Showing papers on "Particle-size distribution published in 1971"

Particle Formation in Polymer Colloids, III: Prediction of the Number of Particles by a Homogeneous Nucleation Theory

Abstract: The formation of particles in polymer colloids ordinarily is accomplished by the free radical polymerization of an organic monomer in a liquid which is a non-solvent (diluent) for the polymer. A surface active material, such as a soap or other amphipathic molecule, is usually added to stabilize the colloidal particles as they are formed. The particle size distribution varies from very narrow to extremely broad depending primarily upon the solubility of the monomer in the diluent, the stabilizer concentration and the ionic strength.

Particle size distributions in the Eastern Equatorial Pacific

Abstract: Size distributions for particles larger than 2.22 μ were measured at selected depths in the eastern equatorial Pacific along with the standard hydrographic variables. The particle size distributions were approximately exponential in shape, but a better fit is provided by the Weibull distribution. Measured, particle concentrations at the surface averaged 5×103cc. Near-surface maxima were found in both number and mean size, especially in regions with sharp thermal gradients. Below the thermocline, the concentration decreased rapidly to a typical value of 5×102/cc. The volume scattering function at 45° and the particle size distribution as measured at several stations were combined to create an optical vector consisting of the specific light scattering of the average particle and the cross section of the mean particle. Plots of the optical vector show a characteristic form, with a decrease in mean area accompanying an increase in specific scattering in the water above the oxygen minimum and little change below the minimum. The change in the optical vector with depth appears to be directly related to the oxidation of the decomposable parts of the nepheloid material.

The effect of particle size distribution on the performance of a phosphate flotation process

Abstract: A 25 cu ft flotation cell was operated continuously to produce an apatite-rich concentrate. The experimental results reported in this paper attempt to elucidate the role of the particle size distribution upon the performance of the cell. The particle size distribution influences performance through its effect on the particle residence time distribution and on the rate of impaction, adherence and detachment of particles and bubbles. A model is developed which is capable of predicting a fractional recovery of apatite in any particular particle size range.

Theoretical study of the scatter of experimental data due to particle-size-distribution

Abstract: The scatter of data due to the size distribution and the number of particles to be required in an experiment in a particulate process are discussed in detail. The process dealt with in this paper is that represented by:y = KDαP. If the log-normal size distribution is valid, the number of particles required in an experiment and the amount of scatter can be determined by use of only one parameter, calculable from the standard geometric deviation of population-particles, basis number β (β = 0 for the count basis and β=3 for the mass basis), the exponent α, and the magnitude of error required in the experiment. Conversely, the error can be estimated from the number of particles used in an experiment.

Size Analysis of Silt and Clay by Hydrophotometer

Abstract: The photo-extinction method of fine particle size analysis by hydrophotometer is significantly faster and more precise than pipette analysis. Six samples are analyzed per hour by the hydrophotometer and calculations can be performed by computer in fifteen minutes. Hydrophotometer reproducibility, expressed as the standard deviation of phi percentiles of the cumulative curve is 0.11 , whereas that of the pipette method is 0.45 . Precision of both methods increases, in the course of analysis, from silt to clay; and the ranges of precision, respectively, are 0.07-0.36 and 0.06-1.69 . Sample treatment for hydrophotometer analysis is non-destructive (no sample drying) and great versatility in the nature of the settling medium and dispersant is afforded.

Simultaneous measurement of the size distribution of aerosol particles and the number of particles of each size in a flowing gaseous medium

Abstract: A method and apparatus are described for measuring the size distribution of aerosol particles in a gas stream and the number of particles of each size Particle-laden gas flows through the apparatus at a controlled velocity A group of particles located in a first region are rapidly charged by a pulsed corona discharge The group of charged particles flows downstream into a second region in which an axial electric field is applied The mobility of the charged particles through the field is a function of their charge, which in turn is a function of their size, so that the larger particles move through the second region faster and thus in less time than slow particles In this manner, particles having a common size are concentrated in an axial direction as they move downstream The magnitude of the charge on particles arriving at the downstream end of the second region is related to the elapsed time between the time of the charging pulse and the moment at which the charge is measured to indicate the particle size distribution and number of particles of each size

The effect of particle size distribution on light transmittance measurement.

