Changes In Particle Size Distribution Research Articles

The mechanics of brittle granular materials with coevolving grain size and shape.

The influence of particle shape on the mechanics of sand is widely recognized, especially in mineral processing and geomechanics. However, most existing continuum theories for engineering applications do not encompass the morphology of the grains and its evolution during comminution. Similarly, the relatively few engineering models accounting for grain-scale processes tend to idealize particles as spheres, with their diameters considered as the primary and sole geometric descriptor. This paper inspires a new generation of constitutive laws for crushable granular continua with arbitrary, yet evolving, particle morphology. We explore the idea of introducing multiple grain shape descriptors into Continuum Breakage Mechanics (CBM), a theory originally designed to track changes in particle size distributions during confined comminution. We incorporate the influence of these descriptors on the elastic strain energy potential and treat them as dissipative state variables. In analogy with the original CBM, and in light of evidence from extreme fragmentation in nature, the evolution of the additional shape descriptors is postulated to converge towards an attractor. Comparisons with laboratory experiments, discrete element analyses and particle-scale fracture models illustrate the encouraging performance of the theory. The theory provides insights into the feedback among particle shape, compressive yielding and inelastic deformation in crushable granular continua. These results inspire new questions that should guide future research into crushable granular systems using particle-scale imaging and computations.

Parametric Study of Residence Time Distributions and Granulation Kinetics as a Basis for Process Modeling of Twin-Screw Wet Granulation.

Twin-screw wet granulation is a crucial unit operation in shifting from pharmaceutical batch to continuous processes, but granulation kinetics as well as residence times are yet poorly understood. Experimental findings are highly dependent on screw configuration as well as formulation, and thus have limited universal validity. In this study, an experimental design with a repetitive screw setup was conducted to measure the effect of specific feed load (SFL), liquid-to-solid ratio (L/S), and inclusion of a distributive feed screw on particle size distribution (PSD) and shape as well as residence time distribution of a hydrophilic lactose/microcrystalline cellulose based formulation. An intermediate sampling point was obtained by changing inlet ports along the screw axis. Camera-based particle size analysis (QICPIC) indicated no significant change of PSD between the first and second kneading section, except for low L/S and low SFL where fines increase. Mean residence time was approximated as a bilinear fit of L/S and SFL. Moreover, large mass flow pulsations were observed by continuous camera measurements of residence time distribution and correlated to hold-up of the twin-screw granulator. These findings indicate fast granulation kinetics and process instabilities for high mean residence times, questioning current standards of two kneading compartments for wet granulation. The present study further underlines the necessity of developing a multiscale simulation approach including particle dynamics in the future.

Effects of ultrasound-assisted cellulase enzymatic treatment on the textural properties and in vitro starch digestibility of brown rice noodles

The effects of ultrasound-assisted enzymatic (ult-enzymatic) treatment on the textural properties and starch digestibility of brown rice noodles were investigated. Brown rice was rich in dietary fibers, mainly insoluble dietary fiber (IDF). After the ult-enzymatic treatment, the IDF content and particle size of brown rice flour decreased, and the soluble dietary fiber (SDF) content increased. The ult-enzymatic treatment significantly influenced the pasting, thermal and rheological properties of rice flour, probably due to the changes of proximate composition and particle size distribution. Accordingly, the ult-enzymatic rice noodles with smooth surface and small air cell microstructure had better texture and cooking qualities, and slightly higher starch digestibility when compared to the untreated rice noodles. The glycemic index (GI) of the ult-enzymatic rice noodles with higher starch relative crystallinity was significantly lower than that of the polished ones. The correlation analyses exhibited that the SDF was beneficial to the reduction of starch digestibility, while had less damage to the texture of rice noodles. These results indicated that the ult-enzymatic treatment was a promising way to improve the textural properties of brown rice noodles and maintain a lower starch digestibility.

