Specific porosity

Specific porosity the accessible pore void space per unit mass. 

Mean pore size either the pore size distribution or the specific porosity divided by the specific surface area. Pores are divided into three categories macro (30-50 nm), meso (intermediate size), and micro (less than 2 nm). 

From Equation 38.3, it results that the mass-transport coefficient in the membrane increases as the porosity increases and as the thickness and tortuosity decrease. These parameters are related to each other the tortuosity, for instance, is a function of the porosity of the membrane and the specific porosity-toituosity relationship depends on the manufacmring method [6]. 

The objective is to produce a plasticized material that is easily shaped in a die plate and has a specific porosity with a defined pore size and a large inner and outer surface area for a good catalytic activity. Therefore, shear is applied to the ceramic to move the particles against each other so that all hollow spaces between the solid particles can be filled with the liquid binder (see Fig. 13) and the so called kneading dough is formed p riSO]. The dispersed binder provides the extruded profile with the strength... 

A typical pore in a dense silica gel is shown in Figure 5.3a. Here the silica spheres are in cubic packing and the pore volume is 48% of the total volume. Since the 52% by volume of silica has a density of 2.2 g cm, the specific porosity is 0.42 cm g . 

Solvent casting and particulate leaching (SC/PL) is a simple and commonly used method for fabricating scaffolds for tissue engineering. With an appropriate thermal treatment, porous constructs of synthetic biodegradable polymers can be prepared with specific porosity, surfaceivolume ratio, pore size and crystallinity for different applications. This method involves mixing water-soluble salt (e.g. sodium chloride, sodium citrate) particles into a polymer solution. The mixture is then cast into the mould of the desired shape. After the solvent is removed by evaporation or lyophilization, the salt particles are leached out to obtain a porous structure with the pore shape limited to the cubic crystal shape of the salt. Removal of soluble particles from the interior of a polymer matrix is difficult and limits the thickness of the films prepared to ca. 2 mm [293]. 

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