Morphology Characteristics Of Particles Research Articles

Photocatalytic, antimicrobial and antibiofilm activities of MgFe2O4 magnetic nanoparticles

This study reports the antibacterial and antibiofilm activities of Magnesium ferrite nanoparticles (MgFe2O4) against gram-positive and gram-negative bacteria. The photocatalytic degradation of Carbol Fuchsin (CF) dye (a class of dyestuffs that are resistant to biodegradation) under the influence of UV-light irradiation is also studied. The crystalline magnesium ferrite (MgFe2O4) nanoparticles were synthesized using the co-precipitation method. The morphology of the resulting nanocomposite was examined using scanning electron microscopy (SEM), while transmission electron microscopy (TEM) was employed for further characterization of particle morphology and size. Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) were utilized to analyze the crystalline structure, chemical composition, and surface area, respectively. Optical properties were evaluated using UV–Vis spectroscopy. The UV-assisted photocatalytic performance of MgFe2O4 nanoparticles was assessed by studying the decolorization of Carbol fuchsin (CF) azo dye. The crystallite size of the MgFe2O4 nanoparticles at the (311) plane, the most prominent peak, was determined to be 28.5 nm. The photocatalytic degradation of 10 ppm CF using 15 mg of MgFe2O4 nanoparticles resulted in a significant 96% reduction after 135 min at ambient temperature (25 °C) and a pH value of 9. Additionally, MgFe2O4 nanoparticles exhibited potent antibacterial activity against E. coli and S. aureus in a dose dependent manner with maximum utilized concentration of 30 µg/ml. Specifically, MgFe2O4 nanoparticles demonstrated substantial antibacterial activity via disk diffusion and microbroth dilution tests with zones of inhibition and minimum inhibitory concentrations (MIC) for E. coli (26.0 mm, 1.25 µg/ml) and S. aureus (23.0 mm, 2.5 µg/ml), respectively. Moreover, 10.0 µg/ml of MgFe2O4 nanoparticles elicited marked percent reduction in biofilm formation by E. coli (89%) followed by S. aureus (78.5%) after treatment. In conclusion, MgFe2O4 nanoparticles demonstrated efficient dye removal capabilities along with significant antimicrobial and antibiofilm activity against gram-positive and gram-negative bacterial strains suggesting their potential as promising antimicrobial and detoxifying agents.

Particle morphology characterization in an over-aged Al-Cu-Mg-Si alloy using TEM

A quantitative analysis of particle morphologies in a heterophase Al-Cu-Mg-Si alloy after over-aging has been performed using conventional transmission electron microscopy (TEM) imaging in dark- and bright-field modes. An appropriate analytical procedure has been suggested separating {100}Al plate- and 〈100〉Al rod-shaped particles using TEM images taken along 〈100〉Al and 〈110〉Al zone axes. The obtained statistical particle morphology parameters were verified by macroscopic strength contribution calculations.

The structural and magnetic properties of Co0.9Ni0.1Fe2O4 as a heavy metal absorbing material

This research uses co-precipitation to synthesize cobalt nickel ferrite as a heavy metal absorbing material from natural iron sand. The co-precipitation method was applied with temperature calcination of 700 °C for 2 h. Characterization of crystal structure using X-ray diffraction (XRD), characterization of magnetic properties using Vibrating Sample Magnetometer (VSM), and characterization of particle morphology using Field Emission Scanning Electron Microscopes (FE-SEM). Characterization of adsorption capacity of samples using Atomic Absorption Spectrophotometer (AAS). From the characterization results, it is known that cobalt nickel ferrite is a hard magnet and has a cubic crystal structure. The magnetic hysteresis curve shows a coercivity of 715.68 Oe and a remanent magnetization of 18.38 emu/g. The absorption capacity obtained from Cu and Cr removal efficiency was 96.26%, with an adsorption capacity of 10.83 mg/L.

Non-invasive characterization of particle morphology of calcareous sands from São Tomé & Príncipe

Calcareous sands of biogenic origin are widely spread throughout the world’s seabed. They are the foundation soils for many offshore geotechnical structures, and, in addition, onshore uses of this material are becoming more significant with the growing demand of backfill material for transport infrastructure. These sands comprise the remains of marine organisms such as shells and tests, and the grains can vary from platy to hollow thin-walled forms with highly angular features. Geotechnical design on calcareous sands is challenging owing to the many uncertainties related to their microscale properties. This study uses non-invasive X-ray micro-computed tomography (μCT) and advanced three-dimensional (3D) image analysis techniques to quantify the morphology of bioclastic calcareous sands from São Tomé & Príncipe. The statistics of particle shape parameters of the São Tomé sand are compared to that of the previously studied Ledge Point sand. In spite of an order of magnitude difference in particle size, São Tomé and Ledge Point sands are markedly similar and, as seen in other calcareous sand, São Tomé shows a strong correlation in 3D sphericity and convexity. The results presented here help to better understand the mechanisms of grain interlocking, and the role of intra-granular void ratio on the mechanical behaviour of calcareous sands from different parts of the world.

