Scanning electron micrograph, silica

Figure C2.17.3. Close-packed array of sub-micrometre silica nanoparticles. Wlren nanoparticles are very monodisperse, they will spontaneously arrange into hexagonal close-packed stmcture. This scanning electron micrograph shows an example of this for very monodisperse silica nanoparticles of -250 nm diameter, prepared in a thin-film fonnat following the teclmiques outlined in [236].

More stringent requirements, especially with regard to separation efficiency and reproducibihty in preparative planar chromatography also, led to increased application of precoated plates in this field. Figure 3.3 shows a scanning electron micrograph of a cross section through a PLC plate silica gel. 

FIGURE 7.1 Scanning electron micrographs of a polystyrene-divinylbenzene monolithic column prepared in a 20-pm fused silica capillary tube (reproduced from the reference, Ivanov et al. (2003), with permission from American Chemical Society). 

FIGURE 7.3 Scanning electron micrographs of monolithic silica prepared from sol-gel methods, (a) monolithic silica prepared from TMOS in a test tube, and monolithic silica columns prepared from a mixture of TMOS and MTMS, (b) in a 50-pm fused silica capillary, (c) in a lOO-pm fused silica capillary, and (d) in a 200-pm fused silica capillary tube (reproduced from the reference, Motokawa et al. (2002), with permission from Elsevier). 

Fig. 1.2 Scanning electron micrographs of (A) the silica wall of the diatom Stephcmopyxis turns (reproduced from [21] by permission ofWiley-VCH) and (B-D) singular morphologies of silica synthesized using poly-L-lysine and pre-hydro-lyzed tetramethyl orthosilicate (TMOS) under...

Figure 4. (a) Adsorption-desorption isotherms of N2 at -196°C of 80°C-outgassed (empty squares) chitosan, (filled trangles) zeolite X-chitosan composite from in-situ zeolite synthesis and (empty triangles) zeolite Y-chitosan composite from encapsulation of the zeolite in the gelling chitosan. (b) Scanning electron micrographs of a calcined zeolite-chitosan bead prepared by zeolitisation of a silica-chitosan composite. 

FIGURE 13.7 Scanning electron micrograph showing flow-through channels in silica-based monolithic rods. 

FIGURE 13.8 Scanning electron micrograph showing nonreticulated porous structures of standard spherical silica particles. 

Fig. 11A-C. Scanning electron micrographs of fused silica capillary surfaces etched with methanolic ammonium hydrogen difluoride solution. (Reprinted with permission from [78], Copyright 2000 Elsevier). Etching process was carried out for A 3 h at 300 °C B, 2 h at 300 °C and 2 h at 400 °C C 2 h at 300 °C and 1 h at 400 °C...

Fig. 18. Scanning electron micrograph of monolithic silica-based capillary column. (Reprinted with permission from [205]. Copyright 2000 American Chemical Society)... 

Fig. 10. Scanning electron micrographs of monolithic poly(divinylbenzene) capillary column. Note that the porous monolith is surrounded by an impervious tubular outer polymer layer resulting from copolymerization of the monomer with the acryloyl moieties bound to the capillary wall. This layer minimizes any direct contact of the analytes with the surface of the fused-silica capillary...

Fig. 2.1.12 Scanning electron micrograph, showing the ordered arrangement of silica particles after a slow sedimentation process. (From Ref. 26.)...

Crosslinked polyacrylamide latexes encapsulating microparticles of silica and alumina have also been prepared by this method [179], Three steps are involved a) formation of a stable colloidal dispersion of the inorganic particles in an aqueous solution containing acrylamide, crosslinker, dispersant, and initiator b) HIPE preparation with this aqueous solution as the dispersed phase and c) polymerisation. The latex particles are polyhedral in shape, shown clearly by excellent scanning electron micrographs, and have sizes of between 1 and 5 pm. 

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. 5.1. Scanning electron micrographs of continuous-bed columns prepared from ODS-silica particles packed in a capillary. Prepared from (a) 75 pm capillary packed with silica particles by sintering in the presence of NaHC03 [9], and (b) large pore (left) and small-pore (right) ODS particles by a sol-gel method [10]. Reproduced from refs. 9 and 10, with permission.

Fig. 5.2. (a), Scanning electron micrograph of a continuous monolithic silica prepared in a fused silica capillary (100 pm) [16] (b), SEM photograph of monolithic silica prepared in a capillary (75 pm). Reproduced from ref. 19, with permission. 

Figure 1.4 in Chapter 1 shows a scanning electron micrograph (SEM) of typical irregular and spherical silica particles for comparison. 

Figure 9. Scanning Electron Micrograph of a Fragment of an Alkaline-Free HZSM-5 Shell Grown on a Pre-Shaped Silica Pellet (scale bar 10 pm).

Figure 8 Scanning electron micrograph of silica-gel thin layer formed on the inner wall of capillary tubing. There are three parts in the photo. The right part is a section of fused-silica capillary glass body, and the center is a cross-sectional view of a section of silica-gel thin layer foamed on the inner wall, thickness ca. 0.3 pm. On the surface of the silica-gel layer, two-thirds of the photo, there are a lot of holes. From the photo, the silica-gel layer has a nano-cell structure.

Figure 3. Scanning electron micrographs of catalyst microspheres before and after leaching with acids, (a) Commercial MCM powder made with ca. 50% colloidal silica 22 nm particle size, (b) Same powder after acid leaching the active metal oxide components. Continued on next page.

FIGURE 8.17 (a) Transmission electron micrograph of aqueous alumina gel (X 125,000). Versal alumina gel, photo cx>urte of Kaiser Aluminum and Chemical Company, (b) Scanning electron micrograph of sol-gel 0.2065 /xm average diameter silica spheres. Prom the work of Kovats and Ring, DC-EPFL, 1992. 

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.)... 

---