Effect Of Primary Particle Size Research Articles

Effects of primary particle size on light absorption enhancement of black carbon aerosols using the superposition T-matrix method

Light absorption enhancement (Eabs) of black carbon (BC) aerosol following atmospheric aging is one of the most challenging issues in the assessment of aerosol radiative forcing. BC Eabs is constrained by complex particle morphologies; however, large uncertainties continue to occur due to certain morphological parameters, including primary particle size. The values of Eabs during BC aging is quantified with diverse primary particle sizes using the superposition T-matrix method (STM). The results show that the uncertainty of absorption enhancement due to the primary particle size of fully aged BC particles ranges from ~10% to 20%, while the uncertainties arising from varied BC volume-equivalent size and fractal dimension are ~20–30% and ~8–12%, respectively. The optical properties of BC particles with volume-equivalent radii ranging from 50 to 70 nm were largely influenced (up to ~50%) by inappropriate assumptions regarding primary particle size. The specific assumptions of primary particle size in optical modeling plays an important role in constraining BC Eabs.

Effect of primary particle size and aggregate size of modified graphene oxide on toughening of unsaturated polyester resin

Graphene‐based nanomaterial tougheners can effectively toughen thermosetting resins at an extremely low loading level with minimal change in Tg or modulus. However, previous research has indicated that this toughening effect shows only small responses to changing graphene oxide (GO) surface modifications, resin dispersion processing methods, and GO loading levels. It is hypothesized that the physical dimensions of GO particles affect the toughening behavior of graphene‐based additives. In this study, the sizes of primary and aggregated surface‐modified GO (mGO) particles were measured directly using scanning electron microscopy. The effects of the differences in size on fracture toughness (KIC), bending modulus, and flexural strength of an unsaturated polyester resin were evaluated. The sizes of primary mGO particles were estimated from the sizes of GO particles prior to their surface modification and the sizes of mGO aggregates after dispersion in the resin. This study shows that as little as 0.005 wt% mGO can increase KIC by nearly 20%. This toughening effect is independent of primary particle size. Reducing mGO aggregate sizes by chemical modification or sonication shifts the optimal loading level of mGO‐based tougheners to lower concentrations, but the maximal achievable toughness cannot be changed by improving dispersion or particle–matrix interactions. POLYM. COMPOS., 40:3886–3894, 2019. © 2019 Society of Plastics Engineers

Dissolution Behavior of Isolated and Aggregated Hematite Particles Revealed by in Situ Liquid Cell Transmission Electron Microscopy.

Dissolution behavior of isolated and aggregated hematite particles in 10, 36, and 103 nm, respectively, was investigated using in situ liquid cell transmission microscopy (LCTEM). The high spatial and temporal resolution of LCTEM enables us to differentiate the respective effects of primary particle size, crystal defects, and aggregation state on particle dissolution. At similar electron-beam irradiation parameters, the initial surface-area normalized dissolution rates ( RSA,Int) of isolated 10, 36, and 103 nm particles are 4.64 ± 3.60, 0.91 ± 0.44, and 0.24 ± 0.04 mg m-2 s-1, respectively. Interface free energy, calculated from the measured RSA,Int, decreases with the decreasing primary particle size. No preferential etching occurs on 10 nm, defect-free nanoparticles, whereas dissolution preferentially originates from crystal defects on 103 nm particles. In dissolution of aggregated particles, dissolution occurs more rapidly on the particles that are more accessible to bulk solution than the others inside the aggregate. As dissolution proceeds, dendritic aggregates break into several smaller aggregates that respectively shrink into even smaller and more compact aggregates, followed by reaggregation together. This study directly shows microscopic dissolution behavior of isolated and aggregated particles in different primary particle sizes, which is important to understand bioavailability, transport, and fate of nanoparticles in aquatic systems.

