Pore size micrograph

Fig. 18. Cross-sectional scanning electron micrograph of a three-layered alumina membrane/support (pore sizes 0.2, 0.8, and 12 p.m, respectively).

SEM micrographs (Figure 4) show the deposition on the a-Al203 grains of small crystallites with the typical hexagonal shape of silicalite. The pore size distribution, as deduced from N2 adsorption, presents a very narrow peak centred on 0.5 nm, also in good agreement with the pore diameter of silicalite-type zeolites. 

For efficient separation, porous inorganic membranes need to be crack-free and uniform in pore size. An important reason for the increasing acceptance of ceramic membranes introduced in recent years is the consistent quality as exemplified in a scanning electron micrograph of the surface of a 0.2 micron pore diameter alumina membrane (Figure 3.3). 

Figure 1 Freeze-fracture electron micrographs of egg phosphatidylcholine large unilamellar vesicles prepared by extrusion through polycarbonate filters with pore sizes of (A) 400 nm, (B) 200 run, (Q 100 nm, (D) 50 nm, and (E) 30 nm. The bar in panel (A) represents 150nm. Source From Ref. 7.

Fig. 19a,b. Pore size distributions obtained from image analysis on SEM micrographs showing a narrow size distributions b bimodal size distributions... 

The SEM micrographs reveal that the pore size and the volume fraction increases with increasing amount of solvent. This qualitative result is also confirmed by image analysis performed on an average of around 150-250 pores, clearly showing the expected increase of pore size with increasing amount of cyclohexane (Fig. 24). This phenomenon has been observed in any polymer-solvent system studied here. 

In the micrograph of the surface of the 85°C annealed membrane (Figure 7), the wave-like features are observed, and the sizes of the wave range between 25 and 75 A. Its appearance resembles that of the unannealed one, but the number of pores is samller than the unannealed one. The pore sizes are at the level about 20 A, and the number of pores is not so many. 

FIGURE 1.4 Morphology and porosity of a typical monolithic rod, prepared by copolymerization of silane precursors, (a) SEM micrograph of the fractured surface of a monolithic silica gel rod. (b) Pore size distribution of a representative monolithic silica rod. (Reprinted from Guiochon, G., J. Chromatogr. A, 1168, 101, 2007. Copyright 2007, with permission from Elsevier.)... 

Figure 25-5 Scanning electron micrographs of silica chromatography particles, (a) Aggregate of spherical particles with 50% porosity and a surface area of 150 m2/g. (b) Spongelike structure with 70% porosity and a surface area of 300 m2/g. Pores are the entryways into the interior of the particles. In both cases, the nominal pore size is 10 nm, but the distribution of pore sizes is greater in the spongelike structure. The spongelike structure also dissolves more readily in base. [From Hewlett-Packard Co. and R. Majors, LCGC May 1997, p. S8.J...

Fig. 2a. Scanning electron micrograph of bare surface of GORE-TEX with 0.02 pm effective pore size. Magnification 20,000 x. Bar represents 500 nm.

Mercury porosimetry measurements for a partially sintered alumina preform showed a bimodal pore size distribution with neck diameter Dn = 0.15 pm [Manurung, 2001], As a comparison with the pore sizes and distribution of the preform measured by porosimetry, SEM micrographs (Fig. 5.1) were taken before and after infiltration. Based on SEM examination, the pores in the preform before infiltration ranged in size from r 0.1-0.5 pm. Assuming an average pore radius of 0.3 pm, this radius is approximately four times larger than the pore-neck radius (Dn = 0.15 pm, so pore radius = 0.075 pm) determined by mercury porosimetry. 

Figure 2.6 SEM micrograph of the top layer surface of an UF membrane from PAN and pore-size distribution from computerized image analysis (reprinted from [9], with permission from Wiley-VCH, 2006).

Fig. 15 SEM micrographs of the nanotubes of hb-P71(6) prepared inside an AAO template with a pore size of 250 nm...

Figure 5. Transmission electron micrograph of a mesoporous M41S-type silicate with pore sizes of 4 nm. The regular hexagonal arrangement of the pores can be seen in the micrograph and in the diffraction pattern shown in the inset.

The wrapping process is typically carried out in liquid medium a PEI chloroform solution (1.5% w/w) is mixed with the SWCNTs under intense stirring. The blend is then treated with an ultrasonic tip for 1 h at 50% oscillation amplitude and 50% cycle time. The resulting dispersion is subsequently filtered using a 0.2 pm pore size PTFE membrane and dried under vacuum at 60°C to assure total evaporation of the solvent. The wrapped SWCNTs can be characterized by different techniques, and some results are included in Table 10.1. Figure 10.5 shows TEM images of acid-treated SWCNTs dispersed in the compatibilizer. Small nanotube bundles shrouded in PEI can be visualized in the micrographs. 

A disordered mesoporous silica material (sample Cl) was obtained by the route outlined for SBA-15, when the Pluronic P123 used as the template was replaced with an equal-weight mixture of Pluronic and trimethylbenzene. SEM micrographs indicate that this material constitutes a system of spherical pores of wide size distribution, connected and accessible by small mesopores and/or micropores only. The nitrogen adsorption isotherm indicates a wide pore size distribution and a H2 type hysteresis loop. Some properties of this material are included in Table 1. 

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