Particle Size Dependence Research Articles

Aerosol optical depth as observed by the Mars Science Laboratory REMS UV photodiodes

Systematic observations taken by the REMS UV photodiodes on a daily basis throughout the landed Mars Science Laboratory mission provide a highly useful tool for characterizing aerosols above Gale Crater. Radiative transfer modeling is used to model the approximately 1.75 Mars Years of observations taken to date taking into account multiple scattering from aerosols and the extended field of view of the REMS UV photodiodes. The retrievals show in detail the annual cycle of aerosol optical depth, which is punctuated with numerous short timescale events of increased optical depth. Dust deposition onto the photodiodes is accounted for by comparison with aerosol optical depth derived from direct imaging of the Sun by Mastcam. The effect of dust on the photodiodes is noticeable, but does not dominate the signal. Cleaning of dust from the photodiodes was observed in the season around Ls=270°, but not during other seasons. Systematic deviations in the residuals from the retrieval fit are indicative of changes in aerosol effective particle size, with larger particles present during periods of increased optical depth. This seasonal dependence of aerosol particle size is expected as dust activity injects larger particles into the air, while larger aerosols settle out of the atmosphere more quickly leading to a smaller average particle size over time.

Effect of particle size and volume fraction of BaTiO3 powders on the functional properties of BaTiO3/poly(ε-caprolactone) composites

A systematic study concerning the effect of particle size and volume fraction of BaTiO3 filler on the functional properties of composite materials with poly-(ε-caprolactone) polymer matrix obtained by solvent casting method was performed. Two series of xBT-(1-x)PCL composites prepared by using BaTiO3 powders with two different particles size (60 nm and 400 nm) in different amounts (x = 2; 5; 10 and 20 vol %) were investigated. The X-ray diffraction analysis indicated a particle size dependence of phase symmetry for BT filler powders (cubic phase for ultrafine particles and tetragonal phase for larger particles size) and the formation of pure composites consisting of orthorhombic PCL and cubic or tetragonal BT with no chemical reactions between them. The micrographs of the composites revealed the formation of homogeneous composites with two distinct phases, a good dispersion of ferroelectric phase into the polymer matrix and a low content of air pores. Dielectric investigations at room temperature showed the increases of permittivity with increasing the particle volume fraction of ferroelectric filler as result of the “sum property” of the effective permittivity in composites. For a given concentration, the permittivity of composites increases with particle size, as result of a size effect of BT powder. The composites with low BT addition presents stable dielectric properties at bending cycles. The polarization-field dependences also show a BT-induced size dependence, i.e. at a given value of field, polarization is higher for the composites with coarser BT particles. The composition x = 0.05 with coarse particles can be considered as an optimum among these series for the stored energy density.

Phase transitions, structures, and rheological properties of hydroxypropyl cellulose–ethylene glycol and ethyl cellulose–dimethylformamide systems in the presence and in the absence of a magnetic field

Phase transitions, structures, and rheological properties of hydroxypropyl cellulose–ethylene glycol and ethyl cellulose–dimethylformamide systems in the presence and in the absence of a magnetic field have been studied. The application of the magnetic-field results in increases in viscosity and supramolecular particle size in solutions of cellulose ethers. Concentration dependences of viscosity and particle size are described by curves with maxima.

Ignition of a coal particle on a heated surface

With the use of high-speed (to 6 × 105 frames per second) video recording facilities, the following three physicochemical transformation regimes were recognized on the induction heating of the single particles (4–6 mm in size) of D coal on a steel plate (at a temperature of no higher than 1000 K): thermal decomposition without ignition, smoldering, and ignition. The limiting (minimum) values of heat source temperatures necessary and sufficient for the initiation of combustion of coal particles were established.The effect of particle sizes on the integral characteristics of the test process was found. The particle-size dependence of the time of heating of a natural solid fuel particle to the intense development of an exothermic reaction was obtained. It was found that the characteristic times of the initiation of the ignition and smoldering regimes were no longer than 10 and 20 s, respectively, with variations in coal particle size.