Experimental research on particle aggregation behavior in nanorefrigerant–oil mixture

The objective of this study is to experimentally investigate the effects of primary particle size, primary particle concentration and temperature on particle aggregation behavior in nanorefrigerant–oil mixture. The nanoparticles, refrigerant and lubricating oil for experiments were TiO2, R141b and ATMOS NM56, respectively. Experimental conditions included primary particle size from 25 to 100 nm, primary particle concentration from 50 to 500 mg L−1, temperature from 6 to 27 °C, and oil concentrations of 1, 3 and 5 wt%. Time evolutions of the hydrodynamic diameter of aggregates were measured by dynamic light scattering (DLS) method. It is shown that the presence of lubricating oil inhibits the particle aggregation, and the inhibition is strengthened with the increase of oil concentration; the hydrodynamic diameter of aggregates is enlarged with the increase of primary particle size, primary particle concentration or temperature, and the enlargement increases with the increase of oil concentration.

Effect of raw powder particle size on microstructure and light transmittance of α-alumina films deposited by granule spray in vacuum

The effect of primary particle size of the raw alumina powder on the microstructure and light transmittance of the 1μm thick α-alumina film was investigated. Granules made from four kinds of alumina powders with different primary particle sizes were sprayed to deposit the alumina films on glass substrates at room temperature in a vacuum. Grains of the alumina film were mostly not much bigger than 10nm for all the samples. Both the film surface roughness and the interface roughness between the alumina film and glass substrate of the samples increased as the primary particle sizes of the alumina powders increased. A small number of hair-like flaws were observed in the alumina films prepared from the coarse powders. The variation of light transmittance was explained in part by change of surface roughness, the interface roughness, and flaw size of the alumina film according to the alumina primary particle size.

Composition limits in granulation with active component in the binder

The process of reactive granulation is considered. Sodium carbonate primary particles react with dodecyl‐benzenesulfonic acid droplets to form granules where the active component is an anionic surfactant formed by the reaction. The effect of primary particle size on the maximum binder/solids ratio was systematically investigated and found to be directly proportional to the specific surface area of the primary particles regardless of how this surface area was achieved—whether by monodisperse powders or bimodal powder mixtures. The effect of binder viscosity on the maximum binder capacity has shown a nontrivial behavior: while the maximum binder content increased with increasing binder viscosity for fine primary particles, the opposite trend was observed in the case of coarse primary particles. This behavior was explained by detailed studies of primary particle wetting and binder penetration into particle beds, as well as by microtomography analysis of the internal granule structure. © 2014 American Institute of Chemical Engineers AIChE J, 61: 395–406, 2015

Effect of primary particle size on spray formation, morphology and internal structure of alumina granules and elucidation of flowability and compaction behaviour

Three different alumina powders with varying particle sizes were subjected to spray drying under identical conditions and effect of particle size on heat transfer efficiency and mechanism of formation of granules was elucidated. Morphology, internal structure and size distribution of granules were studied and evaluated with respect to their flow behaviour. In order to estimate the elastic interaction of granules, the granules were subjected to compaction under progressive loading followed by periodic unloading. Compaction curves were plotted and compressibility factor was estimated and correlated with predicted and measured green density values.

Effect of primary particle size on colloidal stability of multiwall carbon nanotubes

Multiwall carbon nanotubes (MWCNTs) are one type of nanoparticles that have various special properties and potential applications. Due to their increasing production and potential toxicological effects, the environmental behavior and transport of MWCNTs have become important research topics. Particle size is one of the important properties of nanoparticles, yet its effects on MWCNT environmental behaviors have not been fully investigated. In this study, we tested how the length of MWCNTs influenced their settling in the presence of Na(+) and/or natural organic matter (NOM), and postulated the governing mechanisms. The results showed that when adding Na(+) the shorter MWCNTs exhibited preferential aggregation and settling. One possible reason could be that shorter MWCNTs possess larger specific surface area and consequently stronger attraction forces. However, NOM strongly mitigated such aggregation, and helps to disperse MWCNTs regardless of their length and aqueous conditions.

