Properties Of Individual Particles Research Articles

Multidimensional Characterization and Separation of Ultrafine Particles: Insights and Advances by Means of Froth Flotation

Particle systems and their efficient and precise separation are becoming increasingly complex. Therefore, instead of focusing on a single separation feature, a multidimensional approach is needed where more than one particle property is considered. This, however, requires the precise characterization of the particle system, which is especially challenging for fine particles with sizes below 10 µm. This paper discusses the benefits and limitations of different characterization techniques, including optical contour analysis, inverse gas chromatography, flow cytometry, and SEM-based image analysis. The separation of ultrafine particles was investigated for a binary system using froth flotation, where a novel developed flotation apparatus is used. A special focus was placed on the multidimensional evaluation of the separation according to the particle properties of size, shape, and wettability, which was addressed via multivariate Tromp and entropy functions. The results emphasize the intricacy of the flotation process and the complex interaction of the individual particle properties and process parameters. The investigations contribute to the understanding of the characterization of particulate properties as well as the separation behavior of ultrafine particles via froth flotation, especially in the case of a multidimensional approach.

Exploring the combined effect of particle shape and friction on cell structures in granular packings via LS-DEM modeling

To comprehensively understand and predict the macroscopic behavior of a granular system, one must consider not only the properties of individual particles but also the local structures. In this study, we prepare mechanically stable granular packings of super disks using the two-dimensional level set discrete element method (LS-DEM). We identify the cells, the irreducible loops enclosed by contacting particles, in the prepared granular packings and then analyze the statistics of these structures. We find the following. (1) The packing fraction or mean coordination number of studied systems exhibits a non-trivial dependency on particle shapes and inter-particle frictions, making it challenging to establish a direct correlation between them. (2) Using the cell-based description as a bridge, we can measure the packing behavior without considering the influence of particle shape and inter-particle friction. Specifically, the mean coordination number can be explicitly represented as a function of the mean cell order according to Euler’s topological relation. Upon the assumption that all cells are regular polygons, we can also approximately estimate the rattlers-free packing fraction via the mean cell order. (3) We have observed a nearly linear relationship between the mean cell order and rattler fraction. This enables us to determine the packing fraction as well.

Morphological and Elemental Classification of Freshly‐Emitted Individual Particles From Field and Laboratory Residential Biomass Burning

AbstractResidential biomass burning significantly contributes to air pollution in developing countries. However, the microscopic properties of individual particles in their emissions have not been well understood. In this study, individual primary particles from 14 kinds of biomass fuels (including firewood, crop residue, and animal dung) were collected in laboratory and field measurements, and their morphology, composition and mixing state were acquired using transmission electron microscope. These results constitute a source profile database of individual primary particles from residential biomass burning. The database reveals that different types of biomass fuels exhibit different emission characteristics, that is, residential firewood burning mainly emits pure carbonaceous particles (including organic matter (OM) and soot particles), crop residue burning mainly emits K‐containing particles (including OM‐K, soot(‐OM)‐K, and K‐rich particles), and animal dung burning mainly emits pure carbonaceous particles and K‐containing particles. Moreover, our results indicate that the emission characteristics obtained from laboratory and field measurements are different. Field measurements conducted in two selected villages in North China Plain exhibit a higher presence of soot particles compared to laboratory measurements, owing to their higher combustion temperatures. In contrast, field measurements conducted in one selected village in Qinghai‐Tibet Plateau contain less soot particles than those from laboratory measurements in plain areas, due to the deficient oxygen supply during combustion process in the high‐altitude regions. These results warn us that the emission estimation from residential biomass burning should notice the large emission differences among different biomass types and between field and laboratory measurements.

Mechanical Properties of Individual Porous Chitosan Particles: Full Scale and Numerical Experiments

Mechanical Properties of Individual Porous Chitosan Particles: Full Scale and Numerical Experiments

Refining and Validating Thermogravimetric Analysis (TGA) for Robust Characterization and Quality Assurance of Graphene-Related Two-Dimensional Materials (GR2Ms)

