Morphologically and size uniform monodisperse particles and their shape-directed self-assembly

Energy Technology Data Exchange (ETDEWEB)

Collins, Joshua E.; Bell, Howard Y.; Ye, Xingchen; Murray, Christopher Bruce

2017-09-12

Monodisperse particles having: a single pure crystalline phase of a rare earth-containing lattice, a uniform three-dimensional size, and a uniform polyhedral morphology are disclosed. Due to their uniform size and shape, the monodisperse particles self assemble into superlattices. The particles may be luminescent particles such as down-converting phosphor particles and up-converting phosphors. The monodisperse particles of the invention have a rare earth-containing lattice which in one embodiment may be an yttrium-containing lattice or in another may be a lanthanide-containing lattice. The monodisperse particles may have different optical properties based on their composition, their size, and/or their morphology (or shape). Also disclosed is a combination of at least two types of monodisperse particles, where each type is a plurality of monodisperse particles having a single pure crystalline phase of a rare earth-containing lattice, a uniform three-dimensional size, and a uniform polyhedral morphology; and where the types of monodisperse particles differ from one another by composition, by size, or by morphology. In a preferred embodiment, the types of monodisperse particles have the same composition but different morphologies. Methods of making and methods of using the monodisperse particles are disclosed.

Size effects in PbTiO3 nanocrystals: Effect of particle size on spontaneous polarization and strains

Science.gov (United States)

Akdogan, E. K.; Rawn, C. J.; Porter, W. D.; Payzant, E. A.; Safari, A.

2005-04-01

The spontaneous polarization (Ps) and spontaneous strains (xi) in mechanically unclamped and surface charge compensated PbTiO3 nanocrystals were determined as a function of particle size in the range <150nm by differential scanning calorimetry and x-ray powder diffraction, respectively. Significant deviations from bulk order parameters (P,xi) have been observed as the particle size decreased below ˜100nm. The critical size (rc) below which the ferroelectric tetragonal phase transforms to the paraelectric cubic phase was determined as ˜15nm. The depression in transition temperature with particle size is 14 °C at 28 nm. No change in the order of m3m →4mm ferrodistortive phase transition is observed. A simple analysis showed that ΔHtr/(kBT )˜103 at 25 °C for r =16nm, indicating that the stabilization of the cubic phase at rc cannot be linked to an instability in dipolar ordering due to thermal agitations. Comparison of the spontaneous volumetric strains with the strain induced by surface stress indicated that the effect of surface stress on ferroelectric phase stability was negligible. Anomalies in electrostrictive properties were determined for r →rc. The observed size dependence of PS is attributed to the reduced extent of long-range dipole-dipole interactions that arise due to the changes in bonding characteristics of ions with decreasing particle size in the perovskite lattice, in conformity with a recent study by Tsunekawa et al. [Phys. Rev. Lett. 85 (16), 4340 (2000)].

A novel approach for preparation of micrometer-sized, monodisperse dimple and hemispherical polystyrene particles.

Science.gov (United States)

Tanaka, Takuya; Komatsu, Yoshifumi; Fujibayashi, Teruhisa; Minami, Hideto; Okubo, Masayoshi

2010-03-16

Micrometer-sized, monodisperse dimple and hemispherical polystyrene (PS) particles were successfully prepared by heating (55-70 degrees C) of spherical PS particles dispersed in methanol/water media (40/60 to 80/20, w/w) in the presence of decane droplets, and subsequent cooling down to room temperature. Decane was absorbed by the PS particles during the heating process. Decane-absorbed PS particles phase-separated into PS and decane phases in the inside during the cooling process, and eventually dimple and/or hemispherical particles were formed by removal of the decane phase from phase-separated PS/decane particles by evaporation. The size of the dimple, which is determined by the volume of decane phase-separated from decane-absorbed PS particles during the cooling process, increased with increases in the heating temperature and the methanol content.

Toxicity of TiO2 nanoparticles to Escherichia coli: effects of particle size, crystal phase and water chemistry.

Directory of Open Access Journals (Sweden)

Xiuchun Lin

Full Text Available Controversial and inconsistent results on the eco-toxicity of TiO2 nanoparticles (NPs are commonly found in recorded studies and more experimental works are therefore warranted to elucidate the nanotoxicity and its underlying precise mechanisms. Toxicities of five types of TiO2 NPs with different particle sizes (10∼50 nm and crystal phases were investigated using Escherichia coli as a test organism. The effect of water chemistry on the nanotoxicity was also examined. The antibacterial effects of TiO2 NPs as revealed by dose-effect experiments decreased with increasing particle size and rutile content of the TiO2 NPs. More bacteria could survive at higher solution pH (5.0-10.0 and ionic strength (50-200 mg L(-1 NaCl as affected by the anatase TiO2 NPs. The TiO2 NPs with anatase crystal structure and smaller particle size produced higher content of intracellular reactive oxygen species and malondialdehyde, in line with their greater antibacterial effect. Transmission electron microscopic observations showed the concentration buildup of the anatase TiO2 NPs especially those with smaller particle sizes on the cell surfaces, leading to membrane damage and internalization. These research results will shed new light on the understanding of ecological effects of TiO2 NPs.

Toxicity of TiO2 Nanoparticles to Escherichia coli: Effects of Particle Size, Crystal Phase and Water Chemistry

Science.gov (United States)

Lin, Xiuchun; Li, Jingyi; Ma, Si; Liu, Gesheng; Yang, Kun; Tong, Meiping; Lin, Daohui

2014-01-01

Controversial and inconsistent results on the eco-toxicity of TiO2 nanoparticles (NPs) are commonly found in recorded studies and more experimental works are therefore warranted to elucidate the nanotoxicity and its underlying precise mechanisms. Toxicities of five types of TiO2 NPs with different particle sizes (10∼50 nm) and crystal phases were investigated using Escherichia coli as a test organism. The effect of water chemistry on the nanotoxicity was also examined. The antibacterial effects of TiO2 NPs as revealed by dose-effect experiments decreased with increasing particle size and rutile content of the TiO2 NPs. More bacteria could survive at higher solution pH (5.0–10.0) and ionic strength (50–200 mg L−1 NaCl) as affected by the anatase TiO2 NPs. The TiO2 NPs with anatase crystal structure and smaller particle size produced higher content of intracellular reactive oxygen species and malondialdehyde, in line with their greater antibacterial effect. Transmission electron microscopic observations showed the concentration buildup of the anatase TiO2 NPs especially those with smaller particle sizes on the cell surfaces, leading to membrane damage and internalization. These research results will shed new light on the understanding of ecological effects of TiO2 NPs. PMID:25310452

Totally asymmetric exclusion processes with particles of arbitrary size

CERN Document Server

Lakatos, G

2003-01-01

The steady-state currents and densities of a one-dimensional totally asymmetric exclusion process (TASEP) with particles that occlude an integer number (d) of lattice sites are computed using various mean-field approximations and Monte Carlo simulations. TASEPs featuring particles of arbitrary size are relevant for modelling systems such as mRNA translation, vesicle locomotion along microtubules and protein sliding along DNA. We conjecture that the nonequilibrium steady-state properties separate into low-density, high-density, and maximal current phases similar to those of the standard (d = 1) TASEP. A simple mean-field approximation for steady-state particle currents and densities is found to be inaccurate. However, we find local equilibrium particle distributions derived from a discrete Tonks gas partition function yield apparently exact currents within the maximal current phase. For the boundary-limited phases, the equilibrium Tonks gas distribution cannot be used to predict currents, phase boundaries, or ...

Effects of calcination temperature on phase formation and particle size of Zn{sub 2}Nb{sub 34}O{sub 87} powder synthesized by solid-state reaction

Energy Technology Data Exchange (ETDEWEB)

Amonpattaratkit, Penphitcha, E-mail: p.amonpattaratkit@gmail.com [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Ananta, Supon, E-mail: suponananta@yahoo.com [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand)

2013-05-15

The solid-state mixed oxide method via a rapid vibro-milling technique was explored for the preparation of single-phase Zn{sub 2}Nb{sub 34}O{sub 87} nanopowders. Phase formation of zinc niobate was investigated as a function of calcination temperature by using a combination of thermogravimetric/differential thermal analyzer (TG/DTA) and X-ray diffraction (XRD) techniques. Morphology, particle size and chemical composition of the powders were determined by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) technique. The obtained results clearly revealed the influences of calcination temperature on phase formation and particle size of Zn{sub 2}Nb{sub 34}O{sub 87} nanopowder. - Highlights: ► Single phase Zn{sub 2}Nb{sub 34}O{sub 87} was firstly prepared by solid-state mixed oxide method via a rapid vibro-milling technique. ► The influences of calcination temperature on phase formation and particle size were investigated. ► Zn{sub 2}Nb{sub 34}O{sub 87} powders were characterized by TG–DTA, XRD, SEM and EDX.

Measurement of phase interaction in dispersed gas-particle two-phase flow by phase-doppler anemometry

Directory of Open Access Journals (Sweden)

Mergheni Ali Mohamed

2008-01-01

Full Text Available For simultaneous measurement of size and velocity distributions of continuous and dispersed phases in a two-phase flow a technique phase-Doppler anemometry was used. Spherical glass particles with a particle diameter range from 102 up to 212 µm were used. In this two-phase flow an experimental results are presented which indicate a significant influence of the solid particles on the flow characteristics. The height of influence of these effects depends on the local position in the jet. Near the nozzle exit high gas velocity gradients exist and therefore high turbulence production in the shear layer of the jet is observed. Here the turbulence intensity in the two-phase jet is decreased compared to the single-phase jet. In the developed zone the velocity gradient in the shear layer is lower and the turbulence intensity reduction is higher. .

Gas-particle phase partitioning and particle size distribution of chlorinated and brominated polycyclic aromatic hydrocarbons in haze.

Science.gov (United States)

Jin, Rong; Zheng, Minghui; Yang, Hongbo; Yang, Lili; Wu, Xiaolin; Xu, Yang; Liu, Guorui

2017-12-01

Chlorinated and brominated polycyclic aromatic hydrocarbons (Cl/Br-PAHs) are emerging semi-volatile organic pollutants in haze-associated particulate matter (PM). Their gas-particle phase partitioning and distribution among PM fractions have not been clarified. Clarification would increase understanding of atmospheric behavior and health risks of Cl/Br-PAHs. In this study, samples of the gas phase and 4 PM phases (aerodynamic diameters (d ae ) > 10 μm, 2.5-10 μm, 1.0-2.5 μm, and <1.0 μm) were collected simultaneously during haze events in Beijing and analyzed. Normalized histogram distribution indicated that the Cl/Br-PAHs tended to adhere to fine particles. Over 80% of the Cl-PAHs and 70% of the Br-PAHs were associated with fine PM (d ae  < 2.5 μm). The gas-particle phase partitioning and PM distribution of Cl/Br-PAHs when heating of buildings was required, which was associated with haze events, were obviously different from those when heating was not required. The relationship between the logarithmic geometric mean diameters of the Cl/Br-PAH congeners and reciprocal of the temperature (1/T) suggested that low air temperatures during the heating period could lead to high proportions of Cl/Br-PAHs in the fine particles. Increased coal burning during the heating period also contributed to high Cl/Br-PAH loads in the fine particles. Copyright © 2017 Elsevier Ltd. All rights reserved.

Totally asymmetric exclusion processes with particles of arbitrary size

International Nuclear Information System (INIS)

Lakatos, Greg; Chou, Tom

2003-01-01

The steady-state currents and densities of a one-dimensional totally asymmetric exclusion process (TASEP) with particles that occlude an integer number (d) of lattice sites are computed using various mean-field approximations and Monte Carlo simulations. TASEPs featuring particles of arbitrary size are relevant for modelling systems such as mRNA translation, vesicle locomotion along microtubules and protein sliding along DNA. We conjecture that the nonequilibrium steady-state properties separate into low-density, high-density, and maximal current phases similar to those of the standard (d = 1) TASEP. A simple mean-field approximation for steady-state particle currents and densities is found to be inaccurate. However, we find local equilibrium particle distributions derived from a discrete Tonks gas partition function yield apparently exact currents within the maximal current phase. For the boundary-limited phases, the equilibrium Tonks gas distribution cannot be used to predict currents, phase boundaries, or the order of the phase transitions. However, we employ a refined mean-field approach to find apparently exact expressions for the steady-state currents, boundary densities, and phase diagrams of the d ≥ 1 TASEP. Extensive Monte Carlo simulations are performed to support our analytic, mean-field results

Totally asymmetric exclusion processes with particles of arbitrary size

Energy Technology Data Exchange (ETDEWEB)

Lakatos, Greg; Chou, Tom [Department of Biomathematics and Institute for Pure and Applied Mathematics, UCLA, Los Angeles, CA 90095 (United States)

2003-02-28

The steady-state currents and densities of a one-dimensional totally asymmetric exclusion process (TASEP) with particles that occlude an integer number (d) of lattice sites are computed using various mean-field approximations and Monte Carlo simulations. TASEPs featuring particles of arbitrary size are relevant for modelling systems such as mRNA translation, vesicle locomotion along microtubules and protein sliding along DNA. We conjecture that the nonequilibrium steady-state properties separate into low-density, high-density, and maximal current phases similar to those of the standard (d = 1) TASEP. A simple mean-field approximation for steady-state particle currents and densities is found to be inaccurate. However, we find local equilibrium particle distributions derived from a discrete Tonks gas partition function yield apparently exact currents within the maximal current phase. For the boundary-limited phases, the equilibrium Tonks gas distribution cannot be used to predict currents, phase boundaries, or the order of the phase transitions. However, we employ a refined mean-field approach to find apparently exact expressions for the steady-state currents, boundary densities, and phase diagrams of the d {>=} 1 TASEP. Extensive Monte Carlo simulations are performed to support our analytic, mean-field results.

Effects of Sludge Particle Size and Density on Hanford Waste Processing

International Nuclear Information System (INIS)

Poloski, Adam P.; Wells, Beric E.; Mahoney, Lenna A.; Daniel, Richard C.; Tingey, Joel M.; Cooley, Scott K.

2008-01-01

The U.S. Department of Energy Office of River Protection's Waste Treatment and Immobilization Plant (WTP) will process and treat radioactive waste that is stored in tanks at the Hanford Site in southeastern Washington State. Piping and pumps have been selected to transport the high-level waste (HLW) slurries in the WTP. Pipeline critical-velocity calculations for these systems require the input of a bounding particle size and density. Various approaches based on statistical analyses have been used in the past to provide an estimate of this bounding size and density. In this paper, representative particle size and density distributions (PSDDs) of Hanford waste insoluble solids have been developed based on a new approach that relates measured particle-size distributions (PSDs) to solid-phase compounds. This work was achieved through extensive review of available Hanford waste PSDs and solid-phase compound data. Composite PSDs representing the waste in up to 19 Hanford waste tanks were developed, and the insoluble solid-phase compounds for the 177 Hanford waste tanks, their relative fractions, crystal densities, and particle size and shape were developed. With such a large combination of particle sizes and particle densities, a Monte Carlo simulation approach was used to model the PSDDs. Further detail was added by including an agglomeration of these compounds where the agglomerate density was modeled with a fractal dimension relation. The Monte Carlo simulations were constrained to hold the following relationships: (1) the composite PSDs are reproduced, (2) the solid-phase compound mass fractions are reproduced, (3) the expected in situ bulk-solids density is qualitatively reproduced, and (4) a representative fraction of the sludge volume comprising agglomerates is qualitatively reproduced to typical Hanford waste values. Four PSDDs were developed and evaluated. These four PSDD scenarios correspond to permutations where the master PSD was sonicated or not

Rutile nanopowders for pigment production: Formation mechanism and particle size prediction

Science.gov (United States)

Zhang, Wu; Tang, Hongxin

2018-01-01

Formation mechanism and particle size prediction of rutile nanoparticles for pigment production were investigated. Anatase nanoparticles were observed by oriented attachment with parallel lattice fringe spaces of 0.2419 nm. Upon increasing the calcination temperature, the (1 1 0) plane of rutile was gradually observed, suggesting that the anatase (1 0 3) planes undergo internal structural rearrangement of oxygen and titanium ions into rutile phase due to ionic diffusion. Backpropagation neural network was used to predict particle size of rutile nanopowders, the prediction errors were all smaller than 2%, providing an efficient method to control particle size in pigment production.

The effect of particle size on the morphology and thermodynamics of diblock copolymer/tethered-particle membranes

International Nuclear Information System (INIS)

Zhang, Bo; Edwards, Brian J.

2015-01-01

A combination of self-consistent field theory and density functional theory was used to examine the effect of particle size on the stable, 3-dimensional equilibrium morphologies formed by diblock copolymers with a tethered nanoparticle attached either between the two blocks or at the end of one of the blocks. Particle size was varied between one and four tenths of the radius of gyration of the diblock polymer chain for neutral particles as well as those either favoring or disfavoring segments of the copolymer blocks. Phase diagrams were constructed and analyzed in terms of thermodynamic diagrams to understand the physics associated with the molecular-level self-assembly processes. Typical morphologies were observed, such as lamellar, spheroidal, cylindrical, gyroidal, and perforated lamellar, with the primary concentration region of the tethered particles being influenced heavily by particle size and tethering location, strength of the particle-segment energetic interactions, chain length, and copolymer radius of gyration. The effect of the simulation box size on the observed morphology and system thermodynamics was also investigated, indicating possible effects of confinement upon the system self-assembly processes

The effect of particle size on the morphology and thermodynamics of diblock copolymer/tethered-particle membranes.

Science.gov (United States)

Zhang, Bo; Edwards, Brian J

2015-06-07

A combination of self-consistent field theory and density functional theory was used to examine the effect of particle size on the stable, 3-dimensional equilibrium morphologies formed by diblock copolymers with a tethered nanoparticle attached either between the two blocks or at the end of one of the blocks. Particle size was varied between one and four tenths of the radius of gyration of the diblock polymer chain for neutral particles as well as those either favoring or disfavoring segments of the copolymer blocks. Phase diagrams were constructed and analyzed in terms of thermodynamic diagrams to understand the physics associated with the molecular-level self-assembly processes. Typical morphologies were observed, such as lamellar, spheroidal, cylindrical, gyroidal, and perforated lamellar, with the primary concentration region of the tethered particles being influenced heavily by particle size and tethering location, strength of the particle-segment energetic interactions, chain length, and copolymer radius of gyration. The effect of the simulation box size on the observed morphology and system thermodynamics was also investigated, indicating possible effects of confinement upon the system self-assembly processes.

Liquid-phase separation with the rotational particle separator

NARCIS (Netherlands)

Kemenade, van H.P.; Mondt, E.; Hendriks, A.J.A.M.; Verbeek, P.H.J.

2003-01-01

Recently, the rotational particle separator (RPS) was introduced as a new technique for separating solid and/or liquid particles of 0.1 m and larger from gases. In this patented technique the principles of centrifugation are exploited to enhance separation of small-sized phases and particulate

Particle sizing experiments with the laser Doppler velocimeter: Final report

Energy Technology Data Exchange (ETDEWEB)

Giel, T.V. Jr.; Son, J.Y.

1988-06-01

Measurement techniques for in-situ simultaneous measurements of particle size distributions and particle velocities using the dual beam laser Doppler velocimeter (LV) were analytically and experimentally investigated. This investigation examined the different signal characteristics of the LV for determination of particle size and particle velocity, simultaneously. The different size related signal components were evaluated not only singularly but also as simultaneous measurements to determine which characteristic, or combination of characteristics, provided the best measure of particle size. The evaluation concentrated on the 0.5 to 5 ..mu..m particle size range, in which the LV light scattering characteristics are complex often non-monotonic functions of the particle size as well as functions of index of refraction, the laser light wavelength, laser intensity and polarization, and the location and response characteristics of the detector. Different components of the LV signal were considered, but analysis concentrated on Doppler phase, visibility and scatter-intensity because they show the greatest promise. These signals characteristics were initially defined analytically for numerous optical configurations over the 0.5 to 5 ..mu..m diameter range with 0.1 ..mu..m segmentation, for refractive index values from 1.0 to 3.0 with absorptive (imaginary) components varied form 0 to 1.0. Collector orientation and effective f/No., as well as fringe spacing, beam polarization and wavelength, were varied in this analytical evaluation. 18 refs., 42 figs., 5 tabs.

Experimental investigation of particle size distribution influence on diffusion controlled coarsening

International Nuclear Information System (INIS)

Fang, Zhigang; Patterson, B.R.

1993-01-01

The influence of initial particle size distribution on coarsening during liquid phase sintering has been experimentally investigated using W-14Ni-6Fe alloy as a model system. It was found that initially wider size distribution particles coarsened more rapidly than those of an initially narrow distribution. The well known linear relationship between the cube of the average particle radius bar r -3 , and time was observed for most of the coarsening process, although the early stage coarsening rate constant changed with time, as expected with concomitant early changes in the tungsten particle size distribution. The instantaneous transient rate constant was shown to be related to the geometric standard deviation, 1nσ, of the instantaneous size distributions, with higher rate constants corresponding to larger 1nσ values. The form of the particle size distributions changed rapidly during early coarsening and reached a quasi-stable state, different from the theoretical asymptotic distribution, after some time. A linear relationship was found between the experimentally observed instantaneous rate constant and that computed from an earlier model incorporating the effect of particle size distribution. The above results compare favorably with those from prior theoretical modeling and computer simulation studies of the effect of particle size distribution on coarsening, based on the DeHoff communicating neighbor model

Particle size distribution of selected electronic nicotine delivery system products.

Science.gov (United States)

Oldham, Michael J; Zhang, Jingjie; Rusyniak, Mark J; Kane, David B; Gardner, William P

2018-03-01

Dosimetry models can be used to predict the dose of inhaled material, but they require several parameters including particle size distribution. The reported particle size distributions for aerosols from electronic nicotine delivery system (ENDS) products vary widely and don't always identify a specific product. A low-flow cascade impactor was used to determine the particle size distribution [mass median aerodynamic diameter (MMAD); geometric standard deviation (GSD)] from 20 different cartridge based ENDS products. To assess losses and vapor phase amount, collection efficiency of the system was measured by comparing the collected mass in the impactor to the difference in ENDS product mass. The levels of nicotine, glycerin, propylene glycol, water, and menthol in the formulations of each product were also measured. Regardless of the ENDS product formulation, the MMAD of all tested products was similar and ranged from 0.9 to 1.2 μm with a GSD ranging from 1.7 to 2.2. There was no consistent pattern of change in the MMAD and GSD as a function of number of puffs (cartridge life). The collection efficiency indicated that 9%-26% of the generated mass was deposited in the collection system or was in the vapor phase. The particle size distribution data are suitable for use in aerosol dosimetry programs. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

Cluster analysis of rural, urban, and curbside atmospheric particle size data.

Science.gov (United States)

Beddows, David C S; Dall'Osto, Manuel; Harrison, Roy M

2009-07-01

Particle size is a key determinant of the hazard posed by airborne particles. Continuous multivariate particle size data have been collected using aerosol particle size spectrometers sited at four locations within the UK: Harwell (Oxfordshire); Regents Park (London); British Telecom Tower (London); and Marylebone Road (London). These data have been analyzed using k-means cluster analysis, deduced to be the preferred cluster analysis technique, selected from an option of four partitional cluster packages, namelythe following: Fuzzy; k-means; k-median; and Model-Based clustering. Using cluster validation indices k-means clustering was shown to produce clusters with the smallest size, furthest separation, and importantly the highest degree of similarity between the elements within each partition. Using k-means clustering, the complexity of the data set is reduced allowing characterization of the data according to the temporal and spatial trends of the clusters. At Harwell, the rural background measurement site, the cluster analysis showed that the spectra may be differentiated by their modal-diameters and average temporal trends showing either high counts during the day-time or night-time hours. Likewise for the urban sites, the cluster analysis differentiated the spectra into a small number of size distributions according their modal-diameter, the location of the measurement site, and time of day. The responsible aerosol emission, formation, and dynamic processes can be inferred according to the cluster characteristics and correlation to concurrently measured meteorological, gas phase, and particle phase measurements.

Gas-phase laser synthesis of aggregation-free, size-controlled hydroxyapatite nanoparticles

International Nuclear Information System (INIS)

Bapat, Parimal V.; Kraft, Rebecca; Camata, Renato P.

2012-01-01

Nanophase hydroxyapatite (HA) is finding applications in many areas of biomedical research, including bone tissue engineering, drug delivery, and intracellular imaging. Details in chemical composition, crystal phase makeup, size, and shape of HA nanoparticles play important roles in achieving the favorable biological responses required in these applications. Most of the nanophase HA synthesis techniques involve solution-based methods that exhibit substantial aggregation of particles upon precipitation. Typically these methods also have limited control over the particle size and crystal phase composition. In this study, we describe the gas-phase synthesis of aggregation-free, size-controlled HA nanoparticles with mean size in the 20–70 nm range using laser ablation followed by aerosol electrical mobility classification. Nanoparticle deposits with adjustable number concentration were obtained on solid substrates. Particles were characterized by transmission electron microscopy, atomic force microscopy, and X-ray diffraction. Samples are well represented by log-normal size distributions with geometric standard deviation σ g ≈ 1.2. The most suitable conditions for HA nanoparticle formation at a laser fluence of 5 J/cm 2 were found to be a temperature of 800 °C and a partial pressure of water of 160 mbar.

Effect of kaolin particle size and loading on the characteristics of kaolin ceramic support prepared via phase inversion technique

Directory of Open Access Journals (Sweden)

Siti Khadijah Hubadillah

2016-06-01

Full Text Available In this study, low cost ceramic supports were prepared from kaolin via phase inversion technique with two kaolin particle sizes, which are 0.04–0.6 μm (denoted as type A and 10–15 μm (denoted as type B, at different kaolin contents ranging from 14 to 39 wt.%, sintered at 1200 °C. The effect of kaolin particle sizes as well as kaolin contents on membrane structure, pore size distribution, porosity, mechanical strength, surface roughness and gas permeation of the support were investigated. The support was prepared using kaolin type A induced asymmetric structure by combining macroporous voids and sponge-like structure in the support with pore size of 0.38 μm and 1.05 μm, respectively, and exhibited ideal porosity (27.7%, great mechanical strength (98.9 MPa and excellent gas permeation. Preliminary study shows that the kaolin ceramic support in this work is potential to gas separation application at lower cost.

The effects of particle size distribution and induced unpinning during grain growth

International Nuclear Information System (INIS)

Thompson, G.S.; Rickman, J.M.; Harmer, M.P.; Holm, E.A.

1996-01-01

The effect of a second-phase particle size distribution on grain boundary pinning was studied using a Monte Carlo simulation technique. Simulations were run using a constant number density of both whisker and rhombohedral particles, and the effect of size distribution was studied by varying the standard deviation of the distribution around a constant mean particle size. The results of present simulations indicate that, in accordance with the stereological assumption of the topological pinning model, changes in distribution width had no effect on the pinned grain size. The effect of induced unpinning of particles on microstructure was also studied. In contrast to predictions of the topological pinning model, a power law dependence of pinned grain size on particle size was observed at T=0.0. Based on this, a systematic deviation to the stereological predictions of the topological pinning model is observed. The results of simulations at higher temperatures indicate an increasing power law dependence of pinned grain size on particle size, with the slopes of the power law dependencies fitting an Arrhenius relation. The effect of induced unpinning of particles was also studied in order to obtain a correlation between particle/boundary concentration and equilibrium grain size. The results of simulations containing a constant number density of monosized rhombohedral particles suggest a strong power law correlation between the two parameters. copyright 1996 Materials Research Society

Particle size distribution properties in mixed-phase monsoon clouds from in situ measurements during CAIPEEX

Science.gov (United States)

Patade, Sachin; Prabha, T. V.; Axisa, D.; Gayatri, K.; Heymsfield, A.

2015-10-01

A comprehensive analysis of particle size distributions measured in situ with airborne instrumentation during the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) is presented. In situ airborne observations in the developing stage of continental convective clouds during premonsoon (PRE), transition, and monsoon (MON) period at temperatures from 25 to -22°C are used in the study. The PRE clouds have narrow drop size and particle size distributions compared to monsoon clouds and showed less development of size spectra with decrease in temperature. Overall, the PRE cases had much lower values of particle number concentrations and ice water content compared to MON cases, indicating large differences in the ice initiation and growth processes between these cloud regimes. This study provided compelling evidence that in addition to dynamics, aerosol and moisture are important for modulating ice microphysical processes in PRE and MON clouds through impacts on cloud drop size distribution. Significant differences are observed in the relationship of the slope and intercept parameters of the fitted particle size distributions (PSDs) with temperature in PRE and MON clouds. The intercept values are higher in MON clouds than PRE for exponential distribution which can be attributed to higher cloud particle number concentrations and ice water content in MON clouds. The PRE clouds tend to have larger values of dispersion of gamma size distributions than MON clouds, signifying narrower spectra. The relationships between PSDs parameters are presented and compared with previous observations.

Direct deposition of gas phase generated aerosol gold nanoparticles into biological fluids--corona formation and particle size shifts.

Directory of Open Access Journals (Sweden)

Christian R Svensson

Full Text Available An ongoing discussion whether traditional toxicological methods are sufficient to evaluate the risks associated with nanoparticle inhalation has led to the emergence of Air-Liquid interface toxicology. As a step in this process, this study explores the evolution of particle characteristics as they move from the airborne state into physiological solution. Airborne gold nanoparticles (AuNP are generated using an evaporation-condensation technique. Spherical and agglomerate AuNPs are deposited into physiological solutions of increasing biological complexity. The AuNP size is characterized in air as mobility diameter and in liquid as hydrodynamic diameter. AuNP:Protein aggregation in physiological solutions is determined using dynamic light scattering, particle tracking analysis, and UV absorption spectroscopy. AuNPs deposited into homocysteine buffer form large gold-aggregates. Spherical AuNPs deposited in solutions of albumin were trapped at the Air-Liquid interface but was readily suspended in the solutions with a size close to that of the airborne particles, indicating that AuNP:Protein complex formation is promoted. Deposition into serum and lung fluid resulted in larger complexes, reflecting the formation of a more complex protein corona. UV absorption spectroscopy indicated no further aggregation of the AuNPs after deposition in solution. The corona of the deposited AuNPs shows differences compared to AuNPs generated in suspension. Deposition of AuNPs from the aerosol phase into biological fluids offers a method to study the protein corona formed, upon inhalation and deposition in the lungs in a more realistic way compared to particle liquid suspensions. This is important since the protein corona together with key particle properties (e.g. size, shape and surface reactivity to a large extent may determine the nanoparticle effects and possible translocation to other organs.

Direct Deposition of Gas Phase Generated Aerosol Gold Nanoparticles into Biological Fluids - Corona Formation and Particle Size Shifts

Science.gov (United States)

Svensson, Christian R.; Messing, Maria E.; Lundqvist, Martin; Schollin, Alexander; Deppert, Knut; Pagels, Joakim H.; Rissler, Jenny; Cedervall, Tommy

2013-01-01

An ongoing discussion whether traditional toxicological methods are sufficient to evaluate the risks associated with nanoparticle inhalation has led to the emergence of Air-Liquid interface toxicology. As a step in this process, this study explores the evolution of particle characteristics as they move from the airborne state into physiological solution. Airborne gold nanoparticles (AuNP) are generated using an evaporation-condensation technique. Spherical and agglomerate AuNPs are deposited into physiological solutions of increasing biological complexity. The AuNP size is characterized in air as mobility diameter and in liquid as hydrodynamic diameter. AuNP:Protein aggregation in physiological solutions is determined using dynamic light scattering, particle tracking analysis, and UV absorption spectroscopy. AuNPs deposited into homocysteine buffer form large gold-aggregates. Spherical AuNPs deposited in solutions of albumin were trapped at the Air-Liquid interface but was readily suspended in the solutions with a size close to that of the airborne particles, indicating that AuNP:Protein complex formation is promoted. Deposition into serum and lung fluid resulted in larger complexes, reflecting the formation of a more complex protein corona. UV absorption spectroscopy indicated no further aggregation of the AuNPs after deposition in solution. The corona of the deposited AuNPs shows differences compared to AuNPs generated in suspension. Deposition of AuNPs from the aerosol phase into biological fluids offers a method to study the protein corona formed, upon inhalation and deposition in the lungs in a more realistic way compared to particle liquid suspensions. This is important since the protein corona together with key particle properties (e.g. size, shape and surface reactivity) to a large extent may determine the nanoparticle effects and possible translocation to other organs. PMID:24086363

Determination of particle size distribution of salt crystals in aqueous slurries

International Nuclear Information System (INIS)

Miller, A.G.

1977-10-01

A method for determining particle size distribution of water-soluble crystals in aqueous slurries is described. The salt slurries, containing sodium salts of predominantly nitrate, but also nitrite, sulfate, phosphate, aluminates, carbonate, and hydroxide, occur in radioactive, concentrated chemical waste from the reprocessing of nuclear fuel elements. The method involves separating the crystals from the aqueous phase, drying them, and then dispersing the crystals in a nonaqueous medium based on nitroethane. Ultrasonic treatment is important in dispersing the sample into its fundamental crystals. The dispersed crystals are sieved into appropriate size ranges for counting with a HIAC brand particle counter. A preponderance of very fine particles in a slurry was found to increase the difficulty of effecting complete dispersion of the crystals because of the tendency to retain traces of aqueous mother liquor. Traces of moisture produce agglomerates of crystals, the extent of agglomeration being dependent on the amount of moisture present. The procedure is applicable to particles within the 2 to 600 μm size range of the HIAC particle counter. The procedure provides an effective means for measuring particle size distribution of crystals in aqueous salt slurries even when most crystals are less than 10 μm in size. 19 figures

Particle size distribution control of Pt particles used for particle gun

Science.gov (United States)

Ichiji, M.; Akiba, H.; Nagao, H.; Hirasawa, I.

2017-07-01

The purpose of this study is particle size distribution (PSD) control of submicron sized Pt particles used for particle gun. In this report, simple reaction crystallization is conducted by mixing H2PtCl6 and ascorbic acid. Without the additive, obtained Pt particles have broad PSD and reproducibility of experiment is low. With seeding, Pt particles have narrow PSD and reproducibility improved. Additionally, mean particle diameter of 100-700 nm is controlled by changing seeding amount. Obtained particles are successfully characterized as Pt by XRD results. Moreover, XRD spectra indicate that obtained particles are polycrystals. These experimental results suggest that seeding consumed nucleation, as most nuclei attached on the seed surface. This mechanism virtually restricted nucleation to have narrow PSD can be obtained.

An alternative method for determining particle-size distribution of forest road aggregate and soil with large-sized particles

Science.gov (United States)

Hakjun Rhee; Randy B. Foltz; James L. Fridley; Finn Krogstad; Deborah S. Page-Dumroese

2014-01-01

Measurement of particle-size distribution (PSD) of soil with large-sized particles (e.g., 25.4 mm diameter) requires a large sample and numerous particle-size analyses (PSAs). A new method is needed that would reduce time, effort, and cost for PSAs of the soil and aggregate material with large-sized particles. We evaluated a nested method for sampling and PSA by...

Simulation study of effects of initial particle size distribution on dissolution

International Nuclear Information System (INIS)

Wang, G.; Xu, D.S.; Ma, N.; Zhou, N.; Payton, E.J.; Yang, R.; Mills, M.J.; Wang, Y.

2009-01-01

Dissolution kinetics of γ' particles in binary Ni-Al alloys with different initial particle size distributions (PSD) is studied using a three-dimensional (3D) quantitative phase field model. By linking model inputs directly to thermodynamic and atomic mobility databases, microstructural evolution during dissolution is simulated in real time and length scales. The model is first validated against analytical solution for dissolution of a single γ' particle in 1D and numerical solution in 3D before it is applied to investigate the effects of initial PSD on dissolution kinetics. Four different types of PSD, uniform, normal, log-normal and bimodal, are considered. The simulation results show that the volume fraction of γ' particles decreases exponentially with time, while the temporal evolution of average particle size depends strongly on the initial PSD

Size exclusion chromatography with superficially porous particles.

Science.gov (United States)

Schure, Mark R; Moran, Robert E

2017-01-13

A comparison is made using size-exclusion chromatography (SEC) of synthetic polymers between fully porous particles (FPPs) and superficially porous particles (SPPs) with similar particle diameters, pore sizes and equal flow rates. Polystyrene molecular weight standards with a mobile phase of tetrahydrofuran are utilized for all measurements conducted with standard HPLC equipment. Although it is traditionally thought that larger pore volume is thermodynamically advantageous in SEC for better separations, SPPs have kinetic advantages and these will be shown to compensate for the loss in pore volume compared to FPPs. The comparison metrics include the elution range (smaller with SPPs), the plate count (larger for SPPs), the rate production of theoretical plates (larger for SPPs) and the specific resolution (larger with FPPs). Advantages to using SPPs for SEC are discussed such that similar separations can be conducted faster using SPPs. SEC using SPPs offers similar peak capacities to that using FPPs but with faster operation. This also suggests that SEC conducted in the second dimension of a two-dimensional liquid chromatograph may benefit with reduced run time and with equivalently reduced peak width making SPPs advantageous for sampling the first dimension by the second dimension separator. Additional advantages are discussed for biomolecules along with a discussion of optimization criteria for size-based separations. Copyright © 2016 Elsevier B.V. All rights reserved.

Modeling of finite-size droplets and particles in multiphase flows

Directory of Open Access Journals (Sweden)

Prashant Khare

2015-08-01

Full Text Available The conventional point-particle approach for treating the dispersed phase in a continuous flowfield is extended by taking into account the effect of finite particle size, using a Gaussian interpolation from Lagrangian points to the Eulerian field. The inter-phase exchange terms in the conservation equations are distributed over the volume encompassing the particle size, as opposed to the Dirac delta function generally used in the point-particle approach. The proposed approach is benchmarked against three different flow configurations in a numerical framework based on large eddy simulation (LES turbulence closure. First, the flow over a circular cylinder is simulated for a Reynolds number of 3900 at 1 atm pressure. Results show good agreement with experimental data for the mean streamwise velocity and the vortex shedding frequency in the wake region. The calculated flowfield exhibits correct physics, which the conventional point-particle approach fails to capture. The second case deals with diesel jet injection in quiescent environment over a pressure range of 1.1–5.0 MPa. The calculated jet penetration depth closely matches measurements. It decreases with increasing chamber pressure, due to enhanced drag force in a denser fluid environment. Finally, water and acetone jet injection normal to air crossflow is studied at 1 atm. The calculated jet penetration and Sauter mean diameter of liquid droplets compare very well with measurements.

Effect of milling time on the structure, particle size, and morphology of montmorillonite

International Nuclear Information System (INIS)

Abareshi, M.

2017-01-01

In the current research, effect of milling on the structure, particle size and morphology of montmorillonite was investigated. For this purpose, the montmorillonite was analyzed by X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. Then the montmorillonite was milled using high energy planetary ball mill at different milling times (1-60 hours). After that, the structure, particle size and morphology of all samples were investigated by XRD, FTIR, SEM, and transmission electron microscopy. Results showed that the ball milling causes the particle size reduction of clay and separation of the clay layers. Moreover, ball milling increases the overall structural disorder and transforms the crystalline structure into an amorphous phase. Also, the morphology of clay particle changes from layered to aggregates of almost rounded particles after 60 hours of milling.

Particle size determination

International Nuclear Information System (INIS)

Burr, K.J.

1979-01-01

A specification is given for an apparatus to provide a completely automatic testing cycle to determine the proportion of particles of less than a predetermined size in one of a number of fluid suspensions. Monitoring of the particle concentration during part of the process can be carried out by an x-ray source and detector. (U.K.)

Preparing poly (caprolactone) micro-particles through solvent-induced phase separation

DEFF Research Database (Denmark)

Li, Xiaoqiang; Kanjwal, Muzafar Ahmed; Stephansen, Karen

2012-01-01

Poly (caprolactone) (PCL) particles with the size distribution from 1 to 100 μm were prepared through solvent-induced phase separation, in which polyvinyl-alcohol (PVA) was used as the matrix-forming polymer to stabilize PCL particles. The cloud point data of PCL-acetone-water was determined...

Comprehensive Laser-induced Incandescence (LII) modeling for soot particle sizing

KAUST Repository

Lisanti, Joel

2015-03-30

To evaluate the current state of the art in LII particle sizing, a comprehensive model for predicting the temporal incandescent response of combustion-generated soot to absorption of a pulsed laser is presented. The model incorporates particle heating through laser absorption, thermal annealing, and oxidation at the surface as well as cooling through sublimation and photodesorption, radiation, conduction and thermionic emission. Thermodynamic properties and the thermal accommodation coefficient utilized in the model are temperature dependent. In addition, where appropriate properties are also phase dependent, thereby accounting for annealing effects during laser heating and particle cooling.

Pesticides in the atmosphere: a comparison of gas-particle partitioning and particle size distribution of legacy and current-use pesticides

Science.gov (United States)

Degrendele, C.; Okonski, K.; Melymuk, L.; Landlová, L.; Kukučka, P.; Audy, O.; Kohoutek, J.; Čupr, P.; Klánová, J.

2016-02-01

This study presents a comparison of seasonal variation, gas-particle partitioning, and particle-phase size distribution of organochlorine pesticides (OCPs) and current-use pesticides (CUPs) in air. Two years (2012/2013) of weekly air samples were collected at a background site in the Czech Republic using a high-volume air sampler. To study the particle-phase size distribution, air samples were also collected at an urban and rural site in the area of Brno, Czech Republic, using a cascade impactor separating atmospheric particulates according to six size fractions. Major differences were found in the atmospheric distribution of OCPs and CUPs. The atmospheric concentrations of CUPs were driven by agricultural activities while secondary sources such as volatilization from surfaces governed the atmospheric concentrations of OCPs. Moreover, clear differences were observed in gas-particle partitioning; CUP partitioning was influenced by adsorption onto mineral surfaces while OCPs were mainly partitioning to aerosols through absorption. A predictive method for estimating the gas-particle partitioning has been derived and is proposed for polar and non-polar pesticides. Finally, while OCPs and the majority of CUPs were largely found on fine particles, four CUPs (carbendazim, isoproturon, prochloraz, and terbuthylazine) had higher concentrations on coarse particles ( > 3.0 µm), which may be related to the pesticide application technique. This finding is particularly important and should be further investigated given that large particles result in lower risks from inhalation (regardless the toxicity of the pesticide) and lower potential for long-range atmospheric transport.

Nucleation and dissociation of nano-particles in gas phase

International Nuclear Information System (INIS)

Feiden, P.

2007-09-01

This work deals with the study of nano-particles formation in gas phase and their dissociation pathways after an optical excitation. The clusters formation decomposes in two steps: a seed is formed (nucleation phase) and sticks atoms during its propagation in a sodium atomic vapor (growth phase). Those two steps have been observed separately for homogeneous Na n and heterogeneous Na n X particles (X = (NaOH) 2 or (Na 2 O) 2 ). The growth mechanism is well interpreted by a Monte Carlo simulation taking into account an accretion mechanism with hard-sphere cross section. The homogeneous nucleation mechanism has been highlighted by a direct comparison with the Classical Nucleation Theory predictions. The clusters fragmentation of ionic Na + (NaOH) p et Na + (NaF) p particles is studied in the second part. The way clusters fragment with size when they are excited optically is compared with theoretical previsions: this highlights the existence of an energetic barrier for special size of clusters. Finally, the fragmentation of doubly charged Na + Na + (NaOH) p clusters shows a competition between the fission into two single charged fragments and the unimolecular evaporation of a neutral fragment. (author)

Seasonal and particle size-dependent variations in gas/particle partitioning of PCDD/Fs

International Nuclear Information System (INIS)

Lee, Se-Jin; Ale, Debaki; Chang, Yoon-Seok; Oh, Jeong-Eun; Shin, Sun Kyoung

2008-01-01

This study monitored particle size-dependent variations in atmospheric polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Two gas/particle partitioning models, the subcooled liquid vapor pressure (P L 0 ) and the octanol-air partition coefficient (K OA ) model, were applied to each particle sizes. The regression coefficients of each fraction against the gas/particle partition coefficient (K P ) were similar for separated particles within the same sample set but differed for particles collected during different periods. Gas/particle partitioning calculated from the integral of fractions was similar to that of size-segregated particles and previously measured bulk values. Despite the different behaviors and production mechanisms of atmospheric particles of different sizes, PCDD/F partitioning of each size range was controlled by meteorological conditions such as atmospheric temperature, O 3 and UV, which reflects no source related with certain particle size ranges but mixed urban sources within this city. Our observations emphasize that when assessing environmental and health effects, the movement of PCDD/Fs in air should be considered in conjunction with particle size in addition to the bulk aerosol. - Gas/particle partitioning of atmospheric PCDD/Fs for different particle sizes reflects the impacts of emitters of different size ranges

Phenomenological theory of size effects in ultrafine ferroelectric particles (PbTiO3-type)

International Nuclear Information System (INIS)

Jiang, B.; Bursill, L.A.

1998-01-01

A new phenomenological model is proposed and discussed to study the size effects on phase transitions in PbTiO 3 -type ferroelectric particles. This model, by taking size effects on the phenomenological Landau-Ginzburg-Devonshire coefficients into consideration, can successfully explain the size effects on Curie temperature, c/a ratio, thermal and dielectric properties of lead-titanate-type ferroelectric particles. Theoretical and experimental results for PbTiO 3 fine particles are also compared and discussed. The relationship between the current model and the model of Zhong et al (Phys. Rev. B 50, 698 (1994)) is also presented. (authors)

Effect of graphite particle size and content on the formation mechanism of detonation polycrystalline diamond

Science.gov (United States)

Tong, Y.; Cao, Y.; Liu, R.; Shang, S. Y.; Huang, F. L.

2018-03-01

The formation mechanism of detonation polycrystalline diamond (DPD) generated from the detonation of a mixed RDX/graphite explosive is investigated. It is found experimentally that the DPD conversion rate decreases with both the content and the particle size of the graphite. Moreover, the particle sizes of the generated DPD powder are analyzed, which shows that, with the decrease in the graphite particle size, the mean number diameter of DPD decreases, but the mean volume diameter increases. In addition, with the help of scanning electron microscopy, it is observed that the in situ phase change occurs in the graphite particles, by which the small particles combine to form numerous large DPD particles. Based on both the experimental data and the classical ZND detonation model, we divide such a DPD synthesis process into two stages: In the first stage, the in situ phase change from graphite to diamond is dominant, supplemented by some coalescence growth at high pressure and temperature, which is affected mainly by the detonation performance of the mixed explosive under consideration. In the second stage, the graphitization of DPD caused by the residual heat is dominant, which is affected mainly by the unloading rate of the particle temperature.

