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Showing papers on "Grain size published in 1968"


Journal ArticleDOI
TL;DR: In this article, the effects of pressure on electrical resistivity of 30 widely differing crystalline rocks was analyzed, and the effect of pressure of up to 10 kb on resistivity was found to be negligible.
Abstract: The effects of pressure of up to 10 kb on the electrical resistivity of 30 widely differing crystalline rocks is analyzed. For rocks of low porosity (0.01–0.001), degree of saturation affects both resistivity and the effect of pressure on resistivity. At low pressure the difference in the effect of pressure is particularly marked: a partially saturated rock becomes less resistive, whereas saturated rock becomes more resistive as the pressure increases. Porosity is the sole property which determines the high pressure resistivity of water-saturated rocks composed of nonconducting minerals. Grain size, mineralogy, and degree of alteration, when considered apart from porosity, have almost no effect. Variation in resistivity within one formation or rock type is as great as that among widely different rock types. At pressures above about 3 kb, we found close agreement with two empirical laws connecting resistivity, ρ, pressure, P, and porosity, η: ρrock/ρfluid = η−2 and 1/ρ (dρ/dP) = 0.10 kb−1. With the first relation, resistivity of a rock of known porosity can be calculated relative to fluid resistivity, and with the second, the effect of pressure of up to 10 kb. For a rock composed of conductive minerals, pressure at first decreases resistivity sharply and, then, has almost no effect. For rocks in which pressure causes collapse of pores, resistivity may either increase or decrease with pressure depending on initial connectivity of pores; an increase is the more common. Coarse-grained rocks containing calcite became abnormally resistive at high pressure owing to, we believe, flow of the mineral calcite, with sealing off of interstices. This would suggest the presence of local shearing stress in our hydrostatic experiments. There was no indication of flow in rocks containing dolomite, mica, or serpentine.

201 citations


Journal ArticleDOI

186 citations


Journal ArticleDOI
TL;DR: In this article, an explanation for this dependence and for other variations in the ductile-brittle behavior in terms of the theory and experiments underlying the (Hall-Petch) stress-grain size equations is given.

114 citations


Journal ArticleDOI
TL;DR: In this article, the theory of grain growth in the presence of a liquid phase was examined using modifications of equations derived for coalescence of solid particles widely dispersed in a liquid, and the interrelation of grain size, temperature, and time was in agreement with that predicted by the theory.
Abstract: The theory of grain growth in the presence of a liquid phase is examined using modifications of equations derived for coalescence of solid particles widely dispersed in a liquid. Although the grain diameter-time relation can still be represented by d3=kt, the absolute growth rates are increased as the amount of liquid is decreased. The grain growth kinetics in UO2 compacts containing 0.5 wtyo A12O3 were studied for temperatures between 1960° and 2200°C. The interrelation of grain size, temperature, and time is in agreement with that predicted by the theory.

85 citations


Journal ArticleDOI
01 Mar 1968-Wear
TL;DR: In this paper, the number and size of grooves formed on copper samples by sliding for a short distance in contact with silicon carbide abrasive papers was measured for various values of the applied load and for a wide range of abrasive grit sizes.

84 citations


Journal ArticleDOI
TL;DR: In this paper, the authors applied the grain size dependence of dislocation density to Cottrell's theory of the Portevin-Lechatelier effect, and showed that the critical strain ∊0, necessary to initiate serrated flow, should depend on the grain sizes at constant strain rate, according to the relationship ∊ 0 = (constant)μ p, where p=n/(m + β).
Abstract: When the grain size dependence of dislocation density is applied to Cottrell's theory of the Portevin–Lechatelier effect, the result indicates that the critical strain ∊0, necessary to initiate serrated flow, should depend on the grain size μ, at constant strain rate, according to the relationship ∊0 = (constant)μ p , where p=n/(m + β). The parameters n and (m + β) are evaluated by dislocation density measurements and strain rate experiments respectively to give ∊0 ∝ μ½. Direct experimental determination of ∊0 as a function of grain size is in agreement with that predicted theoretically, indicating that the effect arises from the influence of grain size on the average velocity of mobile dislocations. The period and amplitude of the serrations decrease with increasing grain size. This effect is consistent with the idea that each serration corresponds to a yield point followed by a local Luders strain. The period and amplitude of the serrations decrease with increasing grain size. This effect is co...

