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Showing papers on "Grain size published in 1973"


Journal ArticleDOI
TL;DR: In this article, an investigation was made of the relations among porosity, permeability, and texture of artificially mixed and packed sand, to determine the approximate porosity and permeability values to be expected for unconsolidated sand of eight grain-size subclasses and six sorting groups.
Abstract: An investigation has been made of the relations among porosity, permeability, and texture of artificially mixed and packed sand, to determine the approximate porosity and permeability values to be expected for unconsolidated sand of eight grain-size subclasses and six sorting groups. The sand samples were prepared so that the weight fractions were distributed normally about the median grain size. Porosity values were determined for two packings, designated as "dry-loose" and "wet-packed." Porosity data for "wet-packed" sand samples remain about the same for changes in grain size of a given sorting, but decrease from an average of 42.4 percent for extremely well-sorted sand to 27.9 percent for very poorly sorted sand. These experimental data agree within 5 porosity percent with framework porosity values obtained for natural packing of 25 Holocene barrier-island sand samples of a limited size-sorting range, and appear to be representative of minimum porosities expected for natural packing of most unconsolidated, clay-free sand. The 48 artificially mixed and wet-packed experimental sands selected for porosity measurement also were used to determine permeability. Inasmuch as there are some irregularities in the experimental data caused by the inability to pack each sample uniformly, an average adjusted permeability value has been calculated. The average adjusted permeability values become progressively lower with decreasing grain size and poorer sorting, and agree well with permeability values computed by the Krumbein and Monk formula for most grain-size and sorting classes. Reference photographs or visual textural comparators enable a rapid estimation of grain shape, roundness, size, and sorting. Grain-size-sorting comparators, representing photomicrographs of thin sections of the porosity and permeability test samples, are especially useful in estimating original textural parameters form thin sections of severely compacted and silica-cemented sandstones.

734 citations


Journal ArticleDOI
TL;DR: In this article, a group of transparent ferroelectric hot-pressed (Pb0.92La0.08)-(Zr0.65Ti0.35)0.98O3 specimens with controlled grain size and constant porosity were prepared.
Abstract: A group of transparent ferroelectric hot-pressed (Pb0.92La0.08)-(Zr0.65Ti0.35)0.98O3 specimens with controlled grain size and constant porosity and a group of similar specimens with controlled porosity and constant grain size were prepared. The electrical and optical constants and polarization-reversal properties of these ceramics were determined as functions of grain size and porosity. When poled PLZT ceramics were aged, the polarization-reversal characteristic was quite asymmetric, apparently because a space-charge field, E8p, was generated during aging. From a detailed study of the behavior of the E8p, including its (1) generation with increasing aging time, (2) relaxation with repeated polarization reversals, (3) relaxation by heat depolarization, and (4) grain-size and porosity dependence, it is concluded that the space-charge layer is present inside every domain. This layer also explains the grain-size dependencies of the remanent polarization, piezoelectric constants, and Curie point.

408 citations


Journal ArticleDOI
TL;DR: In this paper, a new analytical approach to polycrystal work hardening was devised to understand and describe these data, together with data on 70-30 brass, and it was shown that large-strain cell size in copper ought to depend on grain size, was verified by direct measurement.

309 citations


Journal ArticleDOI
TL;DR: In this paper, an energy criterion was proposed to explain the grain-size effect on microcracking in ceramics exhibiting high degrees of thermal expansion anisotropy, and the results showed that grain sizes smaller than ∼3 μm exhibited none of the micro-cracking attributed to thermal expansion aisotropic properties, whereas those with larger grains had all the characteristics.
Abstract: Properties relating to the effects of thermal expansion anisotropy were measured as functions of grain size in hot-pressed dense MgTi2O5. Samples with grains smaller than ∼3 μm exhibited none of the microcracking attributed to thermal expansion anisotropy, whereas those with larger grains had all the characteristics. An energy criterion is proposed to explain the grain-size effect on microcracking in ceramics exhibiting high degrees of thermal expansion anisotropy.

