Mean pore sizes

Where is the mean pore size and is a constant reflecting the spread of the distribution. The probability that one tip of a single defect will cause failure under applied stress o may now be defined from equations (48) and (49) as ... 

The effect of varying the mean pore size and number of pores on the predicted strength distributions of grade H-451 graphite are shown in Fig. 25. In this instance, both the mean size (SJ and number (N) of pores per unit volume was varied in the "SIFTING" code. This was necessary because the density was held constant, i.e., the pore fraction remains unchanged, and therefore a decrease of the mean pore size must be accompanied by an increase in the number of pores per unit... 

Fig. 25. The effect of mean pore size and number of pores per unit volume on the predicted tensile failure probability distribution for grade H-451 graphite.

Pore Surface area Mean pore size Mass range Size range (nm) SEC... 

A sulfonated ion exchanger catalyst (Research Institute of Synthetic Resins and Varnishes, Pardubice, Czechoslovakia) was a macroreticular styrene-divinylbenzene copolymer containing 25% divinylbenzene and 2.4 meq/g of —SO3H groups. It was dried prior to using at 90°C/14 Torr. The BET surface area, determined in a dry state, was 49 m2/g, and the mean pore size was around 100 A. 

Toyonite D-M (porous ceramic support, Toyo Denka Kogyo Co. Ltd.) has 120 nm of mean pore size having 3-(2-methylpropenoyloxy)propylsilanetrioxyl bridges on the surface. 

However, mean pore sizes are often much larger than micrometers so that no restriction effect will show up in field gradient diffusometry experiments [16]. 

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). 

Hydrophobic gels p-Styragel (polystyrene/DVB) Mean pore size in Angstroms 100 500 0.05 Fractionation range Up to 700 x 104- 1 X 104... 

Completely solid packings produce no mass transfer effects related to solute movement into and out of tortuous pore structures. The principal limitation of solid packings is low total surface area and consequent limited sample capacity. Even with very small particles, the overall surface area generated per unit length of the column is still low compared to the porous materials with mean pore sizes in the 60 to 300 A range. Figures 13.5 A and B show a comparison of surface areas of... 

Having obtained a measure of surface area, a mean pore size may be calculated by simplifying the pore system into np cylindrical pores per unit mass of adsorbent, of mean length Lp and mean pore radius rp. 

Porous texture characterization of all the samples was performed by physical adsorption of N2 at 77K. and CO2 at 273K, using an automatic adsorption system (Autosorb-6, Quantachrome). The micropore volume, Vpp (N2), was determined by application of Dubinin-Radushkevich equation to the N2 adsorption isotherm at 77K up to P/Po< 0.1. The volume of narrow micropores, Vnpp (DR,C02>, (mean pore size lower than 0.7 nm) was calculated from CO2 adsorption at 273 K. 

With an increasing quantity of acid used per mole AlOOH the mean pore size of the membranes after calcination is slightly decreased. Probably the stacking density of the particles in the gel increases with increasing concentration. Typical amounts of acid used range from 0.05-0.1 mol/L. Anderson s work seems to confirm this type of dependence (Anderson et al. 1988). 

Drying without the occurrence of large capillary stresses was obtained with supercritical drying in an autoclave. In this case a mean pore size was obtained which was twice that obtained under normal drying conditions and with a broad pore size distribution in accordance with the expectation for a noncompressed, random packing of particles. 

This transition produces an isomorphous phase and the resulting y-alumina has the same morphology and texture as its boehmite precursor. With increasing temperature and time the mean pore diameter increases gradually and other phases appear (S-, 6-alumina). Due to the broad XRD lines, the distinction between y- and S-alumina cannot be made 6-alumina occurs at about 900°C while the conversion to the chemically very stable a-alumina phase takes place at T> 1000°C. Some typical results for alumina membranes synthesized without binders are given in Table 2.4. When PVA was used as a binder, thermogravimetric analysis showed that, provided the appropriate binder type was used, the binder could be effectively removed at T > 400°C. The ash residue is of the order of 0.01 wt.%. Mean pore size and... 

The testing of battery separators and control of their pore characteristics are important requirements for proper functioning of batteries. Mercury porosim-etry has been historically used to characterize the separators in terms of percentage porosity, mean pore size and pore size distribution. In this method, the size and volume of pores in a material are measured by determining the quantity of mercury, which can be forced into the pores at increasing pressure. Mercury does not wet most materials, and a force must be applied to overcome the surface tension forces opposing entry into the pores. 

In comparison to the results obtained for the samples prepared with hexane, it can be concluded that the mean pore size and volume fraction do not depend on the initial concentration of the solvent, ( )o, but mainly on the difference between ( )o and (Fig. 25). Similar qualitative results are also reported for rubber-modified epoxies prepared via reaction induced phase separation [103]. 

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