Showing papers on "Volume fraction published in 1968"

Permeability of Solutes through Hydrated Polymer Membranes Part I. Diffusion of Sodium Chloride

Abstract: Based on an analysis by the free volume theory of diffusion, a study of the diffusion coefficients, D2, the distribution coefficients, κ2, and the permeability coefficients, P, of NaCl in various hydrophilic polymers was made with the assumptions that the free volume of a polymer/diluent system is linearly proportional to the volume fraction of diluent (H), and that NaCl permeates only through polymer/diluent systems in which the diluent of polymers is also a good solvent of the solute (NaCl). The values of D2 (over five orders of magnitude) were found to vary exponentially with changes in 1/H, as expected from the free volume theory of diffusion, in a wide range of H-values and converge to the value of the diffusion constant of NaCl in pure water. The values of κ2 defined by g NaCl per cm3 polymer/g NaCl per cm3 solution were found to be more characteristic to the type of polymers particularly at a lower range of H-values. At higher ranges of H-values, k2 is nearly equal to H, however, at lower H, k2 values deviate significantly from the value of H and its extent was found to be greatly dependent on the chemical nature of polymers, whereas the diffusion coefficient follows the normal pattern predicted by the free volume theory. The values of P which are given by the product of D2 and k2 also were found to vary exponentially with changes in 1/H at higher range of H, however, at lower range of H it deviates from the relationship due to the varying dependence of factor k2 on 1/H.

Viscosity of Dispersed and Aggregated Suspensions of Spheres

Abstract: Viscosities of suspensions of dispersed spheres and permanent aggregates ranging from doublets and triplets to clusters composed of a very large average number of spheres are reported. In all cases, glass spheres of a very narrow distribution of particle diameter were used and the suspending fluid was a chlorinated biphenyl (Aroclor). Results were obtained using a Couette type viscometer as a function of volume fraction of the dispersed phase. In addition, measurements on the aggregated systems were made as a function of the number of spheres per aggregate with the average aggregate size controlled over a relatively narrow range. Aggregates were obtained by a sintering and sieving technique. For the larger aggregates the shape was generally elliptical. This is the first time rheological data has been reported for suspensions with a dispersed phase composed entirely of permanent aggregates of controlled size, size distribution, and shape. The results for the dispersed and aggregated systems, with concentrations as high as Φ=0.5 volume fraction solids, are shown to fit the Mooney equation over the entire concentration range, if the Einstein coefficient is increased for the aggregated systems to a limiting maximum values as suggested by Gillespie and if experimental values of the maximum volumetric packing fraction of solids are used. The value of the Einstein coefficient is shown to be a function of the hydrodynamic volume of the aggregates and reach a maximum value for the larger aggregates.

The Void Fraction in Subcooled Boiling—Prediction of the Initial Point of Net Vapor Generation

Abstract: The satisfactory prediction of the vapor volume fraction in subcooled boiling depends in large part on the ability to predict the point where a significant amount of net vapor is first formed. A method for the prediction of this point is derived here and compared with experimental measurements at both low and high fluid velocities. The derived relationships for this point include the effect of fluid properties, geometry, and the liquid velocity. A comparison with the empirical formula of Bowring [2] for water is given.

X-ray small-angle scattering of non-graphitizable carbons

Abstract: The small-angle scattering of a non-graphitizable carbon produced from polyacrylonitrile is studied. The evaluation of the scattering data has been based on recent developments in small-angle scattering theory. The results show the existence of a micropore system with diameters in the 10–30 A range. The average pore diameter increases linearly with heat-treatment temperature from 2000 to 3000°C. The volume fraction of micropores determined by absolute intensity measurements varies between 0.17 and 0.25 and is equal to, or smaller than, the volume fraction of pores inaccessible to helium. The pore shapes are very probably irregular polyhedra bounded by graphitic layer planes. A second component of the small-angle scattering can be detected and separated from the scattering of the micropores. This component is due to density fluctuations in the bulk of the carbon material and is produced by the fluctuation of the interlayer spacing and the fluctuation of the layer diameter in a given stack of layers.

Aluminum reinforcement of some polyethylenes

Abstract: Filler reinforcement by aluminum powder was correlated to filler–matrix adhesion and was found to be a simple exponential function of the volume fraction for a series of polyethylenes.