Diagnostic of Structural Changes in Ferromagnetic Powders during Milling in Beater Mill

Problem of obtaining fine powders of strontium hexa-ferrite is actual because of its wide applications. The paper provides the results of studies of particle size distribution and structural characteristic changes of strontium hexa-ferrite powder (SrFe12O19) during milling in impact mill and after its consequent annealing. Mechanical processing of coarse particulate system was carried out in the mill for 120 minutes without electromagnetic effect and with creation of magneto fluidized bed, formed by perpendicular constant and alternating magnetic field with induction gradient of 210 mT/m, providing reciprocating motion of particles and aggregates with sizes of 3 – 4 mm. It was shown that milling of coarse strontium hexa-ferrite with average particle size 1558.5 μm and the most possible size 1500 μm in magneto fluidized bed allowed to intensify milling process and to provide a significant increase of powder particle sizes uniformity. It was found out, that milling in magneto fluidized bed leads to a great decrease of coherent scattering regions sizes and an increase of lattice micro-deformations and relative dislocation density. Consequent annealing of the powder for 2 hours at 850°C refined structural characteristics significantly. The carried out research allows to choose the optimal milling duration for solution of practical problems of powder metallurgy.

Micrometer-sized magnetite synthesis using Fe(OH)2(s) as a precursor for technetium sequestration from liquid nuclear waste streams

• Transformation of Fe(OH) 2 (s) to micrometer-sized magnetite in waste stream at 75 °C. • Solution pH/temperature/oxidation kinetics play key roles in final mineral products. • An increase in pH or Fe(II) amendment improved tc removal from waste streams. • Tc sequestration as TcO 2 •2H 2 O or through Tc(IV)-magnetite incorporation. • More tc incorporation into magnetite at elevated temperatures and pH conditions. Systematic batch experiments under variable adjusted physicochemical conditions were conducted to explore optimization of micrometer-sized magnetite synthesis for Tc sequestration from radionuclide waste streams using Fe(OH) 2 (s) as the precursor. Extensive solid characterizations using X-ray diffraction, microscopy and spectroscopic methods were performed to identify mineral phases, assess changes in particle morphology and size distribution, as well as Tc speciation and incorporation, in the produced mineral phases. The results show that the solution pH, temperature, and oxidation kinetics play key roles in the final mineral products. Micrometer-sized magnetite crystals (0.62–0.96 µm, on average) with well-defined dodecahedral or octahedral structures were synthesized under near neutral (~pH 8) or alkaline (~pH 13) conditions at 75 °C, respectively; whereas goethite dominated the end products at room temperature. An increase in pH at 75 °C improved Tc removal from 27% (near neutral pH) to 42% (alkaline pH), but the removal process remained inhibited by redox-competitive Cr(VI) present in the waste streams. By adding additional Fe(II) to the system, Tc sequestration was dramatically improved up to 87% without observable changes in the solid product. The sequestrated Tc existed as TcO 2 •2H 2 O and/or Tc(IV) incorporated into magnetite, where extended X-ray absorption fine structure (EXAFS) spectroscopy showed that more Tc was incorporated into magnetite at elevated temperatures and pH conditions, with complete Tc(IV) incorporation into magnetite occurring under 75 °C-pH 13 conditions. Our results indicate that optimal micrometer-sized magnetite can be produced for Tc sequestration by reacting Fe(OH) 2 (s) with a waste stream simulant under elevated pH (~13) and temperature (75 °C) conditions. The incorporation of reduced Tc(IV) into stable micrometer-sized magnetite provides a viable supplemental immobilizing technology that may be used to improve nuclear waste treatment and disposal needs.

