Showing papers on "Particle-size distribution published in 1981"
TL;DR: In this article, a steady state processing conditions, characterized by equiaxed powder particles, a constant particle size distribution and a saturation hardness, was found to depend on the size distribution of the initial powders.
Abstract: Mechanical alloying of two aluminum alloy powders to form composite A1-A12O3 powders has been studied. Changes in powder microstructure with processing are reported and interpreted. Mechanical alloying proceeds by the continual cold welding and fracturing of the constituent powder particles when subjected to the large compressive forces of a high speed mill. A suitable organic surfactant must be added so that a balance between cold welding and fracturing is obtained. The organic surfactant is embedded and finely distributed in the powder particles during mechanical alloying and is converted to discrete A14C3 particles after hot pressing. The establishment of steady state processing conditions, characterized by equiaxed powder particles, a constant particle size distribution and a saturation hardness, is found to depend on the size distribution of the initial powders. The oxide particles formed and distributed during mechanical alloying are equiaxed, small (30 nm) and homogeneously distributed with a volumetric center to center distance of about 60 nm.
120 citations
TL;DR: Absorption or extinction measurements at wavelengths of 0.5145 and 10.6 microm lead to determination of the mass concentration of carbonaceous smokes with an accuracy of ~20%.
Abstract: Absorption or extinction measurements at wavelengths of 0.5145 and 10.6 μm lead to determination of the mass concentration of carbonaceous smokes with an accuracy of ~20%. The results do not depend on the details of the particle size distribution or on particulate to void ratio.
71 citations
01 Jan 1981
TL;DR: In this article, a laboratory investigation of the particles in the flue gases of a pulverized coal combustor has been conducted, focusing on physical and chemical characterization of those particles smaller than 2 μm diameter.
Abstract: A laboratory investigation of the particles in the flue gases of a pulverized coal combustor has been conducted. The emphasis was on physical and chemical characterization of those particles smaller than 2 μm diameter. The number concentrations are large, on the order of 1014 particles/m3, and the mean size is small, 0.02 to 0.08 μm diameter. The particle size distribution is extremely narrow, supporting the hypothesis that the particles were formed by nucleation and then grew by coagulation. Predicted particle size distributions are in close agreement with the data. Chemical analyses of the submicron particles by particle induced x-ray emission show two distinct modes in the 0.03 to 3 μm size range. The larger particles consist of the major ash species, Al, Ca, Fe, and Si. The, smallest particles were composed of the more volatile species, Si and S, with a large amount of material not detected by PIXE. Optical absorption measurements suggest that this material was primarily carbon in the form of soot.
55 citations
TL;DR: In this paper, a quadrupole mass spectrometer is used for real-time chemical composition and size data on individual aerosol particles, which separates the particles from the entraining gases by means of aerodynamic nozzles and differential pumping, so that they enter the high vacuum region as a collimated beam.
Abstract: A new analytical instrument has been developed to give real‐time chemical composition and size data on individual aerosol particles. It separates the particles from the entraining gases by means of aerodynamic nozzles and differential pumping, so that they enter the high vacuum region as a collimated beam. Each arriving particle is flash vaporized, the vapor ionized, and the ions analyzed by a quadrupole mass spectrometer. The instrument has been tested with several inorganic and organic aerosols and has yielded mass spectral peaks corresponding to a series of fragment ions. The more stable compounds yielded the parent ion as well. Particles 0.9 μm in diameter are readily detected with signal‐to‐noise ratios of 12:1 on the dominant peak. On this basis, the small‐size sensitivity limit is well under 0.5 μm diameter and, with design improvements, can probably be extended to 0.1 μm or smaller.
45 citations
TL;DR: In this paper, the authors present a Protein precIPITATION-ANALYSIS of PARTICLE SIZE DISTRIBUTION and KINETICS, and discuss the role of particle sizes in particle size distribution.
Abstract: (1981). PROTEIN PRECIPITATION-ANALYSIS OF PARTICLE SIZE DISTRIBUTION AND KINETICS. Chemical Engineering Communications: Vol. 12, No. 1-3, pp. 203-219.
37 citations
TL;DR: In this article, the chemical composition of cosmic ray nuclei with 3≤Z≤28 between ∼100 MeV/nuc and a few hundred GeV/Nuc are compared with a consistent set of propagation calculations.
