Transmission electron micrographs, pore sizes

Figure 10.10 Transmission electron micrograph of ferritin entrapped in POPC liposomes (palmitoyloleoylphosphatidylcholine). Cryo-TEM micrographs of (a) ferritin-containing POPC liposomes prepared using the reverse-phase evaporation method, followed by a sizing down by extrusion through polycarbonate membranes with 100 nm pore diameters ([POPC] = 6.1 mM) and (b) the vesicle suspension obtained after addition of oleate to pre-formed POPC liposomes ([POPC] = 3 mM, [oleic acid - - oleate] = 3 mM). (Adapted from Berclaz et al, 2001a, b.)...

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.

Electron microscope inspection of a film replica of a polished surface of each of the bars as well as direct transmission electron micrographs of thin sections of each bar, reveals that these channels are evenly distributed throughout the bars. The channels are generally tetragonal or triangular in shape and have a diameter (calculated as the diameter of a circle having the same area as the pore cross section) of about 0.1-0.5 p.m. The pores are of such uniformity of size that practically no pores smaller than 0.1 pm or larger than 1 pm are found in the bars. The invention claimed is ... 

Estimates of the particle sizes obtained form the transmission electron micrographs indicated that the large-pore zeolite had an average particle size only about half that of the other zeolite.Since this corresponds to greater surface area per unit weight or volume, smaller particle size is presumably the origin of the better reinforcing ability of this zeolite. 

Fig. 7. Transmission electron micrographs of several MCM-41 materials having pore sizes of 20,40,65,and 100 A (from [7])...

Figure III a and b show cross sectional transmission electron micrographs of the identical systems. The film ecimens were defined by focus ion beams (FIB) to genoate cross sectional thicknesses of (SO-100 nm). Areas containing pores appear lighter in color due to lower attenuation of the electron beam in those regions. The pores in these images are consistent in size to die values observed by SEM.

A mercury poroskneter (Micromeritics model 9305) was used to determine pore size distribution. A Quantasorb adsorption unit (Quantachrome Corporation, USA) was used for BET surface area measurements. Pharma test model PTB 300 equipment was used to measure the side crushing strength of the alumina extrudates. X-ray diffraction patterns were obtained using a Phillips PW 1410 x-ray spectrometer operated at 30 kV and 20 mA with Cu Kq radiation. Transmission electron micrographs were made with JEM-1200 EX microscope. 

It is often beneficial to move away from the theoretical equation and the computergenerated model to the scanning electron microscope and the transmission electron microscope to reveal actual structures with activated carbon. Chapter 7 contains a selection of such micrographs which provide an overall impression that activated carbon is not altogether that homogeneous and perfect in the way that pore sizes are distributed. Such micrographs reveal a heterogeneity of structure. 

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