Size Distribution Of Spherical Particles Research Articles

A discrete element method to model coating layer mechanical properties with bimodal and pseudo-full particle size distributions

The mechanical properties of paper coating layers are important in converting operations such as calendering, printing, and folding. While several experimental and theoretical studies have advanced our knowledge of these systems, a particle level understanding of issues like crack-at-the-fold are lacking. A discrete element method (DEM) model is used to describe bending and tension deformations of a coating layer. The particles in the model are either bimodal distributions or pseudo-full particle size distributions of spherical particles. The impact of particle size distribution on the predicted mechanical properties of the coating layer is reported. Inputs to the model include properties of the binder film and the binder concentration. The model predicts crack formation as a function of these parameters and also calculates the modulus, the maximum stress, and the strain-to-failure. The simulation results are compared to previous experimental results. Reasonable predictions were obtained for both tensile and bending for a range of latex-starch ratios and at various binder concentrations. The influence of particle packing density on mechanical properties is reported.

Production of spherical TiAl alloy powder by copper-assisted spheroidization

A copper-assisted spheroidization method was developed for preparing spherical intermetallic compound TiAl powder. By introducing copper into TiAl alloy, the brittle L21 Heusler structure TiAlCu2 alloy with low melting point (1050 °C) was produced. After preparing the spherical TiAlCu2 powder through solid–liquid interface de-wetting method, the porous TiAl alloy sphere with atomic ratio about 1:1 was prepared by dealloying the Cu element. Finally, the spherical TiAl alloy powder was prepared by sintering and deoxygenation. Compared with the current mature technology for preparing the spherical TiAl alloy powder, the size distribution of spherical particles can be easily regulated, which can meet the requirements for high-quality additive manufacturing technology. We believe that this method provides a new idea for preparing the spherical TiAl alloy powder and other spherical porous alloys.

Spherical particles design of vanillin via crystallization method: Preparation, characterization and mechanism

Vanillin is a natural flavor and is widely used in the fields of medicine, food and optoelectronics. However, the stable form I of vanillin usually shows needle or fiber-like morphology during crystallization, and it has poor powder performance (flowability, bulk density, dissolution rate, etc.), which further limits its applications. In this work, to improve the powder performances of vanillin, the spherical crystals were designed and prepared via spherical agglomeration method, and the spherical particles were systematically characterized using polarized light microscopy (PLM), particle size instrumentation, powder X-ray diffraction (PXRD) and Fourier infrared transform spectroscopy (FTIR). Meanwhile, the effects of BSR (Vbridging liquid:Vsolute), agitation rate and surfactant on the morphology and particle size distribution of spherical particles were analyzed to determine the optimal operating conditions for the spherical crystallization of vanillin as well as its formation mechanism and to improve the powder performance of the products. In addition, the multicomponent spherical particles of vanillin-salicylic acid obtained by crystal co-agglomeration (CCA) meet the formulation requirements in terms of morphology and particle size, which also enhance the dissolution rate of vanillin.

A Study on the Effect of Graphene in Enhancing the Electrochemical Properties of SnO2-Fe2O3 Anode Materials.

To enhance the conductivity and volume expansion during the charging and discharging of transition metal oxide anode materials, rGO-SnO2-Fe2O3 composite materials with different contents of rGO were prepared by the in situ hydrothermal synthesis method. The SEM morphology revealed a sphere-like fluffy structure, particles of the 0.4%rGO-10%SnO2-Fe2O3 composite were smaller and more compact with a specific surface area of 223.19 m2/g, the first discharge capacity of 1423.75 mAh/g, and the specific capacity could be maintained at 687.60 mAh/g even after 100 cycles. It exhibited a good ratio performance and electrochemical reversibility, smaller charge transfer resistance, and contact resistance, which aided in lithium-ion transport. Its superior electrochemical performance was due to the addition of graphene, which made the spherical particle size distribution more uniform, effectively lowering the volume expansion during the process of charging and discharging and improving the electrochemical cycle stability of the anode materials.

Utilization of Olive Pomace in Green Synthesis of Selenium Nanoparticles: Physico-Chemical Characterization, Bioaccessibility and Biocompatibility.

Olive pomace extract (OPE) was investigated as a potential surface modifier for the development of the green synthesis process of selenium nanoparticles (SeNPs). In order to evaluate them as potential nutraceuticals, the obtained nanosystems were characterized in terms of size distribution, shape, zeta potential, stability in different media, gastrointestinal bioaccessibility and biocompatibility. Systems with a unimodal size distribution of spherical particles were obtained, with average diameters ranging from 53.3 nm to 181.7 nm, depending on the type of coating agent used and the presence of OPE in the reaction mixture. The nanosystems were significantly affected by the gastrointestinal conditions. Bioaccessibility ranged from 33.57% to 56.93% and it was significantly increased by functionalization of with OPE. Biocompatibility was investigated in the HepG2 and Caco2 cell models, proving that they had significantly lower toxicity in comparison to sodium selenite. Significant differences were observed in cellular responses depending on the type of cells used, indicating differences in the mechanisms of toxicity induced by SeNPs. The obtained results provide new insight into the possibilities for the utilization of valuable food-waste extracts in the sustainable development of nanonutraceuticals.

