of how activity changes the spring constant of interparticle bonds in the gel with an argument that the number of active fractal clusters in the gel—rather than the number of active particles—drives the activity-induced softening of rheological properties. We estimate that 1 in 40 fractal clusters in the gel is active due to the presence of an active particle. This approach explains how an extremely small fraction of active particles causes a substantial change in both linear and nonlinear rheological properties. The results and modeling are potentially useful for the creation of gels with multistate mechanical properties.

Morphological characterisation of 2D packing with bi-disperse particles

The morphological structure of granular materials can dominate their mechanical, hydraulic, electrical, and thermal properties; thus, the formation of order and disorder arrangement of particles is the key characteristic to describe such micro-structures. During the packing procedure, external energy input and perturbations, such as dynamic cyclic load, and the particle size distribution were mentioned by many previous works to be significant in controlling the structure. This study explores order to disorder transition within 2D binary granular assemblies under vibration. A numerical packing method combining particle size growth and dynamic vibration is implemented and verified against experiments to achieve desired packing structure. The Bond orientation order number and pair distribution function are used as indices for characterising the morphological structure. Our packing simulation results show a combination of appropriate vibration and a proper particle size growth rate can facilitate the formation of granular crystallisation. Additionally, for binary packing, the size ratio, and the number fraction of small particles can play a critical role in determining the morphological transformation.

Numerical simulation of electric field in cylindrical silo based on non-uniform electrostatic charge distribution caused by particle segregation

Size-induced particle segregation during the silo filling process greatly changes the electrostatic charge distribution, influencing the occurrence of the incendiary electrostatic discharge. However, few studies concern the electric field distribution in this condition. In this work, the non-uniform space charge density distribution obtained in DEM simulation of the particle segregation was used for simulating the electric field. A comparison between the electric fields of segregation and uniform cases was conducted. Results show that the electric field of the segregation case is similar to that of the uniform case in the monopolar charging system. While in the bipolar charging system, the electric field of the segregation case can become different from that of the uniform case due to the bipolar space charge density in particle layers. The neutralization of the charges carried on large and small particles can result in the decline of the electric field. In the case with low net charges, the probability of the electrostatic discharge can be more than three times higher than that in uniform cases once the particle segregation happens. Moreover, the enhancement effect of the particle segregation on the electrostatic discharge can be stronger when the volume fraction of small particles is less than 75%. Reducing the charging efficiency of particles and the repose angle and avoiding particle segregation are preferable approaches to lower the risk of the electrostatic discharge.

Opinion: Cloud-phase climate feedback and the importance of ice-nucleating particles

Abstract. Shallow clouds covering vast areas of the world's middle- and high-latitude oceans play a key role in dampening the global temperature rise associated with CO2. These clouds, which contain both ice and supercooled water, respond to a warming world by transitioning to a state with more liquid water and a greater albedo, resulting in a negative “cloud-phase” climate feedback component. Here we argue that the magnitude of the negative cloud-phase feedback component depends on the amount and nature of the small fraction of aerosol particles that can nucleate ice crystals. We propose that a concerted research effort is required to reduce substantial uncertainties related to the poorly understood sources, concentration, seasonal cycles and nature of these ice-nucleating particles (INPs) and their rudimentary treatment in climate models. The topic is important because many climate models may have overestimated the magnitude of the cloud-phase feedback, and those with better representation of shallow oceanic clouds predict a substantially larger climate warming. We make the case that understanding the present-day INP population in shallow clouds in the cold sector of cyclone systems is particularly critical for defining present-day cloud phase and therefore how the clouds respond to warming. We also need to develop a predictive capability for future INP emissions and sinks in a warmer world with less ice and snow and potentially stronger INP sources.

A field, laboratory, and literature review evaluation of the water retention curve of volcanic ash soils: How well do standard laboratory methods reflect field conditions?