Understanding the primary and secondary aggregation states of sputtered silver nanoparticles in thiolate matrix and their immobilization in resin

Abstract We report detailed aggregation mechanisms of sputtered silver nanoparticles in a viscous thiolate liquid matrix. Fluorescent silver nanoparticles were prepared by the sputtering deposition over pentaerythritol tetrakis(3-mercaptopropionate) (PEMP). The dependences of extinction, fluorescence and particle size on time were discussed in terms of two possible aggregation mechanisms. The main aggregation process was secondary aggregation, with primary aggregation (core coalescence) making a small contribution. The four thiol groups in the PEMP structure are the driving force determining the predominance of secondary aggregation. Finally, we successfully prepared a thiourethane resin by the polymerization of a thiolate matrix, and complete immobilization of nanoparticles in the resin resulted in no observable degradation of the photophysical properties. The demonstrations presented here will be beneficial in understanding the detailed aggregation mechanism and optical properties of nanoparticles.

Dependence of CuO particle size and diameter of reaction tubing on tritium recovery for tritium safety operation

Usage of CuO and water bubbler is one of the conventional and convenient methods for tritium recovery. In present work, influence of CuO particle size and diameter of reaction tubing on the tritium recovery was evaluated. Reaction rate constant of tritium with CuO particle has been calculated by the combination of experimental results and a simulation code. Then, these results were applied for exploring the dependence of reaction tubing length on tritium conversion ratio. The results showed that the surface area of CuO has a great influence on the oxidation rate constant. The frequency factor of the reaction would be approximately doubled by reducing the CuO particle size from 1.0mm to 0.2mm. Cross section of reaction tubing mainly affected on the duration of tritium at the temperature below 600K. Reaction tubing with length of 1m at temperature of 600K would be suitable for keeping the tritium conversion ratio above 99.9%. The length of reaction tubing can be reduced by using the smaller CuO particle or increasing the CuO temperature.

Air-jet atomization for preparation of lipid nanoparticles: Dependence of size on solute concentration

Engineering nanoparticles for applications such as drug delivery, needs understanding of dependence of particle size on process and precursor parameters. The size of nanoparticles prepared through the aerosol route using solution droplet drying technique is traditionally governed by a 1/3rd scaling law between dry particle diameter and precursor solute concentration. Here, we experimentally investigate this relationship, for precursor solutions of lipids in organic solvents. Nanoparticles were prepared using air-jet atomization of precursor solutions of stearic acid in organic solvents (acetone, chloroform, methanol and ethanol), in a pulse heat aerosol reactor, at a process temperature of 50°C. The relationship between median mobility diameter of prepared nanoparticles (40–155nm) and solute concentration was governed by a scaling law exponent (SLE) in the range 0.104–0.182. The observed exponents showed significant deviations from the classical 1/3rd law. The experimental investigation indicated an unexpected increase in particle number concentration with increasing solute concentration for all solvents studied. Simulations with a critical super saturation based solute diffusion model and theoretical calculations of size dependent external factors such as coagulation and wall losses during transit, could not explain the deviation in SLE, nor the increased number concentrations. These considerations point to possible effects of solute concentration on the mechanism of droplet formation during the atomization process. A preliminary model based on an area conservation law has been proposed to explain the twin effects of deviation in SLE and increased droplet number concentration with increasing solute concentration. The present study provides empirical data on the relationship between dry particle diameter and solute concentration in the selected lipid-organic solvent systems. Also, it opens avenues for further understanding nanoparticle formation by air-jet atomization.

Soot particle size measurements in ethylene diffusion flames at elevated pressures

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.

Effect of a magnetic field on the rheological properties of the systems hydroxypropyl cellulose–ethanol and hydroxypropyl cellulose–dimethyl sulfoxide

With the use of viscometry, the cloud-point method, polarization microscopy, the turbidity-spectrum method, and a polarization photoelectric apparatus, the relaxation pattern of the rheological behaviors, phase transitions, and structures of the systems hydroxypropyl cellulose–ethanol and hydroxypropyl cellulose–dimethyl sulfoxide are studied. The regions of existence of isotropic and anisotropic phases and the concentration dependence of the sizes of supramolecular particles are determined. It is found that a magnetic field increases the viscosities of solutions. The concentration dependences of viscosity and particle size are described by curves with maxima.