Graphene-related two-dimensional materials available on the global market are manufactured using various production methods, with significant variations in properties and qualities causing serious concerns for the emerging multi-billion graphene industry. To address the limitations of conventional characterization methods probing the properties of individual graphene particles which may overlook the presence of non-graphene carbon impurities at a large (bulk) scale, this paper presents the refining thermogravimetric analysis as a complementary method for the reliable chemical characterization and quality control of graphene powders. A systematic parametric investigation of key experimental conditions such as sample mass and loading, heating rate, and gas environment and flow rate is performed to identify optimized settings for reliable thermal gravimetric measurements. These optimized conditions are evaluated through a series of comparative characterizations using industrially produced graphene, graphene oxide, and reduced graphene oxide powders, including their common carbon impurities. The ability of this method to provide both qualitative and quantitative analyses for characterizing graphene-related materials is confirmed. The optimized method is finally validated through an International Laboratory Comparison study and subsequently incorporated into a new standard. This low-cost, industry-affordable, and complementary characterization method is expected to enhance the quality control of manufactured graphene materials and make a valuable contribution to the growing graphene industry.

Determination of mass concentrations of airborne PET microplastics using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS)

Ubiquitous airborne microplasctics are present in the inhalable fraction of ambient particulate matter. They may induce lesions in the respiratory system dependent on individual susceptibility and particle properties.

Determining the pattern of loose material movement in screw and tubular-comb feeders

The object of this study is the relationship between the structural and technological parameters of feeders for loose materials and the characteristics of particle flows at their outlet, namely: productivity and the magnitude of pulsations. The existing designs of this type of equipment were analyzed, and the most common methods for simulating their operation were determined. A structure of a tubular-comb feeder has been proposed, the performance of which is compared with the well-known screw feeder. Computer models of both structures were built based on the discrete element method. The simulation was carried out in the EDEM 2017 software environment. It was established that the resulting models take into account the discrete nature of the movement of loose materials and allow conducting research taking into account the physical and mechanical properties of individual particles. An experimental bench was fabricated for experimental verification of the modes of operation of the tubular-comb feeder. The performance of this type of feeder was determined for two pipe rotation speeds (6 and 10 rad/s). The amount of material flow pulsations in the outlet nozzle was also determined. The correspondence of the results of calculations based on the computer model to the real process was confirmed. The current study was carried out the steady modes of operation. It was established that with equal overall dimensions and speeds of rotation of the working bodies, the productivity of the screw feeder is 5...5.2 times greater than that of the tubular-comb feeder. But the latter provides 7.3...16.4 times smaller magnitude of pulsations of the flow of loose material. This makes it possible to reduce the heterogeneity of mixtures, especially in the case of using such feeders as part of continuous mixing systems. The results make it possible to analyze the operation of bulk material feeders and reduce their design time

Autonomous and intelligent optical tweezers for improving the reliability and throughput of single particle analysis

Optical tweezers are an interesting tool to enable single cell analysis, especially when coupled with optical sensing and advanced computational methods. Nevertheless, such approaches are still hindered by system operation variability, and reduced amount of data, resulting in performance degradation when addressing new data sets. In this manuscript, we describe the deployment of an automatic and intelligent optical tweezers setup, capable of trapping, manipulating, and analyzing the physical properties of individual microscopic particles in an automatic and autonomous manner, at a rate of 4 particle per min, without user intervention. Reproducibility of particle identification with the help of machine learning algorithms is tested both for manual and automatic operation. The forward scattered signal of the trapped PMMA and PS particles was acquired over two days and used to train and test models based on the random forest classifier. With manual operation the system could initially distinguish between PMMA and PS with 90% accuracy. However, when using test datasets acquired on a different day it suffered a loss of accuracy around 24%. On the other hand, the automatic system could classify four types of particles with 79% accuracy maintaining performance (around 1% variation) even when tested with different datasets. Overall, the automated system shows an increased reproducibility and stability of the acquired signals allowing for the confirmation of the proportionality relationship expected between the particle size and its friction coefficient. These results demonstrate that this approach may support the development of future systems with increased throughput and reliability, for biosciences applications.

Novel Characterization Techniques for Multifunctional Plasmonic-Magnetic Nanoparticles in Biomedical Applications.

In the rapidly emerging field of biomedical applications, multifunctional nanoparticles, especially those containing magnetic and plasmonic components, have gained significant attention due to their combined properties. These hybrid systems, often composed of iron oxide and gold, provide both magnetic and optical functionalities and offer promising avenues for applications in multimodal bioimaging, hyperthermal therapies, and magnetically driven selective delivery. This paper focuses on the implementation of advanced characterization methods, comparing statistical analyses of individual multifunctional particle properties with macroscopic properties as a way of fine-tuning synthetic methodologies for their fabrication methods. Special emphasis is placed on the size-dependent properties, biocompatibility, and challenges that can arise from this versatile nanometric system. In order to ensure the quality and applicability of these particles, various novel methods for characterizing the magnetic gold particles, including the analysis of their morphology, optical response, and magnetic response, are also discussed, with the overall goal of optimizing the fabrication of this complex system and thus enhancing its potential as a preferred diagnostic agent.

