The Effect of Shape on Intermethod Correlation of Techniques for Characterizing the Size Distribution of Powder. Part 2: Correlating the Size Distribution as Measured by Diffractometer Methods,TSI-Amherst Aerosol Spectrometer,and Coulter Counter

In an aerosol spectrometer the size of a powder grain is measured from the time-of-flight of the fineparticle between two laser beams. Due to the flow conditions, irregularly shaped fineparticles align themselves along the direction of flow of the air stream carrying them across the gap between the laser beams. The size distribution measured therefore varies with the shape of the fineparticles. This fact is demonstrated by comparing size distributions generated by image analysis, electrozone stream counter, diffractometer, and time-of-flight aerosol spectrometer.     

Increased Resolution of Size Distributions with the Coulter Counter

The limiting resolution of Coulter size measurements, the size within which two separate populations can be distinguished, is discussed in relation to the standard aperture. Electronic pulse editing, by comparing pulse height to width, enables small particles to be resolved from baseline instrument noise, but can give incomplete resolution of ultra-narrow distributions from artefactually produced peaks using the standard aperture. Improvements in the minimum measurable size and in sizing resolution of narrow size ranges are also shown to be possible by improving the signal quality from the Coulter aperture. A novel mathematical approach is described for the derivation of true size spectra for narrow particle size distributions by deconvolution of the composite spectra resulting from the effect of the inhomogeneous electric field in the Coulter aperture. Simple empirical equations are used derived from the location and amplitude of the spurious peaks observed in such composites relative to the genuine peaks. The method is applied to three “industrial” materials (wide size range samples) to determine the likelihood that such size ranges are affected by the spurious or artefactual peaks. A fresh blood sample deconvoluted by this method is shown to be apparently composed of more than one population of cells.     

The Effect of Shape on Intermethod Correlation of Techniques for Characterizing the Size Distribution of Powder. Part 1: Correlating the Size Distribution Measured by Sieving,Image Analysis,and Diffractometer Methods

In recent years, powder technologists have been increasingly concerned with powder systems having irregular grain shape and texture. Of particular concern is the effect of the shape of the powder grains on the size distribution data generated by characterization methods based on various physical principles. In particular, as many laboratories switched to modern procedures based on analysis of diffraction patterns, the need to know the effect of particle shape on the data generated by the newer methods, as compared to information gathered using classical methods such as sieving or image analysis, has grown. In this study comparative data generated by sieving, image analysis, and diffractometer studies of four iron powders, arc reported and discussed.     

Particle Size of Pneumatically Conveyed Powders Measured Using Impact Duration

CSIRO Minerals has developed a technique for measuring particle size in pneumatically conveyed powders [1] by measurement of the acoustic waves produced by particle impacts upon a specially designed transducer. Previous work has focused on using the peak acoustic wave amplitude to determine particle size. This produces a spectrum that is hard to determine the particle size from, as the peak amplitude is a non‐linear function of particle diameter, and is strongly affected by angle of incidence and velocity of the impacting particle. In this paper impact duration measurements are used to overcome these difficulties while retaining the advantages of being able to measure in high solids loadings of up to at least 0.5 kg/m³ of powder. In laboratory tests the impact size monitor's (ISM) results have been correlated with optical diffraction measurements of the mean (by number) powder size with a correlation coefficient of 0.985 and a relative error of 5.5 %. The ISM operated successfully in the laboratory at a loading of 0.5 kg/m³ of powder and measured particles down to 50 microns in size.     

基于DOAS技术的气溶胶粒谱分布反演方法研究

大气气溶胶不仅对全球的气候变化产生重大影响,其本身也是一种污染物,另外它在许多污染气体的化学反应中起重要作用。因此,实时监测大气气溶胶已成为环境领域的重要研究方向。差分吸收光谱技术是一种基于痕量气体“指纹”特性反演其浓度的光学遥感方法,同时该方法也可用于大气气溶胶消光系数的测量。文章介绍了利用闪烁差分吸收光谱系统监测大气气溶胶粒谱分布的方法,重点阐述了基于蒙特卡罗方法的粒谱分布反演算法,监测结果通过与PM10、能见度及Angstrom波长指数的对比证实了该方法的可行性,为近地面大气气溶胶监测提供了新的手段,同时也扩展了差分吸收光谱技术的应用范围,该方法对大气化学的研究有着重要的意义。     

Characterization of Pyrogenic Powders with Conventional Particle Sizing Technique: I. Prediction of Measured Size Distributions

Pyrogenic powders consist of fractal like aggregates with nanosized primary particles. The formation of such aggregates, their hydrodynamic behavior and their optical properties are in principle well understood. Even so, there is only little experience in interpreting results from particle sizing of such materials. Dramatic differences in size distribution obtained from different measurement techniques give frequently rise to confusion on the “true” aggregate size. However, such differences can be attributed to the different particle properties used for size measurement and to the different types of quantities, by which the frequency of the individual size fractions are weighted. For two conventional sizing techniques, Dynamic Light Scattering and Optical Centrifugation Analysis, the influence of the structural properties on the relevant optical and hydrodynamic aggregate properties is discussed on the basis of virtual aggregates as well as of empirical data for pyrogenic powders. Finally measurable size distributions are predicted in a case study.     