Reactivity with water vapor and hydrogen storage capacity of Be2Ti compound

Beryllium intermetallic compounds show a variety of excellent properties such as neutron multiplication, refractory function, hydrogen storage, and superconductivity. Be12M compounds (M = Ti, V, and Zr) have been investigated as neutron multipliers for fusion reactors, while Be17M2 compounds have been explored as refractory materials. Furthermore, Be2Ms are known to have Laves phases, which are characterized by an A2B type compound having high H2 gas storage potential. Because of its low density, the hydrogen properties of Be2Ms have attracted great interest from viewpoints of reactivity with H2O, trap site of hydrogen, and amount of H2 gas in this compound. However, few studies have dealt with Be2M, and its database remains unsatisfactory.Preliminary synthesis of a beryllium intermetallic compound (=Be2Ti) as a hydrogen storage material was conducted to clarify its reactivity with water vapor at high temperatures and high hydrogen storage capacity. X-ray diffraction profiles and electron-probe microanalysis results confirmed that the preliminary synthesis of single-phase Be2Ti by homogenization treatment and plasma sintering was successful. The hydrogen generation rate of Be2Ti by reaction with 1% H2O increased as the test temperature increased. High temperature exposure to H2O led to the formation of TiO2 on the surface. Furthermore, the hydrogen gas storage concentration of Be2Ti, evaluated using the pressure–concentration–temperature curve, was 0.56 wt.% (=0.125 H/M) at 298 K, which is relatively low considering that H2 pressure was increased up to 13 MPa. Based on additional pressure–composition–temperature measurements, it does not appear to have particle size dependence with regard to hydrogen capacity.A simulation based on first-principles calculation indicated the presence of two hydrogen trap sites, tetrahedral and center of triangle with solution energies of −0.52 and −0.05 eV, respectively, implying that the maximum trap site of hydrogen with 5.4 wt.%. This dissimilarity might be attributed to the fact that the Be2Ti sample contained a large fraction of surface oxide layer, which disturbed the surface penetration of hydrogen.

(Invited) Kinetics of Photocatalytic Multielectron Transfer By Nanoparticles of Bare or Catalyst-Loaded Titania

For heterogeneous photocatalysis, it is well known that photocatalytic oxidation of water into oxygen (O2) is induced by particulate photocatalysts in the presence of electron acceptors. This reaction has been presumed to proceed through a four-electron (hole) process, and therefore it is expected that reaction rate depends on light intensity and particle size of photocatalyst, which influence the number of photons absorbed by one photocatalyst particle. However such dependences have rarely been reported and discussed so far. In this study, we report light-intensity and particle-size dependences of rate of oxygen evolution from suspensions of commercial titania samples using iodate (IO3 -) and iron(III) (Fe3+) ions as an electron acceptor under intense UV-LED irradiation (365 nm; < 300 mW). Figure 1 shows the light-intensity dependence of rate of O2 evolution from a suspension of rutile (Tayca MT-150A; 13 nm) with Fe3+. A higher-order non-linear dependence was observed in the relatively lower (< 190 mW = threshold intensity, I thr), while the rate was almost proportional to the intensity (with slope, a) in the higher intensity range, and those dependences could be reproduced by second and first-order equations, respectively. Similar bimodal dependences, with different a and I thr, were also observed when the other titania samples were used in the presence of IO3 - or Fe3+. Assuming a kinetic model (Scheme 1) in which second-photon absorption by a one photon-absorbing particle (TiO2(h+)) within its lifetime leads to oxygen evolution, a rate equation (eq. 1) was derived using parameters of lifetime of TiO2(h+), secondary photon-absorption efficiency and rate constant of oxygen evolution by a two-photon absorbing particle(TiO2*), and further derivation for lower and higher intensity limits to eqs. 2 and 3, respectively, reproduced the bimodal light-intensity dependences. Threshold intensity (I thr) at which order of light-intensity dependence formally changes from second to first is defined as intensity for the equal rates of eq. 1 and 2 are equal. Differences in I thr and a depending on the kind of electron acceptors, crystalline structure (anatase or rutile) and particle size are discussed. Figure 1

Size dependence of non-magnetic thickness in YIG nanoparticles

This study is focused on particle size dependence of structural and magnetic properties in yttrium iron garnet (Y3Fe5O12) nanoparticles. A series of YIG samples with different particle size were produced by varying the annealing temperatures. The X-ray analysis revealed an inverse correlation between lattice parameter and the crystallite size. The normal distribution is used for fitting the particles size distribution which is extracted from scanning electron micrographs. Also, by using the results of vibrating sample magnetometer, the magnetic diameter was calculated based on Langevin model in order to investigate the variation of dead layer thickness. Furthermore, the observed line broadening in Mössbauer spectra confirmed the increase of non-magnetic thickness due to the reduction of particle size.

