Properties Of Individual Particles Research Articles

Development of a High Irradiance LED Configuration for Small Field of View Motion Estimation of Fertilizer Particles.

Better characterization of the fertilizer spreading process, especially the fertilizer pattern distribution on the ground, requires an accurate measurement of individual particle properties and dynamics. Both 2D and 3D high speed imaging techniques have been developed for this purpose. To maximize the accuracy of the predictions, a specific illumination level is required. This paper describes the development of a high irradiance LED system for high speed motion estimation of fertilizer particles. A spectral sensitivity factor was used to select the optimal LED in relation to the used camera from a range of commercially available high power LEDs. A multiple objective genetic algorithm was used to find the optimal configuration of LEDs resulting in the most homogeneous irradiance in the target area. Simulations were carried out for different lenses and number of LEDs. The chosen configuration resulted in an average irradiance level of 452 W/m2 with coefficient of variation less than 2%. The algorithm proved superior and more flexible to other approaches reported in the literature and can be used for various other applications.

Images and properties of individual nucleated particles

Abstract Atmospheric aerosol particles were collected in Budapest, Hungary in April–June onto lacey Formvar substrates by using an electrostatic precipitator during the beginning phase of the particle growth process in ten nucleation and growth events. Median contribution of the nucleated particles - expressed as the concentration of particles with a diameter between 6 and 25 nm to the total particle number concentration – was 55%, and the median electrical mobility diameter of the particles was approximately 20 nm. The sample was investigated using high-resolution transmission electron microscopy (TEM) and electron energy-loss spectroscopy. Major types of individual particles such as soot, sulphate/organic and tar ball particles were identified in the sample. In addition, particles with an optical diameter range of 10–30 nm were also observed. They clearly differed from the other particle types, showed homogeneous contrast in the bright-field TEM images, and evaporated within tens of seconds when exposed to the electron beam. They were interpreted as representatives of freshly nucleated particles.

Arrays of elliptical Fe(001) nanoparticles: Magnetization reversal, dipolar interactions, and effects of finite array sizes

The magnetic properties of arrays of nanoparticles are determined by the interplay between the individual particle properties and the dipolar interactions between them. Here we present a study of a ...

A Review of Methods for Evaluating Particle Stability in Suspension Based Pressurized Metered Dose Inhalers.

Advances in particle engineering techniques, such as spray drying, freeze drying and supercritical fluid precipitation, have greatly enhanced the ability to control the structure, morphology, and solid state phase of inhalable sized particles (1 - 5 µm) for formulation in pressurized metered dose inhalers (pMDI). To optimize the properties of these engineered particles for formulation in hydrofluoroalkane propellants (HFA 134a / 227) it is necessary to measure both bulk and individual particle properties before, after, and during formulation. This review examines established and recently developed methods for evaluating a variety of particle properties including but not limited to size, surface and internal morphology, chemical composition, and solid state phase. Novel methods for evaluating particle physical and chemical stability directly in propellant or similar environments are also discussed.

Cratering of a particle bed by a subsonic turbulent jet: Effect of particle shape, size and density

The effect of particle properties on scour hole or crater formation, which occurs when a localized jet impinges on a bed of particles, is explored. Individual particle properties, such as particle density, size, and shape, are isolated and a parametric study is performed demonstrating the transient and steady crater growth for several particles. By keeping the particle diameter constant and changing the particle shape, this work shows that the effects of shape are significant. Uniform non-spherical (e.g. cylinders) and irregular frit shaped (e.g. crushed glass) particles are investigated. Non-spherical particles generally have higher friction, and the resulting decrease in recirculation rate of particles along the crater walls generally produces a narrower but deeper crater relative to spheres of the same size. A modification to the densimetric Froude number, which scales the steady crater depth to jet and particle properties is developed that accounts for particle shape. A new description of particle size called the erosion diameter is introduced, which is the average of the longest dimension a particle will align in a shear flow with its orthogonal, and results in the best scaling. The short-term crater depth grows faster for larger particles, which is counter to the long-term growth, and is explained by the early behavior being dominated by the number of particles that can be eroded. The transient crater depth growth is fit by an arctangent fitting function, which predicts the steady crater depth, and is compared to the logarithmic growth function that is generally used for early crater growth. For very large spherical particles, a high velocity is necessary for cratering and a newly identified particle–particle based cratering mechanism dominates. Additionally, cohesion reduces the crater depth and width and the steady crater depth does not scale with non-cohesive particles, but a further modification to the densimetric Froude number to account for cohesion is proposed.

