Search

Chemical mechanical polishing/planarization (CMP) slurry contains mainly abrasive grains (primary particles) with few aggregations (secondary particles). Measuring the particle size distribution (PSD) of CMP slurry is crucial for improving the productivity of the CMP process. For the quality management of CMP slurry, it is necessary to evaluate both the sizes and quantities of both the primary and secondary particles. Conventional PSD analysis methods, except for image analysis, face challenges in identifying primary and secondary particles for PSD measurements. For image analysis, the particles must be transferred from a suspension to a substrate using the conventional sampling method; however, this creates aggregates, resulting in a change in the PSD of the particles on the substrate compared to that in suspension under poly-dispersed conditions. Thus, this study proposed a novel particle sizing method using nanoparticle chip (NPC) to assist in the image analysis of the PSD. The NPC can pick up a single particle in a small volume droplet to avoid aggregation and maintain the poly-dispersed condition of the particles in suspension. The primary and secondary particles can be identified using scanning electron microscope (SEM) or atomic force microscope (AFM), and the PSD can be evaluated by measuring the area and height of the particles. Further, the quantities of both the primary and secondary particles can be counted from the substrate. This study presented a comparison of the diameter measurements using NPC and the conventional method. The results show that the NPC identified the primary and secondary particles and decreased the measurement error of the particle diameters. Consequently, the NPC proves to be superior to the conventional method for use in the PSD analysis of CMP slurry. • Nanoparticle chip (NPC) sizing for CMP slurry particle size distribution (PSD). • NPC avoids particle aggregation, maintains PSD in poly-dispersed suspension. • Primary and secondary particles separated to lower equivalent height diameter error. • PSD of primary particles and number of secondary particles measured using NPC. [ABSTRACT FROM AUTHOR]

This paper presents the feasibility of Fraunhofer diffraction analysis as a measure of the size of fast‐moving inkjet droplets. This measurement method showed that an inkjet droplet measurement tool was possible with a good balance of real‐time measurement and accuracy. [ABSTRACT FROM AUTHOR]

High-solid-content polystyrene and polyvinyl acetate dispersions of polymer particles with a 50 nm to 500 nm mean particle diameter and 12–55% (w/w) solid content have been produced via emulsion polymerization and characterized regarding their optical and physical properties. Both systems have been analyzed with common particle-size-measuring techniques like dynamic light scattering (DLS) and static light scattering (SLS) and compared to inline particle size distribution (PSD) measurements via photon density wave (PDW) spectroscopy in undiluted samples. It is shown that particle size measurements of undiluted polystyrene dispersions are in good agreement between analysis methods. However, for polyvinyl acetate particles, size determination is challenging due to bound water in the produced polymer. For the first time, water-swelling factors were determined via an iterative approach of PDW spectroscopy error (Χ2) minimization. It is shown that water-swollen particles can be analyzed in high-solid-content solutions and their physical properties can be assumed to determine the refractive index, density, and volume fraction in dispersion. It was found that assumed water swelling improved the reduced scattering coefficient fit by PDW spectroscopy by up to ten times and particle size determination was refined and enabled. Particle size analysis of the water-swollen particles agreed well with offline-based state-of-the-art techniques. [ABSTRACT FROM AUTHOR]

The present work envisages the development of a novel and low-cost self-mixing interferometry (SMI) technology-based single particle sensing system in a microchannel chip for real time single micro-scale particle sizing. We proposed a novel theoretical framework to describe the impulse SMI signal expression in the time domain induced by a flowing particle. Using Hilbert transform, the interferometric fringe number of the impulse SMI signal was retrieved precisely for particle size discrimination. For the ease of particle sensing, a hydrodynamic focusing microfluidic channel was employed by varying the flow rate ratio between the sample stream and the sheath liquid, and the particle stream of a controllable width was formed very easily. The experimental results presented good agreement with the theoretical values, providing a 300 nm resolution for the particle sizing measurement. [ABSTRACT FROM AUTHOR]

