Calculated Particle Size Distribution Research Articles

3D printed cell for the in situ dynamic light scattering monitoring of nanoparticle size distribution in microfluidics

Microfluidic systems offer a reproducible approach for material synthesis at microliter quantities. Automatization of such systems requires development of new approaches for insitu diagnostics, which can provide feedback for the optimization algorithms. The knowledge about size distribution at different reaction stages is of key importance for the nanoparticle synthesis, but most laboratory devices are designed to work with batch systems. In this work we have designed 3d printed devices for dynamic light scattering (DLS) characterization. The combination of backscatter DLS module and microfluidic chips enables insitu monitoring of ultra-low (down to nanoliters) volumes of sample solution even at high concentration. We report several types of microfluidic chips compatible with the commercially available systems with analyzer fiber probe for the measurements in flow and static regimes. The latter option does not contribute with the flow speed to the Brownian motion of nanoparticles and thus does not affect the calculated particle size distribution. 3d-printed cell for DLS measurements on the one hand, probes small sample volume, on the other, enables cheap insitu hydrodynamic size determination. The application of developed instruments is demonstrated for Tb-doped GdF3 nanoparticles, tween micelles, and gold nanoparticles.

Effect of the Gas Temperature on Agglomeration of Au Nanoparticles Synthesized by Spark Discharge and Their Application in Surface-Enhanced Raman Spectroscopy

In this work, we have, for the first time, experimentally verified the hypothesis of reducing the agglomeration rate of aerosol nanoparticles produced by spark discharge upon decreasing the carrier gas temperature in the range of 24 °C to –183 °C. The synthesis of nanoparticles was implemented as a result of spark ablation of electrodes manufactured from Au with a purity of 99.998% installed in a specially designed gas chamber dipped into liquid nitrogen (−196 °C) to cool down the carrier gas supplied through one of hollow electrodes. It follows from the analysis of transmission electron microscopy images that both the average size of primary nanoparticles and the degree of their sintering become lower if the gas is cooled. For example, in the case of using nitrogen as a carrier gas, the average size of primary nanoparticles decreases from 9.4 nm to 6.6 nm as the gas temperature decreases from 24 °C to –183 °C. This also causes the aggregates to become more branched, manifested by the reduction in their solidity from 92% to 76%. The agglomeration model of Feng based on Smoluchowski theory was employed to calculate particle size distributions that were found to be consistent with the experimental data. The gold nanoparticles synthesized at room and cryogenic temperatures of the carrier gas (N₂, Ar + H₂, He) were used to pattern plasmonic nanostructures on ceramic alumina substrates by using aerosol jet printing technology for the purpose of demonstrating the possibility of their application in surface-enhanced Raman spectroscopy (SERS). The SERS enhancement factor was estimated at 2 × 106 from the analysis of SERS and normal Raman spectra of 1,2-bis(4-pyridyl)ethylene used as an analyte.

A prediction of blend grinding result based on individual ore size measurements and grinding tests

Dry ball mills of Tata Steel IJmuiden’s pelletizing plant grind a blend of iron ores, coke breeze and mineral additives. Blend composition can be adjusted depending on raw material supply and product demand. A grinding prediction method on blends has been developed in order to aid improvement of blend selection. A batch testing procedure on individual ores was applied. Parameters describing grinding kinetics were determined by using simulation and fitting to the results of the tests. The grinding of certain ore mixtures was simulated using the obtained parameters of the individual ores. The calculated particle size distributions were compared to laboratory grinding results of the mixtures. Grinding parameters of each ore were subsequently summarised in a single parameter, being the time required in a laboratory mill to achieve a specified target average particle diameter. The incorporation of the grinding time into linear models improved the prediction of product quality from the industrial grinding system. Results and mean average error of this prediction were determined by means of cross validation.

Combined releases of oil and gas under pressure; the influence of live oil and natural gas on initial oil droplet formation

Both oil droplets and gas bubbles have simultaneously been quantified in laboratory experiments that simulate deep-water subsea releases of both live oil (saturated with gas) and additional natural gas under high pressure. These data have been used to calculate particle size distributions (50–5000 μm) for both oil and gas. The experiments showed no significant difference in oil droplet sizes versus pressure (from 5 m to 1750 m) for experiments with live oil. For combined releases of live oil and natural gas, oil droplet sizes showed a clear reduction as a function of increased gas void fraction (increased release velocity) and a weak reduction with increased depth (increased gas density/momentum). Oil droplets were reduced by a factor of 3 to 4 during simulated subsea dispersant injection (SSDI) and no significant effect of pressure was observed. This indicates that SSDI effectiveness is not dependent on water depth or pressure.