Investigation of phase and structural states in nanocrystalline powders based on zirconium dioxide

The behavior of a polycrystalline body during sintering ZrO2 is determined not so much by the properties of individual particles but by the properties of aggregates, and the strength of the bonds between powder particles significantly affects the sintering process and the final properties of the ceramic composite materials. An increase in density and a uniform porosity distribution is achieved at such a pressure and sintering temperature when the process of intensive recrystallisation has not yet begun. Conventional sintering at a temperature of 1500 °C with a holding time of 1 h of ZrO2 and ZrO2–20 wt. % Al2O3 samples with an initial particle size of 120 nm and 40 nm, respectively, allowed us to obtain a material with a relative density of 81% (ZrO2) and 86% (ZrO2–20 wt. % Al2O3). The method of electroconsolidation was used to produce bulk samples of submicron ceramics of ZrO2–n wt. % Al2O3 (n = 10; 20; 30) compositions with a density of up to 99% of the theoretical one and a microstructure scale of about 270 nm. It was established that the addition of metastable Al2O3 nanopowders causes a shift in the onset of shrinkage of tetragonal YSZ to high temperatures and affects the reduction of the grain size of tetragonal YSZ to 170–200 nm.

Statistical Characteristics of Geometry, Density and Porosity of Individual Ore Particles: A Case Study

This study aims to develop a methodology to describe and predict the statistical characteristics of individual ore particles in terms of length, width, height, volume, mass, area, circularity, aspect ratio, density, and porosity. The mean value, standard deviation, and appropriate distribution function were calculated or identified for each data set of a given particle property in a given size fraction. It was found that the mean value and the standard deviation of the same particle property can either be predicted from particle size or be approximated by a constant. The best-fit distribution of each kind of particle property was identified by the Anderson–Darling test using Minitab software. Generally, the data sets with the same particle property but different size fractions and ore types follow the same distribution. A methodology was developed to predict the distribution of individual particle properties in a given size fraction by particle size, and the fitting quality is good in most cases. The statistical characteristics of individual ore particles can improve the precise processing of ore feed in concentrators, the preparation of feed samples for lab-scale testing, the calibration of image analysis of ore particle size distribution, etc.

An overview of the optical characterization of free microparticles and their radiative properties

We discuss how the range of information available from microparticle analysis can be extended in a number of applications by measuring a specific set of optical properties of individual particles using light scattering. Central to these measurements are the real and imaginary components of the forward scattered field, the former being equal to the extinction cross-section except for a few particle-independent constants. Although still a niche technique, it has some inherent advantages and great potential for particle characterization, especially in the challenging near-wavelength size range. A selection of cases is covered from an experimental point of view, while some essential models are introduced to illustrate the underlying physical phenomena. We present a benchmark of experimental results from the literature and other examples that support optical diagnostics applied in science and industrial processes. As a key point of this work, we show that by accessing the fundamental properties of scatterers the inversion of light scattering data can be avoided. This provides model-independent results closer to application requirements without the drawbacks of case-specific assumptions.

Classicality of single quantum particles in curved spacetime through the hydrodynamical reformulation of quantum mechanics

Single-particle physics focuses on the behavior and properties of individual particles, providing insight into the building blocks of quantum mechanics. The theory of quantum particles in curved spacetime has been getting attention in recent years for gaining a deeper understanding of the relationship between quantum mechanics and general relativity, the two pillars of modern physics. In this note, we show how single quantum particles can obtain classical behavior. In particular, for a quantum particle that follows the Klein–Gordon equation in curved spacetime in the presence of external potential, we show that when the amplitude of its wavefunction follows the Klein–Gordon equation with an arbitrary effective mass, empty curved spacetime, but with the same curved geometry appearing in the original Klein–Gordon equation of the wavefunction, the quantum force of the particle vanishes, providing a classical description of the quantum particle using a system of coupled classical equations. The result relies on the Madelung hydrodynamical reformulation of quantum mechanics. Understanding how quantum systems transition to a classical behavior is a long-standing challenge in mesoscopic physics, with important implications for a wide range of applications, from quantum computing to condensed matter physics. The result provides a fresh perspective on the relations between quantum and classical effects in curved spacetime.