Abstract: The chemical composition of cosmic ray nuclei with 3≤Z≤28 between ∼100 MeV/nuc and a few hundred GeV/nuc are compared with a consistent set of propagation calculations. These include the effects of spallation (energy-dependent cross sections are used), escape and ionization loss in the interstellar medium and deceleration in the solar cavity. This has enabled a consistent study of the cosmic ray pathlength distribution to be made over this entire energy range. Details of the propagation calculation are left to a forthcoming paper.
32 citations
TL;DR: Two multi-element aerosol components and a third fine particle sulfur component have been identified in the marine atmosphere of Samoa based on elemental composition, time variation, and particle size distribution characteristics as mentioned in this paper.
Abstract: Two multi-element aerosol components and a third fine particle sulfur component have been identified in the marine atmosphere of Samoa based on elemental composition, time variation, and particle size distribution characteristics. On the basis of Pixe (proton induced X ray emission) analyses of 34 cascade impactor samples (17 simultaneous pairs), each of six particle size fractions, collected at 50 m height, July 16 to September 20, 1976, the components are (1) Cl, Br, K, and Sr in >0.5 μm aerodynamic diameter particles, Ca in 0.5–4 μm particles, and S in >1 μm particles, in proportions resembling, but not identical to, seawater composition; (2) a nonseawater component in >4 μm particles, consisting of 80% of the Ca and median weight ratios for excess Ca/Zn = 3.4, Cu/Zn = 0.11, Ti/Pb = 1.0, Ti/Zn = 0.06, and Fe/Zn = 0.24; (3) S in 4 μm particles during prevailing 1–15 m/s winds was evaluated for K, Cl, and S, indicating zero wind speed >4 μm concentrations for component (1) to be on the average 2.0 times greater than measured. Differences in processes for transfer of the elements through the sea surface to jet and film drops may account for the observations.
29 citations
TL;DR: In this paper, the grain size distribution is an important factor in determining the attenuation and a relatively small number of large grains can dominate the scattering processes, and it was concluded that the grain distribution is important in determining attenuation.
Abstract: Ultrasonic attenuation measurements up to a frequency of 30 MHz have been made on a low-carbon steel. The microstructure was controlled to produce a series of specimens with varying ferrite grain size. Analysis of the attenuation data was not possible using a simple Rayleigh scattering model and the mean grain size. It was concluded that the grain size distribution is an important factor in determining the attenuation and that a relatively small number of large grains can dominate the scattering processes.
23 citations
TL;DR: The removal of particles in water treatment plants through flocculation, sedimentation, and filtration depends on the design of each treatment process and physical characteristics of the raw water supply.
Abstract: The removal of particles in water treatment plants through flocculation, sedimentation, and filtration depends on the design of each treatment process and physical characteristics of the raw water supply. Mathematical models, based on design variables for each process and the size distribution and density of the particles in the water, have been developed and linked to predict performance for a typical plant. The models for flocculation and sedimentation allow for broad particle sized distributions, but the filter model is limited to monodisperse suspensions. Quantitative predictions of the effects of changing values of the design variables on the performance of subsequent processes are evaluated. Filtrate concentration and head loss development are sensitive to changes in the velocity gradient during flocculation, the detention time in sedimentation, and the media size in filtration. Suspensions comprised primarily of inorganic particles require higher velocity gradients, longer settling times, and smaller filter media to produce acceptable finished water quality than suspensions containing amorphous precipitates.
23 citations
TL;DR: In this paper, the feasibility of the application of the centrifugal method for particle size analysis on river water samples has been investigated and the efficiency of centrifugation for separating the colloidal and suspended particles from river water sample has been determined.
21 citations
TL;DR: In this article, a method for determining particle size distributions of polymer powders via analysis of the Fickian sorption and desorption kinetics of organic vapors was proposed.
Abstract: A method has been proposed for determination of particle size distributions of polymer powders via analysis of the Fickian sorption and desorption kinetics of organic vapors. The basis for this method is a model describing the kinetics of sorption in homogeneous spherical particles having diameters distributed a-mong a finite set of diameters. A computation procedure has been developed for determining the weight fractions of each particle diameter which optimize the fit between the model and experimental sorption data. This procedure has been applied to gravimetric sorption data for several organic vapors in PVC powders ranging in diameter from 0.2 to 80 μm. For samples whose particle structure meets the assumptions of the model, the procedure yields histographic distributions closely approximating the particle size distributions determined by conventional microscopic and sedimentation methods. For porous or agglomerated particles, the method yields an “equivalent spherical size distribution” whi...