Strong and Coherent Coupling of a Plasmonic Nanoparticle to a Subwavelength Fabry-Pérot Resonator.

A major aim in experimental nano- and quantum optics is observing and controlling the interaction between light and matter on a microscopic scale. Coupling molecules or atoms to optical microresonators is a prominent method to alter their optical properties such as luminescence spectra or lifetimes. Until today strong coupling of optical resonators to such objects has only been observed with atom-like systems in high quality resonators. We demonstrate first experiments revealing strong coupling between individual plasmonic gold nanorods (GNR) and a tunable low quality resonator by observing cavity-length-dependent nonlinear dephasing and spectral shifts indicating spectral anticrossing of the luminescent coupled system. These phenomena and experimental results can be described by a model of two coupled oscillators representing the plasmon resonance of the GNR and the optical fields of the resonator. The presented reproducible and accurately tunable resonator allows us to precisely control the optical properties of individual particles.

Upgrading of Dust Collection Techniques on Mining and Concentrating Mills

There were presented the main scientific and practical results of formation and implementation and engineering tools for capture of dust at mining and concentrating mills. There were defined mechanical, electric, magnetic properties of dust and individual particles of its. There was theoretically substantiated, developed and implemented apparatus of dry cleaning. Results of research were used in the industry with a positive effect, and these results of interest to professional from non-ferrous,coal and other ore mining industry.

Vertical Profiles and Chemical Properties of Aerosol Particles upon Ny-Ålesund (Svalbard Islands)

Size-segregated particle samples were collected in the Arctic (Ny-Ålesund, Svalbard) in April 2011 both at ground level and in the free atmosphere exploiting a tethered balloon equipped also with an optical particle counter (OPC) and meteorological sensors. Individual particle properties were investigated by scanning electron microscopy coupled with energy dispersive microanalysis (SEM-EDS). Results of the SEM-EDS were integrated with particle size and optical measurements of the aerosols properties at ground level and along the vertical profiles. Detailed analysis of two case studies reveals significant differences in composition despite the similar structure (layering) and the comparable texture (grain size distribution) of particles in the air column. Differences in the mineral chemistry of samples point at both local (plutonic/metamorphic complexes in Svalbard) and remote (basic/ultrabasic magmatic complexes in Greenland and/or Iceland) geological source regions for dust. Differences in the particle size and shape are put into relationship with the mechanism of particle formation, that is, primary (well sorted, small) or secondary (idiomorphic, fine to coarse grained) origin for chloride and sulfate crystals and transport/settling for soil (silicate, carbonate and metal oxide) particles. The influence of size, shape, and mixing state of particles on ice nucleation and radiative properties is also discussed.