Derivation of Equations for a Size Distribution of Spherical Particles in Non-Transparent Materials

This paper presents a new proposition on how to derive mathematical formulas that describe an unknown Probability Density Function (PDF3) of the spherical radii (r3) of particles randomly placed in non-transparent materials. We have presented two attempts here, both of which are based on data collected from a random planar cross-section passed through space containing three-dimensional nodules. The first attempt uses a Probability Density Function (PDF2) the form of which is experimentally obtained on the basis of a set containing two-dimensional radii (r2). These radii are produced by an intersection of the space by a random plane. In turn, the second solution also uses an experimentally obtained Probability Density Function (PDF1). But the form of PDF1 has been created on the basis of a set containing chord lengths collected from a cross-section.The most important finding presented in this paper is the conclusion that if the PDF1 has proportional scopes, the PDF3 must have a constant value in these scopes. This fact allows stating that there are no nodules in the sample space that have particular radii belonging to the proportional ranges the PDF1.

Spheroidization of borosilicate glass powder by RF induction coupled plasma

The International Simple Glass (ISG) spherical particles were prepared by Ar–H2 radio-frequency (RF) plasma, the effect of experimental parameters on the volatilization and size distribution of spherical particles was studied. The results show that the spherical powders can be obtained by RF plasma. The spheroidized powders (112 μm) have a smaller diameter than starting particles (124 μm). The high spheroidization (98%) was achieved under low flow rate of carry gas and low feed rate. In addition, the volatilization of B2O3 and Na2O are 23.48% and 56.36%, respectively. The higher feed rate and flow rate of carry gas, the lower volatilization of B2O3 and Na2O and well-spheroidization rate. Meanwhile, the particle surface is not completely smooth at low flow rate of carry gas. The distribution of elements was studied by Electro-probe Microanalyzer (EPMA), which shows the distribution of element is nearly homogeneous that provides a possibility for subsequent research.

Pressureless and Low-Pressure Synthesis of Microporous Carbon Spheres Applied to CO2 Adsorption

In this work, low-pressure synthesis of carbon spheres from resorcinol and formaldehyde using an autoclave is presented. The influence of reaction time and process temperature as well as the effect of potassium oxalate, an activator, on the morphology and CO2 adsorption properties was studied. The properties of materials produced at pressureless (atmospheric) conditions were compared with those synthesized under higher pressures. The results of this work show that enhanced pressure treatment is not necessary to produce high-quality carbon spheres, and the morphology and porosity of the spheres produced without an activation step at pressureless conditions are not significantly different from those obtained at higher pressures. In addition, CO2 uptake was not affected by elevated pressure synthesis. It was also demonstrated that addition of the activator (potassium oxalate) had much more effect on key properties than the applied pressure treatment. The use of potassium oxalate as an activator caused non-uniform size distribution of spherical particles. Simultaneously higher values of surface area and total pore volumes were reached. A pressure treatment of the carbon materials in the autoclave significantly enhanced the CO2 uptake at 25 °C, but had no effect on it at 0 °C.

Single-Stage Synthesis of Submicron Gold Particles

Nanosized and submicron gold particles are of great interest for application in optics, biophotonics, and analytical chemistry. In spite of the great progress that has been made in the development of methods for liquid-phase chemical synthesis of such colloids, no reliable procedures have been proposed for obtaining monodisperse particles with sizes larger than 300 nm. In this work, a method has been developed for single-stage liquid-phase synthesis of submicron gold particles via the reduction of gold ions with dopamine in the presence of poly(vinylpyrrolidone) as a stabilizer. It has been found that the sizes of the targeted particles can be varied within a range of 120–500 nm by varying poly(vinylpyrrolidone) concentration in reaction mixtures. It has been shown that colloids with the narrowest size distribution of spherical particles are obtained at poly(vinylpyrrolidone) concentrations of 0.01–1 mg/mL. The synthesized submicron particles can be used as labels in surface-enhanced Raman scattering spectroscopy and for confocal laser microscopy.