Electrical impedance tomography spectroscopy method for characterising particles in solid-liquid phase

Energy Technology Data Exchange (ETDEWEB)

Zhao, Yanlin [Department of Thermal Energy Engineering, College of Mechanical and Transportation Engineering, China University of Petroleum, Beijing, 102249 (China); Wang, Mi [Institute of Particle Science and Engineering, School of Process, Environmental and Materials Engineering, University of Leeds, Leeds LS2 9JT (China); Yao, Jun [School of Energy Research, Xiamen University, Xiamen 361005 (China)

2014-04-11

Electrical impedance tomography (EIT) is one of the process tomography techniques to provide an on-line non-invasive imaging for multiphase flow measurement. With EIT measurements, the images of impedance real part, impedance imaginary part, phase angle, and magnitude can be obtained. However, most of the applications of EIT in the process industries rely on the conductivity difference between two phases in fluids to obtain the concentration profiles. It is not common to use the imaginary part or phase angle due to the dominant change in conductivity or complication in the use of other impedance information. In a solid-liquid two phases system involving nano- or submicro-particles, characterisation of particles (e.g. particle size and concentration) have to rely on the measurement of impedance phase angle or imaginary part. Particles in a solution usually have an electrical double layer associated with their surfaces and can form an induced electrical dipole moment due to the polarization of the electrical double layer under the influence of an alternating electric field. Similar to EIT, electrical impedance spectroscopy (EIS) measurement can record the electrical impedance data, including impedance real part, imaginary part and phase angle (θ), which are caused by the polarization of the electrical double layer. These impedance data are related to the particle characteristics e.g. particle size, particle and ionic concentrations in the aqueous medium, therefore EIS method provides a capability for characterising the particles in suspensions. Electrical impedance tomography based on EIS measurement or namely, electrical impedance tomography spectroscopy (EITS) could image the spatial distribution of particle characteristics. In this paper, a new method, including test set-up and data analysis, for characterisation of particles in suspensions are developed through the experimental approach. The experimental results on tomographic imaging of colloidal particles

Pesticides in the atmosphere: a comparison of gas-particle partitioning and particle size distribution of legacy and current-use pesticides

Directory of Open Access Journals (Sweden)

C. Degrendele

2016-02-01

Full Text Available This study presents a comparison of seasonal variation, gas-particle partitioning, and particle-phase size distribution of organochlorine pesticides (OCPs and current-use pesticides (CUPs in air. Two years (2012/2013 of weekly air samples were collected at a background site in the Czech Republic using a high-volume air sampler. To study the particle-phase size distribution, air samples were also collected at an urban and rural site in the area of Brno, Czech Republic, using a cascade impactor separating atmospheric particulates according to six size fractions. Major differences were found in the atmospheric distribution of OCPs and CUPs. The atmospheric concentrations of CUPs were driven by agricultural activities while secondary sources such as volatilization from surfaces governed the atmospheric concentrations of OCPs. Moreover, clear differences were observed in gas-particle partitioning; CUP partitioning was influenced by adsorption onto mineral surfaces while OCPs were mainly partitioning to aerosols through absorption. A predictive method for estimating the gas-particle partitioning has been derived and is proposed for polar and non-polar pesticides. Finally, while OCPs and the majority of CUPs were largely found on fine particles, four CUPs (carbendazim, isoproturon, prochloraz, and terbuthylazine had higher concentrations on coarse particles ( >  3.0 µm, which may be related to the pesticide application technique. This finding is particularly important and should be further investigated given that large particles result in lower risks from inhalation (regardless the toxicity of the pesticide and lower potential for long-range atmospheric transport.

Precipitation and Evolution Behavior of Second Phase Particles in Grain-oriented Silicon Steel with Cu

Directory of Open Access Journals (Sweden)

LI Zhi-chao

2017-12-01

Full Text Available The precipitation behavior and distribution of second phase particles in conventional grain-oriented silicon steel during manufacturing process were observed by field emission scanning electron microscopy, and the average particle size, the areal particle density, and the Zener factor were statistically analyzed. The results show that the samples mainly contain two kinds of precipitates:A class is the (Cu,MnS composite precipitates with the average size of 1μm; B class is the Cu2S precipitates with the size of 10-30nm, the key inhibition effect is produced by Cu2S. Hot rolling leads to a large amount of fine second phase particles precipitation, which has the minimum average particle size and the highest areal density; in the manufacturing process before high temperature annealing, the average particle size is increasing and the areal density is decreasing; in the process of high temperature annealing, with the decrease of volume fraction of precipitates, the inhibition ability exhibits reducing trend,obvious aggregation occurs at 960℃,secondary recrystallization will happen when Zener factor A decreases below the critical value of 0.19nm-1, and the residual particles will not produce valid inhibition effect.

Size scaling effects on the particle density fluctuations in confined plasmas

International Nuclear Information System (INIS)

Vazquez, Federico; Markus, Ferenc

2009-01-01

In this paper, memory and nonlocal effects on fluctuating mass diffusion are addressed in the context of fusion plasmas. Nonlocal effects are included by considering a diffusivity coefficient depending on the size of the container in the transverse direction to the applied magnetic field. It is obtained by resorting to the general formulation of the extended version of irreversible thermodynamics in terms of the higher order dissipative fluxes. The developed model describes two different types of the particle density time correlation function. Both have been observed in tokamak and nontokamak devices. These two kinds of time correlation function characterize the wave and the diffusive transport mechanisms of particle density perturbations. A transition between them is found, which is controlled by the size of the container. A phase diagram in the (L,2π/k) space describes the relation between the dynamics of particle density fluctuations and the size L of the system together with the oscillating mode k of the correlation function.

Size-selective sorting in bubble streaming flows: Particle migration on fast time scales

Science.gov (United States)

Thameem, Raqeeb; Rallabandi, Bhargav; Hilgenfeldt, Sascha

2015-11-01

Steady streaming from ultrasonically driven microbubbles is an increasingly popular technique in microfluidics because such devices are easily manufactured and generate powerful and highly controllable flows. Combining streaming and Poiseuille transport flows allows for passive size-sensitive sorting at particle sizes and selectivities much smaller than the bubble radius. The crucial particle deflection and separation takes place over very small times (milliseconds) and length scales (20-30 microns) and can be rationalized using a simplified geometric mechanism. A quantitative theoretical description is achieved through the application of recent results on three-dimensional streaming flow field contributions. To develop a more fundamental understanding of the particle dynamics, we use high-speed photography of trajectories in polydisperse particle suspensions, recording the particle motion on the time scale of the bubble oscillation. Our data reveal the dependence of particle displacement on driving phase, particle size, oscillatory flow speed, and streaming speed. With this information, the effective repulsive force exerted by the bubble on the particle can be quantified, showing for the first time how fast, selective particle migration is effected in a streaming flow. We acknowledge support by the National Science Foundation under grant number CBET-1236141.

Particle clustering within a two-phase turbulent pipe jet

Science.gov (United States)

Lau, Timothy; Nathan, Graham

2016-11-01

A comprehensive study of the influence of Stokes number on the instantaneous distributions of particles within a well-characterised, two-phase, turbulent pipe jet in a weak co-flow was performed. The experiments utilised particles with a narrow size distribution, resulting in a truly mono-disperse particle-laden jet. The jet Reynolds number, based on the pipe diameter, was in the range 10000 developed technique. The results show that particle clustering is significantly influenced by the exit Stokes number. Particle clustering was found to be significant for 0 . 3 financial contributions by the Australian Research Council (Grant No. DP120102961) and the Australian Renewable Energy Agency (Grant No. USO034).

The immersion freezing behavior of size-segregated soot and kaolinite particles

Science.gov (United States)

Hartmann, S.; Augustin, S.; Clauss, T.; Niedermeier, D.; Raddatz, M.; Wex, H.; Shaw, R. A.; Stratmann, F.

2011-12-01

Heterogeneous ice nucleation plays a crucial role for ice formation in mixed-phase and cirrus clouds and has an important impact on precipitation formation, global radiation balances, and therefore Earth's climate (Cantrell and Heymsfield, 2005). Mineral dust and soot particles are found to be a major component of ice crystal residues (e.g., Pratt et al., 2009) so these substances are potential sources of atmospheric ice nuclei (IN). Experimental studies investigating the immersion freezing behavior of size-segregated soot and kaolinite particles conducted at the Leipzig Aerosol Cloud Interaction Simulator (LACIS) are presented. In our measurements only one aerosol particle is immersed in an air suspended water droplet which can trigger ice nucleation. The method facilitates very precise examinations with respect to temperature, ice nucleation time and ice nucleus size. Considering laboratory studies, the picture of the IN ability of soot particles is quite heterogeneous. Our studies show that submicron flame, spark soot particles and optionally coated with sulfuric acid to simulate chemically aging do not act as IN at temperatures higher than homogeneous freezing taking place. Therefore soot particles might not be an important source of IN for immersion freezing in the atmosphere. In contrast, kaolinite being representative for natural mineral dust with a well known composition and structure is found to be very active in forming ice for all freezing modes (e.g., Mason and Maybank, 1958). Analyzing the immersion freezing behavior of different sized kaolinite particles (300, 500 and 700 nm in diameter) the size effect was clearly observed, i.e. the ice fraction (number of frozen droplets per total number) scales with particle surface, i.e. the larger the ice nucleus surface the higher the ice fraction. The slope of the logarithm of the ice fraction as function of temperature is similar for all particle sizes investigated and fits very well with the results of L�

Size effects of solvent molecules on the phase behavior and effective interaction of colloidal systems with the bridging attraction

International Nuclear Information System (INIS)

Chen, Jie; Wang, Xuewu; Kline, Steven R; Liu, Yun

2016-01-01

There has been much recent research interest towards understanding the phase behavior of colloidal systems interacting with a bridging attraction, where the small solvent particles and large solute colloidal particles can be reversibly associated with each other. These systems show interesting phase behavior compared to the more widely studied depletion attraction systems. Here, we use Baxter’s two-component sticky hard sphere model with a Percus–Yevick closure to solve the Ornstein–Zernike equation and study the size effect on colloidal systems with bridging attractions. The spinodal decomposition regions, percolation transition boundaries and binodal regions are systematically investigated as a function of the relative size of the small solvent and large solute particles as well as the attraction strength between the small and large particles. In the phase space determined by the concentrations of small and large particles, the spinodal and binodal regions form isolated islands. The locations and shapes of the spinodal and binodal regions sensitively depend on the relative size of the small and large particles and the attraction strength between them. The percolation region shrinks by decreasing the size ratio, while the binodal region slightly expands with the decrease of the size ratio. Our results are very important in understanding the phase behavior for a bridging attraction colloidal system, a model system that provides insight into oppositely charged colloidal systems, protein phase behavior, and colloidal gelation mechanisms. (paper)

Size effects of solvent molecules on the phase behavior and effective interaction of colloidal systems with the bridging attraction.

Science.gov (United States)

Chen, Jie; Wang, Xuewu; Kline, Steven R; Liu, Yun

2016-11-16

There has been much recent research interest towards understanding the phase behavior of colloidal systems interacting with a bridging attraction, where the small solvent particles and large solute colloidal particles can be reversibly associated with each other. These systems show interesting phase behavior compared to the more widely studied depletion attraction systems. Here, we use Baxter's two-component sticky hard sphere model with a Percus-Yevick closure to solve the Ornstein-Zernike equation and study the size effect on colloidal systems with bridging attractions. The spinodal decomposition regions, percolation transition boundaries and binodal regions are systematically investigated as a function of the relative size of the small solvent and large solute particles as well as the attraction strength between the small and large particles. In the phase space determined by the concentrations of small and large particles, the spinodal and binodal regions form isolated islands. The locations and shapes of the spinodal and binodal regions sensitively depend on the relative size of the small and large particles and the attraction strength between them. The percolation region shrinks by decreasing the size ratio, while the binodal region slightly expands with the decrease of the size ratio. Our results are very important in understanding the phase behavior for a bridging attraction colloidal system, a model system that provides insight into oppositely charged colloidal systems, protein phase behavior, and colloidal gelation mechanisms.

A novel method for determination of particle size distribution in-process

Science.gov (United States)

Salaoru, Tiberiu A.; Li, Mingzhong; Wilkinson, Derek

2009-07-01

The pharmaceutical and fine chemicals industries are strongly concerned with the manufacture of high value-added speciality products, often in solid form. On-line measurement of solid particle size is vital for reliable control of product properties. The established techniques, such as laser diffraction or spectral extinction, require dilution of the process suspension when measuring from typical manufacturing streams because of their high concentration. Dilution to facilitate measurement can result in changes of both size and form of particles, especially during production processes such as crystallisation. In spectral extinction, the degree of light scattering and absorption by a suspension is measured. However, for concentrated suspensions the interpretation of light extinction measurements is difficult because of multiple scattering and inter-particle interaction effects and at higher concentrations extinction is essentially total so the technique can no longer be applied. At the same time, scattering by a dispersion also causes a change of phase which affects the real component of the suspension's effective refractive index which is a function of particle size and particle and dispersant refractive indices. In this work, a novel prototype instrument has been developed to measure particle size distribution in concentrated suspensions in-process by measuring suspension refractive index at incidence angles near the onset of total internal reflection. Using this technique, the light beam does not pass through the suspension being measured so suspension turbidity does not impair the measurement.

Novel Volumetric Size and Velocity Measurement of Particles Using Interferometric Laser Imaging

Science.gov (United States)

Gunawardana, R.; Zarzecki, M.; Diez, F. J.

2008-11-01

Global Sizing Velocimetry (GSV) is a recently developed technique for characterizing the particle size distribution and flow velocity in a plane and in this research we extend this measurement to a volume through a laser scanning system. In GSV, a LASER sheet is used to illuminate translucent particles in a spray or flow field and the camera image is de-focused a known distance to create interference patterns. The diameters of the particles in the flow field are calculated by measuring the inter-fringe spacing in the resulting interferogram. Particle Imaging Velocimetry (PIV) techniques are used to compute velocity by measuring the particle displacement over a known short time interval. Researchers have recently begun applying GSV techniques to characterize sprays in a plane as it offers a larger area of investigation than other well known techniques such as Phase Doppler Anemometry (PDA). In this paper we extend GSA techniques from the current planar measurements to a volumetric measurement. The approach uses a high speed camera to acquire GSA images by scanning multiple planes in a volume of the flow field within a short period of time and obtain particle size distribution and velocity measurements in the entire volume.

Concentration and size distribution of water-extracted dimethylaminium and trimethylaminium in atmospheric particles during nine campaigns - Implications for sources, phase states and formation pathways.

Science.gov (United States)

Xie, Huan; Feng, Limin; Hu, Qingjing; Zhu, Yujiao; Gao, Huiwang; Gao, Yang; Yao, Xiaohong

2018-03-07

In this study, we determined the concentrations of water-extracted dimethylaminium (DMA + ) and trimethylaminium (TMA + ) in size-segregated atmospheric particles collected during three inland campaigns and one sea-beach campaign in Qingdao and five marine campaigns in marginal seas of China and the northwest Pacific Ocean. The averages of DMA + and TMA + in PM 0.056 - 10 (the sum of concentrations from 0.056 to 10μm) during each campaign ranged from 0.045 to 1.1nmolm -3 and from 0.029 to 0.53nmolm -3 , respectively. The increased concentrations of DMA + and TMA + in PM 0.056 - 10 , particularly the 1-2 orders of magnitude increased ratios of DMA + /NH 4 + and TMA + /NH 4 + , in the marine and sea-beach atmospheres indicated that the overwhelming majority was derived from marine sources. Size distributions of TMA + and DMA + were also investigated in terms of phase states and formation pathways, e.g., the dominant modes of particulate DMA + and TMA + in some samples were characterized by the mass median aerodynamic diameter at 0.1-0.2μm against the dominant mode of NH 4 + and SO 4 2- at 0.7-0.9μm, while the ratios of DMA + /NH 4 + and/or TMA + /NH 4 + in 0.2μm particles. This strongly implied that the particulate DMA + and TMA + at 0.2μm size range mainly existed in the aqueous (or solid) phase where the dominance of gas-aerosol equilibria would cause the ratios to be almost size-independent. The size-dependent phase states corresponded to their various formation pathways. Copyright © 2018 Elsevier B.V. All rights reserved.

Radical polymerization of capillary bridges between micron-sized particles in liquid bulk phase as a low temperature route to produce porous solid materials.

Science.gov (United States)

Hauf, Katharina; Riazi, Kamran; Willenbacher, Norbert; Koos, Erin

2017-10-01

We present a generic and versatile low temperature route to produce macro-porous bodies with porosity and pore size distribution that are adjustable in a wide range. Capillary suspensions, where the minor fluid is a monomer, are used as pre-cursors. The monomer is preferentially located between the particles, creating capillary bridges, resulting in a strong, percolating network. Thermally induced polymerization of these bridges at temperatures below 100 °C for less than 5 hours and subsequent removal of the bulk fluid yields macroscopic, self-supporting solid bodies with high porosity. This process is demonstrated using methylmethacrylate and hydroxyethylmethacrlyate with glass particles as a model system. The produced PMMA had a molecular weight of about 500.000 g/mol and dispersity about three. Application specific porous bodies, including PMMA particles connected by PMMA bridges, micron-sized capsules containing phase change material with high inner surface, and porous graphite membranes with high electrical conductivity, are also shown.

Automatic particle-size analysis of HTGR recycle fuel

International Nuclear Information System (INIS)

Mack, J.E.; Pechin, W.H.

1977-09-01

An automatic particle-size analyzer was designed, fabricated, tested, and put into operation measuring and counting HTGR recycle fuel particles. The particle-size analyzer can be used for particles in all stages of fabrication, from the loaded, uncarbonized weak acid resin up to fully-coated Biso or Triso particles. The device handles microspheres in the range of 300 to 1000 μm at rates up to 2000 per minute, measuring the diameter of each particle to determine the size distribution of the sample, and simultaneously determining the total number of particles. 10 figures

Experimental investigation of turbulence modulation in particle-laden coaxial jets by Phase Doppler Anemometry

Energy Technology Data Exchange (ETDEWEB)

Mergheni, M.A. [CORIA UMR 6614 CNRS, Universite et INSA de ROUEN, Avenue de l' Universite, BP 12, 76801 Saint Etienne du Rouvray, Cedex (France)]|[LESTE Ecole Nationale d' Ingenieurs de Monastir, 5019 Monastir (Tunisia); Sautet, J.C.; Godard, G. [CORIA UMR 6614 CNRS, Universite et INSA de ROUEN, Avenue de l' Universite, BP 12, 76801 Saint Etienne du Rouvray, Cedex (France); Ben Ticha, H.; Ben Nasrallah, S. [LESTE Ecole Nationale d' Ingenieurs de Monastir, 5019 Monastir (Tunisia)

2009-03-15

The effect of solid particles on the flow characteristics of axisymmetric turbulent coaxial jets for two flow conditions was studied. Simultaneous measurements of size and velocity distributions of continuous and dispersed phases in a two-phase flow are presented using a Phase Doppler Anemometry (PDA) technique. Spherical glass particles with a particle diameter range from 102 to 212 {mu}m were used in this two-phase flow, the experimental results indicate a significant influence of the solid particles and the Re on the flow characteristics. The data show that the gas phase has lower mean velocity in the near-injector region and a higher mean velocity at the developed region. Near the injector at low Reynolds number (Re = 2839) the presence of the particles dampens the gas-phase turbulence, while at higher Reynolds number (Re = 11 893) the gas-phase turbulence and the velocity fluctuation of particle-laden jets are increased. The particle velocity at higher Reynolds number (Re = 11 893) and is lower at lower Reynolds number (Re = 2839). The slip velocity between particles and gas phase existed over the flow domain was examined. More importantly, the present experiment results suggest that, consideration of the gas characteristic length scales is insufficient to predict gas-phase turbulence modulation in gas-particle flows. (author)

Tailoring the synthesis of supported Pd catalysts towards desired structure and size of metal particles.

Science.gov (United States)

Suresh, Gatla; Radnik, Jörg; Kalevaru, Venkata Narayana; Pohl, Marga-Martina; Schneider, Matthias; Lücke, Bernhard; Martin, Andreas; Madaan, Neetika; Brückner, Angelika

2010-05-14

In a systematic study, the influence of different preparation parameters on phase composition and size of metal crystallites and particles in Pd-Cu/TiO(2) and Pd-Sb/TiO(2) catalyst materials has been explored. Temperature and atmosphere of thermal pretreatment (pure He or 10% H(2)/He), nature of metal precursors (chlorides, nitrates or acetates) as well as of ammonium additives (ammonium sulfate, nitrate, carbonate) and urea were varied with the aim of tailoring the synthesis procedure for the preferential formation of metal particles with similar size and structure as observed recently in active catalysts after long-term equilibration under catalytic reaction conditions in acetoxylation of toluene to benzylacetate. Among the metal precursors and additives, the chloride metal precursors and (NH(4))(2)SO(4) were most suitable. Upon thermal pretreatment of Pd-Sb or Pd-Cu precursors, chloroamine complexes of Pd and Cu are formed, which decompose above 220 degrees C to metallic phases independent of the atmosphere. In He, metallic Pd particles were formed with both the co-components. In H(2)/He flow, Pd-Cu precursors were converted to core-shell particles with a Cu shell and a Pd core, while Sb(1)Pd(1) and Sb(7)Pd(20) alloy phases were formed in the presence of Sb. Metal crystallites of about 40 nm agglomerate to particles of up to 150 nm in He and to even larger size in H(2)/He.

Correcting for particle size effects on plasma actuator particle image velocimetry measurements

Science.gov (United States)

Masati, A.; Sedwick, R. J.

2018-01-01

Particle image velocimetry (PIV) is often used to characterize plasma actuator flow, but particle charging effects are rarely taken into account. A parametric study was conducted to determine the effects of particle size on the velocity results of plasma actuator PIV experiments. Results showed that smaller particles more closely match air flow velocities than larger particles. The measurement uncertainty was quantified by deconvolving the particle image diameter from the correlation diameter. The true air velocity was calculated by linearly extrapolating to the zero-size particle diameter.

Particle size distribution effect on burn rate of ammonium nitrate based propellant

NARCIS (Netherlands)

Miedema, J.R.; Klein, A.J.J.; Zee, F.W.M.

1995-01-01

Burn rate control of a Phase Stabilised Ammonium Nitrate (PSAN) propellant by specific surface area (SSA) tuning of the PSAN oxidiser resulted in unexpected effects of applying a new batch of PSAN having a different particle size distribution. Analysis of the deviations and consultation of

Phase transitions in a system of hard Y-shaped particles on the triangular lattice

Science.gov (United States)

Mandal, Dipanjan; Nath, Trisha; Rajesh, R.

2018-03-01

We study the different phases and the phase transitions in a system of Y-shaped particles, examples of which include immunoglobulin-G and trinaphthylene molecules, on a triangular lattice interacting exclusively through excluded volume interactions. Each particle consists of a central site and three of its six nearest neighbors chosen alternately, such that there are two types of particles which are mirror images of each other. We study the equilibrium properties of the system using grand canonical Monte Carlo simulations that implement an algorithm with cluster moves that is able to equilibrate the system at densities close to full packing. We show that, with increasing density, the system undergoes two entropy-driven phase transitions with two broken-symmetry phases. At low densities, the system is in a disordered phase. As intermediate phases, there is a solidlike sublattice phase in which one type of particle is preferred over the other and the particles preferentially occupy one of four sublattices, thus breaking both particle symmetry as well as translational invariance. At even higher densities, the phase is a columnar phase, where the particle symmetry is restored, and the particles preferentially occupy even or odd rows along one of the three directions. This phase has translational order in only one direction, and breaks rotational invariance. From finite-size scaling, we demonstrate that both the transitions are first order in nature. We also show that the simpler system with only one type of particle undergoes a single discontinuous phase transition from a disordered phase to a solidlike sublattice phase with an increasing density of particles.

Vibro-spring particle size distribution analyser

International Nuclear Information System (INIS)

Patel, Ketan Shantilal

2002-01-01

This thesis describes the design and development of an automated pre-production particle size distribution analyser for particles in the 20 - 2000 μm size range. This work is follow up to the vibro-spring particle sizer reported by Shaeri. In its most basic form, the instrument comprises a horizontally held closed coil helical spring that is partly filled with the test powder and sinusoidally vibrated in the transverse direction. Particle size distribution data are obtained by stretching the spring to known lengths and measuring the mass of the powder discharged from the spring's coils. The size of the particles on the other hand is determined from the spring 'intercoil' distance. The instrument developed by Shaeri had limited use due to its inability to measure sample mass directly. For the device reported here, modifications are made to the original configurations to establish means of direct sample mass measurement. The feasibility of techniques for measuring the mass of powder retained within the spring are investigated in detail. Initially, the measurement of mass is executed in-situ from the vibration characteristics based on the spring's first harmonic resonant frequency. This method is often erratic and unreliable due to the particle-particle-spring wall interactions and the spring bending. An much more successful alternative is found from a more complicated arrangement in which the spring forms part of a stiff cantilever system pivoted along its main axis. Here, the sample mass is determined in the 'static mode' by monitoring the cantilever beam's deflection following the wanton termination of vibration. The system performance has been optimised through the variations of the mechanical design of the key components and the operating procedure as well as taking into account the effect of changes in the ambient temperature on the system's response. The thesis also describes the design and development of the ancillary mechanisms. These include the pneumatic

Particle sizes from sectional data

DEFF Research Database (Denmark)

Pawlas, Zbynek; Nyengaard, Jens Randel; Jensen, Eva Bjørn Vedel

2009-01-01

We propose a new statistical method for obtaining information about particle size distributions from sectional data without specific assumptions about particle shape. The method utilizes recent advances in local stereology. We show how to estimate separately from sectional data the variance due t...

Particle size distribution instrument. Topical report 13

Energy Technology Data Exchange (ETDEWEB)

Okhuysen, W.; Gassaway, J.D.

1995-04-01

The development of an instrument to measure the concentration of particles in gas is described in this report. An in situ instrument was designed and constructed which sizes individual particles and counts the number of occurrences for several size classes. Although this instrument was designed to detect the size distribution of slag and seed particles generated at an experimental coal-fired magnetohydrodynamic power facility, it can be used as a nonintrusive diagnostic tool for other hostile industrial processes involving the formation and growth of particulates. Two of the techniques developed are extensions of the widely used crossed beam velocimeter, providing simultaneous measurement of the size distribution and velocity of articles.

Finite size and Coulomb corrections: from nuclei to nuclear liquid vapor phase diagram

International Nuclear Information System (INIS)

Moretto, L.G.; Elliott, J.B.; Phair, L.

2003-01-01

In this paper we consider the problem of obtaining the infinite symmetric uncharged nuclear matter phase diagram from a thermal nuclear reaction. In the first part we shall consider the Coulomb interaction which, because of its long range makes the definition of phases problematic. This Coulomb effect seems truly devastating since it does not allow one to define nuclear phase transitions much above A ∼ 30. However there may be a solution to this difficulty. If we consider the emission of particles with a sizable charge, we notice that a large Coulomb barrier Bc is present. For T << Bc these channels may be considered effectively closed. Consequently the unbound channels may not play a role on a suitably short time scale. Then a phase transition may still be definable in an approximate way. In the second part of the article we shall deal with the finite size problem by means of a new method, the complement method, which shall permit a straightforward extrapolation to the infinite system. The complement approach consists of evaluating the change in free energy occurring when a particle or cluster is moved from one (finite) phase to another. In the case of a liquid drop in equilibrium with its vapor, this is done by extracting a vapor particle of any given size from the drop and evaluating the energy and entropy changes associated with both the vapor particle and the residual liquid drop (complement)

Effects of Particles Collision on Separating Gas–Particle Two-Phase Turbulent Flows

KAUST Repository

Sihao, L. V.

2013-10-10

A second-order moment two-phase turbulence model incorporating a particle temperature model based on the kinetic theory of granular flow is applied to investigate the effects of particles collision on separating gas–particle two-phase turbulent flows. In this model, the anisotropy of gas and solid phase two-phase Reynolds stresses and their correlation of velocity fluctuation are fully considered using a presented Reynolds stress model and the transport equation of two-phase stress correlation. Experimental measurements (Xu and Zhou in ASME-FED Summer Meeting, San Francisco, Paper FEDSM99-7909, 1999) are used to validate this model, source codes and prediction results. It showed that the particles collision leads to decrease in the intensity of gas and particle vortices and takes a larger effect on particle turbulent fluctuations. The time-averaged velocity, the fluctuation velocity of gas and particle phase considering particles colli-sion are in good agreement with experimental measurements. Particle kinetic energy is always smaller than gas phase due to energy dissipation from particle collision. Moreover, axial– axial and radial–radial fluctuation velocity correlations have stronger anisotropic behaviors. © King Fahd University of Petroleum and Minerals 2013

Determination of particle size distributions from acoustic wave propagation measurements

International Nuclear Information System (INIS)

Spelt, P.D.; Norato, M.A.; Sangani, A.S.; Tavlarides, L.L.

1999-01-01

The wave equations for the interior and exterior of the particles are ensemble averaged and combined with an analysis by Allegra and Hawley [J. Acoust. Soc. Am. 51, 1545 (1972)] for the interaction of a single particle with the incident wave to determine the phase speed and attenuation of sound waves propagating through dilute slurries. The theory is shown to compare very well with the measured attenuation. The inverse problem, i.e., the problem of determining the particle size distribution given the attenuation as a function of frequency, is examined using regularization techniques that have been successful for bubbly liquids. It is shown that, unlike the bubbly liquids, the success of solving the inverse problem is limited since it depends strongly on the nature of particles and the frequency range used in inverse calculations. copyright 1999 American Institute of Physics

Ultraviolet (UV) disinfection of grey water: particle size effects.

Science.gov (United States)

Winward, G P; Avery, L M; Stephenson, T; Jefferson, B

2008-02-01

The impact of water quality on the ultraviolet (UV) disinfection of grey water was investigated with reference to urban water reuse. Direct UV disinfection of grey water did not meet the stringent California State Title 22 criteria for unrestricted urban water reuse due to the presence of particulate material ranging from or = 2000 microm in size. Grey water was manipulated by settling to produce fractions of varying particle size distributions and blending was employed post-disinfection to extract particle-associated coliforms (PACs). The efficacy of UV disinfection was found to be linked to the particle size of the grey water fractions. The larger particle size fractions with a mean particle size of 262 microm and above were observed to shield more coliforms from UV light than did the smaller particles with a mean particle size below 119 microm. Up to 70% of total coliforms in the larger particle size fractions were particle-associated following a UV dose (fluence) of 260 mJ.cm(-2) and would remain undetected by standard coliform enumeration techniques. Implications for urban water reuse are discussed and recommendations made for grey water treatment to ensure removal of particle-associated indicator bacteria and pathogens prior to UV disinfection.

The effects of alfalfa particle size and acid treated protein on ruminal ...

African Journals Online (AJOL)

This study was conducted to investigate the effects of alfalfa particle size (long vs. fine) and canola meal treated with hydrochloric acid solution (untreated vs treated) on ruminal chemical composition, liquid, particulate, escapable and non escapable phases in Zel sheep. Four ruminally cannulated sheep received a mixed ...

Damping of Mechanical Waves with Styrene/Butadiene Rubber Filled with Polystyrene Particle: Effects of Particles Size and Wave Frequency

Directory of Open Access Journals (Sweden)

M. Haghgo

2007-08-01

Full Text Available Utilizing polymeric materials for damping mechanical waves is of great importance in various fields of applications such as military camouflage, prevention of structural vibrational energy transfer, and noise attenuation. This ability originates from segmental dynamics of chain-like polymer molecules. Damping properties of styrene-butadiene rubbercontaining 10 wt% of monosize polystyrene particles with different diameters (from 80 nm to 500 μm was investigated in the frequency range of vibration, sound, and ultrasound via dynamic mechanical thermal analysis, normalsound adsorption test, and ultrasound attenuation coefficient measurement. The obtained results indicated that for different systems, containing different sizes of polystyrene particles, the area under the damping curve does not show significant change comparing to the neat SBR in the frequency range studied. However, addition of polystyrene particles, specifically nanosized particles, resulted in emergence of a secondary glass transition temperature which could be attributed to the modified dynamics of a layer of matrix molecules near the surface of PS particles. In the range of sound frequency, 0.5 to 6.3 kHz, the maximum damping was observed for the system containing polystyrene nanoparticles. However the single damping curve of neat SBR was separated into two or even three distinct curves owing to the presence of the particles. The maximum damping in the ultrasound frequency range was found for the system containing 0.5 mm polystyrene particles. This is attributed to different contributions from matrix chains dynamics and the reflection of mechanical waves from particles-matrix interface at different frequency ranges. On other words, the increase in the glass transition temperature of the elastomeric matrix phase with increasing the mechanical wave frequency causes a reduction in the contribution from matrix chains dynamics while the contribution due to diffraction from dispersed

Concentration and size distribution of particles in abstracted groundwater.

Science.gov (United States)

van Beek, C G E M; de Zwart, A H; Balemans, M; Kooiman, J W; van Rosmalen, C; Timmer, H; Vandersluys, J; Stuyfzand, P J

2010-02-01

Particle number concentrations have been counted and particle size distributions calculated in groundwater derived by abstraction wells. Both concentration and size distribution are governed by the discharge rate: the higher this rate the higher the concentration and the higher the proportion of larger particles. However, the particle concentration in groundwater derived from abstraction wells, with high groundwater flow velocities, is much lower than in groundwater from monitor wells, with minimal flow velocities. This inconsistency points to exhaustion of the particle supply in the aquifer around wells due to groundwater abstraction for many years. The particle size distribution can be described with the help of a power law or Pareto distribution. Comparing the measured particle size distribution with the Pareto distribution shows that particles with a diameter >7 microm are under-represented. As the particle size distribution is dependent on the flow velocity, so is the value of the "Pareto" slope beta. (c) 2009 Elsevier Ltd. All rights reserved.

EFFECTS OF EFFECTS OF PARTICLE SIZE DISTRIBUTION ...

African Journals Online (AJOL)

eobe

The parameters examined were: moisture content, particle size distribution, total isture content, particle size distribution, total hydrocarbon content, soil pH, available nitrogen, available phosphorus, total heterotrophic bacteria and fungi count. The analysis of the soil characteristics throughout the remediation period showed ...

Dependence of strength on particle size in graphite

International Nuclear Information System (INIS)

Kennedy, E.P.; Kennedy, C.R.

The strength to particle size relationship for specially fabricated graphites has been demonstrated and rationalized using fracture mechanics. In the past, similar studies have yielded empirical data using only commercially available material. Thus, experimental verification of these relationships has been difficult. However, the graphites of this study were fabricated by controlling the particle size ranges for a series of isotropic graphites. All graphites that were evaluated had a constant 1.85 g/cm 3 density. Thus, particle size was the only variable. This study also considered the particle size effect on other physical properties; coefficient of thermal expansion (CTE), electrical resistivity, fracture strain, and Young's modulus

Electrical percolation threshold of magnetostrictive inclusions in a piezoelectric matrix composite as a function of relative particle size

Science.gov (United States)

Barbero, Ever J.; Bedard, Antoine Joseph

2018-04-01

Magnetoelectric composites can be produced by embedding magnetostrictive particles in a piezoelectric matrix derived from a piezoelectric powder precursor. Ferrite magnetostrictive particles, if allowed to percolate, can short the potential difference generated in the piezoelectric phase. Modeling a magnetoelectric composite as an aggregate of bi-disperse hard shells, molecular dynamics was used to explore relationships among relative particle size, particle affinity, and electrical percolation with the goal of maximizing the percolation threshold. It is found that two factors raise the percolation threshold, namely the relative size of magnetostrictive to piezoelectric particles, and the affinity between the magnetostrictive and piezoelectric particles.

Influence of particle size on appearance and in vitro efficacy of sunscreens

Directory of Open Access Journals (Sweden)

Débora Granemann e Silva

2013-06-01

Full Text Available Nanotechnology applies to diverse sectors of science. In cosmetic area, investments have strengthened the idea that nanoproducts provide innumerable benefits to consumers. Extreme exposition to solar light can cause undesirable effects, thus, adding UV filters in cosmetic products are often used as prevention. Ethylhexyl methoxycinnamate and benzophenone-3 are UV filters widely used in sunscreen formulations, this UV filters absorb UVB and UVA radiation, respectively. In this study, sunscreen formulations were developed as nano and macroemulsion, but composed by the same raw material. Nanoemulsion was obtained by phase inversion temperature method (PIT. Physical and functional properties were evaluated by visual analysis, particle size distribution and by diffuse reflectance spectrophotometry. Achieved nanoemulsion showed bluish brightness aspect, less apparent consistency than macroemulsion, stability longer than 48 hours (22.0 ± 2.0 °C and bimodal particle size distribution with average (mean sizes around 10 nm (61% and 4.5 µm (39%. Macroemulsion showed milky aspect, higher consistency than nanoemulsion, instability after 48 hours (22.0 ± 2.0 °C and bimodal particle size distribution with average (mean size around 202 nm (9% and 10.4 µm (91%. Effectiveness profile of sunscreen formulations remained apparently similar, based on achieved results of in vitro SPF, UVA/UVB ratio and critical wavelength assays.

Nucleation and dissociation of nano-particles in gas phase; Nucleation et evaporation de nanoparticules en phase gazeuse

Energy Technology Data Exchange (ETDEWEB)

Feiden, P

2007-09-15

This work deals with the study of nano-particles formation in gas phase and their dissociation pathways after an optical excitation. The clusters formation decomposes in two steps: a seed is formed (nucleation phase) and sticks atoms during its propagation in a sodium atomic vapor (growth phase). Those two steps have been observed separately for homogeneous Na{sub n} and heterogeneous Na{sub n}X particles (X = (NaOH){sub 2} or (Na{sub 2}O){sub 2}). The growth mechanism is well interpreted by a Monte Carlo simulation taking into account an accretion mechanism with hard-sphere cross section. The homogeneous nucleation mechanism has been highlighted by a direct comparison with the Classical Nucleation Theory predictions. The clusters fragmentation of ionic Na{sup +}(NaOH){sub p} et Na{sup +}(NaF){sub p} particles is studied in the second part. The way clusters fragment with size when they are excited optically is compared with theoretical previsions: this highlights the existence of an energetic barrier for special size of clusters. Finally, the fragmentation of doubly charged Na{sup +} Na{sup +} (NaOH){sub p} clusters shows a competition between the fission into two single charged fragments and the unimolecular evaporation of a neutral fragment. (author)

Sonochemical synthesis of silica particles and their size control

Energy Technology Data Exchange (ETDEWEB)

Kim, Hwa-Min [Advanced Materials and Chemical Engineering, Catholic University of Daegu, Gyeongbuk 38430 (Korea, Republic of); Lee, Chang-Hyun [Electronic and Electrical Engineering, Catholic University of Daegu, Gyeongbuk 38430 (Korea, Republic of); Kim, Bonghwan, E-mail: bhkim@cu.ac.kr [Electronic and Electrical Engineering, Catholic University of Daegu, Gyeongbuk 38430 (Korea, Republic of)

2016-09-01

Graphical abstract: - Highlights: • Silica particles were easily prepared by an ultrasound-assisted sol–gel method. • The particle size was controlled by the ammonium hydroxide/water molar ratio. • The size-controlled diameter of silica particles ranged from 40 to 400 nm. • The particles were formed in a relatively short reaction time. - Abstract: Using an ultrasound-assisted sol–gel method, we successfully synthesized very uniformly shaped, monodisperse, and size-controlled spherical silica particles from a mixture of ethanol, water, and tetraethyl orthosilicate in the presence of ammonia as catalyst, at room temperature. The diameters of the silica particles were distributed in the range from 40 to 400 nm; their morphology was well characterized by scanning electron microscopy. The silica particle size could be adjusted by choosing suitable concentrations of ammonium hydroxide and water, which in turn determined the nucleation and growth rates of the particles during the reaction. This sonochemical-based silica synthesis offers an alternative way to produce spherical silica particles in a relatively short reaction time. Thus, we suggest that this simple, low-cost, and efficient method of preparing uniform silica particles of various sizes will have practical and wide-ranging industrial applicability.

Particle separation by phase modulated surface acoustic waves.

Science.gov (United States)

Simon, Gergely; Andrade, Marco A B; Reboud, Julien; Marques-Hueso, Jose; Desmulliez, Marc P Y; Cooper, Jonathan M; Riehle, Mathis O; Bernassau, Anne L

2017-09-01

High efficiency isolation of cells or particles from a heterogeneous mixture is a critical processing step in lab-on-a-chip devices. Acoustic techniques offer contactless and label-free manipulation, preserve viability of biological cells, and provide versatility as the applied electrical signal can be adapted to various scenarios. Conventional acoustic separation methods use time-of-flight and achieve separation up to distances of quarter wavelength with limited separation power due to slow gradients in the force. The method proposed here allows separation by half of the wavelength and can be extended by repeating the modulation pattern and can ensure maximum force acting on the particles. In this work, we propose an optimised phase modulation scheme for particle separation in a surface acoustic wave microfluidic device. An expression for the acoustic radiation force arising from the interaction between acoustic waves in the fluid was derived. We demonstrated, for the first time, that the expression of the acoustic radiation force differs in surface acoustic wave and bulk devices, due to the presence of a geometric scaling factor. Two phase modulation schemes are investigated theoretically and experimentally. Theoretical findings were experimentally validated for different mixtures of polystyrene particles confirming that the method offers high selectivity. A Monte-Carlo simulation enabled us to assess performance in real situations, including the effects of particle size variation and non-uniform acoustic field on sorting efficiency and purity, validating the ability to separate particles with high purity and high resolution.

Suppression of coffee ring: (Particle) size matters

Science.gov (United States)

Bansal, Lalit; Seth, Pranjal; Murugappan, Bhubesh; Basu, Saptarshi

2018-05-01

Coffee ring patterns in drying sessile droplets are undesirable in various practical applications. Here, we experimentally demonstrate that on hydrophobic substrates, the coffee ring can be suppressed just by increasing the particle diameter. Particles with larger size flocculate within the evaporation timescale, leading to a significant gravimetric settling (for Pe > 1) triggering a uniform deposit. Interestingly, the transition to a uniform deposit is found to be independent of the internal flow field and substrate properties. Flocculation of particles also alters the particle packing at the nanoscale resulting in order to disorder transitions. In this letter, we exhibit a physical exposition on how particle size affects morphodynamics of the droplet drying at macro-nano length scales.

EFFECTS OF ULTRASOUND ON THE MORPHOLOGY, PARTICLE SIZE, CRYSTALLINITY, AND CRYSTALLITE SIZE OF CELLULOSE

Directory of Open Access Journals (Sweden)

SUMARI SUMARI

2014-05-01

Full Text Available The aim of this study is to optimize ultrasound treatment to produce fragment of cellulose that is low in particles size, crystallite size, and crystallinity. Slurry of 1 % (w/v the cellulose was sonicated at different time periods and temperatures. An ultrasonic reactor was operated at 300 Watts and 28 kHz to cut down the polymer into smaller particles. We proved that ultrasound damages and fragments the cellulose particles into shorter fibers. The fiber lengths were reduced from in the range of 80-120 µm to 30-50 µm due to an hour ultrasonication and became 20-30 µm after 5 hours. It was also found some signs of erosion on the surface and stringy. The acoustic cavitation also generated a decrease in particle size, crystallinity, and crystallite size of the cellulose along with increasing sonication time but it did not change d-spacing. However, the highest reduction of particle size, crystallite size, and crystallinity of the cellulose occurred within the first hour of ultrasonication, after which the efficiency was decreased. The particle diameter, crystallite size, and crystallinity were decreased from 19.88 µm to 15.96 µm, 5.81 Å to 2.98 Å, and 77.7% to 73.9% respectively due to an hour ultrasound treatment at 40 °C. The treatment that was conducted at 40 °C or 60 °C did not give a different effect significantly. Cellulose with a smaller particle and crystallite size as well as a more amorphous shape is preferred for further study.

Assessment of Available Particle Size Data to Support an Analysis of the Waste Feed Delivery System Transfer System

International Nuclear Information System (INIS)

JEWETT, J.R.

2000-01-01

Available data pertaining to size distribution of the particulates in Hanford underground tank waste have been reviewed. Although considerable differences exist between measurement methods, it may be stated with 95% confidence that the median particle size does not exceed 275 (micro)m in at least 95% of the ten tanks selected as sources of HLW feed for Phase 1 vitrification in the RPP. This particle size is recommended as a design basis for the WFD transfer system

Particle-size distribution and phosphorus forms as a function of hydrological forcing in the Yellow River.

Science.gov (United States)

Yao, Qing-Zhen; Du, Jun-Tao; Chen, Hong-Tao; Yu, Zhi-Gang

2016-02-01

Samples were collected monthly from January to December in 2010, and daily observations were made during the water-sediment regulation event in June-July 2010. Sequential extractions were applied to determine the forms of P in different particle-size fractions and to assess the potential bioavailability of particulate phosphorus (PP). The results indicated that exchangeable phosphorus, organic phosphorus, authigenic phosphorus, and refractory phosphorus increased with the decreasing of particulate size; conversely, detrital phosphorus decreased with the decreasing of particulate size. The content of bioavailable particulate phosphorus (BAPP) varied greatly in different sizes of particles. In general, the smaller the particle size, the higher the content of bioavailable phosphorus and its proportion in total phosphorous was found in these particles. Hydrological forcing controlled the variability in the major P phases found in the suspended sediments via changes in the sources and the particle grain-size distribution. The variation of particle sizes can be attributed also to different total suspended sediment (TSS) sources. Water-sediment regulation (WSR) mobilized only particulate matter from the riverbed, while during the rainstorm soil erosion and runoff were the main source. The BAPP fluxes associated with the "truly suspended" fraction was approximately 200 times larger than the dissolved inorganic phosphorus (DIP) flux. Thus, the transfer of fine particles to the open sea is most probably accompanied by BAPP release to the DIP and can support greater primary and secondary production.

THE PHYSICS OF PROTOPLANETESIMAL DUST AGGLOMERATES. VI. EROSION OF LARGE AGGREGATES AS A SOURCE OF MICROMETER-SIZED PARTICLES

International Nuclear Information System (INIS)

Schraepler, Rainer; Blum, Juergen

2011-01-01

Observed protoplanetary disks consist of a large amount of micrometer-sized particles. Dullemond and Dominik pointed out for the first time the difficulty in explaining the strong mid-infrared excess of classical T Tauri stars without any dust-retention mechanisms. Because high relative velocities in between micrometer-sized and macroscopic particles exist in protoplanetary disks, we present experimental results on the erosion of macroscopic agglomerates consisting of micrometer-sized spherical particles via the impact of micrometer-sized particles. We find that after an initial phase, in which an impacting particle erodes up to 10 particles of an agglomerate, the impacting particles compress the agglomerate's surface, which partly passivates the agglomerates against erosion. Due to this effect, the erosion halts for impact velocities up to ∼30 m s -1 within our error bars. For higher velocities, the erosion is reduced by an order of magnitude. This outcome is explained and confirmed by a numerical model. In a next step, we build an analytical disk model and implement the experimentally found erosive effect. The model shows that erosion is a strong source of micrometer-sized particles in a protoplanetary disk. Finally, we use the stationary solution of this model to explain the amount of micrometer-sized particles in the observational infrared data of Furlan et al.

