Showing papers on "Particle-size distribution published in 1974"

Hydrodynamic chromatography a technique for size analysis of colloidal particles

Abstract: When colloidal materials are carried in aqueous suspension through packed beds of spherical particles, it has been observed that the rate of transport of the colloidal particles depends on such factors as the size of the colloid, the size of the packing and the ionic composition of the aqueous phase. From such observations, a chromatographic technique has been developed, called hydrodynamic chromatography, which can yield size information on a variety of colloidal materials in the submicron range. Several examples are provided that illustrate how the technique is applied in the study of polymer latexes to determine particle size, assess particle size distribution, follow emulsion polymerization kinetics and provide evidence for particle agglomeration. The origin of the various transport and separation phenomena is also discussed.

The determination of the index of refraction distribution of oceanic particulates

Abstract: A method is described for determining the index of refraction distribution and the particle size distribution of suspended particles. The distributions are obtained by breaking down an observed volume scattering function into its contributing components. The component scattering functions are calculated using Mie theory. The component functions include all size distributions and indices of refraction that can be expected to be present. The method was applied to a volume scattering function observed in the Sargasso Sea. Forty components were used with five different indices of refraction and eight different particle size distributions. The resultant index of refraction distribution was bimodal. Components with indices of 1.05 and 1.15 dominate the calculated volume scattering function. The calculated particle size distribution falls within experimentally determined limits for the size distribution.

Particle Number and Mass Distributions above 10−4 cm Radius in Sand and Aerosol of the Sahara Desert

Abstract: Measurements of the particle size distribution in surface air and bulk soil (soil surface and 10 cm depth) were performed in the Sahara desert. This desert is a very important source for mineral dust transported over the Atlantic Ocean. Measurement restrictions limited the size range under investigation to 10−4 to 10−1 cm radius. In that range the size distributions in aerosol (toluene-insoluble component) and soil material (water-insoluble component) are similar in shape, except for a secondary maximum in soil particle size distributions. The results indicate that the aerosol and the soil size distributions are influenced by the soil and wind conditions over large areas. Differences between the soil surface and at depths of 10 cm were not observed within the precision of the measurements. Changes in the shape of the size distribution in the soil or surface air during and after a heavy sandstorm were not observed either—an indication that the loss of sand during a sandstorm is small compared to t...

Effect of aerosol composition on cloud droplet size distribution: A numerical study.

Abstract: Numerical computations have been performed to study the effect on the characteristics of a condensationally produced droplet size distribution of a variability in the kind and fraction of soluble material among atmospheric aerosol particles. The model aerosol used in the study is assumed to be comprised only of nuclei containing 1, 10, 50 and 90% soluble material and to have a particle size distribution equal to the mean of the model continental and maritime aerosol size distributions described by Junge and McLaren. The soluble constituent of the nuclei is taken to be ammonium sulfate. Droplet size distributions are computed for a height of 150 m above cloud base. The computations show that the droplet size distribution resulting from condensation upon a population of mixed nuclei (i.e., nuclei composed of both soluble and insoluble components) is not broader than that produced by condensation upon a population of pure salt nuclei. Further, the dispersion of cloud droplet sizes is found to be qui...

Optical measurement of interplanetary particulates from Pioneer 10

Abstract: The spatial concentration and size distribution for particulates measured in situ by the asteroid/meteoroid detector on Pioneer 10 between 1.0 and 3.5 AU are presented. The size distribution includes particles of radii from about 35 microns to 10 cm. Extrapolation from the smallest particle sizes measured shows good agreement with the results of the particle penetration detector carried on the same spacecraft. Within the uncertainties of this experiment, a single size distribution seems appropriate for all but the smallest particles measured. There is evidence for the existence of a planetary sweeping effect in the vicinity of the Mars orbit. As calculated from the particle spatial distribution, the zodiacal light brightness is found to vary approximately as the inverse square of solar distance out to about 2.25 AU and then decrease more rapidly. The absolute value of the zodiacal light brightness as calculated from the particle spatial concentration is found to be too high by a factor of 10.

Process for the production of high apparent density water atomized steel powders

Abstract: The apparent density of molding-grade, water atomized steel powder can be significantly decreased by employing the following prescribed treatment. Coarse particles are removed in order that at least 80% of the initial powders are finer than 80 mesh. The size distribution of the powders is then determined. The powders are then annealed to both reduce the carbon and oxygen contents and soften the particles. The annealed and agglomerated particles are then ground in a disk mill at specified speeds and gap spacings, depending on the size distribution of the initial powders. Apparent densities less than 2.8 gm/cc may be achieved by (a) employing powders with a finer particle size distribution, (b) decreasing the rotational speed of the disks and (c) increasing the mill gap.

Classified toner materials

Abstract: Classified toner materials having a particle size number distribution with a fine index ratio of less than about 2.50, a particle size volume distribution with a coarse index ratio less than about 1.50, and a particle size distribution wherein less than about 30.0 percent by number of the toner particles have an average particle size diameter of less than about 5 microns, about 25 percnt of the particles have a diameter between about 8 microns and about 12 microns and less than about 5 percent by number of the toner particles have an average particle diameter greater than about 20 microns. The toner materials may be mixed with carrier materials to form electrostatographic developer mixtures.