Effect of oxygen concentration and reaction order on char inventory in fluidized bed combustion

Population balance modeling is applied to develop calculation methods for mass inventory of char in fluidized bed combustion (FBC). The focus is on the effect of gas oxygen concentration and the reaction order of char with respect to oxygen, which is important in understanding and simulating combustion in high oxygen concentration. The well-known shrinking particle model describing the single particle combustion is simplified by applying a dimensionless particle size and dimensionless time with a specifically chosen characteristic reference diameter and time constant. Methods and analytical solutions to calculate particle size distribution (PSD), particle combustion time and char mass in FBC are presented.

Characterization of Diamond Nanoparticles by High-Speed Micro-Thermal Field-Flow Fractionation

Micro-thermal field-flow fractionation was used to characterize the particle size distribution of nanometer-sized diamond nanoparticles. Although the experimental conditions were chosen to perform high-speed separation, and, consequently, the resolution achieved experimentally was not very high, the application of the original correction method for the zone spreading allowed for obtaining of very good calculated particle size distribution or, explicitly, a true polydispersity index of the diamond nanoparticle sample. The future use of several samples of diamond nanoparticles of different average sizes and different surface chemistries should allow deeper insight into the effect of these particulate characteristics on the retention in micro-thermal field-flow fractionation.

CFD Model of Particle Agglomeration in Spray Drying

A 3D CFD model of the agglomeration of droplets and particles in a counter-current spray-drying process was developed and verified. An original discrete phase model was elaborated, with an agglomeration module taking into account hydrodynamic segregation of particles, droplet coalescence, and droplet shrinkage for accurate calculations of mass balance of the discrete phase. The characteristic drying curves were applied to the model of particle moisture evaporation, which included the coupling of particle agglomeration with heat, mass, and momentum transfer between the discrete and continuous phases. Two agglomeration zones were observed in the tower: wet particle agglomeration in the atomization zone, and “dry agglomeration” above the air inlets, due to the intensive mixing of particle streams. A comparison of the calculated particle size distributions and experimental data obtained from particle dynamics analysis (PDA) measurements proves the accuracy of the developed methodology. The elaborated model allows the final PSD of the powder in the spray towers to be predicted.

Invited Presentation: Quantifying and Controlling Microstructure in Lithium Ion Battery Porous Electrodes

It is becoming increasing clear that the microstructure of lithium ion battery (LIB) electrodes strongly influences key performance metrics, such as charge and discharge rate, cell life, and safety, and that future, high performance LIBs will require not only improved active materials but also optimized microstructures.To study microstructure on statistically significant porous electrode volumes, we image porous electrodes using synchrotron radiation x-ray tomographic microscopy (SRXTM). We implement a segmentation algorithm that allows identification of individual particles and validate it by showing that the calculated particle size distribution (PSD) is in agreement with experimentally determined PSD obtained with laser diffraction.[1]We then systematically quantify and determine the origin of tortuosity anisotropy in porous electrodes.[2] LIB electrode manufacturing orients non-spherical particles in the plane parallel to the current collector. This increases tortuosity in the direction perpendicular to the current collector, which can limit battery performance (Figure 1a).We demonstrate that based on a simple assessment of the particle shape, obtained for example from scanning electron microscope (SEM) images of the active particles, and estimation of particle alignment, it is possible to use the Differential Effective Medium (DEM) approximation to predict the in-plane (i.e., parallel to the current collector) and through–plane (i.e., perpendicular to the current collector) tortuosities that result from standard porous electrode preparation. We conclude that while anisotropic tortuosity could be mitigated by the use of spherical particles, when non-spherical particles are aligned in the direction perpendicular to the current collectors, low tortuosities can be achieved in this direction.Based on these findings, we present a technique to enable alignment of anisotropic particles within an electrode with a low cost technique that is compatible with current LIB manufacturing. To prove the feasibility of the alignment process, we fabricate vertically-aligned graphite electrodes and use x-ray tomography to quantify the degree of alignment (Figure 1b and c). We further show improved rate capability in thick electrodes using the alignment procedure in agreement with expectations based on simulation. We discuss the engineering challenges associated with this technique as well as its potential.[1] M. Ebner, F. Geldmacher, F. Marone, M. Stampanoni, and V. Wood. “X-ray Tomography of Porous, Transition Metal Oxide Based Lithium Ion Battery Electrodes” Advanced Energy Materials 3 (2013).[2] M. Ebner, D.-W. Chung, R. E. García, and V. Wood. “Tortuosity Anisotropy in Lithium-Ion Battery Electrodes”Advanced Energy Materials(2013). DOI: 10.1002/aenm.201301278 Figure 1: a) In-plane and through-plane tortuosities of spherical Li(Ni1/3Mn1/3Co1/3)O2 (NMC) and platelet-shaped graphite-based electrodes with varying porosities. b, c) in-plane (top) and through-plane(bottom) tomography cross-sections showing graphite porous electrodes with high- and low-tortuosity in the direction perpendicular to the current collector. The microstructure b) is obtained with the lithium ion battery manufacturing techniques today, while the microstructure c) is desirable for high performance lithium ion batteries.