247 citations


Journal ArticleDOI
TL;DR: In this paper, a geologically useful plot is separated into fields by three boundaries which meet at a triple point; within each field, either lattice diffusion, grain-boundary diffusion, or a dislocation flow law is predominant.
Abstract: Rocks which deform by pressure solution obey a diffusion flow law with a linear viscous or Newtonian stress to strain-rate relation. Undeformed relics of original grains preserved within newly grown crystals at grain boundaries under tension and presolved surfaces, together with accumulation of inert particles at grain boundaries under compression, are diagnostic evidence of a diffusion flow law. At a given stress, strain-rate is inversely proportional to the grain size to a power of two or three. A geologically useful plot has inverse temperature versus the logarithm of grain size as coordinates. Such a graph is separated into fields by three boundaries which meet at a triple point; within each field, either lattice diffusion, grain-boundary diffusion, or a dislocation flow law is predominant. It may be possible to calibrate this graph from naturally deformed rocks. Photomicrographs of isoclinally folded greenschist-grade quartzites and rhyolitic flows from the South Mountain–Blue Ridge area in Maryland demonstrate a diffusive mass transfer deformation mechanism, but estimates of effective diffusion coefficient compared to currently available laboratory diffusion data are insufficient to identify the diffusion path with certainty. However, the comparatively low ratio of metamorphic temperature to melting temperature and the physical nature of grain boundaries in metamorphic rocks, particularly concentrations of low-density impurities at grain boundaries, suggest the grain-boundary diffusion flow law.

233 citations


Journal ArticleDOI
TL;DR: In this article, the effect of superplastic deformation on the grain growth kinetics was studied using both constant crosahead speed and creep tests, the grain size was measured as a function of deformation time and strain over a wide range of strain rates.

156 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of grain size on the apparent yield and flow stresses is investigated in polycrystalline aluminum of various grain sizes in the temperature range from 77 to 473°K.

125 citations


Journal ArticleDOI
TL;DR: In this paper, a simple model for current conduction in polycrystalline silicon is described based on grain size, grain doping, and effective barrier height due to the grain boundary, which satisfactorily explains the observed temperature dependence of the resistivity of undoped films and also the large values of resistivity which are observed for dopant concentrations.
Abstract: Polycrystalline silicon is deposited by pyrolysis of silane in an rf heated epitaxial reactor. The grains exhibit a fibrous microstructure having an 〈110〉 preferred orientation in the growth direction. Growth is inhibited in the presence of excess arsine and accelerated in the presence of diborane. The results are explained in terms of catalysis and poisoning of surface adsorption sites responsible for reaction. A simple model for current conduction in polycrystalline silicon is described based on grain size, grain doping, and effective barrier height due to the grain boundary. This model satisfactorily explains the observed temperature dependence of the resistivity of undoped films and also the large values of resistivity which are observed for dopant concentrations .

116 citations


Journal ArticleDOI
Guy Deutscher1, H. Fenichel1, M. Gershenson1, E. Grünbaum1, Zvi Ovadyahu1 
TL;DR: In this article, the average grain size is reduced and critical temperature is increased when the oxygen content is increased and the mean free path becomes smaller than the grain size, indicating a build up of insulating barriers between the grains.
Abstract: Granular aluminum films prepared by evaporation in the presence of oxygen show two different behaviors when the oxygen content is increased. First, the average grain size (as measured by the dark-field electron microscopy technique) is reduced and the critical temperature is increased. This increase is neither due to a variation of the lattice parameter which, following our measurements, stays constant and equal to the value of pure Al, nor to a purely electronic effect linked to the small grain size, because in this first regime the grains are essentially in good electrical contact. In a second stage, the average grain size changes little but the mean free path becomes much smaller than the grain size, indicating a build up of insulating barriers between the grains. The critical temperature decreases and the transition becomes broader as the normal-state resistivity increases. We attribute this behavior to the appearance of large critical fluctuations, due to the fact that the decoupled grains tend to have a zero dimensionality.

111 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of interstitial solute content and grain size on the deformation kinetics and strain hardening in titanium were investigated over the temperature range of 4.2 to 650°K and compared with previous results on single and polycrystals.

111 citations


Journal ArticleDOI
TL;DR: In this article, it has been shown that the limiting grain size is itself temperature dependent, increasing with increasing temperature and decreasing with increasing burn-up, which can be interpreted in terms of a rate equation, due to Burke, which supposes that grain growth continues only until some limiting size has been attained.

