Measurement of particle size and shape by FBRM and in situ microscopy

In this work a model is defined allowing for a rapid calculation of chord length distributions as well as the prediction of in situ microscopy data. Both calculations are done using the same underlying algorithm. The model assumes convex polyhedral particles that are defined by their vertices only, connected by straight lines, but imposes no further restrictions on particle geometry. Due to its speed, the model can easily be used for the prediction of experimental data from in situ monitoring tools based on whole particle populations, also with non-constant shape. The model has been verified using in situ microscopy to characterize a population of disc shaped particles.The applications of the model are focused on crystallization processes, but are not limited to these. Several relations between data measured by in situ instruments and the underlying multidimensional particle size distribution have been derived. The model is used extensively in a method that is presented allowing for the calculation of bidimensional growth rates from Focused Beam Reflectance Measurement or in situ microscopy measurements.     

Particle shape and orientation in laser diffraction and static image analysis size distribution analysis of micrometer sized rectangular particles

Laser diffraction (LD) and static image analysis (SIA) of rectangular particles [United States Pharmacopeia, USP30-NF25, General Chapter <776>, Optical Miroscopy.] have been systematically studied. To rule out sample dispersion and particle orientation as the root cause of differences in size distribution profiles, we immobilize powder samples on a glass plate by means of a dry disperser. For a defined region of the glass plate, we measure the diffraction pattern as induced by the dispersed particles, and the 2D dimensions of the individual particles using LD and optical microscopy, respectively. We demonstrate a correlation between LD and SIA, with the scattering intensity of the individual particles as the dominant factor. In theory, the scattering intensity is related to the square of the projected area of both spherical and rectangular particles. In traditional LD the size distribution profile is dominated by the maximum projected area of the particles (A). The diffraction diameters of a rectangular particle with length L and breadth B as measured by the LD instrument approximately correspond to spheres of diameter Ø_L and Ø_B respectively. Differences in the scattering intensity between spherical and rectangular particles suggest that the contribution made to the overall LD volume probability distribution by each rectangular particle is proportional to A²/L and A²/B. Accordingly, for rectangular particles the scattering intensity weighted diffraction diameter (SIWDD) explains an overestimation of their shortest dimension and an underestimation of their longest dimension. This study analyzes various samples of particles whose length ranges from approximately 10 to 1000 μm. The correlation we demonstrate between LD and SIA can be used to improve validation of LD methods based on SIA data for a variety of pharmaceutical powders all with a different rectangular particle size and shape.     

Monitoring the particle size and shape in the crystallization of paracetamol from water

In this work, a technique capable of restoring bidimensional particle size distributions from images of the particles in suspension is applied to the seeded cooling crystallization of paracetamol from water. The effects of cooling rate and stirring rate on the final particle size and shape are studied and the average growth rates along different directions of particles are found to be strongly dependend on supersaturation. This observation is in line with previous studies, though in this work it has been established for the first time using populations of particles. The technique was capable of quantifying changes in particle size and shape, indicating particle sizes and shapes that correlated well with observations from electron microscopy images.     

Measurement of coal particle size and shape with concentrated coal-water mixtures

The behavior of concentrated coal-water mixtures having narrow particle size ssfractions of coal was investigated. The pulverized coal was fractionated into six distinct particle size ranges, i.e. -70+80, -80+120, -120+140,-140+200, -200+400 and -400 mesh sizes by using a series of sieves. Settling rates were determined as functions of solids concentration for suspensions in water of coal particles to establish the measurement of particle size and shape factor and to assess concentration effect upon the observed hindered settling rates. The settling rates were modelled using the Richardson-Zaki model with the exponent n variable to account for the nonspherical shape of the coal particles. The data was also correlated with the Michaels-Bolger model which explicitly account for the excess water which is dragged down along with the particles undergoing sedimentation. In addition, coal particles and suspensions were characterized by coal analysis, heating value, solid heat capacity and thermal conductivity, densities, maximum packing concentrations and pore size distributions.     