Abstract: Light transmittance by clouds of small particles has long been used as a method to measure particle properties such as size or concentration However, this application of light scattering has resulted in empirical data dependent on the specific instrument Deviations from light extinction theory result when scattered light enters the detector, increasing the apparent transmittance Previous studies of light extinction measurements have mainly considered error as a function of particle size with only limited analysis of polydispersed particle size distributions The ratio of the expected extinction coefficient to the theoretical extinction coefficient is reported as a function of the log-normal size distribution parameters, geometric mass mean radius, and geometric standard deviation, for various detector acceptance angles

Comparison of experiment and theory for the coagulation of aerosols

Abstract: The possibility of a sodium fire as a consequence of an accident in fast nuclear reactors has prompted interest in studying the distribution of airborne sodium-oxide particles generated in such an event. Since these particles may incorporate fission products, knowledge of their ultimate distribution in time and space is needed to evaluate the extent of the associated hazard. The purpose of this paper is to present modifications of a previously reported general equation intended to describe the dynamic behavior of a heterogeneous population of aerosol particles. Solutions of the modified equation are compared with experimental results. In these experiments, liquid sodium at 1000°F is exposed to an environment containing 4% to21% of oxygen. Some fraction of the oxidized sodium is released as an aerosol in a laboratory test chamber. Measurements and computations are made of the airborne mass concentration, mass deposition rates on the floor and walls, and the particle size distribution, each as a function of time.

Effect of particle size distribution on technological properties of stainless steel powder

Abstract: 1. A study was made of the technological properties of Kh18N15 stainless steel powders having different particle size distributions and particle shapes. 2. It is demonstrated that, as the amount of a medium and a fine fraction rises, the apparent density and the flowability increase, while the degree of powder compression during compaction decreases. The apparent density and the flowability of powder mixtures may diminish when the particles of the fine fraction do not arrange themselves in the interparticle pores of the main, coarse fraction.

Particle size measurements and properties of AVIAMIDE®-6 microcrystalline nylon

Abstract: Aviamide-6 microcrystalline nylon is a colloidal form of polycaprolactam prepared from Nylon-6 by controlled hydrolysis of the amide linkages followed by appropriate mechanical action which frees the particles from the polymer matrix. The particles termed microcrystals form stable dispersions in water over a wide range of concentration without the need of dispersing aids. The particle size distribution of Aviamide-6 aqueous gel was measured by centrifugal and gravitational sedimentation techniques over the range of 0.1 to 50 μ. The applicability of this technique was substantiated by electron microscopy studies. Depending on the grade, Aviamide-6 was found to contain as much as 90% by weight of the particles ≤1.0 μ and as much as 86% ≤0.2 μ. Physical properties of aqueous gels and powders were measured including rheological behavior, surface area, and electrophoretic mobility. The properties are interpreted in terms of chemical structure and particle size values. Particle size distribution curves are presented comparing several grades of AVIAMIDE-6. The dependence of the measured values of AVIAMIDE-6 particle sizes on the method of preparing the Aviamide-6 dispersions is discussed.

Electrophotographic photosensitive zinc oxide powder mixture

Abstract: An electrophotographic member comprising a support layer and an electrophotographic photosensitive layer disposed on the support layer, the electrophotographic photosensitive layer comprising a powder mixture dispersed in an electrically insulative film forming binder material, the powder mixture being a mixture of larger zinc oxide particles and smaller zinc oxide particles, the ratio by weight of the larger particles to the smaller particles being within the range from 4 : 6 to 1 : 9, the larger particles having an average particle diameter of 1.2 microns and the smaller particles having an average particle diameter of 0.8 microns, at least 60 percent by weight of the larger particles having a diameter not less than 1 micron and at least 70 percent by weight of the smaller particles having a diameter not more than 1 micron whereby the particle size distribution curve is characterized by the presence of two peaks respectively corresponding to the smaller and larger particles.