Aerosol detection efficiency in inductively coupled plasma mass spectrometry

An electrostatic size classification technique was used to segregate particles of known composition prior to being injected into an inductively coupled plasma mass spectrometer (ICP-MS). Size-segregated particles were counted with a condensation nuclei counter as well as sampled with an ICP-MS. By injecting particles of known size, composition, and aerosol concentration into the ICP-MS, efficiencies of the order of magnitude aerosol detection were calculated, and the particle size dependencies for volatile and refractory species were quantified. Similar to laser ablation ICP-MS, aerosol detection efficiency was defined as the rate at which atoms were detected in the ICP-MS normalized by the rate at which atoms were injected in the form of particles. This method adds valuable insight into the development of technologies like laser ablation ICP-MS where aerosol particles (of relatively unknown size and gas concentration) are generated during ablation and then transported into the plasma of an ICP-MS. In this study, we characterized aerosol detection efficiencies of volatile species gold and silver along with refractory species aluminum oxide, cerium oxide, and yttrium oxide. Aerosols were generated with electrical mobility diameters ranging from 100 to 1000nm. In general, it was observed that refractory species had lower aerosol detection efficiencies than volatile species, and there were strong dependencies on particle size and plasma torch residence time. Volatile species showed a distinct transition point at which aerosol detection efficiency began decreasing with increasing particle size. This critical diameter indicated the largest particle size for which complete particle detection should be expected and agreed with theories published in other works. Aerosol detection efficiencies also displayed power law dependencies on particle size. Aerosol detection efficiencies ranged from 10−5 to 10−11. Free molecular heat and mass transfer theory was applied, but evaporative phenomena were not sufficient to explain the dependence of aerosol detection on particle diameter. Additional work is needed to correlate experimental data with theory for metal-oxides where thermodynamic property data are sparse relative to pure elements. Lastly, when matrix effects and the diffusion of ions inside the plasma were considered, mass loading was concluded to have had an effect on the dependence of detection efficiency on particle diameter.

Abstract C60: Injectable, biodegradable micro- and nano-particles loaded with prodigiosin-based drug for localized anticancer drug delivery

Abstract This paper presents the synthesis and physicochemical characterization of injectable, multi-functional, biodegradable poly (D,L-lactide-co-glycolide) (PLGA)-loaded micro- and nano-particles. These particles were loaded with an anticancer drug from prodigiosin (PG), which was obtained from bacteria, Serratia marcescens subsp. Marcescens. The release of paclitaxel (PT) was also tested as a control. The PG and PT were encapsulated using a single-emulsion solvent evaporation technique with PLGA as a polymer matrix and poly-(vinyl alcohol) (PVA) as an emulsifier. The dependence of particle size and morphology on processing conditions was also evaluated. In vitro release studies were used to elucidate drug loading efficiency, encapsulation efficiency and microparticle morphology using a combination of UV-visible (UV-Vis) spectrophotometry, optical Microscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and atomic force microscopy (AFM). The implications of the results are then explored using MDA-MB-231 cells (breast cancer cells) for the development of injectable, multi-functional, polymeric micro- and nano-particles for the controlled release of cancer drugs and the localized treatment of cancer. Citation Format: John D. Obayemi, Karen A. Malatesta, Olushola S. Odusanya, Danyuo Yiporo, Wei Yu, Kathryn E. Uhrich, Winston O. Soboyejo. Injectable, biodegradable micro- and nano-particles loaded with prodigiosin-based drug for localized anticancer drug delivery. [abstract]. In: Proceedings of the Eighth AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 13-16, 2015; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2016;25(3 Suppl):Abstract nr C60.

