Surface pores, scanning electron micrograph

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 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...

Figure 7.3 Surface scanning electron micrograph and schematic comparison of nominal 0.45-p.m screen and depth filters. The screen filter pores are uniform and small and capture the retained particles on the membrane surface. The depth filter pores are almost 5-10 times larger than the screen filter equivalent. A few large particles are captured on the surface of the membrane, but most are captured by adsorption in the membrane interior...

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.

Fig. 1. The accuracy of e-beam lithography is illustrated in the scanning electron micrograph (top). The size of the features formed in the silicon oxide is 0.5 pm and the typical animal cell (a fibroblast) has a diameter of 20 pm. This kind of cell adheres actively to surfaces, forming thin filopodia which here have all attached to the micro-hillocks. Semiconductor technology is capable of manufacturing micro-electrodes, sensors, pores and electronic networks with sizes smaller than that of the cell. The lower illustration summarises the main detection and measuring methods currently in use...

Fig. 17. a A scanning electron micrograph of square pores etched in a 3 micrometer thick silicon membrane. The pores were produced by anisotropic etching and their width on this side of the membrane is 6 pm. Cells (fibroblasts 3T3) attach to the surface and migrate over the pores, b Electrodes are placed on either side of the membrane and a constant current passed through it (mainly through the pores). The presence of cells is easily detected and movements of cell filopodia of less than 100 nm and the passive electric properties of the cell body can be determined by analysis of the signal fluctuations and impedance... 

Scanning electron micrographs of fractured microspheres reveal that the pores in the polymeric matrix became smaller and more numerous when the level of NaOH was increased. The increased surface area generated by these pores may account for the enhanced drug release observed with microspheres prepared in the presence of base. 

FIGURE 20.4 Scanning electron micrographs (SEM) micrographs of the cross section of a cellulose acetate membrane of 0.45 pm pore size after being used for beer CMF experiments. A dense fouling layer is observed on the membrane surface. (From Moraru, C.I., Optimization and membrane processes with applications in the food industry Beer microfiltration. PhD thesis. University Dunarea de Jos Galati, Romania, 1999.)... 

FIGURE 22.13 Scanning electron micrographs of the surface (a) and the internal structure (h) of a Rotrac capillary pore membrane. (From Klobes et al.. Bull. Int. Dairy Fed., 311, 13, 1996. With permission.)... 

FIGURE 24.2 Scanning electron micrographs. (A) The surface and cross section of a typical nanopore alumina template membrane prepared in the authors lab. Pores with monodisperse diameters that run like tunnels through the thickness of the membrane are obtained. (B) Silica nanotubes prepared by solgel template synthesis within the pores of a template like that shown in (A). After solgel synthesis of the nanotubes, the template was dissolved and the nanotubes were collected by filtration. (From Lee, S.B., Mitchell, D.T., Trofin, L., Li, N., Nevanen, T.K., Sbderlund, H., and Martin, C.R., Science, 296, 2198, 2002. With permission.)... 

Scanning electron micrographs of biooxidized pyrite showed the formation of deep pits in crystal surfaces. The pores appear to be hexagonal in cross-section, consistent with screw dislocations in a cubic crystal lattice (43), and suggesting that the bacteria have attacked... 

Gel-permeation chromatography" is used to compare the pore structure of jute, scoured jute and purified cotton cellulose. Both native and scoured jute have shown greater pore volumes than cotton. The effects of alkali and acid treatment on the mechanical properties of coir fibers are reported." Scanning electron micrographs of the fractured surfaces of the fibers have revealed extensive fibrillation. Tenacity and extension-at-break decrease with chemical treatment and ultraviolet radiation, whereas an increase in initial modulus and crystallinity is observed with alkali treatment. FTIR spectroscopy shows that the major structural changes that occur when coir fibers are heated isothermally in an air oven (at 100, 150 and 200 °C for 1 h) are attributable to oxidation, dehydration and depolymerization of the cellulose component. 

The pores are formed from bubbles during some of the typical manufacturing processes of polymer materials. The size distribution and density distribution of both are important to performance during the polishing process. Figure 6.17 shows two scanning electron micrographs of a polymer with such pore structures the first is the sidewall cross-section of the material, and the second is the top surface after some use. 

Fig. 16. Schematic of experiment to study shock-induced nanopore collapse in real time, (a) One element of a shock target array. A near-IR laser pulse generates shock waves by ablation of an absorbing surface layer. The shock front steepens up to <25 ps in the buffer layer. CARS spectroscopy is used to probe dye molecules in the nanoporous layer, which monitor strain and temperature, and a thin anthracene downstream gauge which monitors changes in the risetime of the shock front caused by pore collapse, (b) Scanning electron micrograph of the surface of the nanoporous layer. The pore size distribution is 100 nm 10%. The distribution appears broader in the image, since it sees only the pore cross-section in the surface plane. Reproduced from ref. [120].

Scanning electron micrographs reveals (60-62, 84) that HF treatment results in rapid dissolution of the surface. The as-quenched Ni and Cu alloys contain furrows that become cracked [Ni-Zr (61)] and contain pores [Cu-Zr, Cu-Ti (62)] or pits [Pd-Zr (60)]. The surface of Ni-Ti is probably too smooth to detect the presence of the cracks (61). 

Figure 1.14 Scanning electron micrograph of membrane cross sections with typical structures (a) symmetric microporous membrane without a "skin" (b) asymmetric membrane with a "finger"-type structure and a dense skin at the surface (c) asymmetric membrane with a "sponge"-type structure, a dense skin, and pore sizes increasing from the surface to the bottom side (d) symmetric membrane with a sponge structure, a dense skin and a uniform pore size distribution in the substructure.

Figure 2.88 shows a scanning electron micrograph that shows a side view of a sample after deposition of Pt particles. The site-selective deposition of Pt is clearly visible. It should be noted that not all nanopores are necessarily filled because, in the progressing oscillation, pores at different phases of their development exist on the surfaces and, depending on the process, some do not make contact with the... 

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