Effects of porosity

The presence of particles in the fluid medium complicates diffusion in a sediment due to the effects of porosity, represented by n, and tortuosity. Since tortuosity of natural sediments is seldom known it is more convenient to use the term "formation factor" or "lithological factor," denoted L, which takes into account everything but porosity. Tick s diffusion constant D is replaced by the whole sediment diffusion constant Ds, where < D. 

Currey, J.D. (1998) The effect of porosity and mineral-content on the Youngs modulus of elasticity of compact-bone. Journal of Biomechanics, 21, 131-139. 

The PVA/PSSNa membranes evidence a high permselectivity, comparable with the one of commercial ion exchange membrane as it can see in table 14, where were presented the permeability coefficient (P) and the ratio P to D (diffusion coefficient) that express the effect of porosity and of the electrolyte exclusion. 

Wyllie, M. R. J. and Gregory, K. R. Ind. Eng. Chem. 47 (1955) 1379-88. Fluid flow through unconsolidated porous aggregates — effect of porosity and particle shape on Kozeny-Carman constants. 

Fig. 8.9 Effect of porosity on composition of kerosene during 14 days of volatilization from fine, medium and coarse sand, as seen from gas chromatograph analyses. Reprinted from Galin Ts, Gerstl Z, Yaron B (1990) Soil pollution by petroleum products. IB Kerosene stability in soil columns as affected by volatilization. J Contam Hydrol 5 375-385. Copyright 1990 with permission of Elsevier...

Typically, the most severe flaws are associated with porosity, surface damage, abnormal grains, or foreign inclusions. The effect of porosity on both modulus and strength is illustrated in Figures 5.48 and 5.49, respectively. The solid curve in Figure 5.48 represents the following equation, which holds for some ceramics ... 

Figure 5.48 Effect of porosity on the elastic modulus of AI2O3 at room temperature. Reprinted, by permission, from W. CaUister, Materials Science and Engineering An Introduction, 5th ed., p. 413. Copyright 2000 by John Wiley Sons, Inc.

Salzmann DL, Kiemer LB, Berman SS, Williams SK. The effects of porosity on endothelialization of ePTFE implanted in subcutaneous and adipose tissue, journal of Biomedical Materials Research 1997, 34, 463 -76. 

In summary, the effect of porosity on electrical conductivity and ion diffusivity in agarose gels is studied. Both electrical conductivity and ion diffusivity increase with porosity. The model obtained from the electrical conductivity data, i.e., Equation (7), can predict the diffusivity of macromolecules in 2% agarose gel for solutes with hydrodynamic radius less than the pore size of the gel. This study suggests that electrical conductivity method used in this study can be applied to investigating diffusion behavior of macromolecules in uncharged porous media. 

Gu, W.Y., Justiz, M.A. and Yao, H. (2002) Electrical conductivity of lumbar annulus fibrosis Effects of porosity and fixed charge density. Spine 27, 2390-2395... 

Effect of porosity on flexural strength of composites with code 1723 matrix (reproduced by permission of Am. Ceram. Soc. Bull.) . 

In a polycrystalline material each crystallite experiences its own effective field, which is determined in part by magnetic anisotropy. Therefore, because of the different orientations of the crystallites, there will be a distribution of resonant frequencies in consequence, narrow linewidths are associated with low anisotropies. Magnetic inhomogeneities - inclusions and pores - also disturb the local effective fields and so lead to line broadening. The effect of porosity on resonance linewidth can be expressed by the relationship... 

The effect of porosity, as accounted for in the various equations given, is illustrated in Figure 72. 

Figure 72. Effect of Porosity on Flow Through Sand According to the Equations of Various Investigators (Referred to Porosity 40 Percent = 100).

V. M. Gun ko and T. J. Bandosz, Heterogeneity of Adsorption Energy of Water, Methanol and Diethyl Ether on Activated Carbons Effect of Porosity and Surface Chemistry, Phys. Chem. Chem. Phys. 5, 2096-2103 (2003). 

TABLE 7.7 Effect of Porosity on Properties of Consolidated Ceramic Materials... 

Compact Property Symbol Equation Incorporating Effect of Porosity on Compact Property... 

Eslamloo-Grami, M., and Munir, Z. A., Effect of porosity on the combustion synthesis of titanium nitride. J. Am. Ceram. Soc., 73, 1235 (1990a). 

Most of the search for improved microwave materials has been mainly empirical, and it is necessary that the intrinsic properties of materials be known to control and design the dielectric properties of materials. Recently there have been reports on the intrinsic properties of materials by the IR reflectivity spectra and calculation of theoretical polarizability. However, there are discrepancies between the intrinsic properties obtained from these methods and the measured properties due to grain, grain boundary, and pores. Therefore the effects of porosity on the dielectric properties should be considered to evaluate the intrinsic dielectric properties and to predict the dielectric properties of ceramics with pores. 

FIG. 22 Effect of porosity on the removal of humic substances by a series of carbon adsorbents (a) humic substances fractionated al pH = 2.8 (b) humic substances fractionated at pH = 6.8. (Adapted from Ref. 546.)... 

FIG. 204. The effect of porosity on the transmission of light through sintered AI2O3 (after Lee and Kingery, 1960). The respective pore sizes are indicated on the curves. Equivalent thickness 0.5 mm. 

P. Suortti, Effects of porosity and surface roughness on the x-ray intensity reflected from a powder specimen, J. Appl. Cryst. 5, 325 (1972). 

---