74 citations


Journal ArticleDOI
TL;DR: In this paper, an experimental investigation of the ratio of grain boundary curvature to grain size is reported, from which it is deduced that the terminal grain size determined by inclusions should be about an order of magnitude less than that predicted by the Zener formula in its usual form.
Abstract: An experimental investigation of the ratio of grain boundary curvature to grain size is reported, from which it is deduced that the terminal grain size determined by inclusions should be about an order of magnitude less than that predicted by the Zener formula in its usual form. It is demonstrated that the Zener formula does not necessarily include the condition that each boundary is impeded by an inclusion, and a supplementary condition is derived to cover this possibility.

67 citations


Journal ArticleDOI
TL;DR: In this paper, the microstructure of Sic from methyltrichlorosilane in a fluidized bed was studied over a range of deposition temperatures, carrier gas flow rates, and reactant fluxes.
Abstract: Vapor deposition of Sic from methyltrichlorosilane in a fluidized bed and the microstructure of the deposit were studied over a range of deposition temperatures, carrier gas flow rates, and reactant fluxes. The rate-determining factor for the deposition of Sic was the rate of supply of reactant. The microstructure of vapor-deposited Sic was primarily dependent on the deposition temperature; however, carrier gas flow rate and reactant flux had a secondary influence on microstructure. At low temperatures and high carrier gas flow rates, laminar deposits containing excess silicon were produced. At higher temperatures and lower carrier gas flow rates deposits were characterized by faulted columnar grains. The grain diameter increased from about LP at 1400°C to about 15 μ at 1800°C. The grain size also increased, but less markedly, with increasing reactant flux. The deposits characterized by columnar grains were predominantly β-Sic with traces of a-SiC and excess carbon.

65 citations


Journal ArticleDOI
TL;DR: In this paper, a polycrystalline spinel (MgA12O4), hot-pressed in graphite dies, yielded densities ranging from ∼64 to ≊100% of theoretical average grain size of compacts.
Abstract: Polycrystalline spinel (MgA12O4), hot-pressed in graphite dies, yielded densities ranging from ∼64 to ≊100% of theoretical Average grain size of compacts varied from 4 to 125μ depending on hot-pressing conditions Room-temperature mechanical properties also varied widely; average strengths for the 15 experimental combinations ranged from 3500 to 34,000 psi in bending and from 21,700 to 389,000 psi in compression, and Young's modulus ranged from 054 X lo7 to 35 X 107 psi Variations in bulk density, average grain size, room-temperature transverse and compressive strengths, and Young's modulus of elasticity were separately expressed as multiple quadratic regressions in terms of 1/T (temperature), In t (time), and P(pressure) over the hot-pressing range 1227’to 1750°C, 5 to 320 min, and 1000 to 3000 psi From these regressions, empirical equations expressing mechanical properties in terms of regression solutions of density and grain size were derived which statistically indicate a principal dependence on density and only a minor grain size dependence

65 citations


Journal ArticleDOI
TL;DR: In this article, the electron microscope was used to examine polycrystalline nickel (grain size 0.04 mm) after annealing and then after plastically straining at room temperature to between 0.4 and 12% elongation.
Abstract: Polycrystalline nickel (grain size 0.04 mm) has been examined with the electron microscope after annealing and then after plastically straining at room temperature to between 0.4 and 12% elongation. In addition to measuring the grain-interior dislocation density (ρ, cm/cm3), the number (n) per cm3 of three-fold nodes was counted and the arrangement and density (p, cm/cm2) of dislocations in the grain boundaries was examined. The applied tensile stress σ = 1.4 Gb ρ½ = 1.3 Gb n⅓ (where G is the shear modulus, b the Burgers vector). The node density was high and the dislocation network tightly linked at all strains, which is a necessary feature if attractive junctions are to contribute substantially to the flow stress. Straining evidently does not change the shape of the network so much as refine it, and the refinement is presumably the essential feature of strain-hardening. Superimposed on the refinement there developed the normal cellular structure. The grain boundaries trapped dislocations and he...

64 citations


Journal ArticleDOI
TL;DR: In this article, a study of 22 cores confirms that certain bulk and textural properties of deep-sea sediments have a definite bearing on the transmission speed of sound through marine deposits.
Abstract: A study of 22 cores confirms that certain bulk and textural properties of deep-sea sediments have a definite bearing on the transmission speed of sound through marine deposits. The higher the porosity, moisture content, and void ratio, the lower is the sound velocity. Increases in wet density are matched by increases in transmission speeds. There is no apparent correlation between sound velocity and either dry density or carbonate content. Shear strength is not a reliable index of transmission speed. Sound velocity is strongly related to grain size. Turbidites have high velocities, ash layers have intermediate velocities, and deep-sea muds and clays have low velocities. There is a relation between transmission speed and sorting, skewness, and transformed kurtosis, but these size measures are dependent upon mean grain size. Grain size governs the bulk and textural properties of unconsolidated marine sediments and is the most important physical property in determining the acoustical nature of deep-sea cores.