We present a novel method for characterizing in near real-time the aerodynamic particle size distributions from pharmaceutical inhalers. The proposed method is based on direct imaging of airborne particles followed by a particle-by-particle measurement of settling velocities using image analysis and particle tracking algorithms. Due to the simplicity of the principle of operation, this method has the potential of circumventing potential biases of current real-time particle analyzers (e.g. Time of Flight analysis), while offering a cost effective solution. The simple device can also be constructed in laboratory settings from off-the-shelf materials for research purposes. To demonstrate the feasibility and robustness of the measurement technique, we have conducted benchmark experiments whereby aerodynamic particle size distributions are obtained from several commercially-available dry powder inhalers (DPIs). Our measurements yield size distributions (i.e. MMAD and GSD) that are closely in line with those obtained from Time of Flight analysis and cascade impactors suggesting that our imaging-based method may embody an attractive methodology for rapid inhaler testing and characterization. In a final step, we discuss some of the ongoing limitations of the current prototype and conceivable routes for improving the technique. [ABSTRACT FROM AUTHOR]

Due to the unique advantages of high specific impulse, high thrust, simplicity and reliability, solid propellant with metal powder additives has emerged as a promising energy carrier for rockets in aerospace engineering. In-situ characterization of the metal particle combustion is crucial for the validation of numerical models and optimization of the propellant formulas. Previous studies mainly focused on the measurement of particle size and velocity near the combusting propellant surface with holography. Whereas, the behavior of the particles away from the surface is also essential for the full understanding the combustion and agglomeration mechanisms. Nevertheless, holography suffers from inaccurate depth estimation due to the large depth-of-focus. To overcome this limitation, a hybrid method which combines three-dimensional (3D) fiber optic imaging with two-color pyrometry is developed to realize simultaneous 3D localization, velocimetry, sizing, and thermometry of combusting aluminum particles in a large field of view. The method is validated both with numerical studies and experiments for a field of view of ∼60 × 50 × 50 m m 3. According to the experimental results, the particle size follows a log-normal distribution which agrees with the specification of the propellants. In addition, the evolution of particle temperature and velocity were recorded for a duration of ∼13.9 ms. The results suggest that the temperature of most particles were between 2000 and 3500 K, while particle velocities were between 1 and 10 m/s. The measurement method proposed here is promising for the quantitative analysis of the complicated combustion process of aluminized propellants. [ABSTRACT FROM AUTHOR]

As a global optimization algorithm, genetic algorithm is an advantageous tool due to its global convergence, great robustness, suitable for parallel computing and so on. Selection of optimal parameters, e.g., maximum generations, population size, and genetic operators (crossover fraction and mutation fraction), is extremely crucial for particle size characterization by ultrasound attenuation spectroscopy with genetic algorithm. A series of particle system with different distribution functions were numerically investigated in this work. It revealed that the simulated results were consistent with the given particle size distribution when the maximum generations, population size crossover fraction and mutation fraction were appropriate chosen. Furthermore, the anti-noise performance of genetic algorithm and its three improved forms applied in particle system with bimodal distribution were also studied. Two groups of samples (micron-sized glass beads-glycerol suspension and aqueous polystyrene suspension) were investigated experimentally by ultrasound attenuation spectroscopy, and it showed a good agreement between Improved Genetic Algorithm 3 (IGA3) and Microscope Image Analysis (MIA). [ABSTRACT FROM AUTHOR]

Accurate measurement of the particle size distribution of pneumatically conveyed pulverized fuel is critical to achieving optimal combustion efficiency and minimum pollutant emissions at coal and biomass-fired power plants. This paper presents a prototype instrumentation system for the on-line continuous measurement of particle size distribution through acoustic emission (AE) detection. The proposed method extracts particle size information from the impulsive AE signals arising from impacts of particles with a metallic waveguide protruding into the flow. The relationship between the particle size and the peak AE voltage is established through mathematical modeling of the particle impact process. Identification of the peak AE voltage is achieved with an energy-based peak detection algorithm. Experimental results obtained with glass beads demonstrate the capability of the system to discriminate particles of different sizes from the recorded AE signals. The system performs better in terms of accuracy for higher speed, lower concentration particles as the impact signals are stronger and better separated in the time domain. [ABSTRACT FROM PUBLISHER]