Thermodynamics of polyisobutylene solutions. III. Thermal behavior and polymer order

Abstract: Considerations based on the Maron theory show that for solutions of an amorphous polymer in a solvent the values of A obtained from heats of solution, heats of dilution, osmotic pressure, and vapor pressure should all be identical. Here λ = (aWaT)2, where μ is the Maron theory interaction parameter, T the temperature, and v2 the volume fraction. On the other hand, for solutions of a crystalline polymer in a solvent the A's obtained from heats of solution should always differ from those given by the other measurements. The difference is due to the heat of fusion involved in melting the crystalline portion of the polymer. A method is presented by means of which this heat of fusion can be found from the observed heats of solution, and this heat of fusion can either be used as a relative measure of crystallinity, or it can be converted to percent crystallinity when the heat of fusion of the completely crystalline polymer is known. The method described is very precise, and highly sensitive to low degr...

Thermodynamics of polyisobutylene solutions. i. Interaction parameters from osmotic pressure data

Abstract: The Maron theory of nonelectrolyte solutions was used to analyze available osmotic pressure data for solutions of polyisobutylene in benzene, chlorobenzene, toluene, and cyclohexane and to evaluate the interaction parameters, μ, for these systems. The results obtained show that for the benzene and chlorobenzene solutions the μ's are linear functions of volume fraction and temperature, but they are not dependent on molecular weight. On the other hand, the solutions of polyisobutylene in toluene and cyclohexane show a dependence of μ on molecular weight and, in all probability, also on volume fraction and temperature. However, the data available are insufficient to establish the exact dependence of μ on v2 and T for the latter two systems.

Effect of Dispersoids on Magnetic Properties of Iron, Cobalt, and Nickel

Abstract: Coercive force and saturation induction of cobalt, iron, and nickel, dispersion strengthened with 0.02 to 0.10 volume fraction of alumina or thoria, were measured at temperatures up to 80%–98% of TC. Saturation magnetization values of iron and cobalt at a given temperature level were found to decrease in direct proportion to the volume fraction of nonmagnetic phase present. The temperature dependence of the measured coercive force was interpreted as a cooperative effect of inclusions and internal stress by reference to coercive force values calculated from the equations of Neel. This was particularly apparent in the Hc vs T curve of nickel where the contribution of inclusions was significant in the low‐temperature region, whereas stress was an influential factor at all temperatures. Close correlation between measured and calculated Hc was obtained for all three metals containing 0.02–0.025 volume fraction of dispersoid.

Thermodynamic Properties of Solutions of m-Terphenyl in Benzene. I. The Vapor Pressures and the Related Thermodynamic Functions at 30 and 50°C

Abstract: Vapor pressures of solutions of m-terphenyl in benzene were measured for the concentration less than 0.23 in mole fraction x of terphenyl at 30 and 50°C. Vapor pressures P mmHg obtained are represented by log10P(30°)=2.076970–0.4343x–0.06569x2–0.4340x3 and log10P(50°)=2.432100–0.4343x–0.14654x2–0.3412x3. Chemical potentials observed were reproduced by the quasi-lattice theory for mixtures of molecules of different sizes. The Miller-Guggenheim expression (r=3, z=6–8) gives w⁄k=100±5°, and the Flory-Huggins expression (r=molecular volume ratio) gives χ=0.272±0.004 (30°) and χ=0.243±0.006(50°). Partial molar heats of mixing are rather fitted by the regular solution theory similarly to the case for benzene+biphenyl, and the Flory-Huggins expression gives a concentration-dependent enthalpy parameter, χH=(0.772+1.716φ)×102⁄T, where φ means a volume fraction of terphenyl. The average value of χH, 0.39 agreed with a theoretical estimate from solubility parameters.