TL;DR: Dependence of Gelation and Fusion Behavior of Poly(vinyl chloride) Plastisols upon Particle Size and Size Distribution was found in this article, where the particle size and size distribution varied with the number of particles.
Abstract: Dependence of Gelation and Fusion Behavior of Poly(vinyl chloride) Plastisols upon Particle Size and Size Distribution
TL;DR: The stratospheric aerosol particle size distribution has been measured at 34°S for the period 1974-1979 as discussed by the authors, and the size distribution is described equally well by either a log-normal or zero-order logarithmic function.
Abstract: The stratospheric aerosol particle size distribution has been measured at 34°S for the period 1974–1979. Results from two measuring techniques—in situ single-particle counting and jet impaction—agree well. The size distribution is shown to be described equally well by either a log-normal or zero-order logarithmic function. Observed distributions below 22 km agree substantially with model predictions for r>0.1 μm but indicate fewer particles at smaller radii.
TL;DR: In this paper, light absorption by samples of atmospheric aerosol particles as a function of size was studied using the integrating sphere method, and optical properties of fog and cloud-water residues were determined.
Abstract: Light absorption by samples of atmospheric aerosol particles as a function of size was studied using the integrating sphere method. In addition, the optical properties of fog and cloud-water residues were determined. The samples were taken at two locations in West Germany: one fairly remote from pollution sources, the other near the industrial area of Frankfurt. The results show that particles <0.4 μm volume equivalent radius significantly alter the values of the absorption coefficient σA. The absorption index k of atmospheric aerosol particles, in general, cannot be considered a property of the sample material. The absorption of light by samples of large particles from background areas exposed to urban influences can be explained quantitatively by the presence of soot particles. The soot content of samples of large particles is ∼−10% of the total particle number. The number of soot particles in samples of giant particles is very small. Starting with the highest absorption of solar radiation the ...
TL;DR: In this paper, an aerosol particle size analyzer based on a laser Doppler velocimeter (LDV) was developed to measure the aerodynamic diameter of individual particles and droplets in real time.
Abstract: An aerosol particle size analyzer based on a laser Doppler velocimeter (LDV) has been developed to measure the aerodynamic diameter da of individual particles and droplets in real time. The particles are electrically charged and then passed through a 40‐kHz electric field. The phase lag φ of the particle motion with respect to the field is measured by the LDV. A microcomputer determines da from φ and stores the aerodynamic size distribution of the sampled particulates. The analyzer has counted and sized particles at a maximum rate of 200 particles/s in the size range of 0.3–5.0 μm in aerodynamic diameter.
TL;DR: In this paper, the authors report the analysis performed on the existing PSDs and show that the results provide further evidence that sintering at temperatures of 700/sup 0/C and below takes place by particle migrations and that during 800/sup 1/C Sintering the atomic migration mechanism becomes operative.
Patent•
29 Sep 1981
TL;DR: In this article, the authors proposed a polymer component consisting of at least 10 weight % of particles having an average diameter of less than 0.2 μm and of 90 weight % at most of particles with a diameter of more than 1.25 μm, and the ratio of average grain size of coarse to fine polymer is at least 2:1.
Abstract: A protective colloid-free plastics dispersion yielding after drying a polymer film which under the influence of moisture has no or little tendency to whitening contains polymer particles having a bimodal size distribution, that is, on the one hand relatively coarse particles and on the other hand relatively fine particles. The polymer component consists of at least 10 weight % of particles having an average diameter of less than 0.2 μm and of 90 weight % at most of particles having an average diameter of more than 0.25 μm, and the ratio of average grain size of coarse to fine polymer is at least 2:1. The plastics dispersion is suitable especially as binder dispersion in plasters and gloss paints.
TL;DR: In this paper, the authors established a relationship between the efficiency of the powder rolling process and the relative apparent density of the starting powder, which is a quantitative indicator of its compactibility.
Abstract: The gauge coefficient Cg is a constant of rolled powder strip, which depends on the relative apparent density of the starting powder. Quantitative relationships have been established between the efficiency of the powder rolling process hs/D·ρ = Cg and rolling angle on the one hand and relative apparent density of powders ρp on the other. The gauge efficiency of the rolling process Cg of a powder and the size of its densification zone depend on the relative apparent density of the powder but not on its particle size distribution. The relative apparent density of a powder is a quantitative indicator of its compactibility.
