Pore types isolated

The pore types FAU, MFI, MOR, and LTA discussed above contain basically all micropore types possible in zeolites. There are accessible and nonaccessible cages (FAU and LTA) and straight or meandering channels in one, two, or three dimensions, which may be either isolated or connected to each other (MFI and MOR). 

Fig. 2.3. Schematic picture of pore types in a porous membrane, a Isolated pore b,f dead end pore c,d tortuous and/or rough pores (d) with constrictions (c) e conical pore.

A schematic picture of different t5q)es of pores is given in Fig. 9.1 and of main types of pore shapes in Fig. 9.2. In single crystal zeolites the pore characteristics are an intrinsic property of the crystalline lattice [3] but in zeolite membranes other pore types also occur. As can be seen from Fig. 9.1, isolated pores and dead ends do not contribute to the permeation under steady conditions. With adsorbing gases, dead end pores can contribute however in transient measurements [1,2,3]. Dead ends do also contribute to the porosity as measured by adsorption techniques but do not contribute to the effective porosity in permeation. Pore shapes are channel-like or slit-shaped. Pore constrictions are important for flow resistance, especially when capillary condensation and surface diffusion phenomena occur in systems with a relatively large internal surface area. 

Generally, there are two types of pores (Fig. 5.44). Open pores are connected with the body s surface while closed pores are isolated within and may be filled with a fluid. Penetrating pores are a special type of open pores they feature at least two ends and connect opposing surfaces of the porous body. 

This complicated multi-level local isolation of particles in the initial powder compacts influenced the structure evolution during sintering that was accompanied by the increasing the particles (aggregates) in size and decreasing the pores in both quantity and size. In particular, the unexpected phenomenon that is the correlation between the pores types mentioned above and the rate of decreasing the pores in quantity and size was revealed (Figs. 1,2). 

Figure 2.2 Schematic representation of the main types of membrane pores (a) isolated (b) dead-end (c) straight cylindrical (d) constricted (e) conical.

But in case of more heterogeneous carbonates with moldic or isolated vuggy pore space, Archie s equation fails. Non-connected parts of the pore volume do not contribute to the conductivity and result in an extremely high resistivity and formation factor. Systematic studies of these pore types have been published, for example, by Focke and Munn (1987) and Fleury (2002) (Fig. 8.12). 

Particulate interferents can be separated from dissolved analytes by filtration, using a filter whose pore size retains the interferent. This separation technique is important in the analysis of many natural waters, for which the presence of suspended solids may interfere in the analysis. Filtration also can be used to isolate analytes present as solid particulates from dissolved ions in the sample matrix. For example, this is a necessary step in gravimetry, in which the analyte is isolated as a precipitate. A more detailed description of the types of available filters is found in the discussion of precipitation gravimetry and particulate gravimetry in Chapter 8. 

The most important characteristic of cement is its pore structure and aqueous phase hence, the microstructure of the hardened cement paste via the pore system. It is highly alkaline (pH >13) due to rapid and almost quantitative dissolution of Na and K salts from the cement clinker. The porosity of the paste comprises interconnected and isolated pores, the pore sizes of which are important to the strength and dimensional stability of cement products. Different types of cement are used to meet different performance criteria. Properties can be estimated from compositions and fineness (i.e., particle size and size distribution). In the past, additives... 

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