Aerosol particle morphology of residential coal combustion smoke

A study carried out at the University of Pretoria characterised aerosol particle morphology of residential coal combustion smoke. The general approach in this study was on individual particle conglomerations because the radiative, environmental, and health effects of particles may depend on specific properties of individual particles rather than on the averaged bulk composition properties. A novel, miniature denuder system, developed and tested at the University of Pretoria, was used to capture particle emissions from the coal fires. The denuder consists of two silicone rubber traps (for gas phase semi-volatile organic compound monitoring) in series separated by a quartz fibre filter (for particle collection). The denuders were positioned 1 m away from the fire and were connected to pumps that sampled ~5 litres of air over a 10 min sampling interval. A JSM 5800LV Scanning Electron Microscope with a Thermo Scientific EDS was used to analyse the structure and morphology of different aerosol samples from the quartz fibre filters. Eight samples from the different fire lighting methods were selected for SEM analysis. The punched samples were sputter coated with gold for ~15 minutes using a K550 Emitech Sputter Coater. Results show that apart from the fine and ultra-fine particles, coal smoke from domestic burning also contains aerosols greater than 5 μm in diameter. Consequently, we describe the potential for generation of ‘giant’ carbonaceous soot conglomerates with outer diameters of 5 to 100 μm. However, the exact mechanism for formation of such large soot conglomerates remains to be determined. We also describe the presence of spherules and solid ‘melted toffee’ irregular surfaces. Circumstantial evidence is used to postulate and discuss the possible modes of formation in terms of condensation, and partial melting. This work provides a description of the modes of formation and transformation of conglomerates originating from low temperature (<8000C) coal combustion.

Qualitative multiplatform microanalysis of individual heterogeneous atmospheric particles from high-volume air samples.

High-resolution microscopic analysis of individual atmospheric particles can be difficult, because the filters upon which particles are captured are often not suitable as substrates for microscopic analysis. Described here is a multiplatform approach for microscopically assessing chemical and optical properties of individual heterogeneous urban dust particles captured on fibrous filters during high-volume air sampling. First, particles embedded in fibrous filters are transferred to polished silicon or germanium wafers with electrostatically assisted high-speed centrifugation. Particles are clustered in an array of deposit areas, which allows for easily locating the same particle with different microscopy instruments. Second, particles with light-absorbing and/or light-scattering behavior are identified for further study from bright-field and dark-field light-microscopy modes, respectively. Third, particles identified from light microscopy are compositionally mapped at high definition with field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. Fourth, compositionally mapped particles are further analyzed with focused ion-beam (FIB) tomography, whereby a series of thin slices from a particle are imaged, and the resulting image stack is used to construct a three-dimensional model of the particle. Finally, particle chemistry is assessed over two distinct regions of a thin FIB slice of a particle with energy-filtered transmission electron microscopy (TEM) and electron energy-loss spectroscopy associated with scanning transmission electron microscopy (STEM).

Numerical Analysis of Carbon Monoxide–Hydrogen Gas Reduction of Iron Ore in a Packed Bed by an Euler–Lagrange Approach

In recent years, various methods to decrease carbon dioxide emissions from iron and steel making industries have been developed. The latest blast furnace operation design is intended to induce the low reducing agent operation, highly reactive material is considered a promising way to improve reaction efficiency. Another method utilizes hydrogen in the blast furnace process for highly efficient reduction. Mathematical modeling may help to predict complex in-furnace phenomena, including momentum, heat, and mass transport. However, the current macroscopic continuum model gives no information on the individual particles. In this work, a new approach based on the discrete element method was introduced to consider the interaction between particles under fluid flow in accordance with the arrangement and properties of individual particles. We used an Euler–Lagrange method to precisely understand the influence of the reaction conditions on the behavior of coke and ore particles in three dimensions. The heterogeneity of the reaction rate and temperature distribution was observed to be influenced by the particle arrangement. The endothermic and exothermic reactions influenced each other in the packed bed. Temperature distributions nearly correlated with the gas velocity distribution because convection processes greatly affected the reaction rate. Although convection heat transfer was not a dominant issue in the packed bed, promotion of the reaction by a gas flow was effective.