Permeability of different size waste particles

Directory of Open Access Journals (Sweden)

Sabina Gavelytė

2015-10-01

Full Text Available The world and life style is changing, but the most popular disposal route for waste is landfill globally until now. We have to think about waste prevention and preparing for re-use or recycling firstly, according to the waste disposal hierarchy. Disposed waste to the landfill must be the last opportunity. In a landfill, during waste degradation processes leachate is formed that can potentially cause clogging of bottom drainage layers. To ensure stability of a landfill construction, the physical properties of its components have to be controlled. The hydrology of precipitation, evaporation, runoff and the hydraulic performance of the capping and liner materials are important controls of the moisture content. The water balance depends also on the waste characteristics and waste particle size distribution. The aim of this paper is to determine the hydraulic permeability in a landfill depending on the particle size distribution of municipal solid waste disposed. The lab experiment results were compared with the results calculated with DEGAS model. Samples were taken from a landfill operated for five years. The samples particle sizes are: >100 mm, 80 mm, 60 mm, 40 mm, 20 mm, 0.01 mm and <0.01 mm. The permeability test was conducted using the column test. The paper presents the results of experiment and DEGAS model water permeability with waste particle size.

Effect of silica particle size on macrophage inflammatory responses.

Directory of Open Access Journals (Sweden)

Toshimasa Kusaka

Full Text Available Amorphous silica particles, such as nanoparticles (<100 nm diameter particles, are used in a wide variety of products, including pharmaceuticals, paints, cosmetics, and food. Nevertheless, the immunotoxicity of these particles and the relationship between silica particle size and pro-inflammatory activity are not fully understood. In this study, we addressed the relationship between the size of amorphous silica (particle dose, diameter, number, and surface area and the inflammatory activity (macrophage phagocytosis, inflammasome activation, IL-1β secretion, cell death and lung inflammation. Irrespective of diameter size, silica particles were efficiently internalized by mouse bone marrow-derived macrophages via an actin cytoskeleton-dependent pathway, and induced caspase-1, but not caspase-11, activation. Of note, 30 nm-1000 nm diameter silica particles induced lysosomal destabilization, cell death, and IL-1β secretion at markedly higher levels than did 3000 nm-10000 nm silica particles. Consistent with in vitro results, intra-tracheal administration of 30 nm silica particles into mice caused more severe lung inflammation than that of 3000 nm silica particles, as assessed by measurement of pro-inflammatory cytokines and neutrophil infiltration in bronchoalveolar lavage fluid of mice, and by the micro-computed tomography analysis. Taken together, these results suggest that silica particle size impacts immune responses, with submicron amorphous silica particles inducing higher inflammatory responses than silica particles over 1000 nm in size, which is ascribed not only to their ability to induce caspase-1 activation but also to their cytotoxicity.

Effects of the finite particle size in turbulent wall-bounded flows of dense suspensions

Science.gov (United States)

Costa, Pedro; Picano, Francesco; Brandt, Luca; Breugem, Wim-Paul

2018-05-01

We use interface-resolved simulations to study finite-size effects in turbulent channel flow of neutrally-buoyant spheres. Two cases with particle sizes differing by a factor of 2, at the same solid volume fraction of 20% and bulk Reynolds number are considered. These are complemented with two reference single-phase flows: the unladen case, and the flow of a Newtonian fluid with the effective suspension viscosity of the same mixture in the laminar regime. As recently highlighted in Costa et al. (PRL 117, 134501), a particle-wall layer is responsible for deviations of the statistics from what is observed in the continuum limit where the suspension is modeled as a Newtonian fluid with an effective viscosity. Here we investigate the fluid and particle dynamics in this layer and in the bulk. In the particle-wall layer, the near wall inhomogeneity has an influence on the suspension micro-structure over a distance proportional to the particle size. In this layer, particles have a significant (apparent) slip velocity that is reflected in the distribution of wall shear stresses. This is characterized by extreme events (both much higher and much lower than the mean). Based on these observations we provide a scaling for the particle-to-fluid apparent slip velocity as a function of the flow parameters. We also extend the flow scaling laws in to second-order Eulerian statistics in the homogeneous suspension region away from the wall. Finite-size effects in the bulk of the channel become important for larger particles, while negligible for lower-order statistics and smaller particles. Finally, we study the particle dynamics along the wall-normal direction. Our results suggest that 1-point dispersion is dominated by particle-turbulence (and not particle-particle) interactions, while differences in 2-point dispersion and collisional dynamics are consistent with a picture of shear-driven interactions.

Silica particles encapsulated poly(styrene-divinylbenzene) monolithic stationary phases for micro-high performance liquid chromatography.

Science.gov (United States)

Bakry, R; Stöggl, W M; Hochleitner, E O; Stecher, G; Huck, C W; Bonn, G K

2006-11-03

In the paper we demonstrate a new approach for the preparation and application of continuous silica bed columns that involve encapsulation (entrapment) of functionalized silica microparticles, which can be used as packing material in micro high performance liquid chromatography (micro-HPLC) and capillary electrochromatography (CEC). Like traditional packed columns, these capillaries possess characterized silica particles that offer high phase ratio and narrow pore size distribution leading to high retention and separation efficiency, respectively. More importantly, immobilization of the microparticles stabilizes the separation bed and eliminates the need for retaining frits. The developed capillary columns were fabricated in exactly the same way as a packed capillary column (slurry packing) but with an additional entrapment step. This immobilization of the packed bed was achieved by in situ polymerization of styrene and divinylbenzene in presence of decanol as a porogen and azobisisobutyronitrile as thermal initiator. Silica particles with different particle sizes and pore sizes ranging from 60 to 4000 A were studied. In addition different modified silica was used, including C-18 reversed phase, anion exchange and chiral stationary phases. Efficient separation of polyphenolic compounds, peptides, proteins and even DNA mutation were achieved using the developed technique depending on the properties of the silica particles used (particles pore size). For example, using 3 microm ProntoSIL C-18 particles with 300 A pore size, separation efficiencies in the range of 120,000-200,000 plates/m were obtained for protein separation, in a 6 cm x 200 microm i.d. capillary column. Using encapsulated silica C-18 with 1000 A pore size, separation of DNA homo and hetero duplexes were achieved under denaturing HPLC conditions for mutation detection. In addition, nucleotides were separated using anion exchange material encapsulated with poly(styrene-divinylbenzene) (PS/DVB), which

Role of dopant concentration, crystal phase and particle size on microbial inactivation of Cu-doped TiO{sub 2} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Sahu, Manoranjan; Wu Bing; Zhu Liying; Jacobson, Craig; Wang Weining; Jones, Kristen; Goyal, Yogesh; Tang, Yinjie J; Biswas, Pratim, E-mail: pbiswas@wustl.edu [Department of Energy, Environmental and Chemical Engineering, Washington University in St Louis, St Louis, MO 63130 (United States)

2011-10-14

The properties of Cu-doped TiO{sub 2} nanoparticles (NPs) were independently controlled in a flame aerosol reactor by varying the molar feed ratios of the precursors, and by optimizing temperature and time history in the flame. The effect of the physico-chemical properties (dopant concentration, crystal phase and particle size) of Cu-doped TiO{sub 2} nanoparticles on inactivation of Mycobacterium smegmatis (a model pathogenic bacterium) was investigated under three light conditions (complete dark, fluorescent light and UV light). The survival rate of M. smegmatis (in a minimal salt medium for 2 h) exposed to the NPs varied depending on the light irradiation conditions as well as the dopant concentrations. In dark conditions, pristine TiO{sub 2} showed insignificant microbial inactivation, but inactivation increased with increasing dopant concentration. Under fluorescent light illumination, no significant effect was observed for TiO{sub 2}. However, when TiO{sub 2} was doped with copper, inactivation increased with dopant concentration, reaching more than 90% (>3 wt% dopant). Enhanced microbial inactivation by TiO{sub 2} NPs was observed only under UV light. When TiO{sub 2} NPs were doped with copper, their inactivation potential was promoted and the UV-resistant cells were reduced by over 99%. In addition, the microbial inactivation potential of NPs was also crystal-phase-and size-dependent under all three light conditions. A lower ratio of anatase phase and smaller sizes of Cu-doped TiO{sub 2} NPs resulted in decreased bacterial survival. The increased inactivation potential of doped TiO{sub 2} NPs is possibly due to both enhanced photocatalytic reactions and leached copper ions.

Artificial neural network based particle size prediction of polymeric nanoparticles.

Science.gov (United States)

Youshia, John; Ali, Mohamed Ehab; Lamprecht, Alf

2017-10-01

Particle size of nanoparticles and the respective polydispersity are key factors influencing their biopharmaceutical behavior in a large variety of therapeutic applications. Predicting these attributes would skip many preliminary studies usually required to optimize formulations. The aim was to build a mathematical model capable of predicting the particle size of polymeric nanoparticles produced by a pharmaceutical polymer of choice. Polymer properties controlling the particle size were identified as molecular weight, hydrophobicity and surface activity, and were quantified by measuring polymer viscosity, contact angle and interfacial tension, respectively. A model was built using artificial neural network including these properties as input with particle size and polydispersity index as output. The established model successfully predicted particle size of nanoparticles covering a range of 70-400nm prepared from other polymers. The percentage bias for particle prediction was 2%, 4% and 6%, for the training, validation and testing data, respectively. Polymer surface activity was found to have the highest impact on the particle size followed by viscosity and finally hydrophobicity. Results of this study successfully highlighted polymer properties affecting particle size and confirmed the usefulness of artificial neural networks in predicting the particle size and polydispersity of polymeric nanoparticles. Copyright © 2017 Elsevier B.V. All rights reserved.

Obtaining of iron particles of nanometer size in a natural zeolite

International Nuclear Information System (INIS)

Xingu C, E. G.

2013-01-01

The zeolites are aluminosilicates with cavities that can act as molecular sieve. Their crystalline structure is formed by tetrahedrons that get together giving place to a three-dimensional net, in which each oxygen is shared by two silicon atoms, being this way part of the tecto silicate minerals, its external and internal areas reach the hundred square meters for gram, they are located in a natural way in a large part of earth crust and also exist in a synthetic way. In Mexico there are different locations of zeolitic material whose important component is the clinoptilolite. In this work the results of three zeolitic materials coming from San Luis Potosi are shown, the samples were milled and sieved for its initial characterization, to know its chemical composition, crystalline phases, morphology, topology and thermal behavior before and after its homo-ionization with sodium chloride, its use as support of iron particles of nanometer size. The description of the synthesis of iron particles of nanometer size is also presented, as well as the comparison with the particles of nanometer size synthesized without support after its characterization. The characterization techniques used during the experimental work were: Scanning electron microscopy, X-ray diffraction, Infrared spectroscopy, specific area by means of BET and thermogravimetry analysis. (Author)

Distribution Of Natural Radioactivity On Soil Size Particles

International Nuclear Information System (INIS)

Tran Van Luyen; Trinh Hoai Vinh; Thai Khac Dinh

2008-01-01

This report presents a distribution of natural radioactivity on different soil size particles, taken from one soil profile. On the results shows a range from 52% to 66% of natural radioisotopes such as 238 U, 232 Th, 226 Ra and 40 K concentrated on the soil particles below 40 micrometers in diameter size. The remained of natural radioisotopes were distributed on a soil particles with higher diameter size. The study is available for soil sample collected to natural radioactive analyze by gamma and alpha spectrometer methods. (author)

Determination of reactivity rates of silicate particle-size fractions

Directory of Open Access Journals (Sweden)

Angélica Cristina Fernandes Deus

2014-04-01

Full Text Available The efficiency of sources used for soil acidity correction depends on reactivity rate (RR and neutralization power (NP, indicated by effective calcium carbonate (ECC. Few studies establish relative efficiency of reactivity (RER for silicate particle-size fractions, therefore, the RER applied for lime are used. This study aimed to evaluate the reactivity of silicate materials affected by particle size throughout incubation periods in comparison to lime, and to calculate the RER for silicate particle-size fractions. Six correction sources were evaluated: three slags from distinct origins, dolomitic and calcitic lime separated into four particle-size fractions (2, 0.84, 0.30 and <0.30-mm sieves, and wollastonite, as an additional treatment. The treatments were applied to three soils with different texture classes. The dose of neutralizing material (calcium and magnesium oxides was applied at equal quantities, and the only variation was the particle-size material. After a 90-day incubation period, the RER was calculated for each particle-size fraction, as well as the RR and ECC of each source. The neutralization of soil acidity of the same particle-size fraction for different sources showed distinct solubility and a distinct reaction between silicates and lime. The RER for slag were higher than the limits established by Brazilian legislation, indicating that the method used for limes should not be used for the slags studied here.

Size-resolved fluxes of sub-100-nm particles over forests

DEFF Research Database (Denmark)

Pryor, Sara; Barthelmie, Rebecca Jane; Spaulding, A.M.

2009-01-01

Dry deposition of atmospheric particles is critically dependent on particle size and plays a key role in dictating the mass and number distributions of atmospheric particles. However, modeling dry deposition is constrained by a lack of understanding of controlling dependencies and accurate size......-resolved observations. We present size-resolved particle number fluxes for sub-100-nm particle diameters (Dp) over a deciduous forest derived using eddy covariance applied to data from a fast mobility particle sizer. The size-resolved particle number fluxes in 18 diameters between 8 and 100 nm were collected during...... leaf-on and are statistically robust. Particle deposition velocities normalized by friction velocity (v d +) are approximately four times smaller than comparable values for coniferous forests reported elsewhere. Comparison of the data with output from a new one-dimensional mechanistic particle...

Effect of particle size on iron nanoparticle oxidation state

International Nuclear Information System (INIS)

Lombardo, Jeffrey J.; Lysaght, Andrew C.; Goberman, Daniel G.; Chiu, Wilson K.S.

2012-01-01

Selecting catalyst particles is a very important part of carbon nanotube growth, although the properties of these nanoscale particles are unclear. In this article iron nanoparticles are analyzed through the use of atomic force microscopy and x-ray photoelectron spectroscopy in order to understand how the size affects the chemical composition of nanoparticles and thus their physical structure. Initially, atomic force microscopy was used to confirm the presence of iron particles, and to determine the average size of the particles. Next an analytical model was developed to estimate particle size as a function of deposition time using inputs from atomic force microscopy measurement. X-ray photoelectron spectroscopy analysis was then performed with a focus on the spectra relating to the 2p Fe electrons to study the chemical state of the particles as a function of time. It was shown that as the size of nanoparticles decreased, the oxidation state of the particles changed due to a high proportion of atoms on the surface.

Particle size control of detergents in mixed flow spray dryers

Directory of Open Access Journals (Sweden)

Mark Jonathan Crosby

2015-03-01

Full Text Available Particle size is a key quality parameter of a powder detergent as it determines its performance, the bulk density and the look and feel of the product. Consequently, it is essential that particle size is controlled to ensure the consistency of performance when comparing new formulations. The majority of study reported in the literature relating to particle size control, focuses on the spray produced by the atomisation technique. One approach advocated to achieve particle size control is the manipulation of the ratio of the mass slurry rate and mass flow rate of gas used for atomisation. Within this study, ratio control was compared with an automatic cascade loop approach using online measurements of the powder particle size on a small-scale pilot plant. It was concluded that cascade control of the mean particle size, based on manipulating the mass flow rate of gas, resulted in tighter, more responsive control. The effect of a ratio change varied with different formulations and different slurry rates. Furthermore, changes in slurry rate caused complications, as the impact on particle size growth in the dryer is non-linear and difficult to predict. The cascade loop enables further study into the effect of particle size on detergent performance.

Liquid-liquid phase separation in aerosol particles: Imaging at the Nanometer Scale

Energy Technology Data Exchange (ETDEWEB)

O' Brien, Rachel; Wang, Bingbing; Kelly, Stephen T.; Lundt, Nils; You, Yuan; Bertram, Allan K.; Leone, Stephen R.; Laskin, Alexander; Gilles, Mary K.

2015-04-21

Atmospheric aerosols can undergo phase transitions including liquid-liquid phase separation (LLPS) while responding to changes in the ambient relative humidity (RH). Here, we report results of chemical imaging experiments using environmental scanning electron microscopy (ESEM) and scanning transmission x-ray microscopy (STXM) to investigate the LLPS of micron sized particles undergoing a full hydration-dehydration cycle. Internally mixed particles composed of ammonium sulfate (AS) and either: limonene secondary organic carbon (LSOC), a, 4-dihydroxy-3-methoxybenzeneaceticacid (HMMA), or polyethylene glycol (PEG-400) were studied. Events of LLPS with apparent core-shell particle morphology were observed for all samples with both techniques. Chemical imaging with STXM showed that both LSOC/AS and HMMA/AS particles were never homogeneously mixed for all measured RH’s above the deliquescence point and that the majority of the organic component was located in the shell. The shell composition was estimated as 65:35 organic: inorganic in LSOC/AS and as 50:50 organic: inorganic for HMMA/AS. PEG-400/AS particles showed fully homogeneous mixtures at high RH and phase separated below 89-92% RH with an estimated 50:50% organic to inorganic mix in the shell. These two chemical imaging techniques are well suited for in-situ analysis of the hygroscopic behavior, phase separation, and surface composition of collected ambient aerosol particles.

Dynamic effect of total solid content, low substrate/inoculum ratio and particle size on solid-state anaerobic digestion.

Science.gov (United States)

Motte, J-C; Escudié, R; Bernet, N; Delgenes, J-P; Steyer, J-P; Dumas, C

2013-09-01

Among all the process parameters of solid-state anaerobic digestion (SS-AD), total solid content (TS), inoculation (S/X ratio) and size of the organic solid particles can be optimized to improve methane yield and process stability. To evaluate the effects of each parameter and their interactions on methane production, a three level Box-Behnken experimental design was implemented in SS-AD batch tests degrading wheat straw by adjusting: TS content from 15% to 25%, S/X ratio (in volatile solids) between 28 and 47 and particle size with a mean diameter ranging from 0.1 to 1.4mm. A dynamic analysis of the methane production indicates that the S/X ratio has only an effect during the start-up phase of the SS-AD. During the growing phase, TS content becomes the main parameter governing the methane production and its strong interaction with the particle size suggests the important role of water compartmentation on SS-AD. Copyright © 2013 Elsevier Ltd. All rights reserved.

Intercomparison of 15 Aerodynamic Particle Size Spectrometers (APS 3321): Uncertainties in Particle Sizing and Number Size Distribution.

Czech Academy of Sciences Publication Activity Database

Pfeifer, S.; Müller, T.; Weinhold, K.; Zíková, Naděžda; dos Santos, S.M.; Marinoni, A.; Bischof, O.F.; Kykal, C.; Ries, L.; Meinhardt, F.; Aalto, P.; Mihalopoulos, N.; Wiedensohler, A.

2016-01-01

Roč. 9, č. 4 (2016), s. 1545-1551 ISSN 1867-1381 EU Projects: European Commission(XE) 262254 - ACTRIS Institutional support: RVO:67985858 Keywords : counting efficiency * aerodynamic particle size spectrometers * laboratory study Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.089, year: 2016

Characterization of condensed phase nitric acid particles formed in the gas phase

Institute of Scientific and Technical Information of China (English)

Long Jia; Yongfu Xu

2011-01-01

The formation of nitric acid hydrates has been observed in a chamber during the dark reaction of NO2 with O3 in the presence of air.The size of condensed phase nitric acid was measured to be 40-100 nm and 20-65 nm at relative humidity (RH) ≤ 5％ and RH = 67％ under our experimental conditions, respectively.The nitric acid particles were collected on the glass fiber membrane and their chemical compositions were analyzed by infrared spectrum.The main components of nitric acid hydrates in particles are HNO3·3H2O and NO3-·xH2O (x≥ 4) at low RH, whereas at high RH HNO3·H2O, HNO3·2H2O, HNO3·3H2O and NO3-·xH2O (x≥ 4) all exist in the condensed phase.At high RH HNO3·xH2O (x ≤ 3) collected on the glass fiber membrane is greatly increased, while NO3-·xH2O (x ≥4) decreased, compared with low RH.To the best of our knowledge, this is the first time to report that condensed phase nitric acid can be generated in the gas phase at room temperature.

Effects of Particles Collision on Separating Gas–Particle Two-Phase Turbulent Flows

KAUST Repository

Sihao, L. V.; Yang, Weihua; Li, Xiangli; Li, Guohui

2013-01-01

A second-order moment two-phase turbulence model incorporating a particle temperature model based on the kinetic theory of granular flow is applied to investigate the effects of particles collision on separating gas–particle two-phase turbulent

Synthesis and characterization of β-phase iron silicide nano-particles by chemical reduction

International Nuclear Information System (INIS)

Sen, Sabyasachi; Gogurla, Narendar; Banerji, Pallab; Guha, Prasanta K.; Pramanik, Panchanan

2015-01-01

Graphical abstract: - Highlights: • β-FeSi 2 nano-particle was synthesized by reducing with Mg and by diluting with MgO. • XRD profile shows the iron di-silicide phase to be semiconducting β-FeSi 2 . • HRTEM and FESEM images indicate the β-FeSi 2 average particle size to be 60–70 nm. • Absorption, reflectance and PL spectroscopy show band gap to be direct 0.87 eV. • Nano-β-FeSi 2 is p-type with hole density of 4.38 × 10 18 cm −3 and mobility 8.9 cm 2 /V s. - Abstract: Nano-particles of β-FeSi 2 have been synthesized by chemical reduction of a glassy phase of [Fe 2 O 3 , 4SiO 2 ] by Mg-metal where MgO is used as diluent to prevent the agglomeration of nano crystallites into micro-particles and also act as a negative catalyst for the formation of other phases. The sample is characterized by XRD, FESEM, HRTEM, EDX, ultra-violet-visible-infrared and PL spectroscopy and electronic properties have been investigated by Hall measurement. XRD profile shows that the synthesized powder consists of purely β-FeSi 2 semiconducting phase. The average crystallite size of β-FeSi 2 is determined to be around 65.4 nm from XRD peaks as well as from FESEM also. The optical absorption and PL spectroscopy shows that synthesized β-FeSi 2 phase is a direct band gap semiconductor with a value of 0.87 eV. Hall measurements show that β-FeSi 2 nano-particles is p-type with hole concentration of 4.38 × 10 18 cm −3 and average hole mobility of 8.9 cm 2 /V s at 300 K

Remote Laser Diffraction Particle Size Distribution Analyzer

Energy Technology Data Exchange (ETDEWEB)

Batcheller, Thomas Aquinas; Huestis, Gary Michael; Bolton, Steven Michael

2001-03-01

In support of a radioactive slurry sampling and physical characterization task, an “off-the-shelf” laser diffraction (classical light scattering) particle size analyzer was utilized for remote particle size distribution (PSD) analysis. Spent nuclear fuel was previously reprocessed at the Idaho Nuclear Technology and Engineering Center (INTEC—formerly recognized as the Idaho Chemical Processing Plant) which is on DOE’s INEEL site. The acidic, radioactive aqueous raffinate streams from these processes were transferred to 300,000 gallon stainless steel storage vessels located in the INTEC Tank Farm area. Due to the transfer piping configuration in these vessels, complete removal of the liquid can not be achieved. Consequently, a “heel” slurry remains at the bottom of an “emptied” vessel. Particle size distribution characterization of the settled solids in this remaining heel slurry, as well as suspended solids in the tank liquid, is the goal of this remote PSD analyzer task. A Horiba Instruments Inc. Model LA-300 PSD analyzer, which has a 0.1 to 600 micron measurement range, was modified for remote application in a “hot cell” (gamma radiation) environment. This technology provides rapid and simple PSD analysis, especially down in the fine and microscopic particle size regime. Particle size analysis of these radioactive slurries down in this smaller range was not previously achievable—making this technology far superior than the traditional methods used. Successful acquisition of this data, in conjunction with other characterization analyses, provides important information that can be used in the myriad of potential radioactive waste management alternatives.

Particle phase distribution of polycyclic aromatic hydrocarbons in stormwater — Using humic acid and iron nano-sized colloids as test particles

DEFF Research Database (Denmark)

Nielsen, Katrine; Kalmykova, Yuliya; Strömvall, Ann-Margret

2015-01-01

The distribution of polycyclic aromatic hydrocarbons (PAHs) in different particulate fractions in stormwater: Total, Particulate, Filtrated, Colloidal and Dissolved fractions, were examined and compared to synthetic suspensions of humic acid colloids and iron nano-sized particles. The distribution...

Initiator Systems Effect on Particle Coagulation and Particle Size Distribution in One-Step Emulsion Polymerization of Styrene

Directory of Open Access Journals (Sweden)

Baijun Liu

2016-02-01

Full Text Available Particle coagulation is a facile approach to produce large-scale polymer latex particles. This approach has been widely used in academic and industrial research owing to its higher polymerization rate and one-step polymerization process. Our work was motivated to control the extent (or time of particle coagulation. Depending on reaction parameters, particle coagulation is also able to produce narrowly dispersed latex particles. In this study, a series of experiments were performed to investigate the role of the initiator system in determining particle coagulation and particle size distribution. Under the optimal initiation conditions, such as cationic initiator systems or higher reaction temperature, the time of particle coagulation would be advanced to particle nucleation period, leading to the narrowly dispersed polymer latex particles. By using a combination of the Smoluchowski equation and the electrostatic stability theory, the relationship between the particle size distribution and particle coagulation was established: the earlier the particle coagulation, the narrower the particle size distribution, while the larger the extent of particle coagulation, the larger the average particle size. Combined with the results of previous studies, a systematic method controlling the particle size distribution in the presence of particle coagulation was developed.

Particle interaction of lubricated or unlubricated binary mixtures according to their particle size and densification mechanism.

Science.gov (United States)

Di Martino, Piera; Joiris, Etienne; Martelli, Sante

2004-09-01

The aim of this study is to assess an experimental approach for technological development of a direct compression formulation. A simple formula was considered composed by an active ingredient, a diluent and a lubricant. The active ingredient and diluent were selected as an example according to their typical densification mechanism: the nitrofurantoine, a fragmenting material, and the cellulose microcrystalline (Vivapur), which is a typical visco-elastic material, equally displaying good bind and disintegrant properties. For each ingredient, samples of different particle size distribution were selected. Initially, tabletability of pure materials was studied by a rotary press without magnesium stearate. Vivapur tabletability decreases with increase in particle size. The addition of magnesium stearate as lubricant decreases tabletability of Vivapur of greater particle size, while it kept unmodified that of Vivapur of lower particle size. Differences in tabletability can be related to differences in particle-particle interactions; for Vivapur of higher particle size (Vivapur 200, 102 and 101), the lower surface area develops lower surface available for bonds, while for Vivapur of lower particle size (99 and 105) the greater surface area allows high particle proximity favouring particle cohesivity. Nitrofurantoine shows great differences in compression behaviour according to its particle size distribution. Large crystals show poorer tabletability than fine crystals, further decreased by lubricant addition. The large crystals poor tabletability is due to their poor compactibility, in spite of high compressibility and plastic intrinsic deformability; in fact, in spite of the high densification tendency, the nature of the involved bonds is very weak. Nitrofurantoine samples were then mixed with Vivapurs in different proportions. Compression behaviour of binary mixes (tabletability and compressibility) was then evaluated according to diluents proportion in the mixes. The

The impact of mass transfer limitations on size distributions of particle associated SVOCs in outdoor and indoor environments

Energy Technology Data Exchange (ETDEWEB)

Liu, Cong; Zhang, Yinping [Department of Building Science, Tsinghua University, Beijing (China); Weschler, Charles J., E-mail: weschlch@rwjms.rutgers.edu [Department of Building Science, Tsinghua University, Beijing (China); Environmental and Occupational Health Sciences Institute, Rutgers University, Piscataway, NJ (United States); International Center for Indoor Environment and Energy, Technical University of Denmark, Lyngby (Denmark)

2014-11-01

Semi-volatile organic compounds (SVOCs) partition between the gas phase and airborne particles. The size distribution of particle-associated SVOCs impacts their fate in outdoor and indoor environments, as well as human exposure to these compounds and subsequent health risks. Allen et al. (1996) previously proposed that the rate of mass transfer can impact polycyclic aromatic hydrocarbon (PAH) partitioning among different sized particles, especially for time scales relevant to urban aerosols. The present study quantitatively builds on this idea, presenting a model that incorporates dynamic SVOC/particle interaction and applying this model to typical outdoor and indoor scenarios. The model indicates that the impact of mass transfer limitations on the size distribution of a particle-associated SVOC can be evaluated by the ratio of the time to achieve gas–particle equilibrium relative to the residence time of particles. The higher this ratio, the greater the influence of mass transfer limitations on the size distribution of particle-associated SVOCs. The influence of such constraints is largest on the fraction of particle-associated SVOCs in the coarse mode (> 2 μm). Predictions from the model have been found to be in reasonable agreement with size distributions measured for PAHs at roadside and suburban locations in Japan. The model also quantitatively explains shifts in the size distributions of particle associated SVOCs compared to those for particle mass, and the manner in which these shifts vary with temperature and an SVOC's molecular weight. - Highlights: • Rate of mass transfer can impact SVOC partitioning among different sized particles. • Model was developed that incorporates dynamic SVOC/particle sorption. • Key parameters: mass-transfer coefficients, partition coefficient, residence time • Model explains observed SVOC size distribution shifts with temperature and MW. • Largest impact of mass transfer constraints: SVOC sorption to coarse

Determining size-specific emission factors for environmental tobacco smoke particles

Energy Technology Data Exchange (ETDEWEB)

Klepeis, Neil E.; Apte, Michael G.; Gundel, Lara A.; Sextro, Richard G.; Nazaroff, William W.

2002-07-07

Because size is a major controlling factor for indoor airborne particle behavior, human particle exposure assessments will benefit from improved knowledge of size-specific particle emissions. We report a method of inferring size-specific mass emission factors for indoor sources that makes use of an indoor aerosol dynamics model, measured particle concentration time series data, and an optimization routine. This approach provides--in addition to estimates of the emissions size distribution and integrated emission factors--estimates of deposition rate, an enhanced understanding of particle dynamics, and information about model performance. We applied the method to size-specific environmental tobacco smoke (ETS) particle concentrations measured every minute with an 8-channel optical particle counter (PMS-LASAIR; 0.1-2+ micrometer diameters) and every 10 or 30 min with a 34-channel differential mobility particle sizer (TSI-DMPS; 0.01-1+ micrometer diameters) after a single cigarette or cigar was machine-smoked inside a low air-exchange-rate 20 m{sup 3} chamber. The aerosol dynamics model provided good fits to observed concentrations when using optimized values of mass emission rate and deposition rate for each particle size range as input. Small discrepancies observed in the first 1-2 hours after smoking are likely due to the effect of particle evaporation, a process neglected by the model. Size-specific ETS particle emission factors were fit with log-normal distributions, yielding an average mass median diameter of 0.2 micrometers and an average geometric standard deviation of 2.3 with no systematic differences between cigars and cigarettes. The equivalent total particle emission rate, obtained integrating each size distribution, was 0.2-0.7 mg/min for cigars and 0.7-0.9 mg/min for cigarettes.

Particle sizes in slash fire smoke.

Science.gov (United States)

David V. Sandberg; Robert E. Martin

1975-01-01

Particulate emissions are the most objectionable atmospheric contaminant from forest burning. Little is known of the particulate sizes, and this research was done under laboratory conditions to obtain particle size information. Comments are made concerning techniques for future work in this field.

MICRON-SIZED POLYMER PARTICLES FROM TANZANIAN ...

African Journals Online (AJOL)

Micron sized polymeric particles were prepared from cashew nut shell liquid and subsequently functionalized to produce micron-sized carboxylated cation exchange resin (MCCER). By titrimetry and analytical procedures employing atomic absorption spectrometry, an assessment of the cation exchange capability of the ...

Mobility particle size spectrometers: harmonization of technical standards and data structure to facilitate high quality long-term observations of atmospheric particle number size distributions

Directory of Open Access Journals (Sweden)

A. Wiedensohler

2012-03-01

Full Text Available Mobility particle size spectrometers often referred to as DMPS (Differential Mobility Particle Sizers or SMPS (Scanning Mobility Particle Sizers have found a wide range of applications in atmospheric aerosol research. However, comparability of measurements conducted world-wide is hampered by lack of generally accepted technical standards and guidelines with respect to the instrumental set-up, measurement mode, data evaluation as well as quality control. Technical standards were developed for a minimum requirement of mobility size spectrometry to perform long-term atmospheric aerosol measurements. Technical recommendations include continuous monitoring of flow rates, temperature, pressure, and relative humidity for the sheath and sample air in the differential mobility analyzer.

We compared commercial and custom-made inversion routines to calculate the particle number size distributions from the measured electrical mobility distribution. All inversion routines are comparable within few per cent uncertainty for a given set of raw data.

Furthermore, this work summarizes the results from several instrument intercomparison workshops conducted within the European infrastructure project EUSAAR (European Supersites for Atmospheric Aerosol Research and ACTRIS (Aerosols, Clouds, and Trace gases Research InfraStructure Network to determine present uncertainties especially of custom-built mobility particle size spectrometers. Under controlled laboratory conditions, the particle number size distributions from 20 to 200 nm determined by mobility particle size spectrometers of different design are within an uncertainty range of around ±10% after correcting internal particle losses, while below and above this size range the discrepancies increased. For particles larger than 200 nm, the uncertainty range increased to 30%, which could not be explained. The network reference mobility spectrometers with identical design agreed within ±4% in the

An investigation on two-phase mixture discharges: the effects of macroparticle sizes

Energy Technology Data Exchange (ETDEWEB)

Deng Heming; He Zhenghao; Xu Yuhang; Ma Jun; Liu Junxiang; Guo Runkai, E-mail: denghem@gmail.co [School of Environmental Science and Engineering, Huazhong University of Science and Technology, Hubei province Wuhan 430074 (China)

2010-06-30

A two-phase mixture (TPM) is a mixture of gas and macroparticles of high concentration, and there has been significant interest in many technical applications and natural phenomena concerning two-phase mixture discharges (TPMDs), but until now there has been no widely accepted analysis for the propagation of discharges in TPMs. In this paper, 21 kinds of different dielectric materials are used to investigate the effects on TPMD. The diameters of macroparticles in 21 kinds of TPMs are measured by microscope, laser particle size analyzer, etc, and the volume fractions are measured by a video camera and particle image velocimetry system. Based on a direct comparison of the breakdown voltages and the percentages of the discharge path in TPMs with those in air, this work reveals that whether TPMs promote the discharge development or not depends mainly on the macroparticle sizes. These macroparticles in TPMs distort the electric field, interact with ions, electrons or photons, and produce corresponding enhancements or decreases in ionization and excitation as the streamer front encounters them, but the details of alterations on the discharge development are highly correlated with the macroparticle sizes.

Particle size- and concentration-dependent separation of magnetic nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Witte, Kerstin, E-mail: witte@micromod.de [University of Rostock, Institute of Physics, Albert-Einstein-Str. 23, 18059 Rostock (Germany); Micromod Partikeltechnologie GmbH, Friedrich-Barnewitz-Str. 4, 18119 Rostock (Germany); Müller, Knut; Grüttner, Cordula; Westphal, Fritz [Micromod Partikeltechnologie GmbH, Friedrich-Barnewitz-Str. 4, 18119 Rostock (Germany); Johansson, Christer [Acreo Swedish ICT AB, 40014 Göteborg (Sweden)

2017-04-01

Small magnetic nanoparticles with a narrow size distribution are of great interest for several biomedical applications. When the size of the particles decreases, the magnetic moment of the particles decreases. This leads to a significant increase in the separation time by several orders of magnitude. Therefore, in the present study the separation processes of bionized nanoferrites (BNF) with different sizes and concentrations were investigated with the commercial Sepmag Q system. It was found that an increasing initial particle concentration leads to a reduction of the separation time for large nanoparticles due to the higher probability of building chains. Small nanoparticles showed exactly the opposite behavior with rising particle concentration up to 0.1 mg(Fe)/ml. For higher iron concentrations the separation time remains constant and the measured Z-average decreases in the supernatant at same time intervals. At half separation time a high yield with decreasing hydrodynamic diameter of particles can be obtained using higher initial particle concentrations. - Highlights: • Size dependent separation processes of multicore nanoparticles. • Concentration dependent separation processes of multicore nanoparticles. • Increasing separation time with rising concentrations for small particles. • Large particles show typical cooperative magnetophoresis behavior.

A system for aerodynamically sizing ultrafine environmental radioactive particles

International Nuclear Information System (INIS)

Olawoyin, L.

1995-09-01

The unattached environmental radioactive particles/clusters, produced mainly by 222 Rn in indoor air, are usually few nanometers in size. The inhalation of these radioactive clusters can lead to deposition of radioactivity on the mucosal surface of the tracheobronchial tree. The ultimate size of the cluster together with the flow characteristics will determine the depositional site in the human lung and thus, the extent of damage that can be caused. Thus, there exists the need for the determination of the size of the radioactive clusters. However, the existing particle measuring device have low resolution in the sub-nanometer range. In this research, a system for the alternative detection and measurement of the size of particles/cluster in the less than 2 nm range have been developed. The system is a one stage impactor which has a solid state spectrometer as its impaction plate. It's major feature is the nozzle-to-plate separation, L. The particle size collected changes with L and thus, particle size spectroscopy is achieved by varying L. The number of collected particles is determined by alpha spectroscopy. The size-discriminating ability of the system was tested with laboratory generated radon particles and it was subsequently used to characterize the physical (size) changes associated with the interaction of radon progeny with water vapor and short chain alcohols in various support gases. The theory of both traditional and high velocity jet impactors together with the design and evaluation of the system developed in this study are discussed in various chapters of this dissertation. The major results obtained in the course of the study are also presented

A system for aerodynamically sizing ultrafine environmental radioactive particles

Energy Technology Data Exchange (ETDEWEB)

Olawoyin, L.

1995-09-01

The unattached environmental radioactive particles/clusters, produced mainly by {sup 222}Rn in indoor air, are usually few nanometers in size. The inhalation of these radioactive clusters can lead to deposition of radioactivity on the mucosal surface of the tracheobronchial tree. The ultimate size of the cluster together with the flow characteristics will determine the depositional site in the human lung and thus, the extent of damage that can be caused. Thus, there exists the need for the determination of the size of the radioactive clusters. However, the existing particle measuring device have low resolution in the sub-nanometer range. In this research, a system for the alternative detection and measurement of the size of particles/cluster in the less than 2 nm range have been developed. The system is a one stage impactor which has a solid state spectrometer as its impaction plate. It`s major feature is the nozzle-to-plate separation, L. The particle size collected changes with L and thus, particle size spectroscopy is achieved by varying L. The number of collected particles is determined by alpha spectroscopy. The size-discriminating ability of the system was tested with laboratory generated radon particles and it was subsequently used to characterize the physical (size) changes associated with the interaction of radon progeny with water vapor and short chain alcohols in various support gases. The theory of both traditional and high velocity jet impactors together with the design and evaluation of the system developed in this study are discussed in various chapters of this dissertation. The major results obtained in the course of the study are also presented.

Tailoring particle size and morphology of colloidal Ag particles via chemical precipitation for Ag-BSCCO composites

International Nuclear Information System (INIS)

Medendorp, N.W. Jr.; Bowman, K.J.; Trumble, K.P.

1996-01-01

The chemical precipitation of silver particles is an effective method for tailoring the particle size and morphology. This article investigates a chemical precipitation method for producing silver colloids, and how processing parameters affected particle size, morphology and adherence. Decreasing the silver nitrate concentration during precipitation with sodium borohydride decreased the colloidal silver particle size. Decreasing the addition rate of the reducing agent produced faceted particles. Reversing the reactant addition order also changed the particle size and the morphology. Precipitated colloids demonstrated a difference between the growth-dominated and the equilibrium structures. Co-dispersing Bi-based superconducting platelets during precipitation allowed Ag colloids to preferentially nucleate on the platelets and to remain adhered even after the additional processing. (orig.)

A 100-kW three-phase ac plasma furnace for spheroidization of aluminum silicate particles

International Nuclear Information System (INIS)

Gold, D.; Bonet, C.; Chauvin, G.; Geinaert, G.; Mathieu, A.C.; Millet, J.

1981-01-01

A 100-kW three-phase ac plasma furnace with sheathed copper electrodes (sheathing gas: air) is presented. It is used for spheroidizing ''chamotte'' (refractory-fired clay) particles having a smooth, pore-free surface. A simple, one-dimensional numerical model for the heat transfer to the particles explains the maximum processing rate and the detrimental influence of an inhomogeneous particle size distribution

Effect of particle-size dynamics on properties of dense spongy-particle systems: Approach towards equilibrium

Science.gov (United States)

Zakhari, Monica E. A.; Anderson, Patrick D.; Hütter, Markus

2017-07-01

Open-porous deformable particles, often envisaged as sponges, are ubiquitous in biological and industrial systems (e.g., casein micelles in dairy products and microgels in cosmetics). The rich behavior of these suspensions is owing to the elasticity of the supporting network of the particle, and the viscosity of permeating solvent. Therefore, the rate-dependent size change of these particles depends on their structure, i.e., the permeability. This work aims at investigating the effect of the particle-size dynamics and the underlying particle structure, i.e., the particle permeability, on the transient and long-time behavior of suspensions of spongy particles in the absence of applied deformation, using the dynamic two-scale model developed by Hütter et al. [Farad. Discuss. 158, 407 (2012), 10.1039/c2fd20025b]. In the high-density limit, the transient behavior is found to be accelerated by the particle-size dynamics, even at average size changes as small as 1 % . The accelerated dynamics is evidenced by (i) the higher short-time diffusion coefficient as compared to elastic-particle systems and (ii) the accelerated formation of the stable fcc crystal structure. Furthermore, after long times, the particle-size dynamics of spongy particles is shown to result in lower stationary values of the energy and normal stresses as compared to elastic-particle systems. This dependence of the long-time behavior of these systems on the permeability, that essentially is a transport coefficient and hence must not affect the equilibrium properties, confirms that full equilibration has not been reached.

A study of particle size distribution in zirconia-alumina powders

International Nuclear Information System (INIS)

Ramakrishnan, K.N.; Venkadesan, S.; Nagarajan, R.

1996-01-01

Powder particles, in general are characterized in terms of particle size, size distributions and composition for reasons associated with manufacturing problem based upon product quality, manufacturing convenience, cost and product handling convenience. Particle size analysis or the measurement of particle size distribution is a common effort in any physical, chemical or mechanical processes. This information and processing methods are intricate factors that relate to material behavior and/or physical properties of the fabricated product. The requirements for the formation of a product of particulate solids and its strength varies as the particle size and the size distribution changes. Also the transport properties and the chemical activity are related to the particle size and the size distribution. The choice of a distribution to represent a physical system is generally motivated by an understanding of the nature of underlying phenomenon and is verified by the available data. After a model has been chosen, its parameter must be determined. The reasonableness of a selected model on the basis of given data is especially important when the model is to be used for prediction. Two different approaches in this problem are probability plotting and statistical tests

The role of particle-size soil fractions in the adsorption of heavy metals

Science.gov (United States)

Mandzhieva, Saglara; Minkina, Tatiana; Pinsky, David; Batukaev, Abdulmalik; Kalinitchenko, Valeriy; Sushkova, Svetlana; Chaplygin, Viktor; Dikaev, Zaurbek; Startsev, Viktor; Bakoev, Serojdin

2014-05-01

Ion-exchange adsorption phenomena are important in the immobilization of heavy metals (HMs) by soils. Numerous works are devoted to the study of this problem. However, the interaction features of different particle-size soil fractions and their role in the immobilization of HMs studied insufficiently. Therefore, the assessment of the effect of the particle-size distribution on the adsorption properties of soils is a vital task. The parameters of Cu2+, Pb2+ and Zn2+ adsorption by chernozems of the south of Russia and their particle-size fractions were studied. In the particle-size fractions separated from the soils, the concentrations of Cu2+, Pb2+, and Zn2 decreased with the decreasing particle size. The parameters of the adsorption values of k (the constant of the affinity)and Cmax.(the maximum adsorption of the HMs) characterizing the adsorption of HMs by the southern chernozem and its particle-size fractions formed the following sequence: silt > clay > entire soil. The adsorption capacity of chernozems for Cu2+, Pb2+, and Zn2+ depending on the particle-size distribution decreased in the following sequence: clay loamy ordinary chernozem clay loamy southern chernozem> loamy southern chernozem> loamy sandy southern chernozem. According to the parameters of the adsorption by the different particle-size fractions, the heavy metal cations form a sequence analogous to that obtained for the entire soils: Cu2+ ≥ Pb2+ > Zn2+. The parameters of the heavy metal adsorption by similar particle-size fractions separated from different soils decreased in the following order: clay loamy chernozem> loamy chernozem> loamy sandy chernozem. The analysis of the changes in the parameters of the Cu2+, Pb2+, and Zn2+ adsorption by the studied soils and their particle-size fractions showed that the extensive adsorption characteristic - the maximum adsorption (Cmax.) - is a less sensitive parameter characterizing the adsorption capacity of the soils than the intensive characteristic of

Dependence of charge transfer phenomena during solid-air two-phase flow on particle disperser

Science.gov (United States)

Tanoue, Ken-ichiro; Suedomi, Yuuki; Honda, Hirotaka; Furutani, Satoshi; Nishimura, Tatsuo; Masuda, Hiroaki

2012-12-01

An experimental investigation of the tribo-electrification of particles has been conducted during solid-air two-phase turbulent flow. The current induced in a metal plate by the impact of polymethylmethacrylate (PMMA) particles in a high-speed air flow was measured for two different plate materials. The results indicated that the contact potential difference between the particles and a stainless steel plate was positive, while for a nickel plate it was negative. These results agreed with theoretical contact charge transfer even if not only the particle size but also the kind of metal plate was changed. The specific charge of the PMMA particles during solid-air two-phase flow using an ejector, a stainless steel branch pipe, and a stainless steel straight pipe was measured using a Faraday cage. Although the charge was negative in the ejector, the particles had a positive specific charge at the outlet of the branch pipe, and this positive charge increased in the straight pipe. The charge decay along the flow direction could be reproduced by the charging and relaxation theory. However, the proportional coefficients in the theory changed with the particle size and air velocity. Therefore, an unexpected charge transfer occurred between the ejector and the branch pipe, which could not be explained solely by the contact potential difference. In the ejector, an electrical current in air might have been produced by self-discharge of particles with excess charge between the nickel diffuser in the ejector and the stainless steel nozzle or the stainless steel pipe due to a reversal in the contact potential difference between the PMMA and the stainless steel. The sign of the current depended on the particle size, possibly because the position where the particles impacted depended on their size. When dual coaxial glass pipes were used as a particle disperser, the specific charge of the PMMA particles became more positive along the particle flow direction due to the contact

Synthesis of nanoparticles in a flame aerosol reactor with independent and strict control of their size, crystal phase and morphology

International Nuclear Information System (INIS)

Jiang Jingkun; Chen, D-R; Biswas, Pratim

2007-01-01

A flame aerosol reactor (FLAR) was developed to synthesize nanoparticles with desired properties (crystal phase and size) that could be independently controlled. The methodology was demonstrated for TiO 2 nanoparticles, and this is the first time that large sets of samples with the same size but different crystal phases (six different ratios of anatase to rutile in this work) were synthesized. The degree of TiO 2 nanoparticle agglomeration was determined by comparing the primary particle size distribution measured by scanning electron microscopy (SEM) to the mobility-based particle size distribution measured by online scanning mobility particle spectrometry (SMPS). By controlling the flame aerosol reactor conditions, both spherical unagglomerated particles and highly agglomerated particles were produced. To produce monodisperse nanoparticles, a high throughput multi-stage differential mobility analyser (MDMA) was used in series with the flame aerosol reactor. Nearly monodisperse nanoparticles (geometric standard deviation less than 1.05) could be collected in sufficient mass quantities (of the order of 10 mg) in reasonable time (1 h) that could be used in other studies such as determination of functionality or biological effects as a function of size

Synthesis of nanoparticles in a flame aerosol reactor with independent and strict control of their size, crystal phase and morphology

Energy Technology Data Exchange (ETDEWEB)

Jiang Jingkun; Chen, D-R; Biswas, Pratim [Aerosol and Air Quality Research Laboratory, Department of Energy, Environmental and Chemical Engineering, Washington University in St Louis, Campus Box 1180, St Louis, MO 63130 (United States)

2007-07-18

A flame aerosol reactor (FLAR) was developed to synthesize nanoparticles with desired properties (crystal phase and size) that could be independently controlled. The methodology was demonstrated for TiO{sub 2} nanoparticles, and this is the first time that large sets of samples with the same size but different crystal phases (six different ratios of anatase to rutile in this work) were synthesized. The degree of TiO{sub 2} nanoparticle agglomeration was determined by comparing the primary particle size distribution measured by scanning electron microscopy (SEM) to the mobility-based particle size distribution measured by online scanning mobility particle spectrometry (SMPS). By controlling the flame aerosol reactor conditions, both spherical unagglomerated particles and highly agglomerated particles were produced. To produce monodisperse nanoparticles, a high throughput multi-stage differential mobility analyser (MDMA) was used in series with the flame aerosol reactor. Nearly monodisperse nanoparticles (geometric standard deviation less than 1.05) could be collected in sufficient mass quantities (of the order of 10 mg) in reasonable time (1 h) that could be used in other studies such as determination of functionality or biological effects as a function of size.