Particle size analysis using computer-synthesized holograms.

Abstract: A holographic correlation method permits the determination of the diameter and size distribution of suspended particles with diameters from 1 μm to 10 μm. The method uses synthetic holograms calculated from the Mie scattering theory.

Narrow particle size distribution catalysts and method therefor

Abstract: Particle size is increased and particle size range is decreased, e.g. narrower particle size distribution obtained of very tiny inorganic catalyst fines, (particles), particularly olefin catalysts by working these fines with very small quantities of polytetrafluoroethylene (PTFE) powder in order to trap the fines in a web of PTFE submicroscopic fibers.

Annealing separator for heat treatment of silicon steel sheets

Abstract: Annealing separator for heat treatment of a silicon steel sheet comprising not more than 0.2% SO3, not more than 0.04% Cl with the balance being MgO and unavoidable impurities, and having a bulk density between 0.18 and 0.30 g/cm3, and a particle size distribution of 40 to 70% of particles not larger than 3μm, 10 to 25% of particles not smaller than 10μm, not more than 15% of coarse particles larger than 15μm with the balance being intermediate particles between 3μm and 10μm.

High surface area carrier

Abstract: Classified high surface area carrier materials having a specific surface area of at least about 150 cm 2 /gram, a particle size volume distribution geometric standard deviation of less than about 1.3, and a particle size distribution wherein the carrier particles have an average particle diameter of less than about 100 microns. The carrier materials are mixed with finely-divided toner materials to form electrostatographic developer mixtures.

Aerosols at 20 kilometers altitude

Abstract: Stratospheric aerosols were collected at the 20 km altitude zone by direct impaction on 0.2mm palladium wires in view of the previously observed minimum in particle size frequency distribution between 0.1 and 0.2 microns. Since no minimum in size distribution around 0.2 microns was found, it is concluded that previous equipment was inefficient in collection in this range. Concentration results suggest that low particle concentrations result from small particles agglomerating to form larger ones. Since no indentations were found on the wires used in this experiment, and since there were no differences in the number of particles found on oil-coated surfaces vs uncoated surfaces, the particles in the stratosphere must be liquid, liquid coated, or a slurry.

Size-graded quaternary batch for bonded basic refractory shapes

Abstract: A refractory of fused or dead-burned dolomitic grain bonded with fine magnesite. The dolomitic grain is divided into one coarse and one intermediate particle size fraction in the batch, while the magnesite is alone in the fine fraction. The fine, intermediate and coarse fractions are separated by large discrete gaps in the size distribution of particles resulting in a burned refractory of high hot strength and corrosion resistance to slags in basic oxygen furnaces. The width of each large gap in the particle size distribution is at least equivalent to the gap created by removing from a ground raw material batch, with a continuous particle size distribution, the particles retained on at least three consecutive primary Tyler sieves after screening (sizing) the batch.

A Stokes' velocity photographic method for measuring the size distribution of aerosols

Abstract: Aerosol particles are allowed to settle in a vertical glass walled vessel, and their settling velocity is determined by photographing them while the light entering the camera is being chopped at a known rate. The settling velocity of each particle can be determined from the photographs, and by applying the Stokes' law, one can calculate the radius of each particle. The Stokes' law for a sphere settling freely in a quiet medium is given. If the volume of the photographed region of the illumination is known, the aerosol number density and size distribution can be obtained. Experiments with alumina particles of given size distributions indicate that the method works accurately. One set of a typical experiment with 3.0-micrometer Al2O3 particles is presented, which shows that the measured size distribution peaks at approximately 3.0 micrometer.

Method for rapid particle size analysis by hydrosizing and nuclear sensing

Abstract: A method and apparatus to practice the method for rapidly determining the size and mass distribution of a sample of randomly sized particles of a known total mass. A series of substantially identical hydrocyclones are connected by conduits to each other and to a temperature controlled water feed. By restricting the cross-sectional areas of these conduits to progressively smaller values, the slurry containing the sample particles is caused to increase its velocity as it moves from hydrocyclone to hydrocyclone. As described by the Stokesian theory which relates particle diameter and settling velocity, the largest sized particles are suspended in the closed apex of the first hydrocyclone with smaller sized particles, in given size ranges, being suspended in the next succeeding hydrocyclone's apexes. In this manner, the particles are separated into discrete fractional sizes with a residual slurry of the very smallest particles being discharged. Before the discrete fractions of particles are suspended in their hydrocyclone apexes, a combined photon source, like a gamma ray source, and detector are calibrated with the water temperature kept constant. When the suspension of particles takes place, an attenuation of the radiation from the source is observed at the detector. This attenuation can be related to the mass or weight of the discrete fractions of suspended particles. Electronic circuitry is used to indicate what this fractional mass or weight is as it relates to the total weight of the sample.

In situ measurement of particulate number density and size distribution from an aircraft

Abstract: Commercial particulate measuring instruments were flown aboard the NASA Convair 990. A condensation nuclei monitor was utilized to measure particles larger than approximately 0.003 micrometers in diameter. A specially designed pressurization system was used with this counter so that the sample could be fed into the monitor at cabin altitude pressure. A near-forward light scattering counter was used to measure the number and size distribution particles in the size range from 0.5 to 5 micrometers and greater in diameter.