Rat pulmonary responses to inhaled nano-TiO2: effect of primary particle size and agglomeration state

BackgroundThe exact role of primary nanoparticle (NP) size and their degree of agglomeration in aerosols on the determination of pulmonary effects is still poorly understood. Smaller NP are thought to have greater biological reactivity, but their level of agglomeration in an aerosol may also have an impact on pulmonary response. The aim of this study was to investigate the role of primary NP size and the agglomeration state in aerosols, using well-characterized TiO2 NP, on their relative pulmonary toxicity, through inflammatory, cytotoxic and oxidative stress effects in Fisher 344 male rats.MethodsThree different sizes of TiO2 NP, i.e., 5, 10–30 or 50 nm, were inhaled as small (SA) (< 100 nm) or large agglomerates (LA) (> 100 nm) at 20 mg/m3 for 6 hours.ResultsCompared to the controls, bronchoalveolar lavage fluids (BALF) showed that LA aerosols induced an acute inflammatory response, characterized by a significant increase in the number of neutrophils, while SA aerosols produced significant oxidative stress damages and cytotoxicity. Data also demonstrate that for an agglomeration state smaller than 100 nm, the 5 nm particles caused a significant increase in cytotoxic effects compared to controls (assessed by an increase in LDH activity), while oxidative damage measured by 8-isoprostane concentration was less when compared to 10–30 and 50 nm particles. In both SA and LA aerosols, the 10–30 nm TiO2 NP size induced the most pronounced pro-inflammatory effects compared to controls.ConclusionsOverall, this study showed that initial NP size and agglomeration state are key determinants of nano-TiO2 lung inflammatory reaction, cytotoxic and oxidative stress induced effects.

Particle size, surface charge and concentration dependent ecotoxicity of three organo-coated silver nanoparticles: Comparison between general linear model-predicted and observed toxicity

Mechanism underlying nanotoxicity has remained elusive. Hence, efforts to understand whether nanoparticle properties might explain its toxicity are ongoing. Considering three different types of organo-coated silver nanoparticles (AgNPs): citrate-coated AgNP, polyvinylpyrrolidone-coated AgNP, and branched polyethyleneimine-coated AgNP, with different surface charge scenarios and core particle sizes, herein we systematically evaluate the potential role of particle size and surface charge on the toxicity of the three types of AgNPs against two model organisms, Escherichia coli and Daphnia magna. We find particle size, surface charge, and concentration dependent toxicity of all the three types of AgNPs against both the test organisms. Notably, Ag+ (as added AgNO3) toxicity is greater than each type of AgNPs tested and the toxicity follows the trend: AgNO3>BPEI-AgNP>Citrate-AgNP>PVP-AgNP. Modeling particle properties using the general linear model (GLM), a significant interaction effect of primary particle size and surface charge emerges that can explain empirically-derived acute toxicity with great precision. The model explains 99.9% variation of toxicity in E. coli and 99.8% variation of toxicity in D. magna, revealing satisfactory predictability of the regression models developed to predict the toxicity of the three organo-coated AgNPs. We anticipate that the use of GLM to satisfactorily predict the toxicity based on nanoparticle physico-chemical characteristics could contribute to our understanding of nanotoxicology and underscores the need to consider potential interactions among nanoparticle properties when explaining nanotoxicity.

The effect of primary particle size on biodistribution of inhaled gold nano-agglomerates

Airborne engineered nanoparticles undergo agglomeration, and careful distinction must be made between primary and agglomerate size of particles, when assessing their health effects. This study compares the effects on rats undergoing 15-day inhalation exposure to airborne agglomerates of gold nanoparticles (AuNPs) of similar size distribution and number concentration (1 × 106 particles/cm3), but two different primary diameters of 7 nm or 20 nm. Inhalation of agglomerates containing 7-nm AuNPs resulted in highest deposition by mass concentration in the lungs, followed by brain regions including the olfactory bulb, hippocampus, striatum, frontal cortex, entorhinal cortex, septum, cerebellum; aorta, esophagus, and kidney. Eight organs/tissues especially the brain retained greater mass concentration of Au after inhalation exposure to agglomerates of 7-nm than 20-nm AuNPs. Macrophage mediated escalation followed by fecal excretion is the major pathway of clearing inhaled AuNPs in the lungs. Microarray analyses of the hippocampus showed mostly downregulated genes, related to the cytoskeleton and neurite outgrowth. Together, results in this study indicate disintegration of nanosized agglomerates after inhalation and show impact of primary size of particles on subsequent biodistribution.