Evaluation of single particle morphological characteristics and human health risks in different functional areas

Purpose This study aims to better understand the morphological characteristics of single particle and the health risk characteristics of heavy metals in PM2.5 in different functional areas of Handan City. Design/methodology/approach High resolution transmission electron microscopy was used to observe the aerosol samples collected from different functional areas of Handan City. The morphology and size distribution of the particles collected on hazy and clear days were compared. The health risk evaluation model was applied to evaluate the hazardous effects of particles on human health in different functional areas on hazy days. Findings The results show that the particulate matter in different functional areas is dominated by spherical particles in different weather conditions. In particular, the proportion of spherical particles exceeds 70% on the haze day, and the percentage of soot aggregates increases significantly on the clear day. The percentage of each type of particle in the teaching and living areas varied less under different weather conditions. Except for the industrial area, the size distribution of each type of particle in haze samples is larger than that on the clear day. Spherical particles contribute more to the small particle size segment. Soot aggregate and other shaped particles contribute more to the large size segment. The mass concentrations of hazardous elements (HEs) in PM2.5 in different functional areas on consecutive haze pollution days were illustrated as industrial area > traffic area > living area > teaching area. Compared with the other functional areas, the teaching area had the lowest noncarcinogenic risk of HEs. The lifetime carcinogenic risk values of Cr and As elements in each functional area have exceeded residents’ threshold levels and are at high risk of carcinogenicity. Among the four functional areas, the industrial area has the highest carcinogenic and noncarcinogenic risks. But the effects of HEs on human health in the other functional areas should also be taken seriously and continuously controlled. Originality/value The significance of the study is to further understand the morphological characteristics of single particles and the health risks of heavy metals in different functional areas of Handan City. the authors hope to provide a reference for other coal-burning industrial cities to develop plans to improve air quality and human respiratory health.

DEM study on role of fines in mobility of dry granular flows considering particle size-shape correlation

Many field observations show that the shape characteristic of particles constituting natural or industrial loose deposits is often size-correlated, that is, either more regular or irregular for larger particles than fines, depending on the particle formation process. Motivated by this, the role of fines in mobility of gravity-driven dry granular flows has been explored numerically through the collapse of granular columns with fractal particle size distributions. A series of granular columns with different combinations of initial aspect ratio, fractal dimension and particle size-elongation correlation (i.e., positively, negatively correlated and uncorrelated cases) are prepared by the discrete element method to conduct column collapse simulations. Among which, a general framework for generating size-shape correlated particles has been proposed using the Fourier-based particle morphology characterization method. Results show that fines may enhance or hardly influence the mobility of dry granular flows, hinging on the actual particle size-shape correlation. Specifically, for the particle size-elongation uncorrelated and negatively correlated cases, the mobility of dry granular flows is almost independent of the fine content, while it increases with the fine content for the size-elongation positively correlated case. The underlying mechanisms are also explored to unravel the observed flow mobility differences from perspectives of the flow characteristic and energy dissipation.

Particle morphology characterization of waste-tyre-stabilized rock aggregates via computational geometric modellings

This study offers a comprehensive understanding of the most important geometrical concepts for concave shape particles with very low sphericity. Study of concave hulls in three-dimensional space is performed with an emphasis on accurate and asymptotically fast algorithms. Based on that a three-dimensional concave hull algorithm is designed to generate the actual shape of irregular particles through a set of 3D surface coordinate data points captured by 3D handy laser scanner and photogrammetry. The algorithm is utilized for a wide range of large-scale waste tyre and rock aggregates to assess several fundamental theoretical hypotheses related to geometric parameters, including surface texture with concavity/convexity, concave hull volume, perimeters of projected area, and concavity computation that have not been tested before for highly irregular concave shape particles. As a result, the morphological characteristics of the waste-tyre-stabilized rock aggregate mixtures are analysed for mining operations. We also provide the details on how the application of the resulting particle morphology is employed in cloning particles with wide range of concavity distribution. The paper identifies the accuracy by implementing the proposed 3D concave hull algorithm for morphology analysis of concave particles and comparing the morphology analysis results against those of Finite Element Method (FEM), polar representation approach (PRA), and experimental data.

