Porous body

In general, therefore, there are three processes, prior to the kind of capillary condensation associated with the hysteresis loop of a Type IV isotherm, which may occur in a porous body containing micropores along with mesoporesia primary process taking place in very narrow micropores a secondary, cooperative process, taking place in wider micropores, succeeded by a tertiary process governed by a modified Kelvin equation. 

Infiltration (67) provides a unique means of fabricating ceramic composites. A ceramic compact is partially sintered to produce a porous body that is subsequently infiltrated with a low viscosity ceramic precursor solution. Advanced ceramic matrix composites such as alumina dispersed in zirconia [1314-23-4] Zr02, can be fabricated using this technique. Complete infiltration produces a homogeneous composite partial infiltration produces a surface modified ceramic composite. 

Funicular state is that condition in diying a porous body when capillary suction results in air being sucked into the pores. 

Absorption - Processes water can be removed from a material by the capillary action of porous bodies. An example is the cream of clay and water used for casting pottery, which is deprived of the greater part of its water by placing it in molds of plaster of Paris. The capillary character of this mold withdraws the water from the liquid clay mixture and deposits upon itself a layer of solid clay, the thickness of which is controlled by the time of standing. Certain types of candies, such as gumdrops, are dried mainly by contact with the starch molds in which they are cast. The drying effect of sponges, towels and materials of this kind is due to this same action. 

Existing statistical methods permit prediction of macroscopic results of the processes without complete description of the microscopic phenomena. They are helpful in establishing the hydrodynamic relations of liquid flow through porous bodies, the evaluation of filtration quality with pore clogging, description of particle distributions and in obtaining geometrical parameters of random layers of solid particles. 

Similar considerations apply to the behaviour of porous bodies in an atmosphere containing vapour. Pores are substantially collections of capillary tubes. If the liquid whose vapour is present wets the body, the resulting surface is con-... 

The external surface of such porous bodies as charcoal, which is in immediate contact with the liquid, adsorbs very rapidly. The internal surface, however, i.e., that of the pores, can only get its supply of solute by diffusion, which is necessarily slow through the very restricted sections, and particularly so with substances of high molecular weight. 

LUIKOV, A. V. Heat and Mass Transfer in Capillary-porous Bodies (Pergamon Press, Oxford, 1966). Masters, K. Spray Drying Handbook (George Godwin, London, 1985). 

Diffusion through liquid films is usually better understood than that through porous bodies. In ion exchange, however, there is an additional flux through the him of mobile co-ions which are not present in the resin. The co-ions will be affected by the relative mobilities of the counter-ions. 

Charpin, J., P. Plurien and S. Mammejac. 1958. Application of general methods of study of porous bodies to the determination of the characteristics of barriers. Proc. 2nd United Nations Inti Conf. Peaceful Uses of Atomic Energy, 4 380-87. 

Toei, R., H. Imakoma, H. Tamon and M. Okazaki. 1983. Water transfer coefficient in adsorptive porous body. J. Chem Eng. Japan 16(5) 364-69. 

Organic polymers and resins have also been used for zeolite binding. An early example is the use polyurethane in the formahon of vibration-resistant zeolite porous bodies for refrigerant drying [90]. Organic binders such as cellulose acetate and other cellulose-based polymers have also used to mitigate problems with binder dissolution in aqueous phase separations [91, 92]. Latex has also been used as a water-stable organic binder [93]. More recently, thermoplastic resins, such as polyethylene have also been used as binders for zeolites [94]. 

The unconventional applications of SEC usually produce estimated values of various characteristics, which are valuable for further analyses. These embrace assessment of theta conditions for given polymer (mixed solvent-eluent composition and temperature Section 16.2.2), second virial coefficients A2 [109], coefficients of preferential solvation of macromolecules in mixed solvents (eluents) [40], as well as estimation of pore size distribution within porous bodies (inverse SEC) [136-140] and rates of diffusion of macromolecules within porous bodies. Some semiquantitative information on polymer samples can be obtained from the SEC results indirectly, for example, the assessment of the polymer stereoregularity from the stability of macromolecular aggregates (PVC [140]), of the segment lengths in polymer crystallites after their controlled partial degradation [141], and of the enthalpic interactions between unlike polymers in solution (in eluent) [142], as well as between polymer and column packing [123,143]. 

TERRA-COTTA, OR POROUS BODIES FOR WATER BOTTLES, KTC. 

These porous bodies are all fired in the glaring oveo. 

Although a few very active solid catalysts are used as fine wire mesh or other finely divided form, catalysts are mostly porous bodies whose total surface is measured in m2/g. These and other data of some commercial catalysts are shown in Table 17.8. The physical characteristics of major importance are as follows. 

Microstructures are generally too complex for exact models. In a polycrystalline microstructure, grain-boundary tractions will be distributed with respect to an applied load. Microstructures of porous bodies include isolated pores as well as pores attached to grain boundaries and triple junctions. Nevertheless, there are several simple representative geometries that illustrate general coupled phenomena and serve as good models for subsets of more complex structures. 

The role of this article was described in sufficient detail in the Introduction. The paper is cited in a number of monographs on catalysis as the first work on the internal diffusion kinetics of processes in powders and porous substances (see, for example, the monograph by G. K. Boreskov).1 Figure 3 from Ya.B. s paper is reproduced in many textbooks and encyclopedic articles on catalysis.2 In the introduction to this book, D. A. Erank-Kamenetskii names Ya.B. as one of his teachers. The region of internal diffusion in kinetics on porous bodies is often called the Zeldovich region (see also ). 

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