Dynamic simulation of industrial-scale gibbsite crystallization circuit

Population balance model is crucial for improving the method of aluminum hydroxide massive crystallization and enhancing the quality of control over industrial precipitation trains. This paper presents the updated population balance model, which can be used for simulation of industrial-scale precipitation. Processes of birth-and-spread and particle breakage are considered integral parts of the precipitation process along with secondary nucleation, growth and agglomeration of particles. The conceptual difference of the proposed system of equations is its ability to reproduce the oscillatory process that occurs in precipitation circuits as a result of cyclic changes in the quality of the seed surface. It is demonstrated that self-oscillations can occur in the system without any external influence. The updated model is adjusted and verified using historical industrial data. The simulation of seed-recycle precipitation circuit showed an exact correspondence between the calculated dynamic pattern of changes in particle size distribution of aluminum hydroxide and the actual data.

Impacts of salinity on the dynamics of fine particles and their associated metals during stormwater management

Abstract Elevated salinity in stormwater runoff may adversely impact the efficacy of stormwater management practices (SMPs) in intercepting contaminants via changing the stability of suspended particles as well as the fate and transport of their associated contaminants. Field-collected soil samples were employed to characterize the impacts of salinity on suspended particles. Varying concentrations (10 mM to 1000 mM) of chloride salts (NaCl, KCl, MgCl2, and CaCl2) were applied to suspended particle samples to assess the changes in particle size distribution (PSD) and metal desorption from particles. The concentration of fine particles (d

Single Particle Inductively Coupled Plasma Mass Spectrometry Study of Ceria Nanoparticle Size Distribution from Oxide CMP with Microreplicated Pads

This work describes the use of Single Particle Inductively Coupled Plasma Mass Spectrometry (spICP-MS) to measure ceria particle number concentrations and compare changes in size distributions to silicon dioxide wafer removal rates from different chemical mechanical planarization (CMP) processes. Particle number concentrations were measured for the 21 to 559 nm size range at 1 nm size resolution. Changes in the ceria particle size distribution after CMP included a decrease in large (>130 nm) particles, an increase in small (<40 nm) particles, an increase in the total number of particles, and a decrease in median particle size. The decrease in median size was as high as 7% and influenced by flow rate, pressure and pad type. A novel microreplicated CMP pad was used which requires no pad conditioning to ensure consistent pad surface features, and the effect of different pad types on removal rate and particle size was isolated. A decrease in the median particle size correlated with higher silicon dioxide removal rates (R2 = 0.96) for a series of pad types with unique combinations of chemistry and surface features. This new combination of nano particle metrology and control of pad surface features is an innovative tool set for modeling advanced CMP processes.

Effect of debranching on the structure and digestibility of octenyl succinic anhydride starch nanoparticles

Starch nanoparticles are known to have potential applications in the encapsulation and delivery of active substances. In this study, waxy maize starch (WMS) was modified with octenyl succinic anhydride (OSA), followed by debranching with pullulanase to obtain linear chains with OSA groups. These chains self-assembled and polymerized into nanoparticles. The structural characteristics of these particles, including the molecular weight, chain length distribution, particle size, and digestibility were investigated. The results indicated that the A-type crystalline structure of the WMS and OSA-modified starch changed to a B-type structure after debranching. Compared with WMS, at a low degree of substitution (DS = 0.016), there was less change in particle size, amylose content, and molecular distribution after debranching. When the DS was high (DS = 0.027, DS = 0.036), the molecular weight distribution of the OSA starch showed three peaks, and the short chain in the starch after debranching was relatively large. Moreover, the resistant starch content of the nanoparticles increased from 3.9% to 30% in WMS. Particle sizes ranged from 100 nm to 300 nm, and OSA-modified nanoparticles had a lower zeta potential and better stability. This method for preparing nanoparticles is potentially applicable to the preparation of delivery carrier materials for active functional substances.