Journal ArticleDOI
TL;DR: In this paper, the effects of hydrostatic pressure on the fracture stress of polycrystalline metals have been analyzed in the dislocation pileup model of Stroh and the wall splitting model of Friedel.
Abstract: The dislocation pileup model of Stroh and the wall splitting model of Stroh and Friedel have been used to calculate the effects of hydrostatic pressure on the fracture stress of polycrystalline metals. For each model, the three critical stages of fracture, nucleation, propagation through a grain, and the propagation across a grain boundary have been considered in turn. The variation of the critical cleavage‐crack orientation with respect to the tensile axis has been shown to be a function of the hydrostatic pressure. The fracture stress depends upon the grain size and at high pressures where grain boundary propagation is the critical stage, a d−1/2 dependence was found. This analysis both predicts and provides a physical interpretation of the ductility‐transition curve.

Journal ArticleDOI
TL;DR: In this paper, tensile creep tests from −3° to −13°C at stresses between 2×105 and 2×106 dyn/cm2 with millimeter range grain-size polycrystalline ice showed that the strain rate was proportional to the stress, and that the viscosity was proportionally to the grain size squared.
Abstract: Tensile creep tests from −3° to −13°C at stresses between 2×105 and 2×106 dyn/cm2 with millimeter range grain‐size polycrystalline ice showed that the strain rate was proportional to the stress, and that the viscosity was proportional to the grain size squared. The flow process had an apparent activation energy of 12 kcal/mol. Calculated diffusion coefficients were several orders of magnitude larger than directly measured diffusion coefficients for single crystals. Enhancement of the diffusion rate in a wide band adjacent to grain boundaries is believed to account for the observed behavior. Previously reported data for ice sintering are interpreted on the same model.

Journal ArticleDOI
TL;DR: In this paper, the tensile properties of ordered and disordered Ni3Fe single crystals have been investigated using X-ray techniques and it was found that in ordered single crystals, the measured tensile axis rotation agrees well with the calculated values if one activated glide system is assumed.
Abstract: The tensile properties of ordered and disordered Ni3Fe single crystals have been investigated. Also, polycrystalline specimens have been tested to show the influence of grain size on the deformation characteristics of Ni3Fe. Measurements have been made to determine the influence of parameters such as the initial orientation of the tensile axis of single crystals, the ordered domain size, and the test temperature on the mechanical properties of Ni3Fe. Tensile axis reorientation during deformation was followed with X-ray techniques. It was found that in ordered single crystals, the measured tensile axis rotation agrees well with the calculated values if one activated glide system is assumed. The influence of secondary slip on the tensile characteristics of ordered crystals was determined by using specimens oriented for multiple glide. It is demonstrated that the work hardening rate increases with the occurrence of secondary slip. The strain-aging phenomena shown previously in polycrystalline Ni3Fe was found to occur also in single crystals. The nature of the observed effects in ordered Ni3Fe is interpreted in terms of the antiphase boundary tube mechanism.

Journal ArticleDOI
TL;DR: In this article, the theory of Clarke for the formation of grain boundary cracks in anisotropic polycrystalline materials, is re-examined in the light of recent experimental data.
Abstract: The theory of Clarke for the formation of grain boundary cracks in anisotropic polycrystalline materials, is re-examined in the light of recent experimental data. The theory predicts correctly the conditions for the formation of grain boundary cracks of length similar to a grain dimension. However, the theory cannot be used to explain the experimentally observed strength/grain size and strength/irradiation dose relationships, for example for BeO. The theory supposes that the process controlling catastrophic fracture is the growth of a crack from a grain boundary pore with an energy absorption rate corresponding to the grain boundary surface energy of ∼103 erg/cm2. In practice, the process controlling catastrophic fracture is the subsequent growth of a crack from a grain dimension, with a higher energy absorption rate corresponding to an effective surface energy of ∼104 erg/cm2.