Liquefaction of wood in hot compressed water Part 2 – Modeling of particle dissolution

The dissolution of wood in subcritical water is analyzed in order to provide insight into the effects of the operating parameters on the product distribution. A comprehensive mathematical model for the decomposition of wood by both the hydrolysis and pyrolysis reaction pathways was developed based on a theoretical understanding of the physical and chemical processes wood undergoes under these conditions and on the results of a series of batch experiments. Due to limitations in the experimental setup, kinetic information needed to be adapted from the literature in order to match the experimental data. By analysis of the experimental products, elemental balances for carbon, hydrogen and oxygen were also implemented in the model. Thus, the model is able to predict the final product distribution and the solid residue composition at different operating conditions. The lack of kinetic data for the fast initial reactions limits the applicability of the model. The model is also able to calculate particle size distributions. Comparison with measured distributions suggests that the wood particles do not shrink uniformly but split off smaller fragments.

Scalable synthesis of delafossite CuAlO2 nanoparticles for p-type dye-sensitized solar cells applications

Delafossite CuAlO2 nanoparticles were prepared using an easily scalable method under controlled partial oxygen pressure (pO2) of 10−5atm at 775°C. Transmission electron microscopy showed a uniform particle size of 35nm, agreeing well with the calculated particle size distribution obtained using the Whole Powder Pattern Method (WPPM) via the PM2K software package. Higher cathodic photocurrents (Jsc=0.954mA/cm2 under AM1.5 sun) were observed in p-type dye sensitized solar cells (DSSCs) fabricated using these CuAlO2 nanoparticles compared to the previous reports on delafossite CuBO2 (B=Al, Ga) nanoparticles. Enhanced current efficiency in these solar cells is attributed to the nano-sized particles and narrow particle size distributions of nanocrystalline delafossite CuAlO2.

Electrodeposition of Zn–Ni Multiwalled Carbon Nanotube Nanocomposites and Their Properties

The Zn–Ni composite coatings on mild steel substrate were prepared by incorporating multiwalled carbon nanotubes (MWCNT) through electrodeposition. The reinforcement of MWCNTs was increased by achieving high dispersion in the plating electrolyte. Surfactants cetyltriammonium bromide (CTAB), sodium lauryl sulfate (SLS), and Triton X 100 were made use. The individual CNTs are active in the UV–vis region, and UV–vis spectroscopy was utilized to evaluate the extent of dispersion. Dynamic light scattering technique (DLS) was applied to calculate particle size distribution statistics with different surfactants. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive X-ray analysis (EDX) were utilized to study the deposits’ morphology, structure, and composition, respectively. The coated specimens were tested for their corrosion resistance in 3.5% NaCl through polarization and electrochemical impedance spectroscopic (EIS) studies. Surfactants deagglomerated the particles and enhanced t...