Effect of Primary Particle Size upon Polarization and Cycling Stability of 5-V Lithium Insertion Material of Li [ Ni1 ∕ 2Mn3 ∕ 2 ] O4

The lithium insertion materials of having different primary particle sizes were prepared by the two-step solid-state reaction at several temperatures and characterized by Fourier transform infrared, X-ray diffraction, and scanning electron microscopy. The primary particle size of depends on the heating temperature. High temperature synthesis gives highly crystallized having large particle sizes with smooth {111} facets of octahedra characteristic of spinel. The steady-state polarization measurements were carried out by applying the sinusoidal voltage of peak amplitude of at to the cell consisting of and . The well-developed primary particles prepared at were superior to the small primary particles prepared at temperatures lower than that value in terms of polarization together with cycling stability.

Effect of Primary Particle Size and Salt Concentration on the Structure of Colloidal Gels

Structures of colloidal gels prepared in the reaction-limited aggregation regime from fluorinated colloidal particles with two different sizes and different salt concentrations have been characterized by combining small-angle and wide-angle light scattering and small-angle neutron scattering techniques. In all cases, the scattering structure factors indicate the coexistence of two types of fractal structures at different scale lengths: a mass fractal scaling at the scale length of the clusters that constitute the gel and a surface fractal scaling for larger scale lengths. It has been found that, at the same particle volume fraction, the mass fractal dimension of the clusters in the gel increases as the primary particle size decreases. On the other hand, we show that both the mass and the surface fractal gel structures are independent of the salt concentration.

Methylmercury and the Brain: Griffiths et al. Respond

Methylmercury and the Brain: Griffiths et al. Respond

Design of granule structure: Computational methods and experimental realization

AbstractThe spatial distribution of solid components and porosity within a composite granule—its microstructure—is an important attribute as it carries information about the processing history of the granule and determines its end‐use application properties, particularly the dissolution rate. In this work, the problem of rational design of granule structure is formulated, and two methods for its solution are proposed—stochastic design, which is based on random permutation of points within the structure using the simulated annealing algorithm, and variational design, which is based on direct simulation of granule formation from its constituent primary particles, followed by direct simulation of granule dissolution. The variational design method is demonstrated in a case study of the effect of primary particle size, radial distribution of components, and composition of a two‐component granule (active, excipient) on the dissolution profile. Selected granule structures designed computationally were also physically made by fluid‐bed granulation, their structure analyzed by X‐ray micro‐tomography, and dissolution curves measured. It was confirmed that the designed structures are feasible to manufacture and that they meet the required dissolution profiles. © 2006 American Institute of Chemical Engineers AIChE J, 2006

Particle size effects on the reducibility of titanium dioxide and its relation to the water–gas shift activity of Pt/TiO 2 catalysts

The effect of primary particle size of titanium dioxide on the reducibility of Pt/TiO 2 catalysts by carbon monoxide and hydrogen was investigated using temperature-programmed reduction (TPR) techniques and in situ Raman and Fourier transform infrared spectroscopy (FTIR). Experiments were conducted over Pt catalysts supported on four commercial titanium dioxide carriers of variable structural characteristics, the water–gas shift (WGS) activity of which increases significantly with decreasing primary crystallite size of the support. TPR profiles obtained for the preoxidized catalysts using H 2 as a reductant are characterized by a low-temperature consumption peak, attributed to the reduction of PtO x species, and a high-temperature peak, attributed to the reduction of TiO 2. The intensity of the latter peak, which is a measure of the reducibility of the support, increases drastically with increasing specific surface area of the catalyst or, conversely, with decreasing primary particle size of TiO 2. In situ Raman experiments conducted under hydrogen flow verified that formation of substoichiometric TiO x species begins at lower temperatures and is more facile over Pt/TiO 2 catalysts with smaller titania particle sizes. The TPR profiles obtained using CO as a reductant gave qualitatively similar results, exhibiting two CO 2 peaks corresponding to reduction of PtO x at low temperatures and of TiO 2 at high temperatures. An additional CO 2 peak located at intermediate temperatures, which was always accompanied by evolution of gas-phase H 2, is attributed to the WGS reaction. FTIR experiments indicate that the reaction occurs via interaction between CO and hydroxyl groups of the support, with intermediate formation of formates. The effect of the titanium dioxide particle size on the reducibility of Pt/TiO 2 catalysts and its relation to their WGS activity is discussed with respect to the “regenerative” and “associative” reaction mechanisms.