Material point method of modelling and simulation of reacting flow of oxygen

Aerospace vehicles are continually being designed to sustain flight at higher speeds and higher altitudes than previously attainable. At hypersonic speeds, gases within a flow begin to chemically react and the fluid's physical properties are modified. It is desirable to model these effects within the Material Point Method (MPM). The MPM is a combined Eulerian–Lagrangian particle-based solver that calculates the physical properties of individual particles and uses a background grid for information storage and exchange. This study introduces chemically reacting flow modelling within the MPM numerical algorithm and illustrates a simple application using the AeroElastic Material Point Method (AEMPM) code. The governing equations of reacting flows are introduced and their direct application within an MPM code is discussed. A flow of 100% oxygen is illustrated and the results are compared with independently developed computational non-equilibrium algorithms. Observed trends agree well with results from an independently developed source.

Novel methods for in situ characterization of individual micro- and nanoscale magnetic particles

Abstract

Plasmon-Enhanced Enzyme-Linked Immunosorbent Assay on Large Arrays of Individual Particles Made by Electron Beam Lithography

Ultrasensitive biosensing is one of the main driving forces behind the dynamic research field of plasmonics. We have previously demonstrated that the sensitivity of single nanoparticle plasmon spectroscopy can be greatly enhanced by enzymatic amplification of the refractive index footprint of individual protein molecules, so-called plasmon-enhanced enzyme-linked immunosorbent assay (ELISA). The technique, which is based on generation of an optically dense precipitate catalyzed by horseradish peroxidase at the metal surface, allowed for colorimetric analysis of ultralow molecular surface coverages with a limit of detection approaching the single molecule limit. However, the plasmonic response induced by a single enzyme can be expected to vary for a number of reasons, including inhomogeneous broadening of the sensing properties of individual particles, variation in electric field enhancement over the surface of a single particle and variation in size and morphology of the enzymatic precipitate. In this report, we discuss how such inhomogeneities affect the possibility to quantify the number of molecules bound to a single nanoparticle. The discussion is based on simulations and measurements of large arrays of well-separated gold nanoparticles fabricated by electron beam lithography (EBL). The new data confirms the intrinsic single-molecule sensitivity of the technique but we were not able to clearly resolve the exact number of adsorbed molecules per single particle. The results indicate that the main sources of uncertainty come from variations in sensitivity across the surface of individual particles and between different particles. There is also a considerable uncertainty in the actual precipitate morphology produced by individual enzyme molecules. Possible routes toward further improvements of the methodology are discussed.

Atomically Precise Gold Nanoclusters as New Model Catalysts

Many industrial catalysts involve nanoscale metal particles (typically 1-100 nm), and understanding their behavior at the molecular level is a major goal in heterogeneous catalyst research. However, conventional nanocatalysts have a nonuniform particle size distribution, while catalytic activity of nanoparticles is size dependent. This makes it difficult to relate the observed catalytic performance, which represents the average of all particle sizes, to the structure and intrinsic properties of individual catalyst particles. To overcome this obstacle, catalysts with well-defined particle size are highly desirable. In recent years, researchers have made remarkable advances in solution-phase synthesis of atomically precise nanoclusters, notably thiolate-protected gold nanoclusters. Such nanoclusters are composed of a precise number of metal atoms (n) and of ligands (m), denoted as Aun(SR)m, with n ranging up to a few hundred atoms (equivalent size up to 2-3 nm). These protected nanoclusters are well-defined to the atomic level (i.e., to the point of molecular purity), rather than defined based on size as in conventional nanoparticle synthesis. The Aun(SR)m nanoclusters are particularly robust under ambient or thermal conditions (<200 °C). In this Account, we introduce Aun(SR)m nanoclusters as a new, promising class of model catalyst. Research on the catalytic application of Aun(SR)m nanoclusters is still in its infancy, but we use Au₂₅(SR)₁₈ as an example to illustrate the promising catalytic properties of Aun(SR)m nanoclusters. Compared with conventional metallic nanoparticle catalysts, Aun(SR)m nanoclusters possess several distinct features. First of all, while gold nanoparticles typically adopt a face-centered cubic (fcc) structure, Aun(SR)m nanoclusters (<2 nm) tend to adopt different atom-packing structures; for example, Au₂₅(SR)₁₈ (1 nm metal core, Au atomic center to center distance) has an icosahedral structure. Secondly, their ultrasmall size induces strong electron energy quantization, as opposed to the continuous conduction band in metallic gold nanoparticles or bulk gold. Thus, nanoclusters become semiconductors and possess a sizable bandgap (e.g., ~1.3 eV for Au₂₅(SR)₁₈). In addition, Aun(SR)m can be doped with a single atom of other metals, which is of great interest for catalysis, because the catalytic properties of nanoclusters can be truly tuned on an atom-by-atom basis. Overall, atomically precise Aun(SR)m nanoclusters are expected to become a promising class of model catalysts. These well-defined nanoclusters will provide new opportunities for achieving fundamental understanding of metal nanocatalysis, such as insight into size dependence and deep understanding of molecular activation, active centers, and catalytic mechanisms through correlation of behavior with the structures of nanoclusters. Future research on atomically precise nanocluster catalysts will contribute to the fundamental understanding of catalysis and to the new design of highly selective catalysts for specific chemical processes.

