Showing papers on "Particle-size distribution published in 1970"

Magnetic Properties of Stable Dispersions of Subdomain Magnetite Particles

Abstract: Stable colloidal dispersions of subdomain‐size magnetic particles have been prepared that retain their liquid characteristics in the presence of a magnetic field. Magnetization versus applied field curves were obtained as a function of particle size and volumetric solids concentration for magnetite dispersions in a wide variety of carrier liquids. The magnetic properties of these colloidal dispersions have been corrolated by superparamagnetic theory in terms of the size distribution of the suspended particles and their volumetric concentration, correcting for the formation of a nonmagnetic surface mantle one‐unit‐cell thick.

The scattering of polarized light by polydisperse systems of irregular particles

Abstract: The elements of the Mueller matrix for polydisperse systems of irregular, randomly oriented particles have been measured in absolute terms as a function of scattering angle for two wavelengths. These results have been compared to the matrix elements that were calculated for assemblies of spherical particles that fit the same particle size distribution function and have the same (real) refractive index.

Light scattering and suspended particles in the eastern equatorial Pacific Ocean

Abstract: The total light scattering coefficient, the volume scattering function at 45°, and the suspended particle size distribution have been determined at the surface, at the depth of maximum turbidity, and at 100 meters at several stations in the eastern equatorial Pacific. The total scattering coefficient and volume scattering function were also measured at several other depths. Total light scattering was measured in situ with a b meter, the volume scattering function was measured in the ship's laboratory with a Brice-Phoenix light scattering photometer, and particle size distributions were determined in the ship's laboratory with a Coulter Counter. The total scattering coefficient is directly proportional to the volume scattering function at 45°. The total number of observed particles, total particulate cross section, and total particulate volume per cubic centimeter of sea water were computed from the measured particle size distributions. Both the total scattering coefficient and the 45° volume scattering function are roughly proportional to these properties of the suspended particles. A significant fraction of the light scattering is believed to be due to particles smaller than 1 μ, which were not measurable by the Coulter Counter.

Determination of particle size distribution

Abstract: In a method for determining the particle size distribution in a fluid stream wherein the concentration of one size fraction is compared with that of another, the concentration of a given fraction is determined by determining the rate of accumulation of the material of that fraction over a series of successive short time intervals.

Limitation of Griffith Flaws in Glass-Matrix Composites

Abstract: The effect of the limitation of Griffith flaws, introduced in an abraded surface of glass, on the strength of glass-tungsten composites was investigated for small sizes of Griffith flaws. Hasselman and Fulrath's proposed fracture theory for this type of system extended to small flaw sizes. The use of tungsten spheres with two particle sizes or a wide distribution about one average size as the dispersed phase in a glass matrix decreased the average mean free path in the matrix more than could be achieved with a single particle size dispersion. Average mean free paths determined experimentally by statistical techniques were in good agreement with those calculated by Fullman's equation. This technique was successfully used when the dispersed phase had two particle sizes or a wide particle size distribution. The strong effect of internal stresses caused by a mismatch of thermal expansion of the phases in reducing the strength of a composite was demonstrated.

Motion of Single Particles in Alluvial Channels

Abstract: Movements of single sand-size radioactive particles were followed in a laboratory alluvial channel. Two sizes of bed material were used with experimental conditions limited to the ripple and dune bed forms of the lower flow regime. It was found that the frequency distribution of the particle step lengths was represented very well by the gamma distribution, and the frequency distribution of the particle rest period was represented adequately by the exponential distribution. The mean step lengths related well to the stream power of the flow; however, the relation cannot be considered general because observations were limited to a single depth of flow. The mean rest period related well to the celerity of the bed forms. Tests of a one-dimensional stochastic model for sediment dispersion showed that the model predicted the mean distance traveled by the tracer particles but did not predict the rate of spreading of the tracer concentration distribution.

Catalyst prepared by homogeneous precipitation under high temperature and pressure

Abstract: A process for preparing a catalyst comprising a metallic catalytic agent on a particulate carrier is disclosed which provides improved uniformity of distribution and fineness of division with narrowness of particle size distribution of the metallic catalytic agent on the carrier. The particles of carrier are suspended by agitation in an aqueous solution of a salt of the metallic catalytic agent and of a source, on heating in aqueous solution, of hydroxyl ions. The suspension is heated in a sealed vessel above 100 DEG C to precipitate the metal or the particles with uniformity of distribution and fineness of division with narrowness of particle size distribution. The metal is converted by conventional procedures to the appropriate active, oxidized or reduced, state. The process is particularly significant with carriers, such as alumina and silica, that in alkaline media are liable to undergo structural charges.