Influence of Particle Morphology and Flow Conditions on the Dispersion Behavior of Fumed Silica in Silicone Polymers

AbstractThe dispersion behavior of agglomerates of several grades of fumed silica in poly(dimethyl siloxane) liquids has been studied as a function of particle morphology and applied flow conditions. The effects of primary particle size and aggregate density and structure on cohesivity were probed through tensile and shear strength tests on particle compacts. These cohesivity tests indicated that the shear strength of particle compacts was two orders of magnitude higher than the tensile strength at the same overall packing density. Experiments carried out in both steady and time‐varying simple‐shear flows indicate that dispersion occurs through tensile failure. In the steady‐shear experiments,enhanced dispersion was obtained at higher levels of applied stress and, at comparable levels of applied stress, dispersion was found to proceed faster at higher shear rates. Experiments conducted in time‐varying flows further corroborated the results obtained in tensile cohesivity tests. Experiments in which the mean and maximum stresses in the time‐varying flows were matched to the stresses produced in steady shear flows highlight the influence of flow dynamics on dispersion behavior.

Effect of primary particle size on granule growth and endpoint determination in high-shear wet granulation

The effect of primary particle size on granule growth and endpoint determination during high-shear wet granulation was investigated. Three different grades of lactose monohydrate, having different volume mean particle sizes (39, 84, and 127 μm), were granulated with water in a 25-l high-shear mixer. Increasing primary particle size results in larger, less porous wet granules. This is consistent with the expectation that both the capillary and viscous interparticle forces decrease with increasing primary particle size, and the resulting granules become more deformable. Increasing the volume of granulating liquid reduces the porosity, but has only a minor influence on wet granule size. In contrast, the apparent dry granule size increases markedly with increasing granulating liquid. Changes in the impeller torque correlated reasonably well with changes in the wet granule size distribution, although torque is not a state function of wet granule size. It is also influenced by primary particle size and the chaotic nature of wall build-up and collapse. Impeller torque correlated poorly with apparent dry granule size. This is because of the changing nature of interparticle forces upon drying. Thus, understanding the relationship between impeller torque and dry granule size requires understanding both wet and dry granule interparticle forces and how they are influenced by pore saturation and primary particle size. One needs to be keenly aware of these limitations if using impeller torque to determine granulation endpoint.

Effect of Primary Particle Size on Granule Growth and Endpoint Determination in High Shear Granulators

ABSTRACT Three different grades of lactose monohydrate having widely differing mean particle sizes, yet similar tap densities, were granulated using a 25L instrumented Fielder mixer. The size distribution, porosity, and pore saturation of the wet granules were determined using a combination of “frozen granule” sieve analysis, mercury pycnometry, and oven drying. The granulating system was found to operate at quasi-steady-state, as granule growth ceased afler liquid addition was terminated. The resultant granule size distributions were strongly dependent on lactose grade. with coarser grades yielding larger granules for identical process conditions. In contrast. the magnitude of the power curves decreased with increasing primary particle size. Both of these observations are consistent with the fact that both the capillary and viscous interparticle fluid forces, which are believed to provide the main interparticle bonding forces in the wet mass, are inversely proportional to particle size.

Enhanced power law agglomerate growth in the free molecule regime

Aerosols generated at high temperatures tend to form agglomerates which can be characterized by a power law exponent, similar to a fractal dimension. The coagulation dynamics of these particles can be described by a modified collision kernel for the free molecule regime. The collision kernel for power law (fractal-like) particles is a homogeneous function, and the equation is solved using self-preserving size distribution theory for fractal dimensions between 2 and 3. The effects of fractal dimension and primary particle size on agglomerate growth and the size distribution are very strong. Agglomerate growth is rapid at low fractal dimension and fine primary particle size, because the collision cross-section is much larger for the same agglomerate mass. The effect of primary particle size on the rate of particle growth becomes more significant with decreasing fractal dimension, and the particle size distribution becomes much broader at low fractal dimensions.