X‐Ray Tomography of Porous, Transition Metal Oxide Based Lithium Ion Battery Electrodes

We implement a segmentation algorithm that allows identifi cation of individual particles and validate it by showing that the calculated particle size distribution (PSD) is in agreement with experimentally determined PSD obtained with laser diffraction. We study the microstructure of LiNi 1/3 Mn 1/3 Co 1/3 O 2 (NMC)-based cathodes, prepared with varying weight percent of carbon black and binder (2–5 wt%) and different compressions (0-2000 bar), and their electrochemical performance. Tomographic data (raw and processed with particles identifi ed and labeled) and the corresponding electrochemical data for 16 different cathodes is provided open source. [ 2 ] The microstructure datasets can be used to study electrode properties like porosity, tortuosity, electrode anisotropy, and homogeneity, or as realistic geometries for three dimensional (3D) electrochemical simulations. The electrochemical data is intended to aid in the verifi cation of simulation models. The large number of studied particles (approx. 7000-19000 per electrode) allows us to investigate spatially resolved PSD and shows that the vicinity of electrode boundaries is populated by smaller particles than the bulk electrode. In addition to insight into electrode morphology, we demonstrate that the technique is capable of resolving features on the sub-particle level such as particle fracture, which is observed here under high compression conditions. It is becoming increasingly clear that the development of next generation, higher performance lithium ion batteries (LIB) will require a concerted effort between experimentalists and simulation experts. In addition to the development of predictive tools for the selection of active materials, realization of LIBs with high C-rate capabilities and energy density will require the development of roadmaps for achieving favorable porous electrode microstructures. [ 3 , 4 ] However, due to the lack of publically

Calculation of Particle Size Distributions from Ultrasonic Measurements: A Mineral Slurry Case Study

AbstractUltrasonic transmission measurements have been used extensively to determine the particle size of solids in slurries. This case study examines the application of mathematical inversion techniques to the determination of the particle size distribution of a mineral slurry from data collected at a minerals processing plant. A new mathematical inversion technique, based on an extension of modified Chahine iteration combined with the principle of maximum entropy has been developed. Four algorithms were constructed and used to calculate particle size distributions from synthetic and raw plant data. These incorporated modified Chahine iteration and its extension, together with two different approaches to applying a density measurement constraint on the particle size distribution. In general the algorithms performed well with regression errors below 3 %. The correlation coefficients and slopes for this technique were 0.86 and 1.35 for the weight fraction of particles less than 75 microns when compared with the laser diffraction analysis. A better match was obtained for the plant data by using the new inversion technique, into which the principle of maximum entropy has been incorporated whereas this was not the case with the synthetic data, illustrating the need to match the inversion technique to the problem.

Inverse problem for aerosol particle size distribution using SPSO associated with multi-lognormal distribution model

Abstract A numerical study, used for particle size distributions of several classical aerosol types, is conducted in this paper. By improving the log-normal distribution model in previous paper, we employ the stochastic particle swarm optimization (SPSO) algorithm associated with a multi-lognormal distribution model. The nonambiguity and robustness of SPSO with this model is validated. We recover particle size distributions of two classical aerosol types using the measured AOT data (at wavelengths λ = 0.400, 0.690, 0.870, 1.020 μm) obtained from AERONET at different time. The results show that the model of this paper presents characteristics of aerosol particle size distributions at different regions and time. And this model shows good practicability to distinguish aerosol types and calculate particle size distributions.

Derivation and verification of an aerosol dynamics expression for the below-cloud scavenging process using the moment method

An aerosol dynamics equation for the below-cloud scavenging process considering phoretic and electric charging effects in addition to the conventional mechanisms (the Brownian diffusion, interception, and impaction) is developed by using the moment method. Then, the dynamics of particle size distribution by the below-cloud scavenging process is calculated by using the developed equation and verified with the measurement data. The calculated particle size distribution changes are quite small compared to the measured changes. The calculated removal rate is smaller by 10−2–10−3 than the measured data when only the conventional mechanisms are considered. With the extended mechanisms, the scavenging coefficient increases upto 20 times, mainly for the particle size range of 0.1 μm<dp<3.0 μm. However, the difference between the calculated and measured scavenging coefficient is still large, especially, for dp<0.1 μm. Other possible scavenging mechanisms that might affect the below-cloud scavenging process such as coagulation and condensational growth of hygroscopic particles, turbulence, and updraft into cloud are discussed. It is recommended that further studies on wet scavenging process are needed.