Organic particle types by single-particle measurements using a time-of-flight aerosol mass spectrometer coupled with a light scattering module

Abstract. Chemical and physical properties of individual ambient aerosol particles can vary greatly, so measuring the chemical composition at the single-particle level is essential for understanding atmospheric sources and transformations. Here we describe 46 days of single-particle measurements of atmospheric particles using a time-of-flight aerosol mass spectrometer coupled with a light scattering module (LS-ToF-AMS). The light scattering module optically detects particles larger than 180 nm vacuum aerodynamic diameter (130 nm geometric diameter) before they arrive at the chemical mass spectrometer and then triggers the saving of single-particle mass spectra. 271 641 particles were detected and sampled during 237 h of sampling in single-particle mode. By comparing timing of the predicted chemical ion signals from the light scattering measurement with the measured chemical ion signals by the mass spectrometer for each particle, particle types were classified and their number fractions determined as follows: prompt vaporization (46%), delayed vaporization (6%), and null (48%), where null was operationally defined as less than 6 ions per particle. Prompt and delayed vaporization particles with sufficient chemical information (i.e., more than 40 ions per particle) were clustered based on similarity of organic mass spectra (using k-means algorithm) to result in three major clusters: highly oxidized particles (dominated by m/z 44), relatively less oxidized particles (dominated by m/z 43), and particles associated with fresh urban emissions. Each of the three organic clusters had limited chemical properties of other clusters, suggesting that all of the sampled organic particle types were internally mixed to some degree; however, the internal mixing was never uniform and distinct particle types existed throughout the study. Furthermore, the single-particle mass spectra and time series of these clusters agreed well with mass-based components identified (using factor analysis) from simultaneous ensemble-averaged measurements, supporting the connection between ensemble-based factors and atmospheric particle sources and processes. Measurements in this study illustrate that LS-ToF-AMS provides unique information about organic particle types by number as well as mass.

Evaluation of Aggregate Size and Shape by Means of Segmentation Techniques and Aggregate Image Processing Algorithms

Morphological properties of mineral aggregates are known to affect pavement and railroad track mechanistic behavior and performance significantly in relation to strength, modulus, and permanent deformation. With imaging technology, an objective and accurate measurement of aggregate particle size and shape properties can be obtained in a rapid, reliable, and automated fashion. But these advances in aggregate imaging must be brought to project sites and quarries in the field. This paper introduces field image-acquisition and image-processing techniques for extraction and analyses of size and shape properties of individual aggregate particles. Referred to as segmentation techniques, image-processing methods developed in this study analyzed two-dimensional field images of aggregates captured by a digital single-lens reflex camera. The segmented aggregate images were fed into the validated University of Illinois aggregate image analyzer to quantify particle size and shape properties by means of its image-processing algorithms for flat-and-elongated ratio, angularity index, and surface texture index. The developed method successfully determined the properties of coarse-aggregate samples collected from various depths in a layer of railroad track ballast. The promising preliminary results indicate that these segmentation techniques could be considered in the field for capturing several aggregate particles rapidly and reliably in a single image so that (a) size and shape properties of individual particles could be analyzed and (b) both spatial property variability and property changes with layer depth and usage (i.e., property degradation in time) could be evaluated under service loading.