Thermal expansion of molybdenum-copper and tungsten-copper pseudo-alloys

Abstract: 1. A study was made of the influence of concentration and temperature on the thermal expansion of W-Cu and Mo-Cu pseudo-alloys obtained by liquid-phase sintering. It has been found that these two systems may constitute a basis for the development of materials having predetermined thermal-expansion characteristics, with coefficients of thermal expansion ranging from 60 × 10−7 to 140−160 × 10−7 1/°C. 2. For temperature ranges between room temperature and 873°K, the concentration dependence of the coefficient of thermal expansion is satisfactorily described by an expression derived for the coefficient of thermal expansion of a two-layer sphere in the elastic state as a function of the volume fraction of the layers, but deviates substantially from the relationship proposed by Turner and Kingery [9, 10] for statistical mixtures. 3. At high temperatures, the coefficient of thermal expansion is found to exhibit a significant increase for alloys rich in the soft phase and a decrease for alloys rich in the refractory phase. This may be attributed to the low resistance to plastic deformation of the soft phase and to the influence of the refractory-phase skeleton. 4. It has been established that the coefficient of thermal expansion of two-phase W-Cu and Mo-Cu pseudo-alloys depends on texture. The thermal expansion of these materials, whose irreversible changes are linked with variation in residual porosity, has been found to exhibit hysteresis.

Hot isostatic compaction of tungsten-uranium dioxide fuels with high-volume fraction of uranium dioxide

Abstract: Smooth surface coating of molybdenum alloys for cermets by hot isostatic compaction of tungsten-uranium dioxide fuels

Fiber‐Reinforced Fe‐50Ni and Fe‐1.35Si Alloys

Abstract: The feasibility of employing fiber reinforcement in order to strengthen soft magnetic materials for high‐temperature applications has been investigated. Specimens of Fe‐50Ni and Fe‐1.35Si containing tungsten fibers (0.003 to 0.010 in. in diameter) in concentrations up to 17.3 vol % were prepared by hot rolling laminations which were encapsulated in a mild steel “envelope”.Short‐time tensile properties, saturation induction, and coercivity were measured at ambient and/or elevated temperatures. The tensile stress‐strain behavior was consistent with the theory for composites containing continuous fibers aligned parallel to the tensile axis. Saturation induction was found to follow the simple dilution law at all temperatures up to the Curie point, being equal to the product of the matrix saturation and volume fraction of matrix in the composite. An anisotropy was observed in coercivity, dependent on the fiber direction with respect to the applied field. In all cases, the measured Hc was higher when the field ...

464. 2相流の蒸気ボイド率に関する研究,(ii)

Abstract: The steam volume fraction α of a two phase mixture flowing upward under atmospheric pressure was measured in a vertical concentric annulus, with inner and outer diameters respectively 9.5mm and 21mm. Use was made of a capacitance type void meter described in a previous paper, and the following correlation was obtained:α=1-√(1-x)3/1+Kx, where K=eρl/ρgV0.50exp (-2×10-6q)e=1.3 (bubble flow), e=1 (slug flow and annular flow)x is the steam weight fraction, ρl/ρg the density ratio of liquid to steam, V0 the superficial velocity (m/s), and q the heat flux (kcal/mm2·hr).The experimental data obtained under high pressure by several investigators for various channel forms correlated very well with use of the formulaK=eρl/ρgV0.50, where e is the same as mentioned above.These correlations are very useful for predicting the steam volume fraction at various pressures below 2, 000 psia.

The effect of microstructure on the cleavage strength of quenched and tempered steels

Abstract: Effects of particle size, distribution, and volume fraction on microscopic cleavage fracture strength of quenched and tempered steels

The influence of microstructural characteristics on the failure properties of a polybutadiene system

Abstract: The stress-strain characteristic of polymeric binders and solid propellants are dependent on the crosslink density, molecular weight between crosslinks, molecular weight distribution in the binder formulation, volume fraction of filler, and the interaction between the binder and filler particles. This investigation is directed toward elucidation of solid propellant microscopic response and failure mechanisms through characterization of the constitutive effects of crosslink density, molecular weight distribution and curing agent ratio in the binder formulation, and filler fraction. This was accomplished on the ERLA/PBAA propellant system through investigation of three binder formulations with the same curing agent ratio but different crosslink densities; five binder formulations with different curing agent ratios; and four formulations with up to 69.9% by volume of filler. Uniaxial stress-strain characteristics were determined on each formulation at displacement rates of 0.2 to 20.0 in/min at isothermal test conditions ranging from 75 to −90°F. The failure characteristics of a viscoelastic material represent a curve in the three-dimensional space of stress, strain, and time. The ultimate property data on each formulation are presented as projections of this failure curve on the stress-strain, stress-time, and strain-time planes, respectively. Relationships are developed for the dependence of the stress-time, strain-time, and stress-strain failure envelopes on the volume fraction of bound rubber, crosslink density, molecular weight distribution and curing agent ration in the binder component, and the volume fraction of filler.