An algorithm based on distribution similarity to determine the representative sample size for particle morphology characterization

Selecting the number of representative particles, expressed as representative sample size (RSS), is a crucial step in characterizing morphology of granular materials. Although the widely-used methods such as the method of standard deviation stabilization are straightforward methods to determine an RSS that has a highly similar probability density function (PDF) to its population, they suffer from several drawbacks such as subjectivity in the RSS selection criterion and overestimation of the required RSS. Thus, conflicting findings have been reported from previous studies even for the same material and same morphological descriptor. To tackle this challenge, this study proposes a new RSS determination method that uses relative entropy in combination with progressive consecutive sampling and nonparametric kernel density estimation. The proposed algorithm ensures the similarity of PDFs between an RSS and its population for both normally distributed and highly skewed morphological descriptors. The robustness of the proposed algorithm against a number of potentially influencing factors such as kernel bandwidth is investigated through sensitivity analysis. Applying the algorithm to real micro-computed tomography (μCT) data showed that more than 95% similarity between the PDFs of an RSS and its population can be ensured. Moreover, the RSS returned by the algorithm depends on both the soil tested and the scale of morphological descriptor used in characterizing the morphology (meso vs macro). Results showed that the RSS ranged between 350 and 500 for capturing morphology distributions of two sands that covered a wide range of angularity.

A particle morphology characterization system and its method based on particle scattering image recognition

The morphology of particles is usually detected by microscopic imaging methods such as scanning electron microscope (SEM). However, this type of direct observation relies on expensive equipment and requires complex preparations. Inspired by the transit method in astronomy, a characterization system based on the scattering patterns change due to the relative motion between the particle and facula was proposed in this work. The scattering patterns of particles could be recognized and analyzed automatically to detect the particle shape. The flow trajectory was studied by the optical fluid field couple (OFFC) model proposed in this work to calculate the size and specific surface area of the particle. For getting more accurate results, particle surface roughness was measured by image recognition to correct the results of specific surface areas. The accuracy of the classification machine learning (CML) model was about 97%, and the errors of the specific surface area results were lower than 10%. Comparing with the previous work, the proportions of different particles in mix sample could be detected successfully by this system with a maximum error less than 6%. This work can offer a valuable reference for the fields of characterization morphology systems based on scattering.

A novel experimental chamber for the characterization of free-falling particles in volcanic plumes.

Volcanic plumes pose a hazard to health and society and a particular risk for aviation. Hazard mitigation relies on forecasting plume dispersion within the atmosphere over time. The accuracy of forecasts depends on our understanding of particle dispersion and sedimentation processes, as well as on the accuracy of model input parameters, such as the initial particle size distribution and concentrations of volcanic particles (i.e., volcanic ash) in the atmosphere. However, our understating of these processes and the accurate quantification of input parameters remain the main sources of uncertainty in plume dispersion modeling. It is usually impractical to sample volcanic plumes directly, but particle sedimentation can be constrained in the laboratory. Here, we describe the design of a new experimental apparatus for investigating the dynamics of free-falling volcanic particles. The apparatus can produce a sustained column of falling particles with variable particle concentrations appropriate to a volcanic plume. Controllable experimental parameters include particle size distributions, types, and release rates. A laser-illuminated macrophotography system allows imaging of in-flight particles and their interactions. The mass of landing particles is logged to inform deposition rates. Quantitative measurements include particle morphology characterization, settling velocities, flow rates, and estimation of concentrations. Simultaneous observations of particle interaction processes and settling dynamics through direct control over a wide range of parameters will improve our parameterization of volcanic plume dynamics. Although the apparatus has been specifically designed for volcanological investigations, it can also be used to explore the characteristics of free-falling particle columns occurring in both environmental and industrial settings.

Characterization of Si and SiO2 in Dust Emitted during Granite Polishing as a Function of Cutting Conditions.

Particles emitted during manufacturing processes such as polishing can represent a serious danger for the environment and for occupational safety. The formation mechanisms responsible for these dust emissions include chip formation, friction at the tool/workpiece and chip/tool interfaces, shearing and cutting. These mechanisms thus depend on workpiece and tool properties, as well as the polishing conditions. In the case of granite polishing, particle emissions during polishing can contain chemical compounds such as silica, which represent harmful health risks for the worker. It is therefore important to characterize the particles emitted and to search for possible interactions between the particles (size and composition) and the machining conditions in order to find ways of reducing emissions at the source. In this study, an investigation was undertaken to characterize the particles emitted during granite polishing as a function of polishing conditions, type of granite, and abrasive grit sizes used. Scanning electron microscopy (SEM) was employed for particle morphology characterization and particle grain size and chemical composition were evaluated using X-ray diffraction (XRD) and energy dispersive X-ray (EDX) techniques, respectively. Results show that the influence of polishing speed and feed rate on particle emission depends mainly on the granite type used, providing useful information for controlling the polishing procedure, and thereby dust emission.