Size-dependent photodegradation of CdS particles deposited onto TiO2 mesoporous films by SILAR method

International Nuclear Information System (INIS)

Ahmed, Rasin; Will, Geoffrey; Bell, John; Wang Hongxia

2012-01-01

The particle size, size distribution and photostability of CdS nanoparticles incorporated onto mesoporous TiO 2 films by a successive ionic layer adsorption and reaction (SILAR) method were investigated by Raman spectroscopy, UV–Visible spectroscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). High-resolution TEM indicated that the synthesized CdS particles were hexagonal phase and the particle sizes were less than 5 nm for up to nine SILAR deposition cycles. Quantum size effect was found with the CdS-sensitized TiO 2 films prepared with up to nine SILAR cycles. The band gap of CdS nanoparticles decreased from 2.65 to 2.37 eV with the increase of the SILAR cycles from 1 to 11. The investigation of the stability of the CdS/TiO 2 films in air under illumination (440.6 μW/cm 2 ) showed that the photodegradation rate was up to 85 % per day for the sample prepared with three SILAR cycles. XPS analysis indicated that the photodegradation was due to the oxidation of CdS, leading to the transformation from sulphide to sulphate (CdSO 4 ). Furthermore, the degradation rate was strongly dependent upon the particle size of CdS. Smaller particles showed faster degradation rate. The size-dependent photo-induced oxidization was rationalized with the variation of size-dependent distribution of surface atoms of CdS particles. Molecular dynamics-based theoretical calculation has indicated that the surface sulphide anion of a large CdS particle such as CdS made with 11 cycles (CdS × 11, average particle size = 5.6 nm) accounts for 9.6 % of the material whereas this value is increased to 19.2 % for (CdS × 3)-based smaller particles (average particle size = 2.7 nm). The photostability of CdS nanoparticles was significantly enhanced when coated with ZnS particles deposited with four SILAR cycles. The growth mechanism of ZnS upon CdS nanoparticles was discussed.

Production of sized particles of uranium oxides and uranium oxyfluorides

International Nuclear Information System (INIS)

Knudsen, I.E.; Randall, C.C.

1976-01-01

A process is claimed for converting uranium hexafluoride (UF 6 ) to uranium dioxide (UO 2 ) of a relatively large particle size in a fluidized bed reactor by mixing uranium hexafluoride with a mixture of steam and hydrogen and by preliminary reacting in an ejector gaseous uranium hexafluoride with steam and hydrogen to form a mixture of uranium and oxide and uranium oxyfluoride seed particles of varying sizes, separating the larger particles from the smaller particles in a cyclone separator, recycling the smaller seed particles through the ejector to increase their size, and introducing the larger seed particles from the cyclone separator into a fluidized bed reactor where the seed particles serve as nuclei on which coarser particles of uranium dioxide are formed. 9 claims, 2 drawing figures

Concentration Measurements of Suspended Load using ADV with Influence of the Particle Size

Science.gov (United States)

Schwarzwälder, Kordula

2017-04-01

ADV backscatter data can be used under certain conditions to gain information about the concentrations of suspended loads. This was shown in many studies before (Fugate and Friedrichs 2002; Chanson et al 2008; Ha et al. 2009). This paper reports on a pre-study to investigate the influence of particle size on concentration measurements for suspended sediment load with ADV. The study was conducted in a flume in the Oskar-von-Miller-Institute using fresh water from a river including the natural suspended load. The ADV used in the experiments was a Vectrino Profiler (Nortek). In addition water samples were taken for TSS and TOC. For the measurements a surge was generated in the flume to ensure that also particles of larger size will be present in the water phase. The measurements and samples were taken during the whole surge event. Therefore we were able to find a good correlation between the backscatter data of the ADV and the TSS as well as TOC results. For the decreasing part of the flow event the concentration of TOC in the suspended load of the water phase is decreasing much slower than the TSS and results in a damped decrease of the backscatter values. This means that the results for concentration measurements might be slightly influenced by the size of the particles. Further evaluations of measurements conducted with a LISST SL (Sequoia) will be investigated to show the trend of the particle sizes during this process and fortify this result. David C. Fugate, Carl T. Friedrichs, Determining concentration and fall velocity of estuarine particle populations using ADV, OBS and LISST, Continental Shelf Research, Volume 22, Issues 11-13, 2002 H.K. Ha, W.-Y. Hsu, J.P.-Y. Maa, Y.Y. Shao, C.W. Holland, Using ADV backscatter strength for measuring suspended cohesive sediment concentration, Continental Shelf Research, Volume 29, Issue 10, 2009 Hubert Chanson, Maiko Takeuchi, Mark Trevethan, Using turbidity and acoustic backscatter intensity as surrogate measures of

Nanoparticle growth by particle-phase chemistry

Science.gov (United States)

Apsokardu, Michael J.; Johnston, Murray V.

2018-02-01

The ability of particle-phase chemistry to alter the molecular composition and enhance the growth rate of nanoparticles in the 2-100 nm diameter range is investigated through the use of a kinetic growth model. The molecular components included are sulfuric acid, ammonia, water, a non-volatile organic compound, and a semi-volatile organic compound. Molecular composition and growth rate are compared for particles that grow by partitioning alone vs. those that grow by a combination of partitioning and an accretion reaction in the particle phase between two organic molecules. Particle-phase chemistry causes a change in molecular composition that is particle diameter dependent, and when the reaction involves semi-volatile molecules, the particles grow faster than by partitioning alone. These effects are most pronounced for particles larger than about 20 nm in diameter. The modeling results provide a fundamental basis for understanding recent experimental measurements of the molecular composition of secondary organic aerosol showing that accretion reaction product formation increases linearly with increasing aerosol volume-to-surface-area. They also allow initial estimates of the reaction rate constants for these systems. For secondary aerosol produced by either OH oxidation of the cyclic dimethylsiloxane (D5) or ozonolysis of β-pinene, oligomerization rate constants on the order of 10-3 to 10-1 M-1 s-1 are needed to explain the experimental results. These values are consistent with previously measured rate constants for reactions of hydroperoxides and/or peroxyacids in the condensed phase.

Selection Of Suitable Particle Size And Particle Ratio For Japanese Cucumber Cucumis Sativus L. Plants

Directory of Open Access Journals (Sweden)

Galahitigama GAH

2015-08-01

Full Text Available This study was conducted to select the best particle size of coco peat for cucumber nurseries as well as best particle ratio for optimum plant growth and development of cucumber. The experiment was carried out in International Foodstuff Company and Faculty of Agriculture University of Ruhuna Sri Lanka during 2015 to 2016. Under experiment one three types of different particle sizes were used namely fine amp88040.5mm T2 medium 3mm-0.5mm T3 and coarse 4mm T4 with normal coco peat T1 as treatments. Complete Randomized Design CRD used as experimental design with five replicates. Germination percentage number of leaves per seedling seedling height in frequent day intervals was taken as growth parameters. Analysis of variance procedure was applied to analyze the data at 5 probability level. The results revealed that medium size particle media sieve size 0.5mm -3mm of coco peat was the best particle size for cucumber nursery practice when considered the physical and chemical properties of medium particles of coco peat. In the experiment of selecting of suitable particle ratio for cucumber plants the compressed mixture of coco peat particles that contain 70 ww unsieved coco peat 20 ww coarse particles and 10 ww coconut husk chips 5 12mm has given best results for growth performances compared to other treatments and cucumber grown in this mixture has shown maximum growth and yield performances.

Controlling the size and morphology of precipitated calcite particles by the selection of solvent composition

Science.gov (United States)

Konopacka-Łyskawa, Donata; Kościelska, Barbara; Karczewski, Jakub

2017-11-01

Precipitated calcium carbonate is used as an additive in the manufacture of many products. Particles with specific characteristics can be obtained by the selection of precipitation conditions, including temperature and the composition of solvent. In this work, calcium carbonate particles were obtained in the reaction of calcium hydroxide with carbon dioxide at 65 °C. Initial Ca(OH)2 suspensions were prepared in pure water and aqueous solutions of ethylene glycol or glycerol of the concentration range up to 20% (vol.). The course of reaction was monitored by conductivity measurements. Precipitated solids were analyzed by FTIR, XRD, SEM and the particles size distribution was determined by a laser diffraction method. The adsorption of ethylene glycol or glycerol on the surface of scalenohedral and rhombohedral calcite was testes by a normal-phase high-performance liquid chromatography. The addition of organic solvents changed the viscosity of reaction mixtures, the rate of carbon dioxide absorption and the solubility of inorganic components and therefore influence calcium carbonate precipitation conditions. All synthesized calcium carbonate products were in a calcite form. Scalenohedral calcite crystals were produced when water was a liquid phase, whereas addition of organic solvents resulted in the formation of rhombo-scalenohedral particles. The increase in organic compounds concentration resulted in the decrease of mean particles size from 2.4 μm to 1.7 μm in ethylene glycol solutions and to 1.4 μm in glycerol solutions. On the basis of adsorption tests, it was confirm that calcite surface interact stronger with glycerol than ethylene glycol. The interaction between scalenohedral calcite and used organic additives was higher in comparison to the pure rhombohedral form applied as a stationary phase.

Estimating particle number size distributions from multi-instrument observations with Kalman Filtering

Energy Technology Data Exchange (ETDEWEB)

Viskari, T.

2012-07-01

Atmospheric aerosol particles have several important effects on the environment and human society. The exact impact of aerosol particles is largely determined by their particle size distributions. However, no single instrument is able to measure the whole range of the particle size distribution. Estimating a particle size distribution from multiple simultaneous measurements remains a challenge in aerosol physical research. Current methods to combine different measurements require assumptions concerning the overlapping measurement ranges and have difficulties in accounting for measurement uncertainties. In this thesis, Extended Kalman Filter (EKF) is presented as a promising method to estimate particle number size distributions from multiple simultaneous measurements. The particle number size distribution estimated by EKF includes information from prior particle number size distributions as propagated by a dynamical model and is based on the reliabilities of the applied information sources. Known physical processes and dynamically evolving error covariances constrain the estimate both over time and particle size. The method was tested with measurements from Differential Mobility Particle Sizer (DMPS), Aerodynamic Particle Sizer (APS) and nephelometer. The particle number concentration was chosen as the state of interest. The initial EKF implementation presented here includes simplifications, yet the results are positive and the estimate successfully incorporated information from the chosen instruments. For particle sizes smaller than 4 micrometers, the estimate fits the available measurements and smooths the particle number size distribution over both time and particle diameter. The estimate has difficulties with particles larger than 4 micrometers due to issues with both measurements and the dynamical model in that particle size range. The EKF implementation appears to reduce the impact of measurement noise on the estimate, but has a delayed reaction to sudden

Effect of particle size on mixing degree in dispensation.

Science.gov (United States)

Nakamura, Hitoshi; Yanagihara, Yoshitsugu; Sekiguchi, Hiroko; Ohtani, Michiteru; Kariya, Satoru; Uchino, Katsuyoshi; Suzuki, Hiroshi; Iga, Tatsuji

2004-03-01

By using lactose colored with erythrocin, we examined the effect of particle size on mixing degree during the preparation of triturations with a mortar and pestle. We used powders with different distributions of particle sizes, i.e., powder that passed through 32-mesh but was trapped on a 42-mesh sieve (32/42-mesh powder), powder that passed through a 42-mesh sieve but was trapped on a 60-mesh sieve (42/60-mesh powder), powder that passed through a 60-mesh sieve but was trapped on a 100-mesh sieve (60/100-mesh powder), and powder that passes through a 100-mesh sieve (> 100-mesh powder). The mixing degree of colored powder and non-colored powder whose distribution of particle sizes was the same as that of the colored powder was excellent. The coefficient of variation (CV) value of the mixing degree was 6.08% after 40 rotations when colored powder was mixed with non-colored powder that both passed through a 100-mesh sieve. The CV value of the mixing degree was low in the case of mixing of colored and non-colored powders with different particle size distributions. After mixing, about 50% of 42/60-mesh powder had become smaller particles, whereas the distribution of particle sizes was not influenced by the mixing of 60/100-mesh powder. It was suggested that the mixing degree is affected by distribution of particle sizes. It may be important to determine the mixing degrees for drugs with narrow therapeutic ranges.

Inverse problem for particle size distributions of atmospheric aerosols using stochastic particle swarm optimization

International Nuclear Information System (INIS)

Yuan Yuan; Yi Hongliang; Shuai Yong; Wang Fuqiang; Tan Heping

2010-01-01

As a part of resolving optical properties in atmosphere radiative transfer calculations, this paper focuses on obtaining aerosol optical thicknesses (AOTs) in the visible and near infrared wave band through indirect method by gleaning the values of aerosol particle size distribution parameters. Although various inverse techniques have been applied to obtain values for these parameters, we choose a stochastic particle swarm optimization (SPSO) algorithm to perform an inverse calculation. Computational performances of different inverse methods are investigated and the influence of swarm size on the inverse problem of computation particles is examined. Next, computational efficiencies of various particle size distributions and the influences of the measured errors on computational accuracy are compared. Finally, we recover particle size distributions for atmospheric aerosols over Beijing using the measured AOT data (at wavelengths λ=0.400, 0.690, 0.870, and 1.020 μm) obtained from AERONET at different times and then calculate other AOT values for this band based on the inverse results. With calculations agreeing with measured data, the SPSO algorithm shows good practicability.

Influence of particle size distributions on magnetorheological fluid performances

International Nuclear Information System (INIS)

Chiriac, H; Stoian, G

2010-01-01

In this paper we investigate the influence that size distributions of the magnetic particles might have on the magnetorheological fluid performances. In our study, several size distributions have been tailored first by sieving a micrometric Fe powder in order to obtain narrow distribution powders and then by recomposing the new size distributions (different from Gaussian). We used spherical Fe particles (mesh -325) commercially available. The powder was sieved by means of a sieve shaker using a series of sieves with the following mesh size: 20, 32, 40, 50, 63, 80 micrometers. All magnetic powders were characterized through Vibrating Sample Magnetometer (VSM) measurements, particle size analysis and also Scanning Electron Microscope (SEM) images were taken. Magnetorheological (MR) fluids based on the resulted magnetic powders were prepared and studied by means of a rheometer with a magnetorheological module. The MR fluids were measured in magnetic field and in zero magnetic field as well. As we noticed in our previous experiments particles size distribution can also influence the MR fluids performances.

Size and Velocity Distributions of Particles and Droplets in Spray Combustion Systems.

Science.gov (United States)

1984-11-01

34Particle Sizing by Optical , Nonimaging Techniques," Liquid Particle Size _Mjur-mentTechnjgjwi, ASTM publications STP848, ed. by J. MI. Tishkoff, R. D... Optical Nonimaging predictions do not account for nonideal lens effects. Techniques," in Liquid Particle Size Measurement Techniques, J.M.Tishkoff, ed...4S E. Dan Hirleman’ Particle Sizing by Optical , Nonimaging Techniques REFERENCE: Hieleman, E. D., "Particle Sizing by Optical , Nonimaging Tech- niques

Effect of particle size distribution on sintering of tungsten

International Nuclear Information System (INIS)

Patterson, B.R.; Griffin, J.A.

1984-01-01

To date, very little is known about the effect of the nature of the particle size distribution on sintering. It is reasonable that there should be an effect of size distribution, and theory and prior experimental work examining the effects of variations in bimodal and continuous distributions have shown marked effects on sintering. Most importantly, even with constant mean particle size, variations in distribution width, or standard deviation, have been shown to produce marked variations in microstructure and sintering rate. In the latter work, in which spherical copper powders were blended to produce lognormal distributions of constant geometric mean particle size by weight frequency, blends with larger values of geometric standard deviation, 1nσ, sintered more rapidly. The goals of the present study were to examine in more detail the effects of variations in the width of lognormal particle size distributions of tungsten powder and determine the effects of 1nσ on the microstructural evolution during sintering

Element content and particle size characterization of a mussel candidate reference material

International Nuclear Information System (INIS)

Moreira, Edson G.; Vasconcellos, Marina B.A.; Santos, Rafaela G. dos; Martinelli, Jose R.

2011-01-01

The use of certified reference materials is an important tool in the quality assurance of analytical measurements. To assure reliability on recently prepared powder reference materials, not only the characterization of the property values of interest and their corresponding uncertainties, but also physical properties such as the particle size distribution must be well evaluated. Narrow particle size distributions are preferable than larger ones; as different size particles may have different analyte content. Due to this fact, the segregation of the coarse and the fine particles in a bottle may lead to inhomogeneity of the reference material, which should be avoided. In this study the element content as well as the particle size distribution of a mussel candidate reference material produced at IPEN-CNEN/SP was investigated. Instrumental Neutron Activation Analysis was applied to the determination of 15 elements in seven fractions of the material with different particle size distributions. Subsamples of the materials were irradiated simultaneously with elemental standards at the IEA-R1 research nuclear reactor and the induced gamma ray energies were measured in a hyperpure germanium detector. Three vials of the candidate reference material and three coarser fractions, collected during the preparation, were analyzed by Laser Diffraction Particle Analysis to determine the particle size distribution. Differences on element content were detected for fractions with different particle size distribution, indicating the importance of particle size control for biological reference materials. From the particle size analysis, Gaussian particle size distribution was observed for the candidate reference material with mean particle size μ = 94.6 ± 0.8 μm. (author)

Synchronization of finite-size particles by a traveling wave in a cylindrical flow

Science.gov (United States)

Melnikov, D. E.; Pushkin, D. O.; Shevtsova, V. M.

2013-09-01

Motion of small finite-size particles suspended in a cylindrical thermocapillary flow with an azimuthally traveling wave is studied experimentally and numerically. At certain flow regimes the particles spontaneously align in dynamic accumulation structures (PAS) of spiral shape. We find that long-time trajectories of individual particles in this flow fall into three basic categories that can be described, borrowing the dynamical systems terminology, as the stable periodic, the quasiperiodic, and the quasistable periodic orbits. Besides these basic types of orbits, we observe the "doubled" periodic orbits and shuttle-like particle trajectories. We find that ensembles of particles having periodic orbits give rise to one-dimensional spiral PAS, while ensembles of particles having quasiperiodic orbits form two-dimensional PAS of toroidal shape. We expound the reasons why these types of orbits and the emergence of the corresponding accumulation structures should naturally be anticipated based on the phase locking theory of PAS formation. We give a further discussion of PAS features, such as the finite thickness of PAS spirals and the probable scenarios of the spiral PAS destruction. Finally, in numerical simulations of inertial particles we observe formation of the spiral structures corresponding to the 3:1 "resonance" between the particle turnover frequency and the wave oscillations frequency, thus confirming another prediction of the phase locking theory. In view of the generality of the arguments involved, we expect the importance of this structure-forming mechanism to go far beyond the realm of the laboratory-friendly thermocapillary flows.

Study of cyclic and steady particle motion in a realistic human airway model using phase-Doppler anemometry

Science.gov (United States)

Jedelský, Jan; Lízal, František; Jícha, Miroslav

2012-04-01

Transport and deposition of particles in human airways has been of research interest for many years. Various experimental methods such as constant temperature anemometry, particle image velocimetry and laser-Doppler based techniques were employed for study of aerosol transport in the past. We use Phase-Doppler Particle Analyser (P/DPA) for time resolved size and velocity measurement of liquid aerosol particles in a size range 1 to 8 μm. The di-2ethylhexyl sabacate (DEHS) particles were produced by condensation monodisperse aerosol generator. A thin-wall transparent model of human airways with non-symmetric bifurcations and non-planar geometry containing parts from throat to 3rd-4th generation of bronchi was fabricated for the study. Several cyclic (sinusoidal) breathing regimes were simulated using pneumatic breathing mechanism. Analogous steady-flow regimes were also investigated and used for comparison. An analysis of the particle velocity data was performed with aim to gain deeper understanding of the transport phenomena in the realistic bifurcating airway system. Flows of particles of different sizes in range 1 - 10 μm was found to slightly differ for extremely high Stokes numbers. Differences in steady and cyclic turbulence intensities were documented in the paper. Systematically higher turbulence intensity was found for cyclic flows and mainly in the expiration breathing phase. Negligible differences were found for behaviour of different particle size classes in the inspected range 1 to 8 μm. Possibility of velocity spectra estimation of air flow using the P/DPA data is discussed.

Study of cyclic and steady particle motion in a realistic human airway model using phase-Doppler anemometry

Directory of Open Access Journals (Sweden)

Jícha Miroslav

2012-04-01

Full Text Available Transport and deposition of particles in human airways has been of research interest for many years. Various experimental methods such as constant temperature anemometry, particle image velocimetry and laser-Doppler based techniques were employed for study of aerosol transport in the past. We use Phase-Doppler Particle Analyser (P/DPA for time resolved size and velocity measurement of liquid aerosol particles in a size range 1 to 8 μm. The di-2ethylhexyl sabacate (DEHS particles were produced by condensation monodisperse aerosol generator. A thin-wall transparent model of human airways with non-symmetric bifurcations and non-planar geometry containing parts from throat to 3rd-4th generation of bronchi was fabricated for the study. Several cyclic (sinusoidal breathing regimes were simulated using pneumatic breathing mechanism. Analogous steady-flow regimes were also investigated and used for comparison. An analysis of the particle velocity data was performed with aim to gain deeper understanding of the transport phenomena in the realistic bifurcating airway system. Flows of particles of different sizes in range 1 – 10 μm was found to slightly differ for extremely high Stokes numbers. Differences in steady and cyclic turbulence intensities were documented in the paper. Systematically higher turbulence intensity was found for cyclic flows and mainly in the expiration breathing phase. Negligible differences were found for behaviour of different particle size classes in the inspected range 1 to 8 μm. Possibility of velocity spectra estimation of air flow using the P/DPA data is discussed.

Particle size effect on formation and stability of β-La2Mo2O9 ionic conductor

International Nuclear Information System (INIS)

Rocha, R.A.; Muccillo, E.N.S.

2007-01-01

The La 2 Mo 2 O 9 compound was prepared by thermal crystallization from a mixed nitrate solution to obtain a precursor material with different particle size than that obtained by the conventional mixing of starting oxides. This precursor material was characterized by several techniques before and after thermal decomposition into the final compound. X-ray diffraction and electron microscopy results evidence the formation of the high-temperature β-La 2 Mo 2 O 9 phase after calcination at 550 deg. C . The well-known α-to-β phase transition was detected at temperatures lower than that for powders prepared from mixing of starting oxides. Electrical conductivity measurements at several oxygen partial pressures show that specimens prepared from nitrates have a different behavior when compared to those specimens obtained by the conventional route. The overall results reveal the role of particle size of the precursor material on phase transition and stability of sintered La 2 Mo 2 O 9

Application of colloidal chemistry in aqueous phase to the preparation of supported metallic catalysts: particles size and aggregation control; Application de la chimie colloidale en phase aqueuse a la preparation de catalyseurs metalliques supportes: controle de la taille et de l`etat d`agregation des particules

Energy Technology Data Exchange (ETDEWEB)

Pages, T.

1998-09-16

This work is an application of colloidal chemistry in aqueous phase on supported metal catalyst preparation. The objective is the control of particle size and aggregation. The preparation of the materials was achieved in two steps: - the synthesis of PdO hydrosols was obtained by two ways: neutralisation of the solution containing metallic salt by adding alkaline solution or by thermo-hydrolysis; the sols were then deposited on carriers (Al{sub 2}O{sub 3}, SIO{sub 2}). The use of partial charge model allowed us to determine the complexes that were able to generate PdO. The preparation of PdO from Pd(H{sub 2}O){sub 4}{sup 2+} was studied and a mechanism of oxide formation was elaborated. The neutralisation of Pd(H{sub 2}O){sub 4}{sup 2+} obtained by adding alkaline solution led to particles with an average size of 1.8 nm and a narrow particle size distribution. Only the thermo-hydrolysis of Pd(H{sub 2}O){sub 4}{sup 2+} led to particles which size is higher than 3.0 nm. In the last case, particle size is controlled by the precursor concentration (Pd(H{sub 2}O){sub 2}(OH){sub 2}) generated in the medium. We have demonstrated that particle aggregation in the sol depends on the Ph and the way of preparation. It can be controlled by adding complexing anions (Cl{sup -}, NO{sub 2}{sup -}). Concerning the deposition of sols on carriers, it led to isolated or aggregated particles according to experimental conditions. Particle size was not modified during the deposition. Moreover, in our experimental conditions, reduction of particles did not modify particle size and aggregation. An application of this original way of preparation on catalysis allowed us to demonstrate the interest of controlling particle size and aggregation. (author) 186 refs.

Nanoparticle growth by particle-phase chemistry

Directory of Open Access Journals (Sweden)

M. J. Apsokardu

2018-02-01

Full Text Available The ability of particle-phase chemistry to alter the molecular composition and enhance the growth rate of nanoparticles in the 2–100 nm diameter range is investigated through the use of a kinetic growth model. The molecular components included are sulfuric acid, ammonia, water, a non-volatile organic compound, and a semi-volatile organic compound. Molecular composition and growth rate are compared for particles that grow by partitioning alone vs. those that grow by a combination of partitioning and an accretion reaction in the particle phase between two organic molecules. Particle-phase chemistry causes a change in molecular composition that is particle diameter dependent, and when the reaction involves semi-volatile molecules, the particles grow faster than by partitioning alone. These effects are most pronounced for particles larger than about 20 nm in diameter. The modeling results provide a fundamental basis for understanding recent experimental measurements of the molecular composition of secondary organic aerosol showing that accretion reaction product formation increases linearly with increasing aerosol volume-to-surface-area. They also allow initial estimates of the reaction rate constants for these systems. For secondary aerosol produced by either OH oxidation of the cyclic dimethylsiloxane (D5 or ozonolysis of β-pinene, oligomerization rate constants on the order of 10−3 to 10−1 M−1 s−1 are needed to explain the experimental results. These values are consistent with previously measured rate constants for reactions of hydroperoxides and/or peroxyacids in the condensed phase.

Effects of WC Particle Size and Co Content on the Graded Structure in Functionally Gradient WC-Co Composites

Directory of Open Access Journals (Sweden)

Yuan Yigao

2016-01-01

Full Text Available Functionally gradient WC-Co composites having a Co depleted surface zone and not comprising the h phase can be manufactured via carburizing process. During carburizing, besides carburizing process parameters, the microstructural parameters of WC-Co materials, such as WC grain size and Co content, also have significant influences on the formation of Co gradient structure. In this study, the effects of WC particle size and Co content on the gradient structure within gradient hardmetals have been studied, based on a series of carburizing experiments of WC-Co materials with different WC particle sizes and cobalt contents. The results show that both the thickness and the amplitude of the gradients within gradient WC-Co materials increase with increasing initial WC particle size and Co content of WC-Co alloys. The reason for this finding is discussed.

[Ultrafine particle number concentration and size distribution of vehicle exhaust ultrafine particles].

Science.gov (United States)

Lu, Ye-qiang; Chen, Qiu-fang; Sun, Zai; Cai, Zhi-liang; Yang, Wen-jun

2014-09-01

Ultrafine particle (UFP) number concentrations obtained from three different vehicles were measured using fast mobility particle sizer (FMPS) and automobile exhaust gas analyzer. UFP number concentration and size distribution were studied at different idle driving speeds. The results showed that at a low idle speed of 800 rmin-1 , the emission particle number concentration was the lowest and showed a increasing trend with the increase of idle speed. The majority of exhaust particles were in Nuclear mode and Aitken mode. The peak sizes were dominated by 10 nm and 50 nm. Particle number concentration showed a significantly sharp increase during the vehicle acceleration process, and was then kept stable when the speed was stable. In the range of 0. 4 m axial distance from the end of the exhaust pipe, the particle number concentration decayed rapidly after dilution, but it was not obvious in the range of 0. 4-1 m. The number concentration was larger than the background concentration. Concentration of exhaust emissions such as CO, HC and NO showed a reducing trend with the increase of idle speed,which was in contrast to the emission trend of particle number concentration.

Sizes of particles formed during municipal wastewater treatment.

Science.gov (United States)

Lech, Smoczynski; Marta, Kosobucka; Michal, Smoczynski; Harsha, Ratnaweera; Krystyna, Pieczulis-Smoczynska

2017-02-01

Volumetric diameters Dv and specific surface area SpS of sludge particles formed during chemical coagulation and electrocoagulation of sewage were determined. The obtained aggregate-flocs differed substantially in both Dv and SpS values. The differences in Dv and SpS values of the analyzed particles were interpreted based on theoretical models for expanding aggregates. The most uniform particles were formed under exposure to: (a) optimal and maximal doses of PIX, (b) optimal doses of PAX, (c) maximal doses of the Al electro-coagulant. The lowest PIX dose produced the least uniform particles. Sludge aggregates-particles produced under exposure to minimal doses of PIX and the Al electro-coagulant were characterized by the lowest SpS values. Sludge particles coagulated by PAX and the particles formed at higher doses of PIX and the Al electro-coagulant had higher SpS values. The particles formed at all doses of the applied coagulants and electro-coagulants were generally classified into two size ranges: the main range and the secondary range. Most particles belonged to the main size range. An increase in the percentage of colloidal hydroxide particles in sewage sludge increased SpS.

The Effect of Grain Size on Mechanical Instability in Single-Phase Li-Alloy Anodes

National Research Council Canada - National Science Library

Wolfenstine, Jeff

2000-01-01

.... The results of this study suggest that decreasing the particle and/or grain size is not a practical approach to solving the mechanical instability problem of single phase Li alloys that are intended to be used as anodes in Li-ion batteries.

Influence of the particle size on phase transformation temperatures of Ni-49at.%Ti shape memory alloy powders

International Nuclear Information System (INIS)

Anselmo, George Carlos. S.; Castro, Walman B. de; Araujo, Carlos Jose de

2009-01-01

It is important to control the martensitic transformation start temperature (Ms) of Ti-Ni alloys because it determines the temperature range over which the shape memory effect and superelasticity appear. Powder metallurgy (PM) is known to provide the possibility of material saving and automated fabrication of at least semi-finished products as well as net-shape components for NiTi alloys. In this study powder with different particle sizes was subjected by gas atomization. The evolution of the control the martensitic transformation start temperature (Ms) was studied by differential scanning calorimetry. The effect of the particle size of powders on the transformation temperatures behaviors was discussed. (author)

Concentration and size distribution of particles in abstracted groundwater

NARCIS (Netherlands)

Van Beek, C.G.E.M.; de Zwart, A.H.; Balemans, M.; Kooiman, J.W.; van Rosmalen, C.; Timmer, H.; Vandersluys, J.; Stuijfzand, P.J.

2010-01-01

Particle number concentrations have been counted and particle size distributions calculated in groundwater derived by abstraction wells. Both concentration and size distribution are governed by the discharge rate: the higher this rate the higher the concentration and the higher the proportion of

Contact freezing of supercooled cloud droplets on collision with mineral dust particles: effect of particle size

Science.gov (United States)

Hoffmann, Nadine; Duft, Denis; Kiselev, Alexei; Leisner, Thomas

2013-04-01

The contact freezing of supercooled cloud droplets is one of the potentially important and the least investigated heterogeneous mechanism of ice formation in the tropospheric clouds [1]. On the time scales of cloud lifetime the freezing of supercooled water droplets via contact mechanism may occur at higher temperature compared to the same IN immersed in the droplet. However, the laboratory experiments of contact freezing are very challenging due to the number of factors affecting the probability of ice formation. In our experiment we study single water droplets freely levitated in the laminar flow of mineral dust particles acting as the contact freezing nuclei. By repeating the freezing experiment sufficient number of times we are able to reproduce statistical freezing behavior of large ensembles of supercooled droplets and measure the average rate of freezing events. We show that the rate of freezing at given temperature is governed only by the rate of droplet -particle collision and by the properties of the contact ice nuclei. In this contribution we investigate the relationship between the freezing probability and the size of mineral dust particle (represented by illite) and show that their IN efficiency scales with the particle size. Based on this observation, we discuss the similarity between the freezing of supercooled water droplets in immersion and contact modes and possible mechanisms of apparent enhancement of the contact freezing efficiency. [1] - K.C. Young, The role of contact nucleation in ice phase initiation in clouds, Journal of the Atmospheric Sciences 31, 1974

Size-dependent photodegradation of CdS particles deposited onto TiO{sub 2} mesoporous films by SILAR method

Energy Technology Data Exchange (ETDEWEB)

Ahmed, Rasin; Will, Geoffrey; Bell, John; Wang Hongxia, E-mail: hx.wang@qut.edu.au [Queensland University of Technology, School of Chemistry, Physics and Mechanical Engineering (Australia)

2012-09-15

The particle size, size distribution and photostability of CdS nanoparticles incorporated onto mesoporous TiO{sub 2} films by a successive ionic layer adsorption and reaction (SILAR) method were investigated by Raman spectroscopy, UV-Visible spectroscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). High-resolution TEM indicated that the synthesized CdS particles were hexagonal phase and the particle sizes were less than 5 nm for up to nine SILAR deposition cycles. Quantum size effect was found with the CdS-sensitized TiO{sub 2} films prepared with up to nine SILAR cycles. The band gap of CdS nanoparticles decreased from 2.65 to 2.37 eV with the increase of the SILAR cycles from 1 to 11. The investigation of the stability of the CdS/TiO{sub 2} films in air under illumination (440.6 {mu}W/cm{sup 2}) showed that the photodegradation rate was up to 85 % per day for the sample prepared with three SILAR cycles. XPS analysis indicated that the photodegradation was due to the oxidation of CdS, leading to the transformation from sulphide to sulphate (CdSO{sub 4}). Furthermore, the degradation rate was strongly dependent upon the particle size of CdS. Smaller particles showed faster degradation rate. The size-dependent photo-induced oxidization was rationalized with the variation of size-dependent distribution of surface atoms of CdS particles. Molecular dynamics-based theoretical calculation has indicated that the surface sulphide anion of a large CdS particle such as CdS made with 11 cycles (CdS Multiplication-Sign 11, average particle size = 5.6 nm) accounts for 9.6 % of the material whereas this value is increased to 19.2 % for (CdS Multiplication-Sign 3)-based smaller particles (average particle size = 2.7 nm). The photostability of CdS nanoparticles was significantly enhanced when coated with ZnS particles deposited with four SILAR cycles. The growth mechanism of ZnS upon CdS nanoparticles was discussed.

Effects of fuel particle size distributions on neutron transport in stochastic media

International Nuclear Information System (INIS)

Liang, Chao; Pavlou, Andrew T.; Ji, Wei

2014-01-01

Highlights: • Effects of fuel particle size distributions on neutron transport are evaluated. • Neutron channeling is identified as the fundamental reason for the effects. • The effects are noticeable at low packing and low optical thickness systems. • Unit cells of realistic reactor designs are studied for different size particles. • Fuel particle size distribution effects are not negligible in realistic designs. - Abstract: This paper presents a study of the fuel particle size distribution effects on neutron transport in three-dimensional stochastic media. Particle fuel is used in gas-cooled nuclear reactor designs and innovative light water reactor designs loaded with accident tolerant fuel. Due to the design requirements and fuel fabrication limits, the size of fuel particles may not be perfectly constant but instead follows a certain distribution. This brings a fundamental question to the radiation transport computation community: how does the fuel particle size distribution affect the neutron transport in particle fuel systems? To answer this question, size distribution effects and their physical interpretations are investigated by performing a series of neutron transport simulations at different fuel particle size distributions. An eigenvalue problem is simulated in a cylindrical container consisting of fissile fuel particles with five different size distributions: constant, uniform, power, exponential and Gaussian. A total of 15 parametric cases are constructed by altering the fissile particle volume packing fraction and its optical thickness, but keeping the mean chord length of the spherical fuel particle the same at different size distributions. The tallied effective multiplication factor (k eff ) and the spatial distribution of fission power density along axial and radial directions are compared between different size distributions. At low packing fraction and low optical thickness, the size distribution shows a noticeable effect on neutron

Effect of Particle Size Distribution on Slurry Rheology: Nuclear Waste Simulant Slurries

International Nuclear Information System (INIS)

Chun, Jaehun; Oh, Takkeun; Luna, Maria L.; Schweiger, Michael J.

2011-01-01

Controlling the rheological properties of slurries has been of great interest in various industries such as cosmetics, ceramic processing, and nuclear waste treatment. Many physicochemical parameters, such as particle size, pH, ionic strength, and mass/volume fraction of particles, can influence the rheological properties of slurry. Among such parameters, the particle size distribution of slurry would be especially important for nuclear waste treatment because most nuclear waste slurries show a broad particle size distribution. We studied the rheological properties of several different low activity waste nuclear simulant slurries having different particle size distributions under high salt and high pH conditions. Using rheological and particle size analysis, it was found that the percentage of colloid-sized particles in slurry appears to be a key factor for rheological characteristics and the efficiency of rheological modifiers. This behavior was shown to be coupled with an existing electrostatic interaction between particles under a low salt concentration. Our study suggests that one may need to implement the particle size distribution as a critical factor to understand and control rheological properties in nuclear waste treatment plants, such as the U.S. Department of Energy's Hanford and Savannah River sites, because the particle size distributions significantly vary over different types of nuclear waste slurries.

Heterogeneous oxidation of saturated organic aerosols by hydroxyl radicals: uptake kinetics, condensed-phase products, and particle size change

Directory of Open Access Journals (Sweden)

I. J. George

2007-08-01

Full Text Available The kinetics and reaction mechanism for the heterogeneous oxidation of saturated organic aerosols by gas-phase OH radicals were investigated under NO_x-free conditions. The reaction of 150 nm diameter Bis(2-ethylhexyl sebacate (BES particles with OH was studied as a proxy for chemical aging of atmospheric aerosols containing saturated organic matter. An aerosol reactor flow tube combined with an Aerodyne time-of-flight aerosol mass spectrometer (ToF-AMS and scanning mobility particle sizer (SMPS was used to study this system. Hydroxyl radicals were produced by 254 nm photolysis of O₃ in the presence of water vapour. The kinetics of the heterogeneous oxidation of the BES particles was studied by monitoring the loss of a mass fragment of BES with the ToF-AMS as a function of OH exposure. We measured an initial OH uptake coefficient of γ₀=1.3 (±0.4, confirming that this reaction is highly efficient. The density of BES particles increased by up to 20% of the original BES particle density at the highest OH exposure studied, consistent with the particle becoming more oxidized. Electrospray ionization mass spectrometry analysis showed that the major particle-phase reaction products are multifunctional carbonyls and alcohols with higher molecular weights than the starting material. Volatilization of oxidation products accounted for a maximum of 17% decrease of the particle volume at the highest OH exposure studied. Tropospheric organic aerosols will become more oxidized from heterogeneous photochemical oxidation, which may affect not only their physical and chemical properties, but also their hygroscopicity and cloud nucleation activity.

Research on bimodal particle extinction coefficient during Brownian coagulation and condensation for the entire particle size regime

International Nuclear Information System (INIS)

Tang Hong; Lin Jianzhong

2011-01-01

The extinction coefficient of atmospheric aerosol particles influences the earth’s radiation balance directly or indirectly, and it can be determined by the scattering and absorption characteristics of aerosol particles. The problem of estimating the change of extinction coefficient due to time evolution of bimodal particle size distribution is studied, and two improved methods for calculating the Brownian coagulation coefficient and the condensation growth rate are proposed, respectively. Through the improved method based on Otto kernel, the Brownian coagulation coefficient can be expressed simply in powers of particle volume for the entire particle size regime based on the fitted polynomials of the mean enhancement function. Meanwhile, the improved method based on Fuchs–Sutugin kernel is developed to obtain the condensation growth rate for the entire particle size regime. And then, the change of the overall extinction coefficient of bimodal distributions undergoing Brownian coagulation and condensation can be estimated comprehensively for the entire particle size regime. Simulation experiments indicate that the extinction coefficients obtained with the improved methods coincide fairly well with the true values, which provide a simple, reliable, and general method to estimate the change of extinction coefficient for the entire particle size regime during the bimodal particle dynamic processes.

Size-based sorting of micro-particles using microbubble streaming

Science.gov (United States)

Wang, Cheng; Jalikop, Shreyas; Hilgenfeldt, Sascha

2009-11-01

Oscillating microbubbles driven by ultrasound have shown great potential in microfluidic applications, such as transporting particles and promoting mixing [1-3]. The oscillations generate secondary steady streaming that can also trap particles. We use the streaming to develop a method of sorting particles of different sizes in an initially well-mixed solution. The solution is fed into a channel consisting of bubbles placed periodically along a side wall. When the bubbles are excited by an ultrasound piezo-electric transducer to produce steady streaming, the flow field is altered by the presence of the particles. This effect is dependent on particle size and results in size-based sorting of the particles. The effectiveness of the separation depends on the dimensions of the bubbles and particles as well as on the ultrasound frequency. Our experimental studies are aimed at a better understanding of the design and control of effective microfluidic separating devices. Ref: [1] P. Marmottant and S. Hilgenfeldt, Nature 423, 153 (2003). [2] P. Marmottant and S. Hilgenfeldt, Proc. Natl. Acad. Science USA, 101, 9523 (2004). [3] P. Marmottant, J.-P. Raven, H. Gardeniers, J. G. Bomer, and S. Hilgenfeldt, J. Fluid Mech., vol.568, 109 (2006).

The effect of particle shape and size distribution on the acoustical properties of mixtures of hemp particles.

Science.gov (United States)

Glé, Philippe; Gourdon, Emmanuel; Arnaud, Laurent; Horoshenkov, Kirill-V; Khan, Amir

2013-12-01

Hemp concrete is an attractive alternative to traditional materials used in building construction. It has a very low environmental impact, and it is characterized by high thermal insulation. Hemp aggregate particles are parallelepiped in shape and can be organized in a plurality of ways to create a considerable proportion of open pores with a complex connectivity pattern, the acoustical properties of which have never been examined systematically. Therefore this paper is focused on the fundamental understanding of the relations between the particle shape and size distribution, pore size distribution, and the acoustical properties of the resultant porous material mixture. The sound absorption and the transmission loss of various hemp aggregates is characterized using laboratory experiments and three theoretical models. These models are used to relate the particle size distribution to the pore size distribution. It is shown that the shape of particles and particle size control the pore size distribution and tortuosity in shiv. These properties in turn relate directly to the observed acoustical behavior.

Thermodynamic-Controlled Gas Phase Process for the Synthesis of Nickel Nanoparticles of Adjustable Size and Morphology

International Nuclear Information System (INIS)

Kauffeldt, Elena; Kauffeldt, Thomas

2006-01-01

Gas phase processes are a successful route for the synthesis of nano materials. Nickel particles are used in applications ranging from catalysis to nano electronics and energy storage. The application field defines the required particle size, morphology, crystallinity and purity. Nickel tetracarbonyl is the most promising precursor for the synthesis of high purity nickel particles. Due to the toxicity of this precursor and to obtain an optimal process control we developed a two-step flow type process. Nickel carbonyl and nickel particles are synthesized in a sequence of reactions. The particles are formed in a hot wall reactor at temperatures below 400 deg. C in different gas compositions. Varying the process conditions enables the adjustment of the particle size in a range from 3 to 140 nm. The controllable crystalline habits are polycrystalline, single crystals or multiple twinned particles (MTP). Spectroscopic investigations show an excellent purity. We report about the process and first investigations of the properties of the synthesized nickel nanomaterial

Method for rapid particle size analysis by hydrosizing and nuclear sensing

International Nuclear Information System (INIS)

Daellenbach, C.B.; Mahan, W.M.

