Agglomerate Particle Size Distribution Research Articles

Particle agglomeration via resonant acoustic mixer for dry powder inhalation

The work presented in this paper employed a resonant acoustic mixing (RAM) process to optimize the fine particle agglomeration process for dry powder inhalation to achieve efficient pulmonary delivery of melatonin. The formulation prepared by acoustic mixing with the double layer grids demonstrated superior agglomerate particle size distribution and approximately 90% of the metered dose in the dosing chamber was emitted from Turbuhaler® (90% emitted dose). Acceleration force during acoustic mixing significantly affected the packing fraction of mixtures and mechanical strength of agglomerates resulting in improved fine particle fraction. The particle agglomeration via RAM can improve the efficiency of agglomerate production by utilizing the internal space of the mixer to induce more particle collision. The agglomerates formulation exhibited ideal fine particle fraction of 47.65 ± 1.46% and 56.02 ± 2.55% at flow rates of 30 and 60 L/min, respectively. The fine particle deposition was only slightly affected at the lower air-flow rate, suggesting a reliable inhalation performance in vivo.

Straw Inputs Improve Soil Hydrophobicity and Enhance Organic Carbon Mineralization

The mechanism of the influence of soil water repellency (SWR) and agglomeration stability on soil organic carbon (SOC) mineralization has not been thoroughly studied following different methods of returning straw to the field. The research background in this study was ordinary black soil, and the addition of straw was accomplished via straw mixing (CT), straw mulching (CM), straw deep burying (CD), and straw tripling deep burial (CE). A 120-day long-term incubation test was used to measure the contact angle between water droplets and soil, the particle size distribution of aggregates and their organic carbon (OC) content, organic carbon pool (OCP) content, OC contribution, and soil CO2-C release, the extent of SWR and the direct effect of agglomerates on SOC mineralization were assessed under different straw return methods. The results revealed that the water-droplet–soil contact angle (CA) was much greater and the rate of CA decline was significantly lower in the CD treatment compared to the CT, CM, and CE treatments, the rate of water droplet penetration on the soil surface was slower, and the SWR was improved. The CD treatment significantly increased the content of macroaggregates and their OCP content, and also significantly increased the content of microaggregates’ OC. The CO2-C emission rate and cumulative emissions were enhanced by adding the same amount of straw, with the most significant enhancement in the deep straw treatment. The cumulative CO2-C emission rate and SOC mineralization significantly increased with increases in SWR, macroaggregates content, and microaggregates OC content, but significantly decreased with increases in macroaggregates’ OC content, according to principal component analysis and Pearson’s correlation analysis. These results highlight the extent of SWR and the direct effect of agglomerate particle size distribution and OC content on SOC mineralization under different straw return methods. This will help to consolidate soil structural stability and nutrient management to support productivity and SOC sequestration in different agricultural systems.

Analysis of agglomeration particle size near the burning surface of aluminized solid propellant based on digital inline holography

Aluminum powder can increase the specific impulse and improve the combustion performance of a solid propellant; however, agglomeration can result in the loss of two-phase flow, a decrease in specific impulse of the propellant, and an increase in the thermal protection pressure of the motor structure. This study employs digital inline holography, which offers the advantage of non-contact three-dimensional measurements, to investigate the agglomeration particle size near the burning surface. This study aims to quantitatively analyze these particle size data to determine the effects of pressure, ammonium perchlorate particle size, coarse and fine ammonium perchlorate content ratio, and aluminum particle size on the agglomeration particle size distribution. The experimental results indicate that increasing the pressure from 0.1 MPa to 0.8 MPa reduces the average particle diameter of agglomeration by at least 9.6%, results in a more concentrated agglomeration particle size distribution, and decreases the volume and number proportion of agglomeration by approximately 7% and 17%, respectively. Furthermore, when the particle size of ammonium perchlorate decreases from 250 μm to 90 μm, the agglomeration particle size distribution becomes more concentrated, the average diameter of agglomeration decreases by at least 37.4%, and the number and volume proportion of agglomeration decrease by approximately 13% and 44%, respectively. The ratio of coarse and fine ammonium perchlorate content has a nonlinear effect on agglomeration. When this ratio is 0.6, the average agglomerate diameter decreases by at least 16%, the agglomeration particle size distribution is more concentrated than that the ratio is 0.39 and 1.29, and the agglomeration number and volume fraction decrease by more than 6% and 32%, respectively. Moreover, decreasing the initial aluminum particle size from 30 μm to 15 μm reduces the average agglomeration particle diameter by more than 21.6%, results in a more concentrated agglomeration particle size distribution, however, increases the number and volume proportion of agglomeration by approximately 17% and 8%, respectively. The conclusions of this study are expected to be significantly helpful in optimizing propellant formulation, reducing the particle size of aluminum agglomeration, and improving the combustion performance of propellants.