Detailed characterisation of TiO2 nano-aggregate morphology using TEM image analysis

A detailed morphological characterisation is performed on flame synthesised TiO2 nano-aggregates (number of primaries, N<10) using transmission electron microscopy (TEM) image analysis and mobility measurements. The size-dependent collection efficiency of the TEM sampling method is accounted for with a simple correction for particle deposition through impaction and diffusion. The TEM-derived sizes show excellent agreement with electrical mobility measurements. Primary particle size, aggregate size, and degree of aggregation distributions were obtained for two different flames and varying precursor loading rates. The analysis reveals some particle aggregation which is likely to occur only very late in the growth stage, leading to the similarity between the primary particle and spherical particle size distributions. The degree of aggregation is defined as the ratio of gyration to spherical equivalent sizes from the projected area analysis, allowing identification of particles with spherical and non-spherical morphologies. The size distributions are found to be strongly affected by precursor loading but not by flame mixture or maximum temperature. In all cases, approximately 60–70% particles are spherical while the rest form small aggregates. The detailed morphological information reported provides the much-needed experimental data for studying the early stage particle formation of TiO2 from titanium tetraisopropoxide (TTIP) in a well-defined burner configuration.

High performance catalytic activity of pure and silver (Ag) doped TiO2 nanoparticles by a novel microwave irradiation technique

This work reports the pure and silver doped-titanium dioxide (Ag-TiO2) nanoparticles prepared by a novel one step microwave irradiation method. The results from powder X-ray diffraction indicate that both pure and Ag-TiO2 nanoparticles are in anatase phase. The measured average crystallite sizes were found to be around 31 and 21 nm respectively. Transmission electron microscope observations revealed a uniform size distribution of spherical particles. The UV absorption edges are estimated from the UV–Vis absorption spectra by using UV–visible absorption spectroscopy. The results prove that the UV radiation absorption of prepared nanoparticles is improved and the absorption edge shifted towards longer wavelength. The photocatalytic degradation of different dyes such as azo-Methyl Red, Congo Red, and Orange G were investigated by using pure and Ag-TiO2 catalyst under UV light irradiation. The result showed that the photocatalytic property is significantly enhanced by doping silver. This is due to charge separation and charge transfer between electron and hole of the Ag-TiO2 catalyst. The samples were further characterized by photoluminescence and Fourier Transform infrared spectra analysis. Moreover, the method is simple, cost effective and high yields compared with other methods.

Synthesis and characterization of uniform spherical shape nanoparticles of indium oxide

Spherical shape nanoparticles of indium oxide (In2O3) has been synthesized by simple and cost effective sol gel method with indium nitrate hydrate as a precursor. The nanoparticles were characterized by X-ray diffraction, Fourier transform infra red spectroscopy (FTIR) and transmission electron microscopy (TEM). Morphological observations showed a uniform size distribution of spherical particles. From TEM, spherical particles size was found to vary from 17 to 23 nm. The most number of the nanoparticles out of total were 17 nm in size. The absorption spectra in ultraviolet region of In2O3 showed optical band gap of 3.6 eV. FTIR study reveals that the nanoparticles are single phase cubic structure of In2O3. Photo-luminescence spectrum at room temperature showed peak at 347 nm in ultraviolet region.

Analytical algorithm to determine the spherical particle size distribution from spectral absorption measurements

A modified anomalous diffraction theory (MADT) by including the effects of reflection and refraction is proposed. With respect to MADT, an analytical technique for retrieval of spherical particle size distribution (PSD), based on absorption was developed. Also, an MADT transform pair between the size distribution and the absorption spectrum was constructed. This provides a new tool to study the related particle optical properties. By Gaver–Stehfest inversion method, the derived complex-inversion formula is finally converted into the new real-inversion formula so that the measured absorption data can be applied directly. The inversion experiments show that the use of extended precision instead of double precision arithmetic can produce more reliable results at the expense of CPU time. The effects of complex refractive index on retrieval of PSD were examined. Also it was found that an appropriate reduction of the truncation number with the smoothing technique improved the anti-noise ability for the algorithm.

Wicksell's Problem in Local Stereology

Wicksell's classical corpuscle problem deals with the retrieval of the size distribution of spherical particles from planar sections. We discuss the problem in a local stereology framework. Each particle is assumed to contain a reference point and the individual particle is sampled with an isotropic random plane through this reference point. Both the size of the section profile and the position of the reference point inside the profile are recorded and used to recover the distribution of the corresponding particle parameters. Theoretical results concerning the relationship between the profile and particle parameters are discussed. We also discuss the unfolding of the arising integral equations, uniqueness issues, and the domain of attraction relations. We illustrate the approach by providing reconstructions from simulated data using numerical unfolding algorithms.