TL;DR: In this article, the effect of nonsphericity of solid particle aggregates on the rate of Brownian agglomeration is investigated theoretically and experimentally, and the basic population balance equation for coagulation of liquid particles is modified for the case of fine solid particles by introducing the dynamic shape factor of aggregate particles.
TL;DR: In this article, a 100kW three-phase ac plasma furnace with sheathed copper electrodes (sheathing gas: air) is presented for spheroidizing "refractory-fired clay" particles having a smooth, pore-free surface.
Abstract: A 100-kW three-phase ac plasma furnace with sheathed copper electrodes (sheathing gas: air) is presented. It is used for spheroidizing “chamotte” (refractory-fired clay) particles having a smooth, pore-free surface. A simple, one-dimensional numerical model for the heat transfer to the particles explains the maximum processing rate and the detrimental influence of an inhomogeneous particle size distribution.
TL;DR: In this paper, a monitoring station in Jerusalem, Israel, during the 1978/79 winter season was used to characterize the processes which occur in suspended dust particles in the metropolitan area.
Abstract: Continuous measurements of particle mass concentration, particle size distribution, and other environmental measurements were conducted at a monitoring station in Jerusalem, Israel, during the 1978/79 winter season in order to characterize the processes which occur in suspended dust particles in the metropolitan area. Most of the man-made aerosol mass is initially emitted to the air in the form of small particles (submicron), but, as a result of atmospheric processes, larger particles are evolved. The rate constant which is characterized in this coagulation process (2.7 x 10 /sup -8/ cm/sup 3//S) was estimated from the field measurements. This rate constant indicated that urban particles coagulate on almost every collision and that the speed of the process is the main mechanism responsible for the sharp decrease in particle number density shortly after midnight. The influence of climatic factors (duststorms and precipitation) on suspended dust particles in Jerusalem air is also discussed.
TL;DR: In this article, an exponential function of the grain size was assumed in calculating the apparent (total) dielectric constant of BaTiO3 thick films with the average grain diameter known.
Abstract: An exponential function of the grain size was assumed in calculating the apparent (total) dielectric constant of BaTiO3 thick films with the average grain diameter known. The function was tested and estimated experimentally, for cases where the grain sizes were calculated using the following methods; the two-dimensional diameter analysis, the Schwartz-Saltykov method and Oel's method for converting a two-dimensional grain distribution to a spacial grain sizedistribution. Using the present assumed function and the extended logarithmic mixing rule to combine the dielectric constants of individual grains, the grain-size distribution-dependence of the dielectric constant was successfully simulated. From the simulated results it was concluded that the dielectric constants of coarse grains of thick films increase with increase of grain size in the range from room temperature up to 135°C.
TL;DR: In this paper, the TPC curves for both the natural and synthetic latexes correlate with the centrifuge curves, which can be used for any size range of particles by altering the rotor speed or eluant density.
Abstract: The two techniques examined in this work yield information about the particle size distribution of the latexes studied. The ease of measurement is improved over previous methods used on broadly distributed latexes. The TPC curves for both the natural and synthetic latexes correlate with the centrifuge curves. Both techniques show the Hevea to have larger particles than the guayule. The techniques also show SBR latex samples 1 and 2 to have larger particles than samples 3 and 4. The TPC is useful only for particles between 0.3 µm and 20 µm in size. The centrifuge can be used for any size range of particles by altering the rotor speed or eluant density. By employing the proper mathematics, these data could be easily converted from optical density distributions to particle size distributions.
01 Jan 1981
TL;DR: Coulter's method as discussed by the authors is a method of determining the number and size of particles suspended in an electrolyte by causing them to pass through a small orifice on either side of which is immersed an electrode.
Abstract: The Coulter technique is a method of determining the number and size of particles suspended in an electrolyte by causing them to pass through a small orifice on either side of which is immersed an electrode. The changes in electrical impedance as particles pass through the orifice generate voltage pulses whose amplitudes are proportional to the volumes of the particles. The pulses are amplified, sized and counted and from the derived data the size distribution of the suspended phase may be determined. The technique was originally applied to blood cell counting [1, 2]. Kubitschek [3, 4] introduced modifications which permitted counting of bacterial cells, and pointed out that this principle could be applied to the measurement of cell-volume distributions as well as number counting. Modified instruments were soon developed with which particles could be sized as well as counted.