Heterogeneous swelling of couscous particles exposed to a high relative humidity air, as revealed by TD-NMR and X-ray tomography

The mechanical behaviour of hygroscopic granular materials is highly influenced by water. The strong dependence of individual particle properties on moisture content affects the response of their packings, which can agglomerate and eventually lead to loss of product functionality. Despite the frequent occurrence of this problem in industry, only few studies tried to explore the underlying phenomena and investigate the fundamental connection between particle and packing behaviour. This work presents an experimental study that aims to link the water uptake to the microstructural changes in assemblies of couscous, a material selected to be representative of hygroscopic granular materials. In the experiments, the samples are exposed to high relative humidity (RH), and the moisture content increase is quantified with TD-NMR, along with the shift in molecular mobility. An analogous test is performed, during which x-ray tomographies are acquired continuously. We analyse the volumetric response of the sample and of thousands of particles. Despite the oversupply of water molecules available to saturate the system, the formation of a swelling heterogeneity is observed, which we attribute to the pressure gradient affecting locally the adsorption kinetics. Combining the results obtained from the two techniques, water uptake and particle swelling are found to be linearly correlated.

Overcoming stereological Bias: A workflow for 3D mineral characterization of particles using X-ray micro-computed tomography

Mineral separation processes operate on properties of individual particle, which can currently be quantified with 2D characterization techniques, namely 2D automated mineralogy. While 2D automated mineralogy data have driven significant developments in particle-based separation models, this data inherently correspond to 2D slices of 3D objects, which leads to stereological bias in the quantification of geometric particle properties. X-ray micro-computed tomography (µCT) is a 3D imaging technique that can quantify particle geometry. However, µCT only collects limited information regarding material composition, making mineral identification quantification a challenge. To overcome this challenge, we present a workflow that utilizes individual particle histograms and corrects image artefacts caused by µCT measurements, such as partial volume effect. We demonstrate the application of the workflow to perform 3D mineral characterisation of a sulfidic gold ore, where mineral phases that are commonly mistaken with µCT could be distinguished: pyrite and chalcopyrite, gold, and galena. Results were verified by comparison with inductively coupled plasma mass spectrometry and 2D automated mineralogy. As a result, the workflow provides the user with a detailed 3D particle dataset containing the modal mineralogy and surface compositions, size, and geometrical properties of each particle in a sample – essential data for modelling mineral separation processes.

Weak values and the past of a quantum particle

We investigate four key issues with using a nonzero weak value of the spatial projection operator to infer the past path of an individual quantum particle. First, we note that weak measurements disturb a system, so any approach relying on such a perturbation to determine the location of a quantum particle describes the state of a disturbed system, not that of a hypothetical undisturbed system. Secondly, even assuming no disturbance, there is no reason to associate the non-zero weak value of an operator containing the spatial projection operator with the classical idea of `particle presence'. Thirdly, weak values are only measurable over ensembles, and so to infer properties of individual particles from values of them is problematic. Finally, weak value approaches to the path of a particle do not provide information beyond standard quantum mechanics (and the classical modes supporting the experiment). We know of no experiment with testable consequences that demonstrates a connection between particle presence and weak values.

THEORETICAL ASPECTS OF VIBRATIONAL SPECTROSCOPY OF CONDENSED SYSTEMS WITH IMPURITY PARTICLES

Some problems of vibrational spectroscopy of particles in condensed systems are considered in this work. One of the aspects of theoretical research is the study of the vibrational properties of individual particles in view of the nano-dimension of the molecules of the condensed system surrounding the particle. Using the apparatus of temperature, Green functions of the operators of polarization of condensed systems, two main mechanisms of influence on impurity particles from the medium, solvation and fluctuation, are distinguished. Theoretical results are obtained within the framework of these two mechanisms for calculating changes in the vibrational spectrum of individual particles. The theoretical results are used to analyze the experimental data on the vibrational spectra of the N2O molecule in polar solvents: methanol, ethyl alcohol, acetone, and 1,2-dichloroethane.