1977-01-01

A method and apparatus to practice the method for rapidly determining the size and mass distribution of a sample of randomly sized particles of a known total mass are described. A series of substantially identical hydrocyclones are connected by conduits to each other and to a temperature controlled water feed. By restricting the cross-sectional areas of these conduits to progressively smaller values, the slurry containing the sample particles is caused to increase its velocity as it moves from hydrocyclone to hydrocyclone. As described by the Stokesian theory which relates particle diameter and settling velocity, the largest sized particles are suspended in the closed apex of the first hydrocyclone with smaller sized particles, in given size ranges, being suspended in the next succeeding hydrocyclone's apexes. In this manner, the particles are separated into discrete fractional sizes with a residual slurry of the very smallest particles being discharged. Before the discrete fractions of particles are suspended in their hydrocyclone apexes, a combined photon source, like a gamma ray source, and detector are calibrated with the water temperature kept constant. When the suspension of particles takes place, an attenuation of the radiation from the source is observed at the detector. This attenuation can be related to the mass or weight of the discrete fractions of suspended particles. Electronic circuitry is used to indicate what this fractional mass or weight is as it relates to the total weight of the sample. 6 claims, 4 figs

Particle size distribution of plutonium contaminated soil

International Nuclear Information System (INIS)

Zeng Ke; Wu Wangsuo; Jin Yuren; Shen Maoquan; Han Zhaoyang; Hu Zhiqian; Ma Teqi

2012-01-01

Wet classification and γ ray spectroscopy had been applied to study the particle size distribution of Pu in the desert soil of somewhere in Northern China. It was found that nearly 90% of Pu exits in 0.1-10 mm particles. only 10% less in particles under 0.05 mm that still poses notable hazards to biosphere if any resuspension. Providing a decontamination target of 239 Pu <4000 Bq/kg, accident condition. (authors)

An absorbing phase transition from a structured active particle phase

Energy Technology Data Exchange (ETDEWEB)

Lopez, Cristobal [Instituto Mediterraneo de Estudios Avanzados IMEDEA (CSIC-UIB), Campus de la Universidad de las Islas Baleares, E-07122 Palma de Mallorca (Spain); Ramos, Francisco [Departamento de Electromagnetismo y Fisica de la Materia and Instituto de Fisica Teorica y Computacional Carlos I, Facultad de Ciencias, Universidad de Granada, 18071 Granada (Spain); Hernandez-GarcIa, Emilio [Instituto Mediterraneo de Estudios Avanzados IMEDEA (CSIC-UIB), Campus de la Universidad de las Islas Baleares, E-07122 Palma de Mallorca (Spain)

2007-02-14

In this work we study the absorbing state phase transition of a recently introduced model for interacting particles with neighbourhood-dependent reproduction rates. The novelty of the transition is that as soon as the active phase is reached by increasing a control parameter a periodically arranged structure of particle clusters appears. A numerical study in one and two dimensions shows that the system falls into the directed percolation universality class.

Relationship between dioxin concentration and particle size for suspended sediment

Energy Technology Data Exchange (ETDEWEB)

Kitamura, K.; Sakurai, T.; Choi, J.W.; Suzuki, N.; Morita, M. [National Inst. for Environmental Studies, Tsukuba (Japan)

2004-09-15

The purpose of the present study was to find out how the amounts of adsorbed dioxins, i.e., polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/Fs), mono-ortho-polychlorinated biphenyls (PCBs) and non-ortho-PCBs, vary with the particle size of suspended sediment. As dioxins are hydrophobic, they tend to adsorb onto particles suspended in water, and the determination of which dioxin congeners readily dissolve in water or adsorb onto particles is central to the characterization of dioxin behavior in water/sediment systems. Presumably suspension of sediments and the size of the particles govern the transfer of dioxins to aquatic organisms. Therefore, in the present study, we investigated the relationship between the amount of dioxins and the particle-size distribution of resuspended, rather than settled, sediment.

Size-resolved particle emission factors for individual ships

Science.gov (United States)

Jonsson, Åsa M.; Westerlund, Jonathan; Hallquist, Mattias

2011-07-01

In these experiments size-resolved emission factors for particle number (EFPN) and mass (EFPM) have been determined for 734 individual ship passages for real-world dilution. The method used is an extractive sampling method of the passing ship plumes where particle number/mass and CO2 were measured with high time resolution (1 Hz). The measurements were conducted on a small island located in the entrance to the port of Gothenburg (N57.6849, E11.838), the largest harbor in Scandinavia. This is an emission control area (ECA) and in close vicinity to populated areas. The average EFPN and EFPM were 2.55 ± 0.11 × 1016 (kg fuel)-1 and 2050 ± 110 mg (kg fuel)-1, respectively. The determined EF for ships with multiple passages showed a great reproducibility. Size-resolved EFPN were peaking at small particle sizes ˜35 nm. Smaller particle sizes and hence less mass were observed by a gas turbine equipped ship compared to diesel engine equipped ships. On average 36 to 46% of the emitted particles by number were non-volatile and 24% by mass (EFPN 1.16 ± 0.19 × 1016 [kg fuel]-1 and EFPM 488 ± 73 mg [kg fuel]-1, respectively). This study shows a great potential to gain large data-sets regarding ship emission determining parameters that can improve current dispersion modeling for health assessments on local and regional scales. The global contributions of total and non-volatile particle mass from shipping using this extensive data-set from an ECA were estimated to be at least 0.80 Tgy-1 and 0.19 Tgy-1.

Size-selective separation of submicron particles in suspensions with ultrasonic atomization.

Science.gov (United States)

Nii, Susumu; Oka, Naoyoshi

2014-11-01

Aqueous suspensions containing silica or polystyrene latex were ultrasonically atomized for separating particles of a specific size. With the help of a fog involving fine liquid droplets with a narrow size distribution, submicron particles in a limited size-range were successfully separated from suspensions. Performance of the separation was characterized by analyzing the size and the concentration of collected particles with a high resolution method. Irradiation of 2.4MHz ultrasound to sample suspensions allowed the separation of particles of specific size from 90 to 320nm without regarding the type of material. Addition of a small amount of nonionic surfactant, PONPE20 to SiO2 suspensions enhanced the collection of finer particles, and achieved a remarkable increase in the number of collected particles. Degassing of the sample suspension resulted in eliminating the separation performance. Dissolved air in suspensions plays an important role in this separation. Copyright © 2014 Elsevier B.V. All rights reserved.

Soot particle size measurements in ethylene diffusion flames at elevated pressures

KAUST Repository

Steinmetz, Scott

2016-05-07

Soot particle size is investigated in laminar nitrogen-diluted ethylene coflow diffusion flames at 4, 8, 12 and 16 atm. Line of sight attenuation and scattering are used to measure two-dimensional soot volume fraction and particle size fields for the first time at elevated pressures. Soot volume fraction dependence on pressure is consistent with the observations of similar studies, scaling approximately with the square of pressure. Scattering intensity is analyzed through Rayleigh and Rayleigh-Debye-Gans polydisperse fractal aggregate theories to provide two estimates of particle size. An increase in overall particle sizes with pressure is found, consistent with similar one-dimensional studies. Particle diameters in the annulus of the flame increase faster with pressure than those on centerline. Contrary to previous studies, the dependence of particle size on pressure was found to taper off between 8 and 12 atm, with little observed growth beyond 12 atm. The measurements provide additional data for one of the International Sooting Flame (ISF) workshop\\'s target pressurized flames.

submitter Phase transition observations and discrimination of small cloud particles by light polarization in expansion chamber experiments

CERN Document Server

Nichman, Leonid; Järvinen, Emma; Ignatius, Karoliina; Höppel, Niko Florian; Dias, Antonio; Heinritzi, Martin; Simon, Mario; Tröstl, Jasmin; Wagner, Andrea Christine; Wagner, Robert; Williamson, Christina; Yan, Chao; Connolly, Paul James; Dorsey, James Robert; Duplissy, Jonathan; Ehrhart, Sebastian; Frege, Carla; Gordon, Hamish; Hoyle, Christopher Robert; Kristensen, Thomas Bjerring; Steiner, Gerhard; McPherson Donahue, Neil; Flagan, Richard; Gallagher, Martin William; Kirkby, Jasper; Möhler, Ottmar; Saathoff, Harald; Schnaiter, Martin; Stratmann, Frank; Tomé, António

2016-01-01

Cloud microphysical processes involving the ice phase in tropospheric clouds are among the major uncertainties in cloud formation, weather, and general circulation models. The detection of aerosol particles, liquid droplets, and ice crystals, especially in the small cloud particle-size range below 50 μm, remains challenging in mixed phase, often unstable environments. The Cloud Aerosol Spectrometer with Polarization (CASPOL) is an airborne instrument that has the ability to detect such small cloud particles and measure the variability in polarization state of their backscattered light. Here we operate the versatile Cosmics Leaving OUtdoor Droplets (CLOUD) chamber facility at the European Organization for Nuclear Research (CERN) to produce controlled mixed phase and other clouds by adiabatic expansions in an ultraclean environment, and use the CASPOL to discriminate between different aerosols, water, and ice particles. In this paper, optical property measurements of mixed-phase clouds and viscous secondary ...

Online differentiation of mineral phase in aerosol particles by ion formation mechanism using a LAAP-TOF single-particle mass spectrometer

Science.gov (United States)

Marsden, Nicholas A.; Flynn, Michael J.; Allan, James D.; Coe, Hugh

2018-01-01

Mineralogy of silicate mineral dust has a strong influence on climate and ecosystems due to variation in physiochemical properties that result from differences in composition and crystal structure (mineral phase). Traditional offline methods of analysing mineral phase are labour intensive and the temporal resolution of the data is much longer than many atmospheric processes. Single-particle mass spectrometry (SPMS) is an established technique for the online size-resolved measurement of particle composition by laser desorption ionisation (LDI) followed by time-of-flight mass spectrometry (TOF-MS). Although non-quantitative, the technique is able to identify the presence of silicate minerals in airborne dust particles from markers of alkali metals and silicate molecular ions in the mass spectra. However, the differentiation of mineral phase in silicate particles by traditional mass spectral peak area measurements is not possible. This is because instrument function and matrix effects in the ionisation process result in variations in instrument response that are greater than the differences in composition between common mineral phases.In this study, we introduce a novel technique that enables the differentiation of mineral phase in silicate mineral particles by ion formation mechanism measured from subtle changes in ion arrival times at the TOF-MS detector. Using a combination of peak area and peak centroid measurements, we show that the arrangement of the interstitial alkali metals in the crystal structure, an important property in silicate mineralogy, influences the ion arrival times of elemental and molecular ion species in the negative ion mass spectra. A classification scheme is presented that allowed for the differentiation of illite-smectite, kaolinite and feldspar minerals on a single-particle basis. Online analysis of mineral dust aerosol generated from clay mineral standards produced mineral fractions that are in agreement with bulk measurements reported by

Improved soil particle-size analysis by gamma-ray attenuation

International Nuclear Information System (INIS)

Oliveira, J.C.M.; Vaz, C.M.P.; Reichardt, K.; Swartzendruber, D.

1997-01-01

The size distribution of particles is useful for physical characterization of soil. This study was conducted to determine whether a new method of soil particle-size analysis by gamma-ray attenuation could be further improved by changing the depth and time of measurement of the suspended particle concentration during sedimentation. In addition to the advantage of nondestructive, undisturbed measurement by gamma-ray attenuation, as compared with conventional pipette or hydrometer methods, the modifications here suggested and employed do substantially decrease the total time for analysis, and will also facilitate total automation and generalize the method for other sedimentation studies. Experimental results are presented for three different Brazilian soil materials, and illustrate the nature of the fine detail provided in the cumulative particle-size distribution as given by measurements obtained during the relatively short time period of 28 min

The impact of ice particle roughness on the scattering phase matrix

International Nuclear Information System (INIS)

Baum, Bryan A.; Yang Ping; Hu Yongxiang; Feng Qian

2010-01-01

The goal of this study is to explore the influence of ice particle habit (or shape) and surface roughness on the scattering phase matrix. As an example, reported here are the results for two wavelengths: 0.67 and 1.61 μm. For this effort, a database of single-scattering properties has been computed for a set of habits including hexagonal plates, hollow and solid columns, hollow and solid 3D bullet rosettes, droxtals, aggregates of solid columns, and aggregates of plates. The database provides properties for each of the habits at 101 wavelengths between 0.45 and 2.24 μm for smooth, moderately roughened, and severely roughened particles. At each wavelength, the scattering properties are provided at 233 discrete particle diameters ranging from 2 to 10,000 μm. A single particle size distribution from a very cold ice cloud sampled during the CRYSTAL-FACE field campaign (T cld =-76 o C) is used to illustrate the influence of habit and roughness on the phase matrix. In all, four different habit mixtures are evaluated. The nonzero elements of the phase matrix are shown to be quite sensitive to the assumed habit, particularly in the case of -P 12 /P 11 that is associated with the degree of linear polarization of scattered radiation. Surface roughness is shown to smooth out maxima in the scattering phase function and in the other elements of the phase matrix, consistent with other studies. To compare with the theoretical simulations of the phase matrix for smooth and roughened particles, a full year of cloud-aerosol lidar with orthogonal polarization (CALIOP) data from 2008 is analyzed to provide global statistics on the values of P 11 and P 22 /P 11 in the backscattering direction. In a comparison of two of the habit mixtures (one used for MODIS Collection 5 and another that incorporates new habits including hollow bullet rosettes and aggregates of plates) with the CALIOP data, the values for P 11 are higher regardless of the degree of particle surface roughness, and the

Influence of Particle Size in Talc Suppression by a Galactomannan Depressant

Directory of Open Access Journals (Sweden)

Zhixiang Chen

2018-03-01

Full Text Available Flotation behavior of different sizes of particles may follow different trends. The influence of particle size in talc suppression by a depressant galactomannan was studied in this research. The flotation response and mechanism were examined by flotation tests, modified flotation rate constant and entrainment recovery calculation, laser particle size experiments, adsorption tests, and advancing contact angle measurement as well as scanning electron microscopy (SEM and energy dispersive X-ray spectrometry (EDS. The maximum recovery increased with particle size increases in the absence of galactomannan FPY (Fenugreek polysaccharide. The obviously suppressed effect was observed for the size fraction of −74 + 38 μm after reacting with FPY, but low efficiency was received for −38 μm and −10 μm, respectively. Laser particle size analysis indicated that the FPY has a certain function for the flocculation of fine particles. It is beneficial for reducing recovery by entrainment. EDS and advancing contact angle test results showed that the difference in contact angles probably is a result of genuine differences in the quantity of O and Mg bearing surface species, while the contact angle varied with particle size fraction in the absence of FPY. Adsorption and SEM test results demonstrated that in the case of −74 + 38 μm, the depressant adsorption density on the mineral surface is higher than the other two size fractions. On the whole, FPY probably is not enough of a depressant for talc suppression.

Preparation of gold nanoparticles and determination of their particles size via different methods

International Nuclear Information System (INIS)

Iqbal, Muhammad; Usanase, Gisele; Oulmi, Kafia; Aberkane, Fairouz; Bendaikha, Tahar; Fessi, Hatem; Zine, Nadia; Agusti, Géraldine; Errachid, El-Salhi; Elaissari, Abdelhamid

2016-01-01

Graphical abstract: Preparation of gold nanoparticles via NaBH_4 reduction method, and determination of their particle size, size distribution and morphology by using different techniques. - Highlights: • Gold nanoparticles were synthesized by NaBH_4 reduction method. • Excess of reducing agent leads to tendency of aggregation. • The particle size, size distribution and morphology were investigated. • Particle size was determined both experimentally as well as theoretically. - Abstract: Gold nanoparticles have been used in various applications covering both electronics, biosensors, in vivo biomedical imaging and in vitro biomedical diagnosis. As a general requirement, gold nanoparticles should be prepared in large scale, easy to be functionalized by chemical compound of by specific ligands or biomolecules. In this study, gold nanoparticles were prepared by using different concentrations of reducing agent (NaBH_4) in various formulations and their effect on the particle size, size distribution and morphology was investigated. Moreover, special attention has been dedicated to comparison of particles size measured by various techniques, such as, light scattering, transmission electron microscopy, UV spectrum using standard curve and particles size calculated by using Mie theory and UV spectrum of gold nanoparticles dispersion. Particle size determined by various techniques can be correlated for monodispersed particles and excess of reducing agent leads to increase in the particle size.

Near surface illumination method to detect particle size information by optical calibration free remission measurements

Science.gov (United States)

Stocker, Sabrina; Foschum, Florian; Kienle, Alwin

2017-07-01

A calibration free method to detect particle size information is presented. A possible application for such measurements is the investigation of raw milk since there not only the fat and protein content varies but also the fat droplet size. The newly developed method is sensitive to the scattering phase function, which makes it applicable to many other applications, too. By simulating the light propagation by use of Monte Carlo simulations, a calibration free device can be developed from this principle.

Phase separation of self-propelled ballistic particles

Science.gov (United States)

Bruss, Isaac R.; Glotzer, Sharon C.

2018-04-01

Self-propelled particles phase-separate into coexisting dense and dilute regions above a critical density. The statistical nature of their stochastic motion lends itself to various theories that predict the onset of phase separation. However, these theories are ill-equipped to describe such behavior when noise becomes negligible. To overcome this limitation, we present a predictive model that relies on two density-dependent timescales: τF, the mean time particles spend between collisions; and τC, the mean lifetime of a collision. We show that only when τF<τC do collisions last long enough to develop a growing cluster and initiate phase separation. Using both analytical calculations and active particle simulations, we measure these timescales and determine the critical density for phase separation in both two and three dimensions.

Particle size-dependent radical generation from wildland fire smoke

International Nuclear Information System (INIS)

Leonard, Stephen S.; Castranova, Vince; Chen, Bean T.; Schwegler-Berry, Diane; Hoover, Mark; Piacitelli, Chris; Gaughan, Denise M.

2007-01-01

Firefighting, along with construction, mining and agriculture, ranks among the most dangerous occupations. In addition, the work environment of firefighters is unlike that of any other occupation, not only because of the obvious physical hazards but also due to the respiratory and systemic health hazards of smoke inhalation resulting from combustion. A significant amount of research has been devoted to studying municipal firefighters; however, these studies may not be useful in wildland firefighter exposures, because the two work environments are so different. Not only are wildland firefighters exposed to different combustion products, but their exposure profiles are different. The combustion products wildland firefighters are exposed to can vary greatly in characteristics due to the type and amount of material being burned, soil conditions, temperature and exposure time. Smoke inhalation is one of the greatest concerns for firefighter health and it has been shown that the smoke consists of a large number of particles. These smoke particles contain intermediates of hydrogen, carbon and oxygen free radicals, which may pose a potential health risk. Our investigation looked into the involvement of free radicals in smoke toxicity and the relationship between particle size and radical generation. Samples were collected in discrete aerodynamic particle sizes from a wildfire in Alaska, preserved and then shipped to our laboratory for analysis. Electron spin resonance was used to measure carbon-centered as well as hydroxyl radicals produced by a Fenton-like reaction with wildfire smoke. Further study of reactive oxygen species was conducted using analysis of cellular H 2 O 2 generation, lipid peroxidation of cellular membranes and DNA damage. Results demonstrate that coarse size-range particles contained more carbon radicals per unit mass than the ultrafine particles; however, the ultrafine particles generated more ·OH radicals in the acellular Fenton-like reaction. The

Cytotoxicity evaluation of ceramic particles of different sizes and shapes.

Science.gov (United States)

Yamamoto, Akiko; Honma, Rieko; Sumita, Masae; Hanawa, Takao

2004-02-01

When artificial hip or knee joints are implanted in the human body, they release metallic, ceramic, and polymeric debris into the surrounding tissues. The toxicity of the released particles is of two types: chemical, caused by the released soluble ions and monomers, and mechanical, a result of mechanical stimulation produced by the insoluble particles. In this study, the cytotoxicity of particles of TiO2, Al2O3, ZrO2, Si3N4, and SiC for murine fibroblasts and macrophages were examined to evaluate just their mechanical toxicity because these particles are not expected to release soluble metal ions. Different sizes and shapes of TiO2 particles were used to evaluate the effect of size and shape on particle cytotoxicity. The results suggest that the cytotoxicity of ceramic particles does not depend on their chemical species. Cytotoxicity levels were lower than those of corresponding metal ions, indicating that the mechanical toxicity of particles is lower than the chemical toxicity of released soluble ions and monomers. The differences in size did not affect the mechanical toxicity of these particles. The dendritic particles had a higher cytotoxicity level for macrophages than did spindle and spheric particles. Copyright 2003 Wiley Periodicals, Inc. J Biomed Mater Res 68A: 244-256, 2004

The influences of ambient particle composition and size on particle infiltration in Los Angeles, CA, residences.

Science.gov (United States)

Sarnat, Stefanie Ebelt; Coull, Brent A; Ruiz, Pablo A; Koutrakis, Petros; Suh, Helen H

2006-02-01

Particle infiltration is a key determinant of the indoor concentrations of ambient particles. Few studies have examined the influence of particle composition on infiltration, particularly in areas with high concentrations of volatile particles, such as ammonium nitrate (NH4NO3). A comprehensive indoor monitoring study was conducted in 17 Los Angeles-area homes. As part of this study, indoor/outdoor concentration ratios during overnight (nonindoor source) periods were used to estimate the fraction of ambient particles remaining airborne indoors, or the particle infiltration factor (FINF), for fine particles (PM2.5), its nonvolatile (i.e., black carbon [BC]) and volatile (i.e., nitrate [NO3-]) components, and particle sizes ranging between 0.02 and 10 microm. FINF was highest for BC (median = 0.84) and lowest for NO3- (median = 0.18). The low FINF for NO3- was likely because of volatilization of NO3- particles once indoors, in addition to depositional losses upon building entry. The FINF for PM2.5 (median = 0.48) fell between those for BC and NO3-, reflecting the contributions of both particle components to PM25. FINF varied with particle size, air-exchange rate, and outdoor NO3- concentrations. The FINF for particles between 0.7 and 2 microm in size was considerably lower during periods of high as compared with low outdoor NO3- concentrations, suggesting that outdoor NO3- particles were of this size. This study demonstrates that infiltration of PM2.5 varies by particle component and is lowest for volatile species, such as NH4NO3. Our results suggest that volatile particle components may influence the ability for outdoor PM concentrations to represent indoor and, thus, personal exposures to particles of ambient origin, because volatilization of these particles causes the composition of PM2.5 to differ indoors and outdoors. Consequently, particle composition likely influences observed epidemiologic relationships based on outdoor PM concentrations, especially in areas

Toxicogenomic analysis of the particle dose- and size-response relationship of silica particles-induced toxicity in mice

International Nuclear Information System (INIS)

Lu Xiaoyan; Jin Tingting; Jin Yachao; Wu Leihong; Hu Bin; Tian Yu; Fan Xiaohui

2013-01-01

This study investigated the relationship between particle size and toxicity of silica particles (SP) with diameters of 30, 70, and 300 nm, which is essential to the safe design and application of SP. Data obtained from histopathological examinations suggested that SP of these sizes can all induce acute inflammation in the liver. In vivo imaging showed that intravenously administrated SP are mainly present in the liver, spleen and intestinal tract. Interestingly, in gene expression analysis, the cellular response pathways activated in the liver are predominantly conserved independently of particle dose when the same size SP are administered or are conserved independently of particle size, surface area and particle number when nano- or submicro-sized SP are administered at their toxic doses. Meanwhile, integrated analysis of transcriptomics, previous metabonomics and conventional toxicological results support the view that SP can result in inflammatory and oxidative stress, generate mitochondrial dysfunction, and eventually cause hepatocyte necrosis by neutrophil-mediated liver injury. (paper)

Influence of particle size on physical and sensory attributes of mango pulp powder

Science.gov (United States)

Sharma, M.; Kadam, D. M.; Chadha, S.; Wilson, R. A.; Gupta, R. K.

2013-09-01

The present investigation was aimed to observe the effect of particle size on physical, sensory and thermal properties of foam-mat dried mango pulp powder. Mango pulp of Dussehri variety was foam-mat dried using 3% egg white at 65ºC. Dried foam-mats were pulverized and passed through a sieve shaker for obtaining three grades of powder with 50, 60, and 85 mesh size sieves. The particle size of these samples measured using laser diffraction particle size analyzer ranged from 191.26 to 296.19 μm. The data was analysed statistically using ANOVA of SAS. There was a linear increase in lightness (`L' value) with a decrease in particle size, however, `a' value decreased with a decrease in particle size, indicating the decrease in redness. An increase in bulk density and decrease in water solubility index and water absorption index % were observed with a decrease in particle size. Particle size had a significant effect on sensory parameters. Particle size in the range of 258.01 to 264.60μmwas found most acceptable with respect to sensory characteristics. This finding can be exploited for various commercial applicationswhere powder quality is dependent on the particle size and has foremost priority for end users.

Strategy for determination of an efficient Cochleate particle size.

Science.gov (United States)

Gil, Danay; Bracho, Gustavo; Zayas, Caridad; del Campo, Judith; Acevedo, Reinaldo; Toledo, Arturo; Lastre, Miriam; Pérez, Oliver

2006-04-12

Cochleate structures obtained from the outer membrane of Neisseria meningitidis serotype B have demonstrated to be high immunogenicity when administrated by intramuscular, oral or intranasal routes, and could be used as adjuvant and meningococcal nasal vaccine candidate. Due to the microparticulate nature of Cochleate it is necessary to control the particle size since it capture by cells of the immune system could be affected by this aspect. We combined optic microscopy and immunisation experiments to select the optimum particle size. Six different processes of producing Cochleate obtaining were evaluated and different mechanical stress conditions were carried out to homogenize and modulate the particles size. The more immunogenic particles were selected on the basis of the levels of specific IgA and IgG antibodies induced after intranasal immunisation in mice. The best treatment parameter for mechanical stress of the Cochleate was prolonged treatment with untrasonic low frequency waves.

A Lagrangian parcel based mixing plane method for calculating water based mixed phase particle flows in turbo-machinery

Science.gov (United States)

Bidwell, Colin S.

2015-05-01

A method for calculating particle transport through turbo-machinery using the mixing plane analogy was developed and used to analyze the energy efficient engine . This method allows the prediction of temperature and phase change of water based particles along their path and the impingement efficiency and particle impact property data on various components in the engine. This methodology was incorporated into the LEWICE3D V3.5 software. The method was used to predict particle transport in the low pressure compressor of the . The was developed by NASA and GE in the early 1980s as a technology demonstrator and is representative of a modern high bypass turbofan engine. The flow field was calculated using the NASA Glenn ADPAC turbo-machinery flow solver. Computations were performed for a Mach 0.8 cruise condition at 11,887 m assuming a standard warm day for ice particle sizes of 5, 20 and 100 microns and a free stream particle concentration of . The impingement efficiency results showed that as particle size increased average impingement efficiencies and scoop factors increased for the various components. The particle analysis also showed that the amount of mass entering the inner core decreased with increased particle size because the larger particles were less able to negotiate the turn into the inner core due to particle inertia. The particle phase change analysis results showed that the larger particles warmed less as they were transported through the low pressure compressor. Only the smallest 5 micron particles were warmed enough to produce melting with a maximum average melting fraction of 0.18. The results also showed an appreciable amount of particle sublimation and evaporation for the 5 micron particles entering the engine core (22.6 %).

Preparation of gold nanoparticles and determination of their particles size via different methods

Energy Technology Data Exchange (ETDEWEB)

Iqbal, Muhammad; Usanase, Gisele [University of Lyon, University Lyon-1, CNRS, UMR-5007, LAGEP, F-69622 Villeurbanne (France); Oulmi, Kafia; Aberkane, Fairouz; Bendaikha, Tahar [Laboratory of Chemistry and Environmental Chemistry(LCCE), Faculty of Science, Material Science Department, University of Batna, 05000 (Algeria); Fessi, Hatem [University of Lyon, University Lyon-1, CNRS, UMR-5007, LAGEP, F-69622 Villeurbanne (France); Zine, Nadia [Institut des Sciences Analytiques (ISA), Université Lyon, Université Claude Bernard Lyon-1, UMR-5180, 5 rue de la Doua, F-69100 Villeurbanne (France); Agusti, Géraldine [University of Lyon, University Lyon-1, CNRS, UMR-5007, LAGEP, F-69622 Villeurbanne (France); Errachid, El-Salhi [Institut des Sciences Analytiques (ISA), Université Lyon, Université Claude Bernard Lyon-1, UMR-5180, 5 rue de la Doua, F-69100 Villeurbanne (France); Elaissari, Abdelhamid, E-mail: elaissari@lagep.univ-lyon1.fr [University of Lyon, University Lyon-1, CNRS, UMR-5007, LAGEP, F-69622 Villeurbanne (France)

2016-07-15

Graphical abstract: Preparation of gold nanoparticles via NaBH{sub 4} reduction method, and determination of their particle size, size distribution and morphology by using different techniques. - Highlights: • Gold nanoparticles were synthesized by NaBH{sub 4} reduction method. • Excess of reducing agent leads to tendency of aggregation. • The particle size, size distribution and morphology were investigated. • Particle size was determined both experimentally as well as theoretically. - Abstract: Gold nanoparticles have been used in various applications covering both electronics, biosensors, in vivo biomedical imaging and in vitro biomedical diagnosis. As a general requirement, gold nanoparticles should be prepared in large scale, easy to be functionalized by chemical compound of by specific ligands or biomolecules. In this study, gold nanoparticles were prepared by using different concentrations of reducing agent (NaBH{sub 4}) in various formulations and their effect on the particle size, size distribution and morphology was investigated. Moreover, special attention has been dedicated to comparison of particles size measured by various techniques, such as, light scattering, transmission electron microscopy, UV spectrum using standard curve and particles size calculated by using Mie theory and UV spectrum of gold nanoparticles dispersion. Particle size determined by various techniques can be correlated for monodispersed particles and excess of reducing agent leads to increase in the particle size.

Size limits for rounding of volcanic ash particles heated by lightning

Science.gov (United States)

Wadsworth, Fabian B.; Vasseur, Jérémie; Llewellin, Edward W.; Genareau, Kimberly; Cimarelli, Corrado; Dingwell, Donald B.

2017-03-01

Volcanic ash particles can be remelted by the high temperatures induced in volcanic lightning discharges. The molten particles can round under surface tension then quench to produce glass spheres. Melting and rounding timescales for volcanic materials are strongly dependent on heating duration and peak temperature and are shorter for small particles than for large particles. Therefore, the size distribution of glass spheres recovered from ash deposits potentially record the short duration, high-temperature conditions of volcanic lightning discharges, which are hard to measure directly. We use a 1-D numerical solution to the heat equation to determine the timescales of heating and cooling of volcanic particles during and after rapid heating and compare these with the capillary timescale for rounding an angular particle. We define dimensionless parameters—capillary, Fourier, Stark, Biot, and Peclet numbers—to characterize the competition between heat transfer within the particle, heat transfer at the particle rim, and capillary motion, for particles of different sizes. We apply this framework to the lightning case and constrain a maximum size for ash particles susceptible to surface tension-driven rounding, as a function of lightning temperature and duration, and ash properties. The size limit agrees well with maximum sizes of glass spheres found in volcanic ash that has been subjected to lightning or experimental discharges, demonstrating that the approach that we develop can be used to obtain a first-order estimate of lightning conditions in volcanic plumes.

Role of the anisotropy in the interactions between nano- and micro-sized particles

OpenAIRE

Rovigatti, Lorenzo

2012-01-01

The present Thesis focuses on the thermodynamic and dynamic behaviour of anisotropically interacting colloids by means of theoretical and numerical techniques. Colloidal suspensions, i.e. micro-- and nano--sized particles dispersed in a continuous phase, are a topic of great interest in several fields, including material science, soft matter and biophysics. Common in everyday life in the form of soap, milk, cream, etc., colloids have been used for decades as models for atomic and molecula...

Synthesis of micro-sized polystyrene magnetic particles

International Nuclear Information System (INIS)

Neves, Juliete S.; Suarez, Paulo A.Z.; Umpierre, Alexandre P.; Machado, Fabricio; Souza Junior, Fernando G. de

2011-01-01

The present work illustrates the synthesis of spherical and micro-sized polystyrene magnetic particles by using a water-based suspension polymerization process to incorporate in situ surface modified superparamagnetic Fe 3 O 4 nanoparticles. The crystallite size of Fe 3 O 4 was determined to be equal to 7.7 nm, based on Scherrer's equation and XRD measurement. According to EDX analyses, Fe 3 O 4 / polystyrene nanocomposites particles show strong characteristic peaks Kα and Kβ of iron at the interval from 6.38 KeV to 7.04 KeV with an amount of iron in the samples equal to 98 %, indicating that the inorganic material dispersed in the polystyrene matrix is essentially Fe in the form of iron oxide (Fe 3 O 4 ). The obtained polymeric materials presented good magnetic behavior, indicating that the modified Fe 3 O 4 nanoparticles were successfully dispersed in the polystyrene particles. (author)

Solid-state 13C magic angle spinning NMR spectroscopy characterization of particle size structural variations in synthetic nanodiamonds

International Nuclear Information System (INIS)

Alam, Todd M.

2004-01-01

Solid-state 13 C magic angle spinning (MAS) NMR spectroscopy has been used to quantify the different carbon species observed in synthetically produced nanodiamonds. Two different diamond-like carbon species were observed using 13 C MAS NMR, which have been attributed to a highly ordered crystalline diamond phase and a disordered crystalline diamond phase. The relative ratio of these different diamond phases was found to vary with the particle size of the nanodiamond materials

Acoustophoretic separation of airborne millimeter-size particles by a Fresnel lens

Science.gov (United States)

Cicek, Ahmet; Korozlu, Nurettin; Adem Kaya, Olgun; Ulug, Bulent

2017-03-01

We numerically demonstrate acoustophoretic separation of spherical solid particles in air by means of an acoustic Fresnel lens. Beside gravitational and drag forces, freely-falling millimeter-size particles experience large acoustic radiation forces around the focus of the lens, where interplay of forces lead to differentiation of particle trajectories with respect to either size or material properties. Due to the strong acoustic field at the focus, radiation force can divert particles with source intensities significantly smaller than those required for acoustic levitation in a standing field. When the lens is designed to have a focal length of 100 mm at 25 kHz, finite-element method simulations reveal a sharp focus with a full-width at half-maximum of 0.5 wavelenghts and a field enhancement of 18 dB. Through numerical calculation of forces and simulation of particle trajectories, we demonstrate size-based separation of acrylic particles at a source sound pressure level of 153 dB such that particles with diameters larger than 0.5 mm are admitted into the central hole, whereas smaller particles are rejected. Besides, efficient separation of particles with similar acoustic properties such as polyethylene, polystyrene and acrylic particles of the same size is also demonstrated.

Ice Particle Transport Analysis With Phase Change for the E(sup 3) Turbofan Engine Using LEWICE3D Version 3.2

Science.gov (United States)

Bidwell, Colin, S.

2012-01-01

Ice Particle trajectory calculations with phase change were made for the Energy Efficient Engine (E(sup 3)) using the LEWICE3D Version 3.2 software. The particle trajectory computations were performed using the new Glenn Ice Particle Phase Change Model which has been incorporated into the LEWICE3D Version 3.2 software. The E(sup 3) was developed by NASA and GE in the early 1980 s as a technology demonstrator and is representative of a modern high bypass turbofan engine. The E(sup 3) flow field was calculated using the NASA Glenn ADPAC turbomachinery flow solver. Computations were performed for the low pressure compressor of the E(sup 3) for a Mach 0.8 cruise condition at 11,887 m assuming a standard warm day for ice particle sizes of 5, 20, and 100 microns and a free stream particle concentration of 0.3 g/cu m. The impingement efficiency results showed that as particle size increased average impingement efficiencies and scoop factors increased for the various components. The particle analysis also showed that the amount of mass entering the inner core decreased with increased particle size because the larger particles were less able to negotiate the turn into the inner core due to particle inertia. The particle phase change analysis results showed that the larger particles warmed less as they were transported through the low pressure compressor. Only the smallest 5 micron particles were warmed enough to produce melting and the amount of melting was relatively small with a maximum average melting fraction of 0.836. The results also showed an appreciable amount of particle sublimation and evaporation for the 5 micron particles entering the engine core (22 percent).

Experimental investigations on friction laws and dryout heat flux of particulate beds packed with multi-size spheres and irregular particles

International Nuclear Information System (INIS)

Li, Liangxing; Ma, Weimin

2011-01-01

This paper is concerned with reducing uncertainty in quantification of debris bed coolability in a hypothetical severe accident of light water reactors (LWRs). A test facility named POMECO-FL is constructed to investigate the friction laws of adiabatic single and two-phase flow in a particulate bed packed with multi-size spheres or irregular particles. The same types of particles were then loaded in the test section of the POMECO-HT facility to obtain the dryout heat flux of the volumetrically heated particulate bed. The POMECO-HT facility features a high power capacity (up to 2.1 MW/m 2 ) which enables coolability study on particulate bed with broad variations in porosity and particle diameters under both top-flooding and bottom-injection conditions. The results show that given the effective particle diameter obtained from single-phase flow through the packed bed with multi-size spheres or irregular particles, both the pressure drop and the dryout heat flux of two-phase flow through the bed can be predicted by the Reed model. The bottom injection of coolant increases the dryout heat flux significantly. Meanwhile, the elevation of the dryout position is moving upwards with increasing bottom-injection flowrate. The experimental data provides insights for interpretation of debris bed coolability, as well as high-quality data for validation of the coolability analysis models and codes. (author)

Electromagnetic wave absorption properties of composites with micro-sized magnetic particles dispersed in amorphous carbon

Energy Technology Data Exchange (ETDEWEB)

Li, Bin Peng [Research Center of Carbon Fiber, Key Laboratory for Liquid–Solid Structural Evolution and Processing of Materials of Ministry of Education, Shandong University, Jinan 250061 (China); Tianjin Binhai New Area Finance Bureau, Tianjin 300450 (China); Wang, Cheng Guo, E-mail: sduwangchg@gmail.com [Research Center of Carbon Fiber, Key Laboratory for Liquid–Solid Structural Evolution and Processing of Materials of Ministry of Education, Shandong University, Jinan 250061 (China); Wang, Wen [Norinco Group China North Material Science and Engineering Technology Group Corporation, Jinan 250031 (China); Yu, Mei Jie; Gao, Rui; Chen, Yang; Xiang Wang, Yan [Research Center of Carbon Fiber, Key Laboratory for Liquid–Solid Structural Evolution and Processing of Materials of Ministry of Education, Shandong University, Jinan 250061 (China)

2014-09-01

Composites with micro-sized magnetic particles dispersed in amorphous carbon were fabricated conveniently and economically by carbonizing polyacrylonitrile (PAN) fibers mixed with micro-sized iron particles under different temperatures. The composites were characterized by X-ray diffraction (XRD) and scanning electric microscope (SEM). The electromagnetic (EM) properties were measured by a vector network analyzer in the frequency range of 2–18 GHz based on which analog computations of EM wave absorption properties were carried out. The influences of temperature on phase composition and EM wave absorption properties were also investigated, indicating that the composites had good electromagnetic absorption properties with both electrical loss and magnetic loss. Effective reflection loss (RL<−10 dB) was observed in a large frequency range of 7.5–18 GHz with the absorber thickness of 2.0–3.0 mm for the paraffin samples with composite powders heated up to 750 °C and the minimum absorption peak around −40 dB appeared at approximately 10 GHz with matching thickness of 2.0 mm for the paraffin sample with composite powders heated up to 800 °C. - Highlights: • High-performance electromagnetic wave absorption materials were fabricated conveniently and economically. • The materials are composites with micro-sized magnetic particles dispersed in porous amorphous carbon. • The influences of temperature on phase composition and electromagnetic wave absorption properties were investigated. • The composites heated up to 750 °C and 800 °C had good electromagnetic wave absorption property.

Preparation and thermodynamic stability of micron-sized, monodisperse composite polymer particles of disc-like shapes by seeded dispersion polymerization.

Science.gov (United States)

Fujibayashi, Teruhisa; Okubo, Masayoshi

2007-07-17

Micron-sized, monodisperse composite polymer particles having "disc-like" and "polyhedral" shapes were prepared by seeded dispersion polymerization of 2-ethylhexylmethacrylate (EHMA) with 2.67-mum-sized polystyrene (PS) seed particles in methanol/water media in the presence of droplets of various saturated hydrocarbons and evaporation of the hydrocarbon after the polymerization. Such nonspherical shapes were based on the volume reduction due to the evaporation. The primary factors influencing the particle shape seemed to be the absorption rate of the hydrocarbon into the resulting PS/poly(EHMA)/hydrocarbon composite particles during the polymerization, which affected the viscosities and the volumes of the PS and poly(EHMA) phases. It was found that the morphological development during the polymerization was retarded at "hamburger-like" morphology, which is a precursor of the disc-like particle, although this morphology is a thermodynamically metastable state.

Online differentiation of mineral phase in aerosol particles by ion formation mechanism using a LAAP-TOF single-particle mass spectrometer

Directory of Open Access Journals (Sweden)

N. A. Marsden

2018-01-01

Full Text Available Mineralogy of silicate mineral dust has a strong influence on climate and ecosystems due to variation in physiochemical properties that result from differences in composition and crystal structure (mineral phase. Traditional offline methods of analysing mineral phase are labour intensive and the temporal resolution of the data is much longer than many atmospheric processes. Single-particle mass spectrometry (SPMS is an established technique for the online size-resolved measurement of particle composition by laser desorption ionisation (LDI followed by time-of-flight mass spectrometry (TOF-MS. Although non-quantitative, the technique is able to identify the presence of silicate minerals in airborne dust particles from markers of alkali metals and silicate molecular ions in the mass spectra. However, the differentiation of mineral phase in silicate particles by traditional mass spectral peak area measurements is not possible. This is because instrument function and matrix effects in the ionisation process result in variations in instrument response that are greater than the differences in composition between common mineral phases.In this study, we introduce a novel technique that enables the differentiation of mineral phase in silicate mineral particles by ion formation mechanism measured from subtle changes in ion arrival times at the TOF-MS detector. Using a combination of peak area and peak centroid measurements, we show that the arrangement of the interstitial alkali metals in the crystal structure, an important property in silicate mineralogy, influences the ion arrival times of elemental and molecular ion species in the negative ion mass spectra. A classification scheme is presented that allowed for the differentiation of illite–smectite, kaolinite and feldspar minerals on a single-particle basis. Online analysis of mineral dust aerosol generated from clay mineral standards produced mineral fractions that are in agreement with bulk

Combinative Particle Size Reduction Technologies for the Production of Drug Nanocrystals

Directory of Open Access Journals (Sweden)

Jaime Salazar

2014-01-01

Full Text Available Nanosizing is a suitable method to enhance the dissolution rate and therefore the bioavailability of poorly soluble drugs. The success of the particle size reduction processes depends on critical factors such as the employed technology, equipment, and drug physicochemical properties. High pressure homogenization and wet bead milling are standard comminution techniques that have been already employed to successfully formulate poorly soluble drugs and bring them to market. However, these techniques have limitations in their particle size reduction performance, such as long production times and the necessity of employing a micronized drug as the starting material. This review article discusses the development of combinative methods, such as the NANOEDGE, H 96, H 69, H 42, and CT technologies. These processes were developed to improve the particle size reduction effectiveness of the standard techniques. These novel technologies can combine bottom-up and/or top-down techniques in a two-step process. The combinative processes lead in general to improved particle size reduction effectiveness. Faster production of drug nanocrystals and smaller final mean particle sizes are among the main advantages. The combinative particle size reduction technologies are very useful formulation tools, and they will continue acquiring importance for the production of drug nanocrystals.

Rock sampling. [method for controlling particle size distribution

Science.gov (United States)

Blum, P. (Inventor)

1971-01-01

A method for sampling rock and other brittle materials and for controlling resultant particle sizes is described. The method involves cutting grooves in the rock surface to provide a grouping of parallel ridges and subsequently machining the ridges to provide a powder specimen. The machining step may comprise milling, drilling, lathe cutting or the like; but a planing step is advantageous. Control of the particle size distribution is effected primarily by changing the height and width of these ridges. This control exceeds that obtainable by conventional grinding.

Studies of particle drying using non-invasive Raman spectrometry and particle size analysis.

Science.gov (United States)

Hamilton, Peter; Littlejohn, David; Nordon, Alison; Sefcik, Jan; Slavin, Paul; Dallin, Paul; Andrews, John

2011-05-21

The evaporation of methanol from needle-shaped particles of cellobiose octaacetate (COA) has been studied directly in a jacketed vacuum drier using in situ measurements by Raman spectrometry. A design of experiments (DoE) approach was used to investigate the effects of three parameters (method of agitation, % solvent loss on drying and jacket temperature), with the intention of minimising the drying time and extent of particle attrition. Drying curves based on Raman signals for methanol and COA in the spectra of the wet particles indicated the end of drying and revealed three stages in the drying process that could be used to monitor the progress of solvent removal in real time. Off-line particle size measurements based on laser diffraction were made to obtain information on the extent of attrition, to compare with the trends revealed by the Raman drying curves. The study demonstrated that non-invasive Raman spectrometry can be used to study the progress of drying during agitation of particles in a vacuum drier, allowing optimisation of operating conditions to minimise attrition and reduce drying times. Although a correlation between particle size and off-line Raman measurements of COA was demonstrated, it was not possible to derive equivalent information from the in situ Raman spectra owing to the greater effects of particle motion or bulk density variations of the particles in the drier.

Characterization of spherical core–shell particles by static light scattering. Estimation of the core- and particle-size distributions

International Nuclear Information System (INIS)

Clementi, Luis A.; Vega, Jorge R.; Gugliotta, Luis M.; Quirantes, Arturo

2012-01-01

A numerical method is proposed for the characterization of core–shell spherical particles from static light scattering (SLS) measurements. The method is able to estimate the core size distribution (CSD) and the particle size distribution (PSD), through the following two-step procedure: (i) the estimation of the bivariate core–particle size distribution (C–PSD), by solving a linear ill-conditioned inverse problem through a generalized Tikhonov regularization strategy, and (ii) the calculation of the CSD and the PSD from the estimated C–PSD. First, the method was evaluated on the basis of several simulated examples, with polystyrene–poly(methyl methacrylate) core–shell particles of different CSDs and PSDs. Then, two samples of hematite–Yttrium basic carbonate core–shell particles were successfully characterized. In all analyzed examples, acceptable estimates of the PSD and the average diameter of the CSD were obtained. Based on the single-scattering Mie theory, the proposed method is an effective tool for characterizing core–shell colloidal particles larger than their Rayleigh limits without requiring any a-priori assumption on the shapes of the size distributions. Under such conditions, the PSDs can always be adequately estimated, while acceptable CSD estimates are obtained when the core/shell particles exhibit either a high optical contrast, or a moderate optical contrast but with a high ‘average core diameter’/‘average particle diameter’ ratio. -- Highlights: ► Particles with core–shell morphology are characterized by static light scattering. ► Core size distribution and particle size distribution are successfully estimated. ► Simulated and experimental examples are used to validate the numerical method. ► The positive effect of a large core/shell optical contrast is investigated. ► No a-priori assumption on the shapes of the size distributions is required.