Effect of Calcium Silicate Hydrate Seeds on Hydration and Mechanical Properties of Cement

C-S-H series are synthesized at different temperatures and ages by pozzolanic reaction. The change of particle size distribution, phase composition, morphology and nanostructure of C-S-H with temperatures and ages, and the effects of C-S-H seeds and seeds parameters on the hydration behavior and mechanical properties development of cement were investigated by DLS, XRD, SEM, 29Si NMR, TAM-air isothermal calorimeter and mechanical properties test. The results show that the particle size, crystallinity, basal spacing and Q2/Q1 ratio of C-S-H increases with the increase of synthesis temperature and age. The addition of synthesized C-S-H seeds to cement pastes results in the strong acceleration effect on cement hydration and significant improvement of the early strength of cement paste and mortar. The 1 day-C-S-H seeds synthesized at room temperature can increase the strength of cement paste by about 30 MPa at 12 h. The effect does not show a very regular change with the increase of the temperature and age of seeds synthesis. Considering the effect of C-S-H seeds on the hydration and mechanical properties of cement, and economy and short cycle of seeds synthesis, the C-S-H seeds synthesized at room temperature for 1 day or 55 °C water bath for 12 hours is recommended.

Langevin Dynamics Calculation of Brownian Coagulation Coefficient for Spherical Equal-size Aerosol Particles in Transient Regime

Coagulation coefficient of aerosol particles due to Brownian motion is an important issue to describe change in particle size distribution. Motion of aerosol particles is diffusive in continuous region (small Knudsen number; Kn), or like free molecular motion of gaseous molecular in free molecular region (large Kn). Fuchs (1964) presented an expression of coagulation coefficient in transition regime by a so-called “Flux Matching” method. In his method, transportation of particles inside of the “limiting sphere” is assumed to be like free molecular, or diffusive outside of the sphere. These days, some researchers presented coagulation coefficient of aerosol particles by direct calculation of motion of aerosol particles. They employed Langevin dynamics equation to represent the stochastic motion of aerosol particles. In this study, we developed new model to calculate the coagulation coefficient. Our model employed spherical calculation space in which one scavenging particle is in the center of it: the calculation sphere moves together with the motion of the scavenging particle. The coagulation coefficient can be calculated from the mean time between collisions and the concentration of collision particles. By using the above numerical model, we have calculated the coagulation coefficient of spherical particles of from 4 nm to 100 nm in diameter.

Change in particle size distribution of low-rank coal in long-term storage

Change in particle size distribution of low-rank coal in long-term storage

Development and Comparison of Intramuscularly Injected Long-acting Testosterone Undecanoate Nano-/Microcrystal Suspensions with Three Different Particle Size.

The aim of this study was to develop and compare the pharmacokinetic property of testosterone undecanoate (TU) nano-/microcrystal suspension with three different particle sizes after intramuscular (i.m.) administration. TU nano-/microcrystal suspensions were prepared by high pressure homogenization method and the mean particle size was 0.30 ± 0.11 μm (A), 1.21 ± 0.37 μm (B), and 4.83 ± 0.60 μm (C), respectively. Scanning electron microscope (SEM) was employed to observe the morphology of nano-/microcrystal suspensions after operation. X-ray Powder diffraction (XRPD) confirmed the crystalline state of TU in nano-/microcrystal suspension. After storage at 4 °C and 25 °C under mechanical shaking for 2 months, physical and chemical stabilities of nano-/microcrystal suspensions were measured by particle size analyzer and high performance liquid chromatography. There was no obvious change in particle size distribution and content of TU. After i.m. administration of suspension C to rats, the concentration of TU in plasma lasted for nearly 12 days that was comparative with the commercial testosterone undecanoate injection. The results showed that microcrystal C with a larger particle size had long-acting effect comparing with other two suspensions. The muscle irritation test in rabbits showed that the local irritation of TU nano-/microcrystal suspensions was lower than that of commercial testosterone undecanoate injection. It can be concluded that appropriate particle size of nano-/microcrystal suspensions for i.m. administration of TU was important to achieve better therapeutic effect.