AbstractAccurate determination of the water retention curve (WRC) of a soil is essential for the understanding and modelling of the subsurface hydrological, ecological, and biogeochemical processes. Volcanic ash soils with andic properties (Andosols) are recognized as important providers of ecological and hydrological services in mountainous regions worldwide due to their large fraction of small size particles (clay, silt, and organic matter) that gives them an outstanding water holding capacity. Previous comparative analyses of in situ (field) and standard laboratory methods for the determination of the WRC of Andosols showed contrasting results. Based on an extensive analysis of laboratory, experimental, and field measured WRCs of Andosols in combination with data extracted from the published literature we show that standard laboratory methods using small soil sample volumes (≤300 cm3) mimic the WRC of these soils only partially. The results obtained by the latter resemble only a small portion of the wet range of the Andosols' WRC (from saturation up to −5 kPa, or pF 1.7), but overestimate substantially their water content for higher matric potentials. This discrepancy occurs irrespective of site‐specific land use and cover, soil properties, and applied method. The disagreement limits our capacity to infer correctly subsurface hydrological behaviour, as illustrated through the analysis of long‐term soil moisture and matric potential data from an experimental site in the tropical Andes. These findings imply that results reported in past research should be used with caution and that future research should focus on determining laboratory methods that allow obtaining a correct characterization of the WRC of Andosols. For the latter, a set of recommendations and future directions to solve the identified methodological issues is proposed.

Surface and segregation energies of Ag based alloys with Ni, Co and Fe: Direct experimental measurement and DFT study

A direct measurement of the surface energy polytherm in Ag + 0.5 at.% Fe alloy and first-principles calculations of segregation energy in silver-based systems with iron, cobalt and nickel were performed. The surface energy was measured in situ on silver foils with 16 μm thickness in the temperature range (0.8 - 0.95) TmAg in Ar+10% H2 atmosphere. Iron was introduced by electrolytic deposition and annealing. The segregation energy calculations were performed using density functional theory (DFT). DFT calculations were used to obtain the segregation energies of Fe, Co and Ni on the (100), (110), and (111) surfaces of Ag. It was shown that alloying of silver with Ni, Co and Fe (~ 0.5 at.%) leads to a significant increase in the surface energy and this effect increased with decreasing temperature. The alloys behaved in a similar way with decreasing temperature: the surface energy of the alloys increased to values close to the surface energy values of the second components in their standard reference states. DFT calculations of the segregation energy showed a strong “anti-segregation” behavior of Ni, Co and Fe in Ag; the segregation energy took positive values of about 0.4 eV/atom for all solute atoms. Surface studies by AFM and AES methods showed that the surface was two-phase, a silver phase and a small fraction of the second bcc-Fe phase particles coated with a thin silver layer. These observations indicated a quite pronounced desorption of iron on silver on one hand and the adsorption of silver on iron on the other hand. The positive segregation energies of Ni, Co and Fe to Ag surfaces, experimentally observed desorption behavior of these solutes as well as an increase of the surface energy with the increasing concentration of the second component, point at the fundamental reversibility of the Gibbs adsorption equation.

Analysis of Tortuosity in Compacts of Ternary Mixtures of Spherical Particles.

Herein, an approach is proposed to analyze the tortuosity of porous electrodes using the radical Voronoi tessellation. For this purpose, a series of particle compacts geometrically similar to the actual porous electrode were generated using discrete element method; the radical Voronoi tessellation was constructed for each compact to characterize the structural properties; the tortuosity of compact porous structure was simulated by applying the Dijkstra’s shortest path algorithm on radical Voronoi tessellation. Finally, the relationships were established between the tortuosity and the composition of the ternary particle mixture, and between the tortuosity and the radical Voronoi cell parameters. The following correlations between tortuosity values and radical Voronoi cell parameters were found: larger faces and longer edges of radical Voronoi cell leads to the increased fraction of larger values of tortuosity in the distribution, while smaller faces and shorter edges of radical Voronoi cell contribute to the increased fraction of smaller tortuosity values, being the tortuosity values more uniform with narrower distribution. Thus, the compacts with enhanced diffusion properties are expected to be obtained by packing particle mixtures with high volume fraction of small and medium particles. These results will help to design the well-packed particle compacts having improved diffusion properties for various applications including porous electrodes.