With the introduction of Quality by Design ( Qb D) to the pharmaceutical industry, there has been an increased focus on understanding the nature of particles and composites, with the aim of understanding and modeling how they interact in complex systems, leading to robust dosage forms. Particle characterization tools have evolved and now enable a greater level of understanding of powder systems and blends. Tools that can elucidate the size and shape of particulate systems can provide significantly more information about the nature of the particles being analyzed, than a conventional particle size measurement. Although accurate size and shape analysis has always been regarded as the 'gold standard' in understanding the nature of particulate systems, neither imaging systems nor IT infrastructure was sufficiently developed to allow this to be performed with sufficient accuracy in a timely manner. The aim of this review is to provide an insight into developments in the field of size and shape analysis of pharmaceutical systems, and how these can now realistically be used as robust development tools. Examples of current uses of such technologies will be explored as well as investigating future applications such as combined image/spectroscopic analyses to track single components within blended systems. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 104:1563-1574, 2015 [ABSTRACT FROM AUTHOR]

Particle analysis tools for the subvisible (<100 μm) size range, such as light obscuration, flow imaging ( FI), and electrical sensing zone ( ESZ), often produce results that do not agree with one another, despite their general agreement when characterizing polystyrene latex spheres of different sizes. To include the effect of shape in comparison studies, we have used the methods of photolithography to create rods and disks. Although the rods are highly monodisperse, the instruments produce broadened peaks and report mean size parameters that are different for different instruments. We have fabricated a microfluidic device that simultaneously performs ESZ and FI measurements on each particle to elucidate the causes of discrepancies and broadening. Alignment of the rods with flow causes an oversizing by FI and undersizing by ESZ. FI also oversizes rods because of the incorrect edge definition that results from diffraction and imperfect focus. We present an improved correction algorithm for this effect that reduces discrepancies for rod-shaped particles. Tumbling of particles is observed in the microfluidic ESZ/ FI and results in particle oversizing and breadth of size distribution for the monodisperse rods. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 104:971-987, 2015 [ABSTRACT FROM AUTHOR]

Modified LDV method is proposed for measuring the diameter and absorption coefficient of a single moving particle by applying the Lambert–Beer’s law to dual burst Doppler signal. The diameter and absorption coefficient of a particle are determined simultaneously from the time difference and intensity ratio between burst components of reflected and refracted rays in a dual burst Doppler signal, using only a single photodetector. This method can be applied to a particle larger than the cross-sectional area of an illuminating beam. The optimum conditions of an optical system were estimated theoretically. Experiments were performed with polystyrene particles in water, water droplets, and water-black ink droplets to confirm usefulness of the proposed method. [ABSTRACT FROM AUTHOR]

We tested the hypothesis that foreign particles shed from filters can accelerate the rate of protein aggregation and particle formation during agitation stress. Various types and brands of syringe filters were tested. Particle counts and size distribution (≥1 µm) in buffer alone or in solutions of keratinocyte growth factor 2 (KGF-2) were determined with a micro-flow imaging. Submicron particle populations were characterized by dynamic light scattering. Loss of soluble protein during filtration or postfiltration incubation was determined by ultraviolet spectroscopy and bicinchoninic acid protein assay. There was a wide range (from essentially none to >100,000/mL) in the counts for at least 1 µm particles shed into buffer or KGF-2 solution from the different syringe filters (with or without borosilicate glass microfibers). Filtration of KGF-2 with units containing glass microfibers above the membrane resulted in 20%-80% loss of protein due to adsorption to filter components. Filtration with systems containing a membrane alone resulted in 0%-20% loss of KGF-2. Effects of 24-h postfiltration incubation were tested on KGF-2 solution filtered with polyether sulfone membrane filters. Loss of soluble protein and formation of particles during agitation were much greater than that in control, unfiltered KGF-2 solutions. Similar acceleration of protein aggregation and particle formation was observed when unfiltered KGF-2 solution was mixed with filtered buffer and agitated. Particle shedding from syringe filters-and the resulting acceleration of protein aggregation during agitation-varied greatly among the different syringe filters and individual units of a given filter type. Our results demonstrate that nanoparticles and microparticles shed from the filters can accelerate protein aggregation and particle formation, especially during agitation. © 2012 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 101:2952-2959, 2012 [ABSTRACT FROM AUTHOR]