Revisiting Hardin’s parameters for the quantification of particle breakage – A statistical entropy approach

It is well recognised that particle breakage in granular materials is affected by stress level, stress path, initial density, and particle size distribution (PSD), amongst others. Furthermore, it has been shown that breakage has a significant influence on the stress-strain behaviour of soils. This paper compares a commonly used breakage parameter with grading entropy coordinates. Such coordinates enable for the representation of any PSD as a single point in a Cartesian coordinate plane. Hence, the evolution of PSD changes may be easily tracked. This paper aims to demonstrate that grading entropy coordinates are as (or more) effective than other breakage parameters, whilst providing additional insight. On the basis of limited data it is shown that grading entropy coordinates are able to capture the dependence of breakage on stress level, stress path and initial PSD.

Investigating the Effects of a Consciousness Field on Enzyme-Like Behavior of Gold Nanozyme

The study of chemical structures with bio-molecular activity that mimic the behavior of biological molecules has always been of interest to researches in the field of early life as well as technology and industry. Among these compounds, a type of nanomaterial with enzyme-like activity, called Nanozyme, has comparable performance with endogenous cellular compounds and has great potentials in replacing natural enzymes. Previously, in several studies, it has been determined that Consciousness Fields (CFs) according to Taheri, have a different nature from the known physical fields and have the ability to affect the matter and energy of a system under study and lead it to a more optimal and functional performance. In this study, we investigate the effects of a type of CF, named CF (A), on the physicochemical structure and function of gold Nano-chemical models. In the present study, using electron microscopy as well as dynamic light scattering and kinetic assays, we observed significant changes in the nanoparticle particle size distribution (about 20%) and its kinetic constants (about 4%) under the influence of the CF. According to the results of this study, we observe a reproducible effect of CF on gold Nanozyme behaviors. Further studies on the effect of CFs on various biomimetic molecules are fully justified to better understand CFs mechanism of action.

Effect of injection timing on particle size distribution of a diesel engine fueled with biodiesel-diesel blends

The purpose of this study is to investigate injection timing affected particle size distribution of a diesel engine fueled with biodiesel/diesel blends. The biodiesel blending ratios include 7, 10 and 20%vol. The experiments were operated at engine speed 1,500 rpm under 25, 50 and 75% engine loads and two different injection timing (25.5 CAD BTDC and 27.5 CAD BTDC). The effects of biodiesel addition and injection timing on the changes in black smoke and particle size distribution were discussed. Results showed that the standard injection timing for the addition of biodiesel, especially for 20% biodiesel blended with diesel fuel (B20) had a significant effect of increasing particle concentration and thus black smoke emission. The advanced injection timing for B20 could improve combustion efficiency and reduce small particles emission in nucleation-mode (Dp 5 – 50 nm) and particles in accumulation-mode (Dp 50 – 1,000 nm) became the smaller particle size, compared to standard and retarded injection timing. Moreover, the oxygen content in biodiesel could improve combustion efficiency and reduce the emission but it is necessary to modify the engine especially fuel injection timing.

CO2-responsive preformed gel particles with interpenetrating networks for controlling CO2 breakthrough in tight reservoirs

Horizontal well re-fracturing of tight reservoirs triggers complex fractures, which induces severe gas channeling and low sweeping efficiency in CO2 flooding due to the significance difference in permeability between matrix and fractures. Herein, novel CO2-responsive preformed gel particles with interpenetrating networks (IPN-ASSAP) was synthesized to mitigate CO2 breakthrough. To reveal the plugging efficiency and EOR potential of IPN-PAASP, the change in particle size distribution, microstructure, strength, and rheology were characterized, followed by core flooding experiments. Experimental results indicated that after IPN-ASSAP contacted with CO2, the median diameter and strength of particles were enhanced due to protonation reaction of IPN-PAASP. Moreover, after IPN-PAASP was injected into fractured core, injection pressure increased from 5.0 kPa to 0.342 MPa with plugging efficiency of 99 %. During water flooding and CO2 flooding, the crude oil in fracture was displaced with oil recovery of 17.1 %. After plugging was formed, injected CO2 entered matrix, and recovery factor increased by 23.1 %. All the experiment results indicated that IPN-PAASP is a promising candidate for fracture plugging during CO2 flooding.

