Effect Of Particle Composition Research Articles

Effect of Particle Composition on Dielectrophoretic Co-Assemblies around Topographic Features: Experiment and Theory

Effect of Particle Composition on Dielectrophoretic Co-Assemblies around Topographic Features: Experiment and Theory

Effect of particle composition and consolidation degree on the wave-induced liquefaction of soil beds

Effect of particle composition and consolidation degree on the wave-induced liquefaction of soil beds

Coupling particle image velocimetry and digital image analysis to characterize cluster dynamics in a fast fluidized bed

Particle clusters affect interphase interaction and dominate the overall performance of gas-solid fluidized beds. In this work, the particle image velocimetry, particle tracking velocimetry and digital image analysis were coupled to characterize clustering dynamics in a lab-scale riser. The clusters were identified by the Otsu algorithm based on grayscale distribution, and the cluster properties such as equivalent size, solids concentration and velocity distribution were extracted and analyzed under various operating conditions. It was found macroscopic operating conditions affect cluster characteristics significantly whereas the effect of particle composition is secondary. A bimodal or skewed probability density function was observed for not only the time-averaged hydrodynamic velocity but also the particle velocity around the cluster interface, indicating the coexistence of dilute and dense phases and the breaking of equilibrium assumption. The nonuniform distributions for laminar and Reynolds-stress-like granular temperatures were further discussed, which show remarkable anisotropy at both the microscopic and mesoscopic scales.

Effect of particle composition on microstructure and resistivity of indium tin oxide targets

Indium tin oxide (ITO) targets are generally prepared with single-size powders. Herein, we proposed a novel strategy to prepare high-quality ITO targets using binary-size particles in different particle count proportions. When the sintering temperature was 1550 ℃ and holding time was 10 h, the target prepared with 118&44 nm powders in particle count proportion of 1:5 showed the maximum relative density of 99.43% and minimum resistivity of 1.41 × 10-4 Ω·cm. We demonstrate that the excellent properties are attributed to the dense microstructure, which is formed by filling the internal gaps among large particles with small particles.

The Effect of Particle Composition and Concentration on the Partitioning Coefficient for Mercury in Three Ocean Basins

The downward flux of sinking particles is a prominent Hg removal and redistribution process in the ocean; however, it is not well-constrained. Using data from three U.S. GEOTRACES cruises including the Pacific, Atlantic, and Arctic Oceans, we examined the mercury partitioning coefficient, Kd, in the water column. The data suggest that the Kd varies widely over three ocean basins. We also investigated the effect of particle concentration and composition on Kd by comparing the concentration of small-sized (1–51 μm) suspended particulate mass (SPM) as well as its compositional fractions in six different phases to the partitioning coefficient. We observed an inverse relationship between Kd and suspended particulate mass, as has been observed for other metals and known as the “particle concentration effect,” that explains much of the variation in Kd. Particulate organic matter (POM) and calcium carbonate (CaCO3) dominated the Hg partitioning in all three ocean basins while Fe and Mn could make a difference in some places where their concentrations are elevated, such as in hydrothermal plumes. Finally, our estimated Hg residence time has a strong negative correlation with average log bulk Kd, indicating that Kd has significant effect on Hg residence time.

Protease encapsulation: effect of particle composition and size on enzymatic reuse

Protease encapsulation: effect of particle composition and size on enzymatic reuse

Packing Characteristics of Aggregate with Consideration of Particle size and Morphology

The packing characteristics of aggregates are very important for aggregate blend design, which is closely related to the performance of mixtures. In this study, an indoor packing experiment was designed to investigate the behaviors of single-size particle packing and two-size particle packing. The effects of particle composition, particle size and size ratio, particle morphology on packing characteristics were also evaluated. Two kinds of aggregates (crushed stone and gravel) with significant morphological differences were selected for the test. The angularity of the aggregates was quantitatively analyzed using the variance of mean curvature ( S C m 2 ) of particle surface in accordance with the 3-D scanning measurements. Based on the test results, the packing characteristics of aggregates were analyzed using the air void content (Va) and the packing function index (Ipf) proposed in this paper. It is shown that the analysis results of packed ideal spheres cannot be directly used to describe the packing characteristics of aggregates. Particle morphology has a significant impact on packing characteristics, especially on the Va. The Va of packed aggregates with poor angularity is significantly smaller than that with good angularity. Ipf can be used to quantitatively distinguish the packing function of particles. The test results show that the packing function of particles cannot be simply divided into the skeleton building and air voids filling. Generally, the particles in packed blend have both of these functions. The packing function of particles depends not only on the particle size, but also on the composition of particles with different size. When the size ratio and volume ratio are the same, the packing characteristics of the two-size particle blends will still change with the change of the particle size. The exploration of packing behaviors of single- size and two- size particle aggregates is helpful for analyzing the packing behaviors of blends with multi-size particles.