Evaluation of gap-graded asphalt concrete mixtures

Abstract: GAP-GRADED AGGREGATES HAVE DRAWN INCREASING ATTENTION BECAUSE OF THE GROWING DEMAND FOR HIGH-QUALITY AND MORE DURABLE PAVING MIXTURE FOR MODERN TRAFFIC, AND BECAUSE OF THE RISING COSTS FOR PRODUCING MAXIMUM DENSITY OR WELL- GRADED AGGREGATES, ESPECIALLY NEAR URBAN AREAS. EXPERIMENTAL RESULTS ARE REPORTED ON A COMPARATIVE STUDY INVOLVING 3 FULLER'S CURVE GRADINGS, 8 GAP GRADINGS, 2 AGGREGATES, AND 90 MIXTURES WITH VARYING ASPHALT CONTENTS. THE PHYSICAL PROPERTIES OF THE MIXTURES WERE EVALUATED IN TERMS OF BOTH MARSHALL DESIGN AND HVEEM DESIGN METHODS. RESULTS HAVE SHOWN THAT GAP-GRADED AGGREGATES CAN PRODUCE MIXTURES WITH PHYSICAL PROPERTIES EQUAL TO OR BETTER THAN CONTINUOUSLY GRADED AGGREGATES AT USUALLY HIGHER OPTIMUM ASPHALT CONTENTS.

Distribution of natural radioactivity on the environmental submicronic aerosols.

Abstract: An electrial ion mobility analyzer has been built for the study of the environmental aerosol particle size spectrum and of the distribution of natural activity on this spectrum in the size range 10?6 cm r > 10?6 cm. The mobility analyzer was carefully tested by a new method to prove the laminarity of flow and the air velocity distribution inside the apparatus. The quantity of charged aerosol particles classified into discrete mobility (or size) groups was estimated by the ?-radioactivity of collected particles tagged before entering the analyzer by ThB ions. The electrical mobility analyzer was then completed by a sonic jet diffusion charger for unipolar aerosol charging by diffusion and the elctrical parameters of this device were tested to ensure reliable operation. The activity size spectra A(r) were transformed to relative particle size distribution curves N(r) . The measurements were carried out in Stockholm, Sweden, under varying physical conditions (varying the activity, the residence time, the collector voltage or applying the diffusion charger for unipolar charging of particles). All experiments gave very similar results. The activity curves A(r) of positive and negative particles as a function of radius show a similar profile with a maximum in the region of radius r = 3–6 times 10?6 cm corresponding to Junge's model of aerosol particle distribution. The calculated relative particle size distribution curves N(r) are not always characterized by a peak as expected from Junge's model but are increasing below radii r < 10?6 cm, so that no peak is evident. DOI: 10.1111/j.2153-3490.1971.tb00588.x

Electrolytic aluminum powder and its properties

Abstract: 1 An electrolysis apparatus and a process for the manufacture of electrolytic aluminum powder have been developed and tested on a large laboratory scale 2 A study was made of the effect of electrolysis variables on the particle size distribution and particle morphology of electrolytic aluminum powder It has been demonstrated that: a) lowering the temperature, increasing the initial current density, and reducing the duration of electrolysis decrease the proportion of coarse fractions in electrodeposited powder and narrow the range of particle sizes; b) with decreasing current density, the particle shape changes from elongated, dendritic to compact and, finally, lamellar; c) the powder particles are perfect single crystals 3 Compared with powders produced by the atomization of liquid aluminum and mechanical comminution of solid aluminum, electrolytic aluminum powder has a larger specific surface, Its gravimetric density and aluminum oxide content per unit surface are less than those of the other powders 4 The amount of the principal metallic impurities is less in electrolytic aluminum powder than in A99 grade aluminum

Method for determining the gram size distribution of ferromagnetic material

Abstract: THE INVENTION DISCLOSED PROVIDES A METHOD FOR MEASURING GRAIN SIZE DISTRIBUTION OF FERROMAGNETIC MATERIALS BY CORRELATING THE AMPLITUDE SIZE DISTRIBUTION OF THE STEPS OF THE MAGNETIZATION CURVE WITH THE GRAIN SIZE DISTRIBUTION.

An electron-microscopic study of nickel carbonyl powders

Abstract: 1. The electron-microscopic technique makes it possible to study the size distribution of the primary particles making up, in the form of aggregates, carbonyl nickel powders, and also the character of the early stages in the aggregation of these particles. 2. The size of the primary particles and the character of their aggregation depend on the conditions of powder preparation. As a general rule, higher rates of powder formation during the thermal decomposition of nickel carbonyl in the volume correspond to smaller sizes and a looser aggregation of the primary particles. 3. The size of the primary particles and the character of their aggregation govern the macroscopic properties, which can readily be determined by experiment, and the particle size distribution of carbonyl nickel powders. 4. During the storage of carbonyl nickel powders, the primary particles within the aggregates spontaneously sinter together, as a result of which compact, coarse (micro-size) nickel particles are formed.