Compaction characteristics of binary coal mixtures during binder less briquetting process

ABSTRACT Dried coal typically had certain Particle Size Distribution (PSD) resulting from the size reduction process. Effect of PSD to the compaction phenomenon was investigated on the binary mixtures of Indonesian middle-rank coal with different mass fraction of small and large particles (%L). Compacted density of each coal mixtures was measured during uniaxial briquetting process and their compaction characteristics were analyzed with Cooper-Eaton model. It was found that Cooper-Eaton model could fit excellently (R2 > 0.99) with the experimental data. Analysis of compaction characteristics of the model (Ai and ki ) and briquette density revealed that mixtures 0%L (PSD Small) and 100%L (PSD Large) were easier to compact compared to binary mixtures. Binary mixture 70%L was hardest to compact, evaluating from its lowest increase of density, from 893 to 1492 kg/m3. Relatively high coordination number at pressure 2 kPa on mixture 70%L (7.81 ± 0.20) might be the reason for high deformation difficulty. It was concluded that binary mixture of coal with the highest bulk density would results in briquette with the lowest density.

Effect of turbulence-driven secondary flow on particle preferential concentration and clustering in turbulent square duct flows

In this study, the preferential concentration and clustering of inertial particles in fully developed turbulent square duct flows are studied using large eddy simulations combined with Lagrangian approach, where the Reynolds number is equal to Reτ=600 (based on the mean friction velocity and duct full height), and the particle Stokes number ranges from 0.0007 to 1.16. The results obtained for duct flows are compared with those for channel flows under the same working conditions. Then, the effect of the secondary flow on the particle concentration in duct flows is investigated. The equation of particle motion is governed by the drag force, lift force, added mass force, pressure gradient force, and gravity. The inter-phase interaction that was considered includes one-way and two-way coupling. The simulations of a single phase are verified and in good agreement with the available literature data. For the discrete phase, particles in the duct flow are found to be more dispersed in the vertical direction compared with the channel flow. In near-wall regions, a small fraction of particles tends to accumulate in duct corners, forming stable particle streaks under the effect of the secondary flow. Meanwhile, most particles are likely to reside preferentially in the low-speed flow regions and form elongated particle streaks steadily in the middle region of duct or channel floors. The Voronoi diagram analysis shows that the near-wall secondary flows in the square duct could cause particle clusters to transfer from regions of high to low concentration, and this trend increases with particle size. In addition, two-way coupling is found to enhance the near-wall particle accumulation and to promote particles to form more elongated streaks than one-way coupling. Finally, the mechanism responsible for the particle preferential concentration in turbulent square duct flows is determined.

Synergetic Effect of Water-Soluble PEG-Based Macromonomers and Cellulose Nanocrystals for the Stabilization of PMMA Latexes by Surfactant-Free Emulsion Polymerization.

The combination of cellulose nanocrystals (CNCs) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) was evaluated to synthesize stable latexes by surfactant-free emulsion polymerization of methyl methacrylate (MMA). Cellulose-particle interaction was provided due to the dual role of PEGMA, acting as water-soluble comonomer with MMA under emulsion polymerization conditions and able to interact with CNCs, recovered from sulfuric acid hydrolysis (H2SO4-CNCs). After preliminary experiments designed to validate the affinity between CNCs and PEG-stabilized PMMA particles obtained by MMA/PEGMA emulsion copolymerization, the effect of the PEGMA content and molar mass and also of the content of CNCs on the kinetics of the polymerization and the stability of the latexes were investigated. The use of PEGMA300 (Mn = 300 g mol-1, 2-10 wt %) allowed the formation of a stable latex, however, with a broad particle size distribution and the presence of both small (ca. 25-50 nm) and large (ca. 425-650 nm) particles (at 10 wt %, Dn = 278 nm and Dw/Dn = 1.34). Increasing the molar mass of PEGMA (PEGMA950 or PEGMA2080) significantly increased the fraction of small particles. This was explained by the nucleation and growth of small polymer particles adsorbed at the CNCs' surface, resulting in a particular organization where the CNCs were covered by several polymer particles. The influence of the initial amount of CNCs in these systems was finally evidenced, the polymerization being faster as the content of CNCs increased, but only the latexes prepared with 2 and 5 wt % of CNCs were stable.