Particle Composition Effects on MERIS-Derived SPM: A Case Study in the Saint Lawrence Estuary

An empirical optical model for estimating the concentration of suspended particulate matter (CSPM) was developed in the upper part of the Saint Lawrence Estuary based on remote sensing reflectance (Rrs) measurements corresponding to medium-resolution imaging spectrometer (MERIS) spectral channels 7 and 9 (i.e., wavelengths centered at 665 and 708 nm, respectively). Sensitivity of CSPM estimates to changes in mineral content of suspended particulates was investigated based on simulated Rrs values. For June 2012 measurements, CSPM varied with values following a power-type relationship (y = 235.7 x8.321, r2 = 0.7, N = 10). In addition, numerical experiments and analysis of regression type II showed that exponent parameter of this biogeo-optical model decreased as suspended particulates become more enriched in organic matter.

Study of Bactericidal Properties of Mg-Doped ZnO Nanoparticles

ABSTRACTThe present work focuses on the polyol-mediated synthesis of pure and Mg-doped ZnO nanoparticles. The synthesized samples were characterized via X-ray diffraction, Fourier transformed infrared spectroscopy, ultraviolet visible spectroscopy and photoluminescence techniques. The Standard Plate Count was used to assess the bactericidal properties of the nanoparticles against E. coli at 1000 ppm and 1500 ppm of concentration. The capacity of the Zn-Mg oxides to generate singlet oxygen (SO) species was also evaluated. X-ray diffraction information evidenced the formation of ZnO-wurtzite; no diffraction peaks corresponding to isolated Mg-phases were detected. The average crystallite size of the Zn-Mg oxide nanocrystals was estimated in the 6nm - 7nm range. Infrared spectroscopy measurements confirmed the formation of the oxide with a Metal-Oxygen band centered on 536 cm-1; other bands associated to the functional groups of polyol by product were also observed. The exciton peak of UV spectrum suggests similarity in the particle size with the dopant addition. The effect of particle composition (i.e. doping level) on the corresponding generation of SO and bactericidal capacity is presented and discussed.

Effects of particle composition and environmental parameters on catalytic hydrodechlorination of trichloroethylene by nanoscale bimetallic Ni-Fe

Catalytic nickel was successfully incorporated into nanoscale iron to enhance its dechlorination efficiency for trichloroethylene (TCE), one of the most commonly detected chlorinated organic compounds in groundwater. Ethane was the predominant product. The greatest dechlorination efficiency was achieved at 22 molar percent of nickel. This nanoscale Ni-Fe is poorly ordered and inhomogeneous; iron dissolution occurred whereas nickel was relatively stable during the 24-hr reaction. The morphological characterization provided significant new insights on the mechanism of catalytic hydrodechlorination by bimetallic nanoparticles. TCE degradation and ethane production rates were greatly affected by environmental parameters such as solution pH, temperature and common groundwater ions. Both rate constants decreased and then increased over the pH range of 6.5 to 8.0, with the minimum value occurring at pH 7.5. TCE degradation rate constant showed an increasing trend over the temperature range of 10 to 25°C. However, ethane production rate constant increased and then decreased over the range, with the maximum value occurring at 20°C. Most salts in the solution appeared to enhance the reaction in the first half hour but overall they displayed an inhibitory effect. Combined ions showed a similar effect as individual salts.

Effect of Particle Size Distribution of Lime Sludge on the Hydrophobicity of Paper

Precipitated calcium carbonate (PCC) is a filler that is widely used for papermaking, and lime sludge is a special type of PCC recovered from the black liquor from kraft pulping. There has been some concern that lime sludge may interfere with the development of paper’s hydrophobicity in comparison with commercial PCC and ground calcium carbonate (GCC) due to the presence of impurities when alkyl ketene dimer (AKD) is used as the sizing additive. In this work, fillers with different particle size distributions were prepared, and the effects of particle composition on surface chemistry of fillers, adsorption for AKD, sizing degree of final paper sheets, and retention behavior of fillers were evaluated. The results showed that, through matching different particle size distributions for lime sludge fillers, the negative zeta potential decreased from -26.2 mV to -20.8 mV, the specific surface area decreased from 15.0 m2/g to 9.1 m2/g, and total pore volume decreased from 0.037 cm3/g to 0.026 cm3/g, which was favorable for the low adsorption for AKD. Consequently the sizing effect of filled paper was improved. Moreover, the retention rate also was increased by changing the particle size distribution of lime sludge.