Theory of flotation of small and medium-size particles

Science.gov (United States)

Derjaguin, B. V.; Dukhin, S. S.

1993-08-01

The paper describes a theory of flotation of small and medium-size particles less than 50μ in radius) when their precipitation on a bubble surface depends more on surface forces than on inertia forces, and deformation of the bubble due to collisions with the particles may be neglected. The approach of the mineral particle to the bubble surface is regarded as taking place in three stages corresponding to movement of the particles through zones 1, 2 and 3. Zone 3 is a liquid wetting layer of such thickness that a positive or negative disjoining pressure arises in this intervening layer between the particle and the bubble. By zone 2 is meant the diffusional boundary layer of the bubble. In zone 1, which comprises the entire liquid outside zone 2, there are no surface forces. Precipitation of the particles is calculated by considering the forces acting in zones 1, 2 and 3. The particles move through zone 1 under the action of gravity and inertia. Analysis of the movement of the particles under the action of these forces gives the critical particle size, below which contact with the bubble surface is impossible, if the surface forces acting in zones 2 and 3 be neglected. The forces acting in zone 2 are ‘diffusio-phoretic’ forces due to the concentration gradient in the diffusional boundary layer. The concentration and electric field intensity distribution in zone 2 is calculated, taking into account ion diffusion to the deformed bubble surface. An examination is made of the ‘equilibrium’ surface forces acting in zone 3 independent of whether the bubble is at rest or in motion. These forces, which determine the behaviour of the thin wetting intervening layer between the bubble and the mineral particle and the height of the force barrier against its rupture, may be represented as results of the disjoining pressure forces acting on various parts of the film. The main components of the disjoining pressure are van der Waals forces, forces of an iono

Current-induced transition from particle-by-particle to concurrent intercalation in phase-separating battery electrodes

KAUST Repository

Li, Yiyang; El Gabaly, Farid; Ferguson, Todd R.; Smith, Raymond B.; Bartelt, Norman C.; Sugar, Joshua D.; Fenton, Kyle R.; Cogswell, Daniel A.; Kilcoyne, A. L. David; Tyliszczak, Tolek; Bazant, Martin Z.; Chueh, William C.

2014-01-01

©2014 Macmillan Publishers Limited. All rights reserved. Many battery electrodes contain ensembles of nanoparticles that phase-separate on (de)intercalation. In such electrodes, the fraction of actively intercalating particles directly impacts cycle life: a vanishing population concentrates the current in a small number of particles, leading to current hotspots. Reports of the active particle population in the phase-separating electrode lithium iron phosphate (LiFePO 4; LFP) vary widely, ranging from near 0% (particle-by-particle) to 100% (concurrent intercalation). Using synchrotron-based X-ray microscopy, we probed the individual state-of-charge for over 3,000 LFP particles. We observed that the active population depends strongly on the cycling current, exhibiting particle-by-particle-like behaviour at low rates and increasingly concurrent behaviour at high rates, consistent with our phase-field porous electrode simulations. Contrary to intuition, the current density, or current per active internal surface area, is nearly invariant with the global electrode cycling rate. Rather, the electrode accommodates higher current by increasing the active particle population. This behaviour results from thermodynamic transformation barriers in LFP, and such a phenomenon probably extends to other phase-separating battery materials. We propose that modifying the transformation barrier and exchange current density can increase the active population and thus the current homogeneity. This could introduce new paradigms to enhance the cycle life of phase-separating battery electrodes.

Current-induced transition from particle-by-particle to concurrent intercalation in phase-separating battery electrodes.

Science.gov (United States)

Li, Yiyang; El Gabaly, Farid; Ferguson, Todd R; Smith, Raymond B; Bartelt, Norman C; Sugar, Joshua D; Fenton, Kyle R; Cogswell, Daniel A; Kilcoyne, A L David; Tyliszczak, Tolek; Bazant, Martin Z; Chueh, William C

2014-12-01

Many battery electrodes contain ensembles of nanoparticles that phase-separate on (de)intercalation. In such electrodes, the fraction of actively intercalating particles directly impacts cycle life: a vanishing population concentrates the current in a small number of particles, leading to current hotspots. Reports of the active particle population in the phase-separating electrode lithium iron phosphate (LiFePO4; LFP) vary widely, ranging from near 0% (particle-by-particle) to 100% (concurrent intercalation). Using synchrotron-based X-ray microscopy, we probed the individual state-of-charge for over 3,000 LFP particles. We observed that the active population depends strongly on the cycling current, exhibiting particle-by-particle-like behaviour at low rates and increasingly concurrent behaviour at high rates, consistent with our phase-field porous electrode simulations. Contrary to intuition, the current density, or current per active internal surface area, is nearly invariant with the global electrode cycling rate. Rather, the electrode accommodates higher current by increasing the active particle population. This behaviour results from thermodynamic transformation barriers in LFP, and such a phenomenon probably extends to other phase-separating battery materials. We propose that modifying the transformation barrier and exchange current density can increase the active population and thus the current homogeneity. This could introduce new paradigms to enhance the cycle life of phase-separating battery electrodes.

Current-induced transition from particle-by-particle to concurrent intercalation in phase-separating battery electrodes

KAUST Repository

Li, Yiyang

2014-09-14

©2014 Macmillan Publishers Limited. All rights reserved. Many battery electrodes contain ensembles of nanoparticles that phase-separate on (de)intercalation. In such electrodes, the fraction of actively intercalating particles directly impacts cycle life: a vanishing population concentrates the current in a small number of particles, leading to current hotspots. Reports of the active particle population in the phase-separating electrode lithium iron phosphate (LiFePO 4; LFP) vary widely, ranging from near 0% (particle-by-particle) to 100% (concurrent intercalation). Using synchrotron-based X-ray microscopy, we probed the individual state-of-charge for over 3,000 LFP particles. We observed that the active population depends strongly on the cycling current, exhibiting particle-by-particle-like behaviour at low rates and increasingly concurrent behaviour at high rates, consistent with our phase-field porous electrode simulations. Contrary to intuition, the current density, or current per active internal surface area, is nearly invariant with the global electrode cycling rate. Rather, the electrode accommodates higher current by increasing the active particle population. This behaviour results from thermodynamic transformation barriers in LFP, and such a phenomenon probably extends to other phase-separating battery materials. We propose that modifying the transformation barrier and exchange current density can increase the active population and thus the current homogeneity. This could introduce new paradigms to enhance the cycle life of phase-separating battery electrodes.

Study on effective particle diameters and coolability of particulate beds packed with irregular multi-size particles

Energy Technology Data Exchange (ETDEWEB)

Thakre, S.; Ma, W.; Kudinov, P.; Bechta, S. [Royal Institute of Technology, KTH. Div. of Nuclear Power Safety, Stockholm (Sweden)

2013-08-15

One of the key questions in severe accident research is the coolability of the debris bed, i.e., whether decay heat can be completely removed by the coolant flow into the debris bed. Extensive experimental and analytical work has been done to substantiate the coolability research. Most of the available experimental data is related to the beds packed with single size (mostly spherical) particles, and less data is available for multi-size/irregular-shape particles. There are several analytical models available, which rely on the mean particle diameter and porosity of the bed in their predictions. Two different types of particles were used to investigate coolability of particulate beds at VTT, Finland. The first type is irregular-shape Aluminum Oxide gravel particles whose sizes vary from 0.25 mm to 10 mm, which were employed in the STYX experiment programme (2001-2008). The second type is spherical beads of Zirconium silicate whose sizes vary between 0.8 mm to 1 mm, which were used in the COOLOCE tests (Takasuo et al., 2012) to study the effect of multi-dimensional flooding on coolability. In the present work, the two types of particles are used in the POMECO-FL and POMECO-HT test facility to obtain their effective particle diameters and dryout heat flux of the beds, respectively. The main idea is to check how the heaters' orientations (vertical in COOLOCE vs. horizontal in POMECO-HT) and diameters (6 mm in COOLOCE vs. 3 mm in POMECO-HT) affect the coolability (dryout heat flux) of the test beds. The tests carried out on the POMECO-FL facility using a bed packed with aluminum oxide gravel particles show the effective particle diameter of the gravel particles is 0.65 mm, by which the frictional pressure gradient can be predicted by the Ergun equation. After the water superficial velocity is higher than 0.0025 m/s, the pressure gradient is underestimated. The effective particle diameter of the zirconium particles is found as 0.8 mm. The dryout heat flux is measured on

Study on effective particle diameters and coolability of particulate beds packed with irregular multi-size particles

International Nuclear Information System (INIS)

Thakre, S.; Ma, W.; Kudinov, P.; Bechta, S.

2013-08-01

One of the key questions in severe accident research is the coolability of the debris bed, i.e., whether decay heat can be completely removed by the coolant flow into the debris bed. Extensive experimental and analytical work has been done to substantiate the coolability research. Most of the available experimental data is related to the beds packed with single size (mostly spherical) particles, and less data is available for multi-size/irregular-shape particles. There are several analytical models available, which rely on the mean particle diameter and porosity of the bed in their predictions. Two different types of particles were used to investigate coolability of particulate beds at VTT, Finland. The first type is irregular-shape Aluminum Oxide gravel particles whose sizes vary from 0.25 mm to 10 mm, which were employed in the STYX experiment programme (2001-2008). The second type is spherical beads of Zirconium silicate whose sizes vary between 0.8 mm to 1 mm, which were used in the COOLOCE tests (Takasuo et al., 2012) to study the effect of multi-dimensional flooding on coolability. In the present work, the two types of particles are used in the POMECO-FL and POMECO-HT test facility to obtain their effective particle diameters and dryout heat flux of the beds, respectively. The main idea is to check how the heaters' orientations (vertical in COOLOCE vs. horizontal in POMECO-HT) and diameters (6 mm in COOLOCE vs. 3 mm in POMECO-HT) affect the coolability (dryout heat flux) of the test beds. The tests carried out on the POMECO-FL facility using a bed packed with aluminum oxide gravel particles show the effective particle diameter of the gravel particles is 0.65 mm, by which the frictional pressure gradient can be predicted by the Ergun equation. After the water superficial velocity is higher than 0.0025 m/s, the pressure gradient is underestimated. The effective particle diameter of the zirconium particles is found as 0.8 mm. The dryout heat flux is measured on

Investigation of Composition of Particle Size in Sediments of Stormwater Sedimentation Tank

Directory of Open Access Journals (Sweden)

Daiva Laučytė

2011-04-01

Full Text Available The main object for the storm water runoff treatment is to remove suspended solids before the storm water runoff is discharged into surface waters. Therefore the sedimentation tank is the most often used treatment facility. In order to optimise the sedimentation, the tendency of particle size distribution in bottom sediments must be known. Two similar size storm water runoff sedimentation tanks in Vilnius city were selected for the analysis of the particle size distribution in sediments. The composite samples of drained storm water runoff sediments were collected at the sedimentation tanks located in the districts of Verkiai and Karoliniskes on the 2nd of June, 2008. The analyses of grain size distribution were performed according the standard ISO/TS 17892-4:2004. The results showed that the particles with the particle size of 1–2 mm were obtained up to 10 m from the inlet and the particles with the size of 0,01–0,05 mm mainly were obtained close to the outlet of sedimentation tank. It is recommended to divide the sedimentation tank in two parts in order to get proper management of sediments: the particles that size is 1–10 mm could be managed as waste from grit chambers and particles of smaller size could be managed as primary sludge.Article in Lithuanian

Effect of Finite Particle Size on Convergence of Point Particle Models in Euler-Lagrange Multiphase Dispersed Flow

Science.gov (United States)

Nili, Samaun; Park, Chanyoung; Haftka, Raphael T.; Kim, Nam H.; Balachandar, S.

2017-11-01

Point particle methods are extensively used in simulating Euler-Lagrange multiphase dispersed flow. When particles are much smaller than the Eulerian grid the point particle model is on firm theoretical ground. However, this standard approach of evaluating the gas-particle coupling at the particle center fails to converge as the Eulerian grid is reduced below particle size. We present an approach to model the interaction between particles and fluid for finite size particles that permits convergence. We use the generalized Faxen form to compute the force on a particle and compare the results against traditional point particle method. We apportion the different force components on the particle to fluid cells based on the fraction of particle volume or surface in the cell. The application is to a one-dimensional model of shock propagation through a particle-laden field at moderate volume fraction, where the convergence is achieved for a well-formulated force model and back coupling for finite size particles. Comparison with 3D direct fully resolved numerical simulations will be used to check if the approach also improves accuracy compared to the point particle model. Work supported by the U.S. Department of Energy, National Nuclear Security Administration, Advanced Simulation and Computing Program, as a Cooperative Agreement under the Predictive Science Academic Alliance Program, under Contract No. DE-NA0002378.

Influence of particle size in silo discharge

Directory of Open Access Journals (Sweden)

Gella Diego

2017-01-01

Full Text Available Recently Janda et al. [Phys. Rev. Lett. 108, 248001 (2012] reported an experimental study where it was measured the velocity and volume fraction fields of 1 mm diameter stainless steel beads in the exit of a two-dimensional silo. In that work, they proposed a new expression to predict the flow of granular media in silos which does not explicitly include the particle size as a parameter. Here, we study if effectively, there is not such influence of the particle size in the flux equations as well as investigate any possible effect in the velocity and volume fraction fields. To this end, we have performed high speed motion measurements of these magnitudes in a two-dimensional silo filled with 4 mm diameter beads of stainless steel, the same material than the previous works. A developed tracking program has been implemented to obtain at the same time both, the velocity and volume fraction. The final objective of this work has been to extend and generalize the theoretical framework of Janda et al. for all sizes of particles. We have found that the obtained functionalities are the same than in the 1 mm case, but the exponents and other fitting parameters are different.

Dust generation in powders: Effect of particle size distribution

Directory of Open Access Journals (Sweden)

Chakravarty Somik

2017-01-01

Full Text Available This study explores the relationship between the bulk and grain-scale properties of powders and dust generation. A vortex shaker dustiness tester was used to evaluate 8 calcium carbonate test powders with median particle sizes ranging from 2μm to 136μm. Respirable aerosols released from the powder samples were characterised by their particle number and mass concentrations. All the powder samples were found to release respirable fractions of dust particles which end up decreasing with time. The variation of powder dustiness as a function of the particle size distribution was analysed for the powders, which were classified into three groups based on the fraction of particles within the respirable range. The trends we observe might be due to the interplay of several mechanisms like de-agglomeration and attrition and their relative importance.

Synthesis and characterization of magnetic and non-magnetic core-shell polyepoxide micrometer-sized particles of narrow size distribution.

Science.gov (United States)

Omer-Mizrahi, Melany; Margel, Shlomo

2009-01-15

Core polystyrene microspheres of narrow size distribution were prepared by dispersion polymerization of styrene in a mixture of ethanol and 2-methoxy ethanol. Uniform polyglycidyl methacrylate/polystyrene core-shell micrometer-sized particles were prepared by emulsion polymerization at 73 degrees C of glycidyl methacrylate in the presence of the core polystyrene microspheres. Core-shell particles with different properties (size, surface morphology and composition) have been prepared by changing various parameters belonging to the above seeded emulsion polymerization process, e.g., volumes of the monomer glycidyl methacrylate and the crosslinker monomer ethylene glycol dimethacrylate. Magnetic Fe(3)O(4)/polyglycidyl methacrylate/polystyrene micrometer-sized particles were prepared by coating the former core-shell particles with magnetite nanoparticles via a nucleation and growth mechanism. Characterization of the various particles has been accomplished by routine methods such as light microscopy, SEM, FTIR, BET and magnetic measurements.

Automatic particle-size analysis of HTGR nuclear fuel microspheres

International Nuclear Information System (INIS)

Mack, J.E.

1977-01-01

An automatic particle-size analyzer (PSA) has been developed at ORNL for measuring and counting samples of nuclear fuel microspheres in the diameter range of 300 to 1000 μm at rates in excess of 2000 particles per minute, requiring no sample preparation. A light blockage technique is used in conjunction with a particle singularizer. Each particle in the sample is sized, and the information is accumulated by a multi-channel pulse height analyzer. The data are then transferred automatically to a computer for calculation of mean diameter, standard deviation, kurtosis, and skewness of the distribution. Entering the sample weight and pre-coating data permits calculation of particle density and the mean coating thickness and density. Following this nondestructive analysis, the sample is collected and returned to the process line or used for further analysis. The device has potential as an on-line quality control device in processes dealing with spherical or near-spherical particles where rapid analysis is required for process control

Phase- and size-controllable synthesis of hexagonal upconversion rare-earth fluoride nanocrystals through an oleic acid/ionic liquid two-phase system.

Science.gov (United States)

He, Meng; Huang, Peng; Zhang, Chunlei; Ma, Jiebing; He, Rong; Cui, Daxiang

2012-05-07

Herein, we introduce a facile, user- and environmentally friendly (n-octanol-induced) oleic acid (OA)/ionic liquid (IL) two-phase system for the phase- and size-controllable synthesis of water-soluble hexagonal rare earth (RE = La, Gd, and Y) fluoride nanocrystals with uniform morphologies (mainly spheres and elongated particles) and small sizes (size are discussed in detail. More importantly, the mechanism of the (n-octanol-induced) OA/IL two-phase system, the formation of the RE fluoride nanocrystals, and the distinctive size- and morphology-controlling capacity of the system are presented. BmimPF(6) is versatile in term of crystal-phase manipulation, size and shape maintenance, and providing water solubility in a one-step reaction. The luminescent properties of Er(3+)-, Ho(3+)-, and Tm(3+)-doped LaF(3), NaGdF(4), and NaYF(4) nanocrystals were also studied. It is worth noting that the as-prepared products can be directly dispersed in water due to the hydrophilic property of Bmim(+) (cationic part of the IL) as a capping agent. This advantageous feature has made the IL-capped products favorable in facile surface modifications, such as the classic Stober method. Finally, the cytotoxicity evaluation of NaYF(4):Yb,Er nanocrystals before and after silica coating was conducted for further biological applications. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Online single particle analysis of ice particle residuals from mountain-top mixed-phase clouds using laboratory derived particle type assignment

Science.gov (United States)

Schmidt, Susan; Schneider, Johannes; Klimach, Thomas; Mertes, Stephan; Schenk, Ludwig Paul; Kupiszewski, Piotr; Curtius, Joachim; Borrmann, Stephan

2017-01-01

In situ single particle analysis of ice particle residuals (IPRs) and out-of-cloud aerosol particles was conducted by means of laser ablation mass spectrometry during the intensive INUIT-JFJ/CLACE campaign at the high alpine research station Jungfraujoch (3580 m a.s.l.) in January-February 2013. During the 4-week campaign more than 70 000 out-of-cloud aerosol particles and 595 IPRs were analyzed covering a particle size diameter range from 100 nm to 3 µm. The IPRs were sampled during 273 h while the station was covered by mixed-phase clouds at ambient temperatures between -27 and -6 °C. The identification of particle types is based on laboratory studies of different types of biological, mineral and anthropogenic aerosol particles. The outcome of these laboratory studies was characteristic marker peaks for each investigated particle type. These marker peaks were applied to the field data. In the sampled IPRs we identified a larger number fraction of primary aerosol particles, like soil dust (13 ± 5 %) and minerals (11 ± 5 %), in comparison to out-of-cloud aerosol particles (2.4 ± 0.4 and 0.4 ± 0.1 %, respectively). Additionally, anthropogenic aerosol particles, such as particles from industrial emissions and lead-containing particles, were found to be more abundant in the IPRs than in the out-of-cloud aerosol. In the out-of-cloud aerosol we identified a large fraction of aged particles (31 ± 5 %), including organic material and secondary inorganics, whereas this particle type was much less abundant (2.7 ± 1.3 %) in the IPRs. In a selected subset of the data where a direct comparison between out-of-cloud aerosol particles and IPRs in air masses with similar origin was possible, a pronounced enhancement of biological particles was found in the IPRs.

Size-dependent multiple magnetic phases and exchange bias effect in hole-doped double perovskite La1.6Sr0.4NiMnO6

International Nuclear Information System (INIS)

Liu, Wenjie; Shi, Lei; Zhou, Shiming; Zhao, Jiyin; Li, Yang; Guo, Yuqiao

2014-01-01

La 1.6 Sr 0.4 NiMnO 6 nanoparticles of different sizes (18–150 nm) have been prepared by a sol–gel method, and the size effects on their magnetic properties are investigated. It is found that there is a ferromagnetic (FM) transition at T C  ∼ 245 K for the sample with particle size D ∼ 150 nm. As the particle size decreases, a spin glass (SG) transition appears at T G  ∼ 60 K and becomes more obvious. Meanwhile, the T C shifts to a lower temperature and the FM transition becomes indistinct. The size dependent saturation magnetization M S , which is in the range 0.78 ∼ 1.27 μ B /f.u., shows a non-monotonic variation with a maximum of 1.27 μ B /f.u. at the particle size D C  ∼ 42 nm. The exchange bias (EB) effect is clearly observed for D > 32 nm and becomes indistinct as D ⩽ 32 nm. As the particle size decreasing, the EB field H E decreases and becomes near nil at D C . Meanwhile, the coercive field H C first increases to a maximum at D C and then decreases. All the results indicate the coexistence of AFM APBs related to the anti-site disorders, FM domains, and SG phase in La 1.6 Sr 0.4 NiMnO 6 nanoparticles. The magnetic properties of the nanoparticles are understood by a complex core-shell model, i.e. both AFM APBs and FM domains coexist in the core, and the SG phase mainly resides on the surface (shell) of each particle, which reveals that the size effects on the FM phase, AFM APBs and surface SG phase in grain are different, even are opposite. The nanometer size effect is a crucial factor to influence the magnetic properties of La 1.6 Sr 0.4 NiMnO 6 nanoparticles. (paper)

Light absorption by coated nano-sized carbonaceous particles

Science.gov (United States)

Gangl, Martin; Kocifaj, Miroslav; Videen, Gorden; Horvath, Helmuth

The optical properties of strongly absorbing soot particles coated by transparent material are investigated experimentally and described by several modeling approaches. Soot is produced by spark discharge and passed through a Sinclair-La Mer generator where non-absorbing carnauba wax is condensed onto it to obtain internal soot-wax mixtures in a controlled way. Measurements of the extinction and volume scattering coefficient show an amplification of absorption by a factor of approximately 1.8. This behavior was described by different approaches of internally mixed materials for the modal diameters of the measured size distributions: concentric-sphere model, effective medium approximations and heterogeneous ellipsoids. The concentric-sphere model describes the absorption increase quantitatively; and hence, it is chosen to be applied to the entire particle population in the size distribution. The growth of the soot particles by condensing wax is described by a simplified growth model to estimate the different contributions of several soot particle diameters to the overall absorption cross-section.

Photometric imaging in particle size measurement and surface visualization.

Science.gov (United States)

Sandler, Niklas

2011-09-30

The aim of this paper is to give an insight into photometric particle sizing approaches, which differ from the typical particle size measurement of dispersed particles. These approaches can often be advantageous especially for samples that are moist or cohesive, when dispersion of particles is difficult or sometimes impossible. The main focus of this paper is in the use of photometric stereo imaging. The technique allows the reconstruction of three-dimensional images of objects using multiple light sources in illumination. The use of photometric techniques is demonstrated in at-line measurement of granules and on-line measurement during granulation and dry milling. Also, surface visualization and roughness measurements are briefly discussed. Copyright © 2010 Elsevier B.V. All rights reserved.

Particle Size Distributions in Chondritic Meteorites: Evidence for Pre-Planetesimal Histories

Science.gov (United States)

Simon, J. I.; Cuzzi, J. N.; McCain, K. A.; Cato, M. J.; Christoffersen, P. A.; Fisher, K. R.; Srinivasan, P.; Tait, A. W.; Olson, D. M.; Scargle, J. D.

2018-01-01

Magnesium-rich silicate chondrules and calcium-, aluminum-rich refractory inclusions (CAIs) are fundamental components of primitive chondritic meteorites. It has been suggested that concentration of these early-formed particles by nebular sorting processes may lead to accretion of planetesimals, the planetary bodies that represent the building blocks of the terrestrial planets. In this case, the size distributions of the particles may constrain the accretion process. Here we present new particle size distribution data for Northwest Africa 5717, a primitive ordinary chondrite (ungrouped 3.05) and the well-known carbonaceous chondrite Allende (CV3). Instead of the relatively narrow size distributions obtained in previous studies (Ebel et al., 2016; Friedrich et al., 2015; Paque and Cuzzi, 1997, and references therein), we observed broad size distributions for all particle types in both meteorites. Detailed microscopic image analysis of Allende shows differences in the size distributions of chondrule subtypes, but collectively these subpopulations comprise a composite "chondrule" size distribution that is similar to the broad size distribution found for CAIs. Also, we find accretionary 'dust' rims on only a subset (approximately 15-20 percent) of the chondrules contained in Allende, which indicates that subpopulations of chondrules experienced distinct histories prior to planetary accretion. For the rimmed subset, we find positive correlation between rim thickness and chondrule size. The remarkable similarity between the size distributions of various subgroups of particles, both with and without fine grained rims, implies a common size sorting process. Chondrite classification schemes, astrophysical disk models that predict a narrow chondrule size population and/or a common localized formation event, and conventional particle analysis methods must all be critically reevaluated. We support the idea that distinct "lithologies" in NWA 5717 are nebular aggregates of

Control over particle size distribution by autoclaving poloxamer-stabilized trimyristin nanodispersions

DEFF Research Database (Denmark)

Göke, Katrin; Roese, Elin; Arnold, Andreas

2016-01-01

Lipid nanoparticles are under investigation as delivery systems for poorly water-soluble drugs. The particle size in these dispersions strongly influences important pharmaceutical properties like biodistribution and drug loading capacity; it should be below 500 nm for direct injection into the bl......Lipid nanoparticles are under investigation as delivery systems for poorly water-soluble drugs. The particle size in these dispersions strongly influences important pharmaceutical properties like biodistribution and drug loading capacity; it should be below 500 nm for direct injection...... treatment thus seems to be a promising approach to achieve the desired narrow particle size distribution of such dispersions. Related to the lipid content, suspension particles needed more emulsifier for stabilization than emulsion droplets, and smaller particles more than larger ones....

Particle number size distributions in urban air before and after volatilisation

Directory of Open Access Journals (Sweden)

W. Birmili

2010-05-01

Full Text Available Aerosol particle number size distributions (size range 0.003–10 μm in the urban atmosphere of Augsburg (Germany were examined with respect to the governing anthropogenic sources and meteorological factors. The two-year average particle number concentration between November 2004 and November 2006 was 12 200 cm⁻³, i.e. similar to previous observations in other European cities. A seasonal analysis yielded twice the total particle number concentrations in winter as compared to summer as consequence of more frequent inversion situations and enhanced particulate emissions. The diurnal variations of particle number were shaped by a remarkable maximum in the morning during the peak traffic hours. After a mid-day decrease along with the onset of vertical mixing, an evening concentration maximum could frequently be observed, suggesting a re-stratification of the urban atmosphere. Overall, the mixed layer height turned out to be the most influential meteorological parameter on the particle size distribution. Its influence was even greater than that of the geographical origin of the prevailing synoptic-scale air mass.

Size distributions below 0.8 μm were also measured downstream of a thermodenuder (temperature: 300 °C, allowing to retrieve the volume concentration of non-volatile compounds. The balance of particle number upstream and downstream of the thermodenuder suggests that practically all particles >12 nm contain a non-volatile core while additional nucleation of particles smaller than 6 nm could be observed after the thermodenuder as an interfering artifact of the method. The good correlation between the non-volatile volume concentration and an independent measurement of the aerosol absorption coefficient (R²=0.9 suggests a close correspondence of the refractory and light-absorbing particle fractions. Using the "summation method", an average diameter ratio of particles before and after volatilisation could

Particle size, magnetic field, and blood velocity effects on particle retention in magnetic drug targeting.

Science.gov (United States)

Cherry, Erica M; Maxim, Peter G; Eaton, John K

2010-01-01

A physics-based model of a general magnetic drug targeting (MDT) system was developed with the goal of realizing the practical limitations of MDT when electromagnets are the source of the magnetic field. The simulation tracks magnetic particles subject to gravity, drag force, magnetic force, and hydrodynamic lift in specified flow fields and external magnetic field distributions. A model problem was analyzed to determine the effect of drug particle size, blood flow velocity, and magnetic field gradient strength on efficiency in holding particles stationary in a laminar Poiseuille flow modeling blood flow in a medium-sized artery. It was found that particle retention rate increased with increasing particle diameter and magnetic field gradient strength and decreased with increasing bulk flow velocity. The results suggest that MDT systems with electromagnets are unsuitable for use in small arteries because it is difficult to control particles smaller than about 20 microm in diameter.

Magnetic Properties of Nanometer-sized Crystalline and Amorphous Particles

DEFF Research Database (Denmark)

Mørup, Steen; Bødker, Franz; Hansen, Mikkel Fougt

1997-01-01

Amorphous transition metal-metalloid alloy particles can be prepared by chemical preparation techniques. We discuss the preparation of transition metal-boron and iron-carbon particles and their magnetic properties. Nanometer-sized particles of both crystalline and amorphous magnetic materials...... are superparamagnetic at finite temperatures. The temperature dependence of the superparamagnetic relaxation time and the influence of inter-particle interactions is discussed. Finally, some examples of studies of surface magnetization of alpha-Fe particles are presented....

Metal uptake by corn grown on media treated with particle-size fractionated biosolids

Energy Technology Data Exchange (ETDEWEB)

Chen, Weiping [Department of Environmental Sciences, University of California, Riverside, CA 92521 (United States)], E-mail: chenweip@yahoo.com.cn; Chang, Andrew C.; Wu, Laosheng [Department of Environmental Sciences, University of California, Riverside, CA 92521 (United States); Zhang, Yongsong [School of Environmental and Natural Resources Sciences, Zhejiang University, Hangzhou, Zhejiang, 31009 (China)

2008-03-15

Particle-size of biosolids may affect plant uptake of heavy metals when the biosolids are land applied. In this study, corn (Zea mays L.) was grown on sand media treated with biosolids to study how particle-size of biosolids affected the plant uptake of cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn). Two biosolids, the Nu-Earth biosolids and the Los Angeles biosolids, of dissimilar surface morphology were utilized. The former exhibited a porous and spongy structure and had considerably greater specific surface area than that of the latter, which was granular and blocky. The specific surface area of the Los Angeles biosolids was inversely proportional to its particle-size, while that of Nu-Earth biosolids did not change significantly with particle-size. For each biosolid, the metal concentrations were not affected by particle sizes. The biomass yields of plants grown on the treated media increased as the biosolid particle-size decreased, indicating that plant uptake of nutrients from biosolids was dependent on interactions at the root-biosolids interface. The effect of particle-size on a metal's availability to plants was element-specific. The uptake rate of Cd, Zn, Cu, and Ni was correlated with the surface area of the particles, i.e., smaller particles having higher specific area provided greater root-biosolids contact and resulted in enhanced uptake of Cd and Zn and slightly less increased uptake of Cu and Ni. The particle morphology of biosolids had limited influence on the plant tissue concentrations of Cr and Pb. For both types of biosolids, total metal uptake increased as biosolid particle-size decreased. Our research indicates that biosolid particle-size distribution plays a deciding role in plant uptake of heavy metals when they are land applied.

Stability of MC Carbide Particles Size in Creep Resisting Steels

Directory of Open Access Journals (Sweden)

Vodopivec, F.

2006-01-01

Full Text Available Theoretical analysis of the dependence microstructure creep rate. Discussion on the effects of carbide particles size and their distribution on the base of accelerated creep tests on a steel X20CrMoV121 tempered at 800 °C. Analysis of the stability of carbide particles size in terms of free energy of formation of the compound. Explanation of the different effect of VC and NbC particles on accelerated creep rate.

A low-cost, high-magnification imaging system for particle sizing applications

International Nuclear Information System (INIS)

Tipnis, Tanmay J; Lawson, Nicholas J; Tatam, Ralph P

2014-01-01

A low-cost imaging system for high magnification and high resolution was developed as an alternative to long-working-distance microscope-based systems, primarily for particle sizing applications. The imaging optics, comprising an inverted fixed focus lens coupled to a microscope objective, were able to provide a working distance of approximately 50 mm. The system magnification could be changed by using an appropriate microscope objective. Particle sizing was achieved using shadow-based techniques with the backlight illumination provided by a pulsed light-emitting diode light source. The images were analysed using commercial sizing software which gave the particle sizes and their distribution. A range of particles, from 6 to 8 µm to over 100 µm, was successfully measured with a minimum spatial resolution of approximately 2.5 µm. This system allowed measurement of a wide range of particles at a lower cost and improved operator safety without disturbing the flow. (technical design note)

Thermal and particle size distribution effects on the ferromagnetic resonance in magnetic fluids

International Nuclear Information System (INIS)

Marin, C.N.

2006-01-01

Thermal and particle size distribution effects on the ferromagnetic resonance of magnetic fluids were theoretically investigated, assuming negligible interparticle interactions and neglecting the viscosity of the carrier liquid. The model is based on the usual approach for the ferromagnetic resonance description of single-domain magnetic particle systems, which was amended in order to take into account the finite particle size effect, the particle size distribution and the orientation mobility of the particles within the magnetic fluid. Under these circumstances the shape of the resonance line, the resonance field and the line width are found to be strongly affected by the temperature and by the particle size distribution of magnetic fluids

Deformation Behavior of Sub-micron and Micron Sized Alumina Particles in Compression.

Energy Technology Data Exchange (ETDEWEB)

Sarobol, Pylin; Chandross, Michael E.; Carroll, Jay; Mook, William; Boyce, Brad; Kotula, Paul Gabriel; McKenzie, Bonnie Beth; Bufford, Daniel Charles; Hall, Aaron Christopher.

2014-09-01

The ability to integrate ceramics with other materials has been limited due to high temperature (>800degC) ceramic processing. Recently, researchers demonstrated a novel process , aerosol deposition (AD), to fabricate ceramic films at room temperature (RT). In this process, sub - micro n sized ceramic particles are accelerated by pressurized gas, impacted on the substrate, plastically deformed, and form a dense film under vacuum. This AD process eliminates high temperature processing thereby enabling new coatings and device integration, in which ceramics can be deposited on metals, plastics, and glass. However, k nowledge in fundamental mechanisms for ceramic particle s to deform and form a dense ceramic film is still needed and is essential in advancing this novel RT technology. In this wo rk, a combination of experimentation and atomistic simulation was used to determine the deformation behavior of sub - micron sized ceramic particle s ; this is the first fundamental step needed to explain coating formation in the AD process . High purity, singl e crystal, alpha alumina particles with nominal size s of 0.3 um and 3.0 um were examined. Particle characterization, using transmission electron microscopy (TEM ), showed that the 0.3 u m particles were relatively defect - free single crystals whereas 3.0 u m p articles were highly defective single crystals or particles contained low angle grain boundaries. Sub - micron sized Al 2 O 3 particles exhibited ductile failure in compression. In situ compression experiments showed 0.3um particles deformed plastically, fractured, and became polycrystalline. Moreover, dislocation activit y was observed within the se particles during compression . These sub - micron sized Al 2 O 3 particles exhibited large accum ulated strain (2 - 3 times those of micron - sized particles) before first fracture. I n agreement with the findings from experimentation , a tomistic simulation s of nano - Al 2 O 3 particles showed dislocation slip and

Structural, magnetic, and electrical properties of Gd-doped BiFeO3 nanoparticles with reduced particle size

International Nuclear Information System (INIS)

Lotey, Gurmeet Singh; Verma, N. K.

2012-01-01

Pure and Gd-doped BiFeO 3 nanoparticles have been synthesized by sol–gel method. The significant effects of size and Gd-doping on structural, electrical, and magnetic properties have been investigated. X-ray diffraction study reveals that the pure BiFeO 3 nanoparticles possess rhombohedral structure, but with 10% Gd-doping complete structural transformation from rhombohedral to orthorhombic has been observed. The particle size of pure and Gd-doped BiFeO 3 nanoparticles, calculated using Transmission electron microscopy, has been found to be in the range 25–15 nm. Pure and Gd-doped BiFeO 3 nanoparticles show ferromagnetic character, and the magnetization increases with decrease in particle size and increase in doping concentration. Scanning electron microscopy study reveals that grain size decreases with increase in Gd concentration. Well-saturated polarization versus electric field loop is observed for the doped samples. Leakage current density decreases by four orders by doping Gd in BiFeO 3 . The incorporation of Gd in BiFeO 3 enhances spin as well as electric polarization at room temperature. The possible origin of enhancement in these properties has been explained on the basis of dopant and its concentration, phase purity, small particle, and grain size.

Liquid crystal phase behaviour of attractive disc-like particles.

Science.gov (United States)

Wu, Liang; Jackson, George; Müller, Erich A

2013-08-08

We employ a generalized van der Waals-Onsager perturbation theory to construct a free energy functional capable of describing the thermodynamic properties and orientational order of the isotropic and nematic phases of attractive disc particles. The model mesogen is a hard (purely repulsive) cylindrical disc particle decorated with an anisotropic square-well attractive potential placed at the centre of mass. Even for isotropic attractive interactions, the resulting overall inter-particle potential is anisotropic, due to the orientation-dependent excluded volume of the underlying hard core. An algebraic equation of state for attractive disc particles is developed by adopting the Onsager trial function to characterize the orientational order in the nematic phase. The theory is then used to represent the fluid-phase behaviour (vapour-liquid, isotropic-nematic, and nematic-nematic) of the oblate attractive particles for varying values of the molecular aspect ratio and parameters of the attractive potential. When compared to the phase diagram of their athermal analogues, it is seen that the addition of an attractive interaction facilitates the formation of orientationally-ordered phases. Most interestingly, for certain aspect ratios, a coexistence between two anisotropic nematic phases is exhibited by the attractive disc-like fluids.

Feed particle size evaluation: conventional approach versus digital holography based image analysis

Directory of Open Access Journals (Sweden)

Vittorio Dell’Orto

2010-01-01

Full Text Available The aim of this study was to evaluate the application of image analysis approach based on digital holography in defining particle size in comparison with the sieve shaker method (sieving method as reference method. For this purpose ground corn meal was analyzed by a sieve shaker Retsch VS 1000 and by image analysis approach based on digital holography. Particle size from digital holography were compared with results obtained by screen (sieving analysis for each of size classes by a cumulative distribution plot. Comparison between particle size values obtained by sieving method and image analysis indicated that values were comparable in term of particle size information, introducing a potential application for digital holography and image analysis in feed industry.

Discrete element method modeling of the triboelectric charging of polyethylene particles: Can particle size distribution and segregation reduce the charging?

International Nuclear Information System (INIS)

Konopka, Ladislav; Kosek, Juraj

2015-01-01

Polyethylene particles of various sizes are present in industrial gas-dispersion reactors and downstream processing units. The contact of the particles with a device wall as well as the mutual particle collisions cause electrons on the particle surface to redistribute in the system. The undesirable triboelectric charging results in several operational problems and safety risks in industrial systems, for example in the fluidized-bed polymerization reactor. We studied the charging of polyethylene particles caused by the particle-particle interactions in gas. Our model employs the Discrete Element Method (DEM) describing the particle dynamics and incorporates the ‘Trapped Electron Approach’ as the physical basis for the considered charging mechanism. The model predicts the particle charge distribution for systems with various particle size distributions and various level of segregation. Simulation results are in a qualitative agreement with experimental observations of similar particulate systems specifically in two aspects: 1) Big particles tend to gain positive charge and small particles the negative one. 2) The wider the particle size distribution is, the more pronounced is the charging process. Our results suggest that not only the size distribution, but also the effect of the spatial segregation of the polyethylene particles significantly influence the resulting charge distribution ‘generated’ in the system. The level of particle segregation as well as the particle size distribution of polyethylene particles can be in practice adjusted by the choice of supported catalysts, by the conditions in the fluidized-bed polymerization reactor and by the fluid dynamics. We also attempt to predict how the reactor temperature affects the triboelectric charging of particles. (paper)

Influence of maize flour particle size on gluten-free breadmaking.

Science.gov (United States)

de la Hera, Esther; Talegón, María; Caballero, Pedro; Gómez, Manuel

2013-03-15

Maize, one of the suitable grains for coeliac consumption, is, together with rice, the most cultivated cereal in the world. However, the inclusion of maize flour in gluten-free bread is a minority and studies are scarce. This paper analyses the influence of different maize flour types and their particle sizes on the quality of two types of bread without gluten (80% and 110% water in the formulation) obtained from them. We also analysed the microstructure of the dough and its behaviour during the fermentation. Finer flours had a lower dough development during fermentation in all cases. Among the different types of flour, those whose microstructure revealed compact particles were those which had higher specific bread volume, especially when the particle size was greater. Among the formulations, the dough with more water gave breads with higher specific volume, an effect that was more important in more compact flours. The higher volume breads had lower values of hardness and resilience. The type of corn flour and mainly its particle size influence significantly the dough development of gluten-free bread during fermentation and therefore the final volume and texture of the breads obtained. The flours having coarser particle size are the most suitable for making gluten-free maize bread. © 2012 Society of Chemical Industry.

Viscous properties of ferrofluids containing both micrometer-size magnetic particles and fine needle-like particles

Energy Technology Data Exchange (ETDEWEB)

Ido, Yasushi, E-mail: ido.yasushi@nitech.ac.jp [Department of Electric and Mechanical Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya (Japan); Nishida, Hitoshi [Department of Electrical and Control Systems Engineering, National Institute of Technology, Toyama College, 13 Hongo-cho, Toyama (Japan); Iwamoto, Yuhiro [Department of Electric and Mechanical Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya (Japan); Yokoyama, Hiroki [KYB Corporation, 2-4-1 Hamamatsu-cho, Minato-ku, Tokyo (Japan)

2017-06-01

Ferrofluids containing both micrometer-size spherical magnetic particles and nanometer-size needle-like nonmagnetic hematite particles were newly produced. Average length of long axis of the needle-like nonmagnetic particles was 194 nm and the aspect ratio was 8.3. Shear stress and viscosity were measured using the rheometer with the additional equipment for viscosity measurements in the presence of magnetic field. When the total volume fraction of particles in the fluid is constant (0.30), there is the specific mixing ratio of the particles to increase viscosity of the fluid drastically in the absence of magnetic field due to the percolation phenomenon. The fluid of the specific mixing ratio shows solid-like behavior even in the absence of magnetic field. Mixing the needle-like nonmagnetic particles causes strong yield stress and strong viscous force in the presence of magnetic field. - Highlights: • Viscous properties of new magnetic functional fluids were studied experimentally. • The new fluids contain spherical magnetic particles and needle-like particles. • Percolation occurs in the fluid of specific mixing ratio of particles without field. • The fluid of the specific mixing ratio behaves like solid without field. • Mixing needle-like particles causes strong yield stress of the fluid in the field.

Micrometer-scale 3-D shape characterization of eight cements: Particle shape and cement chemistry, and the effect of particle shape on laser diffraction particle size measurement

International Nuclear Information System (INIS)

Erdogan, S.T.; Nie, X.; Stutzman, P.E.; Garboczi, E.J.

2010-01-01

Eight different portland cements were imaged on a synchrotron beam line at Brookhaven National Laboratory using X-ray microcomputed tomography at a voxel size of about 1 μm per cubic voxel edge. The particles ranged in size roughly between 10 μm and 100 μm. The shape and size of individual particles were computationally analyzed using spherical harmonic analysis. The particle shape difference between cements was small but significant, as judged by several different quantitative shape measures, including the particle length, width, and thickness distributions. It was found that the average shape of cement particles was closely correlated with the volume fraction of C 3 S (alite) and C 2 S (belite) making up the cement powder. It is shown that the non-spherical particle shape of the cements strongly influence laser diffraction results, at least in the sieve size range of 20 μm to 38 μm. Since laser diffraction particle size measurement is being increasingly used by the cement industry, while cement chemistry is always a main factor in cement production, these results could have important implications for how this kind of particle size measurement should be understood and used in the cement industry.

Ultrasound Assisted Particle Size Control by Continuous Seed Generation and Batch Growth

OpenAIRE

Jordens, Jeroen; Canini, Enio; Gielen, Bjorn; Van Gerven, Tom; Braeken, Leen

2017-01-01

Controlling particle size is essential for crystal quality in the chemical and pharmaceutical industry. Several articles illustrate the potential of ultrasound to tune this particle size during the crystallization process. This paper investigates how ultrasound can control the particle size distribution (PSD) of acetaminophen crystals by continuous seed generation in a tubular crystallizer followed by batch growth. It is demonstrated that the supersaturation ratio at which ultrasound starts s...

Neutron activation analysis of size-separated airborne dust particles, (2)

International Nuclear Information System (INIS)

Aoki, Atsushi; Ishii, Taka; Tomiyama, Tsuyoshi; Yamamoto, Isao.

1976-01-01

The size distribution of the component element concentration in particle floating matters contained in the atmosphere is related closely to atmospheric pollution. In this paper, the results of the neutron activation analysis and the measurement of size distribution of component element concentration are reported, which were carried out in Minami-ku, Kyoto, in May and November, 1975, by collecting airbone dust with Andersen air samples. The activation of samples was carried out with the research reactor in Kyoto University. The gamma-ray spectra of the samples were measured with a Ge(Li) semiconductor detector. The size distributions of Al, Sc, Th and Ti showed the similar pattern. The concentration of Zn was abnormally high as compared with that in other districts, and it is related to the local industry in this district. The size distribution of airborne dust usually follows the logarithmic normal distribution when it is not affected by atmospheric pollution. Accordingly, the size distribution of the concentration also follows the same distribution. The accumulated percentages of the concentrations of Al, Sc and Th fall on the same straight line, and it means that these elements were contained in the same particles as the components. Also it was decided that the particles of Al, Sc, Th, Fe and Ti were soil particles. (Kako, I.)

Saharan Dust Particle Size And Concentration Distribution In Central Ghana

Science.gov (United States)

Sunnu, A. K.

