Backscattered electron imaging studied

Stump, R.F., Pfeiffer, J.R., Schneebeck, M.C., Seagrave, J.C., and Oliver, J.M. (1989) Mapping gold-labeled receptors on cell surfaces by backscattered electron imaging and digital image analysis Studies of the IgE receptor on mast cells. Am. J. Anat. 185, 128-141. 

Studies using ion-thinned sections, wet cells and backscattered electron images of polished sections show that a space develops between the shell and the anhydrous material (S40,S41,S68) (Fig. 7.6c). In this respect, the hydration of cement differs from that of C3S, in which the C-S-H grows directly over the C3S surfaces, without any detectable separation (S41). By 12 h, the spaces are up to 0.5 pm wide. They are likely to be filled with a highly concentrated or colloidal solution, and the shells are evidently sufficiently porous at this stage that ions can readily migrate through them (S68). The existence of spaces shows that reaction proceeds by dissolution and precipitation further evidence for this is provided by the fact that the C-S-H also deposits on the surfaces of pfa particles, if these are mixed with the cement (D28). Some other relatively unreactive or inert admixtures behave in the same way. 

Monazite ubiquitously exhibits this type of behavior. Backscattered electron images and yttrium, thorium, and uranium X-ray maps nearly always reveal complex zonation (e.g., Parrish, 1990 DeWolf et al., 1993 Zhu et al., 1997 Zhu and O Nions, 1999 Williams et al., 1999 Pyle et al., 2001 Townsend et al., 2001 Williams and Jercinovic, 2002 see Figures 27 and 28), and several studies have demonstrated significant age differences between these chemically distinct domains (e.g., DeWolf et al., 1993 Zhu et al., 1997 Zhu and O Nions, 1999 Williams et al., 1999 Townsend et al., 2001 Figures 27 and 28). Extreme compositional and age heterogeneity implies that the analysis of a bulk mineral separate or even of a single grain is not very useful... 

Scrivener (1988) studied the Aspdin paste with backscattered electron imaging (BSE), showing clearly the development of hydration products pseudomor-phic after the original clinker crystals and drawing attention to the occurrence of layers of hydration product ( inner product ). 

A system in which the interdiffusion was much more extensive was studied by Kriven and Risbud, who studied the reaction between copper and cordier-ite glass ceramics. They used cathodoluminescence to observe the intensity of the fluorescence from the Cu ions that diffused into the glass. Quantitatively, electron microprobe data indicated that the copper concentration 100 p,m from the interface was 7 atom %, although the backscattered electron image in the SEM did not indicate the presence of Cu particles, thus confirming the presence of Cu. ... 

Images with elemental contrast can be obtained by detecting the high energy backscattered electrons, whose intensity is a function of the atomic number of the elements in the sample. These electrons also have a greater penetration depth than secondary electrons and so can be used for studying buried structures. 

Electron microscopy is one of the most powerful techniques for studying the microstructure of cementitious materials. Since the publication of the first fracture surface imaged via scanning electron microscopy (SEM) (Chatterji and Jeffery 1966), many advances have been made, perhaps, most notably, the imaging of polished sections by backscattered electrons (BSEs) (Scrivener 2004). Nowadays SEMs are widespread and even benchtop machines are available at relatively low cost. Transmission electron microscopy (TEM) has also made a significant contribution to understanding these materials, although this is much less widely used due to more limited availability of instrumentation and difficult sample preparation. 

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