Abstract: A brief review of the existing particle sizing methods is presented. An optical method under development is introduced from the analysis of the polarization ratio of the light scattered by the particles based on Lorenz–Mie theory. The theoretical background is summarized with the numerical calculation presented. A photogrammteric system has been set up to perform the measurements. Calibration of the experimental setup has been carried out on polystyrene microspheres of different size. The experimental values of the polarization ratio have been obtained by analyzing the particle images taken by the CCD to render the particle size under investigation. Several experiments and their results are demonstrated to illustrate the application fields of the optical method presented in the current study. [Copyright &y& Elsevier]

Abstract: The present work introduces an innovative method for measuring particle size distribution of an airborne powder, based on the application of signal processing techniques to the acoustic emission signals produced by the impacts of the powder with specific metallic surfaces. The basic idea of the proposed methodology lies on the identification of the unknown relation between the acquired acoustic emission signals and the powder particle size distribution, by means of a multi-step procedure. In the first step, wavelet packet decomposition is used to extract useful features from the acoustic emission signals; the dimensionality of feature space is further reduced through multivariate data analysis techniques. As a final step, a neural network is properly trained to map the feature vector into the particle size distribution. The proposed solution has several advantages, such as low cost and low invasiveness which allow the system based on this technique to be easily integrated in pre-existing plants. It has been successfully applied to the PSD measurement of coal powder produced by grinding mills in a coal-fired power station, and the experimental results are reported in the paper. The measurement principle can also be applied to different particle sizing applications, whenever a solid powder is carried in air or in other gases. [Copyright &y& Elsevier]

Abstract: Purpose: The purpose of this study was to understand the behaviour of cohesive powder mixtures of salbutamol sulphate (SS) and micronized lactose (LH300) at ratios of SS:LH300 of 1:1, 1:2, 1:4 and 1:8 under varying air flow conditions. Methods: Aerosolisation of particles less than 5.4μm at air flow rates from 30 to 180lmin−1 was investigated by determining particle size distributions of the aerosolised particles using laser diffraction and fine particle fractions of SS using the twin stage impinger modified for different air flow rates using a Rotahaler®. The de-agglomeration data were best fitted by a 3-parameter sigmoidal equation using non-linear least squares regression and characterised by the estimated parameters. Results: De-agglomeration air flow rate profiles showed that SS:LH300 mixtures with increased lactose content (1:4 and 1:8) improved powder aerosolisation, but lactose had negligible effect on SS aerosolisation at the higher and lower limits of air flow rates studied. De-agglomeration flow rate profiles of SS–LH300 mixtures with increased lactose content (1:4 and 1:8) were greater than theoretically expected based on weighted individual SS and LH300 profiles. This indicated that interactions between the cohesive components led to enhanced de-agglomeration. The composition of the aerosol plume changed with air flow rate. Conclusion: This approach to characterising aerosolisation behaviour has significant applications in understanding powder structures and in formulation design for optimal aerosolisation properties. [ABSTRACT FROM AUTHOR]

We present here a new dynamic light scattering method for investigating the particle size in concentrated suspension. By using the polarization gating and Fourier spatial filter, the optical thickness through the sample is reduced and the multiple scattered light is suppressed. The method is systematically tested using suspensions of latex spheres of 100 nm with a wide range of concentrations. Compared to the current common methods for nanoparticle sizing in concentrated suspension, it has the advantage of simple structure and it is easy to debug and maintain. [ABSTRACT FROM AUTHOR]

Abstract: We analyze the retrieval of the radius and complex refractive index of colloidal particles from the measurement of the effective optical properties of a dilute colloid. We point out some necessary precautions for the measurement of the effective refractive index of colloids and discuss the main sources of uncertainty. [Copyright &y& Elsevier]

