Porosity determination

The density measurements on thermally processed polymers clearly show the formation of a foamed polymer. The initial density values for selected foams together with the respective polyimide homopolymers are shown in Tables 4 and 5. The density values for the ODPA/FDA and PMDA/FDA homopolyimides were both 1.28 g cm 3 and 3FDA/PMDA is 1.34. Most of the propylene oxide-based copolymers derived from these copolymers ranged from 1.09 to 1.27gem-3, which is -85-99% of that of the polyimide homopolymers, irrespective of the architecture of the copolymer (i.e., triblock vs graft). This is consistent with 1-15% of the film being occupied by voids. From these data (i.e., comparison of Tables 2 and 3 with Tables 4 and 5, respectively), it appears that the volume fraction of propylene oxide in the copolymer (i.e., -80% or less). Thus, the efficiency of foam formation is poor, irrespective of the copolymer architecture. Conversely, 

Sample entry Initial labile block Density composition, vol% (gcnr3 Volume fraction of voids (porosity ) % 

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Multivariable Regression Approach for Porosity Determination in Composite Materials. 

Since attenuation and porosity are related, traditional porosity determination in composites is performed as attenuation measurements using ultrasonic tone burst through-transmission. 

An important property of high-T systems is the reservoir formation porosity and the mass fractions of water and steam occupying the pores. These mass fractions and the formation porosity determine how large a fraction of the heat of the system is stored in the fluid and how large a fraction in the rock. Usually the quantity of heat stored in the reservoir rock is considerably larger than that stored in the fluid. This is particularly the case for vapour-dominated systems. For a liquid-dominated system at 250 °C with 10% porosity and no steam, the quantity of heat stored in the fluid in 1 m3 of reservoir rock is about 87 MJ, but that stored in the rock is some 500 MJ. The corresponding number for the heat stored in steam in a vapour-dominated system is only 5.6 MJ. 

On the basis of porosity determined for the granules from particular size fractions of product samples taken from the drum in a specific moment, mean porosity of granules was calculated from the relation... 

Most commercial instruments using gas adsorption for surface area and porosity determination are based on the BET isotherm. In Eq. (1.45), the monolayer capacity Vm can be used to calculate the surface area on the basis of the area occupied by each adsorbed gas molecule. According to Eq. (1.45), a plot of p/[Va(p0 - p)] versus p/po is linear. From the slope and the intercept, Vm can be obtained. Thus, the specific surface area S can be obtained as... 

Figure 8.18. Porosity-depth relations at DSDP sites 504 and 505. Thin line, porosity determinations on ship-board black dots, porosity determinations from samples tested in laboratory dark thick line, best fit to the data. Notice porosity gradient is steeper at the high heat flow site 504 than at the "cooler site 505. (After Wetzel, 1989.)...

A. Static Percolation in Porous Materials, Fractal Concept, and Porosity Determination... 

Similar processes were also observed for 30-pm-thickness samples. The detailed description of the mechanism of the mid-temperature process in the percolation region and porosity determination in PS will be presented below. 

The problems of defining and determining densities of finely porous solids, indicated in Section 5.3.3, apply to hep. A determination of the density of such a material is also one of porosity, since both properties are related to the solid volume the porosity per unit volume of material is equal to 1 -[mJ D X V)], where tn and are, respectively, the mass and density of the solid and V is the total volume. The density and porosity determined by any method entailing contact with a fluid can vary with the extent to which the solid has been dried, how it has been dried and the fluid employed. Fluids may differ in their abilities to penetrate the pore system, and the pore structure may be altered both during drying and by the action of the fluid subsequently introduced. 

Fig. 12.1 Microstructural gradients in the interfacial region of a concrete (a) unreacted clinker phases, (b) porosity, determined using SEM with image analysis. Each point represents a mean from 50 determinations, and the standard errors were approximately 10% relative. Scrivener et al. (SI 14).