Fabrication and characterization of PDMS based magnetorheological elastomers

This paper presents the fabrication and characterization of a new magnetorheological elastomer (MRE) by using polydimethylsiloxane (PDMS) as a matrix. The base and curing agent of PDMS with a weight ratio of 10:1 were mixed first as the carrying matrix, and then carbonyl iron particles were added to the matrix and stirred sufficiently. The final mixture was placed in a vacuum chamber to eliminate bubbles for 30 min and was moulded later to form membranes of 1 mm thickness. A total of four PDMS based MRE samples, with different weight fractions of 60%, 70%, 80%, and 90%, were fabricated. Their mechanical properties under both steady-state and dynamic loading conditions were tested. The effects of particle composition, magnetic field, strain amplitude and frequency on the MRE effects were summarized. With the increase of iron particle composition, the magnetorheological effects of the samples increase steadily. It is also noted that the initial modulus of the MRE samples shows an increasing trend with the iron particle composition. Additionally, the microstructures of the PDMS based MREs were also observed by a low vacuum scanning electric microscope (LV-SEM).

Adsorption of Lipid Liquid Crystalline Nanoparticles: Effects of Particle Composition, Internal Structure, and Phase Behavior

Controlling the interfacial behavior and properties of lipid liquid crystalline nanoparticles (LCNPs) at surfaces is essential for their application for preparing functional surface coatings as well as understanding some aspects of their properties as drug delivery vehicles. Here we have studied a LCNP system formed by mixing soy phosphatidylcholine (SPC), forming liquid crystalline lamellar structures in excess water, and glycerol dioleate (GDO), forming reversed structures, dispersed into nanoparticle with the surfactant polysorbate 80 (P80) as stabilizer. LCNP particle properties were controlled by using different ratios of the lipid building blocks as well as different concentrations of the surfactant P80. The LCNP size, internal structure, morphology, and charge were characterized by dynamic light scattering (DLS), synchrotron small-ange X-ray scattering (SAXS), cryo-transmission electron microscopy (cryo-TEM), and zeta potential measurements, respectively. With increasing SPC to GDO ratio in the interval from 35:65 to 60:40, the bulk lipid phase structure goes from reversed cubic micellar phase with Fd3m space group to reversed hexagonal phase. Adding P80 results in a successive shift toward more disorganized lamellar type of structures. This is also seen from cryo-TEM images for the LCNPs, where higher P80 ratios results in more extended lamellar layers surrounding the inner, more dense, lipid-rich particle core with nonlamellar structure. When put in contact with a solid silica surface, the LCNPs adsorb to form multilayer structures with a surface excess and thickness values that increase strongly with the content of P80 and decreases with increasing SPC:GDO ratio. This is reflected in both the adsorption rate and steady-state values, indicating that the driving force for adsorption is largely governed by attractive interactions between poly(ethylene oxide) (PEO) units of the P80 stabilizer and the silica surface. On cationic surface, i.e., silica modified with 3-aminopropltriethoxysilane (APTES), the slightly negatively charged LCNPs give rise to a very significant adsorption, which is relatively independent of LCNP composition. Finally, the dynamic thickness measurements indicate that direct adsorption of intact particles occurred on the cationic surface, while a slow buildup of the layer thickness with time is seen for the weakly interacting systems.