Enhancement in strength and superelastic cyclic durability by addition of Si in Ni–Ti–Cu–Zr alloy

In this study, the martensitic transformation and superelastic behaviors were investigated in (Ni0.35Ti0.30Cu0.15Zr0.20)100-xSix (x = 0, 0.25, 0.5, and 1.0) alloys. After homogenization treatment, the microstructure consists of a B2 austenite matrix and a small fraction of secondary solidification particles at the grain boundaries. The concentration of Si in the B2 matrix increases with increasing Si content. The martensitic transformation temperature drops significantly as the Si content increases, i.e., an approximately 200 K decrease with the addition of 1.0 at% Si. The stress for inducing the martensitic transformation significantly increases with the increase in Si, whereas the strain to the final fracture decreases. After the cyclic loading test, the normalized stress for inducing the martensitic transformation increases with the addition of Si, whereas the residual plastic strain decreases. Thus, the Ni–Ti–Cu–Zr alloy with a minor addition of Si shows high potential for structural applications, owing to a good combination of strength and superelastic properties.

Impact of powder composition on processing-relevant properties of pharmaceutical materials: An experimental study

In this work, we studied the influence of powder composition on packing density and other processing-relevant properties of binary mixtures, including powder flowability. Binary mixtures of pharmaceutical powders with different particle size ratios, α and varying fractions of large and small particles were analyzed systematically. Mixtures of three excipients and one API with different composition (2, 5, 10, 30, 50, 70, 90, 95 and 98 wt%) were prepared in a Turbula mixer. Powders with different properties and particle size distribution were chosen, in order to obtain three binary mixtures with different size ratios. Then, macroscopic powder properties including bulk (poured) and tapped density (BD and TD) were measured. A powder rheometer was used to measure the flow function coefficient (ffc), cohesion, compressibility and permeability of the binary mixtures. We considered experimentally three classes of binary mixtures, which are characterized by two critical ratios of particle diameter: the critical size ratio of entrance (αc) and the critical size ratio of replacement (αr), where αc = 0.154 and αr = 0.741. Below the critical size ratio of entrance (αc), the particle asymmetry (ratio between large and small particle diameters) is high and small particles can fill the voids between larger ones. Between αc and the critical size ratio of replacement (αr), the smaller particles are too large to fit in the voids between larger particles (packing structure changes). Above αr, the particles are more or less symmetric in size and overall packing structure does not change by mixing the particles. Our experiments show that there is a non-linear and non-monotonic dependence of all relevant properties on composition for powder mixtures that have an α < αr. This non-linear behavior is even more significant for strongly asymmetric binary mixtures with α < αc. We argue that this behavior is related to the composition dependence of random packing of particulate systems. Our results have relevance to pharmaceutical particle processing operations where constant powder mixture properties are needed to ensure quality standards are met; such operations include capsule or die filling during tableting, and the continuous feeding of powders via screw feeders. Our results suggest that for pharmaceutical particle processing operations, where constant powder mixture properties are a prerequisite for process robustness, the size ratio of API and excipient particles, α should not be smaller than αr = 0.741.

Temperature Dependences of the Magnetic Susceptibility of Water-Based Magnetic Fluids

This paper presents the results of a study of the temperature dependences of the magnetic susceptibility of water-based magnetic fluids (magnetic colloids) with magnetite particles stabilized by their electrostatic interaction. The average size of dispersed particles was 8 nm, and the volume concentration of particles in the selected samples under study was 1.4% and 1.6%. The investigations were carried out over a wide temperature range. The temperature dependence of the susceptibility, for the first time, was obtained in the region of the colloidal phase transition under supercooling of the dispersion medium (water). Significant differences were found between the temperature dependences of the magnetic susceptibility of such magnetic fluids, where as similar dependences have been found for the susceptibility of magnetic hydrocarbon-based fluids. The observed behavior of such dependences near the water phase transition temperature is determined by the changes in the water phase state, heat release and structuring of the colloid as a result of water crystallization. Moreover, it is suggested that a certain impact on the dependence behavior in the region of the colloidal solidification temperature can also come from the process of blocking the Brownian degrees of freedom of a small fraction of large dispersed particles. It is concluded that the observed maxima in the investigated susceptibility temperature dependences in the lower temperature region are due to magnetic transformations in the colloidal zones formed at the solidification front of the disperse medium with a dense packing of single-domain colloidal particles.