Impact of atomization gas on characteristics of austenitic stainless steel powder feedstocks for additive manufacturing

Given the complexity of the laser-material interactions prevalent in powder bed fusion additive manufacturing, the need for tight control of alloy composition in the metal powder feedstock is leading to the use of specific gases during atomization. These changes in atomization gas also impact powder flow and packing. In order to identify the magnitude of this impact, two nitrogen atomized and one argon atomized 316 L austenitic stainless steel powders with similar size distributions were characterized using traditional powder characterization tools and rotating drum and annular shear rheological tools. While the traditional characterization tools and particle size measurements did not differentiate between the powders, these rheological tools allowed connections between the particle morphologies and rheological properties and powder performance to be identified. In particular, the argon atomized powders displayed higher aspect ratios, which translate into more spherical morphologies, and improved flow, defined by lower avalanche angles, when tested in the rotating drum. On the other hand, these differences in flow properties were not captured in the corresponding basic flow and specific energy measurements made with the annular shear tools. Variations in the powder packing properties and internal powder porosity in the different powder lots decreased the powder mass and introduced increased uncertainty in the force and torque measurements. The void spacing between loosely packed powders was also measured and showed how changes in particle size distribution and morphology impacted both packing density and permeability. Larger void spacing produced higher permeability values, indicating greater gas flow through the loosely packed powder.

Model for attrition in sorption-enhanced chemical-looping reforming in fluidized beds

A jet attrition model is developed to predict the evolution of the particle size distribution in fluidized beds. This model predicts changes in particle size distribution due to impact attrition in the jet region as a function of operating parameters – temperature, particle impact velocity and time. The model provides good agreement with experimental results for iron and hematite as oxygen carriers, with limestone and lime as CO2 sorbent at temperatures from 20 to 800 °C and jet velocities from 59 to 221 m/s. It is found that fragmentation, abrasion, and material fatigue over the attrition duration must be considered. Two fitting parameters considering fatigue by material properties and repeated collisions are applied in this model, with their values determined based on nonlinear least squares regression following the evolution of the particle size distribution.

Characteristics of Changes in Particle Size and Zeta Potential of the Digestate Fraction from the Municipal Waste Biogas Plant Treated with the Use of Chemical Coagulation/Precipitation Processes

The organic fraction of waste is increasingly used for biogas production. However, the fermentation process used for this purpose also produces waste in the form of digestate in addition to biogas. Its liquid fraction can, among other things, be a source of water, but its recovery requires many advanced technological processes. Among the first in the treatment train is usually coagulation/chemical precipitation. Its application changes properties, including the size and zeta potential (ζ) of the fractions that have to be removed in subsequent processes. Changes in particle size distribution and ζ potential occurring in the liquid fraction of municipal waste biogas plant digestate and solutions after coagulation/chemical precipitation with FeCl₃·6H₂O, PIX 112 and CaO were analyzed. The particle size distribution of the raw digestate was wide (0.4–300 µm; up to 900 µm without ultrasound). The median particle diameter was about 12 µm. The ζ potential ranged from −25 to −35 mV in the pH range 5–12, and the isoelectric point (IEP) was at pH 2. The best treatment results obtained with the use of. 10 g FeCl₃∙6H₂O/dm³ shifted particle size distribution towards finer particles (median diameter: 8 and 6 µm, respectively, before and after ultrasound). The ζ potential decreased by about 5–10 mV in the pH range 2.5–12 without changing IEP. An amount of 20 g/dm³ of FeCl₃∙6H₂O caused the disappearance of the finest and largest fraction. d50 was about 21.5 µm (17.3 µm after ultrasound). An amount of 20 g/dm³ of FeCl₃∙6H₂O generated a positive high electrokinetic potential in the range of pH 1.8–5. The IEP appeared at pH 8, and after reaching about −5 mV it again became positive at pH about 11.