2010-12-01

A.K. Sunnu*, G. M. Afeti* and F. Resch+ *Department of Mechanical Engineering, Kwame Nkrumah University of Science and Technology (KNUST) Kumasi, Ghana. E-mail: albertsunnu@yahoo.com +Laboratoire Lepi, ISITV-Université du Sud Toulon-Var, 83162 La Valette cedex, France E-mail: resch@univ-tln.fr Keywords: Atmospheric aerosol; Saharan dust; Particle size distributions; Particle concentrations. Abstract The Saharan dust that is transported and deposited over many countries in the West African atmospheric environment (5°N), every year, during the months of November to March, known locally as the Harmattan season, have been studied over a 13-year period, between 1996 and 2009, using a location at Kumasi in central Ghana (6° 40'N, 1° 34'W) as the reference geographical point. The suspended Saharan dust particles were sampled by an optical particle counter, and the particle size distributions and concentrations were analysed. The counter gives the total dust loads as number of particles per unit volume of air. The optical particle counter used did not discriminate the smoke fractions (due to spontaneous bush fires during the dry season) from the Saharan dust. Within the particle size range measured (0.5 μm-25 μm.), the average inter-annual mean particle diameter, number and mass concentrations during the northern winter months of January and February were determined. The average daily number concentrations ranged from 15 particles/cm3 to 63 particles/cm3 with an average of 31 particles/cm3. The average daily mass concentrations ranged from 122 μg/m3 to 1344 μg/m3 with an average of 532 μg/m3. The measured particle concentrations outside the winter period were consistently less than 10 cm-3. The overall dust mean particle diameter, analyzed from the peak representative Harmattan periods over the 13-year period, ranged from 0.89 μm to 2.43 μm with an average of 1.5 μm ± 0.5. The particle size distributions exhibited the typical distribution pattern for

Correlating capacity and Li content in layered material for Li-ion battery using XRD and particle size distribution measurements

Science.gov (United States)

Al-Tabbakh, A. A. A.; Al-Zubaidi, A. B.; Kamarulzaman, N.

2016-03-01

A lithiated transition-metal oxide material was successfully synthesized by a combustion method for Li-ion battery. The material was characterized using thermogravimetric and particle size analyzers, scanning electron microscope and X-ray diffractometer. The calcined powders of the material exhibited a finite size distribution and a single phase of pure layered structure of space group Roverline{3} m . An innovative method was developed to calculate the material electrochemical capacity based on considerations of the crystal structure and contributions of Li ions from specified unit cells at the surfaces and in the interiors of the material particles. Results suggested that most of the Li ions contributing to the electrochemical current originated from the surface region of the material particles. It was possible to estimate the thickness of the most delithiated region near the particle surfaces at any delithiation depth accurately. Furthermore, results suggested that the core region of the particles remained electrochemically inaccessible in the conventional applied voltages. This result was justified by direct quantitative comparison of specific capacity values calculated from the particle size distribution with those measured experimentally. The present analysis is believed to be of some value for estimation of the failure mechanism in cathode compounds, thus assisting the development of Li-ion batteries.

The effect of reducing alfalfa haylage particle size on cows in early lactation.

Science.gov (United States)

Kononoff, P J; Heinrichs, A J

2003-04-01

The objective of this experiment was to evaluate effects of reducing forage particle size on cows in early lactation based on measurements of the Penn State Particle Separator (PSPS). Eight cannulated, multiparous cows averaging 19 +/- 4 d in milk and 642 +/- 45 kg BW were assigned to one of two 4 x 4 Latin Squares. During each of the 23-d periods, animals were offered one of four diets, which were chemically identical but included alfalfa haylage of different particle size; short (SH), mostly short (MSH), mostly long (MLG), and long (LG). Physically effective neutral detergent fiber (peNDF) was determined by measuring the amount of neutral detergent fiber retained on a 1.18 mm screen and was similar across diets (25.7, 26.2, 26.4, 26.7%) but the amount of particles >19.0 mm significantly decreased with decreasing particle size. Reducing haylage particle size increased dry matter intake linearly (23.3, 22.0, 20.9, 20.8 kg for SH, MSH, MLG, LG, respectively). Milk production and percentage fat did not differ across treatments averaging 35.5 +/- 0.68 kg milk and 3.32 +/- 0.67% fat, while a quadratic effect was observed for percent milk protein, with lowest values being observed for LG. A quadratic effect was observed for mean rumen pH (6.04, 6.15, 6.13, 6.09), while A:P ratio decreased linearly (2.75, 2.86, 2.88, 2.92) with decreasing particle size. Total time ruminating increased quadratically (467, 498, 486, 468 min/d), while time eating decreased linearly (262, 253, 298, 287 min/d) with decreasing particle size. Both eating and ruminating per unit of neutral detergent fiber intake decreased with reducing particle size (35.8, 36.7, 44.9, 45.6 min/kg; 19.9, 23.6, 23.5, 23.5 min/kg). Although chewing activity was closely related to forage particle size, effects on rumen pH were small, indicating factors other than particle size are critical in regulating pH when ration neutral detergent fiber met recommended levels. Feeding alfalfa haylage based rations of reduced

The effect of SiC particle size on the properties of Cu–SiC composites

International Nuclear Information System (INIS)

Celebi Efe, G.; Zeytin, S.; Bindal, C.

2012-01-01

Graphical abstract: The relative densities of Cu–SiC composites sintered at 700 °C for 2 h are ranged from 97.3% to 91.8% for SiC with 1 μm particle size and 97.5% to 95.2% for SiC with 5 μm particle size, microhardness of composites ranged from 143 to 167 HV for SiC having 1 μm particle size and 156–182 HVN for SiC having 5 μm particle size and the electrical conductivity of composites changed between 85.9% IACS and 55.7% IACS for SiC with 1 μm particle size, 87.9% IACS and 65.2%IACS for SiC with 5 μm particle size. It was found that electrical conductivity of composites containing SiC with 5 μm particle size is better than that of Cu–SiC composites containing SiC with particle size of 1 μm. Highlights: ► In this research, the effect of SiC particle size on some properties of Cu–SiC composites were investigated. ► The mechanical properties were improved. ► The electrical properties were obtained at desirable level. -- Abstract: SiC particulate-reinforced copper composites were prepared by powder metallurgy (PM) method and conventional atmospheric sintering. Scanning electron microscope (SEM), X-ray diffraction (XRD) techniques were used to characterize the sintered composites. The effect of SiC content and particle size on the relative density, hardness and electrical conductivity of composites were investigated. The relative densities of Cu–SiC composites sintered at 700 °C for 2 h are ranged from 97.3% to 91.8% for SiC with 1 μm particle size and from 97.5% to 95.2% for SiC with 5 μm particle size. Microhardness of composites ranged from 143 to 167 HV for SiC having 1 μm particle size and from 156 to 182 HV for SiC having 5 μm particle size. The electrical conductivity of composites changed between 85.9% IACS and 55.7% IACS for SiC with 1 μm particle size, between 87.9% IACS and 65.2% IACS for SiC with 5 μm particle size.

Particle size analysis in estimating the significance of airborne contamination

International Nuclear Information System (INIS)

1978-01-01

In this report information on pertinent methods and techniques for analysing particle size distributions is compiled. The principles underlying the measurement methods are described, and the merits of different methods in relation to the information being sought and to their usefulness in the laboratory and in the field are explained. Descriptions on sampling methods, gravitational and inertial particle separation methods, electrostatic sizing devices, diffusion batteries, optical sizing techniques and autoradiography are included. Finally, the report considers sampling for respirable activity and problems related to instrument calibration

Effect of annealing on particle size, microstructure and gas sensing properties of Mn substituted CoFe{sub 2}O{sub 4} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Kumar, E. Ranjith, E-mail: ranjueaswar@gmail.com [Department of Physics, Dr. NGP Institute of Technology, Coimbatore 641048, Tamil Nadu (India); Kamzin, A.S. [Ioffe Physical-Technical Institute, Russian Academy of Sciences, St. Petersburg 194021 (Russian Federation); Janani, K. [Department of Physics, Kongunadu Arts and Science College, Coimbatore, Tamil Nadu (India)

2016-11-01

Microstructure, morphological and gas sensor studies of Mn substituted cobalt ferrite nanoparticles synthesized by a simple evaporation method and auto- combustion method. The influence of heat treatment on phase and particle size of spinel ferrite nanoparticles were determined by X-ray diffraction and Mossbauer spectroscopy. The XRD study reveals that the lattice constant and crystallite size of the samples increases with the increase of annealing temperature. Last one was confirmed by Mossbauer data. The lowest size of particles of MnCoFe{sub 2}O{sub 4} (~3 nm) is obtained by auto combustion method. The spherical shaped nanoparticles are recorded by TEM. Furthermore, conductance response of Mn–Co ferrite nanomaterial was measured by exposing the material to reducing gas like liquefied petroleum gas (LPG) which showed a sensor response of ~0.19 at an optimum operating temperature of 250 °C. - Highlights: • ~3 nm sized particles were prepared by auto combustion method. • Mossbauer study was analyzed for different annealed samples. • The size of the particles increased with increasing annealing temperature.

Effect of particle size of granules on some mechanical properties of ...

African Journals Online (AJOL)

Solid dosage forms are invariably multiparticulate systems of heterogenous particle size distribution. The purpose of this study was to investigate the effect of particle size distribution of paracetamol granules on some tablet mechanical properties of paracetamol tablets. Granules were formed by wet massing paracetamol ...

On airborne nano/micro-sized wear particles released from low-metallic automotive brakes

International Nuclear Information System (INIS)

Kukutschova, Jana; Moravec, Pavel; Tomasek, Vladimir; Matejka, Vlastimil; Smolik, Jiri; Schwarz, Jaroslav; Seidlerova, Jana; Safarova, Klara; Filip, Peter

2011-01-01

The paper addresses the wear particles released from commercially available 'low-metallic' automotive brake pads subjected to brake dynamometer tests. Particle size distribution was measured in situ and the generated particles were collected. The collected fractions and the original bulk material were analyzed using several chemical and microscopic techniques. The experiments demonstrated that airborne wear particles with sizes between 10 nm and 20 μm were released into the air. The numbers of nanoparticles (<100 nm) were by three orders of magnitude larger when compared to the microparticles. A significant release of nanoparticles was measured when the average temperature of the rotor reached 300 deg. C, the combustion initiation temperature of organics present in brakes. In contrast to particle size distribution data, the microscopic analysis revealed the presence of nanoparticles, mostly in the form of agglomerates, in all captured fractions. The majority of elements present in the bulk material were also detected in the ultra-fine fraction of the wear particles. - Research highlights: → Wear of low-metallic friction composite produces airborne nano-sized particles. → Nano-sized particles contain carbon black and metallic compounds. → Carbon black nano-sized particles are related to resin degradation. → Number of nanoparticles higher by three orders of magnitude than microparticles. - Braking of automobiles may contribute to nano-particulate air pollution caused by friction processes associated with wear of low-metallic brake pads.

Insertion of anisotropic particles in lamellar surfactant phases

International Nuclear Information System (INIS)

Grillo, Isabelle

1998-01-01

We search for the interactions governing the possibility to mix organic and inorganic colloids. We use laponite, a synthetic anionic clay, made of 30 nm diameter and 1 nm thickness anisotropic disks. Three surfactant Systems, an anionic one (AOT), a cationic one (DDAB) and a nonionic one (C_1_2E_5) investigate three different cases of interaction forces. We establish experimentally the equilibrium phase diagrams and characterise the structure of these ternary Systems by SANS and SAXS experiments. We quantify the adsorption. An AOT bilayer surround the particle edges; an almost complete bilayer of DDAB and C_1_2E_5 is formed on the basal faces. SANS contrast variation experiments under controlled conditions along the adsorption isotherm of C_1_2E_5 allow to determine the average thickness of the adsorbed surfactant layer. In the monophasic lamellar domain, the particles stay between the membranes, when the spacing is larger than the particle thickness. In the biphasic domain, dense clay aggregates are in equilibrium with a lamellar phase, containing few amount of particles. They enter in the AOT bilayers when the space between the bilayers are smaller than 8 A. From the phase diagram and interaction forces study, three conditions of stability emerge: - an osmotic one: the osmotic lamellar pressure is higher or equal to the colloidal one. - an energetic one: the interaction energy between a particle and the surfactant bilayer is close to the particle energy in aqueous suspension. - an entropic one: particles should not inhibit the stabilising fluctuations of the lamellar phase. (author) [fr

Development of an ejecta particle size measurement diagnostic based on Mie scattering

Energy Technology Data Exchange (ETDEWEB)

Schauer, Martin Michael [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Buttler, William Tillman [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Frayer, Daniel K. [National Security Tech, Inc., Los Alamos, NM (United States); Grover, Michael [National Security Technologies, Santa Barbara, CA (United States). Special Technologies Lab.; Monfared, Shabnam Kalighi [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Stevens, Gerald D. [National Security Technologies, Santa Barbara, CA (United States). Special Technologies Lab.; Stone, Benjamin J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Turley, William Dale [National Security Technologies, Santa Barbara, CA (United States). Special Technologies Lab.

2017-09-27

The goal of this work is to determine the feasibility of extracting the size of particles ejected from shocked metal surfaces (ejecta) from the angular distribution of light scattered by a cloud of such particles. The basis of the technique is the Mie theory of scattering, and implicit in this approach are the assumptions that the scattering particles are spherical and that single scattering conditions prevail. The meaning of this latter assumption, as far as experimental conditions are concerned, will become clear later. The solution to Maxwell’s equations for spherical particles illuminated by a plane electromagnetic wave was derived by Gustav Mie more than 100 years ago, but several modern treatises discuss this solution in great detail. The solution is a complicated series expansion of the scattered electric field, as well as the field within the particle, from which the total scattering and absorption cross sections as well as the angular distribution of scattered intensity can be calculated numerically. The detailed nature of the scattering is determined by the complex index of refraction of the particle material as well as the particle size parameter, x, which is the product of the wavenumber of the incident light and the particle radius, i.e. x = 2rπ= λ. Figure 1 shows the angular distribution of scattered light for different particle size parameters and two orthogonal incident light polarizations as calculated using the Mie solution. It is obvious that the scattering pattern is strongly dependent on the particle size parameter, becoming more forward-directed and less polarizationdependent as the particle size parameter increases. This trend forms the basis for the diagnostic design.

Scattering by nonspherical particles of size comparable to wavelength - A new semi-empirical theory and its application to tropospheric aerosols

Science.gov (United States)

Pollack, J. B.; Cuzzi, J. N.

1980-01-01

A semiempirical theory is developed which is based on simple physical principles and comparisons with laboratory measurements. The ultimate utility of this approach rests on its ability to successfully reproduce the observed single-scattering phase function for a wide variety of particle shapes, sizes and refractive indices. This approximate theory is developed for evaluating the interaction of randomly oriented, nonspherical particles with the total intensity component of electromagnetic radiation. Mie theory is used when the particle size parameter x (ratio of particle circumference to wavelength) is less than some upper bound x sub zero (about 5). For x greater than x sub zero, the interaction is divided into three components: diffraction, external reflection and transmission. The application of the theory is illustrated by considering the influence of the shape of tropospheric aerosols on their contribution to the earth's global albedo.

Hypercrosslinked particles for the extraction of sweeteners using dispersive solid-phase extraction from environmental samples.

Science.gov (United States)

Lakade, Sameer S; Zhou, Qing; Li, Aimin; Borrull, Francesc; Fontanals, Núria; Marcé, Rosa M

2018-04-01

This work presents a new extraction material, namely, Q-100, based on hypercrosslinked magnetic particles, which was tested in dispersive solid-phase extraction for a group of sweeteners from environmental samples. The hypercrosslinked Q-100 magnetic particles had the advantage of suitable pore size distribution and high surface area, and showed good retention behavior toward sweeteners. Different dispersive solid-phase extraction parameters such as amount of magnetic particles or extraction time were optimized. Under optimum conditions, Q-100 showed suitable apparent recovery, ranging in the case of river water sample from 21 to 88% for all the sweeteners, except for alitame (12%). The validated method based on dispersive solid-phase extraction using Q-100 followed by liquid chromatography with tandem mass spectrometry provided good linearity and limits of quantification between 0.01 and 0.1 μg/L. The method was applied to analyze samples from river water and effluent wastewater, and four sweeteners (acesulfame, saccharin, cyclamate, and sucralose) were found in both types of sample. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Particle-size distribution study: PILEDRIVER event

Energy Technology Data Exchange (ETDEWEB)

Rabb, David D [Lawrence Radiation Laboratory, University of California, Livermore, CA (United States)

1970-05-15

Reentry was made by mining into the chimney of broken rock created by a nuclear detonation in granite at a depth of 1500 feet. The chimney was 160 ft in radius and 890 ft high. An injection of radioactive melt was encountered at 300 ft from shot point. Radiochemical analyses determined that the yield of PILEDRIVER nuclear device was 61 {+-} 10 kt. Two samples of chimney rubble totalling over 5,000 lb were obtained during the postshot exploration. These samples of broken granite underwent screen analysis, a radioactivity-distribution study, and cursory leaching tests. The two samples were separated into 25 different size-fractions. An average of the particle-size data from the two samples showed that 17% of the material is between 20 mesh and I in.; 42% between 1 and 6 in.; and 34% between 6 in. and 3 ft. The distribution of radioactivity varies markedly with the particle size. The minus 100-mesh material comprizes less than 1.5% of the weight but contains almost 20% of the radioactivity. Small-scale batch-leaching tests showed that 25% of the radioactivity could be removed in a few hours by a film-percolation leach with distilled water, and 40% with dilute acid. Brief studies were made of the microfractures in the broken rock and of the radioactivity created by the PILEDRIVER explosion. (author)

Particle-size distribution study: PILEDRIVER event

International Nuclear Information System (INIS)

Rabb, David D.

1970-01-01

Reentry was made by mining into the chimney of broken rock created by a nuclear detonation in granite at a depth of 1500 feet. The chimney was 160 ft in radius and 890 ft high. An injection of radioactive melt was encountered at 300 ft from shot point. Radiochemical analyses determined that the yield of PILEDRIVER nuclear device was 61 ± 10 kt. Two samples of chimney rubble totalling over 5,000 lb were obtained during the postshot exploration. These samples of broken granite underwent screen analysis, a radioactivity-distribution study, and cursory leaching tests. The two samples were separated into 25 different size-fractions. An average of the particle-size data from the two samples showed that 17% of the material is between 20 mesh and I in.; 42% between 1 and 6 in.; and 34% between 6 in. and 3 ft. The distribution of radioactivity varies markedly with the particle size. The minus 100-mesh material comprizes less than 1.5% of the weight but contains almost 20% of the radioactivity. Small-scale batch-leaching tests showed that 25% of the radioactivity could be removed in a few hours by a film-percolation leach with distilled water, and 40% with dilute acid. Brief studies were made of the microfractures in the broken rock and of the radioactivity created by the PILEDRIVER explosion. (author)

α particles and the ''pasta'' phase in nuclear matter

International Nuclear Information System (INIS)

Avancini, S. S.; Barros, C. C. Jr.; Menezes, D. P.; Providencia, C.

2010-01-01

The effects of the α particles in nuclear matter at low densities are investigated within three different parametrizations of relativistic models at finite temperature. Both homogeneous and inhomogeneous matter (pasta phase) are described for neutral nuclear matter with fixed proton fractions and stellar matter subject to β equilibrium and trapped neutrinos. In homogeneous matter, α particles are present only at densities below 0.02 fm -3 and their presence decreases with increase of the temperature and, for a fixed temperature, the α particle fraction decreases for smaller proton fractions. A repulsive interaction is important to mimic the dissolution of the clusters in homogeneous matter. The effect of the α particles on the pasta structure is very small except close to the critical temperatures and/or proton fractions, when it may still predict a pasta phase while no pasta phase would occur in the absence of light clusters. It is shown that for densities above 0.01 fm 3 the α-particle fraction in the pasta phase is much larger than that in homogeneous matter.

Scattering by non-spherical particles of size comparable to a wavelength - A new semi-empirical theory. [atmospheric radiative transfer

Science.gov (United States)

Pollack, J. B.; Cuzzi, J. N.

1978-01-01

Mie theory, which is generally used to describe the scattering behavior of particles at a certain wavelength, is only rigorously correct for spherical particles. Particles found as atmospheric constituents, with the exception of cloud droplets, are, however, decidedly nonspherical. An investigation is, therefore, conducted regarding the significant ways in which the scattering behavior of irregularly shaped particles differs from that of spheres. A systematic method is formulated for treating the real scalar scattering behavior. A description is presented of a new semiempirical theory based on simple physical principles and data obtained in laboratory measurements, which successfully reproduces the single scattering phase function for a wide range of particle shapes, sizes, and refractive indices.

How the Emitted Size Distribution and Mixing State of Feldspar Affect Ice Nucleating Particles in a Global Model

Science.gov (United States)

Perlwitz, J. P.; Fridlind, A. M.; Knopf, D. A.; Miller, R. L.; Pérez García-Pando, C.

2017-12-01

The effect of aerosol particles on ice nucleation and, in turn, the formation of ice and mixed phase clouds is recognized as one of the largest sources of uncertainty in climate prediction. We apply an improved dust mineral specific aerosol module in the NASA GISS Earth System ModelE, which takes into account soil aggregates and their fragmentation at emission as well as the emission of large particles. We calculate ice nucleating particle concentrations from K-feldspar abundance for an active site parameterization for a range of activation temperatures and external and internal mixing assumption. We find that the globally averaged INP concentration is reduced by a factor of two to three, compared to a simple assumption on the size distribution of emitted dust minerals. The decrease can amount to a factor of five in some geographical regions. The results vary little between external and internal mixing and different activation temperatures, except for the coldest temperatures. In the sectional size distribution, the size range 2-4 μm contributes the largest INP number.

How the Emitted Size Distribution and Mixing State of Feldspar Affect Ice Nucleating Particles in a Global Model

Science.gov (United States)

Perlwitz, Jan P.; Fridlind, Ann M.; Knopf, Daniel A.; Miller, Ron L.; García-Pando, Carlos Perez

2017-01-01

The effect of aerosol particles on ice nucleation and, in turn, the formation of ice and mixed phase clouds is recognized as one of the largest sources of uncertainty in climate prediction. We apply an improved dust mineral specific aerosol module in the NASA GISS Earth System ModelE, which takes into account soil aggregates and their fragmentation at emission as well as the emission of large particles. We calculate ice nucleating particle concentrations from K-feldspar abundance for an active site parameterization for a range of activation temperatures and external and internal mixing assumption. We find that the globally averaged INP concentration is reduced by a factor of two to three, compared to a simple assumption on the size distribution of emitted dust minerals. The decrease can amount to a factor of five in some geographical regions. The results vary little between external and internal mixing and different activation temperatures, except for the coldest temperatures. In the sectional size distribution, the size range 24 micrometer contributes the largest INP number.

Electromechanical characterization of individual micron-sized metal coated polymer particles

Energy Technology Data Exchange (ETDEWEB)

Bazilchuk, Molly; Kristiansen, Helge [Department of Structural Engineering, Norwegian University of Science and Technology, Trondheim 7491 (Norway); Conpart AS, Skjetten 2013 (Norway); Pettersen, Sigurd Rolland; Zhang, Zhiliang; He, Jianying, E-mail: jianying.he@ntnu.no [Department of Structural Engineering, Norwegian University of Science and Technology, Trondheim 7491 (Norway)

2016-06-28

Micron-sized polymer particles with nanoscale metal coatings are essential in conductive adhesives for electronics assembly. The particles function in a compressed state in the adhesives. The link between mechanical properties and electrical conductivity is thus of the utmost importance in the formation of good electrical contact. A custom flat punch set-up based on nanoindentation has been developed to simultaneously deform and electrically probe individual particles. The set-up has a sufficiently low internal resistance to allow the measurement of sub-Ohm contact resistances. Additionally, the set-up can capture mechanical failure of the particles. Combining this data yields a fundamental understanding of contact behavior. We demonstrate that this method can clearly distinguish between particles of different sizes, with different thicknesses of metal coating, and different metallization schemes. The technique provides good repeatability and physical insight into the behavior of these particles that can guide adhesive design and the optimization of bonding processes.

Electromechanical characterization of individual micron-sized metal coated polymer particles

International Nuclear Information System (INIS)

Bazilchuk, Molly; Kristiansen, Helge; Pettersen, Sigurd Rolland; Zhang, Zhiliang; He, Jianying

2016-01-01

Micron-sized polymer particles with nanoscale metal coatings are essential in conductive adhesives for electronics assembly. The particles function in a compressed state in the adhesives. The link between mechanical properties and electrical conductivity is thus of the utmost importance in the formation of good electrical contact. A custom flat punch set-up based on nanoindentation has been developed to simultaneously deform and electrically probe individual particles. The set-up has a sufficiently low internal resistance to allow the measurement of sub-Ohm contact resistances. Additionally, the set-up can capture mechanical failure of the particles. Combining this data yields a fundamental understanding of contact behavior. We demonstrate that this method can clearly distinguish between particles of different sizes, with different thicknesses of metal coating, and different metallization schemes. The technique provides good repeatability and physical insight into the behavior of these particles that can guide adhesive design and the optimization of bonding processes.

Polymer-Particle Nanocomposites: Size and Dispersion Effects

Science.gov (United States)

Moll, Joseph

Polymer-particle nanocomposites are used in industrial processes to enhance a broad range of material properties (e.g. mechanical, optical, electrical and gas permeability properties). This dissertation will focus on explanation and quantification of mechanical property improvements upon the addition of nanoparticles to polymeric materials. Nanoparticles, as enhancers of mechanical properties, are ubiquitous in synthetic and natural materials (e.g. automobile tires, packaging, bone), however, to date, there is no thorough understanding of the mechanism of their action. In this dissertation, silica (SiO2) nanoparticles, both bare and grafted with polystyrene (PS), are studied in polymeric matrices. Several variables of interest are considered, including particle dispersion state, particle size, length and density of grafted polymer chains, and volume fraction of SiO2. Polymer grafted nanoparticles behave akin to block copolymers, and this is critically leveraged to systematically vary nanoparticle dispersion and examine its role on the mechanical reinforcement in polymer based nanocomposites in the melt state. Rheology unequivocally shows that reinforcement is maximized by the formation of a transient, but long-lived, percolating polymer-particle network with the particles serving as the network junctions. The effects of dispersion and weight fraction of filler on nanocomposite mechanical properties are also studied in a bare particle system. Due to the interest in directional properties for many different materials, different means of inducing directional ordering of particle structures are also studied. Using a combination of electron microscopy and x-ray scattering, it is shown that shearing anisotropic NP assemblies (sheets or strings) causes them to orient, one in front of the other, into macroscopic two-dimensional structures along the flow direction. In contrast, no such flow-induced ordering occurs for well dispersed NPs or spherical NP aggregates! This work

Size-sensitive particle trajectories in three-dimensional micro-bubble acoustic streaming flows

Science.gov (United States)

Volk, Andreas; Rossi, Massimiliano; Hilgenfeldt, Sascha; Rallabandi, Bhargav; Kähler, Christian; Marin, Alvaro

2015-11-01

Oscillating microbubbles generate steady streaming flows with interesting features and promising applications for microparticle manipulation. The flow around oscillating semi-cylindrical bubbles has been typically assumed to be independent of the axial coordinate. However, it has been recently revealed that particle motion is strongly three-dimensional: Small tracer particles follow vortical trajectories with pronounced axial displacements near the bubble, weaving a toroidal stream-surface. A well-known consequence of bubble streaming flows is size-dependent particle migration, which can be exploited for sorting and trapping of microparticles in microfluidic devices. In this talk, we will show how the three-dimensional toroidal topology found for small tracer particles is modified as the particle size increases up to 1/3 of the bubble radius. Our results show size-sensitive particle positioning along the axis of the semi-cylindrical bubble. In order to analyze the three-dimensional sorting and trapping capabilities of the system, experiments with an imposed flow and polydisperse particle solutions are also shown.

Particle diffusional layer thickness in a USP dissolution apparatus II: a combined function of particle size and paddle speed.

Science.gov (United States)

Sheng, Jennifer J; Sirois, Paul J; Dressman, Jennifer B; Amidon, Gordon L

2008-11-01

This work was to investigate the effects of particle size and paddle speed on the particle diffusional layer thickness h(app) in a USP dissolution apparatus II. After the determination of the powder dissolution rates of five size fractions of fenofibrate, including <20, 20-32, 32-45, 63-75, and 90-106 microm, the present work shows that the dependence of h(app) on particle size follows different functions in accordance with the paddle speed. At 50 rpm, the function of h(app) is best described by a linear plot of h{app} = 9.91sqrt d-23.31 (R(2) = 0.98) throughout the particle diameter, d, from 6.8 to 106 microm. In contrast, at 100 rpm a transitional particle radius, r, of 23.7 microm exists, under which linear relationship h(app) = 1.59r (R(2) = 0.98) occurs, but above which h(app) becomes a constant of 43.5 microm. Thus, h(app) changes not only with particle size, but also with the hydrodynamics under standard USP configurations, which has been overlooked in the past. Further, the effects of particle size and paddle speed on h(app) were combined using dimensionless analysis. Within certain fluid velocity/particle regime, linear correlation of h(app)/d with the square-root of Reynolds number (d\\varpi/upsilon){1/2}, that is, h{app}/d = 1.5207 - 9.25 x 10{- 4} (d\\varpi/n){1/2} (R(2) = 0.9875), was observed.

Polydisperse-particle-size-distribution function determined from intensity profile of angularly scattered light

International Nuclear Information System (INIS)

Alger, T.W.

1979-01-01

A new method for determining the particle-size-distribution function of a polydispersion of spherical particles is presented. The inversion technique for the particle-size-distribution function is based upon matching the measured intensity profile of angularly scattered light with a summation of the intensity contributions of a series of appropriately spaced, narrowband, size-distribution functions. A numerical optimization technique is used to determine the strengths of the individual bands that yield the best agreement with the measured scattered-light-intensity profile. Because Mie theory is used, the method is applicable to spherical particles of all sizes. Several numerical examples demonstrate the application of this inversion method

Size-exclusion chromatography using core-shell particles.

Science.gov (United States)

Pirok, Bob W J; Breuer, Pascal; Hoppe, Serafine J M; Chitty, Mike; Welch, Emmet; Farkas, Tivadar; van der Wal, Sjoerd; Peters, Ron; Schoenmakers, Peter J

2017-02-24

Size-exclusion chromatography (SEC) is an indispensable technique for the separation of high-molecular-weight analytes and for determining molar-mass distributions. The potential application of SEC as second-dimension separation in comprehensive two-dimensional liquid chromatography demands very short analysis times. Liquid chromatography benefits from the advent of highly efficient core-shell packing materials, but because of the reduced total pore volume these materials have so far not been explored in SEC. The feasibility of using core-shell particles in SEC has been investigated and contemporary core-shell materials were compared with conventional packing materials for SEC. Columns packed with very small core-shell particles showed excellent resolution in specific molar-mass ranges, depending on the pore size. The analysis times were about an order of magnitude shorter than what could be achieved using conventional SEC columns. Copyright © 2016 Elsevier B.V. All rights reserved.

Particle size studies in the preparation of AQCS reference materials

International Nuclear Information System (INIS)

Fajgelj, A.; Zeisler, R.; Benesch, T.; Dekner, R.

1994-01-01

Particle size determination is one of the important steps in the characterization of physical properties of each particulate material. However, particle size distribution effects also a chemical composition of the material in terms of homogeneity and representativeness of the sample, as well as allows or not a possible sub-sampling of the material. All this is of great importance in the preparation of reference materials for which the chemical composition and physical properties have to be extremely well characterized. In the present paper we intend to present same efforts which have been done by Analytical Quality Control Services (AQCS) of the International Atomic Energy Agency (IAEA) in the field of particle size determination in the production of reference materials. The Malvern product MasterSizer X, based on laser light scattering is used for this purpose and the technique is also shortly discussed. (author)

Optimizing the particle size of coal for CWM in view of fluidity. [Biomodal

Energy Technology Data Exchange (ETDEWEB)

Matsuo, Seiji; Nonaka, Michio; Okano, Yasuhiko; Inoue, Toshio

1987-10-25

As is well known, the viscosity of CWM is considerably influenced by the distribution of coal particle sizes and has bearing on particle packing density or porosity. A model for representing the viscosity of CWM in terms of particle porosity and specific surface was designed. Also, experimental verification was conducted for the method of optimizing particle size on a two-stage grinding system. The results are as follows: The viscosity of CWM is influenced not only by the porosity of coal particles, but also by the specific surface; also, it is correlated to the distance between suspended particles. At the two-stage grinding experiments, a particle size distribution leading to a low viscosity was obtained by mixing coarse and fine particles at 4:1. This has demonstrated that the use of an agitating mill for fine particles is of help. (11 figs, 2 tabs, 6 refs)

Two-step preparation of nano-scaled magnetic chitosan particles using Triton X-100 reversed-phase water-in-oil microemulsion system

International Nuclear Information System (INIS)

Zhou, Zhengkun; Jiang, Feihong; Lee, Tung-Ching; Yue, Tianli

2013-01-01

Highlights: •A new two-step route for nano-scaled magnetic chitosan particles preparation. •Triton X-100 reversed-phase microemulsion system was used for chitosan coating. •Narrow size distribution of magnetic chitosan nanoparticles was achieved. •Quantitative evaluation of recoverability for the magnetic chitosan nanoparticles. -- Abstract: A new two-step route for the preparation of nano-scaled magnetic chitosan particles has been developed, different from reported one-step in situ preparation and two-step preparation method of reversed-phase suspension, Triton X-100 reversed-phase water-in-oil microemulsion encapsulation method was employed in coating the pre-prepared Fe 3 O 4 nanoparticles with chitosan. The resultant magnetic chitosan particles owned a narrow size distribution ranging from 50 to 92 nm. X-ray diffraction patterns (XRD) indicated that the chitosan coating procedure did not change the spinal structure of Fe 3 O 4 magnetic nanoparticles. The results of Fourier transform infrared (FTIR) analysis and thermogravimetric analysis (TGA) demonstrated that the chitosan was coated on Fe 3 O 4 nanoparticles and its average mass content was ∼50%. The saturated magnetization of the magnetic Fe 3 O 4 /chitosan nanoparticles reached 18.62 emu/g, meanwhile, the nanoparticles showed the characteristics of superparamagnetism. The magnetic chitosan nanoparticles showed a high recoverability of 99.99% in 10 min when pH exceeded 4. The results suggested that the as-prepared magnetic chitosan particles were nano-scaled with a narrow size distribution and a high recoverability

Effect of particle size on colloidal zirconia rheology at the isoelectric point

International Nuclear Information System (INIS)

Leong, Y.K.; Scales, P.J.; Healy, T.W.; Boger, D.V.

1995-01-01

This paper examines the effects of particle concentration and size on the yield stress of ZrO 2 suspensions at a well-defined surface chemistry condition of the isoelectric point (IEP). At the IEP, the relationship between yield stress τ y max and particulate volume fraction φ s , and mean particle size d was evaluated to be τ y max = K φ s 4.0 /d 2.0 . The difference in size distribution of the various ZrO 2 suspensions examined causes some degree of scatter in the data used to establish the τ y max , φ s , and d relation. The use of particle concentration n t based on the fine size fraction instead of volume fraction φ s provided a better correlation, because the fine particles govern the properties of the flocculated network structure

Process R&D for Particle Size Control of Molybdenum Oxide

Energy Technology Data Exchange (ETDEWEB)

Sen, Sujat [Argonne National Lab. (ANL), Argonne, IL (United States); Dzwiniel, Trevor [Argonne National Lab. (ANL), Argonne, IL (United States); Pupek, Krzysztof [Argonne National Lab. (ANL), Argonne, IL (United States); Krumdick, Gregory [Argonne National Lab. (ANL), Argonne, IL (United States); Tkac, Peter [Argonne National Lab. (ANL), Argonne, IL (United States); Vandegrift, George F. [Argonne National Lab. (ANL), Argonne, IL (United States)

2016-12-01

The primary goal of this study was to produce MoO₃ powder with a particle size range of 50 to 200 μm for use in targets for production of the medical isotope ⁹⁹Mo. Molybdenum metal powder is commercially produced by thermal reduction of oxides in a hydrogen atmosphere. The most common source material is MoO₃, which is derived by the thermal decomposition of ammonium heptamolybdate (AHM). However, the particle size of the currently produced MoO₃ is too small, resulting in Mo powder that is too fine to properly sinter and press into the desired target. In this study, effects of heating rate, heating temperature, gas type, gas flow rate, and isothermal heating were investigated for the decomposition of AHM. The main conclusions were as follows: lower heating rate (2-10°C/min) minimizes breakdown of aggregates, recrystallized samples with millimeter-sized aggregates are resistant to various heat treatments, extended isothermal heating at >600°C leads to significant sintering, and inert gas and high gas flow rate (up to 2000 ml/min) did not significantly affect particle size distribution or composition. In addition, attempts to recover AHM from an aqueous solution by several methods (spray drying, precipitation, and low temperature crystallization) failed to achieve the desired particle size range of 50 to 200 μm. Further studies are planned.

Number size distribution of fine and ultrafine fume particles from various welding processes.

Science.gov (United States)

Brand, Peter; Lenz, Klaus; Reisgen, Uwe; Kraus, Thomas

2013-04-01

Studies in the field of environmental epidemiology indicate that for the adverse effect of inhaled particles not only particle mass is crucial but also particle size is. Ultrafine particles with diameters below 100 nm are of special interest since these particles have high surface area to mass ratio and have properties which differ from those of larger particles. In this paper, particle size distributions of various welding and joining techniques were measured close to the welding process using a fast mobility particle sizer (FMPS). It turned out that welding processes with high mass emission rates (manual metal arc welding, metal active gas welding, metal inert gas welding, metal inert gas soldering, and laser welding) show mainly agglomerated particles with diameters above 100 nm and only few particles in the size range below 50 nm (10 to 15%). Welding processes with low mass emission rates (tungsten inert gas welding and resistance spot welding) emit predominantly ultrafine particles with diameters well below 100 nm. This finding can be explained by considerably faster agglomeration processes in welding processes with high mass emission rates. Although mass emission is low for tungsten inert gas welding and resistance spot welding, due to the low particle size of the fume, these processes cannot be labeled as toxicologically irrelevant and should be further investigated.

Particle size distribution in effluent of trickling filters and in humus tanks.

Science.gov (United States)

Schubert, W; Günthert, F W

2001-11-01

Particles and aggregates from trickling filters must be eliminated from wastewater. Usually this happens through sedimentation in humus tanks. Investigations to characterize these solids by way of particle size measurements, image analysis and particle charge measurements (zeta potential) are made within the scope of Research Center for Science and Technology "Fundamentals of Aerobic biological wastewater treatment" (SFB 411). The particle size measuring results given within this report were obtained at the Ingolstadt wastewater treatment plant, Germany, which served as an example. They have been confirmed by similar results from other facilities. Particles flushed out from trickling filters will be partially destroyed on their way to the humus tank. A large amount of small particles is to be found there. On average 90% of the particles are smaller than 30 microm. Particle size plays a decisive role in the sedimentation behaviour of solids. Small particles need sedimentation times that cannot be provided in settling tanks. As a result they cause turbidity in the final effluent. Therefore quality of sewage discharge suffers, and there are hardly advantages of the fixed film reactor treatment compared to the activated sludge process regarding sedimentation behaviour.

Investigation of nucleation kinetics in H2SO4 vapor through modeling of gas phase kinetics coupled with particle dynamics

Science.gov (United States)

Carlsson, Philip T. M.; Zeuch, Thomas

2018-03-01

We have developed a new model utilizing our existing kinetic gas phase models to simulate experimental particle size distributions emerging in dry supersaturated H2SO4 vapor homogeneously produced by rapid oxidation of SO2 through stabilized Criegee-Intermediates from 2-butene ozonolysis. We use a sectional method for simulating the particle dynamics. The particle treatment in the model is based on first principles and takes into account the transition from the kinetic to the diffusion-limited regime. It captures the temporal evolution of size distributions at the end of the ozonolysis experiment well, noting a slight underrepresentation of coagulation effects for larger particle sizes. The model correctly predicts the shape and the modes of the experimentally observed particle size distributions. The predicted modes show an extremely high sensitivity to the H2SO4 evaporation rates of the initially formed H2SO4 clusters (dimer to pentamer), which were arbitrarily restricted to decrease exponentially with increasing cluster size. In future, the analysis presented in this work can be extended to allow a direct validation of quantum chemically predicted stabilities of small H2SO4 clusters, which are believed to initiate a significant fraction of atmospheric new particle formation events. We discuss the prospects and possible limitations of the here presented approach.

Performance of japanese quails fed feeds containing different corn and limestone particle sizes

Directory of Open Access Journals (Sweden)

DA Berto

2007-09-01

Full Text Available This study aimed at evaluating performance and egg quality of Japanese quails fed feeds containing different corn and limestone particle sizes. A total number of 648 birds in the peak of production was distributed in a random complete block experimental design, using a 2x3 factorial arrangement (2 corn particle sizes and 3 limestone particle sizes. Birds were designated to one of two blocks, with six replicates of 18 birds each. Mean geometric diameter (MGD values used were 0.617mm and 0.723mm (corn fine and coarse particle sizes, respectively, and 0.361mm, 0.721mm, and 0.947mm (limestone fine, intermediate and coarse particle sizes, respectively. The following treatments were applied: T1: fine corn feed, with 100% fine limestone; T2: fine corn feed, with 50% fine limestone and 50% intermediate limestone; T3: fine corn feed, with 50% fine limestone and 50% coarse limestone; T4: coarse corn feed, with 100% fine limestone; T5: coarse corn feed, with 50% fine limestone and 50% intermediate limestone; T6: coarse corn feed, with 50% fine limestone and 50% coarse limestone. The experiment lasted 112 days, consisting of 4 cycles of 28 days. No significant interaction was observed among corn and limestone particle sizes for any of the analyzed parameters. There were no significant effects (p>0.05 of the tested corn particle sizes on quail performance or egg quality. There were significant (p<0.05 isolated effects of limestone particle size only on the percentage of cracked eggs, which was reduced when birds fed 50% coarse limestone (0.947mm and 50% fine limestone (0.361mm as compared to those fed 100% fine limestone. Therefore, the inclusion of 50% coarse limestone (0.947mm is recommended for quail egg production.

Algorithm of Data Reduce in Determination of Aerosol Particle Size Distribution at Damps/C

International Nuclear Information System (INIS)

Muhammad-Priyatna; Otto-Pribadi-Ruslanto

2001-01-01

The analysis had to do for algorithm of data reduction on Damps/C (Differential Mobility Particle Sizer with Condensation Particle Counter) system, this is for determine aerosol particle size distribution with range 0,01 μm to 1 μm in diameter. Damps/C (Differential Mobility Particle Sizer with Condensation Particle Counter) system contents are software and hardware. The hardware used determine of mobilities of aerosol particle and so the software used determine aerosol particle size distribution in diameter. The mobilities and diameter particle had connection in the electricity field. That is basic program for reduction of data and particle size conversion from particle mobility become particle diameter. The analysis to get transfer function value, Ω, is 0.5. The data reduction program to do conversation mobility basis become diameter basis with number efficiency correction, transfer function value, and poly charge particle. (author)

Evaluation of instruments used in particle size analysis by using the sedimentation technique

International Nuclear Information System (INIS)

Elmasry, M.A.A.; Abdrahman, A.A.M.; Ahmed, A.Z.

2007-01-01

This study is carried out to evaluate the performance of some instruments in which the sedimentation technique is used for the determination of particle size distribution using Stoke's law. A mathematical formula has been developed to calculate the particle size distribution for different cases and the results were compared to the real ones. The results revealed unsatisfactory agreement between the calculated and the measured values. In addition, illogic results were obtained indicating that the instruments in which the sedimentation technique is used are not the proper ones to provide accurate measurements except for mono particle size cases. More above, the results obtained represent the sedimentation rate but not the particle size distribution.

Combustion synthesis of micron-sized Sm2Co17 particles via mechanochemical processing

International Nuclear Information System (INIS)

Liu, W.; McCormick, P.G.

1998-01-01

Full text: The spontaneous formation of Sm 2 Co 17 micron-sized particles via a mechanically induced combustion reaction has been investigated. Sm 2 Co 17 alloy particles of 0.1--2 μm in size embedded in a CaO matrix formed directly via a combustion reaction induced by milling the powder mixture of Sm 2 O 3 , CoO, CaO and Ca over a critical time. The micron-sized Sm 2 Co 17 particles were found to have the TbCu 7 -type structure and characterized by a coercivity value of 7.8 kOe while embedded in the CaO matrix. The effect of subsequent heat treatment on the structure and magnetic properties of as-milled samples was also investigated. Removal of the CaO by a carefully controlled washing process yielded micron-sized Sm 2 Co 17 particles without significant oxidation of the particles. These fine Sm 2 Co 17 particles can be used to produce anisotropic bulk or bonded magnets

Performance of diethylene glycol-based particle counters in the sub-3 nm size range

CERN Document Server

Wimmer, D; Franchin, A; Kangasluoma, J; Kreissl, F; Kürten, A; Kupc, A; Metzger, A; Mikkilä, J; Petäjä, J; Riccobono, F; Vanhanen, J; Kulmala, M; Curtius, J

2013-01-01

When studying new particle formation, the uncertainty in determining the "true" nucleation rate is considerably reduced when using condensation particle counters (CPCs) capable of measuring concentrations of aerosol particles at sizes close to or even at the critical cluster size (1–2 nm). Recently, CPCs able to reliably detect particles below 2 nm in size and even close to 1 nm became available. Using these instruments, the corrections needed for calculating nucleation rates are substantially reduced compared to scaling the observed formation rate to the nucleation rate at the critical cluster size. However, this improved instrumentation requires a careful characterization of their cut-off size and the shape of the detection efficiency curve because relatively small shifts in the cut-off size can translate into larger relative errors when measuring particles close to the cut-off size. Here we describe the development of two continuous-flow CPCs using diethylene glycol (DEG) as the working fluid. The desig...

Particle Transport and Size Sorting in Bubble Microstreaming Flow

Science.gov (United States)

Thameem, Raqeeb; Rallabandi, Bhargav; Wang, Cheng; Hilgenfeldt, Sascha

2014-11-01

Ultrasonic driving of sessile semicylindrical bubbles results in powerful steady streaming flows that are robust over a wide range of driving frequencies. In a microchannel, this flow field pattern can be fine-tuned to achieve size-sensitive sorting and trapping of particles at scales much smaller than the bubble itself; the sorting mechanism has been successfully described based on simple geometrical considerations. We investigate the sorting process in more detail, both experimentally (using new parameter variations that allow greater control over the sorting) and theoretically (incorporating the device geometry as well as the superimposed channel flow into an asymptotic theory). This results in optimized criteria for size sorting and a theoretical description that closely matches the particle behavior close to the bubble, the crucial region for size sorting.