Characterisation of Particle Size for Polydisperse Powders aerosolised and detected by light scattering

This paper describes a study to determine the most appropriate particle size parameter for polydisperse powders dispersed as aerosol and detected by light scattering. It is relevant to many areas of engineering research. By means of calculations of the intensity of light scattered from particles of different sizes, it has been shown that the surface median aerodynamic diameter (SMAD) is an appropriate measure for polydisperse aerosolised powders. The microscope-based procedure for obtaining the SMAD is described, as well as its implementation for narrowly-graded polydisperse powders of fused alumina of type which have been widely used in studies of particle transport in wind tunnels. It was shown that for the fused alumina powders examined, SMAD = 1.25 x (PASMAD), where PASMAD is the projected area surface median aerodynamic diameter.     

The Size Distribution of Core Shell Polymeric Capsules as Revealed by Low-Field NMR Diffusometry

Time-dependent diffusion studies have been done on hexadecane molecules confined inside core shell polystyrene capsules in order to extract capsule-size distribution. The polymeric capsules were prepared by an emulsification–diffusion technique. The nuclear magnetic resonance (NMR) diffusometry technique implemented in our investigations is the so-called pulse gradient stimulated echo technique. With this technique, diffusion times between 20 and 500 ms could be probed. The distribution of the apparent diffusion coefficients was extracted using a numerical Laplace inversion. These data allowed us to obtain dimension distributions in good agreement with the direct observations from electron micrographs.     

Combination of the Particle Size Distributions of Some Industrial Minerals Measured by Andreasen Pipette and Sieving Techniques

It is known that size of the individual particles is the predominant factor affecting the behavior of particulate materials, and that the size effects become increasingly important as the particles become finer. In this article, particle size distributions (PSDs) measured by different techniques, i.e. sieving and Andreasen pipette sedimentation, were combined for different mill (ball and rod) products of some industrial (talc and quartz) minerals. The corrected sedimentation data came closer to the sieving data. The apparent mean shape factors, r, determined from the corrected PSDs for the talc mineral ground by ball and rod mill were found to be 1.34, 0.62, whereas it was 1.00, 1.12 for the quartz mineral ground by ball and rod mill, respectively. The results show that the ball milled products of talc mineral have more regular (rounder in shape) particles than those of rod milled, but the rod milled products of quartz mineral studied were not more regular in shape than ball milled products of quartz mineral as confirmed by the SEM pictures and reviewed literature.     

Analysis of Particle Size Distribution by Particle Tracking

Particle tracking is performed using a combination of dark field or fluorescence video microscopy with automatic image analysis. The optical detection together with the image analysis software allows for the time resolved localization of individual particles with diameters between 100 and 1000 nm. Observation of their Brownian motion over a set of time intervals leads to the determination of their mean square displacements under the given room temperature and viscosity. Hereby, the radii of a set of particles visible within a given optical frame are derived simultaneously. Rapid data analysis leads to reliable particle size histograms. The applicability of this method is demonstrated on polystyrene latices and PMMA nanospheres with radii between 51 nm and 202 nm.     

Determination of Particle Size Distribution and Electrokinetic Properties with the AcoustoSizer in Comparison with Other Methods

The characterization of suspensions in process concentration is an important task for the optimization of handling and product properties. Only very few instruments are available. The AcoustoSizer (ACS) (Colloidal Dynamics PTY Ltd.) uses the so-called electrokinetic sonic amplitude (ESA) for particle size and zeta potential determination. In this work, the results obtained at moderate concentrations were compared with results of other instruments mostly working with dilute suspensions. For the electrokinetic investigations three methods (beside the ACS) were used: electroacoustics (ESA8000, Matec Applied Sciences), microelectrophoresis (Zetamaster, Malvern Instruments) and streaming current measurements (Particle Charge Detector PCD 03-pH, Miitek). For particle size determination different measuring techniques were applied: laser diffraction spectroscopy (Mastersizer S, Malvern Instruments), dynamic light scattering (Ultra Fine Particle Analyser, Leeds and Northrup), sedimentation analysis (Sedigraph 5000 D, Micromeritics) and scanning electron microscopy. Mainly three powders were used in the investigations: Monospher M1200 silica (Merck), Selectipur titania (Merck) and Aluminiumoxid C alumina (Degussa). The agreement between the different methods for both particle size and zeta potential measurements was excellent. Especially for the electrokinetic investigations, careful sample preparation is needed. The procedure must not change the equilibria determining the physical and chemical state of the suspension.     