1P4-6 Characteristics of particle size distribution of agglomerates in an ultrasonic source with a cylindrical rigid wall

1P4-6 Characteristics of particle size distribution of agglomerates in an ultrasonic source with a cylindrical rigid wall

The role of reactive PAH dimerization in reducing soot nucleation reversibility

Abstract Nucleation of incipient soot or carbon black nanoparticles has significant scientific and industrial importance because it influences the particle size distribution, morphology and composition, hence its health and environmental impact as well as functional properties. R eversible P olycyclic Aromatic Hydrocarbon (PAH) C lustering (RPC) with van der Waals forces (vdW) was proposed recently as opposed to I rreversible P AH C lustering (IPC) for soot nucleation (Eaves et al., Proc. Combust. Inst, 35 (2015) 1787) to relax the assumption of stable dimer formation with physical bonds at flame temperatures. Here, the necessity of considering chemical bond formation between PAHs in a dimer for reducing soot nucleation reversibility in ethylene coflow diffusion flames with a wide range of nitrogen dilution ratios is demonstrated. An RPC model with C hemical B ond F ormation (RPC CBF) is developed and its performance is compared to those of RPC and IPC models. Only the RPC CBF model with low reversibility for PAH addition on the surface of soot primary particles can predict soot volume fraction, average primary particle diameter, primary particle number density and the bimodal size distribution of soot agglomerates on the flame centerline within experimental uncertainty. While the IPC model overpredicts soot concentrations by a factor of five with increased dilution, the RPC model underpredicts it by more than two orders of magnitude for the flame with 68% nitrogen dilution. The RPC model fails to predict the observed bimodality of agglomerate particle size distribution in flames with low dilution because its predicted nucleation rate is much weaker compared to that of growth. Accounting for chemical bond formation for dimers is essential to form enough nuclei with increasing dilution and temperature. Also, low reversibility for PAH addition is required to predict the balance between nucleation and surface growth, hence the average size of soot primary particles.

Fully automated primary particle size analysis of agglomerates on transmission electron microscopy images via artificial neural networks

There is a high demand for fully automated methods for the analysis of primary particle size distributions of agglomerates on transmission electron microscopy images. Therefore, a novel method, based on the utilization of artificial neural networks, was proposed, implemented and validated.The training of the artificial neural networks requires large quantities (up to several hundreds of thousands) of transmission electron microscopy images of agglomerates consisting of primary particles with known sizes. Since the manual evaluation of such large amounts of transmission electron microscopy images is not feasible, a synthesis of lifelike transmission electron microscopy images as training data was implemented.The proposed method can compete with state-of-the-art automated imaging particle size methods like the Hough transformation, ultimate erosion and watershed transformation and is in some cases even able to outperform these methods. It is however still outperformed by the manual analysis.

Mathematical modeling of pigment dispersion taking into account the full agglomerate particle size distribution

The purpose of this work is to develop a mathematical model that can quantify the dispersion of pigments, with a focus on the mechanical breakage of pigment agglomerates. The underlying physical mechanism was assumed to be surface erosion of spherical pigment agglomerates. The full agglomerate particle size distribution was simulated. Data from two previous experimental investigations were used for model validation. The first concerns two different yellow organic pigments dispersed in nitrocellulose/ethanol vehicles in a ball mill and the second a red organic pigment dispersed in a solvent-based acrylic vehicle in a three-roll mill. When the linear rate of agglomerate surface erosion was taken to be proportional to the external agglomerate surface area, simulations of the volume-moment mean diameter over time were in good quantitative agreement with experimental data for all three pigments. The only adjustable parameter used was an apparent rate constant for the linear agglomerate erosion rate. Model simulations, at selected values of time, for the full agglomerate particle size distribution were in good qualitative agreement with the measured values. A quantitative match of the experimental particle size distributions could be obtained using time-dependent fragment distributions, but this resulted in a very slight improvement in the simulated transient mean diameter only. The model provides a mechanistic understanding of the agglomerate breakage process that can be used, e.g., in the development of novel dispersion principles and for analysis of dispersion failures. The general applicability of the model, beyond the three pigments considered, needs to be confirmed.

Agglomeration of Needle-like Crystals in Suspension: I. Measurements

A technique for the detection and measurement of the agglomeration of needle-like particles is presented. A novel image analysis routine, based on a supervised machine learning strategy, is used to identify agglomerates that are subsequently characterized by their volume. Through repeated measurement of a large number of agglomerates, a 1D particle size distribution of agglomerates is reconstructed. Concurrently, established tools are used to characterize needle-like primary crystals, whose shape is described by cylinders and whose population can be described by a separate two-dimensional particle size and shape distribution. The performance of the classifier is evaluated, and the reproducibility of the measurement is demonstrated for the case of β l-glutamic acid. For the same system, the agglomeration behavior is studied for varying operating conditions, and general trends are analyzed.