Effect of Particle Size and Constraint Conditions on Single Particle Strength of Carbonate Sand.

Carbonate sand is often encountered and utilized as construction material in offshore engineering projects. Carbonate sand particles, which are porous and angular, are found to be highly crushable under high stress conditions, whereas the mechanisms and controlling factors for the crushing of carbonate sand particles are not well developed. The crushability and particle strength of around 400 particles from three fractions (5–10 mm, 2–5 mm, and 1–2 mm) of carbonate sand from the South China Sea were investigated via grain-scale single particle crushing tests. Special emphasis was placed on the effect of external constraint conditions (i.e., coordination number) and intrinsic particle morphology characteristics on the particle strength of carbonate soil. The particle strength of carbonate sand was found to be around half of quartz sand in terms of characteristic stress. Negative correlations, which could be depicted by an exponential equation, were found between the particle size and particle strength. Due to elongated particle shape and tensile stress concentration, a higher coordination number may lower the particle strength, which contradicts what was reported for quartz sands. A series of seven fundamental particle dimensions and five particle shape descriptors was characterized, and the aspect ratio was found to be one of the more influential shape descriptors for particle strength. The results enriched the database for the analysis of highly irregular geomaterial and provided insights into controlling factors of particle strength and crushing mechanisms of the carbonate sand.

A Particle Morphology Characterization System and its Method Based on Particle Scattering Image Recognition

A Particle Morphology Characterization System and its Method Based on Particle Scattering Image Recognition

Three-dimensional characterization of powder particles using X-ray computed tomography

A method for particle morphology characterization using X-ray computed tomography (XCT) is explored. Firstly, the voxel data of a metal powder is obtained using XCT and an optimized method using erosion and watershed algorithms is proposed for particle separation. Results from the XCT are compared to those from scanning electron microscopy (SEM) to validate the method; examining the number of particles, mean diameter, diameter variance and maximum diameter for each case. The results acquired using 3D XCT voxel data and two-dimensional (2D) XCT slice data are compared. It shows that the 3D XCT measurement more closely matches the SEM results, when compared to the 2D slice results. In the 3D XCT case, to characterize particles, the particle diameter, sphericity and aspect ratio are computed, and the k-means algorithm is used for cluster analysis. Finally, the morphologies of two different powder batches using 3D XCT are performed. The results show that the cluster analysis provides a comprehensive method of evaluation for metal powders, and that 3D morphology measurement provides a better understanding of powder particles than 2D methods.

Slurry - erosive wear and wear product analysis using a SS430 propeller

The primary aim of this paper was to investigate the influence of specific independent wear variables on slurry - erosive wear using a AISI 430 stainless steel (SS430) 32 mm diameter propeller. The utilization of the statistical design of the experiment enabled the author to collect and analyze erosive wear data to indicate the extent to which a higher understanding of the complex mode/mechanism of slurry – erosive wear should be further explored. The results showed that all of the variation of erodent types, slurry concentration, rotational speed, test duration have effects on both weight loss and pot bulk rising temperature rather differently. The particle morphological characteristics and eroded worn surface analysis showed that the dominated wear mechanism in the SiO2 slurry erosive wear case was primarily from crack propagation due to micro surface fatigue. On the other hand, the wear mechanism in the SiC slurry case by observation of the particle morphology and worn surface demonstrated that it was due to extreme micro fatigue. Plowing and small size wear particle detachment took place in the SiC slurry.

The effect of hemicellulose on the interparticle frictional behavior of lignocellulosic biomass particulates

Lignocellulosic biomass material sourced from plants and herbaceous sources is considered as a prospective feedstock of inexpensive, potentially carbon-neutral energy. Lignocellulosic biomass is structurally built on cellulose, hemicellulose, and lignin, which are present in varying concentrations based on the feedstock type and play distinct and not well understood mechanical functions in the flow behavior. The frictional characteristics of lignocellulosic biomass particulates influence their flow behavior in biorefineries. Thus, it is important to fundamentally investigate the relative contribution of cellulose, hemicellulose, and lignin to the frictional behavior. However, these three biopolymers are interwoven into a complex matrix in the lignocellulosic biomass, thus making it hard to quantify the contribution of each biopolymer. In this study, we selectively remove hemicellulose from switchgrass and investigate the effects of its diminishing concentration on the coefficient of friction.We observed that the angle of repose and, therefore, the coefficient of friction for a loose assembly of the control and treated switchgrass samples decrease with decreasing hemicellulose content. This indicates the frictional resistance to flow for biomass particulate assemblies is at least proportional to the hemicellulose content. We also established that the observed changes in the frictional behavior were not due to particle morphological characteristics.