激光散射法对尿液中纳米微晶粒径及其分布的研究

泌尿系结石已经成为威胁人类健康的一种常见病、多发病,目前对其形成的机制尚不清楚。文章采用激光散射法测定了正常人尿液和尿石症患者尿液中纳米粒子的粒径和粒径分布,该方法快速准确、经济、容易操作。正常人尿液比尿石症患者尿液的稳定性好,归因于正常人尿液中纳米微晶尺寸分布均匀,不容易聚集,而尿石症患者尿液的纳米微晶尺寸分布不均匀,粒子间容易聚集而沉降。通过分析尿样稀释、离心或者用微孔滤膜过滤后体系的光强-自相关函数曲线,得到了制备稳定的尿样悬浮液的方法：尿样先稀释20%,然后离心或用1.2 μm微孔滤膜过滤,可得到稳定的尿液悬浮液。激光散射法结果与TEM检测结果一致。从尿液中存在的范德华力、尿液粘度、酸碱性、离子强度、尿液中纳米微晶的表面电荷和Zeta电位等方面解释了尿液稳定的原因。     

用同步辐射X荧光测量大鼠脑中微量元素的分布

采用同步辐射微探针技术研究了正常大鼠脑中的微量元素的分布,并给出了二维空间分布图.结果显示:Cl,Ca,Zn,主要集中分布在海马区,K,主要分布在海马和 皮层,而,Cu,的分布则相对无规律.元素的聚类分析结果表明,Cl,和,K,的分布相关性较好.由于同步辐射,X,荧光技术可以更直观地给出脑组织的二维元素分布, 因此这种方法可用于研究发生病变的脑中微量元素的变化.     

Restoration of the Initial In-Depth Distribution of an Element from a Profile Measured by SIMS

Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques - Some advantages of the roughness–mixing–recoil (RMR) implantation model over the popular...     

Study on the Range of Particles Size Measured by Backscattering Method in Visual‐infrared Incident Spectrum

For the measurement of particles size with backscattering method, the suitable range of particles size measurement have been presented by independent algorithm in Visual‐infrared incident spectrum. We defined the range according to the retrieved results based on the analysis and comparison to many kinds of R‐R distribution function. The simulation computation results showed that the particles size measurement range is from 0.05 μm to 18 μm with incident spectrum from 0.4 μm to 2 μm and different refractive index. The results retrieved were satisfied even if 1 % noise was added into the backscattering intensity.     

由吸收系数和粒度分布计算浮游植物的散射光谱特征

散射特性在水色卫星遥感模式的开发、水下光辐射传输、优势藻光谱特征的提取以及赤潮监测等方面有着重要的应用价值.在假定藻细胞为均匀球形结构的条件下,建立了浮游植物的散射正演模型.模型输入参量为实际测量的藻细胞吸收系数和粒度分布,输出参量为浮游植物的散射效率和吸收效率光谱.对短伪海链藻和威氏海链藻进行实验,模拟结果与实验结果的比较发现:该模型估箅得到的散射光谱能与实验的散射光谱得到很好的吻合,两种藻的模拟散射效率相对实验散射效率的误差分别为7%和10.6%,吸收效率的误差分别为7.4%和13.4%.模拟与实验结果的吻合表明,由吸收系数和粒度分布可以模拟出藻类的散射光谱特性.单细胞近似球形藻类散射正演模型可行.     

On the Size Distribution of Dispersed Fractal Particles

Technical Physics - Using a thermodynamic approach, a disperse system formed by an ensemble of particles with various shapes and volumes is studied. The shape of a particle is set by the value of...     

Comparative Test of Methods to Determine Particle Size and Particle Size Distribution in the Submicron Range

Among the most important characteristic properties of disperse systems such as latices, pigments, ceramic materials or drug formulations are the particle size and the particle size distribution. To measure these quantities, several methods and measuring instruments based on different physical principles are available. These include turbidimetry, dynamic and static light scattering, electron microscopy with image analysis, ultra- and disc centrifugation, light diffraction and the electrical sensing zone method. All these measuring techniques are doubtless necessary because of the large product variety and the broad particle size range. However, some problems arise if different techniques are used and the results are compared uncritically without considering to the application range and the resolution of the methods. An extensive comparative test was therefore carried out using seven latices in the submicron range with defined monomodal, bimodal and hexamodal particle size distributions. The most important methods of determining average particle size values and particle size distributions were tested and compared. Of the methods to determine only average particle sizes, turbidimetry is the most efficient, followed by dynamic light scattering with cumulants evaluation. Static light scattering only yields accurate results for small particles with narrow particle size distributions. Of the methods to determine particle size distributions, ultracentrifugation and, somewhat less, disc centrifugation and electron microscopy with image analysis are the most efficient. Dynamic light scattering only yields reliable results in the case of small particles with narrow distribution curves. Light diffraction and the electrical sensing zone method are less suitable for the submicron range.