Journal ArticleDOI
TL;DR: In this paper, a mass transport equation which takes into account parallel diffusion paths for anions and cations was derived and applied to the diffusional creep of polycrystalline ionic solids.
Abstract: A mass transport equation which takes into account parallel diffusion paths for both anions and cations was derived and applied to the diffusional creep of polycrystalline ionic solids. From the results of the analysis, several limiting conditions were found for grain-boundary- and lattice-diffusion-controlled kinetics. These conditions depend on temperature, grain size, and type and concentration of cation impurities. Examples of these limiting situations are given for the creep of polycrystalline Fe-doped MgO and transition-metal-doped Al2O3. Summary A mass transport equation which takes into account parallel diffusion paths for anions and cations was derived and applied to the diffusional creep of polycrystalline ionic solids. The effect of grain size and cation impurities of variable valence in solid solution on the relative contributions of lattice and grain-boundary diffusion of different ionic species in polycrystalline MgO and Al2O3 was examined. Depending on the temperature, grain size, impurity level, and O2 partial pressure, several limiting conditions were found: Limit I: At very small grain sizes and reasonably small cation lattice diffusivities the creep rate will be controlled by the slower-moving ion in the grain-boundary regions (i.e. Coble creep). Limit II: For intermediate grain sizes and cation lattice diffusivities the creep rate will be controlled by cation lattice diffusion when anion transport is significantly faster near grain boundaries than in the lattice (i.e. Nabarro-Herring creep). Limit III: For an appropriate combination of large grain size and high cation lattice diffusivity the creep rate will be controlled by anion boundary diffusion (i.e. Coble creep). Well-defined examples of limits I and II have been observed in the creep of Fe-doped polycrystalline MgO, and tentative evidence exists for limit III. Most results of studies of creep in polycrystalline Al2O3 (doped and undoped) fall within limit II, with some overlap with limit III. The model developed in the present work explains much of the data in the literature in which creep rates correspond to cation lattice mobilities. It is concluded that in the creep of polycrystalline ionic solids anion transport near grain boundaries is rapid and can, in some circumstances, be rate-controlling. It should also be possible to apply this model to sintering and thermal-grooving data for such systems, particularly for Al2O3, in which cation lattice diffusion is frequently observed to be rate-controlling.32

Journal ArticleDOI
TL;DR: In this article, low-stress fatigue-crack propagation tests have been carried out on three commercially pure α-titaniumalloys and it was found that decreasing load ratio (R), increasing grain size, and increasing interstitial alloying content could all produce significant reductions in growth rate over the ∆K range studied (4-20 MN/m2).
Abstract: Low-stress fatigue-crack-propagation tests have been carried out on three commercially pure α-titaniumalloys. It was found that decreasing load ratio (R), increasing grain size, and increasing interstitial alloying content could all produce significant reductions in growth rate over the ∆K range studied (4–20 MN/m2). The conclusion was reached that the fatigue-fracture process comprised two stages: (1) the formation of relatively planar facets (primarily ∆K-controlled) and (2) their interconnection by a mechanism involving plastic tearing (primarily K max-controlled). Scanning electron microscope examination of the fatigue-fracture surfaces revealed that the orientations of individual grains exerted a considerable influence on fracture-surface morphology. This effect occurred when the scale of reversed plasticity at the crack tip was of the order of, or less than, the grain size. A transition in fracturesurface appearance occurred in all specimens at an approximately constant value of growth rate ...

Journal ArticleDOI
TL;DR: In this paper, a Hall-Petch relation was found not to describe work hardening in the cases of copper and aluminium, and an approach to poly-crystal workhardening, based in part on Ashby's concepts, was also unsuccessful in describing the behaviour of the same materials.
Abstract: Stress-strain data were obtained over a wide range of grain sizes for brass, copper and aluminium. A Hall-Petch relation was found not to describe work hardening in the cases of copper and aluminium. An approach to poly-crystal work hardening, based in part on Ashby's concepts, was also unsuccessful in describing the behaviour of the same materials. These results indicate the need for a new viewpoint on the influence of grain size on poly-crystal work hardening.