Quantum ring soliton formation by strongly nonlocal plasma wake field response to a relativistic electron beam

The relativistic electron/positron particle beam propagation in overdense magnetized plasmas is studied theoretically, using a fluid plasma model and accounting for the quantum properties of individual particles. The collective character of the particle beam manifests through the macroscopic, beam created, plasma wake field. The transverse dynamics is described by the quantum Schrödinger equation for the single-particle wave function, within the Hartree mean-field approximation, coupled with the Poisson equations for the wake potential. The resulting nonlinear nonlocal Schrödinger equation is solved analytically in the strongly nonlocal regime, yielding breathing/wiggling Hermite-Gauss ring solitons. The nonstationary rings may be parametrically unstable. The conditions for instability and the growth rates are estimated analytically.

The Effects of Aggregation on Electronic and Optical Properties of Oligothiophene Particles

Solution processing of oligothiophene molecules is shown to produce a range of particles with distinct morphologies. Once isolated on a substrate, the optical and electronic properties of individual particles were studied. From polarized scanning confocal microscopy experiments, distinct particles that are identifiable by shape were shown to have similar emission spectra except in regard to the 0-0 vibronic band intensity. This suppression of the 0-0 vibronic band correlates to the amount of energetic disorder present in a weakly coupled H-aggregate. The studied particles ranged from moderate to almost complete suppression of the 0-0 vibronic band when compared to the emission spectrum of the isolated molecule in solution. All particles were found to have a high degree of geometric order (molecular alignment) as observed from the fluorescence dichroism (FD) values of around 0.7-0.8 for all the studied morphologies. The structural and electronic properties of the particles were investigated with Kelvin probe force microscopy (KPFM) to measure the local contact potential (LCP) difference, a quantity that is closely related to the differences in intermolecular charge distribution between the oligothiophene particles. The LCP was found to vary by as much as 70 mV between different oligothiophene particles and a trend was observed that correlated the LCP changes with the amount of energetic disorder present, as signified by the suppression of the 0-0 vibronic peak in the emission spectra. Combined polarized scanning confocal microscopy studies, along with KPFM measurements, help to provide fundamental insights into the role of morphology, molecular packing, and intermolecular charge distributions in oligiothiophene particles.

Critical Characteristics for Corticosteroid Solution Metered Dose Inhaler Bioequivalence

Determining bioequivalence for solution pressurized metered dose inhalers (pMDI) is difficult because the critical characteristics of such products are poorly defined. The aim of this study was to elucidate the non-aerodynamic properties of the emitted aerosol particles from two solution pMDI products that determine their biopharmaceutical differences after deposition. Novel particle capture and analysis techniques were employed to characterize the physicochemical and biopharmaceutical properties of two beclomethasone dipropionate (BDP) products: QVAR and Sanasthmax. The BDP particles emitted from the Sanasthmax inhaler were discernibly different those emitted from QVAR in terms of size (50% larger, less porous), solid state (less crystalline) and dissolution (20-fold slower). When deposited onto the surface of respiratory epithelial cell layers, QVAR delivered ∼50% more BDP across the cell layer in 60 min than Sanasthmax. Biopharmaceutical performance was not attributable to individual particle properties as these were manifold with summative and/or competing effects. The cell culture dissolution-absorption model revealed the net effect of the particle formed on drug disposition and was predictive of human systemic absorption of BDP delivered by the test inhalers. This illustrates the potential of the technique to detect the effect of formulation on the performance of aerosolized particles and contribute to assessment of bioequivalence.