J.D.F. Ramsay, P.J. Russell and S.W. Swanton, Gel precipitated oxide gels with controlled porosity-Determination of structure by small angle neutron scattering and adsorption isotherms measurements, in F. Rodriguez-Reinoso, J. Rouquerol, K.S.W. Sing and K.K. Unger (Eds.), Characterization of Porous Solids II, Studies in Surface Science and Catalysis Vol. 62, Proc. of the lUPAC Symposium (COPS II), Alicante, Spain, May 1990, Elsevier, Amsterdam, 1991, pp. 257-265. 

Criteria for immobilized liquid membrane (ILM) support selection can be divided into two categories structural properties and chemical properties. Structural properties include geometry, support thickness, porosity, pore size distribution and tortuosity. Chemical criteria consist of support surface properties and reactivity of the polymer support toward fluids in contact with it. The support thickness and tortuosity determine the diffusional path length, which should be minimized. Porosity determines the volume of the liquid membrane and therefore the quantity of carrier required. The mean pore size determines the maximum pressure difference the liquid membrane can support. The support must be chemically inert toward all components in the feed phase, membrane phase, and sweep or receiving phase. 

The porosity of the support refers to the percentage of the total volume which is void space. The porosity determines the total volume of the liquid membrane which can be immobilized in the pore volume. The volume of liquid membrane solvent and the carrier solubility determine the maximum amount of carrier which can be immobilized in the membrane. Increasing the amount of carrier in the membrane will increase the solute fluxes. The strength of the functional dependence of the solute flux on carrier concentration will depend on whether the facilitated transport system is reaction or diffusion limited. Consequently, a high porosity support is desirable for liquid membrane applications. 

Chemical composition and surface area/porosity determinations... 

With these values for (a) and (m) calibrated porosity logs are calculated which agree well with porosities determined on discrete samples (Fig. 

Fig. 2.8 Porosity logs determined by resistivity measurements on three gravity cores from the South Atlantic (see also Fig. 2.7 and Table 2.1). Gray curve Boyce s (1968) values were used for the constants (a) and (m). Black curve (a) and (m) were derived from the slope and intercept of a linear least square fit. These values are given at the top of each log. Superimposed are porosities determined on discrete samples by weight and volume measurements (unpublished data from P. Muller, University Bremen, Germany).

Gerland S., Richter M., Villinger H., Kuhn G, 1993. Nondestructive porosity determination of Antarctic marine sediments derived from resistivity measurements with the inductive method. Marine Geophy-... 

Mancini CE, Bemdt CC, Stm L, Kucuk A (2001) Porosity determinations in thermally sprayed hydroxylapatite coatings. J Mater Sci 36 3891-3896... 

The basic technique is quite simple. A sheet of cellulose filter paper, such as Whatman No. 1, serves as the separation medium. For one-dimensional paper chromatography (PC), the paper is cut into strips about 5 cm wide and 20 cm long for two-dimensional PC (below), a 20 X 20-cm sheet is commonly used. The papers come in various porosities (fine, medium, coarse) the porosity determines the rate of movement of the developing solvent. Low-porosity paper gives slow solvent movement but good resolution. Thick papers, which have increased sample capacity, are available for preparative separations. 

Fig. 5.60 Relation between the total porosity (determined with helium method) and permeability of water saturated pastes (according to [133]) empty circles—Portland cement pastes, black circles—pastes from cements with mineral additions, cured at 20-80 C, one year measurements...

It is clear that the permeability of material to water depends mainly on the volume of capillary pores. It is not linked with total porosity but depends rather on the pore size distribution. However, Marsh [133] gives attention to a fairly good correlation between the total porosity, determined by means of helium method, and permeability. This relation is shown inFig. 5.60 [133]. The diying of samples by substitution of water with propan-2-ol and -pentane was applied. Porosity and pore size distribution determined with mercuiy porosimeter do not correspond to the real stmcture, because the intmsion of mercury under a high pressure, causes the destmction of hydrates plugging the pores, particularly in the pastes of cements with fly ash. 

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