Journal ArticleDOI
01 Apr 1973
TL;DR: A comprehensive review of the currently available data for lunar grain size distributions has been made by as discussed by the authors, who concluded that there is little or no statistical difference among the large majority of the soil samples from the Apollo 11, 12, 14, and 15 missions.
Abstract: A comprehensive review has been made of the currently available data for lunar grain size distributions. It has been concluded that there is little or no statistical difference among the large majority of the soil samples from the Apollo 11, 12, 14, and 15 missions. The grain size distribution for these soils has reached a steady state in which the comminution processes are balanced by the aggregation processes. The median particle size for the steady-state soil is 40 to 130 µm. The predictions of lunar grain size distributions based on the Surveyor television photographs have been found to be quantitatively in error and qualitatively misleading.

Journal ArticleDOI
TL;DR: In this paper, the effects of both anodic and cathodic polarization on accelerated creep rates of oxide-free copper wires immersed in an acetate buffer solution at 25°C were studied.

Journal ArticleDOI
TL;DR: In this paper, the effects of porosity, pore distribution, and grain size on fracture energy were evaluated and a grain-size effect dominates in dense material; the fracture energy decreases with increasing grain size.
Abstract: Alumina specimens were fabricated under a wide range of conditions using cold-pressing and sintering techniques. Fracture energies were measured by an analytical technique (notched beam) and by the Tattersall-Tappin method. Problems in using the latter method are discussed. The effects of porosity, pore distribution, and grain size on fracture energy are evaluated. Connected porosity has a deleterious effect on fracture energy. A grain-size effect dominates in dense material; the fracture energy decreases with increasing grain size.

Journal ArticleDOI
TL;DR: In this article, lattice constants, grain size, electrical conductivity, and luminescence were measured for sintered BaTiO3 ceramics doped with 0 to 1.2% rare-earth ions.
Abstract: Lattice constants, grain size, electrical conductivity, and luminescence were measured for sintered BaTiO3 ceramics doped with 0 to 1.2 at.% rare-earth ions. BaTiO3 doped with low levels of rare-earth ions contains grains 10 μm in size and has lattice constants nearly equal to those of undoped ceramics. In this case, rare-earth ions occupy Ba2+ sites and yield donors. When grain growth is inhibited by high doping levels or by insufficient sintering, the lattice constants change, the rare-earth ions occupy both Ba2+ and Ti4+ sites, and, consequently, BaTiO3 becomes insulative because of charge compensation.

Journal ArticleDOI
TL;DR: In this article, the results showed that on the surfaces which gave good intercrystalline fracture, the Bi is strongly segregated within 1nm of the boundary and is uniformly spread over each boundary, and the amount of segregation varies from boundary to boundary.

Journal ArticleDOI
TL;DR: In this paper, the effect of ultrasonic agitation of the plating solution on the grain size, hardness, internal stress, porosity and brightness of electrodeposited metals is discussed.

Journal ArticleDOI
TL;DR: In this paper, the broadening and decrease of the superconducting transition temperature observed in high resistivity films of granular aluminum is analyzed in terms of a critical fluctuation model.
Abstract: The broadening and the decrease of the superconducting transition temperature observed in high resistivity films of granular aluminum is analyzed in terms of a critical fluctuation model. Detailed grain size measurements indicate that the enhanced transition temperature observed in lower resistivity films is due to changes in the electron-phonon coupling rather than to an excitonic mechanism.

Journal ArticleDOI
TL;DR: Magnetic domains in high-coercivity sintered Co5Sm magnets have been studied using polarized light as discussed by the authors, showing that large reverse fields are required to nucleate magnetization reversal.
Abstract: Magnetic domains in high-coercivity sintered Co5Sm magnets have been studied using polarized light. Grain boundaries block the propagation of magnetic reversal from grain to grain. General domain-wall pinning is low, and oversized grains show low-coercivity, multidomain behaviour. In most grains, however, once domain walls are removed, large reverse fields are required to nucleate magnetization reversal. Magnetische Bereiche in gesinterten, hoch-koerzitiven Co5Sm-Magneten wurden mit polarisiertem Licht untersucht. Korngrenzen verhindern die Verbreitung der Ummagnetisierung. Die Blochwandverankerung im Innern der Korner ist schwach, und grose Korner zeigen Viel-Domanen-Verhalten mit niedrigen Koerzitivkraften. Nachdem die Blochwande beseitigt werden, sind jedoch in den meisten Kornern hohe Gegenfelder notwendig, um Ummagnetisierungskeime zu bilden.