Wicksell's Problem in Local Stereology

Wicksell's classical corpuscle problem deals with the retrieval of the size distribution of spherical particles from planar sections. We discuss the problem in a local stereology framework. Each particle is assumed to contain a reference point and the individual particle is sampled with an isotropic random plane through this reference point. Both the size of the section profile and the position of the reference point inside the profile are recorded and used to recover the distribution of the corresponding particle parameters. Theoretical results concerning the relationship between the profile and particle parameters are discussed. We also discuss the unfolding of the arising integral equations, uniqueness issues, and the domain of attraction relations. We illustrate the approach by providing reconstructions from simulated data using numerical unfolding algorithms.

Retrieval of spherical particle size distribution using ant colony optimization algorithm

The ant colony optimization (ACO) algorithm based on the probability density function is applied for the retrieval of spherical particle size distribution (PSD). The spectral extinction data based on the Mie theory and the Lambert-Beer Law served as input for estimating five commonly use monomodal PSDs, i.e., Rosin-Rammer distribution, normal distribution, logarithmic normal distribution, modified beta distribution, and Johnson's SB distribution. The retrieval results show that the ACO algorithm has high feasibility and reliability, thus providing a new method for the retrieval of PSD.

Retrieval of spherical particle size distribution with an improved Tikhonov iteration method

The problem of retrieval for spherical particle size distribution in the independent mode is studied, and an improved Tikhonov iteration method is proposed. In this method, the particle size distribution is retrieved from the light extinction data through the Phillips-Twomey method firstly in the independent mode, and then the obtained inversion results of the particle size distribution is used as the initial distribution and the final retrieved particle size distribution is obtained. Simulation experiments indicate that the spherical particle size distributions obtained with the proposed method coincide fairly well with the given distributions.

The Truncated Geometric Approximation and the Size Distribution of Small Atmospheric Particles

Abstract This paper describes a simple relationship between the slope of particulate optical depth as a function of wavelength and the size distribution of spherical particles. It is based on approximating extinction using a truncated geometric optics relationship and is applicable when optical depth decreases with wavelength. The new relationship suggests that extinction versus wavelength measurements are most sensitive to particles that are comparable in size to the wavelength. When optical depth is expressed as a power-law function of wavelength, the resulting particle size distribution is also a power-law function of size, with the two exponents reproducing the well-known relationship between the Ångström and Junge exponents. Examples of applying the new relationship are shown using both numerical calculations based on Mie theory and measurements from the Aerosol Robotic Network (AERONET) sun photometer at NASA Goddard Space Flight Center (GSFC). Since the truncated geometric approximation makes no assumptions per se concerning the form of the particle size distribution, it may find application in supplementing solar aureole profile measurements in retrieving the size distributions of particles in thin clouds—for example, cirrus—or when they are present.

Particle size tailoring and luminescence of europium(III)-doped gadolinium oxide obtained by the modified homogeneous precipitation method: Dielectric constant and counter anion effects

This work reports on controlling the particle size distribution of europium(III)-doped gadolinium oxide samples prepared through a topochemical reaction carried out by thermal treatment of europium(III)-doped gadolinium hydroxycarbonate. Hydroxycarbonate samples were obtained by a modified homogeneous precipitation method using different solvent mixtures, such as water:ethanol, water:ethylene glycol, water:tert-butanol, and different counter ions such as nitrate and chloride. The luminescent properties of the oxide samples, are characteristics of europium(III) ions, with the hypersensitive transition ( 5D 0 → 7F 2) being the most intense emission peak and the emission lifetime values are typical for this system. The spherical particle size distribution of europium(III)-doped gadolinium oxide can be tailored by selecting the counter anion types, the chemical nature of the alcohol and the dielectric constant of the reaction media. The appropriate control of these parameters allows the preparation of rare-earth doped gadolinium samples having monomodal particle size distributions with mean sizes between 30 and 90 nanometers.

Comparison of Nanometric Particle Size Distributions as Determined by SAXS, TEM and Analytical Ultracentrifuge

AbstractIn this paper the particle size distribution of SiO2 spherical nanoparticles is determined by small angle X‐ray scattering (SAXS). The experimental scattering intensity data were compared with theoretical intensities based on different numeric procedures and different assumptions for the distribution of the particles. Hereby two fixed shapes of distribution, Gauss and log normal, were used and compared to a free particle distribution which is determined with the maximum entropy method (MEM). The results were further compared with the particle size distributions obtained from the transmission electron microscopy (TEM) and analytical ultracentrifuge (AUC). The comparison demonstrated SAXS to be a generally reliable method for determining size distributions of spherical particles in the nanometer range. Assuming a fixed distribution in the SAXS method, reliable data can be obtained even in the case of bad statistical data or higher concentrations. The MEM procedure allows shape determination but is restricted to scattering data of dilute samples and high statistical quality if one wishes to avoid artefacts in the resulting size distribution.