Discussion of “Effect of Overconsolidation on K in Centrifuge Models Using CPT and Tactile Pressure Sensor” by W. El-Sekelly, T. Abdoun, and R. Dobry. The Regular Article Was Published in Geotechnical Testing Journal, Vol. 38, No. 2, 2015. [DOI:10.1520/GTJ20140101

Abstract This discussion dealt with two questions: (1) Is data from tactile sensing technologies reliable enough to consider basic conceptions of soil mechanics? and (2) Has the calibration of tactile sensing devices been rigorously approached, and is there sufficient basis to apply tactile sensing to particulate media with all the issues that it may involve, such as particle size, compliance, stiffness, stress history, and time dependence? On the face of things, it seems that the submission of El-Sekelly et al. has not included a rigorous approach.

Exploring the detection limits of infrared near-field microscopy regarding small buried structures and pushing them by exploiting superlens-related effects.

We present a study on subsurface imaging with an infrared scattering-type scanning near-field optical microscope (s-SNOM). The depth-limitation for the visibility of gold nanoparticles with a diameter of 50 nm under Si3N4 is determined to about 50 nm. We first investigate spot size and signal strength concerning their particle-size dependence for a dielectric cover layer with positive permittivity. The experimental results are confirmed by model calculations and a comparison to TEM images. In the next step, we investigate spectroscopically also the regime of negative permittivity of the capping layer and its influence on lateral resolution and signal strength in experiment and simulations. The explanation of this observation combines subsurface imaging and superlensing, and shows up limitations of the latter regarding small structure sizes.

Enhancement of photo-thermal conversion using gold nanofluids with different particle sizes

This work describes an experimental study of the particle size dependence of gold nanofluids during photo-thermal conversion in a direct absorption solar collector (DASC). Au nanoparticles (NPs) with different sizes were synthesized using a seed mediated method. Au NPs play a significant role in enhancing the solar light absorption with respect to a pure base fluid at a very low concentration due to the localized surface plasmon resonance effect. Experimental results of the photo-thermal conversion showed that the photo-thermal conversion efficiency of Au nanofluids obtained an average enhancement of 19.9% and 21.3% for a cube shaped DASC and a flat shaped DASC, respectively, compared with H2O at a relatively low mass fraction (∼0.000008% weight). Reducing the Au NP size led to the enhancement of the photo-thermal conversion efficiency under the present experimental conditions, which could be an effective way for the modification of optical properties and thermodynamic characteristics. However, the size of Au NPs did not significantly influence the efficiency for the cube shaped DASC. The cube shaped DASC model usually had the higher efficiency than the flat DASC model using the same working fluids since the heat loss percentage of the cube shaped DASC was lower.

Catalytic Oxidation of Volatile Organic Compounds by Using Spinel Mixed Oxide Catalyst- A Review

Volatile organic compounds (VOCs) are the main sources of air pollution because of their toxic properties. Recently, catalytic combustion presents many advantages, such as high combustion efficiency and low emission of unburnt hydrocarbons. Among some techniques used to reduce VOC emission, catalytic oxidation is recommended especially for highly diluted VOCs. Selection of catalytic materials for the reduction of VOCs is not easy because the activity depends on the specific molecule, synthesis method and many parameters can affect the catalyst activity and resistance. Spinel type mixed metal oxides are considered as novel catalysts for remediation of volatile organic compounds promising because of their catalytic activity and robust stability. The present review focuses on the application of spinel type mixed oxides in combustion of VOCs. The effects of synthesis method, promoter and particle size dependence are discussed. The proposed reaction mechanism for combustion of VOCs over these catalysts is addressed.

金属ナノ粒子の電界トラップを用いた自己修復型金属配線の粒径依存性

金属ナノ粒子の電界トラップを用いた自己修復型金属配線の粒径依存性

Hyperbranched polymer mediated size-controlled synthesis of gadolinium phosphate nanoparticles: colloidal properties and particle size-dependence on MRI relaxivity.

Hyperbranched polymers based on the poly(amidoamine), HyPAM, were used to synthesize gadolinium phosphate nanowires under mild conditions. Control of the average particle size was obtained by adjusting polymer concentration. Proton relaxivity measurements reveal an optimum particle size, reaching relaxivity values as high as 55 ± 9 mM(-1) s(-1) for r1 and 67 ± 11 mM(-1) s(-1) for r2. The colloidal stability of these hybrid systems were optimized through the use of functionalized core-shell polymers containing PEG segments and C18-PEG segments, structures which also offer the possibility of imparting additional function into the polymer-particle hybrids.