Method and means for automating computer-controlled production of particulate materials

Abstract: The particle size and particle size distribution of the particulate TiO2 solids in a solids burdened reaction product gas produced in a vapor phase process for making pyrogenic TiO2 are measured by diluting a sample of the solids burdened gas by an order of magnitude of at least about 1012 and feeding the diluted sample to measuring-means in the form of a multi-channel light scattering sensor the read-out of which constantly measures the particle size and particle size distribution of the particulate solids in the reaction product gases being produced. It is, of course, well known that particle size and particle size distribution of particulate TiO2 particles may be correlated with the optical properties of the pigment. Hence the read-out of the light scattering sensor will be indicative of the quality of TiO2 pigment being produced and may be usedd manually i.e. visual observation or by electronic means to effect adjustments in the appropriate plant operational controls so as to maintain the optical properties of the pigment substantially constant and at optimum levels throughout a plant run.

Particle size distribution in various zones of a spray jet

Abstract: The results of an investigation of the size distribution of particles suspended at various points in an axisymmetric spray jet are presented.

Preparation and Analyses of Ultrafine Pure Iron Particles

Abstract: Ultrafine pure iron particles have been prepared by carefully controlled thermal decomposition of dilute iron pentacarbonyl vapor with hot helium. The particle size distribution of the prepared sample was extremely narrow, averaging 120 A diameter. Particle size distribution was analyzed by electron micrography and confirmed by the B.E.T. method and x-ray line broadening. Chemical analyses and electron diffraction showed the sample to be essentially pure iron. The particles though smaller than the critical size for superparamagnetism, due to interparticle interaction, did not have this property.

Particle-Size and Particle-Size Distribution of Microcapsules Prepared by The Interfacial Polymerization Method

Abstract: くな されてい る。 ここでは,粉 体工学におけ る造粒の考 え方を も加味 してマ イク官カプセル化技術,特 に粒径お よび粒径分布 につい て解説す る。 マ イクPtカ プセル(microcapsules)は 一般に粒径がお よそ200μ 以下 の顕微鏡的 な高分子 の微 小 容 器 を意 味 し,内 容物 の保護,内 容物 の放 出の調節 な どの機能 をも ってい る。現在 までにカプセル化 が行 なわれた 内容物質 には,ペ イ ン ト,食 品,医 薬 品,触 媒,イ ンキ,顔 料, 樹脂,溶 媒,安 定剤,染 料,香 料,接 着剤,硬 化剤,発 泡剤,農 薬,洗 剤,バ クテ リア,ビ ールス,そ の他 な ど 数多 くあ り,こ れ らの応用面 についての詳 しい解説 はす でに他誌1)に なされ ているので参照 され たい。 マイ クロカプセルの世界最初 の商 品化 はア メ リカのN CR(ナ シ ョナル金銭登録機iK.K)に よって行 なわれ, その商 品が感圧複写紙であ った ことは周 知 の通 りで あ る。化学 的なマイ クロカプセルの製 法は現在 の ところ コ アセルベ ーシ ョン法(coacervationrnethod)と 界 面 重 合法(interfacialpolymerizationmethod)が 主な もの であ るが,こ の感圧紙お よびその後の大部分 の商 品は コ アセルベ ーシ ョン法に よって作 られた ものであ った。最 近では界面重合法で調製 されたマ イク旨カプセル化商品 も出現 してい るよ うであ る。 コァセルベ ーシ ョンはマ イクρカプセル化に とって重

Determination of Size Distribution of Condensed Metal Particles

Abstract: A method was developed for measuring the size distribution of particles condensed from metal vapor, at ambient conditions. Particles were collected on a carbon coated surface of mica cleaved along its crystal plane and were shadowed with chromium. The collected samples were photographed through an electron microscope. Size distributions were determined by actual count of the particle images in the photographs after enlargement. The metal vapor was obtained by evaporating metal wires electrically (exploding) at ambient conditions. Primarily platinum wire was used but some zinc and iron were also employed. While the kind of metal and the amount of energy transferred play a role, in all cases it was shown that the particle size distribution is much wider than the distribution of particles from condensation in supersonic nozzles. There appear to be definite limits to the flow fields for which the common assumption that condensed particles are uniform in size is valid.

The Formation and Characteristics of Powders by Wire Explosion (2nd Report)

Abstract: The formation of powders in an electric discharge with heavy current through a metallic wire in the atmosphere was studied, and the characteristics of the resulting powder were examined.The results obtained were as follows.(1) The powders obtained at the optimum conditions had a wide particle size distribution. Coarse particles were spherical similar to atomized ones.(2) With increasing discharging voltage, particles of molybdenum powder became fine. As for tungsten, the above mentioned tendency was not confirmed with X-ray diffraction line breadth alone.(3) In the atmosphere, metallic powder was collected mainly in an acryl case, and the particle size had a wide distribution.However, in a vacuum cleaner, the ultra fine oxide powder (aerosol) was mainly collected.(4) The alloy powder was formed easily from alloy wire by wire-explosion method.(5) As for molybdenum, with increasing discharging voltage, the latice spacing increased.