Growth of arrays of oriented epitaxial platinum nanoparticles with controlled size and shape by natural colloidal lithography

We developed a method for production of arrays of platinum nanocrystals of controlled size and shape using templates from ordered silica bead monolayers. Silica beads with nominal sizes of 150 and 450 nm were self-assembled into monolayers over strontium titanate single crystal substrates. The monolayers were used as shadow masks for platinum metal deposition on the substrate using the three-step evaporation technique. Produced arrays of epitaxial platinum islands were transformed into nanocrystals by annealing in a quartz tube in nitrogen flow. The shape of particles is determined by the substrate crystallography, while the size of the particles and their spacing are controlled by the size of the silica beads in the monolayer mask. As a proof of concept, arrays of platinum nanocrystals of cubooctahedral shape were prepared on (100) strontium titanate substrates. The nanocrystal arrays were characterized by atomic force microscopy, scanning electron microscopy, and synchrotron X-ray diffraction techniques.     

Induced pulsing in trickle beds — Particle shape and size effects on pulse characteristics

Periodic liquid feeding of the ON-OFF type is investigated — at sufficiently high frequencies to be classified as “fast” mode of induced pulsing — in the range of mean gas and liquid flow rates corresponding to the steady “trickling flow” regime. Two of the most common types of catalyst-support particles, i.e. porous spherical and cylindrical extrudates, are employed to study the imposed pulse characteristics. Detailed information is obtained, on the axial propagation and attenuation of pulses, from instantaneous, cross-sectionally averaged holdup measurements. Key fluid-mechanical parameters studied include, aside from dynamic holdup and pressure drop, pulse celerity and intensity, as a function of fluid feed rates (G,L) and liquid cyclic frequency. Similar published data, for 6 mm glass spheres, are employed for comparison; it is shown that, for the particles examined, particle size has a pronounced effect, but not as significant as that of particle shape. For particles of comparable size, the cylindrical shape is associated with much greater global dynamic holdup and pressure drop, and with increased pulse attenuation. Moreover, packed extrudates exhibit a significant increase of holdup in the axial direction, recently also observed in steady trickling flow. For spherical particles, both time-average holdup and pulse celerity are practically constant along the bed for fixed L,G. Pressure drop, global holdup and pulse celerity are not affected by cyclic liquid feeding frequency, for both spherical and cylindrical extrudate particles. Based on the pulse attenuation characteristics, for the three particle types examined, recommendations are made on preferred conditions for induced pulsing (from the fluid dynamics point of view) which would maximize benefits. Overall, it appears that spherical packings hold significant advantages over cylindrical extrudates of comparable size. Finally, in view of the observed significant decay of imposed pulses along the bed, care should be exercised to properly interpret data obtained in short laboratory reactors (where pulse attenuation is limited) for scale-up of the much longer industrial beds.     

A study of particle shape and size effects on hydrodynamic parameters of trickle beds

Uniform-spherical and cylindrical-extrudate particles are employed to study air-water downflow in a packed bed of 14 cm i.d. The effect of particle shape, neglected in the literature so far, is shown to be very significant. A packed bed of extrudates displays significantly greater global dynamic liquid holdup h_d and pressure drop, as well as a trickling-to-pulsing transition boundary at higher gas flow rates, compared to beds of spheres of comparable size. Moreover, packed extrudates exhibit a significant increase of holdup, h_d, in the axial flow direction, a trend reported for the first time as there are no similar data available in the literature; on the contrary beds of spherical particles are characterized by practically constant h_d in the axial direction. Although an explanation for this h_d axial variation is not obvious, one might attribute it to the anisotropy and non-uniformity of interstitial voids of packed cylindrical particles. For beds of uniform spheres, in the diameter range examined (3-6 mm), the effect of size on both dynamic holdup and pressure drop, although quite pronounced, is not as significant as the effect of particle shape. An extensive survey of literature data, obtained with similar spherical particles, suggests that small bed diameters have an appreciable influence on trickling-to-pulsing transition boundary. Comparisons are reported with literature methods for predicting the measured parameters; discrepancies between data and predictions may be partly due to the inadequacy of a single “equivalent” diameter to represent both shape and size of non-spherical particles; predictive methods performing best are also identified.     