Clone granular soils with mixed particle morphological characteristics by integrating spherical harmonics with Gaussian mixture model, expectation–maximization, and Dirichlet process

Computers have been taught to clone granular soil particles for discrete element method simulations to alleviate difficulties of using three-dimensional imaging techniques for scanning a large number of particles. In this process, computers analyze a few scanned particles to extract morphological characteristics of the target soil, which are used to clone as many particles as necessary. However, many natural granular soils contain a wide range of particle shapes mixing more than one type of morphological characteristics, causing difficulties in cloning. This research aims to address this challenge by integrating spherical harmonics with Gaussian mixture model, expectation–maximization, and Dirichlet process. Spherical harmonics coefficients are used to characterize morphological information of the granular soil. Gaussian mixture model is used to fit a function to the mixed morphological characteristics. The expectation–maximization and Dirichlet process are used to estimate the fitting parameters in Gaussian mixture model. Then, Gaussian mixture model is used to generate new spherical harmonics coefficients and then generate new particles. The effectiveness and accuracy of the proposed methodology are verified using a Griffin sand. Although this approach is developed for granular soils, the proposed technique can also be used to clone other particulate materials.

Microscopic Mechanism of the Macroscopic Mechanical Properties of Cement Modified Subgrade Silty Soil Subjected to Freeze-Thaw Cycles

In order to study the effects of the microstructure parameters of cement modified subgrade silty soil (CMSS) in a frozen area under freeze-thaw (F-T) cycles on the macroscopic mechanical properties, the static triaxial test, scanning electron microscopy (SEM), and grey relation analysis (GRA) were implemented on silty soil modified with 0% and 2% cement at optimum moisture content from the northwest in Jilin Province in China. The results showed that the shear strength, the cohesion of 0% and 2% CMSS, decreased with the increase of F-T cycles, while the internal friction angle was not obviously changed. The shear strength and its parameters of 2% CMSS doubled compared to that of 0% CMSS. The micro-parameters, representing the particle morphological characteristics, particle arrangement, and pore characteristics of CMSS, changed differently under F-T cycles. If the cement was not added, the cohesion and the internal friction angle were most sensitive to the average particle diameter (Dp) and the average particle abundance (C), respectively. When the cement content was 2%, the cohesion was chiefly affected by the particle size fractal dimension (Dps), while the internal friction angle was mainly related to the average pore diameter (Dh). The main principle of cement improvement was to decrease Dh of soil under F-T cycles.

Effects of morphology on the dispersibility of instant whole milk powder

The functionality and performance of instant whole milk powder (IWMP) can be related to its physical and chemical properties; i.e. particle size, morphology and fat distribution. Dispersibility, a measure of rehydration, has become one of the most important quality characteristics of IWMP. Many milk powder properties may affect the dispersibility. Based on literature and our own experience, particle size and morphology may be the two most important factors. This work investigated the quantitative relationship between particle size, morphology and dispersibility. Samples of different brands of IWMPs were fractionated using sieving and then remixed. The powder dispersibility was then measured, and the particle morphology characteristics obtained using light microscopy combined with image processing. Principal component analysis (PCA), partial least squares (PLS) and artificial neural network (ANN) methods were used to process the data. It was found that IWMP produced by different plants have different shape factors (circularity, convexity, and area) and the trends of the dispersibility versus the changes in the shape factors (circularity, convexity and area) for different particle size groups are different. Then, by the use of the size fractions and shape factors, prediction models for dispersibility were developed. A further experiment addressed the validity of the ANN model.

Coupling HAADF-STEM Tomography and Image Reconstruction for the Precise Characterization of Particle Morphology of Composite Polymer Latexes

The performance of waterborne polymer–polymer composite materials strongly depends on the particle morphology, but the precise quantitative characterization of complex morphologies is a long-standing problem. In this work, high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) has been used to obtain a 3D quantitative characterization of the morphology of polymer–polymer particles. The potential of this technique was demonstrated in the study of the effect of process variables (Tg of the seed, type of initiator, and instantaneous conversion of the monomer) on particle morphology during the semicontinuous emulsion copolymerization of styrene and butyl acrylate on methyl methacrylate-rich seeds. This analysis unveiled new mechanisms of morphology development.