Nanoscale physical and chemical properties of individual airborne magnetic particles from vehicle emissions

Diesel and petrol powered vehicles are contributors to the magnetic fraction of atmospheric particles in the urban atmosphere. For an assessment of the health effects of vehicle-emitted magnetic particles, the mineralogical characters of particles present in engine exhaust vs. those produced by braking need to be understood. We collected magnetically separated individual particles directly from both brake wear and engine exhaust, from the air inside a car cabin while driving on a motorway, and from the ambient urban atmosphere. The morphologies, sizes, chemical compositions and spatial associations of magnetic particles with other constituents of vehicle emissions were characterized using scanning and transmission electron microscopy techniques. Magnetic separates typically contained particles that were aggregates of a large number of nanocrystals. Particles from engine exhaust, car cabin and urban air were similar, with diameters ∼1–4 μm, consisting predominantly of ∼10 nm-sized, randomly oriented crystals of magnetite and minor hematite. In contrast, brake debris particles were larger (∼1–10 μm in diameter) and contained mostly ∼7 nm-sized hematite, in addition to metallic iron and minor goethite. Particles in all samples comprised carbonaceous constituents besides iron oxides. In the exhaust and ambient particles carbon was present in both amorphous and semi-ordered forms, encompassing the nanocrystals, suggesting a high-temperature formation. In contrast, only amorphous carbon was found in brake wear. Besides the main components (Fe, O, C) several additional elements, including Mg, Al, Si, P, S, Cl, Sn, Ca, Mn, Zn, Cu, Pb and Zr occurred in the particles, with some minor differences between the distinct types of samples. Whereas the overall characteristics of magnetic particles in exhaust emissions were similar to those of ambient particles, the brake emissions produced slightly different particle types, particularly in terms of size and mineralogy. Thus, based on the qualitative assessment of particle properties in direct emissions and ambient air, a significant portion of magnetic particles in urban air appears to originate from vehicle emissions. Although the aggregate particles have sizes in the μm range, they still may represent a potential health risk on inhalation. Synopsis: This article discusses the nanoscale properties of magnetic particles from vehicle emissions, for a better understanding of their sources and health effects. • The magnetic fraction of vehicle-derived airborne particulate matter can be collected using a simple device. • Exhaust emissions may constitute a substantial source of magnetic particles in urban environments. • Magnetic fraction of brake wear predominantly originates from the corrosion of the brake disc. • The primary magnetic agglomerates are small enough to reach the lungs upon inhalation.

Fast imaging-based single particle analysis method for solubility determination

The solubility and dissolution rates of chemical compounds are crucial properties in several fields of industry and research. However, accurate, rapid and green methods for their measurement, which only consume micrograms of compound, are lacking. Here, the unique approach of non-specific, image-based single particle analysis (SPA) for solubility testing is directly compared to and thus validated on the mid-solubility range with the current gold standard shake-flask method with UV–Vis spectroscopy employed for determining sample concentrations. Five biologically active compounds representing a range of physicochemical properties including pKa and logP were analyzed with both methods. The comparison of SPA and the shake-flask (SF) analysis shows excellent linear correlation (R2 = 0.99). Higher variability of the SPA method is attributed to variability between the properties of individual particles, which cannot be detected with traditional methods. Due to the similar average solubility values compared to those produced with SF, it is concluded that the SPA method has great potential as an analytical tool for small-scale solubility studies. It also has several practical advantages over the current gold standard shake-flask method, such as speed, low consumables consumption, and no requirement for prior knowledge of compound chemistry.

Identification and particle sizing of submicron mineral dust by using complex forward-scattering amplitude data

An accurate observational dataset of the size-resolved concentration of mineral dust particles in the atmosphere, hydrosphere, and cryosphere is needed for investigating the effect of mineral dust on the climate with earth system models. However, automated measurements of dust particles remain challenging due to the complexities of the physicochemical properties (e.g., shape and mineralogy) of individual dust particles and the difficulties in discriminating dust from other particulate components (e.g., black carbon). Here, we suggest the use of complex forward-scattering amplitude data obtained by the single particle extinction and scattering (SPES) method as a low-cost optical approach for identification and quantification of silicate (aluminosilicates + quartz) particles, the major particulate component of desert dust. We focus here on the submicron particle-size range to challenge the robust identification of wavelength or smaller scale dust solely according to the principle of elastic light scattering. The two-dimensional nature of the complex scattering amplitude data allows us to identify silicate-dominant particles in waterborne dust samples and discriminate them from light-absorbing particulate components (e.g., hematite). We demonstrate that the two-dimensional dataspace of the complex amplitude allows an accurate retrieval of the particle-size distribution of silicate particles thanks to the simultaneous retrieval of the particle’s effective refractive index. We discuss some notable differences in our results from those retrieved from conventional elastic light scattering approaches.Copyright © 2022 American Association for Aerosol Research