Microstructural and Tribological Characteristics of Sn-Sb-Cu-Based Composite Coatings Deposited by Cold Spraying

Sn-based Babbitt coatings are widely used for sliding in hydrodynamic bearings. The Babbitting of bearing surfaces is among others accomplished by casting; however, this implies some disadvantages such as segregations, or susceptibility to shrinkage defects. Thermal spraying represents a promising method to overcome these challenges. To date, no studies on Babbitt coatings deposited by means of low-pressure cold spraying (LPCS) are available in the literature. In this study, a first attempt is made to produce a Sn-Sb-Cu-based composite coating reinforced with alumina particles by means of LPCS which enables the coating of internal diameters (IDs) of cylindrical components. A tailor-made feedstock was utilized which consists of a powder mixture of Sn, Sb, Cu and alumina. The composite coating is investigated with regard to its microstructural and tribological characteristics using scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), x-ray diffraction (XRD), as well as dry sliding experiments. Metallographic investigations demonstrate the feasibility of depositing an alumina-reinforced Sn-Sb-Cu-based composite coating with a dense microstructure and low porosity. The composite coating mainly consists of Sn, SbSn, Cu and hexagonal CuSn. Despite a small fraction of alumina particles, the microhardness of the composite coating is primarily determined by the formation of SbSn intermetallic phases dispersed in the soft Sn-Sb-rich matrix. The composite coating possesses a coefficient of friction of 0.43 ± 0.01 and wear coefficient k of 17.27 ± 7.77 × 10−5 mm3 N m−1 sliding against a 100Cr6 counterbody.

Study on Electrical Explosion Mechanism and Ignition Characteristics of Copper and Aluminum Powder Under Ignition Solid Propellant

In order to study the characteristic of the electrical explosion of copper and aluminum powders, a multilayer generator was designed, an experimental system was set up, and the parameters of metal powder electrical explosion were measured and analyzed. The results show that the duration of the electrical explosion process increases significantly due to the addition of metal powder. The duration of aluminum powder electrical explosion jet flow is ~86.36 ms due to its self-sustained combustion, which releases a large amount of energy, and a small fraction of aluminum powder particles is not burned. The duration of copper powder electrical explosion jet flow is ~15.84 ms, and most of the copper powder particles are in the solid state. The current pause process is absent; instead, the first discharge process is connected to the second discharge process. The effect of copper powder on the first discharge process is greater than that of aluminum powder. Furthermore, the ignition ability of copper powder electrical explosion to solid propellant is stronger than that of aluminum powder in a closed bomb experiment. These results are indubitably meaningful for the application of metal powder electrical explosion and ignition of solid propellant in an electrothermal chemical gun.

Adding active particles for overall aggregation in a mixing tank: A computational study

AbstractIn order to achieve flocculation in a dense agitated solid‐liquid suspension of nonaggregating particles, we explore scenarios where we add a limited amount of aggregative (ie, active) particles that can bind the nonaggregative particles. The performance of this process hinges on the competition between mixing (spreading the active particles over the flow volume) and aggregation among the active particles, with the latter reducing their effectiveness. The research has been conducted in a computational manner: direct simulations of transitional flow in a mixing tank (at an impeller‐based Reynolds number of 4000) are two‐way coupled with the dynamics of a collection of spherical, equally sized particles that are given specific aggregative properties. The overall solids volume fraction is 10%. A small fraction of all solid particles (5.8%) is active. Aggregation is quantified by means of the average coordination number as well as the aggregate size distribution. The way the active particles are released in the tank volume has a significant effect on the overall levels of aggregation, specifically for active particles with a strong aggregative force.

Filtration efficiency of surgical and FFP3 masks against composite dust.

The aim of this study was to investigate the protection efficiency of two types of face masks against composite dust and to characterize the particles that penetrated through the masks. Composite dust was created by grinding a commercial nano-filled composite in a plexiglass box without using water cooling or high vacuum evacuation, in order to obtain a worst-case exposure. Dust particles were collected using a personal inhalable aerosol sampler (IOM) fixed inside a custom-made phantom head. Surgical and filtering facepiece (FFP3) masks were tested, and the situation without a mask served as control. The IOM sampler contained a cassette with two filters to collect large inhalable (4-100µm) and respirable dust particles (<4µm). The amount of particles was determined gravimetrically by weighing filters before and after composite grinding, and further characterized by electron microscopy. Particle collection for both inhalable and respirable dust was the highest when no mask was used, and the lowest with the use of a FFP3 mask. Different sizes and shapes of particles were observed, with the largest particles (>1µm) being seen when no mask was applied, whereas only nanoparticles could be detected when either type of face mask was applied. Even though FFP3 masks showed a higher filtration efficacy than surgical masks of the inhalable dust fraction, penetration of a small respirable particle fraction was inevitable for both masks.