Surfactant Distribution in Waterborne Acrylic Films. 1. Bulk Investigation

The distribution of an anionic surfactant, sodium dodecyl sulfate (SDS), in waterborne acrylic films was investigated, focusing on the effects of particle composition and size, and pH of the latex. The observed surfactant distributions could be classified in two categories: homogeneous and heterogeneous, the latter showing SDS aggregates. The shape of the profiles was related to the stability of the latex during drying, at short interparticular distances. The stability of the latex was determined by the presence or not of fixed charges at the surface of the particles. The latices with particles carrying neutralized acrylic acid at high pH (COO(-)) led to homogeneous distributions, whereas the latices with acrylic acid at low pH (COOH) or without acrylic acid led to heterogeneous distributions. Our interpretation is that the stable latices present a narrow network of paths between particles at high polymer volume fraction, limiting the mobility of the surfactant, whereas in the less stable latices wider routes between flocs allow enough mobility for large aggregate formation. Thermal treatments of the dry films confirmed the strong confinement of the surfactant in the dense film structure obtained at high pH and the more open structure, allowing easier surfactant transport and oxygen penetration, observed at low pH. In order to account for the shapes of the profiles more quantitatively, a model was developed based on the diffusion of the surfactant and its transport by the drying front. It was found that the apparent diffusion coefficient of SDS micelles had to be lowered to a great extent (D = 10(-13)-10(-14) m(2)/s) during drying in order to explain aggregate formation. It should be even lower (D = 10(-15) m(2)/s) to interpret homogeneous surfactant profiles. These results are consistent with our hypothesis of the key importance of the surfactant mobility during drying.

Effects of Particle Composition and Mixture (Glutinous and Nonglutinous) of Rice Powder on Evaluation of Sensory Attributes of “Dango”

Effects of Particle Composition and Mixture (Glutinous and Nonglutinous) of Rice Powder on Evaluation of Sensory Attributes of “Dango”

Effects of particle composition and species on toxicity of metallic nanomaterials in aquatic organisms

Metallic nanoparticles are among the most widely used types of engineered nanomaterials; however, little is known about their environmental fate and effects. To assess potential environmental effects of engineered nanometals, it is important to determine which species are sensitive to adverse effects of various nanomaterials. In the present study, zebrafish, daphnids, and an algal species were used as models of various trophic levels and feeding strategies. To understand whether observed effects are caused by dissolution, particles were characterized before testing, and particle concentration and dissolution were determined during exposures. Organisms were exposed to silver, copper, aluminum, nickel, and cobalt as both nanoparticles and soluble salts as well as to titanium dioxide nanoparticles. Our results indicate that nanosilver and nanocopper cause toxicity in all organisms tested, with 48-h median lethal concentrations as low as 40 and 60 microg/L, respectively, in Daphnia pulex adults, whereas titanium dioxide did not cause toxicity in any of the tests. Susceptibility to nanometal toxicity differed among species, with filter-feeding invertebrates being markedly more susceptible to nanometal exposure compared with larger organisms (i.e., zebrafish). The role of dissolution in observed toxicity also varied, being minor for silver and copper but, apparently, accounting for most of the toxicity with nickel. Nanoparticulate forms of metals were less toxic than soluble forms based on mass added, but other dose metrics should be developed to accurately assess concentration-response relationships for nanoparticle exposures.

A study of poly(butadiene/methacrylic acid) dispersions: From pH-responsive behaviour to the effects of added Ca 2+

This study investigates the effects of added Ca 2+ on the properties of poly(Bd/MAA) dispersions (1,3-butadiene and methacrylic acid) and considers the effect of particle composition on the p K a . Four latex dispersions are considered in detail. These include poly(Bd/6MAA) and poly(Bd/20MAA) which contain, 6 and 20 wt% MAA, respectively, based on the total monomer mass used for dispersion preparation. Two model systems are also used for comparison. These are poly(Bd) and poly(EA/33MAA/BDDA) (EA and BDDA are ethyl acrylate and butanediol diacrylate). The latter is a well-studied model pH-responsive microgel. The apparent p K a of the poly(Bd/MAA) dispersions was determined from potentiometric titrations and found to increase with Bd content. The pH-dependence of the particle size was studied using photon correlation spectroscopy. Electrophoretic mobility measurements were also used. The hydrodynamic diameters and mobilities exhibited major changes as the pH approached the p K a for the particles. The critical coagulation concentrations were also measured. The results indicate that Ca 2+ caused pronounced dispersion instability at low pH. Moreover, Ca 2+ prevents swelling of the poly(Bd/MAA) particles at high pH. It was found that efficient ionic binding of all of the RCOO − groups within the poly(Bd/20MAA) particles occurred when the mole ratio of RCOO − to Ca 2+ was less than or equal to 2.0. Consideration of all the data leads to the suggestion that poly(Bd/MAA) particles have a core–shell structure. It is suggested that the particle core contains mostly poly(Bd) and that the shell is comprised of lightly crosslinked poly(Bd- co-MAA) copolymer.