微细物料颗粒大小的测定(续)

4.2 显微镜法 显微镜法包括使用光学显微镜和电子显微镜,是唯一可以观察和测量颗粒的方法。几种显微镜在测定颗粒大小时的性能如表3。     

An improved estimation of size distribution from particle profile measurements

Several methods are available to measure particle size. The majority of them, such as sieving, are off-stream techniques where samples must first be separated from the main stream for analysis.Therefore, the search for on-line particle size analysis systems has provided the impetus for the introduction of image-based particle size analysers to the mineral industry in the past three decades. Generally, the estimation of particle size distribution on the basis of image analysis depends on measuring a single parameter of particle profile. For example the equivalent area diameter (d_A) or mean Feret's diameter (d_F) distributions, then transforming this data to the equivalent size distribution. However, due to the irregularity of particles being analysed, it is believed that this kind of analysis may increase the error in estimation of particle size distribution since profiles of irregular particles carry more information than can be represented by a single parameter.In this paper, a proposed technique which measures two parameters, equivalent area diameter (d_A) and mean Feret's diameter (d_F), for each particle profile has been developed. The accuracy of the technique has then been investigated in the laboratory by successfully estimating (unfolding) the size distribution, where size refers to sieve size, of three samples of different particle shapes with known size distribution.     

Measurement of number and size distribution of particles emitted from a mid-sized transportation multipoint port fuel injection gasoline engine

This study was carried out to characterize the engine-exhaust particulate emissions from a typical multipoint port fuel injection gasoline engine used in transportation sector. Though gasoline engine showed no visible tail pipe emissions yet its particle concentrations were comparable to mineral diesel, particularly at high engine loads. Average sizes of particles emitted in gasoline exhaust are found to be way smaller than particles emitted in diesel exhaust under similar operating conditions. The peak particle concentrations for mineral diesel never go below 40 nm size however for gasoline engine, it was as low as 20 nm for most engine operating conditions. Within a very limited operating range, gasoline engine performance was superior to its diesel counterparts in terms of particulate size and number distribution however it deteriorates very quickly as soon as the fuel-air mixture becomes closer to stoichiometric ratio, typically under high engine load and speed conditions.     

A particle analyser for measuring particle size distribution and shape,on-line or in the laboratory

Norsk Hydro has developed a Particle Analyser for on-line or laboratory use, which measures particle size, size distribution and the deviation from sphericity (called nonspherical).The principle for this system is that the particles fall in a monolayer curtain in front of a high resolution CCD camera. The computer unit in the analyser measures and calculates the particle size and a sphericity factor for each particle. The data are presented as four real time trend curves, shown simultaneously for the on-line version. These curves show % oversize and fines, d₅₀ and the percentage nonspherical particles. For the laboratory version the data are presented in table and cumulative form.The on-line particle analyser has been installed in two of Norsk Hydro's prilling plants in Norway. The analyser has in both plants improved the product quality during the two years of installation.     

Fabrication and characterization of platinum nanoparticle arrays of controlled size, shape and orientation

We present a rigorous approach for the shape design of supported metal nanoparticle catalysts, morphologically identical to each other and epitaxially grown on strontium titanate substrates using electron beam lithography. We predict the particle shapes using Wulff construction based on density functional theory calculations of surface energies. Then, according to the theoretical predictions, we are able to tweak morphologies of the already produced nanocrystals by changing annealing conditions. The ability to design, produce and characterize the catalyst nanoparticles allows us to relate microscopic morphologies with macroscopic oxygen-reduction activities in perchloric acid [Komanicky et al., J. Am. Chem. Soc. 131 (2009) 5732]. The unexpectedly high oxygen-reduction activities proportional to inactive (1 0 0) facets led us to suggest a model where the reaction intermediates can cross over to neighboring facets in nanoscale proximity.     

Image analysis method for determining 3-D shape of coarse aggregate

A 3-D method for particle shape determination of coarse aggregates using image analysis, IA, is presented. It is based on the measures the axial length of all three axis of every particle in a coarse aggregate sample. Two images of the entire aggregate sample are taken, in lying and standing positions. Since the particle's intermediate axes are measured in both images they can be used to couple the shortest and longest axial dimensions for each particle. The method allows an interpretation of length/thickness, length/width and width/thickness ratios of all the particles and is thus comparable to the flakiness and shape index tests.     