Stress transmission in cemented bidisperse granular materials.

We analyze stress distributions in a two-dimensional bidisperse cemented granular packing for a broad range of the values of particle-size ratio, the volumes of large and small particles, and the amount of cementing matrix. In such textured porous materials, the stress concentration, which controls the fracture and fragmentation of the material under tensile loading or in grinding processes, reflects not only the porosity but also the contact network of the particle phase and the resulting stress chains. By means of peridynamic simulations under tensile loading, we show how both the texture and stress distribution depend on size ratio, volume ratio, and the amount of the cementing matrix. In particular, the volume fraction of the class of small particles plays a key role in homogenizing stresses across the system by reducing porosity. Interestingly, the texture controls not only the porosity but also the distribution of pores inside the system with its statistical variability, found to be strongly correlated with the homogeneity of stresses inside the large particles. The most homogeneous stress distribution occurs for the largest size ratio and largest volume fraction of small particles, corresponding to the lowest pore size dispersion and the cushioning effect of small particles and its similar role to the binding matrix for stress redistribution across the packing. At higher porosity, the tensile stresses above the mean stress fall off exponentially in all phases with an exponent that strongly depends on the texture. The exponential part broadens with decreasing matrix volume fraction and particle-size ratio. These correlations reveal the strong interplay between size polydispersity and the cohesive action of the binding matrix for stress distribution, which is significant for the behavior of textured materials in grinding operations.

Packing void ratios of very dense ternary mixtures of similar ellipsoids

The paper presents a numerical study on the void ratio of a ternary mixture of similar ellipsoids. The effect of particle size distribution on the void ratio was investigated through samples of various volume fractions of large, medium, and small particles. The particle size ratio of large, medium, and small particles is 16:4:1. The ratio between the major and minor axes of an ellipsoid is 1.5. Thirty-nine very dense ternary samples and sixteen samples of very dense binary samples have been created using the discrete element method. The void ratios of the ternary samples are similar to those of the round washed sands of broader particle sizes. The void ratios of these numerical samples were estimated by an existing model of ternary mixtures of spheres without adjusting the constants to examine the effect of particle shape. A novel phenomenological model is suggested for the void ratio of a ternary mixture. The model is applied to the ternary mixture of similar ellipsoids, and the ternary mixture of round washed sands. A good agreement is observed in both cases.

The effect of heat treatment on the mechanical and tribological properties of dual size SiC reinforced A357 matrix composites

In the present work, the effect of aging temperature and particle size ratio of SiC particles on the mechanical and tribological properties of A357 composites reinforced with dual particle size SiC were investigated. The composites were prepared by melt-stirring assisted permanent mold casting technique with different weight fractions (3% coarse +3% fine, 4% coarse +2% fine, and 2% coarse +4% fine) of large and small size SiC particles. These three prepared composites are referred as DPS1, DPS2 and DPS3 composites. The solutionizing temperature was maintained constant at 540°C for 9h while the aging was done at 160°C, 180°C and 200°C (T6 treatment) for 6h. Optical and scanning electron microscopy studies showed fairly uniform dispersion of dual size SiC particles in A357 matrix with good interfacial bonding. High-resolution transmission electron microscopy images showed formation of uniformly dispersed needle-like β″ phase and spherical shaped β-Mg2Si precipitates under peak aging conditions. Compared to T6 treated A357 alloy, the T6 treated DPS A357 composites showed improved yield strength, tensile strength, hardness and wear resistance. Among the three composites, hardness and wear resistance of T6 treated DPS2 composite was found to be significantly higher when compared to the other two composites (DPS1 and DPS3). Ratio of large particles to small particles also seems to effect the mechanical and tribological properties. Presence of more small particles was found to be good for strength and ductility whereas more large particles were found to be good for hardness and wear resistance.