Journal ArticleDOI
TL;DR: In this article, the effect of grain size on the elastic wave amplitude was investigated with plane wave explosive loading experiments on SAE 1018 mild steel, and it was concluded that dislocations do not move sufficient distances to interact significantly with grain boundaries.

Journal ArticleDOI
TL;DR: In this article, the influence of grain size of the fluorescent phase on the intensity of the characteristic radiation of the investigated element is investigated and a theory of this effect is proposed on the basis of the model assumed by the authors.

Journal ArticleDOI
TL;DR: In this paper, the average size of the particles in submicron nickel is determined from a comparison of various measures of breadth of broadened profiles with the breadths of ''standard' lines.
Abstract: The procedure for interpreting broadened diffraction maxima in terms of particle size is illustrated by means of two samples of nickel powder. The average size of the particles in submicron nickel is determined from a comparison of various measures of breadth of broadened profiles with the breadths of `standard' lines. Information about the shape of the particles and an indication of the distribution of size are also obtained. The size from X-ray methods (about 200 A) is in close agreement with the value obtained from electron micrographs of the powder, indicating that the grains observed in the latter are mainly single crystals. The limitations of this technique are discussed for cases in which diffraction broadening is not appreciable. An advantage of the variance as a measure of breadth is that it provides a direct method of investigating crystal imperfections. Data from a sample of carbonyl nickel powder, with an average grain size of 5.5 μm, are used to illustrate this method. The mean particle size is 650 A, indicating that each grain consists of several coherently diffracting regions, or 'particles' as determined by X-ray methods.

Journal ArticleDOI
TL;DR: In this paper, the effect of particle size on the luminescence efficiency of LiF exposed to monochromatic X-rays and γ-rays has been studied.
Abstract: The variation with particle size of the luminescence efficiency of LiF exposed to monochromatic X-rays and γ-rays has been studied. The efficiency has been found to decrease considerably with particle size, and the magnitude of the effect depends on the photon energy. The effect could, among other factors, be due to an ` inactive ' surface layer.

Journal ArticleDOI
TL;DR: In this paper, a suite of igneous, metamorphic, and sedimentary rocks which had been artificially fragmented to five size fractions were studied to determine changes in textural properties with progressive size reduction and the feasibility of identifying parent rock textures in fragments ranging from granule to fine sand size.
Abstract: An experimental study was conducted on a suite of igneous, metamorphic, and sedimentary rocks which had been artificially fragmented to five size fractions: granule, very coarse sand, coarse sand, medium sand, and fine sand. These fractions were studied to determine changes in textural properties with progressive size reduction and the feasibility of identifying parent rock textures in fragments ranging from granule to fine sand size. The diagnostic textures of all the rocks studied are preserved to essentially the same degree in granule-sized fragments as in thin sections of parent rocks. Identification is less reliable in smaller sizes and depends upon the mean grain size and sorting of the parent rock.


Journal ArticleDOI
TL;DR: In this article, the authors measured the change in curvature of circular substrates with an interferometer and determined the residual stress in Co-Ni-Fe and Ni-Fe films.
Abstract: The stress measured at 25°C in vapor‐deposited Co‐Ni‐Fe and Ni‐Fe films was investigated as a function of composition, grain size, substrate temperature, film thickness, and annealing parameters. The stress was determined by measuring the change in curvature of circular substrates with an interferometer. Various compositions were studied. The ranges of each constituent were 0%–50% Co, 50%–90% Ni, and 10%–50% Fe. A dependence of stress on composition existed even when the substrate temperature and grain size remained constant.The residual stress has a nearly parabolic dependence on substrate deposition temperature with a minimum in the vicinity of 275°C. This is in general agreement with the results for Ni‐Fe films using different techniques and previously reported by Weiss and Smith.The stress is nearly constant for film thicknesses 1000–10 000 A and can be reduced by annealing, provided the annealing temperature is greater than the temperature of deposition.



Book ChapterDOI
01 Jan 1968
TL;DR: In this paper, carbonate sediments of different grain size and with different carbonate content were compacted under pressures of up to 650 atm. The reduction of porosity with increasing pressure as well as the progress of compaction with time at constant pressure and their dependance on grain size, temperature and chemical nature of the pore medium were evaluated and presented graphically.
Abstract: Recent carbonate sediments of different grain size and with different carbonate content were compacted under pressures of up to 650 atm. The reduction of porosity with increasing pressure as well as the progress of compaction with time at constant pressure and their dependance on grain size, temperature and chemical nature of the pore medium were evaluated and presented graphically. Of special importance for a comparison with natural processes is the differentiated investigation of the various interdependent mechanisms which produce compaction: reorientation of the individual grains, plastic and shear deformation of the components and chemical processes such as pressure solution and solution transport.