Micrometer-sized Water Ice Particles for Planetary Science Experiments: Influence of Surface Structure on Collisional Properties

Science.gov (United States)

Gaertner, Sabrina; Gundlach, Bastian; Headen, Thomas F.; Ratte, Judy; Oesert, Joachim; Gorb, Stanislav N.; Youngs, Tristan G. A.; Bowron, Daniel T.; Blum, Jürgen; Fraser, Helen

2018-06-01

Models and observations suggest that particle aggregation at and beyond the snowline is aided by water ice. As icy particles play such a crucial role in the earliest stages of planet formation, many laboratory studies have exploited their collisional properties across a wide range of parameters (particle size, impact velocity, temperature T, and pressure P).However, not all of these parameters have always been varied systematically, leading to apparently contradictory results on collision outcomes. Previous experiments only agreed that a temperature dependence set in above ≈210 K. Open questions remain as to what extent the structural properties of the particles themselves dictate collision outcomes. The P–T gradients in protoplanetary disks mean that the ices are constantly processed, undergoing phase changes between different solid phases and the gas phase. To understand how effectively collision experiments reproduce protoplanetary disk conditions, environmental impacts on particle structure need to be investigated.We characterized the bulk and surface structure of icy particles used in collision experiments, exploiting the unique capabilities of the NIMROD neutron scattering instrument. Varying temperature at a constant pressure of around 30 mbar, we studied structural alterations to determine which of the observed properties matches the temperature dependencies observed in collisional behaviour.Our icy grains are formed under liquid nitrogen and heated from 103 to 247 K. As a result, they undergo changes in the crystalline ice-phase, sublimation, sintering and surface pre-melting. An increase in the thickness of the diffuse surface layer from ≈10 to ≈30 Å (≈2.5 to 12 bilayers) suggests increased molecular mobility at temperatures above ≈210 K.Because none of the other changes ties in with the temperature trends in collisional outcomes, we conclude that the diffuse interface plays a key role in collision experiments at these temperatures

Hydrodynamics of multi-sized particles in stable regime of a swirling bed

Energy Technology Data Exchange (ETDEWEB)

Miin, Chin Swee; Sulaiman, Shaharin Anwar; Raghavan, Vijay Raj; Heikal, Morgan Raymond; Naz, Muhammad Yasin [Universiti Teknologi PETRONAS, Perak (Malaysia)

2015-11-15

Using particle imaging velocimetry (PIV), we observed particle motion within the stable operating regime of a swirling fluidized bed with an annular blade distributor. This paper presents velocity profiles of particle flow in an effort to determine effects from blade angle, particle size and shape and bed weight on characteristics of a swirling fluidized bed. Generally, particle velocity increased with airflow rate and shallow bed height, but decreased with bed weight. A 3 .deg. increase in blade angle reduced particle velocity by approximately 18%. In addition, particle shape, size and bed weight affected various characteristics of the swirling regime. Swirling began soon after incipience in the form of a supra-linear curve, which is the characteristic of a swirling regime. The relationship between particle and gas velocities enabled us to predict heat and mass transfer rates between gas and particles.

Diffusion of Finite-Size Particles in Confined Geometries

KAUST Repository

Bruna, Maria

2013-05-10

The diffusion of finite-size hard-core interacting particles in two- or three-dimensional confined domains is considered in the limit that the confinement dimensions become comparable to the particle\\'s dimensions. The result is a nonlinear diffusion equation for the one-particle probability density function, with an overall collective diffusion that depends on both the excluded-volume and the narrow confinement. By including both these effects, the equation is able to interpolate between severe confinement (for example, single-file diffusion) and unconfined diffusion. Numerical solutions of both the effective nonlinear diffusion equation and the stochastic particle system are presented and compared. As an application, the case of diffusion under a ratchet potential is considered, and the change in transport properties due to excluded-volume and confinement effects is examined. © 2013 Society for Mathematical Biology.

Measurement of particle size distribution and mass concentration of nuclear fuel aerosols

International Nuclear Information System (INIS)

Pickering, S.

1982-01-01

The particle size distribution and particle mass concentration of a nuclear fuel aerosol is measured by admitting the aerosol into a vertically-extending container, positioning an alpha particle detector within the container so that its window is horizontal and directed vertically, stopping the admission of aerosol into the container, detecting the alpha-activity of the particles of the aerosol sedimenting onto the detector window (for example in a series of equal time intervals until a constant level is reached), and converting the alpha-activity measurements into particle size distribution and/or particle mass concentration measurements. The detector is attached to a pivotted arm and by raising a counterweight can be lowered from the container for cleaning. (author)

Alpha spectrometric characterization of process-related particle size distributions from active particle sampling at the Los Alamos National Laboratory uranium foundry

Energy Technology Data Exchange (ETDEWEB)

Plionis, Alexander A [Los Alamos National Laboratory; Peterson, Dominic S [Los Alamos National Laboratory; Tandon, Lav [Los Alamos National Laboratory; Lamont, Stephen P [Los Alamos National Laboratory

2009-01-01

Uranium particles within the respirable size range pose a significant hazard to the health and safety of workers. Significant differences in the deposition and incorporation patterns of aerosols within the respirable range can be identified and integrated into sophisticated health physics models. Data characterizing the uranium particle size distribution resulting from specific foundry-related processes are needed. Using personal air sampling cascade impactors, particles collected from several foundry processes were sorted by activity median aerodynamic diameter onto various Marple substrates. After an initial gravimetric assessment of each impactor stage, the substrates were analyzed by alpha spectrometry to determine the uranium content of each stage. Alpha spectrometry provides rapid nondestructive isotopic data that can distinguish process uranium from natural sources and the degree of uranium contribution to the total accumulated particle load. In addition, the particle size bins utilized by the impactors provide adequate resolution to determine if a process particle size distribution is: lognormal, bimodal, or trimodal. Data on process uranium particle size values and distributions facilitate the development of more sophisticated and accurate models for internal dosimetry, resulting in an improved understanding of foundry worker health and safety.

Effect of particle size on thermal decomposition of alkali metal picrates

International Nuclear Information System (INIS)

Liu, Rui; Zhang, Tonglai; Yang, Li; Zhou, Zunning

2014-01-01

Graphical abstract: The smaller-sized picrate has greater gas emission than do its larger counterpart. The small size effect reduces the thermal decomposition activation energy, accelerates the reaction rate, and promotes the reaction activity. - Highlights: • Picrates were prepared into three micron sizes by microemulsion synthesis. • Thermal decomposition kinetics and thermodynamics were studied by DPTA and DSC. • Smaller-sized picrate has higher activity and faster reaction rate. • Particle size effect on thermal decomposition kinetics and thermodynamics was revealed. - Abstract: Three alkali metal picrates, KPA, RbPA and CsPA, were prepared into three micron sizes by microemulsion synthesis, and their thermal decomposition behaviors were investigated by DPTA at different temperatures and by DSC at different heating rates. The smaller-sized picrate has greater gas emission and smaller kinetic and thermodynamic parameters than do its larger counterpart. It can be attributed to the decreasing particle size which leads to the high surface energy, the fast mass and heat transfer, and the increasing active sites on the reaction interface. The small size effect and surface effect cause the autocatalysis which reduces the activation energy and promotes the reaction activity. The particle size does not affect the reaction mechanism. However, the picrates with different central alkali metals exhibit different reaction mechanisms even though they are of the same size. This is because the central metal determines the bond energy and consequently affects the stability of picrate

Effect of particle size on thermal decomposition of alkali metal picrates

Energy Technology Data Exchange (ETDEWEB)

Liu, Rui; Zhang, Tonglai, E-mail: ztlbit@bit.edu.cn; Yang, Li; Zhou, Zunning

2014-05-01

Graphical abstract: The smaller-sized picrate has greater gas emission than do its larger counterpart. The small size effect reduces the thermal decomposition activation energy, accelerates the reaction rate, and promotes the reaction activity. - Highlights: • Picrates were prepared into three micron sizes by microemulsion synthesis. • Thermal decomposition kinetics and thermodynamics were studied by DPTA and DSC. • Smaller-sized picrate has higher activity and faster reaction rate. • Particle size effect on thermal decomposition kinetics and thermodynamics was revealed. - Abstract: Three alkali metal picrates, KPA, RbPA and CsPA, were prepared into three micron sizes by microemulsion synthesis, and their thermal decomposition behaviors were investigated by DPTA at different temperatures and by DSC at different heating rates. The smaller-sized picrate has greater gas emission and smaller kinetic and thermodynamic parameters than do its larger counterpart. It can be attributed to the decreasing particle size which leads to the high surface energy, the fast mass and heat transfer, and the increasing active sites on the reaction interface. The small size effect and surface effect cause the autocatalysis which reduces the activation energy and promotes the reaction activity. The particle size does not affect the reaction mechanism. However, the picrates with different central alkali metals exhibit different reaction mechanisms even though they are of the same size. This is because the central metal determines the bond energy and consequently affects the stability of picrate.

Effect of particle size on microstructure and mechanical properties of composites produced by ARB process

Energy Technology Data Exchange (ETDEWEB)

Jamaati, Roohollah, E-mail: r.jamaatikenari@ma.iut.ac.ir [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Amirkhanlou, Sajjad; Toroghinejad, Mohammad Reza; Niroumand, Behzad [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)

2011-02-25

Research highlights: {yields} Microstructure of MMC with larger particles becomes completely uniform, sooner. {yields} When the number of cycles increased, tensile strength for both samples improved. {yields} Up to the seventh cycle, tensile strength of MMC with larger particles was bigger. {yields} First, the tensile elongation of MMCs was decreased, and then it was improved. - Abstract: In the present work, Al/10 vol.% SiC metal matrix composite (MMC) was manufactured by accumulative roll bonding (ARB) process. The silicon carbide particles with two various particle sizes of 40 and 2 {mu}m were used. Effect of particle size on microstructure (by scanning electron microscopy) and mechanical properties (tensile strength and elongation) at various ARB cycles was investigated. It was found that the microstructural evolution in MMC with 40 {mu}m particle size was more salient compared to the MMCs with 2 {mu}m particle size. Also, the composite strip with 40 {mu}m particle size became uniform with high bonding quality and without any porosity sooner than the strip of 2 {mu}m particle size. Moreover, when the number of cycles was increased, the tensile strength for both samples was improved. The tensile strength of the composite strip with 40 {mu}m particle size was more than the composite strip with 2 {mu}m up to the seventh cycle. By increasing the number of cycles after the seventh cycle, the value of tensile strength of MMC with 40 {mu}m particle size became saturated and then decreased, and its tensile strength became less than that of the composite with 2 {mu}m particle size for the ninth and eleventh cycles. Up to the seventh cycle, when the number of ARB cycles was increased, the elongation of composite strips was decreased, but after the ninth cycle, the tensile elongation for both samples was improved.

Effect of particle size on microstructure and mechanical properties of composites produced by ARB process

International Nuclear Information System (INIS)

Jamaati, Roohollah; Amirkhanlou, Sajjad; Toroghinejad, Mohammad Reza; Niroumand, Behzad

2011-01-01

Research highlights: → Microstructure of MMC with larger particles becomes completely uniform, sooner. → When the number of cycles increased, tensile strength for both samples improved. → Up to the seventh cycle, tensile strength of MMC with larger particles was bigger. → First, the tensile elongation of MMCs was decreased, and then it was improved. - Abstract: In the present work, Al/10 vol.% SiC metal matrix composite (MMC) was manufactured by accumulative roll bonding (ARB) process. The silicon carbide particles with two various particle sizes of 40 and 2 μm were used. Effect of particle size on microstructure (by scanning electron microscopy) and mechanical properties (tensile strength and elongation) at various ARB cycles was investigated. It was found that the microstructural evolution in MMC with 40 μm particle size was more salient compared to the MMCs with 2 μm particle size. Also, the composite strip with 40 μm particle size became uniform with high bonding quality and without any porosity sooner than the strip of 2 μm particle size. Moreover, when the number of cycles was increased, the tensile strength for both samples was improved. The tensile strength of the composite strip with 40 μm particle size was more than the composite strip with 2 μm up to the seventh cycle. By increasing the number of cycles after the seventh cycle, the value of tensile strength of MMC with 40 μm particle size became saturated and then decreased, and its tensile strength became less than that of the composite with 2 μm particle size for the ninth and eleventh cycles. Up to the seventh cycle, when the number of ARB cycles was increased, the elongation of composite strips was decreased, but after the ninth cycle, the tensile elongation for both samples was improved.

Numerical sedimentation particle-size analysis using the Discrete Element Method

Science.gov (United States)

Bravo, R.; Pérez-Aparicio, J. L.; Gómez-Hernández, J. J.

2015-12-01

Sedimentation tests are widely used to determine the particle size distribution of a granular sample. In this work, the Discrete Element Method interacts with the simulation of flow using the well known one-way-coupling method, a computationally affordable approach for the time-consuming numerical simulation of the hydrometer, buoyancy and pipette sedimentation tests. These tests are used in the laboratory to determine the particle-size distribution of fine-grained aggregates. Five samples with different particle-size distributions are modeled by about six million rigid spheres projected on two-dimensions, with diameters ranging from 2.5 ×10-6 m to 70 ×10-6 m, forming a water suspension in a sedimentation cylinder. DEM simulates the particle's movement considering laminar flow interactions of buoyant, drag and lubrication forces. The simulation provides the temporal/spatial distributions of densities and concentrations of the suspension. The numerical simulations cannot replace the laboratory tests since they need the final granulometry as initial data, but, as the results show, these simulations can identify the strong and weak points of each method and eventually recommend useful variations and draw conclusions on their validity, aspects very difficult to achieve in the laboratory.

Particles size distribution effect on 3D packing of nanoparticles in to a bounded region

International Nuclear Information System (INIS)

Farzalipour Tabriz, M.; Salehpoor, P.; Esmaielzadeh Kandjani, A.; Vaezi, M. R.; Sadrnezhaad, S. K.

2007-01-01

In this paper, the effects of two different Particle Size Distributions on packing behavior of ideal rigid spherical nanoparticles using a novel packing model based on parallel algorithms have been reported. A mersenne twister algorithm was used to generate pseudo random numbers for the particles initial coordinates. Also, for this purpose a nano sized tetragonal confined container with a square floor (300 * 300 nm) were used in this work. The Andreasen and the Lognormal Particle Size Distributions were chosen to investigate the packing behavior in a 3D bounded region. The effects of particle numbers on packing behavior of these two Particle Size Distributions have been investigated. Also the reproducibility and the distribution of packing factor of these Particle Size Distributions were compared

Raman spectroscopic identification of size-selected airborne particles for quantitative exposure assessment

International Nuclear Information System (INIS)

Steer, Brian; Gorbunov, Boris; Price, Mark C; Podoleanu, Adrian

2016-01-01

In this paper we present a method for the quantification of chemically distinguished airborne particulate matter, required for health risk assessment. Rather than simply detecting chemical compounds in a sample, we demonstrate an approach for the quantification of exposure to airborne particles and nanomaterials. In line with increasing concerns over the proliferation of engineered particles we consider detection of synthetically produced ZnO crystals. A multi-stage approach is presented whereby the particles are first aerodynamically size segregated from a lab-generated single component aerosol in an impaction sampler. These size fractionated samples are subsequently analysed by Raman spectroscopy. Imaging analysis is applied to Raman spatial maps to provide chemically specific quantification of airborne exposure against background which is critical for health risk evaluation of exposure to airborne particles. Here we present a first proof-of-concept study of the methodology utilising particles in the 2–4 μm aerodynamic diameter range to allow for validation of the approach by comparison to optical microscopy. The results show that the combination of these techniques provides independent size and chemical discrimination of particles. Thereby a method is provided to allow quantitative and chemically distinguished measurements of aerosol concentrations separated into exposure relevant size fractions. (paper)

How does dietary particle size affect carnivore gastrointestinal transit: A dog model.

Science.gov (United States)

De Cuyper, A; Hesta, M; Tibosch, S; Wanke, C; Clauss, M; Janssens, G P J

2018-04-01

The effect of dietary particle size on gastrointestinal transit in carnivores has not been studied and might offer more insight into their digestive physiology. This study evaluated the effect of two dietary particle sizes (fine = 7.8 mm vs. coarse = 13 mm) of chunked day-old chicks on transit parameters in dogs. Six beagle dogs were fed both dietary treatments in a crossover design of 7 days with transit testing on the fifth day. Transit parameters were assessed using two markers, that is a wireless motility capsule (IntelliCap ® ) and titanium oxide (TiO 2 ). Dietary particle size did not affect gastric emptying time (GRT), small bowel transit time (SBTT), colonic transit time (CTT) and total transit time (aTTT) of the capsule (p > .05). There was no effect of dietary particle size on TiO 2 mean retention time (MRT) (p > .05). The time of last TiO 2 excretion (MaxRT) differed (p = .013) between diets, being later for the coarse diet. Both MRT (R = 0.617, p = .032) and MaxRT (R = 0.814; p = .001) were positively correlated to aTTT. The ratio MRT/aTTT tended towards a difference between diets (p = .059) with the coarse diet exceeding fine diet values. Results show that the difference between capsule measurements and TiO 2 is larger for the fine than the coarse diet suggesting that the capsule becomes more accurate when dietary particle size approaches marker size. Dietary particle size might have affected transit parameters but differences are too small to claim major physiological consequences. © 2017 Blackwell Verlag GmbH.

Inhalation risk and particle size in dust and mist

Energy Technology Data Exchange (ETDEWEB)

Davies, C N

1949-01-01

This paper presents a critical overview of particle uptake and retention from literature through 1949. Particles > 6-..mu..m are retained in nose, or by secondary bronchi with mouth breathing. Few > 2-..mu..m particles are exhaled, trapped mostly in bronchioles (some by alveoli) by sedimentation. Maximal deposition is 0.4- to 0.8-..mu..m size in bronchioles and alveoli. Minimim retention is at 0.1 to 0.15 ..mu..m; approx. 80% are exhaled. Brownian settling of smaller particles in alveoli occurs. Particles of low density penetrate farther. Slow breathing enhances retention. Soluble toxins may be absorbed at any point along respiratory tract, so deep penetration percentage is moot in most cases.

High-resolution extraction of particle size via Fourier Ptychography

Science.gov (United States)

Li, Shengfu; Zhao, Yu; Chen, Guanghua; Luo, Zhenxiong; Ye, Yan

2017-11-01

This paper proposes a method which can extract the particle size information with a resolution beyond λ/NA. This is achieved by applying Fourier Ptychographic (FP) ideas to the present problem. In a typical FP imaging platform, a 2D LED array is used as light sources for angle-varied illuminations, a series of low-resolution images was taken by a full sequential scan of the array of LEDs. Here, we demonstrate the particle size information is extracted by turning on each single LED on a circle. The simulated results show that the proposed method can reduce the total number of images, without loss of reliability in the results.

Clearance of iron oxide particles in rat liver: effect of hydrated particle size and coating material on liver metabolism.

Science.gov (United States)

Briley-Saebo, Karen C; Johansson, Lars O; Hustvedt, Svein Olaf; Haldorsen, Anita G; Bjørnerud, Atle; Fayad, Zahi A; Ahlstrom, Haakan K

2006-07-01

We sought to evaluate the effect of the particle size and coating material of various iron oxide preparations on the rate of rat liver clearance. The following iron oxide formulations were used in this study: dextran-coated ferumoxide (size = 97 nm) and ferumoxtran-10 (size = 21 nm), carboxydextran-coated SHU555A (size = 69 nm) and fractionated SHU555A (size = 12 nm), and oxidized-starch coated materials either unformulated NC100150 (size = 15 nm) or formulated NC100150 injection (size = 12 nm). All formulations were administered to 165 rats at 2 dose levels. Quantitative liver R2* values were obtained during a 63-day time period. The concentration of iron oxide particles in the liver was determined by relaxometry, and these values were used to calculate the particle half-lives in the liver. After the administration of a high dose of iron oxide, the half-life of iron oxide particles in rat liver was 8 days for dextran-coated materials, 10 days for carboxydextran materials, 14 days for unformulated oxidized-starch, and 29 days for formulated oxidized-starch. The results of the study indicate that materials with similar coating but different sizes exhibited similar rates of liver clearance. It was, therefore, concluded that the coating material significantly influences the rate of iron oxide clearance in rat liver.

Measurement of cylindrical particles with phase Doppler anemometry.

Science.gov (United States)

Mignon, H; Gréhan, G; Gouesbet, G; Xu, T H; Tropea, C

1996-09-01

Light scattering from cylindrical particles has been described with geometric optics. The feasibility of determining the particle diameter with a planar phase Doppler anemometer has been examined by simulations and experiments. In particular, the influence of particle orientation on measurability and measurement accuracy has been investigated. Some recommendations for realizing a practical-measurement instrument have been presented.

Two-step preparation of nano-scaled magnetic chitosan particles using Triton X-100 reversed-phase water-in-oil microemulsion system

Energy Technology Data Exchange (ETDEWEB)

Zhou, Zhengkun; Jiang, Feihong [College of Food Science and Engineering, Northwest A and F University, Yangling, Shaanxi 712100 (China); Lee, Tung-Ching, E-mail: lee@aesop.rutgers.edu [Department of Food Science, Rutgers, the State University of New Jersey, 65 Dudley Road, New Brunswick, NJ 08901 (United States); Yue, Tianli, E-mail: yuetl305@nwsuaf.edu.cn [College of Food Science and Engineering, Northwest A and F University, Yangling, Shaanxi 712100 (China)

2013-12-25

Highlights: •A new two-step route for nano-scaled magnetic chitosan particles preparation. •Triton X-100 reversed-phase microemulsion system was used for chitosan coating. •Narrow size distribution of magnetic chitosan nanoparticles was achieved. •Quantitative evaluation of recoverability for the magnetic chitosan nanoparticles. -- Abstract: A new two-step route for the preparation of nano-scaled magnetic chitosan particles has been developed, different from reported one-step in situ preparation and two-step preparation method of reversed-phase suspension, Triton X-100 reversed-phase water-in-oil microemulsion encapsulation method was employed in coating the pre-prepared Fe{sub 3}O{sub 4} nanoparticles with chitosan. The resultant magnetic chitosan particles owned a narrow size distribution ranging from 50 to 92 nm. X-ray diffraction patterns (XRD) indicated that the chitosan coating procedure did not change the spinal structure of Fe{sub 3}O{sub 4} magnetic nanoparticles. The results of Fourier transform infrared (FTIR) analysis and thermogravimetric analysis (TGA) demonstrated that the chitosan was coated on Fe{sub 3}O{sub 4} nanoparticles and its average mass content was ∼50%. The saturated magnetization of the magnetic Fe{sub 3}O{sub 4}/chitosan nanoparticles reached 18.62 emu/g, meanwhile, the nanoparticles showed the characteristics of superparamagnetism. The magnetic chitosan nanoparticles showed a high recoverability of 99.99% in 10 min when pH exceeded 4. The results suggested that the as-prepared magnetic chitosan particles were nano-scaled with a narrow size distribution and a high recoverability.

The effect of particle size distributions on the microstructural evolution during sintering

DEFF Research Database (Denmark)

Bjørk, Rasmus; Tikare, V.; Frandsen, Henrik Lund

2013-01-01

Microstructural evolution and sintering behavior of powder compacts composed of spherical particles with different particle size distributions (PSDs) were simulated using a kinetic Monte Carlo model of solid state sintering. Compacts of monosized particles, normal PSDs with fixed mean particle...

Building predictive models of soil particle-size distribution

Directory of Open Access Journals (Sweden)

Alessandro Samuel-Rosa

2013-04-01

Full Text Available Is it possible to build predictive models (PMs of soil particle-size distribution (psd in a region with complex geology and a young and unstable land-surface? The main objective of this study was to answer this question. A set of 339 soil samples from a small slope catchment in Southern Brazil was used to build PMs of psd in the surface soil layer. Multiple linear regression models were constructed using terrain attributes (elevation, slope, catchment area, convergence index, and topographic wetness index. The PMs explained more than half of the data variance. This performance is similar to (or even better than that of the conventional soil mapping approach. For some size fractions, the PM performance can reach 70 %. Largest uncertainties were observed in geologically more complex areas. Therefore, significant improvements in the predictions can only be achieved if accurate geological data is made available. Meanwhile, PMs built on terrain attributes are efficient in predicting the particle-size distribution (psd of soils in regions of complex geology.

Determination of the particle size distribution of aerosols by means of a diffusion battery

International Nuclear Information System (INIS)

Maigne, J.P.

1978-09-01

The different methods allowing to determine the particle size distribution of aerosols by means of diffusion batteries are described. To that purpose, a new method for the processing of experimental data (percentages of particles trapped by the battery vs flow rate) was developed on the basis of calculation principles which are described and assessed. This method was first tested by numerical simulation from a priori particle size distributions and then verified experimentally using a fine uranine aerosol whose particle size distribution as determined by our method was compared with the distribution previously obtained by electron microscopy. The method can be applied to the determination of particle size distribution spectra of fine aerosols produced by 'radiolysis' of atmospheric gaseous impurities. Two other applications concern the detection threshold of the condensation nuclei counter and the 'critical' radii of 'radiolysis' particles [fr

Separation and chemical characterization of finely-sized fly-ash particles

International Nuclear Information System (INIS)

Campbell, J.A.; Laul, J.C.; Nielson, K.K.; Smith, R.D.

1978-01-01

The concentrations of 43 major, minor, and trace elements were measured by x-ray fluorescence, atomic absorption, and instrumental neutron activation for nine well-defined size fractions, with mass median diameters of 0.5 μ to 50 μm, of fly ash from a western coal-fired steam plant. There was generally good agreement in concentrations of elements analyzed by more than one technique. Concentration profiles as a function of mean particle size were established for various elements. Based on the concentration profiles, the elements can be divided into three distinct groups. One group consists primarily of the volatile elements or elements partially volatilized during coal combustion (examples include As, Se, Zn, Ga, etc.), and their concentrations decrease with increasing particle size. A second group, which shows a minor or direct dependence on particle size, as in the case of Si, is apparently associated primarily with the fly-ash matrix. The last group of elements, which includes Ca, Sr, Y, and the rare earths, shows small changes in their concentration profiles with a maximum in concentration at approximately 5 μm. 6 tables, 6 figures

Influence of Emulsion Polymerization Techniques to Particle Size of Copoly(styrene/butyl acrylate/methyl methacrylate

Directory of Open Access Journals (Sweden)

Tresye Utari

2008-04-01

Full Text Available In the majority of applications, particle size and particle size distribution are highly significant factors that determine the properties of a polymer dispersion, such as its flow behavior or its stability. For example, a coating material with small particle size will give smooth coating result, good adhesive strength, good water resistance and latex stability. This article describes influence of various emulsion polymerization techniques to particle size of copoly(styrene/butyl acrylate/methyl methacrylate with mix surfactant SDBS linear chain and nonyl fenol (EO10 and initiator ammonium persulphate. DSC data, solid content and IR spectrum showed that copoly(styrene/butyl acrylate/methyl methacrylate was produced. Batch emulsion polymerization technique gave the highest particle size i.e. 615 nm and also the highest % conversion of monomer i.e. 97%. The more concentration of monomer was seeded to initial charge gave greater particle size and greater poly dispersity index.

Efficiency in supercritical fluid chromatography with different superficially porous and fully porous particles ODS bonded phases.

Science.gov (United States)

Lesellier, E

2012-03-09

The chromatographic efficiency, in terms of plate number per second, was dramatically improved by the introduction of sub-two microns particles with ultra-high pressure liquid chromatography (UHPLC). On the other hand, the recent development of superficially porous particles, called core-shell or fused-core particles, appears to allow the achievement of the same efficiency performances at higher speed without high pressure drops. CO₂-based mobile phases exhibiting much lower viscosities than aqueous based mobile phases allow better theoretical efficiencies, even with 3-5 μm particles, but with relative low pressure drops. They also allow much higher flow rates or much longer columns while using conventional instruments capable to operate below 400 bar. Moreover, the use of superficially porous particles in SFC could enhance the chromatographic performances even more. The kinetic behavior of ODS phases bonded on these particles was studied, with varied flow rates, outlet (and obviously inlet) pressures, temperatures, by using a homologous series (alkylbenzenes) with 10% modifier (methanol or acetonitrile) in the carbon dioxide mobile phase. Results were also compared with classical fully porous particles, having different sizes, from 2.5 to 5 μm. Superior efficiency (N) and reduced h were obtained with these new ODS-bonded particles in regards to classical ones, showing their great interest for use in SFC. However, surprising behavior were noticed, i.e. the increase of the theoretical plate number vs. the increase of the chain length of the compounds. This behavior, opposite to the one classically reported vs. the retention factor, was not depending on the outlet pressure, but on the flow rate and the temperature changes. The lower radial trans-column diffusion on this particle types could explain these results. This diffusion reduction with these ODS-bonded superficially porous particles seems to decrease with the increase of the residence time of compounds

How comparable are size-resolved particle number concentrations from different instruments?

Science.gov (United States)

Hornsby, K. E.; Pryor, S. C.

2012-12-01

The need for comparability of particle size resolved measurements originates from multiple drivers including: (i) Recent suggestions that air quality standards for particulate matter should migrate from being mass-based to incorporating number concentrations. This move would necessarily be predicated on measurement comparability which is absolutely critical to compliance determination. (ii) The need to quantify and diagnose causes of variability in nucleation and growth rates in nano-particle experiments conducted in different locations. (iii) Epidemiological research designed to identify key parameters in human health responses to fine particle exposure. Here we present results from a detailed controlled laboratory instrument inter-comparison experiment designed to investigate data comparability in the size range of 2.01-523.3 nm across a range of particle composition, modal diameter and absolute concentration. Particle size distributions were generated using a TSI model 3940 Aerosol Generation System (AGS) diluted using zero air, and sampled using four TSI Scanning Mobility Particle Spectrometer (SMPS) configurations and a TSI model 3091 Fast Mobility Particle Sizer (FMPS). The SMPS configurations used two Electrostatic Classifiers (EC) (model 3080) attached to either a Long DMA (LDMA) (model 3081) or a Nano DMA (NDMA) (model 3085) plumbed to either a TSI model 3025A Butanol Condensed Particle Counting (CPC) or a TSI model 3788 Water CPC. All four systems were run using both high and low flow conditions, and were operated with both the internal diffusion loss and multiple charge corrections turned on. The particle compositions tested were sodium chloride, ammonium nitrate and olive oil diluted in ethanol. Particles of all three were generated at three peak concentration levels (spanning the range observed at our experimental site), and three modal particle diameters. Experimental conditions were maintained for a period of 20 minutes to ensure experimental

Diffusion of Finite-Size Particles in Confined Geometries

KAUST Repository

Bruna, Maria; Chapman, S. Jonathan

2013-01-01

The diffusion of finite-size hard-core interacting particles in two- or three-dimensional confined domains is considered in the limit that the confinement dimensions become comparable to the particle's dimensions. The result is a nonlinear diffusion equation for the one-particle probability density function, with an overall collective diffusion that depends on both the excluded-volume and the narrow confinement. By including both these effects, the equation is able to interpolate between severe confinement (for example, single-file diffusion) and unconfined diffusion. Numerical solutions of both the effective nonlinear diffusion equation and the stochastic particle system are presented and compared. As an application, the case of diffusion under a ratchet potential is considered, and the change in transport properties due to excluded-volume and confinement effects is examined. © 2013 Society for Mathematical Biology.

Hanford Tank Waste Particle Atlas

Energy Technology Data Exchange (ETDEWEB)

Herting, D. L. [Washington River Protection Solutions LLC (WRPS), Richland, WA (United States); Cooke, G. A. [Washington River Protection Solutions LLC (WRPS), Richland, WA (United States); Page, J S [Washington River Protection Solutions LLC (WRPS), Richland, WA (United States); Valerio, J. L. [Washington River Protection Solutions LLC (WRPS), Richland, WA (United States)

2015-08-01

Several methods have been utilized to perform solid phase characterization. Polarized light microscopy (PLM) is used to identify individual particles based on size, shape, color, and optical properties (e.g., refractive index1, birefringence, extinction positions, and interference figures). Scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS) is used to detect which elements are present in individual particles and to infer chemical phase identification based on the metals present in combination with the size and shape of the particles. Powder X-ray diffraction (XRD) is used to identify crystalline phases present in bulk samples by matching the X-ray patterns with a library of known patterns for pure phases. Transmission electron microscopy (TEM) is used to identify individual particles by their X-ray diffraction patterns. RAMAN analysis is used to identify bulk sample compositions by matching RAMAN spectra with a library of known patterns. Other specialized techniques have not been employed routinely for Hanford tank waste samples.

Investigation of the low-speed impact behavior of dual particle size metal matrix composites

International Nuclear Information System (INIS)

Cerit, Afşın Alper

2014-01-01

Highlights: • AA2124 matrix composites reinforced with SiC particles were manufactured. • Low-speed impact behaviors of composites were investigated. • Composites were manufactured with single (SPS) and dual particle sizes (DPS). • Impact behaviors of DPS composites are more favorable than the SPS composites. • Approximately 50–60% of input energy was absorbed by the composite samples. - Abstract: SiC-reinforced aluminum matrix composites were manufactured by powder metallurgy using either single or dual particle sized SiC powders and samples sintered under argon atmosphere. Quasi-static loading, low-speed impact tests and hardness tests were used to investigate mechanical behavior and found that dual particle size composites had improved hardness and impact performance compared to single particle size composites. Sample microstructure, particle distributions, plastic deformations and post-testing damages were examined by scanning electron microscopy and identified microstructure agglomerations in SPS composites. Impact traces were characterized by broken and missing SiC particles and plastically deformed composite areas

Defining the sizes of airborne particles that mediate influenza transmission in ferrets.

Science.gov (United States)

Zhou, Jie; Wei, Jianjian; Choy, Ka-Tim; Sia, Sin Fun; Rowlands, Dewi K; Yu, Dan; Wu, Chung-Yi; Lindsley, William G; Cowling, Benjamin J; McDevitt, James; Peiris, Malik; Li, Yuguo; Yen, Hui-Ling

2018-03-06

Epidemics and pandemics of influenza are characterized by rapid global spread mediated by non-mutually exclusive transmission modes. The relative significance between contact, droplet, and airborne transmission is yet to be defined, a knowledge gap for implementing evidence-based infection control measures. We devised a transmission chamber that separates virus-laden particles by size and determined the particle sizes mediating transmission of influenza among ferrets through the air. Ferret-to-ferret transmission was mediated by airborne particles larger than 1.5 µm, consistent with the quantity and size of virus-laden particles released by the donors. Onward transmission by donors was most efficient before fever onset and may continue for 5 days after inoculation. Multiple virus gene segments enhanced the transmissibility of a swine influenza virus among ferrets by increasing the release of virus-laden particles into the air. We provide direct experimental evidence of influenza transmission via droplets and fine droplet nuclei, albeit at different efficiency. Copyright © 2018 the Author(s). Published by PNAS.

Particle Size Effects of TiO2 Layers on the Solar Efficiency of Dye-Sensitized Solar Cells

Directory of Open Access Journals (Sweden)

Ming-Jer Jeng

2013-01-01

Full Text Available Large particle sizes having a strong light scattering lead to a significantly decreased surface area and small particle sizes having large surface area lack light-scattering effect. How to combine large and small particle sizes together is an interesting work for achieving higher solar efficiency. In this work, we investigate the solar performance influence of the dye-sensitized solar cells (DSSCs by the multiple titanium oxide (TiO2 layers with different particle sizes. It was found that the optimal TiO2 thickness depends on the particle sizes of TiO2 layers for achieving the maximum efficiency. The solar efficiency of DSSCs prepared by triple TiO2 layers with different particle sizes is higher than that by double TiO2 layers for the same TiO2 thickness. The choice of particle size in the bottom layer is more important than that in the top layer for achieving higher solar efficiency. The choice of the particle sizes in the middle layer depends on the particle sizes in the bottom and top layers. The mixing of the particle sizes in the middle layer is a good choice for achieving higher solar efficiency.

Karna Particle Size Dataset for Tables and Figures

Data.gov (United States)

U.S. Environmental Protection Agency — This dataset contains 1) table of bulk Pb-XAS LCF results, 2) table of bulk As-XAS LCF results, 3) figure data of particle size distribution, and 4) figure data for...

Measurement of Turbulence Modulation by Non-Spherical Particles

DEFF Research Database (Denmark)

Mandø, Matthias; Rosendahl, Lasse

2010-01-01

The change in the turbulence intensity of an air jet resulting from the addition of particles to the flow is measured using Laser Doppler Anemometry. Three distinct shapes are considered: the prolate spheroid, the disk and the sphere. Measurements of the carrier phase and particle phase velocities...... at the centerline of the jet are carried out for mass loadings of 0.5, 1, 1.6 and particle sizes 880μm, 1350μm, 1820μm for spherical particles. For each non-spherical shape only a single size and loading are considered. The turbulence modulation of the carrier phase is found to highly dependent on the turbulence......, the particle mass flow and the integral length scale of the flow. The expression developed on basis of spherical particles only is applied on the data for the non-spherical particles. The results suggest that non-spherical particles attenuate the carrier phase turbulence significantly more than spherical...

Mechanism for Particle Transport and Size Sorting via Low-Frequency Vibrations

Science.gov (United States)

Sherrit, Stewart; Scott, James S.; Bar-Cohen, Yoseph; Badescu, Mircea; Bao, Xiaoqi

2010-01-01

There is a need for effective sample handling tools to deliver and sort particles for analytical instruments that are planned for use in future NASA missions. Specifically, a need exists for a compact mechanism that allows transporting and sieving particle sizes of powdered cuttings and soil grains that may be acquired by sampling tools such as a robotic scoop or drill. The required tool needs to be low mass and compact to operate from such platforms as a lander or rover. This technology also would be applicable to sample handling when transporting samples to analyzers and sorting particles by size.

Nanosize stabilization of cubic and tetragonal phases in reactive plasma synthesized zirconia powders

Energy Technology Data Exchange (ETDEWEB)

Jayakumar, S., E-mail: sjayakumar.physics@gmail.com [Research and Development Centre, Bharathiar University, Coimbatore 641 014 (India); Department of Physics, Pollachi Institute of Engineering and Technology, Pollachi 642 205 (India); Ananthapadmanabhan, P.V.; Thiyagarajan, T.K. [Laser and Plasma Technology Division, BARC, Trombay, Mumbai 400 085 (India); Perumal, K. [Vision for Wisdom, Temple of Consciousness, Aliyar 642 101 (India); Mishra, S.C. [Department of Metallurgical and Materials Engg, National Institute of Technology, Rourkela 769 008 (India); Suresh, G. [Department of Physics, Park College of Engineering and Technology, Coimbatore 641 659 (India); Su, L.T.; Tok, A.I.Y. [School of Materials Science and Engg, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639 798 (Singapore)

2013-06-15

Pure zirconium oxide powders with particle size 2–33 nm are synthesized by reactive plasma processing. Transmission electron microscopy investigation of these particles revealed size dependent behavior for their phase stabilization. The monoclinic phase is found to be stable when particle size is ≥20 nm; Tetragonal is found to be stabilized in the range of 7–20 nm and as the particle size decreases to 6 nm and less, the cubic phase is stabilized. - Highlights: ► Direct conversion of micron-sized zirconium hydride powder to single crystal ZrO{sub 2} nanopowder. ► Size dependent stabilization of cubic, tetragonal and monoclinic phases in the reactive plasma synthesized ZrO{sub 2} nanopowder. ► Transmission electron microscopic investigation to identify particles of different sizes and their corresponding phase structure.

Fabrication, Characterization, and Biological Activity of Avermectin Nano-delivery Systems with Different Particle Sizes

Science.gov (United States)

Wang, Anqi; Wang, Yan; Sun, Changjiao; Wang, Chunxin; Cui, Bo; Zhao, Xiang; Zeng, Zhanghua; Yao, Junwei; Yang, Dongsheng; Liu, Guoqiang; Cui, Haixin

2018-01-01

Nano-delivery systems for the active ingredients of pesticides can improve the utilization rates of pesticides and prolong their control effects. This is due to the nanocarrier envelope and controlled release function. However, particles containing active ingredients in controlled release pesticide formulations are generally large and have wide size distributions. There have been limited studies about the effect of particle size on the controlled release properties and biological activities of pesticide delivery systems. In the current study, avermectin (Av) nano-delivery systems were constructed with different particle sizes and their performances were evaluated. The Av release rate in the nano-delivery system could be effectively controlled by changing the particle size. The biological activity increased with decreasing particle size. These results suggest that Av nano-delivery systems can significantly improve the controllable release, photostability, and biological activity, which will improve efficiency and reduce pesticide residues.

Polybutadiene latex particle size distribution analysis utilizing a disk centrifuge

NARCIS (Netherlands)

Verdurmen, E.M.F.J.; Albers, J.G.; German, A.L.

1994-01-01

Polybutadiene (I) latexes prepd. by emulsifier-free emulsion polymn. and having particle diam. 50-300 nm for both unimodal and bimodal particles size distributions were analyzed by the line-start (LIST) method in a Brookhaven disk centrifuge photosedimentometer. A special spin fluid was designed to

Electronic structure and size of TiO sub 2 nanoparticles of controlled size prepared by aerosol methods

CERN Document Server

Soriano, L; Sanchez-Agudo, M; Sanz, J M; Ahonen, P P; Kauppinen, E I; Palomares, F J; Bressler, P R

2002-01-01

A complete characterization of nanostructures has to deal both with electronic structure and dimensions. Here we present the characterization of TiO sub 2 nanoparticles of controlled size prepared by aerosol methods. The electronic structure of these nanoparticles was probed by x-ray absorption spectroscopy (XAS), the particle size by atomic force microscopy (AFM). XAS spectra show that the particles crystallize in the anatase phase upon heating at 500 sup o C, whereas further annealing at 700 sup o C give crystallites of 70 % anatase and 30 % rutile phases. Raising the temperature to 900 sup o C results in a complete transformation of the particles to rutile. AFM images reveal that the mean size of the anatase particles formed upon heating at 500 sup o C is 30 nm, whereas for the rutile particles formed upon annealing at 900 sup o C 90 nm were found. The results obtained by these techniques agree with XRD data. (author)

Analysis of tecniques for measurement of the size distribution of solid particles

Directory of Open Access Journals (Sweden)

F. O. Arouca

2005-03-01

Full Text Available Determination of the size distribution of solid particles is fundamental for analysis of the performance several pieces of equipment used for solid-fluid separation. The main objective of this work is to compare the results obtained with two traditional methods for determination of the size grade distribution of powdery solids: the gamma-ray attenuation technique (GRAT and the LADEQ test tube technique. The effect of draining the suspension in the two techniques used was also analyzed. The GRAT can supply the particle size distribution of solids through the monitoring of solid concentration in experiments on batch settling of diluted suspensions. The results show that use of the peristaltic pump in the GRAT and the LADEQ methods produced a significant difference between the values obtained for the parameters of the particle size model.

WOOD STOVE EMISSIONS: PARTICLE SIZE AND CHEMICAL COMPOSITION

Science.gov (United States)

The report summarizes wood stove particle size and chemical composition data gathered to date. [NOTE: In 1995, EPA estimated that residential wood combustion (RWC), including fireplaces, accounted for a significant fraction of national particulate matter with aerodynamic diameter...

Performance of japanese quails fed feeds containing different corn and limestone particle sizes

OpenAIRE

Berto,DA; Garcia,EA; Móri,C; Faitarone,ABG; Pelícia,K; Molino,AB

2007-01-01

This study aimed at evaluating performance and egg quality of Japanese quails fed feeds containing different corn and limestone particle sizes. A total number of 648 birds in the peak of production was distributed in a random complete block experimental design, using a 2x3 factorial arrangement (2 corn particle sizes and 3 limestone particle sizes). Birds were designated to one of two blocks, with six replicates of 18 birds each. Mean geometric diameter (MGD) values used were 0.617mm and 0.72...

Spatial Variability of CCN Sized Aerosol Particles

Science.gov (United States)

Asmi, A.; Väänänen, R.

2014-12-01

The computational limitations restrict the grid size used in GCM models, and for many cloud types they are too large when compared to the scale of the cloud formation processes. Several parameterizations for e.g. convective cloud formation exist, but information on spatial subgrid variation of the cloud condensation nuclei (CCNs) sized aerosol concentration is not known. We quantify this variation as a function of the spatial scale by using datasets from airborne aerosol measurement campaigns around the world including EUCAARI LONGREX, ATAR, INCA, INDOEX, CLAIRE, PEGASOS and several regional airborne campaigns in Finland. The typical shapes of the distributions are analyzed. When possible, we use information obtained by CCN counters. In some other cases, we use particle size distribution measured by for example SMPS to get approximated CCN concentration. Other instruments used include optical particle counters or condensational particle counters. When using the GCM models, the CCN concentration used for each the grid-box is often considered to be either flat, or as an arithmetic mean of the concentration inside the grid-box. However, the aircraft data shows that the concentration values are often lognormal distributed. This, combined with the subgrid variations in the land use and atmospheric properties, might cause that the aerosol-cloud interactions calculated by using mean values to vary significantly from the true effects both temporary and spatially. This, in turn, can cause non-linear bias into the GCMs. We calculate the CCN aerosol concentration distribution as a function of different spatial scales. The measurements allow us to study the variation of these distributions within from hundreds of meters up to hundreds of kilometers. This is used to quantify the potential error when mean values are used in GCMs.

Temperature and particle-size dependent viscosity data for water-based nanofluids - Hysteresis phenomenon

International Nuclear Information System (INIS)

Nguyen, C.T.; Desgranges, F.; Roy, G.; Galanis, N.; Mare, T.; Boucher, S.; Angue Mintsa, H.

2007-01-01

In the present paper, we have investigated experimentally the influence of both the temperature and the particle size on the dynamic viscosities of two particular water-based nanofluids, namely water-Al 2 O 3 and water-CuO mixtures. The measurement of nanofluid dynamic viscosities was accomplished using a 'piston-type' calibrated viscometer based on the Couette flow inside a cylindrical measurement chamber. Data were collected for temperatures ranging from ambient to 75 deg. C, for water-Al 2 O 3 mixtures with two different particle diameters, 36 nm and 47 nm, as well as for water-CuO nanofluid with 29 nm particle size. The results show that for particle volume fractions lower than 4%, viscosities corresponding to 36 nm and 47 nm particle-size alumina-water nanofluids are approximately identical. For higher particle fractions, viscosities of 47 nm particle-size are clearly higher than those of 36 nm size. Viscosities corresponding to water-oxide copper are the highest among the nanofluids tested. The temperature effect has been investigated thoroughly. A more complete viscosity data base is presented for the three nanofluids considered, with several experimental correlations proposed for low particle volume fractions. It has been found that the application of Einstein's formula and those derived from the linear fluid theory seems not to be appropriate for nanofluids. The hysteresis phenomenon on viscosity measurement, which is believed to be the first observed for nanofluids, has raised serious concerns regarding the use of nanofluids for heat transfer enhancement purposes

Assessment of particle size distribution in CO 2 accidental releases