Abstract: Ultrasound is an attractive technique for nanoparticle sizing as it offers non-invasive, suitable for highly turbid and concentrated samples, and potentially no sample dilution needed features. This paper presents a factor analysis method for the determination of the concentration range and frequency domain for the use of ultrasound techniques for particle sizing when ECAH (Epstein, Carhart, Allegra and Hawley) model is applied. The advantage of using this method is by dealing with experimental data, some practically useful information, which the current theory cannot be employed to produce, may be identified, for instance, the critical volume concentration of particles below which sound attenuation is linearly dependent on particle concentration and the frequency domain in which frequencies have higher contribution to the attenuation than those outside the domain. To use this method, each data matrix is constructed by ultrasound attenuation data with frequency as variables and concentration as observations. Attenuation data are obtained with the measurements of ultrasound spectroscopy of oil/water emulsions and solid/water suspensions at different concentrations. As a result of the factor analysis, for emulsions up to 40%vol concentration, the linear dependence of attenuation on concentration and a same level contribution of frequency ranging from 1 to 120MHz are found. However, for solid suspensions, attenuation appears to be nonlinearly related to solid concentration and the critical concentration value at which attenuation is turning into nonlinear from a linear trend can also be calculated. It is also found that in solid suspensions, frequencies less than 10MHz have less contribution to attenuation than that of higher than 10MHz. Therefore, for ultrasound particle sizing using ECAH model, before the inversion of attenuation to particle size distribution takes place, using this method the range of concentration and frequency to which the use of ECAH model is valid can be determined. [Copyright &y& Elsevier]

Abstract: Two methods are proposed for measuring the refractive index or the absorption coefficient simultaneously with the diameter and velocity of a moving spherical particle by using a polarized-type phase Doppler method. A particle refractive index is determined from phases of reflected and refracted rays detected individually by using different polarization angles of scattered light, whereas an absorption coefficient is obtained by applying the Lambert–Beer law to intensity of a dual-burst Doppler signal generated by the reflected and refracted rays. The optimum conditions of an optical system were estimated theoretically. Experiments were performed with polystyrene particles in water, water droplets, and water-black ink droplets to confirm usefulness of the proposed methods. [Copyright &y& Elsevier]

Fast online acquisition of particle size distribution has become a significant technique for both laboratory research and industrial application. In this paper, a particle sizing method based on the analysis of scatted light through image processing is proposed. Polarization ratio, which is defined by the ratio of the scattered intensity component polarized perpendicular to that polarized parallel, is induced to quantify the polarization status which, according to Mie scattering theory, is dependent on the particle diameter under a certain operating condition when the refractive index of the particle is known. Test rig is set up to realize the simultaneous acquisition of particle images polarized both perpendicular and parallel on CCD camera. Through image processing, the polarization ratio of the scattered light is obtained, based on which inverse calculation is performed according to Mie theory. The presented method is then applied to the size distribution determination of polystyrene particles suspending in water. The results obtained from experiments are compared with the calibrated values which renders a deviation less than 10%. The optical setup is also applied to the sizing of water droplets generated by an atomizer, which provides reasonable size distributions under different operating conditions in line with the reference values provided by the fabricator. [ABSTRACT FROM AUTHOR]

Light scattering is used for remote diagnostics of certain physical properties of particulate systems. The main purpose of this review is to coherently present an updated theoretical background of forward and inverse analysis for particle size distribution measurements of disperse samples. In particular, both well-tried and recent methods for analytical and numerical treatment of measurement data inversion are examined. An extensive bibliography is included for further study. [ABSTRACT FROM AUTHOR]

Abstract: Single-pulse time-resolved laser-induced incandescence (TiRe-LII) signal transients from soot particulates were acquired during unsteady high pressure Diesel combustion in a constant volume cell for typical top dead center conditions during a Diesel engine cycle. Measurements were performed for initial gas pressures between 1 and 3 MPa, injection pressures between 50 and 130 MPa and laser probe timings between 5 and 16 ms after start of fuel injection. In separate experiments and for the same cell operating conditions gas temperatures were deduced from spectrally resolved soot pyrometry measurements. Implementing the LII model of Kock et al. [Combust. Flame 147 (2006) 79–92] ensemble mean soot particle diameters were evaluated from least-squares fitting of theoretical cooling curves to experimental TiRe-LII signal transients. Since in the experiments the environmental gas temperature and the width of an assumed particle size distribution were not known, the effects of the initial choice of these parameters on retrieved particle diameters were investigated. It is shown that evaluated mean particle diameters are only slightly biased by the choice of typical size distribution widths and gas temperatures. For a fixed combustion phase mean particle diameters are not much affected by gas pressure, however they become smaller at high fuel injection pressure. At a mean chamber pressure of 1.39 MPa evaluated mean particle diameters increased by a factor of two for probe delays between 5 and 16 ms after start of injection irrespective of the choices of first-guess fitting variables, indicating a certain robustness of data analysis procedure. [Copyright &y& Elsevier]