Heat conduction in metal-filled polymers: The role of particle size,shape, and orientation

Elongated metal or other conductive particles can be added to a polymer or other poor conductor to produce a composite of enhanced conductivity. Elongated particles are generally more effective than spherical or irregular particles but very slender particles can be dramatically more effective. For example, cylindrical copper particles with length/diameter (L/D) = 20, randomly dispersed in epoxy resin at a loading of 5 percent copper by volume yield a composite with a thermal conductivity about 1.5 times that of the base resin. However, the same volume of copper particles with L/D = 50 can increase the conductivity by a factor of 5 or more. This paper presents a new type of analysis for predicting the thermal conductivity of disperse composites from the properties of the component phases and elementary characterizations of particle shapes and orientation. This analysis successfully predicted the sensitivity to particle shape which was confirmed by experiments also reported in this paper. These results suggest that highly elongated particles may be used to achieve dramatic modifications of thermal conductivity and the analysis presented here may be a useful tool in the design or development of disperse composites of specific thermal conductivity. The analysis may also apply to other properties such as electrical conductivity or magnetic permeability.     

干磨与湿磨对粒配及粒形的影响

本文着重从流变学角度探讨干法及湿法球磨对粒子形貌和粒子级配的影响,并得出湿磨效率优于干磨,干磨粒形更为圆整的结论。     

Surface coating properties of different shape and size pigment blends

The effect of different shape and size of pigments in blends on latex coating surface properties was investigated. Two pigment blends were compared. Both blends were made of plate-like kaolin pigment but with different size prismatic precipitated calcium carbonate at different volume ratios. All coatings were applied on absorbent as well as non-absorbent substrates. Surface coating properties investigated include surface morphology, surface chemistry and surface energy. Surface morphology was characterized by measuring gloss and roughness, surface chemistry was characterized by X-ray Photoelectron Spectroscopy and surface energy was estimated by Kaelable approach.     

The importance of surface hydration and particle shape on the rheological property of silica-based suspensions

Two types of ball milling methods, wet planetary ball milling and dry tumbling ball milling, were used to grind fused silica powders for the preparation of silica-based suspensions in this experiment. The effect of surface hydration and particle shape caused by the two milling methods on the slurry rheology was investigated. The results showed that, with similar particle size distribution, the viscosity of the suspensions prepared from the powders milled by wet ball milling ranged from 275 mPa s to 311 mPa s within 20 min and the suspension exhibited a continuous shear thickening behaviour whereas the viscosity of the suspensions prepared from the powders milled by dry ball milling ranged from 69 mPa s to 74 mPa s and the suspension exhibited a shear thinning behaviour first, and then exhibited a slightly shear thickening behaviour. The reasons were attributed to the differences in surface hydration and particle shape. It was postulated that the two factors affected the slurry rheology through the modification of particle interactions during the flow of high concentration suspensions.     

Quantitative calculation of the orientation angles of adsorbed polyamides nanofilms

Polyamides (PA) PA66, 610 and 612 were adsorbed as thin films on functionalized substrates. The conformational changes after adsorption are studied. New conformations due to the rotation of diamine/diacid planes were evidenced by infrared reflection absorption spectroscopy (IRRAS) and polarization modulation IRRAS (PM-IRRAS). The study of some infrared vibrators, which have a well defined transition moment direction with respect to the principal chain axis, allows us to access a qualitative information on the molecular orientation of PA chains. In this paper, we will discuss the possibility to obtain quantitative data on polyamide conformations on the basis of PM-IRRAS experiments. Values of orientation angles of diamine/diacid planes versus surface plane were determined. Similar angles are found in the four cases of gold, OH, NH₂ and COOH functionalized substrates, and for the three PA. Twist angle of about 20° is found between diamine and diacid planes. The chain orientation angles and conformations obtained do not depend on the substrate functionality and thus suggest that they are only the consequence of an adsorption effect.     

Measurement of size and shape distributions of particles through image analysis

The size and shape of particles can be described using a 2D particle size distribution (PSD) where two characteristic lengths define each particle in the population. The determination of 2D PSDs based on microscopic pictures of particles in suspension is studied. The experimental data are represented as an axis length distribution (ALD) that can be extracted from a series of microscopic pictures by a fully automated image analysis. The problem of finding the underlying bi-dimensional PSD is stated as an optimization problem. For the solution a genetic algorithm is used. The approach is tested on simulated ALDs, as well as on an experimentally measured ALD obtained from carbon fiber particles.