Effect of Polydispersity Index on the Grinding Limits of Highly Concentrated Limestone Suspensions

AbstractThe impact of polydispersity index (PDI) values and doses of two sodium polyacrylates on grinding limits and particle size distributions of highly concentrated limestone suspensions was studied. The results indicated that viscosity and agglomerate particle size, and thus the apparent grinding limit, depended on the sodium polyacrylate dose as well as PDI value of sodium polyacrylate. The higher the sodium polyacrylate dose, the lower the viscosity and the smaller the apparent grinding limit were. The smallest primary particle size, the smallest apparent grinding limit, the narrowest agglomerate particle size distribution, and the lowest viscosity curve were obtained with sodium polyacrylate having a low PDI.

Effect of Nafion® ionomer aggregation on the structure of the cathode catalyst layer of a DMFC

The effect of Nafion® ionomer aggregation in solution on the structure of the cathode catalyst layer of a direct methanol fuel cell (DMFC) was investigated by dynamic light scattering (DLS), laser particle sizer, electron probe microanalysis (EPMA) and scanning electron microscopy (SEM). The results showed that large aggregation particles were suppressed by the addition of NaOH to aqueous solutions of Nafion®, which led to a smaller agglomerate particle size distribution in the catalyst ink. The cathode catalyst layer made from the catalyst ink with NaOH addition showed a more uniform distribution of sulfur and Pt elements, a higher electrochemical active surface area (48% increase) and achieved a better performance in the DMFC than one made from the catalyst ink without NaOH addition.

粉砕を伴う回転円錐型容器による複合微細造粒粒子の連続生成 電子線マイクロアナライザーによる複合形態の観察

Small binary composite granules of SiC- and CaCO3-powders were prepared via simultaneous operation of granulation, grinding and separation in a continuous rotating conical vessel.The structure (morphology) of composite granules obtained under various granulating conditions was studied by measuring distributions of SiC- and CaCO3- powder in the cross section of a granule with an electron probe microanalyzer (EPMA). The morphology measured by EPMA was compared with the structure models of composite granules estimated from the particle size distributions of SiC- powder agglomerates in a granule by an image analyzer.As a result, it was shown that the morphology of composite granules measured by EPMA qualitatively agreed with the structure models estimated in our previous paper, and that it was more effective to statistically evaluate the morphology of many composite granules from the particle size distributions of agglomerates contained in the granules using the image analyzer. Furthermore, the effects of granulating conditions on the morphology of composite granules were discussed.

湿式球形造粒時の撹はん動力

The power requirement characteristics of an agitating impeller in a spherical agglomeration tank were investigated. Two spherical agglomeration systems were adopted in the experiment: coal-heavy oil-water; and CaCO3-CaCl2aq. soln. -CCl4. The uniform suspension in the tank was maintained through the agglomeration process.During the progress of spherical agglomeration, the particle size distribution of agglomerates shifted to the large size range, and the compaction of the agglomerates was promoted. The power requirement increased with increasing mean agglomerate size, with the bulk volume of agglomerates in the slurry, and with the density of the agglomerate.The empirical equation, which shows the relationship between the ratio of the power number in the spherical agglomeration to that in the agitation of the disperse medium without agglomerates and the suspending conditions of the agglomerates, was obtained.

Crystallization and agglomeration kinetics in the batch precipitation of strontium molybdate

Kinetic processes were studied during the batch precipitation of SrMoO/sub 4/ (mixing equimolar solutions of SrCl/sub 2/ and Na/sub 2/MoO/sub 4/ at 25/sup 0/C) over a range of supersaturations and under different stirring modes. Primary heterogenous nucleation was predominant, with homogeneous nucleation becoming significant at S > 27, following which diffusion-controlled growth became dominant. Secondary nucleation was not detected under the conditions studied. Soon after the induction period, the small individual crystals agglomerated orthokinetically and the agglomerate size depended on both the intensity of stirring and the initial supersaturation. Toward the end of the precipitation, the agglomerate particle size distribution stabilized and was no longer affected by prolonged agitation.

Effect of ZrO2 inclusions on fracture properties of MgCr204

The effects of unstabilized ZrO2 inclusions on the strength, fracture surface energy and thermal-shock resistance of MgCr2O4 have been evaluated. The fracture surface energy for MgCr2O4-ZrO2 composites was observed to depend on the agglomerate particle size distribution, and volume fraction of the ZrO2 inclusions. Large, nonuniformly distributed ZrO2 inclusions tended to produce a relatively small increase in the fracture surface energy of MgCr2O4. The fracture surface energy increased with increasing ZrO2 content to a maximum value of 24.5J m−2 at 16.5 vol % ZrO2, and decreased as the ZrO2 content increased further. It is proposed that this four-fold increase in fracture surface energy results from the absorption of energy due to microcrack formation in the MgCr2O4 matrix, which results primarily from the tensile stresses due to the tetragonal → monoclinic phase transformation of ZrO2 and the associated volume expansion. The improvement in mechanical properties, specifically the four-fold increase in fracture surface energy, resulted in a substantial increase in thermal-shock resistance of MgCr2O4-ZrO2 composites as indicated by the results of thermal-shock experiments.