Pore types conical

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.

Different types of pores may co-exist in the porous membranes isolated pore, dead-end pore, cylindrical pore, constricted pore, and conical... 

The chief cases that are the subject of the problems here are zero, first and second order in spheres, slabs and cylinders with sealed flat ends, problems P7.03.03 to P7.03.ll. A summary of calculations of effectiveness is in P7.03.02. The correlations are expressed graphically and either analytically or as empirical curve fits for convenience of use with calculator or computer. A few other cases are touched on L-H type rate equation, conical pores and changes in volume. Nonisothermal reactions are in another section. 

The most simple pore morphologies (Figs. 2.1A and B) are those of more or less straight cylindrical or conical-shaped pores. This type of pore is formed in so-called track etch and in "anopore" membranes. The latter is obtained by anodic oxidation of A1 metal foils and results in porous (amorphous) alumina (mesoporous) membranes. A detailed discussion is given by Burggraaf and Keizer in Ref. [1]. These types of membrane are useful for fundamental trans-... 

Two types of porous electrodes can be considered two- and three-phase systems, where the latter is the special case of a triphasic interface in fuel cells, where the gas, liquid, and solid coexist. In the former, the liquid reactant is dissolved in the electrolyte and transported to the active sites of the electrocatalyst. In each case, we can consider uniform, parallel, cylindrical, or conical pores that are topped at the bottom by the metal substrate and at the top by the electrolyte [19,20],... 

A number of theoretical approaches explained the retention by a simple size-exclusion mechanism presented in the Introduction. Such explanations were associated with more or less complicated pore shapes that were considered as a system of cylindrical, conical, etc., holes that spherical solute molecules can penetrate. The size distribution of the pores was not given much importance. Nevertheless, experiments whose objective was to correlate the molar mass dependence of the retention volume of different solute molecules with the pore size distribution curves did not provide satisfactory results. Although more sophisticated models of this type were more successful when compared with the experiments, they are not considered now as they are not sufficiently general and do not accruately describe the physical reality. 

The stability of membrane is determined not only by macroscopic parameters, such as surface and linear tension, but also by the molecular geometry of lipids conic molecules of the broad head-narrow tail type are prone to forming inverted pores, and membranes made up of them have a short life-time. 

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

As demonstrated in Fig. 6 the brass plates had a thickness of 30 p,m and average distance between the conical pores of 100 or 500 p m. A syringe pump delivered the pressure at constant flow rates and we reduced the flow resistance using a polysiloxane coating at the surface of the brass plates. The obtained droplets showed average diameters between 15 and 35 pm (Fig. 7). The emulsion droplet size depended on several parameters like the surfactant type, the amphiphile concentration and the flow rate. With Dodecane as organic solvent and Lecithine as emulsifier the mean droplet diameter reached a minimum of 15 pm. 

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