Journal ArticleDOI
TL;DR: The etching of prior austenite grain boundaries in martensite for detailed quantitative metallography of British standard En 18 steel has been carried out using aqueous or ethereal solutions of picric acid, whereas alcohol was an unsuitable solvent as discussed by the authors.

Journal ArticleDOI
TL;DR: In this article, the effect of stress, grain size and temperature on the creep rate of pure and two phase nickel-doped alumina has been investigated in the stress range 0.70 to 4.57 kgf mm−2 (1000 to 6500 psi).
Abstract: Creep in pure and two phase nickel-doped alumina has been investigated in the stress range 0.70 to 4.57 kgf mm−2 (1000 to 6500 psi), and temperature range 1450 to 1800° C, for grain sizes from 15 to 45 μm (pure alumina) and 15 to 30 um, (nickel-doped alumina). The effect of stress, grain size and temperature on the creep rate suggests that diffusion controlled grain-boundary sliding is the predominant creep mechanism at low stresses and small grain sizes. However, the stress exponents show that some non-viscous boundary sliding occurs even at the lowest stresses investigated. This mechanism is confirmed by metallographic evidence, which shows considerable boundary corrugation in the deformed aluminas. At higher stresses and larger grain sizes the localized propagation of microcracks leads to high stress exponents in the creep rate equation. The nickel dopant, which introduces an evenly distributed spinel second phase into the alumina matrix, increases the creep rate and enhances boundary sliding and localized crack propagation. The weakening effect of the second phase increases with grain size, and tertiary creep occurs at strains of 0.5% and below in large grained material.


Journal ArticleDOI
TL;DR: In this paper, a comparative study of the chemical composition of the gases from micro-inclusions in allanite was performed using the methods of heating to decrepitation and grinding in vacuum.

Journal ArticleDOI
TL;DR: In this article, the creep of uranium dioxide has been investigated as a function of grain size and grain boundaries exert a strengthening effect and this strengthening is correlated with the Hall-Petch equation.
Abstract: The creep of uranium dioxide has been investigated as a function of grain size. At high stresses, when creep is controlled by dislocation movement, grain boundaries exert a strengthening effect and this strengthening is correlated with the Hall-Petch equation. The degree of strengthening diminishes with increases in temperature. At lower stresses, when creep is controlled by mass transport, grain boundaries exert a weakening effect owing to the reduction in diffusion path length as grain size is reduced. In this range behaviour is correlated with the Nabarro-Herring equation with stress σ replaced by an effective stressσ E=σ−σ0 whereσ 0 is a threshold stress for diffusional creep associated with the limitation of the ability of boundaries to emit and absorb vacancies.σ 0 appears to decrease as grain size is increased.

Patent
30 Jan 1973
TL;DR: In this paper, the authors present a framework for RAMMING MONOLITHIC this paperRACTORY LININGS SUCH as for CUPOLAS and BLAST FURNACES.
Abstract: A REFRACTORY COMPOSITION SUITABLE FOR RAMMING MONOLITHIC REFRACTORY LININGS SUCH AS FOR CUPOLAS AND BLAST FURNACES COMPRISES COARSE PARTICLES OF CALCINED CLAY OR CALCINED BAUXITE AND COARSE PARTICLES OF AMOEPHOUS CARBON OR GRAPHITE WITH PLASTIC CLAY, AND MAY ASLO INCLUDE PARTICLES OF SILICON OR FERROSILICON, PITCH AND GREEN BINDERS. THE PARTICLE SIZE OF THE CALCINED CLAY, BAUXITE AND CARBON IS SUCH THAT AT LEAST 30 MESH TO 11/2 INCHES DIAMETER, AND A GRAIN SIZE FROM 30 MESH TO 11/2 INCHES DIAMETER, AND PREFERABLY AT LEAST 60 PERCENT FROM 30 MESH TO 1/4 INCH DIAMETER. I SUCH COMPOSITIONS THE CARBON IS PROTECTED AT ELEVATED TEMPERATURES SUCH AS 1600*F.-2600*F.