Analysis of Optical Absorbance Spectra for the Determination of ZnO Nanoparticle Size Distribution, Solubility, and Surface Energy

We present a model to calculate particle size distributions (PSDs) of colloidal ZnO nanoparticles from their absorbance spectra. Using literature values for the optical properties of bulk ZnO and correlating the measurement wavelengths in the UV-visible regime with distinct particle sizes by a tight binding model (TBM), an algorithm deconvolutes the absorbance spectra into contributions from size fractions. We find an excellent agreement between size distributions determined from TEM images and the calculated PSDs. For further validation, bimodal PSDs have been investigated and an approach to determine not only particle size but also solid concentration is introduced. We will show the applicability of our model by the determination of temperature-dependent ripening rates, which enables the calculation of solubilities, surface tensions, and the activation enthalpy of ripening. In principle, our methodology is applicable to different semiconductor nanoparticles in various solvents as long as their bulk properties are known and scattering is negligible.

Part V: Dynamic evolution of the multivariate particle size distribution undergoing combined particle growth and aggregation

The present paper presents a study on the application of the Galerkin finite element method (FEM) for the solution of the dynamic multivariate population balance equation (PBE) in batch particulate systems undergoing aggregation as well as combined aggregation and growth. The performance of the Galerkin FEM in terms of accuracy and stability was assessed by a direct comparison of the calculated particle size distributions and/or their corresponding moments to available analytical solutions as well as by comparison to univariate numerical solutions. Numerical simulations were carried out for a variety of particle aggregation and growth mechanisms including constant, Brownian, and modified Brownian aggregation as well as constant and linear growth rate functions and for a wide range of values for the aggregation and growth rate coefficients. The simulation results revealed that the proposed Galerkin FEM produces very accurate numerical solutions but at significant computational cost.

Performance Comparison of Scanning Electrical Mobility Spectrometers

Scanning electrical mobility spectrometers (SEMS) are commonly used for near real-time ultrafine particle size distribution measurements. Analysis of SEMS measurements to calculate particle size distributions requires detailed understanding of instrument characteristics and operation. Varying instrument designs are used in the different commercial SEMS systems, and data analysis with these instruments requires accurate knowledge of their relative performance. In this study, an experimental approach to evaluate and reconcile differences between different SEMS instruments is established. This approach is used to characterize the relative performance of two SEMS systems—TSI's SMPS 3936-L22 and MSP's WPS XP1000—for particle sizes in the range of 20 to 300 nm. In these tests, the instruments were operated under a low flowrate condition with aerosol and sheath air flows of 0.3 and 3 LPM, respectively. Measurements show that the particle sizing characteristics of the instruments are very consistent with each oth...

A discrete-sectional model for particle growth in aerosol reactor: Application to titania particles

A one-dimensional discrete-sectional model has been developed to simulate particle growth in aerosol reactors. Two sets of differential equations for volume and surface area, respectively, were solved simultaneously to determine the size distributions of agglomerates and primary particles. The surface area equations were derived in such a way that the coagulation integrals calculated for the volume equations could be used for the surface area equations as well, which is new in this model. The model was applied to a production of TiO2 particles by oxidation of titanium tetrachloride. Model predictions were compared with experimental data and those of a two-dimensional sectional model. Good agreement was shown in calculated particle size distributions between the present model and the two-dimensional model, which is more rigorous but demands a large amount of computer time and memory. Compared to experimental data, the primary particle size calculated by the model was more sensitive to the variation of reactor temperature.

Polydisperse particle size characterization by ultrasonic attenuation spectroscopy for systems of diverse acoustic contrast in the large particle limit

Ultrasonic attenuation spectroscopy offers advantages over other spectrometric methods for the determination of suspension and emulsion size distributions. One advantage is the possibility of conducting measurements in highly concentrated or optically opaque dispersions. Models useable for the inversion of measured attenuation spectra to calculate particle size distributions are available and widely used, but their applied forms only allow for the characterization of particles smaller than 10μm. In this paper, a methodology using the Faran model for elastic scatterers is examined in the region of micrometer-sized particles with respect to its suitability for the prediction of measured attenuation spectra and size distributions of various material combinations. All selected particle fractions and fluid materials were characterized independently from ultrasonic attenuation spectroscopy with respect to their material properties, size distributions, and shape. A comparison of measured and calculated attenuation spectra shows an acceptable agreement. The chosen methodology for particle sizing applications is further confirmed if a fit of the model to the measurement data is performed. In this approach, the solids volume fraction is treated as the only fit parameter. The findings indicate that the methodology is suitable for polydisperse particle size characterization for a wide range of acoustic contrast.