Journal ArticleDOI
A. Baltz1
TL;DR: In this article, the effect of annealing on the microstructure of cylindrical electrodeposited 81-percent Ni, 19-percent Fe films was studied with the electron microscope.
Abstract: The effect of annealing on the microstructure of cylindrical electrodeposited 81-percent Ni, 19-percent Fe films was studied with the electron microscope. The films were deposited onto 5-mil Be-Cu wires having either Au or Cu intermediate layers. The annealing was performed on both free-standing films and on films still attached to the substrate. The initial change in the free-standing films was a rapid recrystallization. After the whole film had recrystallized, normal grain growth was observed. There is evidence that the driving force for the annealing is provided by stresses present in the films. Films annealed while attached to a Au-Be-Cu substrate did not exhibit recrystallization or grain growth, and the electron microscope studies showed that the Ni-Fe grains were pinned by Be-Au which diffuses into the grain boundaries but does not alloy with the Ni-Fe. The films which were annealed while attached to a Cu-Be-Cu substrate behaved essentially like free-standing films. Electron beam microanalysis and electron diffraction studies revealed that Be-Cu diffuses into the Ni-Fe grain boundaries and then alloys with the Ni-Fe. Recrystallization of the alloy can then take place freely.

Journal ArticleDOI
TL;DR: In this paper, the authors measured the induced thermoremanent moment in selected samples, and the results seem to agree with past work in the field in that small ferromagnetic aligned clusters of 0.2 ± 0.1μ diameter exist in an essentially nonmagnetic matrix.
Abstract: Samples of naturally occurring beach sand ilmenite from Swansea, New South Wales, and Capel, Western Australia, were used. In general, the magnetic properties were found to be independent of grain size for grains larger than about 10μ. It was found that oxidizing the ilmenite in air at temperatures between 700° and 750°C leads to a more magnetic form of ilmenite, whilst annealing these samples further enhances their magnetic properties. Samples which were heated in excess of 800°C were nonmagnetic. The measurement of the induced thermoremanent moment in selected samples allows the domain configuration to be postulated, and the results seem to agree with past work in the field in that small ferromagnetically aligned clusters of 0.2 ± 0.1μ diameter exist in an essentially nonmagnetic matrix.

Patent
15 Jan 1968
TL;DR: In this paper, a movie of a cartoon of a stylized version of a lion cub is shown on an ELECTRICALLY INSULATING SURFACE of a substrate.
Abstract: A FILM OF A POLYCRYSTALLINE MATERIAL IS DEPOSITED PYROLYTICALLY ON AN ELECTRICALLY INSULATING SURFACE OF A SUBSTRATE. BY CONTROLLING THE RATE OF DEPOSITION OF THE MATERIAL ON THE SUBSTRATE AND THE TEMPERATURE OF THE SUBSTRATE, THE GRAIN SIZE OF THE POLYCRYSTALLINE FILM IS REGULATED SO THAT PN JUNCTIONS HAVING A SHARP REVERSE BIASED BREAKDOWN MAY BE FORMED THEREIN.

Journal ArticleDOI
TL;DR: In this paper, the use of carbon as grain growth inhibitor gave a density of 99% theoretical at 0.7μm grain size, and an extension of the procedure gave a range of electrically conducting ceramics.
Abstract: The techniques of slow sintering, addition of a volatile flux, and grain growth inhibition have been used to produce high density sintering in pure barium titanate. The use of carbon as grain growth inhibitor gave a density of 99% theoretical at 0.7μm grain size. This technique may be used for other suitable ceramics, when the proposed application requires improved physical properties. An extension of the procedure gives a range of electrically conducting ceramics.

Patent
27 Nov 1968
TL;DR: In this paper, the material consists of blast furnace slag pref. containing SiO2, Al2O3 and CaO and having a grain size up to 10 mm and a specific gravity of 900 to 1000 kg/m3.
Abstract: The material consists of blast furnace slag pref. containing SiO2, Al2O3 and CaO and having a grain size up to 10 mm (preferably 3 mm) and a specific gravity of 900 to 1000 kg/m3. The slag is mixed with strongly absorbing material, pref. dried clay, with a grain size no greater than 50u (pref. 30u). The clay is pref. added in amounts of 5 wt.% of the slag.