Many systems contain populations of individuals. Often, they are regarded as a lumped phase, which might, for some applications, lead to inadequate model predictive power. An alternative framework, Population Balance Models, has been used here to describe such a system, activated sludge flocculation in which particle size is the property one wants to model. An important problem to solve in population balance modelling is to determine the model structure that adequately describes experimentally obtained data on for instance, the time evolution of the floc size distribution. In this contribution, an alternative method based on solving the inverse problem is used to recover the model structure from the data. In this respect, the presence of similarity in the data simplifies the problem significantly. Similarity was found and the inverse problem could be solved. A forward simulation then confirmed the quality of the model structure to describe the experimental data. [ABSTRACT FROM AUTHOR]

A novel light-scattering technique is presented in this paper. Unlike the traditional methods, white light is used as the light source, and the light-scattering signals are collected within only one solid angle, from which the particle size and its distribution can be obtained by an inversion calculation. The basic principle is discussed. Results of the computer simulation and experimental studies made with monodisperse polystyrene latex spheres and polydisperse industrial samples are given. [Copyright &y& Elsevier]

We present three optical particle sizers properly conceived for different on-line applications in industrial plants. The first one is a diffraction-based particle sizer utilising an innovative optical scheme that allows the instrument to operate at very low particle concentration regimes (i.e. at extinction values as small as 10−5) in the size range 0.9–90 μm. The second one is based on the same principle of operation, but has been designed with a different optical configuration that makes it suitable for the characterisation of high concentration particle laden flows (like for e.g. pulverised coal downstream of the grinding mills) in the size range 3–300 μm. The third instrument is based on a multi-wavelength extinction technique and provides measurements over long optical paths (up to 10 m) in the 0.1–3 μm size range. [Copyright &y& Elsevier]

[Display omitted] The current study demonstrated that the presence of excipients can interfere with the measurement of particle size distribution (PSD), a critical quality attribute of ophthalmic suspensions, by laser diffraction (LD) and that a placebo background subtraction approach can eliminate the impact of excipients on the PSD measurement. Commercially available loteprednol etabonate and brinzolamide ophthalmic suspensions were used as model suspensions. The impact of excipients in these formulations on the LD measurements was determined using a one-factor-at-a-time experimental design approach, using National Institute of Standards and Technology (NIST) traceable polystyrene particle size standards as references. Among the evaluated excipients, polymers containing polyacrylic acid were found to interfere with the PSD analysis by creating the LD signals correspond to particles ranging from a few micrometers to a hundred micrometers in size. As a result, the measured PSD of active pharmaceutical ingredient (API) particles in the formulation overlapped with or superimposed on the excipient PSD signal, leading to erroneous interpretation of the API particle size. Additionally, dispersion of brinzolamide particles in unsaturated solutions led to rapid dissolution of brinzolamide particles during the measurement, resulting in underestimation of the particle size range. Here, a placebo background subtraction approach was developed to eliminate the interference of the excipients. This newly developed LD method was also evaluated using orthogonal methods, including polarized light microscopy and scanning electron microscopy (SEM). The strategy used in this study to eliminate the interference of excipients may also be useful for other heterogeneous dispersions where excipient interference may be of concern. [ABSTRACT FROM AUTHOR]

Abstract: The need is well recognized for suitable reference populations for calibrating and verifying the size and concentration accuracy of particle analysis instruments for use in the measurement of suspended protein particles in biopharmaceuticals. Polystyrene bead standards are normally used as a reference material for calibrating and validating particle analyzers. However, these standards, unlike protein particles, are easily detected and do not challenge the sensitivity of optical instruments. Groups of instruments verified only with beads can still exhibit significant differences in measuring concentrations of more challenging protein particles. To minimize these and obtain consistent concentration measurements between instruments, reference populations must closely resemble protein aggregates in possessing high transparency and a refractive index close to typical protein matrix fluids. This paper describes work on evaluating a promising reference candidate and the use of this to harmonize the performance of Micro-Flow Imaging instruments. Results show that use of a suitable reference population can significantly increase measurement consistency when multiple instruments are used to characterize the same protein particle suspension. [Copyright &y& Elsevier]