TL;DR: In this paper, three different techniques, Coulter counter, light transmission and disc centrifugation, have been used to characterize various cationic bitumen emulsions, and the agreement between the Coulter counter and the light transmission method was good.
Patent•
27 May 1981
TL;DR: In this paper, the particle size distribution of a dust sample is determined by suspending the sample homogeneously in a carrier and measuring during the sedimentation of the particles in a measuring column the static pressure along the height.
Abstract: The particle size distribution of a dust sample is determined by suspending the sample homogeneously in a carrier liq. and by measuring during the sedimentation of the particles in a measuring column the static pressure along the height. The sedimentation height is subdivided into several (four) sections for which the integral pressure, referred to the top zero point, is scanned in a given sequence. This produces the curve for the pressure profile over the sedimentation distance which indicates the size consist. This method creates a fast, accurate and reproducible measurement of the particle size distribution of dust samples. It is suitable for a wider range of size consists than conventional methods.
Patent•
28 Aug 1981
TL;DR: In this paper, JPO and Japio proposed a method to obtain an aggregate of polyhedral corundum particles having a narrow particle size distribution by mixing alumina hydrate as a starting material with fine corundrum particles having specified shape factor and by hydrothermally treating the mixture to deposit alumina on the surfaces of the particles.
Abstract: PURPOSE: To obtain an aggregate of polyhedral corundum particles having a narrow particle size distribution by mixing alumina hydrate as a starting material with fine corundum particles having a specified shape factor and by hydrothermally treating the mixture to deposit alumina on the surfaces of the particles. CONSTITUTION: Particles of alumina hydrate such as aluminum hydroxide as a starting material are mixed with fine corundum particles adjusted to 1.0W1.4 shape factor by classification as seed crystals. The mixture is hydrothermally treated to deposit alumina in the alumina hydrate as corundum on the surfaces of the fine corundum particles. To the hydrothermal synthetic reaction system may be added a boron compound such as sodium borate. By this method the desired aggregate of polyhedral corundum particles havong a narrow particle size distribution is obtd. COPYRIGHT: (C)1983,JPO&Japio
Patent•
02 Dec 1981
TL;DR: In this paper, a transfer type magnetic toner has the following characteristics, that is to say, saturated magnetization is 25-260emu/g, and coercive force is 150-350 oersteds.
Abstract: PURPOSE:To improve development and transfer characteristics, by setting the magnetic characteristics, electric resistance, charge quantity and particle size distribution of a transfer type magnetic toner, to a specific range. CONSTITUTION:This transfer type magnetic toner has the following characteristics, that is to say, (1) saturated magnetization is 25-260emu/g, and coercive force is 150-350 oersteds, (2) >=1X10 OMEGA in a DC electric field of 10,000V/cm, (3) charge quantity of >=151muC/g, and (4) weight or volume mean particle diameter is within a range of 5-25mum, and the toner has particle size containing 3- 50% in the number of particles of <=5mum. Development is executed satisfactorily by a megnetic brush developing method by (1), the transfer characteristics can be improved and stabilized against humidity by (2), the development and the transfer characteristics can be improved by (3), and generation of ground fog can be prevented by (4).
Patent•
22 Sep 1981
TL;DR: In this article, a photographic sensitive material is manufactured contg. silver halide particles having >= 0.3mu average particle size after allowing an electron receptor such as pinacryptol yellow to be adsorbed on the particle surfaces.
Abstract: PURPOSE:To obtain a sensitive material provided with superior re-reversal characteristics by flash exposure by adding fogged silver halide particles a specified percentage or more of which has a particle size distribution within a specified average particle size after allowing an electron receptor to be adsorbed on the particle surfaces. CONSTITUTION:a photographic sensitive material is manufactured contg. silver halide particles having >=0.3mu average particle size after allowing an electron receptor such as pinacryptol yellow to be adsorbed on the particle surfaces. The particle size distribution of >=90wt% of all the particles is within + or -40% of the average size. The sum of the anode and cathode potentials of the receptor measured with ''Polarograph '' is positive. The material is a direct positive sensitive material with high sensitivity giving a reversal image and a re-reversal image at the same time by development after flash exposure for sec, and especially fine very small letters are formed.