Study of pH-Responsive Microgels Containing Methacrylic Acid: Effects of Particle Composition and Added Calcium

pH-responsive microgel dispersions contain cross-linked polymer particles that swell when the pH approaches the pKa of the ionic monomer incorporated within the particles. In recent work from our group, it was demonstrated that the mechanical properties of degenerated intervertebral discs (IVDs) could be restored to normal values by injection of pH-responsive microgel dispersions (Saunders, J. M.; Tong, T.; LeMaitre, C.; Freemont, A. J.; Saunders, B. R. Soft Matter 2007, 3, 486). These dispersions change from a fluid to a gel with increasing pH. The present work investigates the pH-dependent properties of dispersions of microgel particles containing MAA (methacrylic acid) and also the effects of added Ca2+. Two microgels are discussed: microgel A is poly(EA/MAA/AM) (EA and AM are ethyl acrylate and allyl methacrylate), and microgel B is poly(EA/MAA/BDDA) (butanediol diacrylate). The pH-dependent particle properties investigated include hydrodynamic diameters and electrophoretic mobilities. The critical coagulation concentrations (CCC) of dilute dispersions and the elastic modulus (G') of concentrated, gelled microgel dispersions were also investigated. In the absence of added Ca2+, the particle swelling and G' were smallest and largest, respectively, for microgel A. The changes in hydrodynamic diameter and mobility with pH were explained in terms of a core-shell swelling mechanism. Added Ca2+ was found to significantly decrease the CCCs, extents of particle swelling, and magnitude of the electrophoretic mobility. This was attributed to the ionic cross-linking of neighboring RCOO- groups by Ca2+. It is suggested that the formation of ionic cross-links is inefficient within the microgel particles because of the presence of covalent cross-links that oppose the large-scale conformational rearrangement of neighboring RCOO- groups. The effect of Ca2+ on the properties of the gelled dispersions is important from the viewpoint of potential application in vivo. Rheological studies of the gelled microgel dispersions showed that added Ca2+ did not have a specific influence on G'. The differences observed in the presence of Ca2+ were attributed to ionic strength effects (screening). The key parameter that controls G' of the gelled microgel dispersions is pH. The results from this work suggest that the elasticity of the gels would be slightly reduced in vivo as a consequence of the high ionic strength present.

Electrical Properties of Copper-Filled Electrically Conductive Adhesives and Pressure-Dependent Conduction Behavior of Copper Particles

This study focuses on the effects of particle composition, particle shape, particle size and oxidizing temperature on the electrical properties of copper-filled electrically-conductive adhesives (CFECAs) and the pressure-dependent conduction behavior of compressed copper particles (CCPs). Silver-coated copper particles and un-coated copper particles of both spherical and flake-shaped types were oxidized at 30°C, 175°C and 240°C for two hours. The copper particles were dispersed in an epoxy matrix for CFECAs or compressed in a mold for CCPs. Silver-coated copper particles showed significantly greater oxidation resistance than un-coated copper particles since the silver coating provides good oxidation resistance at temperatures lower than 175°C. Thermogravimetric Analysis (TGA), X-ray diffraction (XRD) and Auger Electron Spectroscopy were used to observe how metal oxides such as AgO and Cu2O affected the electrical properties of CFECAs and the conduction behavior of CCPs. The electrically-conductive adhesives (ECAs) filled with flake-shaped copper particles offer better electrical conduction than the ECAs filled with spherical copper particles.

Determination of corrosion potential of coated hollow spheres

Copper hollow spheres were created on porous iron particles by electro-less deposition. The consequent Ni plating was applied to improve the mechanical properties of copper hollow micro-particles. Corrosion properties of coated hollow spheres were investigated using potentiodynamic polarisation method in 1 mol dm −3 NaCl solution. Surface morphology and composition were studied by scanning electron microscopy (SEM), light microscopy (LM) and energy-dispersive X-ray spectroscopy (EDX). Original iron particles, uncoated copper spheres and iron particles coated with nickel were studied as the reference materials. The effect of particle composition, particularly Ni content on the corrosion potential value was investigated. The results indicated that an increase in the amount of Ni coating layer deteriorated corrosion resistivity of coated copper spheres. Amount of Ni coating layer depended on conditions of Ni electrolysis, mainly on electrolysis time and current intensity. Corrosion behaviour of sintered particles was also explored by potentiodynamic polarisation experiments for the sake of comparison. Formation of iron rich micro-volumes on the particle surface during sintering caused the corrosion potential shift towards more negative values. A detailed study of the morphological changes between non-sintered and sintered micro-particles provided explanation of differences in corrosion potential ( E corr).